湍流扰动对液滴破碎的影响及模拟方法研究

摘要

为考虑射流内部湍流扰动对雾化的影响,本文将喷嘴内部湍流扰动量用湍流长度和时间尺度来表示,并以权重的形式加入初次破碎模型中.对比分析了单液滴表面不稳定波和湍流扰动对液滴破碎的影响.计算结果表明:湍流扰动随液滴运动时间的增加对破碎的影响逐渐减小,不稳定波的影响比重逐渐增大;喷嘴内流速越大,湍流扰动量越强,影响的时间越久.对本文提出的破碎模型进行了验证,计算结果表明:湍流扰动会导致液滴的索特尔平均直径(SMD)减小4%左右;随入射压力升高,湍流扰动对贯穿距的影响逐渐增大;虽然二次破碎发生在距离喷嘴较远处,但初始湍流值的大小,还是能影响到二次破碎后液滴大小和速度.%In this paper,the effect of turbulence perturbation inside a jet during atomization was investigated.The turbulence inside the nozzle was characterized by the turbulence characteristics of length and time scale, and this was then added into a primary breakup model in the form of a weighted coefficient.First,the effects of an unstable wave and turbulence perturbation on single droplet breakup were analyzed.The results show that the effect of turbu-lence on droplet breakup gradually reduced with increasing time,while the influence of the unstable wave increased step by step.In addition,a larger jet rate resulted in larger turbulence perturbation energy and a longer influencing time.The model was then validated using experimental data.The predictions showed that the turbulence term can decrease the Sauter mean diameter(SMD)by about 4%,and with increasing injection pressure the effect of turbu-lence perturbation on breakup length increases.Although secondary breakup occurred far from the nozzle,the ini-tial value of the turbulence term still determined the size and velocity of the secondary droplet.