A global model for flame pulsation frequency of buoyancy-controlled rectangular gas fuel fire with different boundaries

Pulsation frequency is an important characteristic parameter for buoyancy-controlled fuel diffusion flames. Fire experiments of a rectangular source with different aspect ratios were conducted in an open space and against sidewalls made from a calcium silicate board. Due to the blocking effect to restrict air entrainment to fire plumes, sidewall significantly reduced the flame pulsation frequency. Furthermore, the effect of the fuel exit velocity on the pulsation frequency became intense as the aspect ratio of the rectangle was increased to 7.45. Based on the modified hydraulic diameter for a rectangular fire source with a sidewall and corner, a global model was developed for predicting the flame pulsation frequency of the rectangular fire source with free, sidewall, and corner boundaries. The coefficient of determination of this improved model is 0.9991, and the local errors of this model are less than 15% considering all of the experimental data in the present work and available in the literature. This work provides a method for predicting flame pulsation frequency, accounting for sidewall effect and aspect ratio.