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Showing 1 to 20 of 38 for “"thermoacoustic instabilities"”.
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Probabilistic machine learning for the elimination of thermoacoustic instabilities
Thermoacoustic instabilities have hindered the development of high energy density combustors, such as those in jet engines, gas turbines or rockets, for decades. They are notoriously difficult to model and despite efforts to eliminate them, can show up unexpectedly. The current thesis demonstrates …
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A system identification approach to active control of thermoacoustic instabilities
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.
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Implementation of Adaptive Filter Algorithms for the Suppression of Thermoacoustic Instabilities
The main goal of this work was to develop adaptive filter algorithms and test their performance in active combustion control. Several algorithms were incorporated, which are divided into gradient descent algorithms and pattern searches. The algorithms were tested on three separate platforms. The …
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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 thermoacoustic instabilities in a swirl combustor through microjet air injection
Thermoacoustic or combustion instability, a positive feedback loop coupling heat release rate and acoustic oscillations in a combustor, is one of the greatest challenges currently facing the development of new gas turbine systems for propulsion and power generation. Traditional gas turbine designs …
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Subharmonic and Non-Subharmonic Pulsed Control of Thermoacoustic Instabilities: Analysis and Experiment
Thermoacoustic instabilities are a problem in modern pre-mixed combustors causing reduced performance and leading in the extreme to combustor failure from excessive pressure cycles. Much work has been done using linear controllers to eliminate these instabilities. Many experimenters in the field …
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Phase Shift Control: Application and Performance Limitations With Respect to Thermoacoustic Instabilities
… control of the pressure oscillations, called thermoacoustic instabilities, has been sought as passive abatement of these instabilities does not provide adequate damping and is often impractical on a large scale. Phase shift control of the instabilities is perhaps the simplest and most popular …
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Modeling and Stability Analysis of Thermoacoustic Instabilities in Gas Turbine Combustor Sections
… which could be used by industry to predict where instabilities were likely to occur during the design phase. Results show that the system based stability analysis can predict some of the instability frequencies seen in the experimental data, but more refined models are needed to predict every …
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Linear Modeling and Analysis of Thermoacoustic Instabilities in a Gas Turbine Combustor
… function depicting the frequency response of the thermoacoustic system. These blocks include the system acoustic response to unsteady heat release forcing, the air-side coupling of acoustic particle velocity to inlet fuel mass fraction, transport delays present in the mixing nozzle and combustion …
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Development and Characterization of a Synchronously Actuated Response Atomizer for Studying Thermoacoustic Instabilities
… burning combustor designs are susceptible to thermoacoustic instabilities. The SARA or Synchronously Actuated Response Atomizer is a liquid fuel atomizer and supply system designed to allow for the active control of droplet size, cone angle, and mass flow rate. These three parameters have been …
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A Computational Fluid Dynamics Investigation of Thermoacoustic Instabilities in Premixed Laminar and Turbulent Combustion Systems
… 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 of the …
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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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Nonlinear Control of a Thermoacoustic System with Multiple Heat Sources and Actuators
<p>Thermoacoustic instabilities can occur in thermal devices when unsteady heat release is coupled with pressure perturbations. This effect results in excitation of Eigen-acoustic modes of the system. These instabilities can lead to unpredictable behavior of the system. Gas-turbine combustion …
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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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Data assimilation into physics-based thermoacoustic models using Bayesian neural network ensembles
Thermoacoustic instabilities, driven by the interaction between the heat release rate from the combustion process with the combustion chamber pressure waves, have long been a problem in jet and rocket engine design. Unacceptably large oscillations often appear during full-scale engine tests, …
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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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Active Stabilization of Thermoacoustic Oscillation
… addresses the problem of actively controlling thermoacoustic instabilities in a laboratory test com- bustion chamber. Different strategies for actuation are discussed and evaluated experimentally. Relations to industrial relevance are taken into consideration, and a fuel actuator is developed …
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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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Acoustic Transfer Functions Derived from Finite Element Modeling for Thermoacoustic Stability Predictions of Gas Turbine Engines
… Derived from Finite Element Modeling for Thermoacoustic Stability Predictions of Gas Turbine Engines Design and prediction of thermoacoustic instabilities is a major challenge in aerospace propulsion and the operation of power generating gas turbine engines. This is a complex problem in …
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Development of Reduced-Order Flame Models for Prediction of Combustion Instability
… modern gas turbines, but it is susceptible to thermoacoustic instabilities, which can result in large amplitude pressure oscillations in the combustion chamber. The thermoacoustic limit cycle is generated by the unsteady heat release dynamics coupled to the combustor acoustics. In this …
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