Flame-vortex Dynamics in a Model Ramjet Combustor PDF Download
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Author: Chandler W. Crimmins
Publisher:
ISBN:
Category :
Languages : en
Pages : 27
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Book Description
Previous research into the flame-vortex dynamics of bluff-body stabilized flames has helped to verify the characteristic flame-flow field and identify the effects of turbulence and pressure gradient tailoring. Such work has indicated that increases in a favorable pressure gradient will both increase the material acceleration of the flow and increase the total magnitude of vorticity seen in domain. This result is specifically tied to the increased baroclinicity of the flow. In addition, it has been shown that as the turbulence level of an incoming flow is increased, the vortex stretching transport term will come to dominate the flow dynamics. This results in the flow beginning to resemble the characteristics of a nonreacting case. In more specific terms, Bénard von Kármán vortex shedding, which is usually suppressed due to combustive heat release, will begin to reappear in the domain. To further cement and verify these conclusions, six experimental test cases were carried out to study the flame-vortex dynamics of a stoichiometric propane-air flame stabilized on a ballistic-type bluff body. Particle imaging velocimetry data was recorded using an optically accessible combustion facility. Velocity vector fields were derived using PIVLab software and further analyzed using both Eulerian and Lagrangian analysis methods. The results and analysis have been plotted and included within the following document.
Author: Chandler W. Crimmins
Publisher:
ISBN:
Category :
Languages : en
Pages : 27
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Book Description
Previous research into the flame-vortex dynamics of bluff-body stabilized flames has helped to verify the characteristic flame-flow field and identify the effects of turbulence and pressure gradient tailoring. Such work has indicated that increases in a favorable pressure gradient will both increase the material acceleration of the flow and increase the total magnitude of vorticity seen in domain. This result is specifically tied to the increased baroclinicity of the flow. In addition, it has been shown that as the turbulence level of an incoming flow is increased, the vortex stretching transport term will come to dominate the flow dynamics. This results in the flow beginning to resemble the characteristics of a nonreacting case. In more specific terms, Bénard von Kármán vortex shedding, which is usually suppressed due to combustive heat release, will begin to reappear in the domain. To further cement and verify these conclusions, six experimental test cases were carried out to study the flame-vortex dynamics of a stoichiometric propane-air flame stabilized on a ballistic-type bluff body. Particle imaging velocimetry data was recorded using an optically accessible combustion facility. Velocity vector fields were derived using PIVLab software and further analyzed using both Eulerian and Lagrangian analysis methods. The results and analysis have been plotted and included within the following document.
Author: Z. Shu
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Cal Rising
Publisher:
ISBN:
Category :
Languages : en
Pages : 44
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Book Description
Modern propulsion systems primarily operate under highly turbulent conditions in order to promote greater efficiency through an increase in mixing. The focus of this thesis is to identify the turbulent flame-vortex interaction to provide insights into the turbulent combustion process. This work is accomplished through the use of turbulent ramjet-style combustor which is stabilized through use of a bluff-body. The facility is equipped with a custom turbulence generator to modulate the incoming turbulence levels to allow flames across various regimes to be analyzed. High-speed particle image velocimetry (PIV) and CH* chemiluminescence diagnostics are implemented to resolve the flow field and flame position. The flame-vortex interaction can be described by the vorticity transport which has four terms; vortex stretching, baroclinic torque, dilatation, and viscous diffusion. The vorticity mechanisms are calculated through the implementation of a Lagrangian tracking scheme, which allows for the individual mechanisms to be decomposed along the path of individual tracks. The mechanisms are compared across different turbulence levels to determine the effects of turbulence on the vorticity mechanisms. The mechanisms are calculated along the flame front as well to determine the individual effects of the vorticity mechanisms on the evolving structure of the turbulent premixed flame. The flame front curvature is also compared across the various turbulence conditions. The results confirm that as the flame-front experiences increased turbulence levels the combustion induced mechanisms of baroclinic torque and dilation decrease, while vortex stretching increases. This is a result of the turbulent energy exchange becoming the controlling factor within the flow-field. In addition, increased flame curvature is experience by the flame front due to increased local baroclinicity and turbulent energy exchange.
Author: Luc Bauwens
Publisher:
ISBN:
Category :
Languages : en
Pages : 226
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Book Description
Author: Gautam Choubey
Publisher: Butterworth-Heinemann
ISBN: 0323995667
Category : Technology & Engineering
Languages : en
Pages : 198
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Book Description
Scramjet Combustion explores the development of a high-speed scramjet engine operating in the supersonic/hypersonic range for various air and space transport applications. The book explains the basic structure, components, working cycle, and the relevant governing equations in a clear manner that speaks to both advanced and more novice audiences. Particular attention is paid to efficient air–fuel combustion, looking at both the underlying fundamentals of combustion as well strategies for obtaining optimum combustion efficiency. Methods for reaching the chemically correct air–fuel ratio, subsequent flame, and combustion stabilization as air enters at supersonic speed are also outlined. Further, it includes the continuous on-going efforts, innovations, and advances with respect to the design modification of scramjet combustors, as well as different strategies of fuel injections for obtaining augmented performance while highlighting the current and future challenges. - Outlines the fundamentals of scramjet engines including their basic structure and components, working cycle, governing equations, and combustion fundamentals affecting the combustion and mixing processes - Presents new design modifications of scramjet combustors and different fuel injection strategies including combined fuel injection approaches - Discusses core topics such as chemical kinetics in supersonic flow, fuel–air mixing methods, strategies for combating combustion difficulties, and subsequent flame and combustion stabilization that can be applied to scramjets - Describes the pedagogy for computational approaches in simulating supersonic flows
Author: T. R. Meyer
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Mostafa Barzegar Gerdroodbary
Publisher: Butterworth-Heinemann
ISBN: 0128211407
Category : Technology & Engineering
Languages : en
Pages : 230
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Book Description
Scramjet engines are a type of jet engine and rely on the combustion of fuel and an oxidizer to produce thrust. While scramjets are conceptually simple, actual implementation is limited by extreme technical challenges. Hypersonic flight within the atmosphere generates immense drag, and temperatures found on the aircraft and within the engine can be much greater than that of the surrounding air. Maintaining combustion in the supersonic flow presents additional challenges, as the fuel must be injected, mixed, ignited, and burned within milliseconds. Fuel mixing, along with the configuration and positioning of the injectors and the boundary conditions, play a key role in combustion efficiency. Scramjets: Fuel Mixing and Injection Systems discusses how fuel mixing efficiency and the advantage of injection systems can enhance the performance of the scramjets. The book begins with the introduction of the supersonic combustion chamber and explains the main parameters on the mixing rate. The configuration of scramjets is then introduced with special emphasis on the main effective parameters on the mixing of fuel inside the scramjets. In addition, basic concepts and principles on the mixing rate and fuel distribution within scramjets are presented. Main effective parameters such as range of fuel concentration for the efficient combustion, pressure of fuel jet and various arrangement of jet injections are also explained. This book is for aeronautical and mechanical engineers as well as those working in supersonic combustion who need to know the effects of compressibility on combustion, of shocks on mixing and on chemical reactions, and vorticity on the flame anchoring. - Explains the main applicable approaches for enhancement of supersonic combustion engines and the new techniques of fuel injection - Shows how the interaction of main air stream with fuel injections can develop the mixing inside the scramjets - Presents results of numerical simulations and how they can be used for the development of the combustion engines
Author: Tarek Echekki
Publisher: Springer Science & Business Media
ISBN: 9400704127
Category : Technology & Engineering
Languages : en
Pages : 496
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Book Description
Turbulent combustion sits at the interface of two important nonlinear, multiscale phenomena: chemistry and turbulence. Its study is extremely timely in view of the need to develop new combustion technologies in order to address challenges associated with climate change, energy source uncertainty, and air pollution. Despite the fact that modeling of turbulent combustion is a subject that has been researched for a number of years, its complexity implies that key issues are still eluding, and a theoretical description that is accurate enough to make turbulent combustion models rigorous and quantitative for industrial use is still lacking. In this book, prominent experts review most of the available approaches in modeling turbulent combustion, with particular focus on the exploding increase in computational resources that has allowed the simulation of increasingly detailed phenomena. The relevant algorithms are presented, the theoretical methods are explained, and various application examples are given. The book is intended for a relatively broad audience, including seasoned researchers and graduate students in engineering, applied mathematics and computational science, engine designers and computational fluid dynamics (CFD) practitioners, scientists at funding agencies, and anyone wishing to understand the state-of-the-art and the future directions of this scientifically challenging and practically important field.
Author: Marissa Kelley Geikie
Publisher:
ISBN:
Category :
Languages : en
Pages : 124
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Book Description
Furthermore, a change in the relative balance of the combustion-induced vorticity mechanisms and turbulence energy transport occurs as a result of increasing the turbulence and pressure gradient.
Author: Paul Palies
Publisher: Academic Press
ISBN: 0128199970
Category : Technology & Engineering
Languages : en
Pages : 402
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Book Description
Stabilization and Dynamic of Premixed Swirling Flames: Prevaporized, Stratified, Partially, and Fully Premixed Regimes focuses on swirling flames in various premixed modes (stratified, partially, fully, prevaporized) for the combustor, and development and design of current and future swirl-stabilized combustion systems. This includes predicting capabilities, modeling of turbulent combustion, liquid fuel modeling, and a complete overview of stabilization of these flames in aeroengines. The book also discusses the effects of the operating envelope on upstream fresh gases and the subsequent impact of flame speed, combustion, and mixing, the theoretical framework for flame stabilization, and fully lean premixed injector design. Specific attention is paid to ground gas turbine applications, and a comprehensive review of stabilization mechanisms for premixed, partially-premixed, and stratified premixed flames. The last chapter covers the design of a fully premixed injector for future jet engine applications. - Features a complete view of the challenges at the intersection of swirling flame combustors, their requirements, and the physics of fluids at work - Addresses the challenges of turbulent combustion modeling with numerical simulations - Includes the presentation of the very latest numerical results and analyses of flashback, lean blowout, and combustion instabilities - Covers the design of a fully premixed injector for future jet engine applications
