On Flow of Turbulent Jet Flames PDF Download

Author: Bjørn F. Magnussen
Publisher:
ISBN:
Category : Combustion
Languages : en
Pages : 148

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Author: Ricardo Cabra
Publisher:
ISBN:
Category :
Languages : en
Pages : 530

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Author: Sina Rafati
Publisher:
ISBN:
Category :
Languages : en
Pages : 408

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Book Description
This research aims to investigate the nonlinear dynamics of the non-reacting jets and non-premixed lifted jet flames. The goal is to understand better how the flow system dynamics change over time and identify the path toward unwanted conditions such as flashback, extinction, or blowout to limit combustors' dynamical failure. The existence of these undesirable conditions is bound to the fluid's history, meaning that initiated perturbation may persist in the system for time scales comparable to large-scale flow timescales. Hence, the notion is to utilize jet and jet flames as a study test case to work out how the flow evolves dynamically with the hope of understanding how to limit occurrences of the chaotic unwanted condition. Initially, planar particle image velocimetry has been used for the development of the methodologies. I have used planar data to investigate the nonlinear dynamics of non-reacting turbulent jets, with a low-to-moderate Reynolds number using the single-trajectory framework and ensemble framework. I have used Lyapunov exponents to calculate the spectra of scaling indices of the attractor. Then, I used Lagrangian Coherent Structures (LCSs), which are defined as manifolds that are locally Euclidean and invariant, to study the relationship between Lyapunov exponent changes with flow topological features. These LCSs behave as hypersurfaces with maximally repelling or attracting properties. These various methodologies were used to investigate flame-turbulence interaction in lifted jet flames. The Lagrangian framework is shown to be effective at revealing the kinematics associated with flame-turbulence interaction. The LCSs' time history represents how eddy structures interact with the flame and highlight their role in the dynamics of the lifted jet flames. Finally, I have investigated the flame and turbulence interaction using high-speed luminosity imaging and simultaneous three-dimensional particle image velocimetry. The three-dimensional Lagrangian structures provide us a more detailed flow-flame interaction. It is shown that the flow features associated with attracting LCSs can create a barrier attracting the flame that makes the flame move upstream. In contrast, the presence of repelling LCSs near stationary flames breaks the balance between the gas velocity and flame propagation speed, causing the flame to become non-stationary and move downstream. It was also found that the repelling LCSs induce negative curvature on the flame surface whereas pushing the flame toward the products. However, the attracting LCSs induce positive curvature on the flame surface and draws the flame toward the reactants

Author: Kian Mehravaran
Publisher: LAP Lambert Academic Publishing
ISBN: 9783848428434
Category :
Languages : en
Pages : 140

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In the first part of this work, the impact of gravity on transitional and turbulent jet flames is investigated through Direct and Large Eddy Simulations (LES). It is shown that in the absence of gravity, combustion damps the flow instability; hence reduces "turbulence production" and jet growth. However, in the "finite-gravity" conditions, combustion generated density variations may promote turbulence and enhance both the mixing and combustion through buoyancy effects. In the second part, the LES/FMDF model is extended towards multi-step chemistry with realistic thermodynamic properties, such that the predictions could be compared with laboratory flame measurements. The consistency of the Eulerian and the Lagrangian solutions are discussed, and an efficient algorithm for parallelization of the hybrid code is presented. Comparisons with the Sandia's piloted methane jet flames (flame D and F) are performed and good agreements in the case of the near-equilibrium flame D have been achieved with a flamelet-based chemistry model, as well as with multi-step kinetics.

Author: Norbert Peters
Publisher: Cambridge University Press
ISBN: 1139428063
Category : Science
Languages : en
Pages : 322

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The combustion of fossil fuels remains a key technology for the foreseeable future. It is therefore important that we understand the mechanisms of combustion and, in particular, the role of turbulence within this process. Combustion always takes place within a turbulent flow field for two reasons: turbulence increases the mixing process and enhances combustion, but at the same time combustion releases heat which generates flow instability through buoyancy, thus enhancing the transition to turbulence. The four chapters of this book present a thorough introduction to the field of turbulent combustion. After an overview of modeling approaches, the three remaining chapters consider the three distinct cases of premixed, non-premixed, and partially premixed combustion, respectively. This book will be of value to researchers and students of engineering and applied mathematics by demonstrating the current theories of turbulent combustion within a unified presentation of the field.

Author: J. Nathan Kutz
Publisher: SIAM
ISBN: 1611974496
Category : Science
Languages : en
Pages : 241

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Book Description
Data-driven dynamical systems is a burgeoning field?it connects how measurements of nonlinear dynamical systems and/or complex systems can be used with well-established methods in dynamical systems theory. This is a critically important new direction because the governing equations of many problems under consideration by practitioners in various scientific fields are not typically known. Thus, using data alone to help derive, in an optimal sense, the best dynamical system representation of a given application allows for important new insights. The recently developed dynamic mode decomposition (DMD) is an innovative tool for integrating data with dynamical systems theory. The DMD has deep connections with traditional dynamical systems theory and many recent innovations in compressed sensing and machine learning. Dynamic Mode Decomposition: Data-Driven Modeling of Complex Systems, the first book to address the DMD algorithm, presents a pedagogical and comprehensive approach to all aspects of DMD currently developed or under development; blends theoretical development, example codes, and applications to showcase the theory and its many innovations and uses; highlights the numerous innovations around the DMD algorithm and demonstrates its efficacy using example problems from engineering and the physical and biological sciences; and provides extensive MATLAB code, data for intuitive examples of key methods, and graphical presentations.

Author: Jay A. Hammer
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 280

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Author: Lowell M. Bollinger
Publisher:
ISBN:
Category : Bunsen burner
Languages : en
Pages : 22

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Book Description
For fully developed flow, turbulent as well as laminar, the velocity gradient at the burner wall is a satisfactory variable for correlating the fuel-air ratio required for blow-off of seated flames for fuel-air ratios of less than 15 percent. For turbulent flames, wall velocity serves as a correlating variable in the same fuel-air ratio range.

Author: Prashanth Srinivasa Kothnur
Publisher:
ISBN:
Category :
Languages : en
Pages : 190

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Author: Joseph Hun-wei Lee
Publisher: Springer Science & Business Media
ISBN: 1461504074
Category : Science
Languages : en
Pages : 391

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Book Description
Jets and plumes are shear flows produced by momentum and buoyancy forces. Examples include smokestack emissions, fires and volcano eruptions, deep sea vents, thermals, sewage discharges, thermal effluents from power stations, and ocean dumping of sludge. Knowledge of turbulent mixing by jets and plumes is important for environmental control, impact and risk assessment. Turbulent Jets and Plumes introduces the fundamental concepts and develops a Lagrangian approach to model these shear flows. This theme persists throughout the text, starting from simple cases and building towards the practically important case of a turbulent buoyant jet in a density-stratified crossflow. Basic ideas are illustrated by ample use of flow visualization using the laser-induced fluorescence technique. The text includes many illustrative worked examples, comparisons of model predictions with laboratory and field data, and classroom tested problems. An interactive PC-based virtual-reality modelling software (VISJET) is also provided. Engineering and science students, researchers and practitioners may use the book both as an introduction to the subject and as a reference in hydraulics and environmental fluid mechanics.