An experimental and theoretical study of horizontal turbulent diffusion jet flames is described. Measurements of the mean and fluctuating velocities (using LDV), mean temperature distributions, flame trajectory and size and shape, flame intermittency, and total radiation heat flux are obtained for three horizontal flames and their vertical counterparts. The use of a two dimensional analysis to predict flame trajectories is reported. The development of a three dimensional boundary layer analysis in a curvilinear coordinate system using the finite difference technique is presented. Two turbulence models, i.e., the standard k - varepsilon two-equation model and the algebraic stress model (ASM) are applied to horizontal flames using the FLUENT CFD software package. The study has indicated that horizontal flames are entirely different from that of the corresponding vertical flames in the Reynolds number range studied. Two distinct regions in the upper and lower flame interfaces have been identified. The lower flame interface of horizontal flames shows similar behavior as that of the vertical flames. However, the upper flames interface exhibits a highly fluctuating flow pattern. Enhancement of turbulence by buoyancy-turbulence interactions is quantified. Total radiative heat flux measurements show that the radiative heat loss fraction of horizontal flames are significantly higher than those of the corresponding vertical flames. The flame trajectories can be correctly predicted using the two dimensional finite difference analysis. The three dimensional boundary layer analysis predicts the vertical flames with fairly good accuracy and is able to capture the asymmetric characteristics of horizontal flames. The study shows that the mixing length turbulence model with buoyancy correction provides better results than that of the standard k - varepsilon turbulence model. The standard k - varepsilon turbulence model shows its limitation in coping with buoyancy -turbulence interactions and the streamline curvature. The ASM has captured a number of the unique characteristics of horizontal flames and shows encouraging signs towards predicting horizontal turbulent diffusion jet flames.
- Pub Date:
- January 1992