Abstract
High pressure injection systems have essential roles in realizing highly controllable fuel injections in internal combustion engines. The primary atomization processes in the near field of the spray, and even inside the injector, determine the subsequent spray development with a considerable impact on the combustion and pollutant formation. Therefore, the processes should be understood as much as possible; for instance, to develop mathematical and numerical models. However, the experimental difficulties are extremely high, especially near the injector nozzle or inside the nozzle, due to the very small geometrical scales, the highly concentrated optical dense spray processes and the high speed and drastic transient nature of the spray. In this study, several unique and partly recently developed techniques are applied for detailed measurements on the flow inside the nozzle and the spray development very near the nozzle. As far as possible, the same three-hole injector for high pressure diesel injection is used to utilize and compare different measurement approaches. In a comprehensive section, the approach is taken to discuss the measurement results in comparison. It is possible to combine the observations within and outside the injector and to discuss the entire spray development processes for high pressure diesel sprays. This allows one to confirm theories and to provide detailed and, in parts, even quantitative data for the validation of numerical models.
Highlights
High pressure injection systems are commonly used in modern internal combustion engines.The systems have essential roles for realizing highly controllable fuel injections, for example, multiple injections in a cycle, short injection duration and accurate injection quantity
In order to reach a comprehensive experimental based knowledge, several partly new and mostly optical measurement approaches are described in this work
Further enhanced geometric setups for such transparent measurements have to be evaluated, e.g., with three holes, where the redirection effects of the flow inside the injector are regarded as well. It would be of value if the details of the turbulence production induced by the collapse of cavitation bubble in the nozzle flow could be measured quantitatively
Summary
High pressure injection systems are commonly used in modern internal combustion engines. At the outside of the nozzle, sac geometry, the orifice inlet curvature, and the nozzle hole geometry The investigations of these the liquid is fragmented aerodynamically by the velocity difference between the liquid core and effects are challenging work due to the conditions of the measurements, such as the high velocity of the surrounding air. The flow inside the nozzle is affected by the inner structures, such as the needle movement, the sac geometry, the orifice inlet curvature, and the nozzle hole geometry The investigations of these effects are challenging work due to the conditions of the measurements, such as the high velocity of flow inside the nozzle (up to 800 m/s in some cases), the small size target (the diameter of 100 μm and length of 1 mm), and the optical inaccessibility of nozzles. To publish the experimental data of this work, as well as that of further experimental configurations, in such a way that other researchers can improve and validate their numerical models
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