High speed propagation of premixed flame in swirling flow - II. Ignition position and process of combustion

The previous research of vortex-bursting shows that in the swirling condition, premixed methane-air combustion can be stable in the high inlet velocity gas. Based on the investigation of both the combustion efficiency of swirling premixed combustor and the effect of distribution of inlet velocity on enhancement of combustion efficiency in the previous paper, the numerical research of ignition position effect on the flame stability is carried on in this work. It is found that inappropriate ignition position can affect the process of flame evolution. Under the same condition, development of combustion will evolve in different trends if the flame is ignited at different positions in the flow field. A non-dimensional parameter is put forward for describing the ignition position. When ignition position is located on the axis and low velocity area of tube, the resulting flame will be stable. Instead, when ignition position is in high velocity area, the flame is finally blown out. In this work, the useful theoretical and applicable results for enhancing stability of premixed combustion are achieved.