Flame surface properties of premixed flames in isotropic turbulence: Measurements and numerical simulations

Abstract

An experimental and theoretical investigation of free turbulent premixed flames propagating in isotropic turbulence at neutrally stable preferential diffusion conditions is described. Experiments were limited to the wrinkled thin laminar ftamelet regime and involved mixtures of hydrogen, air, and nitrogen ignited within a fan-stirred combustion chamber. Measurements included flame tomography for flame surface statistics and two-point laser velocimetry for unburned gas turbulence properties. Flame surface properties were numerically simulated using a two-dimensional flame propagation algorithm combined with statistical time series simulation of unburned gas velocities along the flame surface. Measurements showed progressively increasing flame radius fluctuations, flame surface fractal dimensions, and turbulent/laminar flame perimeters with increasing mean frame radius. The rate of increase of these properties all increased with increasing turbulence intensities relative to the laminar flame speed. Simulated flame properties duplicated these trends but underestimated the effects of turbulence-a deficiency mainly attributed to the limitations of a two-dimensional simulation. Extension of the method to a three-dimensional simulation, to obtain a more definitive evaluation of the simulation, appears to be computationally feasible.

Simulation of Front Propagation at Large Non-dimensional Flow Disturbance Intensities

“…Said and Borghi (1988), using a cellular automaton technique that does not assume Huygens propagation, found that U T~I + U, which is slightly higher than Equation (2),for U~6. Values of U up to 40 and 20 were studied by Poinsot et al (1990) and Wu and Driscoll (1992), respectively, but only for isolated vortex pairs; it is difficult to infer values of U T from this configuration. Hence, there appear to be no Huygens-DNS studies in the literature which might be compared with experiments or statistical predictions of U T at large U.…”

Turbulence effects on cellular burning structures in lean premixed hydrogen flames

“…Goix et al [8] and Kwon et al. [9] studied the turbulent flame brush. Turbulent burning velocity has been measured by Kido et al [10] and Aung et al [11].…”

Experimental investigation of three-dimensional flame-front structure in premixed turbulent combustion

“…Lean hydrogen/air combustion is therefore chosen in this continuation paper in view of the substantial difference in the fuel Lewis number and in the flame chemistry. Previous experimental work on turbulent hydrogen/air premixed combustion has addressed issues regarding its fractal nature [6,7], preferential diffusion phenomena [8,9], and the effects on global properties of the turbulent flame brush [10,11]. Measurements of the turbulent burning velocity have been made in enclosed combustion chambers [12,13] as well as in an explosion tube with obstructions [14,15].…”