Experimental research on the effect of shock wave on the evolution of high-pressure diesel spray

With the increase in the diesel injection pressure in modern diesel engines, the velocity of the diesel spray increases accordingly, and shock waves are induced when the spray is supersonic. To better understand the effect of shock waves on the spray development, the evolution of the high-pressure diesel spray and shock wave under different diesel injection pressures and ambient pressure has been investigated using the Schlieren imaging method. The results show that the shock wave affects the development of the spray and the mixing effect between the spray and surrounding air. The shock wave promotes development of the spray tip penetration and enhances the gas entrainment effect. However, the shock wave has an inhibitory effect on the spray development in the radial direction. In addition, the shock wave angle determines the range of influence on the ambient air, which affects atomization of the spray. The shock wave angle increases with the decrease in the spray front Mach number. An empirical correlation of the shock wave angle and spray front Mach number was proposed in this paper. The calculated results are in good agreement with the experimental data. In addition, a diagram of the shock wave generation and classification in a diesel engine is proposed.