TheInfoList

Laminar flame speed is an intrinsic characteristic of premixed combustible mixtures  that plays a key role in understanding a mixture’s reactivity, diffusivity, and exothermicity. It is the speed at which an un-stretched laminar flame will propagate through a quiescent mixture of unburned reactants. Laminar flame speed is defined as the normal component of velocity of flame relative to unburned gas. 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:

$s_{\mathrm {L} }^{\circ }={\sqrt {\alpha {\dot {\omega }}\left({\dfrac {T_{\mathrm {b} }-T_{\mathrm {i} }}{T_{\mathrm {i} }-T_{\mathrm {u} }}}\right)}}$ $\alpha$ is thermal diffusivity,

${\dot {\omega }}$ is reaction rate,

and the temperature subscript u is for unburned, b is for burned and i is for i

$s_{\mathrm {L} }^{\circ }={\sqrt {\alpha {\dot {\omega }}\left({\dfrac {T_{\mathrm {b} }-T_{\mathrm {i} }}{T_{\mathrm {i} }-T_{\mathrm {u} }}}\right)}}$ $\alpha$ is thermal diffusivity,

${\dot {\omega }}$ is reaction rate,

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

Laminar flame speed is a property of the mixture (fuel structure, stoichiometry) and thermodynamic conditions upon mixture ignition (pressure, temperature). Turbulent flame speed is a function of the aforementioned parameters, but also heavily depends on the flow field. 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 speed that is not only a function of the mixture's chemical and transport properties but also properties of the flow and turbulence.

Normal Exit PeriodicService.php