中文摘要：

将包括完整发动机循环的三维计算流体力学（CFD）模型与详细反应动力学机理耦合，研究进气门晚关（LIVC）对柴油均质压燃（HCCI）发动机燃烧和排放的影响。结果发现，使用LIVC可降低有效压缩比，进而有效地控制着火点并显著降低氮氧化物（NOx）排放，由于降低了燃烧温度和缸内缺少氧气，会增加碳烟、碳氢（HC）和一氧化碳（CO）的排放。为揭示LIVC策略降低柴油HCCI发动机排放的潜力，进一步通过在调整进气门关闭定时的情况下，研究了进气压力、废气再循环（EGR）率和喷油定时（SOI）的影响。计算表明，通过LIVC和增加进气压力可实现NOx的超低排放，保持较低的碳烟、HC和CO排放，但在运行过程中需要足够的EGR量和优化的喷油定时加以辅助。在部分负荷下，通过使用260°CA的进气门关闭时刻、0．18MPa的进气压力、50％的EGR量和20°CA BTDC的喷油定时，可避免NOx和碳烟的排放。

英文摘要：

A full-cycle three-dimensional computational fluid dynamics （CFD） model coupled with detailed chemical kinetics was developed to investigate the effect of late intake valve closing （IVC） on combustion and emission characteristics in a diesel homogeneous charge compression ignition （HCCI） engine. Utilization of late IVC provides effective ignition timing controlling and significant reduction of nitrogen oxides （NOx） by decreasing effective compression ratio, but it increases soot, hydrocarbon （HC） and carbon monoxide （CO） emissions due to low combustion temperature and lack of oxygen. Parametric studies by varying intake pressure, exhaust gas recirculation （EGR） rate and start of injection （SOl） timing by changing IVC timing were conducted to explore the potential of late IVC on emission reduction of diesel HCCI engines. Results show that, late IVC and boosting intake pressure realize ultra-low NOx while maintain low soot, HC and CO emissions if sufficient EGR and optimized SOI timing are set. By retarding IVC timing to 260°CA and employing 0.18 MPa intake pressure, 50%EGR and 20°CA BTDC SO1, both NOx and soot formation regions can be suppressed under partial engine load.