SPRAY CHARACTERISTICS OF AN AIR-DRIVEN ROTARY ATOMIZER WITH A DOUBLE-LAYER CUP FOR USE IN AN INDUSTRIAL OIL BURNER

Abstract

An experimental investigation of spray characteristics in a rotary burner with an air-driven double-layer cup atomizer is reported. The air stream generated by a centrifugal blower was used to rotate a vane propeller attached to the double-layer cup, and to assist disintegration of liquid sheets formed from the rim of the double-layer cup at the air nozzle exit. As the blower power increased, the rotational speed of the cup and the gas-to-liquid mass ratio (GLR) increased, and the atomizing crossflow velocity at an annular slot increased as well. For some given operating conditions, the effect of the crossflow velocity on the spray quality was investigated by varying the outer diameters of the air nozzle (88, 83, and 79.5 mm). The spray cone angles were measured by analyzing stroboscopic images. As the air velocity at the annular slot increased, the spray cone angle decreased. The spray radial and streamwise dispersion distributions were obtained by two liquid-collecting devices. The crossflow velocity at the annular slot, the GLR, and the diameter of air nozzles had an impact on the drop sizes and size distribution. The drop sizes of the spray were obtained using laser diffraction spectroscopy. The spray performance was described in terms of Sauter mean diameter (SMD), maximum drop diameter, relative span factor, and some representative drop diameters such as D0:9, D0:5, and D0:1. The SMD and maximum drop diameter were correlated with liquid Weber number (WeL) only. The atomization quality was improved with increasing GLR and crossflow velocity at the annular slot.