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Old 06-19-2004, 06:10 PM
winap winap is offline
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Diesel Engine Efficiency

I am looking for a book to calculate diesel engine efficiency. I am trying to gain a better understanding what makes a diesel engine fuel efficient. Many times we can buy a standard engine off the shelf and have nice working item. I looking to for extreme fuel economy and looking to understand the engine completely so when I talk to a consultant or a custom engine manufacturere with some degree of intelligence.

The specific engines I am looking are for traditional and diesel electric propulsion systems. The HP range I am looking for this extreme economy are 450 to 600 hp for diesel electric set up and 2000 HP to 2800 HP for traditional propulsion.

Any tips or leads in custom diesel engine manufactures will be helpful.
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Old 06-19-2004, 08:55 PM
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SailDesign SailDesign is offline
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"custom diesel engine manufacturers" is kind of an oxymoron unless you have a LOT of cash to play with.
But... google produced these guys:

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Old 07-07-2004, 08:47 AM
marinedummy marinedummy is offline
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if you want to fully understand your diesel engine learn the thermodynamic processes it takes. just a suggestion as i learned it this year at uni and it helps.
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Old 07-07-2004, 10:30 PM
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Corpus Skipper Corpus Skipper is offline
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The HP range I am looking for this extreme economy are 450 to 600 hp for diesel electric set up and 2000 HP to 2800 HP for traditional propulsion.
Why the big difference in power? Anyway, at these power levels, diesel is your only choice anyway, unless you're drag racing and don't care about longevity. Direct drive is more efficient than diesel-electric, as you don't have to convert mechanical energy to electric power, then back to mechanical energy again. Generators and motors are not 100% efficient, more like lower 90's for modern gennies and motors. Plus, a transmission is a lot cheaper than the gen/motor. What kind of vessel are we talking about, and what is the intended use?
Craig Cavanaugh
Silver King Custom Marine
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Old 07-08-2004, 02:51 PM
Thunderhead19 Thunderhead19 is offline
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The actual difference between the power available in the Diesel fuel and the power output of a diesel engine at the shaft is 30-40% Gasoline engines are around 20%, and it's even less at the prop. Turbines can get above that though by a good margin.

Winap, do you want the sunday school explanation or the university level thermodynamics explanation?
Diesels are simple, this is the main reason why they are efficient. The fuel ignites by itself from the compression it is under in the cylinder. You'll probably get into a discussion about two-stroke or four stroke. Two strokes make gobs of power for their size, but use gobs of fuel too. You'll have to decide what's more important range or ooomph!. Let me guess, you're towing something? A barge?? A small island maybe?

Last edited by Thunderhead19 : 07-08-2004 at 02:55 PM. Reason: mental lapse
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Old 07-08-2004, 03:10 PM
ClarkT ClarkT is offline
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Like Steve said, it takes a lot of money to play this game. These guys are in the custom diesel business
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Old 07-08-2004, 05:15 PM
winap winap is offline
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Well I will take the mystery out of what I am looking for. I am looking for the most fuel economy engine. These engines will be used around 3000 to 4000 hours a year for continuous operation on an ocean going vessel. The idea behind the diesel electric is to use a series of engines to power the vessel for both domestic supply and propulsion. The concept is to rotate the usage. Instead of having two large engines with direct drive it will be powered with 8 smaller engines in a genset configuration. When more power is required more engines fire up and less power less engines are used. This concept allows the engineer on board to service one engine a time and overhaul it underway.

The custom engine idea comes to gain te ultimate economy. What I understand that the most economical engines on the market are Cummins.

An college technical paper on the subject are fine.
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Old 07-11-2004, 03:06 AM
Black Swan Black Swan is offline
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Gawd... I've forgotten most of the old thermodynamic theory stuff, but I seem to remember that the "actual" efficiency of intrnal combustion engines ended up being something obscene like 15% once all the friction losses and parasitic drivetrain losses were calculated. Most of the energy is wasted in the production of heat, which for the most part is thrown away. Seems to me that once the BTU's are removed from energy conversion, internal combustion engines are a lousy way to convert fuel to kinetic energy. But that's mostly theory and philosophy.

The factor that determines the amount of energy produced by any group of engines is not only the design of the engine, but the fuel used and it's manner of conversion. The more refined the fuel is, the less energy is available from it - ie. Natural gas is a nice clean burning fuel, but relative to gasoline, it produces less power because the fuel contains less carbon atoms in the molecule of fuel. It's the combustion of the fuel that creates the power. Consequently, diesel engines produce more power than gasoline engines, and bunker fuel engines (compression ignition design) produce even more power, but on a much larger scale (ships, not boats). In our little world, however, we're seeking to find economically realizable propulsion systems. The diesel generator / electric motor option is certainly realizable, and the technology is there, but the design should be left to the professionals. The control system for such a driveline and system integration will be somewhat of a daunting task. FEYS has a fairly simple diesel electric drive system, and VETUS has had one on the drawing board for some time.
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