In order to deepen understanding the flashback due to combustion induced vortex breakdown(CIVB) and prevent it,the effects of swirl strength on CIVB flashback in methane/air premixed flames were investigated.Flashback limits of methane/air premixed flames at different swirl numbers were obtained by numerical simulation with two-dimensional axisymmetric model and implementing user defined function(UDF) to simulate swirl by modifying the momentum conservation equations.Vortex breakdown during flashback was an...