实际气体介质离心压缩机级气动性能相似性分析

Similarity Analysis of Aerodynamic Performance on a Centrifugal Compressor Stage with Real Gas

为研究某一离心压缩机模型级气动性能是否随不同实际气体介质变化,通过验证数值模拟与实验结果的符合性,采用数值方法对比分析了以空气为原始工作介质和以R134a(氟利昂)、CH_4(甲烷)为实际气体介质在当量转速与变转速下的气动性能的相似性及变化规律:无论以设计工况还是非设计工况为当量转换点,均能获得一致的当量转速值,且不同实际气体介质在当量转速下的多变效率及多变能量头系数曲线与原始气体性能曲线能够保持很好的符合度.以实际气体CH_4为例,说明了在变转速条件下,压缩机气动性能在亚音速时,不同马赫数的性能曲线及工况范围变化趋势一致;跨音速时,气体的最高效率点明显移向大流量工况,且马赫数越大,运行工况范围显著变窄,同时性能曲线不再满足相似性规律.

To investigate whether the aerodynamic performance of a centrifugal compressor stage would change withdifferent real gas media,based on the conformity verification between numerical simulation and experimental results,the numerical method was adopted to compare and analyze the aerodynamic similarity and variation law ofcompressor stage,with air as original working medium and R134a and CH4 as real gas medium,separately,andwith the operating rotation speed of both equivalent rotation speed and variable rotation speed. The results demon-strate that no matter the design point or the off-design point is regarded as the base point of equivalent conversion,the equivalent rotation speeds are pretty much the same,and the polytropic efficiency and energy head coefficient curves of the compressor stage at equivalent rotation speed for different real gas media also agree well with those of the origi-nal gas medium. Taking the real gas of CH4 as an example,the subsonic performance curves and working range at different Mach numbers almost display the same distribution trend at variable rotation speeds. But for transonic flow,the maximum efficiency value of performance markedly moves towards the working condition of large mass flow rate,and the higher Mach number,the narrower the operating range. As a result,the performance curves no longer meet the law of similarity at transonic rotation speeds.