Examinando por Materia "COMBUSTION"
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Tesis de maestría CFD simulation of a hydrogen explosion experiment in an ISO container(2017) Weber, Philipp; Schulenberg, Thomas; Jordan, Thomas; Kotchourko, Alexei"The EU project HySEA is dedicated to explosion risk reduction by deflagration venting of industrial hydrogen installations. In 20-foot ISO containers, several experiments have been conducted to provide data for combustion model improvement and validation. The first experimental campaign included a blindprediction study concerning two lean premixed configurations. The hydrogen research group of IKET submitted a model prediction based on the in-house code COM3D. The experimental results were not matched. Therefore, the objective of this thesis was to improve the predictability of the CFD code by carrying out post-blind simulations. Over the course of this work, the roles of thermodiffusive instability and the turbulent flame speed model in the process of flame acceleration were analyzed and clarified. As a consequence, the numerical model for the transition from laminar to turbulent flame speed was developed and implemented in the COM3D code. Validating simulations demonstrated satisfactory agreement compared to the experimental results. This represents a first step toward extending the applicability of the code to a wider range of combustion scenarios."Tesis de maestría Evaluation of StarCCM+ to predict thermoacoustic instabilities using Large Eddy Simulation(2017) Indlekofer, Thomas; Ariatabar, Behdad; Bauer, Hans-Jörg; Hermeth, Sebastian"Self-sustained pressure and heat-release oscillations yielded by thermoacoustic coupling are a major problem of gas turbine operation and methods to predict them are needed. This work investigates the capabilities of Large Eddy Simulation (LES) in StarCCM+ to predict these instabilities in the academic Volvo bluff-body combustor. First, simplified cases are studied to assess boundary condition treatment and numerical accuracy of the methods available. The non-reactive operating point is predicted accurately, showing good agreement for velocity fields as well as the ability to predict the vortex shedding frequency in the intrinsically unsteady region of the recirculation zone. For a reacting-stable operating point the acceleration downstream of the bluff body is overpredicted and the flow fields are not predicted accurately. Low frequency oscillations of the unstable operating points are evidenced coincididing with experimental results and an acoustic analysis based on Comsol Multiphysics. Up to = 1:0 the coherence of the equivalence ratio and the magnitude of the instabilities is predicted qualitatively."