利用气体模拟技术研究直喷式柴油机的燃油喷雾特性

A Study of the Fuel Spray Characteristics in a D.I. Diesel Engine by Gaseous Jet Simulation

本文利用气体模拟技术研究了直喷式柴油机的燃油喷雾特性。研究结果表明,瞬态燃油喷雾的前端存在一个强烈的紊流混合前锋区,其后是浓度分布处于平衡状态的雾锥。雾锥轴线上的浓度随贯穿距离的增加而线性衰减;雾锥的径向浓度分布与剖面至喷孔的距离有关,对于充分发展的雾锥,径向浓度不同于稳定自由射流的浓度分布,而服从指数型分布规律。当喷雾与壁面撞击时,可观察到紊流混合过程出现一个从强化到减弱的有利于混合的过渡过程,但过量壁喷会在壁面上出现浓混合气层的堆积,恶化混合。

A study of the fuel spray characteristics in a D.I. diesel engine was conducted by gaseous jet simulation. The experimental results reveal that a pulsed spray is headed by a highly turbulent mixing front zone. Behind the front zone, a steady spray cone is formed where the fuel concentration is in equilibrium. As the spray impinges on wall, a transient process of air/fuel mixing near the wall is observed. During this process, the measured concentration fluctuation near the wall is increased rapidly and then reduced after the transient process, A stable layer of rich mixture is formed on the wall when an exessive amount of fuel is injected onto the wall, the air/fuel mixing process is deteriorated.