基于PIV测试技术的涡轮动叶栅流场可视化研究

Visualization Study of the Flow Field in a Rotor Cascade of a Turbine Based on the PIV Measurement and Testing Technology

针对某设计转速为1 500 r/min的涡轮动叶叶栅在780-1 680 r/min之间的4个转速工况,利用干冰作为示踪粒子进行了内流场的PIV(粒子图像测速技术)实验研究,获得了动叶叶栅流道中间截面及其下游区域的速度场和涡量场的二维分布并进行了比较分析。研究表明:利用PIV技术测量的瞬态结果可以很好地捕捉动叶栅尾缘分离涡的形成和发展过程;在所研究的实验工况以内,动叶出口及其下游区域速度随着动叶转速的增大而不断增大,流道内部气流速度随转速增加会出现先增大后减小的特点,叶轮输出功率与流道内部气流速度随转速变化的规律一致;在设计转速工况附近动叶流道的涡量场强度较弱,随着叶轮转速降低,叶栅流道内特别是动叶吸力面下游区域的涡量强度明显增强。

In the light of four operating conditions at four rotating speeds from 780 to 1680 r /min of a rotor blade cascade of a turbine with its design rotating speed being 1 500 r /min,experimentally studied was the PIV( particle image velocimetry) technology in measuring the inner flow field by employing dry ice as the tracer particles and obtained were2 D distribution of the speed field and vorticity field in the middle section and its downstream areas of the flow passages of the rotor blade cascade. It has been found that the transient results measured by using the PIV technology can capture very well the formation and evolution process of the vortices separated from the trailing edge of the rotor blade cascade. Within the operating conditions under the test,the velocity at the outlet and the downstream of the rotor blades continuously increased while the velocity of the gas in the flow passages was characterized by its first increase and then decrease with an increase of the rotating speed of the rotor blades. The output power of the blade wheel had a same variation law governing the air flow speed in the flow passages. In adjacent to the design rotating speed operating condition,the intensity of the vorticity field in the flow passages of the rotor blades was relatively weak and with a decrease of the rotating speed of the blade wheel,the intensity of the vorticity field inside the flow passages of the cascade,especially in the downstream of the suction surface of the rotor blades was obviously enhanced