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Research Papers

Turbine Aerodynamic Performance Measurement Under Nonadiabatic Conditions

[+] Author and Article Information
Nicholas R. Atkins1

Whittle Laboratory,  University of Cambridge, Cambridge CB3 0DY, UKnra27@cam.ac.uk

Roger W. Ainsworth

Department of Engineering Science,  University of Oxford, Oxford OX1 3PJ, UKrog.ainsworth@stcatz.ox.ac.uk

1

Previously at the Department of Engineering Science, University of Oxford, Oxford, UK.

J. Turbomach 134(6), 061001 (Aug 27, 2012) (8 pages) doi:10.1115/1.4004857 History: Received February 03, 2009; Revised July 29, 2011; Published August 27, 2012; Online August 27, 2012

The practical performance, both the efficiency and durability, of a high-pressure (HP) turbine depends on many interrelated factors, including both the steady and unsteady aerodynamics and the heat transfer characteristics. The aerodynamic performance of new turbine designs has traditionally been tested in large scale steady flow rigs, but the testing is adiabatic, and the measurement of heat transfer is very difficult. Transient facilities allow fully scaled testing with simultaneous heat transfer and aerodynamic performance measurements. The engine matched gas-to-wall temperature ratio simulates more closely the boundary layer and secondary flow development of the engine case. The short duration of the testing means that the blades are effectively isothermal with a rise of only a few degrees during a test. To isolate the aerodynamic losses, and thus the entropy generation due to the viscous losses, the entropy reduction due to heat transfer during the expansion needs to be determined. This entropy reduction is path dependent and requires knowledge of the full temperature and heat flux fields. This paper demonstrates a simple methodology for estimation of this entropy reduction, which allows the calculation of the adiabatic efficiency from the results of engine representative nonadiabatic testing. The methodology is demonstrated using a computational fluid dynamics (CFD) prediction which is validated against experimental heat flux data. Details of the other corrections required for transient test techniques such as unsteady leakage flows are also discussed.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

A schematic of the Oxford Rotor Facility turbine stage showing the thermodynamic stations and the vane and rotor control volumes

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Figure 2

Enthalpy-entropy chart showing turbine expansion with and without heat transfer, indicative of a transient test and steady state test respectively

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Figure 3

Enthalpy-entropy chart showing detail of the elemental entropy drop caused by heat transfer

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Figure 4

Detail of the multiblock mesh

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Figure 5

Blade surface heat flux contours showing the effect of the secondary flows on the surface heat flux

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Figure 6

Comparison of ORF experimental casing heat flux data and HYDRA prediction. The horizontal axis shows circumferential position in degrees. The calculation is performed in the blade relative frame which gives an arbitrary origin.

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Figure 7

(a) Comparison of ORF experimental tip heat flux data [17] and HYDRA prediction at three gauge locations. (b) Detail of the gauge locations on the blade tip casing heat flux.

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Figure 8

Comparison of the integral and approximate enthalpy corrections

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