PARTIALLY PREMIXED HYDROGEN-METHANE FLAME SIMULATIONS AT RELEVANT GAS TURBINE CONDITIONS WITH A THICKENED FLAME MODEL ENHANCEMENT

The prediction of the behavior of stratified flames involving the hydrogen will represent a crucial task for the improvement of the Gas Turbine (GT) combustors performance in the next years. The Computational Fluid Dynamic (CFD) models usually employed to help the design definition need major revisions and improvements to provide reliable insights in this context. In this paper, an enhancement of the standard Thickened Flame Model (TFM) will be introduced trying to adapt the transport equation source term of each species to the combustion regime, the latter identified by the local flame index value. Being the TFM mainly devoted to describing a perfectly premixed flame, its mathematical formulation needs be redefined when also the diffusive regime has to be accounted for. The proposed approach will be validated against detailed measurements executed on a Jet in Cross Flow (JICF) fed with two moderate volumetric contents of H2 in blend with CH4. The selected operating conditions are relevant for the transfer of the methodology to real GT applications in terms of both temperature and pressure of the oxidizer. In particular, the ability of the model to predict the anchoring of the flame close to the fuel injection location only in the case of high H2 content (as highlighted by the experiments) will be investigated. Analogously, the correlation between the strain rate and the thermal field leading to a different flame anchoring mechanism of the jet when a low H2 mixture is considered will be addressed as well. The numerical findings in terms of flame position and morphology will be compared with the PLIF acquisition while the flow field will be characterized through the PIV measurements.