Assessment of the application of oxygen enrichment in the hydrogen-fueled Wankel rotary engine

Hydrogen-fueled Wankel rotary engines (WREs) with excellent dynamic and emission characteristics have the potential to become a substitute for current fossil-fueled reciprocating piston engines. Oxygen enrichment can be employed to solve the lower power of hydrogen-fueled internal combustion engines, however, it has not been applied in hydrogen-fueled WRE at present. Hence, the goal of this work is to experimentally assess the application of oxygen enrichment in the hydrogen-fueled WRE. This work is conducted at 1500 r/min, wide-open throttle and 2.0 excess air ratio. The work found that within the test range, oxygen enrichment can effectively improve the brake torque of hydrogen-fueled WRE, however, penalize the brake thermal efficiency and NO emission. When the oxygen fraction in air increases from 21% to 29.1%, the brake torque is increased by about 45% while the brake thermal efficiency is lowered by about 8.5% and NO emission deteriorates by three orders of magnitude. Oxygen enrichment can accelerate flame development and propagation process. Besides, as the oxygen-enriched level is increased, abnormal combustion, including knock, backfire and pre-ignition, began to occur and affected the normal operation of hydrogen-fueled WRE. In general, compared with the high oxygenenriched level, which has severe penalties on performance except for power output, low oxygen-enriched level has higher application potential.

Automated summary

The aim of this study is to experimentally assess the application of oxygen enrichment in hydrogen-fueled Wankel rotary engines. The results show that oxygen enrichment can effectively improve the brake torque of the engine, but it also decreases the brake thermal efficiency and increases NO emissions. Additionally, abnormal combustion phenomena start to occur as the oxygen-enriched level increases, affecting the normal operation of the engine.