Swirling atomization characteristics of waste oil biodiesel

Abstract

ABSTRACT In this study, we investigate the macroscopic structure and atomization characteristics of biodiesel produced by sewage oil in swirl atomizing nozzle through numerical simulations and experiments. The simulation is based on Euler-Lagrange method to solve the coupled equations of discrete and continuous phases. This model can boost the practical application of biodiesel in industrial furnaces. The results reveal that when the fuel injection pressure is 0.5 MPa, the size of the atomized particles ranges between 87 and 158 μm, wherein the droplets of particle size less than 50 μm are concentrated in the center of the flow field, and large droplets with size of nearly 150 μm dominate the tail of the spray. This is because in the dense spray area near the nozzle outlet, the turbulent energy of air and droplets is maximum. Therefore, at the outlet of the nozzle, a violent momentum exchange occurs, and the droplet breaks up again, so the particle size of the droplet in the rear part of the dense zone (center of the flow field) decreases. Then, the atomization momentum gradually weakens along the axial direction, and some droplets aggregate in the tail of the dilute zone and in front of the extremely dilute zone, resulting in an increase in droplet size in the extremely dilute zone (tail of the flow field). As the injection pressure increases, Sauter mean diameter of particles fluctuates more drastically, and as time passes, the size of the droplets decreases stepwise and gradually stabilizes in the range of 25–75 μm, keeping the atomization effect in a stable state.