中文摘要：

本文采用大涡模拟方法详细解析了缸内直喷汽油机的进气和喷雾混合过程，研究了缸内亚格子尺度之上湍流脉动的随机特性及其对混合气形成的影响。在源代码KIVA—CHEMKIN平台下引入LES亚网格动能输运一方程模型，对缸内直喷汽油机进气过程和喷雾混合过程中缸内湍流流场进行了模拟，分析了湍流脉动对于发动机进气过程中缸内速度场、湍流黏度和湍流湍动能分布的影响。计算得到了缸内滚流比和平均湍动能随曲轴转角的变化，速度场和混合气的分布及其随时间的变化规律。相比雷诺平均方法，采用大涡模拟方法能够更合理反映出缸内滚流的瞬态变化，以及缸内直喷汽油喷雾混合气形成过程中的浓度分布特性。

英文摘要：

The intake and spray process in a gasoline direct injection （GDI） engine was simulated using LES to investigate the characteristics of the turbulent fluctuations above sub-grid length scale and its effects on the mixture formation. A k-equation SGS model was implemented in the KIVA-Chemkin code. The flow field in the combustion chamber during intake and spray process was simulated and the effects of turbulence fluctuations on velocity fields, turbulent viscosity and turbulent kinetic energy distribution were analyzed. The simulation results predict the variation of tumble ratio, averaged turbulence kinetic energy, velocity fields and mixture distribution with crank angles. Compared with RANS method, the LES method predicts better transient result of the tumble motion and mixture formation during spray process.