高增压汽油机爆震的可视化研究

Optical Investigation of Knock in a Highly Boosted Gasoline Engine

基于一台单缸可视化汽油机研究了缸内的爆震现象。通过调节发动机运行参数及运用高速摄影技术,在更大的观测视角内拍摄了缸内不同强度爆震的火焰发展过程。试验所记录的图像信息结合缸内压力数据,为爆震形成的原因及强烈爆震中大幅度压力振荡波的产生提供了分析依据。研究发现:末端气体自燃引起的轻微爆震与强烈爆震的压力振荡和火焰图像明显不同;爆震自燃点的发展模式影响了缸内压力波的震动幅度,诱发强烈爆震的自燃点接近缸壁区域,但并非壁面点火。自燃点可形成自燃反应锋面的扩散,其传播路径受到主火焰与缸壁的限制。

Knocking was studied on a boosted single cylinder optical gasoline engine.The auto-ignition and extreme-knock development processes have been captured in a wider view with the adjustment of engine operating parameters and high-speed imaging technology.The combination of the recorded images and incylinder pressure data has provided the information for understanding the origins of the auto-ignition and the huge pressure oscillation magnitude of super-knock.The results show that the pressure oscillation and flame image of the light knock caused by the auto-ignition of unburned end gas are remarkably different from those of the extreme-knock caused by pre-ignition.The development modes of auto-ignition play an important role in the in-cylinder pressure oscillation magnitude,causing auto-ignition kernels to get close to but in direct contact with the cylinder walls,therefore surface ignition can be ruled out.Auto-ignition kernels can generateame propagation,which is restricted by the mainame and cylinder walls.