More questions about LPG 2

[rdd48856]

Well I have several LPG questions:

1) On a French study (CFBP) it was found that on some gaseous sequential multiport injections systems CO emissions were higher while on LPG than on gasoline. They justified this as a deliberate strategy to protect valves by richening the mixture on deceleration. Does this make any sense? I read(on your site FranzH) that when burning gaseous fuels richening the mixture actually increases combustion temps, while leaning decreases temps, but I also read on an IANGV report (

http://www.iangv.org/files/IANGVREPpart3final.pdf

) that Nox emissions increases until l aprox. 1.3. Could this mean that temps only start to decrease from this point on.

2) What is the reason for increasing timing ignition advance for lower revs while decreasing for high? A balance between higher flame speeds and higher minimum ignition energy for LPG than for gasoline?

3) Would it be possible to use Liquid LPG injection on dual fuel pilot injection Diesel engines in a similar fashion of Westport cicle?

Thank you in advance for your contributions, specially to FranzH…
J.Tavares

 

[rdd48856]

On the latest IANGV meeting it was presented a tank capable of storing CNG at “only” 40 bar. This was achieved with surface adsortion. Furthermore, with slow refill at night or with LNG distribution, you can avoid the costs of high speed CNG compression. On Europe, where we both live, OEM are engaging now on CNG. The latest oil and refined products prices will boost that.

 

[j2bprometheus]

Hi-
Honda is now doing limited marketing of natural gas powered vehicles in California.
The user rents a natural gas filling station called "
PHIL" for 30-80 US dollars per month. I wonder if the users pay any road taxes....
The vehicles are Honda Civics and meet ULEV emissions. Range is limited to about 175 miles
Honda highlights the high "well to wheel" efficiency of natural gas.

Natural gas powered urban buses are fairly widely used in the US and there are a few used in India & China. The fuel is stored at high pressure ( ~ 3600 psi = 250 bar). The max fuel pressure limits the range and there are few public fueling stations. So these urban buses return to a central location every night.

Natural gas is also used in the US to power recreational go-carts used at indoor tracks. Again, the natural gas is stored at high pressure.

In the US, there are also natural gas powered garbage trucks, tree trimmers, shuttle buses, etc.


j2bprometheus

 

[marcdeluca]

I just stumbled upon this forum and it looks really interesting. I have a Duramax that I have run supplemental lp on since new. I use a regulator that introduces the gas ahead of the turbo. It responds to the small preturbo vacuum and modulates fuel according to the amount of vacuum. I typically use at least 2 gal of lp to one gal of diesel, and have achieved as much as 53 mpg on diesel. The truck would normally get 19 mpg on straight diesel.

 

[turbocohen]

Marc, have you calculated your cost per mile? Do you use a pyrometer? Just curious

 

[marcdeluca]

At 19 mpg #2 only, that would be 16.3¢/mi with fuel at $3.10. At 53 mpg, that comes to 5.9¢. My lp cost $1.23, and it gets around 21 mpg at a steady 70 mph. That would be 5.9¢ for the lp/mi. Together, they come to 11.8¢/mi. So, at that price for each, it is saving me 4.5¢/mi. I feel that is significant. When I tow, I can't run as much lp because of detonation, but it still helps alot. I recently took a 6000 lb travel trailer for FEMA from Elkhart, IN, to Hattiesburg, MS, and got 18 mpg on #2, running 75 mph. I don't have a EGT gauge in it yet, but plan to put one in soon. I have to be careful in 5th (Allison), it is easy to overpower and slip the clutches when towing uphill.

 

[turbocohen]

If you are detonating LP then your in cylinder temps are excessive aside from valve temps. Severe detonation is not less stressful than diesel clatter and can ruin any diesel.

 

[marcdeluca]

I don't tolerate any detonation. When it starts it is very light, and I have a flow control to cut back the lp. With my setup, the propane/#2 ratio increases as load comes on, so I must be approaching the point where the mixture can ignite under compression. The light detonation is easy to hear because the engine is quieter while running lp.