Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 78 for “"Heat Release Rate"”.
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Controlling Object Heat Release Rate using Geometrical Features
… the effect of complex geometries on the burning rate of materials made using additive manufacturing. Controlling heat release rate has applicability in limiting fire hazards as well as for designing fuels for optimal burning rate. The burning rate of a structure is a function of the material …
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Computational Study of Parameters Affecting Electric Cabinet Fire Heat Release Rate
… cabinet fires, which are quantified as the heat release rate (HRR), and properly categorize them. With this knowledge, optimal parameter-response relationships can be developed to predict the electrical cabinet fire behavior. Statistical analysis conducted in this study on historical fire …
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Equivalence Ratio Gradient Effects on Local Flame Front Topology and Heat Release Rate in Stratified, Iso-Octane/Air Turbulent V-Flames
… a novel rectangular slot burner that could generate controlled, transverse variations in mixture strength along its exit plane. Turbulent, iso-octane/air V-flames were anchored in reactant mixtures of varying mean gradients in equivalence ratio (ϕ) and a unique windowing approach was devised in …
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Vortex driven flame dynamics and combustion instability
… mostly arises due to the coupling between heat release rate dynamics and system acoustics. It is crucial to understand the instability mechanisms to design reliable, high efficiency, low emission gas turbine combustors. In this thesis, elementary processes acting as a source of unsteady …
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A Five-Zone Model for Direct Injection Diesel Combustion
… 3) rich premixed products 4) diffusion flame sheath 5) surrounding bulk gas. Temperature and composition in each zone is calculated. Composition in combusting zones was calculated using an equilibrium model that includes 21 species. Sub models for ignition delay, premixed burn duration, heat …
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Spatially Resolved Analysis of Flame Dynamics for the Prediction of Thermoacoustic Combustion Instabilities
… to look for more environmentally combustion strategies. For gas turbine combustion, one promising technology is lean premixed combustion, which results in lower flame temperatures and therefore the possibility of significantly reduced nitric oxide emissions. While lean premixed combustion …
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Linear Stability Analysis of a Rijke Tube and Modeling of Turbulent Combustion Using Dynamic Well-Stirred Reactors
… which is comprised of the summation of chemical heat release rate and heat transfer due to convection, correctly predicts instability where older models of acoustic forcing based solely on chemical heat release rate incorrectly predicted stability. This stability analysis correctly predicts the …
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Machine Learning-Driven Uncertainty Quantification and Parameter Analysis in Fire Risk Assessment for Nuclear Power Plants
… uncertainties, especially in predicting the heat release rate (HRR) — a key parameter for assessing fire severity. This dissertation presents an innovative framework that integrates machine learning (ML) models, particularly neural networks and tree-based algorithms, with uncertainty …
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Nano-filled Epoxy: Mechanical and Fire Behavior and Modeling of Nanocomposite Columns Under Fire
… stress intensity factor, and the critical energy release rate. With static mechanical tests the tensile and flexural properties of the nanocomposites are measured. Flammability tests made by cone calorimetry are used to determine the Heat Release Rate, Mass Loss Rate, time to ignition, to Peak of …
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Shape Optimization of Annular Combustors with an Open Source Parallelized Thermoacoustic Helmholtz Solver
… combustors due to the dynamic coupling between heat release rate and acoustic oscillations. If the unsteady heat release rate is sufficiently in phase with the acoustic pressure, then the amplitude of the acoustic pressure intensifies. This increases the fatigue of the components and can lead to …
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Experimental Sensitivity Analysis and Control of Thermoacoustic Systems in the Linear Regime
… to feedback between acoustic waves and unsteady heat release rate when the fluctuating heat release rate is sufficiently in phase with the unsteady pressure. The primary aim of designers is to design linearly stable thermoacoustic systems in which these dangerous oscillations do not arise. In …
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Modelling of fire spread and the growth of fire in buildings using computational fluid dynamics
… model of fire spread over a surface, and to integrate this model with a computational fluid dynamics (CFD) model that is capable of making predictions of the environment associated with full-scale fires in enclosures. The research focuses on the growth and spread stage of such fires, where a …
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A Computational Fluid Dynamics Investigation of Thermoacoustic Instabilities in Premixed Laminar and Turbulent Combustion Systems
… instabilities, which manifest as pressure and heat release oscillations in the combustor. To be able to predict and control these instabilities, it is required that both the acoustics of the system, and a frequency-resolved response of the combustion process to incoming perturbations be …
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The effect of fuel injection pressure and in cylinder temperature on igniton delay, combustion performance and emission
… during the ignition delay period and initial heat release in combustion process that strongly affects the exhaust emissions. This study investigated effects of ambient temperature,Ti and injection pressure, Pinj on the heat release process during ignition delay periods. Rapid compression …
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Numerical Modeling of Turbulent Combustion and Flame Spread
… These developed models have been fully incorporated into CFD (Computational Fluid Dynamics) code and coupled with other CFD sub-models, including the DT (Discrete Transfer) radiation model, EDC (Eddy Dissipation Concept) combustion model, flamelet combustion model, various soot models and …
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CFD investigation on hydrogen enrichment effect to dual-fuel direct injection diesel engine
… bar at 1.4 equivalence ratio and 0 % hydrogen. Heat release rate (HRR) increased when both mole fraction of hydrogen and equivalence ratio increased, with 37.98 KJ as the maximum heat release rate observed at 90 % hydrogen addition and 1.4 equivalence ratio.
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Physics-Based Statistical Learning in Thermoacoustics
… waves inside a duct or a combustion chamber, and heat release rate oscillations at the flame or heater location. When certain conditions are met, these oscillations may grow significantly in time and cause severe problems, particularly in gas turbines used for propulsion, i.e. in systems …
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A Parametric Study of the Effect of Fire Source Elevation in a Compartment
… fire source elevations were studied for heat release rates ranging from 20 kW to 150kW. The species yields were obtained from performing detailed mapping measurements at the compartment and hallway exit planes. The measurements included local specie mole fractions of oxygen, carbon …
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A method for the numerical analysis of combustion instabilities with an application to afterburner screech
… numerical method is used that includes separate calculations of the mean flow and of the perturbed field due to the acoustic oscillations. This modularity supports the choice of models that are the most appropriate for combustion and for acoustic wave propagation, which are the processes …
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Polydimethylsiloxane Modification of Segmented Thermoplastic Polyurethanes and Polyureas
… The PDMS oligomer was successfully incorporated into the polyurethane backbone via one step solution polymerization. The effect of PDMS content on thermal stability, morphology, surface composition, mechanical properties, and fire resistance of polyurethane was investigated. These polymers …
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