General geometry and height of diffusion flames and the height-dependence of centerline temperature above propane burners of relatively low heat release rate for the fuel size are described. The flame behavior is classified into 3 regimes according to the difference in the height-dependence of centerline temperature and in the general behavior of the flame. Flame height is represented as a function of Q∗ = Q/ρ0CpT0g1/2D5/2. The criterion for the adequacy of the concept of "virtual source" for the prediction of centerline temperature from the point-source turbulent plume theory is discussed.
