Reduced Kinetic Mechanisms for Premixed Laminar Flames PDF Download
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Author: Weigang Wang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Weigang Wang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Norbert Peters
Publisher: Springer Science & Business Media
ISBN: 3540475435
Category : Science
Languages : en
Pages : 364
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Book Description
In general, combustion is a spatially three-dimensional, highly complex physi co-chemical process oftransient nature. Models are therefore needed that sim to such a degree that it becomes amenable plify a given combustion problem to theoretical or numerical analysis but that are not so restrictive as to distort the underlying physics or chemistry. In particular, in view of worldwide efforts to conserve energy and to control pollutant formation, models of combustion chemistry are needed that are sufficiently accurate to allow confident predic tions of flame structures. Reduced kinetic mechanisms, which are the topic of the present book, represent such combustion-chemistry models. Historically combustion chemistry was first described as a global one-step reaction in which fuel and oxidizer react to form a single product. Even when detailed mechanisms ofelementary reactions became available, empirical one step kinetic approximations were needed in order to make problems amenable to theoretical analysis. This situation began to change inthe early 1970s when computing facilities became more powerful and more widely available, thereby facilitating numerical analysis of relatively simple combustion problems, typi cally steady one-dimensional flames, with moderately detailed mechanisms of elementary reactions. However, even on the fastest and most powerful com puters available today, numerical simulations of, say, laminar, steady, three dimensional reacting flows with reasonably detailed and hence realistic ki netic mechanisms of elementary reactions are not possible.
Author: Mitchell D. Smooke
Publisher: Springer
ISBN: 9783662138533
Category : Science
Languages : en
Pages : 248
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Book Description
In this comprehensive text a systematic numerical and analytical treatment of the procedures for reducing complicated systems to a simplified reaction mechanism is presented. The results of applying the reduced reaction mechanism to a one-dimensional laminar flame are discussed. A set of premixed and non-premixed methane-air flames with simplified transport and skeletal chemistry are employed as test problems that are used later on to evaluate the results and assumptions in reduced reaction networks. The first four chapters form a short tutorial on the procedures used in formulating the test problems and in reducing reaction mechanisms by applying steady-state and partial-equilibrium approximations. The final six chapters discuss various aspects of the reduced chemistry problem for premixed and nonpremixed combustion.
Author: Mitchell D. Smooke
Publisher: Springer
ISBN:
Category : Science
Languages : en
Pages : 264
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Book Description
In this comprehensive text a systematic numerical and analytical treatment of the procedures for reducing complicated systems to a simplified reaction mechanism is presented. The results of applying the reduced reaction mechanism to a one-dimensional laminar flame are discussed. A set of premixed and non-premixed methane-air flames with simplified transport and skeletal chemistry are employed as test problems that are used later on to evaluate the results and assumptions in reduced reaction networks. The first four chapters form a short tutorial on the procedures used in formulating the test problems and in reducing reaction mechanisms by applying steady-state and partial-equilibrium approximations. The final six chapters discuss various aspects of the reduced chemistry problem for premixed and nonpremixed combustion.
Author: Bernd Rogg
Publisher:
ISBN:
Category : Combustion
Languages : en
Pages : 36
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Author: T. P. Coffee
Publisher:
ISBN:
Category :
Languages : en
Pages : 41
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Book Description
A number of kinetic schemes have been used to model premixed, laminar, one-dimensional methane/air flames. Seven such kinetic schemes, including two new models, are compared with one another and with experimental data. The two new models, one with 14 species and one with 20 species, both agree with the experimental data over a range of stoichiometries from lean to rich. All of the models show good agreement for lean to slightly rich flames. This does not validate any of the models, even for this limited range. Rather, it is shown that the quantities measured are fairly insensitive to much of the mechanism. Therefore, models with incorrect kinetics can agree with the experimental data. In particular, the contribution of the C2 species to methane combustion is examined. While these species are important, we conclude that there is insufficient data to determine quantitatively the effects of the C2 chemistry reactions.
Author: Joshua S. Hsu
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Sylvie Honnet
Publisher: Cuvillier Verlag
ISBN: 386727391X
Category :
Languages : en
Pages : 147
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 31
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Book Description
This report pertains to the detailed kinetics governing premixed, laminar, one-dimensional hydrogen/nitrous oxide flames. The long range goal is to understand the kinetics governing propellant decomposition, where nitrogen chemistry is important. Hydrogen/nitrous oxide flames are the simplest case of a flame controlled by nitrogen chemistry. A model has been developed for premixed, laminar, one-dimensional hydrogen/nitrous oxide flames. Results have been compared with a range of experimental data. The present model roughly reproduces the data, but inaccuracies still exist. Sensitivity and screening analyses have been used to indicate the additional experimental data needed to improve the model. Keywords: Burning Velocity.
Author: Ji-Woong Park
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
This dissertation investigates different approaches to developing efficient yet accurate real-fuel chemistry for multi-dimensional computational fluid dynamics (CFD) simulations and computational flame diagnostics for premixed combustion. First, reduced kinetic models of real fuels are systematically developed based on detailed mechanisms with a hybrid chemistry (HyChem) approach. A two-stage reduction is utilized including a directed relation graph (DRG) and sensitivity analysis followed by linearized quasi-steady state approximation (LQSSA). Comprehensive validations are performed in homogeneous and diffusive systems over wide parameter ranges, showing good agreement between reduced and detailed mechanisms. The second approach focuses on spark ignition (SI) engine applications where laminar flame speed (LFS) plays a crucial role. Typically, in SI-engines, combustion starts at relatively high pressure and temperature. However, most chemical mechanisms are not validated in LFS at such conditions due to the lack of experimental data. The tailoring methodology of a chemical mechanism is proposed to improve prediction of LFS at engine-relevant conditions. Rate coefficients of the selected reactions important to LFS are identified through sensitivity analysis and adjusted within their uncertainty limits to match calculated LFS to experiment-based empirical correlation. The developed tailored mechanism is utilized in 3D SI-engine simulations and improved predictions are observed compared with experimental data. Lastly, a computational flame diagnostic tool to identify the extinction state of premixed flames is developed based on the chemical explosive mode (CEM) analysis (CEMA). Counterflow twin premixed flames show two different extinction modes with increasing stretch due to reaction incompleteness (Mode I) and preferential diffusion effect (Mode II). In Mode I, increasing stretch pushes the flame front, identified as zero-crossing of CEM eigenvalue, toward the stagnation plane such that twin flames merge and form a hot spot approaching extinction. The extinction Mode I can be identified by the zero-crossing of the CEM eigenvalue at the stagnation plane. For Mode II, the extinction occurs away from the stagnation plane due to the combined effect of stretch and preferential diffusion. A new criterion is constructed to quantify the contribution of back-diffusion of heat and radicals to the CEM in the preheat zone. The CEMA-based criteria are then validated in wide ranges of operating conditions covering lean to rich mixtures, elevated inlet temperature and pressure conditions, and small to large real-fuels, showing that it can be used as a leading order indicator for premixed flame extinction.
