不同氢气喷孔直径对汽油掺氢X型转子发动机性能及污染物排放的影响

Aiming at the issue that the combustion of gasoline in high-efficiency X-type rotary engine is insufficient, a method of cylinder hydrogen direct injection is proposed to improve the combustion efficiency and thermodynamic performance of the engine. The three-dimensional CFD numerical model of X-type rotary engine is established and validated via the experimental data of cylinder pressure, heat release rate and power. Under the same hydrogen injection total mass, pressure, and start time, the impact of hydrogen injection nozzle diameter on the in-cylindcr flow, combustion, thermodynamic performance and pollutant emission of the engine when hydrogen in-cylindcr direct injection and premixed gasoline are adopted. The advantages of hydrogen in- cylinder direct injection method are revealed by comparing with pure gasoline premixed engine. The results show that when the hydrogen injection nozzle diameter is small (2 mm), the flame propagation is more uniform, and relatively large symmetrical flames are found in the slits of both sides of combustion chamber, making the combustion more sufficient. The maximum indicated thermal efficiency of corresponding engine reaches of 37. 07%, which is 10. 23% and 7. 85% higher than that of the engine without hydrogen injection and with a large hydrogen injection nozzle diameter (4 mm), respectively. In addition, compared with the large hydrogen injection nozzle diameter, although the NO_xemissions increase by 21. 12% when the hydrogen injection nozzle with small diameter is adopted, the HC and soot emissions decrease by 79. 08% and 2. 17%, respectively. Thus, the small hydrogen injection nozzle diameter (2 mm) is the optimal hydrogen injection strategy. This study provides guidelines for the design and optimization of the hydrogen injection strategy of X-type rotary engine.