Investigation into ignition and flame propagation in a combustor with prefilming and non-prefilming atomization

Prefilming atomization is widely used in advanced combustors, whereas the effects of interactions between liquid fuel and the wall on ignition-related processes are complex and require further exploration. We investigate ignition and flame propagation in a combustor with prefilming (S1) and non-prefilming (S2) airblast atomizers. High-speed imaging, laser-based technique, and flame-tracking algorithm were used to investigate the swirling flow fields, atomization performances, and the evolution of flame kernels. Results show that the combustor with S1 exhibited a wider ignition boundary than that with S2. The flame kernel split and the sub-kernels extinguished more quickly in the combustor with S2. We used the characteristics of the flame in these combustors to identify several stages of the ignition process and compared them in the two schemes of atomization. The extracted trajectories of the flame kernel indicated that once the spark had been generated by the ignition electrode, flame formation involved an upstream movement. However, the trajectories of the flame kernels in schemes S1 and S2 were completely different. Its upstream movement in S2 was more direct while that in S1 was more tortuous. Scheme S1 initially featured downstream movement before upstream movement while the flow in S2 moved directly upstream. This trajectory significantly shortened the duration of movement of the flame kernel to reduce unnecessary energy dissipation. The swirling flow field was responsible for the difference in trajectories of the flame kernel between the schemes. These findings can inform investigations into atomization-related performance and the optimization of ignition in combustors.