This paper proposes a method by which to infer the turbulent structure in a vortex wake shed from a finite-length inclined circular cylinder in a uniform flow using the power spectrum and cross correlation. It is inferred from the results of cross correlation that the shedding vortex from the inclined circular cylinder forms a step like vortex line or a sawtooth-shaped vortex line. It was observed through the power spectrum that the end condition of the inclined circular cylinder gives a sensitive influence to the spanwise distribution of the turbulent structure in a vortex wake. It is also found that the inferred turbulent structure agrees with an aspect inferred from the results of a numerical calculation.

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This experimental work on Taylor vortex flow in a gap with a small aspect ratio is concerned with two extra vortices and a twin vortex system depending on an anomalous cell of the anomalous mode. Extra vortices are smaller than other vortices such as defined cells, and stay at the corners of the inner rotating cylinder and the outer stationary one and the end plate with anomalous cells at any Reynolds number and aspect ratio. For one-cell flow (anomalous one-cell mode) in a symmetric system, an outer extra vortex develops and grows to the same size as the main cell, only in a certain range of aspect ratio of less than one. A twin vortex is observed to form when two vortices line up in the direction of the radius. On the end plate there are three flow fields; two are extra vortex flows and the other is the main cell flow. It appears that the flow direction of the anomalous cell is from the inner cylinder to the outer one, opposite to the flow direction of the normal cell.

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In order to investigate the fundamental rule for obtaining the adequate outflow velocity boundary condition of spatially developing unsteady flow, numerical simulation was performed for a simple model problem-a vortex convected with uniform mean flow by means of the pseudospectral matrix element (PSME) method. The results show that for the high Re number flows, the convective for mulation can be an accurate and a stable outflow velocity boundary condition if it is used together with the pressure solver enable to ensure divergence free on boundary.

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The equation of motion for a bubble in blood subjected to an oscillating pressure is derived by using a modified Casson model, which well represents the rheology of human blood. The natural frequency of a bubble is approximately obtained. According to computational analyses, the frequency response curves for bubble ocsillation in blood are delineated. As a result, the values of nondimensional amplitude in the neighborhood of primary resonance and harmonic resonance increase with decreasing in hematocrit of blood. It is found that the amplitude of oscillation of the bubble decreases with an increase of hematocrit, and that the pressure produced during the bubble shrinkage lowers with a decrease of hematocrit.

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Control valves have been applied to the water supply systems of collective and multistory buildings. The noise in control valves is unwanted and annoying sound. In order to reduce the cavitation noise in control valves, we tried to modify the shape of the valve casing and the length of the orifice in a practical control valve. We then compared the practical valve and the modified valve quantitatively in noise and vibrational acceleration for various discharges. Here, it is worth noting that a marked reduction in cavitation noise is possible by modifying a few parts in a practical control valve.

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Numerical and aeroacoustic analyses are carried out on the emission of a propagating compression wave from an open end of a tube with an infinite baffle plate at the end. In the numerical analysis, the axisymmetric unsteady conservation equations are solved by a TVD scheme. A sample calculation shows that a rarefaction wave is reflected inward and an impulsive wave is generated and radiated outward from the open end. In the aeroacoustic analysis, a method of open-end correction is proposed. The magnitude of a generated impulsive wave and its attenuation with distance obtained by the numerical calculations are compared and discussed with the results by the aeroacoustic analysis with the proposed open-end correction.

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In this paper, the nonlinear effects of compression waves propagated in a tube were numerically investigated. The equations of the one-dimensional, unsteady compressible flow with the skin friction of the wall in which the area of a tube varies with time are transformed into characteristic equations, and the variations of the pressure gradient and the strength of compression waves are numerically solved by the method of characteristics. The calculations are performed for tubes with various diameters and compression waves which have various strengths and pressure gradients with time. The calculated results clarified quantitatively the effects of these parameters for nonlinear effects of compression waves propagated in a tube.

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Fully developed oscillatory flow in curved tubes is numerically solved by SIMPLER method. The calculation was carried out for Womersley number a=18, Peak Dean number x=370, and the curvature ratio δ=1/2, 1/3, 1/7. The velocity profile obtained in this study shows an inertia dominant flow due to fairly high α, however secondary flow of Lyne type does not appear for curvature ratio. It should be noted that large curvature effect induces a strong secondary flow, although the effect of curvature on the axial velocity is minor.

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The fully developed pulsating laminar flows of an incompressible Bingham plastic fluid through a pipe of circular cross section coiled in a circle were investigated experimentaly and numerically. The flow fields were characterized by the Dean number De, Hedstrom number He, the Womersley number Wo and the curvature ratio δ. The friction factors were measured experimentaly for various volumetric ratio in the case of Wo=4. The calculations were carried out for a fixed He. The flow patterns and the axial velocity profiles were required in the calculations. It was clarified that the effects of the curvature of the pipes appeared easily for Newtonians compared with the plastic fluids. That is, the values of the amplitudes of the friction factor λ_ac of the plastic fluid were smaller than that of Newtonians for a range of high Dean number, especially in the case of lower curvature ratio. In the calculations, it was found in the case of a plastic fluids that, in the axial velocity distributions a typical plug flow area appeared near the outer side of the vent in all of a period, and that the strength of the secondary flows were greater than that of Newtonians especially within the period the volumetric rates increased.

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This study has developed a computer-aided simulation and analysis package that allows engineers who are not familiar with the theory of fluid wave motion in a pipe and numerical simulation, to simulate and analyze the pulsations in any hydraulic pipelines generated by fluid power pumps, and then to substitute components and vary design and/or operational parameters in the design stage for a reduction of fluidborne vibration. The present PC computer-aided engineering tool for the analysis of pulsation can simulate the following five key items which are of the greatest concern for fluid power engineers with regard to the pulsation phenomena in hydraulic systems: (1) frequency characteristics of pressure pulsation level at every point in the circuit (and so on), (2) frequency characteristics of the ratio of pressure pulsations at two arbitrary points, (3) frequency characteristics of the ratio of fluid acoustic powers at two arbitrary points (that is, transmission loss), (4) pressure pulsation waveforms and those spectra, and (5) fluid acoustic powers and those spectra. The experiments carried out on the several basic hydraulic systems show that the calculated results obtained by the present simulation package, HYPULSIP (an acronym for (Hy)___-draulic (Pul)___-sation (Si)___-mulation P___-ackage), agree with the experimental results with sufficient accuracy for practical use.

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A numerical analysis is conducted without introducing any turbulence model for the turbulent flow in a square pipe. The direct numerical calculation approach generally requires a huge computational time and memory size, and is possibly performed on a relatively coarse grid system. Therefore, evaluation of the solution for the coarse grid system is important in practical applications. Comparison with the experiment and the large eddy simulation (LES) reveals that the present calculation successfully predicts the characteristic feature of the turbulent flow even with the coarse grid system. Quantitative improvement of the solution is achieved nearly in proportion to the grid resolution squared.

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A numerical analysis has been performed for three-dimensional developing turbulent flow in an equilateral duct by a modified Reynolds stress equation model. Governing equations are transformed from the physical plane to the calculation plane by boundary-fitted coordinate systems. Special attention was paid to the developing process of secondary flow of the second kind and redistribution process of turbulent energy. The calculated results suggest that the secondary flow of the second kind is generated in a corner region by anisotropy turbulence and it has maximum value at which momentum transfer is caused actively by interaction with the boundary layer. In addition, it was clarified that the interaction terms of mean strain and fluctuating velocities played more important roles in the redistribution process than the interaction term of fluctuating velocities.

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A technique has been presented to measure mean velocities and Reynolds stresses in complex three-dimensional turbulent flows using a hot-wire anemometer. The output of the hot-wire was acquired by rotating a probe with a single inclined hot-wire to two different directions at the same location in the flow field. The data reduction was executed by the algorithm of iterative computation, which was composed of the conjugate gradient method to solve the nonlinear equation derived from the directional performance of the hot-wire and the least squares method to estimate the most reliable result from measured outputs of the hot-wire.

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The flow characteristics of turbulent jets with and without flame were studied at the low Reynolds numbers of 2000 and 3000, with fuel-rich mixtures (equivalence ratios of 6, 24, ∞) of propane and air. Axial and radial time mean velocities and fluctuation velocities have been measured by LDV. Temperature and luminosity have been measured by a fine thermocouple and a photomulti-plier, respectively. Potential core length was presented by normalized mass flux along the axis, and by radial mean velocities in the flow with and without flames. The potential core length in the flow with flame is about twice that in the flow without flame. The turbulent intensity, measured to study the effect of charged soot, in the highly luminous soot region was smaller than that in the non-luminous region, in spite of the same temperature and the same velocity gradient. The radial displacement of particles caused by the repulsive force between charged soot makes induces an increase in apparent gas viscosity in the flame gas. Order estimation of the viscosity by the movement of soot was carried out using electrical mobility and the equation of motion of particles in the shear region.

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Flow pattern, presure drop and heat transfer are investigated for R113 boiling two-phase flow in extremely narrow channels with a thickness of 35-110μm between horizontal parallel plates. It is clarified from the exeriments that the friction multiplier of two-phase flow is well estimated by the empirical correlation proposed for adiabatic systems, and that the heat transfer coefficient of two-phase flow is 3-20 times as large as that of the liquid single-phase flow. An analytical model based on viscous flow and the effect of the capillary number on the thickness of the liquid film is proposed. It provides an explanation for the frictional pressure drop and the heat transfer coefficient.

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Flow pattern, presure drop, void fraction, and phase velocity are measured for N₂-R113 adiabatic gas-liquid two-phase flow in extremely narrow channels with a thickness of 5-100μm between horizontal parallel plates. It is clarified from the experiments that the friction multiplier of two-phase flow is smaller than Chisholm's correlation applied for normally sized channels, and that the void fraction becomes smaller as the channel becomes narrower. Empirical correlations are proposed.

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The effects of flow channel gap width and orientation on two-phase flow pattern, void fraction and frictional pressure drop have been investigated using an adiabatic air-water flow in a channel between two flat plates, 240mm long × 80mm wide, with gap widths of 1.465mm and 0.778mm. The six orientaions studied were vertically upward and downward, 45°inclined upward and downward, horizontal flow between horizontal plates and horizontal flow between vertical plates. The results showed that the effect of the flow channel orientation is small for both gap widths, except for the horizontal flow between vertical plates. In the last orientation, both void fraction and frictional pressure data showed a strong effect of mass velocity. Results of comparisons of several two-phase friction pressure drop correlations with the present data are also discussed.

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The flow around a permeable rectangular plate with the aspect ratio w/h and the open-area ratio β, standing vertically against a flat Wall on which a turbulent boundary layer is developing, was investigated experimentally. The surface pressure distribution on the flat wall and the flow visualization by both smoke-wire and oil-film techniques clarified the following. The circulation region behind the permeable rectangular plate was moved downstream with increase of both the open area ratio and the width of the plate, and disappeared for a large open-area ratio. The critical values of the open-area ratio in which there is a circulation region behind the present plates are between 0.325 and 0.485, and become large with increasing aspect ratio. The reattachment distance on the x axis behind the plate can be effectively estimated by both w/h and β. It seems that the wall pressure distributions on the x axis normalized by both the reattachment distance and the maximum suction pressure in the circulation region become similar for the range of 0.5≤w/h≤4 and β≲0.196.

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Alternating vortices are generated by an oscillating plate when a plate is abruptly started to oscillate from rest. It is an interesting problem to examine the flow around the plate. We analyze the flow around a flat plate acting in a combination of rotational and translational oscillations in a stationary fluid, using a discrete vortex model with the conformal mapping method. Numerical calculations are performed for various angles in rotational oscillation, amplitudes in translational oscillation, and frequencies and phase angles in both oscillations, Vortex patterns and unsteady forces are obtained. As a result, vortex clusters stay near the plate. The thrust on the plate is generated by these clusters.

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The flow on a flat-plate wing with low aspect ratio suffers the effect of side wall boundary layer and also of wing tip vortex. In this study, the flow on the suction surface of the wing is observed by the oil film visualization, and the pressure distribution on the wing surface along the chord is measured in many spanwise positions. The results obtained are as follows. The side wall boundary layer induces secondary flow which suppresses the separation of the flow near the root of the wing, and the wing tip vortex suppresses flow separation near the tip of the wing. On a small aspect ratio wing, the separation of the flow is suppressed more strongly by the effects of both the side wall boundary layer and the wing tip vortex.

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The hydrodynamic forces generated by interaction between water and diagonal square cylinder have been investigated experimentally. A diagonal square cylinder model of 56.6mm diagonal length and 200mm span length was used. The cylinder supported by two endplates was oscillated horizontally in standing water by mechanical oscillation machinery. The force was measured by means of a quartz force transducer. Period parameters ranging from 0.2 to 3.0 and Reynolds numbers from 5000 to 40000 were covered in the investigation. The results have shown that the force amplitude coefficients of the two-dimensional diagonal square cylinder, which are obtained at end-plate dimensions of greater than 5 times the cylinder diagonal length, and the force waveforms depend on the period parameter but not on the Reynolds number. It is further shown that the force coefficient increases with the period parameter. The results are compared with the data of the square cylinder and the circular cylinder reported by the authors. The comparison indicates that the correlations between the phase difference and the force coefficient are the same.

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In a pool of solution, an upper spherical surface is first approached (or separated) and subsequently made to separate (or approach) relative to a lower flat plate at a constant speed. The transmitted forces are measured, and the following are observed. In the cases of Separan solutions, the measured force overshoots the force estimated by viscous stress at the inception of the subsequent squeezing when a pause time taken in transit between the two squeezing is sufficiently long. However, when the pause time is short, the overshoot in the subsequent squeezing decreases because of an unrelaxed part of the stress produced in the preceding squeezing and the stress generated in the slow squeezing due to the springback of the load cells utilized. If more than 20% of the opposite force evaluated by viscous stress is unrelaxed and left at the inception of the subsequent squeezing, then no overshoot is developed. In the case of PEO solution, whose properties are similar to those of the Separan solution in steady flow, the force measured can be predicted by the viscous stress alone. It is considered that there is a difference between these two solutions in the molecular size of the polymer in water.

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A constitutive equation yielding the stress overshoot is used in the analysis of the squeezing flow successively generated in the normal and reverse directions. Transmitting forces generated in the flows between a spherical surface and a flat plate are calculated, and the following results are obtained. The contribution of normal stress in the transmitting force is negligible. The transmitting forces analytically obtained can qualitatively show the decrease of overshoot or no overshoot, which is experimentally observed in the subsequent squeezing flow. When the first squeezing is stopped in the midst of an overshoot process and the second reverse one is begun successively, the transmitting force generated in the second reverse squeezing increases more rapidly than the one generated after the overshoot is finished in the first squeezing.

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Membrane methods have been used to separate substances from solutions. However, in these cases; it is very difficult to avoid the growing of gel layers or cake layers, and the concentration polarization on the surface of the membrane. These phenomena decrease the effect of the filtration. Creating a turbulence on the surface of the membrane is one of the more effective ways to prevent these problems. However, there are few reports which provide details about them. In this report, a fundamental analysis is carried out experimentally about the influence of turbulence on the surface of the membrane on the permeation flux. A stirring bar, as the type of turbulence promoter, is set on the surface of the membrane. Filtrations of machining fluids are carried out with three cellulose-nitrate- type membranes for microfiltration, which have respective pore diameters of 0.1, 0.2 and 0.45μm. The effects of revolution of the stirring bar, feed concentration and pore diameter on permeation flux and solute rejection are examined. The behavior of this flux is analyzed by resistance of the membrane itself, the plugging and the cake layer.

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The SMAC method was improved by modifying the treatment of boundary conditions on free boundaries to simulate fluid flows with complicated free boudaries. This new method was applied to liquid flows in a tray-type distillation column, and the flow conditions for different locations of inlet flow were investigated. Good agreements were obtained between simulated results and experimental ones as to the liquid surface levels. The mechanism of downcomer flooding was also investigated and the following conclusions were obtained. The location of the inlet flow affects the condition of the main flow under the downcomer. In the case of the inlet flow falling down along the downcomer surface, the velocity of the main flow under the downcomer is not sufficiently recovered from the deceleration caused by the collision with the bottom. In this case, the downcomer disturbs the main flow and causes downcomer flooding at a large flow rate.

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The characteristics of representative spectral methods (Galerkin, tau and collocation), which are applied to the direct numerical simulation of turbulence, are investigated from the solutions of the Burgers equation. Two types of trial functions, i. e., trigonometric function and Chebyshev polynomials, are used to approximate a truncated series expansion of solution. It is shown that the pseudospectral method gives the solutions almost in perfect agreement with those obtained with the Galerkin method if the aliasing contributions to the nonlinear term are properly eliminated. Aliasing removal by padding and phase shifts is examined: a dealiasing technique using random phase shifts is considerably cost-efficient although aliasing removal is not complete (but acceptable). At higher wave numbers, the differences are noted in the results obtained by the tau and Galerkin methods, which are due to the different treatment of incorporating the boundary conditions into the governing equation.

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Scale model experiments were made to investigate the steady and unsteady airflow characteristics in an underground railway station. The experimental apparatus consists of a scale model of a two-layer underground railway station and train wind generators that simulate the steady and unsteady airflow caused by trains. The steady and unsteady airflows were measured with hotwire anemometers at several points of the station for several cases. The unsteady airflow patterns were almost identical to the estimated airflow patterns obtained from steady values. The method of reducing the train wind effect in a station by means of tunnel ventilation dynamic control was considered and its effectiveness was confirmed through experimentation.

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The solidification of supercooled solution was studied for the system of the conventional solidification processing. In this system, solidification does not occur massively at the nucleation stage, and the second stage of solidification continues under local equilibrium conditions. On the basis of the physical model presented by simulating experiments using aqueous solution, the relaxation process of thermodynamically unstable fields was clarified theoretically as the thermal and solutal diffusion problem with phase change in the mushy zone.

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An experimental study of solidification is performed for a super-eutectic sodium carbonate solution (Na₂CO₃-H₂O) in a confined cavity with varying initial concentration and temperature. We show important features of transport processes of heat and species during horizontal solidification by quantitative measurements of temperature and concentration. The development of the vertical density stratification that forms as a result of solidification can effectively damp thermal convection in the liquid region, and leads to the establishment of either a stagnant fluid region double-diffusive cells. Initial superheat is found to be responsible for the initiation of the double-diffusive cells. For a higher initial concentration, a larger initial superheat is required for the onset of the double-diffusive cells.

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Microbubble emission boiling (MEB) is the regime that occurs in the subcooled transition boiling region. This experimental investigation reveals that this phenomenon includes two regimes, i. e., the stormy and calm microbubble emission boilings. This study also shows temperature fluctuations of a heat transfer surface and pressure fluctuations in the liquid near the surface to classify MEB into the above regimes. The temperature fluctuations in either regime are smaller than those at the critical heat flux. The pressure fluctuations are larger in the stormy MEB, and smaller in the calm MEB as compared with those at the critical heat flux. The liquid subcooling and flow velocity approaching the surface are important aspects by which to generate those regimes. A number of experiments lead to the map of MEB regimes that consists of liquid subcooling and flow velocity. An oscillatory character between the two regimes appears under several conditions.

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The condensation heat transfer of ethanol-water binary vapor mixture is theoretically examined with regard to the assumption of thermal equilibrium in the vapor boundary layer. If the vapor in the boundary layer is subcooled, liquid droplets appear. Under this condition, the effects of the temperature difference between the wall and ambient, and the ambient ethanol mole fraction, on the heat transfer process are investigated. The results show that the heat transfer coefficient under equilibrium conditions decreases from that obtained without droplet formation (nonequilibrium) according to the total amount of the generated liquid droplets.

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Experiments have been performed on the evaporation performance of the refrigerant-oil mixtures inside a smooth tube for CFC12 and HFC134a. Two kinds of oil were used: mineral oil for CFC12 and HFC134a, which was not miscible with HFC134a, and synthetic oil for HFC134a, which was miscible with HFC134a. The straight, horizontal test section, 11.8mm id with a length of 1.0m, was heated by an electric heater, and the heat flux was 7.4kW/m². The oil mass concentration was 1% for the mineral oil experiments and 0.1, 0.2, 0.8% for the synthetic oil at the exit of the condenser. The evaporation temperature was about 0°C, and qualities at the measuring point of the heat transfer coefficients changed from about 0.3 to 1.0. Measurements and observations showed clearly the effects of oil miscibility and oil concentration on the flow patterns and heat transfer.

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Concerning the behavior of stability margins of forced-flow cooled conductors, it is known experimentally that the multiple stability margins for certain combinations of operation current, magnetic field, ambient helium pressure and externally imposed helium flow appear. This work is a study of the mechanism of multiple stability and of the influence of heat transfer on multiple stability margins by means of our own numerical code. It is obvious that the multiple stability margins of forced-flow cooled conductors are due to the interaction between enhancement of heat transfer by heating-induced flow and increase of temperatures of conductors and ambient helium. Also, it has been possible to give a qualitative explication of the complex multiple behavior of the stability margins using only the steady state heat transfer formula and to give a quantitative explication of that using both transient and steady-state heat transfer formulae.

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Heat transfer of natural convection along a vertical flat plate was investigated semi-analytically. In natural convection, measurements of turbulent quantities near wall are usually difficult as a result of its strong temperature fluctuation. On the other hand, a number of attempts to describe turbulent heat transfer have been made and reliable data were presented. Therefore, in this study, a penetration model was introduced and natural convection heat transfer was considered in relation to its turbulent structure.

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Experimental investigations were carried out on the fluid flow and heat transfer around a rectangular cylinder with a chord length of 50mm and an aspect ratio of 5/1. The angle of attack a was varied from 25 to 90deg, the freestream velocity from 6 to 20m/s. The flow on the upper-end-side face changes in the order laminar, separated-reattached and near wake with an increase in α. The flow on the front face is always laminar. The lower-end-side and rear faces are always exposed to separated flows, whose Nusselt numbers are given by Nu=CRe^2/3. The average Nusselt number on the rear face is correlated with the fluctuating pressure coefficient, C'_p, which is given as (Nu)^^^-=0.38(√(C'_pRe_c))^0.60, and the overall Nusselt Nusselt number is given by Nu_m=0.275Re^0.60_c, where Nu and Re are defined by the chord length.

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In dropwise condensation, the behavior of the condensate is one of the important factors influencing the heat transfer. When the condensate is flowing down the condensing surface, it usually displays two significant effects: i. e., sweeping and covering effects. However, it is difficult to clarify the behavior of the condensate in a practical condenser because of the complex phenomenon. Therefore, the behavior of the passing water on wettable and nonwettable tubes was investigated in air. As a result, the passing ratio of a flow rate was obtained for each experimental condition, and it was found that the ratio was affected by the material, the outer diameter and the height of the arranged tube. On the glass tube, the passing ratio decreased gradually as passing flow rate increased/ In the case of the teflon tube, the minimum passing ratio was obtained in a passing flow rate of Q_a: 500≲Q_a≲1000L/mh.

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The temperature stratification of heated air flow in a fire tunnel is investigated by the two- and three-dimensional experiments and numerical models described in previous papers. It is found that the heated air flow can appear to be either a stratified or a mixed flow pattern in accordance with different ventilation velocities, heat release rates, and downstream positions. To deal with tunnel fire circumstances, the mixed convection is evaluated by a macro nondimensional variable Gr^*/Re_H^5/2, and a quantitative relationship between Gr^*/Re_H^5/2 and a parameter which identifies the varying degrees of the stratification at each tunnel crossection has been established. By comparing the results from two- and three-dimensional analysis, the effects of secondary flow on temperature stratification are discussed. The conclusions obtained are directly relevant to the safety considerations in tunnel fires.

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A study on the thermal resistance of finned LSI packages mounted on a circuit board is performed on a semi-empirical base. Based on the result of flow visualization, a physical model which is suitable for finned LSI packages mounted on a circuit board is developed. The recommended correlations obtained by modifying those for finned LSI packages in the free stream predict the thermal resistance of the LSI package very accurately. The estimation error is found to be within ±10% compared with experimental data. The thermal resistance of finned LSI packages in the downstream can be predicted with reasonable accuracy by considering the effect of thermal wake from the packages in the upstream on those in the downstream.

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A method using a modified LDV optical system for simultaneous measurement of velocity and temperature of water has been developed. The laser-induced fluorescence of Rhodamine B was used for the temperature measurement of water. The fluorescence of Rhodamine B decreased with temperature and its temperature coefficient was 3.2%/K. A dimensionless calibration curve was obtained which was not affected by laser intensity, concentration of Rhodamine B, laser wavelength or optical configuration. Simultaneous measurement of velocity and temperature was performed in a natural convection field. The fluorescence intensity traced well the velocity change of the thermal plume.

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The characteristics and performance of pulsed jet ignition are confirmed by combustion tests carried out in a disk-shaped combustion vessel with a lean methane-air mixture, in comparison to those of plasma jet ignition and standard spark plug ignition. The results show that plasma jet ignition has a greater combustion enhancement effect in its initial period than pulsed jet ignition has. After the initial period, however, pulsed jet ignition demonstrates superiority in its combustion performance. As a result, pulsed jet ignition shows a higher maximum pressure and shorter combustion period than plasma jet ignition.

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The three different discharge regimes of diffuse, micro-arc, and big-arc modes, between the combustion gas plasma flow and the cathode wall, have been clearly separated, and the arc generation behaviors have been statistically investigated using a multichannel analyzer for the measurements of height and frequency of arc pulses. In the micro-arc mode region, the arcs are generated at random, while in the big-arc mode region, the arcs have regularity of generation, which was obtained from the comparison between the Poisson distribution and the probability density function of arc generation. The correlation functions show that the big-arcs are generated continuously, and the micro-arcs often occur again after the decay of the big-arc trigger.

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The ignition of a suspended droplet in high-temperature ambient was investigated experimentally for n-heptane/n-hexadecane blends. The effects of initial fuel mixture ratio, initial droplet diameter and ambient temperature on ignition time were observed. For pure n-heptane droplets, ignition time is roughly constant with the initial droplet diameter, and it decreases gradually with increase in the initial droplet diameter under lower ambient temperatures. On the other hand, ignition time increases with increase in the initial droplet diameter for pure n-hexadecane. For the case of mixed fuel, the results show that there exists an initial droplet diameter at which the ignition time takes the maximum value, and that this diameter increases with decrease in the initial concentration of n-heptane or the ambient temperature.

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An experimental study has been carried out to investigate the onset of microexplosion of emulsified fuel. Silicone oil and water emulsions contained in a Pyrex glass capillary after degasification were immersed in oil bath. The waiting time for the onset of microexplosion was measured at atmospheric pressure in the temperature range of 423K to 463K. The results showed that the waiting time at constant temperature correlated with the Weibull distribution and that the shape parameter was found to be unity. It was also found that the mean waiting time for microexplosion decreased exponentially with increasing liquid temperature, and the experimental equation was proposed as a function of the superheat of emulsified water. The probability density of the onset of microexplosion during the unsteady heating period was predicted on the basis of the above equation.

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Combustion of a monosized fuel-droplet spray is discussed in terms of two kinds of nondimensional parameters which are identified as group combustion numbers. The rate and the type of combustion are controlled by these parameters. The basic formulation is based on the Schvab-Zel'dovich formulation.

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This paper describes the relationship between the flow noise generated secondarily in cylindrical expansion chambers and chamber resonance. In a sound pressure spectrum measured inside each chamber tested, the resonance components appear at the frequency determined by the chamber dimensions and the mode of vibration in the cylindrical sound field produced in the chamber. The resonance in connection with the radial vibration mode is intensified when its frequency approaches that of the dominant component of flow-generated noise caused by the impact of the jet to the exit of the chamber of which the length is less than four times of pipe diameter. In this case, the sound pressure level of flow noise emitted from the tail-pipe end excels by a very large amount at the frequency close to the resonance frequency, so that its overall value increases. The ranges of chamber size and mean flow velocity, in which the amplified chamber resonance occurs, may be presumed by using Fig. 11 arranged with a Strouhal number and the formula for resonance frequency on the circular sound field.

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This paper presents visualization and analysis of the unsteady interaction and reflection of shock waves between stationary and moving blades in a rotating turbine. The stroboscope-type Schlieren method in which a reflection mirror is installed at the stationary blade flow path is utilized. The experimental turbine was running at 2000rpm with a pressure ratio over 2.5. The periodical interaction and reflection of shock waves caused by the effects a of rotating blades were observed clearly by photograph. The locations and deviations are verified from the calculations of the shock waves.

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The fuel economy in a vehicle deteriorates at low temperature. The main reason is the increase of friction loss. In the previous report, it was shown that the friction loss changes with cylinder wall temperature, and that the cylinder wall temperature can be estimated by a simplified heat transfer model. In this report, the indicated thermal efficiency was obtained from the heat balance measured at road load conditions. It was found that the indicated thermal efficiency correlated with the cylinder wall temperature. Thus, when the cylinder wall temperature was simulated, the friction loss and the indicated thermal efficiency were estimated. Since the indicated power is the sum of running resistance and friction loss, the fuel consumption can be calculated from the equation between the indicated power and the indicated thermal efficiency.

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For the evaluation of the heat flow in the cylinder heads of automotive gasoline engines, thermal boundary conditions were measured and then the heat flows were analyzed by the FEM. The model used for the analysis was half of the second cylinder head in a 1600cm³, 4-cylinder, in-line gasoline engine. The heat flux from the combustion chamber to the coolant, obtained by cycle simulations with Eichelberg's heat transfer expression, agreed well with measured values. The heat transfer coefficient on the coolant side was found to be in proportion to the 0.25 power of the water flow rate because of forced convective and boilling heat transfer phenomena. The heat flow distribution and surface temperature of the combustion chamber were analyzed using multiple regression functions of the measured results.

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The history of mechanical engineering education at the University of Tokyo is surveyed and the trend of evolution in the curricula and their requirement conditions is studied. The survey covers the past 106 years between 1886 and 1991, and ten representative curricula are selected from that period. Courses of each curriculum are classified into seven categories and listed for comparison. The history of curricula indicates that the traditional mechanical engineering curriculum, which features heavy concentration in applied mechanics education, took its present form half a century ago and continued until the mid 1980s. The shift from power-driven machines to information-driven ones required qualitative change in mechanical engineering education, and a new generation of curriculum with the combination of natural and artificial sciences appeared in recent years.

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In the previous reports, effects of an impeller blade tip clearance and the blade number on the inlet reverse flow starting point were clarified for three and five blades open-type and closed-type impellers with good suction performences. Then, in this paper, for the close-type and open-type impellers with the blade inlet angle decided by conventional design method, the same experiment was carried out to know effects of the blade inlet angle on the inlet flow condition at low flow rates and the inlet reverse flow starting point, and the results were compared with the previous ones. Furthermore, the inlet reverse flow occurrence mechanism of the centrifugal pump impeller was examined based on the experimental results. It was particularly shown that the inlet reverse flow inception point can be predicted by investigating the relative flow along the impeller shroud surface.

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