Droplet diameter measurement near a nozzle exit of a gasoline DISI injector using PDA

The purpose of this study is to measure the droplet diameter distribution very close to the nozzle hole of DISI injector using a phase Doppler anemometer (PDA). In this experiment, droplet diameter and axial velocity in spray formed by one hole of multi-hole injector were measured with HiDense PDA system to investigate atomization characteristics near the nozzle exit of the DISI injector. HiDense PDA system permits accurate measurements in spray with extremely high particle concentrations, and it is the only PDA system available that provide high quality measurements in the core region of the spray cone. Firstly, optimization of optical set-up and measurement condition of signal processor were carried out to measure the accurate droplet diameter distribution very close to the nozzle exit under higher injection pressure conditions. It is possible to measure the droplet diameter distribution at the 5mm from the nozzle exit under 20MPa as the injection pressure. Secondary, the effects of refractive index of multi-component fuel on droplet diameter measurement using PDA were investigated. Mass fraction of each component can be considered to define the refractive index of multi-component fuel for PDA measurement. The result showed that SMD increases in the case of TRF (mixed fuel with iso-octane, n-heptane and toluene), while droplet velocity was almost the same.