Download or read book HyChem A Physics based Approach to Modeling Real fuel Combustion Chemistry written by Rui Xu (Mechanical engineer) and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Real fuels usually contain hundreds to thousands of hydrocarbon components. Over a wide range of combustion conditions, large hydrocarbon molecules undergo thermal decomposition first to form a small set (usually less than 10 species) of low molecular weight products, followed by the oxidation of those products, which is usually rate limiting. Hence, the composition of the decomposed products determines the overall global combustion properties. For conventional distillate fuels, the pyrolysis products comprise ethylene (C2H4), hydrogen (H2), methane (CH4), propene (C3H6), 1-butene (1-C4H8), iso-butene (i-C4H8), benzene (C6H6) and toluene (C7H8). From a joint consideration of thermodynamics and chemical kinetics, it is shown that the composition of the thermal decomposition products is a weak function of the thermodynamic condition, the equivalence ratio and the fuel composition within the range of temperatures relevant to high temperature combustion phenomena. In this dissertation study, I demonstrate a hybrid chemistry (HyChem) approach to modeling the high-temperature oxidation of real, liquid fuels. In this approach, the kinetics of fuel pyrolysis is modeled using experimentally derived, lumped reaction steps, while the oxidation of the pyrolysis fragments is described by a detailed foundational fuel chemistry model. A wide range of modeling results are provided to support the approach, including three conventional aviation fuels (JP-8 POSF10264, Jet A POSF10325, JP-5 POSF10289), two rocket fuels (RP2-1 POSF7688, RP2-2 POSF5433), and a bio-derived alternative jet fuel (Gevo alcohol-to-jet fuel, C1 POSF11498). The HyChem models of those fuels were developed using advanced speciation data obtained from shock tubes and a flow reactor, and the models were subsequently tested against global combustion properties, including ignition delay time, laminar flame speed, and flame extinction strain rates across a wide range of pressure, temperature and reactant mixture conditions. Sensitivity analysis of the model predictions with respect to the measurement uncertainties and rate parameter uncertainties of foundational fuel chemistry model is assessed. In this dissertation, the HyChem modeling approach was also extended to three key aspects critical to modeling fuel combustion over an even wider range of condition. First, a modified HyChem model was formulated for capturing the physics in negative temperature coefficient (NTC) and low-temperature oxidation regimes. Sensitivity test and suggestions on future NTC enabled HyChem model development are presented. Second, the HyChem approach was applied to modeling the blend of a conventional Jet A fuel and an alternative, alcohol-to-jet synthetic fuel. The pyrolysis as well as the combustion properties of several blended fuels were predicted by a simple combination of the HyChem models of the two individual fuels, thus demonstrating that the HyChem models for two jet fuels of very different compositions can be "additive" as far as high-temperature properties are concerned. Lastly, I will discuss a case study in which the HyChem model of Jet A is extended to NOx prediction after combining it with a recently updated reaction model of nitrogen chemistry. The combined reaction model is shown to predict NOx formation in premixed stretched-stabilized Jet A flames satisfactorily.
Download or read book Combustion written by Jürgen Warnatz and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 309 pages. Available in PDF, EPUB and Kindle. Book excerpt: Combustion is an old technology, which at present provides about 90% of our worldwide energy support. Combustion research in the past used fluid mechanics with global heat release by chemical reactions described with thermodynamics, assuming infinitely fast reactions. This approach was useful for stationary combustion processes, but it is not sufficient for transient processes like ignition and quenching or for pollutant formation. Yet pollutant formation during combustion of fossil fuels is a central topic and will continue to be so in future. This book provides a detailed and rigorous treatment of the coupling of chemical reactions and fluid flow. Also, combustion-specific topics of chemistry and fluid mechanics are considered, and tools described for the simulation of combustion processes. For the 2nd edition, the parts dealing with experiments, spray combustion, and soot were thoroughly revised.
Download or read book Towards a Practical Modeling Approach for Low Temperature Oxidation of Fuels written by Rishav Choudhary and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The diversity of reactivities, intermediates, and pathways associated with the low-temperature oxidation of various component classes that constitute real fuels is perhaps the most challenging aspect of modeling combustion chemistry of these fuels. Unlike high-temperature oxidation (T > 1000 K), where the law of large numbers renders global combustion properties of real, multicomponent fuels weakly sensitive to compositional variability, reactions controlling low-temperature oxidation are very sensitive to fuel composition. Despite this fuel specificity, the formation of intermediates during low-temperature oxidation exhibits certain commonalities which can be observed in carefully designed shock tube experiments. Combining these observations with elemental balance, chemical kinetic considerations, and with the already mature Hybrid Chemistry (HyChem) approach for high-temperature oxidation of real fuels, I first propose an approach to develop simplified, physics-based chemical kinetic models for low-temperature oxidation of real fuels. In this approach, the low-temperature oxidation is described by lumped, fuel-specific reactions whose rate constants and stoichiometric parameters are determined using shock tube species time history measurements. These reactions augment the already developed high-temperature HyChem models which encompass fuel-specific reactions describing thermal and oxidative pyrolysis at high temperatures, and a detailed model describing kinetics of small hydrocarbons. Detailed arguments in support of the model formulation are presented. The model is then exercised to identify species to be targeted for measurements in shock tubes. Carbon monoxide (CO), and formaldehyde (CH2O) were identified as the most important species for determining the model parameters followed by OH, and HO2. Laser absorption spectroscopy based diagnostics for measuring some of these species were also developed in parallel with this work. The feasibility of the targeted speciation studies is first demonstrated during oxidation of five neat hydrocarbons, i.e., n-decane, n-octane, n-heptane, and its two branched isomers, 2-methyl hexane, and 3,3-dimethyl pentane. These studies not only demonstrated the feasibility of the diagnostics, but also highlighted the deficiency in the existing detailed models for low-temperature oxidation of heavy hydrocarbons. They also provided further evidence supporting some of the assumptions made while formulating the LT-HyChem approach. With the speciation strategy developed, and target experimental conditions verified, the application of the LT-HyChem approach to three classes of fuels is presented: a) A simple, three-component hydrocarbon mixture (TPRF-60), b) A jet fuel, c) Two high-performance gasoline fuels. Validation of the model against a range of ignition delay time (IDT) measurements conducted across a range of facilities worldwide is presented. The model predictions for all fuels show excellent agreement with the IDTs reported in the literature over a wide range of conditions. Moreover, the constraints imposed on the model parameters by the species time history measurements conducted in shock tubes result in a significant reduction in the uncertainty in the model's predictions. A detailed uncertainty analysis is presented and is supplemented with sensitivity analysis to identify the dominant contributing factors to the uncertainty in model predictions. The success of the LT-HyChem approach is encouraging as this approach can be extended to the sustainable fuels that will drive the engines of tomorrow. This will enable a rapid screening of candidates for the sustainable fuels of tomorrow.
Download or read book Combustion written by Jürgen Warnatz and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: Combustion is an old technology, which at present provides about 90% of our worldwide energy support. Combustion research in the past used fluid mechanics with global heat release by chemical reactions described with thermodynamics, assuming infinitely fast reactions. This approach was useful for stationary combustion processes, but it is not sufficient for transient processes like ignition and quenching or for pollutant formation. Yet pollutant formation during combustion of fossil fuels is a central topic and will continue to be so in future. This book provides a detailed and rigorous treatment of the coupling of chemical reactions and fluid flow. Also, combustion-specific topics of chemistry and fluid mechanics are considered, and tools described for the simulation of combustion processes.
Download or read book Gas Phase Combustion Chemistry written by W.C., Jr. Gardiner and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 553 pages. Available in PDF, EPUB and Kindle. Book excerpt: Superseding Gardiner's "Combustion Chemistry", this is an updated, comprehensive coverage of those aspects of combustion chemistry relevant to gas-phase combustion of hydrocarbons. The book includes an extended discussion of air pollutant chemistry and aspects of combustion, and reviews elementary reactions of nitrogen, sulfur and chlorine compounds that are relevant to combustion. Methods of combustion modeling and rate coefficient estimation are presented, as well as access to databases for combustion thermochemistry and modeling.
Download or read book Combustion written by J. Warnatz and published by Springer Science & Business Media. This book was released on 2006-08-18 with total page 389 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a rigorous treatment of the coupling of chemical reactions and fluid flow. Combustion-specific topics of chemistry and fluid mechanics are considered and tools described for the simulation of combustion processes. This edition is completely restructured. Mathematical Formulae and derivations as well as the space-consuming reaction mechanisms have been replaced from the text to appendix. A new chapter discusses the impact of combustion processes on the atmosphere, the chapter on auto-ignition is extended to combustion in Otto- and Diesel-engines, and the chapters on heterogeneous combustion and on soot formation are heavily revised.
Download or read book Turbulent Combustion Modeling written by Tarek Echekki and published by Springer. This book was released on 2013-01-27 with total page 0 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 Introduction to Physics and Chemistry of Combustion written by Michael A. Liberman and published by Springer Science & Business Media. This book was released on 2008-09-09 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most of the material covered in this book deals with the fundamentals of chemistry and physics of key processes and fundamental mechanisms for various combustion and combustion related phenomena in gaseous combustible mixture. It provides the reader with basic knowledge of burning processes and mechanisms of reaction wave propagation. The combustion of a gas mixture (flame, explosion, detonation) is necessarily accompanied by motion of the gas. The process of combustion is therefore not only a chemical phenomenon but also one of gas dynamics. The material selection focuses on the gas phase and with premixed gas combustion. Premixed gas combustion is of practical importance in engines, modern gas turbine and explosions, where the fuel and air are essentially premixed, and combustion occurs by the propagation of a front separating unburned mixture from fully burned mixture. Since premixed combustion is the most fundamental and potential for practical applications, the emphasis in the present work is be placed on regimes of premixed combustion. This text is intended for graduate students of different specialties, including physics, chemistry, mechanical engineering, computer science, mathematics and astrophysics.
Download or read book Modeling of Combustion Systems written by Joseph Colannino and published by CRC Press. This book was released on 2006-03-24 with total page 675 pages. Available in PDF, EPUB and Kindle. Book excerpt: Increasing competitive pressure for improved quality and efficiency on one hand and tightening emissions and operating requirements on the other leave the modern process engineer squeezed in the middle. While effective modeling can help balance these demands, the current literature offers overly theoretical treatments on modeling that do not transl
Download or read book Hydrocarbon Combustion Reaction Models from Both Ends the Foundational Fuels and JP10 written by Yujie Tao and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the hierarchical nature of high-temperature hydrocarbon oxidation, modeling the combustion chemistry of higher hydrocarbon fuels typically requires a fuel-specific reaction model that describes the fragmentation of the fuel to small species, and a foundational fuel chemistry model that describes the oxidation of these species. Shared by the combustion of large hydrocarbons, the foundational fuel chemistry is also the rate-limiting step and therefore a crucial part for constructing reliable combustion models for any higher hydrocarbons. The dissertation studies the aforementioned problems from both ends. A detailed reaction kinetic model of the foundational fuel combustion is comprised of elementary chemical reactions and their associated rate coefficients. Each of the rate coefficients comes with some uncertainty. The inherent uncertainties of the rate parameters propagate into model predictions and need to be properly quantified. Without characterizing the uncertainty, a reaction model merely represents a feasible combination of rate parameters within a high-dimensional uncertainty space. The Foundational Fuel Chemistry Model (FFCM) is an effort directed at developing a reliable combustion model for the foundational fuels with rate parameters optimized and uncertainty minimized. The first version, FFCM-1, optimized for H2, H2/CO, CH2O and CH4 combustion was constrained with carefully evaluated fundamental combustion data that includes laminar flame speeds, shock tube ignition delay times, shock tube species profiles, and flow reactor species profiles. It has been shown that the model reconciles all the experimental targets chosen and has significantly reduced prediction uncertainties. The remaining kinetic uncertainties in FFCM-1 were further analyzed with extinction and ignition residence time predictions in perfectly-stirred reactor conditions. The reactions that were responsible for the remaining prediction uncertainties were studied with an impact factor analysis over a wide range of temperature, pressure and equivalence ratio. The optimization and uncertainty quantification procedure was then extended to also include temperature dependency by considering the joint optimization of pre-exponential factors and activation energies. An effective temperature was defined for every target and utilized in the response surface derivation. The resulting temperature-dependent uncertainties of key reactions in H2/CO flames in a test problem were discussed. JP10 was studied as a single-component large-fuel example, using the Hybrid Chemistry (HyChem) approach. The HyChem approach assumes a decoupled fuel pyrolysis and oxidation of pyrolysis products. The pyrolysis model is described with highly-lumped steps and optimized against experimental data from shock tube and flow reactor species profiles and shock tube ignition delay. Special attention was paid to the unique molecular structure of the fuel in the lumped pyrolysis reactions, and the overall performance of the model is shown to be satisfactory.
Download or read book Combustion Chemistry written by W. C. Jr. Gardiner and published by Springer. This book was released on 2012-02-01 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Detailed study of the rates and mechanisms of combustion reactions has not been in the mainstream of combustion research until the recent recognition that further progress in optimizing burner performance and reducing pollutant emission can only be done with fundamental understanding of combustion chemistry. This has become apparent at a time when our understanding of the chemistry, at least of small-molecule combustion, and our ability to model combustion processes on large computers have developed to the point that real confidence can be placed in the results. This book is an introduction for outsiders or beginners as well as a reference work for people already active in the field. Because the spectrum of combustion scientists ranges from chemists with little computing experience to engineers who have had only one college chemistry course, everything needed to bring all kinds of beginners up to the level of current practice in detailed combustion modeling is included. It was a temptation to include critical discussions of modeling results and computer programs that would enable outsiders to start quickly into problem solving. We elected not to do either, because we feel that the former are better put into the primary research literature and that people who are going to do combustion modeling should either write their own programs or collaborate with experts. The only exception to this is in the thermochemical area, where programs have been included to do routine fitting operations. For reference purposes there are tables of thermochemical, transport-property, and rate coefficient data.
Download or read book Reduced Kinetic Mechanisms for Applications in Combustion Systems written by Norbert Peters and published by Springer Science & Business Media. This book was released on 1993-01-22 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Recent Advances in Combustion Modelling written by Bernard Larrouturou and published by World Scientific. This book was released on 1991 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume gathers the contributions of six world experts to a course on combustion modelling. Therefore, a pedagogical effort has been made in writing up these texts, which cover state of the art advances in most aspects of combustion science. The book is aimed at students, researches and engineers, as was the course.
Download or read book Cleaner Combustion written by Frédérique Battin-Leclerc and published by Springer Science & Business Media. This book was released on 2013-09-06 with total page 657 pages. Available in PDF, EPUB and Kindle. Book excerpt: This overview compiles the on-going research in Europe to enlarge and deepen the understanding of the reaction mechanisms and pathways associated with the combustion of an increased range of fuels. Focus is given to the formation of a large number of hazardous minor pollutants and the inability of current combustion models to predict the formation of minor products such as alkenes, dienes, aromatics, aldehydes and soot nano-particles which have a deleterious impact on both the environment and on human health. Cleaner Combustion describes, at a fundamental level, the reactive chemistry of minor pollutants within extensively validated detailed mechanisms for traditional fuels, but also innovative surrogates, describing the complex chemistry of new environmentally important bio-fuels. Divided into five sections, a broad yet detailed coverage of related research is provided. Beginning with the development of detailed kinetic mechanisms, chapters go on to explore techniques to obtain reliable experimental data, soot and polycyclic aromatic hydrocarbons, mechanism reduction and uncertainty analysis, and elementary reactions. This comprehensive coverage of current research provides a solid foundation for researchers, managers, policy makers and industry operators working in or developing this innovative and globally relevant field.
Download or read book A Complete Methodology for the Predictive Simulation of Novel Single and Multi Component Fuel Combustion written by Sebastian K. Crönert and published by Springer Nature. This book was released on 2023-10-31 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sebastian K. Crönert presents a new, automated process that makes it possible to obtain all the fuel properties required for combustion simulation. If necessary, these are then transferred - also automatically - into specially created correlation equations through which they are then made available again at simulation runtime. This method makes it possible to represent even more complex correlations and cross-influences on calculation variables in a resource-optimised way (memory requirements and access time) while maintaining the same accuracy. The procedure is validated using test bench measurement data for the pure fuels anisole and cyclopentanone and their blends with regular petrol (RON95E10). Additional validations include more established synthetic fuels and hydrogen. It is shown that an extraordinarily high prediction quality can be achieved for the model class.
Download or read book Mathematical Modeling in Combustion and Related Topics written by Claude-Michel Brauner and published by Springer Science & Business Media. This book was released on 1988-03-31 with total page 620 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains invited lectures and contributed papers presented at the NATO Advanced Research Workshop on Mathematical Modeling in Combustion and related topics, held in. Lyon (France), April 27 - 30, 1987. This conference was planned to fit in with the two-month visit of Professor G.S.S. Ludford to the Ecole Centrale de Lyon. He kindly agreed to chair the Scientific and Organizing Committee and actively helped to initiate the meeting. His death in December 1986 is an enormous loss to the scientific community in general, and in particular, to the people involved in the present enterprise. The subject of mathematical modeling in combustion is too large for a single conference, and the selection of topics re flects both areas of recent research activity and areas of in terest to Professor G.S.S. Ludford, to whose memory the Advanced Workshop and this present volume are dedicated. The meeting was divided into seven specialized sessions detonation theory, mathematical analysis, numerical treatment of combustion problems, flame theory, experimental and industrial aspects, complex chemistry, and turbulent combustion. It brought together researchers and engineers from University and Industry (see below the closing remarks of the workshop by Prof. N. Peters). The articles in this volume have been judged and accepted on their scientific quality, and language corrections may have been sacrificed in order to allow quick dissemination of knowledge to prevail.
Download or read book Reduced Chemical Kinetic Models for Real Fuels and Computational Flame Diagnostics of Premixed Combustion written by Ji-Woong Park and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
