Large eddy simulation of hydrogen-air premixed flames in a small scale combustion chamber

While hydrogen is attractive as a clean fuel, it poses a significant risk due to its high-reactivity. This paper presents Large Eddy Simulations (LES) of turbulent premixed flames of hydrogen-air mixtures propagating in a small scale combustion chamber. The sub-grid-scale model for reaction rate uses a dynamic procedure for calculating the flame/flow interactions. Sensitivity of the results to the ignition source and to different flow configurations is examined. Using the relevant parameter from the calculations, the flames are located on the regimes of combustion and are found to span the thin and corrugated flamelet regimes, hence confirming the validity of flamelet modelling. The calculations are compared to published experimental data for a similar configuration. It is found that both the peak overpressure and flame position are affected by the number of baffles positioned in the path of the flame and this is consistent with earlier findings for hydrocarbon fuels. Also, the LES technique is able to reproduce the same flame shape as the experimental images. A coarse study of sensitivity to the ignition source shows that the size of the ignition kernel does not affect the flame structure but influences only the time where the peak overpressure appears while moving the ignition source away from the base plate leads to a decrease in the peak overpressure.