Dynamics and Characteristics of Combustion Product Gases
Menna Elghannam
Experienced Technical Safety Engineer in the oil & gas industry, passionate about designing safety systems and conducting safety studies using the latest tools/software and engineering standards.
The fire's combustion reactions elevate the temperature of the air directly above it, releasing hot combustion by-products and radiant energy. This heated mixture ascends in a buoyant column or plume, expanding from the fire towards the ceiling.
As the fire burns, it continues to produce additional hot combustion product gases, which flow upward as a buoyant plume. When the plume collides with the ceiling, it turns and flows horizontally beneath the ceiling. this horizontal flow of combustion product gases beneath the ceiling is called a ceiling jet.
The ceiling jet consists of a layer of hot air and combustion gases that expand radially away from the fire plume centreline, as shown in exhibit 17.1., the ceiling jet moves more slowly due to frictional losses and is slightly cooler due to heat transfer to the ceiling.
References: NFPA 72 Handbook
.