Measurement and evaluation of near-field spray kinematics for nozzles with asymmetrical inlet geometries

Licentiatavhandling, 2022

In diesel engines, fuel injection parameters have a commanding effect on mixing and
combustion quality. This research aims to enhance the fundamental knowledge of fuel
sprays and their primary break-up. In addition, this research provides statistical data to
validate simulation models and improve the prediction accuracy in mixing and combustion.
This thesis report is based on evaluating the behavior and velocity profiles of near-field
sprays generated by different inlet geometries under a range of injection pressures. The
studied nozzles include single-hole nozzles with on-axis and off-axis orifices and a two-hole
nozzle with angled orifices. We applied time-gated ballistic imaging to capture high-resolution
spray images at the near-field. These high-resolution images provide a clear
liquid/gas interface, which enables tracking of the spray structures. Furthermore, the
displacement of the spray interface in two consecutive images over a specific time frame
yields spray kinematics in two dimensions.
The results show how velocity measurements can describe spray development and evolution.
Asymmetrical inlet geometries significantly affect near-field spray profile and targeting
because the distribution of velocity magnitude on the two sides of the spray is not
symmetric. In addition to inlet geometry, internal flow characteristics play a significant
role in spray behavior. The outlook for this project mainly consists of the validation
and development of simulation models. The obtained results provide an opportunity
to correlate the near-field spray to the internal nozzle flow and study the effect of
asymmetrical inlets on the internal flow.