Effect of hydrogen and DME injection in homogeneous charge compression ignition engine with DME second injection strategy

Abstract

The effect of dimethyl-ether (DME) second injection was investigated in a single-cylinder direct injection compression ignition engine for homogeneous charge compression ignition combustion. Two different fuels, hydrogen and DME were used as main fuels. DME second injection timing and quantity were varied to control the combustion phasing of homogeneous charge compression ignition engine combustion. DME second injection timing was varied from 100 crank angle degrees before top dead centre to 5 after top dead centre. The DME injection quantity was varied from 5 mg to 9 mg. When DME injection was 9 mg, DME was injected by two strategies, which are single injection and split injection. Both single fuel and dual fuel combustion were influenced by DME second injection timing. When DME was used as a main fuel, combustion was stable regardless of the all injection timing while indicated mean effective pressures were lower than the dual-fuelled combustion. The Ignition delay of DME was much shorter than that of hydrogen due to its low auto-ignition temperature and higher cetane number. DME injection timing and quantity controlled the hydrogen ignition delay when hydrogen was used as a main fuel. With 5 mg of DME second injection, some injection timing showed misfire, therefore, increased DME injection quantity was required for stable combustion. 7 mg of DME second injection lead the highest indicated mean effective pressure.