Combustion Behavior Associated with Alternative Fuels in Lean Premixed, High-swirl Stabilized Distributed Reactions PDF Download
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Author: Amin Akbari
Publisher:
ISBN: 9781303167799
Category :
Languages : en
Pages : 195
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Book Description
Lean blowoff, flashback and pollutant emission associated with lean premixed combustion of alternative fuels stabilized by high swirl are evaluated in this work. Alternative fuel compositions include blends of natural gas and hydrogen. Lean blowoff refers to events where the fuel-to-air ratio is not sufficient to sustain the reaction. Blowoff is often a dynamic process consisting of several stages. Correlations based on constant Damköhler (Da) number are able to estimate the impact of fuel composition on lean blowoff for the conditions studied. The accuracy of estimating initiation of blowoff is superior compared to estimation of subsequent stages of blowoff. Flashback refers to propagation of the reaction upstream into the premixing zone. In high swirl combustion applications, the concept of a quench criterion has been proposed for predicting flashback. For the present work, this concept only holds for some measured cases, which indicates multiple flashback modes even in high swirl combustion applications. The other major combustion challenge is pollutant emission. In this study NOx, CO, and N2O levels are experimentally measured. In addition, a chemical reaction network (CRN) was developed to study the details of emission formation. To develop a CRN, details of the reacting flow were needed. Hence, computational fluid dynamics (CFD) simulations were conducted. To validate CFD simulations, particle image velocimetry (PIV) and OH* chemiluminescence flame front imaging were applied. OH* chemiluminescence was also employed to visualize the flame structure and shape for different fuel compositions. The CRN simulations indicate that the NNH NOx formation pathway dominates the other formation pathways. Thus, conditions that enhance NNH NOx, such as an increase of hydrogen in fuel composition, and decrease of residence time, will result in more total NOx. The CRN also illustrates how the relative contribution of each NOx formation pathway to total NOx changes with adiabatic flame temperature (AFT). The NNH NOx formation pathway is dominant for AFT below 1900K; the Zeldovich mechanism is dominant for AFT above 1900K. In terms of N2O emissions measured and simulated results suggest the levels are negligible even for very low combustion temperatures.
Author: Amin Akbari
Publisher:
ISBN: 9781303167799
Category :
Languages : en
Pages : 195
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Book Description
Lean blowoff, flashback and pollutant emission associated with lean premixed combustion of alternative fuels stabilized by high swirl are evaluated in this work. Alternative fuel compositions include blends of natural gas and hydrogen. Lean blowoff refers to events where the fuel-to-air ratio is not sufficient to sustain the reaction. Blowoff is often a dynamic process consisting of several stages. Correlations based on constant Damköhler (Da) number are able to estimate the impact of fuel composition on lean blowoff for the conditions studied. The accuracy of estimating initiation of blowoff is superior compared to estimation of subsequent stages of blowoff. Flashback refers to propagation of the reaction upstream into the premixing zone. In high swirl combustion applications, the concept of a quench criterion has been proposed for predicting flashback. For the present work, this concept only holds for some measured cases, which indicates multiple flashback modes even in high swirl combustion applications. The other major combustion challenge is pollutant emission. In this study NOx, CO, and N2O levels are experimentally measured. In addition, a chemical reaction network (CRN) was developed to study the details of emission formation. To develop a CRN, details of the reacting flow were needed. Hence, computational fluid dynamics (CFD) simulations were conducted. To validate CFD simulations, particle image velocimetry (PIV) and OH* chemiluminescence flame front imaging were applied. OH* chemiluminescence was also employed to visualize the flame structure and shape for different fuel compositions. The CRN simulations indicate that the NNH NOx formation pathway dominates the other formation pathways. Thus, conditions that enhance NNH NOx, such as an increase of hydrogen in fuel composition, and decrease of residence time, will result in more total NOx. The CRN also illustrates how the relative contribution of each NOx formation pathway to total NOx changes with adiabatic flame temperature (AFT). The NNH NOx formation pathway is dominant for AFT below 1900K; the Zeldovich mechanism is dominant for AFT above 1900K. In terms of N2O emissions measured and simulated results suggest the levels are negligible even for very low combustion temperatures.
Author: Derek Dunn-Rankin
Publisher: Academic Press
ISBN: 0080550525
Category : Technology & Engineering
Languages : en
Pages : 282
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Book Description
Combustion under sufficiently fuel-lean conditions can have the desirable attributes of high efficiency and low emissions, this being particularly important in light of recent and rapid increases in the cost of fossil fuels and concerns over the links between combustion and global climate change. Lean Combustion is an eminently authoritative, reference work on the latest advances in lean combustion technology and systems. It will offer engineers working on combustion equipment and systems both the fundamentals and the latest developments in more efficient fuel usage and in much-sought-after reductions of undesirable emissions, while still achieving desired power output and performance. This volume brings together research and design of lean combustion systems across the technology spectrum in order to explore the state-of-the-art in lean combustion and its role in meeting current and future demands on combustion systems. Readers will learn about advances in the understanding of ultra lean fuel mixtures and how new types of burners and approaches to managing heat flow can reduce problems often found with lean combustion such as slow, difficult ignition and frequent flame extinction. The book will also offer abundant references and examples of recent real-world applications. Covers all major recent developments in lean combustion science and technology, with new applications in both traditional combustion schemes as well as such novel uses as highly preheated and hydrogen-fueled systems Offers techniques for overcoming difficult ignition problems and flame extinction with lean fuel mixtures Covers new developments in lean combustion using high levels of pre-heat and heat re-circulating burners, as well as the active control of lean combustion instabilities
Author: Donald McKinley Wicksall
Publisher:
ISBN:
Category : Combustion
Languages : en
Pages : 424
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Book Description
Author: Derek Dunn-Rankin
Publisher: Academic Press
ISBN: 0128005777
Category : Science
Languages : en
Pages : 282
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Book Description
Lean Combustion: Technology and Control, Second Edition outlines and explains the latest advances in lean combustion technology and systems. Combustion under sufficiently fuel-lean conditions can have the desirable attributes of high efficiency and low emissions. The book offers readers both the fundamentals and latest developments in how lean burn (broadly defined) can increase fuel economy and decrease emissions, while still achieving desired power output and performance. This volume brings together research and design of lean combustion systems across the technology spectrum in order to explore the state-of-the-art in lean combustion. Readers will learn about advances in the understanding of ultra-lean fuel mixtures and how new types of burners and approaches to managing heat flow can reduce problems often found with lean combustion (such as slow, difficult ignition and frequent flame extinction). This book offers abundant references and examples of real-world applications. New to this edition are significantly revised chapters on IC engines and stability/oscillations, and new case studies and examples. Written by a team of experts, this contributed reference book aims to teach its reader to maximize efficiency and minimize both economic and environmental costs. Presents a comprehensive collection of lean burn technology across potential applications, allowing readers to compare and contrast similarities and differences Provides an extensive update on IC engines including compression ignition (diesel), spark ignition, and homogeneous charge compression ignition (HCCI) Includes an extensive revision to the Stability/Oscillations chapter Includes use of alternative fuels such as biogas and hydrogen for relevant technologies Covers new developments in lean combustion using high levels of pre-heat and heat recirculating burners, as well as the active control of lean combustion instabilities
Author: Vincent G. McDonell
Publisher:
ISBN:
Category : Gas as fuel
Languages : en
Pages : 198
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Book Description
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: J. Warnatz
Publisher: Springer Science & Business Media
ISBN: 3540453636
Category : Technology & Engineering
Languages : en
Pages : 389
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Book Description
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.
Author: Akhilendra Pratap Singh
Publisher: Springer Nature
ISBN: 9811615136
Category : Technology & Engineering
Languages : en
Pages : 404
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Book Description
This monograph covers different aspects related to utilization of alternative fuels in internal combustion (IC) engines with a focus on biodiesel, dimethyl ether, alcohols, biogas, etc. The focal point of this book is to present engine combustion, performance and emission characteristics of IC engines fueled by these alternative fuels. A section of this book also covers the potential strategies of utilization of these alternative fuels in an energy efficient manner to reduce the harmful pollutants emitted from IC engines. It presents the comparative analysis of different alternative fuels in a variety of engines to show the appropriate alternative fuel for specific types of engines. This book will prove useful for both researchers as well as energy experts and policy makers.
Author: Rodrigo Villalva Gómez
Publisher:
ISBN:
Category :
Languages : en
Pages : 288
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Book Description
Experimental research on lean direct injection (LDI) combustors for gas turbine applications is presented. LDI combustion is an alternative to lean premixed combustion which has the potential of equivalent reduction of oxides of nitrogen (NOx) emissions and of peak combustor exit temperatures, but without some drawbacks of premixed combustors, such as flashback and autoignition. Simultaneous observations of the velocity field and reaction zone of an LDI swirl-stabilized combustor with a mixing tube at atmospheric conditions, with the goal of studying the flame stabilization mechanism, are shown. The flame was consistently anchored at the shear layer formed by the high-speed reactants exiting the mixing tube and the low speed recirculation region. Individual image analysis of the location of the tip of the recirculation zone and tip of the reaction region confirmed previously observed trends, but showed that calculation of the distance between these two points for corresponding image pairs yields results no different than when calculated from random image pairs. This most likely indicates a lag in the anchoring of the flame to changes in the recirculation zone, coupled with significant stochastic variation. An alternate LDI approach, multi-point LDI (MLDI), is also tested experimentally. A single large fuel nozzle is replaced by multiple small fuel nozzles to improve atomization and reduce the total volume of the high-temperature, low velocity recirculation zones, reducing NOx formation. The combustor researched employs a novel staged approach to allow good performance across a wide range of conditions by using a combination of nozzle types optimized to various power settings. The combustor has three independent fuel circuits referenced as pilot, intermediate, and outer. Emissions measurements, OH* chemiluminescence imaging, and thermoacoustic instability studies were run in a pressurized combustion facility at pressures from 2.0 to 5.3 bar.Combustor performance was analyzed for three fuel staging configurations, using local equivalence ratio of the individual circuits as a predictive parameter. Pilot-only mode enabled combustor operation at very low overall equivalence ratios while limiting NOx formation in idle power settings due to its configuration approximating a rich-quench-lean combustor. Pilot and intermediate staging tests demonstrated the range of equivalence ratios that are effective in reducing NOx formation while keeping other pollutants in check; very low equivalence ratio results in high unburned hydrocarbon and carbon monoxide, while very high equivalence ratios result in a detrimental effect as more fuel is routed through the intermediate fuel circuit. Using all three fuel circuits simultaneously in high power operation resulted in very low NOx levels (emissions index at or below 0.5 g/kg), particularly when fuel distribution was such that local equivalence ratio was equal among all circuits. The observed NOx levels compared favorably with other MLDI designs which do not have the operational flexibility of the combustor tested. Thermoacoustic instabilities occurred in the MLDI combustor for some test conditions. The local equivalence ratio of the intermediate fuel circuit was found to be one of the major predictor of the onset of instabilities. Detailed analysis of a two-circuit instability (pilot and intermediate) is presented.
Author: Justin Legg
Publisher:
ISBN: 9781267693037
Category :
Languages : en
Pages : 140
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Book Description
The development of alternative liquid fuels has shifted from fuels such as ethanol and biodiesel, which are often created from food sources, to more advanced feedstocks, such as Algae, and synthetic fuels, such as Fischer-Tropsch diesel and other "renewable" fuels. This study was designed to characterize the physical combustion performance of ethanol, biodiesel, and an algae-derived "Hydrotreated Renewable Diesel." The physical properties of the fuels were characterized in order to describe the atomization behavior. In addition, Gas Chromatography/Mass Spectrometry provided insight into the chemical composition of each fuel. A swirl-stabilized research combustor was used to conduct experiments to simulate gas turbine combustion, and emissions and lean stability limits were measured. At cold-flow conditions, ensemble laser diffraction provided measurements of atomization characteristics, and high-speed cinematography provided additional insight. Most of the fuels had similar atomization characteristics, despite having a wide range of physical properties, which is attributed to the atomization strategy used in this work. However, biodiesel did exhibit larger droplets (5 microns larger on average), indicating that viscosity does have some effect on prompt atomization. Due to the nature of its production, the Hydrotreated Renewable Diesel performed similar to the conventional petroleum fuels, suggesting a high degree of interchangeability with conventional fuels. Ethanol, with the highest oxygen content, and the lowest heating value produced the lowest NOx emissions. Among the fuels examined, differences in emissions were attributed to differences in the evaporation and chemical behavior; with alternative fuels showing benefit over the conventional fuel.
