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Turbulent Premixed Hydrogen/Air Flames.
Final rept. 1 Aug 1987-31 Dec 1990
MICHIGAN UNIV ANN ARBOR DEPT OF AEROSPACE ENGINEERING
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The properties of turbulent premixed flames were investigated both theoretically and experimentally. Attention was limited to hydrogenair mixtures burning as either turbulent jet flames or a freely propagating flames in isotropic turbulence. The research has application to a variety to premixed turbulent combustion processes underwater metal cutting at great depth, primary combustors for high-speed airbreathing propulsion systems, afterburners, fuel air explosions, and spark-ignition internal combustion engines. Major findings of this phase of the investigation are as follows 1 effects of preferential diffusion are relevent for flames at high Reynolds number, retarding and enhancing the distortion of the flame surface by turbulence for stable and unstable conditions, respectively 2 local turbulent burning velocity, flame brush thickness and the fractal dimension of the flame surface all increase with distance from the flameholder, with larger rates of increases at larger turbulence intensities 3 estimates of flame properties using contemporary turbulence models were only fair because these methods cannot account for effects of preferential diffusion, distance from the flameholder and finite laminar flame speeds and 4 the stochastic simulation duplicated measured trends of flame surface properties for neutral preferential diffusion conditions the only case considered but underestimated effects of turbulence particularly near the flame tip due to the limitations of a two-dimensional simulation.
APPROVED FOR PUBLIC RELEASE