Abstract: The relative circumference position of the bent pipe and asymmetric structure of the volute will change the compressor performance. To clarify the reason why the performance of compressor changes and to further provide the theoretical guidance for the choice of the bent installation and the design of compressor，the performances and internal flow characteristics of a centrifugal compressor connected with a straight pipe and a 180° bent pipe of different circumferential installation positions were investigated in experimental and numerical methods. The results show that the flow field distortion area at the bent pipe outlet will vary with the change of the relative circumferential position bent pipe and asymmetric structure of the volute. This changes the coupling effect of distortion flow field of the impeller outlet and varies the compressor performance. The interaction of these two kinds of distortion flow fields will affect the circumferential uniformity of the impeller internal flow field. When the low static pressure area at the bent pipe outlet and the high static pressure at impeller export act on the same blade channel outlet region，the flow field distribution in the impeller internal is the most uneven，in this case，the compressor performance is lower than that of the other bent pipe installation angle. In order to ensure the performance degradation degree of the centrifugal compressor is less than 3% compared with the straight inlet model after the installation of the bent pipe，the high static pressure of the bent pipe outlet and the high static pressure of the impeller outlet should be acted on the same blade channel. Based on this principle，the installation circumferential position range of the bent pipe for the small efficiency drop of the compressor is determined.

Key words: Bent intake；Non-axisymmetric；Centrifugal compressor；Distortion

摘要： 离心压气机进气弯管与蜗壳非对称结构在周向上的相对位置会使压气机性能发生变化，为了明确引起压气机性能发生改变的原因，给弯管安装方式的选择及压气机的设计提供理论指导，采用实验和计算相结合的方法，研究了带有直管和不同周向安装位置的180°弯管进气方式的离心压气机工作特性及内部流动特性。结果表明:改变弯管与蜗壳非对称结构在周向上的相对位置，弯管出口流场畸变区域在周向上的位置会发生变化，从而改变了其与叶轮出口畸变流场的耦合作用效果，因此压气机性能发生变化。两种畸变流场间的相互作用会影响叶轮内部流场的周向均匀程度。当弯管出口低静压区域与叶轮出口高静压区域作用于相同叶片槽道进出口时，叶轮内部流场周向上的分布最不均匀，在这种情况下的压气机性能低于其他弯管安装角度下的压气机性能。为了保证安装弯管后离心压气机性能相对直管进气的下降程度不超过3%，应该使弯管出口高静压区域与叶轮出口高静压区域施加于相同叶片槽道。基于上述原则，确定了压气机效率下降较小的弯管安装周向位置的选择范围。

关键词: 弯管进气；非轴对称；离心压气机；畸变