Effects of nozzle configuration on flash boiling fuel sprays of twin-orifice nozzle with aviation kerosene

To investigate the effects of nozzle configuration on flash boiling fuel sprays of the twin-orifice nozzle with aviation kerosene, five different two-dimensional transparent slit nozzles with various orifices' diameter ratio and expansion chamber's aspect ratio are fabricated and studied. Both internal two-phase flow and near-nozzle fuel jet under subcooled and superheated conditions are studied via a high-speed camera with backlit measurement and image processing methods. The experimental results indicate that the bubbles nucleation from cavitation at the inlet-orifice wall can accumulate within the expansion chamber with enhanced bubble growth and aggregation under higher-level superheated conditions, which can significantly promote the fuel atomization and evaporation. In addition, a smaller orifices' diameter ratio leads to larger in-nozzle bubble volumes within the twin-orifice nozzle, while the internal bubble inception may be inhibited by increasing the expansion chamber's aspect ratio. Furthermore, decreasing the orifices' diameter ratio can promote the flash boiling process, while better-quality spray at flare flash boiling state may be facilitated by the near-nozzle mechanical breakup. The nozzle with a lower expansion chamber's aspect ratio has a larger spray cone angle and weaker jet instability, benefited from larger bubble volume and higher effective bubble rate, which accelerates the bubble disruption and fulfills the potential of in-nozzle flash boiling on near-nozzle jet disintegration.