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Ichiro HIGASHINO
1986 Volume 52 Issue 480 Pages
2775-2778
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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Norio SANADA, Kazuyoshi TAKAYAMA, Osamu ONODERA, Jun IKEUCHI
1986 Volume 52 Issue 480 Pages
2779-2786
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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In the present experiment, interaction of an air bubble with a shock wave generated by explodinga 10 mg PbN
6 pellet in water was observed using double exposure holographic interferometry. The reconstructed interferograms clarified the detailed behavior of the collapsing bubble near the solid walls with different acoustic impedances. It was found that the shock wave and micro-liquid jet could be induced when the volume of the bubble was minimum. The impact pressure induced by the bubble collapse was measured by a pressure gauge with a side frequency response and found to be about 400 MPa.
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Koichi NAKABAYASHI, Yoichi TSUCHIDA
1986 Volume 52 Issue 480 Pages
2787-2793
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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The spatial and temporal characteristics of wavy and modulated wavy Taylor vortex flow (WVF and MWVF) between two concentric spheres with the inner sphere rotating (the spherical Couette system) are investigated using the aluminum-flake method. The WVF and MWVF having no spiral Taylor-Gortler vortices are realized by a slightly greater acceleration rate of the Reynolds number than that of quasi-static increasing. Four mirrors are used in the case of the front lighting of the whole region to determine the time evolution of the entire wave pattern around the sphere. Observing the meridional cross-section of the spherical annulus by slit illumination, and taking a photograph of it are also employed to obtain more quantitative data than those in the case of front lighting. The results of the spherical Coutte system are compared with those of the circular Couette system.
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Takaaki SHIZAWA, Shinji HONAMI
1986 Volume 52 Issue 480 Pages
2794-2801
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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Turbulent shear flows over a concave surface are subjected to streamline curvature. The objective of the present paper is to clarify experimentally the response of the turbulence structure to the concave curvature without the substantial pressure gradient. Measurements of Reynolds stresses and triple products of the velocity fluctuations are made. The momentum thickness Reynolds number is 2, 900 and the effective curvature parameter kδ deduced from streamline curvature is -0.023 at the onset of curvature. A fast response of Reynolds stresses and triple products to a step change in the surface curvature is prescribed by the behavior of the effective curvature parameter.
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Takaaki SHIZAWA, Shinji HONAMI
1986 Volume 52 Issue 480 Pages
2802-2809
Published: August 25, 1986
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Turbulent shear flows over a concave surface are subjected to streamline curvature. The objective of the present paper is to clarify experimentally the turbulence kinetic energy and shear stress balance in a boundary layer having a mild surface curvature without substantial pressure gradient. Each term in the transport equation for the turbulence kinetic energy and shear stress is deduced from the data. The extra rate of mean strain 2kU due to curvature makes a positive contribution to the production of v^
-2. The effect of the concave curvature on the production of the Reynolds stress - (uv)^^^ is larger than the production of the turbulence kinetic energy. The structure of the turbulent boundary layer over a concave surface is prescribed by the energy balance.
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Michinori MATSUSHITA, Fumio BEPPU, Teruaki AKAIMATSU
1986 Volume 52 Issue 480 Pages
2810-2818
Published: August 25, 1986
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A new method is proposed for solving the initial value problem of a partial differential equation with both convective (hyperbolic) and diffusive (parabolic) term. The hyperbolic and parabolic term are approximated by the third order upwind and second order central difference method respectively. The resulting set of ODEs are solved by the third order Adams-Bashforth method. Linear stability analysis is performed and the amplification factor is examined.
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Yoshikazu SUEMATSU, Tadaya ITO, Norihiko KATO
1986 Volume 52 Issue 480 Pages
2819-2827
Published: August 25, 1986
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In the preceding report, the authors proposed a theoretical model based on the inviscid linear theory, which explains the growing process of the axisymmetric type vortex breakdown, namely the process of birth and growth of a bubble in the swirling pipe flow. The present work describes the numerical analysis of the vortex breakdown (axisymmetric). The Navier-Stokes equations are solved in the range of Reynolds number R
e = 100 300, under the boundary condition of pipe entrance that the swirling velocity is varied abruptly. The aspect of streamlines and streaklines in time sequence clearly shoed the growing process of the bubble. And it is clarified that results from the inviscid theory mentioned above are in qualitative agreement with those of this work. Further, the occurring condition of the vortex breakdown and the axial position of the bubble in the pipe were also discussed using numerical solutions for various entrance boundary conditions.
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Tohru FUKANO, A.A. TALUKDER
1986 Volume 52 Issue 480 Pages
2828-2836
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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The effect of the angle of attack, the shape of the rear part of a test plate and the free stream velocity on the discrete frequency noise (DFN) generated from an inclined flat plate immersed in the flow were investigated experimentally. To explain the relationship between these and the sound pressure level of the DFN, detailed measurement of the flow properties around the plate has been carried out. It was shown that the equations proposed by Clark and the authors are both usefull in predicting the DFN sound pressure level.
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Yukio TOMITA, Susumu INAGAKI, Shoji SUZUKI
1986 Volume 52 Issue 480 Pages
2837-2843
Published: August 25, 1986
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In the turbulent wake behind an upstream cylinder in a uniform flow, the downstream cylinder was set in the form of an intersection with the upstream cylinder. It was found that the acoustic radiation from the two circular cylinders forming an intersection was far smaller in comparison with that of a single cylinder. The variation of the acoustic radiation was measured by varying the intersectional angle of the two cylinders, the point of mutual contact and the angle between the downstream cylinder and the uniform flow. Moreover, the pressure distributions around both cylinders were measured. The flow pattern has been verified by oil-film and smoke-wire flow visualization. Then, the relationship between the flow and the noise generation was studied.
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Atsushi OKAJIMA, Kenichiro SUGITANI, Taketo MIZOTA
1986 Volume 52 Issue 480 Pages
2844-2850
Published: August 25, 1986
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Flow and aerodynamic characteristics of a pair of circular cylinders arranged side by side in a uniform flow were experimentally studied at high Reynolds numbers near and over the critical one. Pressure distributions, lift and drag coefficients and Strouhal numbers were measured at different spacings in a wind tunnel. There are good agreements between the present results and others at subcritical Reynolds numbers. At high Reynolds numbers over critical one, we examined the relationships among the formation of separation bubbles, the aspect of wakes, and the lift and drag coefficients. Separation bubbles are formed only on the outward sides of two cylinders at small spacings and this leads to a positive and significant increase in lift coefficient, and biased flow with a high Strouhal number like at subcritical Reynolds numbers cannot be observed to appear.
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Tong ZHAO, Ato KITAGAWA, Toshiharu KAGAWA, Toshio TAKENAKA
1986 Volume 52 Issue 480 Pages
2851-2859
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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This paper presents approximate functions of the transfer functions among the pressure gradient, the mean flow velocity and the centerline velocity in axially symmetrical laminar flow, and a new real time measuring method of unsteady flow rate and velocity by the use of an analog electronic circuit whose transfer characteristic is equivalent to the approximate function. Approximate functions are simple but highly precise, and so the analog electronic circuits equivalent to them can be made easily. The unsteady flow rate and the centerline flow velocity obtained from the measured value of pressure difference in the pipe by the use of the analog electronic circuit had a good agreement with the results of numerical calculation and the measured value by LDA. The method presented in this paper makes simple but precise measurements of unsteady flow rate and velocity possible, and is very useful for practical application.
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Soon Bum KWON, Kazuyasu MATSUO, Shigetoshi KAWAGOE, Toshiaki SETOGUCHI ...
1986 Volume 52 Issue 480 Pages
2860-2864
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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The rapid expansion of moist air or steam in a supersonic nozzle gives rise to condensation, and the total pressure of the flow is reduced by this nonequilibrium phenomenon. In the present paper, a loss in total pressure due to condensation has been studied experimentally by pressure measurements in the case of moist air expanding in a supersonic circular nozzle, and the effects of the degree of supersaturation of moist air and the shape of the nozzle on the total pressure loss have been discussed. The length of the region where the total pressure decreases due to condensation is longer than that of the nonequilibrium condensation zone, and the difference in these two lengths increases with the degree of supersaturation. Furthermore, the higher the expansion rate of the nozzle is, and the larger the degree of supersaturation and the total temperature at the reservoir are, the larger the total pressure loss of flow is. These values are about 3 to 8 percent in the present experiment.
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Masataka SHIRAKASHI, Hidenori NISHIYAMA, Shoichi WAKIYA
1986 Volume 52 Issue 480 Pages
2865-2871
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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An aqueous solution of Separan AP-30 (2 or 4 wt%) was pushed out through a circular pipe with a diameter d = 4 or 6 mm, attached to the bottom of a large reservoir. A plane wall was set in the reservoir parallel to the bottom, the distance z from the bottom being adjustable. The flow in the reservoir was observed and the pressure distribution along the channel was measured. The upper wall significantly affected the flow pattern above the pipe inlet ; the transition shear rates from the radial flow with vortex to the spiralling flow and from the spiralling flow to the random flow became lower with a decreasing z/d, and the period of the spiralling flow was shorter with a smaller z/d. For the random flow, the inlet pressure loss increased over a wide range of z/d. For the spiralling flow it decreased in the range z/d = 5 20.
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Toshihiko SHAKOUCHI, Tadaya ITO, Yoshikazu SUEMATSU
1986 Volume 52 Issue 480 Pages
2872-2880
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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A two dimensional jet begins to transverse oscillation hen it impinges on a wedge-shaped object. This is well known as the edgetone phenomenon. Nevertheless the real state of affairs of the phenomenon has not yet been clarified completely. In the preceding paper, the authors proposed a theoretical method which can be applied for prediction of the frequency, from a viewpoint that the oscillation of a jet is nothing but the occurrence of an internal wave in the flow field of a jet. This paper is a sequel of the preceding one. Here, consideration is given to the oscillation mechanism of a jet, and an explanation of the phenomenon is proposed, taking account of the effect of pressure feedback from the wedge in addition to the internal wave conception. And the propriety of this explanation is verified by the comparison of experimental and theoretical results.
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Masaru SUMIDA, Kouzou SUDOU
1986 Volume 52 Issue 480 Pages
2881-2887
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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Numerical and experimental investigations were made of the laminar oscillatory flow of incompressible fluids in curved pipes having rectangular cross-sections. The investigations were carried out for a wide range of four parameters, i.e. aspect ratio of a pipe a, radius ratio R/a, Dean number D and Womersley number a. The velocity profiles and the stream lines of the secondary flow were made clear by numerical analysis. The pressure gradients were obtained by calculations and experiment. The results suggest that the flow through a square curved pipe is most sensitive to pipe curvature.
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Shuzo OSHIMA, Ryuichiro YAMANE, Yoshihiro MOCHIMARU, Toshihiro MATSUOK ...
1986 Volume 52 Issue 480 Pages
2888-2896
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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Continuous casting is becoming standard practice in industrial metallurgy. Some subsequent process could perhaps be saved and the quality of solidified ingots improved if the non-contacting shape control method was developed. In this paper we present the results of an experimental investigation of a jet of mercury emanating from circular and rectangular non-conducting nozzles situated at the end of electromagnetic pole pieces where the magnitude of the magnetic field decreases to zero. The shapes of the free surface of the jet are measured by a spot electrode probe under various experimental conditions. In such a non-uniform magnetic field, there is a longitudinal, recircular current flow which induces the cross-sectional force and increases the jet aspect ratio b
j/h
j. The value of the aspect ratio of the jet issuing from a rectangular nozzle 15 mm wide and 3 mm high increases up to 80.
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Shuzo OSHIMA, Ryuichiro YAMANE, Yoshihiro MOCHIMARU, Toshihiro MATSUOK ...
1986 Volume 52 Issue 480 Pages
2897-2904
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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The shape of a horizontal slender jet of a liquid metal issuing from non-conducting circular nozzles under a non-uniform magnetic field is discussed. Our primary interests are to determine the shape of the free surface of the jet under such a field, and to demonstrate the possibility of the magnetic shape-control of liquid metal jets. The basic equations of MHD flows are simplified by neglecting the terms concerning the viscosity, and solutions of the approximate analysis are presented. Parameters on which the magnetic shaping of jets are dependent are made clear. A jet with a circular initial shape forms a thin sheet, but maintains the same cross-sectional area. The shapes obtained by the approximate analysis are shown to be in good agreement with those of the experimental results.
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Kazuyuki SHIZAWA, Takahiko TANAHASHI
1986 Volume 52 Issue 480 Pages
2905-2912
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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The strong interaction of colloidal ferromagnetic particles dispersed in nonconducting mother liquors shows extraordinary magneto-optical phenomena and non-Newtonian flow characteristics. In this case, a term caused by the strain energy must be added into the constitutive equation of stress in magnetic fluids. In the present paper, a new constitutive equation of magnetic fluids with viscoelastic effect are formulated by the thermodynamic method wherein free energy and dissipation function are used on the basis of kinematical balance equations in the polar fluid theory. As result, not only an interaction term due to internal rotation but also an elastic interaction term are introduced into the system of the equations. And by use of a constitutive equation of magnetization determined here, we can show that an anisotropy of magnetic permability due to a polar effect causes an anisotropy of the refractive index of light in magnetic fluids.
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Seizo KATO, Tetsuo FUJIMOTO, Hirosumi WATANABE
1986 Volume 52 Issue 480 Pages
2913-2919
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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An attempt is made to control the wake behind a bluff-based body and to reduce its form drag with the aid of thin circular-arc guide vanes installed at the base corner. Measurements of the drag, base pressure and pressure distribution of the wake, and visualization of the near wake flow are carried out. They are performed over a wide range of the chord length, C, curvature radius, R, setting clearance, S, and Reynolds number, R
e. The wake is able to be well controlled by adequately installing guide vanes, and the ase pressure remarkably improves. As a result, the drag coefficient decreases to about 25 per cent. The optimum configuration of vanes is R/B ≃ 1, C/B ≃ 0.5 and S/δ
* ≃ 1 or R/B ≃ 0.75, C/B ≃ 0.5 and S/δ≃ 0.5, where B is the body width, and δ and δ
* is the boundary layer thickness and its displacement thickness, respectively.
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Hiroshi KOBAYASHI
1986 Volume 52 Issue 480 Pages
2920-2929
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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The low back pressure supersonic compressor blade flutter in the torsional mode were studied with a controlled-oscillating annular cascade test facility. The unsteady aerodynamic moment acting on an oscillating blade was measured with 18 pressure transducers on a blade surface, in 240 experimental cases which consist of reduced frequencies based on a half chord from 0.0375 to 0.547, 6 interblade phase angles and 5 inlet flow velocities from subsonic to supersonic. The region of unstall flutter occurrence and the significance of 3 parameters on aerodynamic instability were made clear, including the important role of unsteady pressure on the blade suction side upstream of the torsional axis for aerodynamic instability and the effect of shock wave movement due to blade oscillation on flutter.
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Hiromu TSURUSAKI, Kensaku IMAICHI, Ryo MIYAKE
1986 Volume 52 Issue 480 Pages
2930-2938
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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The rotational speeds of stall cells in vaneless diffusers and critical inlet flow angles for rotating stalls under the condition of no scroll were studied experimentally. Two experimental equations on the rotational speeds are derived and a prediction method is presented. The predicted rotational speeds agree well with measured values in the literature. A simple equation on the critical inlet flow angle is derived from the experimental data. The equation is usefull to predict the onset of the rotating stall. In the experiment, a weak velocity fluctuation was found at the position of the reverse flow on the diffuser wall just before the rotating stall. It is concluded that the reverse flow is the cause for the rotating stall in the vaneless diffuser. The conditions of the reverse flow layers on the diffuser wall just before the rotating stall are made clear by a numerical analysis. The properties of the fully developed rotating stall are also presented.
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Yoshito KIMURA, Hirotaka HIGASHIMORI, Norio WATABIKI
1986 Volume 52 Issue 480 Pages
2939-2946
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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Experimental studies were carried out to clarify the mechanism of pressure pulsations, so-called "Inlet Cone Vortex", which is induced by centrifugal fans with inlet guide vanes at partial load. We made detailed investigations into the amplitude and frequency of the pressure pulsations and time-dependent changes of the velocity distribution in the inlet cone. It is shown that the rotation of pressure distribution caused by distorted velocity distribution in the inlet cone emits discrete pressure pulsations.
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Yutaka KAWATA, Kenji EBARA, Sakuichiro UEHARA, Tomoshige TAKATA
1986 Volume 52 Issue 480 Pages
2947-2953
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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The system instability of a centrifugal pump and pipe network is encountered at a power plant. The frequency of the instability is confined to a very low level (4.0 Hz). Judging from the observation that this instability occurs at the pump operating point with negative gradient of head-flow (stable) characteristics and with sufficient NPSH, it is concluded that this is a new type of system instability, different from the classical surging or the cavitation surge of inducers. A series of experimental research to solve the mechanism of this instability is carried out. The research program consists of the measurement of the dynamic behaviour of the centrifugal pump, the confirmation test using similar pipeline and the stability analysis of the system. Our result shows that the matching of the frequency of unstable pump impedance and the pipeline's resonant frequency result in this new type of system instability.
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Yoshinobu TSUJIMOTO, Allan.J. ACOSTA, Christopher.E. BRENNEN
1986 Volume 52 Issue 480 Pages
2954-2962
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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The characteristics of a centrifugal impeller under a condition with leading edge cavitation are analyzed by using conformal mapping methods. It is assumed that the thickness of the cavity is small, and linear cavity models are used. Concerning the treatment of the Bernoulli equation, two different models are considered. The first one is based on a full Bernoulli equation in a rotating frame. In the second model, the Bernoulli equation is linearized on the assumption that the disturbance due to cavity is small. The second model predicts shorter cavity, but the differences in the pressure distribution and in the head coefficient are small for the conditions with the same cavity length. The results of the first model are in general agreement with those by a singularity method and experiments.
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Junichi KUROKAWA, Takayuki ITAMI, Hideaki NAGAHARA
1986 Volume 52 Issue 480 Pages
2963-2972
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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In order to establish a design method of the optimum configurations for the spiral casings of water turbines, a series of studies are performed. In the first report, the flow characteristics in a fixed channel from a spiral casing to guide vane channels are determined theoretically and experimentally using the configurations of a decelerated flow type of spiral casing. The results show that the flow pattern in a spiral casing is a free vortex rV
θ = C, in which only the value of C changes according to each sectional aerea, and that the flow characteristics in a fixed channel are well predicted by a two-dimensional theory if a suitable flow model is introduced. They also show that the flow characteristics at the middle of a guide vane channel become almost axisymmetric in spite of strong non-axisymmetrisity of the inlet flow into the stay vane channel, while the total pressure decreases largely in the range π/2 ≤ θ ≤ 3/2 due to a mixing loss of the distorted flow and a shock loss at the stay vane inlet.
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Izumi USHIYAMA, Hiroshi NAGAI, Jinkichi SHINODA
1986 Volume 52 Issue 480 Pages
2973-2982
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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The Savonius rotor was proposed in the early 1920's. Until now, there has been no systematic work on the optimum design configuration of Savonius rotors. Therefore, in the present work, various model tests were carried out in a wind tunnel, in order to ascertain the optimum design configuration of Savonius rotors. The effects of six design parameters on the aerodynamic performance of the rotors were experimentally determined. These were the rotor aspect ratio, the overlap and the separation gap between rotor buckets, the profile of the bucket cross-section, the number of the buckets, and the presence or absence of rotor endplates. In addition, the flow around the rotor was investigated by the flow-visualization method. From this study, the influence of important design parameters of the Savonius rotor have been investigated and the rotor configuration giving the maximum torque and power has been determined.
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Hiroshi MAEKAWA
1986 Volume 52 Issue 480 Pages
2983-2989
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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The purpose of this investigation is to develop the lifting surface theory of horizontal-axis wind turbines and devise the numerical method to solve the theory. The velocity potential is derived by the vortex theory. The integral equation that relates an upwash distribution to an unknown lift distribution is the same as that of a screw propeller. With the boundary condition pertinent to a wind turbine, the integral equation is solved by the method of Hanaoka. Furthermore, the pressure distributions of two kinds of rotor are measured. One is designed by means of the design method based on the lifting line theory, the other has rectangular blades of expanded shape with a constant geometric pitch. The pressure distributions on the blades of various working conditions are calculated using the concept of equivalent two-dimensional wing, and compared with the experimental ones. It is concluded that the presented lifting surface theory and the numerical method are applicable to wind turbines.
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Hisanori UENO, Kazuhiko TANAKA, Atsushi OKAJIMA
1986 Volume 52 Issue 480 Pages
2990-2997
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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Wear tests of vanes and a cam ring in a vene pump are carried out under various operating conditions, using different types of pumps. The results may be summarized as follows : (i) The inner surface of a cam ring suffers from wear in the region where a contact force acts. (ii) The effects of the delivery pressure, the hydraulic fluids, the rotational speed, the eccentricity and the hardness of the cam ring, and the curvature of a vane tip on wear rate are clarified. (iii) Three types of wear appear in the present test; that is, mild wear, severe wear occuring after long sliding distance, and severe wear like adhensive wear or scoring. (iv) The wear rate cannot be simply estimated from the value of friction work consisting of factors of the delivery pressure, the rotational speed and so on. An occurrence of severe wear, however, can be predicted by the value of P
HV where V means the sliding distance per unit time, and P
H is a maximum of the Hertz normal pressure.
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Kinichi TORIKAI, Kohoichi SUZUKI
1986 Volume 52 Issue 480 Pages
2998-3002
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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Heat transfer from a rough heating surface in pool boiling was investigated experimentally for city water and pure water in the region of nucleate boiling, transition boiling and the beginning of film boiling. The conventional relation of heat transfer and roughness of the heating surface in pool boiling was referred to in this experiment. The condition of the heating surface had a strong effect on the characteristics of heat transfer, especially in the transition region. The coefficient of heat transfer was large and the fluctuation of the heat flux and the rate of super heating became smaller, compared with the case of a smooth surface. These effects were observed remarkably for city water.
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Hideo KIMOTO
1986 Volume 52 Issue 480 Pages
3003-3010
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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In this paper, it is clarified that a straight acoustic streaming is generated in a progressive sound field in front of a loud-speaker, by measuring the flow field with a hot-wire anemometer and by visualizing the thermal field around a heated cylinder. Then, the influence of the acoustic streaming on the heat transfer from a horizontal isothermal cylinder in a progressive sound field is investigated. The results show the heat transfer of the cylinder in a progressive sound field increases mainly at the speaker side, and the effect depends on the velocity of the streaming rather than on the sound pressure level. Consequently, it is clarified that we should note straight acoustic streaming, which has been ignored in previous research works, on heat transfer augmentation in a sound field.
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Tamotsu IGARASHI
1986 Volume 52 Issue 480 Pages
3011-3016
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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Experimental investigations on the fluid flow and heat transfer around rectanglar cylinders were carried out in the range 3.85×10
3≤R
e≤1.54×10
4. The total heat transfer around the cylinders is given by N
um = 0.095R
2/3e, except c/d = 2.5 immediately before the separated shear layer reattaches on the side face. Beyond c/d = 2.5, the heat transfer coefficient of the rear face, h
b increases drastically. It is correlated with the rms values of the fluctuating pressure, Δp, by the expression h
b = CΔp
0.22 regardless of the reattachment.
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Takao NAGASAKI, Kunio HIJIKATA, Yasuo MORI, Teruhiro SAKURAI
1986 Volume 52 Issue 480 Pages
3017-3025
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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Characteristics of two-phase mist flow in a mist lift tube have been investigated both experimentally and theoretically. Hot water is sprayed upward into an evacuated vertical tube, the top of which is connected to a condenser. Since the top of the tube is cooled, vapor flashes from the sprayed droplets, which are entrained upward by the vapor flow. From measurements of vapor and droplets temperatures, it is clarified that initial flashing is accomplished rapidly. Variations of droplets' size and their velocities along the flow direction are also measured, and it is shown that the size of droplets increases rapidly due to their collision and coalescence. To predict the motion and the growth rate of the droplet, a theoretical model is proposed, in which the coalescence and collision-induced breakup of droplets are considered. When the turbulence in vapor flow is small, the calculated result agrees well with the experimental one.
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Masanori ARITOMI, Akira INOUE, Hiroshi ISHIDA
1986 Volume 52 Issue 480 Pages
3026-3034
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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Thermo-hydraulic instability has been investigated experimentally in a boiling two-phase flow system composed of a vertical N-shaped boiling channel and an adiabatic bypass between an inlet and an outlet plenums, using Freon 113. The instability caused by the blockage of vapor to flow, which does not belong to Boure's classification of two-phase flow instabilities, is observed. The flow maps in each section, the static characteristics, the stable flow limits and the characteristics of this instability have been studied under various conditions to clarify the occurring mechanism. It makes the inlet velocity decrease for a vapor slug combined in the inverted U-shaped bend to obstruct the flow. The vapor slug flowing into the downcomer with the growth rises the void fraction in the downcomer and causes the gravitational loss to increase. Therefore, flow instability is brought about.
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Tetsuaki TAKEDA, Hiroshi KAWAMURA, Masahiro SEKI
1986 Volume 52 Issue 480 Pages
3035-3042
Published: August 25, 1986
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When forced circulation of the coolant is lost t in Gas Cooled Reactor, natural circulation takes place in the rector core. The natural circulation among the many parallel vertical channels with different temperatures is quite complicated because the flow rate and direction depend on the time history of the channel temperatures. Since only a few previous studies were concerned with this problem, an experimental and analytical study was made on the natural circulation in many parallel channels with different heat inputs. The experimental apparatus consisted of four vertical channels filled with water. Each channel was furnished with a heater pin and heated by various combinations of time-varying heat inputs. Flow velocity of the water was measured, and an abrupt change of the flow direction was observed. An analytical code predicted well the experimental results.
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Masahiro HIRANO, Toshio MIYAUCHI, Yoshikazu TAKAHIRA
1986 Volume 52 Issue 480 Pages
3043-3051
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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This study aims at establishing a heat transfer analysis of non-gray gas in a flow system. An integro-differential equation of energy conservation is established for the laminar channel flow of non-gray gas, which includes the multi-band feature of radiative gas. The numerical analysis was conducted and the results are compared with the results obtained from the analysis based on the conventional gray gas assumption. From the comparison of these results, it is made clear that the radiative heat flux q
r obtained from the gray analysis is greater than that of the non-gray analysis, and convective heat flux q
c is vice versa. By comparing the divergence of radiative heat flux and temperature profile, it is made clear that the gray gas analysis estimates excessively small absorption of radiation in the cold region near the heat absorbing surfaces. This results in the large q
r and small q
c compared with the non-gray analysis.
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Koji AKAGAWA, Terushige FUJII, Junichi OHTA, Shigeo TAKAGI
1986 Volume 52 Issue 480 Pages
3052-3058
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
JOURNAL
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From the viewpoint of energy saving and the development of new energy resources, it is important to utilize water-dominated geothermal resources and waste-heat sources from factories. As systems utilizing such resources, steam flashing system, binary-fluid systems, and total flow turbine systems are considered for power generation. In this study, thermodynamic consideration on such systems as single and double total flow turbine systems (1 TS, 2 TS) is made under the condition of saturated hot water at the inlet of the systems, compared with single flash turbine systems (1 FS). First, the available energy of 1 TS and 2 TS is explained graphically on a T-S diagram, and an optimum intermediate temperature in 2 TS, which maximizes the system efficiency, is given. Second, the superiority of total flow system efficiency to that of 1 FS is clarified and the magnitude of the improvement is estimated. Furthermore, the effects of each factor on the cycle performance of 1 TS and 2 TS are shown.
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Yoshisuke HAMAMOTO, Eiji TOMITA, Yutaka TANAKA, Tetsuya KATAYAMA
1986 Volume 52 Issue 480 Pages
3059-3067
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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In order to investigate the effect of swirl on combustion in a spark-ignition engine, a new experimental apparatus was developed. The test engine has a 78 mm bore, an 85 mm stroke and a pancake type combustion chamber. In this test engine, the combustion phenomena for various intensities of swirl flow can be investigated. The swirl flow in the cylinder was visualized by a smoke-wire method, and a laser Doppler anemometer and a hot-wire anemometer were adopted for the measurement of the velocity. The turbulence intensity was determined on the basis of the hot-wire data. Stoichiometric propane and air mixture was ignited at the center of the combustion chamber. The effect of swirl on combustion in the cylinder was investigated under various conditions of compression ratio and engine speed. As a result, it was found that the burn duration could be expressed as a function of the turbulence intensity. The effects of engine speed and the swirl ratio are not explicit and are included implicitly in the term of turbulence intensity.
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Yasuo TAKAGI, Teruyuki ITOH, Tamotsu IIJIMA
1986 Volume 52 Issue 480 Pages
3068-3074
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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In this study the relationship between the amount of mixture fraction burned with autoignition and the timing of the onset of autoignition and knock intensity is investigated with a combination of high speed laser shadowgraphy and thermodynamic calculation. It is made clear that over 40 percent of the whole mixture burns with autoignition in a crank angle of less than 5 to 8 degrees when an engine is operated under the so called heavy knocking condition. This burn rate is about ten times higher than that of the combustion seen in a normally propagating flame. This abrupt heat release causes an oscillation in cylinder gases and results in a knocking sound. It is also clarified that the earlier the timing of the onset of autoignition, the more the amount of mixture fraction which burns with the autoignition is and the stronger the knock intensity of the corresponding cycle results in.
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Tatsuyuki OKAMOTO, Toshimi TAKAGI, Satoshi FUJIWARA
1986 Volume 52 Issue 480 Pages
3075-3083
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
JOURNAL
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Significantly low NO
x emission was achieved by the appropriate combination of air staging and secondary fuel injection. Optimum operation conditions for low fuel NO
x emission were investigated, and it was found that the oxygen concentration in combustion products, into which secondary fuel is injected, is a desirable 1 or 2 %. Consequently, final NO
x concentration is reduced by approximately half, in comparison with that attained by air staging only.
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Hiroyuki KIDO, Yutaro WAKURI, Kenshiro NAKASHIMA, RuiBin CAI, Takashi ...
1986 Volume 52 Issue 480 Pages
3084-3090
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
JOURNAL
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In order to clarify the influences of oxygen concentration and ignition energy on turbulent burning velocity, experiments on turbulent burning velocity have been carried out in a closed bomb using premixed mixtures. In the first series of experiments, only the oxygen concentration has been varied, keeping the other parameters, such as laminar burning velocity, laminar flame thickness, turbulence intensity, and mean spatial scale, constant. As to the hydrogen and methane mixtures, larger turbulent burning velocities were obtained for mixtures with higher oxygen concentration. But for propane mixtures, the above tendency was inversed. In the next series of experiments, turbulent burning velocities have been measured for comparatively large and small ignition energies, keeping the other parameters, including the oxygen concentration, constant. As a result, the upper limit of turbulence intensity at which flames can propagate without extinction has apparently increased with a rise in ignition energy.
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Masatake YOSHIDA, Shinya ASHIKARI, Tsutomu GOMI
1986 Volume 52 Issue 480 Pages
3091-3097
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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Recently, many authors have reported an equation for the heat transfer coefficient between the mixture and the cylinder wall of an engine. The dependency of these equations on the temperature, pressure and velocity of the mixture is different among the reports. Especially, the difference of the dependency on the temperature is great. Therefore, the authors reach the conclusion that the effect of the mixture-temperature is negligible. According to the above mentioned fact, the authors present an equation for the heat transfer coefficient on the basis of assumptions as follows : (1) the velocity is the sum of the mean piston velocity and the exhaust-suction gas velocity ; (2) the effect of the cylinder wall temperature is dominant. This equation is as follows : [numerical formula]
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Masakazu OBATA, Joji YAMAGA, Hiroshi TANIGUCHI
1986 Volume 52 Issue 480 Pages
3098-3106
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
JOURNAL
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This paper presents an analytical method for computing the cooling performance and pressure loss in internal convective steam-cooling gas turbine blades of return flow type. Experimental results of steam-heating, steam-cooling, and air-cooling cascade tests carried out with a model blade so as to examine the validity of the calculation method are also given. Comparison is made in terms of the average blade temperature at mid span and the steam temperature at outlet of the cooling passage with cooling-flow rate, Reynolds number, and temperature at outlet of the cooling passage with cooling-flow rate, Reynolds number, and temperature ratio as the variables. It is shown that the cooling performance can be predicted with a good accuracy. Finally, cooling characteristics and pressure loss characteristics of steam are shown in comparison with air under an engine operating condition.
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Yuzuru SHIMAMOTO, Kazuhiro KANAMARU, Jae-sung CHOI
1986 Volume 52 Issue 480 Pages
3107-3113
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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This paper describes briefly the simulation program for predicting the perfomance of a high speed turbocharged four cycle diesel engine. The wave phenomena in the intake and exhaust systems are calculated by the characteristic mesh method. The combustion process in the power cycle is represented by the heat release pattern which is given by the Wiebe's function or the pattern based on measured values. Turbocharging matching for the engine is described by utilizing the characteristic maps of both the compressor and the turbine, which are obtained from quasi-steady states. A comparison of experimental and calculated results shows a good agreement. Then the influences of the intake system, the period of valve overlap and the characteristics of the turbine are numerically investigated by the simulation.
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Jae-sung CHOI, Yuzuru SHIMAMOTO, Kazuhiro KANAMARU
1986 Volume 52 Issue 480 Pages
3114-3120
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
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This paper describes briefly the approach for the matching of turbochargers in two-stage turbocharged four cycle diesel engines. The simulation program has been developed from the program for one-stage turbocharged engines, in which the characteristic method is used as reported in an earlier paper. In this paper, the computing methods for two entry turbines, air coolers and waste-gate valves are described. In comparison with experimental results, it is cleared that overall engine performance may be predicted fairly by the simulation. It is found that the ratio of effective areas of turbines (HP/LP) is an available factor to estimate the engine performance and the inertia charging is effective even for two-stage turbocharging. Then the influence of the pipe systems and the air cooling system to the operating state of two compressors (HP, LP) are numerically investigated.
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Yoichiro OKUBO, Masayoshi OTSUKA, Junji KATO, Kazuhiro KOZUKA, Katsuhi ...
1986 Volume 52 Issue 480 Pages
3121-3126
Published: August 25, 1986
Released on J-STAGE: March 28, 2008
JOURNAL
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The purpose of this paper is to clarify the air motion of swirl flow in a reciprocating engine. The swirl velocities under motoring conditions were measured by a back scattered LDV using a bottom-view research engine. Experiments were conducted with three different combustion chambers having the same compression ratios. The results are as follows: (1) The swirl velocity in the cylinder increases in proportion to the engine speed. (2) The swirl velocity at the compression stroke increases due to the fact that the swirl flow is pushed into the cavity on the piston top. (3) At the compression TDC, the swirl ratio of a deep dish chamber is higher than the ratios of a pancake and a shallow dish chamber.
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