NUMERICAL MODELLING OF NOX EMISSIONS AND FLAME STABILIZATION MECHANISMS IN GAS TURBINE BURNERS OPERATING WITH HYDROGEN AND HYDROGEN-METHANE BLENDS

Main objective of this paper is to assess the capability of numerical models in predicting NOx emissions and flame stabilization mechanisms of a heavy-duty gas turbine burner when operated with hydrogen and hydrogen-methane blends. Effort focused on the selection of the proper input to pretabulated Flamelet Generation Manifold combustion model. A dedicated sensitivity to laminar flame speed formulation has been performed as well, since it primarily affects flame stabilization through the closure term of the progress variable transport equation. Available NOx emissions data from full scale annular combustor rig test with hydrogen-air mixtures are presented first in this paper: test results have been used to validate the numerical setup for the reference geometry. Then, the model has been used to predict NOx emissions of alternative geometries in case of pure hydrogen, allowing screening of viable options to reduce the scope of a dedicated test campaign. Concerning flame stabilization mechanisms, simulations have been carried out for a reference geometry first: data from dedicated tests have been used to specialize the tool. Results of modified geometries are shown, to explore the effect of different fuel injection patterns or internal channel modifications. Based on the analysis outcomes, a discussion is provided regarding advantages and drawbacks of each proposed solution, as well as the ability of modelling setup in catching varied flame stabilization mechanisms.