Effects of Simulated Rotation on Tip Leakage in a Planar Cascade of Turbine Blades: Part I—Tip Gap Flow

Yaras, M. I.; Sjolander, S. A.

doi:10.1115/1.2929189

Cited by 75 publications

(9 citation statements)

References 9 publications

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“…The chordwise velocity vector distributions at different spanwise distance within the tip gap were studied by Yaras and Sjolander. 39 They found that apart from the areas very close to the leading edge and trailing edge, the tip leakage flow crossed the tip perpendicular to the chord. Hence it was concluded that the flow momentum mainly changed in the direction normal to the chord.…”

Section: Methodsmentioning

confidence: 99%

Effect of in-service burnout effect on the transonic leakage flows over cavity tip model

Saleh

Avital

Korakianitis

2021

Proceedings of the Institution of Mechanical Engineers, Part A:

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Increasing the gas temperature at the inlet to the high pressure turbine of gas turbine engines is known as a proven method to increase the efficiency of these engines. However, this will expose the blades’ surface to very high heat load and thermal damages. In the case of the un-shrouded turbine blades, the blade tip will be exposed to a significant thermal load due to the developed leakage flows in the tip gap, this leads to in-service burnout which degrades the blade tip and shortens its operational life. This paper studies the in-service burnout effect of the transonic tip flows over a cavity tip which is a configuration commonly used to reduce the tip leakage flows. This investigation is carried out experimentally within a transonic wind tunnel and computationally using steady and unsteady Reynolds Averaged Navier Stokes approaches. Various flow measurements are established and different flow behaviour including separation bubbles, shockwave development and distinct flow interactions are captured and discussed. It is found that when the tip is exposed to the in-service burnout, leakage flow behaves in a significantly different way. In addition, the effective tip gap becomes much larger and allows higher leakage mass flow rate in comparison to the sharp-edge tip (i.e. a tip at the beginning of its operational life). The tip leakage losses are found much higher for the round-edge cavity tip (i.e. a tip exposed to burn-out effect). Experimental and computational flow visualisations, surface pressure measurements and discharge coefficient variation are given and analysed for several pressure ratios across the tip gap.

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Section: Methodsmentioning

confidence: 99%

Effect of in-service burnout effect on the transonic leakage flows over cavity tip model

Saleh

Avital

Korakianitis

2021

Proceedings of the Institution of Mechanical Engineers, Part A:

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“…One of the reasons for the different behaviour of tip leakage flows in linear cascades and rotors is due to the omission of end wall motion. Though the literature is not exhaustive few investigators have studied the effect of wall motion on the tip gap aerodynamics (Graham, et al [7], Morphis and Bindon [8], Yaras and Sjolander [9]). Substantial decrease in the gap flow rate as a result of the wall motion is reported by Yaras and Sjolander [9] and Krishnababu and Whitney [10].…”

Section: Introductionmentioning

confidence: 99%

Aerodynamics of Tip Leakage Flows Near Partial Squealer Rims In an Axial Flow Turbine With and Without Wall Motion

Bansode

2023

joast

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The objective of present investigation is to study aerodynamics of tip leakage flows near partial squealer rims in an axial flow turbine cascade with and without end wall in motion. The reaction turbine blade used in the present investigations has a blade length of 400 mm and a geometric deflection of 82°. The blade chord is 102 mm with an aspect ratio of 3.9. The tip gap is maintained at 2% (2.04 mm) and the squealer rims were of 1.02 mm height. A total of seven cases were investigated with different squealer geometries including case without squealer rim. The coefficient of secondary loss coefficient (CSKE) is used as objective function. Minimum CSKE indicates minimum losses. From the investigations it is concluded that full suction side squealer rim is the optimum squealer geometry among all cases studied as CSKE was found to be minimum for this geometry. The optimum case was selected for wall motion studies. Three wall motions, namely; 75%,100% and 125% of the inlet meridional velocity were maintained and investigated. The CSKE is reduced with all three end wall motions except very close to the end wall. The exit flow angle is reduced near the end wall as compared to no wall motion.

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“…The effect of relative motion had been investigated by Morphis and Bindon 13 and Yaras and Sjolander. 14 In their major studies, shear effects (or scraping flow) would presumably become more important at small clearances. The countereffect of the scraping flow reduces the leakage, whereas the flow pattern at the clearance has not been affected by it greatly.…”

Section: Introductionmentioning

confidence: 99%

Tip leakage flow analysis of an axial turbine under the effect of separation at low Reynolds number

Shao

Zhu

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part A:

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The tip clearance flow could lead to work reduction and loss generation in turbomachines. However, the effect of separation at low Reynolds number on leakage flow is seldom studied. The previous method for evaluating tip leakage characteristics should also be further researched. Thus, numerical investigations on the tip clearance flow in an unshrouded axial-inflow turbine are conducted at low Reynolds number (3.5 × 104 of the rotor outlet at the designed condition) in the present study. The flow patterns and leakage mass flow rate of the clearance have been analyzed in detail. It is found that the tip clearance flow is greatly affected by the flow separation caused by low Reynolds number. The scraping ratio adopted in previous references does not accord with the clearance flow characteristics at low Reynolds number, especially in the front part of the clearance. A coefficient by −0.70 power of the Reynolds number is proposed to modify the scraping ratio in the present study. The synergy between the velocity and the pressure gradient is innovatively employed to research the tip clearance flow characteristics, and it gives a reliable criterion of indicating the flow patterns in the tip clearance.

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Effects of Simulated Rotation on Tip Leakage in a Planar Cascade of Turbine Blades: Part I—Tip Gap Flow

Cited by 75 publications

References 9 publications

Effect of in-service burnout effect on the transonic leakage flows over cavity tip model

Effect of in-service burnout effect on the transonic leakage flows over cavity tip model

Aerodynamics of Tip Leakage Flows Near Partial Squealer Rims In an Axial Flow Turbine With and Without Wall Motion

Tip leakage flow analysis of an axial turbine under the effect of separation at low Reynolds number

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