The progress of the two-phase flow research has been divided into four stages i this series of the report. These periods are (I) 1948-1959, (II) 1960-1970, (III) 1971-1979, amd (IV) 1980-1988. A chronological table during period (I)-(IV) composed by columns of development of the theoretical analysis for flow instsbilities, computer codes for thermal-hydraulic analyses in two-phase flow systems, progress of computers, and situation of computer installation in universities in Japan. In this 11th Report, the general view of the Table is described from the historical aspect concerning the development and transition of method-of the theoretical analysis and the computational method for the flow instabilyties in two-phase flow
The following thermal-hydraulic performance is necessary to develop the new fuel assembly for Boiling Water Reactor.(1) critical power under steady state and unsteady conditions (2) pressure drop (3) void fraction (4) channel stability. The purpose of this report is to explain about the test section and measurement technique for thermal-hydraulic performance of BWR fuel.
The optical fiber probe technique has been widely used in the analysis of gas-solid fluidized bed phenomena owing to the small size, quick response and flexibility of the probe as well as wide ranges of applicability of the technique as a whole. However, they give us only local information of the fluidized bed behavior and then it is hard to understand the macro phenomena in the fluidized bed. Therefore, multi optical fiber probe system and multifunctional optical fiber probe system were developed to clarify the macro scale analysis of the fluidized bed behavior. Also, a particle image scope consisting of an image fiber and a high speed video system was developed for micro scope observations of solid particles in circulating fluidized beds. In this article, we introduce the basic probe structures, examples of the obtained signals, analyzed flow behavior, single particle motion and particle collision patterns.
Blast furnace involves the complex flow conditions of the upward gas flow and unburnt char/coke fines, and the downward flows of coke and molten iron and slag. Under the recent high rate injection operation of pulverized coal, permeability in the furnace has been prevented due to the accumulation of such fine powder in the lower part. Therefore, it becomes more important to understand the essential flow characteristics of the fine powder in the blast furnace to attain the stable operation. This article discusses the recent development of the analytical method and the numerical modeling of powder behavior, particularly focuses on the combustion behavior of pulverized coal, generation of coke fines and the movement and accumulation of fine powder in the lower part of the blast furnace.
An ultrasonic computed tomography (UCT) developed for measuring time-averaged cross-sectional distributions of gas and solid concentrations in three-phase flow is described. The ultrasonic computed tomography is a coupling of a transmission mode ultrasonic sensor developed in Department of Chemical Engineering, Shizuoka University and a tomographic reconstruction technique based on dynamic neural network optimization algorithm developed in Department of Chemical Engineering, The Ohio State University. The ultrasonic sensor is based on measurements of the energy attenuation and the velocity change of ultrasonic pulse waves transmitted through the three-phase medium, enabling the measurements of the gas and the solid concentrations in the system simultaneously. The tomographic reconstruction technique has been proven to reconstruct simulated tomographic data accurately even with a very small number of projection data as used in the measurement. The application of the technique to a water-air-particles flow system in a bubble column is described.Glass-beads with diameters of 100, 260 and 350 micron meters are used as the solid phase. The time-averaged macroscopic flow structure and the behavior of the gas bubbles and solid particles distributions are investigated. The effects of gas velocity, solid loading and particle diameter to the behaviors of bubbles and particles distributions in the three-phase system are also discussed.
It is known that the Eulerian-Lagrangian approaches for dispersive multiphase flows can simulate detailed flow structures with a much better spatial resolution than the Eulerian-Eulerian approaches. However, there are still unsettled problems regarding the calculation method for two-way interaction. Especially, numerical instability due to the dispersion's migration beyond computational mesh is a serious issue for accurate prediction of flow instability in multiphase systems as well as multiphase turbulent flows. This paper describes revised methods for calculating the continuous phase flow which is induced by the spherical dispersion's migration. Basic principle of the methods are of introduction of template functions which convert discrete mass and momentum sources of the dispersion to spatially continuous sources. Performance of Gaussian and sine wave's template functions are examined and good pridictionability of local two way interaction have been confirmed.
Fluidized-bed combustion systems are composed of many kinds of particles with a variety of sizes, e.g. coal, sand, RDF, limestone etc. In such a binary system of particles, the segregation, if occurs, may harm the combustion, mixing and heat transfer in the bed, depending on the particle movement. The particle movement or circulation in the fluidized-bed depends on many factors, such as the density ratio, size ratio, shape of particle, fluidization velocity. Owing to the difficulty of flow visualization, such particle movement has not been fully understood so far. This paper describes large-particle movement obtained by the flow visualization using neutron radiography. Tracer particles mixed into the fluidized particles indicated clearly bubbles and the cloud behavior around the bubble. Image processing, i.e. PIV and PTV, gives rather clear understanding on the interaction between the large particle, emulsion and/or cloud behavior in the bed.
Velocity distributions adjacent to the interface between a water-drop and surrounding oil were measured using PTV. By analyzing the measured velocity data, the physical properties such as surface slip conditions, circulating flow in a drop, distributions of contamination skin, are quantitatively obtained. Relating to the heat and mass transfer in multi-phase flows, information about microscopic phenomena occurred at the interface of fluids has been estimated so far from macroscopic measurements. Difficulties to directly measure the phenomena on the interface come from their special conditions of moving boundaries, transient, and spatially distributed phenomena. Most of those difficulties can be resolved by the PTV technique. Since it is the quantitative visualization method, only if some of those phenomena can be visually captured, it is not difficult to obtain a part of the required information.