Ignition Source Effect on Modelling Hydrogen Premixed Combustion

This paper presents numerical study of premixed combustion of hydrogen-air mixtures inside a laboratory scale combustion chamber. The study is carried out on a premixed lean mixture of hydrogen/air flames with an equivalence ratio of 0.7. The main focus of the current work is to examine the effects of the way the source of ignition would have on the overall characteristics of combustion. An in-house Large Eddy Simulation (LES) modelling technique has been used to carry out the numerical simulations. The model predictions have been validated against available published experimental data where ignition has been introduced through the use of a laser beam. Successful numerical representation of the experimental initial and boundary conditions has resulted in good agreement between the experimental and numerical results for the generated combustion flame and pressure-time history. It was concluded that the combustion characteristics are sensitive to the size of the ignition source in terms of the timing occurrence of the peak pressure but not its magnitude. This finding has practical importance in analyzing explosion hazards, internal combustion engines and gas turbine combustors.