Effect of Variable Gravity on Premixed Turbulent Flames Mark Ratner

Premixed Flames in Microgravity Allows the studying of phenomena in flames usually obscured by the effects of buoyancy Combustion in microgravity has been shown to alter flame characteristics like flammability limits, flame stability, and flame speeds Different flame geometries observed at microgravity, e.g. “flame balls” Spherical “flame balls” are only observed in microgravity due to lack of buoyancy effect “Flame balls” drift in microgravity due to enthalpy gradients cause by nearby neighbors

Premixed Flames in Microgravity Turbulent Flame surface wrinkling a strong function of effective gravity Different heat transfer mechanisms present in microgravity than at high/Earth gravity Heat transfer due to convection/buoyancy effects are minimized Radiation and conduction are primary mechanisms of heat transfer Low gravity tends to allow flame to break apart to break into a cellular structure

Results: mass flow = .1kg/s G=10-3G0 G=10-2G0 G=G0 G=10G0

Results: mass flow = .25kg/s G=10-3G0 G=10-2G0 G=G0 G=10G0

Results: mass flow = .5kg/s G=10-3G0 G=10-2G0 G=G0 G=10G0

Results: Summary Flame height clearly proportional to total mass flow rate of Methane/Air mixture Flame wrinkling is most dramatic at low effective gravity Increased gravity suppresses flame wrinkling Decreasing gravity increases the average flame height due to the increased wrinkling effect

Future Work Vary the type of fuel in order to vary energy content and density of the mixture Vary the incoming fuel mixture to allow for partially premixed and non-premixed flames Allow for gravity to be in the opposite direction to observe more significant flame stretching effects