Experimental and numerical study of spray generated by a high pressure gasoline swirl injector

Experimental measurements and numerical computations were made to characterize a spray generated by a high-pressure swirl injector. The Phase Doppler technique was applied to get information on droplet sizes (d10) and axial velocities at defined distances from the injector tip. Global spray visualization was also made. Computations were carried out using a modified version of KIVA 3V. In particular, the break-up length of the sheet and its dimension were computed from a semi-empirical correlation related to the wave instability theory suggested by Dombrowski and Hooper, including the modifications introduced by Han and Reitz. Two different approaches were used to describe the initial spray conditions. According to the first, discrete particles with a characteristic size equal to the thickness of the sheet are injected. The second approach assumes, that the particles having a SMD computed by a semi-empirical correlation are injected according to a statistical distribution. In both cases droplet break-up occurs when the traveling distance becomes greater than the sheet break up length. In addition, in both cases, the secondary break up is based on the TAB model. A simple model based on mass and momentum conservation has been set up to calculate the sheet thickness at nozzle exit and to describe the evolution of axial and tangential components of motion at the start of injection.