  The entire process of atomization of the fuel in an internal combustion
engine plays a very important role in determining the overall efficiency of
these engines. A good atomization process could help the fuel to mix with the
air properly leading to its efficient combustion, thereby reducing the emitted
pollutants as well. The recent trend followed by the engineers focused on
designing fuel injectors for more efficient atomization is to increase the
atomization pressure while decreasing the nozzle orifice diameter. A
consequence of this is the development of cavitation (formation of vapor
cavities or bubbles in the liquid) inside the injector close to the nozzle. The
main reason behind this is the sudden changes in the pressure inside the
injector and these cavities or bubbles are usually formed where the pressure is
relatively low.This work mainly focuses on studying the formation of cavitation
and its effect on the velocity of the spray in the near nozzle region using
asymmetrical transparent nozzle equipped with a needle lift sensor with nozzle
diameter of 0.35 mm at 300 bar of injection pressure. The experiment consists
in recording of several image-pairs, which are separated by about 300 ns,
capturing the dynamics of the spray, a few millimeters from the nozzle in the
direction of the flow. These image-pairs are then used to compute the velocity
from the displacement of the liquid structures and ligaments by correlating the
first image with the second. About 200 of such velocity graphs are then
averaged to obtain a velocity map and is compared with the similar average
velocity maps obtained at different times from the start of the injection. The
angular spread of the spray from each of these images is calculated as well.
The images showing cavitation inside the injector are also recorded at these
same instants of time so as to understand the effects of cavitation on the
velocity and angular spread of the spray close to the nozzle.
