非对称叶轮对双面离心压气机流量分配特性的调节作用

Regulation Effects of Asymmetric Impeller on Flow Distribution Characteristics of Double-Sided Centrifugal Compressor

关键词:  双面离心压气机  对称叶轮  非对称叶轮  流量分配

Key words:  Double-sided centrifugal compressor  Symmetric impeller  Asymmetric impeller  Flow distribution

摘要:

涡轮增压器使用的双面离心压气机，由于前后方叶轮进口流场存在着差异，导致随着流量减小，前后方叶轮流量分配失衡，出现前方单侧叶轮工作模式。为了进一步拓宽双面离心压气机的稳定工作范围，提出增大双面离心压气机后方叶轮半径的方法，实现两个叶轮流量分配的再平衡，主要目的是研究非对称模型在双面离心压气机流量分配调节方面发挥的作用，采用数值模拟方法对两种双面叶轮压气机整机模型的工作特性进行对比分析。结果表明:通过增大后方叶轮半径的方法，能够有效调节中等流量和小流量工况下两个叶轮的流量，从而改善了两个叶轮流量的平衡状况，同时改变了双面离心压气机的工作模式转变过程。前方叶轮各叶片槽道流量分配主要受蜗壳内部静压周向分布形式的影响，而后方叶轮各叶片槽道流量还受弯曲管道出口流场的影响，弯曲管道出口形成的交汇区域下游的叶片槽道内流量明显偏小。弯曲管道出口交汇区域内两股气流的相互作用强度受后方叶轮流量的影响，流量越小，交汇区域内两股气流的作用强度越弱。增大后方叶轮半径，增强了后方叶轮的做功能力，使设计工况的压比提高了4%，延缓了双面叶轮并行工作向单面叶轮工作模式的转换过程，并使双面压气机的稳定工作范围拓宽了12.6%。

Abstract:

For the applications of the double-sided centrifugal compressor in the turbocharger，due to the inlet flow field differences at the front and rear impellers，the imbalanced flow distribution between the front and rear impeller are produced with the flow decrease，resulting in the single front impeller working mode. In order to further broaden the stable working range of the double-sided centrifugal compressor，the method of increasing the rear impeller radius in present paper is proposed to achieve the flow regulation between the front and rear impellers. The numerical simulation has been carried out on the two double-sided centrifugal compressor models to comparatively analyze the working mode of the compressor.The results show that the increase of the rear impeller radius，can effectively regulate the flow distribution between the two impellers at medium flow and small flow conditions，thus improve the flow balanced condition of two impellers. It also changes the working mode conversion process of the double-sided centrifugal compressor. The flow distribution of each blade channel of the front impeller is mainly decided by the distribution of the static pressure distribution in the volute，but the blade channel flow of the rear impeller is also influenced by the outlet flow field of the rear bending pipe. The air-flow intersection area is formed at the bending pipe outlet，which caused the mass flow of the downstream blade channel obviously smaller than the other blade channels. The intersection strength of the two air-flow in the area of the bent duct outlet is affected by the flow-rate of the rear impeller and the interaction strength weakens with the flow rate decrease. The working capacity of the rear impeller will be enhanced by increasing the rear impeller radius，which delays the double-sided impellers converting from the parallel working mode to single-sided impeller working mode. The pressure ratio increased by 4% under design flow，and the stable working range of the double-sided centrifugal compressor can be broadened by 12.5%.