Characterization of turbulent premixed hydrogen-enriched methane-air flames using large eddy simulation

Abstract

Environmental concerns are nowadays at the forefront of geopolitical discussions. Global warming and atmosphere pollution constitute the main threats to the planet Earth, and as they need to be reduced, industrialists and designers are developing new solutions. One of the most promising technology is lean premixed combustion (LPM), as operating combustion devices with lean fuel mixtures reduces pollutant emissions but also flame stability. Hydrogen-enrichment consists of a solution to enhance stability and reduce pollutant emissions of lean premixed flames. Practically, with the current trend to operate industrial combustion devices in lean mode, turbulent fully/partially premixed flames are required to fall in the high turbulence, high Karlovitz number Ka thin/broken reaction zone regime to fulfill power requirements. High Karlovitz number flames need further investigations, especially in terms of pollutant emissions and for the impact of different operating conditions. In order to study these effects, a turbulent counterflow flame configuration is selected for its versatility and simplicity. Numerical simulations are carried out by solving the Navier-Stokes equations for turbulent reacting flows using large eddy simulation combined with finite rate chemistry. CFD and chemistry simulations are performed using standard and modified solvers of two open source codes, namely OpenFOAM and CANTERA. The emphasis is first put on the ability of the LES model to reproduce essential features of the flame and predict species emissions by validation with DNS data, and a comparative study of hydrogen-enriched premixed flames on swirling flows. Finally, the turbulent counterflow flame is investigated for several operating conditions and different mixture compositions for a better understanding of high Karlovitz premixed flames enriched with hydrogen.