Numerical Studies of Hydrogen and LPG Turbulent Premixed Flames

This paper presents numerical studies of turbulent premixed flames for lean hydrogen and stoichiometric LPG mixtures. The transient flames under investigation propagate past repeated solid baffle plate(s) and a square obstruction with varied area blockage ratios in a lab-scale combustion chamber. The chamber allows for up to three removable baffle plates to be equipped in addition to a square obstacle to increase turbulence intensity within the chamber. The hydrogen mixture is studied at an equivalence ratio of 0.7 and the LPG mixture is investigated at an equivalence ratio of 1.0. An in-house computational fluid dynamics (CFD) model is applied to numerically evaluate transient flame propagation. The large eddy simulation (LES) technique is applied for turbulence modelling. Reaction rate calculations are carried out using a dynamic flamelet model for turbulent premixed flames. Four flow configurations with different area blockage ratios (ABRs) are used to investigate combustion overpressure. Numerical results are compared against published experimental data to ascertain the ability of the numerical model in reproducing key combustion events for hydrogen and LPG. A conclusion is drawn that the increase in blockage ratio raises peak combustion overpressure and the maximum rate of pressure rise. Hydrogen combustion, albeit at a lower equivalence ratio, results in higher maximum overpressures and peak rate of pressure rise when compared with LPG.