Global ETD Search
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Showing 1 to 12 of 12 for “"Flame Response"”.
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Analyses of flame response to acoustic forcing in a rocket combustor
… elements in the center of the chamber. The response of the elements to the imposed acoustic disturbance is observed using high speed optical diagnostics. The main aim of this project is to develop methods for predicting the flame response to high frequency acoustic forcing representative of …
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EXPERIMENTAL INVESTIGATION OF THE RESPONSE OF FLAMES WITH DIFFERENT DEGREES OF PREMIXEDNESS TO ACOUSTIC OSCILLATIONS
… describes an experimental investigation of the response of lean turbulent swirling flames with different degrees of premixedness (i.e. different mixture patterns) to acoustic forcing using the same burner configuration and varying only the fuel injection strategy. Special emphasis was placed on …
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Effects of curvature and strain on a lean premixed methane-hydrogen-air flame
The elemental flame is a subgrid model for turbulent combustion, parameterized by time-varying strain rate and curvature. This thesis develops the unsteady one-dimensional governing equations for the elemental flame incorporating detailed chemical kinetics and transport and a robust and efficient …
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Spatially Resolved Equivalence Ratio Measurements Using Tomographic Reconstruction of OH*/CH* Chemiluminescence
… equivalence ratio perturbations within the flame field. These instabilities can cause irreparable damage to critical turbine components, requiring an understanding of the spatial/temporal variations in equivalence ratio values to predict flame response. The technique of computed tomography …
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Fundamental studies in hydrogen-rich combustion : instability mechanisms and dynamic mode selection
… to explore the dynamic interactions between the flame and the flow field of the combustor. Stable, quasi-stable, and unstable operating modes were identified in each combustor, with each mode characterized by a distinct dynamic flame shape and acoustic response which is dependent on the …
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Physics-based flame dynamics modeling and thermoacoustic instability mitigation
… for thermoacoustic instabilities under different flame anchoring configurations, (ii) to develop reduced-order models to predict the dynamic flame response, and (iii) to develop passive instability mitigation strategies by modifying the dynamics of the flame anchoring zone. The two different …
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The bending effect in turbulent flame propagation
In the present thesis, the sensitivity of flame propagation to the turbulent motion of burning gases is investigated. The long-standing issue of the 'bending effect' is focused upon, which refers to the experimentally-observed inhibition of flame propagation velocity at high intensities of …
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A method for the numerical analysis of combustion instabilities with an application to afterburner screech
… by acoustic transverse modes at the afterburner flameholder. These vortices trap fresh reactants that burn after a certain time delay, therefore feeding energy into the oscillation. Within a linear approximation, the effect of small amplitude acoustic fluctuations on the flame is studied by …
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Numerical simulations of perforated plate stabilized premixed flames with detailed chemistry
… perforated-plate stabilized laminar premixed flames. The developed code is used to examine the impact of the operating conditions and the perforated plate design on the steady flame characteristics. It is also used to numerically investigate the response of these flames to imposed inlet …
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A Computational Fluid Dynamics Investigation of Thermoacoustic Instabilities in Premixed Laminar and Turbulent Combustion Systems
… of the system, and a frequency-resolved response of the combustion process to incoming perturbations be understood. Currently, a system-level approach is being used widely to predict the thermoacoustic instabilities. This approach requires simple, yet accurate models which would describe …
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Turbulent flame microstructure, dynamics, and thermoacoustic instability in swirl-stabilized premixed combustion : measurements, statistics, and analysis
… combustion system, and that the frequency-based response of the flame is a function of the flame geometry. In the first part of the thesis, we focus on the flame geometry, identifying several discrete transitions that take place in the swirl-stabilized flame as we adjust the equivalence ratio. By …
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The Effects of Porous Inert Media in a Self-Excited Thermoacoustic Instability: A Study of Heat Release and Reduced Order Modelling
… is often used to study a systems' stability response to geometric changes and mitigation approaches. These reduced order models rely on flame transfer functions (FTF) which numerically represent the relationship between heat release and acoustic perturbations. The accurate quantification of …