低压EGR对增压直喷汽油机燃烧和油耗的影响

Influence of Low Pressure Exhaust Gas Recirculation on Combustion and Fuel Consumption of Turbocharged Direct Injection Gasoline Engine

摘要:

基于一台增压直喷米勒循环发动机，加装低压废气再循环系统（ LP-EGR），通过改变EGR率，研究LP-EGR对汽油机燃烧和油耗的影响。研究结果表明：在中小负荷工况下，EGR通过降低泵气损失来减小发动机油耗，油耗最高能减小8.41%；在大负荷工况下，EGR通过抑制爆震，修正点火时刻来降低油耗，油耗最高能减小5.67%；在近全负荷工况下，EGR通过降低排气温度，减少“过喷油”来降低油耗，油耗可减小20.4%。在燃烧方面，EGR会导致燃烧放缓，燃烧循环变动增大。随着EGR率的增大，着火时刻推迟，燃烧持续期增大，最大放热率降低，缸内最高温度降低；由于优化了点火提前角，缸内最高压力增大。

Abstract:

A turbocharged direct injection miller cycle engine was selected and a low pressure exhaust gas recirculation (LP-EGR) was installed. By changing the EGR rate, the influence of LP-EGR on the combustion and fuel consumption of gasoline engine was studied. The results show that: under medium and small load conditions, fuel consumption reduces with the decreasing of pumping loss by changing the EGR rate, and the fuel consumption can be reduced by up to 8.41%. Under heavy load conditions, fuel consumption reduces with the EGR by inhibiting knock and modifying ignition time, and the fuel consumption can be reduced by up to 5.67%. Under near full load conditions, fuel consumption reduces by lowering exhaust temperature and “over injection”, and fuel consumption can be reduced by 20.4%. With the EGR, combustion will slow down and coefficient of variation will increase. With the increasing of EGR rate, the ignition time delays and the combustion duration increases, but the maximum heat release rate and the maximum temperature in the cylinder decrease. Because of optimized ignition advance angle, the maximum pressure in cylinder increases.