Download or read book Modeling of Premixed Turbulent Combustion for Afterburners and Low Emission Combusters written by and published by . This book was released on 1998 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulent Combustion Modeling written by Tarek Echekki and published by Springer Science & Business Media. This book was released on 2010-12-25 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Turbulent Premixed Flames written by Nedunchezhian Swaminathan and published by Cambridge University Press. This book was released on 2011-04-25 with total page 447 pages. Available in PDF, EPUB and Kindle. Book excerpt: A work on turbulent premixed combustion is important because of increased concern about the environmental impact of combustion and the search for new combustion concepts and technologies. An improved understanding of lean fuel turbulent premixed flames must play a central role in the fundamental science of these new concepts. Lean premixed flames have the potential to offer ultra-low emission levels, but they are notoriously susceptible to combustion oscillations. Thus, sophisticated control measures are inevitably required. The editors' intent is to set out the modeling aspects in the field of turbulent premixed combustion. Good progress has been made on this topic, and this cohesive volume contains contributions from international experts on various subtopics of the lean premixed flame problem.

Download or read book Fundamentals of Premixed Turbulent Combustion written by Andrei Lipatnikov and published by CRC Press. This book was released on 2012-10-24 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lean burning of premixed gases is considered to be a promising combustion technology for future clean and highly efficient gas turbine combustors. Yet researchers face several challenges in dealing with premixed turbulent combustion, from its nonlinear multiscale nature and the impact of local phenomena to the multitude of competing models. Filling

Download or read book Modeling and Simulation of Turbulent Combustion written by Santanu De and published by Springer. This book was released on 2017-12-12 with total page 663 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive review of state-of-the-art models for turbulent combustion, with special emphasis on the theory, development and applications of combustion models in practical combustion systems. It simplifies the complex multi-scale and nonlinear interaction between chemistry and turbulence to allow a broader audience to understand the modeling and numerical simulations of turbulent combustion, which remains at the forefront of research due to its industrial relevance. Further, the book provides a holistic view by covering a diverse range of basic and advanced topics—from the fundamentals of turbulence–chemistry interactions, role of high-performance computing in combustion simulations, and optimization and reduction techniques for chemical kinetics, to state-of-the-art modeling strategies for turbulent premixed and nonpremixed combustion and their applications in engineering contexts.

Download or read book Large Eddy Simulations of Premixed Turbulent Flame Dynamics written by Gaurav Kewlani and published by . This book was released on 2014 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: High efficiency, low emissions and stable operation over a wide range of conditions are some of the key requirements of modem-day combustors. To achieve these objectives, lean premixed flames are generally 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 premixed flames, can couple with the acoustics of the combustion system. This acoustic coupling creates a feedback loop with the heat release that can lead to severe thermoacoustic instabilities that can damage the combustor. Understanding these dynamics, predicting their onset and proposing passive and active control strategies are critical to large-scale implementation. For the numerical study of such systems, large eddy simulation (LES) techniques with appropriate combustion models and reaction mechanisms are highly appropriate. These approaches balance the computational complexity and predictive accuracy. This work, therefore, aims to explore the applicability of these methods to the study of premixed wake stabilized flames. Specifically, finite rate chemistry LES models that can effectively capture the interaction between different turbulent scales and the combustion fronts have been implemented, and applied for the analysis of premixed turbulent flame dynamics in laboratory-scale combustor configurations. Firstly, the artificial flame thickening approach, along with an appropriate reduced chemistry mechanism, is utilized for modeling turbulence-combustion interactions at small scales. A novel dynamic formulation is proposed that explicitly incorporates the influence of strain on flame wrinkling by solving a transport equation for the latter rather than using local-equilibrium-based algebraic models. Additionally, a multiple-step combustion chemistry mechanism is used for the simulations. Secondly, the presumed-PDF approach, coupled with the flamelet generated manifold (FGM) technique, is also implemented for modeling turbulence-combustion interactions. The proposed formulation explicitly incorporates the influence of strain via the scalar dissipation rate and can result in more accurate predictions especially for highly unsteady flame configurations. Specifically, the dissipation rate is incorporated as an additional coordinate to presume the PDF and strained flamelets are utilized to generate the chemistry databases. These LES solvers have been developed and applied for the analysis of reacting flows in several combustor configurations, i.e. triangular bluff body in a rectangular channel, backward facing step configuration, axi-symmetric bluff body in cylindrical chamber, and cylindrical sudden expansion with swirl, and their performance has been be validated against experimental observations. Subsequently, the impact of the equivalence ratio variation on flame-flow dynamics is studied for the swirl configuration using the experimental PIV data as well as the numerical LES code, following which dynamic mode decomposition of the flow field is performed. It is observed that increasing the equivalence ratio can appreciably influence the dominant flow features in the wake region, including the size and shape of the recirculation zone(s), as well as the flame dynamics. Specifically, varying the heat loading results in altering the dominant flame stabilization mechanism, thereby causing transitions across distinct- flame configurations, while also modifying the inner recirculation zone topology significantly. Additionally, the LES framework has also been applied to gain an insight into the combustion dynamics phenomena for the backward-facing step configuration. Apart from evaluating the influence of equivalence ratio on the combustion process for stable flames, the flame-flow interactions in acoustically forced scenarios are also analyzed using LES and dynamic mode decomposition (DMD). Specifically, numerical simulations are performed corresponding to a selfexcited combustion instability configuration as observed in the experiments, and it is observed that LES is able to suitably capture the flame dynamics. These insights highlight the effect of heat release variation on flame-flow interactions in wall-confined combustor configurations, which can significantly impact combustion stability in acoustically-coupled systems. The fidelity of the solvers in predicting the system response to variation in heat loading and to acoustic forcing suggests that the LES framework can be suitably applied for the analysis of flame dynamics as well as to understand the fundamental mechanisms responsible for combustion instability. KEY WORDS - large eddy simulation, LES, wake stabilized flame, turbulent premixed combustion, combustion modeling, artificially thickened flame model, triangular bluff body, backward facing step combustor, presumed-PDF model, flamelet generated manifold, axi-symmetric bluff body, cylindrical swirl combustor, particle image velocimetry, dynamic mode decomposition, combustion instability, forced response.

Download or read book Experiments and Numerical Simulations of Diluted Spray Turbulent Combustion written by Bart Merci and published by Springer Science & Business Media. This book was released on 2011-06-20 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reflects the outcome of the 1st International Workshop on Turbulent Spray Combustion held in 2009 in Corsica (France). The focus is on reporting the progress of experimental and numerical techniques in two-phase flows, with emphasis on spray combustion. The motivation for studies in this area is that knowledge of the dominant phenomena and their interactions in such flow systems is essential for the development of predictive models and their use in combustor and gas turbine design. This necessitates the development of accurate experimental methods and numerical modelling techniques. The workshop aimed at providing an opportunity for experts and young researchers to present the state-of-the-art, discuss new developments or techniques and exchange ideas in the areas of experimentations, modelling and simulation of reactive multiphase flows. The first two papers reflect the contents of the invited lectures, given by experts in the field of turbulent spray combustion. The first concerns computational issues, while the second deals with experiments. These lectures initiated very interesting and interactive discussions among the researchers, further pursued in contributed poster presentations. Contributions 3 and 4 focus on some aspects of the impact of the interaction between fuel evaporation and combustion on spray combustion in the context of gas turbines, while the final article deals with the interaction between evaporation and turbulence.

Download or read book Improved Modeling of Finite Rate Turbulent Combustion Processes in Research Combustors written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-25 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this thesis is to further develop and test a stochastic model of turbulent combustion in recirculating flows. There is a requirement to increase the accuracy of multi-dimensional combustion predictions. As turbulence affects reaction rates, this interaction must be more accurately evaluated. In this work a more physically correct way of handling the interaction of turbulence on combustion is further developed and tested. As turbulence involves randomness, stochastic modeling is used. Averaged values such as temperature and species concentration are found by integrating the probability density function (pdf) over the range of the scalar. The model in this work does not assume the pdf type, but solves for the evolution of the pdf using the Monte Carlo solution technique. The model is further developed by including a more robust reaction solver, by using accurate thermodynamics and by more accurate transport elements. The stochastic method is used with Semi-Implicit Method for Pressure-Linked Equations. The SIMPLE method is used to solve for velocity, pressure, turbulent kinetic energy and dissipation. The pdf solver solves for temperature and species concentration. Thus, the method is partially familiar to combustor engineers. The method is compared to benchmark experimental data and baseline calculations. The baseline method was tested on isothermal flows, evaporating sprays and combusting sprays. Pdf and baseline predictions were performed for three diffusion flames and one premixed flame. The pdf method predicted lower combustion rates than the baseline method in agreement with the data, except for the premixed flame. The baseline and stochastic predictions bounded the experimental data for the premixed flame. The use of a continuous mixing model or relax to mean mixing model had little effect on the prediction of average temperature. Two grids were used in a hydrogen diffusion flame simulation. Grid density did not effect the predictions except fo...

Download or read book Stabilization and Dynamic of Premixed Swirling Flames written by Paul Palies and published by Academic Press. This book was released on 2020-07-03 with total page 402 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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

Download or read book Improved Modeling of Finite rate Turbulent Combustion Processes in Research Combustors written by Thomas Julius VanOverbeke and published by . This book was released on 1998 with total page 576 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modeling Turbulent Combustion and CO Emissions in Partially Premixed Conditions Considering Flame Stretch and Heat Loss written by Noah Eugen Klarmann and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Enabling Advanced Modeling and Simulations for Fuel Flexible Combustors written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The overall goal of the present project is to enable advanced modeling and simulations for the design and optimization of fuel-flexible turbine combustors. For this purpose we use a high-fidelity, extensively-tested large-eddy simulation (LES) code and state-of-the-art models for premixed/partially-premixed turbulent combustion developed in the PI's group. In the frame of the present project, these techniques are applied, assessed, and improved for hydrogen enriched premixed and partially premixed gas-turbine combustion. Our innovative approaches include a completely consistent description of flame propagation, a coupled progress variable/level set method to resolve the detailed flame structure, and incorporation of thermal-diffusion (non-unity Lewis number) effects. In addition, we have developed a general flamelet-type transformation holding in the limits of both non-premixed and premixed burning. As a result, a model for partially premixed combustion has been derived. The coupled progress variable/level method and the general flamelet tranformation were validated by LES of a lean-premixed low-swirl burner that has been studied experimentally at Lawrence Berkeley National Laboratory. The model is extended to include the non-unity Lewis number effects, which play a critical role in fuel-flexible combustor with high hydrogen content fuel. More specifically, a two-scalar model for lean hydrogen and hydrogen-enriched combustion is developed and validated against experimental and direct numerical simulation (DNS) data. Results are presented to emphasize the importance of non-unity Lewis number effects in the lean-premixed low-swirl burner of interest in this project. The proposed model gives improved results, which shows that the inclusion of the non-unity Lewis number effects is essential for accurate prediction of the lean-premixed low-swirl flame.

Download or read book Turbulent Combustion Modeling written by Tarek Echekki and published by Springer. This book was released on 2011-04-09 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Experiments and Numerical Simulations of Turbulent Combustion of Diluted Sprays written by Bart Merci and published by Springer Science & Business Media. This book was released on 2014-03-27 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reflects the results of the 2nd and 3rd International Workshops on Turbulent Spray Combustion. The focus is on progress in experiments and numerical simulations for two-phase flows, with emphasis on spray combustion. Knowledge of the dominant phenomena and their interactions allows development of predictive models and their use in combustor and gas turbine design. Experts and young researchers present the state-of-the-art results, report on the latest developments and exchange ideas in the areas of experiments, modelling and simulation of reactive multiphase flows. The first chapter reflects on flame structure, auto-ignition and atomization with reference to well-characterized burners, to be implemented by modellers with relative ease. The second chapter presents an overview of first simulation results on target test cases, developed at the occasion of the 1st International Workshop on Turbulent Spray Combustion. In the third chapter, evaporation rate modelling aspects are covered, while the fourth chapter deals with evaporation effects in the context of flamelet models. In chapter five, LES simulation results are discussed for variable fuel and mass loading. The final chapter discusses PDF modelling of turbulent spray combustion. In short, the contributions in this book are highly valuable for the research community in this field, providing in-depth insight into some of the many aspects of dilute turbulent spray combustion.

Download or read book Modeling Non premixed Turbulent Combustion in Aeronautical Engines Using PFD generator written by F. Ravet and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Studies in Premixed Turbulent Combustion and Carbon Particle Burning written by Ding-Guo Xie and published by . This book was released on 1985 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book PDF Modeling of Turbulent Combustion written by and published by . This book was released on 2006 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: In both space and aircraft applications, the design of combustors in propulsion systems remains a significant technical challenge. Given the cost, difficulty and time consumed in experimental testing, it is well recognized that computer modeling is essential to exploring different design concepts, and to reducing the cost and time of the design cycle. While many phenomena may be involved - sprays, radiation, combustion dynamics, etc. - a central problem is that of modeling turbulent-chemistry interactions in turbulent combustion. The PDF approach to turbulent combustion has the advantages of fully representing the turbulent fluctuations of species and temperature, and of allowing realistic combustion chemistry to be implemented (e.g., of order 50 species). This methodology is also being applied in conjunction with large-eddy simulations, in which case it is referred to as LES/FDF. The overall objective of the proposed work is to advance and extend the PDF and LES/FDF approaches to modeling turbulent combustion in flows of relevance to aerospace propulsion systems. Currently, PDF methods are being applied to flames in vitiated co-flows, both lifted methane non-premixed flames and also attached piloted premixed flames. In future work, the LES/FDF approach will be applied to piloted jet flames and to bluff-body jet flames. This will enable a three-way comparison between experimental data, the LES/FDF calculations, and previous PDF calculations. In all of these calculations, realistic and reliable combustion chemistry is used (e.g., involving of order 20-50 species) so that turbulence-chemistry interactions such as local extinction and re-ignition can be investigated. Collaboration with the University of Pittsburgh continues and has resulted in one of the first LES/PDF calculations of a turbulent flame (Sheikhi et al. 2005).