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Showing 1 to 20 of 21 for “"thermo-acoustic"”.
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Computational analysis of thermo-acoustic instabilities in combustion chambers and afterburners
A simplified model is introduced to study thermo-acoustic instabilities in asymmetric combustion chambers. Such instabilities can be triggered when correlations between heat-release and pressure oscillations exist, leading to undesirable effects. Gas turbine designs typically consist of a periodic …
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Systematic Prediction and Parametric Characterization of Thermo-Acoustic Instabilities in Premixed Gas Turbine Combustors
… the coincident prediction and observation of thermo-acoustic instabilities in a turbulent, swirl-stabilized research combustor using a stability model constructed from validated reduced-order component models. The component models included the acoustic response to flame heat release rate at …
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Application of Multi-Port Mixing for Passive Suppression of Thermo-Acoustic Instabilities in Premixed Combustors
… to a resonant interaction between the combustor acoustics and the flame. A primary feedback mechanism responsible for driving these systems is the propagation of Fuel/Air Ratio (FAR) fluctuations into the flame zone. These fluctuations are formed inside of the premixing chamber when fuel is …
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The Design and Construction of a High Bandwidth Proportional Fuel Injection System for Liquid Fuel Active Combustion Control
… a sudden increase of interest in the control of thermo-acoustic instabilities, in particular through the use of fuel modulation techniques. The primary goal of this research was to design, construct and characterize a high bandwidth proportional fuel injection system, which could be used to study …
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System Level Approach towards Intelligent Healthcare Environment
… ex-vivo imaging, energy for sensors, and acoustic communication. These technologies are: locomotion mechanism for wireless capsule endoscope (WCE), multifunctional image guided surgical (MIGS) platform, shape memory alloy (SMA) thermal energy harvester and thermo-acoustic sonar using …
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Damping Parameter Study of a Perforated Plate with Bias Flow
… is the dynamic instability also known as thermo-acoustic instability. Concerns with this ongoing problem have grown with the introduction of Lean Premixed Combustion (LPC) systems developed to address the environmental concerns associated with the conventional combustion systems.</p><p>The …
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Impact of fuel and oxidizer composition on premixed flame stabilization in turbulent swirling flows : dynamics and scaling
… combustion and several challenges, notably thermo-acoustic instability, arise when using other fuels or oxidizers because of their different thermochemical and transport properties. While these phenomena constitute a major challenge under conventional operations, using hydrogen-rich fuels or …
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A Parallel Solution-Adaptive Method for Turbulent Non-Premixed Combusting Flows
… readily accommodate large density variations and thermo-acoustic phenomena. A preconditioned multigrid algorithm is used to obtain the solution on highly stretched meshes in a more efficient manner. A flexible block-based hierarchical data structure is used to maintain the connectivity of the …
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The study of acoustic properties of P205-doped silica fiber
… to numerous fields. The interactions between acoustic phonons and the optical wave are involved in several of these applications. A significant stimulated scattering mechanism observed is stimulated Brillouin scattering (SBS), resulting in strong backward scattering typically within the …
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Evaluating energy dissipation during expansion in a refrigeration cycle using flue pipe acoustic resonators
… evaluates the feasibility of using a flue pipe acoustic resonator to dissipate energy from a refrigerant stream in order to achieve greater cooling power from a cryorefrigeration cycle. Two models of the acoustic operation of flue pipe resonant systems are examined: an electrical circuit analog …
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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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Thermophony in real gases
A thermophone is an electrical device for sound generation. The advantages of thermophones over conventional sound transducers such as electromagnetic, electrostatic or piezoelectric transducers are their operational principle which does not require any moving parts, their resonance-free behavior, …
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Simulation of Flow in a Solid Fuel Ramjet Cavity
… is used to analyze CFD results to determine acoustic modes in the ramjet. Peak acoustic frequencies are compared between between numerical and experimental results. Comparisons are made between simulations performed with a 2D axisymmetric domain and full 3D domain. Cold-flow LES simulations …
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A Study of the Dynamics of Laminar and Turbulent Fully and Partially Premixed Flames
… increased the likelihood of the occurrence of thermo-acoustic instabilities. The experimental techniques developed during the dynamic studies conducted on laminar flat flames were applied to swirl stabilized turbulent flames. Experiments were performed for QAir = 15 scfm and 20 scfm, F = 0.55, …
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Reduced-Order Models for the Prediction of Unsteady Heat Release in Acoustically Forced Combustion
… novel formulations for models describing acoustically forced combustion in three disjoint regimes; highly turbulent, laminar, and the moderately turbulent flamelet regime. Particular emphasis is placed on simplification of the models to facilitate analytical solutions while still …
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Flame Stabilisation in the Transition to MILD Combustion
… reduction of CO and NOx pollutants, soot and thermo-acoustic instabilities compared to conventional combustion. Whilst combustion in the MILD regime offers considerable advantages over conventional combustion, neither the structure of reacting jets under MILD conditions, nor the boundaries of …
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Numerical Analysis of Flow and Heat Transfer through a Lean Premixed Swirl Stabilized Combustor Nozzle
… the resulting pressure fluctuations leading to thermo-acoustic instabilities there by creating a feedback loop with incoming reactants resulting in flow instabilities leading to flame lift off, flame extinction etc. Hence understanding combustion driven swirling flow in combustors continues to …
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Applications of femtosecond coherent anti-stokes Raman scattering in combustion
… (CPP fs-CARS) for applications of gas phase thermometry and extension to methane concentration measurements. The main effort has been to assess the usefulness and robustness of the technique in turbulent combustors of practical interest. A primary aim has been to evaluate the use of CPP …
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A Computational Fluid Dynamics Investigation of Thermoacoustic Instabilities in Premixed Laminar and Turbulent Combustion Systems
… These combustors are often susceptible to thermo-acoustic 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 …
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Pyrolysis and Flamelet Model for Polymethyl Methacrylate in Solid Fuel Sc(ramjet) Combustors
… numerical schemes that inhibit the study of thermo-acoustic interactions between coherent pressure waves and the burning walls of the cavity. These limitations in current models suggest the need for a Navier-Stokes solver based on a high-order, discontinuous Galerkin method, incorporating …
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