Performance enhancement in transonic axial compressors using blade tip injection coupled with casing treatment

Abstract

The casing treatment and flow injection upstream of the rotor tip are two effective approaches in suppressing instabilities or recovering from a fully developed stall. This paper presents numerical simulations for a high-speed transonic compressor rotor, NASA Rotor 37, applying a state-of-the-art design for the blade tip injection. This is characterized by introducing a jet flow directly into the casing treatment machined into the shroud. The casing treatment is positioned over the blade tip region and exceeds the impeller axially by ∼30 per cent of the tip chord both in the upstream and in the downstream directions. To numerically solve the governing equations, the three-dimensional finite element based finite volume method CFD solver CFX-TASCflow (version 2.12.1) is employed. For a compressible flow with varying density, Reynolds-averaging leads to appearance of complicated correlations. To avoid this, the mass-weighted or Favre-averaging is applied. Using an injected mass flow of 2.4 per cent of the annulus flow, the present design can improve stall margin by up to 7 per cent when compared with a smooth casing compressor without tip injection. This research can lead to an optimum design of recirculating casing treatments or other mechanisms for performance enhancement applying tip flow injection.

The Effects of Wet Compression and Blade Tip Water Injection on the Stability of a Transonic Compressor Rotor

“…Also, the stall margin improvement of approximately 1.8% is achievable with the water injection at the blade tip. It must be noted that 6.5% improvement in stall margin with air injection at the blade tip was reported by Beheshti et al [8] for the same rotor as examined in this study.…”

“…This technology has been investigated by many researchers [7][8][9][10][11] and continues to be studied. Inlet fogging, in particular the wet compression, can also act as a technology for controlling the compressor stability as it was researched by Li and Zheng [12,13] using the Moore-Greitzer stability model and more recently by Luo et al [14] with the numerical method.…”

Aerodynamic performance of transonic axial compressor with a casing groove combined with blade tip injection and ejection

“…Dimensionless parameters of the reference casing groove [8]. the front surface of the groove perpendicular to the shroud, and flow is ejected through the ejection slot located on the rear surface of the groove perpendicular to the shroud.…”

“…The mass flow rate of the injection at the front of the casing groove was set to 2.4% of the choking mass flow rate with the smooth casing, as used by Beheshti et al [8] and Kim et al [11,12]. 1.3% of the choking mass flow rate with the smooth casing was set for the ejection at the rear of the casing groove in order to predict the aerodynamic performance of the axial compressor combined with injection and ejection.…”

“…Tip injection combined with a casing groove has been investigated in order to improve compressor aerodynamic performance parameters including efficiency, stall margin, and stable range extension. Beheshti et al [8] studied numerically the performance enhancement of a transonic axial compressor using blade tip injection coupled with a casing groove. The stall point predicted by their numerical simulation is 93.60% of the choking mass flow rate with a predicted stall margin of 9.34%.…”