在发动机燃用稀薄混合气时，喷油定时对排放和经济性的影响较为明显。

Compared with stoichiometric mixture operation, fuel economy and emissions are remarkably influenced by injection timing when lean mixture is applied.

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结果表明，该直喷汽油机具有较强的滚流性能，有利于分层混合气的形成和稀薄燃烧。

The results show that a rather strong tumble motion exists in this GDI engine, which is beneficial to the formation of stratified mixture and lean combustion.

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模拟计算表明，利用早喷可以形成稀薄准均质混合气；燃烧室形状影响混合气浓度场和温度场。

The results show that the lean quasi-homogeneous mixtures can be formed by early-injection, and the shape of combustion chamber has an obvious effect on density and temperature fields of mixture.

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