On Mon, 14 Apr 2008 00:48:23 -0400, "Ed Huntress"
wrote:


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

I have no idea. Where's the data?

You want data - THAT I can give you.(Except for burn speed)




Property Ethanol Gasoline Propane #2 fuel
Chemical Formula C2H5OH C4 to C12 C3H8 C3 to C25
Molecular Weight 46.07 100€“105 44.1 200
Carbon 52.2 85€“88 82 84-87
Hydrogen 13.1 12€“15 18 33-16
Oxygen 34.7 0 0 0
Specific gravity, 60° F/60° F 0.796 0.72€“0.78 .508 0.81-0.89
Density, lb/gal @ 60° F 6.61 6.0€“6.5 4.22 6.7-7.4
Boiling temperature, °F 172 80€“437 -44 370-650
Reid vapor pressure, psi 2.3 8€“15 208 0.2
Research octane no. 108 90€“100 112 NR
Motor octane no. 92 81€“90 97 NR
(R + M)/2 100 86€“94 104 NR
Cetane no.(1) NR 5€“20 NR 40-55
Lower Flammability limit 4.3% 1.4% 2.2% 1%
Upper flammability limit 7.6% 19% 9.5% 6%
Flash point (open cup) 55 -45 -100-150 165
Autoignition temp 793F 495 850-950 600

Source: http://www.methanol.org/pdf/FuelProperties.pdf

Lower combustability range from 1.4 to 4.3%
Upper combustability range from 7.6 to 19%
Autoignition from495 to 950F
SG from 0.5 to 0.8
RVP from 2.3 to 208

Total octane spread (RON) 100 to 112 (high test gasoline)
Total MON spread (MON) 90 to 97 (high test gasoline)



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.

Where's the data?


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.

Well, it's commonly said in the literature that cetane and octane have an
inverse relationship.


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

Clare, I don't think I've heard most of those myths, and we've departed
pretty far from the question of what gasoline does in a diesel engine.

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