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LPG and NAT GAS conversion for deisel
4

LPG and NAT GAS conversion for deisel

LPG and NAT GAS conversion for deisel

(OP)
The buses in my city are diesel but they also use natural gas. This is done via a dual injector. I.e a small amount of diesel is used to ignite the natural gas. My question is, can this be done for say a turbo diesel commonly found in light commercial vehicles? or 4WD vehicles if so are there any companies that sell these?

I live in Sydney Australia where LPG is near half price diesel and petrol a like. So Now that direct injection is common in diesel's does this mean that there would not be a reduction in power for such a conversion? I'm sure if it can be done there would be a lot to save in fuel. LPG is readly available in the city here anyways.

Cheers
Mark

RE: LPG and NAT GAS conversion for deisel

tbuelna,
        I have come across dual-fuel CI engines, specifically,  CNG ingestion cum (diesel) pilot-injection.

         This is the first time, though, that I see CNG (or LPG) injection cum (diesel) pilot-injection, dual-fuel CI engines
         
         As for the first type, it is said that EGT tends to top out at full-load, thereby reducing engine-life.

         Wonder if the same applies if the CNG (or LPG) is injected - probably not.

RE: LPG and NAT GAS conversion for deisel

2
The Cummins Westport is a VERY sophisticated fuel management system, not just a port for dumping in natural gas.  The technology for NG with diesel does not transfer to propane, they are totally different fuels with different combustion characteristics.
NG can be used for major fraction substitution, whereas propane can only be used effectively for minor fraction substitutions.
The technology for high pressure direct injection is fuel specific, natural gas easily compresses into a high pressure gas whereas propane will condense into a liquid which has little or no lubricating properties.  Tests have shown unacceptable wear in high pressure direct propane injectors.  It is a workable solution, but deep pockets, lots of research time and lab work is needed.
Franz

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RE: LPG and NAT GAS conversion for deisel

franzh,
       Have you looked at Westport´s site ?

        They do not seem to make the same distinction as you have concerning CNG and LPG.

        In fact, they sing high praise for the latter, for occupying but a THIRD of the volume of an equivalent (calorific) CNG charge.

        It has to be stored on board in thermally-isolated vessels, though, and it will gaseify promptly if you open the valve to the atmosphere (just as it does when you use it for your stove while out camping).

        Could have an associated drill, specific to LPG, to compress it and flow it it into the dual-fuel injector.

RE: LPG and NAT GAS conversion for deisel

Paulista;
Uh, yes I have, many times, in depth.  Their program is sound and deserves more than what they are getting.  Lets just say that I have a more than little passing interest and engineering experience with the 5.9 B series on LPG and NG.
I speak from experience about high pressure LPG injection, it doesnt exist with any practicality, yet.  
The Westport LPG B series engine is spark ignited, not high pressure injected, and not dual fuel.
Franz

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RE: LPG and NAT GAS conversion for deisel

Franzh,
       So it seems they currently operate LPG-fuelled engines on the less-efficient Otto cycle (SI).

       Judging from your hands-on experience, they would still need to surmount considerable technological hurdles to make LPG a viable fuel for diesel-like injection.

        Seems a bit wicked though that nature should allow one fuel to double-up with diesel but make things difficult for another closely related one !

        But Westport paints a picture of blue skies in their sales pitch. I suppose that I am a bit gullible, plus a dose of wishful thinking to boot !
       

RE: LPG and NAT GAS conversion for deisel

With the exception of a very few throttle-less SI engines, all SI engines are throttled Otto Cycle engines.  Therein is one inherent deficiency that the diesel engine is blessed to be without.  Diesel fuel has a higher calorific value than propane, benefit #2.  Diesel engines may operate at higher compression ratios, benefit #3.
The LPG engines described by Westport and a select other few OEM manufacturers can operate at emission levels that are hard to obtain by diesel engines, but not without cost, or loss of efficiency.
All in all, it is a tradeoff.  The emission values of a gaseous fuel engine, or the power and dependability of a CI engine.  This discussion will NOT end with the closure of this thread, it is the topic of many engineering workshops.
Franz.

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RE: LPG and NAT GAS conversion for deisel

There was a push to provide what they called "fumigation" systems for commercial (over the road) diesels about 20-25 years ago, and it seemed to go nowhere.  Fumigation was bleeding a controlled amount of vaporous propane fuel into the air intake of a diesel to displace some of the diesel required, and to (theoretically) add to the engine's HP output.

My understanding was that there was a problem with stretching the engine's head bolts because of some characteristic of the the combined combustion process.

I always wondered if this was an accurate report or what.  The concept seemed viable, but died on the vine.  If anyone knows, please advise.

rmw

RE: LPG and NAT GAS conversion for deisel

(OP)
Thanks guys that helped!! franz are you familiar with the orbital combustion process?

http://www.orbeng.com.au/orbital/flash_index.htm

They term there combustion process as low pressure direct injection, and they use two stroke engines with low emisson results ;o). Was thinking since it is low pressure direct injection, they probably get that term from the fact the fuel is spark ignited and injected before TDC and hence low pressure than needed for diesel injection ATDC.

Soo my question is would LPG handle direct injection in this manner without condensing? these guys promote there technology as lean burning thus high efficiency in the performance of a two stroke with low emission running on cheaper LPG is this too good to be true?

Cheers
Mark

RE: LPG and NAT GAS conversion for deisel

Rmw,
    The "fumigation systems" that you mention are available for sale as kits at aftermarket shops such as ATS Turbo in the American mid-West.
     However, there is no mention of the phenomenon of stretching head-bolts while using this method for augmenting power output !
      Perhaps things may not get as drastic if instead the operator settles for just fuel substitution with pilot-injection of diesel, and not upping power output with the settings on the diesel injection pump unaltered.

RE: LPG and NAT GAS conversion for deisel

The fumigation process is as old as old man Diesel himself, it was actually the first process used before injection was introduced.  They called it "Erd Gas" or "Earth Gas", more commonly known as methane.  Small to moderate amounts of methane allow for substantial power increases of the engine, so the diesel amount was reduced to retain the standard power levels.  This system is in wide use around the world, and may known as "Pilot Ignition".
Propane has different combustion characteristics than methane.  Using small amounts can provide significant amounts of power increases but using more will provide combustion pressure spikes which can indeed pop head bolts, burn turbos, scorch pistons and cylinders.  Repeated in field tests show that using propane substitution for diesel at ratios much over 15% can lead to dangerous engine conditions, but higher substitution ratios can be used if diesel levels are reduced.
Some of the do-it-yourself websites claim "user adjustable power levels"(!), "easily removed if the vehicle needs to be returned to the dealer for engine warranty service"(!), "the use of LPG acts as a catalyst to make the diesel fuel burn more completely"(!).
Hmmm, maybe I missed something in the "hype and marketing" classes I was supposed to attend!  Sounds like bull droppings to me!
Franz

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RE: LPG and NAT GAS conversion for deisel

The systems I was referring to were for the commercial "over the road" diesels of hte day, Cummins, Cats, Detrioit, etc., as opposed to the market that ATS Turbo (I am an ATS user in my private PU truck-which I might add has the pump pushed pretty far) addresses.

I suspect, since I owned some trucks in those days (got that out of my blood, thank God) and I had some drivers who monkeyed around with the fuel pump settings, that what should have been a good augmentaion to normal diesel fuel firing was abused by those trying to "push" their engines to the max, and hence, the damage that Franz verifies.

I just noticed that it started out with a big push, and then just seemed to fizzle on the vine, and I think Franz's explaination explains what happened to what should have been a good thing.

One of my rigs was very distinctively and uniquely painted and striped, and I would hear drivers on their CB radioes talking about how fast that truck had pulled "such and such" hill hundreds of miles away.  Shortly thereafter, the driver brought that one in with a melted down engine.  Go figure.  So, I can imagine what that same driver would have done with some propane if he had had it.

rmw

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