Effect of n-Butane and propane on performance and emission characteristics of an SI engine operated with DME-blended LPG fuel

In this study, a spark ignition engine operated with DME-blended LPG fuel was studied experimentally. In particular, the effect of n-Butane and propane on performance, emissions characteristics (including hydrocarbon, CO, and NOx), and the combustion stability of an SI engine fuelled with DME-blended LPG fuel were examined. Four kinds of test fuel with different blend ratios of n-Butane, propane, and DME were used. The percentage of DME in the fuel blend was 20% by mass.The results showed that stable engine operation was possible for a wide range of engine loads with propane containing LPG/DME-blended fuel rather than n-Butane containing LPG/DME-blended fuel since the octane number of propane is higher than that of n-Butane. Also, engine power output, break specific fuel consumption (BSFC), and combustion stability when operating with propane containing DME-blended fuel were comparable to those values in case of pure LPG fuel operation. Engine power output was decreased and BSFC was increased with n-Butane containing DME-blended fuel due to the lower energy density of DME. To examine the effect of n-Butane and propane on emissions and fuel economy in an actual vehicle, a vehicle was tested during an FTP-75 cycle. Through the emission and fuel economy test in the FTP-75 cycle, we conclude that the differences in emission level and fuel economy were not significant according to the blend of n-Butane, propane, and DME.Considering the experimental results from the engine bench and the actual vehicle, the 20% content of DME-blended fuel, regardless of LPG type, can be used as an alternative fuel for LPG.