水雾对火箭射流压力脉动抑制效果的数值研究

Numerical Investigation on Pressure Pulsation Suppressionof Rocket Jet Flow by Water Mist

关键词:  水雾  火箭  压力脉动  燃气流场  数值计算  抑制

Key words:  Water mist  Rocket  Pressure pulsation  Jet flow field  Numerical computation  Suppression

摘要:

为研究水雾对火箭射流压力脉动的抑制效果，以火箭在地下有限空间内发射为研究对象，采用平面波跨介质传播理论分析了水雾对压力脉动的抑制机理和效果。采用计算流体力学方法，考虑水滴破碎和蒸发作用，详细揭示了射流压力脉动与水雾的作用过程，并研究了水雾参数对压力脉动抑制效果的影响规律。数值结果表明，不同水滴直径的水雾对压力脉动有2种不同的抑制机理，当水雾的水滴直径大于0.7mm时，水雾对压力脉动的抑制效率随水滴直径增大而降低；当水滴直径小于0.7mm时，抑制效率受水滴直径变化的影响可以忽略；临界直径的值是压力脉动时间特性的函数。此外，水雾的浓度越高，水雾对射流压力脉动的抑制效果越好；压力脉动抑制效果与水雾层厚度之间呈类似抛物线关系，当水雾层厚度为0.3m时，传递系数不大于0.43，水雾对射流压力脉动有最优的抑制效果。

Abstract:

In order to research on pressure pulsation suspension of rocket jet flow by water mist， the rocket launch in confined underground space is taken as the research object. The theory of plane waves propagation in different medium is applied to expose the suppression mechanism and performance for the pressure pulsation suppression of rocket jet flow by water mist. And， a rocket launch jet flow field’s numerical model is proposed to characterize basic features of the rocket motor exhaust plume discharging in silo. Water droplets breakup and evaporation are also taken into account in the numerical simulations. Then， the computational fluid dynamics method is used to solve the numerical model and reveal the interaction between pressure pulsation and water mist. Meanwhile， influences of water mist parameters on the suppression effect are studied. Numerical results demonstrate that there are two different interaction mechanisms between water droplet and pressure pulsation which are closely related to droplet diameter. If water droplet diameter is larger than 0.7mm， the suppression efficiencies decrease with droplet diameter increasing. If water droplet diameter is smaller than 0.7mm， influence of droplet diameter variation on suppression efficiencies can be ignored. And， the critical diameter between different mechanism is function of pressure pulsation time characteristic. Furthermore， the mitigation efficiency increases as the water droplets volume fraction increases. In addition， there is parabola relationship between mitigation efficiency and mist layer thickness. The transmission coefficient is not bigger than 0.43 when mist layer thickness is 0.3m. And， the water mist layer provides the best suppression performance.