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The substitution of Ca for Sr in the LnSr3-xCaxFe3O10-δ (x = 0–1.5, Ln = La, Pr, and Sm), Ruddlesden-Popper (RP) intergrowth structure was investigated to determine how the physical and electrochemical properties of this potential cathode material in solid oxide fuel cells (SOFCs) are impacted. A small amount of Ca incorporated into the structure reduced the thermal expansion coefficient, improved the electrical conductivity, and increased power density by up to 30% of a La0.8Sr0.2Ga0.8Mg0.2O3 electrolyte-supported single cell. The microstructure and oxygen permeability of the materials were independent of Ca substitution. A phase transformation of LaSr3-xCaxFe3O10-δ to perovskite was observed when the Ca composition of x > 1.0. Among the substitution of Pr and Sm for La in LaSr2.7Ca0.3Fe3O10-δ, only PrSr2.7Ca0.3Fe3O10-δ was pure with no phase transformation found. The co-substitution of Pr and Ca promoted the reduction of Fe, enhanced the oxygen permeation and active surface, and diminished the contact resistance at the cathode-electrolyte interlayer. The co-substitution of Ca and Pr delivered good electrochemical performance of approximately 354 mWcm−2 at 800 °C on a 0.3 mm thick La0.8Sr0.2Ga0.8Mg0.2O3 electrolyte-supported cell and the lowest area specific resistance (ASR).

The Ni0.5Co0.5-MgO-TiO2-(8 mol%Y2O3-ZrO2) (NCMTO-YSZ) cermet anode showed a higher cell performance than NiO-YSZ and Ni0.5Co0.5O-YSZ cermet anodes under dry CH4 fuel, while the cell performance between Ni0.5Co0.5O-YSZ and NCMTO-YSZ cermet anodes were not significantly different under H2 fuel. NCMTO-YSZ decreased the anodic overvoltage and polarization resistance because Ni0.5Co0.5-MgO solid solution existing in the cermet anode contributes to increase active sites for the electrochemical oxidation of methane. The enhancement of the direct methane oxidation was caused by the microstructure improvement owing to MgO and a small amount of TiO2 solid solution.

A mathematical model has been developed for predicting unsteady behavior of a ring-roller mill. The model is based on specific rates of breakage, primary breakage distributions, classification actions of particles in the mill and mass transport relation of mill hold-up and flow rates through the mill. The validity of the model was verified by pilot mill testing. Transient behavior of the mills during rapid changes of load, feed and operating conditions were then demonstrated.

The objectives of the present study are to clarify breakage properties of coals in ring-roller mills and to develop a mathematical mill model capable of predicting steady-state mill performance in full scale mills. It was found that ring-roller mills have a higher coal grinding capability than ring-ball mills with an equal grinding efficiency. It was also demonstrated that breakage characteristics of coals in the mill could not be predicted by the conventional Hardgrove grindability index, HGI, under low filling conditions. On the basis of basic experimental results, a mathematical model was constructed to describe the behaviour in the mill. The model proposed here is based on breakage parameters determined form a batch ring-roller mill and utilizing a new scale-up rule employing apparent grinding energy rates in the batch ring-roller mills as well as large scale ring-roller mills. Furthermore, empirical rule of classification were also added to the mill model. The validity of the model was verified thereafter in large scale mills.

In order to establish a useful monitoring method for predicting the erosion induced by high-speed submerged water jets, we attempt to clarify the relation between the jet-structure and the cavitation noise arising around the free jets, by using two hydrophones, and also analyze the AE characteristics of the impulsive pressures induced by cavitation on the specimen of the impinging jets. It is found that the energies of high-frequency components in the jets change markedly with the injection pressure and the standoff distance. It is found that the AE characteristics are closely related to the impinging erosion.

In order to establish useful techniques of cutting, drilling, peening and flushing by high-speed submerged water jets, we systematically observe the eroded surface on aluminum-alloy specimens in relation to the characteristics of cavitating jets, especially for the impinging jet through lucite specimens, for several types of nozzles. The impulsive pressures induced by the cavitating jets are also measured by means of pressure-sensitive film. It is concluded that the erosion characteristics are quite different in two typical standoff distances, i. e., the 1st and the 2nd peak. Cylindrical, small and deep pits predominantly occur at the 1st peak, while small lots of plastic deformations predominantly occur in the 2nd peak. Therefore, the 1st peak is suitable for cutting, while the 2nd peak is suitable for peening.

In order to extend the working range of high-speed submerged water jets and to improve its accuracy confidence, the jet working characteristics are studied under the condition of widely varying ambient pressures P2. The erosion tests were systematically carried out by using aluminum-alloy specimens, and the aspects of the cavitation clouds around the jets were simultaneously observed. Clearly, the pressure P2 drastically affects the aspects of cavitation and its occurrence region. With increasing P2, the length of the cavitating jet decreases, so that the standoff distance, where the most severe erosion appears, shifs upstream. In short, the intensity and the distribution of the impulsive pressures induced by the cavitating jets also drastically change with P2. The impinging erosion characteristics are also sensitive to the standoff distance and the injection time.

In order to clarify structures of high-speed submerged water jets and to predict the jet working capacity, we systematically measured the cavitation noise around the jets using a hydrophone, for several nozzles. The power spectra and the rms values of the cavitation noise are carefully analyzed. Clearly, cavitation noise created by the jets is related to the behavior of cavitation bubble clouds, and the cavitation noise characteristics are markedly changed with the injection pressure and nozzle geometry.

High-Speed submerged water jets have two characteristic peaks with respect to the stand-off distance, in the same manner as high-speed water jets in air. In order to clarify the behavior of the impulsive pressures at these two peaks, we systematically carried out erosion tests using an aluminum-alloy specimen in a wide range of the injection pressure P1 from 10 to 70 MPa, and microscopically observed the eroded surfaces by SEM. We find that the mass loss rate Δm^^· at the 1st peak is decidedly due to the water-column impact, so that it is very sensitive to the injection pressure P1, while Δm^^· at the 2nd peak is due to the shock pressures of cavitation bubble collapse, so that it is not necessarily sensitive to P1. We also indicate that the form and the speed of erosion change markedly with the differences in the jet structure with the stand-off distance x/D.

In this paper, we attempt to clarify the jet structure and the behavior of severely erosive cavitation clouds around a high-speed submerged water jet, using a high-speed movie camera with a framing rate of ten thousand frames. The effects of the injection pressure and the nozzle geometry on cavitation are also investigated. The experiments are performed with both a free jet and an impinging jet. It is clearly found that the cavitation clouds are periodically discharged. The cavitation clouds are also closely related to downstream instability and to the impinging erosion.

In order to establish techniques of cutting, drilling, peening and flushing by high-speed submerged water-jets, we systematically observe the eroded surface on aluminum-alloy test-pieces in relation to the aspects of cavitating jets, especially for the impinging jet through lucite-test-pieces, for several types of nozzles. The impulsive pressures induced by the impinging jets are also measured by means of pressure-sensitive film. It is concluded that the erosion characteristics are quite different in two regions differentiated by the standoff distance. Cylindrical, small and deep pits occur in one of the regions, while small lots of plastic deformations occur in the other region. The former is suitable for cutting, while the latter is for peening.

This paper aims to clarify peculiar phenomena arising around a ultra high-speed submerged water jet accompanied by very severe cavitation. By means of a flow visualization technique with a xenon flash light, three kinds of water jets are carefully observed, and the spatial distributions of cavitation-pressure pulses around the jets are also measured with pressure-sensitive film. The effects of the working pressure and the shape of nozzles are clarified systematically. Thus, the characteristics and the structures of ultra high-speed cavitating submerged water jets are clearly shown.

This paper describes pneumatic atomization test results of Coal-Water-Mixture (CWM) conducted at Babcock-Hitachi K.K. The main purpose of our study is to delineate the effects of CWM properties and the atomizer structure on spray characteris-tics.In order to obtain the necessary data concerning the structure of atomizers and to de-termine the optimum atomizing conditions, numerous experiments have been carried out under various liquid flow rates and air-to-liquid mass ratios using water instead of CWM for various types of internal mixing atomizers. As a result, it has been clarified that ato-mization improves as the liquid flow rate increases provided that the air-to-liquid mass ratio is kept constant. The optimum configurations of the exit ports has been determined ex-perimentally in the aim of reducing spray droplet sizes.The test results achieved in the experiments using various CWMs suggest that pseudo-plastic CWMs are easier to atomize than CWMs of other apparent rheological characteris-tics; that is, pseudo-plastic CWMs reduce the amount of coarser droplets produced by disin-tegration of film-like CWM at the exit ports of the atomizer.The mathematical expression of the spray mean droplet sizes of CWMs and water de-rived from the present study for pneumatic internal mixing atomizers correlated with the test results.

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An experimental study was carried out to clarify the effect of the droplet and coal particle sizes of coal—water mixtures (CWM) on combustibility, using a twin-fluid atomizer in a small-scale test furnace of 80 kg CWM/h. It was found that the spray mean droplet size became smaller as the coal particle size decreased, while other conditions remained constant, giving rise to better combustibility. However, the combustion efficiency decreased by the blow-off of flame phenomena when the atomizing speed increased even though the spray mean droplet size decreased. It was also confirmed that the combustion efficiency was influenced by the specific surface area of coal particles even if the spray mean droplet sizes did not change. When CWM with a nominal top size of 150 μm was compared with that of 590 μm but containing more fines of less than 5 μm, the size distribution of fly ash was found to be independent of coal particle size distributions of CWM, resulting in no difference in the unburned content in the fly ash.

The effect of fine particles on the storage stability of CWM has been investigated, and the method to improve the stability has also been studied. The stability of CWM is considered to depend upon the amount of fine particles present in the slurries, and it improves with an increase in the amount of fine particles. The characteristic parameters in the particle size distributions and slurry rheology are correlated with the stability of CWM.

In order to elucidate the atomizing mechanism of Coal Water Mixture (CWM), several experiments on the atomization of CWM will be carried out with twin fluid atomizers. The effect of coal sizes on the formation of CWM spray droplets is investigated in detail. It is also found that large droplets of CWM spray consist of numerous fine coal particles and that large coal particles do not form "Nucli" of large spray droplets. From these experimental results, the breakup mechanism of CWM uneer high shear stress by gas-blasting at the exitport of the atomizer is proposed.