Effects of Buoyancy on Vortices in Laminar n-Butane Diffusion Flame under Microgravity Condition

Abstract

Flow characteristic, non-buoyancy, laminar jet diffusion flames are described, based on experiments carried out in microgravity condition during 1.5 seconds of dropping from tower. Experimental conditions were conducted in both normal and microgravity condition. Methane (CH4), ethylene (C2H4) and n-butane (C4H10) fuels were burned in steady air at an ambient temperature and atmospheric pressure. Additionally n-butane flame tests were carried out under microgravity.

Under normal gravity, the experimental study on flow characteristic in various laminar coflow diffusion flames have been conducted with a particular focus on the buoyancy force exerted from gaseous hydrocarbon fuels. Methane, ethylene and n-butane were used as fuels for the experiments. Coflow burner and Schlieren system were used to observe the fuel flow field near nozzle exit and flow characteristics in flames. The result showed that the recirculation zone was appeared near the nozzle exit with the strong negative buoyancy on the fuel stream when burning n-butane which has heavier density than air. As Reynolds number increases by the control of fuel velocity of n-butane, the vortices were increased and the vortices tips were moved up from the nozzle exit. In addition, it can be found that the heated nozzle can affect the flow fields of fuel stream near the nozzle exit.

Under microgravity condition, the experimental studies on flow characteristic of n-butane flames have been conducted with a particular focus on the non-buoyancy force exerted from gaseous hydrocarbon fuels. The axial velocities of fuel stream were slow up toward the upstream. An indication of absence buoyancy and acceleration due to gravity, the axial velocity were slowly toward the downstream and the particles of fuels stream were not moved in the pockets near the nozzle exit. Therefore, the recirculation zones were disappeared near nozzle exit in n-butane flame under microgravity condition.