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Experimental investigation of syngas combustion using a novel two-stage combustor
No full textIn recent years, syngas has gained research interest as the focus shifts from fossil to renewable fuels. Syngas generated from biomass such as wood, agricultural residue, and paper is a promising fuel to achieve net-zero carbon emissions. It is mainly composed of CO, H2 and diluents such as CO2 and N2. The combustion characteristics of biomass-derived syngas significantly differ from the well-studied fuels in terms of calorific value, stoichiometric fuel-to-air ratio, ignition delay, and flammability limits. In the present study, a combination of catalytic and swirl combustion is explored using a two-stage combustor to achieve low emissions without losing combustion stability. The first stage is the catalytic stage, and the second stage is the swirl stage. A preheated and premixed syngas-air mixture (Фfirst = 4) is supplied to the first stage, where syngas is consumed partially. The remaining unburnt fuel is combusted using an oxidizer in the second stage. In this stage, the flame is stabilized by two co-centric swirling streams where the inner stream is the unburnt gases coming from the first stage, and the outer stream is the oxidizer. By changing the swirling direction of the streams, co and counter-swirl flames are obtained.
In this thesis, the experimental results are described in six parts organized as follows. The first part of the study investigates the catalytic combustion of syngas in the first stage at an equivalence ratio of 4. The transient temperature measurements show three distinct regions of catalytic combustion: kinetically controlled, light-off, and steady-state regions. It is found that the start-up time depends on the conductivity of the monolith placed inside the first stage. The NOx emission is found to be low (< 1 ppm) at the exit.
The second part of the study explores the lean unconfined co/counter-swirl flame stabilized in the second stage. Both flames can be stabilized at a higher flow rate, maintaining a constant overall equivalence ratio. Co-swirl creates a ‘U’-shaped flame, and counter-swirl creates a more distributed and compact flame. A low NOx concentration (< 20 ppm) is found in the flame; however, the CO emission is more than 10000 ppm.
In the third part, the emission characteristics are studied, with the second stage being confined. The emission, temperature, flame shape and noise are investigated at three overall equivalence ratios (Фoverall). The CO emission reduces drastically in the presence of confinement, and the emission is found to be ~10 when Фoverall = 0.55. The NOx emission is below 2 ppm for all cases. The shape of co and counter-swirl flames behave differently when Фoverall changes. Planar laser-induced fluorescence (PLIF) shows the radicals are well distributed over the combustor for co/counter-swirl flames at a higher equivalence ratio, unlike existing studies. Particle image velocimetry (PIV) indicates that the flame shape is related to the shape of the inner recirculation zone. The sound pressure level (SPL) for co/counter-swirl flames is ~110 dB. The frequency domain contains a dominating peak at all Фoverall. The high-speed OH* chemiluminescence (5 kHz) confirms that the combustion is exciting the axial mode of the combustor, which is captured in the noise data.
The sound pressure level can be reduced by changing the O2 concentration in the oxidiser stream. Thus, in the fourth part of the thesis, we investigate the effect of O2 concentration in the oxidizer stream on swirling flames, which is discussed in the fourth part. The OH* chemiluminescence intensity reduces, and flame height increases when O2 concentration decreases. The sound pressure level (SPL) also shows a decreasing trend with O2. The global luminosity calculated from high-speed chemiluminescence indicates that the peaks corresponding to axial mode and PVC are suppressed at low O2 concentrations. In terms of emissions, CO emission increases with a reduction in O2. The feasibility of achieving distributed combustion is assessed from emission, chemiluminescence intensity, SPL, and combustion stability. It is found that the co-swirl configuration is suitable for studying distributed combustion.
In the fifth part, we investigated the combustion dynamics for co and counter-swirl flames. The noise emitted by the combustor shows signatures of intermittency. Pressure signals can be divided into periodic and aperiodic zones, and aperiodic epochs randomly appear between periodic epochs. The high-speed OH* chemiluminescence unravels two motions of the combustion. One oscillates in the axial direction, and the other represents the precessing vortex core (PVC) motion. Axial fluctuation of heat release decreases with an increase in momentum ratio; however, the PVC motion remains prevalent. Interestingly, both fluctuations are suppressed when the oxygen percentage is reduced to 13.13%, indicating that low-oxygen dilution can be an effective strategy to reduce combustion instability.
Finally, in the last part of the study, the effect of momentum ratio (M), density ratio and heat-release rate on the flow field is studied in detail. For counter-swirl configuration, the flow field shows a drastic change at M = 1.7 as the vortex breakdown mode changes from bubble to conical form. The vortex breakdown mode influences the shape of the flame. In the bubble mode, the flame is distributed, whereas ‘V’-shaped for the conical mode.
Thus, the current study has led to an improved understanding of fuel-rich catalytic combustion and shape, dynamics, and flow field of co/counter-swirl flames under various conditions. The present study also establishes that the two-stage rich-catalytic lean-swirl stabilized combustor is suitable for stationary power production applications with ultra-low NOx and low CO emissions
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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