结合热力学第一定律和第二定律深入分析了EGR对增压直喷汽油机在全负荷和中等负荷时热效率的影响机理.全负荷时,EGR的引入可以消除缸内混合气加浓,增加工质比热容比,改善燃烧放热等容度,减少传热损失,从而提高热效率,但其燃烧不可逆损失增加；中等负荷时,EGR的引入除了上述几个因素的改善外,还减少了进排气行程的泵气损失,从而较显著地提高了热效率.尽管EGR使得燃烧过程中产生的不可逆损失增加,但在全负荷和中等负荷时汽油机的有效效率均得到改善.%The effect of EGR on thermal efficiency in full load and medium load of boosted spark-ignition direct-injection (SIDI) gasoline engine was analyzed by combining the first and second laws of thermodynamics.In full load,the introduction of EGR eased the enrichment of fuel,increased the specific heat ratio,improved the heat release of constant volume and decreased the heat transfer loss,and hence the heat efficiency increased,but the irreversible loss of combustion increased.In medium load,the introduction of EGR also decreased the pump loss besides the improvements of full load and hence the heat efficiency obviously improved.Although the irreversible loss during the combustion process caused by EGR increased,the effective thermal efficiency in full load and medium load both improved.
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