Investigation of Velocity Profiles in Dense GDI Sprays by Phase Doppler Anemometry

The optimization of the commercial Phase Doppler Anemometer (Dantec Dynamics) was performed in order to obtain trustworthy velocity data in dense sprays. A commercially available five-hole injector was used to provide a spray. Optimization of the system parameters and subsequent characterization of the velocity fields were performed considering only one spray stream. For the reliable system optimization, the same operating conditions were provided and the same spatial locations were investigated. Afterward, the optimized experimental setup was applied to measure two component velocity fields at different measurements planes: 5nm, 10 nm, 15 nm, 20 nm, 30 nm and 50 nm away from the nozzle tip. Test conditions were chosen to observe the spray at non-flashing and flashing states. The velocity at the nozzle orifice was extrapolated from the downstream flow. Additionally, we performed the analysis of drop sizes obtained by the PDA system. This analysis found to be an indispensable procedure to provide a better understanding of the velocity data.

The results showed that flash boiling has the potential to increase the droplet velocity and enhance the atomization process. Moreover, the validation rate at flashing conditions was found to be higher, which is also associated with the enhanced atomization of a spray.