LPG on gasoline direct injection engines 1

[rdd48856]

Direct injection is spreading quickly as environmental legislation is more severe. What future to bi-fuel(LPG and gasoline) cars? Would it be possible to use the same injector to one or another fuel(both on liquid fase, of course)? Any ideas? Thanks!

 

[pbloore]

Not too sure I agree that GDI's spreading quickly. Although there is a lot of theoretical promise, there are quite a few practical hurdles.

With regard to injecting liquid LPG through a GDI injector I suspect that the lack of lubricity would be one big problem followed by ice formation. No fundamental reason why it couldn't be made to work, but I suspect a different injector would be required making Bi-Fuel tricky.

 

[25362]

Taxi fleets in Buenos Aires move on dual fuel: they start on gasoline and then switch to CNG.

http://www.worldbank.org/transport/publicat/td-ut8.pdf

 

[unclesyd]

I posted this URL previously.
The idea is being looked at.

http://www.me.utexas.edu/~sae/37chevy.html

 

[rdd48856]

The focus is on converting a Direct Injection Gasoline engine and not on LPPI or on standard convertions. Here on Europe all major car makers have already Direct Injection Gasoline Engines and it is expected that in 10 years this engines will share 50% of the market...

 

[franzh]

DI with LPG does have some advantages over gasoline: no wall wetting, good homoginization, and lean burn options. The problem is handling it at high pressures in liquid phase, plus as already stated, no lubrication. As of now, its in concept stages, but for when it will meet the road is anyones guess. The same University of Texas website above has been investigating the LPG-DI project.
Franz

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[rdd48856]

There is a number of Liquid LPG kits available on the aftermarket(here on Europe) which proved reliable. The problem is that with Direct gasoline injection there isn't space to another lpg dedicated injector...

 

[patprimmer]

If lubrication is such a problem, why can't a little 2 stroke oil be mixed with the fuel, like 1:1000 sort of ratio to reduce smoke and pollution problems.

Maybe the minimum amount to be effective already causes smoke problems?

I have access to some technologies with plastic bearings that can far outperform metals under some circumstances with no external lubrication.

Regards
pat pprimmer@acay.com.au
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[pbloore]

There have been a number of attempts at producing a liquid phase LPG (propane) injection system in Europe, but to my knowledge I don't know of a really successful one. Certainly the vast majority of systems currently available are all gas phase port injection. Ford did a liquid phase system on the Focus a few years back, but dropped it in favour of a gas phase system becuase of problems.

Regarding gasoline GDI the problem is that the control is quite tricky and achieving the theoretical benefits in practise has proved to be difficult. There is a lot of development work at the moment though including running in HCCI mode for part of the load range.

 

[rdd48856]

Well, I’m talking about LPPI systems that are being sold since 2000 for aftermarket installers or OEM. Yes you can order a new car here in Europe equipped with LPPI. I’m not talking about experimental systems (as an example you can see Dutch company Vialle here

http://www.lpg.be/lpi-2.htm).

Regarding gasoline direct injection just search for “Citroen HPI”, “VW FSI”, “Mitsubishi GDI” or “Volvo V40 1.8i”, for example. So my question is how can a system work both for LPPI and GDI. Because as I told in 10 years only a few small engines will work with standard indirect gasoline injection, at least here in Europe.

 

[Azmio]

There are few researches in Japan for CNG DI engine. One research reported about the slow flame speed during stratified combustion mode that cause the combustion idle to be poor and later lead to uncontrollable misfire.

Another research reported about the poor fuel consumption and tailpipe emission.

 

[franzh]

Historically, DI engines have had emission problems, relying on extensive exhaust after-treatment (catalysts). The DI process injects high pressure liquid fuel against the piston dome which has a unique shape that is designed to control the air and fuel mixture. If the piston dome is relatively cool, the fuel tends to condense and misfires occur. Also, if the liquid fuel hits the cylinder wall (wall wetting), high HC's result, along with misfire conditions.
High Pressure CNG has an advantage over LPG since it is not compressible into a liquid. Injecting liquid propane directly into a cylinder will quickly cool the interior of the combustion area and may result in combustion pockets, high HC, and poor drivability. Azimo's reports are correct.
DI has its place and can provide very good performance, and this process is a "hot topic" in many research facilities.
Franz

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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Lou Scannon]

Many of the posts to this thread are discussing liquid phase port injection when the question was regarding liquid phase direct injection.
The two-phase nature of LPG makes it problematic for handling as a liquid. This issue may well be exacerbated in the high temperature environment of a direct injector.
It would be remarkable indeed for an injector design that was optimized for gasoline to be at all suited to liquid LPG.
Direct CNG injection (gaseous phase, of course) is showing some promise. Check out

http://www.westport.com

 

[rdd48856]

LPG - Auto is mostly butane in many countries, with a boiling point near 0ºC. I was thinking on an injector optimized for LPG and gasoline capable, although not optimal. May be not stratified charge capable. The original gasoline injector would be replaced by the LPG one. I would like to know, from you all, new ideas. For example, would it be possible to run on gasoline via port injection on the manifold while using direct injection to LPG? I must stress that if there isn’t a solution shortly, it would be impossible to convert new cars to LPG. Thank you.
I wasn’t able to find any information on your link, hemi. Please take a look at it, thank you again

 

[Lou Scannon]

Try this link, it's a couple of steps in from the home page.

http://www.westport.com/expertise/injectors.php

 

[dwedel]

rdd,

I'm not familiar with auto engine technology that well, how much stratification can you achive?

We have slow speed natural gas engines as drivers for our natural gas pipeline. These turn at about 300 rpm and have very poor mixing characteristics. I have seen some discussion about duel fuel for these units. When you lean burn these engines it is diffucult to get them to ignite. People use pre-combustion chamber igniters, but the rich mixture in the pre-combustion chamber causes enough Nox, that it is a significant portion of your total Nox output. The idea was to use a liquid fuel in the precombustion chamber to light the lean natural gas mixture in the main chamber. The liquid burned was very small and was in this situation much cleaner than the vapor fuel alone. The natural gas fuel was introduced in the air manifold for this application.

 

[Azmio]

the flame speed of the stratified CNG is really slow that the COV is bad and causes misfire. One solution is to premix the incoming air with hydrogen. It will surely speed up the flame speed and improves the combustion quality