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带热传导效应平面涡轮叶栅流动直接数值模拟

DIRECT NUMERICAL SIMULATION OF TURBINE CASCADE FLOW WITH HEAT TRANSFER EFFECTS

  • 摘要: 低雷诺数流动对高空动力装置, 特别是涡轮部件的性能产生重要的影响. 本文采用具有7阶精度的差分格式, 通过直接求解二维瞬态可压缩Navier-Stokes方程组, 对雷诺数为241 800 (基于叶片弦长)时的叶片表面带有热传导效应的平面涡轮叶栅流动进行了二维直接数值模拟, 对低雷诺数平面涡轮叶栅流动的非定常流动现象作了初步的探索.数值结果表明:在叶栅通道入口处, 流场的非定常性很弱;在叶栅尾缘处, 具有正负涡量的尾涡交替地从压力面和吸力面上脱落;周期性的涡脱落使得叶栅通道内和尾迹区的总压发生(准)周期的变化, 并且, 尾迹区总压变化主频率是通道内总压变化主频率的2倍;在时均流场中, 叶片表面压力的分布与实验值吻合良好, 表征热传导效应的斯坦顿数除湍流区外与实验值基本吻合;尾迹区速度脉动的2阶统计量与圆柱绕流尾迹区速度脉动2阶统计量具有基本相似的分布特征.

     

    Abstract: Low-Reynolds number flow has a significant effect on the performance of high-altitude aircraft engines, especially the turbine parts. In this paper, the low-Reynolds number flow around a turbine cascade was numerically simulated by directly solving the two-dimensional compressible Navier-Stokes equations using a finite difference scheme with 7th-order. The flow Reynolds number is 241800 based on the blade chord, and there exists thermal conduction on the turbine blade surfaces. In the time-averaged flowfield, the pressure on the blade surface agrees well with the experimental data. So does the distribution of Stanton number, except in the turbulence region on the suction surface. For the instantaneous flow, the unsteady flow near the entrance of cascade passage is very weak. But, at the trailing edge of the blade, there exists periodical vortex-shedding on both the pressure and suction surfaces. The vortex-shedding makes the total pressure in the cascade passage and the wake varies periodically, and the main frequency in the wake is double of that in the cascade channel. Besides, the distribution of the second order statistic of pulse velocity in the wake is similar to that of the flow around the cylinder.

     

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