PIV Investigation on Flows Induced by Fuel Sprays from an Outwards Opening Pintle Injector for GDI engines

Pintle-type outwards opening injectors actuated by piezoelectric technique have demonstrated the ability to meet the challenging requirements in spray-guided gasoline direct injection engines. Previous studies carried out by spray visualisation showed that the spray had a stable spray cone angle against elevated in-cylinder back pressures, which have been be determined by the integral spray images using continuous or flash white light illumination. However the fuel cloud structure at the end of injection was not well defined when the injection was completed in the white light Mie scattering visualisation. In order to show the details of the spray cloud structure, two dimensional flow visualisation illuminated by a laser sheet was used under the atmospheric condition. The results showed complex multiple vortices forming a recirculation zone inside the fuel cloud. To further study the structure of such vortices, a double pulsed laser sheet illumination was employed to obtain the instantaneous velocity fields of fuel droplets using the Particle Image Velocimetry (PIV) technique. The PIV system was also used to study air motion induced by the spray near the injector nozzle; a good agreement was found in the air entrainment velocities when compared to the LDV measurements.