Transmitting forces were measured during the time when a upper spherical surface was approaching to a lower flat plate at a constant speed and after the movement of the upper surface was stopped. The forces measured for glycerin and PEO solutions were predicted by the theory of viscous fluids. In the case of Separan solutions, however, overshoot of the force was seen at the inception of the squeezing motion and the maximum in magnitude was about 1.5 times larger than the force estimated with the viscous stress. This trend agrees well with those of the stress overshoot in simple shear flows. After the squeezing motion was stopped, the clearance between two surfaces was observed to slowly decrease because of the spring back of the load cell attached to the lower plate. At this stage, the larger transmitting force was maintained for the Separan solution than that for the viscous fluids. This result is considered to be related to the stress relaxation.

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A storage requirement of the finite-element method (FEM), which is a result of using un-structured meshes, can be considerably reduced by using iterative solvers. However, the acceleration of the convergence is still an important and urgent problem in spite of currently available vector processors. In this paper, the convergence acceleration for solving the time-dependent incompressible viscous flow by using the iterative solver is given. The variable transformation is applied to the finite-element discretized equations in order to obtain the diagonal-dominant equation system. The usual framework of the primitive variables (velocity and pressure) is transformed into that of newly introduced variables : rotational velocity and velocity potential. The effectiveness of the present technique is demonstrated through the lid-driven cavity flow and the flow past a cylinder.

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Laser Doppler velocity measurements were performed on developing oscillatory flow in a strongly curved tube, in which a curvature ratio, a/R (defined as the ratio of the tube radius to the radius of curvature) of 1/2 was achieved. At the Womersley number of 4.5, curvature effects enhanced the secondary flow and maximum secondary flow velocity incresed to 60 % of the amplitude of the cross-sectional averaged axial velocity in the curved tube of a/R = 1/2. On the other hand, for a larger Womersley number ( = 18), the velocity at the edge of the boundary layer at the inner wall significantly increased just downstream of the entrance due to the formation of potential vortex, which is strongly dependent on large curvature effect.

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A numerical technique for the analysis of three-dimensional unsteady turbulent flows in a turbine stage is presented. To calculate the unsteady interaction flow fields in a nozzle and bucket simultaneously, the nozzle outlet elements and the bucket inlet elements are overlapped in the axial direction and are used for unsteady data transfer between flow regions. On the periodic and connecting boundaries, a time phase shift boundary condition is introduced for computations of different blade number between nozzle and bucket. To calculate the flows in arbitrarily shaped geometries, a control volume method combined with a body-fitted curvilinear coordinate system is used to obtain spatially discretized governing equations, while the second-order accurate Adams-Bashforth method is employed for time integration. In the present analysis, a two-equation model of turbulence is introduced to estimate the turbulence effect. In order to assure the effectiveness of the present method, computations are carried out for the flow in a subsonic turbine stage of three different axial distances between nozzle and bucket. It is shown that unsteady flow phenomena such as the nozzle wake and pressure field interactions are well predicted, and the periodic aerodynamic forces acting on the buckets, including the effect of the axial distance difference, are obtained by the present method.

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The flow accompanied with turbulent Taylor vortices between inner-rotating and outer-stationary cylinders is analytically treated by using two kinds of κ-ε models. The results obtained with both models are generally in good agreement with the existing experimental results. No marked tendency for the secondary flow to disappear with increasing rotating speed is found within the range of the calculation. For a fixed value of Reynolds number, there exists a certain radius ratio which makes the intensity of the vortex maximum. The more this intensity decreases, the more the turbulence energy increases. As the radius ratio approaches unity, the intensity of the vortex decreases monotonously. Conversely, the intensity of the circumferential component of the secondary flow continues to increase until a radius ratio very close to unity. The hypothesis that the vortex determines its shape so that the total amount of the dissipation rate becomes maximum is substantially consistent with the experimental evidence.

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

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Inevitable errors in X-probe measurement are investigated in simulated Gaussian velocity fields generated on a digital computer. Two types of X arrangements are studied : one is a conventional X-probe comprised of two slant hot wires, and the other is that which consists of slant and normal hot wires (modified X-probe). The numerical simulation results indcate that the most significant factor producing measurement errors is the difference in an instantaneous velocity field between two wires. Especially, the measurement accuracy of the modified X-probe depends strongly on the effect of wire separation, and at worst, data obtained with such a probe result in fallacious information. To confirm the error analysis, turbulent quantities in a pipe flow have been measured using these X-probes. Experiment clearly shows the same results as those of error analysis.

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An efficient numerical method of the Boltzmann equation has been developed for inviscid transonic flow. In this method, the convective terms in the Boltzmann equation are approximated by the second order upwind finite difference with limiter: The rational Runge-Kutta scheme is used for the corresponding time integration. The residual averaging technique is incorporated into the method so that the rate of convergence is improved to a steady-state solution. The solution of the collision integral is obtained as thermodynamic equilibrium states. The number of grid points in molecular velocity space is reduced to 4 for each direction to shorten the CPU time in the present approach. As an example, the one-dimensional unsteady shock-tube problem is solved and the results are compared with the exact solution. The feasibility of the present method is demonstrated for the two-dimensional transonic flow in a channel, and over the NACA0012 airfoil and the RAE2822 airfoil. Those results are compared with the results of the Euler equations.

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The surface pressure distributions of a circular cylinder as a model with large streamwise pressure gradients were measured for various static pressure hole diameters and depths in incompressible laminar flow. The error of pressure measurements is proportional to the hole diameter and not affected by the depth within the experimental regions. Simple and available formulae of correction are proposed for the Reynolds number range between 5 × 10³ and l.5 × 10⁴. It is expected that the range is extended to about 2 × 10⁵, where Newton's drag law is applicable. The formulae of correction may be developed into the surface pressure of a sphere or a cone placed on a plate.

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We have developed a method of local temperature measurement in the rarefied gas flow using laser-induced fluorescence of iodine molecules seeded in carrier gas. lodine molecules have many absorption lines in visible region and radiate intense fluorescence. The fluorescence intensity is proportional to the number of molecules in the energy level excited by the laser beam. From the dependence of this number on the temperature, the local temperature can be decided through the ratio between the fluorescence intensities of two visualized images which are obtained by irradiations of laser beams with different wave length. This method allows to measure the temperature distribution of the entire flow field instantaneously by means of a laser sheet and a high sensitive vidicon camera. This method is applied to the local temperature measurement of the flow field of a supersonic free jet in which temperature varies drastically. It is found that the temperature distribution along the centerline of the jet measured by P26R28 and P16R18 absorption lines agrees well with the theoretical one.

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It is extremely important to obtain basic knowledge of shock waves formed in turbo machines rotating at supersonic speed. The main purpose of this research is to develop an advanced 3-dimensional visualization technique using double-pulsed holographic interferometry with diffused laser light. As the initial step of this research, this technique was applied to observation of the oblique shock waves generated at a "U" -shaped pin, which was utilized in order to get better understanding of the 3-dimensionality of an object flying counter to the supersonic flow in this 1st report. The oblique shock waves generated at each edge could be visualized by the interference fringes and clearly separated in the reconstructed real image. Also by employing the reconstructed process coupled with a spatial filter, it could be verified that this diffused double-pulsed holography is effectively applicable to the 3-dimensional measuring technique of the shock wave. Furthermore, the algorithm for real-time data processing was developed.

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The growing demand for more fuel-efficient aero gas turbine engines has led to the need for a detailed understanding of the aerodynamic behavior of components. The optical technique of holography has recently achieved importance as a means of providing the experimental data necessary for the development and validation of relevant design calculation methods. This paper describes the double-pulsed holographic flow visualization technique which has been developed at IHI and provides information on 3-dimensional shock structures of the transonic flow region between the blades and shock/casing wall boundary layer interaction in rotating aeroengine fan at various rotor speeds and throttling conditions.

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Two-dimensional peristaltic flows are calculated by the finite difference method. In order to concentrate grid points near the wall, Thompson's grid generation method is employed. Pressure is calculated by solving the Poisson equation which is derived by the MAC method. The Kawamura-Kuwahara scheme is applied for the non linear term in the Navier-Stokes equation. As the result of this investigation, it is clear that the finite difference method is useful for analysis in peristaltic flows.

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Compressible flow analysis in turbine cascades was carried out by the use of the modified field singularity (sink/source) method that was originally developed by Van den Braembussche. This method has many noteworthy features : simplicity. compactness of program size and small memory size. all of which allow the program to run even on a desk-top personal computer. A comparison is made between experimental data or calculations of another numerical method (Denton method) and the results obtained with the proposed method in this paper. which shows its capability for subsonic blade-to-blade flow analysis.

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Rotating stall induced in a vaneless diffuser is examined. Combination of several low specific speed impellers and three types of diffusers with different inlet shape are tested. In the lower specific speed stages, the critical inlet flow angle for rotating stall depends not only on diffuser width ratio b/r₂, and contraction ratio b/b₂, but also on the inlet shape of the diffuser. As the inlet shape parameter Δr/r₂ becomes smaller than value of 0.1, the critical inlet flow angle becomes larger than the predicted value by the Senoo method. The empirical prediction formula of critical inlet flow angle in the first report is corrected by considering the influence of inlet shape. Influence of inlet shape on rotating stall phenomenon is also shown.

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To investigate influences of the distribution of tip clearance on the performance of centrifugal compressors, the mixed-flow impeller of a centrifugal compressor with l0:1 pressure ratio was tested with various distributions of the tip clearance varied by not only the axial movement but also the radial reforming of the shroud casing relative to the impeller. Measured data on the decrements of the input head and of the impeller efficiency due to the distribution of tip clearance are compared with the predicted values. The change in the available flow range due to the distribution of tip clearance is also discussed.

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Generally, the cross-flow turbine is operated at a defined minimum clearance between a nozzle and a runner because increase of the clearance increases the leakage loss. Moreover, the dimension of nozzle-runner clearance influences not only the leakage flow but also the interference between the nozzle and the runner. The interference causes the change of flow conditions at the nozzle exit or inside the runner and thus influences the turbine efficiency. This paper describes the effects of the clearance on the leakage loss and the turbine efficiency. As a main result, it is found that a runner with many blades (30, 34 blades) shows the maximum efficiency at a suitable clearance, and at smaller clearance, the turn-over flow increases and the turbine efficiency decreases.

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In order to understand the influence of spanwise loading distributions of mixed flow impellers on internal flow patterns of a pump, the pressure distributions on the pump casing wall were examined for four impellers. They had identical sectional blade shapes on every development surface, and their inlet and outlet angles were kept constant at the mean surface but were varied at the tip and hub surfaces to give spanwise loading distributions. The results of the pressure measurements were compared with oil flow patterns of the suction surface of the impeller blade, and the relationship between the flow conditions of pump internal flow and the pressure distributions was clarified. Three dimensional calculations by the finite-element method were also carried out.

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The characteristics of pressure reduction are studied experimentally to investigate the behavior of an air brake apparatus which receives a pressure reduction in compressible flow. Improvement of sensitivity and response of the air brake apparatus is required to increase maximum train speed. In order to understand the characteristic of pressure reduction, we devised a test equipment using a new concept and applied it to a few rolling stock apparatuses. It is confirmed that the complicated pressure fluctuation of an actual rolling stock was reproduced to high accuracy by using this characteristic test equipment in a laboratory. As an example, the sensitivity of three types of pneumatic control valves was investigated quantitatively and the characteristic of their sensitivity in emergency braking is discussed. The effectiveness of the equipment is shown through the experiments.

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For a snow-melting system for railway tracks, from an economical point of view, it is necessary to manufacture a water sprinkler with variable flow rates in response to snowfall intensity and atmospheric temperature. A newly developed sprinkler was constructed and operated to control water flow rates by water pressure, using either a module valve or an inverter pump installed in the pipe line. The experiment confirmed that the snow-melting system with the proposed sprinklers is technically and economically promising in terms of energy conservation.

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A nonsimilar solution for the free convective condensation of binary vapor mixtures on a vertical plate was obtained. The dependences of the nonsimilar solution for R113-R11 on the temperature difference between the wall and ambient and the mole fraction of R11 far away from wall were investigated. The results agreed with the experimental measurements very well. Comparison with the simpler quasi-similar solution, which was previously used to estimate the heat transfer coefficient, was also performed.

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Saturated liquid densities of the binary refrigerant mixture HFC 152 a (CH₃CHF₂) + CFC 114(CCIF₂CCIF₂) were measured along four iso-composition lines, i. e., 10, 20, 50, 80 wt% HFC 152a, by a magnetic densimeter coupled with a variable volume method using a metallic bellows. The results of forty-four points cover the range of temperatures from 280 K to 390 K. Experimental uncertainties in temperature and density were estimated to be within ± 15 mK and ± 0.5%, respectively. The results were compared with the modified Rackett equation proposed by Spencer and Danner and the Hankinson-Brost-Thomson equation.

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Initial droplet formation in dropwise condensation is one of the important mechanisms for nucleation in the phase change phenomenon. Film fracture hypothesis has been proposed by other researchers and they have estimated film thickness. But they could not observe the initial droplet formation. Here three experimental studies based on microscopic observations were performed. The authors observed that dropwise condensation nuclei were grown from a very thin film. Film thickness was from 0.1 μm to 0.3 μm and critical droplet size was from 0.8 μm to 1.3 μm. Critical droplet size densities of 1.4-2.8 × 10⁷ sites/cm² were found.

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The information of the wire response is necessary for the estimation of corrections and uncertainty of temperature measurements. This paper describes the theoretical response of cold-wire sensors to temperature fluctuations in a fluid flow. Existing transfer functions of cold wires are approximate and implicit functions of frequency. We present the explicit exact solutions of heat conduction equations for a cold wire and stubs taking account of the prong effect. Because the solutions have simple forms of primary functions, we can easily calculate the frequency response of cold wires. Sample calculations are given under several typical conditions. Also, the instantaneous temperature profiles of a cold wire are obtained for the first time.

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As a convective boundary condition in thermal analysis by a finite-element method, heat transfer coefficients and circumferential fluid temperatures are generally specified. However, when fluid temperature varies greatly along a flow path, it is difficult to specify fluid temperature distribution in advance. In the case of a combined analysis of flow and heat transfer, a large-scale computer is needed. Furthermore, it takes much time to solve the flow equation. In designing machines, a simple method for predicting cooling performance is often more desirable than precise flow analysis. This paper shows a simple thermal analysis method considering the temperature change of a fluid along a path without flow analysis by specifying heat transfer coefficients. An example of the thermal analysis of a general-purpose inverter is shown.

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Thermal convection of fluids heated from below occurs when the Rayleigh number becomes greater than a critical value. In general, convection gradually evolves to complex, often time-dependent, states as the Rayleigh number increases. The process involves various forms of transition, such as from one convecting pattern to another, steady to time dependent and simply periodic to chaotic oscillation. The present research focuses on an evolution process of infinite Pr convection in a cubical geometry with stress-free boundary conditions. The numerical computations have been carried out up to Ra = 2×10⁵ using an efficient scheme based on the pseudospectral method. With increasing Ra, a convecting pattern starts losing its symmetries at about Ra = 7×10⁴, but does not evolve to time-dependent states. Effects of truncation number on the numerical accuracy are also investigated. For example, a truncation number of N = 12 is adequate at Ra = 10⁴, while N = 16 is needed at Ra = 10⁵. The Nusselt number appears to grow at a rate of Ra^1/3 when Ra exceeds 10⁴, suggesting the formation of distinct thermal boundary layers.

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An automatic heat transfer measuring system is designed and fabricated to demonstrate the usefulness of the transient heat transfer testing method. New techniques are utilized in both air-heating and air-temperature measuring systems. A computer system is incorporated to calculate the temporally and spatially averaged heat transfer coefficient using the measured disturbance and response of the fluid temperature. The present system was applied to evaluating the heat transfer performance of parallel plate stacks. The test results are compared with the existing theoretical and experimental data. It was confirmed that the present system not only has high accuracy (within 5% ) but also advantages of time and labor saving over conventional steady-state methods.

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Experimental investigations are conducted on the pressure loss and heat transfer characteristics for packed beds of spherical particles. The spherical particles used in this experiment are glass and polystyrene beads, and the working fluid is air. The experiments on heat transfer characteristics are conducted by the unsteady method, and volumetric heat transfer coefficients are given by the method of fitting between transient temperature profiles of the solid and the gas phase calculated from the analysis and those obtained by the experiment. As a result of arranging these data by using a characteristic length which is defined by the pressure loss, it has been revealed that the experimental data are well arranged. Moreover, as a result of adding the data of the nonparticulate porous media such as a foamed metal and rearranging by the characteristic length, the heat transfer correlation which is able to comparatively well arranged has been obtained.

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We have measured the thermal conductivities and electrical resistivities of Y₁Ba₂Cu₃0₇-_y, Er₁Ba₂Cu₃0₇-_y and Bi₁Sr₁Ca₁Cu₂0_y using the steady-state comparative method and conventional four-probe method. Below the transition temperature, T_c, the thermal conductivities had strikingly large values and peaks. By applying the Wiedemann-Franz law, λR/T=L₀, with the electrical resistivity data at T_c, the phonon-thermal conductivities were found to predominate in those superconductors. The normalizations of the measured thermal conductivities of those superconductors with respect to λ_c, critical thermal conductivity, show that the temperature dependencies of thermal conductivity are similar. Most of the normalized thermal conductivities agree with our theory, λ_s=2ξ²·λ_n/(1+ξ⁴), in which the value n of the phonon thermal conductivity, λ_n=ξⁿ, in the normal conducting state is between -1 and -1.5 below T_c.

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The discovery of superconductivity above 90K opens up the possibility of powerful hybrid electronic circuits. Superconductive electronic devices exhibit effects of temperature not present in semiconductors. Heat dissipations in transistors cause temperature fields in hybrid chips that affect the performance of the superconductive element, the Josephson junctions. The minimum distance between semiconductor and superconductor elements results in a thermal packaging limit for hybrid chips. This work presents a novel methodology to determine this limit, based on the basic thermal phenomena in superconductive elements. An approximate one-dimensional thermal analysis of a generic hybrid chip design determines the temperature field and the minimum distance.

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An analysis has been made of two-dimensional, steady-state, laminar film condensation heat transfer on a finite-size, isothermal, horizontal plate facing upward in a stagnant saturated vapor, taking into account the effect of the plate edge. The boundary-layer equations for the condensate flow on the plate are solved using an integral method. The solutions are obtained under the two conditions that (i) the inclination angle of the vapor-liquid interface may be given at the plate edge, and (ii) the thickness of condensate film is minimized. For the former case, the effect of the inclination angle upon the condensate film thickness and heat transfer rate are investigated. For the latter case, the thickness of the condensate film and heat transfer rate are calculated. An approximate solution for the heat transfer rate is proposed in terms of the Nusselt number. Also, the present analyses are compared with the correlation equation by Leppert et al.

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Experiments were performed to investigate the fluid flow and heat transfer around a rectangular cylinder in a flat plate laminar boundary layer. The height of the cylinder H was varied and the width c was constant. The Reynolds number, defined as U_∞c/ν, ranged from 3.8×10³ to 1.2×10⁴, and the value of the ratio H/δ was varied from 0.48 to 5.2, where δ is the thickness of the laminar boundary layer without the cylinder. The local heat transfer coefficients on each face were measured and discussed in relation to the fluid flow, that is, the flow visualization and the turbulent intensity around the cylinder. The flow pattern on the upper side of the cylinder changes from laminar flow type to separation and reattachment flow types increasing the value of H/δ or (U_∞H/ν)·(H/c). The heat transfer performance corresponds to these flow patterns. Especially, introducing the characteristic length d=(2H+c)/π, the average Nussel numbers on each face are generally correlated to the form Nμ_d=C(Re_d√(H/c))ⁿ.

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Because of the integro-differential nature and high nonlinearity of the energy conservation equation in the combined convective-radiative heat transfer, it is not easy to solve the equation by numerical method. The method based on the solution procedure for a partial differential equation has been used when the convective term dominates, while the numerical method based on the solution procedure for an integral equation has been used when the radiative term dominates. In this study, we make clear the problems involved in these methods, and by changing the grid points, we propose a new numerical method based on the partial differential equation which can be applicable to the radiation dominant region. Also, we propose a new numerical method which quasi-linearizes the radiative term. This method has advantage that the computational time is short and the calculation speed shows weak dependence on the relaxation parameter.

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Analytical techniques for the prediction of cooling curves by quenching of steel are reported. The nonlinear transient heat conduction problem including heat of phase transformation and transient boiling of water at the surface of a cylindrical specimen is analyzed numerically. In this report, the authors' former reports are extended to calculate cooling curves inside of a specimen up to 300mm. Calculated cooling curves clearly show dependency on latent heat of phase transformation and correspondence to reference data by the continuous-cooling-transformation diagram (CCT diagram).

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The reactor vessel auxiliary cooling system (RVACS) is one of the decay heat removal systems for the fast breeder reactor. This system is so simple that it can attain high reliability and plant cost reduction. However, the heat removal capacity of this system is small compared to that of an immersed type of decay heat exchanger, because the heat transfer coefficient at the outside of the reactor vessel is not large. The object of this study is to propose a new method which is able to use thermal radiation effectively. The tests reveal that the heat transfer coefficient, using high-porosity porous bodies as a heat collector, surpasses that with no collector, especially at the upper end.

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Melting of a phase-change material in an elemental test region surrounded by two fins. a tube wall, and a shell wall has been investigated experimentally. Experiments have been performed to examine the effects of various parameters, i.e., the orientation of the elemental test region, the angle between the two fins, and the tube wall temperature. The solid/liquid phase-change process has been clarified from observations of timewise variations in the solid/liquid interface, flow visualization, and measurement of temperature distributions in the phase-change material.

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This paper investigates the diesel-soot suppressing effect of catalytic fuel additives for a range of fuels with different fuel properties. It was found that the effect of catalytic fuel additives was different among the fuels and was approximately described by a parameter including cetane number and kinematic viscosity of fuels. The behavior of the soot-suppressing effect was explained approximately by soot oxidation characteristics for different fuels.

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A theoretical study has been conducted to investigate the burning rate of sodium pool fires, which may be caused by the spillage of liquid sodium in fast-breeder nuclear reactors. In the present model, a thin layer (approximately l mm in thickness) of vapor is assumed to exist upon the surface of the liquid pool. The sodium vapor diffuses toward the flame front at which a chemical reaction between sodium and oxygen occurs. The calculated results are in good agreement with experimental data obtained by other investigators for the burning rates of sodium pool fires. The earlier conventional model, however, tends to underestimate the burning rates since the vapor layer is neglected and the flame temperature is assumed to be equal to the pool surface temperature.

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When a cetane droplets column freely falling from an ultrasonic atomizer is ignited behind a reflected shock, no ignition occurs at a temperature below ca, 1100K even if the pressure is sufficiently high (∼1 MPa). Although a higher temperature ensures ignition, no flame so luminous as to be recorded by high-speed photography appears, and even if a luminous flame lump appears, it disappears without spreading throughout the droplets column. If, on the other hand, fuel is injected into a diesel cylinder or an electric furnace, ignition occurs even at a temperature as low as 650K with a luminous flame spreading over the entire spray. Supposing that the above difference resulted from the difference in intensity of turbulent mixing of droplets with hot air, turbulence-generating rods were placed on the upstream side of the spray column. As a result, the ignition limit was lowered down to ca. 840K, and the combustion made shifted from a blue-flame mode or locally confined ignition mode into an ordinary spray combustion mode.

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In order to obtain clear prefiles of the fluid dynamic and thermal behavior in a tailpipe of the valveless pulse combustor, cold pulsating air flows in a circular pipe are first experimentally investigated with a hot-wire anemometer of constant temperature type, which is equipped with a single I-probe. Then, the flow and turbulence characteristics of the pulsating flows are qualitatively clarified by comparing them with those of the ordinary turbulent pipe flows. The results show that the pulsation induces intense velocity fluctuations, not only in the low frequency regions, centered on the pulsation frequency and its harmonics, but also in a relatively high frequency region up to about 500Hz, causing rms values greater than those of the ordinary pipe flow by about one order of magnitude. Also, the effects of the pulsation on the turbulence generation across a section are found to be less remarkable in the near-wall region than the central one.

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The structure and behavior of radiation controlled flame in a highly porous medium which has a finite length along the flow direction have been clarified in detail through the numerical calculation on the basis of the rigorous treatment for the radiative transfer and of the simplified one-dimensional flame theory. The results demonstrate that the flame is stabilized in the porous medium over a wide range of the mixture velocity. Under the high velocity condition, the gas phase heat conduction is the dominant mode of heat transfer for the flame propagation just as being found in the case of the ordinary flame. On the other hand, under the low velocity condition, the radiation is a significant heat transfer process for the flame propagation in the porous medium. Further, the combustion is enhanced to a considerable extent because of the energy recirculation by radiation heat transfer even if the flame temperature is much lower than that for the ordinary flame.

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The flow visualization technique was used to measure the in-cylinder flow of an internal combustion engine. In this paper, metaldehyde was used as a tracer of the gas flow and the PLZT was adopted as the shutter on the basis of its merit of electrical controllability. First, the flow velocity obtained by this measuring system and that from LDV were compared and found to be in agreement ; this demonstrated the validity of the measuring system. Two examples of the measured velocity were also shown. One is that cyclic variation of the in-cylinder flow and differences in the velocity on each radius at one moment existed. The other is that the rotational centers of the flow traces were calculated and found to distribute around the cylinder center at the compression stroke, gather near the cylinder center at the compression end, and distribute widely around the cylinder center at the expansion stroke.

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