Computational Study of Compartment Size Effects on Backdraft Intensity

A computational study was performed to evaluate the effects of compartment size on backdraft intensity. The compartment sizes were selected such that each direction was enlarged by a factor of 2, 2.5, 2.625, and 3 based on the reduced-scale compartment of a previous experimental study. A fire dynamics simulator was used for the computation, and a large eddy simulation and a mixing-controlled fast chemistry combustion model were adopted. Results revealed that the overall equivalence ratio defined by the amounts of fuel inside the compartment and oxygen induced from the opening had similar values at the moment when the air reached the inside wall. The fuel–air mixing inside the compartment was found to be achieved more rapidly with a decreased compartment size. The peaks of pressure and heat release rate inside the compartment increased with an increase in compartment size. However, these peaks were found to increase exponentially with an increase in the ratio of the compartment volume and opening size, and the correlation showed a very high R-squared value.