Flamelet Modelling of Stabilization in Turbulent Non-premixed Combustion PDF Download
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Author: Jorge Ferreira
Publisher:
ISBN:
Category :
Languages : en
Pages : 176
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Author: Jorge Ferreira
Publisher:
ISBN:
Category :
Languages : en
Pages : 176
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Author: Norbert Peters
Publisher: Cambridge University Press
ISBN: 1139428063
Category : Science
Languages : en
Pages : 322
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Book Description
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: S. K. Sadasivuni
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
A large eddy simulation (LES) model has been developed and validated for turbulent non-premixed and partially premixed combustion systems. LES based combustion modelling strategy has the ability to capture the detailed structure of turbulent flames and account for the effects of radiation heat loss. Effects of radiation heat loss ismodelled by employing an enthalpy-defect based non-adiabatic flamelet model (NAFM) in conjunction with a steady non-adiabatic flamelet approach. The steady laminar flamelet model (SLFM) is used with multiple flamelet solutions through thedevelopment of pre-integrated look up tables. The performance of the non-adiabatic model is assessed against experimental measurements of turbulent CH4/H2 bluff-body stabilized and swirl stabilized jet flames carried out by the University of Sydney combustion group. Significant enhancements in the predictions of mean thermal structure have been observed with both bluff body and swirl stabilized flames by the consideration of radiation heat loss through the non-adiabatic flamelet model. In particular, mass fractions of product species like CO2 and H2O have been improved with the consideration of radiation heat loss. From the Sydney University data the HM3e flame was also investigated withSLFM using multiple flamelet strategy and reasonably fair amount of success has been achieved. In this work, unsteady flamelet/progress variable (UFPV) approach based combustion model which has the potential to describe both non-premixed and partially premixed combustion, has been developed and incorporated in an in-house LES code. The probability density function (PDF) for reaction progress variable and scalardissipation rate is assumed to follow a delta distribution while mixture fraction takes the shape of a beta PDF. The performance of the developed model in predicting the thermal structure of a partially premixed lifted turbulent jet flame in vitiated co-flow has been evaluated. The UFPV model has been found to successfully predict the flame lift-off, in contrast SLFM results in a false attached flame. The mean lift-off height is however over-predicted by UFPV-? function model by ~20% for methane based flame and under-predicted by ~50% for hydrogen based flame. The form of thePDF for the reaction progress variable and inclusion of a scalar dissipation rate thusseems to have a strong influence on the predictions of gross characteristics of the flame. Inclusion of scalar dissipation rate in the calculations appears to be successful in predicting the flame extinction and re-ignition phenomena. The beta PDFdistribution for the reaction progress variable would be a true prospect for extending the current simulation to predict the flame characteristics to a higher degree.
Author: Nedunchezhian Swaminathan
Publisher: Cambridge University Press
ISBN: 1139498584
Category : Technology & Engineering
Languages : en
Pages : 447
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Book Description
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.
Author: S. K. Liew
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Sastri Purushottama Nandula
Publisher:
ISBN:
Category : Flame
Languages : en
Pages : 364
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Author: Satyanarayana M. Ravikanti Veera Venkata
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Alessandro Coclite
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: National Aeronautics and Space Adm Nasa
Publisher: Independently Published
ISBN: 9781731360588
Category : Science
Languages : en
Pages : 160
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Book Description
The current Final Report contains results of the study which was performed in Scientific Research Center 'ECOLEN' (Moscow, Russia). The study concerns the development and verification of non-expensive approach for modeling of supersonic turbulent diffusion flames based on flamelet consideration of the chemistry/turbulence interaction (FL approach). Research work included: development of the approach and CFD tests of the flamelet model for supersonic jet flames; development of the simplified procedure for solution of the flamelet equations based on partial equilibrium chemistry assumption; study of the flame ignition/extinction predictions provided by flamelet model. The performed investigation demonstrated that FL approach allowed to describe satisfactory main features of supersonic H 2/air jet flames. Model demonstrated also high capabilities for reduction of the computational expenses in CFD modeling of the supersonic flames taking into account detailed oxidation chemistry. However, some disadvantages and restrictions of the existing version of approach were found in this study. They were: (1) inaccuracy in predictions of the passive scalar statistics by our turbulence model for one of the considered test cases; and (2) applicability of the available version of the flamelet model to flames without large ignition delay distance only. Based on the results of the performed investigation, we formulated and submitted to the National Aeronautics and Space Administration our Project Proposal for the next step research directed toward further improvement of the FL approach. Secundov, A. and Bezgin, L. and Buriko, Yu. and Guskov, O. and Kopchenov, V. and Laskin, I. and Lomkov, K. and Tshepin, S. and Volkov, D. and Zaitsev, S. TURBULENT COMBUSTION; TURBULENT DIFFUSION; DIFFUSION FLAMES; SUPERSONIC JET FLOW; COMPUTATIONAL FLUID DYNAMICS; TURBULENCE MODELS; CHEMICAL REACTIONS; IGNITION; EXTINCTION; GAS MIXTURES; AIR JETS; OXIDATION; DIFFERENTIAL EQUATIONS; MATHEMATICAL MODEL...
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.
