The throttle loss produced by the throttle of gasoline engine had a serious effect on turbocharged engine pumping loss especially at medium and low load.In order to solve the problem, the effects of waste gate opening on turbocharged GDI engine performance were researched at medium and low load.The results showed that the running of turbocharger at low load and small throttle opening would lead to too high exhaust back pressure influencing adversely on engine performance.However, the full opening of waste gate could reduce the exhaust back pressure so that the power and economy of engine improved by about 3%.Accordingly, the appropriate control of exhaust gas bypass valve could realize the switch between the naturally aspirated and turbocharged mode.%汽油机节气门产生的节流损失对增压发动机泵气损失的影响相当严重,尤其是在中小负荷时,针对这一问题采用试验的方法研究了中小负荷下旁通阀开度对增压直喷汽油机性能的影响.研究结果表明,在节气门开度较小的小负荷工况下,涡轮增压器不宜工作,否则排气背压过大,对发动机非常不利;而废气旁通阀全开可以减小排气背压,能使发动机的动力性和经济性提高3%左右.对废气旁通阀的合理控制可以实现发动机在自然吸气和涡轮增压两种模式之间的转换.
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