Experimental and numerical study on the effect of dimensionless parameters on the characteristics of droplet atomization caused by periodic inertial force

摘要

Fuel atomization will seriously affect the combustion and emission characteristics of IC engine. It is important to study the atomization characteristics of single droplet under dynamic inertial force for improving the high precision secondary atomization model in cylinder. Firstly, the process of droplet atomization under sinusoidal inertial force was studied experimentally. Then, the effects of dimensionless parameters, including Bond number (Bo), gas-liquid density ratio (rho(G/L)), gas-liquid viscous ratio (mu(G/L)), Weber number (We) and Reynolds number (Re), on the average wavelength and atomization time of droplet surface wave were numerically investigated. The results show that with the development of time, the droplet surface appears zonal standing wave, radial standing wave and volcanic standing wave in turn. When the droplet atomizes, the sub droplet sprays first from the top of the droplet, and the atomization intensity at the top is stronger than that at both sides. Bo, rho(G/L) and Re have little influence on the average wavelength of droplet surface wave, mu(G/L )has no effect, while We has a great influence. As Bo, We and Re increase, the atomization time decreases rapidly at first, and then converges. When We > 10(4) or Re > 10(4), the effect of surface tension and viscous force on atomization time can be neglected. As rho(G/L) increases, the atomization time first remains unchanged and then increases rapidly. When rho(G/L) < 0.1, its influence can be neglected. mu(G/L) has no effect on the atomization time. Furthermore, according to the variation of the average wavelength and We number, the dimensionless form of the empirical formula for the average diameter of droplets is obtained: d(m)*= (1.0 +/- 0.1).We(-)(1/3). Finally, the critical conditions of droplet atomization are determined based on the actual atomization time of IC engine.