To provide a reference for future burner design,a numerical simulation method on the influence on coaxle swirl burner of change of flaring angle of primary air tube was proposed.The method used the turbulent model with κ-ε equations based on the renormalization group theory to simulate cold flow field of burner outlet.Study of the flow filed distribution and the change of the back flow size relative to the different primary air tube flaring angles of the co-axis swirl burner showed that the swirl jet axle v...