Numerical Investigation for the Impact of Single Groove on the Stall Margin Improvement and the Unsteadiness of Tip Leakage Flow in a Counter-Rotating Axial Flow Compressor

Xiaochen Mao,Bo Liu,Hang Zhao

doi:10.3390/en10081153

Abstract

A low-speed counter-rotating axial flow compressor (CRAC) with single circumferential grooved casing treatment (CT) was investigated numerically. Both steady and time-accurate numerical calculations were performed to study the effects of the single grooved CTs over the rear rotor on the stability enhancement and the unsteadiness of tip leakage flow (TLF) in the CRAC. Parametric studies indicate that the best position of the single groove should be located near about 20% axial tip chord in terms of the stall margin improvement (SMI). The coincidence of the effective CT locations and the high fluctuating region on blade pressure surface in the smooth wall case shows that the unsteadiness of TLF plays an important role in the stall inception process. Frequency analysis for the static pressure signals near the blade tip shows that both the disappearance of the low frequency components and the suppression of unsteady TLF are beneficial to the SMI. Detailed observation of the flow structures illustrates that the action of the grooves on the different parts of TLF is responsible for the difference of SMI in the CTs. It is more effective to improve the flow stability by controlling the critical TLF released from near the mid-chord.

Highlights

Tip leakage flow (TLF) is well known as an important factor to impact the compressor performance, as measured in terms of pressure rise ability, efficiency and stability [1,2]
It has been found that the TLF could become unsteady at high loading operating conditions and the tip leakage vortex plays an important role in the stall inception process
Past research showed that the interaction between the unsteadiness of the TLF and the casing treatment (CT) is of great importance for the compressor performance

Summary

Introduction

Tip leakage flow (TLF) is well known as an important factor to impact the compressor performance, as measured in terms of pressure rise ability, efficiency and stability [1,2]. It has been found that the TLF could become unsteady at high loading operating conditions and the tip leakage vortex plays an important role in the stall inception process. Both active flow control method (such as plasma actuation [13], fluidic actuators [14], and aspiration techniques [15]) and passive flow control method (such as blade tip modifications [16], blade tip winglet [17] and casing treatment) have been carried out by a large number of researchers to expand stall margin and improve the compressor performance by controlling the impact of the TLF. Zhao and Lu [18]

Methods

Results

Conclusion