Dynamics of an Airblast Spray in a Double Swirled Stabilized Flame

Abstract

The present study aims to provide experimental data describing the characteristics of kerosene droplets in a swirl-stabilized spray flame. The fuel injector is a prefilming airblast atomizer where the fuel is sandwiched between two co-swirling turbulent air streams. Measurements are obtained by application of the phase Doppler anemometry technique for a simultaneous measurement of a droplet's size and velocity. In order to develop a full understanding of the aerodynamic and mixing processes of the droplets, spatially resolved information (i. e., liquid flux and concentration, velocity fluctuations of the both phases) are also determined. The measured mean tangential velocity component indicates that the rotating gas flow is the combined forced-free vortex. From determination of the Sauter's mean diameter, a strong separation of particles is observed, resulting in a radial increase of the particles' size. This effect is a result of the strong spreading of the swirling jet and the action of centrifugal forces. The liquid flux is closely associated with the number density change of the droplets. The maximum liquid flux is situated at the edge of the jet, while only a small amount of liquid is transported by the smaller droplets at the central part of the burner. Further downstream, its distribution is found to be V-shaped with an inclination angle of 85°. It is uniform in the center and gradually increases with radial distance to reach a peak followed by a decrease towards the outer edges of the spray. The concentration of liquid is small in the central region and increases towards the edge of the jet. The centrifugal effect is again evident since the liquid fuel's concentration is larger at the edge of the spray.