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Title: Experimental and computational study of hybrid diffusers for gas turbine combustors
Authors: Walker, Alastair Duncan
Denman, Paul A.
McGuirk, James J.
Issue Date: 2004
Publisher: © ASME
Citation: WALKER, A.D., DENMAN, P.A. and MCGUIRK, J.J., 2004. Experimental and computational study of hybrid diffusers for gas turbine combustors. Journal of Engineering for Gas Turbines and Power, 126 (4), pp. 717-725
Abstract: The increasing radial depth of modern combustors poses a particularly difficult aerodynamic challenge for the pre-diffuser. Conventional diffuser systems have a finite limit to the diffusion that can be achieved in a given length and it is, therefore, necessary for designers to consider more radical and unconventional diffuser configurations. This paper will report on one such unconventional diffuser; the hybrid diffuser which, under the action of bleed, has been shown to achieve high rates of diffusion in relatively short lengths. However, previous studies have not been conducted under representative conditions and have failed to provide a complete description of the relevant flow mechanisms making optimization difficult. Utilizing an isothermal representation of a modern gas turbine combustor an experimental investigation was undertaken to study the performance of a hybrid diffuser compared to that of a conventional, single-passage, dump diffuser system. The hybrid diffuser achieved a 53% increase in area ratio within the same axial length generating a 13% increase in the pre-diffuser static pressure recovery coefficient which, in turn, produced a 25% reduction in the combustor feed annulus total pressure loss coefficient. A computational investigation was also undertaken in order to investigate the governing flow mechanisms. A detailed examination of the flow field, including an analysis of the terms within the momentum equation, demonstrated that the controlling flow mechanisms were not simply a boundary layer bleed but involve a more complex interaction between the accelerating bleed flow and the diffusing mainstream flow. A greater understanding of these mechanisms enabled a more practical design of hybrid diffuser to be developed that not only simplified the geometry but also improved the quality of the bleed air making it more attractive for use in component cooling.
Description: This item is closed access. It is an article from the serial, Journal of Engineering for Gas Turbines and Power [© ASME ]. For more information on how to obtain this article please visit the ASME Digital Library, http://www.asmedl.org/ .
Version: Closed access
DOI: 10.1115/1.1772403
URI: https://dspace.lboro.ac.uk/2134/5877
ISSN: 0742-4795
Appears in Collections:Closed Access (Aeronautical and Automotive Engineering)

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