氮液滴在气流中的破碎和碰撞模拟

To obtain the droplet behavior in spray cooling, a CFD model based on volume of fluid (VOF) approach is built to study the droplet collisions in the high-speed gas flow. The changes of droplet shape and gap pressure during the collision process are determined. Four different conditions are considered including the collisions between two droplets of same or different size, the center collision and eccentric collision. The impact of initial conditions on droplet morphology and the subsequent droplets size are discussed under various collision conditions. The results show that the breakup form mainly depends on the velocity of gas flow when droplets collide in high-speed gas flow. Collision parameter B mainly determines the direction of the elongated ligament. A gas gap is formed before droplets merge, and the pressure in the gap increases at the beginning of the collision and then decreases to gas pressure. Since the merged droplet can rotate during the eccentric collision process, pressure in the gas gap can release faster compared with center collision process. The droplet detachment is the poorest in the collisions between droplets of same size because the elongated ligament is in the direction of gas flow. Under this condition, there is no breakup of the liquid film, and therefore the droplet evaporation is worst.