Unsteady Tip Clearance Flow in a Low-Speed Axial Compressor Rotor With Upstream and Downstream Stators

TLDR: In this article, the authors investigated the unsteady tip clearance flow in the second rotor of a two-stage low-speed axial compressor and its interaction with upstream and downstream stators.

Abstract: In the course of advancing the understanding of the unsteady flow nature of compressor tip clearance flows, the present paper investigates the unsteady tip clearance flow in the second rotor of a two-stage low-speed axial compressor and its interaction with upstream and downstream stators. Numerical methods were adopted in the present study and the research focused on clarifying the unsteadiness of tip clearance flow behavior and its link to the change of rotor performance, subjected to the variables of axial gap sizes between the rotor and upstream and downstream stators. The result shows how and why the tip leakage vortex trajectory changes its shape with the change of gap size, and its impact on the rotor pressure rise characteristic. Within all the computed operating range, the pressure rise increases monotonically with the decrease of upstream axial gaps, but no monotonic variation was observed with the change of downstream axial gaps. This trend of performance change could be explained by the unsteady effect of upstream stator wakes, and the overall result is that the rotor performance was found to be more influenced by the upstream interaction than the downstream interaction. The frequency characteristic of the tip clearance vortex, under the influence of gap size and compressor operating condition, was also analyzed to provide a quantified estimation of its periodic flow behavior and a comparison with the recent results of other researchers.Copyright © 2005 by ASME