轴流风机叶尖泄漏流动的大涡模拟（英文）  

Large-Eddy Simulation of the Tip-Leakage Flow in an Axial Fan

作　　者：Alexej Pogorelov Matthias Meinke Wolfgang Schroder 

机构地区：[1]Institute of Aerodynamics,RWTH Aachen University

出　　处：《风机技术》2018年第1期1-15,共15页Chinese Journal of Turbomachinery

摘　　要：本文采用大涡模拟(LES)的方法研究了在基于外壳直径的雷诺数为9.36×105条件下5叶片的轴流式风扇的流动特性,并且着重分析了叶尖泄漏的流动现象。本文使用了基于有限体积法和分层笛卡尔网格的可压流求解器进行数值计算,并应用了体积守恒的切割网格方法处理风扇几何结构的浸入式边界。同时开发了用于笛卡尔网格的旋转周期性边界条件,这样只需分析由2.5亿网格构造的包含一片叶片的72°区域。该研究首先对网格质量进行了分析,之后讨论了瞬态和时均流场的特性,并与使用RANS的5叶片模拟结果进行了对比。RANS和LES模拟结果的主要不同之处体现在叶尖泄漏涡尾流中的湍流动能。本文进而研究了叶尖间隙对叶尖泄漏涡的影响。研究表明,间隙的大小会影响叶尖泄漏涡的大小形状。此外,间隙中更多的分离现象和反向旋转涡会导致较低的湍流动能。The flow around a 5-bladed axial fan at a Reynolds number of 9.36×105 based on the outer casing diameter is investigated by large-eddy simulation(LES)with special focus on the tip-leakage flow region.A finitevolume flow solver for compressible flows based on hierarchical Cartesian meshes is used.The immersed boundaries of the fan geometry are handled by a fully conservative cut-cell method.A 72°segment,which includes one of the five fan blades,is resolved with approx.250 million cells,for which a rotational periodic boundary condition for Cartesian meshes has been developed.First,a grid convergence study is performed and subsequently results of the instantaneous and the mean fan flow field are discussed and compared to Reynolds-averaged Navier-Stokes(RANS)results of a 360°simulation.The main differences are observed for the turbulent kinetic energy in the wake region generated by the tipgap vortex.Furthermore,the influence of the tip-gap size on the vortical structures is investigated.It is shown that a reduction of the tip-gap size leads to a change of the shape and size of the tip-gap vortex.Additionally,more separation and counter-rotating vortices are generated inside the tip-gap,which,however,result in a lower turbulent kinetic energy.

关 键 词：叶尖泄漏涡 大涡模拟 泄漏流动 轴流风机 笛卡尔网格 周期性边界条件 轴流式风扇 有限体积法 

分 类 号：TH432.1[机械工程—机械制造及自动化] TK05[动力工程及工程热物理]