VII PTNSS Congress - 27th-29th June 2017
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Investigation of Detailed Injection Processes Inside the Injector and in the Spray Near Field

The injection of liquid fuel like diesel or gasoline is done with highest pressure injection systems. However, the physical processes especially inside the nozzle and in the near field of the nozzle are only partly understood due to the complex processes. Also the small dimensions the short timing and the dense spray are a challenge for detailed measurements. At the Institut für Technische Verbrennung at Hannover University some approaches are taken to investigate this processes. Firstly, the near field of the diesel spray is investigated with the transient high speed optical connectivity method, where the light is guided from inside the injector nozzle to the near field of the spray. Also the development of the optically coupled version (Remote Optical Connectivity Method) is shown. Current work tries to compare the near field spray measurement with other methods.  
Secondly, transient measurements are performed of the injection process inside transparent diesel or SI engine nozzle systems. This allows the determination of local cavitation processes. In ongoing work this situation is also simulated with transient threedimensional methods of computational fluid dynamics. Qualitatively the modelling of the two-phase flow and the cavitation is already possible.  
A third work combines several methods to investigate the influence of varied spray hole geometry on the cavitation and spray processes as well as on the emissions of a heavy duty diesel injector. Five different spray hole geometry, some of them with rather unusual shaping are compared here. It is found that the tendency to cavitation is dominant for the spray and emission behaviour. 
Topic: Fuel injection systems and mixture formation
Author: F. Dinkelacker
Co-authors: L. Thimm, K. Gröger, M. Kaiser, N. Kawaharada, H. Hansen,