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 28 for “"thermoacoustic instability"”.
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Physics-based flame dynamics modeling and thermoacoustic instability mitigation
… unsteady heat release mechanisms responsible 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 …
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Shape optimization for thermoacoustic instability with an adjoint Helmholtz solver
Thermoacoustic instabilities, which occur due to the feedback between confined flames and acoustics, constitute a major threat to the safe operation of gas turbines and rocket engines. These oscillations can become large enough to cause noise, vibrations or, in the worst cases, extinction of the …
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Model-based active control of thermoacoustic instability in continuous combustion processes
Thermoacoustic instability is frequently found in continuous combustion processes in propulsion, power generation, and heating. Active control has been increasingly pursued in recent years to suppress the pressure oscillations which result from this instability, while maintaining performance …
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Turbulent flame microstructure, dynamics, and thermoacoustic instability in swirl-stabilized premixed combustion : measurements, statistics, and analysis
… the task of finding and eliminating modes of instability to a lengthy and expensive trial-and-error process. Lean-premixed combustion, one of the leading technologies for low emission combustors, is particularly susceptible to these types of instabilities. The sealed systems that are necessary …
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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
… combustion is utilized but is susceptible to thermoacoustic instabilities. These instabilities occur due to an in-phase relationship between acoustic pressure and unsteady heat release in a combustor. Thermoacoustic instabilities have been shown to cause structural damage and limit operability …
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Computational Investigations of Boundary Condition Effects on Simulations of Thermoacoustic Instabilities
… Computational Fluid Dynamics (CFD) simulation of thermoacoustic instability problems. The proposed sensitivity analysis approach only requires a single run of the CFD simulation. Moreover, the sensitivities of field variables, pressure, velocity and temperature to boundary-condition parameters are …
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Suppression of premixed combustion dynamics utilizing microjet air injection
The problem of thermoacoustic instability in continuous combustion systems is a major challenge in the field of propulsion and power generation. With the current environmental and political pressure that is being placed on the consumption of fossil fuels, this subject has become even more critical. …
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Shape Optimization of Annular Combustors with an Open Source Parallelized Thermoacoustic Helmholtz Solver
Thermoacoustic instability occurs in gas turbine 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 …
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Hydrogen Enrichment Effects on Thermoacoustics of Turbulent Partially Premixed Flames
… rendering them susceptible to undesirable thermoacoustic instabilities. Additionally, meeting decarbonisation targets require incorporation of hydrogen into the existing combustion infrastructure. This doctoral thesis addresses the challenges of hydrogen combustion and thermoacoustic …
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Adaptive Control Methods for Non-Linear Self-Excited Systems
… of adaptive control approaches for controlling a thermoacoustic instability, a physical self-excited system. Initially, a static feedback controller loopshaping design and associated system identification method is presented. This design approach is shown to effectively stabilize an unstable Rijke …
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A Thermoacoustic Characterization of a Rijke-type Tube Combustor
Pressure pulsations, or thermoacoustic instabilities, as they are called in the research community, can cause extensive damage in gas turbine combustion chambers. To understand the phenomena related to thermoacoustics, a simple Rijke-type tube combustor was built and studied. Extensive experimental …
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A Method for Measuring Spatially Varying Equivalence Ratios with Application to Thermoacoustics
… on flame behavior including but not limited to thermoacoustic instability, NOx and CO formation, and flame stabilization. Local equivalence ratios are determined from a OH*/CH* ratio of tomographically reconstructed intensity fields and relating them to equivalence ratio. The correlation of …
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Active combustion control : modeling, design and implementation
… power generation applications are susceptible to thermoacoustic instability, which occurs under lean burn conditions close to the flammability where most emissions and efficiency benefits are achieved, and near stoichiometry where often high power density can be realized. This instability is …
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Effects of Thermoacoustic Oscillations on Spray Combustion Dynamics with Implications for Lean Direct Injection Systems
Thermoacoustic instabilities in modern high-performance, low-emission gas turbine engines are often observable as large amplitude pressure oscillations and can result in serious performance and structural degradations. These acoustic oscillations can cause oscillations in combustor through-flows …
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Experimental Sensitivity Analysis and Control of Thermoacoustic Systems in the Linear Regime
Thermoacoustic instability is one of the most significant problems faced in the design of some combustion systems. Thermoacoustic oscillations arise due to feedback between acoustic waves and unsteady heat release rate when the fluctuating heat release rate is sufficiently in phase with the …
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Dynamics of Lean Direct Injection Combustors
… This dissertation focuses on the dynamics of thermoacoustic instability and lean blowout (LBO), two of the major complications that industry will face when they attempt to incorporate LDI in a production engine. The present dissertation investigates these dynamics from a fundamental and …
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Development of a Single-Point SV-LDI-1 System: A Benchmark Study for Future Experiments
… due to two critical system-level complications: thermoacoustic instability and lean blowout (LBO). These phenomena present significant barriers to operational reliability, and understanding their behavior is essential for advancing LDI to practical use. This thesis investigates the operability …
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Spatially Resolved Equivalence Ratio Measurements Using Tomographic Reconstruction of OH*/CH* Chemiluminescence
Thermoacoustic instabilities in gas turbine operation arise due to unsteady fluctuations in heat release coupled with acoustic oscillations, often caused by varying equivalence ratio perturbations within the flame field. These instabilities can cause irreparable damage to critical turbine …
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Adjoint-accelerated Bayesian inference in thermoacoustics
We demonstrate a new approach to thermoacoustic modelling, in which we use an efficient Bayesian inference framework to assimilate experimental data into thermoacoustic models. The framework provides four main tools: (i) parameter inference, (ii) uncertainty quantification, (iii) model comparison, …
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An Exploration of Secondary Fuel Injection as Actuation for Control of Combustion Instabilities in a Laminar Premixed Tube Combustor
… Much work has gone into controlling these thermoacoustic instabilities with secondary fuel control. Control of a laminar premixed tube combustor through secondary fuel actuation is the concentration of this work. It is the first known published attempt to control a laminar premixed tube …
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