Liquified Petroleum Gas (LPG) Part 3 of 4
Greg Buenas
LPG
Liquid state propane is not heavy. Its S.G. (0.5) is lower than that of
Petrol (0.72). In practical terms this is of no benefit to a vehicle
designer as a pressurised vessel designed for LPG storage must be
stronger (made of thicker material) negating any weight saving.
Vapourised LPG, however, is 'heavy', i.e. heavier than the surrounding
air if allowed to escape.
Many a pleasure boat has been blown up at the end of the season, the small amounts of gas leaked before every lighting of the stove combining to make a lethal charge in the boat's bilge area. All that is needed is an ignition source (an electrical spark caused by a fault or maybe a thoughtless owner striking a match for light) and the stage is set for disaster. This is mentioned to underline the importance of venting any leakage from your vehicle's gas tank, say after an accident impact.
Unlike petrol, LPG is in a pure or real gaseous state at normal atmospheric pressures and temperatures. It needs very little encouragement to vapourise and lends itself more readily to mixing with air (to get the Oxygen required for a combustible mixture). It needs no fuel pump to get it out of the tank and up to the engine, as the large pressure differential between the tank's interior and the atmosphere takes care of that for free.
The Octane rating of LPG is far higher than that of raw Petrol, thus no Octane enhancing additives are required. Interestingly, in practical terms the only thing added to LPG is the pungent smell, designed to warn us of its presence. In its pure state the gas is colourless and odourless although it can be seen as 'waves' apparently 'bending' what we can see through it (this is 'refraction').
In economic terms LPG is cheap to produce (less additives and filtering are required). In the past it has been regarded as a 'waste' material occurring when more popular petroleum products were sought and made. In the UK, and most other oil or gas producing countries, there is currently a surplus of LPG.
In environmental terms the burning of LPG produces less CO2, virtually no CO or SO2. No harmful compounds of benzine or lead result form combustion simply because they are not added to enhance the octane of the fuel. Also note that when set against Diesel, LPG combustion produces NO particulates or ultra-fine particles.
It's not just the environment that benefits (as if that were not enough). Your engine will not suffer the attack of acidic combustion products increasing internal wear and erosion. Engine oil deteriorates at a far slower rate as no acids and almost no carbon deposits reduce its effectiveness. Less oil sludge (and resultant blocking or restricting of crucial engine oil supply drillings or capilliaries) is a large gain. Average engine oil temperatures may be significantly reduced if circulated oil volumes are maintained, further reducing oil degradation and reducing engine wear. As for other parts of the vehicle, the useful life of exhaust systems has been proven to be extended by three times when LPG is used as a fuel.