基于混合控制低温燃烧，以降低柴油机排放和提高有效热效率为目的，在1台单缸柴油机上评价了两种混合控制低温燃烧策略。首先通过常规方式引入大量冷EGR降低缸内燃烧温度，其次采用Miller循环，通过推迟进气门关闭时刻减小有效压缩比，并耦合增压压力实现低温燃烧。研究发现，大EGR率和Miller循环均可同时降低NO_x和Soot排放，但二者作用机理并不相同：大EGR率通过降低燃烧温度避开NO_x和Soot生成区域，而Miller循环的燃烧温度降低幅度有限，所以NO_x降低程度较小，但局部当量比大幅降低使Soot排放显著降低。大EGR率以牺牲效率为代价，有效热效率（BTE）由净指示热效率（ITEg）和燃烧效率决定，Miller循环燃烧效率较高，具有更优的排放和效率折中，并存在一个最小有效压缩比，有效压缩比过低对进气压力的要求更高，BTE由ITEg和泵气损失决定。

Two strategies were evaluated on a single-cylinder diesel engine to reduce the emissions and improve the thermal efficiency based on the mixing-controlled LTC. The high rates of cooled EGR were first introduced to decrease the in-cylinder combustion temperature by the traditional method. Retarding the intake valve closing angle was used to reduce the effective compression ratio by using Miller cycle. Low-temperature combustion was realized by further coupling with boost pressure. The results show that both high EGR rate and Miller cycle can reduce NO_x and soot emissions based on different mechanisms. High EGR rate decreases the combustion temperature to reduce NO_x and soot emissions. Miller cycle has little influence on the decrease of combustion temperature and hence the reduction of NO_x emission is less. But the large decrease of local equivalent ratio will reduce soot emission obviously. High EGR rate implies a sacrifice of combustion efficiency, the brake thermal efficiency (BTE) is determined by the ITEg and combustion efficiency. Miller cycle with a higher combustion efficiency has a good compromise between emission and efficiency and the smallest effective compression ratio as well. The too low effective compression ratio will lead to the high requirement of intake pressure, and BTE is determined by ITEg and pumping loss.