排气道EGR策略下CAI燃烧缸内工质混合状态的模拟研究

利用三维设计软件Catia以及三维流体计算软件Fire建立了CAI发动机模型,着重研究了排气道EGR策略下压缩行程缸内工质的混合状态。结果表明,在压缩行程初期缸内工质呈如下混合状态:混合工质处于弱流动阶段,速度场分布均匀;缸内混合工质湍流动能小;缸内汽油浓度场分布不均,进气门一侧浓度大,排气门一侧浓度小;缸内工质的温度场与浓度场分布相反,进气门一侧缸内温度低,排气门一侧缸内温度高。随着活塞的上行,缸内混合工质流速和湍流动能先增大后减小,混合工质的浓度场和温度场越来越均匀。

Simulation of In-cylinder Charge Mixing State for CAI Based on Exhaust Port EGR Strategy

With the CATIA and FIRE software,the controlled auto-ignition model was established.Based on the exhaust port EGR strategy,the charge mixing state at compression stroke was studied.The results show that the velocity field of mixing charge is uniform when the velocity of mixing charge is small.The in-cylinder turbulent momentum is low.The in-cylinder gasoline density is not uniform,which is high near the intake port and low near the exhaust port.The temperate field is just opposite,which is low near the intake port and high near the exhaust port.With the ascending of piston,the velocity and turbulent momentum first increase and then decrease,and the temperature field and density field become more and more uniform.