基于湍流非平衡输运特性和各向异性提高湍流模型预测压气机转子尖区复杂流动精度

Rotor tip flows have a large impact on compressor pressure rise, efficiency, and stability. And the tip flows are characterized by complex large-scale vortices, such as the tip-leakage vortex and the corner vortex. The research purpose of this project is to improve turbulence models based on turbulence mechanisms for predicting tip flows accurately in compressor rotor. Firstly, SPIV will be conducted to investigate the rotor tip flows in a low-speed large-scale axial compressor facility at Beijing University of Aeronautics and Astronautics. Then LES/DES will be employed to predict the flows in the compressor rotor and the numerical results should be validated by SPIV results. The data base of averaged flow and turbulence flow fields for rotor tip flows will be set up by SPIV results and LES/DES results. Physical mechanisms about turbulence nonequilibrim transport nature and anisotropy in rotor tip flows will be systematically analyzed based on above data base. The correlations between turbulence nonequilibrim transport nature, turbulence anisotropy and large-Scale tip vortices will be tried to set up. Based the correlations, an improving method for turbulence models will be proposed, and turbulence models will be improved to take account of the turbulence nonequilibrim transport nature and anisotropy. The improved turbulence models will be validated systematically to make sure that can predict the tip flows in compressor rotor accurately at different operating conditions. At last, the improved turbulence models will be implemented in the in-house steady/unsteady/time-averaging flow solver. The modified flow solver can be a more reliable numerical tool for advanced compressor routine design. The project will make effort to improve the performance of advanced gas turbine and aero engine.

压气机转子尖区存在着非常复杂的大尺度旋涡流动结构，对压气机压比、效率、裕度等性能有重要影响。本研究旨在基于复杂湍流机理改进湍流模型，有效提高对压气机转子尖区复杂流动预测精度。以北航低速大尺寸压气机试验台转子为研究对象，采用SPIV实验测量和LES/DES相结合的方法，建立不同工况下转子尖区复杂流动的平均流场和湍流场数据库；深入分析转子尖区湍流非平衡输运特性和各向异性的物理机制，建立湍流非平衡输运特性和各向异性与大尺度旋涡流场细节之间的关联，提出工程实用的改进湍流模型的新方法；把大尺度旋涡中湍流非平衡输运特性和各向异性物理机制内化到湍流模型中，进行系统校验，使改进的湍流模型能有效提高对不同工况下转子尖区复杂流动的模拟精度；把改进的湍流模型植入到自行发展的定常/非定常/时均模拟程序中，为高性能压气机日常设计提供更为可靠的数值模拟工具，为提高我国先进燃气轮机和航空发动机的性能提供关键技术支撑!

压气机是航空发动机的关键部件，对发动机的性能有重要影响，高效率高负荷压气机设计仍是先进航空发动机设计的技术瓶颈。压气机转子尖区存在着非常复杂的大尺度旋涡流动结构，对压气机压比、效率、裕度等性能有重要影响，在工程设计中需要准确预测及有效控制。目前而言，准确预测压气机转子尖区流动对CFD 提出了巨大的挑战，高精度的DNS/LES等无法应用于工程实际，而工程广泛采用的RANS又存在湍流模型精度不高的问题。因此，亟需开展湍流模型方面的研究工作。.本课题针对转子尖区复杂流动，主要以北航低速大尺寸压气机试验台转子为研究对象，采用SPIV实验测量和DDES相结合的方法，建立了不同工况下转子尖区复杂流动的平均流场和湍流场数据库；为了获得更详细的湍流场信息，还提出了一个能考虑间隙射流主流剪切机制的压气机转子尖区泄漏流动的模型，并针对不同雷诺数开展了DNS和LES研究；系统研究了工程常用湍流模型及多个湍流模型修正方法对转子尖区流动模拟的性能，并提出了研究湍流模型的非平衡输运特性和各向异性的“冻结法”，分析了存在的问题；基于所建立的数据库，深入分析转子尖区复杂流动中湍流非平衡输运特性和各向异性的物理机制，建立湍流的非平衡输运特性和各向异性与大尺度旋涡流场细节之间的关联，提出工程实用的改进湍流模型的新方法；基于湍流非平衡输运特性，提出了采用螺旋度改进湍流模型的新方法，有效提高了SA、RKE、SST等几个湍流模型对尖区流动的模拟精度，尤其是大大提高了对泄漏涡内湍动能的预测精度；结合基于湍流各向异性改进模型的方法，进一步提高了对转子尖区流动的模拟精度，可以更为准确预测转子尖区流动。相应研究成果，为高性能压气机日常设计提供更为可靠的数值模拟方法，可为提高我国先进燃气轮机和航空发动机的性能提供关键技术支撑!