scenario-based
4
Fire and Combustion
Felicia St. Luce
Columbia Southern University
Fire Behavior and Combustion
Professor James Golden
Luminous flame zone, intermittently flame zone, and a buoyant plume is the overall fire plume structure. A burning fire plume in an apartment is comprised of the three mentioned zones. The first zone is the lowest zone which is luminous and contains gasses accelerating upwards. The middle zone is intermittent and in which there is a constant upward velocity and gas temperature. Additionally, there is an upper zone, the nonluminous buoyant whose velocity and temperature decrease with height. When a fire plume hits a ceiling, it spreads horizontally (Salasinska et al.,2020). This helps one to understand how the ceiling jet triggers automatic smoke and the sprinklers radiate thermal energy onto combustibles, thus accelerating fire growth. This idea is vital as it exemplifies how to manage the presence of combustibles and hot gas at the ceiling level of buildings.
The firefighters will be in a position to understand the flow path during operations as the flow path poses a significant risk to the flow of smoke, heat, and fire. Therefore, understanding the two-way flow that occurs through the doorway of a fire room enables a firefighter to understand the behaviors of hot smoke and flames (Gann & Friedman, 2013). Knowledge about this hot upper layer is crucial to assessment of life safety in a building fire. The layer thickness, temperature, and optical density all affect the intensity of downward thermal radiation incident on people and combustibles in the lower part of the compartment. The rate of outflow of the hot layer influences life safety in and fire spread to the adjacent space(s) (Gann & Friedman, 2014.) The hot upper layer temperature and optical density during a fire in a compartment with an opening are affected by the total volume of air supplied to the fire and the position at which the air enters the compartment. In limited ventilated compartments, fires produce different temperature profiles compared to well-ventilated compartments.
Optical density is interrelated to the type of ventilation and fuel. For instance, fuels such as Hydrocarbons and synthetic fuels under well-ventilated conditions increase the optical density (Fent et al.,2020). Worth noting is that, recognizing the idea of a neutral plane can assist in determining the ground the fire is situated on. The neutral plane marks the level in a building fire where below it air will be drained into the building and above it will result in exhaustion of the combustion gases.
Fent, K. W., LaGuardia, M., Luellen, D., McCormick, S., Mayer, A., Chen, I. C., ... & Horn, G. P. (2020). Flame retardants, dioxins, and furans in air and on firefighters’ protective ensembles during controlled residential firefighting. Environment international, 140, 105756.
Gann, R., & Friedman, R. (2013). Principles of fire behavior and combustion. Jones & Bartlett Publishers.
Gann, R. (2014). Principles of Fire Behavior and Combustion. [VitalSource Bookshelf]. Retrieved from https://online.vitalsource.com/#/books/9781284081879/
Salasinska, K., Celiński, M., Barczewski, M., Leszczyński, M. K., Borucka, M., & Kozikowski, P. (2020). Fire behavior of flame retarded unsaturated polyester resin with high nitrogen content additives. Polymer Testing, 84, 106379.