Reduction of Tip Clearance Losses Through 3-D Airfoil Designs

Staubach, J. B.; Sharma, Om P.; Stetson, Gary M.

doi:10.1115/96-ta-013

Cited by 13 publications

(7 citation statements)

References 4 publications

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“…Blade twist, lean, and sweep have been implemented to control the flow in modern turbine designs, and a detailed review was presented by Denton and Xu [3]. In industrial applications, blade lean has been applied to increase the stage reaction [4], control endwall losses [5], and reduce tip-leakage loss [6]. Blade twist near the endwalls has been investigated to control the local pressure distribution and outlet angle, and it is interesting to find that both closing [7] and opening [8] of the blade throat near the endwalls have been proven to positively affect the turbine efficiency.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional optimal design of a cooled turbine considering the coolant-requirement change

Wang

et al. 2019

Open Physics

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Cooling technology is widely applied in modern turbines to protect the turbine blades, and extracting high-pressure cooling air from a compressor exerts a remarkable influence on the gas-turbine performance. However, the three-dimensional optimal design of a turbine in modern industrial practice is usually carried out by pursuing high component efficiency without considering possible changes in coolant requirement; hence, it may not exactly lead to improvement in the gas-turbine cycle efficiency. In this study, the turbine stator was twisted and leaned to achieve higher comprehensive efficiency, which is the cycle-based efficiency definition for a cooled turbine that considers both turbine aerodynamic performance and coolant requirement. First, the influence of twist and compound lean on turbine aerodynamic performance, considering stator-hub leakage, was investigated. Then, a method to predict the coolant requirement for turbines with different stator designs was applied, to evaluate coolant-requirement change at the design condition. The optimized turbines were finally compared to demonstrate the necessity of considering the coolant-requirement change in the optimal design. This indicated that proper twisting to open the throat area in the stator hub and compound lean to the pressure surface side could help improve the cooled-turbine comprehensive efficiency.

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Section: Introductionmentioning

confidence: 99%

Three-dimensional optimal design of a cooled turbine considering the coolant-requirement change

Wang

et al. 2019

Open Physics

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“…Staubach et al [12] achieved the off-loading of the tip by applying 3D design strategies to the profiles. Tip lean was found to be beneficial for this purpose, however its application is limited due to stresses within the rotor blade.…”

Section: Introductionmentioning

confidence: 99%

Control of Rotor Tip Leakage Through Cooling Injection From the Casing in a High-Work Turbine: Experimental Investigation

Behr

Kalfas

Abhari

2007

Volume 6: Turbo Expo 2007, Parts a and B

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This paper presents an experimental investigation of a novel approach for controlling the rotor tip secondary flow by injecting cooling air from the stationary casing onto the rotor tip. It contains a detailed analysis of the unsteady flow interaction between the injected air and the flow in the rotor tip region and its impact on the rotor secondary flow structures.The experimental investigation has been conducted on a one-and-1/2-stage, unshrouded turbine, which has been especially designed and built for the current investigation. The turbine test case models a highly-loaded, high-pressure gas turbine stage. Measurements conducted with a twosensor fast response pressure probe (FRAP) have provided data describing the time-resolved behavior of flow angles and pressures, as well as turbulence intensity in the exit plane of the rotor. Cooling air has been injected in circumferential direction at a 30° angle from the casing tangent, opposing the rotor turning direction through a circumferential array of 10 equidistant holes per rotor pitch. Different cooling air injection configurations have been tested. Injection parameters such as massflow, axial position and size of the holes have been varied to see the effect on the rotor tip secondary flows.The results of the current investigation show that with the injection, the size and the turbulence intensity of the rotor tip leakage vortex and the rotor tip passage vortex reduce. Both vortices move towards the tip suction side corner of the rotor passage. With an appropriate combination of injection massflow rate and axial injection position the isentropic efficiency of the stage was improved by 0.55 percent points.

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“…Such efforts directed toward reducing the leakage flows have been termed tip desensitization. Example of such desensitization studies include (i) addition of tip winglets (Harvey and Ramsdan [16]; Dey and Camci [17]); (ii) modification of the tip blade profile (Bindon and Morphis [18]); (iii) incorporating a nonuniform tip gap in the direction normal to the blade surface (Tallman and Lakshminarayana [19]); (iv) normal/angled injection of fluid into the squealer tip regions (Chen et al [20]); and (v) generation of high intensity turbulence upstream of the rotor for weakening the tip vortex (Staubach et al [21]). These desensitization strategies have shown the potential benefits of such an approach, but additional work is needed to explore their range of applicability, and to optimize the benefits from the desensitization approach.…”

Section: Introductionmentioning

confidence: 99%

Blade Tip Leakage Flow and Heat Transfer With Pressure-Side Winglet

Saha

Acharya

Prakash³

et al. 2003

Volume 5: Turbo Expo 2003, Parts a and B

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A numerical study has been conducted to explore the effect of a pressure-side winglet on the flow and heat transfer over a blade tip. Calculations are performed for both a flat tip and a squealer tip. The winglet is in the form of a flat extension, and is shaped in the axial chord direction to have the maximum thickness at the chord location where the pressure difference is the largest between the pressure and suction sides. For the flat tip, the pressure side winglet exhibits a significant reduction in the leakage flow strength and an associated reduction in the aerodynamic loss. The low heat transfer coefficient “sweet-spot” region is larger with the pressure-side winglet, and lower heat transfer coefficients are also observed along the pressure side of the blade. The winglet reduces the average heat transfer coefficient by about 7%. In the presence of a squealer, the role of the winglet decreases significantly, and only a 0.5% reduction in the pressure ratio is achieved with the winglet with virtually no reduction in the average heat transfer coefficient.

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Reduction of Tip Clearance Losses Through 3-D Airfoil Designs

Cited by 13 publications

References 4 publications

Three-dimensional optimal design of a cooled turbine considering the coolant-requirement change

Three-dimensional optimal design of a cooled turbine considering the coolant-requirement change

Control of Rotor Tip Leakage Through Cooling Injection From the Casing in a High-Work Turbine: Experimental Investigation

Blade Tip Leakage Flow and Heat Transfer With Pressure-Side Winglet

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