Download or read book Chemical Structures of Low pressure Premixed Methylcyclohexane Flames as Benchmarks for the Development of a Predictive Combustion Chemistry Model written by and published by . This book was released on 2011 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: The chemical compositions of three low-pressure premixed flames of methylcyclohexane (MCH) are investigated with the emphasis on the chemistry of MCH decomposition and the formation of aromatic species, including benzene and toluene. The flames are stabilized on a flat-flame (McKenna type) burner at equivalence ratios of [phi] = 1.0, 1.75, and 1.9 and at low pressures between 15 Torr (= 20 mbar) and 30 Torr (= 40 mbar). The complex chemistry of MCH consumption is illustrated in the experimental identification of several C7H12, C7H10, C6H12, and C6H10 isomers sampled from the flames as a function of distance from the burner. Three initiation steps for MCH consumption are discussed: ring-opening to heptenes and methyl-hexenes (isomerization), methyl radical loss yielding the cyclohexyl radical (dissociation), and H abstraction from MCH. Mole fraction profiles as a function of distance from the burner for the C7 species supplemented by theoretical calculations are presented, indicating that flame structures resulting in steeper temperature gradients and/or greater peak temperatures can lead to a relative increase in MCH consumption through the dissociation and isomerization channels. Trends observed among the stable C6 species as well as 1,3-pentadiene and isoprene also support this conclusion. Relatively large amounts of toluene and benzene are observed in the experiments, illustrating the importance of sequential H-abstraction steps from MCH to toluene and from cyclohexyl to benzene. Furthermore, modeled results using the detailed chemical model of Pitz et al. (Proc. Combust. Inst. 2007, 31, 267-275) are also provided to illustrate the use of these data as a benchmark for the improvement or future development of a MCH mechanism.

Download or read book Experimental and Kinetic Modeling Study of Cyclohexane and Its Mono alkylated Derivatives Combustion written by Zhandong Wang and published by Springer. This book was released on 2018-01-23 with total page 225 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis investigates the combustion chemistry of cyclohexane, methylcyclohexane, and ethylcyclohexane on the basis of state-of-the-art synchrotron radiation photoionization mass spectrometry experiments, quantum chemistry calculations, and extensive kinetic modeling. It explores the initial decomposition mechanism and distribution of the intermediates, proposes a novel formation mechanism of aromatics, and develops a detailed kinetic model to predict the three cycloalkanes’ combustion properties under a wide range of conditions. Accordingly, the thesis provides an essential basis for studying much more complex cycloalkanes in transport fuels and has applications in engine and fuel design, as well as emission control.

Download or read book Chemical Kinetic Modeling of Low Pressure Methylcyclohexane Flames written by and published by . This book was released on 2013 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Chemistry in Premixed Flames written by Charles Paine Fenimore and published by Pergamon. This book was released on 1964 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thermochemical Kinetics written by Sidney William Benson and published by . This book was released on 1976 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Lean Premixed Flames for Low NO subscript X Combustors written by and published by . This book was released on 1995 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: The overall objectives of the research at Purdue are to: obtain a reduced mechanism description of high pressure NO formation chemistry using experiments and calculations for laminar lean premixed methane air flames, develop a statistical model of turbulence NO chemistry interactions using a Bunsen type jet flame, and utilize the high pressure chemistry and turbulence models in a commercial design code, then evaluate its predictions using data from an analog gas turbine combustor. Work to date has resulted in the following achievements: spatially resolved measurements of NO in high-pressure high-temperature flat flames, plus evaluation of the influence of flame radiation on the measured temperature profile; measurements of temperature and velocity PDFs for a turbulent methane/air flame were obtained for the first time, under operating conditions which allow their study in the distributed regimes, and the increase in EINO(subscript x) with equivalence ratio predicted using a chemical kinetics model; and simulation of non-reacting combustor flow fields from ambient to elevated pressure and temperature conditions and comparison of those results with experimental velocity profiles.

Download or read book Fundamentals of Combustion Processes written by Sara McAllister and published by Springer Science & Business Media. This book was released on 2011-05-10 with total page 315 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamentals of Combustion Processes is designed as a textbook for an upper-division undergraduate and graduate level combustion course in mechanical engineering. The authors focus on the fundamental theory of combustion and provide a simplified discussion of basic combustion parameters and processes such as thermodynamics, chemical kinetics, ignition, diffusion and pre-mixed flames. The text includes exploration of applications, example exercises, suggested homework problems and videos of laboratory demonstrations

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 Micro mixing in Turbulent Premixed Flames written by Michael Joseph Kuron and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

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.

Download or read book Structure of Partially Premixed Flames Using Detailed Chemistry Simulations written by Celine D. Kluzek and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: State-of-the-art reacting-flow computations have to compromise either on the detail of chemical reactions or on the dimensionality of the solution, while experiments in flames are limited by the flow accessibility and provide at best a limited number of observables. In the present work, the partially premixed laminar flame structure is examined using a detailed-chemistry, one-dimensional simulation. The computational results are compared to unpublished single-point multiscalar measurements obtained at Sandia National Labs in 2001. The study is focused on axisymmetric laminar partially-premixed methane/air flames with varying premixture strength values of 1.8, 2.2, and 3.17. The combination of computational and experimental results is used to analyze the spatial and scalar flame structure under the overarching concept of flamelets. The computations are based on the Cantera open-source software package developed at CalTech by D. Goodwin, and incorporating the GRI 3.0 chemical kinetic mechanism utilizing 325 chemical reactions and 53 species for methane combustion. Cross-transport effects as well as an optically-thin radiation model are included in the calculations. Radiation changes the flame profiles due to its effect on temperature, and the attendant effects on a number of species. Using the detailed analysis of different reaction rates, the adiabatic and radiative nitric oxide concentrations are compared. The cross-transport effects, i.e. Soret and Dufour, were studied in detail. The Soret term has a small but important effect on the flame structure through a reduction of the hydrogen mass fraction, which changes the conserved scalar values. Based on the flamelet approach and a unique formulation of the conserved scalar, the flame thermochemistry can be analyzed and understood. A number of interesting effects on the flame thermochemistry can be discerned in both experiments and computations when the premixture strength is varied. An increase in premixing results in a counterintuitive decrease in intermediate species such as carbon monoxide and hydrogen, as well as an expected increase in nitric oxide concentrations. Good agreement is found between experiments and calculations in scalar space, while the difference in dimensionality between axisymmetric measurements and opposed jet computations makes comparison in physical space tentative.

Download or read book International Aerospace Abstracts written by and published by . This book was released on 1997 with total page 940 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Chemical Kinetics in Combustion and Reactive Flows Modeling Tools and Applications written by V. I. Naoumov and published by Cambridge University Press. This book was released on 2019-08-22 with total page 449 pages. Available in PDF, EPUB and Kindle. Book excerpt: Introduces advanced mathematical tools for the modeling, simulation, and analysis of chemical non-equilibrium phenomena in combustion and flows, following a detailed explanation of the basics of thermodynamics and chemical kinetics of reactive mixtures. Researchers, practitioners, lecturers, and graduate students will find this work valuable.

Download or read book Transport Phenomena in Fires written by Mohammad Faghri and published by WIT Press. This book was released on 2008 with total page 497 pages. Available in PDF, EPUB and Kindle. Book excerpt: Controlled fires are beneficial for the generation of heat and power while uncontrolled fires, like fire incidents and wildfires, are detrimental and can cause enormous material damage and human suffering. This edited book presents the state-of-the-art of modeling and numerical simulation of the important transport phenomena in fires. It describes how computational procedures can be used in analysis and design of fire protection and fire safety. Computational fluid dynamics, turbulence modeling, combustion, soot formation, thermal radiation modeling are demonstrated and applied to pool fires, flame spread, wildfires, fires in buildings and other examples.

Download or read book Development of a Comprehensive and Predictive Reaction Mechanism of Liquid Hydrocarbon Combustion written by and published by . This book was released on 2007 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Studies were conducted in several relevant areas, including (1) validation of the chemistry and transport models against the extinction of ultra-lean premixed hydrogen-air mixtures, (2) a comprehensive theoretical analysis of the reaction kinetics of carbon monoxide and the hydroxyl radical, (3) a theoretical kinetic study of the decomposition of ethylene oxide; (4) a gas-kinetic analysis for the transport properties of long chain molecules in dilute gases, (5) quantum-chemistry, master equation modeling of the unimolecular decomposition of ortho-benzyne, (6) extension of the previously developed hydrogenicarbon model to combustion pressures as high as 600 atm, (7) an updated kinetic mechanism of small-hydrocarbon fuel combustion for use as a kinetic foundation of higher hydrocarbon combustion, and (8) a methodology for kinetic uncertainty propagation. These projects represent the two key ingredients for meeting the overall project objectives: (a) an accurate physico-chemical property database for combustion kinetics, and (b) a unified and optimized kinetic model for liquid aliphatic and aromatic fuel combustion with quantifiable uncertainties.

Download or read book Experimental and Kinetic Modeling Study of Cyclohexane and Its Mono alkylated Derivatives Combustion written by Zhandong Wang and published by Springer. This book was released on 2018-01-30 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis investigates the combustion chemistry of cyclohexane, methylcyclohexane, and ethylcyclohexane on the basis of state-of-the-art synchrotron radiation photoionization mass spectrometry experiments, quantum chemistry calculations, and extensive kinetic modeling. It explores the initial decomposition mechanism and distribution of the intermediates, proposes a novel formation mechanism of aromatics, and develops a detailed kinetic model to predict the three cycloalkanes’ combustion properties under a wide range of conditions. Accordingly, the thesis provides an essential basis for studying much more complex cycloalkanes in transport fuels and has applications in engine and fuel design, as well as emission control.

Download or read book Combustion Chemistry of Alcohols written by and published by . This book was released on 2013 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: