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Showing 1 to 20 of 26 for “"lean premixed combustion"”.
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Active Stabilization of Thermoacoustic Oscillation
Combustion processes serve as important sources of energy for both power generation and for transport, ranging from large scale power stations to micro turbines and aeroplane engines. Lean premixed combustion offers a potential to reduce the emission levels, but suffers from instability problems …
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Effects of curvature and strain on a lean premixed methane-hydrogen-air flame
… elemental flame is a subgrid model for turbulent combustion, parameterized by time-varying strain rate and curvature. This thesis develops the unsteady one-dimensional governing equations for the elemental flame incorporating detailed chemical kinetics and transport and a robust and efficient …
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Facility and Methodologies for Evaluation of Hydrogen-Air Mixer Performance
… all pose various threats to the environment. Lean premixed combustion of hydrogen provides a potential solution to these concerns. A key component of successful lean hydrogen combustion is the fuel-air mixer. A facility and methodology for the evaluation of such a hydrogen-air mixer is …
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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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Numerical Analysis of Flow and Heat Transfer through a Lean Premixed Swirl Stabilized Combustor Nozzle
… driven thermal NOX also needs to be addressed. Lean premixed combustion has been found as one of the solutions to these objectives. However, since less amount of air is available for backside cooling of liner walls, it becomes very important to characterize the convective heat transfer that …
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Computations of Turbulent Premixed Flames Using Conditional Moment Closure
Lean premixed combustion is at present one of the most promising methods to reduce emissions and to maintain high efficiency in combustion systems. As the emission legislation becomes more stringent, modelling of turbulent premixed combustion has become an important tool for designing efficient and …
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Determination of Flame Dynamics for Unsteady Combustion Systems using Tunable Diode Laser Absorption Spectroscopy
Lean, premixed combustion has enjoyed increased application due to the need to reduce pollutant emissions. Unfortunately, operating the flame at lean conditions increases susceptibility to thermoacoustic (TA) instability. Self-excited TA instabilities are a result of the coupling of the unsteady …
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Feedback control of oscillations in combustion and cavity flows
This thesis considers the control of combustion oscillations, motivated by the susceptibility of lean premixed combustion to such oscillations, and the long and expensive development and commissioning times that this is giving rise to. The controller used is both closed-loop, employing an actuator …
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An Investigation of Lean Premixed Hydrogen Combustion in a Gas Turbine Engine
… about the carbon emissions associated with the combustion of conventional hydrocarbon fuels, hydrogen is gaining more attention as a clean alternative. The combustion of hydrogen in air produces no carbon emissions. However, hydrogen-air combustion does have the potential to produce oxides of …
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Combustion Instability Mechanism of a Reacting Jet in Cross Flow at Gas Turbine Operating Conditions
Modern 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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Modelling of turbulent stratified flames
Due to concerns about pollutant emission combustion systems are increasingly being designed to operate in a lean premixed mode. However, the reduction in emissions offered by lean premixed combustion can be offset by its susceptibility to instabilities and ignition and extinction problems. These …
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Experimental investigation of nitrogen oxide production in premixed reacting jets in a vitiated crossflow
… It is motivated by interest in axial staging of combustion as an approach to reduce undesirable NOx emissions from gas turbine combustors operating at high flame temperatures (>1900K). In lean-premixed combustion, NOx levels are exponential functions of temperature and linear functions of …
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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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Damping Parameter Study of a Perforated Plate with Bias Flow
… the main impediments to successful operation of combustion systems in industrial and aerospace applications including gas turbines, ramjets, rocket motors, afterburners (augmenters) and even large heaters/boilers is the dynamic instability also known as thermo-acoustic instability. Concerns with …
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Scalar dissipation rate based flamelet modelling of turbulent premixed flames
Lean premixed combustion has potential for reducing emissions from combustion devices without compromising fuel efficiency, but it is prone to instabilities which presents design difficulties. From emissions point of view reliable predictions of species formation rates in the flame zone are …
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The Role of Swirl in the Flow Structure and Response of Premixed Flames
… challenge with no single solution. Combustion needs to be optimised and lean premixed combustion is an attractive approach to face this challenge. Unfortunately, lean premixed flames are often unstable as they may operate close to the flame blow off limit. Therefore, a suitable …
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Design of a viable homogeneous-charge compression-ignition (HCCI) engine : a computational study with detailed chemical kinetics
… from automotive sources. HCCI engines use lean-premixed combustion to achieve good fuel economy and low emissions of nitrogen-oxides and particulate matter. However, experimentally these engines have demonstrated a viable operating range that is too narrow for vehicular applications. …
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Fundamental studies in hydrogen-rich combustion : instability mechanisms and dynamic mode selection
… fuel 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 …
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A Lean-Premixed Hydrogen Injector with Vane Driven Swirl for Application in Gas Turbines
… has a wide range of flammability limits, fuel lean combustion can take place at lower equivalence ratios than those with typical hydrocarbon fuels. Numerous efforts have been made to develop gas turbine fuel injectors that premix methane/natural gas and air in fuel lean proportions prior to the …
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Turbulent partially premixed combustion: DNS analysis and RANS simulation
… pollutant emission has motivated the search for cleaner and more efficient combustion devices, which remain the primary means of power generation and propulsion for all kinds of transport. Fuel-lean premixed combustion technology has been identified to be a promising approach, despite many …
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