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关键词： Compressor cascade   Curved blade   Flow loss   Vortex structure   Vortex dynamic mechanism  

摘要： In general, understanding the cascade flow loss mechanism is crucial for the design and optimisation of the cascade from the basically essential. The research objective of this study was to develop a highly loaded compressor linear cascade, and a numerical simulation was performed to obtain both the vortex structures and the flow loss of the cascade during the corner stall process. The results indicate that the curved blade affects the influence range of the vortex structures by changing the pressure gradients of the cascade, and subsequently changes the transport process of the vortex structure to low-energy fluid clusters, thus affecting the weight distribution of the flow loss. Additionally, the weight coefficients of the passage vortex and concentrated shedding vortex are merged together, and accounts for half of the total flow losses. Finally, the innovation of this paper is to propose a topological analysis method based on the accurate and quantitative identification of the singular points' positions serves as a useful research method to reveal the vortex dynamic mechanism of the weight distribution of the flow loss affected by the curved blade, and the vortex criterion of the corner stall is proposed additionally. (C) 2018 Elsevier Masson SAS. All rights reserved.

关键词： Superconducting RF   Superconducting phase transition   Complex oxides   Interfaces   Strongly correlated systems   Superconducting devices   Transition metal oxides  

摘要： We explore the superconducting phase diagram of the two-dimensional electron system at the LaAlO3/SrTiO3 interface by monitoring the frequencies of the cavity modes of a coplanar waveguide resonator fabricated in the interface itself. We determine the phase diagram of the superconducting transition as a function of the temperature and electrostatic gating, finding that both the superfluid density and the transition temperature follow a dome shape but that the two are not monotonically related. The ground state of this two-dimensional electron system is interpreted as a Josephson junction array, where a transition from long- to short-range order occurs as a function of the electronic doping. The synergy between correlated oxides and superconducting circuits is revealed to be a promising route to investigate these exotic compounds, complementary to standard magnetotransport measurements.

关键词： Continuous spray granulation   Fluidized bed   Wurster equipment   Process control   Population balances   Simulation   Straight-duct air classification  

摘要： The realization of continuous operation in fluidized bed spray granulation raises issues of process stability and product specification. It requires an appropriate process control strategy and a suitable granulator design. In previous work, a two-zone population balance (PB) model was developed and simulated product size distributions were evaluated by experiments in a Wurster granulator with external straight-duct air classification, however only regarding the process stability. The present contribution extends this population balance model with further equations for the purpose of product size control whereby the parameter setting of the former investigation serves as basis of the shown simulation study. Three process control strategies have been developed, implemented into the PB-model and investigated for diverse desired particle growth ratios and various separation sharpnesses. The simulation results show that only one of these strategies is able to provide the targeted requirements of both, process stability and product specification, but only for sufficiently good separation performance. (C) 2018 Published by Elsevier B.V.

关键词： Particle distribution   Pressure drop   Liquid solid circulating fluidized bed   Horizontal pipe   Heat transfer enhancement   Fouling preventing and descaling  

摘要： A horizontal liquid-solid circulating fluidized bed with a transparent single pipe is designed and built to investigate flow characteristics. The effects of the operating parameters, such as the fluid velocity, amount of added particles, particle types and pipe inner diameter on particle distribution and pressure drop in the horizontal test pipe, are systematically investigated by using the image measurement and acquisition system of a charge coupled device (CCD) and a differential pressure transducer. Results show that the solid holdup increases with the increase in fluid velocity, amount of added particles and pipe inner diameter, but decreases with the increase in the sediment velocity of particle. The non-uniform degree decreases with the increase in fluid velocity, but fluctuates with the increase in the amount of added particles. The particles with small sediment velocity are fluidized and distributed better. The non-uniform degree increases initially and then decreases with the increase in pipe inner diameter. The pressure drop ratio is not always positive and decreases generally with the increase in fluid velocity, but fluctuates with the increase in the amount of added particles, the sediment velocity of particle and the pipe inner diameter. The amplitude and laws of fluctuation depend on particle types. The difference in pressure drop ratio decreases apparently with the increase in fluid velocity, but fluctuates slightly with the increase in the amount of added particles. The difference in pressure drop ratio generally decreases with the increase in pipe inner diameter. Phase diagrams are established to display the variation ranges of the operating parameters for particle distribution and pressure drop. The results can be used to select conditions for relatively uniform particle distribution in the horizontal circulating fluidized bed. (C) 2018 Elsevier B.V. All rights reserved.

关键词： Fluidized bed   Powder classification   CPFD simulations   CFD simulations   Calcium looping   Carbon capture   High temperature solids classification  

摘要： In the present work, improvements to a novel fluidized bed solids classification system previously published by Jayarathna et al. are discussed (Jayarathna et al., 2018 111). The system is designed for a high temperature application, namely solids classification in a CO2 capture plant incorporated with a coal-fired power plant. The capture plant is proposed to be equipped with the latest calcium looping technology, fully integrated calcium looping (FICaL). The classifier will be fed with a mixture of sorbent and heat transfer (inert) particles in the real plant at the operating temperature in between 910 degrees C and 600 degrees C. Due to the higher temperature it is not possible to use any sensitive process equipment such as filters or metal screens or any mechanically moving parts. Stepwise development of a such a system is explained in the previous publication by the authors (Jayarathna et al., 2018 [1]). In this work, the system is down-scaled into a smaller cold flow system, and zirconia and steel particles are used to mimic the sorbent and heat transfer solids particles in the hot flow system, respectively. Experiments and CFD simulations are carried out for the cold flow classification system. The previous fluidized bed design (Jayarathna et al., 2018 [1]) reached an efficiency of 90% and 99% recovery (10% and 1% loss) of the lighter (zirconia) and heavier (steel) components, respectively, but a 10% loss of sorbent particles in the real system would not be economical. The new modified system reached recovery efficiencies of 97% and 98% (3% zirconia loss and 2% steel loss) of the lighter and heavier component, respectively. CFD is used as a supporting tool in the design process, and also in making improvements to the design. Improvements are made by modifying the classifier geometry such as shape, height and internal design features. The experimental results from the improved classifier are compared with the CFD predictions made by the commercially available

关键词： Radiative transfer   Radiation transport   Photoreactor design   Photoreactor model   Optimization  

摘要： The concepts of "initial rate of photon absorption" (IRPA), "dimensionless boundary layer of photon absorption" and "apparent optical thickness (tau(app))" are presented to evaluate the radiative transfer phenomena in solar, slurry, planar, photocatalytic reactors. The radiation field produced by suspensions of TiO2 and goethite, two photocatalysts with profoundly different optical properties used in heterogenous photocatalysis and heterogeneous photo-assisted Fenton reactions, was determined by the six-flux radiation absorption-scattering model coupled to the Henyey-Greenstein scattering phase function (SFM-HG). The concept of IRPA, defined by the differentiation at the local volumetric rate of photon absorption (LVRPA) at the reactor window boundary, is proposed as a new approach to determine the impact of catalyst loading and optical properties on the extinction of light inside a photoreactor. The IRPA showed that the extinction of light follows a second order dependency on the photocatalyst concentration while the impact of the optical properties can be expressed by a decoupled function (Psi function). The Psi function increased with photocatalyst concentration and approached a maximum at the same optimal photocatalyst concentration determined from the analysis of the total rate of photon absorption (TRPA) in the reactor. The analysis of TRPA and boundary layer of photon absorption redefined here in dimensionless form, as a function of tau(app), determined that the most efficient rate of radiation absorption in solar powered planar reactors occurs at tau(app) = 4.1-4.4, with approximately 10% of the reactor width under darkness. tau(app) is a similarity dimensionless parameter exclusively derived from the SFM approach, which clusters the effects of photocatalyst loading, reactor dimension and photocatalyst optical properties, providing an ideal parameter for designing and scaling photocatalytic reactors operated with any kind of photocatalytic material.

关键词： Caking coal   CFBC   Co-combustion   FSI   Pilot-scale plant  

摘要： Co-firing of Russian caking coal with non-caking coals (mixtures of Australian bituminous and Korean anthracite coals) was performed on a pilot scale using a circulating fluidized bed combustor (CFBC). The free swelling index (FSI) of caking coal was very high and the alkali index of non-caking coals was relatively high. However, stable fluidization and combustion were attained using various coal blends (containing up to 20 wt% of strongly caking coal). The average particle size in bottom ash increased slightly as the proportion of caking coal increased, triggering a slight temperature rise in the lower part of the combustor. Scanning electron microscopy/energy dispersive spectrometry and X-ray diffraction analyses of coarse particles showed that Al-rich bottom ash captured problematic K to form kalsilite (KAlSiO4), with a melting point much higher than the operating temperature of a typical CFBC. Such data strongly suggest that stable CFBC co-combustion is possible using mixtures featuring strongly caking coals. The unburnt carbon content of fly ash and the O-2 concentration in flue gas at the steady state increased linearly as the proportion of caking coal increased, indicating reduced co-combustion of caking coal. Morphological analyses of unburnt carbon in bottom ash revealed that pore clogging progressed on addition of caking coal, decreasing char reactivity by blocking oxygen access during co-combustion. In terms of pollutants, NO emission from fuel N in flue gas increased slightly on addition of caking coal, but N2O emission decreased slightly, attributable to a temperature rise in the dense combustor bed. However, the conversion rate of fuel S to SO2 did not significantly change when the proportion of caking coal increased.

摘要： This paper studies how the underlying factors that determine an individual's wage changes over their life-cycle, how these factors change at di erent education levels, and when a worker makes job-to-job moves. Using a longitudinal matched employer-employee data set from the Portuguese Ministry of Labor; I nd that human capital accumulation and job mobility play an important role in wage growth during the beginning of an individual's career. More speci cally, I nd that after 20 years of work wages increase, on average 41%. A large fraction of the returns to labor market experience is rooted in the returns to general training (25%) but sorting into better paying rms and job/titles is responsible for a signi cant 19% and 10% of the returns to labor market experience, respectively. Job-to-job mobility also enhances life-cycle earning (14%), as does the ability of the worker (32%).

关键词： Kihong Park  

摘要： While there are several computational studies on differential mobility analyzers (DMA), there is none for high flow DMA to classify nanoparticles less than 3 nm. A specific design of a high flow DMA, a half mini DMA, is investigated to predict its performance through numerical modeling in the incompressible flow regime. The governing equations for flow field, electric field and aerosol transport are solved using COMSOL 5.3. The transfer function of the half mini DMA is compared with that of a nano DMA (TSI 3085). The results show that both the height of the transfer function and resolution (R) of the half mini DMA are much better than those of nano DMA in sub-2 nm particle size range. Finally, the transfer function of half mini DMA is evaluated for different values of aerosol flow rate to the sheath flow rate (q/Q). Comparison of the simulated transfer function with existing models from Knutson-Whitby and Stolzenburg is also elucidated. It is found that the former model overestimates the resolution;whereas the latter is close to the simulation results for q/Q above 0.067. This work provides a useful method to study the flow regimes and transfer function of a high flow DMA. Copyright (c) 2018 American Association for Aerosol Research

关键词： Binary particle systems   discrete element method   fluidized bed   mixing characteristics   particle properties  

摘要： The fluidization of quartz in the fluidized bed has great influence on the combustion and gasification of refuse-derived fuel (RDF). The combined computational fluid dynamics (CFD) and discrete element method (DEM) approach was used to explore the gas-solid hydrodynamics and mixing characteristics in a three-dimensional fluidized bed. All numerical analyses were performed referring to the experiments (Goldschmidt, Beetstra, and Kuipers 2004). The simulation results indicated that the quartz volume fraction agrees well with the experimental data. Furthermore, the cylinder-shaped RDF particles can mix well with the quartz particles as they were added from upside. For binary systems, it is necessary to investigate solid flow characteristics as well as pressure drops and examine the influence of superficial gas velocity on the solid mixing. Two main parameters are discussed: mixing degree and the time required to reach the steady state. It is also found that inlet gas velocity and particle properties (particle density ratio, shape and size) are significant factors on particle mixing in a fluidized bed.