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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#41
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The Most Powerful Diesel Engine in the World!
If the engines are running in about the same BMEP range as smaller
engines, the pressure would be about the same, and so would injection system, then. I am under impression very large engines do not have higher BMEP nor instantaneous pressure. "Kenneth W. Sterling" wrote: On Wed, 10 Sep 2003 12:17:57 -0500, Jon Elson wrote: Jim Stewart wrote: Bob Swinney wrote: I make no claim to knowledge in thermodynamics - but - I think the increase in efficiency is partly due to the increase in size. Larger objects lose a lesser amount of heat (energy) than smaller ones. Common steam engines are also more efficient in the larger sizes. More specifically, size and speed. By turning slowly, the combustion gasses have more time to expand and convert heat to mechanical force. But, they also have more time to conduct heat to the cylinder walls, head and piston. The extensive cooling of the piston makes me think they are running this engine VERY hot, with a higher compression ratio (including the supercharging) than usual. Notice also the extremely long stroke, 2.58 times the bore. Jon Which brings to my mind another question - being diesel and with a 3' bore and 8' stroke the compressions pressures have got to be large - so the injection pump would have to put out some high pressure to be able to spray into the combustion chamber. The injection pump(s) for this thing have gotta be pretty impressive also. Ken. -- Don Stauffer in Minnesota webpage- http://www.usfamily.net/web/stauffer |
#42
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The Most Powerful Diesel Engine in the World!
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#43
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The Most Powerful Diesel Engine in the World!
"Dan Thomas" wrote in message
om... All diesels work that way. There is no other way to control ignition timing. The high compression heats the air charge to a temperature that will ignite the fuel as it is injected, so that injection timing controls ignition timing, and the length of the injection time, and therefore the volume of fuel injected, controls the power produced. There is no throttle butterfly to control incoming air. Full air charge is needed to generate the high pressure and temperature. So deisels don't know the meaning of the word mixture? Tim -- In the immortal words of Ned Flanders: "No foot longs!" Website @ http://webpages.charter.net/dawill/tmoranwms |
#44
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The Most Powerful Diesel Engine in the World!
"This is very likely a two-stroke engine, so any
mention of valves is questionable." It is two-stroke but it is a valve uniflow engine and has a single exhaust valve per cylinder. See: http://home.pacifier.com/~rboggs/SULZER.HTML for an animated cutaway I made several years ago. Rick C/E Steam and motor |
#45
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The Most Powerful Diesel Engine in the World!
"Tim Williams" wrote in message ...
"Dan Thomas" wrote in message om... All diesels work that way. There is no other way to control ignition timing. The high compression heats the air charge to a temperature that will ignite the fuel as it is injected, so that injection timing controls ignition timing, and the length of the injection time, and therefore the volume of fuel injected, controls the power produced. There is no throttle butterfly to control incoming air. Full air charge is needed to generate the high pressure and temperature. So deisels don't know the meaning of the word mixture? Tim Basically, though full lean mix is idle and full rich is full power. Dan |
#46
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The Most Powerful Diesel Engine in the World!
The injector breaks the fuel into a mist. Pre-ignition finishes the mixing.
Dan Thomas wrote in message om... "Tim Williams" wrote in message ... "Dan Thomas" wrote in message om... All diesels work that way. There is no other way to control ignition timing. The high compression heats the air charge to a temperature that will ignite the fuel as it is injected, so that injection timing controls ignition timing, and the length of the injection time, and therefore the volume of fuel injected, controls the power produced. There is no throttle butterfly to control incoming air. Full air charge is needed to generate the high pressure and temperature. So deisels don't know the meaning of the word mixture? Tim Basically, though full lean mix is idle and full rich is full power. Dan |
#47
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The Most Powerful Diesel Engine in the World!
Karl Townsend wrote: I'm curious, they claim a thermal efficiency of 50%, nearly double that of an automotive diesel. How do they do it? and why can't it be done in the automotive size engine? Karl I don't think that 50% efficiency is thermodynamically possible. The best designed fossil fuel powerplants barely make thirty percent. Carnot cycle limitation? Wonder where Pete is when we need him. Mike Eberlein |
#48
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The Most Powerful Diesel Engine in the World!
Dave,
They claim: "At maximum economy the engine exceeds 50% thermal efficiency. This is a turbocharged engine; that may be where the extra input VS output advantage comes from. The supercharger(s) looked, um, wicked big. -- Regards, Terry King ...In The Woods In Vermont The one who Dies With The Most Parts LOSES!! What do you need? |
#49
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The Most Powerful Diesel Engine in the World!
Dave Ficken wrote: Part of the efficiency equation is that waste heat is recovered from the exhaust and cooling water. The jacket water from the engine is run through an evaporater. We were able to make 24 metric tons of fresh water a day from a single effect evaporator running off the jacket water. We also had a larger double-effect evaporator with a greater capacity that used steam heat. Exhaust gases from the main engine pass through a Turbo charger, followed by a waste-heat boiler and create steam when the engine is running. The waste heat boiler was not enough to run the Double-effect evaporator by itself, so an auxilliary oil-fired boiler would supplement as needed. The aux boiler is also needed in port. Dave, They claim: "At maximum economy the engine exceeds 50% thermal efficiency. That is, more than 50% of the energy in the fuel in converted to motion." This is the generally agreed definition of thermal efficiency (work output divided by thermal energy input). I didn't think it was possible to get this high an efficiency from a Diesel cycle, is it? Maybe they are taking credit for re-using heat rejected from the process as you implied? |
#50
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The Most Powerful Diesel Engine in the World!
"Terry King" wrote in message
.. . The supercharger(s) looked, um, wicked big. I wonder how many cupolas you could blow with that Tim -- In the immortal words of Ned Flanders: "No foot longs!" Website @ http://webpages.charter.net/dawill/tmoranwms |
#51
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The Most Powerful Diesel Engine in the World!
On Sun, 14 Sep 2003 17:33:24 -0700, mikee wrote:
I don't think that 50% efficiency is thermodynamically possible. The best designed fossil fuel powerplants barely make thirty percent. Carnot cycle limitation? Actually the best fossil power plant, a combined cycle plant, currently holds the efficiency record at 52%. That's primary energy to electrical energy, so the prime mover efficiency has to be higher than that to account for generator losses. Large diesel electric plants typically run about 45%. The Carnot cycle limit is Ec = 100* (Th-Tc)/Th where Th is the high temperature source and Tc is the low temperature sink, both expressed in degrees Kelvin, and Ec is Carnot efficiency. As you can see by inspection, you can only reach 100% efficiency if the sink temperature is absolute zero. But we don't have access to an absolute zero sink of sufficient capacity to be useful. 50% efficiency is possible if the difference between source and sink is half the high temperature. That's achievable in practical systems. The Carnot limit actually permits any efficiency up to 99.999999......%. But to approach that, the Th has to be very high, and the Tc has to be very low. That's where practical limits come into play. Materials can't stand extremely high temperatures, and the atmosphere puts a practical limit on Tc. Gary |
#52
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The Most Powerful Diesel Engine in the World!
Pretty neat link.
Mike Eberlein Colin French wrote: read all links and learn "Harold & Susan Vordos" wrote in message ... Miniature engines, anyone? Enjoy! These engines are truly awesome! www.bath.ac.uk/~ccsshb/12cyl/ Harold Name: MAN B&W Reversing Principle.url MAN B&W Reversing Principle.url Type: Internet Shortcut (application/x-unknown-content-type-InternetShortcut) Encoding: x-uuencode |
#53
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The Most Powerful Diesel Engine in the World!
ICs are now well over thirty. Yes, they are reaching 50% range.
Figures typically quoted for car engines (SI) are very old. Modern ones can get over 33-34% at full throttle (or at least near best specific fuel consumption settings). Increases in compression ratio and other factors account for this. 25% is very low for even an automotive or truck Diesel. This value must be for an old one. For powerplants reaching the 50% mark, these are stationary power plants, for the most part. There is a scale efficiency factor at work here (which is close to what started this thread),and they are very large, and room for various regneration and other neat accessories. mikee wrote: Karl Townsend wrote: I'm curious, they claim a thermal efficiency of 50%, nearly double that of an automotive diesel. How do they do it? and why can't it be done in the automotive size engine? Karl I don't think that 50% efficiency is thermodynamically possible. The best designed fossil fuel powerplants barely make thirty percent. Carnot cycle limitation? Wonder where Pete is when we need him. Mike Eberlein -- Don Stauffer in Minnesota webpage- http://www.usfamily.net/web/stauffer |
#54
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The Most Powerful Diesel Engine in the World!
On Sat, 13 Sep 2003 05:02:59 GMT, Rick
wrote: "This is very likely a two-stroke engine, so any mention of valves is questionable." It is two-stroke but it is a valve uniflow engine and has a single exhaust valve per cylinder. See: http://home.pacifier.com/~rboggs/SULZER.HTML for an animated cutaway I made several years ago. It looks like it exhausts at TDC but intakes at BDC. Is it sucking vacuum all the way down? John Please note that my return address is wrong due to the amount of junk email I get. So please respond to this message through the newsgroup. |
#55
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The Most Powerful Diesel Engine in the World!
"It looks like it exhausts at TDC but intakes at BDC. Is it sucking vacuum all the way down?" The animation only has a few frames so timing is not precisely represented. It is a two-sroke engine. The exhaust valve opens shortly before BDC and before the scavenging ports are uncovered. Since it is a two-stroke engine there is no intake stroke as in a four-stroke engine. "Intake" occurs when the piston uncovers scavenging ports around the cylinder wall shortly before BDC. Since at this point scavenging air pressure is greater than cylinder pressure the remaining exhaust gases are pushed out the open exhaust valve. The valve closes shortly after the piston begins moving upward and compression begins for another power stroke. Rick |
#56
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The Most Powerful Diesel Engine in the World!
On Thu, 11 Sep 2003 03:20:59 -0400, Gary Coffman
wrote: On Wed, 10 Sep 2003 14:12:24 GMT, "Karl Townsend" wrote: I'm curious, they claim a thermal efficiency of 50%, nearly double that of an automotive diesel. How do they do it? and why can't it be done in the automotive size engine? Cube square relation. The larger the engine, the more volume it has with respect to surface area. Heat losses are through the surface area. So the larger the engine, the smaller the percentage of total heat is lost through the engine surfaces. Thus more heat is retained in the combustion gases, where it can do useful work expanding against the piston. So it can be more efficient. Gary Same thing for an engine with fewer cylinders and same displacement. The relativley long stroke (vs bore) also has no bearing on the compression ratio (and peak cylinder pressure) - that's determined by the ratio of cylinder volume at TDC vs BDC (which would be the same for any given bore size). Laurie Forbes |
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