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I think, it could lead to, for example, very environment friendly and very efficient urban traffic.

But I also think, it required very precise part construction.

Do such things exist? At least in plan?

Extension: Clarification added, waiting for acceptable answer again.

Extension #2: Despite the "common sense", diesel engines aren't so simple. Although there is no spark, there is a part which injects the fuel in exactly the perfect moment into the piston. This happens with around 2000atm pressure. Maybe this would be hard in case of gases.

peterh
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It depends on what you mean by "diesel-like". If you mean an engine with compression ignition running on gaseous fuel, then the answer is no. The high autoignition temperature of fuels such as natural gas prohibits sparkless ignition of pure natural gas1. @mart is right that compression ignition engines running on gaseous fuels need a pilot fuel which ignites the mixture.

However, diesel engines have been modified to run on gaseous fuels by adding spark ignition2. These engines are "diesel-like" in that they have high compression ratios (and were made from actual diesel engines for purposes of research convenience) so again, it depends on what you mean by "diesel-like".

regdoug
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The only ones I know of are pilot-oil gas motors. The ones I know burn biogas or methane plus a small amount of oil, typically rape oil. The oil is neccesary for combustion but the biggest part of the power comes from the gasous fuel. Typically, the lower limit for oil consumption is about 5% (by energy content), the engines can run on oil solely. Efficencies are advertised as 45-50% for a 500kW stationary engine used as a CHP plant (with utilization of exhaust pressure). This is better than gas-only engines. One producer is Schnell Motoren, maybe you can find further information on their site.

mart
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On this website, Wartsila states it has made diesel-gas engines and that the first ones have been operating for 70 000 hours.

hazzey
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Fred
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2

If you count gasoline as "gas", many car manufacturers are already testing homogeneous charge compression ignition engines. It is where they use the compression stroke to ignite the fuel mixture in the cylinder. The fuel is not direct injected, it is premixed in the intake charge before it makes it into the cylinder, so diesel type direct injectors are not necessary.

The same technology could be used for other gaseous fuels such as compressed natural gas. Such as the experimental compression ignition natural gas engine made by toyota, referenced here http://papers.sae.org/2007-01-0176/

So such things do exist, though uncommon.

Netduke
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