Validation of leading-point-concept-based approach to predicting an increase in turbulent burning rate due to diffusional-thermal effects

Journal article, 2026

A promising approach to predicting a significant increase in turbulent burning rate due to diffusional-thermal phenomena in lean H₂-containing mixtures is based on the leading point concept and consists in substituting characteristics of unstretched laminar flames with the counterpart characteristics of highly strained, twin, counterflow laminar flames. In the present work, the predictive capabilities of this approach are validated by processing two experimental databases obtained recently by independent research groups from (i) piloted, statistically stationary, Bunsen-type lean CH₄/H₂/air weakly turbulent (Re_T = 64) flames at Karlovitz numbers ranging from 0.5 to 100 and (ii) statistically spherical turbulent flames expanding in various mixtures (stoichiometric CH₄/O₂/N₂, lean H₂/O₂/N₂, H₂/O₂/He, and H₂/O₂/Ar) under different pressures and temperatures. In each set of experiments, an increase in the burning velocity, U_T, due to diffusional-thermal effects is well pronounced and the use of standard characteristics of laminar flames to fit the data yields a significant scatter. On the contrary, when adopting the consumption velocities and thicknesses of highly strained laminar counterflow twin flames, computed using detailed chemistry, both databases on U_T are well parameterized.