低雷诺数涡轮叶栅损失的实验与数值模拟研究

Experimental and Numerical Investigation of Loss inTurbine Cascade with Low Reynolds Number

发动机涡轮部件在高空低速飞行条件下工作雷诺数降低 ,其损失显著增大、效率显著降低。本研究的目的是应用实验分析与数值模拟相结合的方法 ,深入认识高空低雷诺数条件下涡轮流动损失的特征和规律 ,数值计算是基于 Jameson中心差分格式和 Runge- Kutta时间推进的方法求解N- S方程完成 ,实验是在西北工业大学低速涡轮平面叶栅实验风洞进行。研究表明 ,随着雷诺数降低 ,涡轮叶栅流动损失增大 ,当雷诺数小于 40 0 0 0之后 ,涡轮叶栅流动损失呈明显增大的趋势。数值计算结果表明在低雷诺数条件下 ,涡轮叶栅吸力面后部流动产生了分离 ,这是流动损失增大的主要原因。

Low Reynolds number of turbine at high-altitude results in the notable drop of efficiency of turbine. Refs. 3, 4 and 5 gave experimental results of the aerodynamic performance of low-pressure turbine blade at low Reynolds number, but they did not give technical details. Our aim is to provide technical details, reveal the aerodynamic performance of low-pressure turbine blades at low Reynolds number, and also analyze theoretically the cause of the notable drop of turbine efficiency at low Reynolds number. In the investigation, experiments and numerical simulations have been performed to study the behavior of low-pressure turbine blade at several Reynolds numbers. The airfoil is the mid-span section of the low-pressure turbine rotor blade of a turbofan. The Reynolds number, based on the cascade outlet velocity and blade chord, was varied from 180000 to 10000. A finite volume scheme, based on the Jameson cell-centered method for solving the Reynolds averaged Navier-Stokes equations, was used. The experiment was conducted on the low-speed linear cascade tunnel at Northwestern Polytechnical University. Both the calculated and experimental results indicate increased cascade losses as the Reynolds number is reduced to the values associated with aircraft cruise conditions. And they also indicate that, when the Reynolds number is around 40000, the cascade losses begin to increase notably with decreasing Reynolds number. The calculated results indicate that the main cause of increased cascade losses is the flow separation on the suction side of turbine blade. Overall, the calculated aerodynamic and performance results exhibit fair agreement with experimental data.