Mass flux measurements for burning rate determination of premixed turbulent flames

Abstract

A method for measuring the burning rate integral B T in turbulent premixed flames and data obtained from several V-flames via the method are reported. B T is determined by integration over the flame brush of data for the mass fluxes normal and tangent to c¯ constant surfaces. The determination of both convective and turbulent mass fluxes is made by simultaneous two-component velocity (axial and lateral) and temperature measurements using a combination of laser Doppler velocimetry (LDV) and compensated, finewire thermocouples, where the instantaneous gas density is obtained from the instantaneous temperature through the equation of state and the assumption of constant pressure. B T data for turbulent premixed CH 4 -air flames, with equivalence ratios between 0.7 and 0.75, mean axial flow velocities between 2 and 6.37 m/s, and ratios of turbulence intensities to laminar burning velocities between 0.643 and 3.16, are reported. The data demonstrate the utility of simultaneous velocity and temperature measurements for determining the burning rate integral for premixed flames in laboratory burners. They further show (1) that conditional velocity data alone cannot be used with confidence to estimate mass fluxes in the flamelet regime, (2) that the use of velocity data from the reactant side of the turbulent flame brush to estimate B T (or the turbulent burning velocity) results in estimates that are quite high, and (3) that B T is a strong function of u′/S L .