Numerical and experimental study on the spray characteristics of full-cone pressure swirl atomizers

Numerical and experimental studies have been performed to investigate the macroscopic spray structure and spray characteristics of sprays generated by a full-cone pressure swirl atomizer. The simulation employs Eulerian-Lagrangian scheme to account for the multiphase flow and the linearized instability sheet atomization model to predict film formation, sheet breakup and atomization. Reynolds-Averaged Navier-Stokes (RANS) equations are solved for turbulent gas flow. The model predictions show great consistency with the experimental measurements of the spatial variation of the droplet size and velocity obtained from Phase Doppler Particle Analyser (PDPA). The robustness of this model makes it useful to predict the structures and characteristics of co-flow sprays produced by pressure-swirl atomizers. This particular spray is quite important in spray cooling application but is not extensively studied. The study reveals that the entrainment effect and intense central-region atomization cause small droplets to concentrate on the spray axis and large droplets to dominate in the peripheral region of the spray. This finding is consistent with the observation that turbulence kinetic energy of air is maximum near the nozzle exit, where atomization is intense and momentum exchange is strong, and gradually decreases in both radial and axial directions. Moreover, the drops inside the full cone are relatively small, and evaporate more easily than their large counterparts in the peripheral region, hence removing substantial sensible heat from surrounding air and creating low-temperature region in the central of the spray.