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SECOND-MOMENT CLOSURE STUDY ON COMBINED EFFECTS OF EXPANSION RATIO AND SWIRL INTENSITY ON TURBULENT MIXING IN MODEL COMBUSTORS

Suad Jakirlic
Department of Mechanical Engineering Institute of Fluid Mechanics and Aerodynamics (SLA) / Center of Smart Interfaces (CSI) Technische Universitat Darmstadt Petersenstrasse 17, D-64287 Darmstadt, Germany

Roland Jester-Zurker
Department of Mechanical Engineering, Darmstadt University of Technology, Petersenstr. 30, D-64287, Germany

Cameron Tropea
Technische Universität Darmstadt, Institute of Fluid Mechanics and Aerodynamics, Center of Smart Interfaces, International Research Training Group Darmstadt-Tokyo on Mathematical Fluid Dynamics, Germany

Resumo

An isothermal, incompressible, swirling flow in three generic combustor configurations featuring different inflow structure with respect to the circumferential velocity type (both configurations with annular and central swirling jet were considered), combustor confinement (in terms of expansion ratio ER) and swirl intensity (S) was studied computationally by means of Reynolds Averaged Navier-Stokes method (RANS), using Second-Moment Closure (SMC) models. The work focuses on the investigation of the combined effects of the above-mentioned flow parameters on the mixing between a swirling annular jet (representing air stream) and the non-swirling inner jet (representing fuel) within a combustor. Both the basic high-Reynolds number SMC model, modified to account for the non-linearities in the pressure scrambling and dissipation processes, and a low-Reynolds number SMC model, accounting separately for the viscous and non-viscous wall blockage, were applied. Inflow conditions are computationally generated, rather than prescribed. In the course of the inflow data generation, a number of the "equilibrium" swirling flows in the concentric annulus and pipe geometries, from which coaxial and central swirling jets expand into a combustion chamber, are computed. The SMC results reproduced all important mean flow and turbulent features in good agreement with available experimental and LES data.