Transient Nozzle-Exit Velocity Profile in Diesel Spray and Its Influencing Parameters

Abstract

Article Transient Nozzle-Exit Velocity Profile in Diesel Spray and Its Influencing Parameters Ya Gao 1, Weidi Huang 2,*, Raditya Hendra Pratama 2, and Jin Wang 1 1 Advanced Photon Source, Argonne National Laboratory, 9700 S Cass Ave, Lemont, IL 60439, United States 2 Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology, Ibaraki 305-8564, Japan * Correspondence: wd.huang@aist.go.jp     Received: 24 September 2022 Accepted: 10 November 2022 Published: 25 December 2022   Abstract: The primary breakup in the diesel spray relies closely on the initial dynamics at the nozzle exit. However, solid experimental results are still missing due to the great difficulties in measuring the near-nozzle spray dynamics. This study proposed an investigation focusing on the transient nozzle-exit spray dynamics by taking advantage of the X-ray phase contrast imaging technique. The in-nozzle needle motion, spray morphology, and dynamics at a commercial diesel nozzle exit were obtained. Experimental results were then examined, linking with the needle motion to understand the transient spray dynamics. The effect of the initial conditions (i.e., the injection pressure and ambient density) on the resulting trends were also considered. It is found that the nozzle-exit spray morphology and velocity profile highly relate to the in-nozzle needle lift. Once the needle sufficiently opens, the spray reaches steady status, and the nozzle-exit velocity becomes almost constant. The spray width slightly increases with the increasing ambient gas density or the decreasing injection pressure. Injection pressure significantly affects the spray velocity amplitude, whereas the ambient gas density alters the spray-velocity profiles mainly in the periphery of the spray. Finally, an analytic analysis was conducted to further examine the transient spray axial velocity with the changing radial locations. It is found the nozzle-exit spray velocity can be predicted in the Gaussian-type formula. This feature likely relates to in-nozzle flow characteristics.