LPG as a fuel?

[High Wing Drifter]

Just starting to be curious about getting our cars converted to LPG. Are there any reasons why LPG conversions for at least some aircreaft would not be feasible? The reasons that I can think of are:


Additional weight?


Reduced range?


Reduced cooling?


Any thoughts?

[Mike Cross]

One of the issues with LPG is that it freezes. Propane at a lower temperature than Butane. The container also cools as the fuel is used (the white frost round the propane bottles at Popham on a humid day indicates the LPG level).

Also of course as the temp reduces the volatility decreases. I spent 6 months living on a boat one winter and the LPG bottle would freeze up and the supply of gas for my morning shower dwindle away to nothing!

It's the inverse of the mogas problem, where it gets too volatile and gives you vapour lock:(

[High Wing Drifter]

Thanks Mike,

The pro LPG site suggests that LPG is usable to "arctic tempratures" which, I guess, could be anywhere between +10 and -70 depending when and where.

[MEON VALLEY FLYER]

LPG freezing at height :

Think about it. I had a LPG forklift until last year (now electric, a lot less hassle). This was in use @ Portsmouth, lets say 50 ft above see level. We always had problems with freezing of the gas. To prevent it the gas come from the bottle and staight into a pressure valve that has a water jacked aroung it from the cooling system. Theory being the running engime would stop the gas freezing. But with short use runs and winter months, it was a pig. (1991 mitsubishi compact 25 if anyone wants to know).

Now most aircraft have no water cooling to aid anti freezing and would you really want a fuel that 'could' freeze very easily and cause things to go very quite up front.

Petrol and JetA1 are perfectly good at what they do

[Deaf]

Things may be different in the UK but in oz there are 2 types of LPG.

Propane used as domestic and camping fuel. Generally has the evaporation occuring in the bottle with the heat supplied by the environment. At high usage rates (industrial WAY outside intended) water condenses from the atmosphere and forms an insulating blanket of ice on the bottle hence gas supply tails off.

Propane/Butane mix (plus anything else of low BP from the cat cracker) used for vehicle fuel. Vaporization in the tank is only to provide pressure for delivery of liquid to a vaporizer with heat supplied by the engine coolant, Not to be used for domestic/camping use as there would be a variation in the mixture strength with the propane coming off first.

LPG works fine for car use (12 years, 240,000K including a fair bit of snow work) can't see why it couldn't be used for a/c with an appropriate vaporizer. The tank weight could be addressed with filament wound kevlar as for oxy bottles.

[Andy_RR]

LPG will only freeze at -190°C. Not really likely in GA!

The freezing that is actually happening is atmospheric water vapour. If you deliver the LPG as a liquid and allow vapourisation near (but preferably within) the combustion chamber, then you could get it to work.

As with all engineering problems, there are ways...

BTW, I suspect the reason it's not used is similar to the reasons that it's only marginally accepted in the auto industry - packaging, safety concerns and ignorance. It actually is close to the most perfect fuel for an SI engine.

A