多级轴流压气机失速边界预估
PREDICTION OF STALL MARGIN FOR MULTISTAGE AXIAL FLOW COMPRESSORS
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摘要: 本文提出了两种预估多级轴流压气机旋转失速边界方法。前者把关于单叶排的半经验准则推广至多级压气机。取前一级的出囗条件为后一级的进囗条件,每级进行类似运算,对比各级的失速起始流量来判别多级压气机的失速起始边界。预估结果得到了实验验证。后者以小扰动理论为基础,应用非定常二元不可压流的流动模型,导出了双级轴流压气机的旋转失速起始判别准则。利用 Newton- Raphson方法求解特性方程根据设计的程序完成了几个实例的理论估算。预估值和实验值的吻合证实了理论分析的可靠性。并对比不同情况下衰减因子的变化规律,分析了各叶排损失随进口相对气流角的变化趋势。Abstract: Two methods for predicting the onset of rotating stall in multistage axial flow compressors are provided in this paper.First,the semi-empirical criterion about the isolated blade row is extended to the analysis of the multistage axial flow compressors.The downstream condition of preceding stage is considered as the upstream one of next stage and similar calculation is made for every stage.By comparison of the flows for each unit at the onset of rotating stall,the stall margin of the multistage compressor can be determined.The results of prediction agree with the experimental data fairly well.Secondly,with the help of the unsteady two-dimensional incompressible flow model,the inception criterion of rotating stall for a double stages axial flow compressor is derived in detail according to a small disturbance stability theory.Characteristic equation is solved iteratively using a Newton-Raphson scheme.Some numerical examples have been predicted with the aid of the written computer codes.Good agreement between the analytical and experimental results indicates that the analysis is believable.The variations of damping factor under the different conditions are compared and the rate of loss variation is analysed as inlet relative airflow angle increases for each blade row.The above-mentioned two approaches both can be used to predict the stall margin for subsonic and transonic multistage axial flow compressors.
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