Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2014-11-10T12:28:16Z No. of bitstreams: 0 / Made available in DSpace on 2014-11-10T12:28:16Z (GMT). No. of bitstreams: 0 / O dissilicato de ítrio (Y2Si2O7) por apresentar propriedades luminescentes consideráveis, é um potencial substituto dos óxidos de terras raras na tecnologia de queimadores de gás para iluminação. Em processos de conformação a partir de suspensões, o controle da estabilidade das partículas em meio líquido consiste em uma importante etapa para a produção de componentes com microestrutura homogênea e estabilidade estrutural. Neste sentido, este trabalho apresenta estudos sobre o comportamento de superfície, de estabilidade e reológico de suspensões aquosas de Y2Si2O7 e β-Y1,95Dy0,05Si2O7 com o objetivo de preparar suspensões compatíveis para o processo de conformação por réplica, usando-se fibras vegetais como matriz para a confecção de componentes reticulados para queimadores de gás. Neste estudo foram avaliados parâmetros determinantes na estabilidade e comportamento de fluxo das suspensões, como também a luminescência estimulada pela temperatura desses materiais na forma de pó e a eficiência radiante do protótipo de queimador de gás. Os resultados obtidos para o β-Y1,95Dy0,05Si2O7 comparados com a ítria (Y2O3) e concentrado de terras raras contento ítria (YTR) mostram-se promissores. Desenvolveu-se por processamento coloidal do β-Y1,95Dy0,05Si2O7 e utilizando-se o processo de conformação por réplica a partir da esponja vegetal Lufa Cylindrica, um protótipo de lâmpada de queimador de gás com boa resistência mecânica ao manejo, emissividade espectral no visível (λ=580nm) e eficiência radiante de 13%, com grande potencial para iluminação de ambientes internos de acordo com as recomendações da Comissão Internacional de Iluminação (CIE). / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

This work deals with general drifts in the sphere of plasma cutting and with technological possibilities of plasma ray with intention on individual parameters of plasma designations. Here is described temporary state and direction of development of consumer parts, burners and sources for plasma cutting. Detailed adumbration of direction of development is described in the peroration.

The diploma thesis is focused on the combustion of the low calorific gaseous fuels. The first part is devoted to the characterization and usage of low calorific fuels. Then combustion theory focused mainly on emissions and thermodynamics. Next characterization of burners and their modifications for low calorific value fuels is described. Safe storage and handling of chosen gases is also included in the last chapter of the theoretical part. Practical part includes the description of the laboratory experiment, which was a part of this thesis. It consists of the experiment description, experimental plan, calculation and evaluation of emissions, high and low heating value, density, flame temperatures and heat flux. Laboratory experiment was carried out with different fuels. Low calorific fuels were simulated by gradual increase of the concentration of inert gasses in the natural gas. Increased concentration of inert gasses had positive effect on the emissions. Measurement of the flame temperatures confirmed that the decrease of emissions corresponds to the inert gas addition to the noble fuel. Heat flux and thermal efficiency of the combustion was almost identical for each configuration.

La réduction des émissions polluantes des turboréacteurs nécessite une plus grande maîtrise du dimensionnement du système d’injection du mélange air-carburant au sein de la chambre de combustion.L’objectif de la thèse est d’améliorer la compréhension de la dynamique des écoulements swirlés, rencontrés dans les chambres aéronautiques. La simulation aux grandes échelles, qui exploite les super-calculateurs les plus puissants, est devenue un outil d’analyse incontournable. Cependant, la taille des simulations et le volume de données générées rendent difficile l’extraction des phénomènes à grande échelle. A cette fin, de nouvelles méthodes de post-traitement parallèles qui permettent d’accéder à l’évolution temporelle des structures tourbillonnaires dans des géométries complexes sont proposées.Ces méthodes sont appliquées à l’étude de la dynamique de flammes swirlées diphasiques dans lesquelles les structures cohérentes interagissent avec la zone réactive et le brouillard de gouttes. / The reduction of pollutant emissions of aeronautical devices requires to optimize the design of the injection systems in the combustion chamber. The objective of this work is to improve the understandingof the flow dynamics in swirl stabilized burners. Large Eddy Simulation has become a major tool for the analysis of such flows. The steady increase in computational power enables to perform high-fidelity simulations, that generates a large amount of data, making it difficult to extract relevant information regarding the large scale phenomena. To this aim, massively parallel post-processing methods, suited for complex geometries, were developed in order to extract large-scale structures in turbulent flows. These methods were applied to simulations of spray flames in swirl burners, to get a better insight of how the large scale structures interact with the flame topology and the spray dynamics.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg 2016 / Stringent worldwide emissions legislation, the drive to lower carbon emissions, together with the ever increasing demand to preserve the environment has led to a considerable demand for cleaner and more efficient coal combustion technologies. A primary technology for the reduction of emissions of oxides of nitrogen (NOx) is the installation of low NOx coal combustion burners. Extensive research into various burner characteristics and, in particular, the aerodynamic characteristics required to improve combustion performance of low NOx coal burners has been extensively undertaken and is ongoing. In this work the aerodynamic behaviour of a full-scale, aerodynamically staged, single low-NOx coal burner was numerically investigated. The objective of the study was to develop a single low NOx burner CFD model in Ansys Fluent, to better characterize and understand the flame shape in terms of the temperature profile achieved. CFD serve as an additional tool to assist with plant optimization, design proposals and occurrence investigations. To have confidence in the single burner coal combustion CFD model, the results of the model were compared to data obtained from an existing operational low NOx burner on site during a pre-defined load condition. To further improve on the theoretical CFD combustion model, drop tube furnace (DTF) experiments have been done to calculate the single rate Arrhenius kinetic parameters (pre-exponential factor and activation energy) for coal devolatilization and char combustion of the specific South African coal used. The combustion CFD simulations showed with a lower than design air flow through the burner, a reduced amount of swirl was achieved. This reduced amount of swirl produces a jet like flame and influences the way in which the combustion species are brought together. Under these operating conditions the flame distance from the burner mouth was predicted to be 1.2 (m). A very promising result was obtained through CFD and compared well with the in-flame temperature measurement obtained through the burner centre-line of approximately 1.4 (m). In an attempt to improve the aerodynamic profile of the burner under the same operating conditions the swirl angle on the tertiary air (TA) inlet was increased. The increased swirl on the TA inlet of the burner showed an improvement on the aerodynamic profile and had a significant impact on the temperature distribution within the flame. The increased swirl resulted in an improved flame distance of approximately 0.5 (m) from the burner mouth. The effect of increased swirl on the temperature profile of the flame displayed the aerodynamic dependence of the low NOx burner on combustion performance. / MT2017

The master’s thesis deals with the environmental aspects of combined heat and power station Červený Mlýn (Red Mill). The introductory part of the thesis focuses on the current production technology and the electricity balance of the power station. The heat and power station (also called combined cycle heat and power plant) is scrutinized in terms of emissions sources, focusing on pollutant emissions to air in the following chapter. In this part of the thesis the quantities of the released emissions, namely solid particulate matter (TZL), sulfur dioxide (SO2), carbon dioxide (CO2) are also calculated. The calculation is worked out according to the valid Czech legislation. Further on, the current production technology of the power station is compared with the best available technologies according to the valid directive 2008/1/EC of the European Parliament and of the Council concerning integrated pollution prevention and control. The last chapter presents the innovative technologies which could possibly be installed to reduce pollution emissions (especially nitrogen oxides - NOx) to air at the heat and power station Červený Mlýn.