高压比离心压气机二次流旋涡结构研究

Study on Secondary Flow Vortex Structure in HighPressure Ratio Centrifugal Compressor

关键词:  离心压气机  二次流  旋涡结构  串列叶轮

Key words:  Centrifugal compressor  Secondary flow  Vortex structure  Tandem impeller

摘要:

为揭示高压比离心压气机的流动特性，采用数值方法对高压比离心压气机的旋涡结构和流动损失的产生及演变规律进行了研究。根据不同类型旋涡的具体特征，给出了分别适用于受迫涡和自由涡的二次流识别方法，包括截面旋线法和拟定主流的截面流线法。应用给出的二次流识别方法并结合耗散函数，探讨了压气机内旋涡的形成机理以及旋涡与损失的关联性。研究表明：当涡量与截面法矢量夹角的余弦值大于零时，旋线方向与实际气流方向定性一致，否则相反；旋线显示的涡轴方向与截面法矢量夹角大于90°时，识别出的旋涡不存在；刮削涡和泄漏涡既是低能流体的聚集区也是能量的耗散区，是影响离心压气机损失产生及分布的关键因素；诱导轮尾迹会抑制导风轮流道内叶表通道涡的形成。

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.