关键词: 离心压气机;二次流;旋涡结构;串列叶轮

Abstract: To reveal the flow characteristics in high pressure ratio centrifugal compressor, study on the occurrence and development of vortex structures and flow loss in a high pressure ratio centrifugal compressor are established by numerical simulation. Based on the specific features of forced vortex and free vortex, two methods for identifying secondary flow are presented, namely, sectional spin lines and sectional streamlines deviated from assumed primary flow. Combined application of dissipation function and the secondary flow recognition approaches, the formation mechanism of vortex and relation between vortex and loss are discussed. The results of the analysis show that when the cosine of the angle between vorticity and normal vector of the cross section is greater than zero, the direction of sectional spin lines qualitatively matches the actual flow, or the opposite. In case the angle between axis of vortex and normal vector of the cross section is greater than 90°, the vortex identified by sectional spin lines does not exist. Scraping vortex and leakage vortex are low energy fluid gathering areas, as well as zones of loss source. Scraping vortex and leakage vortex are the key factors that influence the generation and distribution of loss in centrifugal compressor. The wake of the inducer has inhibitory effects on rolling up of the blade surface vortices in exducer passage.

Key words: Centrifugal compressor;Secondary flow;Vortex structure;Tandem impeller