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关键词： Non-spherical particles   Nano-iron powder metal fuel motor   Nozzle two-phase flow losses   Characteristics analysis   Combustion experiment  

摘要： Metal iron powder is a promising new energy source that is of significant practical and research interest for future automotive power systems. However, the shapes of the particles are typically assumed to be spherical or an equivalent sphere when estimating the specific impulse of motors. Such an assumption lacks objectivity and can result in unreasonable estimations of two-phase flow losses. In order to better optimize the design of an engine, this study focuses on the influence of non-spherical particles (such as ellipsoidal and cuboid particles) on the characteristics of nozzle two-phase flow. Models for the governing equations of nozzle two-phase flow are developed to conduct a theoretical study to analyze the combustion properties of iron oxide particles and flow in the nozzle. In addition, experimental studies involving nanometer iron-powder particle combustion and engine thrust measurements are conducted to validate the results obtained from numerical calculations that are conducted using a fourth order Runge-Kutta-Gill method. The results indicate that particle morphology, size, and coagulation content play a significant role in the motor performance and the two-phase flow losses. Specifically, the hypothesis of the ellipsoidal model is in better agreement with the experimental findings compared to the other particle models. (C) 2019 Elsevier Masson SAS. All rights reserved.

关键词： Binary mixture   Computational fluid dynamics simulation   Internally circulating fluidized bed   Mixing   Solids circulation rate  

摘要： The process where solids circulate in an internally circulating fluidized bed (ICFB) with two or more chambers can be developed by applying unequal gas velocities in these chambers. In this study, a twin chamber ICFB with a binary mixture (two particles comprising G116 and P275, which differed in terms of their size and density) was simulated using the multi fluid Eulerian model. The effects of variations in the gas velocities, mixing of solids, and mixture composition were investigated, and the results were quantified in terms of the solids circulation rate (G(s)). An increase in the gas velocity in the reaction chamber (RC), U-R, at a constant gas velocity in the heat exchange chamber (HEC), U-H, resulted in an increase in the circulation rate for the binary mixture. Solid particles flowed upward in the RC and downward into the HEC. The ratio of the circulation rate for G116 relative to that for P275 was approximately equal to the ratio of their masses in the ICFB. An increase in U-H at constant U-R led to a decrease in the circulation rate of the binary mixture. Similar to U-R and U-H, the mixture composition played a critical role in controlling the circulation rate of the binary mixture in the ICFB. Furthermore, the ICFB exhibited a higher capacity for solids mixing compared with a conventional bubbling fluidized bed. (C) 2019 Elsevier Inc. All rights reserved.

摘要： Measured streamflow and flood series of 43 gauging stations from 25 west flowing rivers in Kerala, India, were analysed for their descriptive characteristics to study their spatial and temporal variation. The spatial and temporal variations in streamflow are influenced by many factors including climatic and basin characteristics. Streamflow data from each station (length varies from 14 to 43years) is analysed for their internal characteristics such as trend, stationarity, homogeneity, noise and periodicity to incorporate it in hydrological models, so that their predictions would be more accurate. The internal characteristics were studied along with the statistical analysis. For analysing each internal characteristic, more than one method of analysis has been used to have reliable result. The trend characteristic was analysed using Mann-Kendall (MK) test, Sen's slope test, Spearman's rank correlation coefficient and Pearson correlation coefficient methods. Stationarity characteristics have been tested using augmented Dickey-Fuller test (ADF), Phillips-Perron test and Kwiatkowski-Phillips-Schmidt-Shin (KPSS) test. For identifying homogeneous nature, Pettitt test, standard normal homogeneity (SNH) test, Buishand test and von Neumann tests were used. Noise in the streamflow was verified using Box-Peirce, Ljung-Box and McLeod-Li tests. From the study, it is found that the daily series is non-homogeneous, stationary data with white noise, whereas flood series shows mixed characteristics. Based on the variations in the time series, the daily streamflow and flood series are classified into different categories such as high, average, moderate, minor and no variation stations. In most of the river basins, daily flow shows average variation. Flood series shows average variation in 44% of stations and moderate variation in 28% of stations.

关键词： Channels between stages   axially split   entropy production analysis   numerical simulation   centrifugal pump  

摘要： The double-stage axially split centrifugal pump is widely used in water diversion and water pumping stations due to their ability to deliver at high heads and large flow rate for long running hours. Their flow characteristics can be greatly influenced by the geometry of the channels between the stages, which is a prominent place for irreversible loss to occur. Numerical investigations were extensively carried out and a comparison was drawn between two multistage axially split centrifugal pumps, with different channel designs between its stages. The reliability of the numerical model was confirmed after a good agreement existed between numerical results and the experiments. Subsequently, entropy generation terms were used to evaluate turbulence dissipation to characterize the flow losses. The modified channels had a great effect on reducing swirl near the impeller eye, thereby improving pump head by 12.5% and efficiency by 4.98% at the design condition. They however induced flow impact, causing an unusual separation, which generated high turbulence dissipation at the blade surfaces. The channels and second stage impeller were identified as major areas for selective optimization since their turbulence dissipation was dominant. Consequently, entropy production analysis with computational fluid dynamics could be relied upon to reveal the loss locations for selective optimization in centrifugal pumps.

关键词： imaging flow cytometry   phytoplankton   taxonomic resolution   morphology   microscopy   cyanobacteria  

摘要： Phytoplankton are aquatic, microscopically small primary producers, accounting for almost half of the worldwide carbon fixation. As early indicators of environmental change, they play a crucial role in water quality management. Human activities like climate change, eutrophication, or international shipping traffic strongly impact diversity of these organisms. Phytoplankton monitoring is a crucial step in the recognition of changes in community composition. The common standard for monitoring programs is manual microscopic counting, which strongly limits sample number and sampling frequency. In contrast, high-throughput technologies like standard flow cytometry (FCM) are restricted to a low taxonomic resolution, which makes them unsuitable for the identification of indicator species. Imaging flow cytometers (IFC) could overcome these limitations as they combine microscopy and high-throughput analysis. In comparison to single fluorescence values, image information not only allows for a wide variety of possibilities to characterize different species as well as immediate and fast measurements but also provides an archivable data output. Taxonomic resolution of IFC (ImageStream X Mk II) was proven comparable to standard FCM (FACSAria II) by the help of numerical evaluations. This is demonstrated on different levels of taxonomic differentiation of laboratory grown cultures in this study. Phytoplankton species discrimination by an imaging flow cytometer could be useful as supportive tool to make machine-learning classifications more robust, reliable, and flexible. Furthermore, this study provides examples, demonstrating the possibility of discrimination between species with similar fluorescence properties, strains, and even subpopulations. In contrast to standard FCM, each cell is not only represented as a dot in a cytogram but is also linked to microscopic brightfield and the author presents a new way to visualize this as image-based cytograms. The source code is supplied

关键词： Chemical structure   Bubbles   Animal feed   Fluxes   Hydrodynamics  

摘要： The hydrodynamic properties of a dual fluidized bed (DFB) with continuous feeding and discharging of solids were investigated on a pilot-scale plant in cold mode and simulated coupled with the structure-based drag model. We present a deep analysis that focuses directly on the problem of predicting the fluid dynamics behavior of this type of system for which empirical data is limited or unavailable. The fluidization of a DFB shows complex hydrodynamic characteristics because of the intricate interactions between different compartments experimentally. We prove that the simulation based on the structure-based drag model involving different fluidized structures is able to give an accurate prediction of pilot-scale DFB fluidization and capture the correct flow behaviors under different conditions. This work is expected to give thorough analysis and further exploration of the overall fluidization dynamics for DFB optimization and scale-up.

关键词： 成矿流体   流体包裹体   矿床地质   地质找矿  

摘要： 成矿流体与成矿作用之间的关系,一直以来是地质学界研究热点之一。从流体包裹体研究中我们可以获得当时成矿环境和物理化学条件(温度、压力、成分等)。目前,流体包裹体研究手段已经广泛应用于各类热液矿床,并且积累了大量研究数据。它们对成矿环境、流体演化和矿质沉淀特征都具有重要指示作用,能够反映成矿物化条件及成矿过程,因此具有重要的理论研究意义。由于实际工作中,地质特征和流体包裹体特征可能存在矛盾,为此,需要更好的建立矿床地质与流体包裹体之间的衔接,以便更好开展地质找矿工作。