Laminar and turbulent burning velocities

Although the onset of end gas autoignition is influenced primarily by the autoignition chemistry in the end gas, it is also affected by the speed with which the flame propagates across the combustion volume. This is because the pressure and temperature of the end gas depend, not only 

Velocity components and curvature that stretch the flame surface can change the burning velocity. This is because the flame strueture is changed 

The proportionality constant, L, is called the Markstein length [97]. Equation (7.2) can be written, in dimensionless form, as 

On the other hand, the turbulence also causes the flamelet surface to be stretched. In addition it also creates a distribution of stretch rates. 

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Fundamental, laminar, and turbulent burning velocities describe three modes of flame propagation (see the Glossary for definitions). The fundamental burning velocity, S, is as its name implies, a fundamental property of a flammable mixture, and is a measure of how fast reactants are consumed and transformed into products of combustion. Fundamental burning velocity data for selected gases and vapors are listed in Appendix C of NFPA68 (1998). 

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