离心压缩机模型级尺寸缩放对性能影响数值研究

选用流量系数分别为0.015 0、0.033 5、0.068 0和0.120 0的4组离心压缩机模型级为研究对象,几何缩放比尺分别选取0.78、1.00、1.89和2.67.采用数值方法对这些模型级进行计算,进而获得每个模型级的气动性能.同时,对流量系数为0.033 5和0.068 0两个模型级的计算结果与实验值进行对比,对计算精度进行了评价.综合4组模型级的计算结果,可以发现:几何相似放大后的模型级由于雷诺数增大,边界层流动改善,因而其气动性能比基准级提高了.相反,几何相似缩小后的模型级由于雷诺数减小,边界层相对变厚,黏性损失增加,因而其多变效率比大尺寸模型级降低了,但缩放后的模型级能头系数变化不大.在研究的流量系数范围内,流量系数越小,尺寸缩放对多变效率的影响就越显著.模型级尺寸放大后,其最大效率所对应的流量系数将向增大的方向偏移,比尺越大偏移越大,但偏移量较小.

Numerical study of scale effects on performance of centrifugal compressor model stage

Four groups of centrifugal compressor model stages are chosen with flow coefficients of 0.015 0, 0.033 5, 0.068 0 and 0.120 0. Scales of 0.78, 1.00, 1.89 and 2.67 are set. Numerical methods are applied in order to investigate aerodynamic performance of each model stage. Meanwhile, calculation results for two model stages with flow coefficients of 0.033 5 and 0.068 0 are compared with experimental data, and the calculation accuracy is evaluated. Synthesizing calculation results of these four groups of model stages, it can be found that aerodynamic performance of geometric similarity enlarged model stages is improved due to the increase in Reynolds number and improvement of flow in boundary layers. In contrast, the polytropic efficiency of geometric similarity shrunken model stages declines due to the increase in thickness of boundary layers and in viscous loss caused by the decrease of Reynolds number. However, head coefficients do not change much for these scaled model stages. Within the range of flow coefficients studied, the smaller the flow coefficient is, the more significant the scale effect on polytropic efficiency is. The flow coefficients corresponding to the maximum polytropic efficiency make a shift to the direction of increase. The larger the scale is, the larger the displacement is, but the shift is relatively small.