Abstract
Numerical simulations have been performed to study the effect of the circumferential single-grooved casing treatment (CT) at multiple locations on the tip-flow stability and the corresponding control mechanism at three tip-clearance-size (TCS) schemes in a transonic axial flow compressor rotor. The results show that the CT is more efficient when its groove is located from 10% to 40% tip axial chord, and G2 (located at near 20% tip axial chord) is the best CT scheme in terms of stall-margin improvement for the three TCS schemes. For effective CTs, the tip-leakage-flow (TLF) intensity, entropy generation and tip-flow blockage are reduced, which makes the interface between TLF and mainstream move downstream. A quantitative analysis of the relative inlet flow angle indicates that the reduction of flow incidence angle is not necessary to improve the flow stability for this transonic rotor. The control mechanism may be different for different TCS schemes due to the distinction of the stall inception process. For a better application of CT, the blade tip profile should be further modified by using an optimization method to adjust the shock position and strength during the design of a more efficient CT.
Highlights
It has long been known that rotor tip-leakage flow (TLF) has a significant influence on the compressor overall performance in terms of efficiency, pressure rise capability and safe operating range [1,2]
The main explanations for this phenomenon are tip-leakage vortex (TLV) breakdown and self-excited vibration. The former states that the vortex breakdown is the root cause of passage blockage and unsteady flow near the blade tip [8,9]. The latter holds that the real reason for the occurrence of stall inception is the inherent dynamic balance between the blade force and the loss force caused by the TLF [10,11,12], while there is no absolute association with the TLV breakdown
Rolfes et al [32,33] experimentally found that the increment of normal operating range benefited from the circumferential groove casing treatment (CT) at the small-tip clearance is negligible for a low-speed axial flow compressor; both the compressor stall margin and efficiency were improved for the large-tip clearance case
Summary
It has long been known that rotor tip-leakage flow (TLF) has a significant influence on the compressor overall performance in terms of efficiency, pressure rise capability and safe operating range [1,2]. Rolfes et al [32,33] experimentally found that the increment of normal operating range benefited from the circumferential groove CT at the small-tip clearance is negligible for a low-speed axial flow compressor; both the compressor stall margin and efficiency were improved for the large-tip clearance case. There is still a lack of relevant research of an impact of single-grooved CT location on the tip-flow stability with considering tip-clearance effect in a transonic compressor rotor. The present work will investigate the effect of single-grooved CT at different locations on the tip-flow stability under the influence of tip clearance of a transonic. The present work will investigate the effect of single-grooved CT at different locations on the tip-flow stability under the influence of tip clearance of a transonic ccoommpprreessssoorrrroottoorr.
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