Dust generation at an underground coal mine working face continues to be a health and safety issue. Prolonged exposure to high concentrations of airborne respirable dust can cause a debilitating and often fatal respiratory disease called Black Lung. In addition, the deposition of float dust in mine return airways poses a serious safety hazard if not sufficiently diluted with inert rock dust. A localized methane explosion can transition into a self-propagating dust explosion. Since dust is a byproduct of various mining activities, such as cutting and loading, crushing, and transportation, the dust-related issues cannot be totally eliminated. However, the adverse health effects and safety concerns can be minimized if a significant amount of the generated dust is removed from the ventilation air by a mechanical device, such as a dust scrubber. Over the last three decades, flooded-bed dust scrubbers integrated into continuous miners have been successfully applied for capturing and removing airborne dust generated at the working face. According to the National Institute for Occupational Safety and Health (NIOSH), a flooded-bed scrubber can achieve more than 90% capture and cleaning efficiencies under optimum conditions. Although flooded-bed scrubbers have proven useful in the vast majority of cases, they have not yet been successfully applied to a longwall face. In the United States, numerous attempts have been made to reduce dust concentration at a longwall face through the application of a scrubber; but, none were successfully implemented. Encouraged by the successful use of a flooded-bed scrubber system at continuous miner faces, this research revisits the flooded-bed scrubber concept for a longwall shearer. For this investigation, a full-scale physical model of a Joy 7LS longwall shearer, modified with an integrated flooded-bed dust scrubber, was designed and fabricated at the University of Kentucky. The scope of work for this research was limited to capturing and cleaning dust generated near the shearer headgate drum only. The mock-up was transported to, and assembled in, the full-scale longwall dust gallery at the NIOSH Pittsburgh Research Laboratory (PRL). Tests were conducted to examine: (1) the effect of the scrubber on headgate-drum dust reduction and (2) the combined effect of the scrubber and splitter sprays on headgate drum dust reduction. Analysis of test results for the scrubber-alone condition indicates a significant dust reduction of up to 57% in the return airway and 85% in the test gallery walkway, whereas the combination of scrubber and splitter-arm sprays shows dust reduction of up to 61% and 96% in the return and walkway, respectively. These results indicate that a flooded-bed scrubber integrated into a longwall shearer can be used as a viable technique to reduce a large portion of airborne dust at a longwall face. Subsequently, a Computational Fluid Dynamics (CFD) model of the longwall gallery and shearer was developed and validated using the results of the experimental study. The CFD simulation results are in good agreement with the experimental results with a maximum of 9.7% variation. This validated CFD model can be used in future research to predict the effects of modifications to the scrubber system, including modifications to the scrubber inlet, to optimize the scrubber design, and to evaluate the effectiveness of adding a tailgate drum dust scrubber.

This master thesis describes the co-firing concept, benefits and opportunities of pretreated biomass in pulverized coal boilers for industrial use. Burning fossil fuels, i.e. coal is under immense political pressure as European Union (EU) and other countries are trying to bring down the CO2 emission. Biomass combustion is already a proven technology and it plays a greater role in reducing CO2 emission. The main objective of this thesis is the brief study of computational fluid dynamics (CFD) modelling to examine the co-firing of greater amount of pretreated biomass and pulverized coal in a 200MWe pulverized coal boiler. Here, we exchange around 50 % of existing fuel in pulverized coal boiler with torrefied biomass. Torrefied biomass aids to increase the efficiency of existing coal boiler and cut down the CO2 emission. In this work, two cases of co-firing of pretreated biomass and coal have been investigated by CFD. Firstly, an experimental work was done in a laboratory scale to have few different types of torrefied biomass with different degrees of torrefaction. The devolatilization kinetics and char oxidation kinetics were also determined by experiments and other parameters have been calculated. One important aspect of this work has been to evaluate the performance of torrefaction based co-firing. Therefore, co-firing case has been compared to the 100 % coal feed case to understand the performance of torrefaction based co-firing. Furthermore, fluid flow, particles trajectories, heat transfer, and different emission behaviors have been studied. In addition, mechanisms of corrosion during co-firing have been studied and a guideline has been provided for corrosion model for analyzing the characteristics of alkali metals and their effects in co-firing coal boiler. The outcome from the CFD simulation indicated that boiler efficiency increases and the net CO2 emission reduced with increasing the biomass percentage in the co-firing system.

Approved for public release, distribution is unlimited / Methods used for designing the ramjet included conic shock tables; isentropic flow tables and the GASTURB code was used for aerothermodynamic performance prediction. The flow field through the proposed geometry was computed using the OVERFLOW code, and small modifications were made. Geometry and solid models were created and built using SolidWorks 3D solid modeling software. A prototype ramjet was manufactured with wind tunnel mounting struts capable of measuring axial force on the model. Shadowgraph photography was used in the Mach 4 supersonic wind tunnel at the Naval Postgraduate School's Turbopropulsion Laboratory to verify predicted shock placement, and surface flow visualization was obtained of the airflow from fuel injection ports on the inlet cone of the model. All indications are that the cold-flow tests were successful. / Ensign, United States Naval Reserve

Made available in DSpace on 2016-06-02T19:56:47Z (GMT). No. of bitstreams: 1 4497.pdf: 8936250 bytes, checksum: a23101fb063b44abfcf0e8b680623fc7 (MD5) Previous issue date: 2012-03-26 / The development of the design of chemical processes has received increasing improvement, incorporating sophisticated mathematical models, which allowed better simulation of its real behavior. The distillation column is one of the most widely used separation equipment in the industry and therefore, its perfect working and optimization are economically crucial factors. Thus, the study of the hydrodynamic in distillation column sieve trays has increased over the years with the purpose to optimize the flow patterns, which is of great importance on the mass and energy transfer efficient. Due to the development of powerful computers, advances in numerical methods and improvement in models of multiphase flows, the investigation of complex flow problems is possible. One way to investigate these problems is to use Computational Fluid Dynamics. Thus, in this work we used commercial package CFD software to predict the hydrodynamics in a sieve tray, with the main objective to evaluate the velocity fields and compare them with the experimental work of Solari and Bell (1986). We proposed a two-fluid model with Eulerian-Eulerian framework, three-dimensional (3D), steady-state and the standard k-ε turbulence model for air/water system at 1 atm. The continuity and momentum conservation equations were used to describe the gas and liquid phases. The simulated sieve tray geometry was based on experimental work of Solari e Bell (1986). The simulation domain included the downcomer region. New sieve tray geometry design was proposed to evaluate the hydrodynamics. The results show the velocity profiles, volume fractions and liquid recirculation zones on the sieve tray for several combination of liquid and gas flow rates. The simulation indicated the presence of recirculation and stagnation zones, and it reproduced satisfactorily the results of Solari e Bell (1986) and the new geometry design reduced the liquid recirculation zones on tray. The proposed methodology in this work proved to be appropriate and the Computational Fluid Dynamics (CFD) techniques presented to be an important tool in the design and optimization of sieve trays. / O desenvolvimento de projetos de processos químicos tem recebido aperfeiçoamento cada vez maior, incorporando modelos matemáticos mais sofisticados, os quais possibilitam uma maior aproximação do seu comportamento real. A coluna de destilação é um dos equipamentos de separação mais empregados na indústria e por isso, o perfeito funcionamento e otimização são fatores economicamente cruciais. Deste modo, o estudo da hidrodinâmica de pratos perfurados em coluna de destilação vem crescendo ao longo dos anos, no intuito de otimizar os fluxos de escoamento, que tem uma grande importância sobre a eficiência na transferência de massa e energia. Com o desenvolvimento de poderosos computadores, avanços em métodos numéricos e aperfeiçoamento em modelos de fluxos multifásicos, é possível a investigação de problemas complexos de escoamentos. Uma das formas de investigar esses problemas é a utilização da Fluidodinâmica Computacional. Assim, neste trabalho foi utilizado um pacote comercial de CFD para prever a hidrodinâmica em um prato perfurado, tendo como objetivo principal avaliar os campos de velocidades e compará-los com o trabalho experimental de Solari e Bell (1986). Foi proposto um modelo de duas equações com abordagem Euleriana-Euleriana, tridimensional (3-D), estado estacionário e o modelo de turbulência k-ε padrão para um sistema ar/água a 1 atm. As equações da continuidade e de conservação de quantidade de movimento foram empregadas no modelo para descrever a fase líquida e a fase vapor. A geometria do prato perfurado foi baseada no trabalho experimental de Solari e Bell (1986), na qual foi incluída a região do downcomer. Uma nova geometria de prato foi proposta para observar a hidrodinâmica. Os resultados mostram os perfis de velocidades, frações volumétricas e zonas de recirculação de líquido no prato perfurado para várias combinações de vazões de líquido e vapor. A simulação indicou a presença de zonas de recirculação e estagnação. A simulação reproduziu satisfatoriamente os resultados experimentais de Solari e Bell (1986) e a nova geometria reduziu as zonas de recirculação de líquido no prato. A metodologia proposta neste trabalho foi adequada e a técnica da Fluidodinâmica Computacional mostrou-se uma ferramenta viável e importante no desenvolvimento e otimização de pratos perfurados.

During the conceptual design stage several concepts are generated, and a few are selected for detailed analyses. CAD models from conceptual design often follow the "over-the-wall" approach for downstream analyses such as FEA, CFD, heat transfer, and vibrations. A CAD-centric approach will be applied to the CAD-to-CFD process to help industry in an ongoing quest to shorten the design cycle time. The CAD-centric approach consists of using the CAD model as a source of data for downstream applications such as mesh generation, and CFD setup. The CAD model used in the CAD-centric approach contains the geometry to be analyzed and non-geometric data required to solve the CFD problem in the form of attributes. Attributes can be associated to entities of the geometry such as the faces, edges, and volumes. Any operations changing geometry require the CAD-centric model be reworked. One class of topology alterations is the discrete feature problem that is encountered when an array of features change in number. A method is proposed, developed and reported on that adapts the CAD-centric approach to account for discrete feature changes that occur during preliminary design.

The purpose of this research is to develop and architect a preliminary multidisciplinary design optimization (MDO) tool that creates multiple types of generalized rocket fairing models. These models are sized relative to input geometric models and are analyzed and optimized, taking into account the primary objectives, namely the structural, thermal, and aerodynamic aspects of standard rocket flights. A variety of standard nose cone shapes is used as optimization proof of concept examples, being sized and compared to determine optimal choices based on the input specifications, such as the rocket body geometry and the specified trajectory paths. Any input models can be optimized to their respective best nose cone style or optimized to each of the cone styles individually, depending on the desired constraints. Two proof of concept example rocket model studies are included with varying sizes and speeds. Both have been optimized using the processes described to provide delineative instances into how results are improved and time saved. This is done by optimizing shape and thickness of the fairings while ascertaining if the remaining length downstream on the designated rocket model remains within specified stress and temperature ranges. The first optimized example exhibits a region of high stress downstream on the rocket body model that champions how these tools can be used to catch weaknesses and improve the overall integrity of a rocket design. The second example demonstrates how more established rocket designs can decrease their weight and drag through optimization of the fairing design.