【摘要】 为削弱泵气损失大、压缩比和工质比热容低等问题对汽油机常用部分负荷热效率的制约作用,基于配备进气道喷射(portfuelinjection,PFI)和缸内直喷(directinjection,DI)双喷系统的高压缩比米勒循环汽油机,系统探究了进气门早关策略对汽油机部分负荷热效率的影响规律.研究表明,应用米勒循环可有效调控歧管压力和泵气损失,通过综合优化气门相位、点火策略和节气门开度,相较于原机在2000 r/min,平均指示有效压力(IMEP)0.36 MPa工况指示热效率由32.4%提升至36.4%.针对高压缩比米勒循环小负荷燃烧稳定性恶化问题,提出采用分层火焰引燃(stratifiedflameignition,SFI)混合燃烧技术实现对燃烧放热过程的优化控制.研究表明,SFI燃烧可有效提高燃烧稳定性,平均指示有效压力的循环变动COVIMEP降幅达64.9%.而后期自燃的参与使得放热更为集中迅速,指示热效率由纯米勒循环下的36.4%提升至37.8%.更多还原

【Abstract】 To weaken the restrictive effect of the pumping loss, low compression ratio, and specific heat ratio on the thermal efficiency of gasoline engines,we investigated the influence of the Miller cycle on the partial-load thermal efficiency of a high-compression-ratio Miller-cycle gasoline engine equipped with a dual-injection system(i.e.,port fuel injection and direct injection). The results indicate that the Miller cycle can effectively regulate the manifold pressure and pumping loss. By optimizing the intake and exhaust valve phases,spark timing,and throttle opening,we increased the thermal efficiency from 32.4% to 36.4%,as compared to that of the original engine under 2 000 r/min,IMEP 0.36 MPa. Then,we realized stratified flame ignition(SFI) hybrid combustion to improve the combustion stability of the Miller cycle. The results indicate that SFI combustion can optimize the combustion process and effectively reduce the COVIMEP by 64.9%. Supported by late-stage auto-ignition,we achieved further improvement in the thermal efficiency from 36.4% to 37.8%.更多还原