Study on flow atomization characteristics and structure optimization of swirl nozzle for biodiesel

Abstract

In this paper, the influence of external conditions and structural parameters on the characteristics of a nozzle flow field is studied, and orthogonal tests have been used to optimize the nozzle structure. The results show that the inlet pressure, nozzle aperture, nozzle outlet aspect ratio, vortex chamber height, and screw core height affect the pressure and velocity distributions of the flow field inside the nozzle. With increasing axial distance, the pressure in the inlet area remains unchanged; however, the pressure gradually decreases inside the screw core region and vortex chamber. Meanwhile, the velocity in the nozzle drainage basin first increases and then decreases. With increasing radial distance, the pressure in the nozzle drainage basin gradually increases, whereas the velocity increases first and then decreases. The velocity contour plot and vector diagram of the nozzle outlet section elucidate the influence of structural parameters on the flow field characteristics inside the nozzle. The nozzle length-to-diameter ratio has the greatest effect on the Sauter mean diameter (SMD). Besides, biodiesel atomization is sequentially affected by the vortex chamber height, screw core height, and nozzle aperture. The best atomization performance of biodiesel is observed at a nozzle aperture of 0.8mm, nozzle outlet length-to-diameter ratio of 0, vortex chamber height of 5mm, and screw core height of 4mm. Compared to the original nozzle, the optimized nozzle increases the atomization cone angle of biodiesel by 30.9% and reduces the SMD by 45.3%.