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Liquefied Petroleum Gas (LPG)-powered vehicles use a pressure regulator/vaporizer to expand and modulate the gas pressure to meet the engine's operational demands. This expansion process is accompanied by a phase change wherein liquid LPG is converted to its gaseous form. This consequently reduces the temperature of the working fluid which may result in freezing (Joule-Thompson effect). In order to aid complete phase change and avoid any freezing, the vaporizer is heated either electrically or by the engine coolant circulation. Any inefficiency in the heating may lead to improper phase change and can result in a phenomenon known as "liquid carryover," wherein a liquid LPG gets entrained in the downstream gas circuit where the gaseous form is demanded. The liquid carryover (if any) leads to the improper engine functioning leading to driveability and emission issues.

Most of the energy consumed in today's mobility industry is derived from fossil fuels. The demand for clean, renewable and affordable alternative energy is forcing the automotive industry to look beyond the conventional fossil fuels. Fuels options like liquefied petroleum gas (LPG), compressed natural gas (CNG) and ethanol blends are quickly finding widespread acceptance as alternative sources. This paper presents the results of experimental studies conducted on a 1.2-liter MPI engine with three different alternate fuels. The fuels considered for the evaluation (apart from base gasoline) are 10% ethanol-blended fuel (E10), LPG (gaseous propane: butane mix) and CNG (gaseous methane). Experiments were conducted to compare their effect on engine performance and emissions. The test results show that E10 has the lowest power drop whereas CNG has the highest power drop (12%) as compared to gasoline. The maximum power drop in LPG is 4%, which is close to the theoretical predictions.

Demand for cleaner, cheaper and renewable alternate fuel sources has opened a lot of new avenues in area of automotive fuels. Moving away from the existing dependency on the fossil fuels with a stress on the renewable sources and eco-friendliness has become one of the key-driver for the development. Ever increasing cost and limited availability of the fossil fuels has led many automotive manufacturers to look at alternate sources for fuel. Some important alternate fuels like biogas, vegetable oil and its esters, alcohols, compressed natural gas (CNG), liquefied petroleum gas (LPG) and hydrogen are rapidly finding a place in automotive applications. Ethyl alcohol popularly known as ethanol, produced from renewable energy sources like biomass has been tested extensively in internal combustion engines. Due to the high latent heat of evaporation, high octane number and high flammability temperature, ethanol has positive influence on the engine performance.