可变涡流直喷汽油机流动及燃油喷射的数值模拟

Numerical Simulation of Flow and Spray Characteristics for a Direct Injection Engine with Variable Tumble Intake Port

建立了带可变涡流进气道的缸内直喷汽油机的三维数值模型,利用数值模拟方法分析了汽油机在2000r/min全负荷工况下,涡流调节阀开启和关闭时进气、喷雾及混合气形成过程。结果表明:低转速时,通过涡流阀开启和关闭可以改变进气门周围进气流动速度分布,进而调节缸内滚流强度;涡流阀关闭时,缸内滚流强度明显提高,是相同气门升程涡流调节阀开启时的4～6倍;较大的滚流强度加快了缸内燃油雾化速度,有助于在点火时刻形成浓度均匀一致的混合气。

A three--dimensional moving mesh with variable tumble intake ports used for a gasoline direct injection（GDI） engine was established. With numerical simulation, the processes of intake, spray, mixture formation at the speed of 2000r/min full load were simulated and analyzed at two cases of opening and closing the tumble control valve（TCV）. The simulation results show that： under low speed conditions, the flow rate around the intake valves at two cases is greatly different; tumble intensity in--cylinder is changed. When TCV is closed, tumble intensity in--cylinder is greatly enhanced, the tumble ratio is 446 times that when TCV is open. The effects of increased tumble intensity due to TCV close were considerable in promoting the evaporation of the droplets, and homogeneous charge mixture was achieved at start of ignition.