Reference data set for three-dimensional measurements of double droplet combustion of p-xylene

In order to provide fundamental information for droplet interactions in the versatile and promising flame spray pyrolysis (FSP) technique, double droplet combustion experiments of p-xylene have been conducted via an improved piezoelectric droplet-on-demand generator. Using a steel nozzle plate with two laser-drilled nozzles, the generator can simultaneously generate two upwards-flying droplets with initial diameters of around 100 µm. A three-dimensional (3D) measurement technique using two time-synchronized high-speed cameras has been developed to detect double droplet combustion processes. Droplet diameters, flame diameters, droplet 3D trajectories, droplet 3D velocities, and the center distances between the two burning droplets are highly time-resolved measured, and then visualized via 3D videos and images. Flame spacing, as a new definition, is proposed to describe the interactions between the two flame fronts. The influences of the flame spacing and the oxygen concentration in the ambience on double droplet combustion were experimentally investigated. The obtained 3D data can serve as an ideal validation case for modeling and simulating droplet interactions during combustion as well as a highly time-resolved reference data set in the future.