Development of the Optical Connectivity Method for Diesel Injectors for Modeling the Primary Spray Breakup

The phenomenon of diesel spray remains to be fully understood, necessitating a comprehensive collection of complementary measurement techniques to facilitate a more profound insight. Detailed measurement of the primary spray breakup is particularly challenging due to the prevalence of opacity, high pressure gradients, and liquid velocities, as well as the extensive range of scales that are covered. This study focuses on the primary breakup zone, which can be defined as the liquid core just after nozzle exit and its near-field spray.
To this end, a set of specialized simultaneous techniques was developed, including a tailored Elastic Photon Optical Connectivity system in combination with a "focused" shadowgraphy setup. This approach enabled microscopically resolved measurements of the near nozzle region. The application within a High-Pressure High-Temperature Injection Chamber facilitated the measurement of the intact core length, ICL, and spray cone angle, Ø, under different charge densities and for various fuel temperatures.
These experiments allowed for a deeper understanding of the influence of these parameters. Consequently, the measured values of ICL and Ø were employed to calibrate spray models from the literature, which were extended to include a dependency on the fuel temperature.
In the future, these enhanced models may serve to elucidate the interrelation of the sub-processes turbulence and cavitation.