内部EGR及增压拓展柴油HCCI燃烧负荷范围试验研究

在135单缸柴油机上对比了传统燃烧模式和HCCI燃烧模式的负荷特性,优化了HCCI燃烧模式的喷油始点,分析了内部EGR率及增压压力对HCCI燃烧负荷范围及排放的影响。试验结果表明:对于负气门重叠期喷油的HCCI燃烧模式,1 500r/min下,最佳喷油始点为370°BTDC,气门重叠期为-30°时既保证了较低的NOx排放,又可以获得较佳的负荷范围;提高增压压力不仅可以拓展HCCI燃烧的负荷上限,对负荷下限的燃烧稳定性也有利;将增压压力提高到0.18MPa时,负荷上限从传统燃烧的0.594MPa上升到0.723MPa,但负荷下限较传统燃烧模式要高,CO排放、烟度和燃油经济性都较差。

Experimental Investigation on Extending Load Range of Diesel HCCI Engine by Internal EGR and Boost

On a single cylinder diesel engine,the load characteristics between traditional combustion and HCCI combustion were compared,the injection timing of HCCI was optimized and the influences of internal EGR rate and boost pressure on HCCI combustion load range and emissions were analyzed.The results show that the best injection timing of HCCI mode with the negative valve overlap at 1 500 r/min is 370°BTDC.The-30° valve overlap can guarantee lower NOx emission and better load range.The increase of boost pressure extends the upper load limit of HCCI combustion and is beneficial to the combustion stability of lower load limit.Improving the boost pressure on 0.18 MPa,the upper load limit increases from 0.594 MPa to 0.723 MPa,but lower load limit also increases,which gives worse CO emission,smoke and fuel economy.