Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第18931号 / 工博第3973号 / 新制||工||1612 / 31882 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 間瀬 肇, 教授 平石 哲也, 准教授 森 信人 / 学位規則第4条第1項該当

This dissertation investigates the impact of 2000-2050 climate change on fine particulate matter \((PM_{2.5})\) air quality. We first applied a multiple linear regression model to study the correlations of total \(PM_{2.5}\) and its components with meteorological variables using the past decadal \(PM_{2.5}\) observations over the contiguous US. We find that daily variation in meteorology can explain up to 50% of \(PM_{2.5}\) variability. Temperature is positively correlated with sulfate and organic carbon (OC) almost everywhere. The correlation of nitrate with temperature is negative in the Southeast but positive in California and the Great Plains. Relative humidity (RH) is positively correlated with sulfate and nitrate, but negatively with OC. Precipitation is strongly negatively correlated with all \(PM_{2.5}\) components. We then compared the observed correlations of \(PM_{2.5}\) with meteorological variables with results from the GEOS-Chem chemical transport model. The results indicate that most of the correlations of \(PM_{2.5}\) with temperature and RH do not arise from direct dependence but from covariation with synoptic transport. We applied principal component analysis and regression to identify the dominant meteorological modes controlling \(PM_{2.5}\) variability, and showed that 20-40% of the observed \(PM_{2.5}\) daily variability can be explained by a single dominant meteorological mode: cold frontal passages in the eastern US and maritime inflow in the West. From 1999-2010 observations we further showed that interannual variability of annual mean \(PM_{2.5}\) in most of the US is strongly correlated with the synoptic period T of the dominant meteorological mode as diagnosed from a spectral-autoregressive analysis. We then used the observed local \(PM_{2.5}\)-to-period sensitivity to project \(PM_{2.5}\) changes from the 2000-2050 changes in T simulated by fifteen IPCC AR4 GCMs following the SRES A1B scenario. We project a likely increase of \(\sim 0.1 \mu g m^{-3}\) in annual mean \(PM_{2.5}\) in the eastern US arising from less frequent frontal ventilation, and a likely decrease of \(\sim 0.3 \mu g m^{-3}\) in the northwestern US due to more frequent maritime inflows. These circulation-driven changes are relatively small, representing only a minor climate penalty or benefit for \(PM_{2.5}\) regulatory purpose. / Engineering and Applied Sciences

Magistriniame darbe tirtas turbulentinis dvifazis srautas C- 30 ir KDG ciklonuose (įrenginys KD atskirti iš oro srauto) su tangentiniu srauto įtekėjimu problema. Pagrindinis tyrimo objektas – dviejų skirtingų konstrukcijų ciklonų oro valymo įrenginiai nuo KD. Magistrinio darbo tikslas yra ištirti turbulentinio dvifazio srauto judėjimą C-30 ir KDG ciklonuose ir atlikti matematinį modeliavimą. Magistrinį darbą sudaro 106 puslapiai, 3 skyriai, 21 lentelių, 58 paveikslai, bendrosios darbo išvados ir rekomendacijos, literatūros sąrašas. Pirmajame skyriuje analizuota literatūra, išnagrinėta oro tarša KD, pasaulyje ir Lietuvoje naudojamų ciklonų konstrukcijos. Aprašyti KD judėjimo ciklone matematiniai modeliai. Antrajame skyriuje pateiktos tyrimo metodikos: eksperimentiniuose tyrimuose naudotų medžiagų, įrangos bei aparatūros charakteristikos, pateikiamos mėginių ėmimo sąlygos, taikomi KD koncentracijų analizavimo metodai (svorinis ir spektroskopinis) bei skaitinio modeliavimo („Gentra“ ir „IPSA“) metodikos. Trečiajame skyriuje pateikti eksperimentinių tyrimų ir matematinio modeliavimo rezultatai. Eksperimentiniais tyrimais buvo siekiama ištirti C-30 ir KDG ciklonų efektyvumus, nustatyti medienos skiedrų, kūrenamomis kūrykloje išsiskiriančių kietųjų dalelių koncentracijas, kvarcinio smėlio ir kvarcinio smėlio dulkių įeinančio ir išeinančio oro dulkių sraute. Atliktas skaitinis oro srauto judėjimo modeliavimas. Oro srauto judėjimui C-30 ir KDG ciklonuose aprašyti naudotas trimačių... [toliau žr. visą tekstą] / The paper aims to analyse the problem og numerical modeling of two-phase flow in the C- 30 ir CRF cyclone with tangential inlet (equipment for seperation of solid particles from gaseous fluid flow). The main research object is two different structures of cyclone air cleaning equipment used to remove solid particles. The master is aimed to investigate the turbulent two-phase flow in the C-30 and CRF cyclones and describes the numerical modeling The master work consists of an 106 papers, 3 chapters, 21 tables, 58 pictures, general conclusions and recommendations, lists of references. The first chapter is intended for literature review. It investigates air pollution with solid particles, cyclones structures and charges applied worldwide and Lithuania. It also describes the mathematical models of a solid particle flow in cyclone. The second chapter presents the methodologies of research: experimental research of the materials, characteristics of equipment and hardware, present the sampling conditions, used analysis methods of solid particle concentrations (weighted and spectroscopic) and method of numerical modeling (Gentra and IPSA). The third chapter presents results of experimental research and mathematical modeling. In experimental analysis was to investigate efficiency of air cleaning equipment C-30 and CRF cyclones and assess the wood chips, combustion emissions from burning the particles concentrations of quartz sand and quartz sand dust of incoming and outgoing air... [to full text]

In power generation from solid fuel such as coal-fired power plants, combustion efficiency can be monitored by the loss on ignition (LOI) of the pulverised fuel. It is the role of the pulveriser-classifier combination to ensure pulverised fuel delivered to the burners is within the specified limits of fineness and mass flow deviation required to keep the LOI at an acceptable level. However, government imposed limits on emissions have spurred the conversion of many coal fired power plants to convert to the use of Low NOx Burners. To maintain good LOI or combustion efficiency, the limits of fineness and mass flow deviation or inter-outlet fuel distribution have become narrower. A lot of existing pulveriser units cannot operate efficiently within these limits hence retrofits of short term solutions such as orifice balancing and classifier maintenance has been applied. The work performed in this thesis relates to an investigation into coal classifier devices that function to control fineness and inter pipe balancing upstream of the burner and downstream of the pulverisers. A cold flow model of a static classifier was developed to investigate the flow characteristics so that design optimisations can be made. Dynamic similarity was achieved by designing a 1/3 scale model with air as the continuous phase and glass cenospheres of a similar size distribution as pulverised fuel, to simulate the coal dust. The rig was operated in positive pressure with air at room temperature and discharge to atmosphere. The Stokes number similarity (0.11-prototype vs. 0.08-model) was the most important dimensionless parameter to conserve as Reynolds number becomes independent of separation efficiency and pressure drop at high industrial values such as 2 x 10 4 Hoffman, 2008). Air-fuel ratio was also compromised and an assumption of dilute flow was made to qualify this. However, the effect of air fuel ratio was ascertained by its inclusion as an experimental variable. Experiments were conducted at air flow rates of 1.41-1.71kg/s and air fuel ratios of 4.8-10 with classifier vane angle adjustment (30°- 60°) and inlet swirl umbers (S) of 0.49 – 1. Radial profiles of tangential, axial and radial velocity were obtained at several cross sections to determine the airflow pattern and establish links with the separation performance and outlet flow balance. Results show a proportional relationship between cone vane angle and cut size or particle fineness. Models can be derived from the data so that reliable predictions of fineness and outlet fuel balance can be used in power stations and replace simplistic and process simulator models that fail to correctly predict performance. It was found that swirl intensity is more significant a parameter in obtaining balanced flow at the classifier outlets than uniform air flow distribution in the mill. However the latter is important in obtaining high grade efficiencies and cut size. The study concludes that the static classifier can be further improved and retrofit-able solutions can be applied to problems of outlet flow imbalance and poor fineness at the mill outlets.

The production of high quality silicon requires the use of ultraclean coal containing less than 1.5% ash. The magnetite used to clean the coal in a dense medium process is a contaminant that seriously impacts the quality of the final silicon product. As such, research has been conducted to evaluate the potential to substitute the magnetite with fine silica–based alternative material generated during the silicon production process. Dense medium cyclone tests were performed based on a statistically designed program to determine the optimum conditions that maximize organic efficiency and minimize probable error and low–density bypass. The results revealed that a clean coal product with less than 1.5% ash can be produced using a medium formed from the silicon production waste with an organic efficiency value of around 99% and a probable error value below 0.02. There was no measurable bypass of high density particles into the product stream or low–density particles into the reject stream.

No description available.

The tropical cyclone is a majestic, yet violent atmospheric weather system occurring over tropical waters. Their majesty evolves from the significant range of spatial scales they operate over: from the mesoscale, to the larger synoptic-scale. Their associated violent winds and seas, however, are often the cause of damage and destruction for settlements in their path. Between 10/11/07 and 16/11/07, tropical cyclone Sidr formed and intensified into a category 5 hurricane over the southeast tropical waters of the northern Indian Ocean. Sidr tracked west, then north, during the course of its life, and eventually made landfall on 15/11/07, as a category 4 cyclone near the settlement of Barguna, Bangladesh. The storm affected approximately 2.7 million people in Bangladesh, and of that number 4234 were killed. In this study, the dynamics of tropical cyclone Sidr are simulated using version 2.2.1 of Advanced Weather Research and Forecasting — a non-hydrostatic, two-way interactive, triply-nested-grid mesoscale model. Three experiments were developed examining model sensitivity to ocean-atmosphere interaction; initialisation time; and choice of convective parameterisation scheme. All experiments were verified against analysed synoptic data. The ocean-atmosphere experiment involved one simulation of a cold sea surface temperature, fixed at 10 °C; and simulated using a 15 km grid resolution. The initialisation experiment involved three simulations of different model start time: 108-, 72-, and 48-hours before landfall respectively. These were simulated using a 15 km grid resolution. The convective experiment consisted of four simulations, with three of these using a different implicit convective scheme. The three schemes used were, the Kain-Fritsch, Betts-Miller-Janjic, and Grell-Devenyi ensemble. The fourth case simulated convection explicitly. A nested domain of 5km grid spacing was used in the convective experiment, for high resolution modelling. In all experiments, the Eta-Ferrier microphysics scheme, and the Mellor-Yamada-Janjic planetary boundary layer scheme were used. As verified against available observations, the model showed considerable sensitivity in each of the experiments. The model was found to be well suited for combining ocean-atmosphere interactions: a cool sea surface caused cyclone Sidr to dissipate within 24 hours. The initialisation simulations indicated moderate model sensitivity to initialisation time: variations were found for both cyclone track and intensity. Of the three simulations, an initialisation time 108 hours prior to landfall, was found to most accurately represent cyclone Sidr’s track and intensity. Finally, the convective simulations showed that considerable differences were found in cyclone track, intensity, and structure, when using different convective schemes. The Kain-Fritsch scheme produced the most accurate cyclone track and structure, but the rainfall rate was spurious on the sub-grid-scale. The Betts-Miller-Janjic scheme resolved realistic rainfall on both domains, but cyclone intensity was poor. Of particular significance, was that explicit convection produced a similar result to the Grell-Devenyi ensemble for both model domain resolutions. Overall, the results suggest that the modelled cyclone is highly sensitive to changes in initial conditions. In particular, in the context of other studies, it appears that the combination of convective scheme, microphysics scheme, and boundary layer scheme, are most significant for accurate track and intensity prediction.

The thesis comprises two separate journal articles that together form a coherent body of work. In this thesis, the key physical processes responsible for the 23-26 September 2012 UK floods are investigated using a case study approach. The cyclone responsible for the floods developed near the Azores on 20¬-22 September following the interaction between an equatorward-moving potential vorticity (PV) streamer and tropical storm Nadine. Convectively-driven latent heat release associated with the developing cyclone reduced upper-level PV and resulted in the fracture of the PV streamer into a discrete anomaly as the cyclone intensified. In Paper 1, convection-permitting model simulations and diabatic heating rate and PV tendency calculations along trajectories demonstrate that deposition heating strongly reduced upper-level PV in the vicinity of the PV streamer, contributing to its fracture into a discrete anomaly. The cyclone deepened further over the UK on 23-26 September, ahead of a second upper-level PV anomaly. In Paper 2, sensitivity simulations of the storm are presented. PV inversion is used to modify the strength and position of the PV anomaly in the initial conditions and to examine whether the event could have been even more extreme with different upper-level forcing. Results show that quasigeostrophic forcing for ascent ahead of the PV anomaly contributed to the maintenance of the rainfall band over the UK. Counterintuitively however, strengthening the upper-level forcing produced a shallower cyclone with lower rainfall totals. Instead of moving eastward over the UK to interact with the cyclone, the strengthened anomaly rotated cyclonically around a large-scale trough over Iceland, resulting in a fragmented rainfall band. The counterintuitive results suggest that the verifying analysis represents almost the highest-impact scenario possible for this flooding event.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-11-06T12:07:41Z No. of bitstreams: 1 JOSSYL AMORIM RIBEIRO DE SOUZA - TESE (PPGEP) 2012.pdf: 4079251 bytes, checksum: 61afd7c27f07e71708a7cb82095876a4 (MD5) / Made available in DSpace on 2018-11-06T12:07:41Z (GMT). No. of bitstreams: 1 JOSSYL AMORIM RIBEIRO DE SOUZA - TESE (PPGEP) 2012.pdf: 4079251 bytes, checksum: 61afd7c27f07e71708a7cb82095876a4 (MD5) Previous issue date: 2012-08-31 / Nos últimos anos o ciclone vem sendo utilizado como uma tecnologia de secagem moderna. Neste sentido, nesta pesquisa propõe-se estudar numericamente a secagem do bagaço de cana-de-açúcar usando o ciclone como secador. Adotou-se os modelos Euleriano-Lagrangeano no regime permanente e o de turbulência das tensões de Reynolds (LRR) para a fase gás, e um modelo concentrado transiente de transferência de calor e massa para a fase particulada. Considerou-se a partícula com forma irregular e constituída de uma mistura binária formada por bagaço de cana-de-açúcar e água. A solução do modelo proposto foi obtida usando o software comercial Ansys CFX 12. Resultados do teor de umidade, temperatura, variações dimensionais e trajetória das partículas, e distribuição de velocidade, pressão e temperatura da fase gás no interior do ciclone são apresentadas e analisadas. Verificou-se que as componentes de velocidade axial e tangencial no interior do ciclone obtidos numericamente apresentaram boa concordância com dados experimentais disponibilizados na literatura e que as cinéticas de secagem, aquecimento, variações dimensionais e tempo de permanência das partículas (bagaço de cana-de-açúcar) são afetadas pela forma do perfil de velocidade de entrada da fase gasosa, pela velocidade de entrada das partículas e pelo sentido do fluxo de gás e partículas na entrada do duto de alimentação (horário e anti-horário). / In recent years, cyclones have been used as a modern drying technology. In this sense, this research proposes a numerical study to describe drying of sugarcane bagasse, using the cyclone as dryer. To this end, it was adopted the Eulerian-Lagrangian model in steady state. The Reynolds stress model was adopted to describe turbulence of the gas phase, while the lumped model in transient state was adopted to describe heat and mass transfer of the particulate phase (sugarcane bagasse). Particles were considered with irregular shape, composed of a binary mixture (solid part and water). The solution of the proposed model was obtained using the commercial software Ansys CFX 12. Results obtained for moisture content, temperature, dimensional variation, and paths of particles, as well as velocity distribution, pressure, and temperature of the gas phase inside the cyclone are presented and analyzed. It has been found that the obtained components for axial and tangential velocity inside the cyclone are in good agreement with experimental data available in the literature, and that the drying kinetics, heating, dimensional variations, and residence time of particles are affected by the velocity profile of the gas phase, by the velocity of particles, and the direction of flow of gas and particles at the entrance of the feed duct (clockwise and counter-clockwise).

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-07-17T10:20:54Z No. of bitstreams: 1 JOÃO PAULO PAES DE ARAÚJO SILVA - DISSERTAÇÃO (PPGEM) 2016.pdf: 4486747 bytes, checksum: 6130f70f7b461e429f7b944096577d56 (MD5) / Made available in DSpace on 2018-07-17T10:20:55Z (GMT). No. of bitstreams: 1 JOÃO PAULO PAES DE ARAÚJO SILVA - DISSERTAÇÃO (PPGEM) 2016.pdf: 4486747 bytes, checksum: 6130f70f7b461e429f7b944096577d56 (MD5) Previous issue date: 2016-10-16 / CNPq / Nos últimos anos o ciclone vem sendo utilizado como uma tecnologia de secagem moderna. Neste sentido, nesta pesquisa propõe-se estudar numericamente a secagem do bagaço de cana-de-açúcar usando o ciclone como secador. Adotou-se os modelos Euleriano-Lagrangeano no regime permanente e o de turbulência RNG k-epsilon para a fase gás, e um modelo concentrado transiente de transferência de calor e massa para a fase particulada. Considerou-se a partícula de bagaço de cana-de-açúcar com forma irregular e constituída somente de água. A solução do modelo proposto foi obtida usando o software comercial Ansys CFX 15.0. Resultados do teor de umidade, temperatura, variações dimensionais e trajetória das partículas, e distribuição de velocidade, pressão e temperatura da fase gás no interior do ciclone são apresentadas e analisadas. Verificou-se que o campo de temperatura e pressão, bem como o campo vetorial no interior do ciclone obtidos numericamente apresentaram boa concordância com dados experimentais disponibilizados na literatura e que as cinéticas de secagem, aquecimento, variações dimensionais e tempo de permanência das partículas (bagaço de cana-de-açúcar) são afetadas pelas condições de entrada do gás de secagem. / In recent years, cyclones have been used as a modern drying technology. In this sense, this research proposes a numerical study to describe drying of sugarcane bagasse, using the cyclone as dryer. To this end, it was adopted the RNG-K epsilon model in steady state. The Reynolds stress model was adopted to describe turbulence of the gas phase, while the lumped model in transient state was adopted to describe heat and mass transfer of the particulate phase (sugarcane bagasse). It was considered the particle sugarcane bagasse with irregular shape and consists of water only, in order to simplify the model. The solution of the model was obtained using commercial software Ansys CFX 15.0. Moisture content results, temperature, dimensional variations and trajectory of the particles, and distribution of velocity, pressure and temperature of the gas phase inside the cyclone are presented and analyzed. It was found that the temperature and pressure field and the vector field within the numerically obtained cyclone showed good agreement with experimental data available in the literature and that the kinetics of drying, heating, dimensional variations and particle residence time (sugarcane bagasse) are affected by the inlet condition of the drying gas.