Numerical Analysis of Flow in a Transonic Compressor With a Single Circumferential Casing Groove: Influence of Groove Location and Depth on Flow Instability

Abstract

The effect of circumferential single grooved casing treatment on the stability enhancement of NASA Rotor 37 has been examined with computational fluid dynamics analysis. Stall inception mechanism of Rotor 37 is presented first with principal focus on the tip leakage flow behavior, passage blockage, and the vortical flow structures. Detailed observation showed that the combined interaction of the stagnated flow of tip leakage vortex breakdown and the jetlike leakage flow from the midchord region leads to the blade tip-initiated stall inception. The result of numerical parametric study is then demonstrated to show the effect of varying the axial location and the depth of a circumferential single groove. The evaluation based on stall margin improvement showed a higher potential of deeper grooves in stability enhancement, and the optimal position for the groove to be located was indicated to exist near the leading edge of the blade.

Numerical Study on the Effect of Single Shallow Circumferential Groove Casing Treatment on the Flow Field and the Stability of a Transonic Compressor

“…In a transonic compressor, when the mass flow rate reduces, the intensity of the interaction between the shock wave and the tip leakage vortex increases, so the vortex core expands through passing the shock wave and generates a vortex breakdown zone. This blockage region leads the compressor toward the stall as reported by other researchers (Wilke and Kau 2004;Sakuma et al 2014). It has been shown in Fig.9 that narrow grooves have the ability to reduce the size of vortex breakdown zone.…”

“…The near-stall point and numerical stall point of smooth wall condition obtained through imposing the outlet static pressure on 122.45 and 122.6 kPa respectively. This technique of finding the stalling mass flow rate using RANS solutions has been used by many researchers (such as Ito et al 2008;Sakuma et al 2014). However, the limitation of this method was noted that the stall is not properly modeled using RANS solutions because of its inherently unsteady phenomenon.…”

“…Also they studied the effect of number and shape of circumferential groove in other papers. Sakuma et al (2014) numerically studied the effect of varying the axial location and the depth of a single circumferential groove on the stability improvement of NASA Rotor 37. They explained higher potential of deeper grooves in the stability enhancement, and the best position for the groove to be located was pointed out to exist near the blade leading edge.…”

Design and Optimization of Multiple Circumferential Casing Grooves Distribution Considering Sweep and Lean Variations on the Blade Tip

“…Müller et al [5] simulated four CGCT configurations under both design and off-design conditions, and they noticed that the grooves segmented the tip leakage vortex (TLV) and alleviated the blockage, which delayed the spillage of the low-energy fluid from the leading edge of the adjacent blade. Sakuma et al [6] studied the effects of a single segmented the tip leakage vortex (TLV) and alleviated the blockage, which delayed the spillage of the low-energy fluid from the leading edge of the adjacent blade. Sakuma et al [6] studied the effects of a single circumferential groove with different axial locations on NASA Rotor 37.…”

“…Sakuma et al [6] studied the effects of a single segmented the tip leakage vortex (TLV) and alleviated the blockage, which delayed the spillage of the low-energy fluid from the leading edge of the adjacent blade. Sakuma et al [6] studied the effects of a single circumferential groove with different axial locations on NASA Rotor 37. They concluded that the CGCT reduced both the tip loading and the momentum of the tip leakage flow.…”