Development of ghosting flames in an under-ventilated compartment

This work examines the transition of an enclosure fire to an under-ventilated scenario such that conditions are conducive to a ghosting flame within the enclosure. Ghosting flames were observed when flames generated from a burner using propane were lifted off the burner and sporadically occupied other regions of the compartment. All experiments were conducted within a reduced-scale enclosure with a varying width of either 2.0 cm, 4.0 cm, or 10.0 cm. Each opening configuration was subjected to a range of fire sizes within the enclosure to determine the conditions conducive to ghosting flame. The compartment was observed to transition to under-ventilated conditions, such that significant concentrations of hydrocarbons were generated within the enclosure when the global equivalence ratio in the upper region was equal to 1. Ghosting flames were observed when the measured global equivalence ratio in the upper compartment region reached 2.3 $\pm$ 0.2 and were found to continuously occur as the ratio continued to exceed that value steadily. This suggests that a ghosting flame phenomenon occurs when the rate at which fuel is introduced is more than a factor of ten relative to the airflow into the compartment.