Coupling Analysis of 180° Bend and Volute of a Centrifugal Compressor

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.