离心压缩机级通流与盘盖侧泄漏流的耦合分析

Coupling Analysis between Through Flow and Hub-Shroud Side Leakage Flow of a Centrifugal Compressor Stage

为揭示离心压缩机通流与轮盘及轮盖侧迷宫密封泄漏流动之间的耦合作用机理,以某天然气管线用离心压缩机首级为研究对象,数值分析了压缩机级在不考虑密封结构模型以及考虑密封结构模型下的流场分布。结果表明:在考虑密封结构的情况下,压缩机整级的等熵效率和总压比都有所下降,且在小流量工况时下降更为明显;等厚度高低密封齿和梯形密封齿均能有效衰减泄漏气流压力能和动能,从而有效降低泄漏量;密封通道内的泄漏气流在叶轮进出口与通流区气流掺混时易造成通流分离;受轮盖密封泄漏气流的影响,在叶轮进口轮盖侧存在明显的熵增区域,使得压缩机整级性能下降。研究工作为深入了解离心压缩机密封流动结构及其对通流的影响、完善离心压缩机在实际运行状态下的气动性能预测模型奠定了坚实理论基础。

In order to reveal the coupling interaction between centrifugal compressor＇s through flow and hub-shroud labyrinth seal leakage flow, the inlet stage of a centrifugal compressor in natural gas pipeline was studied in this paper. Numerical simulations of internal flow fields of the centrifugal compressor stage with and without labyrinth seal were carried out. The results showed that the model with seal has lower isotropic efficiency and total-to-total pressure ratio than the model without seal, especially at low flow rates. Both the seal cavities with the alternate long-short seal teeth of identical thickness and with the trapezoid seal teeth are capable of dissipating the gas pressure and kinetic energy into heat energy, thus significantly decreasing the leakage flow rate. The mixing of leakage flow and through flow can lead to the separation of through flow near inlet and outlet of centrifugal impeller. Subject to shroud-side leakage flow, the through flow near the impeller inlet suffers significant increase in entropy and hence a deterioration in the aerodynamic performance of the whole stage. The present work would provide a theoretical foundation for the in-depth understanding of the interaction between through flow and hub-shroud side leakage flow and for the improvement in the aerodynamic performance prediction model of the in-service centrifugal compressors.