径流式涡轮出口旋流测量试验

Experimental Study on Swirling Flow Measurement at the Outlet of Radial Flow Turbine

高压级涡轮在非设计工况下由于叶轮高速旋转存在强旋流结构,该流场结构作用于低压级涡轮进口,进而导致低压级涡轮性能产生显著异化效应,该异化效应与旋流的形态相关性大,而现有研究未涉及涡轮出口旋流在不同工况的变化机制,基于自主设计的X-型二维恒温热线步进机构探明了高压级涡轮旋流的演化规律.结果表明:涡轮出口旋流形态强烈地依赖于膨胀比和转速,旋流强度随转速增加呈先减后增的非单调变化趋势,且在膨胀为1.1、速比为0.1时发生旋流方向逆转现象;此外,旋流轴向速度和周向速度呈现强耦合的关系.旋流强度与周向速度增加,导致轴向速度分布呈现尾流状(Wake-like)的特征.在脉冲来流条件下,涡轮出口速度波动与脉冲来流频率相同,随着脉冲频率的增加,轴向速度逐渐增加,最大增幅约为5%,但周向速度变化较小.

A strong swirling structure exists in the high-pressure stage turbine under non-design conditions,which affects the low-pressure stage turbine performance.This deterioration effect has a strong correlation with the swirling pattern,while existing researches have not covered the variation mechanism of the turbine outlet swirling at different operating conditions.In this study,the evolution law of the swirling flow on the high-pressure stage turbine was investigated experimentally using an independently designed X-type two-dimensional isothermal hot-wire stepper structure.Results demonstrate that turbine outlet swirling patterns are strongly dependent on the expansion ratio and speed.Swirling intensity exhibits a non-monotonic trend as the speed increases,with the swirling direction reversal occurring at an expansion ratio of 1.1 and a speed ratio of 0.1.Moreover,the axial and circumferential velocities of the swirling have a strong coupling relationship,with increases in swirling intensity and circumferential velocity leading to Wake-like characteristics in axial velocity distribution.Under pulsating inflow conditions,velocity fluctuations at the turbine outlet depend on pulsating inflow frequency,with axial velocity gradually increased by up to 5%and little change in circumferential velocity.