Spray Visualization and Characterization of a Dual-Fuel Injector using Diesel and Gasoline

This paper focuses on the spray and atomization characteristics of a Dual-Fuel Injector (DFI) which includes a primary and a secondary fuel inlet. Three injectors were analyzed in this study. Apart from the DFI, two conventional diesel injectors were tested as baselines for comparison - a piezo-electric and a solenoid injector. The rail pressures ranged from 200 - 500 bar for the conventional injectors. The DFI was tested first as a single-fuel injector (by sealing the secondary inlet) at pressures ranging from 100 - 300 bar, and then in its dual-fuel mode with the primary inlet pressure ranging from 100 - 300 bar, and the secondary inlet at 25 bar higher than the primary pressure. Injection duration of 0.5 ms was chosen for the experiment. High-speed Mie scattering images were recorded to capture the spray evolution. Phase Doppler Anemometry (PDA) measurements were conducted at different locations in the spray for the acquisition of droplet sizes and velocity distributions. The high-speed images showed that the conventional injectors produced a spray with a wider spray cone angle, relative to the DFI injector which had a narrower spray cone angle leading to equal radial and axial spray penetration, and displaying a fine mist of gasoline droplets surrounding the diesel fuel jets. The DFI injector's spray provided superior atomization compared to the conventional injectors. The drop size of the dual-fuel spray was slightly higher than the single-fuel spray due to collision and coalescence of the diesel droplets with the fine gasoline droplets.