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Numerical Study On Thermodiffusive Instabilities In Laminar And Turbulent Hydrogen Flames
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Book Synopsis Numerical Study on Thermodiffusive Instabilities in Laminar and Turbulent Hydrogen Flames by : Lukas Berger
Download or read book Numerical Study on Thermodiffusive Instabilities in Laminar and Turbulent Hydrogen Flames written by Lukas Berger and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Numerical Analysis of Mixture Formation and Combustion in a Hydrogen Direct-Injection Internal Combustion Engine by : Udo Gerke
Download or read book Numerical Analysis of Mixture Formation and Combustion in a Hydrogen Direct-Injection Internal Combustion Engine written by Udo Gerke and published by Cuvillier Verlag. This book was released on 2008-02-05 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present work investigates the mixture formation and combustion process of a direct-injection (DI) hydrogen internal combustion engine by means of three-dimensional numerical simulation. The study specifies details on the validity of turbulence models, combustion models as well as aspects on the definition of hydrogen-air burning velocities with respect to hydrogen IC engine applications. Results of homogeneous, stratified and multi-injection engine operation covering premixed, partially premixed and non-premixed combustion of hydrogen are presented. Results of the numerical simulations are validated using data of experimental analysis from parallel works, employing a one-cylinder research engine and a research engine with optical access. As a fundamental contribution to combustion modelling of hydrogen IC engines, a new correlation for laminar burning velocities of hydrogen-air mixtures at engine-relevant conditions is derived from measurements of premixed outwards propagating flames conducted in a single-cylinder compression machine. Numerical results of the direct-injection mixture formation give a detailed understanding of the interrelation between injection timing and the degree of mixture homogenisation. A favourable agreement between the computed fuel concentration and results of Planar Laser Induced Fluorescence (PLIF) measurements is reported for various injection timings. Different two-equation turbulence models, a Shear Stress Transport (SST) model and a k-ε model based on Renormalisation Group (RNG) theory as well as a Reynolds Stress Model (RSM) are discussed. The impact of the models on the level of turbulent kinetic energy proves to be of major importance. State-of-the-art turbulent combustion models on the basis of turbulent flame speed closure (TFC) and on the basis of a flame surface density approach, the Extended Coherent Flame Model (ECFM), are examined. The models are adapted to hydrogen internal combustion engines and are interfaced to the established three-dimensional flow field solver ANSYS CFX within the framework of the international research project HyICE. Two different approaches are investigated as input for the laminar burning velocities of hydrogen. Firstly, flame speed data are computed with a kinetic mechanism. Secondly, an existing experimentally derived laminar flame speed correlation is extended to rich air/fuel equivalence ratios (λ 1) and is compared to measurements conducted within the present work. In general, the TFC-models show a satisfying agreement for DI operating points compared to experimental data, when mixing computations are conducted with the SST turbulence model. Also, port fuel injection (PFI) operating points demonstrate a good performance with these models, however, the constant model prefactor (multiplier for the closure of turbulent flame speed) has to be defined individually for PFI and DI computations. This effect might be caused by the dissimilar sources of turbulence for the two engine types (PFI and DI) which cannot be adequately predicted by the turbulence models. Combustion computations on the basis of mixture results obtained by the RNG-model generally underrate the level of turbulence intensity for stratified operation points, effecting too weak rates of heat release. The ECFM combustion model shows a satisfying predictability for the PFI case using a constant model prefactor. Computations of DI operating points with this model, however, require a readjustment of the prefactor for each operating point in order to match experimental results. Regarding turbulent combustion, the hydrogen laminar flame speed is recognised to be the crucial quantity for the employed modelling approaches. Since direct-injection hydrogen engines in the stratified case engender a wide range of equivalence ratios, fundamental data for the laminar flame speed has to be provided as a model input within the entire boundaries of ignition limits. A lack of experimental data of laminar flame speed at engine-relevant conditions (high pressure, high temperature) is noticed. In order to perform a detailed study on hydrogen burning velocities, a single-cylinder compression machine is selected to conduct flame speed measurements of hydrogen-air mixtures at ignition temperatures and pressures up to T = 700 K and p = 45 bar, considering air/fuel equivalence ratios between λ = 0.4 and 2.8. Flame front velocities are acquired by means of optical methods using OH-chemiluminescence and thermodynamic, multi-zone evaluation of pressure traces. In comparison to data of laminar flame speed derived from reaction mechanisms and flame speed correlations found in literature, the experimental results show increased burning velocities due to flame front wrinkling caused by hydrodynamic and thermo-diffusive instabilities. a href="http://ec.europa.eu/research/transport/news/article_5199_en.html" EU Transport Research
Book Synopsis Experimental and Numerical Study of Dynamics of Premixed Hydrogen-Air Flames Propagating in Ducts by : Huahua Xiao
Download or read book Experimental and Numerical Study of Dynamics of Premixed Hydrogen-Air Flames Propagating in Ducts written by Huahua Xiao and published by Springer. This book was released on 2015-11-03 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis offers important new insights into and a deeper understanding of premixed flame instabilities and hydrogen safety. Further, it explains the underlying mechanisms that control the combustion processes in tubes. The author’s previous scientific accomplishments, which include a series of high-quality publications in the best journals in our field, Combustion and Flame and International Journal of Heat and Mass Transfer, are very impressive and have already made a significant contribution to combustion science.
Book Synopsis Turbulent Premixed Flames by : Nedunchezhian Swaminathan
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.
Book Synopsis Direct Numerical Simulations of Strained Laminar and Turbulent Nonpremixed Flames by : Chunsang Yoo
Download or read book Direct Numerical Simulations of Strained Laminar and Turbulent Nonpremixed Flames written by Chunsang Yoo and published by . This book was released on 2005 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis An Experimental and Numerical Study on the Stability and Propagation of Laminar Premixed Flames by : Christina M. Vagelopoulos
Download or read book An Experimental and Numerical Study on the Stability and Propagation of Laminar Premixed Flames written by Christina M. Vagelopoulos and published by . This book was released on 1999 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Numerical Study of Cellular Instability in Burner Stabilized Adiabatic Laminar Premixed Flames by :
Download or read book Numerical Study of Cellular Instability in Burner Stabilized Adiabatic Laminar Premixed Flames written by and published by . This book was released on 2013 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Turbulent Combustion by : Norbert Peters
Download or read book Turbulent Combustion written by Norbert Peters and published by Cambridge University Press. This book was released on 2000-08-15 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Direct Numerical Simulation for Turbulent Reacting Flows by : Thierry Baritaud
Download or read book Direct Numerical Simulation for Turbulent Reacting Flows written by Thierry Baritaud and published by Editions TECHNIP. This book was released on 1996 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contents: Description of accurate boundary conditions for the simulation of reactive flows. Parallel direct numerical simulation of turbulent reactive flow. Flame-wall interaction and heat flux modelling in turbulent channel flow. A numerical study of laminar flame wall interaction with detailed chemistry: wall temperature effects. Modeling and simulation of turbulent flame kernel evolution. Experimental and theoretical analysis of flame surface density modelling for premixed turbulent combustion. Gradient and counter-gradient transport in turbulent premixed flames. Direct numerical simulation of turbulent flames with complex chemical kinetics. Effects of curvature and unsteadiness in diffusion flames. Implications for turbulent diffusion combustion. Numerical simulations of autoignition in turbulent mixing flows. Stabilization processes of diffusion flames. References.
Book Synopsis Further Experiments on the Stability of Laminar and Turbulent Hydrogen-air Flames at Reduced Pressures by : Burton Fine
Download or read book Further Experiments on the Stability of Laminar and Turbulent Hydrogen-air Flames at Reduced Pressures written by Burton Fine and published by . This book was released on 1957 with total page 31 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stability limits for laminar and turbulent hydrogen-air burner flames were measured as a function of pressure, burner diameter, and composition. On the basis of a simple flame model, turbulent flashback involved a smaller effective penetration distance than laminar flashback. No current theoretical treatment predicts the observed pressure and diameter dependence of laminar and turbulent blowoff.
Book Synopsis DNS of Hydrodynamic Instabilities of Laminar H2/O2/N2 Flames at Elevated Pressure by :
Download or read book DNS of Hydrodynamic Instabilities of Laminar H2/O2/N2 Flames at Elevated Pressure written by and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The atypical combustion properties of hydrogen have long provided an interest for hydrogen-enriched combustion, emphasized in recent years by increasingly stringent emission regulations. Significant work has been focused on the small hydrocarbon(C1-C3)/hydrogen blends, but much less is known about the effect of hydrogen on heavier hydrocarbon combustion, of interest for the aviation and automotive industry. In this work, we perform direct numerical simulations (DNS) of spherically expanding laminar n-dodecane/H2 flames in a constant-volume vessel at elevated pressure and a range of hydrogen seeding levels. A low Mach number model is used to represent the gas and flame dynamics allowing for a temporally varying, spatially homogeneous pressure field, while also enabling numerical evolution of the system numerically at time step sizes governed by the advective CFL limit rather than acoustic processes. We use an adaptive mesh refinement (AMR) approach to tackle the large separation of scales associated with high pressure premixed flame surfaces propagating in a laboratory-scale closed domain. We incorporate detailed chemistry and transport models for the reacting flow and focus the analysis on the effects of the pressure rise on the flame propagation characteristics and morphology as the hydrogen content is increased. The presence of fast diffusive H2 and the pressure rise results in dramatic thinning of the flame and the potential onset of hydrodyanmic and theromdiffusive instabilities. We assess the potential role of these instabilities on the ability to accurately measure laminar burning speed experimentally based on the mean flame surface propagation speed.
Book Synopsis Transition to Renewable Energy Systems by : Detlef Stolten
Download or read book Transition to Renewable Energy Systems written by Detlef Stolten and published by John Wiley & Sons. This book was released on 2013-05-13 with total page 882 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this ready reference, top academic researchers, industry players and government officers join forces to develop commercial concepts for the transition from current nuclear or fossil fuel-based energy to renewable energy systems within a limited time span. They take into account the latest science and technology, including an analysis of the feasibility and impact on the environment, economy and society. In so doing, they discuss such complex topics as electrical and gas grids, fossil power plants and energy storage technologies. The contributions also include robust, conceivable and breakthrough technologies that will be viable and implementable by 2020.
Book Synopsis Instability of Premixed Lean Hydrogen Laminar Tubular Flames by : Carl Alan Hall
Download or read book Instability of Premixed Lean Hydrogen Laminar Tubular Flames written by Carl Alan Hall and published by . This book was released on 2016 with total page 91 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Direct Numerical Simulation of Lean Premixed Turbulent Flames at High Karlovitz Numbers Under Elevated Pressures by : Xujiang Wang
Download or read book Direct Numerical Simulation of Lean Premixed Turbulent Flames at High Karlovitz Numbers Under Elevated Pressures written by Xujiang Wang and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Numerical Methods in Laminar Flame Propagation by : Norbert Peters
Download or read book Numerical Methods in Laminar Flame Propagation written by Norbert Peters and published by Vieweg+teubner Verlag. This book was released on 1982 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume collects the results of a workshop held at Aachen, West-Germany, Oct. 12 - Oct. 14, 1981. The purpose in bringing together scientists actively working in the field of numerical methods in flame propagation was two-fold: 1. To confront them with recent results obtained by large ac tivation-energy asymptotics and to check these numerically. 2. To compare different numerical codes and different trans port models for flat flame calculations with complex che mistry. Two test problems were formulated by the editors to meet these objectives. Test problem A was an unsteady propagating flat flame with one-step chemistry and Lewis number different from unity while test problem B was the steady, stoichiometric hy drogen-air flame with prescribed complex chemistry. The parti cipants were asked to solve one or both test problems and to present recent work of their own choice at the meeting. The results of the numerical calculations of test problem A are challenging just as much for scientists employing numerical me thods as for those devoted to large activation-energy asympto tics: Satisfactory agreement between the five different groups were obtained only for two out of six cases, those with Lewis number Le equal to one. The very strong oscillations that oc cur at Le = 2 and a nondimensional activation energy of 20 were accurately resolved only by one group. This case is par ticular interesting because the asymptotic theory so far pre dicts instability but not oscillations.
Book Synopsis Further Experiments on the Stability of Laminar and Turbulent Hydrogen-air Flames at Reduced Pressure by : Burton Fine
Download or read book Further Experiments on the Stability of Laminar and Turbulent Hydrogen-air Flames at Reduced Pressure written by Burton Fine and published by . This book was released on 1957 with total page 31 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Combustion Theory by : Forman A. Williams
Download or read book Combustion Theory written by Forman A. Williams and published by CRC Press. This book was released on 2018-03-05 with total page 549 pages. Available in PDF, EPUB and Kindle. Book excerpt: Combustion Theory delves deeper into the science of combustion than most other texts and gives insight into combustions from a molecular and a continuum point of view. The book presents derivations of the basic equations of combustion theory and contains appendices on the background of subjects of thermodynamics, chemical kinetics, fluid dynamics, and transport processes. Diffusion flames, reactions in flows with negligible transport and the theory of pre-mixed flames are treated, as are detonation phenomena, the combustion of solid propellents, and ignition, extinction, and flamibility pehnomena.
