基于Gama-Theta转捩模型的气冷涡轮气热耦合研究

Conjugate Heat Transfer Simulation of Air-Cooled Turbine

关键词:  非结构化网格  直接耦合  气冷涡轮  气热耦合  转捩

Key words:  Unstructured mesh  Direct-coupled method  Air-cooled turbine  Conjugate heat transfer  Transition

摘要:

基于非结构化混合网格，采用有限体积法求解了N-S方程，对流项格式为AUSM+，梯度的求解方法为加权最小二乘法，求解器采用LUSGS隐式求解方法，并进行了预处理和网格重排序。与导热方程耦合，搭建了气热耦合平台，采用直接耦合方法，交界面互相传递温度，并且采用能保证通量守恒的面积加权类的插值方式实现数据传递，将[γ-Reθt]两方程转捩模型应用在流场程序中。通过MARKII叶片4311和5411工况的实验结果进行了验证，结果表明采用转捩模型对压力分布的影响不大，与实验值吻合较好，通过间歇因子的分布可以看出，[γ-Reθt]模型成功地预测了从层流到湍流的转捩过程，在层流区采用[γ-Reθt]模型计算的涡粘系数与真实流动情况更加吻合，由于涡粘系数对传热的影响很大，从而有效地提高了边界层的层流区和转捩区的传热计算的精度，得到的温度和换热系数与实验值吻合更好，但是该模型是和SST模型耦合在一起的，由于SST模型的局限性，所以对激波和边界层干扰区域的模拟产生了7%左右的温度误差。

Abstract:

The finite volume method was adopted to solve the N-S equation based on unstructured meshes. The scheme of convective flux was AUSM+，and the method for calculating gradient was weighted least squares method. The LUSGS implicit method was applied with precondition and reordering of grids. The conjugate heat transfer(CHT)simulation platform，which coupled with the heat conduction equation，was established. The direct-coupled method was adopted，and the temperature was transmitted between interfaces by the interpolation method，which can maintain the conservation of flux. The[γ-Reθt]transition model was used in the calculation of the flow field in order to study the impact of transition on the CHT. The numerical results were compared with experimental data of the 5411 and the 4311 experimental condition of MARKII blade. It indicates that the transition model has little effect on pressure distribution and agrees well with the experimental ones. It can be seen from the distribution of intermittency that [γ-Reθt]transition model successfully predicts transition process from laminar to turbulent flow. The eddy viscosity calculated in laminar region agrees better with the real flow. Because the eddy viscosity has great influence on heat transfer simulation，the[γ-Reθt] transition model effectively improves the accuracy of heat transfer simulation in laminar and transition area，and the temperature and heat transfer coefficient agree better with the experimental results. However，because the model is coupled with the SST model，due to limitations of the model SST，a greater simulation error was produced in the shock and boundary layer interaction region.