Search

The spatial and temporal development of a spray strongly depends on the local characteristics of turbulence. The turbulence-droplet coupling gives rise to droplet dispersion, which is the underlaying physical phenomenon of interest in this study. Large eddy simulations (LES) provide details of the instantaneous flow field and anisotropy of the larger scales. Hence, LES has the potential of improved spray simulations in flows that are highly nonisotropic/nonstationary. A numerical study on the effect of droplet diameter (d) on spray shape is described by carefully varying d. The droplets are assumed to be non-interacting with each other. They are also assumed to maintain their shape and diameter. The droplet Stokes numbers are within the range 0.07

The near-nozzle characteristics of a transient fuel spray were investigated via the measurement of drop sizes and velocities, and microphotographs of the near-nozzle region for a range of gas-to-liquid density ratios. In addition, a steady-state single-phase hydrodynamic simulation of the internal nozzle flow was performed to observe the effects of needle position on the internal flow. Measurement of droplet size and velocity near the nozzle on the edge of the spray showed that the average droplet velocity peaked during needle opening and needle closing, and changed throughout the spray event. Drop sizes tended to be small on the spray edge. Microphotographs of the near-nozzle region showed that the spray was most widely dispersed immediately after injection begins, narrowing rapidly to a constant spray angle. The same behavior was observed even for injection into near-vacuum conditions. However, once the spray was established, aerodynamic interactions were necessary for near-nozzle atomization.