考虑转捩的气冷涡轮气热和热弹耦合计算

Conjugate heat transfer and thermal elastic coupling simulation of air cooledturbine by taking account of transition flows

摘要:

基于非结构化网格与Gama-Theta转捩模型,将全三维NS方程组与热传导方程进行耦合求解,采用直接耦合以及LUSGS隐式求解方法,开发了气热耦合求解系统. 采用能保证通量守恒的面积加权类的插值方式,保证精度,实现交界面处温度的准确传递. 对MARKII叶片5411工况进行气热耦合数值模拟,并与实验结果进行了对比验证. 开发了基于二次单元的热弹耦合求解器,通过导入气热耦合计算的边界温度实现对位移和热应力的有限元求解. 计算结果表明：采用转捩模型后计算的涡黏系数在压力面的大部分和吸力面转捩点之前的区域与真实流动吻合更好,由于涡黏系数主要通过影响温度扩散项系数影响边界层的传热,因此在该区域计算的温度与实验值误差更小,热传导计算的精度更高,同时静压的计算结果与实验值吻合较好；得到的MARKII叶片位移和热应力分布趋势比较合理,采用Gama-Theta转捩模型在提高热传导计算精度的同时,能够获得更加合理的热弹耦合计算结果.

Abstract:

The 3D NS equation solver was coupled with the heat conduction solver based on unstructured meshes and Gama-Theta transition model, the direct-coupled method and LUSGS implicit method were adopted, and the conjugate heat transfer (CHT) simulation platform was established. The temperature was transmitted between interfaces by the area-weighted interpolation method to ensure the flux conservation and accuracy. The CHT numerical results were compared with experimental data of the 5411 experimental condition of MARKII blade. The thermal-elastic coupling solver based on second unit was developed, and was compared with analytic solutions of the hollow cylinder. The boundary temperature calculated by CHT simulation was transmitted into the finite element solver to calculate the displacement and thermal stress. It is indicated from the result of CHT simulation that the eddy viscosity calculated in the most of pressure surface and the area before transition of the suction surface is better agreement with the real flow. Because the eddy viscosity has a great influence on heat transfer simulations by influencing the temperature diffusion coefficient, the accuracy of heat transfer calculations is higher, and the result of static pressure simulations of Gama-Theta and SST is in good agreement with experimental results. The thermal-elastic coupling simulation results show that the distribution trend of the thermal stress and displacement of MARKII blade is reasonable. The Gama-Theta model affects the accuracy of the thermal-elastic coupling simulation indirectly by affecting the CHT simulation, and makes the calculated thermal stress more reasonable.