燃烧室EGR策略下汽油CAI燃烧试验Ⅱ：CAI燃烧区域优化与控制

摘要

Controlled auto-ignition（CAI）was realized with combustion chamber EGR strategy in a single-cylinder testing system equipped with electro-hydraulic variable valve-train system.Testing results show that,with intake valve opening timing（IVO）between-38°CA ATDC and 167°CA ATDC,and exhaust valve closing timing（EVC）between 68oCA BTDC and 118oCA BTDC,a stable CAI combustion is real-ized at engine speed of 1 000 r/min.In this valve timing region,the negative valve overlap angle（NVO） can vary between 35°CA and 280°CA,EGR rate varies between 26% and 89%,and BMEP ranges be-tween 0.177 MPa and 0.495 MPa.However,knocking appears about half of the region,and cold EGR needs to be introduced to suppress the knocking and reduce NOx emission.To realize the normal CAI com-bustion,valve timing needs to be controlled to ensure EGR rate larger than 40%.The BMEP range of normal CAI combustion is 0.177,MPa to 0.45,MPa.EVC timing region can be extended.%在装备电控液压驱动可变气门机构的单缸试验发动机上,通过燃烧室EGR策略将废气截留在缸内,在关闭点火系统后发动机仍然稳定工作则实现了CAI燃烧.研究结果表明,在1,000,r/min、过量空气系数为1工况下,在IVO定时为-38～167°CA,ATDC、EVC定时为68～118°CA BTDC可以实现稳定的CAI燃烧.在该区域内,可实现35～280°CA的负气门重叠角,EGR率变化为26%～89%,BMEP为0.177～0.495,MPa.但该区域中有一半的区域存在爆燃现象,需要导入外部EGR用于控制燃烧以