叶片式预旋喷嘴出口流场实验研究

叶片式预旋喷嘴具有尺寸小,落后角大的特点。为了详细研究小尺寸预旋喷嘴的预旋性能,采用五孔探针对叶片式预旋喷嘴的出口流场进行了实验研究。测量了Ma=0.2,0.3时喷嘴出口的压力分布、速度分布和出口气流角度分布,实验获得了喷嘴的落后角和预旋效率,并进行了与实验工况相同的数值计算。通过实验获得的总压云图以及速度云图,可以发现叶片式预旋喷嘴的端壁二次流损失、尾迹损失严重,有明显的边界层分离现象。Ma=0.2时,喷嘴Re数为5.76×104,落后角2.84°,实验测得的预旋效率为0.73;Ma=0.3时,喷嘴Re数为1.06×105,预旋效率提高至0.77。实验模型端壁的影响使预旋效率实验结果偏低6.5%左右。数值结果与实验测得各参数符合较好:数值结果与测得的喷嘴出口截面平均总压、静压偏差在1%以内;出气速度、周向速度以及出气角度与实验结果偏差在4%以内。数值计算表明,叶片式预旋喷嘴的预旋效率基本不受压比影响,随Re数增大先增大后基本不变,最后基本稳定在0.85。

Test of Outlet Flow Field for Cascade Vane Nozzle

Cascade vane pre-swirl nozzle has the characteristics of small geometry size and large deviation angle. In order to investigate the performance of the pre-swirl nozzle with small size, the outlet flow field was tested using five hole probe for the cascade vane nozzle. The pressure, velocity and outlet flow angle distributions were measured at Ma=0.2 and 0.3. Deviation angle and pre-swirl effectiveness of the cascade vane nozzle were obtained experimentally, and the numerical simulations were also conducted for the same experimental operating conditions. The significant secondary endwall flow loss, trailing edge loss and obvious boundary layer separation can be observed through the measured total pressure contour and velocity contour. At Ma=0.2 with Reynolds number 5.76×10⁴, the deviation angle of cascade vane nozzle is around 2.84° and the tested pre-swirl effectiveness is only 0.73. At Ma=0.3 with Reynolds number 1.06×10⁵, the pre-swirl effectiveness increases to 0.77. However, the end wall of the experiment makes the tested pre-swirl effectiveness values 6.5% lower. Results also show that the calculations have good agreement with all the measured parameters: the deviations of area averaged total pressure and static pressure were less than 1%, and the deviations of velocity, tangential velocity and outlet flow angle were less than 4%. In addition, the pressure ratio has no influence on the pre-swirl effectiveness, while it would increase first and then remain almost constant with the Reynolds number. At high Reynolds number, the pre-swirl effectiveness of cascade vane nozzle remains 0.85.