非线性谐波法在叶轮机械非定常计算中的应用

Application of Non-Linear Harmonic in Turbomarchinery 3D Flow Field Unsteady Simulation

关键词:  非定常，非线性谐波法，谐波阶次，叶轮机械

Key words:  Unsteady  Nonlinear harmonic method  Harmonic order  Turbomachinery

摘要:

非线性谐波法(NLH)进行叶轮机械非定常计算，具有占用资源少、计算时间短等优点，本文探讨了该方法在叶轮机械三维瞬态非定常流场计算中的应用。采用非线性谐波法和传统双时间步法对跨风速风扇和液力涡轮分别进行非定常计算分析。分析表明，在相同计算机硬件条件下，两种方法达到相同的计算精度，非线性谐波法可节省40%的计算时间。探讨了关键参数谐波阶次对计算精度的影响，结果表明，对于高雷诺数进口条件下的跨风速风扇采用三阶谐波逼近即可达到与传统双时间步法相当的计算精度；对于低雷诺数进口条件下的不可压缩液力涡轮，采用二阶谐波逼近即可达到与双时间步法相当的计算精度。

Abstract:

Nonlinear harmonic method has the advantages of less occupied resource，and shorter computing time in turbomachinery unsteady simulation. The application of nonlinear harmonic method in turbomachinery 3D transient flow field simulation was investigated. Two different kinds of turbomachinery，including two-stage axial compressor and one-stage axial turbine，were simulated with both nonlinear harmonic method and dual time stepping method. Results show that，in the same computer hardware and the same precision condition，nonlinear harmonic method could save computation time by 40%. The effects of the number of harmonics were also discussed. Results also show that the same accuracy within dual time stepping method could be achieved by third harmonic approximation，for compressible compressor with high Reynolds numbers inlet conditions. For incompressible flow turbine with low Reynolds numbers inlet conditions，the same accuracy could be achieved by second harmonic approximation.