为了深刻揭示涡轮叶栅湍流附面层中的黏性底层和对数律层在叶栅内分层流动的特征,本文以超临界二氧化碳涡轮高压静叶栅下端部为研究对象,采用ANSYS CFX软件基于雷诺时均NS方程和sst湍流模型对叶栅流场进行数值模拟,通过采用流谱分析和流向涡量分析方法进一步研究不同轴向和周向截面上的端部附面层流动细节,揭示了黏性底层流体和对数律层流体在叶栅内分层流动的机理.结果显示:超临界二氧化碳静叶栅端壁附近微小区域内不同径向高度回转平面的流谱存在明显差异,该差异表明湍流附面层内的黏性底层、对数律层和主流流体的运动轨迹各不相同,叶栅端壁附面层内存在分层流动现象;黏性底层流体和对数律层流体在通过叶栅流道时获得了相反的流向涡量,这一特征与叶栅内的涡系形成有关.%In order to reveal the stratified flow characteristics of the viscous bottom layer and logarithmic layer in turbulent boundary layer of the hub endwall of turbine cascades, numerical simulation on the cascade flow field was carried out by using the ANSYS CFX software, based on the Reynolds time averaging Navie-Stokes equations and SST Turbulence model, taking the supercritical carbon dioxide turbine high-pressure static cascade as the study object. Moreover, the flow spectrum analysis and streamwise vorticity analysis were applied to further study the details of endwall boundary layer flow on different axial and circumferential sections, and the mechanism of stratified flow of viscous layer fluid and logarithmic layer fluid in cascades was revealed. The results show that, there are obvious differences in the flow spectrum of the rotating planes at different radial heights in the small area near the hub endwall of the supercritical carbon dioxide stator cascade. The differences indicate that the streamlines of the viscous layer, the logarithmic layer and the mainstream fluid near the hub endwall in the turbine cascades are different, which is stratified flow phenomena in the endwall boundary layer of the cascades. It is found that the opposite streamwise vorticity is obtained by the viscous layer fluid and logarithmic layer fluid when they are passing through the cascades, which eventually leads to the formation of turbine vortex system.
展开▼
