乱流拡散火炎の巨視的性状のモデル化

抄録

A mathematical model to predict deterministic properties of turbulent diffusion flames is derived based on similarity analysis. In order to determine a few parameters appearing in the model, measurements of temperature, velocity, irradiance and flame geometry were made on the turbulent diffusion flames from a porous refractory burner of the diameter of 0.30m with propane as fuel. Excess temperature and velocity along the centerline of flame and flame height are formulated as functions of the properties of air and fuel, physical constants and the parameters governing the flame structure; θ_a = 1.77kq_fc_r/mC_p, w_a = 1.76√gβkq_fc_rz/mC_p and L_f = 0.00154 (mQ/Dπρq_fc_r)², where Q is the heat input, C_p is specific heat of air, q_f is combustion heat of fuel and c_r is the mass fuel to air ratio. Ratio of heat dissipation due to convection to heat input, k air excess ratio, m and the parameter characterizing the turbulence D are estimated experimentally as k≈0.65, m≈3.96 and D≈0.000069Q^4/5 respectively. Characteristics of turbulent diffusion flames as radiation heat source is also studied on the basis of the above model, and it was derived that the heat dissipation due to radiation is proportional to Qⁿ, where n takes 0.8-1.2 depending on the composition of carbon in the fuel.