Effect of Variable Stator Vanes With Penny Cavities on the Performance and Secondary Flow of a Single-Stage Axial Compressor

Abstract

Abstract The present study focuses on the first stage of the E3 which is a typical variable compressor, comparing its performance with and without pennies. The changes in overall performance from the penny structures are investigated. Furthermore, a detailed analysis is carried out to investigate how the two kinds of gap influences the three-dimensional flow field at the blade tip and the corner separation zone. Using unsteady calculation methods, the flow characteristics and unsteady behavior of two kinds of gap leakage flow caused by the penny structures in the shroud and hub are discussed. The results show that the pennies on the endwalls significantly diminishes overall performance at the design speed, leading to a decline in isentropic efficiency and total pressure ratio by 1.79% and 1.8%, respectively. The secondary flow losses caused by the variable stator vanes structures accounts for 68.6% of the stator losses. Compared with the hub, the momentum rate distribution of penny cavity leakage flow at the casing is stronger and more concentrated, resulting in larger losses and wider influence range. At the same time, the counter-rotating leakage vortex pairs are found in the flow field near the shroud and hub, in which the radial gap leakage vortices have a relatively stable vortex structure in the flow field, while the penny cavity leakage vortices are generated in the form of shedding vortices and then broken into smaller three-dimensional vortices, and dissipate while rotating around the radial gap leakage vortices.