Transparent Injection Nozzles

The fuel supply by means of a direct injection into the combustion chamber has meanwhile become established in engine construction both for the diesel and the gasoline engine sector. The mixture preparation is of particular importance for the efficiency of the energy conversion of the engine and the resulting emissions.

In the optimization of injection systems, the injection nozzle itself is increasingly becoming the focus of current research. The geometries inside the nozzle have a big influence on the exiting spray. A deeper understanding of the processes within the injector is therefore fundamental to engine development.

Depending on the application, the fuel is injected at over 2000 bar through injection holes of less than 100 μm in diameter. The relevant processes take place in very short time periods of sometimes less than a millisecond. They represent a great challenge for numerical simulation and measuring technology.

In the project "internal nozzle flow", transparent injection nozzles are used to investigate this problem. These nozzles allow high-speed imaging techniques to be used to study the various phenomena occurring within the nozzle. Because of the extreme flow conditions, cavitation bubbles occur inside the nozzle. The purpose of the transparent nozzles is to gain more knowledge about the flow within the injector under realistic injection pressures and nozzle geometries.

Furthermore, numerical simulations on the same injection conditions as transparent nozzle experiments are used for verifying the limitation of current simulation models and requirements for new simulation models. These results will be an open database for the validation and development of simulation models in future.