LPG for propulsion ?

[Pete of Ebor]

Following on from Canallegs topic about fuel cells to power a boat, I just wondered whether anyone uses or has ever considered using LPG for propulsion ? LPG cars are 'relatively' common so the technology for an LPG powered engine is there.. While it's not terribly convenient to plug a new gas bottle into a car ( - hence the fixed tank often in the boot) boaters are well used to changing gas bottles, and the infrastructure is there already in the form of gas suppliers. The only downside I see is the need for an engine with an ignition system (leading to possible problems due to dampness) as opposed to the 'simpler' (!) diesel engines which don't.. I'm sure it would appeal to those of a green bent.. (..a green bent what ? )

 

Tin hat on..

 

Pete

[churchward]

Following on from Canallegs topic about fuel cells to power a boat, I just wondered whether anyone uses or has ever considered using LPG for propulsion ? LPG cars are 'relatively' common so the technology for an LPG powered engine is there.. While it's not terribly convenient to plug a new gas bottle into a car ( - hence the fixed tank often in the boot) boaters are well used to changing gas bottles, and the infrastructure is there already in the form of gas suppliers. The only downside I see is the need for an engine with an ignition system (leading to possible problems due to dampness) as opposed to the 'simpler' (!) diesel engines which don't.. I'm sure it would appeal to those of a green bent.. (..a green bent what ? )

 

Tin hat on..

 

Pete

Why would LPG be considered green?

[Yoda]

You have to work out the cost against the calorific value of the fuel. This means how big a bang per buck.

[Pete of Ebor]

Why would LPG be considered green?

Well, green-er OK, it's still a petroleum by-product, as is diesel but it burns much cleaner (no PM10s) and won't pollute the waterway like diesel would should it escape. It could cause an explosion but I'm sure they must have looked at this possibility before it was allowed in LPG cars. We couldn't have cars exploding all over the place, could we..

[churchward]

Well, green-er OK, it's still a petroleum by-product, as is diesel but it burns much cleaner (no PM10s) and won't pollute the waterway like diesel would should it escape. It could cause an explosion but I'm sure they must have looked at this possibility before it was allowed in LPG cars. We couldn't have cars exploding all over the place, could we..

We won't mention greenhouse gases then?

[magpie patrick]

We won't mention greenhouse gases then?

 

I think there are a few problems, but LPG boats have been tried, I'm remembering vaguely an article in WW in the early to mid eighties.

 

Safety is definitely an issue, a gas leak into your bilge is serious bad news, and would probably need sniffers and blowers to circumvent the risk (the WW article predates BSS)

 

LPG IS a greenhouse gas, its release unburnt is bad news but if burned efficiently the only one it gives off is water, unlike diesel, petrol, paraffin, meths etc which give off CO2

 

On the plus side, I seem to remember that LPG engines were very quiet

[Machpoint005]

I should think it's possible get a compression-ignition engine to run on LPG too, although the only ones I have seen (big industrial engines) were modified diesels running on natural gas (mainly methane).

[O'Mali]

I should think it's possible get a compression-ignition engine to run on LPG too.

I worked with a hiab operator who said his truck (scammel) was converted to run on LPG.

[Tony Brooks]

I should think it's possible get a compression-ignition engine to run on LPG too, although the only ones I have seen (big industrial engines) were modified diesels running on natural gas (mainly methane).

 

 

I do not see how because if its to be injected I doubt it will lubricate the injection equipment satisfactorily AND the injection pump expects fuel at no more than about 6psi inside it.

 

I understand that LPG fuelled CI road engines (diesels) supply 70 to 80% of the fuel required, as gas into the manifold and the burn is initiated by a small injection of diesel.

 

It may well be economic to modify the "injection equipment" on those big, specialist diesels but I doubt that would be the case for our sorts.

 

Typical car LPG engines are SI (petrol engines) where the burn is still initiated by the spark so the lower compression ration would reduce the potential fuel economy compared with a CI engine.

[the grinch]

Keith Jones tried it in the 80's when he built the first powered steam hire boat. running from Foxton Boats and then later on from Welford it was a great boat the LPG tank was in the bow and supplied the boiler in the stern.

[MoominPapa]

LPG IS a greenhouse gas, its release unburnt is bad news but if burned efficiently the only one it gives off is water, unlike diesel, petrol, paraffin, meths etc which give off CO2

I think you have LPG mixed up with hydrogen. LPG is hydrocarbons and burning it very definitely does produce CO2.

 

MP.

[eightpot]

When I had my Range Rover back in 2000, I converted it to run dual fuel - in actuality it only ever ran on gas since it was less than half the price of petrol per litre. From a combustion point of view the ignition timing had to be advanced a few degrees due to the different burn characteristics and the ignition system itself had to be in tip top condition - the LPG/air mix had a greater 'resistance' for the spark to arc across the sparkplug gap compared to petrol.

 

Other than the state of tune of the engine, not a lot of modification was required. It was a V8 (hence my moniker) running a pair of SU carbs and would run either fuel as required and ran in that state for 40k miles with no real problems. The kit was later transferred to another Range Rover with EFI and with a suitable mixer (to introduce the lpg to the induction) and is still running now.

 

There is no real magic to LPG, it allowed me to run my Rangie for Ford Escort money and the engine ran much cleaner to boot as was evident at every oil change.

[NB Willawaw]

I designed the electrical system for a 58ft boat which runs from LPG.

The gas powers an integral Honda genset which charges a bank of 48V batteries.

 

The drive is electric and the boat cruises for about 30km on a charge.

 

The gas was the owners idea because he doesn't like diesel and believes LPG produces less emissions.

 

The good thing about the electric DC drive is it's very quiet and consumes no power in locks.

[badgerburger]

Following on from Canallegs topic about fuel cells to power a boat, I just wondered whether anyone uses or has ever considered using LPG for propulsion ? LPG cars are 'relatively' common so the technology for an LPG powered engine is there.. While it's not terribly convenient to plug a new gas bottle into a car ( - hence the fixed tank often in the boot) boaters are well used to changing gas bottles, and the infrastructure is there already in the form of gas suppliers. The only downside I see is the need for an engine with an ignition system (leading to possible problems due to dampness) as opposed to the 'simpler' (!) diesel engines which don't.. I'm sure it would appeal to those of a green bent.. (..a green bent what ? )

 

Tin hat on..

 

Pete

 

Problem with using gas bottles is that an LPG engine requires a liquid phase take-off, whereas gas bottles give you a vapour feed. Taking enough LPG from a vapour feed to run an engine would cause it to freeze solid.

 

You can bodge a gas cylinder to give a liquid feed, but this is "not recommended" (i.e. **** stupid). Car LPG conversions use a custom vaporiser to convert liquid to gas & this is kept warm by the engine coolant.

 

However, LPG is 'greener'. Propane has a higher ratio of Hydrogen to Carbon than either petrol or diesel. When it burns, it produces around 40% more H20 and correspondingly less CO2.

 

B.B.

[Albion]

snipped

However, LPG is 'greener'. Propane has a higher ratio of Hydrogen to Carbon than either petrol or diesel. When it burns, it produces around 40% more H20 and correspondingly less CO2.

 

B.B.

 

Umm, I'm not so sure. It is a common perception that LPG is greener/less polluting than petrol but, when I worked in development at Rover Cars (some years ago just before BMW got rid) the emissions guys put an LPG car into the emissions labs and it wasn't as clean as it was cracked up to be. I asked why this would be and they could only surmise that LPG had not been developed for car combustion (it's a heating fuel after all) whereas petrol (and DERV for that matter) have been gradually and relentlessly developed to minimise emissions (in conjunction with improved engine/after-treatment technology of course).

Roger

[badgerburger]

Umm, I'm not so sure. It is a common perception that LPG is greener/less polluting than petrol but, when I worked in development at Rover Cars (some years ago just before BMW got rid) the emissions guys put an LPG car into the emissions labs and it wasn't as clean as it was cracked up to be.

 

I asked why this would be and they could only surmise that LPG had not been developed for car combustion (it's a heating fuel after all) whereas petrol (and DERV for that matter) have been gradually and relentlessly developed to minimise emissions (in conjunction with improved engine/after-treatment technology of course).

Roger

 

True, but the emissions guys would have been measuring hydrocarbons / CO, rather than CO2 efficiency.

 

Engines have been developed to minimise emissions for petrol/DERV, so running on LPG will only improve hydrocarbons emissions if you're converting an old/ inefficient engine. However, CO2 output will be much less - which is the reason for the different tax rate on LPG.

 

B.B.