Numerical study on the atomization mechanism and energy characteristics of synthetic jet/dual synthetic jets

Abstract

Due to high-frequency oscillating flow characteristic, the synthetic jet/dual synthetic jets (SJ/DSJ) can break up the liquid film into fine droplets. SJ/DSJ atomization nozzle has been designed and studied in the early stage, but its atomizing mechanism is still unclear. Through numerical and experimental methods, this study reveals how the unsteady jet with high turbulence level causes instability at the gas–liquid interface. The SJ/DSJ atomization during the blowing stroke is mainly divided into two stages, namely the primary breakup induced by K-H instability and secondary atomization induced by R-T instability. While the liquid fragmentation caused by the reverse jet during the suction stroke includes two modes: passive-fracture mode induced by the aerodynamic force and active-detachment mode induced by the velocity difference. The variation of spray particle number with time obeys the lognormal distribution. The particle size ranges from 4 to 150 μm, and 60% of the spray particles are fine droplets with diameter less than 50 μm. The traditional method to improve the atomization performance is to increase the gas–liquid two-phase pressure, which requires more energy consumption. In this study, by comparing the atomization characteristics of SJ/DSJ and continuous jet, it’s proved that the atomization performance can be enhanced by leaps and bounds through active flow control. 63% of the SJ/DSJ kinetic energy is fully converted into liquid kinetic energy to form high-speed spray.