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 24 for “"combustion instability"”.
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Modeling and control of combustion instability
Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.
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Vortex driven flame dynamics and combustion instability
Combustion instability in premixed combustors 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 …
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Modeling of combustion instability at different Damkohler conditions
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.
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Development of Reduced-Order Flame Models for Prediction of Combustion Instability
Lean-premixed combustion has the advantage of low emissions for 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 …
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Fundamental studies in hydrogen-rich combustion : instability mechanisms and dynamic mode selection
… produced by coal gasification. Lean premixed combustion, the preferred high-efficiency, low-emissions operating mode in these combustors, is susceptible to strong instabilities even in ordinary fuels. Because hydrogen-rich fuels have combustion properties which depend strongly on composition, …
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An investigation of the effect of a tangential gas velocity on combustion instability.
… built to study the effects of a vortex flow on combustion instability. Normal heptane and air were used as propellants with the air being divided into two flows; a primary flow at the center of the combustion chamber and a secondary flow at the periphery of the chamber. The secondary air …
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Combustion Instability Mechanism of a Reacting Jet in Cross Flow at Gas Turbine Operating Conditions
… gas turbine designs often include lean premixed combustion for its emissions benefits; however, this type of combustion process is susceptible to self-excited combustion instabilities that can lead to damaging heat loads and system vibrations. This study focuses on identifying a mechanism of …
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Swirl-stabilized lean-premixed flame combustion dynamics: An experimental investigation of flame stabilization, flame dynamics and combustion instability control strategies
Though modern low-emission combustion strategies have been successful in abating the emission of pollutants in aircraft engines and power generation gas turbines, combustion instability remains one of the foremost technical challenges in the development of next generation lean premixed combustor …
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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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Random Sphere Packing Model of Heterogeneous Propellants
… promise for understanding the origins of the combustion instability of heterogeneous propellants, and is believed to become a valuable tool for the development of safe and reliable rocket engines.
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Reconstruction of cross-modal visual features from acoustic pressure time series in combustion systems
… sensing modality. One such example is detecting combustion instability using flame images where deep learning frameworks have demonstrated high performance. The proposed frameworks are shown to be quite trustworthy such that the domain experts can have sufficient confidence to use these models in …
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Large eddy simulations of premixed turbulent flame dynamics : combustion modeling, validation and analysis
… preferred as they achieve efficient and clean combustion. A drawback of lean premixed combustion, however, is that the flames are more prone to dynamics. The unsteady release of sensible heat and flow dilatation in combustion processes create pressure fluctuations which, particularly in …
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Analyses of flame response to acoustic forcing in a rocket combustor
High frequency combustion instabilities in liquid propellant rocket engines are spontaneously occurring pressure fluctuations that are coupled with unsteady combustion processes. Under the right conditions the unsteady fluctuations can grow to a point where they affect the operation 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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Design and Validation of a Proportional Throttle Valve System for Liquid-Fuel Active Combustion Control
… one of the most promising methods for active combustion control. To attenuate the large pressure oscillations in the combustion chamber, the fuel is pulsed so that the heat release rate fluctuations damp the pressure oscillations in the combustor. This thesis focuses on the development and …
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Thermoacoustic Effects of a Variable Equivalence Ratio in a Single Element Methane Combustor
<p>Combustion instability is one of the leading factors in limiting the progress and innovations of liquid rocket engines and power plants. Under certain operating conditions, unsteady heat release and acoustic wave interactions can couple and lead to instabilities, such as self-sustaining pressure …
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Turbulent flame microstructure, dynamics, and thermoacoustic instability in swirl-stabilized premixed combustion : measurements, statistics, and analysis
… which link the combustor acoustics to the combustion process-can result in significant levels of thermal and mechanical stress on combustion systems, leading to reduced operational lifetime, potentially dangerous failure modes, and significant deviations from the desired operating …
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Combustion, Ionization And Sporadic Pre-Ignition In A Turbocharged Gasoline Direct Injection Engine.
… research is focused on the use of ionization of combustion products in hydrocarbons-air flames to gain a better understanding of the combustion process in turbocharged gasoline direct injection engines. A GM 2.0 L Ecotec GDI-T engine is used in this investigation. The ion current is measured …
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Spatially Resolved Analysis of Flame Dynamics for the Prediction of Thermoacoustic Combustion Instabilities
… stringent emissions regulations have led combustion system designers 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 …
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Opposing effects of recirculated gases during cranking on cold start of diesel engines
… rate of recirculated gases. Since there is no combustion during cranking, these gases contain evaporated hydrocarbons (HCs) and partial oxidation products such as formaldehyde (HCHO). HCs and HCHO have two opposing effects. HCs enhance the autoignition process, while the HCHO has an opposite …
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