A Study on the Autoignition Characteristics of DME-LPG Dual Fuel in the HCCI Engine

This study investigated the potential increase of engine power through the mixture of dimethyl ether (DME) and liquefied petroleum gas (LPG) with homogeneous charge compression ignition combustion. The effects of mixing ratio of DME/LPG at a constant intake temperature were confirmed experimentally in a single-cylinder diesel engine. A numerical analysis was conducted through the detailed chemical kinetics by using CHEMKIN-PRO for the mixing model of DME and n-butane to clarify the underlying mechanism of autoignition, while considering the gas mixture heat loss to the cylinder wall to compare with the experiment. The results show that the increased amount of LPG reduces the low-temperature heat release and activates the high-temperature heat release, which increases in-cylinder pressure. Therefore, it has potential to raise the indicated mean effective pressure when mixing ratio was adjusted appropriately. Also, thermal efficiency was increased to 51.2% at the mixing ratio of 0.6. Finally, engine out emissions including total hydrocarbon increased a small amount and carbon monoxide was decreased to almost zero when the mixing ratio of DME decreased until the combustible zone. Numerical results agreed with the experiment, indicating weakened low-temperature oxidation from the increase of the n-butane amount.