无量纲叶高对叶型喷嘴流动特性的影响

Effects of Non-Dimensional Blade Height on Flow Characteristics of Cascade Vane Preswirl Nozzle

预旋喷嘴作为预旋系统中的重要元件,其性能优劣直接关系到预旋系统的温降效果。在保持喷嘴几何出气面积不变的条件下,对预旋角度为12°,无量纲叶高分别为0.12,0.25,0.5,1和2的叶型喷嘴在压比1.1~1.9范围内进行了数值模拟。计算域包含进气腔、预旋喷嘴和出气腔,研究内容包括速度场、出气速度、出气角度、流量系数和预旋效率。对比了直孔型喷嘴、扩口孔型喷嘴以及叶型喷嘴的性能差异。结果表明叶型喷嘴的流量系数和预旋效率比直孔型喷嘴均增大20%以上,预旋效率比扩口孔型喷嘴略微增大5%左右。叶型喷嘴的流量系数和预旋效率均随压比的增大而增大,随无量纲叶高的增大先增大后微弱减小;叶型喷嘴的无量纲叶高低于0.5时,流量系数和预旋效率将显著减小。

Preswirl nozzle is regarded as an important part of the preswirl system, whose performance is di- rectly related to the temperature drop of preswirl system. The cascade vane preswirl nozzle with the same outlet area, with the preswirl angle of 12° and with the non-dimensional blade height of 0.12, 0.25, 0.5, 1, 2 , were numerically simulated respectively under pressure ratio range from 1.1 to 1.9. The computational models are standalone models which contain only the inlet chamber, preswirl nozzle and exit chamber. The investigated parameters are velocity contour, outlet velocity, outlet flow angle, discharge coefficient and preswirl effectiveness. The flow characteristics of simple drilled hole nozzle, aerodynamic hole nozzle and cascade vane preswirl nozzle are compared as well. Results show that the discharge coefficient and preswirl effectiveness of the cascade vane preswirl nozzle increased by more than 20%, compared with that of the simple drilled hole, and the preswirl effectiveness of the cascade vane preswirl nozzle increased by about 5%, compared with that of aerodynam- ic hole. Both the discharge coefficient and preswirl effectiveness increase with the increase of pressure ratio. Dis- charge coefficient and preswirl effectiveness increase firstly and then decrease slightly with the increase of non- dimensional blade height. When non-dimensional blade height is less than 0.5, the discharge coefficient and preswirl effectiveness of the cascade vane preswirl nozzle will decrease remarkably.