Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 24 for “"downdraft"”.
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Downdraft gasification of biomass
… affecting the gasification process within downdraft gasifiers using biomass feedstocks. In addition to investigations with an open-core gasifier, a novel open-topped throated gasifier was designed and used. A sampling system was designed and installed to determine the water, tar and …
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Downdraft impacts on tropical convection
Downdrafts are an integral part of the convective cycle, and have been observed and documented for more than a hundred years. But many questions still surround convective downdrafts and their most difficult to observe properties. These questions have made the parameterization of convective …
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Gasification of biomass in a downdraft reactor
The objective of this study was to design, construct, commission and operate a laboratory scale gasifier system that could be used to investigate the parameters that influence the gasification process. The gasifier is of the open-core variety and is fabricated from 7.5 cm bore quartz glass tubing. …
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Gasification of rubberwood in a downdraft gasifier
… fabrication and commissioning of a throated downdraft gasifier in Malaysia. The gasifier was subsequently used to investigate the effect of moisture content, dry wood capacity and particle size of rubberwood on gasifier performance. Additional experiments were also conducted to investigate …
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Design, fabrication, operation and Aspen simulation of oil shale pyrolysis and biomass gasification process using a moving bed downdraft reactor
… focuses on 1. Design and operation of a vertical downdraft reactor, 2. Establishing an optimum operating methodology and parameters to maximize syngas production through process testing. Finally in Paper IV, a proposed Aspen model for biomass gasification simulates a real biomass gasification …
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Characteristics of Coherent Structures in Marine Atmospheric Surface Layer
… coherent structures, there exist the plume and downdraft motions in the unstable marine atmospheric surface layer. It has been observed that the streamwise spatial length of the ejections and sweeps is 20-250 m and their mean frequency is of order of 0.01-0.001 /s at mean wind speed of 5-12.6 …
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Small-Scale Batch-Fed Biomass Gasification and Combustion
… the top of the fuel bed this is called a reverse downdraft process. The air supply has a major influence on both the conversion and combustion processes, but the necessary amounts of, and relationships between, the air supply stages are not fully understood. At a low primary air supply, as is …
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The Effect of The Gust Front on The Generation of New Convection
… new cells form about 25-30 min apart due to the downdraft from the previous cell enhancing the convergence along the gust front. A comparison with observation data shows qualitative agreement. Comparison of results with those obtained by other modelers for different storms is also included.
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A Cumulus Parameterization Study With Special Attention to the Arakawa-Schubert Scheme (semi-Prognostic, Meso-Scale Simulation)
… and Tao, 1980; Tao, 1983). An inclusion of the downdraft effects, as formulated by Johnson (1976), appears to alleviate this deficiency.
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Improving Storm-Scale Analyses of Convection via Assimilation of Polarimetric Radar Observations
… cooling at the surface within the forward flank downdraft region of the storm. Instead, there was an elevated cold pool along the forward storm flank that rested on a capping inversion layer. Comparison of the retrieved atmospheric state variables between the simple and advanced microphysical …
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Internal vs. External Forcings in Supercell Interactions and Their Impact on Storm Morphology and Intensity
… intensification is coupled with unsteady downdraft bursts in the forward flank. Downburst-driven, surface-based circulation centers form along the forward flank gust front, propagate toward the main updraft, and are stretched immediately prior to mesocyclogenesis events. These discrete …
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Investigation of Agricultural Residues Gasification for Electricity Production in Sudan as an Example for Biomass Energy Utlization under Arid Climate Conditions in Developing Countries
… and electricity production system. As a result downdraft gasifier and ICE were suggested as suitable systems. In chapter 4, fuel properties and fuel properties of agricultural residues were studied, different samples were tested and the results were presented. The main conclusions derived were: …
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Microphysical Influences on cold pools
Downdrafts extending from within convective clouds to the ground can produce cold pools, regions of air at the surface cooled by melting or sublimating ice and/or evaporation of rain within the downdrafts. These cold pools can propagate outward, sometimes initiating new convection along their …
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Emissions, efficiency, and combustion chamber conditions of a smokeless, hand-fired coal heater
… been studied. It was desired to determine if the downdraft design of the Prince would lead to low emissions when operated on American coals. Temperature and species concentrations were measured in the unit's secondary combustion chamber. Temperatures and gas residence times in the secondary …
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Toward assessing the effects of aerosols on deep convection: a numerical study using the WRF-Chemistry model
… parameters such as total precipitation, updraft/downdraft speed, distribution of hydrometeor species, and organizational features, within idealized maritime and continental thermodynamic environments. Initial results were obtained using WRFv3.0.1, and a second series of tests were run using …
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Idealized modeling of the role of stability and shear on mesoscale gravity wave evolution
… line. This evaporatively-cooled air generates a downdraft that then depresses the surface-based stable layer and causes pressure decreases, strong wind speeds and MGW genesis. Using the Weather Research and Forecast Model (WRF) version 3.0, evaporative cooling is simulated using an imposed cold …
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Biosphere-Atmosphere Exchange of Peroxyacetyl Nitrate: Development of a Flux Measurement System and its Application on a Grassland Ecosystem
… by capillary columns, which were used as up- and downdraft reservoirs for the HREA application and enabled simultaneous sampling at two measurement heights, which is an important feature for the MBR method. A major challenge of the design was the resolution of small PAN mixing ratio differences by …
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Characterization and agronomic evaluation of biochar amendments in a midwestern loam soil: effects on soybean yield, soil nutrient retention, and leachate quality
… and a commercial wood biochar (WB) produced via downdraft gasification. Proximate and elemental analyses, ATR-FTIR spectroscopy, surface area estimation, and molar ratio assessments were used to evaluate carbon stability, aromaticity, surface functionality, and nutrient content. The WSB biochar …
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Numerical simulations of mesoscale convective systems: techniques for comparison with observations and a high resolution analysis of flow patterns in the convective region and transition zone of a simulated mcs
… Chapter 3 investigates the mechanism(s) by which downdrafts at the rear of the convective precipitation and in the transition zone affect the maintenance and evolution of a simulated “early nocturnal” (approximately one hour after sunset) MCS. Additionally, the impact of melting in the transition …
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