Aerodynamic and thermodynamic characteristics of kerosene-spray flames

Abstract

Measured values of velocity, turbulence intensity, temperature, temperature fluctuations and droplet concentration are reported in four kerosene spray flames burning vertically in atmospheric air. The results are compared with calculated values, obtained with the aid of a numerical solution of modelled conservation equations in differential form, and appropriate to a gaseous flame of the same available enthalpy. Velocity, turbulence intensity and droplet measurements were obtained with a laser anemometer operating in forward scatter: a frequency tracking demodulator provided the velocity information and the number of particles crossing the control volume at a given time were measured with the aid of a digital counter. Measured mean and fluctuating temperature were obtained with platinum-rhodium thermocouple wires of bead diameters 180 and 40 μm respectively. Corrections were made for conduction and radiation effects on the mean temperature and for the effect of the thermal inertia, of the smaller wire on the rms measurements. The comparison between measurements and simulated gaseous flames, indicates that the flames have properties which are similar in general but significantly different in detail. The length of the flame decreases significantly from a spray of 100 μm to 50 μm droplets; and the simulated gaseous flame is still shorter and is not, therefore, a good approximation to spray flames. The measurements of rms velocity and temperature indicate values in excess of 0.75 and 0.30 respectively and the maxima appear to be coincident with the inflection points of the corresponding mean distributions.