Abstract: The effects of length-to-diameter ratio and pressure ratio on the flow characteristics of a pre-swirl nozzle were numerically investigated to promote the temperature drop performance in a pre-swirl system. The investigated nozzle angle is 30°,length-to-diameter ratio range is 1~5, and pressure ratio range is 1.1~1.9. Data of such parameters as exit flow angle, actual flow area, velocity magnitude and tangential velocity, discharge coefficient and pre-swirl effectiveness were obtained and analyzed. Discharge coefficients of pre-swirl nozzle with length-to-diameter ratio equal to 1.75and 4, respectively,were measured. It is found that pre-swirl effectiveness is a non-dimensional parameter that can reflect the integrated performance of a pre-swirl nozzle like flow deflection, acceleration, and pressure loss, etc. Results show that the pre-swirl effectiveness of a pre-swirl nozzle rises dramatically and then down slightly with the increase of length-to-diameter ratio, with an optimized value of 2.5. Any case of length-to-diameter ratio smaller than 2should be avoided in a real engine pre-swirl nozzle design, because the exit flow angle and actual flow area departure from its design value remarkably. 

Key words: Pre-swirl; Pre-swirl nozzle; Pre-swirl hole; Pre-swirl effectiveness; Discharge coefficient

摘要： 采用数值方法研究了长径比和压比对预旋孔流动特性的影响,所研究的预旋角度为30°,长径比范围为1～5,压比范围为1.1～1.9。计算获得了出气角度、出气面积、出气速度及其周向分量,流量系数和预旋效率等参数随压比和长径比的变化。对长径比1.75和4的预旋孔流量系数进行了实验测量。结果表明预旋效率是一个可以综合反映预旋喷嘴气流偏转、加速和流动损失等主要性能的无量纲参数。预旋效率随长径比的增加先显著增加后微弱减小,最佳长径比为2.5左右。长径比小于2时由于出气角度和实际出气面积都明显偏离设计值,预旋效率显著偏低,在设计中应避免出现。 

关键词: 预旋;预旋喷嘴;预旋孔;预旋效率;流量系数 