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Showing 1 to 20 of 23 for “"Combustion instabilities"”.
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Addressing nonlinear combustion instabilities in highly dilute spark ignition engine operation
"Dilute operation is a promising approach for increasing spark-ignition engine efficiency, in the form of either lean burn (air dilution) or EGR (inert dilution). High levels of charge dilution, however, lead to cyclic variability that is largely deterministic in nature. The determinism and …
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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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A method for the numerical analysis of combustion instabilities with an application to afterburner screech
… thermoacoustic oscillations in gas turbine combustion systems by computational means. A framework is laid out to predict numerically the frequency and stability of thermoacoustic oscillations, with focus on the high frequency screech instability of afterburners. A hybrid numerical method is …
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Design and Validation of a High-Bandwidth Fuel Injection System for Control of Combustion Instabilities
… of fuel injection hardware used for active combustion control is not well established in the gas turbine industry. The primary reason for this is that the underlying mechanisms governing the flow rate authority downstream of the nozzle are not well understood. A detailed investigation of two …
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An Exploration of Secondary Fuel Injection as Actuation for Control of Combustion Instabilities in a Laminar Premixed Tube Combustor
Active control of combustion instabilities through secondary fuel injection is a control method that has gained a lot of attention in the past decade. Previous control schemes with acoustic loudspeakers are not practical in full-scale gas turbines due to the extreme temperatures and acoustic power …
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Influences of the internal residual on combustion instabilities in the misfire and partial burn regimes of a dilute spark-ignition engine
… or exhaust gas recirculation (EGR) causes combustion to become more strained and cycle-to-cycle variations increase. At high levels of dilution incomplete combustion events (i.e. misfires and partial burns) start to occur, which cause combustion instabilities and eventually a dilute limit …
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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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An Experimental Investigation of Self-Excited Combustion Dynamics in a Single Element Lean Direct Injection (LDI) Combustor
<p>The management of combustion dynamics in gas turbine combustors has become more challenging as strict NOx/CO emission standards have led to engine operation in a narrow, lean regime. While premixed or partially premixed combustor configurations such as the Lean Premixed Pre-vaporized (LPP), Rich …
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Numerical Simulation of UVA Ramjet/Scramjet Hypersonic Engine with Hydrogen-Air Combustion Using Wind-US
… however, this case shows large numerical and combustion instabilities.</p>
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Inverse problems in thermoacoustics
… helpless in this subject is that problems of combustion instabilities involve physical and chemical matters that are still not well understood. Moreover, they exist in practical circumstances which are not readily approximated by models suitable to formulation within CFD. Hence, the methods …
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An Original Method for Computing Complex Non-Premixed Flows in Chemical Equilibrium
… In this way, overall performance, and combustion instabilities, can be more accurately predicted. Transport phenomena due to molecular motion such as diffusion of the elemental masses, viscosity and conductivity are also considered, and their properties are modeled with the …
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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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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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Dynamic stability, blowoff, and flame characteristics of oxy-fuel combustion
Oxy-fuel combustion is a promising technology to implement carbon capture and sequestration for energy conversion to electricity in power plants that burn fossil fuels. In oxy-fuel combustion, air separation is used to burn fuel in oxygen to easily obtain a pure stream of carbon dioxide from the …
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Application of Joint Time-Frequency Methods and Artificial Neural Networks for Monitoring Co-Firing Burners
… need to efficiently burn the fuel, ensure stable combustion and result in the lowest emissions. However, recent requirements to reduce CO2 emissions from coal-red boiler plant as part of the drive to<br/>reduce the carbon footprint of energy suppliers has focussed on the co-ring of biomass, …
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Physical aspects and modelling of turbulent MILD combustion
Moderate or Intense Low-oxygen Dilution (MILD) combustion is one of combustion technologies which can improve efficiency and reduce emissions simultaneously. This combustion type is characterised by the highly preheated reactant temperature and the relatively small temperature rise during …
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Behaviour of accelerating entropy spots
Combustion noise has become a major research interest within the aerospace community. Stricter pollutant emission regulations have forced the introduction of lean premixed pre-vaporised combustors, which produce less NOx but burn more unsteadily, generating more noise and creating the potential for …
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The development and implementation of a hybrid rocket motor thrust stand to investigate the relationship between combustion chamber pressure and graphite rocket nozzle erosion in hybrid rocket motors
… to insulate the motor from the heat produced by combustion. Over time these inserts will erode due to oxidation at the surface wherein oxidizing species found in the combustion products react with the carbon to form carbon monoxide. It has been shown that the largest contributors/oxidants to …
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Reactive flow visualization through high-speed optical laser diagnostics
Turbulent combustion is a complex phenomenon that involves the interaction between fluid mechanics and chemical kinetics. Turbulence plays an important role in combustion because it ensures a thorough mixing between the oxidizer and fuel at a molecular level. Improper mixing can lead to incomplete …
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