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research-article

AN EXPERIMENTAL INVESTIGATION OF ADIABATIC FILM COOLING EFFECTIVENESS AND HEAT TRANSFER COEFFICIENT ON A TRANSONIC SQUEALER TIP

[+] Author and Article Information
Andrew J. Saul

Flat 1 Queens Court 36 Kelburne Road Oxford, Oxfordshire OX4 3SH United Kingdom andrew.saul@eng.ox.ac.uk

Peter T. Ireland

Department of Engineering Science Osney Mead Oxford, OX2 0ES United Kingdom peter.ireland@eng.ox.ac.uk

John D. Coull

Whittle Laboratory 1 J J Thomson Ave Cambridge, Cambs CB3 0DY United Kingdom jdc38@cam.ac.uk

Tsun Holt Wong

Osney Thermo-Fluids Laboratory Department of Engineering Science Oxford, OX2 0ES United Kingdom holt.wong@eng.ox.ac.uk

Haidong Li

PO Box 3, Filton Bristol Bristol, BS34 7QE United Kingdom haidong.li@rolls-royce.com

Eduardo Romero

Turbines Design Engineering PO BOX 3, Gipsy Patch Lane, Filton, Patchway Bristol, BS34 7QE United Kingdom eduardo.romero@rolls-royce.com

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Turbomachinery. Manuscript received October 30, 2018; final manuscript received March 20, 2019; published online xx xx, xxxx. Assoc. Editor: Kenneth Hall.

ASME doi:10.1115/1.4043263 History: Received October 30, 2018; Accepted March 20, 2019

Abstract

The effect of film cooling on a transonic squealer tip has been examined in a high speed linear cascade, which operates at engine realistic Mach and Reynolds numbers. Tests have been performed on two uncooled tip geometries with differing pressure side rim edge radii, and a cooled tip matching one of the uncooled cases.

The pressure sensitive paint technique has been used to measure adiabatic film cooling effectiveness on the blade tip at a range of tip gaps and coolant mass flow rates. Complementary tip heat transfer coefficients have been measured using transient infrared thermography, and the effects of the coolant film on the tip heat transfer and engine heat flux examined.

The uncooled data show that the tip heat transfer coefficient distribution is governed by the nature of flow reattachments and impingements. The squealer tip can be broken down into three regions, each exhibiting a distinct response to a change in the tip gap, depending on the local behaviour of the overtip leakage flow. Complementary CFD shows that the addition of casing motion causes no change in flow over the pressure side rim.

Injected coolant interacts with the overtip leakage flow, which can locally enhance the tip heat transfer coefficient. The film effectiveness is dependent on both the coolant mass flow rate and tip clearance. At increased coolant mass flow, areas of high film effectiveness on the pressure side rim coincide strongly with a net heat flux reduction and in the subsonic tip region with low heat transfer coefficient.

Copyright © 2019 by Rolls-Royce plc
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