某涡轮级三维流场非定常数值研究

Numerical investigation of 3-D unsteady flow in a gas turbine stage

关键词:  涡轮  非定常流  雷诺数  效率  间隙流动+  尾迹干涉+  压力脉动  数值仿真  计算气动声学+

Key words:  Turbine  Unsteady flow  Reynolds number  Efficiency  Leakage flow+  Stator-rotor interaction+  Pressure fluctuation  Numerical simulation  Computational aero-acoustic+

摘要:

基于耦合Lantry-Menter转捩模型的SST(Shear stress transport)湍流模型,对某涡轮级在3个雷诺数工况下的全三维流场分别进行了定常、非定常数值模拟,目的在于对比分析两种计算方法所得结果之间的差异。计算结果表明,进口雷诺数为4×104时和5×105时,定常与非定常计算的涡轮级效率的差异较大,最大相差0.6个百分点,而当雷诺数为8×104时,两者差异很小;非定常计算能够较好的模拟叶尖泄漏涡的发展过程、低雷诺数下上游尾迹与下游转子叶片吸力面分离边界层干涉诱导卷起涡的形成、输运及其所导致的叶片吸力面表面压力大幅波动等非定常流动现象。最后,给出了转子出口截面上周向与径向的非定常压力脉动的分布,为基于Lighthill声类比方法的计算气动声学研究奠定了基础。

Abstract:

Based on SST turbulence model coupled with Lantry-Menter transition model,the 3D flow under 3 different Reynolds number(Re) conditions in a turbine stage were computed using steady and unsteady numerical simulations,respectively,in order to give the differences of numerical simulation results between steady and unsteady calculation.The predicted results show that,the difference between the turbine stage efficiency obtained by steady and unsteady calculation is large both at Re=4×104 and Re=5×105,with the maximal efficiency difference to be 0.6% at Re=4×104,while that is quite small at Re=8×104.The unsteady calculation could reasonably simulate the development of leakage vertex,and the roll up vortex leading to large pressure fluctuation on the rotor blade suction surface caused by the interaction of upstream wake and downstream separated boundary layer on rotor blade at low Reynolds number.Additionally,the distribution of unsteady pressure fluctuation at the turbine stage outlet is presented,which provides an elementary work for computational aero-acoustic,based on the method of Lighthill sound analogy.