基于一台奥托循环增压发动机，通过采用高压缩比、进气门早关型线和高滚流进气道，再引入低压EGR，将其改造为混动专用发动机。通过试验研究米勒循环和低压EGR对混动专用发动机燃烧特性和经济性的影响。研究结果表明，在3 200 r/min的不同负荷工况点，与奥托循环相比，米勒循环点火提前角增大，且随负荷的增加，点火提前角的增幅先增加后减小；CA50减小至8°左右，燃烧持续期增大，排气温度增加；泵气损失减小，且随负荷的增加，降幅先增加后减小；米勒循环泵气损失的降低和CA50的减小使燃油消耗率降低了6.8%~11%，且将高效区域拓宽至全运行区的60%。在米勒循环发动机高效区工况引入低压EGR，随EGR率的增大，点火提前，CA50减小，燃烧持续期延长；EGR抑制爆震的作用使燃烧改善效果明显，在中负荷和大负荷工况获得的燃油消耗率最大降幅分别为5.6%和15.9%。
An Otto-cycle turbocharged PFI engine was selected to upgrade to a dedicated hybrid engine by increasing compression ratio, designing EIVC cam profile and high tumble intake port, and introducing low-pressure EGR. Experimental research was conducted to find the effects of Miller cycle and low-pressure EGR on combustion and economy performance of dedicated hybrid engine. The results show that Miller cycle has a larger ignition advance angle and the increase of ignition advance angle increases first and then decreases with the increase of load under different loads at 3 200 r/min. In addition, combustion duration and exhaust gas temperature increase when CA50 decreases to 8° approximately, and the PMEP reduces and the reduction increases at first and then decreases with the increase of load. With the decrease of PMEP and CA50, the BSFC reduces by 6.8%-11% and the region of high thermal efficiency extends to 60% of the whole working area. The ignition advance angle and combustion duration increase, and CA50 decreases with the increase of low-pressure EGR after introducing low-pressure EGR at high thermal efficiency working points of Miller cycle. The low-pressure EGR can improve combustion obviously and the biggest drops of BSFC are 5.6% and 15.9% at medium and high load respectively.
