Tip leakage aerodynamics over the cavity squealer tip equipped with full coverage winglets in a turbine cascade

Cheon, Joo Hong; Lee, Sang Woo

doi:10.1016/j.ijheatfluidflow.2015.07.003

Cited by 40 publications

(13 citation statements)

References 46 publications

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“…And the flat winglet geometries were studied in Lee et al 25 and Cheon and Lee. 29 The major difference with the existing winglets in open literatures lies in the optimized geometry of winglet-cavity tip without gutter. The outlet flow field of the cascade is measured with an L-type five-hole probe at the location 0.5b downstream of the trailing edge.…”

Section: Experimental Apparatus and Methodsmentioning

confidence: 99%

“…The blade tip treatment combined with the winglet and squealer tips is able to obtain better aerodynamic performance than the squealer tip. 24,27,29 Coull et al 26,27 studied the effects of a winglet-cavity tip and cavity tip on the aerothermal performance of high-pressure turbines by numerical calculations. They concluded that the efficiency of the cavity tip is higher than that of the flat winglet tip and that the wingletcavity tip has the highest aerodynamic efficiency.…”

Section: Introductionmentioning

confidence: 99%

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Experiment study of the winglet-cavity tip on the aerodynamic performance in a turbine cascade

Chen

Zhou

Meng

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part A:

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The effects of a novel winglet-cavity tip on the flow field and aerodynamic performance of a turbine blade with tip clearance have been investigated in a low-speed wind tunnel. A calibrated five-hole probe is used for the measurement of three-dimensional flows downstream of the cascade. The method of oil-flow visualization is used to show the endwall flow field structure. The distribution of endwall static pressure is measured particularly by using the special moveable endwall. The downstream results show that, compared with the flat tip and cavity tip, the winglet-cavity tip reduces aerodynamic loss in the region of tip leakage vortex and passage vortex effectively and gives a 8.5% reduction of total pressure losses at a tip clearance of τ/ H = 1.0%. Meanwhile, a more uniform flow angle is obtained with the winglet-cavity tip. Thus, the winglet-cavity tip provides better aerodynamic performance. It was found that more endwall flow enters the cavity from the front of suction side gap, combines with the flow entering the tip from the pressure side, and then separates upon the cavity. This reduces the loss of passage vortex. The endwall static pressure indicates that the winglet-cavity tip reduces the driving pressure difference and weakens the tip leakage flow. With the tip clearance increasing, the leakage flow is significantly enhanced. This strengthens the interaction between the tip leakage vortex and the passage vortex. With respect to the flat tip and cavity tip, the winglet-cavity tip obtains the lowest total pressure loss at all tested tip clearances.

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Section: Experimental Apparatus and Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experiment study of the winglet-cavity tip on the aerodynamic performance in a turbine cascade

Chen

Zhou

Meng

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part A:

View full text Add to dashboard Cite

show abstract

“…With increasing winglet width-to-pitch ratio (w/p), the tip leakage vortex stretches less towards the mid-span and the total pressure loss increases for w/p ≤ 2.64%, decreases for 2.64% < w/p < 10.55%, and then becomes nearly constant [123].…”

Section: Squealers and Winglets (Classification: Passive Geometric)mentioning

confidence: 99%

Flow Control Methods and Their Applicability in Low-Reynolds-Number Centrifugal Compressors—A Review

Tiainen

Grönman

Jaatinen-Värri

et al. 2017

IJTPP

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Abstract:The decrease in the performance of centrifugal compressors operating at low Reynolds numbers (e.g., unmanned aerial vehicles at high altitudes or small turbomachines) can reach 10% due to increased friction. The purposes of this review are to represent the state-of-the-art of the active and passive flow control methods used to improve performance and/or widen the operating range in numerous engineering applications, and to investigate their applicability in low-Reynolds-number centrifugal compressors. The applicable method should increase performance by reducing drag, increasing blade loading, or reducing tip leakage. Based on the aerodynamic and structural demands, passive methods like riblets, squealers, winglets and grooves could be beneficial; however, the drawbacks of these approaches are that their performance depends on the operating conditions and the effect might be negative at higher Reynolds numbers. The flow control method, which would reduce the boundary layer thickness and reduce wake, could have a beneficial impact on the performance of a low-Reynolds-number compressor in the entire operating range, but none of the methods represented in this review fully fulfil this objective.

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“…With the additional design of winglets, the tip leakage loss of the squealer-winglet tip is believed to be lower than that of the flat-winglet tip. The aerodynamic performance of the squealer-winglet tip has been studied on both linear cascades (Zhou et al, 2013;Schabowski et al, 2014;Cheon and Lee, 2015) and rotating rigs (Harvey et al, 2006). In general, it was found that squealer-winglet tips performed better than the squealer tips.…”

Section: Introductionmentioning

confidence: 99%

Tip gap size effects on thermal performance of cavity-winglet tips in transonic turbine cascade with endwall motion

Zhong

Zhou

2017

J. Glob. Power Propuls. Soc.

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The thermal performance of two cavity-winglet tips with endwall motion is investigated in a transonic high pressure turbine cascade, which operates at an engine representative exit Mach number of 1.2 and an exit Reynolds number of 1.7 × 106. The numerical method is first validated with experimental data and then used to investigate blade heat transfer at three different tip clearances of 1.1, 2.1 and 3.1% chord. The effects of relative endwall motion are considered. The present results show that as the size of the tip gap increases, the heat transfer coefficient and heat load on the tip increases. The winglet geometries on the blade tip mainly affect the tip flow structure close to them. At a larger tip clearance, the size of the separation bubble above the pressure side winglet increases. The heat transfer coefficient is high on the pressure side winglet due to the flow reattachment at all tip clearances. Within the tip gap, when the size of the tip clearance increases, the size of the cavity vortex increases and the cavity scraping vortex due to relative endwall motion becomes smaller. The impingement of the both two vortexes can lead to high heat transfer coefficient on the cavity floor surface. On the blade suction surface, when the size of the tip clearance increases, the heat transfer coefficient of the cavity tip increases, but those of the winglet tips decreases. The heat transfer coefficient is high on the side surface of the suction side winglet at all tip clearances because of the tip leakage flow impingement.

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Tip leakage aerodynamics over the cavity squealer tip equipped with full coverage winglets in a turbine cascade

Cited by 40 publications

References 46 publications

Experiment study of the winglet-cavity tip on the aerodynamic performance in a turbine cascade

Experiment study of the winglet-cavity tip on the aerodynamic performance in a turbine cascade

Flow Control Methods and Their Applicability in Low-Reynolds-Number Centrifugal Compressors—A Review

Tip gap size effects on thermal performance of cavity-winglet tips in transonic turbine cascade with endwall motion

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