Thermal stresses in plate structures subjected to heat transfer on both surfaces are analyzed. Through analytical study, new design charts for temperature and stress are developed. Design charts for plate, where one surface is adiabatic, are conventionally used. By using new ones, the applicable area of design charts can be greatly extended. New temperature charts are normalized by steady-state temperature. New stress charts are normalized by the steady-state stress at a fixed back surface temperature in order to reduce reading errors. Maximum stress charts for step or ramp change of fluid temperature are developed. Stress reduction by transferring step change to ramp change can be read directly from the charts.

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In reciprocating internal combustion engines, Otto cycle indicates the best thermal efficiency under the same compression ratio among ideal cycles. To achieve this, combustion must take place instantaneously at top dead center, but it is actually impossible. Meanwhile, if a slower piston motion around top dead center was allowed, both the in-cylinder pressure and degree of constant volume would increase, leading to higher thermal efficiency. In order to verify this idea, an engine with a slow piston motion by adopting a large ratio between the connecting-rod length and the crank radius was tested. As expected, while degree of constant volume was increased, thermal efficiency was not improved due to increased heat loss. Further experiments were carried out using a direct injection stratified charge combustion system which allows selective reduction of heat loss, and high thermal efficiency was attained. On the contrary, an engine with a faster piston motion by adopting a smaller ratio between the connecting-rod length and the crank radius attained high thermal efficiency under the quick burn pre-mixed spark ignition combustion.

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In reciprocating internal combustion engines, Otto cycle indicates the best thermal efficiency under the same compression ratio. To achieve this, combustion must take place instantaneously at top dead conter, but it is actually impossible. Meanwhile, if slower piston motion around top dead center was allowed, both the in-cylinder pressure and degree of constant volume would increase, leading to higher thermal efficiency. In order to verify this idea, an engine with slower piston motion by ideal constant volume comcustion was tested. It was revealed that the thermal efficiency could not be improved nevertheless an increase in degree of constant volume and lower pumping loss. Numerical analysis deduced that increased heat loss cancelled out the effect of the higher degree of constant volume and that faster piston motion around top dead center rather achieves an improvement of thermal efficiency in a case where rapid combustion was realized.

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After-treatment systems consisting of new catalyst technologies and particulate filters will be indispensable to meet increasingly stringent global regulations limiting particulate matter (PM) and NO_x emissions from heavy duty and light duty diesel vehicles. Diesel particulate filter (DPF) has been established as a key technology in reducing diesel particulate emission. But particulate filtering characteristics in a DPF have not been fully understood yet. We investigated effects of particle size and particulate load on particle trapping efficiency in a DPF both by flow reactor experiments and computer simulations for the purpose of developing high-performance DPF. In a flesh DPF, the dominant particle trapping mechanism transferred from the Brownian diffusion to the interception at around 200 nm in particle diameter, and these particles showed the lowest particle trapping efficiency. Particle size dependency of the particle trapping efficiency disappeared when PM accumulated in a DPF. These results led to availability of DPF for the reduction of diesel nanoparticles.

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The MPS method is a particle method which simulates motion of continua with a finite number of particles. Thus it is relatively easy to simulate complex flows such as those in a bioreactor in which the geometry of flow is continuously modified by adhesion of cells. In this study, flows with adhesion of cells in a micro channel are simulated using the MPS method. The adhesion pattern of cells is well reproduced by the simulation.

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The behavior of two subsonic streams through a single converging nozzle is numerically analyzed from the viewpoint of the choking of the compound nozzle flow. And a new criterion of the compound choking is presented taking the growth of the sonic line extending across the entire exit passage into consideration. The present criterion is compared and discussed with the one based upon the one-dimensional flow model presented by Bernstein et al.

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The results of the control of tip leakage vortex cavitation, and cavitation instabilities, are discussed. The control was made by adjusting the axial location of the leading and trailing edges of shallow grooves, called J-grooves, on the casing wall. If the leading edge of the groove is too close to the leading edge to the impeller blade, the tip leakage vortex is trapped by the groove leading edge and the tip leakage vortex cavitation approaches the leading edge of the next blade. A premature severe cavitation surge occurs when the tip leakage vortex cavitation starts to interact with the leading edge. This type of cavitation surge can be avoided by extending the groove leading edge upstream. However, in this case another type of cavitation surge occurs at much lower cavitation number caused by the cavitation between the blade surface and the tip leakage vortex cavitation. Thus, the importance of the tip leakage vortex cavitation for cavitation instability are shown by a series of experiments using J-grooves.

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In supersonic flight, airplanes cause strong sonic booms and wave drags accompanied by shock waves. It is necessary that airplanes have low noises and high efficiencies to realize next generation supersonic transports. It has high possibility that these two objectives can be achieved using a concept of Busemann Biplane. Motivated by the concept, aerodynamic design of biplane configuration in supersonic flight is discussed based on Computational Fluid Dynamics (CFD). In order to focus on the shock wave characteristics around a biplane configuration, inviscid flow (Euler) analyses are performed, which is particularly suitable for wave drag analyses. The purpose of this paper is to examine characteristics of Busemann Biplane and to demonstrate new biplane configurations which have better aerodynamic performance based on Busemann Biplane. The aerodynamic design is performed using an iterative inverse design method that has been recently implemented. This is the method that geometries are detemined by given target pressure distributions. We expect that the inverse design method may prove to be a highly appropriate tool in finding a biplane configuration to achieve minimum wave drag under a given lift condition. By the use of the inverse design method an improved airfoil shape for the biplane has been obtained

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A flow around a 2-D aerofoil that has a NACA 0012 cross-section is simulated by large eddy simulation with the dynamic Smagorinsky model on a high-resolution C-type mesh that consists of approximately 8 million hexahedral elements. The Reynolds number based on the chord length of the aerofoil and the uniform-flow velocity is 2.0×10⁵ and the angle of attack is set to 9 degrees that nearly corresponds to the maximum lift condition at this Reynolds number. The results show that the boundary layer on the suction-side surface separates just downstream of the leading edge and reattaches on the surface approximately at 8% chord length downstream of the leading edge with transition to turbulence being initiated around the reattachment point. In order to investigate the accuracy of the fluctuating quantities predicted by the LES, distributions of surface pressure and wake velocity are compared with measured equivalents in terms of time-average, intensity of the fluctuations and their power spectra. The results show that the present LES is capable of predicting the separation-transition process of the boundary layer and providing accurate sound sources for the numerical prediction of aerodynamic sound.

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The development of waves on a fluid-fluid interface, excited by a vertical, relative motion of a solid wall enclosing the fluids, is affected significantly by the mobility of the interface on the wall. The effective, cycle-averaged mobility depends on the amplitudes of excitation and waves, because of a non-linear dependence of the velocity of the fluid-fluid-wall contact line on the angle of the interface hitting the wall. At higher amplitudes of excitation and waves, moreover, the interface motion is tied to the low mobility of the contact line only for a limited fraction of each cycle ; for the rest of the cycle the interface is virtually untied from the wall, being connected to the contact line only through the surface of a thin, flat liquid film left on the wall. An analytical model is developed on the wall surface boundary conditions for the interface profile, in terms of non-linear relationship between the interface velocity along the wall and the near-wall inclination angle of interface. The model is based on optical data taken in a quasi-static experiment where measurements of near-wall interface configuration were essentially unaffected by wave generation on the interface. Numerical simulation with this model reproduces successfully the changes in the near-wall configuration of the interface in the experiment, including development and depletion of a liquid film on the wall associated with relative motion between the contact line and the interface elevation away from the wall.

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The analytical model developed in the previous paper is applied to a problem where an axisymmetric wave of the fundamental mode is excited on a circular, immiscible fluid-fluid interface enclosed by a vertical cylinder. The excitation is caused by a forced vertical motion of the fluids relative to the stationary solid wall. Model analyses reproduced experimental results on the interface wave amplitude and phase relationship to the forced excitation. It is found that the time fraction of the 'stick' phase in each cycle provides a measure of the effective, cycle-averaged mobility of the interface on the wall. The stick phasd is the time period where the interface is tied directly to the fluid-fluid-wall contact line of low mobility and hence the near-wall interface profile is subjected to deformation as a result of the forced fluid motion relative to the wall. For the rest of the cycle the interface is virtually untied from the wall due to the presence of a liquid film between the moving interface and the contact line, which can stretch or shrink without imposing additional forces on the moving interface. The fraction of the stick phase in each cycle decreases as the excitation amplitude is increased, or the wave amplitude increases. The effective, cycle-averaged mobility of the interface, dependent on this time fraction, affects the natural frequency of the interface as well as the efficiency of wave excitation.

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This study deals with an experimental investigation on the suppression of flow-induced vibrations of two circular cylinders in tandem arrangement. In this study, the tripping rods which are attached in symmetry about the stagnation point of circular cylinders are used to suppress the flow-induced vibrations in cross-flow vibration. The response characteristics on elastically supported two circular cylinders are examined by a free vibration test when the spacing ratio L/D (L is the gap spacing between two cylinders, D is the diameter of cylinder) and the position of the tripping rods are variously changed. Also, the behavior of the shear layers separated from the two circular cylinders are investigated on the basis of the visualized flow patterns. The main findings are that (i) the effect of suppression for flow-induced vibrations of two circular cylinders terrifically changes by the installing angle of the tripping rods on the cylinder surface, (ii) when the tripping rods are installed at 20 and 30 degrees from stagnation point, the flow-induced vibrations of the two cylinders are almost suppressed at which less than the critical spacing L/D=2.7, (iii) when the tripping rods are installed at the position beyond 40 degrees, the flow-induced vibrations of the two cylinders are considerably larger than those of the cylinders without the tripping rods.

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In nuclear power plants, the steam control valves are used to control the flow from the steam generator to the steam turbine under various pressure ratios and openings. Serious flow oscillations can occur due to instabilities of transonic flow through the valve. In the present paper, the two-dimensional study of the flow oscillation in the steam control valve is conducted. The main focus of the present study is the scale effect on the characteristics of the flow patterns. Two sizes of the test models are examined both experimentally and numerically. The result that the frequency of the flow oscillation and the conditions which the flow oscillation occurs are changed by the difference of the size. The frequency is inversely proportion to the height of the duct. The operating range with the oscillation is wider in the larger model than in the smaller model.

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The effects of a volute angle of scroll casing and a groove on the suction surface of blades were investigated relating to the characteristics of aerodynamics and noise of a multi-blade centrifugal fan with forward swept blades. It was shown that in the aerodynamic characteristics, the optimal volute angle existed between 4.8 and 7.2 degrees, and in the characteristics of noise, that existed in the near 7.2 degrees. The wake width of grooved blade fan became narrower than that of the ordinary blade fan. Therefore, the grooved blade fan was superior in noise characteristics to the ordinary blade fan. Using the method of predicting width of wake and the formulae to estimate the turbulent noise level which we proposed in this paper, the sound pressure level can be predicted with the accuracy of about ±3 dB within these experiments.

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Various compact schemes for the spatial derivatives of the compressible Navier-Stokes equations are in the evaluation, providing an improved representation of a range of scales to study structures of a compressible plane wake undergoing transition to turbulence and shock-vortex interactions. Two different kinds of compact schemes of upwind/central compact schemes are tested with a coarse grid. A local Lax-Friedrich method with upwind-biased 5th and 9th-order compact schemes is implemented for the Euler terms. Numerical differencing errors of the results calculated by the upwind and central compact schemes are investigated for the evolution of wake structure from the linear regime and the acoustic field generated by the schock-vortex interaction. A comparison between the numerical results obtained with the upwind and central compact schemes indicates that an appropriate error construction at high wave number ranges beyond an effective wavenumber of the resolution shows an advantage to resolve vortical fine structures in the wake at high Reynolds numbers. The numerical results of high-order upwind biased compact schemes show and improved representation of the vortex distortion by the vortex interaction with a relatively strong shock. The 6th-order central compact scheme with filtering by a pentadiagonal compact scheme is found to be acceptable for the shock-vortex interaction simulation.

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Mean velocity profiles in velocity recovery region of pure Poiseuille, pure Couette and Couette-Poiseuille type turbulent channel flows over a backward-facing step are measured and investigated experimentally. The flows are turbulent channel flows between moving and step-side stationary walls with different non-dimensional upstream pressure gradients β₀ (flow type parameter). The channel expansion ratio is 1.50. The upstream flows are fully developed pure Poiseuille (β₀=-1), pure Couette (β₀=0) and Couette-Poiseuille (β₀=-0.5) turbulence plane channel flows. The reattachment region is specified by tuft visualization method. The central point of the reattachment region is less dependent on β₀. Velocity profiles are measured by hot-wire anemometry for the flows at Re_τ0=300, where Re_τ0 is the Reynolds number based on the friction velocity and channel half width at the upstream flow. The logarithmic law of velocity is observed even for sections just after the reattachment region. The additive constant appeared in the logarithmic law decreases with increase of β₀. The half power law is formed at the beginning of the recovery region for the flows with β₀=-0.5 and 0, while it is not observed for the flow with β₀=-1.

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A new simulation technique called the “System Modal Approximation” method (SMA method for short) for fluid transients in compound pipeline systems has been proposed by the authors, which is able to predict fast and accurately, and superiority of this technique to other existing methods has been verified. There, however, detailed considerations have been limited to the cases where either of the pressure or flow-rate is known at every boundary. This paper presents the case study for enhancement of the analytical functions of the SMA method so as to be widely applicable to compound pipeline systems with various kinds of boundary conditions. Specifically, the calculation methods of time response of the wanted output variables at any points are newly proposed for the case whose boundary conditions are given by the time-variant non-linear relationship between pressure and flow-rate like a safety valve used for controlling fluid transients. For fluid transients produced in three kinds of compound pipeline systems with safety valve by the instantaneous valve closure, simulation results are compared with experimental results and then the usefulness of the generalized SMA method is verified.

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High time-resolution flow field measurements in a micro-flow is performed by a micro digital-holographic particle-tracking velocimetry (micro-DHPTV) method. The system consists of an objective lens, a high-speed camera, and a single high-frequency double pulsed laser. Particle positions in a three-dimensional field can be reconstructed by a computer-generated hologram. The error of reconstruction in the z-directions is evaluated by traverse of particles on a glass plate. A velocity error in z-direction is obtained by uncertainty analysis. The time evolution of a three-dimensional water flow in a semicircular micro-channel of 101.9 [μm] width and 32.5[μm] depth and in a circular micro-pipe of 92 [μm] inner diameter are obtained successfully using this micro-DHPTV system. The volume of the system is defined by 409.6 [μm] ×92 [μm] ×92 [μm], and is irradiated by a laser beam with a resolution time of 100 [μs], and a repetition rate of 1 [kHz]. Consequently, approximately 100 instantaneous velocity vectors on each 1 000 frames for 1 [s] in the micro-channel can be obtained.

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Many studies have shown that the Mach disk is one of the most important factors specifying the highly underexpanded sonic jets. However, there has been no acceptable explanation to clarify the dependence of nozzle configuration on the Mach disk. In the present study, a computational fluid dynamics method has been applied to clarify the near field structure of highly underexpanded sonic free jets. Several different nozzles have been employed to investigate the influence of the nozzle configuration on the Mach disk. Based upon the present computational results, a concept of an imaginary straight nozzle was introduced to the orifice flows with a sharp edge. Consequently it was found that the near field structure of highly underexpanded sonic free jets is a unique function of the pressure ratio, regardless of nozzle configuration.

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We have investigated the validity of the application of the dissipative particle dynamics (DPD) method to ferromagnetic colloidal dispersions by conducting DPD simulations for a two-dimensional system. Firstly, the interaction between dissipative and magnetic particles has been idealized as some model potentials, and DPD simulations have been carried out using such model potentials for a two magnetic particle system. In these simulations, we have concentrated our attention on the collision time for the two particles approaching each other and touching from an initially separated position, and such collision time has been evaluated for various cases of the mass and diameter of dissipative particles and the model parameters, which are included in defining the equation of motion of dissipative particles. Next, we have treated a multi-particle system of magnetic particles, and have evaluated particle aggregates and the pair correlation function along an applied magnetic field direction. Such characteristics of aggregate structures have been compared with the results of Monte Carlo and Brownian dynamics simulations in order to clarify the validity of the application of the DPD method to particle dispersion systems. The present simulation results have clearly shown that DPD simulations with the model interaction potential presented here give rise to physically reasonable aggregate structures under circumstances of strong magnetic particle-particle interactions as well as a strong external magnetic field, since these aggregate structures are in good agreement with those of Monte Carlo and Brownian dynamics simulations.

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As a purpose of developing liquid crystalline micro-actuators, transient behaviors of a nematic liquid crystal between two parallel plates are computed with various parameters such as applied voltage, gap of the plates, and twist and tilt angles. When the twist angle is 0 deg, the induced flow is planar, and when the twist angle is not 0 deg, on the other hand, the flow has an out of plane component. With increasing the applied voltage, the shear stress acting on the plate, the velocity, and the flow rate are increased and the response is improved. The effect of the gap of the plates is large ; when the gap is reduced to 5 μm, for example, the response is so high that the physical quantities become maxima within a couple of milliseconds. However, if the electric field intensity is kept constant, the effect of the gap is negligible. The tilt angle has comparatively little effect. We can develop micro-actuators with arbitrary characteristics by controlling properly applied voltage, size of actuators, and anchoring conditions.

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Micro-bubbles are very small air bubbles with diameters of the order of less than several tens microns and have become to attract people's concerns rapidly in the past several years due to their wide potential in practical applications to a variety of advanced technologies (e. g. water quality purification, fish culture and sterilization). Their generating technologies are also splendidly developed. However, a complex device and a high power supply are required for conventional microbubble generators. In this study, the compact and low power micro-bubble generator has been developed and the micro-bubbles are generated by the local shear stress in the flow through a pipe with slits. The small bubbles with 40-50μm of the diameter were generated and the micro-bubble generation was affected by the slit angle. Finally in order to verify the applicability of purification system, a floatation experiment was carried out for three models with a different slit angle (θ=30, 60 and 90 deg). The θ=60 deg case shows the superior performance compared to the other models.

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We present a novel microwave drying as an effective drying method for seafood. The drying time was successfully shortened an compared with the warm-air drying and the drying at room-temperature results in good quality for dried seafood. In this study, we examined the internal resistance for water transport based on the porous media model. The permeability of scallop was estimated experimentally by measuring the perfusion rate of water injected from a syring into the scallop. And we examined the morphological change of the muscular fiver-cell. It is found that the microwave-vacuum drying can prevent the surface shrinkage and the expansion of inner-cell due to the increase of osmotic pressure observed in the warm-air drying. The internal channel for the water transportation can be kept during the microwave-vacuum drying and this results in the high permeability at the wide range of moisture content. The porous media model agrees very well with both experiments of the microwave-vacuum drying and warm-air drying.

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We deal with the emission characteristics of thermal radiation by a surface film system which consists of a metal substrate and a semi-transparent film. First, a spectroscopic experiment is made on emitted thermal radiation of this film system. It is reconfirmed that thermal radiation emitted by this system shows clear interference phenomenon. This system is suggested to be prospective for a spectrally-functional surface which emits radiation in a spectral band region selectively. Next, in order to analyze the thermal radiation emission of the film system, we present a theoretical model of an electromagnetic theory for spherical wave, which is combined with the Planck theory of thermal radiation. Mechanism of interference of emitted thermal radiation wave is discussed on the basis of the model. It is suggested that thermal radiation waves emitted by plural number of dipoles of the metal substrate can be coherent to each other.

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The flow and mixing process of unsteady jets are fundamentally analyzed by using large eddy simulation (LES). The effects of nozzle velocity and turbulence intensity on the turbulent eddy structure and mixing process between nozzle fluid and ambient fluid were investigated. The results show that toroidal-shape vortex, which is growing up around jet tip, mainly accelerate the entraining flow. Also, increasing the turbulence intensity in the nozzle encourages the mixing in the jet without change of the jet-contour. Furthermore, when the rise-up time of initial nozzle velocity is elongated, turbulent mixing is suppressed.

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This paper deals with heat transportation by oscillatory flow in grooved ducts. The heat transportation rate, work rate, heat transportation efficiency and variances of fluid particles and heat were analyzed with the computer code FLUENT. The frequency and amplitude of the oscillatory flow was 0.05 Hz and 45 mm. The internal diameters of the contraction section and the expansion section were 6 and 12 mm respectively and the length of the contraction section was fixed to be 10 mm with the length of groove varying from 0 to 40 mm. We found : (1) Heat transportation rate reached about 4.5 times as large as that of smooth round pipe at the groove length of around 10-15 mm. (2) Heat transportation efficiency increased to about 6.4 times that of smooth pipe at the groove length of 20 mm. (3) The dispersion of fluid particles caused the augmentation of the heat transportation of grooved ducts with 40 mm≥groove length≥5 mm. (4) The grooved ducts with the groove length of 10-15 mm had the maximum value of the variance of fluid particles which accounted for their high heat transportation rates.

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3-D Movement of Flame Fronts in a Turbulent Premixed V Flame has been examined at two positions, i. e., the highest position and half height of the highest posion in the turbulent flame brush. In the V flame, the unburnt mixture in the outer side and the burnt gas is in the inner side of the burner. The average gas flow is from the inner side to the outer side because of the average gas expansion occuring not only upward but also outward. When the flame front moves in the unburnt-to-burnt direction, it moves from the inner side to the outer side, follow the gas flow. When the flame front moves in the burnt-to-unburnt direction, it moves from the outer side to the inner side, against the gas flow. As the result, the magnitude of the velocity vectors of the flame front in the unburst-to-burnt direction are larger than those in the burnt-to-unburnt direction. The axial component of the velocity of the flame front in the unburnt-to-burnt direction can be negative.

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The instability of hydrogen-air premixed flames with heat loss has been investigated by two-dimensional, unsteady calculations of reactive flows. The numerical model containing the detailed hydrogen-oxygen combustion with 17 elementary reactions of 8 reactive species and a nitrogen diluent, compressibility, viscosity, heat conduction, molecular diffusion, and heat loss of Newtonian type was used. Estimating the diffusive-thermal effect on the instability of premixed flames, the equivalence ratio was varied 0.75 to 1.25. A sufficiently small disturbance was superimposed on a planar flame to obtain the dispersion relation and linearly most unstable wave number. To invistigate the characteristics of cellular flames, the disturbance with the linearly most unstable wave number, i.e. the critical wave number, was superimposed. The superimposed disturbance evolves owing to intrinsic instability, and then the cellular-flame front forms. With an increase in the heat-loss parameter, the burning velocity of a cellular flame becomes monotonously smaller, which is due to the decrease in thermal expansion. However, the burning velocity of a cellular flame normalized by that of a planar flame at equivalence ratios lower than unity becomes larger near the quenching point.

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The transition process from cool flame to thermal flame in homogeneous charge compression ignition is discussed in this paper. It was confirmed in HCCI engine experiments using dimehtyl ether, n-heptane and n-decane as fuels that the heat release rate during transition process from the cool ignition to the thermal ignition exhibits linear shape in an Arrhenius plot, and activation energies are in agreement with that of H₂O₂ thermal decomposition reaction, regardless of the fuels. These features were not affected by methanol addition, which suppresses the cool ignition and retards the ignition timing, although the heat release rates were lowered. The results of simulation, using SENKIN in CHEMKIN II package with reaction mechanisms of Lawrence Livermore National Laboratory, were consistent with the experimental results. The mechanism in this process was explained quantitatively by thermal explosion theory, in which rate determining reaction is H₂O₂ thermal decomposition, assuming this reaction obeys an Arrhenius type rate constant, and considering OH reproduction process and the amount of heat release during fuel and intermediate species oxidation process.

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Energy recycling of recycled plastic-resin is focused in this investigation. Polyethylene terephthalate resin powder is employed as an auxiliary fuel, whereas high temperature oxidizing atmosphere is generated downstream of the annular burner. Temperature and O₂ concentration fields downstream of the annular burner without PET-powder supply are first examined by varying the slit-jet and nozzle-jet velocities with both equivalence ratios kept constant at 1.0. PET-powder is then introduced into the high temperature oxidizing region by varying the slit-jet velocity, the nozzle-jet velocity and the median diameter of PET-powder. Variations of temperature and O₂ concentration fields with PET-powder combustion are discussed qualitatively. According to the results, the dependency of the PET-powder unburnt rate on the properties of high temperature oxidizing atmosphere is examined.

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Relevant to Self-propagating High-temperature Synthesis (SHS) process, burning velocity and range of flammability are examined theoretically. Use has been made of the heterogeneous theory for the SHS flame propagation in multi-layer foils, consisting of alternating layers of constituents, has been extended to multicomponent systems, by describing a premixed mode of bulk flame propagation supported by a non-premixed reaction that proceeds at the layer surface of a constituent with higher melting-point. The formulation allows for finite rate Arrhenius reaction at the layer surface, temperature-sensitive Arrhenius mass diffusion in the liquid phase, and existence of intermixed region between constituent layers. It is confirmed that thickness ratio of the constituent layers is related to mixture ratio and that thickness ratio of the intermixed region and the constituent layer is related to degree of dilution. Results show that the burning velocity first increases, reaches the maximum, and then decreases rapidly, with decreasing alloy layer thickness, and that the decrease in the burning velocity can be attributed to the increase in the substance in the intermixed region between constituent layers, playing a role of diluent. The range of flammability is also obtained by the general restriction that the combustion temperature should be higher than the melting point of a constituent with lower melting-point. In experimental comparisons, it has been demonstrated that the analytical results agree with available experimental data in the literature, indicating that the present formulation has captured the essential features of the adiabatic, heterogeneous SHS process.

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In order to clarify the mechanism of heat loss in DI diesel engines, total amount of heat loss and local heat flux at various locations on the piston head were measured by using a rapid compression and expansion machine. High-speed direct photography of spray flame was carried out and flame temperature distribution was obtained by two-color method. In order to investigate the effects of combustion characteristics, such as flame temperature, on heat loss, oxygen volume fraction was varied as experimental parameter in two different ways. In the first way, the oxygen volume fraction was varied from 21% to 15% at a constant intake gas pressure (0.1 MPa). In the second way, the oxygen volume fraction was varied from 21% to 15% by adding nitrogen at a constant amount of oxygen in the cylinder. Measurement results in the first case showed that the flame temperature decreased and the heat loss slightly decreased with decrease in oxygen volume fraction. However, the ratio of the heat loss to the gross heat release was almost constant regardless of the oxygen volume fraction. On the other hand, in the second case, the heat loss and the ratio of the heat loss to the gross heat release decreased with decrease in oxygen volume fraction. This decrease of the heat loss is due to the lower flame temperature and the reduced area and period of direct contact between the flame and the chamber wall, caused by the higher heat capacity and density of the ambient gas.

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Six-stroke diesel engine proposed here has six processes in one cycle, i.e. intaka, 1st compression, 1st combustion, 2nd compression, 2nd combustion and exhaust. By the effect of direct EGR in the 2nd combustion process, NO concentration could be expected to decrease. However, by a weak mixing in the 2nd combustion process, much soot was exhausted and NO concentration was hardly decreased compared with the conventional four-stroke diesel engine. To improve the fuel/air mixing at the 2 nd combustion process, high pressure injection with common rail system was applied to the engine. As the result, NO concentration was increased owing to the increase of premixed combustion of 1st combustion process, although soot was reduced. Therefore, the 1st injection timing was extremely advanced to control the 1st combustion process. It changed 1st combustion process into HCCI-like combustion, and NO concentration was greatly decreased. Moreover, soot was reduced with no increase of NO concentration in the 2nd combustion process. As the result, trade-off curve of NO and soot was improved compared with the conventional four-stroke diesel engine. But CO concentration was increased.

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