Title: URANS modelling of pulsed turbulent jets and premixed jet flames

Authors: M. Hettel, H. Buchner, M. Weiss, P. Habisreuther, N. Zarzalis, H. Bockhorn

Addresses: Division of Combustion Technology, Engler-Bunte-Institute, University of Karlsruhe (TH), Engler-Bunte-Ring 1, Karlsruhe 76131, Germany. ' Division of Combustion Technology, Engler-Bunte-Institute, University of Karlsruhe (TH), Engler-Bunte-Ring 1, Karlsruhe 76131, Germany. ' Division of Combustion Technology, Engler-Bunte-Institute, University of Karlsruhe (TH), Engler-Bunte-Ring 1, Karlsruhe 76131, Germany. ' Division of Combustion Technology, Engler-Bunte-Institute, University of Karlsruhe (TH), Engler-Bunte-Ring 1, Karlsruhe 76131, Germany. ' Division of Combustion Technology, Engler-Bunte-Institute, University of Karlsruhe (TH), Engler-Bunte-Ring 1, Karlsruhe 76131, Germany. ' Division of Combustion Technology, Engler-Bunte-Institute, University of Karlsruhe (TH), Engler-Bunte-Ring 1, Karlsruhe 76131, Germany

Abstract: The formation of self-excited pressure oscillations in technical combustion systems depends on the dynamical behaviour of the flames used. One goal of future combustor development is the prediction of combustion instabilities during the design process. The first aim of the work was to calculate the flame transfer function of forced flames with CFD codes using |Unsteady-Reynolds-Averaged-Navier-Stokes| approaches. Pulsed isothermal turbulent jets as well as pulsed premixed jet flames with different thermal loads (20/40/60 kW) were modelled using forcing frequencies of up to 200 Hz. Three different versions of the κ-ε turbulence model and a |Turbulent-Flamespeed-Closure| combustion model were applied. A variation of discretisation schemes and turbulent diffusion allowed the estimation of numerical errors. An important mechanism driving combustion instabilities is the interaction of the flame with large-scale ring vortices. The second aim was to investigate how the interaction works to get more insight and understanding of this phenomenon. The results obtained were validated against experimental data.

Keywords: flame transfer function; flame frequency response; combustion modelling; turbulent premixed flames; combustion instabilities; ring vortex; URANS; pulsed turbulent jets; computational fluid dynamics; CFD code; forced flames; thermal loads; turbulent diffusion; large-scale ring vortices.

DOI: 10.1504/PCFD.2005.007425

Progress in Computational Fluid Dynamics, An International Journal, 2005 Vol.5 No.7, pp.386 - 397

Published online: 18 Jul 2005 *

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