噴流拡散火炎の遷移に与える燃料の影響

抄録

A numerical study on the transition from laminar to turbulent flow of two-dimensional fuel jet flames developed in a co-flowing air stream was made by adopting the flame surface model with infinite chemical reaction rate and unit Lewis number. The time-dependent compressible Navier-Stokes equation was solved numerically with the equation for mixture fraction using a finite difference method. The numerical calculation was performed for the pure methane fuel jet, diluted methane fuel jet and hydrogen fuel jet, with Reynolds numbers 2 000 and 4 000. The effect of fuel containing an inert gas on the structure and the stability of the flame jet was studied. It was found that the transition length of hydrogen fuel jet was longer than that of methane fuel jet. In the downstream turbulent region, the axial velocity decreased due to the density increase, resulting in shorter flame length. Moreover, the lateral expansion of fluctuating flame surface was suppressed due to the low density inside the flame.