Flow calculations for a premixed flame behind a bluff body flame holder using a conventional finite difference code with a standard k-ε turbulence model have been found to give poor predictions of the overall flow field. A major factor is believed to be the inadequately modelled large scale turbulence in the wake region. In order to improve the numerical prediction capability a large eddy simulation (LES) technique, which has recently given very good predictions for the non-reacting flow around the same flame holder, has been extended to handle reacting flow. This paper presents a combustion model which considers the influence of turbulence on the effective chemical reaction rates and which is adapted to the LES framework. The combustion model is of the “eddy dissipation type” previously developed by Magnussen. The present flow simulation code has been applied on the premixed bluff body flow case and results are compared with measurement data from gas analysis, LDA (Laser Doppler Anemometry) and CARS techniques. Significant improvements in the overall predictions are demonstrated even on a coarse mesh.

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The design of a generic experimental LPP-combustor (Lean Premixed Prevaporized) is described. The combustor was tested at inlet pressures between 3 and 7 bar and with an inlet temperature between 500 K and 700 K. Tests were run with Diesel No.2 and Jet A-1 fuels comparing emissions of CO and NOx. The tests showed low NOx and CO values for a range of conditions although difficulties of using the LPP-technique close to the final boiling point of the fuel were encountered. To increase the understanding of the flow situation inside the combustor, numerical simulations using a large eddy simulation code was also performed. The main interest in the calculations was the evaporation process of the liquid fuel.

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