Fire Dynamics and Behavior Flashcards

Which equation or relationship is used to estimate the volumetric flow rate of smoke entrained into a fire plume at a given height above the fire source?

Answer: Morton-Taylor-Turner (MTT) plume equations

The Morton-Taylor-Turner (MTT) plume equations describe entrainment of ambient air into a buoyant fire plume and are used to calculate smoke production rates.

A fire is described as 'spreading by radiation' when:

Answer: Electromagnetic energy from the flame or hot surfaces ignites nearby fuel without direct contact

Radiant fire spread occurs when electromagnetic thermal radiation from a fire source heats a nearby fuel to its ignition temperature without physical contact.

The 'oxygen-depletion calorimeter' (Cone Calorimeter) measures heat release rate based on the principle that:

Answer: Approximately 13.1 kJ of heat is released per gram of oxygen consumed

Oxygen consumption calorimetry exploits the fact that combustion releases approximately 13.1 kJ per gram of oxygen consumed, regardless of the fuel type.

In the context of fire dynamics, 'stoichiometric combustion' means:

Answer: The fuel and oxidizer are present in the exact proportions for complete combustion with no excess of either

Stoichiometric combustion occurs when fuel and oxygen are present in theoretically perfect proportions, yielding complete oxidation to CO₂ and H₂O with no excess reactants.

Which factor has the MOST significant effect on the upward flame spread rate on a vertical combustible surface?

Answer: The preheated zone length above the current flame tip

The preheated zone ahead of the advancing flame front on a vertical surface is the primary determinant of upward flame spread rate; a longer preheated zone leads to faster spread.

What is 'char' in the context of solid fuel combustion, and what fire behavior role does it play?

Answer: A carbonaceous residue that forms on wood surfaces and acts as a thermal insulator, slowing pyrolysis

Char is the solid carbonaceous layer remaining after pyrolysis of wood; it insulates underlying uncharred wood from heat, reducing pyrolysis rate and overall burning rate.

The 'fire plume' centerline temperature decays with height above the virtual fire source according to which relationship?

Answer: Temperature decays in proportion to height raised to the negative five-thirds power (z^(-5/3))

According to Heskestad's and McCaffrey's plume models, centerline temperature in the buoyant plume above the flame zone decays approximately as z^(-5/3) due to air entrainment.