基于源项和贴体网格CFD的翼型冠涡轮叶栅气动性能预测对比

Comparison of Aerodynamic Performance Prediction of Winglet Shroud Turbine Cascades Based on Source Terms and Body-Fitted Grid CFD

翼型冠是控制涡轮叶片叶顶泄漏流动的一种叶顶结构。在翼型冠涡轮叶栅气动性能的数值模拟中,为降低计算成本,本文采用了一种基于源项的CFD技术。该方法无需构建翼型冠真实几何结构和生成贴体网格,只需在叶顶附近构建源项域并采用均匀网格进行离散,随后在网格点上定义材料多孔度,并在控制方程中引入与多孔度有关的源项函数。采用基于源项的数值模拟方法,首先计算了某一翼型冠涡轮平面叶栅的气动流场,并分析均匀网格尺寸和湍流模型方程源项对计算结果的影响。然后,在翼型冠源项基础上,分别增加了密封齿和叶顶喷气源项,以研究源项法在有密封齿和有叶顶喷气翼型冠叶栅性能计算中的准确性。通过与基于贴体网格(即真实结构)的数值模拟结果相对比,发现源项法计算能够较准确地评估翼型冠、密封齿和叶顶喷气对涡轮叶栅气动性能的影响。此外,降低均匀网格尺寸能提高源项法的可靠性。研究有助于发展用于模拟包含任意复杂结构流动问题的计算方法,能为基于源项法的翼型冠叶顶结构优化提供快速准确的数值模拟工具。

Winglet Shroud is a kind of tip structure to control leakage flow of turbine blade tip. In order to reduce the computational cost, a CFD technology based on source terms is adopted in the numerical simulation of aerodynamic performance of winglet shroud turbine cascade. The method does not need to construct the real geometry of winglet shroud,and generate body-fitted grids, but only needs to construct source terms domains near the blade tip and use uniform grids for discretization, then defines the porosity of the material on the grid points, and introduces the source terms function related to the porosity into the governing equation. Numerical simulation method based on source terms is adopted to calculate the aerodynamic flow field of a winglet shroud turbine plane cascades, and the influence of uniform grid size and source terms of turbulence model on the calculation results is analyzed. Then, on the basis of winglet shroud, seals source terms and tip jet source terms are added respectively to study the accuracy of source terms method in the performance calculation. Compared with the numerical simulation results based on body-fitted grid(i.e. real structure), it is found that the source terms method can accurately evaluate the influence of winglet shroud, seals and tip jet on the aerodynamic performance of turbine cascade.In addition, reducing the uniform grid size can improve the reliability of the source terms method. The research is helpful to the development of computational methods for simulating flow problems involving arbitrary complex structures, and can provide a fast and accurate numerical simulation tool for winglet shroud structure optimization based on source terms method.