Towards Best Practice for Predicting a Lifted Hydrogen Diffusion Flame Using a Flamelet Generated Manifold Approach

Abstract

Abstract This paper examines a lifted turbulent H2/N2 diffusion flame in a vitiated co-flow, using a Flamelet Generated Manifold (FGM) combustion model. FGM is commonly used in combusting simulations in the gas turbine industry as it is cheaper than solving detailed chemistry as part of the simulation. The aim of this paper is to examine the ability of the FGM model to reproduce experimental results, and its sensitivity to modelling choices, using an implementation within the commercial code, Simcenter STAR-CCM+. Hence, the current study systematically examines the impact of turbulence modelling, inlet conditions, the flamelet model used to generate the FGM table and the chemical mechanisms. Both Reynold Averaged Navier Stokes (RANS) and Large Eddy Simulations (LES) are presented with focus on the effect of inlet conditions, three different flamelet generation methods and two chemical mechanisms. The flame lift-off height is shown to be highly sensitive to chemical mechanism and flamelet table generation method, with the 0D flamelet giving a higher lift-off than the 1D flamelets. The inlet velocity profile was found to have less of an impact on LES results. This work shows that care should be taken when attempting to identify an accurate simulation methodology and that modelling choices are not considered in isolation as the apparent superiority of a modelling choice may be an artefact of other modelling choices.