The purpose of this research was to determine if it is feasible to apply Lorentz mixing to supersonic diffusion flames, such as those found in SCRAMjet engines. The combustion rate in supersonic diffusion flames is limited by the rate at which air and fuel mix. Lorentz mixing increases turbulence within a flow, which increases the rate at which species mix and thus increases the rate of combustion. In order to determine the feasibility of Lorentz mixing for this application, a two-dimensional model of supersonic reacting flow with the application of a Lorentz force has been examined numerically. The flow model includes the complete Navier-Stokes equations, the ideal gas law, and terms to account for diffusion of chemical species, heat release due to chemical reaction, change in species density due to chemical reaction, and the Lorentz forces applied during Lorentz mixing. In addition, the Baldwin-Lomax turbulence model is used to approximate turbulent transport properties. A FORTRAN program using the MacCormack method, a commonly used computational fluid dynamics algorithm, was used to solve the governing equations. The accuracy of the program was verified by using the program to model flows with known solutions. Results were obtained for flows with Lorentz forces applied over a series of power levels and frequencies. The results show significant increases in the rate of combustion when Lorentz mixing is applied. The amount of power required to drive Lorentz mixing is small relative to the rate at which energy is released in the chemical reaction. An optimum frequency at which to apply Lorentz mixing was also found for the flow being considered. The results of the current study show that Lorentz mixing looks promising for increasing combustion rates in supersonic reacting flows, and that future study is warranted. In particular, researchers attempting to improve combustion in SCRAMjet engines may want to consider Lorentz mixing as a way to improve combustion. / Graduation date: 1997

In this study the catalytic pyrolysis and combustion characteristics of Turkish coal samples in O2/N2 and O2/CO2 (oxy-fuel conditions) ambient conditions were explored and the evolution of emissions during these tests was investigated using non-isothermal Thermo-gravimetric Analysis (TGA) technique combined with Fourier Transform Infrared (FTIR) spectroscopy. Potassium carbonate (K2CO3), calcium hydroxide (Ca(OH)2), iron (III) oxide (Fe2O3) and iron (III) chloride (FeCl3) were employed as precursors of catalysts to investigate the effects of potassium (K), calcium (Ca) and iron (Fe). Furthermore the effects of these catalysts on calorimetric tests of Turkish coal samples were investigated. TGA-FTIR pyrolysis tests were carried out in 100 % N2 and 100 % CO2 ambient conditions which are the main diluting gases in air and oxy-fuel conditions. Lignite pyrolysis tests revealed that the major difference between pyrolysis in these two ambient conditions was observed beyond 720

Orientador: Caio Glauco Sanchez / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-26T13:07:12Z (GMT). No. of bitstreams: 1 Simoes_SheilaGrandinetti_M.pdf: 2912915 bytes, checksum: d05a793ded2290cefd198b098da0f329 (MD5) Previous issue date: 2014 / Resumo: Este estudo teve como objetivo o projeto e a construção de um fogão doméstico alimentado continuamente por etanol, com a avaliação de rendimento de queima. O Brasil como o maior produtor de etanol, produzido a partir da cana-de-açúcar e elevado grau de desenvolvimento tecnológico, tornou esse combustível uma opção viável para substituição do GLP (gás liquefeito de petróleo) em fogões domésticos. Para a utilização do etanol foram necessários estudos para modificações tanto na forma de armazenamento, como no desenvolvimento de um novo design do queimador, visando uma queima compatível ao combustível já utilizado. Foram feitas análises termodinâmicas, a fim de descobrir os parâmetros mais relevantes na modificação. A partir dessas modificações foram desenvolvidos dois queimadores que se encaixam nas categorias semirrápido e auxiliar, com eficiências de 69% e 72% respectivamente, enquadrando ambos os queimadores na categoria A de eficiência / Abstract: This study aimed the project and built of a household stove fed continuously by alcohol fuel, evaluating burning efficiency. Brazil as the largest sugar-cane ethanol producer and with high technologic development degree, made this fuel a viable option to replace LPG (liquefied petroleum gas) in household stoves. For the utilization of ethanol, studies have been necessary both for the modification of storage and the development of a new burner¿s design, seeking a compatible burn with the already used fuel. Thermodynamics analyses have been made to discover the most relevant parameters for the modification.From these modifications, were developed two burners with efficiency of 69% and 72%, that fits onto the categories of semi-fast and auxiliary in brazilian norm, respectively, both in category A from brazilian norm of efficiency / Mestrado / Termica e Fluidos / Mestra em Engenharia Mecânica

Gold-based catalysts can be replaced with platinum group catalysts in catalytic automotive exhaust aftertreatment if their thermal stability and durability issues can be resolved. Hence, one of the potential markets for gold catalysis is the automotive after treatment market, our interest is to synthesize a gold-based catalyst which has practical applications in automotive industry specifically for diesel-methane dual fuel low-temperature combustion strategy where the exhaust temperature is varying from ~ 200 to400° C. Our research focused on synthesizing a bimetallic gold-copper catalyst which is not only highly active for CO oxidation reaction but also sinter-resistant at temperatures normally observed at LTC engine exhaust. The Au-Cu@SiO2 catalyst exhibited excellent efficacy for CO oxidation with >95% conversion to CO2 achieved at 300 °C. While the presence of Cu enhanced CO conversion at low to intermediate temperatures (50-300 °C), silica encapsulation of the Au-Cu nanocomposites facilitated for remarkable stability of the catalyst. Moreover, the catalyst exhibited remarkable stability at high reaction temperatures which could be attributed to the SiO2 encapsulation of nanoparticles. The activity and stability of Au-Cu@SiO2 catalyst are suitable for its application in automotive after treatment devices, especially in low-temperature combustion engine exhaust.

No description available.

A new method of power production, called pressurized oxy-fuel combustion, burns coal with CO2 and oxygen, rather than air, bringing us closer to the end goal of developing zero emission coal-fired utility boilers. However, high-pressure, high-temperature systems such as these are under-studied, and their behavior is difficult to measure. An accurate model for previously untested conditions requires data for validation. The heat release profile of flames and their radiative intensity is one of the key data sets required for model validation of an oxy-coal combustion system. A radiometer can be used to obtain the necessary radiative heat flux data. However, several studies show significant measurement errors of past radiometer designs. This work focuses on developing a narrow angle radiometer that can be used to describe radiative heat transfer from a pressurized oxy-coal flame. The sensitivity of the instrument to outside environmental influences is thoroughly examined, making it possible to obtain the axial radiative heat flux profile of the flame in a 100kW pressurized facility by accurately converting the measured quantities into radiative heat flux. Design aspects of the radiometer are chosen to improve the accuracy of radiative heat flux measurements as well as conform to the physical constraints of the 100kW pressurized facility. The radiometer is built with a 0.079-inch aperture, an 8.63-inch probe internally coated with high emissivity coating, four baffles spaced evenly down the length of the probe, no optic lens, a thermopile as the sensor, argon purge gas, and a water-cooled jacket. The radiometer has a viewing angle of 1.33 degrees. The instrument is calibrated with a black body radiator, and these calibration data are used in combination with radiation models to convert the radiometer signal in mV to radiative heat flux in kW/m2. Environmental factors affecting accuracy are studied. The results of the calibration data show that the radiometer measurements will produce a calculated heat flux that is accurate to within 5.98E-04 kW/m2.

<p>This licentiate thesis describes development of modellingtools, experimental physical modelling and numerical modellingto simulate real combustion processes for advanced industrialutility boiler before and after retrofit.</p><p>The work presents extended study about formation,destruction and control of pollutants, especially NOx, whichoccur during combustion process.</p><p>The main aim of this work is to improve mixing process incombustion chamber. To do this, the optimization of placementand direction of additional air and fuel nozzles, the physicalmodelling technique is used. By using that method, it ispossible to obtain qualitative information about processes,which occur in the real boiler. The numerical simulationsverify the results from physical modelling, because duringmathematical modelling quantitative informations about flow andmixing patterns, temperature field, species concentration areobtained.</p><p>Two 3D cases, before and after retrofit, of pulverized fuelfired boiler at 125 MW output thermal power are simulated. Theunstructured mesh technique is also used to discretize theboiler. The number of grid was 427 656 before retrofit and 513362 after retrofit. The comparisons of results of numericalsimulation before and after retrofit are presented. The resultsfrom physical modelling and numerical simulation are alsoshown.</p><p>Results present that nozzles of additional air and fuel givea considerably better mixing process, uniform temperature fieldand CO2 mass fraction. The whole combustion chamber worksalmost as a "well stirred reactor", while upper part of boilerworks as a "plug flow reactor".</p><p>Differences between from measured of temperatures andpredicted temperatures are not too big, the maximum differenceis about 100 K. It seems, that calculated temperatures showgood agreement with measurement data.</p><p>The results illuminate the potential of physical andnumerical modelling methods as promising tools to deal with thecomplicated combustion processes, even for practicalapplication in the industry.</p><p><b>Keywords:</b>air staging, fuel staging, boiler, furnace,computational fluid dynamics, numerical simulation, pollutants,physical modeling, pulverized fuel combustion.</p>

Oxy-fuel combustion technology, which is based on burning coal in a mixture of oxygen and recycled flue gas (RFG), is suggested as one of new promising technologies for capturing CO2 from power plants. In this thesis study, the pyrolysis and combustion behaviour of various fuels including imported coal, petroleum coke, two different types of indigenous lignites, olive residue and their blends with different proportions in air and oxy-fuel conditions were investigated by using non-isothermal thermogravimetric method (TGA) coupled with Fourier-transform infrared (FTIR) spectrometer. Pyrolysis tests were carried out in nitrogen and carbon dioxide environments, which are the main diluting gases of air and oxy-fuel environment, respectively. Pyrolysis results reveal that weight loss profiles are similar up to high temperature zone in both pyrolysis environments, indicating that CO2 behaves as an inert gas in this temperature range. However, further weight loss takes place in CO2 atmosphere v after 700oC due to CO2-char gasification reaction which is observed in pyrolysis of all fuel samples. Combustion experiments were carried out in four different atmospheres / air, oxygen-enriched air environment (30 % O2 &ndash / 70 % N2), oxy-fuel environment (21 % O2 &ndash / 79 % CO2) and oxygen-enriched oxy-fuel environment (30 % O2 &ndash / 70 % CO2). Combustion experiments show that replacing nitrogen in the gas mixture by the same concentration of CO2 does not affect the combustion process significantly but leads to slight delay (lower weight loss rate and higher burnout temperature) in combustion. Overall comparison of weight loss profiles shows that higher oxygen content in the combustion environment is the dominant factor affecting the combustion rather than the diluting gas. As O2 concentration increases profiles shift through lower temperature zone, peak and burnout temperatures decrease, weight loss rate increases and complete combustion is achieved at lower temperatures and shorter times. Pyrolysis and combustion behaviour of three different fuel blends were also investigated. Results reveal synergistic interactions in combustion tests of all blends in all combustion environments. During pyrolysis and combustion tests gaseous products CO2, CO, H2O, CH4, SO2 and COS were identified in flue gas and analyzed by using FTIR. Results indicate that higher CO and COS formation take place during pyrolysis tests due to gasification reaction in CO2 atmosphere at high temperature zone. Gaseous species evolution trends in combustion tests are found specific for each fuel. However, evolution trends slightly shift to lower temperatures in oxygen-enriched conditions.

Fossil fuel combustion produces fly-ash particles that are released into the atmosphere and deposited in the environment. A particularly characteristic kind of fly-ash is spheroidal carbonaceous particles. They are composed of an amorphous carbon matrix in which other elements are dispersed. The elemental carbon content makes them very resistant to chemical degradation and these particles can be relatively easily extracted from sediment and soil samples using a method described in this thesis. The distribution of spheroidal carbonaceous particles in lake sediment profiles, surface sediments and forest soils has been studied. Cores from several Swedish lakes have been analysed and, although the lakes are from different parts of the country, consistent trends in the deposition of the carbonaceous particles have been found. The analyses of dated cores show that the carbonaceous particle deposition in the sediments follows the same general pattern as statistics for Swedish coal and oil combustion over the last two centuries. This indicates that the sediment records reflect the history of the atmospheric deposition of particulate pollutants from fossil fuel combustion. Analysis of surface sediment samples provides an integrated picture of the deposition over the preceding few years and can be used to indicate the contemporary geographical pattern of deposition from the atmosphere. Two sets of surface sediment samples (0-1 cm) were analysed. One comprised samples from 66 lakes around Sweden's second largest city, Gothenburg, and showed very high carbonaceous particle concentrations within a distance of 50 to 100 km from the city. The second set comprised surface sediment samples from 114 lakes distributed all over Sweden. This survey of Sweden demonstrated a geographical north-south gradient with more than a hundred times higher particle concentrations in the south than in the north. This distribution is similar to the distribution of other air pollutants (data obtained from a moss survey and an air monitoring program) and suggests that carbonaceous particles in palaeolimnological investigations of air pollution, can be used as tracers for pollutants that are otherwise difficult to determine in lake sediments. Spheroidal carbonaceous particles also accumulate in soils, and forest soil samples can be used for geographical surveys of particle deposition. In Swedish podzol soils the particles mainly accumulate in the thin organic horizon and concentrations in this layer reflect the total deposition since industrialisation, although most will have been deposited during the last few decades. Since the spheroidal carbonaceous particle record in Swedish lake sediments has a characteristic temporal pattern, carbonaceous particle profiles can be used for indirect dating of recent sediment cores. Analyses of multiple sediment cores from three lakes demonstrate that carbonaceous particles can also be used for studies of sediment distribution in lake basins. Results from Gårdsjön indicate that the acidification of the lake changed sediment distribution processes from a normal sediment focusing regime to a more even distribution of sediments over the lake bottom. Liming of the lake seems to have restored normal sedimentation processes. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1992, Härtill 8 uppsatser</p> / digitalisering@umu

Carbon capture and storage technologies are necessary to start lowering greenhouse gas emissions while continuing to utilize existing thermal power generation infrastructure. Calcium looping is a promising technology based on cyclic calcination/carbonation reactions which utilizes limestone as a sorbent. Steam is present in combustion flue gas and in the calciner used for sorbent regeneration. The effect of steam during calcination on sorbent performance has not been extensively studied in the literature. Here, experiments were conducted using a thermogravimetric analyzer (TGA) and subsequently a dual-fluidized bed pilot plant to determine the effect of steam injection during calcination on sorbent reactivity during carbonation. In a TGA, various levels of steam (0-40% vol.) were injected during sorbent regeneration throughout 15 calcination/carbonation cycles. All concentrations of steam were found to increase sorbent reactivity during carbonation. A level of 15% steam during calcination had the largest impact. Steam changes the morphology of the sorbent during calcination, likely by shifting the pore volume to larger pores, resulting in a structure which has an increased carrying capacity. This effect was then examined at the pilot scale to determine if the phase contacting patterns and solids heat-up rates in a fluidized bed were factors. Three levels of steam (0%, 15%, 65%) were injected during sorbent regeneration throughout 5 hours of steady state operation. Again, all levels of steam were found to increase sorbent reactivity and reduce the required sorbent make-up rate with the best performance seen at 65% steam.