废气再循环和进气加热实现汽油机HCCI燃烧的性能对比

摘要

废气再循环和进气加热是实现汽油机HCCI燃烧的两种不同方式,其对HCCI燃烧性能的影响也不同,为此,在同一台汽油机上分别采用废气再循环和进气加热实现HCCI燃烧,并分析了其在HCCI燃烧性能上存在差异的机理.试验结果表明,相对于进气加热,废气再循环的工质比热容高,但由于稀释比较小,使得其工质总热容反而低,从而缸内燃烧温度高.废气再循环HCCI燃烧的未燃HC排放比进气加热的排放值低41％ ～ 59％；NOx排放是后者的2 ～ 20倍；而CO排放与负荷有关；其燃烧效率比迸气加热HCCI的值高0.8％～14％.然而,由于进气加热的PMEP低,缸内工质比热比大,传热损失小,最终使得进气加热HCCI燃烧的ISFC比废气再循环HCCI燃烧的值低6.6％～16.4％.%Exhaust gas recirculation(EGR)and intake heating are two different approaches for gasoline engine to achieving homogeneous charge compression ignition (HCCI) combustion and have different performances on HCCI combustion. Therefore, experiments were carried out on a single-cylinder gasoline engine with HCCI combustion using EGR and intake heating, respectively, to study the different performance mechanisms of the two approaches on HCCI combustion. The experimental results show that, compared with the HCCI combustion with intake heating, the specific heat of charge with EGR is higher. However, lower dilution ratio leads to lower total specific heat of charge , which results in higher in-cylinder combustion temperature. The unburned hydrocarbons (UHC)emission generated by HCCI combustion with EGR is 41%?9% lower than that by HCCI combustion using intake heating. NO, emission of the former is 2?0 times that of the latter, and the CO emission depends on the IMEP. The combustion efficiency of HCCI combustion with EGR is 0.8%?4% higher than that of HCCI combustion with intake heating. However, due to lower pumping mean effective pressure, higher specific heat ratio of charge and lower heat transfer loss, the fuel consumption of HCCI combustion with intake heating is 6.696?6.4% lower than that with EGR.