Effect of a Gap Between Inner Casing and Stator Blade on Axial Compressor Performance

Abstract

The small gap at stator hub section of 10-stage axial compressor of small power class industrial gas turbine engine was studied to confirm its effect on compressor analysis result. This gap is allowed for manufactural tolerance and thermal expansion during engine operation. For the convenient purpose of CFD geometric modeling, such gap was simplified and the 3D Navier-Stokes code was used to predict the compressor performance then compared the results with the case without a gap. In the case of calculation without a gap, the performance was estimated to be lower than that of test result. It is because of the presence of 3D separation at hub corner of every stator except on the 1st and 2nd stator. The CFD calculation shows that, with a gap, the stall observed at hub corner vanished and the predicted compressor performance agrees well with the test result. From this, it is concluded that the existence of a gap between inner casing and stator brings a considerable effects on the compressor flow distribution and must be taken into account in the design.

Comparative study on stator corner separation vortex characteristics in axial-flow pump and tubular pump: To understand the effects of guide-vane cone diffusion on horn-like vortices

“…Currently, research on flow separation with regard to axial-flow compressors is more extensive than that for axial-flow pumps, providing valuable insights for this study. Based on existing research, it is known that flow separation is primarily influenced by structural differences, such as hub gaps, blade thickness, and area ratio [10][11][12]. For instance, Lee et al [10] found that in multi-stage axial-flow compressors, the presence of stator hub gaps reduces the pressure ratio of the compressor, eliminating flow separation in the hub corner and improving compressor performance.…”

“…Goel et al [11] discovered that when the thickness of guide vane blades decreases, the pressure changes on the suction side of the blades become smoother, reducing flow separation and enhancing the hydraulic performance of the pump. Liu et al [12] found that increasing the area ratio of the guide vane causes severe separation of the fluid from the surface of the blade, resulting in complex flow phenomena such as backflow, secondary flow, and vortices. This weakens the constraint ability of the guide vane on the fluid motion, increases hydraulic losses, and subsequently affects the pump's optimal efficiency and high-efficiency region.…”

Numerical Investigation of the Effect of Hub Gaps on the 3D Flows Inside the Stator of a Highly Loaded Axial Compressor Stage

“…Many studies have been conducted about the detailed flow mechanism of the interplay between these two secondary flows. Many studies have suggested that the corner separation is weakened by the leakage flow, which suppresses the migration of the low energy flow [1,3,[5][6][7], while Dong et al [8] thought that the leakage flow has an energizing effect on the low energy flow in the corner, which is the primary reason for the suppression of corner separation, and Gbadebo et al [9] noted that the elimination of the corner separation is caused by the suppression of the horseshoe vortex in the leading edge. In total, there is still no uniform conclusion on this question.…”

Experimental Investigation of the Flow Mechanisms and the Performance Change of a Highly Loaded Axial Compressor Stage with/without Stator Hub Clearance

“…The first one is the flow mechanism of the interaction between the leakage flow and the corner separation. For example, Dean [15], Lakshminarayana and Horlock [18], Singh and Ginder [19], Lee, et al [20], and George, et al [21] thought it is the suppression of the migration of the low energy flow by the leakage flow that weakens the corner separation, while Gbadebo, et al [22] pointed out that it is the suppression of the horseshoe vortex in the leading edge that causes the removal of the corner separation, and Dong, et al [23] considered that the suppression of corner separation is mainly caused by the mixing of the high energy leakage flow with the low energy flow in the corner. The second one is the effect of the clearance size on the compressor or the cascade performance.…”