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Thesis (M.A. Sc.)--University of Toronto, 2004. / Adviser: J.P. Sislian.

Thesis (M. S.)--Aerospace Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Zinn, Ben; Committee Member: Ferri, Aldo; Committee Member: Lieuwen, Timothy; Committee Member: Prasad, J. V. R.; Committee Member: Ruzzene, Massimo.

Combustion of Minto coal, a sub-bituminous eastern coal which is highly agglomerating and has a high sulphur content, was carried out in a 0.15 m internal diameter half-column spout-fluid bed combustor in inert beds of sand, with limestone addition for sulphur capture. The average bed temperature ranged from 800 to 900°C, flue gas oxygen level was 2.5 to 11.0%, auxiliary to total air was 0 to 0.50, and Ca/S molar ratio was 2.5. High vale coal was employed in hydrodynamic runs. Aspects studied included combustion efficiency, sulphur capture efficiency, axial and radial temperature profiles, axial O₂ and CO₂ concentration profiles, axial SO₂ concentration profiles, minimum spouting velocity, spouting stability, and maximum spoutable bed height. The principal problem encountered with Minto coal in this equipment was agglomeration during the heat-up period. A spout-fluid bed has proved to be great favourable for handling agglomerating coal relative to the standard spouted bed. When limestone was used as bed material, less sintering was encountered. However, limestone could not stand up to spouting for prolonged periods because of excessive attrition. Combustion efficiencies were found to be higher than 80% in the temperature range of 800 to 900°C without solid fines recycle. An increase of temperature between 800°C and 840°C was beneficial for combustion efficiency, while a further increase up to 885°C did not seem to have a significant effect on combustion efficiency. Increase of auxiliary/total air ratio was favourable to combustion efficiency at elevated temperatures. Sulphur capture efficiency passed through a maximum with increasing temperature between 800°C and 900°C The maximum value was obtained at around 830°C. NOx emission increased linearly with increasing flue gas oxygen level. No abrupt temperature increase above the bed surface was observed in both spouted and spout-fluid beds investigated in the present study. Temperature may increase above the bed surface for low excess oxygen runs in view of the substantial amount of combustion found to occur in the freeboard. Temperatures were more uniform after the introduction of auxiliary air. Most oxygen was consumed below the bed surface. Axial profiles showed a significant SO₂ jump in the spout over the bed height. Combustion and sulphation could be considered to occur in two main stages: (1) Combustion of carbon, at the same time as most of the sulphur is released. (2) Sulphation of the sorbent. The Mathur and Gishler (1955) and Wu et al. (1987) equations gave poor agreement with the minimum spouting velocity, Ums, over the entire range of temperature. For large particles Ums tended to increase with increasing temperature, while for small particles it decreased with increasing temperature. Gas viscosity should be taken into consideration for predicting Ums. A considerably greater effect of auxiliary to total air ratio, q/Qt, on total minimum spouting velocity was found at elevated temperatures than at room temperature. At the maximum spoutable bed height, the value of Um/Umf was found to decrease with increasing temperature and to be smaller than unity at elevated temperatures. The McNab and Bridgwater (1977) expression correctly predicted the observed trends of Hm and worked reasonably well at high temperatures, although it was found to over-predict Hm at lower temperatures. Hm decreased with increasing temperature for all particle sizes, with a faster decrease for smaller particles. Fluidization in the annulus was never observed as the termination mechanism of spouting at high temperatures. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

A thesis submitted to the faculty of engineering university of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy Johannesburg 1991 / Analysis of temperatures measured in an experimental coal bed (using the classical conductive-convective approach) confirm previously published permeabilities of similar beds, and furthermore validate the use of heat- transfer coefficients at exposed surfaces of coal stockpiles, The range of the estimated heat transfer coefficients is similar to natural convective coefficients at flat horizontal surfaces, which is expected. [Abbreviated Abstract. Open document to view full version] / GR2017

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by John Adam Keklak. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Stephen Gregory Poulos. / M.S.

Thermoacoustic engines convert thermal energy into acoustic energy with few or no moving parts, thus they require little maintenance, are highly reliable, and are inexpensive to produce. These traits make them attractive for applications in remote or portable power generation, where a linear alternator converts the acoustic power into electric power. Their primary application, however, is in driving thermoacoustic refrigerators, which use acoustic power to provide cooling at potentially cryogenic temperatures, also without moving parts. This dissertation examines the feasibility of a new type of thermoacoustic engine, where mean flow and an internal pulse combustion process replace the hot heat exchanger in a traditional closed cycle thermoacoustic engine, thereby eliminating the heat exchangers cost, inefficiency, and thermal expansion stresses. The theory developed in this work reveals that a large temperature difference must exist between the hot face of the regenerator and the hot combustion products flowing into it, and that much of the convective thermal energy input from the combustion process is converted into conductive and thermoacoustic losses in the regenerator. The development of the Thermoacoustic Pulse Combustion Engine, as described in this study, is designed to recover most of this lost thermal energy by routing the inlet pipes through the regenerator to preheat the combustion reactants. Further, the developed theory shows that the pulse combustion process has the potential to add up to 7% to the engines acoustic power output for an acoustic pressure ratio of 10%, with linearly increasing contributions for increasing acoustic pressure ratios. Computational modeling and optimization of the Thermoacoustic Pulse Combustion Engine yield thermal efficiencies of about 20% for atmospheric mean operating pressures, though higher mean engine pressures increase this efficiency considerably by increasing the acoustic power density relative to the thermal losses. However, permissible mean engine pressures are limited by the need to avoid fouling the regenerator with condensation of water vapor out of the cold combustion products. Despite lower acoustic power densities, the Thermoacoustic Pulse Combustion Engine is shown to be well suited to portable refrigeration and power generation applications, due to its reasonable efficiency and inherent simplicity and compactness.

Soot is a combustion generated pollutant that is both a direct risk to human health and a contributing source to global environmental change. Soot can also be a controlling factor in heat transfer inside combustion systems. Thus there is a growing interest in being able to measure soot and understand its production in practical, turbulent combustion environments. Therefore, the specific objectives of this research work were: (1) developing a way to measure velocity of sooty regions that is compatible with existing methods for measuring temporally and spatially resolved soot concentration fields and (2) using these methods to make quantitative measurements of soot in an unsteady, turbulent-like combustor. The Particle Vaporization Velocimetry (PVV) technique was developed and is compatible with Laser Induced Incandescence (LII), a soot concentration measurement approach. PVV is a flow tagging approach, where a high intensity laser (~2-3 J/cm2) is used to vaporize a small region in the soot field. This approach was demonstrated to produce a long lasting and easily readable flow tag that allows for velocity measurements over a wide range of velocities. LII proved to be the best method for detection the motion of the tag after a fixed delay. PVV and LII were used to measure velocity and two-dimensional soot concentration fields in an acoustically excited burner. In addition, images of soot luminosity were obtained. Both laminar and transitional acetylene diffusion flames were studied. The results reveal that strong acoustic forcing can significantly reduce total flame soot, as well as maximum soot concentrations, while simultaneously increasing the average soot temperature. The influence of acoustically generated vortices on soot formation was studied, and soot and products mixture mostly likely dominant high soot concentration regions. Eventually, these mixtures will be propagated downstream and oxidized as a diffusion flame.