This paper describes the image processing of visualized streak lines. Two-dimensional steady jet flow from the restriction of a spool valve is visualized by the hydrogen bubble method. The photographs of streak lines are taken with a 35mm camera, and the coordinates of streak lines are fed into a microcomputer using a digitizer. Since streak lines coincide with streamlines for steady flow, a streamline coordinate system is used to conveniently calculate free streamlines of the free jet flow. A flow net, consisting of streamlines and curves orthogonal to the streamlines, is constructed. Finite difference approximation is applied to the basic equation of the streamline coordinate system. The velocity, vorticity and pressure at each node of the flow net are calculated using finite difference equations. To estimate the accuracy, these values are substituted into the equations of continuity and metric coefficient. The calculated results of residuals show that the present method is useful for analyzing flow with free streamlines.

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Power expended theorems or energy methods are generally used for structural analysis in materials science. These theorems are constructed from the standpoint of statics and most of them cannot be employed when dissipative phenomena are considered. In the present paper, a power expended theorem for magnetic fluids is obtained for the first time considering both internal rotation and electrical conduction. The derivation is based on the kinematic balanced equations and constitutive equations for conducting magnetic fluids assuming that suspended fine particles rotate rigidly and the velocity of fluids is much smaller than that of light. In developing this theorem, we expect to find some useful information concerning both the flow field and the electro-magnetic field in the flow of magnetic fluids.

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A new procedure for a numerical analysis of a two-dimensional incompressible potential flow through cascades of airfoils with arbitrary profiles has been presented. The procedure consists of three steps. At first, a cascade of airfoils in a physical plane are transformed into a near-circle row using a simple mapping function; then the flow field through near circles in the mapped plane is calculated with the singularity method. Finally, the flow in the mapped plane is transformed back into the physical plane. The method for determination of parameters of the mapping function to obtain near-circles with sufficiently smooth contours in the mapped plane, which is indispensable in achieving the highest numerical accuracy in the singularity method, has been proposed. The validity of the procedure is demonstrated by comparing the present results with exact solutions, which indicates that the present procedure is very useful for the computation of the cascade flow with simple thin airfoils as well as many practical airfoils with a camber and thickness.

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An analysis is performed on the trailing edge noise which is one of the important mechanisms of noise generation in flow machines. An acoustic field is treated where a semi-infinite flat plate is placed parallel to the inviscid uniform flow with incident vorticity waves convected from the upstream direction. Applying the Wiener-Hopf technique, we obtain an exact solution to the sound pressure proportional to the amplitude of the incident vorticity wave without restriction of frequency or velocity. The calculated acoustic field, which varies with flow velocity, exhibits general features of the sound pressure level (SPL) in a cardioid pattern with the constant phase surface distorted by the main flow. The relationship between flow velocity and SPL is ascertained to be dependent on the 5th law at low Mach numbers. However, the results show that such dependence does not hold at higher Mach numbers where the radiated noise level rises progressively as the flow velocity increases.

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The momentum transfer across an air-water interface was experimentally studied in a horizontal rectangular channel. The water flow Reynolds number, based on a hydraulic diameter, was fixed at 11500, while the air flow Reynolds number was varied from 0 to 5000. The streamwise air flow velocity was measured by a hot-wire probe. For the water flow, streamwise and vertical velocities were measured by using a split-film probe. The behavior of streamwise turbulence intensities showed their dependence on the interfacial shear stress. On the other hand, the vertical turbulence intensities showed less dependence on the interfacial shear stress. When the interfacial waves were formed, the increased Reynolds stress near the interface was measured. As a possible explanation of this increased Reynolds stress, nonlinear motion caused by the nonuniform distribution of the interfacial shear stress was proposed.

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Oscillation modes of nearly circular shock waves in supersonic radial flow were investigated both theoretically and experimentally. The shock waves deformed from circular shape were obtained by the asymmetric back pressure produced by down-stream obstacles. Oscillation modes of the shock waves were investigated by means of statical study of the phase function and mean coherence in each static mode. The oscillation consisted of mode 0 and the same mode as the original static shape. The frequency of each static mode depended on the deformation from the real circle.

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The interaction of a weak normal shock wave with a turbulent boundary layer developing along the wall surface of a supersonic diffuser was investigated experimentally, where the flow Mach number was 1.14∼1.53 and the Reynolds number based upon boundary layer thickness was 1.35∼2×10⁴. Detailed streamwise surface pressures were measured, and a number of data sets obtained by wall pressure transducers were statistically analyzed. The power spectral density function, the intermittency and the higher-order moments of the surface pressure fluctuations were taken. The objective of the present experiment was to investigate the behaviors of the oscillations caused by the normal shock wave/turbulent boundary layer interaction (STBI). The results show that the intermittent feature of the unsteady shock motion is similar to those in external flows and that the maximum standard deviations correspond to points where the intermittency factor approaches 0.5 and are significantly influenced by flow separation. Also the present study indicates that far downstream from the STBI region the amplitude of pressure fluctuations is nearly independent of the flow Mach number.

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This paper deals with a real-time measuring method of the progressive wave of fluid velocity pulsation in a pipe, which is necessary for the development of an active attenuator of pressure pulsation in liquid piping systems. The principle of the present measurement is to obtain the fluid velocity (cross-sectional average velocity) signal by integrating the difference between signals produced by two pressure transducers spaced a suitable distance apart, on the basis of the momentum equation, and then to obtain the progressive wave component of fluid velocity pulsation from the pressure and velocity signals by a simple algebraic operation according to the plane wave theory. A general-purpose digital signal processor (DSP) has been used for the high-speed calculation necessary for the real-time measurement. The measured values agree with the theoretical results within the experimental errors which are mainly due to the detection accuracy of the pressure transducer and the resolving power of the A/D converter of the DSP, except for the frequency ranges of nearby resonant frequencies. The applicable limit of this measurement is the frequency range above about 15Hz, mainly because of the detection accuracy of the pressure transducer.

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The response of an axially excited cylindrical liquid column consisting of frictionless and incompressible liquid has been investigated for a harmonic excitation. The column is located between two discs such that the free liquid surface exhibits there a stuck-edge boundary condition. Free surface displacement and velocity response have been determined. The results will be used for the efficient planning of the "LICOR" experiments in the second German Spacelab mission (D-2).

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This paper presents the results of an experimental study on the deflection and reattachment of a radial turbulent jet (main jet) discharged from a cylindrical nozzle onto an adjacent disk plate in the presence of a lateral control flow from an annular nozzle. The main content of this report concerns the effects of various nozzle distances, control flow rates and control momentum fluxes on the deflection properties of the main jet in the region near the nozzle exit. The relationship between the deflection angle of the main jet, the control flow rate and the control momentum flux was clarified. The changes of the maximum jet velocity, the turbulence intensities at the velocity maxima and the jet half-width along the deflected distance measured from the virtual origin of the jet were obtained for various experimental conditions.

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In this paper, a high-speed digital valve whose switching speed is within 100 microseconds is developed. Commercially available multilayered piezo devices are used to drive coupled poppet-type valves directly. By introducing a kind of feed forward control and employing some new methods, on-off-type coupled poppet valves with high-speed response to within 100 microseconds of switching speed are successfully developed. The valve is ascertained by experiment to respond and follow a 2kHz rectangular wave input. In addition, in one of its applications, a high-speed, two-stage digital servo valve is developed by using the high-speed digital valves as the first stage. The second-stage spool valve, as a load, is driven by a couple of the first-stage on-off valves.

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The streamwise development of turbulence in the free convection flow between vertical parallel plates (5m long and various spacings B) was experimentally studied. To control inlet disturbance, a bell-mouth entrance was installed at the lower end of the vertical parallel plate channel. The turbulent quantity profiles (velocity, intensity, turbulent heat flux and kinetic energy production) were measured in the vertical channel at heights X (110, 820, 1690, 2630 and 3840mm) and at spacings B of 50, 100 and 200mm. The streamwise development of intensity profiles of vertical velocity and the beginning of the transition seem to be closely related to the development vertical velocity profiles through buoyancy effects. The measured profiles of the turbulent kinetic energy production and the turbulent heat fluxes seem to clarify the characteristics of turbulence intensity.

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The aim of this research is to obtain a basic quantitative understanding of the effect of a noncondensable gas on the absorption of water vapor by a H₂O/LiBr combination with n-octanol as the surfactant. Nonflowing aqueous solutions of LiBr (40, 45, 50 mass%) were exposed to saturated water vapor following the addition of an n-octanol surfactant (0.01 and 0.6 mass%). A small amount of a noncondensable gas (air) was allowed into the absorber (3×10^-7 moles, i.e., 0.03 volume%) and its effect was analyzed by measuring the temperature and amount of water vapor absorbed. The results indicate that, in the presence of small amounts of a noncondensable gas, vapor absorption enhancement ratios are less than half of those obtained under the same experimental conditions when a noncondensable gas is not present. The presence of a noncondensable gas causes the partial vapor pressure of air to increase at the vapor/liquid interface, which results in a lower vapor absorption rate and, hence, in an inhibition of interfacial turbulence.

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A model for the premixed turbulent flame structure has been developed in which the flame zone of a turbulent flame is composed of two parts: a wrinkled flame front and some island flamelets behind it. Their fractions are supposed to vary continuously according to a proposed function of u'/S_LO, where u' is the turbulence intensity and S_LO is the laminar burning velocity. All flamelets were assumed to be fractal ones. The concepts of "flame thickness" and "transition time" for laminar flames were introduced into the model for turbulent flames. The model provides not only the structural parameters, but also the burning velocities of turbulent flames.

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The temperature has been measured in a field in which laminar hydrogen (6.0m/s at the center of a burner exit) was injected into a coflowing air stream (6.0m/s) with certain kinds of grid turbulence. It is shown that the ratio of a laminar flame length to the turbulent one is proportional to the turbulent Reynolds number, Re_l, (integral scale is considered a characteristic length) in the measured extent (Re_l≤1000), and therefore, that the integral scale of a reactant flow is an important parameter for the flames in this paper. The width of a flame displacement is estimated from the temperature profiles when the flame is assumed to be a wrinkled laminar flamelet. The width is also measured directly by a flow visualization method. Both the widths obtained by the two different methods agree well with each other. This indicates that the turbulent flame in this paper can be treated as a wrinkled laminar flamelet.

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Experimental investigations on the aerodynamic structure of a laminar boundary layer diffusion flame over a horizontal flat plate have been performed. When a fuel (methane) is injected upward, the velocity around a flame zone is locally accelerated, and the velocity gradient at the wall is increased as compared with that of an isothermal flow. On the other hand, when a fuel is injected downward, the velocity is retarded, and the velocity gradient at the wall is decreased not only in the downstream region of the leading flame edge but also in the upstream region. This shows that the gravitational force varies the local pressure distribution not only in the downstream region of the leading flame edge but also in the upstream region. It is also elucidated that the velocity gradient of the free stream velocity varies the velocity profiles in a boundary layer.

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The effects of various basic factors of combustion conditions and coal properties on thermal NO_x formation behaviors in pulverized coal combustion have been experimentally clarified, and a theoretical analysis for the flame structural change around a coal particle has been performed, including full chemical kinetics of prompt NO_x formation. Thermal NO_x concentrations much higher than those predicted by the extended Zeldovich mechanism have been experimentally observed even in the usual pulverized coal combustion conditions. The contribution of thermal NO_x to the total NO_x rapidly increases with the increase of flame temperature and oxygen-fuel stoichiometric ratio, especially for highly volatile coals. Both the large amount of thermal NO_x formation and the effects of various factors on it have been well explained by considering the prompt NO_x formation in the flame zone around each coal particle through HCN and NH formed by the reactions between N₂ in air and hydrocarbons in the evoluted volatile matter.

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A new combustion system called a jet-mixing-type combustor was designed to obtain a nonluminous blue flame of a kerosene spray. A spray was injected by a conventional-type swirl atomizer into the combustor, and combustion air was introduced through a baffle plate with 16 inlet holes. The principle of this combustion method was revealed as a prompt mixing of the air and spray, which was achieved by high-speed air jets. The combustion characteristics such as combustion stability, temperature distribution and exhaust emissions were compared with a conventional swirler-type combustor. NO and THC emissions exhausted from nonluminous kerosene flame were at lower levels than those exhausted from the swirler-type combustor.

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It is generally acknowledged that NO_x emissions and unburned gasoline from engines play an important role in their formation of low-temperature sludge. This report describes the process by which unburned gasoline is absorbed into the engine oil. This was clarified by analyzing the blowby gas condensate, crankcase gas condensate and engine oil. It was found that unburned gasoline is mainly absorbed into the oil through oil film on the cylinder wall and oil in the ring grooves, and it is vaporized from the oil in the crankcase. The effects of the engine operating conditions on the quantity of unburned gasoline in the oil and the crankcase gas were also clarified, as well as their effects on the composition of the unburned gasoline in the crankcase gas.

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This paper deals with a successful attempt to employ the exhaust gas of a two-stroke cycle gasoline engine as an energy source to a burner and heat a Stirling engine, and to clean the exhaust gas by a catalyzer. By means of a rotary valve and the exhaust pipe sections, the exhaust was separated into a high concentration of fresh gas and a high concentration of combustion gas. The former gas was burned by a burner, and then used to heat a Stirling engine. The latter gas was disposed of by an oxidization catalyzer. The investigation revealed the enthalpy and exergy flows of a two-stroke cycle gasoline engine, a burner, a catalyzer and a Stirling engine, and then the emission gases (HC, CO) were disposed of by the burner and catalyzer. The investigative analysis shows a method of successfully transferring the energy available in the exhaust gas for the combustion of a burner and the operation of a Stirling engine, and the near-perfect elimination of the emission gases in the exhaust gas by a burner and a catalyzer.

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This paper reviews the design of the EPDC's Wakamatsu high-temperature turbine and the operating performance of its first-step verification test, STEP I, which features main/reheat steam temperatures of 593°C/593°C. In designing this turbine, a number of new concepts for elevated temperature use were incorporated, and several types of new heat-resistant steels were used in the major parts. Since the initial startup in November 1986, the operating performance of the Wakamatsu high-temperature turbine STEP I has so far demonstrated high reliability, and many valuable data are being obtained, proving the practicality of a large-capacity USC turbine.

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In recent years, a wide variety of papers on the Stirling engine and its unique properties have been published. However, the available knowledge on noise and vibration characteristics of Stirling engines is very limited. This paper presents experimental results which are useful for modifying the engine parts influencing the noise and vibration characteristics of the reciprocating kinematic Stirling engines. In order to clarify the noise and vibration sources of a 3 kW-class Stirling engine, the modal analysis for the engine parts and the measurement of sound intensity were examined. As a result, it was clarified that modifications for the combustion system and the driving system, particularly with respect to the crankshaft, can be made for decrement of the engine noise and vibration. Through the application of the proposed modifications, the 1987 engine noise was greatly decreased, and the 59 dB(A) noise level was measured under normal conditions.

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