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.