Reverse Stratified Flow in Duct Fires: A Two Dimensional Approach.
Hwang-CC; Chaiken-RF; Singer-JM; Chi-DNH
16th Int'l Symp on Combustion the Combustion Inst Pittsburgh Pennsylvania, 1977 :1385-1395
In ventilated duct fires, smoke and other combustion products may form a layer near the ceiling and flow in the direction opposite to the ventilation flow. Previous workers have shown that backing of hot combustion products occurs if the ratio of the buoyancy head hat/t to the velocity head v2/g is greater than unity. A two- dimensional mathematical model of the phenomenon is developed based upon the interaction of a steady-state fire plume with a cross ventilation flow. The objective of this Bureau of Mines paper is to gain some understanding of the behavior of the hot gas layer flow and its response to changes at the fire source and in the ventilation current. Through the present mathematical treatments it appears possible to predict the effects of ventilation speed, duct inclination, mass flux of fire plume, etc., on the critical length of the reverse flow layer. The detailed flow behavior of plumes and gas layers can also be studied with the model.
16th Int'l. Symp. on Combustion; the Combustion Inst., Pittsburgh, Pennsylvania, 1977, PP. 1385-1395