A Study on the Local Flame Displacement Velocity of Premixed Turbulent Flames(<Special Issue>Experimental Mechanics in Heat and Fluid Flow)

The local flame properties of turbulent propagating flames with respect to the ratio of the turbulence intensity to the laminar burning velocity u'/S_<L0> in the flamelet regime have been investigated experimentally for methane, propane and hydrogen mixtures having nearly the same laminar burning velocity with different equivalence ratios, u'/S_<L0> is varied as 1.4 and 2.3. A 2D laser tomography technique is used to obtain the flame configuration and movement in a constant-volume vessel and then the local flame displacement velocity S_F is quantitatively measured as a key parameter of turbulent combustion. As a result, the mean value of S_F shows to be affected by u'/S_<L0>, which indicates a relation between the characteristic chemical reaction time and the characteristic flow time, to some extent, especially for leaner and richer mixtures. S_F is also discussed by the concept of preferential diffusion and Markstein number which can affect the local burning velocity characteristics.