超级爆震中火焰传播转爆轰现象的研究

Study of Deflagration-to-Detonation Transformation in Super Knock Combustion

模拟了一台高压缩比发动机下超级爆震的燃烧过程,分析火焰传播转爆轰(DDT)过程中压力如何影响末端混合气自燃,以及发生爆轰后的自维持过程.结果表明:压力是火焰传播作用于自燃并引发爆轰的主要原因,在短时间内经历压力波两次压缩,这不同于活塞压缩的原因在于这种压缩具有方向性.此外,维持爆轰需要压力波前新自燃点能量释放加速压力波,存在能量释放速度较压力波速度减小和增大两种自燃点状态,整个过程表现为:自燃释放压力波传递引发自燃状态1,压力波缓慢增强引发自燃状态2,自燃状态1下能量释放速度相对压力波速度减小,自燃状态2下能量释放速度相对压力波速度增大.

The process of super-knock combustion under a high compression ratio engine was conducted to analyze the role of pressure on end-gas auto-ignition during deflagration-to-detonation transformation(DDT),and the way of self-sustainment during developing detonation. Analysis result shows that pressure is the main connection between deflagration and spontaneous spots as well as the trigger of detonation. Furthermore,different from the piston compression,this compression of pressure is directional with experiencing two compression waves in a short period of time,which results in the onset of auto-ignition always near cylinder wall. In addition,maintaining the detonation requires the new spontaneous ignition in front of the pressure wave to accelerate pressure wave speed.These kind of new spontaneous ignition points have two different state,in which the energy release rate decreases and/or increases compared with the pressure wave speed. The whole process is as follows:spontaneous ignition develops into spontaneous ignition state 1 caused by pressure wave triggering,and the pressure wave slowly increases to initiate spontaneous ignition state 2. In state 1,the energy release velocity decreases relative to the pressure wave velocity,and in state 2,the energy release velocity increases relative to the pressure wave velocity.