Prediction of Tip-Leakage Losses in Axial Turbines

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

doi:10.1115/1.2927987

Cited by 90 publications

(36 citation statements)

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“…These losses can be reduced if the discharge coefficient is decreased. A discussion of the tip discharge coefficient for axial turbine blades is given by Heyes et al [10] or Willinger and Haselbacher [18]. Their results are valid for blades with flat tips as well as squealers.…”

Section: Fig 3 Blade Tip Geometrymentioning

confidence: 93%

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An innovative passive tip-leakage control method for axial turbines: Basic concept and performance potential

Hamik

Willinger

2007

J. of Therm. Sci.

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Section: Fig 3 Blade Tip Geometrymentioning

confidence: 93%

“…The blockage effect is proportional to the injection mass flow rate. Based on these findings, the discharge coefficient model without any tip injection, presented by Willinger and Haselbacher [18] will be extended to take into account the blade tip injection.…”

Section: Fig 3 Blade Tip Geometrymentioning

confidence: 99%

An innovative passive tip-leakage control method for axial turbines: Basic concept and performance potential

Hamik

Willinger

2007

J. of Therm. Sci.

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“…The leakage vortex has high total pressure loss and strong rotary motion. Yaras and Sjolander [6] mentioned from their earlier investigations that secondary loss which is attributed to passage vortex fell off quickly with clearance and at 2% clearance it accounted for an insignificant fraction compared with loss in the tip leakage flow. The passage vortex grows in size as it moves axially.…”

Section: C~ • D R (1)mentioning

confidence: 97%

Experimental investigations of the three-dimensional flow in a large deflection turbine cascade with tip clearance

1998

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Results obtained from an experimental study of the three-dimensional flow survey within and exit of a large deflection linear turbine cascade are presented for a tip clearance levels of 0.08, 1.5, 3.0 percent of chord and compared with the help of boundary layer probes and that within and exit of a blade passage was done with a miniaturised five hole probe. End wall and blade tip surface static pressures were also obtained, in addition to flow visualisation studies. A strong horse-shoe vortex forms in front of the leading edge for zero clearance whereas this vortex does not appear for 3 percent clearance indicating that for large clearance the pressure forces have dominating influence than the viscous forces. In addition to normally known clearance vortex, a small tip separation vortex was noticed on the blade tip surface inside the tip gap. Due to the area contraction caused by the tip separation vortex, the fluid moving towards the tip gap from the pressure side is accelerated. Downstream of the vortex, the endwall pressure increases due to flow mixing. Both vortices increase in size and strength along the chord. The mixing is incomplete in the aft portion of the blade. The tip gap velocity profiles exhibit wake like characteristics especially at axial positions where the mixing is incomplete. The passage vortex in the present investigations did not diminish with increase in clearance. The discharge coefficient and the total pressure loss coefficient within the tip gap show similar tendency with lower values near the leading and trailing edge regions. K e y w o r d s : t u r b i n e c a s c a d e , t i p c l e a r a n c e v o r t e x , t i p s e p a r a t i o n v o r t e x , h o r s e -s h o e v o rt e x ,

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“…With a suitable discharge coefficient, good predictions were then obtained for the gap mass flow rate. The model was subsequently used in a loss prediction method (Yaras and Sjolander, 1992) since it was found that tip-leakage losses are strongly dependent on the mass flow rate through the gap. The model is extended here to account for the effects of relative wall motion.…”

Section: Flow In the Gap Main Stream And Near The Tipmentioning

confidence: 99%

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

Yaras

Sjolander

1992

Journal of Turbomachinery

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The paper presents further results from a continuing study on tip leakage in axial turbines. Rotation has been simulated in a linear cascade test section by using a moving-belt tip wall. Measurements were made inside the tip gap with a three-hole pressure probe for a clearance size of 3.8 percent of the blade chord. Two wall speeds are considered and the results are compared with the case of no rotation. As in other experiments, significant reduction in the gap mass flow rate is observed due to the relative motion. The detailed nature of the measurements allows the dominant physical mechanism by which wall motion affects the tip gap flow to be identified. Based on the experimental observations, an earlier model for predicting the tip gap flow field is extended to the case of relative wall motion. Part II of the paper examines the effect of the relative motion on the downstream flow field and the blade loading. 652/Vol. 114, JULY 1992Transactions of the ASME Copyright © 1992 by ASME Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 03/30/2015 Terms of Use: http://asme.org/terms Journal of Turbomachinery JULY 1992, Vol. 114/655 Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 03/30/2015 Terms of Use: http://asme.org/terms Journal of Turbomachinery JULY 1992, Vol. 114/657 Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 03/30/2015 Terms of Use: http://asme.org/terms 658/Vol. 114, JULY 1992 Transactions of the ASME Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 03/30/2015 Terms of Use: http://asme.org/terms

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Prediction of Tip-Leakage Losses in Axial Turbines

Cited by 90 publications

References 0 publications

An innovative passive tip-leakage control method for axial turbines: Basic concept and performance potential

An innovative passive tip-leakage control method for axial turbines: Basic concept and performance potential

Experimental investigations of the three-dimensional flow in a large deflection turbine cascade with tip clearance

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

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