Session: 34-04 Endwall, Seal & Leakage Flows II

Paper Number: 82342

82342 - Unsteady Effects of Casing Treatment on Tip Flow Structures in a Subsonic Compressor Rotor 

With the help of the dynamic mode decomposition (DMD) analysis, the unsteady effects of casing treatment on tip flow structures in a subsonic compressor rotor were numerically studied. Taking the change of casing treatment geometric parameters into account, the frequency characteristics and dynamic modes were compared and discussed, for further revealing the stability enhancement mechanism of casing treatment. At smooth casing, the mode analysis showed that the tip flow structures were dominated by tip leakage vortex (TLV) and tip secondary vortex (TSV) at near stall condition, which was consistent with 0.43 blade passing frequency (BPF). After applying casing treatment, the unsteady characteristics of tip flow field changed significantly. When the rear edge of slot passed through the rotor pressure surface, the tip leakage flow kinked and was sucked into slots, yet significantly weakened when the rear edge of slot passed through the rotor suction surface. The mode analysis indicated that the tip flow structures were dominated by intermittent high-energy excitation, which was caused by suction and injection effects of casing treatment. By comparing the casing treatment configurations with different slot number, it could be found that the suction and injection effects of casing treatment were closely related to the dominant frequency brought by the slots. When the slot number was not adequate (less than 3 per passage), the excitation energy of suction and injection effects on tip flow field were limited. With the slot number increasing, the excitation energy raised gradually, so the stability enhancement brought by casing treatment was better. Besides, the dynamic mode decomposition of tip flow field at casing treatment near stall condition was also analyzed. At casing treatment near stall condition, it existed a strong interaction between induced vortex by casing treatment and tip leakage vortex, which weakened seriously the positive effects of casing treatment.

Presenting Author: Zhidong Chi Northwestern Polytechnical University

Presenting Author Biography: Name: Chi Zhidong<br/>Major: Aerospace science and technology

Authors:

Zhidong Chi Northwestern Polytechnical University
Wuli Chu Northwestern Polytechnical University
Haoguang Zhang Northwestern Polytechnical University
Bo Luo Northwestern Polytechnical University