热态壁面条件下的液膜冷却实验与仿真

Experimental and Numerical Study on Liquid Film Cooling Based on Heated Wall Conditions

为了获得射流流量和射流角对液膜铺展形态、壁面温度、液膜厚度的影响规律,设计并自主搭建了基于热态壁面条件的液膜冷却实验系统,开展了射流角为25°~45°、射流流量为200~400 mL·min^(-1)的液膜冷却实验研究。研究结果表明,随着入射角的增大,铺展长度减小,铺展宽度、扩张角增加;而在射流角一定时,随着液膜流量的增加,液膜铺展的长度、宽度和扩张角都有所增加。特别地,当射流角为25°、射流流量从300 mL·min^(-1)增加至400 mL·min^(-1)时,液膜长度最大增加量为20.94 mm,且增加射流流量能够有效降低壁面温度,当入射角为35°、液膜流量为300 mL·min^(-1)时,冷却前后壁面温度最大可降低141.81℃;液膜在壁面撞击点处有厚度峰值,且液膜流量越大峰值越高,当入射角为25°、流量为400 mL·min^(-1)时,最大峰值达679.32μm。采用流体体积法(VOF)构建了液膜冷却仿真模型,计算液膜的蒸发吸热、流动铺展过程,研究结果表明,射流流量为300 mL·min^(-1)时,液膜厚度模拟结果与实验结果最大偏差为7.9%,误差控制在工程应用允许的10%范围内,从而验证了VOF方法对射流撞壁形成液膜模拟的可行性。该研究可为液体火箭发动机液膜冷却技术提供一定的参考。

To understand the impact of jet flow rate and jet angle on liquid film spreading shape,wall temperature,and liquid film thickness,an independent liquid film cooling experiment system based on the heated wall conditions was designed and constructed.The experiment focused on liquid film cooling with a jet angle of 25°—45°and a jet flow rate of 200—400 mL·min^(-1) was conducted.The results show that increasing the jet angle leads to a decrease in spreading length,while spreading width and spreading angle increase.At a certain jet angle,liquid film spreading length,width and angle both increase with the growth of jet flow rate.Notably,when the jet angle is 25°,the jet flow rate increases from^(3)00 mL·min^(-1) to 400 mL·min^(-1),the maximum increase in the liquid film spreading length is 20.94 mm,and the increase in the jet flow rate can effectively reduce the wall temperature,when the jet angle is 35°and the jet flow rate is 300 mL·min^(-1),the maximum wall temperature can be reduced by 141.81℃after cooling;The liquid film has a peak thickness at the impingement point on the wall,and the higher the liquid film flow rate,the higher the peak value.For instance,when the incidence angle is 25°and the flow rate is 400 mL·min^(-1),the maximum peak value reaches 679.32μm.Additionally,a numerical model for liquid film cooling was established with the volume of fluid(VOF)method to calculate the evaporative heat absorption and flow spreading process of the liquid film.It is shown that when the jet flow rate is 300 mL·min^(-1),the maximum deviation between the simulation results of liquid film thickness and the experimental results is 7.9%,which is within the 10%error allowed for engineering applications,so as to verify the feasibility of the VOF method for the simulation of liquid film formation on jet impingement wall.The present research can provide significant reference for the liquid film cooling technology in liquid rocket engine.