Influences of pressure on reduced-gravity combustion of 1-propanol droplets

Abstract

Reduced-gravity experiments on combustion of individual 1-propanol droplets with initial diameters of about 1 mm were conducted in air at standard temperature and with pressures ranging from 0.1 MPa to 1.0 MPa. Flames at 0.1 MPa were non-sooting with blue coloring during most of the combustion process. At higher pressures, flames exhibited significant amounts of soot during most of the combustion history. Flames were also non-spherical at elevated pressure, which is likely a result of the increased importance of buoyant convection at elevated pressure. Droplet burning rates increased as the ambient pressure was increased. Empirical correlations indicate that buoyant convection did not significantly influence droplet burning rates. Calculations indicate, however, that increasing the ambient pressure increased the liquid temperature, which decreased the liquid density and enthalpy of vaporization, leading to burning rate increases that are consistent with experimental results. Calculations also indicate that absorption of water into droplets was not significant in the experiments.