A New Model for Nonequilibrium Mixing :bchemistry Coupling in Nonpremixed and Partially Premixed Turbulent Combustion PDF Download

Author: Eric Scott Bish
Publisher:
ISBN:
Category :
Languages : en
Pages : 368

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Author: Andrew Pollard
Publisher: Springer Science & Business Media
ISBN: 9401719985
Category : Science
Languages : en
Pages : 454

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The goals of the Symposium were to draw together researchers in turbulence and combustion so as to highlight advances and challenge the boundaries to our understanding of turbulent mixing and combus tion from both experimental and simulation perspectives; to facilitate cross-fertilization between leaders in these two fields. These goals were noted to be important given that turbulence itself is viewed as the last great problem in classical physics and the addition of chemical reaction amplifies the difficulties enormously. The papers that have been included here reflect the richness of our subject. Turbulence is rich and complex in its own right. And, its inner structure, hidden in the morass of scales, large and small, can dominate transport. Earlier IUTAM Symposia have considered this field, Eddy Structure Identification in Free Turbulent Flows, Bonnet and Glauser (eds) 1992 and Simulation and Identification of Organized Structures in Flows, Sorensen, Hopfinger and Aubry (eds) 1997. The combustion community is well served by its specialized events, most notable is the bi annual International Combustion Symposium, held under the auspices of the Combustion Institute. Mixing is often considered somewhere in between these two. This broad landscape was addressed in this Sym posium in a somewhat temporal linear fashion of increasing complexity. The lectures considered the many challenges posed by adding one ele ment to the base formed by others: turbulence and turbulent mixing in the absence of combustion through to turbulent mixing dominated by chemistry and combustion.

Author: N. Swaminathan
Publisher: Cambridge University Press
ISBN: 1108572758
Category : Technology & Engineering
Languages : en
Pages :

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Explore a thorough and up to date overview of the current knowledge, developments and outstanding challenges in turbulent combustion and application. The balance among various renewable and combustion technologies are surveyed, and numerical and experimental tools are discussed along with recent advances. Covers combustion of gaseous, liquid and solid fuels and subsonic and supersonic flows. This detailed insight into the turbulence-combustion coupling with turbulence and other physical aspects, shared by a number of the world leading experts in the field, makes this an excellent reference for graduate students, researchers and practitioners in the field.

Author: Michael Joseph Kuron
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages :

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Accurate turbulent combustion models are key to establishing a predictive capability for combustion simulations at the device level. The transported probability density function (TPDF) methods provide an elegant solution to the challenge of closing the mean chemical source term in turbulent combustion modelling as it appears in closed form in the TPDF equations and thus the turbulence-chemistry interaction can be solved for without aggressive assumptions. This is crucial for predicting low temperature combustion, turbulent flames with the presence of local limit phenomena, and pollutant emissions. Despite some reported success in the literature, challenges remain when applying the TPDF method to turbulent premixed flames as the molecular mixing or micro-mixing term is unclosed, the modeling of which is considered to be a primary challenge. The objective of this dissertation is to evaluate the application of existing mixing models to turbulent premixed flames and to create high-fidelity scalar dissipation rate models to predict turbulent premixed combustion. In this dissertation, direct numerical simulation (DNS) data is utilized at each stage to obtain statistical information on the scalar dissipation rate and mixing timescales for turbulent premixed flames. In the first step, DNS of a temporally evolving premixed flame is used as a numerical test bed to evaluate commonly used mixing models in the context of turbulent premixed flames. This study demonstrates that the Euclidean Minimum Spanning Tree (EMST) model is capable of predicting the behavior of a turbulent premixed flame assuming that an accurate model for the scalar mixing rate, and thus the scalar dissipation rate, can be provided. In the next stage of the dissertation, chemical explosive mode analysis (CEMA) and DNS data with realistic chemistry are used to identify physiochemical processes that govern the conditional scalar dissipation rate behavior in a turbulent premixed flame and evaluate mixing timescales. A local Damköhler number is defined based on the CEMA results and four flame zones are identified. It is found that large fluctuations in the instantaneous scalar dissipation rate occur in the explosive zone, where the local Damköhler number is much larger than unity. Two mechanisms are identified to account for the large degree of scatter in the explosive zone: flame-flame interactions and flame-assisted ignition. A model for the Favre-averaged scalar dissipation rate is subsequently developed based on the insight gleaned from the DNS analysis. The new hybrid mixing rate model is developed to account for the scalar mixing rate behavior in both the turbulent mixing limit and the flamelet limit. The new hybrid timescale model is notable for its treatment of the flamelet mixing limit, an area where existing timescale models do not properly recover the correct mixing behavior. Comparisons to the DNS are performed with both a priori and a postereori comparisons, with the new hybrid model performing exceptionally well. Finally, in the last stage of the dissertation, a transport equation for the conditional scalar dissipation rate of a reactive scalar is derived and an order of magnitude analysis is performed to evaluate the importance of each term in the governing equation. The order of magnitude analysis is verified with the DNS data of turbulent premixed flames and an equation of the leading order terms is identified. Models for the unclosed terms in the leading order equation are developed and evaluated with DNS data, and a modelled equation for the conditional scalar dissipation rate is proposed. The modelled equation is then compared to the DNS data, and excellent agreement between the new model and the DNS is observed.

Author: Andrei Lipatnikov
Publisher: CRC Press
ISBN: 1466510250
Category : Science
Languages : en
Pages : 548

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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

Author: Alessandro Coclite
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 9

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The aim of the project was to validate various implementations of the flamelet approach to turbulent combustion modeling, in particular in the context of large eddy simulations of turbulent flames. A hybrid mathematical-numerical-asymptotic approach has been used by Bourlioux and her students, in collaboration with Majda, to systematically exploit Majda and co-workers theoretical results in an applied computational framework. The idealized models utilized in the project were amenable to rigorous asymptotic predictions regarding the effective behavior of turbulent flames at large scales in terms of their effective burning rate. New numerical tools were designed to carry on the asymptotic procedures for relevant test-cases. A strong emphasis was placed on providing the physical intuition behind the various turbulent regimes identified by the theory. The asymptotic predictions were compared with ad-hoc modeling procedures to identify their pros and cons. Additionally, direct numerical simulations were carried on for the idealized test-cases to provide practitioners with some intuition regarding the relationship between the theoretical asymptotic limit results and finite parameters realizations.

Author: Alessandro Parente
Publisher: Frontiers Media SA
ISBN: 2889717003
Category : Technology & Engineering
Languages : en
Pages : 160

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Author: Hiroshi Tsuji
Publisher: CRC Press
ISBN: 1420041037
Category : Nature
Languages : en
Pages : 425

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Maximize efficiency and minimize pollution: the breakthrough technology of high temperature air combustion (HiTAC) holds the potential to overcome the limitations of conventional combustion and allow engineers to finally meet this long-standing imperative. Research has shown that HiTAC technology can provide simultaneous reduction of CO2 and nitric

Author: Abdallah Khellaf
Publisher: Springer Nature
ISBN: 9811565953
Category : Technology & Engineering
Languages : en
Pages : 517

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This book examines a broad range of advances in hydrogen energy and alternative fuel developments and their role in the energy transition. The respective contributions were presented at the International Symposium on Sustainable Hydrogen, held in Algiers, Algeria on November 27-28, 2019. The transition from non-renewable polluting energy to sustainable green energy requires not only new energy sources but also new storage techniques and smart energy management. This situation has sparked renewed interest in hydrogen and alternative fuels, as they could help meet these needs. Indeed, hydrogen can not only be used as a clean energy vector or as an alternative fuel, but also as a storage medium or as an intermediary that enables improved energy management. This text offers a valuable reference guide for those working in the professional energy sector, as well as for students and instructors in academia who want to learn about the state of the art and future directions in the fields of hydrogen energy, alternative fuels and sustainable energy development.