传热对微型离心叶轮间隙泄漏流动影响的数值研究

Numerical investigation on effect of heat transfer on tip clearance flow in micro centrifugal impellers

针对某微型燃气轮机的微型离心叶轮,采用三维数值模拟方法,将绝热壁面情况和考虑传热影响情况下的叶轮性能和内部流场进行对比研究,重点分析壁面传热情况对微型离心叶轮间隙泄漏流动的影响.研究发现:传热对叶轮性能的影响主要集中在其对间隙泄漏流的作用上.绝热条件下间隙泄漏流轨迹沿叶片吸力面向下游发展,传热则使得间隙泄漏流动迹向相邻叶片压力面偏转,增强间隙泄漏流与主流的掺混导致间隙泄漏流损失增大.与绝热情况相比,传热虽然在一定程度上减弱了叶片通道内的压力梯度,但由于热量的传入会导致间隙泄漏流初始堵塞增大,最终仍会在叶片通道内造成更大的间隙泄漏流堵塞.

Three-dimensional numerical simulations were carried out on a centrifugal micro impeller under adiabatic and isothermal wall temperature boundary conditions in order to compare the impeller performance and the detailed flow features affected by heat transfer.The comparison was especially focused on the heat transfer effect on tip clearance flow in micro centrifugal impeller.It is found out that the performance of impeller is mainly attributed to the influence of heat transfer on tip clearance flow.The trajectory of tip clearance flow develops along the suction side of the blade towards impeller outlet under adiabatic condition,while the tip clearance flow is driven away from the suction side of the blade towards the pressure side of the adjacent blade when heat transfer is involved.Meanwhile,heat transfer also lead to the increase of mixing between tip clearance flow and the main flow resulted in greater loss.Although heat transfer can reduce the pressure gradient within blade passage to certain extent as compared with adiabatic condition,it eventually causes more tip blockage in impeller passage as the initial tip clearance blockage was enlarged due to heat addition.