Rotating Instabilities in a Low-Speed Single Compressor Rotor Row with Varying Blade Tip Clearance

Abstract

When a compressor is throttled to the near stall point, rotating instability (RI) is often observed as significant increases of amplitude within a narrow frequency band which can be regarded as a pre-stall disturbance. In the current study, a single compressor rotor row with varying blade tip clearance (1.3%, 2.6% and 4.3% chord length) was numerically simulated using the zonal large eddy simulation model. The mesh with six blade passages was selected to capture the proper dynamic feature after being validated in comparison to the measured data, and the dynamic mode decomposition (DMD) approach was applied to the numerical temporal snapshots. In the experimental results, RIs are detected in the configurations with middle and large tip gaps (2.6% and 4.3% chord length), and the corresponding characterized frequencies are about 1/2 and 1/3 of the blade passing frequency, respectively. Simulations provide remarkable performance in capturing the measured flow features, and the DMD modes corresponding to the featured RI frequencies are successfully extracted and then visualized. The analysis of DMD results indicates that RI is essentially a presentation of the pressure wave propagating over the blade tip region. The tip leakage vortex stretches to the front part of the adjacent blade and consequently triggers the flow perturbations (waves). The wave influences the pressure distribution, which, in turn, determines the tip leakage flow and finally forms a loop.

Design of a Compressor Test Rig for Immobilization of the Stall Cell

“…Several test rigs have been documented in the literature for investigating the structure of a rotating stall flow [16][17][18][19][20][21]. While some of these rigs offer a suitable platform for experimental analysis of the flow field, most lack specific design considerations for rotating stall research, resulting in inadequate axial dimensions to encompass the entire range of stall cells.…”

Rotor Dynamics of Turbocompressor Based on the Finite Element Analysis and Parameter Identification Approach Author(s):

“…In most cases, the technical level of such machines is assessed by their vibroacoustic characteristics determined by the vibration state of the rotor [2]. Therefore, the rotordynamic problems are of significant practical importance, and the range of these tasks is predetermined by the number of constructive types of rotor machines, their features, and operating conditions.…”