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Abstract

A method for calculating the turbulent isothermal flow in axisymmetric annular dump diffuser geometries is described and appraised. The calculation method is based on the numerical solution of the time-averaged transport equations for momentum, continuity, turbulence kinetic energy and energy dissipation, using a finite difference formulation. A boundary-fitted curvilinear orthogonal grid obtained from a solution of the inverse Laplace equations is used to represent the curved combustor head accurately and reduce numerical diffusion errors due to better alignment of the flow streamlines with the grid lines. Comparison between predicted results and measurements indicates that variations in (a) the overall pressure recovery and (b) the loss coefficient performance of the dump diffuser system, with changes in diffuser design features (for example inner/outer annulus mass flow split or dump gap), can be predicted to within 7 per cent of the inlet dynamic head without adopting a more refined turbulence closure. The method is therefore demonstrated to be a useful design tool for dump diffuser geometries.

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Numerical Calculations of the Flow in Annular Combustor Dump Diffuser Geometries

Abstract

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