4气门直喷式汽油机缸内湍流场多周期循环变动的大涡模拟

应用大涡模拟方法对一台4气门直喷式汽油机(DISI)缸内冷态湍流流场进行了三维瞬态数值分析.通过连续13个工作循环的模拟计算,探索缸内湍流流动的循环变动特征与规律,并与PIV流场测试结果进行了对比.模拟相平均值及循环变动的均方值和试验值在总体上吻合得较好.计算结果表明:在进气过程前期缸内流场湍流脉动和循环变动都很强烈,两者强度为同一量级;但在后续过程中,湍流脉动不断衰减,其与循环变动的比值小于15%.大涡模拟方法不仅可以真实地反映内燃机循环过程中缸内气体流动的细节和规律,而且非常适合于研究内燃机的循环变动特性.

Large Eddy Simulation of In-Cylinder Turbulent Flows Cycle-to-Cycle Variation in a DISI Gasoline Engine

A large eddy simulation(LES)approach was used to study the in-cylinder turbulent flows of a direct injection gasoline engine.Characteristics of the flow field were analyzed with the emphasis on the cycle-to-cycle variation and compared with PIV measurement data.Computational results show that,at early stage of the intake stroke,both the turbulent fluctuations and cyclic variations are intensive and they are of the same magnitude order;while in the subsequent phases,the turbulent fluctuation decays continuously and its ratio to the cyclic variations is less than 15%.It is demonstrated that LES is not only able to describe more real details and rules of the highly transient turbulent flows,but also very suitable to study the cycle-to-cycle variation of engine in-cylinder flow.