MERGING CONICAL LIQUID SHEETS FROM COAXIAL PRESSURE-SWIRL INJECTORS

Abstract

The conditions for merging two liquid sheets in a coaxial pressure-swirl external mixing injector were assessed experimentally and numerically. Fast imaging was employed based on the backlighting technique to experimentally investigate the behavior of the exit liquid sheet. The simulation was also carried out using a volume of fluid model considering two-dimensional axisymmetric swirl conditions. Performance characteristics including discharge coefficient, sheet angle, and sheet pattern at different injection pressures were assessed experimentally and by simulation for separate and simultaneous spraying conditions. To study the merging condition, the gas phase pressure field just downstream of the injector exit was numerically investigated separate and simultaneous results show that the lowest gas pressure occurs in the region inside the liquid cone produced. The larger the diameter of the injector outlet, the greater the volume of the hollow cone and the smaller the amount of this vacuum. When the internal and external injectors worked simultaneously, three areas were distinguished: the inner space of the internal injector, the space between the two liquid sheets, and the outer space of the external injector. The largest pressure gradients in the gas pressure occurred in the space between the two liquid sheets. By increasing the injection pressure of the external injector, the static pressure between the two sheets decreased and reached the pressure required to merge the two sheets, thus, the two liquid sheets can merge.