叶型预旋喷嘴流动及温降特性实验与计算研究

Experimental Testing and Numerical Analysis on Flow Characteristics and Cooling Performance for Two Vane Pre-Swirl Nozzles

为了研究转速、压比、雷诺数对叶型喷嘴流量系数及盖板式预旋系统温降的影响,介绍了在压比1.1～1.5,转速0～10kr/min条件下稳定运行的预旋系统旋转实验台。通过实验测量预旋系统内的温度和压力分布,对比分析了两种叶型预旋喷嘴(叶片式喷嘴和叶孔式预旋喷嘴)的性能差异,并采用数值计算揭示喷嘴流动损失及预旋系统温降机理。结果表明,叶孔式预旋喷嘴与叶片式预旋喷嘴流量系数均随压比的增大而增大;随雷诺数的增大先逐渐增大,当Re>2×105,流量系数基本不变。系统温降效率随着压比的增大逐渐增大;压比1.5时,温降随转速增大先增大后减小,存在一个极值。叶孔式预旋喷嘴流量系数与叶片式喷嘴流量系数相差不大,约为0.95;但叶孔式喷嘴可以减小端壁二次流损失和尾迹损失,降低喷嘴出口落后角,提高喷嘴出口旋转比和系统温降效率。压比1.5,转速8.1kr/min时,叶孔式预旋喷嘴系统温降效率比叶片式喷嘴的提高了40%。

In order to investigate the effects of pressure ratio,Reynolds number and rotational speed on the nozzle discharge behavior and cover-plate pre-swirl system cooling performance,a pre-swirl system test rig running at pressure ratio(π)1.1~1.5 and rotational speed 0~10 kr/min was introduced first in the current study.Pressure and temperature distributions in a cover-plate system were measured to compare the performance of two types of vane pre-swirl nozzle(cascade vane nozzle and vane shaped hole nozzle).Numerical simulations were also performed to help analyze the physics of aerodynamic losses and cooling performance.Results show that the discharge coefficients of the two pre-swirl nozzles both increase slightly with the pressure ratio increase.As the Reynolds number rises,discharge coefficients increase first,and then remain constant when Re>2×105.In addition,temperature drop effectivenessηtof the system rises as the pressure ratio increases.With an increase in the rotation speed,the value ofηtwould increase first and then decline at pressure ratio(π=1.5),existing a maximum value.Vane shaped hole nozzle and cascade vane nozzle have the similar discharge coefficient,both around0.95.However,vane shaped hole nozzle has the advantage of reducing the secondary endwall flow loss and trailing edge loss,resulting in the significantly decreased deviation angle and increased swirl ratio at nozzle exit.Therefore,it could achieve an advanced cooling performance.Atπ=1.5 andω=8.1 kr/min,ηtfor vane shaped hole nozzle is about 40%higher than that of cascade vane nozzle.