06 Fakultät Luft- und Raumfahrttechnik und Geodäsie

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/7

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Institute: search.filters.UBSInstitut.Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)Institute: search.filters.UBSInstitut.Institut für Verbrennungstechnik der Luft- und RaumfahrtPublication Type: search.filters.UBSTyp.Zeitschriftenartikel

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Now showing 1 - 4 of 4
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    Development of an uncertainty quantification predictive chemical reaction model for syngas combustion
    (2017) Slavinskaya, Nadezda; Abbasi, Mehdi; Starcke, Jan Hendrik; Whitside, Ryan; Mirzayeva, Aziza; Riedel, Uwe; Li, Wenyu; Oreluk, Jim; Hegde, Arun; Packard, Andrew; Frenklach, Michael; Gerasimov, G. Ya.; Shatalov, Oleg
    An automated data-centric infrastructure, Process Informatics Model (PrIMe), was applied to validation and optimization of a syngas combustion model. The Bound-to-Bound Data Collaboration (B2BDC) module of PrIMe was employed to discover the limits of parameter modifications based on uncertainty quantification (UQ) and consistency analysis of the model−data system and experimental data, including shock-tube ignition delay times and laminar flame speeds. Existing syngas reaction models are reviewed, and the selected kinetic data are described in detail. Empirical rules were developed and applied to evaluate the uncertainty bounds of the literature experimental data. The initial H2/CO reaction model, assembled from 73 reactions and 17 species, was subjected to a B2BDC analysis. For this purpose, a dataset was constructed that included a total of 167 experimental targets and 55 active model parameters. Consistency analysis of the composed dataset revealed disagreement between models and data. Further analysis suggested that removing 45 experimental targets, 8 of which were self-inconsistent, would lead to a consistent dataset. This dataset was subjected to a correlation analysis, which highlights possible directions for parameter modification and model improvement. Additionally, several methods of parameter optimization were applied, some of them unique to the B2BDC framework. The optimized models demonstrated improved agreement with experiments compared to the initially assembled model, and their predictions for experiments not included in the initial dataset (i.e., a blind prediction) were investigated. The results demonstrate benefits of applying the B2BDC methodology for developing predictive kinetic models.
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    Investigating 3-D effects on flashing cryogenic jets with highly resolved LES
    (2023) Gärtner, Jan Wilhelm; Kronenburg, Andreas; Rees, Andreas; Oschwald, Michael
    For the development of upper stage rocket engines with laser ignition, the transition of oxidizer and fuel from the pure cryogenic liquid streams to an ignitable mixture needs to be better understood. Due to the near vacuum conditions that are present at high altitudes and in space, the injected fuel rapidly atomizes in a so-called flash boiling process. To investigate the behavior of flashing cryogenic jets under the relevant conditions, experiments of liquid nitrogen have been performed at the DLR Lampoldshausen. The experiments are accompanied by a series of computer simulations and here we use a highly resolved LES to identify 3D effects and to better interpret results from the experiments and existing 2D RANS. It is observed that the vapor generation inside the injector and the evolution of the spray in the combustion chamber differ significantly between the two simulation types due to missing 3D effects and the difference in resolution of turbulent structures. Still, the observed 3D spray dynamics suggest a suitable location for laser ignition that could be found in regions of relative low velocity and therefore expected low strain rates. Further, measured droplet velocities are compared to the velocities of notional Lagrangian particles with similar inertia as the measured droplets. Good agreement between experiments and simulations exists and strong correlation between droplet size and velocity can be demonstrated.
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    Low temperature oxidation of cyclohexane: uncertainty of important thermo-chemical properties
    (2018) Abbasi, Mehdi; Slavinskaya, Nadezda; Riedel, Uwe
    The study of the standard formation enthalpy, entropy, and heat capacity for key species relevant to the low-temperature combustion of cyclohexane has been performed by applying the group additivity method of Benson. The properties of 18 Benson groups (8 of them for the first time), and 10 ring correction factors for cyclic species were estimated through different empirical and semi-empirical methods. The method validation proceeded through comparison of predicted values for certain number of newly estimated groups and available literature data derived from quantum chemistry estimations. Further validations of the estimated properties of groups have been provided by comparing estimated properties of test species with data in literature and kinetic databases. Also the standard deviation between prediction and reported values has been evaluated for each validation case. A similar approach has been applied for validation of the estimated ring correction groups. For selected well-studied cyclic molecules the predicted values and the literature data have been compared with each other, and the standard deviations have been also reported. The evaluated properties of the cyclohexane relevant species were also compared with similar ones available in other kinetic models and in databases. At the end the estimated properties have been presented in a tabulated form of NASA polynomial coefficients with extrapolation up to 3500 K.
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    Additive manufacturing enabled annular μ-slit injection in low NOX jet-stabilised liquid fuel combustion
    (2026) Kang, Yeonse; Lammel, Oliver; Ruf, Matthias; Steeb, Holger; Möhring, Hans-Christian; Hampp, Fabian
    Advanced fuel injection systems are vital for improving combustion performance and reducing emissions in liquid-fuel-powered, high-momentum jet-stabilised combustion systems. This paper introduces an additively manufactured (AM) μ-scale annular slit injector with a nominal gap width of 50μm, realised by laser powder bed fusion in Inconel 718. μ-XRCT measurements confirm a manufacturable width of 52μm and reveal a transition towards statistically isotropic circumferential discharge at the slit exit. Compared with conventional dual airblast injection (AB), the μ-slit topology generates more uniformly fine droplets (d32 ≈ 10μm) and a markedly reduced radial asymmetry in fuel placement. The homogenised annular fuel discharge suppresses sectional bias and intermittency at the nozzle edge while enhancing fuel-air mixing, redistributing clustering length scales, and promoting more robust combustion across variations in jet velocity and fuel loading. Structural variants, e.g., μ-bumps and a low-swirler configuration, further modulate near-field multi-phase interaction and flame anchoring while enhancing overall flame homogeneity. This mixing-optimised stabilisation enhances the symmetry of the OH∗-marked heat-release structures and enables stable low-NOX combustion under lean atmospheric conditions. The injector operates with a comparatively low pressure drop with excellent reproducibility across all investigated mass flow rates, facilitating a wide dynamic operating range, yet heat transfer within the μ-channels under elevated preheating conditions requires further investigation. These results establish the AM μ-slit injector as a scalable low-emission architecture for compact, jet-stabilised micro gas turbine and hybrid aero-engine combustors.