Temperature and Velocity Measurements in Premixed Turbulent Flames

Abstract

Turbulent flame-speed data for premixed flames of methane-air, propane-air, and ethylene-air mixtures stabilized in grid turbulence are reported and discussed. It is shown that turbulence effects on flame speed cannot be correlated fully by the turbulence length scale and rms velocity in the cold flow. Rather there appear to be significant flame-flow turbulence interactions affecting both turbulence level in the reaction zone and measured flame speeds. Results of detailed velocity measurements, including autocorrelations, by laser velocimetry are used to elucidate the nature of these interactions. It is concluded that flame-speed experiments must be designed and conducted to provide sufficient information (e.g., boundary conditions) to allow for reconstruction of the flowfield and these interactions by modelers if the data are to be of value in turbulent combustion model development and evaluation. Nomenclature ? = integral scale of turbulence P = pressure R ( = turbulence Reynolds number, uV/v R x = microscale turbulence Reynolds number, u\/v S L = laminar flame speed S T = turbulent flame speed u = rms velocity, = vw 77 u" = U-U U = instantaneous velocity U = Favre average velocity U = Reynolds average velocity e = Favre average energy dissipation rate X =Tay lor's microscale p = gas density p(r) = autocorrelation coefficient, = <w' (t)u' (t+r))/u 2 0 = equivalence ratio Subscripts C = cold reactants H = hot products / = component along x t

Conditional Sampling of Turbulence Intensities and Reynolds Stress in Premixed Turbulent Flames

“…I n many experimental investigations, the turbulence intensities are found t o increase within the flame brush (Kleine, 1974;Yoshida and Tsuji, 1979;Smith and Gouldin, 1981 ; Bill u / a/., 1982;Dandekar and Gouldin, 1982).…”

Time-resolved density measurements in premixed turbulent flames

“…8 In this paper, we report the results of Rayleigh scattering measurements in a lean, methane-air flame on the same burner. Data on mean density and rms density fluctuations, on pdf's of density, and on density fluctuation power spectra are reported and discussed along with velocity data to draw conclusions concerning the flame structure and important flame processes.…”

On defining the turbulent burning velocity in premixed V-shaped turbulent flames

“…Subsequent work of Dandekar and Gauldin [11] involves measurement of turbulent burning velocity in methane/air, propane/air and ethylene/air flames. They question whether or not the length scales and fluctuating velocities of lhe incident turbulence are sufficient to correlate the turbulent burning velocity.…”

“…All of the previous experimental measurements [9][10][11] are concerned with determining St for a fixed location above the flame stabilizer. As shown in our previous work [7], the properties of the turbulent flame change along the flame brush.…”