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LPG in Diesels


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#1 Wuzak

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Posted 24 January 2013 - 10:17

There are a few companies selling LPG kits for Diesel vehicles, where LPG is added to the Diesel to improve performance and emissions. The LPG looks to make up about 25% of the fuel blend.

But can LPG be used as a Diesel fuel by itself?

What about LNG? I seem to recall seeing a compression ignition stationary power generating engine running on natural gas.

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#2 Greg Locock

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Posted 24 January 2013 - 10:55

There are a few companies selling LPG kits for Diesel vehicles, where LPG is added to the Diesel to improve performance and emissions. The LPG looks to make up about 25% of the fuel blend.

But can LPG be used as a Diesel fuel by itself?

What about LNG? I seem to recall seeing a compression ignition stationary power generating engine running on natural gas.

You can certainly run CI engines on compressed natural gas, so LNG->CI seems like a small step.

Dunno about pure LPG as a diesel fuel, it has a high octane which is an indicator of poor CI suitability, but it is more complex than that.

#3 Wuzak

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Posted 24 January 2013 - 11:51

I found a report which tests the suitability of LPG in SI and CI engines.

From the conclusions:

2. The cetane number of LPG is so low that normal diesel engine operation on LPG alone is not possible. Increasing the concentration of cetane number improver (DTBP) resulted in shorter ignition delays, and lower cyclic variation. When more than 5 wt % DTBP was added to the 100% butane base fuel, stable engine operation over a wide range of engine loads (BMEP of 0.03 to 0.60 MPa) was possible

3. The thermal efficiency with cetane enhanced LPG fuel was comparable to conventional diesel operation, when the concentration of DTBP exceeded 5 wt%. Also, exhaust emissions showed that NOx and the smoke emissions could be significantly reduced using the DTBP doped LPG fuel, compared to a light diesel fuel at the same experimental conditions .

5. When propane was added to the butane base fuel, the ignition delay increased. Thus, if propane is used for a compression ignition fuel, more cetane enhancing additive is necessary than that required for 100% butane



#4 Wuzak

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Posted 24 January 2013 - 12:01

It seems you would have to use a lot of cetane booster in Australia:

Origin Energy Autogas

Propane varies between 50-90% of Australian LPG.

#5 gruntguru

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Posted 24 January 2013 - 22:28

You can certainly run CI engines on compressed natural gas, so LNG->CI seems like a small step.

Dunno about pure LPG as a diesel fuel, it has a high octane which is an indicator of poor CI suitability, but it is more complex than that.

NG has an even higher octane # than LPG. In both cases their use in CI engines is usually as a secondary fuel ie the gas is pre-mixed with air before combustion. NG burns very slowly or not at all if the mixture gets too far from stoich, so NG conversions generally run at lambda 1 - 1.2 and use either a plot injection of diesel (typically 5%) or convert to spark ignition. For LPG, the octane is usually not high enough to permit this type of operation at diesel CR's so typical conversions will "fumigate" at up to 40 - 50% substitution. The very lean pre-mix will not detonate in fact it won't even support a continuous flame front, relying instead on a substantial diesel injection to ignite all regions of the pre-mixed LPG-Air. This often results in incomplete combustion, high HC emissions and poor utilisation of the LPG fuel. The viability of the conversion often relies on low LPG pricing or a client motivated by power increase rather than cost savings.

#6 Lee Nicolle

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Posted 25 January 2013 - 10:08

There is a few buses running around Adelaide on CNG,,, with LPG stickers on the numberplates.
I seem to remember Catalina mentioned CNG in concrete trucks too.

#7 just me again

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Posted 25 January 2013 - 10:13

There is a few buses running around Adelaide on CNG,,, with LPG stickers on the numberplates.
I seem to remember Catalina mentioned CNG in concrete trucks too.


Yes there is plenty of gas buses. But do they run with or without sparkplugs.

Bjørn

#8 Catalina Park

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Posted 25 January 2013 - 11:10

With.

#9 gruntguru

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Posted 26 January 2013 - 02:38

With.

Yep - these are essentially Otto cycle engines.

#10 rory57

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Posted 26 January 2013 - 17:25

There is a few buses running around Adelaide on CNG,,, with LPG stickers on the numberplates.
I seem to remember Catalina mentioned CNG in concrete trucks too.


There were CNG signed street buses in Los Angeles when I was last there 12 years ago. They were dreadfully noisy, noisy in a worn-out Diesel sort of way. Would they have been Diesels sucking a bit of methane to go with the primary fuel ? Was the idea the cheaper fuel or to improve exhaust emissions?

#11 gruntguru

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Posted 28 January 2013 - 10:09

Gas engines are quieterthan diesel. So much so that they are often specified for garbage collection trucks which operate at odd hours.

#12 WhiteBlue

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Posted 28 January 2013 - 13:49

I am fascinated by the dual fuel technology. If it were available today I would add a kit for burning liquid natural gas to my BMW 180D turbodiesel and run it on 75% natural gas. That would be very cool.

#13 Canuck

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Posted 29 January 2013 - 00:12

Given the price of diesel (premium over premium gasoline prices) vs. LPG (half of regular gasoline or slightly less) so would I.

#14 Wuzak

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Posted 11 February 2013 - 00:08

So, what is the best way to use LPG in an ICE?

Higher than normal compression in a spark ignition engine that is relatively low revving?


What other "clean" alternatives are there for use in compression ignition engines?

#15 Lee Nicolle

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Posted 12 February 2013 - 21:20

Saw one on the news the other night that had caught on fire. I dont know where, just that it was on gas.
Pics in the paper of a Commodore that crashed and exploded too. Melted the back wheels off it.
When using gas beware of the implications. This seems to be a too common occurence.
A rubbish truck. The quietest thing is the engine, the clang bang thump and the blurp from the exhaust to the next bin is the noisy bits. Lucky my rubbish is collected during the day by 2 trucks, one rubbish and the other recycle or green waste on alternate weeks. And you can hear them a kilometre away!

#16 gruntguru

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Posted 12 February 2013 - 23:44

A rubbish truck. The quietest thing is the engine, the clang bang thump and the blurp from the exhaust to the next bin is the noisy bits.

You forgot to mention the radiator fan - WHHIIIIRRRRRR. Surely someone can design a quiet fan? Variable speed electric with an efficient (quiet) blade?