Characterizing Spray Behavior of Diesel Injection Systems Using X-Ray Radiography

In Diesel engines, fuel injection plays a critical role in performance, efficiency, and emissions. Altering parameters such as injection quantity, duration, pressure, etc. influences the injector's performance. Changes in the injection system architecture can also affect the spray behavior. Understanding of the flow near the nozzle exit can lead to the establishment of correlation to spray characteristics further downstream, and eventually its combustion behavior in the engine. Because of its high density, the near-nozzle region of the spray is difficult to study using optical techniques. This near-nozzle region of spray from high pressure injectors was studied using the quantitative and time-resolved x-ray radiography technique. This method provides high spatial and temporal resolution without significant scattering effects. Comparisons of spray characteristics are made between a Caterpillar HEUI multi-hole injector, a single-hole common rail Bosch injector, and multi-hole common rail Bosch injectors. Notable dissimilarities between the systems are observed. Differences in internal flow between the multi-hole and single-hole nozzles lead to significantly broader sprays from the multi-hole nozzles. In addition, spray from the Valve-Covered Orifice (VCO) nozzle and Mini-Sac nozzles differ in the distribution of mass with VCO nozzles yielding sprays with higher concentration towards the center.