Experimental Investigation of Flame Kernel in Turbulent Partial Premixed Flames

The flame kernel propagation is believed to be influenced by many operating parameters such as mixing level, turbulent intensity, and the mixture equivalence ratio. The purpose of this study is to investigate the effect of the mixture equivalence ratio and turbulence intensity on the flame kernel and flow field interlinks in partially premixed natural gas flames. Three jet equivalence ratios of 1, 1.5, and 2 are considered at values of jet velocities in the range from 10 to 20 m/s. This study was done under constant degree of partial premixing. A pulsed Nd: YAG laser is used for the flame ignition, and the turbulent flow field is captured at several time intervals from ignition using two-dimensional Planar Imaging Velocimetry (PIV). The mean flow field doesn’t influence with the flame kernel propagation. The turbulent flow field indicates an increase in the global turbulence intensity in flames associated with the kernel propagation in comparison with the isothermal case. The jet equivalence ratio of one enhances the flame kernel propagation and it gives the highest rate of kernel propagation. Increasing the jet equivalence ratio to 1.5 and 2 reduces the intensity of chemical reaction and hence the effect of turbulence becomes the dominant factor effecting the propagation of the flame kernel.At jet velocity of 20 m/s, an early flame kernel extinction is recorded without any respect to jet equivalence ratio. At the early stage of the kerne