A fine interfacial wave pattern was observed on the thin liquid sheet jet in a cocurrent gas stream. The experimental observation revealed that this wave motion affected on the disintegration of the liquid sheet. To clarify the factor affecting the liquid sheet wave motion and disintegration, the fine interfacial waves were investigated experimentally. The fundamental mechanism of the fine interfacial waves was described. Then, the instability of the plane liquid sheet was also analyzed by numerically solving the Orr-Sommerfeld equation. Comparing the theoretical results with the experimental results, the hydrodynamical mechanism of interfacial wave occurrence was explained. Also, it was suggested that the interfacial wave was caused by the internal instability of the plane liquid sheet.

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Due to the surface tension, the liquid viscosity and the liquid inertia, the pressure in a mixture element containing either a gas or a vapour bubble is distributed nonuniformly and shows discontinuity at the bubble boundary. This fact is taken into account by means of an equivalent pressure, which is used in the momentum equation. Two models of wave propagation are analysed. In the first, the inertia during spherical motion of the liquid surrounding the bubble is taken into account whereas in the other, it is neglected. Formulas for group velocities corresponding to both models are derived.

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Damage due to the coupled action of cavitation erosion and silt abrasion, in which artificial silt (Al₂O₃) was included, was experimentally studied using submerged jets. The magnitudes of the acoustic emission energy, impact pressure and material damage rate caused by the cavitating jet impingement were greater than those caused by the noncavitating one. Good correlations between the above three erosion intensity parameters were also confirmed. The SEM photographs of damaged surfaces showed that the edge of the abrasion trace was partially broken into pieces by cavitation. The material surface was smoother and the abrasion pattern was changed compared to that of pure abrasion.

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Vibratory-erosion tests on a typical ductile material, 304 stainless steel, were carried out under a specified condition of uniform cavitation-nuclei-size distributions. We systematically investigated the behavior of fracture modes on a smooth surface one order of magnitude smaller in roughness than the ASTM recommended value, as well as the small roughness effect in the development and/or propagation of cracks and particle fall-off in the second stage of the incubation period by means of a scanning electron microscope. It is clear that the mode is fatigue and ductile fracture, and also that slight roughness plays an important role in the development and/or propagation of the cracks and also in microscopic removals, which shorten the incubation period.

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In order to establish an accurate measurement method of flow rates Q and particle concentrations C_v in heterogeneous solid-water flows, the discharge coefficients of the Hershel venturi are carefully investigated in both horizontal and vertical arrangements for six kinds of solid-water flows for various Q and C_v. The results shown in simple formulas indicate that the Venturi is an accurate meter for spherical particle-water flows.

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An indirect measuring method with self-check function for high-frequency pulsating flow rate is proposed, and a measuring system based on the method is set up in this paper. The system can examine by means of its self-check function whether measured results of flow rate are accurate and reliable without using any other fluid measurement or flowmeters. The experimental results show that the system can be applied not only to the measurement of various unsteady flow rate signals, such as high-frequency pulsating flow or even nonperiodic random flow, but can also be used as a comparison standard for evaluating other measuring methods. The research provides an important measuring means for studying the dynamic characteristics of hydraulic components or systems and for developing new instantaneous flowmeters.

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A set of steady inviscid equations governing the flow along a given S₂ relative stream surface in a mixed-flow turbine runner having a finite number of thick blades was obtained. By applying the streamline-curvature method, this set of equations can be solved. A computer program is developed in order to calculate the flow field on the S₂ surface. The comparison with the results of the potential flow theory shows a marked effect of the blade loading.

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The effects of mistuning on flutter suppression for a fully stalled cascade in pitching motion in which two kinds of blades, each with a different natural frequency, are arranged next to each other, are examined. Numerical results are obtained for several cases by changing the natural frequency of the blade, and some fundamental aspects are clarified. As a result, it is found that the flutter suppression effect is observed in the case of a fully stalled cascade well as an unstalled cascade, but the effect of the former is much stronger with small chane of mistuning compared to the latter. Furthermore, the effect is more remarkable for the turbine side compared to the compressor side.

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Research was carried out on the pumping effect of a vibrating pipe system. Measurements were made on the relative displacement of the vibrating pipe and the valve, and the pressure and flow rate in the pumping system. Relevant time historical data are compared and details on the hydrodynamic mechanism of the pumping effect are discussed in this report. Analysis on the fundamental pumping energy for investigating the energy conversion between the vibrating pipe and fluid was also carried out and these results are introduced as well.

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We have measured the thermal conductivities and electrical resistivities of Y₁Ba₂Cu₃O_7-y, Er₁Ba₂Cu₃O_7-y and Bi₁Sr₁Ca₁Cu₂O_y compounds using the steady-state comparative method and conventional four-probe method. Below the transition temperature, T_c, the thermal conductivities had strikingly large values and a maximum value. By applying the Wiedemann-Franz law, λR/T=L₀, with the electrical resistivity data at T_c, the phonon-thermal conductivities were found to predominate in those superconductors. The normalizations of the measured thermal conductivities of those superconductors with respect to λ_C, critical thermal conductivity, show that the temperature dependence of the thermal conductivity of Y₁Ba₂Cu₃O_7-y is similar to the dependence of La_1.8Sr_0.2Cu₁O_4-y, Er₁Ba₂Cu₃O_7-y and Bi₁Sr₁Ca₁Cu₂O_y compounds. Most of the normalized thermal conductivities agree with our theory, λ_s=2ξ²·λ_n/(1+ξ⁴), in which the value n of the phonon thermal conductivity in the form λ_n=ξⁿ in the normal conducting state is between -1 and -1.5 below T_c.

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Heat transfer experiments have been conducted for strongly heated gas flow in an annular duct. Special attention is paid to the laminar-turbulent transitional region. The results show that laminarization was not observed within the range of the experiments, although this phenomenon took place in a heated circular pipe when other conditions were the same. Above a certain heat flux, the heat transfer coefficient in the downstream region tends to follow a new correlation : Nu_s=0.071Re^0.6_b Pr^0.4_b, which is independent of the heat flux. Numerical analyses are made using three types of turbulence models : k-kL-(uv)^^^-, k-ε-(uv)^^^-, and k-εmodels. The calculations were compared with the measurements, and better agreement was obtained for the k-kL-(uv)^^^- model.

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The purpose of this study is to obtain basic knowledge of the heat and mass transfer processes in the absorber, as affected by Marangoni convection induced by surfactant addition. We apply a nonflowing bulk absorption model and assume that a dropwise surfactant is fixed on the absorbent surface. The surface-tension difference between the surfactant (n-octanol) and the absorbent solution (H₂O/LiBr) is considered to be of a constant value (Δσ=20x10^-3N/m). Four governing equations-continuity, laminar momentum, energy, and diffusion-are solved numerically to obtain the unsteady temperature and concentration distributions from the time when Marangoni convection starts until dimensionless time is t=10, for various aspect ratios (AR=thickness of absorbent solution/length of model cell). The influence of the absorbent-solution depth on the occurrence of Marangoni convection is quantified in terms of a mean Sherwood number and a mean Nusselt number for several AR values. As a result of these calculations, absorption-enhancement ratios are obtained for each calculation parameter AR by comparison of the surfactant-added and nonadded conditions (vapor-absorption amount with surfactant addition/vapor-absorption amount without surfactant addition).

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Absorption and desorption of fuel by motor oil that coats the side wall of the cylinder with a thin oil film is thought to be one of the important sources of unburnt hydrocarbon emissions from spark ignition engines. In order to determine the effect of oil layers on exhaust hydrocarbon emissions, the total hydrocarbon concentration (THC) in the exhaust gas is measured by a flame ionization detector when a constant amount of motor oil or castor oil is placed on the piston crown. Experiments show that the THC in the exhaust gas increases in proportion to the amount of added oil, and that the addition of castor oil causes a higher increase of the THC than the addition of motor oil. A numerical model which describes the process of fuel absorption and desorption in the additional oil layer on the piston crown is developed. Calculated results confirm that the increase of measured THC occurs because the absorbed fuel in the oil layer on the piston crown is released in the cooling cylinder gas during the expansion and exhaust strokes.

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The Sauter mean diameter and size distribution of a diesel spray in a vaporizing process were studied to obtain detailed information of the diameter change of the spray in an elevated-temperature and-pressure environment. In this study, direct photographs of the diffracted light from particles or spray drops were taken using a pulsed laser and analyzed directly. The mean particle size could be measured even if the diffracted light from particles passed through a high-ambient-temperature and-pressure environment. The liquids used for studying a vaporizing diesel spray were diesel fuel and n-heptane. The Sauter mean diameter increased to a maximum, then decreased with a further increase of the ambient temperature. The change of the Sauter mean diameter was different for different fuel evaporation rates. The increase of the Sauter mean diameter of n-heptane spray occurred at a lower ambient temperature condition than did that for the diesel spray.

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Numerical simulation was carried out to clarify three-dimensional air motion in the swirl chamber of a diesel engine. Simulations have been performed using spherical swirl chambers with different sorts of connecting ports. The results obtained are as follows. (1) Toward the end of the compression stroke, the swirling flow becomes strong. On the other hand, the flow normal to the swirling surface becomes comparatively weak. (2) According to the jet of a subconnecting port, the swirling flow in the end stage of the compression stroke becomes weak in the central part. (3) The spatial distribution of strong turbulent intensities corresponds to the strong flow field and the shear force field based on inlet flow.

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In a two-stroke-cycle gasoline engine, the scavenging flow plays a very important role in the combustion performance. The scavenging flow discharges the burned gas from the cylinder and draws the mixture of fresh air and gasoline into it. However, the flow pattern in the loop-flow scavenging system of this type of engine is very complicated and the measurement of the gas velocity and the gas concentration is difficult. Thus, there is little information on the flow characteristics in the cylinder. The authors have developed a simulation method for the uniflow scavenging two-stroke-cycle diesel engine. In this report, the authors outline the development of this method, applying it to the loop-flow scavenging two-stroke-cycle gasoline engine. The characteristics of the gas flow and the gas concentration in this engine are made clear by the simulation method.

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Measurements of cylinder bore deformation were made along the circumferential direction during actual engine operation. A piston, whose upper part was capable of turning, was installed on the pin boss and was slowly turned from an outside power source by means of a gear train. A heat-proof inductance-type gap sensor was embedded on the second land surface. When the engine was under steady-state operation, the piston position at any crank angle was fixed every cycle, not only axially but also inside the corresponding cylinder cross section. As a result, the cylinder bore deformation was continuously measured by one sensor along its entire periphery at one desired axial piston position. One of the important measurement results was that the compound effect of head bolt force and thermal stress had a significant influence on the bore deformation.

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Recently, due to need for longer blades, titanium alloy, in which 12% Cr stainless steel has been used, is targeted for use as a blade material. The 12% Cr stainless steel has been protected with Co-base alloy. The longer blade with higher peripheral speed is subjected to severer conditions involving erosion caused by water droplets in wet steam. Because titanium alloy will not accept application of Co-base alloy, a new erosion-shield material must be developed. Prior to the design of longer blade, a shorter blade of titanium alloy had been put on a 50-MW unit which has been in service for 15 years. This paper describes that the predicted erosion rate which had been derived from the evaluation method coupled with laboratory test results corresponded to the actual observed results on the unit and that titanium alloy is stronger than the conventional material.

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