离心压气机实际气体三维粘性流场分析

应用时间推进法求解连续性方程、时均N-S方程、能量方程、实际气体状态方程及Yang＆Shih紊流模型,对压缩重介质实际气体(丙稀)的大流量离心压气机整级流场(闭式叶轮、扩压器、弯道及回流器)进行了数值分析,其中实际气体的热力学属性均表示成温度的函数.分析了压缩实际气体丙稀时模型级内部尤其是弯道及回流器内部的流动规律,将计算结果与丙稀作为理想气体时模拟的结果进行对比分析,并与实验值进行了比较.结果表明:采用实际气体模型进行模拟时压气机性能更接近于实际性能.压缩实际气体及理想气体时叶轮内部速度分布及模型级出口参数是不同的,叶轮出口流场参数分布差别主要集中在轮盘、轮盖两侧.沿弯道及回流器中央流线的压力系数差别显著,模型级出口理想气体的压力系数明显高于实际气体.为了加快收敛,计算时采用了隐式残差平均法及完全多重网格技术.

Numerical Investigation to the Flow of Real Gas in a Centrifugal Compressor

The time marching method is adopted to solve the governing equations, and the computational analysis to the flow field in a centrifugal compressor with shrouded impeller, vaneless diffuser, bend and return channel compressing perfect and real gas respectively, is carried out, where the three-dimensional N-S code with the Yang & Shih two-equation turbulence model is employed, and a user-defined real gas property program is applied for the thermodynamic analysis. The calculations are performed with a central space discretization scheme and second/fourth order artificial dissipation terms. A special attention is focused on the flow characteristic of the bend and return channel, the different distribution pattern of the flows in compressor compressing the perfect and real gas. The simulated results demonstrate that the flow parameters in the outlet of the impeller compressing real gas are quite different from that compressing perfect gas and the differences are observed mainly near the hub and shroud of the impeller. The static pressure coefficient along the bend and the return channel for the perfect gas is higher than that for the real gas. The characteristic of the compressor compressing real gas approaches more closely to the experimental data.