06 Fakultät Luft- und Raumfahrttechnik und Geodäsie
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/7
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Item Open Access Reaction mechanism development and numerical modeling of biomass gasification process(2021) Fernando, Niranjan; Riedel, Uwe (Prof. Dr. rer. nat.)Item Open Access Quantification and mitigation of PIV bias errors caused by intermittent particle seeding and particle lag by means of large eddy simulations(2021) Martins, Fabio J. W. A.; Kirchmann, Jonas; Kronenburg, Andreas; Beyrau, FrankIn the present work, a standard large eddy simulation is combined with tracer particle seeding simulations to investigate the different PIV bias errors introduced by intermittent particle seeding and particle lag. The intermittency effect is caused by evaluating the velocity from tracer particles with inertia in a region where streams mix with different seeding densities. This effect, which is different from the vastly-discussed particle lag, is frequently observed in the literature but scarcely addressed. Here, bias errors in the velocity are analysed in the framework of a turbulent annular gaseous jet weakly confined by low-momentum co-flowing streams. The errors are computed between the gaseous flow velocity, obtained directly from the simulation, and the velocities estimated from synthetic PIV evaluations. Tracer particles with diameters of 0.037, 0.37 and 3.7 µm are introduced into the simulated flow through the jet only, intermediate co-flowing stream only and through both regions. Results quantify the influence of intermittency in the time-averaged velocities and Reynolds stresses when only one of the streams is seeded, even when tracers fulfil the Stokes-number criterion. Additionally, the present work proposes assessing unbiased velocity statistics from large eddy simulations, after validation of biased seeded simulations with biased PIV measurements. The approach can potentially be applied to a variety of flows and geometries, mitigating the bias errors.Item Open Access Modeling and simulation of electronic excitation in oxygen-helium discharges and plasma-assisted combustion(2018) Kuntner, Nikolaj; Riedel, Uwe (Prof. Dr. rer. nat.)The present work concerns the generation of electronically excited oxidizers in non-thermal discharges in the context of plasma-assisted hydrogen and methane combustion at atmospheric pressures. These conditions are of practical relevance for the combustion technology. However, as the conversion of electrical power into particular, chosen chemical degrees of freedom is facilitated by low molecular interaction, the atmospheric parameter range is often neglected in the literature. This work provides the design and validation of accurate and efficient computational models for several experiments in this parameter range.Item Open Access Novel modeling approaches for the entrained-flow gasification of bio-slurries(2020) Fradet, Quentin; Riedel, Uwe (Prof. Dr. rer. nat.)