Premium
Effect of Ullage on Properties of Small‐Scale Pool Fires
Author(s) -
Dlugogorski B. Z.,
Wilson M.
Publication year - 2000
Publication title -
developments in chemical engineering and mineral processing
Language(s) - English
Resource type - Journals
eISSN - 1932-2143
pISSN - 0969-1855
DOI - 10.1002/apj.5500080110
Subject(s) - combustion , freeboard , fuel efficiency , materials science , mechanics , environmental science , extinction (optical mineralogy) , copper , convection , composite material , waste management , chemistry , metallurgy , engineering , mineralogy , aerospace engineering , physics , organic chemistry , fluidized bed
An experimental technique is described for accurately measuring the steady‐state fuel consumption rates in small‐scale pool fires, less than 7 cm diameter. The technique is applied to studying ethanol fires burning in cylindrical vessels constructed from various materials. The results indicate that the distance between the top of a vessel and the fuel surface profoundly influences the properties of liquid pool fires, including their structure and their burning rates. For combustion in glass cylinders, the burning rates decrease exponentially with increasing freeboard until a critical ullage is attained. At this ullage, the fuel begins to burn on the inside of the vessel, and the burning rate tends to increase slightly. With a further increase of the lip height, flame instabilities develop leading ultimately to flame self‐extinction. The exponential decline in fuel consumption with the lip height depends strongly on the vessel material of construction. For fires in cylinders constructed from better conducting materials (copper and mild steel), the ethanol starts to boil beyond a certain ullage. The appearance of this phenomenon redefines the fuel consumption curve. Finally, free convection leads to non‐negligible heat losses, especially from the more conducting copper and steel vessels, with the burning rates becoming dependent on the outside surface area of the cylinders.