On Sat, 12 Apr 2008 00:16:41 -0500, Tim Wescott
wrote:


Take this for as much verification as you think it's worth...

On at least one occasion my dad came home from the fire station with a
story of a truck engine running away when the guys put gasoline in the
tank instead of diesel fuel.

I don't see why this should happen _in theory_ as a diesel is throttled
by controlling the amount of fuel injected, but I could certainly see it
happening in practice if the lower viscosity of gas let it flow at a too-
high volume.

IIRC one shuts down a runaway diesel by shutting off the air. There is
(was) supposed to be an emergency shut-off valve in the intake of every
diesel motor, but in a pinch one could use articles of clothing stuffed
into the intake.


I was working on a drilling rig when we hit a gas pocket, and a cloud
of it wound up being pulled into the intake of the 398 Cat (about the
side of a small garage) driving the mud pump.

We wound up stuffing about 5 pairs of Carrhart insulated coveralls in
the intake....she was climbing and climbing in rpm...scary **** to
hear a big! diesel winding up like a GE turbofan, and starting to move
on its base.

Gunner


"[L]iberals are afraid to state what they truly believe in, for to do so
would result in even less votes than they currently receive. Their
methodology is to lie about their real agenda in the hopes of regaining
power, at which point they will do whatever they damn well please. The
problem is they have concealed and obfuscated for so long that, as a group,
they themselves are no longer sure of their goals. They are a collection of
wild-eyed splinter groups, all holding a grab-bag of dreams and wishes. Some
want a Socialist, secular-humanist state, others the repeal of the Second
Amendment. Some want same sex/different species marriage, others want voting
rights for trees, fish, coal and bugs. Some want cradle to grave care and
complete subservience to the government nanny state, others want a culture
that walks in lockstep and speaks only with intonations of political
correctness. I view the American liberals in much the same way I view the
competing factions of Islamic
fundamentalists. The latter hate each other to the core, and only join
forces to attack the US or Israel. The former hate themselves to the core,
and only join forces to attack George Bush and conservatives." --Ron Marr

On Sat, 12 Apr 2008 01:38:50 -0400, "Ed Huntress"
wrote:

Something is funny here, Tim. I wonder if those guys told your dad what
actually happened?

The cetane rating of gasoline is so low that, if you can ignite it at all in
a diesel, the gasoline burns so slowly that the engine knocks like crazy,
and it's still burning past the end of the power stroke. Thus, the white
smoke that someone else mentioned. At low temperatures, a diesel fueled with
gasoline may not ignite at all.

At the risk of oversimplifying, octane and cetane have roughly opposite
burning characteristics. A high cetane rating (as in premium diesel)
indicates that the fuel ignites easily from the heat of compression and that
it burns quickly once ignited. In fact, the cetane rating is based on the
time it takes for fuel ignited at high temperature and compression to reach
a specified cylinder pressure.

An octane rating, which is very low in diesel and much higher in gasoline,
indicates the *resistance* of the fuel to burning under those same
conditions. Higher octane allows higher compression ratios without premature
ignition from the heat of compression. However, what octane rating really
measures, if I recall correctly, is the speed with which a flame progresses.
High octane, slow burning.

Your recollection is not quite correct, which is where the confusion
comes in. Octain has NOTHING to do with the temperature at which the
fuel will auto-ignite, nor the speed of burn, when you get right down
to it. It has everything to do with resistance to dissassociation, and
resultant detonation.
The flash point of gasoline is lower than the flashpoint of diesel
fuel. The vapour pressure is higher. Therefore it actually takes less
heat to light gasoline than diesel. However, the flamability range of
gasoline is lower - too lean or too rich and it won't light.

When you inject gasoline into a diesel, if you get it injected in a
proper cone, at the right time, some of the fuel will ignite
immediately and will burn very quickly, causing a knock. The rest of
the fuel is dissipated in an overlean mixture, and does not burn.
(severe lean misfire)This goes out the pipe as white "smoke" and also
causes the flame in the exhaust if it ends up lighting on the way out.

If the throttle is advanced enough to get sufficient fuel into the cyl
to get the mixture rich enough to burn more completely, SEVERE
"detonation" shock occurs - the engine knocks badly, smokes profusely,
and makes very little power. High octane fuel will not behave much
differently than low octane fuel in a deisel.
A diesel depends on s relatively slow even burn, and a reasonably long
calibrated injection period provides the fuel to keep building cyl
pressure constantly untill the piston is almost at BDC.

So they aren't exactly opposite characteristics, but they're pretty close.
FWIW, ethanol is even harder to ignite with compression than gasoline. But
ether, which has a cetane rating around 80 (compared to petroleum diesel's
rating of 40 to 55), ignites much easier than any of them, with either
compression or a spark.

** Posted from http://www.teranews.com **

"ED" wrote in message
news
Brazil has no petrolium resources and relied on sugar cane
to produce ethenol. I believe they were/are 100%
independent from oil imports..

We should be doing more in this country--not with corn
but with sugar beets....and oil seeds..


Be careful what you wish for. On all bio fuels I have seen touted so far,
it seems to be a proposition where it takes more energy put in to the
production of the fuel than you get out of the fuel when you use it.

Think for a moment about how many gallons of oil you get per acre of farm
land, the cost of pumping water to irrigate the crop and the energy required
to run the tractors, truck and process the produce.

Brazil has a whole lot of bio-mass to ferment into alcohol, and they have
very little demand.

Conversely, in the US we are burning a whole lot of natural gas to generate
electricity. Motor vehicles can use natural gas with very little
modification, yet few use this fuel because of the price and availability.

If we were to build some more nuclear power plants, we could free up the
supply of natural gas, and get cheaper and cleaner electricity. Political
pressures from scare mongers have thwarted this however. As a result of
this stupidity, we generate about half of our electricity by burning coal
and therefore dump thousands of tons of radioactive pollution into the
atmosphere from burning the coal.

Cheap electricity would also allow for cheap hydrogen to be produced.
Hydrogen could also be used as a motor fuel with zero smog, or carbon
emissions.


--
Roger Shoaf
If you are not part of the solution, you are not dissolved in the solvent.

On Sat, 12 Apr 2008 02:41:13 -0400, "Ed Huntress"
wrote:



Well, assuming that's really the bottom line, maybe it's safe to pick apart
some of your answer without obscuring the point. g

That certainly was a long answer, and it really runs around the horn, but
some of your concepts in there just aren't right. First, gasoline's tendency
to burn from high compression would be an issue in a diesel except that the
gasoline (or diesel) never has a chance to "preignite". It's injected long
after preignition could take place. The environment it's injected into (high
heat, high pressure) burns the fuel progressively and its cetane rating
determines how fast it burns. Conversely, its octane rating reflects its
resistance to burn rapidly from the heat of compression. Thus, if you inject
gasoline into a diesel engine it will burn, but it does so slowly, and the
engine may not run at all. That's entirely different from mixing the fuel
with the air before it gets into the engine. At a compression ratio of 20:1
or so, gasoline/air mixes would burn in a way that you could describe as an
explosion (although there was contention about this as of a couple of
decades ago -- the high-speed flame-front versus acoustic shock wave
theories of engine detonation they were then studying at MIT's Sloan labs --
I never read how it was concluded) but that's really a side issue here and
not worth discussing. The point is, there is no gasoline (or diesel fuel) in
the cylinder until it's injected, so there is no pre-ignition, no
detonation, no explosion, and the gasoline actually burns slower than diesel
fuel does in that environment. Gasoline actually can be hard to ignite at
all when it's sprayed into a diesel cylinder, at least at low temperatures,
despite what we know about the tendency of gasoline to detonate when it's
pre-mixed with the air charge in spark-ignition engines with excessively
high compression ratios. When you go to direct injection, you're changing
some of the crucial dynamics of the whole process.

The flamability range of gasoline and air is rather narrow - so only
some of the fuel in the highly stratified charge in a deisel will
ignite. Putting an air throttle on a deisel would enhance the running
of the engine on gasoline

Another point: there is nothing that would cause gasoline to detonate in the
injector system. Some of the current common-rail, direct (cylinder)
injection gasoline engines use pressures similar to those of common-rail,
high-pressure injection in modern diesel engines. And that's very high
pressure indeed.

Gasoline will not burn hotter in a diesel engine than diesel fuel does. In
fact, diesel has somewhat higher caloric value per unit volume ( 11% - 15%,
depending on who's measuring) and the diesel fuel will produce more heat in
the cylinder. More importantly, it will produce higher peak cylinder
temperatures because (again, due to its higher cetane rating) it burns
faster.

You may be aware that there are, or were, dual-fuel spark-ignition engines
that run on gasoline or kerosene (once they're heated up), so the volatility
of fuel oils of that grade is not so low that you can't spark-ignite it at
gasoline-engine compression ratios. They were industrial and agricultural
engines that enjoyed a reasonable operating life. I reported on a line of
such engines, made in Italy back in the '70s, that were widely used for ag
jobs throughout Europe at the time.

These dual fuel engines, almost without exception, would not cold
start on Kero, and would knock, smoke and generally complain loudly if
switched to kero (or "distillate" before fully warmed up.

I listened in to an online discussion about this very subject around 20
years ago, by some very knowledgable engineers from MIT and Carnegie Mellon,
and one of them pointed out that there are a lot of incorrect assumptions
people make about these fuels based on our experience using them to start
charcoal fires. g The properties of fuels at atmospheric pressure, when
you throw a match into them to light a fire, are very different from their
behavior in an enclosed environment at high pressure and with different
systems of ignition. The idea that diesel fuel can burn faster in an engine
than gasoline does is one of the things that runs counter to our sensible
experience.


The fact that diesel will burn at a much leaner mixture than gasoline
helps here. At the lean combustion limit, gasoline burns much faster
than at the rich combustion limit. Diesel generally runs at a leaner
overall mixture in the cyl than gasoline does.
** Posted from http://www.teranews.com **

On Sat, 12 Apr 2008 06:25:41 -0500, "DanG" wrote:

Ed. as always, I appreciate your response. I used to run a bit of
diesel in old gasoline engines before computers and what not. I'm
sure it was as ignorant as adding gasoline to diesel fuel.

I was believing your frank, honest style, but the technical
article just made it dance. Thanks. I wish more people would
limit their comments to facts, not hyperbola.


A bit of diesel or stove-oil was commonly used as an "upper cyl
lubricant" in years gone by. On Mopar Flatties they'd run well on 20%
stove oil and stink like crazy. Just don't forget to downshift and
make it lug at low RPMs. Then they'd knock something awfull, and
smoke. At medium engine speeds, even under heavy load, they were OK.

** Posted from http://www.teranews.com **

On Sat, 12 Apr 2008 12:39:32 -0400, "Ed Huntress"
wrote:


"Ed Huntress" wrote in message
...

snip

Unless you go to the SME or MIT research sources...

That should be SAE, not SME.

And regarding the corners of the combustion chambers, that should be the
corners of the combustion *space*. Detonation is most likely to occur where
the piston meets the cylinder walls.

Detonation is most likely to occur wherever fuel is exposed to high
temperature and pressure for an "extended" periosd of time.
The pressure and temperature "crack" the hydrocarbons into hydrogen
radicals and carbon. This process takes a finite amount of time (which
is why detonation is much less of a problem at high speeds than at low
speeds). The hydrogen radicals "explode" as soon as they find a
molecule of oxygen to attach to - fire or no fire.
** Posted from http://www.teranews.com **

Gerald Miller wrote:


A lot of the older International bulldozers were started as gasoline
engines and switched over to diesel once they warmed up, right down to
the spark plugs.
Gerry :-)}
London, Canada

I recently saw such a critter running a saw mill. I *think* it was a
very old Detroit, but not positive on that.

On Sat, 12 Apr 2008 13:12:06 GMT, RAM³ wrote:
"SteveB" wrote in news:4ut5d5-efo2.ln1
@news.infowest.com:

IHMO, it would take someone with brass balls to climb up there and do it!

Don't worry - they've got them.
Proof: Who else would go into a burning building voluntarily just to see if
there's anyone in it?

There's a burning building, and then there's an _unsafe_ burning
building. Not always the same thing.

There's an excellent reason that, while Law Enforcement Officers may be
known as the "Finest", Fire Fighters are referred to as the "Bravest".

Hrrm, not so sure about that. When I go into a fire situation, the fire
is responding predictably, more or less, and obeying laws of physics and
nature. If you see the signs, and know how it's going to work, then you
can anticipate what it's going to do.

Do you want to know who'd qualify as the "Craziest"?
*Volunteer* Fire Fighters.

(shrug) I don't mind doing it for a buck an hour "reimbursement", but I
sure wouldn't want to do it for a living.

They're the ones who pay for and/or build their own equipment, consider
themselves to on-duty 24/7, and still work for a living doing something
unrelated.

I've spent hundreds on my own equipment, but it's all the optional "nice
to have" stuff. The NFPA-mandated stuff is all supplied by our
taxpayer-funded department.

On Sat, 12 Apr 2008 07:58:02 -0600, ED
wrote:


Brazil has no petrolium resources and relied on sugar cane
to produce ethenol. I believe they were/are 100%
independent from oil imports..

We should be doing more in this country--not with corn
but with sugar beets....and oil seeds..


Google "rapeseed"

Gunner


"[L]iberals are afraid to state what they truly believe in, for to do so
would result in even less votes than they currently receive. Their
methodology is to lie about their real agenda in the hopes of regaining
power, at which point they will do whatever they damn well please. The
problem is they have concealed and obfuscated for so long that, as a group,
they themselves are no longer sure of their goals. They are a collection of
wild-eyed splinter groups, all holding a grab-bag of dreams and wishes. Some
want a Socialist, secular-humanist state, others the repeal of the Second
Amendment. Some want same sex/different species marriage, others want voting
rights for trees, fish, coal and bugs. Some want cradle to grave care and
complete subservience to the government nanny state, others want a culture
that walks in lockstep and speaks only with intonations of political
correctness. I view the American liberals in much the same way I view the
competing factions of Islamic
fundamentalists. The latter hate each other to the core, and only join
forces to attack the US or Israel. The former hate themselves to the core,
and only join forces to attack George Bush and conservatives." --Ron Marr

On Sat, 12 Apr 2008 11:33:40 -0700, Gunner Asch
wrote:

On Sat, 12 Apr 2008 07:58:02 -0600, ED
wrote:


Brazil has no petrolium resources and relied on sugar cane
to produce ethenol. I believe they were/are 100%
independent from oil imports..

We should be doing more in this country--not with corn
but with sugar beets....and oil seeds..


Google "rapeseed"

Gunner

Or Canola

** Posted from http://www.teranews.com **

After reading the other comments I think you have multiple issues going
on to switch from diesel to gasoline:
-the gasoline will have a MUCH lower viscosity, you are going to get way
different (more)amounts of fuel through the injector. I'd think that is
what causes the white smoke a lousy performance, it's too rich.
-at the same time, gasoline has lower fuel value per gallon or
milliliter, same volume of fuel will cause the engine to go lean, never
a good thing
-gasoline has a much higher flame front speed, ie it will detonate,
really does bad things to the top of the piston.
-gasoline has no lubricating qualities, will tear up a standard injector
pump in short order.

Very interesting discussion. I've been asked to be the project manager
for an alternate fuels project based around a 100kw Cat diesel
generator. Fire up on a new fuel, check for short term issues, go to a
50% load then 100% load for 8 to 24 hours, then tear down and look for
damage. Looks like I would be spending more time than planned dealing
with the injector pump. Hmmmmmmmmmmmmm.

Ivan Vegvary wrote:
Sorry about the OT, but, I do contribute once in a while and this is such a
knowledgeable group!

Many decades ago (1950's) when people talked about diesel engines (lot of
this talk was from 'old country' poor Europeans), they would always tout the
fact that they (the engines) would run on anything. The list, if I remember
correctly included diesel, gas, lighter fluid, heating oil, liquefied lard,
charcoal lighter, veggie oil etc., etc., etc.

If any of the above is true, why don't people, today, put gasoline into
their diesel engines, considering the higher cost of diesel fuel?

Just want to know what would happened if you did use gasoline.
BTW, my only diesel is my small Kubota tractor.

Thanks for replies.

Ivan Vegvary

RoyJ wrote:
After reading the other comments I think you have multiple issues
going on to switch from diesel to gasoline:
-the gasoline will have a MUCH lower viscosity, you are going to get
way different (more)amounts of fuel through the injector. I'd think
that is what causes the white smoke a lousy performance, it's too rich.
I don't think that would be the case as unlike a petrol engine the
diesel uses a positive displacement pump for the injection AFAIK so
injected fuel quantity wouldn't be effected by the viscosity.

-at the same time, gasoline has lower fuel value per gallon or
milliliter, same volume of fuel will cause the engine to go lean,
never a good thing
-gasoline has a much higher flame front speed, ie it will detonate,
really does bad things to the top of the piston.
-gasoline has no lubricating qualities, will tear up a standard
injector pump in short order.

Very interesting discussion. I've been asked to be the project manager
for an alternate fuels project based around a 100kw Cat diesel
generator. Fire up on a new fuel, check for short term issues, go to a
50% load then 100% load for 8 to 24 hours, then tear down and look for
damage. Looks like I would be spending more time than planned dealing
with the injector pump. Hmmmmmmmmmmmmm.

Ivan Vegvary wrote:
Sorry about the OT, but, I do contribute once in a while and this is
such a knowledgeable group!

Many decades ago (1950's) when people talked about diesel engines
(lot of this talk was from 'old country' poor Europeans), they would
always tout the fact that they (the engines) would run on anything.
The list, if I remember correctly included diesel, gas, lighter
fluid, heating oil, liquefied lard, charcoal lighter, veggie oil
etc., etc., etc.

If any of the above is true, why don't people, today, put gasoline
into their diesel engines, considering the higher cost of diesel fuel?

Just want to know what would happened if you did use gasoline.
BTW, my only diesel is my small Kubota tractor.

Thanks for replies.

Ivan Vegvary

Dave Hinz wrote:
On Sat, 12 Apr 2008 13:12:06 GMT, RAM³ wrote:
"SteveB" wrote in news:4ut5d5-efo2.ln1
@news.infowest.com:

IHMO, it would take someone with brass balls to climb up there and do it!

Don't worry - they've got them.
Proof: Who else would go into a burning building voluntarily just to see if
there's anyone in it?

There's a burning building, and then there's an _unsafe_ burning
building. Not always the same thing.

VERY true. A well built structure can handle a LOT of fire before it is
unsafe. Now your typical mobile home on the other hand....

There's an excellent reason that, while Law Enforcement Officers may be
known as the "Finest", Fire Fighters are referred to as the "Bravest".

Hrrm, not so sure about that. When I go into a fire situation, the fire
is responding predictably, more or less, and obeying laws of physics and
nature. If you see the signs, and know how it's going to work, then you
can anticipate what it's going to do.

The only catch to this becomes the instances of meth labs or other
incendiary time bombs out there.


Do you want to know who'd qualify as the "Craziest"?
*Volunteer* Fire Fighters.

(shrug) I don't mind doing it for a buck an hour "reimbursement", but I
sure wouldn't want to do it for a living.

Same here. The good thing in this area is that we don't get a lot of the
stupid calls like the paid departments seem to get. Nothing like going
to the same building 30 times a week on average for "burnt food" or
"smoking in the room".


They're the ones who pay for and/or build their own equipment, consider
themselves to on-duty 24/7, and still work for a living doing something
unrelated.

I've spent hundreds on my own equipment, but it's all the optional "nice
to have" stuff. The NFPA-mandated stuff is all supplied by our
taxpayer-funded department.


I tend to buy my own turnout gear as well. Mainly because I take care of
it and any repairs or problems get taken care of NOW instead of the
normal chain of dysfunction...
--
Steve W.

"RoyJ" wrote in message
...
After reading the other comments I think you have multiple issues going on
to switch from diesel to gasoline:
-the gasoline will have a MUCH lower viscosity, you are going to get way
different (more)amounts of fuel through the injector. I'd think that is
what causes the white smoke a lousy performance, it's too rich.
-at the same time, gasoline has lower fuel value per gallon or milliliter,
same volume of fuel will cause the engine to go lean, never a good thing

You raise an intriguing question there, Roy. How do you make a diesel run
lean? g

-gasoline has a much higher flame front speed, ie it will detonate, really
does bad things to the top of the piston.

It will detonate, but it's because of the *slower* flame front speed. That's
the thing that's indirectly measured by the cetane rating: gasoline around
25, diesel typically 45+.

-gasoline has no lubricating qualities, will tear up a standard injector
pump in short order.

Very interesting discussion. I've been asked to be the project manager for
an alternate fuels project based around a 100kw Cat diesel generator. Fire
up on a new fuel, check for short term issues, go to a 50% load then 100%
load for 8 to 24 hours, then tear down and look for damage. Looks like I
would be spending more time than planned dealing with the injector pump.
Hmmmmmmmmmmmmm.

Ivan Vegvary wrote:
Sorry about the OT, but, I do contribute once in a while and this is such
a knowledgeable group!

Many decades ago (1950's) when people talked about diesel engines (lot of
this talk was from 'old country' poor Europeans), they would always tout
the fact that they (the engines) would run on anything. The list, if I
remember correctly included diesel, gas, lighter fluid, heating oil,
liquefied lard, charcoal lighter, veggie oil etc., etc., etc.

If any of the above is true, why don't people, today, put gasoline into
their diesel engines, considering the higher cost of diesel fuel?

Just want to know what would happened if you did use gasoline.
BTW, my only diesel is my small Kubota tractor.

Thanks for replies.

Ivan Vegvary

Ed Huntress wrote:
"RoyJ" wrote in message
...

After reading the other comments I think you have multiple issues going on
to switch from diesel to gasoline:
-the gasoline will have a MUCH lower viscosity, you are going to get way
different (more)amounts of fuel through the injector. I'd think that is
what causes the white smoke a lousy performance, it's too rich.
-at the same time, gasoline has lower fuel value per gallon or milliliter,
same volume of fuel will cause the engine to go lean, never a good thing


You raise an intriguing question there, Roy. How do you make a diesel run
lean? g


-gasoline has a much higher flame front speed, ie it will detonate, really
does bad things to the top of the piston.


It will detonate, but it's because of the *slower* flame front speed. That's
the thing that's indirectly measured by the cetane rating: gasoline around
25, diesel typically 45+.


Ed,

I'm wondering if some of the problem here is with the nature of the
combustion in the 2 engines. My understanding is that the SI engine
burns a vapourised fuel air mix which burns like any gaseous fuel air
mix but in the diesel combustion the fuel droplets burn at the surface
of the droplet in the combustion air, the lighter fractions burning
first leaving the heavier fractions, hence the particulates left behind.
The modern diesels in small vehicles, at least in Europe as I think
regulations have constrained small diesels in the US, have much finer
atomisation of the fuel due to the high pressures used which allows
shorter burn times and higher resultant RPM but the nature of the
combustion still differs from that of a petrol engine.

-gasoline has no lubricating qualities, will tear up a standard injector
pump in short order.

Very interesting discussion. I've been asked to be the project manager for
an alternate fuels project based around a 100kw Cat diesel generator. Fire
up on a new fuel, check for short term issues, go to a 50% load then 100%
load for 8 to 24 hours, then tear down and look for damage. Looks like I
would be spending more time than planned dealing with the injector pump.
Hmmmmmmmmmmmmm.

Ivan Vegvary wrote:

Sorry about the OT, but, I do contribute once in a while and this is such
a knowledgeable group!

Many decades ago (1950's) when people talked about diesel engines (lot of
this talk was from 'old country' poor Europeans), they would always tout
the fact that they (the engines) would run on anything. The list, if I
remember correctly included diesel, gas, lighter fluid, heating oil,
liquefied lard, charcoal lighter, veggie oil etc., etc., etc.

If any of the above is true, why don't people, today, put gasoline into
their diesel engines, considering the higher cost of diesel fuel?

Just want to know what would happened if you did use gasoline.
BTW, my only diesel is my small Kubota tractor.

Thanks for replies.

Ivan Vegvary

On Sat, 12 Apr 2008 16:50:08 -0500, RoyJ
wrote:

After reading the other comments I think you have multiple issues going
on to switch from diesel to gasoline:
-the gasoline will have a MUCH lower viscosity, you are going to get way
different (more)amounts of fuel through the injector. I'd think that is
what causes the white smoke a lousy performance, it's too rich.
-at the same time, gasoline has lower fuel value per gallon or
milliliter, same volume of fuel will cause the engine to go lean, never
a good thing

Except a deisel is ALWAYS lean,(except possibly at full power) and
direct injection gives a stratified charge, which even on gasoline,
CAN run very lean without overheating.
-gasoline has a much higher flame front speed, ie it will detonate,
really does bad things to the top of the piston.
-gasoline has no lubricating qualities, will tear up a standard injector
pump in short order.

Very interesting discussion. I've been asked to be the project manager
for an alternate fuels project based around a 100kw Cat diesel
generator. Fire up on a new fuel, check for short term issues, go to a
50% load then 100% load for 8 to 24 hours, then tear down and look for
damage. Looks like I would be spending more time than planned dealing
with the injector pump. Hmmmmmmmmmmmmm.

Ivan Vegvary wrote:
Sorry about the OT, but, I do contribute once in a while and this is such a
knowledgeable group!

Many decades ago (1950's) when people talked about diesel engines (lot of
this talk was from 'old country' poor Europeans), they would always tout the
fact that they (the engines) would run on anything. The list, if I remember
correctly included diesel, gas, lighter fluid, heating oil, liquefied lard,
charcoal lighter, veggie oil etc., etc., etc.

If any of the above is true, why don't people, today, put gasoline into
their diesel engines, considering the higher cost of diesel fuel?

Just want to know what would happened if you did use gasoline.
BTW, my only diesel is my small Kubota tractor.

Thanks for replies.

Ivan Vegvary



** Posted from http://www.teranews.com **

On Sat, 12 Apr 2008 23:15:53 +0100, David Billington
wrote:

RoyJ wrote:
After reading the other comments I think you have multiple issues
going on to switch from diesel to gasoline:
-the gasoline will have a MUCH lower viscosity, you are going to get
way different (more)amounts of fuel through the injector. I'd think
that is what causes the white smoke a lousy performance, it's too rich.
I don't think that would be the case as unlike a petrol engine the
diesel uses a positive displacement pump for the injection AFAIK so
injected fuel quantity wouldn't be effected by the viscosity.



Except on "common rail" engines which use a timed injector on constant
pressur instead of positive displacement.



-at the same time, gasoline has lower fuel value per gallon or
milliliter, same volume of fuel will cause the engine to go lean,
never a good thing
-gasoline has a much higher flame front speed, ie it will detonate,
really does bad things to the top of the piston.
-gasoline has no lubricating qualities, will tear up a standard
injector pump in short order.

Very interesting discussion. I've been asked to be the project manager
for an alternate fuels project based around a 100kw Cat diesel
generator. Fire up on a new fuel, check for short term issues, go to a
50% load then 100% load for 8 to 24 hours, then tear down and look for
damage. Looks like I would be spending more time than planned dealing
with the injector pump. Hmmmmmmmmmmmmm.

Ivan Vegvary wrote:
Sorry about the OT, but, I do contribute once in a while and this is
such a knowledgeable group!

Many decades ago (1950's) when people talked about diesel engines
(lot of this talk was from 'old country' poor Europeans), they would
always tout the fact that they (the engines) would run on anything.
The list, if I remember correctly included diesel, gas, lighter
fluid, heating oil, liquefied lard, charcoal lighter, veggie oil
etc., etc., etc.

If any of the above is true, why don't people, today, put gasoline
into their diesel engines, considering the higher cost of diesel fuel?

Just want to know what would happened if you did use gasoline.
BTW, my only diesel is my small Kubota tractor.

Thanks for replies.

Ivan Vegvary


** Posted from http://www.teranews.com **

On Sat, 12 Apr 2008 19:08:43 -0400, "Ed Huntress"
wrote:


"RoyJ" wrote in message
...
After reading the other comments I think you have multiple issues going on
to switch from diesel to gasoline:
-the gasoline will have a MUCH lower viscosity, you are going to get way
different (more)amounts of fuel through the injector. I'd think that is
what causes the white smoke a lousy performance, it's too rich.
-at the same time, gasoline has lower fuel value per gallon or milliliter,
same volume of fuel will cause the engine to go lean, never a good thing

You raise an intriguing question there, Roy. How do you make a diesel run
lean? g

-gasoline has a much higher flame front speed, ie it will detonate, really
does bad things to the top of the piston.

It will detonate, but it's because of the *slower* flame front speed. That's
the thing that's indirectly measured by the cetane rating: gasoline around
25, diesel typically 45+.


It's not realy detonation, and it's not really the speed of the burn
that is involved (flame front). It is the speed at which the cyl
pressure goes up with gas vs diesel. You DO get a faster pressure
spike when burning gasoline than when burning deisel at high cyl
pressures.

-gasoline has no lubricating qualities, will tear up a standard injector
pump in short order.

Very interesting discussion. I've been asked to be the project manager for
an alternate fuels project based around a 100kw Cat diesel generator. Fire
up on a new fuel, check for short term issues, go to a 50% load then 100%
load for 8 to 24 hours, then tear down and look for damage. Looks like I
would be spending more time than planned dealing with the injector pump.
Hmmmmmmmmmmmmm.

Ivan Vegvary wrote:
Sorry about the OT, but, I do contribute once in a while and this is such
a knowledgeable group!

Many decades ago (1950's) when people talked about diesel engines (lot of
this talk was from 'old country' poor Europeans), they would always tout
the fact that they (the engines) would run on anything. The list, if I
remember correctly included diesel, gas, lighter fluid, heating oil,
liquefied lard, charcoal lighter, veggie oil etc., etc., etc.

If any of the above is true, why don't people, today, put gasoline into
their diesel engines, considering the higher cost of diesel fuel?

Just want to know what would happened if you did use gasoline.
BTW, my only diesel is my small Kubota tractor.

Thanks for replies.

Ivan Vegvary


** Posted from http://www.teranews.com **

On Sat, 12 Apr 2008 10:43:21 -0700, "Roger Shoaf"
wrote:

snippage


I agree with what you are saying especially in
regards to nuclear and natural gas. With some
decent leadership we could turn around the current
situation in a decade or so.

It won't be a single thing/event more like
an accumilation of technologys.

On the oil seed front there are ag producers in eastern
MT that are running their operations on what they produce.
There was a news article published last week on how it is working.
Safflower can/is being grown at a big +++ net energy gain. Commodity
revenues are up %200 year to year in this area.

The farmer in the article bought a crusher from an India company for
$5K and is very happy with the fuel. He sells the extra
left over meal at $125 a ton for cattle feed. Super high quality
feed. Camelina is going to be huge--check it out.. There's
two $100Mil plants going online this year....just for camelina.


Growing corn for ethenol is best if it's sold by
the bottle :-) ED

On Sat, 12 Apr 2008 11:33:40 -0700, Gunner Asch
wrote:

On Sat, 12 Apr 2008 07:58:02 -0600, ED
wrote:


Brazil has no petrolium resources and relied on sugar cane
to produce ethenol. I believe they were/are 100%
independent from oil imports..

We should be doing more in this country--not with corn
but with sugar beets....and oil seeds..


Google "rapeseed"

Gunner

Theres a lot of canola (aka rapeseed) grown around here but the
inputs are rather high..check out camelina or safflower for even
better numbers.,.ED





"[L]iberals are afraid to state what they truly believe in, for to do so
would result in even less votes than they currently receive. Their
methodology is to lie about their real agenda in the hopes of regaining
power, at which point they will do whatever they damn well please. The
problem is they have concealed and obfuscated for so long that, as a group,
they themselves are no longer sure of their goals. They are a collection of
wild-eyed splinter groups, all holding a grab-bag of dreams and wishes. Some
want a Socialist, secular-humanist state, others the repeal of the Second
Amendment. Some want same sex/different species marriage, others want voting
rights for trees, fish, coal and bugs. Some want cradle to grave care and
complete subservience to the government nanny state, others want a culture
that walks in lockstep and speaks only with intonations of political
correctness. I view the American liberals in much the same way I view the
competing factions of Islamic
fundamentalists. The latter hate each other to the core, and only join
forces to attack the US or Israel. The former hate themselves to the core,
and only join forces to attack George Bush and conservatives." --Ron Marr

"David Billington" wrote in message
...
Ed Huntress wrote:
"RoyJ" wrote in message
...

After reading the other comments I think you have multiple issues going
on to switch from diesel to gasoline:
-the gasoline will have a MUCH lower viscosity, you are going to get way
different (more)amounts of fuel through the injector. I'd think that is
what causes the white smoke a lousy performance, it's too rich.
-at the same time, gasoline has lower fuel value per gallon or
milliliter, same volume of fuel will cause the engine to go lean, never
a good thing


You raise an intriguing question there, Roy. How do you make a diesel run
lean? g


-gasoline has a much higher flame front speed, ie it will detonate,
really does bad things to the top of the piston.


It will detonate, but it's because of the *slower* flame front speed.
That's the thing that's indirectly measured by the cetane rating:
gasoline around 25, diesel typically 45+.


Ed,

I'm wondering if some of the problem here is with the nature of the
combustion in the 2 engines. My understanding is that the SI engine burns
a vapourised fuel air mix which burns like any gaseous fuel air mix but in
the diesel combustion the fuel droplets burn at the surface of the
droplet in the combustion air, the lighter fractions burning first leaving
the heavier fractions, hence the particulates left behind. The modern
diesels in small vehicles, at least in Europe as I think regulations have
constrained small diesels in the US, have much finer atomisation of the
fuel due to the high pressures used which allows shorter burn times and
higher resultant RPM but the nature of the combustion still differs from
that of a petrol engine.

The ignition and combustion processes definitely are very different. It
happens that gasoline is only partly vaporized when it enters a cylinder --
there was a lot of research on this in the '70s and they learned that
complete vaporization is not the best thing -- but the essential difference
is something else.

The big thing is that the fuel burns as it's injected, and the period of
injection stretches out the combustion so there is a minimal amount of shock
from the sudden high pressure. Unlike a SI engine, a diesel doesn't depend
upon the mixture to control the combustion rate. The ideal situation is to
have a fuel that burns quickly -- that's why you want a high cetane
rating -- and to control the combustion rate by the rate of injection. Some
of the newest engines divide the injection into several distinct periods.

All of which suggests why gasoline, with its low cetane equivalent and slow
burning, can foul up the process. If you burn gasoline in a diesel that's
set up for conventional diesel fuel, fuel is injected faster than it burns,
so you wind up with regions of unburned fuel/air mix in the cylinder, at
extremely high compression, that are invitations to detonation. That was
what I was guessing before, but I did some digging today and learned that is
apparently what happens.

I went through a lot of SAE paper abstracts today, to try to catch up, and I
see that there are all kinds of experiments going on with different fuels
and mixes, including gasoline, in diesels. The primary purpose of the
gasoline is to slow down combustion and thereby to reduce NOx emissions.
They have to advance injection by quite a bit and, apparently, use complex
strategies for injection, including multiple shots and different kinds of
aiming of the injectors. The most interesting research is on something
called HCCI (homogeneous charge/compression ignition) engines that are
basically diesels, but some of which have "spark assist." Some of these run
at compression ratios that are intermediate between conventional SI engines
and conventional diesels.

There is a lot going on. It's pretty interesting, especially since they now
have better tools to analyze combustion in an engine.

--
Ed Huntress

clare at snyder dot ontario dot canada wrote in message
...
On Sat, 12 Apr 2008 12:39:32 -0400, "Ed Huntress"
wrote:


"Ed Huntress" wrote in message
...

snip

Unless you go to the SME or MIT research sources...

That should be SAE, not SME.

And regarding the corners of the combustion chambers, that should be the
corners of the combustion *space*. Detonation is most likely to occur
where
the piston meets the cylinder walls.

Detonation is most likely to occur wherever fuel is exposed to high
temperature and pressure for an "extended" periosd of time.
The pressure and temperature "crack" the hydrocarbons into hydrogen
radicals and carbon. This process takes a finite amount of time (which
is why detonation is much less of a problem at high speeds than at low
speeds). The hydrogen radicals "explode" as soon as they find a
molecule of oxygen to attach to - fire or no fire.

I'd like to know what your source is for this model of the process. It
sounds like one of the theories that was under discussion around 30 years
ago, and it seems to have been superceded by newer understandings.

In fact, it appears there are at least three modes of combustion that are
part of "knock." I'd like to get some of the papers for which I've been
reading the abstracts, but they cost a bundle. However, here's a part of an
abstract that suggests multiple modes:

==============================================
A Theoretical and Experimental Study of the Modes of End Gas Autoignition
Leading to Knock in S.I. Engines -- J. Pan - University of Leeds, C.G.W.
Sheppard - University of Leeds

Abstract:
A 2-D simulation of fluid dynamic and chemistry interaction following end
gas autoignition has demonstrated three distinct modes of reaction,
dependent upon the temperature gradient about an exothermic center. All
three modes (deflagration, developing detonation and thermal explosion) can
contribute to knock; the developing detonation case, associated with
intermediate temperature gradient, has been identified as the more damaging.
The simulation code (LUMAD) has been used in a systematic parametric study
designed to separate the complex interacting events which can lead to mixed
modes in real engines. A most significant finding related to the sequential
autoignition of multiple exothermic centers. For two exothermic centers
characterized by large temperature gradients, which would normally yield the
relatively benign deflagrative mode, it was found that pressure waves
emanating from the first could modify the temperature gradient and so
promote violent developing detonation mode at the adjacent center.
=============================================

This paper, and at least a dozen others that discuss multiple modes, seem to
be the resolution to that debate that was going on when I last studied the
subject. The answer appears to be that there are different phenomena going
on, that the chemistry of it is very complex, and that the old models of
knock and detonation don't really explain it.

Where is your information coming from, Clare?

--
Ed Huntress

On Sat, 12 Apr 2008 14:04:53 -0400, clare at snyder dot ontario dot
canada wrote:

On Sat, 12 Apr 2008 12:39:32 -0400, "Ed Huntress"
wrote:


"Ed Huntress" wrote in message
...

snip

Unless you go to the SME or MIT research sources...

That should be SAE, not SME.

And regarding the corners of the combustion chambers, that should be the
corners of the combustion *space*. Detonation is most likely to occur where
the piston meets the cylinder walls.

Detonation is most likely to This process takes a finite amount of time (which
is why detonation is much less of a problem at high speeds than at low
speeds). The hydrogen radicals "explode" as soon as they find a
molecule of oxygen to attach to - fire or no fire.
** Posted from http://www.teranews.com **

That is pure gobble-gook!

Detonation is the extremely rapid burning of the fuel-air charge, a
near explosion, and can happen at any engine speed. At low engine
speeds you typically hear it as a "pinging" noise but it can happen at
wide open throttle settings as easily. In fact a caterpillar 3516
"lean burn" engine that operates at, basically, wide open throttle is
equipped with detonation sensors because detonation can and does
happen at high engine speeds.

Detonation has nothing to do with "occur wherever fuel is exposed to
high temperature and pressure for an "extended" periods of time." Nor
does "The pressure and temperature "crack" the hydrocarbons into
hydrogen radicals and carbon."

What typically happens in high RPM detonation is that the mixture
leans to the point that it burns extremely rapidly, an explosion one
might say, rather then burning evenly.

What is amazing about this post is that here we have a device, an
internal combustion engine, that has been in existence for something
like a hundred years and still people don't understand it..... Thank
God we still aren't using buggy whips. Can you imagine what people
would be writing about them?





Bruce-in-Bangkok
(correct email address for reply)

Ed Huntress wrote:
{..]

Ed,

I'm wondering if some of the problem here is with the nature of the
combustion in the 2 engines. My understanding is that the SI engine burns
a vapourised fuel air mix which burns like any gaseous fuel air mix but in
the diesel combustion the fuel droplets burn at the surface of the
droplet in the combustion air, the lighter fractions burning first leaving
the heavier fractions, hence the particulates left behind. The modern
diesels in small vehicles, at least in Europe as I think regulations have
constrained small diesels in the US, have much finer atomisation of the
fuel due to the high pressures used which allows shorter burn times and
higher resultant RPM but the nature of the combustion still differs from
that of a petrol engine.


The ignition and combustion processes definitely are very different. It
happens that gasoline is only partly vaporized when it enters a cylinder --
there was a lot of research on this in the '70s and they learned that
complete vaporization is not the best thing -- but the essential difference
is something else.

The big thing is that the fuel burns as it's injected, and the period of
injection stretches out the combustion so there is a minimal amount of shock
from the sudden high pressure. Unlike a SI engine, a diesel doesn't depend
upon the mixture to control the combustion rate. The ideal situation is to
have a fuel that burns quickly -- that's why you want a high cetane
rating -- and to control the combustion rate by the rate of injection. Some
of the newest engines divide the injection into several distinct periods.

Yes I'm aware of some of the modern developments as a mate of mine works
for Ricardo and gets involved in diesel design. He has mentioned that
some of the modern automotive engine management systems for diesel
engines are more sophisticated than those for SI engines. One of the
things he mentioned recently that was mentioned to him was a limitation
of a diesel is that the fuel has to be injected when the air is hot
enough to ignite it. I wonder what happens if it is injected too early
and the air charge isn't hot enough.
All of which suggests why gasoline, with its low cetane equivalent and slow
burning, can foul up the process. If you burn gasoline in a diesel that's
set up for conventional diesel fuel, fuel is injected faster than it burns,
so you wind up with regions of unburned fuel/air mix in the cylinder, at
extremely high compression, that are invitations to detonation. That was
what I was guessing before, but I did some digging today and learned that is
apparently what happens.

I went through a lot of SAE paper abstracts today, to try to catch up, and I
see that there are all kinds of experiments going on with different fuels
and mixes, including gasoline, in diesels. The primary purpose of the
gasoline is to slow down combustion and thereby to reduce NOx emissions.
They have to advance injection by quite a bit and, apparently, use complex
strategies for injection, including multiple shots and different kinds of
aiming of the injectors. The most interesting research is on something
called HCCI (homogeneous charge/compression ignition) engines that are
basically diesels, but some of which have "spark assist." Some of these run
at compression ratios that are intermediate between conventional SI engines
and conventional diesels.

There is a lot going on. It's pretty interesting, especially since they now
have better tools to analyze combustion in an engine.

--
Ed Huntress

clare at snyder dot ontario dot canada wrote in message
...
On Sat, 12 Apr 2008 01:38:50 -0400, "Ed Huntress"
wrote:

Something is funny here, Tim. I wonder if those guys told your dad what
actually happened?

The cetane rating of gasoline is so low that, if you can ignite it at all
in
a diesel, the gasoline burns so slowly that the engine knocks like crazy,
and it's still burning past the end of the power stroke. Thus, the white
smoke that someone else mentioned. At low temperatures, a diesel fueled
with
gasoline may not ignite at all.

At the risk of oversimplifying, octane and cetane have roughly opposite
burning characteristics. A high cetane rating (as in premium diesel)
indicates that the fuel ignites easily from the heat of compression and
that
it burns quickly once ignited. In fact, the cetane rating is based on the
time it takes for fuel ignited at high temperature and compression to
reach
a specified cylinder pressure.

An octane rating, which is very low in diesel and much higher in gasoline,
indicates the *resistance* of the fuel to burning under those same
conditions. Higher octane allows higher compression ratios without
premature
ignition from the heat of compression. However, what octane rating really
measures, if I recall correctly, is the speed with which a flame
progresses.
High octane, slow burning.

Your recollection is not quite correct, which is where the confusion
comes in. Octain has NOTHING to do with the temperature at which the
fuel will auto-ignite, nor the speed of burn, when you get right down
to it. It has everything to do with resistance to dissassociation, and
resultant detonation.

I don't want to turn this into a battle of citations, but what you're saying
disagrees with the research -- particularly the recent research. Because of
the interest in HCCI engines a lot of work is being done in this area,
because octane is suddenly of interest in compression-ignition and
spark-assisted compression-ignition engines. Here are a few remarks from
recent research papers:

================================================== ====
[The Effect of Prf Fuel Octane Number on Hcci Operation - 2004]

"The test results show that, with the increase of the octane number, the
ignition timing delayed, the combustion rate decreased, and the cylinder
pressure decreased."

[A Method of Defining Ignition Quality of Fuels in Hcci Engines - 2003]

"The higher the OI [octane index], the more the resistance to autoignition
and the later is the heat release in the HCCI engine at a given condition.
When the engine is run with a boost pressure of 1 bar and with the intake
air temperature maintained at 40\mDC, K is highly negative and fuels of low
MON, such as those containing aromatics, olefins or ethanol, have a higher
OI and ignite later than paraffinic fuels of comparable RON."

[Note that the study above examines the burn characteristics of aliphatics
versus paraffinics -- more about that later.]

[Knock in Spark-Ignition Engines: End-Gas Temperature Measurements Using
Rotational Cars and Detailed Kinetic Calculations of the Autoignition
Process - 1997]

"It is found that calculations with different RONs of the fuel lead to
different levels of radical concentrations in the end-gas. The appearance of
the first stage of the autoignition process is marginally influence by the
RON, while the ignition delay of the second stage is increased with
increasing RON."

[There are two stages to controlled autoignition, and the final one is
delayed as octane number increases.]

[Experimental Investigation into HCCI Combustion Using Gasoline and Diesel
Blended Fuels - 2005]

"Gasoline and diesel, the two fuels with very different characteristics and
with wide availability for conventional engine use, were blended as a HCCI
engine fuel. Gasoline, with high volatility, easy vaporization and mixture
formation, is used to form the homogeneous charge. Diesel fuel, which has
good ignitability and fast combustion at the conditions predominating in the
HCCI environment, is used to dominate the auto-ignition and restrain the
knocking combustion."

================================================== ======

The flash point of gasoline is lower than the flashpoint of diesel
fuel. The vapour pressure is higher. Therefore it actually takes less
heat to light gasoline than diesel. However, the flamability range of
gasoline is lower - too lean or too rich and it won't light.

The flashpoints of gasoline and diesel have little to do with ignition in a
high-compression engine that ignites the fuel by autoignition. The
autoignition temperature for gasoline is 246 deg. C; for diesel, it is 210
deg. C. So diesel ignites faster in a compression-ignition engine.

As for the amount of heat required to ignite either, since the initial
in-cylinder conditions are the same in both cases, the amount of heat is the
same. The quicker ignition of the diesel relates to its lower autoignition
temperature, not to the amount of heat involved.


When you inject gasoline into a diesel, if you get it injected in a
proper cone, at the right time, some of the fuel will ignite
immediately and will burn very quickly, causing a knock.

What's your reference for this? The resources I've checked (I read over 200
abstracts during the past 24 hours), at least those that address the
question, say that gasoline is slow to ignite in a diesel.

The rest of
the fuel is dissipated in an overlean mixture, and does not burn.
(severe lean misfire)This goes out the pipe as white "smoke" and also
causes the flame in the exhaust if it ends up lighting on the way out.

If the throttle is advanced enough to get sufficient fuel into the cyl
to get the mixture rich enough to burn more completely, SEVERE
"detonation" shock occurs - the engine knocks badly, smokes profusely,
and makes very little power. High octane fuel will not behave much
differently than low octane fuel in a deisel.
A diesel depends on s relatively slow even burn, and a reasonably long
calibrated injection period provides the fuel to keep building cyl
pressure constantly untill the piston is almost at BDC.

Again, diesel burns more quickly in an engine environment than gasoline
does.

--
Ed Huntress

clare at snyder dot ontario dot canada wrote in message
...
On Sat, 12 Apr 2008 19:08:43 -0400, "Ed Huntress"
wrote:


"RoyJ" wrote in message
...
After reading the other comments I think you have multiple issues going
on
to switch from diesel to gasoline:
-the gasoline will have a MUCH lower viscosity, you are going to get way
different (more)amounts of fuel through the injector. I'd think that is
what causes the white smoke a lousy performance, it's too rich.
-at the same time, gasoline has lower fuel value per gallon or
milliliter,
same volume of fuel will cause the engine to go lean, never a good thing

You raise an intriguing question there, Roy. How do you make a diesel run
lean? g

-gasoline has a much higher flame front speed, ie it will detonate,
really
does bad things to the top of the piston.

It will detonate, but it's because of the *slower* flame front speed.
That's
the thing that's indirectly measured by the cetane rating: gasoline around
25, diesel typically 45+.


It's not realy detonation, and it's not really the speed of the burn
that is involved (flame front). It is the speed at which the cyl
pressure goes up with gas vs diesel. You DO get a faster pressure
spike when burning gasoline than when burning deisel at high cyl
pressures.

Reference? You may be comparing a homogeneous mixture in a spark-ignition
engine with the timed spray in a diesel. If you create a homogeneous mixture
with diesel alone, it burns faster than gasoline. That's what the
HCCI-engine research shows.

--
Ed Huntress

"David Billington" wrote in message
...
Ed Huntress wrote:
{..]

Ed,

I'm wondering if some of the problem here is with the nature of the
combustion in the 2 engines. My understanding is that the SI engine
burns a vapourised fuel air mix which burns like any gaseous fuel air
mix but in the diesel combustion the fuel droplets burn at the surface
of the droplet in the combustion air, the lighter fractions burning
first leaving the heavier fractions, hence the particulates left behind.
The modern diesels in small vehicles, at least in Europe as I think
regulations have constrained small diesels in the US, have much finer
atomisation of the fuel due to the high pressures used which allows
shorter burn times and higher resultant RPM but the nature of the
combustion still differs from that of a petrol engine.


The ignition and combustion processes definitely are very different. It
happens that gasoline is only partly vaporized when it enters a
cylinder -- there was a lot of research on this in the '70s and they
learned that complete vaporization is not the best thing -- but the
essential difference is something else.

The big thing is that the fuel burns as it's injected, and the period of
injection stretches out the combustion so there is a minimal amount of
shock from the sudden high pressure. Unlike a SI engine, a diesel doesn't
depend upon the mixture to control the combustion rate. The ideal
situation is to have a fuel that burns quickly -- that's why you want a
high cetane rating -- and to control the combustion rate by the rate of
injection. Some of the newest engines divide the injection into several
distinct periods.

Yes I'm aware of some of the modern developments as a mate of mine works
for Ricardo and gets involved in diesel design. He has mentioned that some
of the modern automotive engine management systems for diesel engines are
more sophisticated than those for SI engines. One of the things he
mentioned recently that was mentioned to him was a limitation of a diesel
is that the fuel has to be injected when the air is hot enough to ignite
it. I wonder what happens if it is injected too early and the air charge
isn't hot enough.

Ya' got me. My guess is that you get a smoke-belching engine. But you
probably could find something on it with some judicious choice of search
terms on the SAE website.

--
Ed Huntress

On Sun, 13 Apr 2008 09:02:45 -0400, "Ed Huntress"
wrote:


clare at snyder dot ontario dot canada wrote in message
.. .
On Sat, 12 Apr 2008 12:39:32 -0400, "Ed Huntress"
wrote:


"Ed Huntress" wrote in message
...

snip

Unless you go to the SME or MIT research sources...

That should be SAE, not SME.

And regarding the corners of the combustion chambers, that should be the
corners of the combustion *space*. Detonation is most likely to occur
where
the piston meets the cylinder walls.

Detonation is most likely to occur wherever fuel is exposed to high
temperature and pressure for an "extended" periosd of time.
The pressure and temperature "crack" the hydrocarbons into hydrogen
radicals and carbon. This process takes a finite amount of time (which
is why detonation is much less of a problem at high speeds than at low
speeds). The hydrogen radicals "explode" as soon as they find a
molecule of oxygen to attach to - fire or no fire.

I'd like to know what your source is for this model of the process. It
sounds like one of the theories that was under discussion around 30 years
ago, and it seems to have been superceded by newer understandings.

In fact, it appears there are at least three modes of combustion that are
part of "knock." I'd like to get some of the papers for which I've been
reading the abstracts, but they cost a bundle. However, here's a part of an
abstract that suggests multiple modes:

==============================================
A Theoretical and Experimental Study of the Modes of End Gas Autoignition
Leading to Knock in S.I. Engines -- J. Pan - University of Leeds, C.G.W.
Sheppard - University of Leeds

Abstract:
A 2-D simulation of fluid dynamic and chemistry interaction following end
gas autoignition has demonstrated three distinct modes of reaction,
dependent upon the temperature gradient about an exothermic center. All
three modes (deflagration, developing detonation and thermal explosion) can
contribute to knock; the developing detonation case, associated with
intermediate temperature gradient, has been identified as the more damaging.
The simulation code (LUMAD) has been used in a systematic parametric study
designed to separate the complex interacting events which can lead to mixed
modes in real engines. A most significant finding related to the sequential
autoignition of multiple exothermic centers. For two exothermic centers
characterized by large temperature gradients, which would normally yield the
relatively benign deflagrative mode, it was found that pressure waves
emanating from the first could modify the temperature gradient and so
promote violent developing detonation mode at the adjacent center.
=============================================

This paper, and at least a dozen others that discuss multiple modes, seem to
be the resolution to that debate that was going on when I last studied the
subject. The answer appears to be that there are different phenomena going
on, that the chemistry of it is very complex, and that the old models of
knock and detonation don't really explain it.

Where is your information coming from, Clare?


Ed, the new information does't disprove the old - it just enhances the
understanding.
The multiple modes can now be recorded - but have they explained in
any way, more completely, what actually HAPPENS chemically in any or
all 3 of these modes? And exactly what CAUSES them?

The explanation I have used IS several years old - but is more
accurate than the other, more common belief that higher octane gas
must necessarily burn slower, or produce less power, etc etc.

A faster burning fuel, in a combustion chamber which is designed to
promote a faster burn, is more detonation resistant because the "end
gasses" are not exposed to the high heat, high temperature stagnation
that allows (or causes) the fuel to dissassociate.
Same thing for higher speed operation. Less time under the conditions
that produce the dissassociation means less chance of detonation.

I can't remember the guy who brought this theory out - don't think it
was Riccardo, but it may have been. It is information that I was
taught years ago when it was "cutting edge" and which I have found in
many places over the years as an (accepted) explanation of detonation
and how to control it.
It is also what I taught as an explanation at the trade level.

I know it is not a FULL explanation, and more is beeing learned all
the time.
** Posted from http://www.teranews.com **

"Michael A. Terrell" wrote in
m:

I had the local chief of a volunteer fire department screaming at me
that it wasn't legal to hang temporary work lights from overhead wires
at the job site. The firehouse was less than 100 feet away. I asked
him to follow me, and walked into the firehouse. I hit their breaker box
with my fist, and sparks lit up the room. I told him that I had
reported it as defective when I was a boy scout and our troop held our
meetings there, over 20 years earlier and they still hadn't had it
fixed. He informed me they didn't have to obey the law.

During my decade with a Volunteer Fire Dept. in a rural county, our biggest
problems came from some of the local Deputy Sheriffs who had no notion of
the laws concerning Arson.

More than once Arsonists that had been caught - and confessed - were simply
told to "get lost" by Deputies.

As to the breaker box, why hadn't you already fixed it for them? That way,
you could have written off both time and materials - at retail pricing - on
your taxes. grin

"RAM³" wrote:

"Michael A. Terrell" wrote in
m:

I had the local chief of a volunteer fire department screaming at me
that it wasn't legal to hang temporary work lights from overhead wires
at the job site. The firehouse was less than 100 feet away. I asked
him to follow me, and walked into the firehouse. I hit their breaker box
with my fist, and sparks lit up the room. I told him that I had
reported it as defective when I was a boy scout and our troop held our
meetings there, over 20 years earlier and they still hadn't had it
fixed. He informed me they didn't have to obey the law.

During my decade with a Volunteer Fire Dept. in a rural county, our biggest
problems came from some of the local Deputy Sheriffs who had no notion of
the laws concerning Arson.

More than once Arsonists that had been caught - and confessed - were simply
told to "get lost" by Deputies.

As to the breaker box, why hadn't you already fixed it for them? That way,
you could have written off both time and materials - at retail pricing - on
your taxes. grin


The truth? I was waiting for their building to burn down. Under that
fire chief the state of Ohio listed it as the worst in the entire state.
Five years earlier it was in the top 5%. It could take 30 minutes to
get a crew together, but it didn't stop the members from driving around
with lights and sirens on their private vehicles, or their kids from joy
riding. They would tailgate people, then turn on the lights and sirens
for kicks. I saw one of the little *******s turn onto the highway behind
me one night, and sure enough, on went the lights and siren. I locked
up the brakes on my stepvan and almost got rear ended. The idiot came
running up to my door screaming that he was going to call the police. I
reminded him that he was impersonating a fireman, and that he would go
to jail. He peeled rubber, and left, but not before I got the tag
number. I confronted his dad at the next monthly meeting at the
firehouse, and told them all that if I ever saw anything else illegal, I
was going to the State Attorney General. A few months later, I left
Ohio for good.



Their performance was so bad that no insurance company would
recognize them. Even though their hose tower could fall into my yard
and to within a few feet of the kitchen, the nearest accepted fire
department was over 10 miles away. Add that to the fact that fire chief
was supposed to be 100% disabled, yet he could climb ladders and pull
hose during a fire made everyone in the area despised them. Because of
their bad rating homeowner's insurance was about 20% higher than areas
closer to the rated city operated firehouses.




--
aioe.org is home to cowards and terrorists

Add this line to your news proxy nfilter.dat file
* drop Path:*aioe.org!not-for-mail to drop all aioe.org traffic.

http://improve-usenet.org/index.html


Use any search engine other than Google till they stop polluting USENET
with porn and junk commercial SPAM

On Sun, 13 Apr 2008 20:42:22 +0700, Bruce in Bangkok
wrote:

On Sat, 12 Apr 2008 14:04:53 -0400, clare at snyder dot ontario dot
canada wrote:

On Sat, 12 Apr 2008 12:39:32 -0400, "Ed Huntress"
wrote:


"Ed Huntress" wrote in message
...

snip

Unless you go to the SME or MIT research sources...

That should be SAE, not SME.

And regarding the corners of the combustion chambers, that should be the
corners of the combustion *space*. Detonation is most likely to occur where
the piston meets the cylinder walls.

Detonation is most likely to This process takes a finite amount of time (which
is why detonation is much less of a problem at high speeds than at low
speeds). The hydrogen radicals "explode" as soon as they find a
molecule of oxygen to attach to - fire or no fire.
** Posted from http://www.teranews.com **

That is pure gobble-gook!

Detonation is the extremely rapid burning of the fuel-air charge, a
near explosion, and can happen at any engine speed. At low engine
speeds you typically hear it as a "pinging" noise but it can happen at
wide open throttle settings as easily. In fact a caterpillar 3516
"lean burn" engine that operates at, basically, wide open throttle is
equipped with detonation sensors because detonation can and does
happen at high engine speeds.

Detonation has nothing to do with "occur wherever fuel is exposed to
high temperature and pressure for an "extended" periods of time." Nor
does "The pressure and temperature "crack" the hydrocarbons into
hydrogen radicals and carbon."

What typically happens in high RPM detonation is that the mixture
leans to the point that it burns extremely rapidly, an explosion one
might say, rather then burning evenly.

What is amazing about this post is that here we have a device, an
internal combustion engine, that has been in existence for something
like a hundred years and still people don't understand it..... Thank
God we still aren't using buggy whips. Can you imagine what people
would be writing about them?





Bruce-in-Bangkok
(correct email address for reply)
Bruce do your research. This is all proven accepted scientific theory.
Detonation can, and does, happen with rich mixtures as well as with
lean, untill you get so over-rich that you are cooling the engine with
gasoline.
An OVER LEAN mixture actually burns cooler than a proper mixture, and
the speed of the "normal" flame front does NOT contribute to
detonation. There are , as Ed has noted, other modes of operation that
cause engine knock or ping. PreIgnition is one.
Pre ignition is NOT detonation, but when pre-ignition exists,
detonation is not far behind. Conversely, when detonation occurs,
pre-ignition also often follows. Both pre-ignition and detonation tend
to disrupt the insulating boundary layer, allowing excess heat to be
absorbed by the piston and or cyl head.
This is why one of the definitive ways of determining the onset of
detonation is a drop in exhaust temperatures accompanied by a
simultaneous increase in cyl head temperatures. If the power level is
not reduced in short order detonation usually escalates to also
produce pre-ignition. Out of control, the engine usually suffers
mechanical damage in a very short time.

It is the disruption of the boundary layer that causes holes in
pistons from detonation. When the boundary layer is disrupted by
detonation, the head and/or pistons heat up, increasing the
temperature to the point where autoignition takes place. If the
autoignition occurs before the spark, it is detonation. If it occurs
after the spark, we get multiple flame fronts which cause what is
sometimes referred to as "spark knock" which is similar to, but not
exactly, detonation.
This is the rattle that GM tells you is "normal" under moderate
accelleration under load.It GENERALLY does not cause severe engine
damage.

True detonation is not just extremely fast burning (conflargation?).
It is the equivalent to a small charge of high explosive being set off
in the cyl.It is almost always detrimental to engine life as well as
power output.

Perhaps this is whed Ed is aluding to with the multiple modes of
detonation?
** Posted from http://www.teranews.com **

On Sun, 13 Apr 2008 15:57:28 +0100, David Billington
wrote:

Ed Huntress wrote:
{..]

Ed,

I'm wondering if some of the problem here is with the nature of the
combustion in the 2 engines. My understanding is that the SI engine burns
a vapourised fuel air mix which burns like any gaseous fuel air mix but in
the diesel combustion the fuel droplets burn at the surface of the
droplet in the combustion air, the lighter fractions burning first leaving
the heavier fractions, hence the particulates left behind. The modern
diesels in small vehicles, at least in Europe as I think regulations have
constrained small diesels in the US, have much finer atomisation of the
fuel due to the high pressures used which allows shorter burn times and
higher resultant RPM but the nature of the combustion still differs from
that of a petrol engine.


The ignition and combustion processes definitely are very different. It
happens that gasoline is only partly vaporized when it enters a cylinder --
there was a lot of research on this in the '70s and they learned that
complete vaporization is not the best thing -- but the essential difference
is something else.

The big thing is that the fuel burns as it's injected, and the period of
injection stretches out the combustion so there is a minimal amount of shock
from the sudden high pressure. Unlike a SI engine, a diesel doesn't depend
upon the mixture to control the combustion rate. The ideal situation is to
have a fuel that burns quickly -- that's why you want a high cetane
rating -- and to control the combustion rate by the rate of injection. Some
of the newest engines divide the injection into several distinct periods.

Yes I'm aware of some of the modern developments as a mate of mine works
for Ricardo and gets involved in diesel design. He has mentioned that
some of the modern automotive engine management systems for diesel
engines are more sophisticated than those for SI engines. One of the
things he mentioned recently that was mentioned to him was a limitation
of a diesel is that the fuel has to be injected when the air is hot
enough to ignite it. I wonder what happens if it is injected too early
and the air charge isn't hot enough.

You get that white, smelly, acrid smoke typical of a cold engine with
bad glow plugs on startup. If all cyls are involved the engine most
likely will not start.

All of which suggests why gasoline, with its low cetane equivalent and slow
burning, can foul up the process. If you burn gasoline in a diesel that's
set up for conventional diesel fuel, fuel is injected faster than it burns,
so you wind up with regions of unburned fuel/air mix in the cylinder, at
extremely high compression, that are invitations to detonation. That was
what I was guessing before, but I did some digging today and learned that is
apparently what happens.

I went through a lot of SAE paper abstracts today, to try to catch up, and I
see that there are all kinds of experiments going on with different fuels
and mixes, including gasoline, in diesels. The primary purpose of the
gasoline is to slow down combustion and thereby to reduce NOx emissions.
They have to advance injection by quite a bit and, apparently, use complex
strategies for injection, including multiple shots and different kinds of
aiming of the injectors. The most interesting research is on something
called HCCI (homogeneous charge/compression ignition) engines that are
basically diesels, but some of which have "spark assist." Some of these run
at compression ratios that are intermediate between conventional SI engines
and conventional diesels.

There is a lot going on. It's pretty interesting, especially since they now
have better tools to analyze combustion in an engine.

--
Ed Huntress




** Posted from http://www.teranews.com **

clare at snyder dot ontario dot canada wrote in message
...

snip


True detonation is not just extremely fast burning (conflargation?).
It is the equivalent to a small charge of high explosive being set off
in the cyl.It is almost always detrimental to engine life as well as
power output.

Perhaps this is whed Ed is aluding to with the multiple modes of
detonation?

What I was referring to is just what was in the abstract I posted ("A
Theoretical and Experimental Study of the Modes of End Gas Autoignition
Leading to Knock in S.I. Engines") from the University of Leeds. I don't
have the full article, so I don't have a further explanation.

But that basic definition shows up in several papers I encountered on the
SAE website. There is conflagration (very rapid burning); developing
detonation; and explosion. Several papers say it is the developing
detonation phase that causes most of the damage.

--
Ed Huntress

On Sun, 13 Apr 2008 11:28:11 -0400, "Ed Huntress"
wrote:


clare at snyder dot ontario dot canada wrote in message
.. .
On Sat, 12 Apr 2008 01:38:50 -0400, "Ed Huntress"
wrote:

Something is funny here, Tim. I wonder if those guys told your dad what
actually happened?

The cetane rating of gasoline is so low that, if you can ignite it at all
in
a diesel, the gasoline burns so slowly that the engine knocks like crazy,
and it's still burning past the end of the power stroke. Thus, the white
smoke that someone else mentioned. At low temperatures, a diesel fueled
with
gasoline may not ignite at all.

At the risk of oversimplifying, octane and cetane have roughly opposite
burning characteristics. A high cetane rating (as in premium diesel)
indicates that the fuel ignites easily from the heat of compression and
that
it burns quickly once ignited. In fact, the cetane rating is based on the
time it takes for fuel ignited at high temperature and compression to
reach
a specified cylinder pressure.

An octane rating, which is very low in diesel and much higher in gasoline,
indicates the *resistance* of the fuel to burning under those same
conditions. Higher octane allows higher compression ratios without
premature
ignition from the heat of compression. However, what octane rating really
measures, if I recall correctly, is the speed with which a flame
progresses.
High octane, slow burning.

Your recollection is not quite correct, which is where the confusion
comes in. Octain has NOTHING to do with the temperature at which the
fuel will auto-ignite, nor the speed of burn, when you get right down
to it. It has everything to do with resistance to dissassociation, and
resultant detonation.

I don't want to turn this into a battle of citations, but what you're saying
disagrees with the research -- particularly the recent research. Because of
the interest in HCCI engines a lot of work is being done in this area,
because octane is suddenly of interest in compression-ignition and
spark-assisted compression-ignition engines. Here are a few remarks from
recent research papers:

================================================= =====
[The Effect of Prf Fuel Octane Number on Hcci Operation - 2004]

"The test results show that, with the increase of the octane number, the
ignition timing delayed, the combustion rate decreased, and the cylinder
pressure decreased."

[A Method of Defining Ignition Quality of Fuels in Hcci Engines - 2003]

"The higher the OI [octane index], the more the resistance to autoignition
and the later is the heat release in the HCCI engine at a given condition.
When the engine is run with a boost pressure of 1 bar and with the intake
air temperature maintained at 40\mDC, K is highly negative and fuels of low
MON, such as those containing aromatics, olefins or ethanol, have a higher
OI and ignite later than paraffinic fuels of comparable RON."

[Note that the study above examines the burn characteristics of aliphatics
versus paraffinics -- more about that later.]

More to do with the actual fuel composition than the actual octane
rating, wouldn't you agree? Ethanol., intrinsically has a higher
octane than gasoline, yet they are stating low RON fuels containing
ethanol.

Aromatics and olefins DO behave differently than parafins, and MON and
RON are different - which is why the typical automotive octane ratings
(ron+mon/2) are somewhat misleading and confusing.
Kinda like aircraft octane, where you have a rich and a lean number.
Which actualy tells you more than ron+mon/2.


ANyway - enough arguing
There is always going to be more research, with morefindings to be
proven or disproven when it comes to fuel and combustion technology.
Suffice it to say taht gasoline in a compression ignition engine is
NOT a good idea for reasons pertaining to the difference in combustion
characteristics alone - and then there are the issues of lubricity etc
which can be circumvented by mixing lubricating oils with the fuel lie
in typical 2 stroke (fuel lubricated) gasoline practice.

There is so much TOTAL MISUNDERSTANDING of fuel octane and detonation
issues out there in both automotive and aviation worlds.

Your explanations (or the explanations which may or may not exist in
the citations given) may go a lot farther in the explanation of how it
actually works, but without paying for and reading the complete
documentation (which in most cases would go right over the heads of
most on this list) it is impossible to say for certain. They may or
may not disprove (or support) the theory I have been taught and that
has been accepted for years. ANd just because some scientist or
scholar has presented a thesis, and supported it with scientific
method, does not mean that thesis will not be proven totally false (or
substantially in error) by some other scientist or scholar in the
short or long term.

[Knock in Spark-Ignition Engines: End-Gas Temperature Measurements Using
Rotational Cars and Detailed Kinetic Calculations of the Autoignition
Process - 1997]

"It is found that calculations with different RONs of the fuel lead to
different levels of radical concentrations in the end-gas. The appearance of
the first stage of the autoignition process is marginally influence by the
RON, while the ignition delay of the second stage is increased with
increasing RON."

[There are two stages to controlled autoignition, and the final one is
delayed as octane number increases.]


ANd this disproves or dissagrees with my explanation how? The "radical
concentrations" refer to what? Higher RON reduces the radical
concentrations, which delay the "second stage of autoignition" -
which in spark engine parlance is "detonation"

In my words, high octane gasoline resists thermal dissassociation of
the hydrocarbons, resulting in lower production of hydrogen radicals
and a marked reduction in the propensity of the engine to detonate.


You are talking DIESEL ENGINE RESEARCH - where autoignition is a good
thing (particularly stage one) Second stage autoignition (also
referred to as detonation) is apparently also an issue in the engines
in question.

In spark ignition engines, autoignition is a BAD THING, even in stage
one (spark knock or the so-called non-destructive engine knock)but
particularly in stage 2 (detonation)

[Experimental Investigation into HCCI Combustion Using Gasoline and Diesel
Blended Fuels - 2005]

"Gasoline and diesel, the two fuels with very different characteristics and
with wide availability for conventional engine use, were blended as a HCCI
engine fuel. Gasoline, with high volatility, easy vaporization and mixture
formation, is used to form the homogeneous charge. Diesel fuel, which has
good ignitability and fast combustion at the conditions predominating in the
HCCI environment, is used to dominate the auto-ignition and restrain the
knocking combustion."

================================================= =======

The flash point of gasoline is lower than the flashpoint of diesel
fuel. The vapour pressure is higher. Therefore it actually takes less
heat to light gasoline than diesel. However, the flamability range of
gasoline is lower - too lean or too rich and it won't light.

The flashpoints of gasoline and diesel have little to do with ignition in a
high-compression engine that ignites the fuel by autoignition. The
autoignition temperature for gasoline is 246 deg. C; for diesel, it is 210
deg. C. So diesel ignites faster in a compression-ignition engine.

As for the amount of heat required to ignite either, since the initial
in-cylinder conditions are the same in both cases, the amount of heat is the
same. The quicker ignition of the diesel relates to its lower autoignition
temperature, not to the amount of heat involved.


When you inject gasoline into a diesel, if you get it injected in a
proper cone, at the right time, some of the fuel will ignite
immediately and will burn very quickly, causing a knock.

What's your reference for this? The resources I've checked (I read over 200
abstracts during the past 24 hours), at least those that address the
question, say that gasoline is slow to ignite in a diesel.

Slow to ignite - but fast flame front/pressure rise when ignited.

The rest of
the fuel is dissipated in an overlean mixture, and does not burn.
(severe lean misfire)This goes out the pipe as white "smoke" and also
causes the flame in the exhaust if it ends up lighting on the way out.

If the throttle is advanced enough to get sufficient fuel into the cyl
to get the mixture rich enough to burn more completely, SEVERE
"detonation" shock occurs - the engine knocks badly, smokes profusely,
and makes very little power. High octane fuel will not behave much
differently than low octane fuel in a deisel.
A diesel depends on s relatively slow even burn, and a reasonably long
calibrated injection period provides the fuel to keep building cyl
pressure constantly untill the piston is almost at BDC.

Again, diesel burns more quickly in an engine environment than gasoline
does.

Which is why the fuel is NOT injected in one instantaneous shot, but
in a prolonged spray to maintain a constantly expanding charge or
burn, maintaining more or less even pressure on the piston for the
full power stroke - unlike the situation in a spark ignition gasoline
engine.



** Posted from http://www.teranews.com **

clare at snyder dot ontario dot canada wrote in message
...
On Sun, 13 Apr 2008 11:28:11 -0400, "Ed Huntress"
wrote:


clare at snyder dot ontario dot canada wrote in message
. ..
On Sat, 12 Apr 2008 01:38:50 -0400, "Ed Huntress"
wrote:

Something is funny here, Tim. I wonder if those guys told your dad what
actually happened?

The cetane rating of gasoline is so low that, if you can ignite it at
all
in
a diesel, the gasoline burns so slowly that the engine knocks like
crazy,
and it's still burning past the end of the power stroke. Thus, the white
smoke that someone else mentioned. At low temperatures, a diesel fueled
with
gasoline may not ignite at all.

At the risk of oversimplifying, octane and cetane have roughly opposite
burning characteristics. A high cetane rating (as in premium diesel)
indicates that the fuel ignites easily from the heat of compression and
that
it burns quickly once ignited. In fact, the cetane rating is based on
the
time it takes for fuel ignited at high temperature and compression to
reach
a specified cylinder pressure.

An octane rating, which is very low in diesel and much higher in
gasoline,
indicates the *resistance* of the fuel to burning under those same
conditions. Higher octane allows higher compression ratios without
premature
ignition from the heat of compression. However, what octane rating
really
measures, if I recall correctly, is the speed with which a flame
progresses.
High octane, slow burning.

Your recollection is not quite correct, which is where the confusion
comes in. Octain has NOTHING to do with the temperature at which the
fuel will auto-ignite, nor the speed of burn, when you get right down
to it. It has everything to do with resistance to dissassociation, and
resultant detonation.

I don't want to turn this into a battle of citations, but what you're
saying
disagrees with the research -- particularly the recent research. Because
of
the interest in HCCI engines a lot of work is being done in this area,
because octane is suddenly of interest in compression-ignition and
spark-assisted compression-ignition engines. Here are a few remarks from
recent research papers:

================================================ ======
[The Effect of Prf Fuel Octane Number on Hcci Operation - 2004]

"The test results show that, with the increase of the octane number, the
ignition timing delayed, the combustion rate decreased, and the cylinder
pressure decreased."

[A Method of Defining Ignition Quality of Fuels in Hcci Engines - 2003]

"The higher the OI [octane index], the more the resistance to autoignition
and the later is the heat release in the HCCI engine at a given condition.
When the engine is run with a boost pressure of 1 bar and with the intake
air temperature maintained at 40\mDC, K is highly negative and fuels of
low
MON, such as those containing aromatics, olefins or ethanol, have a higher
OI and ignite later than paraffinic fuels of comparable RON."

[Note that the study above examines the burn characteristics of aliphatics
versus paraffinics -- more about that later.]

More to do with the actual fuel composition than the actual octane
rating, wouldn't you agree?

No, they're talking about octane ratings, and you'll find the same pattern
for gasoline and other high-octane fuels versus diesel fuel, throughout the
literature. The issue here is the differences in performance relative to
different octane rating systems.

Ethanol., intrinsically has a higher
octane than gasoline, yet they are stating low RON fuels containing
ethanol.

Where do they say that? MON, RON, and OI are not the same things. The most
useful octane rating, based on relative performance in an engine, is the
Octane Index. Ethanol has a higher OI than gasoline.


Aromatics and olefins DO behave differently than parafins, and MON and
RON are different - which is why the typical automotive octane ratings
(ron+mon/2) are somewhat misleading and confusing.
Kinda like aircraft octane, where you have a rich and a lean number.
Which actualy tells you more than ron+mon/2.

When you normalize for performance in an engine, you get OI.

ANyway - enough arguing
There is always going to be more research, with morefindings to be
proven or disproven when it comes to fuel and combustion technology.
Suffice it to say taht gasoline in a compression ignition engine is
NOT a good idea for reasons pertaining to the difference in combustion
characteristics alone - and then there are the issues of lubricity etc
which can be circumvented by mixing lubricating oils with the fuel lie
in typical 2 stroke (fuel lubricated) gasoline practice.

There is so much TOTAL MISUNDERSTANDING of fuel octane and detonation
issues out there in both automotive and aviation worlds.

Your explanations (or the explanations which may or may not exist in
the citations given) may go a lot farther in the explanation of how it
actually works, but without paying for and reading the complete
documentation (which in most cases would go right over the heads of
most on this list) it is impossible to say for certain. They may or
may not disprove (or support) the theory I have been taught and that
has been accepted for years. ANd just because some scientist or
scholar has presented a thesis, and supported it with scientific
method, does not mean that thesis will not be proven totally false (or
substantially in error) by some other scientist or scholar in the
short or long term.

It looks to me like someone gave you some misinformation regarding flame
speeds, but that the rest of what you're saying looks reasonably right. As I
was reading all of this yesterday (I have a respiratory infection, or you
wouldn't catch me dead inside, and not fishing, on a Saturday in April g),
some of what I was taught 40 years ago came back to me. I remembered that
gasoline was harder to ignite by compression than diesel. I had forgotten
that flame speed was slower for gasoline, which was counterintuitive and
struck me funny 40 years ago. But that's the same thing they're saying in
all of this current research. Abstracts or full text, those conclusive
statements are the same either way.

I got another dose of all this in the late '70s, when I was covering
materials for _American Machinist_ and most of that was automotive; I took
the time then to re-study engine dynamics. They knew about turbulence and
lean burning, and all of that, by then.

What's new is that they have sensors and photogrammetry that let them detect
all kinds of things. Now they can describe not only the outcomes, but also
the how and why of much of it. I was startled to see that one piece of
research identified 669 chemical species in the combustion process. g! Now
they can tell us why different fuels that deliver the same MON or RON
numbers in a standardized test, but which are chemically different fuels,
may perform radically different under real-world conditions. One test showed
a 2:1 ratio in detonation resistance, between two fuels that have the same
RON.

None of that changes the fact that cetane and octane are close to being
opposite scales of the same thing, and that gasoline resists ignition, and
burns slower, than diesel in an engine. This explains why that MIT engineer
jokingly said 20 years ago that it's not like using those fuels to start
your charcoal grill. Flashpoint and volatility at ambient temperatures,
which are important in starting a grill, become trivial with direct
injection at high compression ratios.



[Knock in Spark-Ignition Engines: End-Gas Temperature Measurements Using
Rotational Cars and Detailed Kinetic Calculations of the Autoignition
Process - 1997]

"It is found that calculations with different RONs of the fuel lead to
different levels of radical concentrations in the end-gas. The appearance
of
the first stage of the autoignition process is marginally influence by the
RON, while the ignition delay of the second stage is increased with
increasing RON."

[There are two stages to controlled autoignition, and the final one is
delayed as octane number increases.]


ANd this disproves or dissagrees with my explanation how? The "radical
concentrations" refer to what? Higher RON reduces the radical
concentrations, which delay the "second stage of autoignition" -
which in spark engine parlance is "detonation"

No, they're talking about controlled autoignition. Detonation is
uncontrolled autoignition that progesses to an explosive, or near-explosive
state. And they're talking about diesels, not SI engines.


In my words, high octane gasoline resists thermal dissassociation of
the hydrocarbons, resulting in lower production of hydrogen radicals
and a marked reduction in the propensity of the engine to detonate.

But it also slows down the flame front, which contradicts, apparently, what
you were taught. This appears over and over again in those research papers.

FWIW, there is a lot of research that picks apart the multiple stages of
intermediate combustion products, which are heavily involved in the rate of
combustion and which vary widely between fuels. The simplified idea that the
hydrocarbons are just dissociated and then burn doesn't cut it at the level
of engineering science they're working at today.


You are talking DIESEL ENGINE RESEARCH - where autoignition is a good
thing (particularly stage one) Second stage autoignition (also
referred to as detonation) is apparently also an issue in the engines
in question.

They aren't talking about detonation. There are two stages of controlled
autoignition.

snip

This could go on, but you'll find it interesting to pick through the current
research. They debunk a few old misconceptions, but the basics haven't
changed.

And, as you say, the important thing is, don't burn gasoline in a diesel
that's tuned to run on diesel fuel.

--
Ed Huntress

On Sun, 13 Apr 2008 11:30:58 -0400, "Ed Huntress"
wrote:


clare at snyder dot ontario dot canada wrote in message
.. .
On Sat, 12 Apr 2008 19:08:43 -0400, "Ed Huntress"
wrote:


"RoyJ" wrote in message
...
After reading the other comments I think you have multiple issues going
on
to switch from diesel to gasoline:
-the gasoline will have a MUCH lower viscosity, you are going to get way
different (more)amounts of fuel through the injector. I'd think that is
what causes the white smoke a lousy performance, it's too rich.
-at the same time, gasoline has lower fuel value per gallon or
milliliter,
same volume of fuel will cause the engine to go lean, never a good thing

You raise an intriguing question there, Roy. How do you make a diesel run
lean? g

-gasoline has a much higher flame front speed, ie it will detonate,
really
does bad things to the top of the piston.

It will detonate, but it's because of the *slower* flame front speed.
That's
the thing that's indirectly measured by the cetane rating: gasoline around
25, diesel typically 45+.


It's not realy detonation, and it's not really the speed of the burn
that is involved (flame front). It is the speed at which the cyl
pressure goes up with gas vs diesel. You DO get a faster pressure
spike when burning gasoline than when burning deisel at high cyl
pressures.

Reference? You may be comparing a homogeneous mixture in a spark-ignition
engine with the timed spray in a diesel. If you create a homogeneous mixture
with diesel alone, it burns faster than gasoline. That's what the
HCCI-engine research shows.


But what is the difference between timed spray of diesel vs timed
spray of gasoline. That was not, from what I saw, addressed.
Diesel combustion is NOT a homogenous mixture under normal operating
conditions.
Running deisel fuel in a spark ignition engine, with more or less
homogenous mixtures, the burn speed of the deisel is DEFINITELY faster
than the burn speed of gasoline in a homogenous mixture, but NOT as
fast as the burn speed of decomposed endgas, which is involved in
detonation.
** Posted from http://www.teranews.com **

On Sun, 13 Apr 2008 19:04:55 -0400, "Ed Huntress"
wrote:



More to do with the actual fuel composition than the actual octane
rating, wouldn't you agree?

No, they're talking about octane ratings, and you'll find the same pattern
for gasoline and other high-octane fuels versus diesel fuel, throughout the
literature. The issue here is the differences in performance relative to
different octane rating systems.


You will admit, will you not, that propane, ethanol, and leaded racing
fuel will have 3 very widely varying burn speeds, very different
flamability ranges, extremely differing autoignition specs, widely
disparate energy densities,just as widely disparate specific gravities
and reid vapour pressures, yet very close to the same octane?

SO.
Octane has NOTHING to do with flame front speed, nothing to do with
autoignition temperatures, nothing to do with vapour pressure, power
density,specific gravity, or ANY other property except the resistance
to detonation in a spark ignition internal combustion engine.

It MAY have an effect on the operation of a compression ignition
engine as well - I would say there is little chance that any fuel with
high octane would run successfully in a standard CI engine - but
octane, by it's definition has little if any to do with compression
ignition engine operation.

The big MYTHS out there are several, including but not limited to the
following:

ALL high octane fuels MUST burn slower than low octane fuels.
ALL high octane fuels must produce less power in a low
compression engine than low octane fuels.
Using ANY fuel with higher than recommended octane rating MUST
produce poorer fuel economy
SG of a fuel indicates octane
High octane fuel can be differentiated from low octane fuel by
RVP.

The truth is:
FASTER burning fuels are less prone to detonation, all else
being equal.
SOME high octane fuels will produce just as much power (or
even more power) than some low octane fuels in low compression engines
SOME high octane fuels will provide as good or better fuel
economy in low compression engines than low octane fuels.
RVP in itself has no bearing on Octane

There is so much TOTAL MISUNDERSTANDING of fuel octane and detonation
issues out there in both automotive and aviation worlds.

Your explanations (or the explanations which may or may not exist in
the citations given) may go a lot farther in the explanation of how it
actually works, but without paying for and reading the complete
documentation (which in most cases would go right over the heads of
most on this list) it is impossible to say for certain. They may or
may not disprove (or support) the theory I have been taught and that
has been accepted for years. ANd just because some scientist or
scholar has presented a thesis, and supported it with scientific
method, does not mean that thesis will not be proven totally false (or
substantially in error) by some other scientist or scholar in the
short or long term.

It looks to me like someone gave you some misinformation regarding flame
speeds, but that the rest of what you're saying looks reasonably right. As I
was reading all of this yesterday (I have a respiratory infection, or you
wouldn't catch me dead inside, and not fishing, on a Saturday in April g),
some of what I was taught 40 years ago came back to me. I remembered that
gasoline was harder to ignite by compression than diesel. I had forgotten
that flame speed was slower for gasoline, which was counterintuitive and
struck me funny 40 years ago. But that's the same thing they're saying in
all of this current research. Abstracts or full text, those conclusive
statements are the same either way.

Flame speeds vary with fuel mixture and fuel composition, as well as
with compression pressure. Lean mixtures burn faster than rich. High
compression causes faster fuel burn ( at least in most cases, as
chemical activity goes up with temperature, and compression raises
temperature)
Flame front and rate of expansion are highly variable and influenced
by compression pressure, temperature, mixture, and fuel composition.

Because Gasoline is NOT a tightly defined compund, but (particularly
in recent years) a very wide-ranging chemical soup, it is difficult,
if not impossible, to generalize about how "Gasoline" behaves in an
engine under specific conditions.

It's been 40 years since I was taught a lot of this stuff too.
The issue date on my C of Q says December 17, 1971

I got another dose of all this in the late '70s, when I was covering
materials for _American Machinist_ and most of that was automotive; I took
the time then to re-study engine dynamics. They knew about turbulence and
lean burning, and all of that, by then.
But they have learned a lot more about both since, as well.

What's new is that they have sensors and photogrammetry that let them detect
all kinds of things. Now they can describe not only the outcomes, but also
the how and why of much of it. I was startled to see that one piece of
research identified 669 chemical species in the combustion process. g! Now
they can tell us why different fuels that deliver the same MON or RON
numbers in a standardized test, but which are chemically different fuels,
may perform radically different under real-world conditions. One test showed
a 2:1 ratio in detonation resistance, between two fuels that have the same
RON.

And just as wide a difference in detonation resistance between engines
with the same compression ratios - and many cases where high
compression engines are so much MORE detonation RESISTANT than other
engines of exactly the same design with reduced compression ratios.

None of that changes the fact that cetane and octane are close to being
opposite scales of the same thing, and that gasoline resists ignition, and
burns slower, than diesel in an engine. This explains why that MIT engineer
jokingly said 20 years ago that it's not like using those fuels to start
your charcoal grill. Flashpoint and volatility at ambient temperatures,
which are important in starting a grill, become trivial with direct
injection at high compression ratios.

For all intents and purposes, Cetane and Octane ratings are very CLOSE
to opposites, but there are subtle differences.
Most definitely, behaviour under atmospheric conditions does NOT
predict how a fuel will behave under elevated temperatures and
pressures.


** Posted from http://www.teranews.com **

On Sun, 13 Apr 2008 14:31:27 -0400, with neither quill nor qualm, "Ed
Huntress" quickly quoth:


clare at snyder dot ontario dot canada wrote in message
.. .

snip


True detonation is not just extremely fast burning (conflargation?).
It is the equivalent to a small charge of high explosive being set off
in the cyl.It is almost always detrimental to engine life as well as
power output.

Perhaps this is whed Ed is aluding to with the multiple modes of
detonation?

What I was referring to is just what was in the abstract I posted ("A
Theoretical and Experimental Study of the Modes of End Gas Autoignition
Leading to Knock in S.I. Engines") from the University of Leeds. I don't
have the full article, so I don't have a further explanation.

But that basic definition shows up in several papers I encountered on the
SAE website. There is conflagration (very rapid burning); developing
detonation; and explosion. Several papers say it is the developing
detonation phase that causes most of the damage.

Damage is most likely caused by the advanced timing effect which is
brought about by detonation. The mixture explodes as the piston is
coming -up- to TDC on the compression stroke. Rods, pistons, head
gaskets, and rod bearings don't like that at all. It's almost as much
fun as that neat trick called "hydrostatic lock."

--
Save the whales! Trade them for valuable prizes.

On Sat, 12 Apr 2008 16:50:08 -0500, RoyJ
wrote:

Very interesting discussion. I've been asked to be the project manager
for an alternate fuels project based around a 100kw Cat diesel
generator. Fire up on a new fuel, check for short term issues, go to a
50% load then 100% load for 8 to 24 hours, then tear down and look for
damage. Looks like I would be spending more time than planned dealing
with the injector pump. Hmmmmmmmmmmmmm.

What are the alternate fuels they want to check?

If it's natural gas, Caterpillar has off the shelf engines to do
that. No experimenting or reinventing the wheel needed - just couple,
plumb and go.

If it's canola or other vegetable oils, they have specs for getting
the glycerine out, and the concentrations allowed. IIRC they only
allow B-20 right now (80% regular diesel) if you still want warranty
coverage, but that may well have changed.

For B-100, yeah you'd want to keep an eye on the injector pump.

-- Bruce --

clare at snyder dot ontario dot canada wrote in message
...
On Sun, 13 Apr 2008 11:30:58 -0400, "Ed Huntress"
wrote:


clare at snyder dot ontario dot canada wrote in message
. ..
On Sat, 12 Apr 2008 19:08:43 -0400, "Ed Huntress"
wrote:


"RoyJ" wrote in message
...
After reading the other comments I think you have multiple issues
going
on
to switch from diesel to gasoline:
-the gasoline will have a MUCH lower viscosity, you are going to get
way
different (more)amounts of fuel through the injector. I'd think that
is
what causes the white smoke a lousy performance, it's too rich.
-at the same time, gasoline has lower fuel value per gallon or
milliliter,
same volume of fuel will cause the engine to go lean, never a good
thing

You raise an intriguing question there, Roy. How do you make a diesel
run
lean? g

-gasoline has a much higher flame front speed, ie it will detonate,
really
does bad things to the top of the piston.

It will detonate, but it's because of the *slower* flame front speed.
That's
the thing that's indirectly measured by the cetane rating: gasoline
around
25, diesel typically 45+.


It's not realy detonation, and it's not really the speed of the burn
that is involved (flame front). It is the speed at which the cyl
pressure goes up with gas vs diesel. You DO get a faster pressure
spike when burning gasoline than when burning deisel at high cyl
pressures.

Reference? You may be comparing a homogeneous mixture in a spark-ignition
engine with the timed spray in a diesel. If you create a homogeneous
mixture
with diesel alone, it burns faster than gasoline. That's what the
HCCI-engine research shows.


But what is the difference between timed spray of diesel vs timed
spray of gasoline. That was not, from what I saw, addressed.

It wasn't, in the papers from which I quoted. It was in some of the other
200 or so.

Diesel combustion is NOT a homogenous mixture under normal operating
conditions.

It is in an HCCI engine running on diesel, which is what I said.

You don't need HCCI to have diesel burning faster. It burns faster in a
conventional stratified charge diesel, as well. It just doesn't happen in a
way that you can compare it with a SI engine, which is what that paragraph
was about.

Running deisel fuel in a spark ignition engine, with more or less
homogenous mixtures, the burn speed of the deisel is DEFINITELY faster
than the burn speed of gasoline in a homogenous mixture, but NOT as
fast as the burn speed of decomposed endgas, which is involved in
detonation.

?? I'm not sure if we just got off on a siding, or what...

--
Ed Huntress