Liquefied petroleum gas (LPG) as an alternative fuel in spark ignition engine: Performance and emission characteristics

In the present study, the performance and emission characteristics of a four-stroke spark ignition engine operated on liquefied petroleum gas (LPG) were investigated experimentally. The LPG was supplied from a LPG tank which was purchased from a local gas distributor. The primary content of LPG is 60% propane and 40% butane. The four-stroke spark ignition engine has an engine capacity of 183 cc and a compression ratio of 6.3:1, and it was coupled to a 5 kW eddy current dynamometer for performance measurement. A 5-gas Non-Dispersive Infra-Red (NDIR) analyzer was used for CO, CO₂, unburnt HC, and NO_x measurement. Two sets of experimental data obtained were analyzed; (i) 100% gasoline, and (ii) 5%, 10%, and 20% of LPG in gasoline. It was found that in general, the engine´s power output and torque suffer a drop in performance compared to 100% gasoline fueled engine, when tests were evaluated with 5%, 10%, and 20% LPG in gasoline. However, the brake specific fuel consumption, BSFC shows an improvement with LPG as a fuel replacement. The concentration levels of CO, CO₂, unburnt HC, and NO_x recorded are found to be lower than the gasoline fueled engine.