Insight into the combustion and emission characteristics of an ammonia-hydrogen dual-fuel opposed rotary piston engine

The opposed rotary piston (ORP) engine is distinguished by its compact architecture as well as elevated power density, making it an optimal power source for vehicles in the future. In this numerical investigation, the performance of an ammonia-hydrogen dual-fuel (AHDF) ORP engine with different ammonia energy ratio and ignition timing is investigated. The engine speed of the naturally aspirated ORP engine studied is 1000 r/min, with the ammonia energy ratio set at 85 %, 75 %, 65 %, and 55 %, respectively. The simulation results indicate that ammonia energy ratio and ignition timing are contributing factors to the behaviour of the AHDF ORP engine. The decline of ammonia energy ratio and advance of ignition result in an elevated in-cylinder pressure, which also brings about an enhance in heat release rate and fuel mass burn fraction. The ORP engine performance shows that the performance indicators improve with the reduction of ammonia energy ratio and the earliness of ignition timing. Nitrogen oxides emissions reduce with the ignition timing being brought forward. The AHDF ORP engine achieves a peak indicated power of 11.90 kW and an optimum efficiency of 38.59 % with relatively low NO_x emissions at 65 % ammonia ratio and −10 °CA ignition timing.