This paper proposes an ALE(Arbitrary Lagrangian-Eulerian) finite element method for gas-liquid two-phase flow, based on an incompressible two-fluid model, so as to analyze the two-phase flow including moving boundaries. The conservation equations for the two-fluid model are derived with the use of the ALE method. The solution algorithm is parallel to a fractional step method, and the Galerkin method is employed for the formulation. Quadrilateral element with four nodes is used for the discretization of the calculating domain. The present method is also applied to the calculation of the flow around a cylinder, which is forced to oscillate in air-water two-phase mixture, to demonstrate the validity of the method. The drag coefficients of the cylinder exhibit periodical change in accordance with the variation of the flow around the cylinder. The time variations of the flow field and drag coefficients are discussed in relation to the oscillation of the cylinder.

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Numerical analysis of a diffusion flame established in a laminar boundary layer over a flat surface with fuel injection has been carried out for typical three cases. The conservation equations of continuity, momentum, energy and chemical species are solved using a finite-difference method for two-dimensional flow field with single step raction of methane with air. The flame shape, flow field, diffusion of component gas, heat transfer, and the structure of leading flame edge are examined in detail. A separation region is found to be formed in front of the leading flame edge, which brings a slow gas steam region near the flame edge. Caused by the concentration of oxygen diffusion in the slow gas stream region, a sharp peak of the reaction rate appears at the leading flame edge. Such an aerodynamic structure is inferred to take an important role in the flame stabilization. The reaction rate at the center of the flame zone is found to depend strongly on the free stream velocity, however, to be almost independent of the fuel injection velocity.

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Pulsatile flow and mass transport between flat plates with asymmetric stenosis is analyzed numerically. The fluid is assumed to be Newtonian and incompressible, and the flow is assumed to be periodic in time. The effect of asymmetric stenosis on mass transport is investigated. Flow pattern, concentration pattern and distribution of wall concentration are obtained. It is found that the asymmetry of stenosis increases concentration on the wall downstream of stenosis. In high Schmidt number flow, concentration on the wall of asymmetric stenosis recovers in smaller Stokes number compared with that of symmetric stenosis.

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The non-equilibrium flow near a solid surface is simulated using the molecular dynamics method. The fluid is set to be a Lennard-Jones fluid in which the interacting potential between the fluid molecules is the Lennard-Jones potential. The fluid molecule is given the parameters of Xe and the solid molecule is that of Pt. First, the system is kept at thermal equilibrium and the density distribution, radial distribution, surface coverage, pressure distribution, interface tension, and adsor-ption coefficient of the fluid molecule is analyzed. Next, the solid molecules were given shear velocity to drive the fluid molecules. The density distribution, velocity distribution, and temperature distribution of the fluid molecule is analyzed and results are shown.

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Unseady fluid flow and heat transfer on a heated rotating disk are investigated by using a three-dimensional numerical method. It is found that the flow field changes from a forced convection flow to a mixed convection flow as the Grashof number increases. At the high Grashof numbers, vortices appear on the disk and move in the radial and azimuthal directions with stretching in the azimuthal direction. These vortices affect heat transfer on the disk. The growth mechanism of the vortices is discussed in the calculation of the production of turbulent energy. The critical Grashof number where the transition of the flow field occurs and averaged Nusselt numbers on the disk are in good agreement with available experimental data.

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Two improvements have been done on VOF(Volume of Fluid) method. First, accuracy of surface tension calculation was improved by selecting surface locations of interface cells. The Second, we developed new method to estimate liquid volume fraction in interface cells that are different from each transport property in staggered mesh system. Comparison between arithmetic and harmonic means has been made both for dielectric constant and viscosity. The result by harmonic mean is closer to exact value than that by arithmetic mean.

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Numerical method for gas-liquid two-phase flow is of quite importance in nuclear/oil power plants and chemical plants for estimation of plant performance and components design. While macroscopic one-dimensional calculations are widely used, detailed three dimensional simulation is being expected for considering microscopic mechanism. The present three dimensional program using an improved VOF method has been developed. This method enables high accurate and stable interface calculation in spite of large density ratio between the phases, because non-staggered finite volume method, which is suitable for treatment of discontinuity, and minimum numerical diffusion is adopted. The program was applied to fundamental microscopic phenomena, i.e.coalescence of bubbles and collision of droplets. The plausible results showed the program is able to simulate collective motion of bubbles and droplets with interactions among them with small finite volume number and time steps. The present method is hopefully applicable to direct calculation of two phase flow in every flow pattern.

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In this thesis, we show a new FEM(finite element method)-BEM(boundary element method) analysis of molten metal under alternating currents. Nowadays, it becomes more and more important to calculate MHD(magneto-hydrodynamics) flows under AC(Alternating current) magnetic field in order to control the molten metal processing in a furnace by an electromagnetic force. A former research makes clear the three-dimensional analysis for the circulating molten metal is rarely reported even today. Therefore, we try to carry out a three-dimensional calculation with the A-φ method using hybrid FEM-BEM, the improved method of the conventional FEM, and to capture the surface shape which influences the ALE method. The numerical analysis of an electromagnetic fluid using mercury is carried out and thus we can observe the complicatedly tangled physical parameters of an electromagnetic field in the vessel. To stabilize the meniscus shape, DC magnetic field is imposed and the shape of the surface is held in this case.

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Viscoelastic properties (first normal stress difference and shear viscosity) of high viscous silicone oil (0.01, 0.03 and 0.06 m²/s) were measured with a rhometer. Numerical simulation by a finite difference method have been made for viscoelastic flow due to a rotating disc enclosed in a cylindrical casing. The Giesekus model and Phan Thien-Tanner model which were viscoelastic models and power-law model which was non-viscoelastic model were applied as the constitutive equations. The profiles of velocity component V₀ and radial velocity component V_r obtained by the numerical simulation with Giesekus model and PTT model were in agreement with those measured using particle tracking velocimetry (PTV). The profile of V_r obtained by the numerical simulation with power-law model was not in agreement with those measured by PTV. The moment coefficient C_m and the axial thrust coefficient C_t were obtained for small H/R by the numerical simulation with Giesekus model.

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To perform the DNS of turbulence with a sufficient accuracy, several conditions must be satisfied. Those are (1) spatial resolution high enough to resolve the smallest eddies, (2) computational domain large enough to capture the largest ediies and (3) discretization scheme accurate enough to integrate the governing equations with a sufficient accuracy. In the present study, the DNS of fully developed turbulent channel flow is performed with different mesh sizes, computational domains and discretization schemes. The obtained results are compared with each other. The effects of the factors are discussed quantitatively.

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A ring groove arrangement is proposed to suppress unstable flow or surge in a centrifugal blower. The ring groove arrangement connects the upstream position of impeller inlet and the inducer throat tip through a bypass. The recirculation flow was formed by the pressure difference between the two positions, and the recirculation flow rate was changed by increasing the ring groove widths. The inlet recirculation results in a decrease in the flow rate of unstable flow inception, and an up to 8% improvement in stall limit was obtained by the ring groove arrangement at a small expense of the delivery pressure drop. The improvement of stall limit in the present experiment seems to be mainly due to decrease in flow incidence based on the inlet recirculation flow. Tre flow incidence decreases more as the recirculation flow rate increases, thus resulting in a larger improvement in stall limit.

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The ring groove arrangement was proposed to improve surge margin in a centrifugal blower. The inlet recirculation formed by the arrangement at small flow rates resulted in a significant decrease in the flow rate of the unstable flow inception at a small expense of the delivery pressure drop. The effect of inlet recirculation on the main through-flow in the impeller and the unstable flow suppression is analyzed by the 3-D turbulent flow calculation, and the calculated results are compared with the experimental ones. The critical flow incidence is about 7 degrees for the separation bubble formation at the blade-leading edge. In the tested impeller, the separation bubble on the blade suction surface extends alongthe blade leading edge from the blade root to a radial position of the root-mean-square radius at the stall limit flow rate. It is found that the surge suppression is mainly due to decrease in flow incidence at the blade-leading based on the inlet recirculation flow.

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Effects of periodic disturbances on the development of a two-dimensional jet issuing from a contraction nozzle were studied experimentally. The disturbances were fed into the jet at the nozzle lips so as to excite the opposing shear layers with either symmetric or antisymmetric mode of velocity fluctuation. The forcing Strouhal number St_e, based on forcing frequency and nozzle width, was varied in the range of 0.08-1.2. The symmetric forcing at St_e≑0.4 and 0.8 increased the jet entrainment rate through frequency-halving processes. The maximal change of the jet width was achieved by the antisymmetric forcing at St_e≑0.1, which promoted the jet flapping motion in the region beyond the potential wedge.

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The axial velocity and concentration of a high Schmidt number matter were measured simultaneously in an axisymmetric turbulent jet. The diffusing fluid is a water solution of the commercial dye (Schmidt number S_c≃3800), and an issuing Reynolds number is 6300. A combined probe of a fiber optic concentration sensor and a sigle hot film was used to measure the axial velocity and the concentration simultaneously. The axial velocity and concentration power spectra show the log-normality in the scale region smaller than the integral scale of velocity. The decreases of the correlations of the axial velocity and the concentration are observed in the same region as the power region of the velocity spectra. And they have almost no correlation in the scale region smaller than that region.

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Turbulence modulation in particle-laden fluid flow, especially the influence of vortex shedding, was investigated by means of the direct numerical simulation. To this end, we developed a finite-difference scheme to resolve the flow around each particle moving in turbulence. Our method was applied to the flow around a sphere and the accuracy was confirmed up to the Reynolds number region with vortex shedding. The agreement between our 4th-order central finite-difference method and spectral method for turbulent channel flow without particles was also fine. Then, we simulated upward flow in a vertical channel including solid particles. The velocity and vorticity fluctuations as well as Reynolds shear stress were strongly affected by wakes from particles. The shed vortices were elongated in the mainstream direction by the velocity gradient and resulted in the hairpin vortices. They increased the energy production rate in couple with production due to particle-turbulence correlation.

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Measurements of time-mean velocity, velocity fluctuation intensities, vorticy and shear stress have been made (2hU_b/ν=15000;U_b, moving belt speed;2h, channel height)to study the large streamwise vortical structure in a plane Couette Flow. A wing is installed in the inlet of the wind tunnel to fix the vortex spatially. The existence of large-scale structure in the core region of the Couette flow is shown. A wake of the wing changes into a large longitudinal vortex. A vorticity of the large longitudinal vortex keeps a certain value at fully developed region. And the vortex gets energy from a mean flow. The large streamwise vortex causes a three dimensional structure on the mean velocity and turbulent statistics.

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In the large eddy simulation (LES) of turbulent flow, grid scale (GS) flow field is described by solving discretized governing equations of flow motion with a subgrid scale (SGS) model. Hence, the reliability of the LES data depends strongly not only on the reliability of the SGS model but also on the accuracy of the numerical method. In the LES a finite difference method (FDM) is widely used for practical problems. However, the truncation error of FDM is usually not so small compared with the SGS stress. The problem can be removed by increasing grid resolution, but it is still difficult to keep enough grid resolution in the LES of high Reynolds number flows. In this study, the effects of the order of accuracy of FDM and grid resolution on the LES of plane channel turbulent flow are estimated by the fully conservative higher order staggered FDM scheme proposed recently. The simulations of the flow at Re_r=100 are submitted without SGS model with various grid resolution and several order of FDM up to 12th-order accuracy, and the fact that the FDM discretization has the effects of both truncation error and sharp cutoff is revealed. The effect of truncation error decreases the wall friction loss, while the effect of sharp cutoff increases it. Then, the flow at Re_r=180 is simulated with the dynamic SGS model, and it is pointed out that we have to take the numerical error into consideration in constructing the SGS model for LES of practical problems.

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Diffusion of shocked gas flow by a high porosity porous elastic foam is investigated experimentally. We investigate unsteady process occurring when shock wave passing through porous material. Especially we compare two cases : In the non fixed foam condition, the down stream side of the foam is fixed to the rear end wall of the driven tube. In the fixed foam condition, the foam is also fixed to the side wall of the driven tube. Two kinds of porous materials are treated in both cases (high-porosity φ_g=0.98 and low density ρ_c≃27 kg/m³. One-dimensional experiments are conducted by using a shock tube (50 mm inner diameter and 6.4 m in length). The diameter of polyurethane foams are 49.7 mm with 60, 90 and 180 mm in length, respectively. In the fixed foam condition, the integrated impulse obtained at the rear end wall D, decreases down to about 74% of the non fixed foam condition, showing that the momentum loss is higher than the non fixed foam condition.

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In order to clarify the deterioration mechanism of the pump head due to cavitation, the exit flow of a centrifugal pump impeller with cavitation was studied experimentally. The velocity and total pressure near the exit of the impeller passages were measured by Laser Doppler Velocimetry(LDV) and a total pressure tube both under the cavitating and non-cavitating conditions. From the measured velocities, the slip factor was calculated for different values of the cavitation coefficient and flow rate. It was found that the exit flow pattern was considerably deformed by the existence of the cavities inside the impeller passages and that the increase of slip factor as well as the increase of the hydraulic loss were generated when the cavitation coefficient is decreased.

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Three-dimensional numerical analysis of heat transfer was conducted by thermal conjugate fields inside and outside a blade, which consist of convection heat transfer and thermal conduction. The target of the analysis was a 1st-stage blade of gas turbine with multiple cooling holes. In order to make an accurate estimation of the blade temperature, heat exchange in cooling passages, outflow of cooling air and effect of rotation were taken into account by the numerical method. Predicted distribution of surface temperature was in good agreement with the observed surface pattern on an actual blade. Also case studies for blade temperature were carried out using the present numerical method. It was shown that a temperature field inside the blade was severely influenced by the assumed distribution of inlet gas temperature and cooling air flow conditions. As a result, it is clear that the present analytical method is useful for prediction of blade temperature depended on various conditions in operation.

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An analytical method using Laplace transformation has been developed for one-dimensional heat conduction. This method succeeded in explicitly deriving the analytical solution by which the surface temperature for the first kind of boundary condition can be predicted well. The analytical solutions for the surface temperature and heat flux are applied to the second and the third of boundary conditions. These solutions are also found to estimate the corresponding surface conditions with a high accuracy when the surface conditions smoothly change. On the other hand, when these conditions sharply change such as the first derivative of temperature with time, the accuracy of the estimation becomes a little less than that for a smooth condition. This trend in the estimation accuracy is similar irrespective of any kind of boundary condition.

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The horizontal continuous casting process is widely used from the economical and operational merits, recently. In the process, an intermittent withdrawal cycle is used to keep the stiffness of the solidifying part of the products. This complicated mode of the withdrawal cycle leaves the interface of the crystal, called the witness mark, on the surface of the products. In order to make the iron slab of good quality, it is necessary to decrease the depth of the witness mark. In this paper, the effects of the casting conditions on the solidification process of a horizontal continuous casting were investigated analytically. Considering the flow of the melted iron due to the withdrawal cycle, the simulation was carried out. The calculation parameters were the inflow iron temperature, the break ring temperature, the mold temperature, the withdrawal speed, the withdrawal frequency and the withdrawal time chart. The effect of the each parameter was estimated in the viewpoint of the growth of the witness mark and the thickness of the solid shell.

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A three-dimensional steady numerical computation was made for a component model of fin and tube type of compact heat exchangers situated in a uniform flow. In this study, in order to find a clue to design high-efficient heat exchangers, numerical computation was made in the case where two fences are attached on the plate fin surface and their geometrical effects such as their locations, their heights and their attack angles on flow and heat transfer characteristics were investigated especially in the low Reynolds number range. The effect of a hole, open in the plate fin behind the fence, on heat transfer and flow structures was also examined. This hole simulates the hole of the plate fin to be produced in practical application, when a fence is produced by punching from the original plain fin plate. Two fences with holes were found to show several important effects on flow and heat transfer structures and to work well in heat transfer augmentation. They reduce the dead water area downstream the tube so that heat transfer enhancement was obtained there. Heat transfer enhancement was also attained on the fin surfaces around them. As a result, total heat transfer performance becomes 17% up compared to the normal plain fin case.

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Experimental studies were performed to investigate on the fluid flow and local heat transfer around two cubes arranged in tandem on a flat plate turbulent boundary layer. The Reynolds number based on the cube height d ranged from 4.0×10³ to 3.2×10⁴. The turbulent boundary layer thickness δ was δ/d≩2.17. The surface temperatures around the cubes were measured with thermocouples under the condition of a constant heat flux. The effect of spacing b between two cubes was cleared in the range of 0.33≨b/d≨1.33. In case of b/d≩0.67, the horseshoe vortex is formed in front of each cube, however it is not formed in front of the 2 nd cube at b/d=0.33. The local heat transfer is high in the horseshoe vortex regions and the reattachment regions. The average Nusselt numbers of 1 st and 2 nd cubes are expressed as follows;(Nu₁)^^^-=0.24 Re^0.66 and (Nu₂)^^^-=0.27 Re^0.64respectively. They are almost constant with various spacing. However that of plate between two cubes has a maximum of (Nu_p12)^^^-=0.47 Re^0.60 around b/d=0.67.

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The present work experimentally investigates the effect of vortex generators, in the form of small tabs projecting normally into the flow at the nozzle exit, on the flow and heat transfer characteristics of an axisymmetric impinging air jet at the subcritical Reynolds number range, with this comes the expectation of the large eddy structure variation and the possibility of the active control. Local heat transfer and static pressure were measured on the target plate for a round air jet issuing from a circular nozzle with rectangular tabs whose numbers and lengths changed at the constant nozzle-to-plate gap (L/d=8) and jet Reynolds number (Re=34000). The main results are the following:When two tabs were set at the exit of the circular nozzle, C_pw and Nu profiles flatten in the direction of the tab setting. In the case of three tabs, however, among both C_pw and Nu profiles a concentric profiles is expressed, as well as in one without the tab.

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This paper has dealt with the flow resistance and heat transfer characteristics of flowing cold water with flow drag reduction additive in curved pipes. A cationic surfactant was used as the flow drag reduction additive. The flow drag resistance and the local heat transfer coefficient of cold water flow in some curved pipes were measured under the constant heat flux heating wall condition. It was found that the flow drag and heat transfer reduction effect by the surfactant was depended on the angle and curved ratio of the curved pipes. The nondimensional correlative equations of flow resistance and heat transfer coefficient of cold-water flow with the surfactant in the curved pipe were derived in terms of various nondimensional parameters.

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In this paper, thermal network method using effective specific heat model of refrigerant with phase change is proposed for predicting the capacity of a plate fin and tube type heat exchanger. Effective specific heat model suits for obtaining an accurate result of a heat exchanging capacity of a condenser with small number of elements. By comparing calculated results with experiment, it is clarified that an error of calculated capacity of condenser is less than 1% in case that the range of sub-cool degree is from 15K to 22K at outlet of refrigerant flow.

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The mechanism of the KrF laser ablation of high-density polyethylene (HDPE) is investigated experimentally. The sample in a vacuum chamber is irradiated with the excimer laser. High speed camera with a frame rate of 40500 frames/sec is used to visualize the plume generation and motion due to KrF laser irradiation of the HDPE sample. The plume is deposited on a plate in order to characterize the molecular stucture of the ablated material. Although the FTIR data of the sputtered ablation plume shows similar characteristics to HDPE, the data shows a difference before and after the ablation. The molecular weight distribution is measured for both sputtered material and HDPE sample before laser irradiation. These data indicates the unique mechanism of KrF laser ablation of HDPE.

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This paper proposes a method of measurement of the thermal resistance of scale adhered to the inner surface of a boiler tube. The principle of the method is to measure the temperature rise due to the scale when the tube is radiatively heated from outside. An experiment was performed with a test piece composed of three tubes of 30 cm in length, which had been cut away from a supercritical pressure boiler. 120 mm×140 mm area of the test pieces was radiatively heated, boiling of water took place inside the tubes, and the temperature at the top of the tube was measured with welded thermocouples of 80 μm, in diameter. Similar measurement was performed after cleaning the inside of the tubes with hydrochloric acid, and both measured data were compared. An example of the results is as follows;the difference of the temperature rise was 8.24 K for heat flux of 100 kW/m², and the estimated thermal resistance of the scale was 0.082 m² K/kW.

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In this study the artificial disturbance was introduced into the natural convection field above horizontal heated sources and the stability of their convection fields was experimentally examined. The Experimental data were processed by smoothing and lowpass-filtering technique and the largest Lyapunov exponent which is one of the indicators of the chaotic characteristics was calculated. The results were arranged by the method based on a dimensional analysis. As a result, following facts are confirmed;(1)the stability-instability characteristics above the heated wire evaluated from the experimental data agree well with the analytical results, (2)the difference in the characteristics compared with the case of heated wire is large near heated cylinders, (3)the data-smoothing method based on the Kalman filter is effective to compute the largest Lyampunov exponent and (4)above the heated sources the chaotic characteristics of the thermal convection field are similar to the stability ones.

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Recently a lean-rich combustion is drawing attention as a way to decrease the level of NO_χ. In the lean-rich combustion flame, the oscillation and the noise is generated by the velocity difference between the lean-side flame and the rich-side flame. This oscillation and the flame structure in the unsteady-state have not been made clear. Numerical unsteady-state analysis was performed in order to make clear the flame structure of the methane-air lean-rich combustion flame in unsteady-state. In the lean-rich flames, the lean and the rich slit burners were set side by side in the combustor. A two-dimensional numerical analysis was performed based on skeletal chemistry proposed by Smooke M.D.which includes 35 elementary reactions of 16 chemical species.

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Numerical computations are made of axisymmetric laminar jet H₂ diffusion flames, taking account of multicomponent diffusion and detailed chemical kinetics. Availability of multicomponent diffusion calculation is investigated by comparison between the computational results with exact multicomponent diffusion coefficients or effective binary diffusivity and experimental results. The effect of thermal diffusion is also investigated. Computational results with exact method are close to experimental results for major species. Consideration of thermal diffusion improves the accuracy of the prediction. When fuel is H₂ diluted with N₂, mass flux of major species calculated with effective binary diffusivity agrees with that with exact multicomponent diffusion coefficient except for N₂ and the results of concentration agree with experimental results. In the pure H₂ diffusion flame, concen-tration and mass flux of N₂ and H₂O obtained by the numerical method with effective binary diffusivity disagree with that by exact method or experimental results. Excessive diffusion of H₂ is caused by the assumption that spatial gradient of mean molecular weight is neglected.

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The cross-sectional flame images were measured during the late stage of flame propagation in closed combustion chamber. The initial flame had larger wrinkles and the late flame had smaller structure as the flame propagated in the chamber. The fractal analysis of the flame boundaries was performed. The fractal dimension increased and inner cutoff scale decreased with the increase of mixture density. It was found that the fractal dimension is expressed as a function of the turbulence intensity, laminar burning velocity and mixture density during the flame propagation.

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Spatially resolved chemiluminescent spectra were obtained in the reaction zone in a laminar premixed methane/air flame (φ=0.9-1.5) using local flame emission measurements with a new Cassegrain mirror system and spectrometers. The distributions of the OH^*, CH^*, and C₂^* emission intensities in the flame front were obtained at atmospheric pressure using this method. C₂^* was found to have the thinnest reaction zone. Highly spectrally resolved OH^*, CH^* and C₂^* emission were obtained at the local flame front. The linear correlations between the peak intensity ratios of OH^*/CH^*, C₂^*/CH^*, and C₂^*/OH^* in the reaction zone to the equivalence ratio could be used to investigate the local flame stoichiometry. OH^*/CH^* could be used to determine the local flame stoichimetry in the reaction zone of premixed flames for a wider range of equivalence ratios.

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An experimental study has been made of the ignition process of a binary fuel droplet subjected to a laminar flat flame propagating through a lean homogeneous propane-air mixture at constant pressure. A combustion chamber made of a transparent duct was installed with spark electrodes, a fine quartz fiber to suspend a fuel droplet and a shutter to allow the burned gas to flow out. A high speed video camera was provided for the photographic observation of the droplet ignited by the propagating flame and for the determination of the ignition delay. The ignition delay showed a peak as a function of initial droplet diameter and the diameter at the peak ignition delay decreased with an increase in the n-hexane or the benzene volume concentration. Also evident was that the ignition delay decrased largely with an increase in the n-hexane or the benzene volume concentration.

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A theoretical model for a deforming single droplet with aerodynamic force is presented. The droplet shape is assumed to be spheroidal. A nonlinear oscillating equation is derived from energy conservation in a droplet. The present (OSD) model is compared with other droplet deformation models, Taylor Analogy Breakup (TAB), Droplet Deformation Breakup (DDB) and Synthesized Spheroidal Particle (SSP) models. It is found that the linearized OSD model is reduced to the TAB model. Numerical studies show that only present model and TAB model are compatible with Lamb's fundamental oscillating mode for a liquid droplet. On a droplet deformation at the initial stage of aerodynamic breakup, the calculation by the OSD model and TAB model agree well with the measurement.

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This paper describes performance simulations and test results of a prototype to develop a multi-fuel gas engine driven Stirling heat pump. It is mainly driven by engine shaft power and is partially assisted by thermal power from the engine exhaust heat source. We have developed the D-3 machine, the fourth generation prototype of the heat-assisted Stirling heat pump. This machine uses helium gas as a working gas and is constructed as a combination of two Stirling sub-systems;one a power producer and one a heat pump. Utilizing both shaft power and thermal power, performance is controlled by phase shifting of the hot-side piston to adjust the absorbing of thermal power. This heat pump produced colling and heating water at high COP over 4 on an indicated basis. Developing this machine will provide a CFC-free thermal utilization system technology that satisfies both wide heat demands and various fuel systems.

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In order to establish the optimum fueling in a natural gas fueled dual fuel engine, tests were made for some operational parameters and their combination on the engine performances and the exhaust emissions. The results show that the gas oil quantity should be increased and gas oil injection timing should be advanced to suppress unburned hydrocarbon emission at middle and low output range, while the quantity should be reduced and the timing should be retarded to avoid onset of knock at high loads. The unburned hydrocarbon emission and the thermal efficiency are improved at the same load avoiding too lean natural gas premixture by restriction of intake charge air. However the improvement is limited because the ignition and initial combustion of pilot diesel fuel is deteriorated when the cylinder pressure is excessively lowered by throttling. The increase in pilot gas oil amount is effective for low-load operation and the adequate combination of throttle control and equivalence ratio ensures low hydrocarbon emission and the thermal efficiency comparable to diesel operation.

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To investigate the ignition processes in a diesel spray, the two-dimensional techniques of silicone oil particle scattering imaging (SSI) and laser induced fluorescence (LIF) were used. The sequential and two-dimensional images of SSI reveal that the first ignition occurs in the periphery of spray head vortices, not in spray tip. The fluorescent images of intermediate products which are formed during the ignition reaction were taken by the LIF method with the laser sheet of the 3rd harmonic of Nd:YAG laser. We conducted these visualization techniques and measured the chamber pressure under the same conditions. The the ignition delays obtained by each technique were compared. This comparison showed that both the time when the first local heat release is detected by SSI method and the time when the first fluorescence is detected by LIF method are nearly equal to the time when the total heat release due to ignition reaction exceeds the heat absorption of fuel evaporated.

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In an attempt to promote the atomization of fuel spray and the mixing of fuel and air in diesel engines, a micro-hole nozzle which has orifices with a diameter smaller than 0.10 mm was developed. In this study, the combustion tests were carried out using a single cylinder diesel engine equipped with a micro-hole nozzle and a common rail type high-pressure fuel injection system. A comparison with the results of a conventional nozzle experiment showed that the peak of initial premixed combustion increased, but the peak of diffusion combustion decreased. As a result, when nozzle orifice diameter become small from φ0.15 mm to φ0.10 mm, the combustion was accompanied by smokeless with the same levels of NOx emission and fuel economy. And results of a comparison the toroidal type chamber with the shallow dish type chamber revealed that the optimization of combustion chamber is necessary for the increase of the injection stage with increasing of the number of nozzle orifice. If an orifice diameter becomes φ0.06 mm, the diffusion combustion can not be observed and the combustion is formed of only premixed combustion. The combustion in the case of φ0.06 mm was accompanied with the drastic deterioration of fuel economy, smoke and HC with all over load. But the micro-hole nozzle has a potential for the formation of the lean and homogeneous premixed mixture until the fuel-air mixture ignites.

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