The Effect of Work Processes on the Casing Heat Transfer of a Transonic Turbine

[+] Author and Article Information
Steven J. Thorpe

Department of Aeronautical and Automotive Engineering, Loughborough University, Loughborough LE12 7TW, UKs.j.thorpe@lboro.ac.uk

Robert J. Miller

Whittle Laboratory, University of Cambridge, Cambridge CB3 0DY, UK

Shin Yoshino

 Tokyo Electric Power Company, Yokohama 230-8510, Japan

Roger W. Ainsworth

Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, UK

Neil W. Harvey

 Rolls-Royce plc, Derby DE24 8BJ, UK

J. Turbomach 129(1), 84-91 (Feb 01, 2005) (8 pages) doi:10.1115/1.2372772 History: Received October 01, 2004; Revised February 01, 2005

This paper considers the effect of the rotor tip on the casing heat load of a transonic axial flow turbine. The aim of the research is to understand the dominant causes of casing heat transfer. Experimental measurements were conducted at engine-representative Mach number, Reynolds number, and stage inlet to casing wall temperature ratio. Time-resolved heat-transfer coefficient and gas recovery temperature on the casing were measured using an array of heat-transfer gauges. Time-resolved static pressure on the casing wall was measured using Kulite pressure transducers. Time-resolved numerical simulations were undertaken to aid understanding of the mechanism responsible for casing heat load. The results show that between 35% and 60% axial chord the rotor tip-leakage flow is responsible for more than 50% of casing heat transfer. The effects of both gas recovery temperature and heat transfer coefficient were investigated separately and it is shown that an increased stagnation temperature in the rotor tip gap dominates casing heat transfer. In the tip gap the stagnation temperature is shown to rise above that found at stage inlet (combustor exit) by as much as 35% of stage total temperature drop. The rise in stagnation temperature is caused by an isentropic work input to the tip-leakage fluid by the rotor. The size of this mechanism is investigated by computationally tracking fluid path lines through the rotor tip gap to understand the unsteady work processes that occur.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 5

Experimentally measured casing heat transfer coefficient in the rotor tip gap and rotor passage

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Figure 6

Measurement of the time-resolved gas recovery temperature on the casing wall

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Figure 7

Time-mean computational prediction of casing flow total temperature

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Figure 8

Time-mean computational prediction of casing static pressure

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Figure 9

Experimental measurements of the time-resolved casing static pressure

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Figure 10

Computationally predicted temporal gradient in static pressure and experimentally measured pressure

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Figure 11

Fluid path lines through the rotor tip gap

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Figure 12

Computationally predicted stagnation temperature variations along seven path lines (these path lines are shown in Fig. 1)

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Figure 1

Location of pressure and heat transfer measurements on the casing wall

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Figure 2

Time-resolved measurements of the casing heat transfer rate

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Figure 3

Experimentally measured casing heat load caused by rotor tip and passage flows

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Figure 4

Experimentally measured casing recovery temperature in the rotor tip gap and rotor passage




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