Injection Pressure Effects Upon Droplet Behavior in Transient Diesel Sprays

Abstract

Abstract : This paper reports on the investigation of injection pressure upon the droplet behavior in transient diesel sprays. Phase/Doppler results for a Diesel spray with a maximum fuel injection line pressure of 105 MPa are compared with previously acquired droplet size and velocity measurements for a Diesel spray with an injection pressure of 21 MPa. All measurements reported here were made in atmospheric conditions at a position near the nozzle. It is shown in these results that the droplet velocity and size profiles do maintain similarity despite the substantial change in injection pressure. Specific characteristics, for example, the appearance of subtle waves in the time dependent spray data, are present in both data sets. Comparison of the measured droplet velocities and diameters with Weber number based stability criteria shows that increased injection pressure produces a higher percentage of droplets that are likely to breakup. This is mostly the result of increases in droplet velocities with higher injection pressure. The interior region of the higher pressure spray is an area extremely difficult to probe, despite the application of temporal optimization of the phase/Doppler anemometer. Inherent characteristics of the injection that affect the ability to acquire data are described, as well as some of the operational difficulties experienced in using a phase/Doppler for diesel spray droplet measurements.