Running diesels on Gas (Update)

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Thu 13 Dec 2001 08:57
Running diesels on Gas (Update) - John S
Following on from previous questions about using LPG in diesel engines I saw the following today in 'Professional Engineering'. Referes to natural gas, but there are obvious parallels.

'Engineers at Ford's Dunton Engineering Centre are evaluating a prototype Ford Focus believed to be the world's first car to use natural gas with a diesel cycle engine. The Focus has already been road tested in the US and Ford's Dunton Engineers are said to be interested in the gas engine's potential for use in the Transit van.

The prototype engine has been developed by Westport Innovations, a Canadian firm specialising in the R & D of natural gas engine fuel systems. Unlike other gas engines that use spark ignition, Westport's system uses the diesel cycles high compression. The fuel is added only after the piston has compressed the air. As a result, Westport claims that the diesel engines efficiency and torque are maintained.'

Reading between the lines there is a problem with smoothness as the intended application is a van, not a passenger car. I imagine the possible problem is very rapid ignition of a fuel which burns much faster than diesel. I'm also confused about the statement that 'fuel is added after the compression is complete, so maintaining efficiency and torque', as this mimics exactly the standard diesel cycle.

Still it's getting there. Certainly shows it not yet a DIY option though.

Regards

John
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Thu 13 Dec 2001 18:22
Re: Running diesels on Gas (Update) - Tomo
I wonder how they get the gas into the cylinder against compression. In the early days of diesels, before injection pumps, they blew the oil in with an air blast (a somewhat hazardous affair), and presumably now there is some sort of gas blast - unless they can liquify it?
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Thu 13 Dec 2001 20:22
Re: Running diesels on Gas (Update) - Brian
I'm not a techie, but doesn't natural gas liquify at room temperature under pressure. If so, it can be injected in the same as any other fuel.
The injection pressure on a diesel has to be higher than the compression in the combustion chamber in any case; someone is sure to have the exact figures but 15:1 compression ratio would be just over 200 psi and the injector must exceed that by quite a big margin.
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Fri 14 Dec 2001 11:01
Re: Running diesels on Gas (Update) - John S
Yes, it's not clear from the article if the gas is injected in liquid or gaseous form. I imagine it's in liquid form, as that reduces the volume dramatically. It would also minimise speed of combustion, noise and vibration. I believe there may be problems in injecting it as a gas in a high speed engine - volumes and injection times would be too great.

Regards

JS
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