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Large Eddy Simulations (LES) provide instantaneous values indispensable to conduct statistical studies of relevant fluctuating quantities for diesel sprays. However, numerous realizations are generally necessary for LES to derive statistically averaged quantities necessary for validation of the numerical framework by means of measurements and for conducting sensitivity studies, leading to extremely high computational efforts. In this context, the aim of this work is to explore and validate alternatives to the simulation of 20-50 single realizations at considerably lower computational costs, by taking advantage of the axisymmetric geometry and the Quasi-Steady-State (QSS) condition of the near nozzle flow at a certain time after start-of-injection (SOI).

Diesel spray simulation with a Lagrangian approach for the dispersed phase and a Eulerian approach for the continuum phase is known to be sensitive to mesh resolution and its structure. Inaddition a dependency to turbulent length scale at nozzle exit has been reported in the computational literature. The aim of this work is to quantify these sensitivities and verify computational results for an extensive series of parameters on the basis of detailed shadowgraphy and PDA experiments in a constant volume bomb. The analysis consists of temporal and spatial resolution studies, initial turbulent length scale variation, investigation of the sensitivity to two different atomization models and the influence of the injection direction to the mesh orientation. This study has been done both for non-evaporating and evaporating diesel sprays. The calculations showed a high mesh sensitivity on spray penetration.

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.