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In the present work numerical simulations were carried out investigating the effect of fuel type, nozzle-geometry variations and back-pressure changes on high-pressure gas injections under application-relevant conditions. Methane, hydrogen and nitrogen with a total pressure of 500 bar served as high-pressure fuels and were injected into air at rest at 200 bar and 100 bar. Different nozzle shapes were simulated and the analysis of the results lead to a recommendation for the most advantageous geometry regarding jet penetration, volumetric growth, mixing enhancement and discharge coefficient. Additionally an artificial inlet boundary conditions was tested for the use with real-gas thermodynamics and was shown to be capable of reducing the simulation time significantly.

There is experimental evidence that flow optimised Diesel injectors using ks-nozzles show an increased tendency towards the formation of deposits. These deposits reduce spray quality and have an adverse effect on soot emissions and engine performance. Since deposit formation is known to be caused by locally high temperatures, the thermal behaviour of Diesel injectors using cylindrical and ks-nozzle was investigated. For this reason a coupled fluid-thermal analysis for a Diesel fuel injector was performed using a 3D-CFD-Code for both the solid structures and the fluid domain. As a first focus of this work the thermal conditions at the injector tip have been extracted from a complete in-cylinder-flow-simulation and a subsequent sensitivity study at the injector tip showed the influence of boundary conditions and configuration changes.