In order to make clear the cavitation aspects in branch ducts, we carefully observed the cavitation for several cavitation numbers σ, radii of curvature on the corners R/b, flow ratios between the upstream duct and the downstream branched duct K, by means of high speed photography and a high speed stereo movie camera, in various kinds of right-angled branch ducts with square cross-section. Typical types of cavitation, their interference, behavior, domain of occurrence are shown.

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Fluctuating pressure fields on the surface and in the wake of a circular cylinder at a Reynolds number of 3.7×10⁴ are investigated using a computer aided flow visualization technique. The phase averaged pressure distribution on a cylinder is obtained and oscillating lift and drag forces are evaluated. Then instantaneous pressure fields in the wake region are determined, from which the coherent structure of the wake flow is discussed. On the basis of these results, the variation of fluctuating forces in time is quantitatively related to the details of the wake flow such as instantaneous static pressure fields and vorticity fields.

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To know the unsteady laminar flow along an accelerating or decelerating disk in a closed cylindrical vessel, experimental and theoretical studies were performed. The unsteady pressure distribution on the rotating disk and the axial thrust were derived, and compared with that for the turbulent flow. As a result, the following points were made clear: (1) For the accelerating flow, the angular velocity of a center core at a small radii is considerably smaller than that at a large radii, under the laminar flow condition. This phenomenon is much different from the turbulent flow; (2) The time delay of flow is comparatively small owing to the viscous effect; (3) Calculated results coincide quite well with experimental ones.

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Differential pressure fluctuations are used to measure flow patterns of horizontal two-phase flow because the fluctuations seem to be closely connected with the flow structure. The differential pressure is used to eliminate the effect of pressure fluctuations occurring outside the test section and is measured at the interval between the top and the bottom at a cross-section of a tube to detect a local and instantaneous flow change. The experimental results show that the horizontal flow of nitrogen gas (or air)-water mixture exhibits peculiar features of statistical properties such as the probability density function, the power spectral density and the cross-correlation, and its flow patterns can be classified by using the features. The results suggest that it is possible to identify the flow patterns of horizontal two-phase flow.

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A new computational technique to find zeroes and poles of complex functions has been developed. The idea is based upon the Cauchy's theorem: when the complex variable z describes an entire contour of a specified domain, the resultant locus of a complex function F(z) helps reveal number of its zeroes and poles within the domain. The procedure of the `locus'method is demonstrated with use of a spherical Bessel function of the second kind as an example. The method is also applied with success to detecting mode eigenvalues for viscous harmonic waves in a double pipe. Similarly to the Scarton's results for a single pipe, two different families of eigenvalues are evidently observed.

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Some finite-diffrence methods, which use primitive variables, are proposed to solve incompressible fluid flow. Especially, two methods are developed: one is to calculate the accurate pressure field immediately after the fluid starts to flow (two-step method); the other allows a larger time-step than the corresponding explicit method (non-iterative implicit method). As a numerical example, the two-dimensional transient Womersley flow is calculated. It is shown that the two-step method can calculate flow field from the instance when the fluid starts to flow, and the non-iterative implicit method requires less amounts of computer time compared with the explicit method.

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The mean flow and statistical property measurements have been made in the vicinity of the roughness element for a boundary layer over a d-type surface roughness. The results show that profile of the mean velocity and the turbulence intensity varies to be wavy in the similitude of the roughness geometry, due to the periodic nature of the present rough wall, and that both quantities rise fairy sharply at the region immediately above the grooves. The flow formed in the cavity is not completely independent of the external flow over the groove, and considerable exchange of fluid in the cavity with the boundary layer occurs. A discussion of some terms in both the momentum and the turbulent energy equations is given. From these results, the feature of present flow in the region near the roughness element has been clarified.

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Approximate calculations of the bounded jet have been carried out by adding an assumption for the diffusion width of the bounded jet to the velocity distribution on the center-plane of the bounded jet which was already proposed by the authors. In order to determine the parameter contained in the assumed velocity distribution function and to compare the results of calculation with those of experiments, the experiments have been done, as an example, using a nozzle having an aspect ratio of 1. As a result, the approximate calculations of the velocity distributions on the center-plane, the diffusion width and the isotach patterns of the bounded jet agree well with the experimental results regardless of the initial turbulence intensity and the downstream location.

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This paper deals with some space correlations of velocity fluctuations at two points in the turbulent shear flow around a circular cylinder spinning in a quiescent fluid. One of the dynamical correlation equations and one of the continuity relations are considered, to investigate the <spatial>--- structure of this turbulent flow field. Measured correlation distributions total twelve, of which u_Au_B shows the strongest correlation; and its shape near the peak has large curvature indicating a small eddy. On the other hand, the wide separation range is covered until it tends to zero, which implies the existence of large-scale eddy-lumps. The <ringed>--- eddy structure is well inferred by mixing length theory based on the measured profiles of u_Av_B in the axial direction. Balances of the continuity equation and the dynamic correlation equations are estimated.

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Experiments have been conducted in the 7m channel where one of the walls in the upstream half was roughened and all the remaining parts were left smooth, providing a fully developed asymmetric flow at the midsection and a fully developed symmetric flow at the channel exit. Extensive measurement of the mean velocity, Reynolds normal and shear stresses made downstream of the step change in wall roughness indicate that the readjustment to a symmetric flow requires a streamwise distance of 50 times the channel height 2h; whereas the evaluation of the momentum equation shows that for x/h6gt;20 the pressure gradient balances practically with the wall shear stress. It is found also that the adjustment process is quite different between the rough to smooth and the smooth to smooth sides. Non-monotonical adjustment is essential only in the rough to smooth side.

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Hot wire measurements were made on the propagation of turbulent slugs in a pulsatile pipe flow. The pulsatile pipe flow was produced by imposing a sinusoidal oscillation on a steady flow. Two types of slug behavior are observed according to whether the pulsation frequency f is low or high, and this paper presents two typical examples with f=0.300 and 2.082 Hz. In both examples the ap·pear·ance of the turbulent slug is periodic, in contrast to the randomness that is characteristic of transition in steady flows. Such periodicity is also known in transitional pulsatile boundary layers on a flat plate. At f=0.300 Hz a turbulent slug generates near the entrance (x/D≒3) and propagates downstream, where x is the axial coordinate and D is the pipe diameter. The velocities of leading and trailing edges of the slug can be predicted by steady flow data. Meanwhile at f=2.082 Hz numerous slugs are generated in the region downstream of x/D≒25 in the middle stage of the accelerating period. After a short time, a new slug appears at x/D≒3 and propagates downstream. Later its leading edge merges with the preceding slugs at x/D≒40 and then these slugs become a single slug. This slug disappears at almost the same time as in an earlier stage of the following accelerating period, due to the combined effect of viscous dissipation and acceleration. The velocity and tur·bu·lence intensity downstream of x/D≒50 were found not to change axially.

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Utilizing a flash photolysis method, a non-disturbing technique was developed to measure the flow velocity of liquid-fuel film formed on the surface of the intake pipe of internal combustion engines. A tracer, in the form of a blue line, was generated instantaneously by applying a high energy laser beam to the liquid film of a fuel which contains very dilute 2-(2, 4-dinitro-benzyl)-pyridine. AN₂ pulse laser with 900 kW peak power was used as the light source. The arrival of the tracer was detected by the He-Ne laser and photodiode system at an appropriate fixed point located a short distance downstream from the tracer generating point. The flow velocity of the film was determined from the time the tracer required to travel the distance between the two points. It was disclosed that the film flow velocity is of the order of 1/100 of the mean air velocity within the intake pipe. The present technique offers a strong tool to measure the velocity of the film flow within the intake pipe even when the engines are operated under the firing conditions.

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Performance of a mixed-flow pump under air-water two-phase flow conditions was investigated experimentally, and compared with those for radial-and axial-flow pumps. Distributions of water velocity and void fraction were also measured just before and just before and just after the impeller. The performance of the mixed-folw pump handling two-phase mixtures is similar to that for radial-flow pumps, and the greater the specific speed of the pump, the greater the degradation ratio of the performance becomes. But the performance curve shows an abrupt drop at a fairly small air quantity, corresponding to a change in flow patterns.

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A new design method for a valve plate of axial piston pumps and motors is presented. By adopting the valve plate with hydrostatic pads, fluid film lubrication can be realized on the sliding part between the plate and the cylinder block under wide operating conditions. This is in the rare case of a valve plate with conventional hydro-dynamic pads. The effects of the main related dimensions and the operating conditions are numerically clarified, and the supporting of the cylinder block is also discussed.

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A computational scheme was developed using both a scalar and a vector potential which was originally proposed by Hirasaki and Hellums and was recently rephrased by Richardson and Cornish on the boundary conditions in detail. This equation system has not been apparently employed for numerical calculation so far but herein was applied to a number of cases of flow. Isothermal two-dimensional flow through a square box with openings at R_e=81.6 was studied. Computed velocity field agreed very well with the results obtained by a classical way of stream function whose gradient is given at the opening for a plug flow. Two-dimensional steady mixed convection and three-dimensional unsteady buoyant flow were further studied and found to give a stable solution.

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An experimental study was conducted to determine the heat transfer characteristics in radially outward flow between two parallel disks. The local heat transfer coefficients along the disk radius were measured in detail and the flow patterns between the two disks were visualized using a paraffin mist injection technique. It was disclosed that self-sustained periodic flow separation, a unique characteristic of radially outward flow between the disks, occurs when the Reynolds number reaches about 1200. With a further increase in the Reynolds umber, oscillating flow results in a flow transition into a turbulent flow, and three distinct regions of heat transfer, namely, laminar, oscillating laminar and turbulent coexist along the disk radius.

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Minimum heat flux as well as well as minimum film boiling temperature was measured for R113 under pressures from 0.05 to 0.90 MPa. The diameter of the heated surface was 62 mm, which is about five times larger than the most dangerous wavelength of R113. At the periphery of the heated surface, an auxiliary ring was set in order to prevent the collapse of the vapor film. Data obtained agree with Berenson's equation at atmospheric pressure, but at both low and high pressures they deviate markedly. Dimensional analysis shows that the liquid-vapor density ratio should be included in the correlation of Berenson. Present data can be correlated well in dimensionless form as a function of density ratio. It is also shown that the author's theory in a previous paper explains the result in a high pressure region fairly well.

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The isobaric process of one-dimensional unsteady evaporation is considered for such a binary component system that liquid and gas phases are initially in different spacially uniform states. By virtue of the similarity nature of the flow fields involved, a set of ordinary differential equations for the heat flux and concentration as functions of temperature is derived, which is very useful in the examination of evaporation characteristics at high pressures. An asymptotic analysis is made of the heat and mass transfers which occur near the gas-liquid interface, just in a critical state of the binary mixture. It is especially shown that the binary mutual diffusion coefficient must vanish in such a critical state.

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A control system design study for a two-shaft gas turbine with a variable geometry turbine is described. A two-shaft configuration has the disadvantage of a lower transient response compared with a single shaft configuration. The overcoming of this disadvantage has a significant meaning for its practical usage. First, the lower order linear model formulated by the author is evaluated using a simulator which was developed considering conservations of mass, momentum and energy. Secondly, considering small perturbations of state variables, the optimal regulator problem is formulated. Finally, a"suboptimal"feedback control law is proposed so as to make possible treatment of cases of large changes of state variables, in which it is necessary to consider some constraints. Then improvements in stability and response during any transient state due to this control law are confirmed by simulations. As for implementation of the law, storage of only three gain matrices is required.

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Using the simulation program, the exhaust manifold and the exhaust valve system to optimize the exhaust brake performance in automotive engines have been investigated on the basis of the evaluations of the exhaust valve behavior, the pumping loss and the intake noise level. It is found that exhaust brake performance can be improved effectively by utilizing the pressure pulsation in the exhaust manifold, and am manifold of the divided type is desirable for this improvement. The intake noise level on the condition of exhaust braking is increased due to two back flows: one is the flow from the exhaust manifold to the intake manifold in the period of the valve over-lap, and the other is the flow from the exhaust manifold to the cylinder due to the re-opening of exhaust valve which occurs on the suction stroke.

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Application of the pulsed laser laser holography technique was made to observe diesel sprays injected into a high pressure and temperature atmosphere in a quiescent bomb. Two different holography techniques, that is, single-pulsed laser holography and double-pulsed holographic interferometry were adopted in this study. Shadowgraphs, schlieren photographs and micrographs of a reconstructed image of the spray were taken. The spray widths and equivalence ratios of fuel droplets were microscopically measured. The fuel droplets and vapor around the spray in a high pressure and temperature atmosphere could be observed by single-pulsed laser holography. By double-pulsed holographic interferometry, interference fringes were observed at the spray edge, and the contrast between the spray edge and the atmosphere was made more striking. The spray width has a tendency to decrease when the atmospheric temperature is increased. Some droplets were observed around the spray up to the pressure 3.1 MPa and the temperature 773K.

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As an initial combustion period involving the growing process of a initial flame kernel, is easily affected by the cycle-to-cycle air-fuel ratio and gas motion, combustion always fluctuates unstably in a spark ignited engine. In this study, by measuring the phenomena of spark ignition and engine combustion simultaneously, it is clarified that a decrease in cycle-to-cycle spark ignition fluctuation is achieved by increasing spark current. The spark ignition, however, is mainly fluctuated by cycle-to cycle gas motion in-cylinder during ignition timing. When a long durational spark which has a high spark current is given to stabilize the engine combustion, a new aspect has been obtained showing that the initial combustion period can be made to shorten and reduce its fluctuation. Especially, this characteristic of spark ignition is effective for a lean burn, which is fundamentally unstable combustion.

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The observation of fuel atomization and the measurements of fuel droplets are performed to examine the spray flow in the double venturies of carburetor, which is the interaction process between spouted fuel and air flow. Based on the above results, the spray transportation in the small venturi is analized using one dimensional model. It is concluded that the unbalancing by fuel spout in pressure between small venturi and large venturi is not caused from the evaporation of fuel or momentum losses of air flow, but from the change of the air flow pattern.

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The object of this work was to know a pressure effect of the maximum loading for a practical combustion chamber at high pressure condition. Conventional loading parameter indicates inverse proportionality to the squared pressure. In present investigation, flame-out limit of a can type practical combustion chamber related good to the loading parameter only at the atmospheric condition and the maximum loading value was very much dependent on the direction of the fuel jet in the primary zone. Experimental results at high pressure condition showed rapid decrease of maximum loading as the pressure increased in the combustion chamber, especially at the range above 2MPa.

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Through numerical calculation based on the simulation program, the effect of the resonator, which is installed for the purpose of improving the volumetric efficiency of four cycle diesel engines. The results show that in single cylinder engines the resonator can increase the volumetric efficiency at the low engine speed without decreasing volumetric efficiency at the high speed ranges. The diameter of the resonator pipe must be chosen so as to generate an adequate flow loss in the resonator. The optimum sizes of the resonator can not be estimated by only the natural acoustic frequency. However, the ratio of the natural frequency of the resonator to that of the intake system for the open period of intake valve may be used to estimate roughly the resonator effect. The resonator effect is considered to be slight in multi-cylinder engines.

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This paper investigates the effects of combustion and infection systems on HC and particulate emissions from a DI diesel engine with a dish type combustion chamber. Diesel particulate was sampled using a mini-dilution tunnel. Gaseous HC was analysed with gas chromatography, and the PAH in SOF in the particulates was measured with liquid chromatography. The results show that the emission characteristics of the deep dish type chamber greatly differs from those of the shallow dish type chamber, depending on the number of nozzles, injection direction, and swirl intensity. The HC analysis shows that the main constituents of gaseous HC are carbon number HC, and there is a tending towards increasing polynucleation PAH in SOF corresponding to the increase in soot formation. Additionally it was found that the particulate concentration can be expressed as an exponential function of the Bosch smoke density for a wide range of engine combustion conditions.

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The effects of gas flow (swirl and squish) and fuel spray jet on local instantaneous heat flux on the piston crown of a small size direct injection diesel engine are experimentally investigated. Under the motoring operation, local heat flux on the piston with a flat crown increases with increasing local swirl velocity; and the local Nusselt number is found to be proportional to R^<0.636gt;_e, where R_e=2πrv_{θ, r}/ν with v_{θ, r} the local swirl velocity at radius r andνthe kinematic viscosity. While for the piston with cavity, local heat flux is strongly influenced by squish flow. Under the firing operation, it is observed that the heat flux at the position where the fuel spray jet collides is mostly determined by the fuel spray jet.

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This paper deals with simultaneous heat and mass transfer in laminar free convection along a vertical plate. By rewriting the similarity solution with combined Grashof numbers, namely G_{rX, T} +(P_r/S_c)^1/2Gr_{rX, C} for heat transfer and G_{rX, C}+(S_c/P_r)<1/2>G_;lt;r_{X, T}> for mass treansfer, which were introduced in the integral solution, simple and practical expressions of the local Nusselt number and local Sherwood number are proposed. Futhermore, therse expressions are expanded in full consideration of effect of the finite interfacical velocity.

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