An Empirical Prediction Method For Secondary Losses In Turbines—Part II: A New Secondary Loss Correlation

[+] Author and Article Information
M. W. Benner1

National Research Council of Canada, Institute for Aerospace Research, Ottawa, ON K1A 0R6, Canadamichael.benner@nrc-cnrc.gc.ca

S. A. Sjolander

Department of Mechanical and Aerospace Engineering, Carleton University, Ottawa, ON K1S 5B6, Canada

S. H. Moustapha

 Pratt and Whitney Canada, Ltd., Longueuil, PQ, J4G 1A1 Canada


To whom correspondence should be addressed.

J. Turbomach 128(2), 281-291 (Feb 01, 2005) (11 pages) doi:10.1115/1.2162594 History: Received October 01, 2004; Revised February 01, 2005

A new empirical prediction method for design and off-design secondary losses in turbines has been developed. The empirical prediction method is based on a new loss breakdown scheme, and as discussed in Part I, the secondary loss definition in this new scheme differs from that in the conventional one. Therefore, a new secondary loss correlation for design and off-design incidence values has been developed. It is based on a database of linear cascade measurements from the present authors’ experiments as well as cases available in the open literature. The new correlation is based on correlating parameters that are similar to those used in existing correlations. This paper also focuses on providing physical insights into the relationship between these parameters and the loss generation mechanisms in the endwall region. To demonstrate the improvements achieved with the new prediction method, the measured cascade data are compared to predictions from the most recent design and off-design secondary loss correlations (Kacker, S. C. and Okapuu, U., 1982, ASME J. Turbomach., 104, pp. 111-119, Moustapha, S. H., Kacker, S. C., and Tremblay, B., 1990, ASME J. Turbomach., 112, pp. 267–276) using the conventional loss breakdown. The Kacker and Okapuu correlation is based on rotating-rig and engine data, and a scaling factor is needed to make their correlation predictions apply to the linear cascade environment. This suggests that there are additional and significant losses in the engine that are not present in the linear cascade environment.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Evaluation of the Kacker and Okapuu/Moustapha secondary loss correlations: (a) Engine-representative, and (b) cascade-representative loss levels

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Figure 2

Evaluation of the secondary loss correlation given by Eq. 19

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Figure 3

The influence of convergence ratio and total airfoil loading on secondary losses (based on the secondary loss correlation of Wolf (28))

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Figure 4

The influence of aspect ratio on secondary losses

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Figure 5

Evaluation of the new secondary loss correlation (Eq. 20)





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