Research on Decoupling of In-Cylinder Combustion Process of Diesel/Ammonia Dual Fuel Engine

Abstract

Ammonia fuel is a potential alternative fuel of diesel engine. However, the narrow flammability range and high ignition energy of ammonia limit its application. In this paper, the diesel engine bench test of ammonia and diesel dual fuel was carried out with three ammonia replacement rates of 0%, 10%, and 20%. The in-cylinder pressure and instantaneous heat release rate at 2700r/min, 75% load were measured and analyzed. A model of the combustion process of ammonia/diesel dual fuel was established to analyze the combustion process of ammonia and diesel fuel further, and a method of decoupling the combustion process of diesel/ammonia dual fuel was proposed. The results showed that the increase in ammonia replacement rate led to a decreased peak instantaneous heat release rate and the prolongation of combustion duration. Compared with the 10% ammonia replacement rate, the 20% ammonia replacement rate delayed the combustion center of gravity by 4.2°CA and caused an increase in the escape of unburned ammonia. The study of chemical reaction kinetics showed that NH3+O2=NH2+HO2 maintained a large negative sensitivity with the increase of ammonia concentration at high temperatures. However, NH2+NO2=H2NO+NO became the main reaction to promote ammonia combustion with the increase of ammonia at high temperature.

Keywords: diesel, ammonia, combustion process, engine