Experimental study on the cycle variation characteristics of direct injection hydrogen engine

Hydrogen energy is an important technical route to achieve carbon peak and carbon neutrality. Direct injection hydrogen engine is one of the ways of hydrogen energy application. It has the advantages of high thermal efficiency and limit/reduce abnormal combustion phenomena. In order to explore the cycle characteristics of direct injection hydrogen engine, based on a 2.0L direct injection hydrogen engine, an experimental study on the cycle characteristics of direct injection hydrogen engine was carried out. The experimental results show that cycle variation increases from 0.67% to 1.02% with the increasing of engine speed. The cycle variation decreases from 1.52% to 0.64% with the increasing of engine load. As the equivalence ratio increases, the cycle variation first decreases significantly from 2.52% to 0.35% and then stabilizes. The ignition advance angle has a better angle to minimize the cycle variation. An experimental study on the influence of the start of injection on the cycle variation was carried out. As the engine speed/engine load is 2000 rpm/4bar, the cycle variation increases from 0.72% to 2.42% with the start of injection changing from −280°CA to −180°CA; then rapidly decreases to 0.99%, and then increases to 2.26% with the start of injection changing from −180°CA to −100°CA. The experimental results show that SOI could cause significant influence on cycle variation because of intake valve closing and shortening mixing time, and both the process of intake valve closing and lagging the SOI could cause the cycle variation to increase. The SOI remarkably affects the cycle variation at low engine load/equivalence ratio and high engine speed. This study lays the foundation for the follow-up research of hydrogen engine performance matching of the cycle variation.