How do you find burning velocity?

Answer 1

Laminar flame speed is a property of a combustible mixture.[1] It is the speed at which an un-stretched laminar flame will propagate through a quiescent mixture of unburned reactants. Laminar flame speed is given the symbol sL. According to the thermal flame theory of Mallard and Le Chatelier, the un-stretched laminar flame speed is dependent on only three properties of a chemical mixture: the thermal diffusivity of the mixture, the reaction rate of the mixture and the temperature through the flame zone:

is thermal diffusivity,

is reaction rate,

and the temperature subscript u is for unburned, bis for burned and i is for ignition temperature.

While the laminar flame speed is a property of the mixture alone, the same is not true for turbulent flame speed - or turbulent burning velocity as it is more correctly called. As flow velocity increases and turbulence is introduced, a flame will begin to wrinkle, then corrugate and eventually the flame front will be broken and transport properties will be enhanced by turbulent eddies in the flame zone. As a result, the flame front of a turbulent flame will propagate at a velocity that is not only a function of the mixture's chemical properties but also properties of the flow and turbulence.

Answer 2

Burning velocity is typically determined experimentally using a constant-volume combustion chamber where the rate of combustion of a fuel-air mixture is measured. The burning velocity can also be calculated using a formula involving the flame speed and the density of the unburned mixture. Additionally, numerical simulations can be used to predict burning velocity based on the chemical kinetics of the combustion process.