The Influence of Suction-Side Winglet on Tip Leakage Flow in Compressor Cascade

Proceedings of the Institution of Mechanical Engineers, Part G:

Cui

Xiang

et al. 2021

The interactions of tip leakage flow with mainstream and shock wave result in larger aerodynamic losses and blockage in high loading compressors and tend to be one of the triggers for flow instability. In order to attenuate the influence of leakage flow and improve the stall margin of highly loaded compressor, the new rotors surrounded by tip winglet are investigated by a numerical method. The tip winglet is designed by extending the flat blade tip section in outer 1.5% span of rotor blade. As the angle between the leakage flow and main flow decreases due to winglet, the losses and flow blockage have been weakened near stall condition, and the stall margin of new rotor with pressure-side winglet has an increase of over 10%. The migration and accumulation of low-energy fluids near the corner of casing endwall are affected significantly by tip winglet. As a result, the pressure-side winglet causes an increase of static pressure near the casing corner of pressure surface. Although the driving pressure difference near the leading edge of blade has increased slightly in the tip region, the strength and massflow rate of leakage flow appear to be decreased. As the leakage flow weakens in the new rotor with pressure-side winglet, its interaction with mainstream and shock has been suppressed obviously, and the delay of rotating stall occurs as well. Moreover, the flowfields of the new rotor with pressure-side winglet have been simulated at 40%, 60%, and 80% design speed. It is shown that the flow blockage and losses in the tip region have also reduced near stall point, and an improvement of overall performance is present in the new rotor with pressure-side winglet. All the changes of tip flow structure caused by winglet benefit to an increase of aerodynamic performance of new rotor at full rotational speed range.

Section: Introductionmentioning

confidence: 99%

Numerical investigation of blade tip winglet on flow structure in a high loading transonic rotor

Proceedings of the Institution of Mechanical Engineers, Part G:

Cui

Xiang

et al. 2021

Section: Introductionmentioning

confidence: 99%

“…Although a few investigations of tip winglet on 2-D compressor cascades and low speed rotors have been performed, the detailed effects of winglet on flow characteristics and stall margin of high loading compressor rotors have not been illustrated clearly, and its application in compressor blades is also restricted inevitably. 23 Therefore, the following problems will be discussed in this paper:The effects of winglet geometry on static pressure distribution and flow pattern near blade tip.How does different geometry size of tip winglet affect the mass flow rate and aerodynamic losses of leakage flow in tip region of a transonic rotor?The fundamental impacts of winglet geometry on overall performance and stall margin of transonic rotors.…”

Section: Introductionmentioning

confidence: 99%

Investigation on the effects of winglet geometry in a high loading compressor rotor

Cui

Proceedings of the Institution of Mechanical Engineers, Part A:

et al. 2021

The tip winglet is employed to improve the flow stability of NASA Rotor 37. Two suction-side winglets with the maximum width of 0.25 and 0.5 times of the width of local blade tip section and two pressure-side winglets with the maximum width of 0.5 and 0.9 times of the width of local blade tip section are designed and evaluated by numerical analysis of 3-D flowfield. The results show a rough leakage channel with two static pressure peaks over blade tip is formed due to the existing of pressure side winglet, and it benefits to reduce the effective through-flow area and massflow rate of leakage flow. The blocking effect on leakage flow weakens in new rotor with suction side winglet and it brings out the dramatical increase of leakage massflow rate and additional losses in tip region of rotor. With the comprehensive effects produced by tip winglet on leakage flow, the low-velocity region concerned on the interaction of leakage flow with passage shock has been reduced obviously in rotor with pressure side winglet and it leads to an over 11% increase of stall margin of transonic rotor with no penalty of efficiency. On the contrary, the suction side winglet contributes to a significant deterioration of tip flow characteristics of rotor with full expanded leakage flow and a smaller stall margin with over 17% decrease.

“…Nevertheless, it has been studied from a long time ago due to its immoderate loss on the compressor performance, and in particular, on the compressor performance in stall condition and researchers have tried to minimize the tip clearance loss by understanding the effects of tip clearance on the flow inside a compressor. Numerous methods such as implementing casing treatment (Kim et al, 2013), swept and leaned blades (Kroger et al, 2011), utilizing winglet on the suction side of blade Zhong et al, 2011) and using vertical impact jet (Bae et al, 2003) have been proposed to control the tip clearance flow and to achieve higher stability and better overall efficiency in the compressor. (Zhong et al, 2013) experimentally studied the effect of winglet on a cascade and concluded that the location of winglet has a considerable influence on the vortex produced as a result of blade tip leaked flow, and that the placement of winglet on the suction side proves effective in reducing the total outlet pressure and the secondary flow as a result of leakage flow from the tip clearance (Zhong et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

An Investigation on the Effect of Blade Tip Clearance on the Performance of a Single-Stage Axial Compressor

Ostad

Kamali

2019

JAFM

In the present study, the numerical analysis of blade tip geometry effect on the performance of a single-stage axial compressor has been the focus of attention. The studied geometries included a rotor with variable tip clearance. For the first model, the tip clearance increases as it moves toward the blade trailing edge. The tip clearance of the second model reduces as it approaches the trailing edge, whereas in the third model, the tip clearance remains constant. The results indicated that the tip clearance of the first sample, as the worst tip clearance case, creates a 10% reduction in the stall margin with respect to the third standard model, and the second sample tip clearance brings about a stall margin reduction of 4% efficiency with respect to the third standard model. Then, the effect of blade tip clearance geometry on outlet flow angle of the rotor was inspected. The results showed that in the first model, the outlet flow angle has the largest deviation than the third standard model and the second model performance places somewhere between the two other tip clearance geometries. Also evident from the result is that taking advantage of the variable blade tip clearance is not an appropriate method for improving compressor performance.