Science Fair Project Encyclopedia
Liquified petroleum gas
Liquid Petroleum Gas (LPG or LP Gas) is a mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles, and increasingly replacing fluorocarbons as an aerosol propellant and a refrigerant to reduce damage to the ozone layer. The gases are a mix of propane and butane usually with propylene and butylenes present in small concentration. A powerful odorant, ethanethiol, is added to these so that leaks can be detected easily. LPG is manufactured during the refining of crude oil, or extracted from oil or gas streams as they emerge from the ground.
It becomes liquid at room temperature at 6 bar pressure, so it is supplied in pressurised steel bottles. These are usually filled to 85% of their capacity with the liquified gas to provide room for the gas to expand if the bottle gets hot. The liquified gas has an expansion ratio of about 250:1.
LPG or 'Autogas' is widely used as 'green fuel' for internal combustion engines as it decreases exhaust emissions. It has a RON of 110 and an energy content of 95475 BTU/gallon. Toyota made a number of LPG engines in their 1970s M, R, and Y engine families.
Currently, a number of automobile manufacturers -CitroŽn, Daewoo, Fiat, Ford, Hyundai, Opel/Vauxhall, Peugeot, Renault, Saab and Volvo- have OEM bi-fuel models that will run equally well on both LPG and petrol.
LPG as cooking fuel
According to the 2001 Census of India, 17.5% of Indian households or 33.6 million Indian households used LPG as cooking fuel in 2001.  76.64% of such households were from urban India making up 48% of urban Indian households as compared to a usage of 5.7% only in rural Indian households. LPG is subsidised by the government. Increase in LPG prices has been a politically sensitive matter in India as it potentially affects the urban middle class voting pattern.
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