Combustion-induced turbulent flow fields in premixed flames

Combustion-induced turbulence is studied in explosions of methane/air a steel sphere with optical access. Rms turbulent velocities, u', created by four peripheral variable speed fans, were measured Particle Image Velocimetry, PIV, which indicated near-uniform, isotropic turbulence, small mean velocities. The gaseous expansion near-spherical propagating flame generated radially outwards velocity unburned mixture, the intensity depended upon burning and volume increase due to combustion. study measure any extra this pulse. Only wave lengths less than circumference can wrinkle velocity, ut. Consequently effective rms at front affecting its propagation, uk', u'. Analysis shows, be function radius. pulse additional enhancing uk'. This enhanced ut, giving further positive feedback. higher value designated as spatial us'. PIV-measured gas velocities are resolved into radial U-r and, us', their profiles. These derived from different equivalence ratios, pressures, temperatures. At radii ut measured, us'/uk' high rates volumetric expansion. ratio attained 2.5, stoichiometric CH4/air. Values those steady-state burners, attributable induced explosions, no such effect burners.