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Research Papers

Improved Trench Film Cooling With Shaped Trench Outlets

[+] Author and Article Information
Habeeb Idowu Oguntade

The Centre for CFD,
School of Process, Environment,
and Materials Engineering,
University of Leeds,
Leeds, LS2 9JT, UK
e-mail: mnhio@leeds.ac.uk

Gordon E. Andrews

Energy and Resources Research Institute,
School of Process, Environment,
and Materials Engineering,
University of Leeds,
Leeds, LS2 9JT, UK

Derek B. Ingham

The Centre for CFD,
School of Process, Environment,
and Materials Engineering,
University of Leeds,
Leeds, LS2 9JT, UK

Mohammed Pourkashanian

Energy and Resources Research Institute,
School of Process, Environment,
and Materials Engineering,
University of Leeds,
Leeds, LS2 9JT, UK;
The Centre for CFD,
School of Process, Environment,
and Materials Engineering,
University of Leeds,
Leeds, LS2 9JT, UK

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Turbomachinery. Manuscript received September 6, 2011; final manuscript received November 11, 2011; published online November 1, 2012. Editor: David Wisler.

J. Turbomach 135(2), 021009 (Nov 01, 2012) (10 pages) Paper No: TURBO-11-1201; doi: 10.1115/1.4006606 History: Received September 06, 2011; Revised November 11, 2011

The influence of the shape of the downstream edge of trench film cooling hole outlets on film cooling effectiveness was investigated using CFD for flat plate film cooling. A 90 deg trench outlet wall with impinging 30 deg film cooling jets results in improved transverse film cooling effectiveness but produces a vertical slot jet into the cross flow, which is not the best aerodynamics for optimum film cooling. It was considered that improvements in the cooling effectiveness would occur if the trailing edge of the trench outlet produced a flow that was inclined in the direction of the crossflow. Beveled and filleted trench outlet shapes were investigated. The CFD predictions were shown to predict well the conventional sharp edged trench outlet experimental results for a flat plate geometry. The flat plate CFD predictions were also shown to predict the experimental results for trench cooling on the suction side of a turbine vane, where the local curvature was small relative to the trench width. The beveled and filleted trench outlets were predicted to suppress the vertical jet momentum and give a Coanda effect that allowed the cooling air to attach to the downstream wall surface. This produced an improved transverse spread of the coolant. Also, it was predicted that reducing the coolant mass flow per hole and increasing the number of rows of holes gave, for the same total coolant mass flow and the same surface area, a superior surface averaged cooling effectiveness.

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References

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Figures

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Fig. 1

View of the computational grid for the 15 deg bevelled trench configuration

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Fig. 2

Trench outlet configurations

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Fig. 3

Comparison of the computed and measured data of the lateral averaged film cooling effectiveness for blowing ratio of (a) M = 0.5 and (b) 1.0

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Fig. 4

Comparison of the computed and measured data of the lateral averaged film cooling effectiveness for blowing ratio of (a) M = 0.6, (b) 1.0, and (c) 1.4

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Fig. 5

Predicted influence of the trench depth on the η¯ (a) M = 0.6, (b) M = 1.0, and (c) M = 1.4

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Fig. 6

Predicted influence of the trench depth on the local lateral effectiveness distribution (a) M = 0.6 and (b) M = 1.0 at and X/D = 3

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Fig. 7

Influence of the shaped trench outlet on film cooling effectiveness for same overall trench depth of 0.75D for (a) M = 0.6, (b) M = 1.0, and (c) M = 1.4

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Fig. 8

Laterally averaged adiabatic film cooling effectiveness as a function of M at a range of X/D from the hole exit for Case V

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Fig. 9

Comparison of the cooling of a surface area X/D = 10 by Z/D = 2.8 using the same coolant mass flow rate for one film hole and for four holes with a blowing rate per hole of 1/4 that of the single hole

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Fig. 10

Spatial film cooling effectiveness contours of the test surface

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Fig. 11

Dimensionless spatial temperature profile at the plane of X/D = 3

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Fig. 12

Local lateral distributions of adiabatic film cooling effectiveness at X/D = 3 for M = 0.6

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Fig. 13

Local lateral distributions of adiabatic film cooling effectiveness at X/D = 3 for M = 1.0

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