喷孔直径对重型柴油机燃烧和排放的影响

Effect of Nozzle Diameter on Combustion and Emissions of a Heavy Duty Diesel Engine

为改善重型柴油机大负荷工况下的燃油经济性,通过一台高强化重型柴油单缸机研究了喷油器不同喷孔直径对燃烧和排放的影响,结果表明:随喷孔直径增大(从0.169 mm增大至0.218 mm),最高爆发压力和瞬时放热率峰值均有升高,燃烧持续期缩短,指示热效率提高.喷油器喷孔直径为0.203 mm时的NOx排放最高,而碳烟排放则随着喷孔直径增大而上升.对于大孔径(0.218 mm)喷油器,改善喷雾的雾化性能是提升燃烧速率的关键,通过与高增压和高轨压的协同作用,可进一步提高放热速率和燃烧等容度.模拟结果中,增大喷孔直径会增加单位时间内的气相燃油生成量,且在活塞凹坑底部易产生较大尺度的涡团,利于物质输运,促进混合.

In order to improve the fuel economy of a heavy duty diesel engine under heavy load conditions,the ef-fect of nozzle diameter on combustion and emissions were studied on a single cylinder diesel engine with high intensification.The result shows that with the increase of nozzle diameter from 0.169 mm to 0.218mm,the maximum cylinder pressure and the peak of heat release rate increase,the combustion duration shortens,and the indicated thermal efficiency increases.The 0.203 mm injector has the highest NOx emissions,while the soot emissions increase with the increase of the nozzle diameter.For the largest orifice injector of 0.218mm,improving the atomization performance of the spray is the key to improve the combustion rate.The heat release rate of combustion and combustion isovolumetric degree can be further increased by synergizing with high boost pressure and high rail pressure.The numerical simulation results show that with the increase of nozzle diameter,the amount of gas-phase fuel generated per unit time increases,and large-scale vortices are easily generated at the bottom of the piston pit,which is conducive to air/fuel transport and mixing.