A new reconstruction method called Generalized Vector Sampled Pattern Matching (GVSPM) has been applied to an ill-posed inverse problem involving an electrical capacitance CT for solid air two-phase flow. This new mehod is able to achieve stable convergence without the use of an empirical value. This accurate reconstruction is accomplished using an objective function that is calculated as the inner product calculation between the experimental capacitance and the reconstructed image capacitance. The GVSPM method is compared with the conventional Landweber (LW) and Iterative Tikhonov regularization (ITR) methods in terms of capacitance residual, image error and image correlation. Overall, the accuracy is strongly dependent upon the image type and the iteration number, however the GVSPM method proved superior to the LW and the ITR methods in the case of annular pseudo particle images.

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A bluff body like a marine structure can be vibrated variously by a separation flow around it. In this study, we focused on in-line oscillation of a circular cylinder under free vibration tests in two degrees of freedom. We studied typical characteristics of in-line oscillation of circular cylinders both in a smooth flow and in a turbulent flow in water tunnel tests. The circular cylinders with finite span lengths were supported elastically in two degrees of freedom. As a result, the response amplitude in the 2nd excitation region is dampened more sensitively with increasing reduced mass-damping parameter C_n than in the 1st excitation region compared with the results of circular cylinder that can oscillate only in one degree of freedom. Also the amplitude in 2nd excitation region is dampened in a turbulent flow, and the lissajous figure of a circular cylinder changed from a figure of 8 to a complex ellipse.

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When a shock wave propagates over a dust layer composed of many small solid particles, the particles are lifted and dispersed, leading to a dust cloud in the shock induced flow. In the present study, the initial process of forming the dust cloud was numerically simulated to examine its dynamic mechanism. A continuous model was used for the gas phase and a discrete model for the solid particles, where gas-particle and particle-particle interactions were taken into account. The simulated dust cloud was close to experimental results. It was found by comparing several types of dust layers that the upward velocity of lifted particles was more produced by particle-particle interactions than by fluid lift forces such as the Saffman force and the Magnus force. Moreover, it was confirmed that a relatively strong downward flow was induced just behind the foot of the shock by its curved shape, which promotes the interactions and causes an overpressure on the wall.

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This paper describes three-dimensional numerical simulation of double helical ribbon agitators using discrete element method (DEM). Double helical ribbon agitators have been used to blend powders, it is very important to know the mixing characteristics for scale-up of agitation system. To validate the computed results experiments were carried out with a 30 L cold model. Circulation time and mixing time of particles in the agitator and the shape of vortex predicted by this simulation agreed well with those obtained by experiments. Further, to evaluate the relation of scale up law based on mixing time, some cases of simulation, which volumes were both 90 L and 150 L, were performed. The results show the effect of scale-up factor on the mixing time strongly depends on Fr number.

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Numerical analysis has been performed for three-dimensional and time-depending vortex breakdown in an open and confined cylindrical container flow generated by a rotating disk. Vortex breakdown in swirling flows has been the sudject of much attention since it was first recognized in the tip of delta winged aircraft. Under certain conditions vortex flows undergo sudden structural changes near their rotation axis, called vortex breakdown, which are characterized by the existence of free stagnation point upstream of a region with reversed axial flow. Recently, experimental results suggest that the asymmetry of the vortex breakdown is found to be related to the existence of asymmetric flow separation on the container wall. Adding to this, it is important to reproduce such asymmetry vortex breakdown by numerical method because there is no report to predict an asymmetric vortex breakdown numerically. In the numerical calculation, boundary fitted coordinate system has been used for this flow in order to make the cause of asymmetry vortex clear. Calculated results of angular moment and flow vectors in circular cross section are compared with the experimental data in order to examine the validity of the presented numerical method. As a result of this analysis, it has been found out that the present method can reproduce vortex breakdown reasonably for an open and confined cylindrical container. Although the present method could not predict the separated flow near the wall which has been reported experimentally as the cause of asymmetry vortex generation, we have showed numerically that asymmetry vortex is also able to be produced by shifting rotating axis from center within the gap between rotating disk and cylindrical wall of experimental apparatus.

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The experimental study for flow characteristics in the rectangular channels with a sharp 180-deg turn was conducted. PIV measurements were performed both in symmetry plane and in four cross-section planes after the turn for three aspect ratios, AR=1, 2, and 4, at a Reynolds number of 2.0× 10⁴. Proper orthogonal decomposition (POD), which decomposes a field of a time-dependent variable into an orthogonal set of deterministic functions, was demonstrated on the PIV snapshots to identify coherent structures in the flow. Based on the data, the influence of the channel aspect ratio on flow characteristics in the channel is discussed in detail. The unsteadiness of the longitudinal vortices generated in the cross sectional planes after the turn are also investigated.

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In order to atomize a liquid, the authors have investigated the behavior of air-water jets. In a series of experiments, we have discovered a strange phenomenon that the water jet accompanied with an air suction from the free surface has made a periodic radial splash of water drop. The purpose of the present paper is clear out the origin of this phenomenon and the behavior of water jet accompanied with an air suction. The behavior of water jet has been photographed by a digital camera aided with a flash light and high-speed video camera. Those experiments enable us to find the origin of a periodic radial splash due to a formation of single air bubble at the flow separation region inside the nozzle and due to explosive expansion of the bubble after injected in the free space. In order to analyze the radial splash of water, we have conducted the equation of spherical liquid membrane. The numerical results obtained have been compared with the experimental results and good agreement has been obtained in radial expansion velocity.

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Experimental study was made on the multi-dimensional behavior of upward gas-liquid two-phase flow through a vertical pipe with an axisymmetric sudden expansion. In this study, the measurement on the void fraction distribution was carried out for the sudden expansion channel. The void fraction distributions below and above the sudden expansion point were measured at the different axial and radial positions using a point-electrode resistivity probe for various gas and liquid flow conditions. The results of measured void fraction distributions showed that how the two-phase flow develops along the direction of the downstream of the sudden expansion. Furthermore, the development of the void fraction distribution also revealed quite complicated behaviors depending upon flow rates of gas and liquid phases and bubble size. Based on the measured void fraction distribution in the sudden expansion, cross-sectional averaged void fraction and phase distribution parameter were evaluated at the different tube cross sections in the sudden expansion. As a result, it revealed that the void fraction along the flow direction in the sudden expansion might be predicted by using the appropriate distribution parameter representing the void fraction distributions in the sudden expansion.

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The cavitation jet technique has progressively developed in several industrial fields, such as cleanings and peenings in water, since the destructive capabilities of the jets are directly related to the unsteady behavior of the cavitating jet. As such behavior deeply depends on the interferences between the discharge of the cavity and the explosive growth of the bubble-cloud, it is therefore necessary to study such interferences. We study the time-dependent feature of the bubble-clouds on the cavity boundary as well as the discharge in cavitating jets within x/d=0-90 of the standoff distance, by means of a high-speed camera, a high-speed video-camera and image processing system. It is found that the periodical discharge of the cavity does not take place simultaneously with the periodical growth of the bubble cloud.

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The objective of this study is to promote disintegration of liquid jet by cavitation inside the nozzle. In this report, the effects of the pressure variartion inside 2-dimensional (2D) nozzle on behavior of liquid flow and the breakup of issuing liquid are investigated. When the nozzle length/ nozzle width ratio L/W value is large, the pressure inside nozzle decreases at the nozzle inlet, and increases before the middle section is reached, and any disturbance in the liquid flow inside the nozzle decreases in the vicinity of the outlet. When L/W value is small, the injection pressure increases, the pressure that decreased at the nozzle sharp corner part maintains negative pressure until the vicinity of the nozzle outlet. This trend prevents any disturbance due to the generation and disappearance of cavitation from attenuating.

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As a train runs at higher speeds, the aerodynamic drag increases. On long train-sets such as those of Shinkansen, the aerodynamic drag is mainly generated by intermediate vehicles. In previous researches, we proved that smoothing the under-floor surface reduces the aerodynamic drag. To investigate the mechanism of this effect, we performed wind tunnel tests with train models consisted of three vehicles, each representing a head, intermediate and tail vehicle, and measured the aerodynamic drag and pressure distributions on the intermediate vehicle. We divided the aerodynamic drag of the intermediate vehicle into the components at different parts of the carbody and clarified the effect of smoothing the under-floor surface to decrease the aerodynamic drag.

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A non-intrusive technique for measurement of the velocity and pressure fields adjacent to a moving fluid surface is developed. The technique is based on the measurement of fluid surface profile. The velocity and pressure fields are derived with use of the boundary element method (BEM) by seeking for an incompressible flow field that satisfies the kinematic boundary condition imposed by the time-dependent fluid surface profile. The proposed technique is tested by deriving the velocity and pressure fields inversely from the fluid surface profiles obtained by a forward BEM calculation of fluid surface response to externally-imposed pressure. The inverse calculation results show good agreement with the imposed pressure distribution in the forward calculation.

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The drag and lift coefficient characteristics of rotating cylinder with arc grooves is investigated. The circular cylinders with grooves have thirty-two arc grooves of different depth on the cylinder surface. Pressure of the cylinder surface is measured with the Reynolds number Re= (0.4-1.8) ×10⁵, and rotation of 0-4500rpm.The drag and lift coefficients are calculated from pressure distribution. At Re=0.4×10⁵, the drag coefficient C_D of smooth cylinder is constant until the spin rate ratio α (α=rotating speed/uniform flow) =0.6, and C_D decreases afterwards at 0.6<α<1.0. As Reynolds number increase, this decreasing part shift to low a side. In the case of cylinder with grooves, the decreasing part of C_D exists only in Re= (0.4-0.8) ×10⁵ (subcritical, critical region of stationary condition), and C_D has monotonic increase at Re>1.0×10⁵.As groove depth becomes deep, C_D becomes constant value as α increase. The lift coefficient C_L of smooth cylinder increases as a increase.However, C_L decreases to the minimum value as α further increase and C_L increases again with the increase of α, C_L indicated negative lift in Re>1.0×10⁵.C_L of cylinder with grooves become monotonous increases tendency in Re>1.0×10⁵.As groove depth becomes deep, the increasing gradient of C_L becomes small.

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The reattaching flow behind a swept backward-facing step, at a Reynolds number Re_m=8 000 for the swept angle of 30 degrees, is investigated experimentally. Measurements for the turbulent flow field are made by using the rotated hot-wire method. In the early stage of the recovery region, all components of fluctuating velocities and Reynolds shear stresses have large values in the middle region of the boundary layer compared to those in two-dimensional boundary-layer. This may be attributed mainly to the large values of turbulent-energy and Reynolds-stress production terms as well as the advection of the highly turbulent fluid from the upstream. The eddy-viscosity ratio exhibits anisotropy of the eddy viscosity in the near region of the reattachment. To examine anisotropy of the eddy viscosity a comparison is made of the directions of the shear-stress vector and the strain vector. The difference of these angles becomes smaller as goes to the downstream, and the eddy viscosity could be presumed isotropic in the region of _x/H >12.5. The structure parameter varies from a larger value just behind the reattachment point than in two-dimensional flows to the value of two-dimensional flow in the far downstream

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Characteristics of a micro bubble generator using a strong swirl jet were studied experimentally and numerically. Experiments were conducted by changing the nozzle diameter, the inflow pressure and the gas flow rate, systematically. For measurements of the bubble distribution function of PDF, a simple method using a light transmission was proposed. Principle of the method was based on changes of the light transmission due to the bubble rising to the surface of water. The bubble distribution measured by the method agreed well with that by a usual backlight method. In this study four non-dimensional parameters governing the micro bubble generation were adopted, that is, Weber number for the average diameter of bubbles, Reynolds number, the ratio of flow rate and the velocity ratio for the swirl jet. It was found that the relationship between Weber number and Reynolds number could be arranged with each velocity ratio as a parameter. An approximate experimental expression for the average diameter showed that the micro bubble diameter strongly depended on the axial flow velocity and the rotational speed of the swirl jet.

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A new primary standard for hydrocarbon flow measurements has been constructed at NMIJ, National Metrology Institute of Japan. The facility had been designed for the calibration of hydrocarbon flowmeters in the flow rate range between 3 and 300m³/h. An expanded uncertainty is estimated to be 0.03% for volumetric flow rate and 0.02% for mass flow rate (coverage factor : k= 2). The primary standard is based on a static and gravimetric method with flying start and finish. The facility consists of two test rigs with kerosene and light oil as working fluid. The test lines for flowmeters are 50, 100 and 150 mm in diameter and three servo PD meters are used as working standards. To verify the calibration performance, a coriolis flowmeter, a turbine meter and an positive displacement flowmeter have been calibrated at the both test rigs. Furthermore, an international comparison with SP, Swedish National Testing Research Institute, had been carried out. A screw-type positive displacement flowmeter was selected as the transfer standard and was calibrated at NMIJ and SP. The result shows that the two national standards at the two institutes agree within the quoted expanded uncertainties

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The effects of mechanical vibration on fluid mixing and chemical reaction in a micro channel were experimentally investigated. The fluids before flowing into the micro channel were mechanically oscillated through the inlet tubes by using a small vibrating motor. Instantaneous velocity and concentration in the micro channel were measured using the micro PIV (Particle Image velocimetry) and LIF (Laser Induced Fluorescence), respectively. The results show that fluid mixing and chemical reaction is remarkably promoted by the vibrating technique. The mixing rate is well correlated with the streamwise fluid velocity fluctuation. When the basic frequency of the vibrating tube is lower than about 20 Hz, the fluid motion hardly changes and the mixing is little enhanced. However, the fluid intensively fluctuates for the higher frequency than 75 Hz and almost complete mixing accomplished.

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A basic experimental study was carried out to investigate the parameters in a vibration equation of a viscous damper utilizing a magnetic responsive fluid in order to design a semi-active viscous damper. We used the magnetic piston which has made with alternating layers of magnet and non-magnetic material disks for particles of the fluids not to sediment. To clarify the damping effect, we measured a frequency response and a relationship between inertia force and displacement. The results of the dynamic characteristic of the damper can be explained by the cluster of particles aggregated like a chain in the fluid. We also clarify that MCF is suitable for the damper. The damping effect is strongly influenced by an apparent density around the piston of the damper.

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This paper proposes a rational, explicit and practicable approach for incorporating the spectral non-uniformity of absorption coefficient within a narrow band into a nongray analysis of radiative heat transfer in a nonisothermal field including a single infrared-active species. In the development of this new approach, attention is paid to securing rationality and explicitness even when the approach is applied to nonisothermal fields. This aim is achieved based on the fact that the line center of each absorption line does not move even if the gas temperature varies. Validity of the proposed approach is examined in detail trough comparison of the results obtained by the proposed approach with the results of line-by-line analysis base on a high-resolution database of absorption lines. It was confirmed in a typical nonisothermal field that the proposed approach can properly incorporate the influence of narrow band non-uniformity into a nongray analysis of radiative heat transfer in a nonisothermal field including a single infrared-active species.

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It is necessary to consider the interrelation of absorption coefficients of emitting side and absorbing side when we carry out numerical predictions of radiative heat transfer through infrared-active gases. If we utilize the combination of a wide-band model and a narrow-band model for dealing with radiative heat transfer through a infrared-active gas that has remarkable narrow band nonumiformity, we have to consider the interrelation of absorption coefficient not only about the representative value within a narrow band but also about the fine structure in a narrow band. Calculation method for radiative transfer in nonisothermal field is constructed considering narrow band nonuniformity. It is compared with line-by-line calculation based on absorption line database HITEMP, and its validity is confirmed.

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In recent years, honeycomb elements made of ceramics have often been used for such purposes as heat exchangers, catalysts and adsorbents. Because such honeycomb elements have a smooth flow path surface, laminar flow prevails at or near the design point (Re=1000-4000), thereby leading to frequent cases of insufficient heat transfer coefficient. However, there have been quite few studies on the heat transfer enhancement in honeycomb elements. In the present research, experiments were conducted to investigate the effects of spacing and lateral shifting of elements on heat transfer coefficient using honeycomb elements of ceramics 6.07 mm width of opening and 1.13 mm in wall thickness, and enhancements in heat transfer by these effects were clarified. It was found that lateral shifting of elements was more effective in making the flow more turbulent to enhance the heat transfer than spacing of elements.

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As sugars and related compounds are increasingly being used as potential cryo- and lyoprotective agents for preservation of rare and valuable mammalian cells and tissues, introduction of these compounds, especially saccharide, into a living cell is one of the key technology. In the present study, volume changes of human T-lymphocytes (Jurkat line) exposed to hypotonic carbohydrate-substituted solutions of different composition and osmolality were studied by videomicroscopy. The complex volumetric data were analyzed with a membrane transport model that allowed the estimation of the hydraulic conductivity and volume-dependent solute permeabilities. We found that under hypotonic stress of 100 mOsm, the membrane permeability to monomeric carbohydrates inereased dramatically (apparently due to channel activation caused by extensive cell swelling), whereas oligosaccharide permeability remained very poor. The size-selectivity of the swelling-activated sugar permeation was confirmed by direct chromatographic measurements of intracellular sugars. The results of this study are of interest for biotechnology.

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A two-phase flow thermal control system, which utilizes the latent heat of fluid, is paid attention to for the heat removal in the space station and the Space Solar Power System (SSPS). The characteristics are that the system weight is lower than that in single-phase flow and that the temperature can be controlled by changing the pressure of the loop. Conventionally, the control of the temperature in a loop has been performed by operating the pressure of the accumulator. In this paper, the temperature control of the loop by the vapor valve is proposed as a new control method. For the proposal of new control method, an active thermal control system which can give a maximum 1 kW heat load to an evaporator was built and an experiment of the dynamic characteristics under 1 G was carried out in the extensive quality range with a partial heat load, using alternative freon HCFC-123 as the working fluid. As a result, the effects of the vapor valve opening on the dynamic response and the possibility of the loop control by the vapor valve were clarified.

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This paper proposes a practical approach for the robust optimization method using a combination of Design of Experiments (DOE), Response Surface Methodology (RSM) and Monte Carlo Simulation (MCS). This simple practical robust design method can overcome the difficulty of the reliability calculation in terms of procedure and calculation time when compared to previous related other approach. This method was applied to the development of a new heat pipe product for the spacecraft panel, and the dimension parameters of new heat pipe could be optimized with considering the total mass and the thermal robustness toward the uncontrollable variables. Consequently, the robust optimization could be performed through large numbers of direct sampling simulation by using a meta mathematical approximation equation model within a short time, and the efficiency of our practical optimization method was proved.

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The three-dimensional, time-dependent thermal plume with variable density and properties is rising upward in non-stratified air from a heated square plate on a horizontal, solid ground with an extremely wide area. Formulations and numerical methodology without assuming laminar, transitional, or turbulent state in this complicated plume are presented. The grid size and time step employed in the present computation give computed results without a grid dependency at laminar conditions, and resolve the Kolmogorov's microscale at turbulent conditions. The Courant number and the diffusion number are valid because time-records of turbulent velocity and temperature are stable. Furthermore, the X-shape distribution of the limiting vectors in the present model agree well with that by the experimental visualization in the similar model. As shown above, the present formulation, numerical methods, and computed results satisfy the necessary condition of validation.

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Fundamental study on a solidifying phenomenon in a rectangular water-saturated porous medium was carried out when vigorous convection occupies the liquid layer. The system is cooled from the upper boundary and heated from below. In this study, the dynamic response of the solid-liquid interface to the periodical temperature fluctuation at the cooling surface was investigated in detail. Especially, the amplitude of solid-liquid interface and the phase lag to the time-varying cooling temperature were monitored for various periods and cooling temperatures. One-dimensional numerical model was developed by assuming the constant convective heat flux from liquid regime. The numerical model explains well the observed experimental results. It is found that the amplitude of oscillating solid-liquid boundary increases in proportion to the temperature fluctuation period, and that both the thicker solid layer and the shorter period cause the greater phase lag.

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In an actual boiling channel, e.g. boililer water-tubes, the circumferential heat flux is not uniform. Thus, critical heat flux (CHF) of non-uniformly heated tube becomes an important design factor of conventional boilers, especially for the compact water-tube boiler with tube-nested combustor. The small compact boiler is operated at low-pressure and low-mass flux condition compared with the large scale boiler, thus the redistribution of liquid film will strongly affect on the characteristics of CHF. In this investigation, non-uniformly heat flux distribution along the circumferential direction was generated by using the Joule heating of SUS304 tubes which had the wall thickness distribution. The heated length of test-section was 900mm, inner diameter was 20mm and outer diameter was 24mm. The center of the inner tube surface was shifted by ε=0, 0.5, 1.0, 1.5mm from the center of the outer tube surface. The heat flux ratio between maximum and minimum heat fluxes of these tubes correspond to 1.0, 1.7, 3.0 and 7.0, respectively. Experimental conditions were as follows ; system pressures were 0.3 and 0.4 MPa, mass flux range were 10-100kg/m²s, inlet temperatures were 30 and 80 deg. C. The experimental results showed an increase in the critical heat flux by the existence of the redistribution of the flow. These characteristics have been well explained by using the similar concept of Butterworth's spreading model.

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In a core disruptive accident (CDA) of a Fast Breeder Reactor, the post accident heat removal (PAHR) is crucial for the accident mitigation. The molten core material should be solidified in the sodium coolant in the reactor vessel. In the present experiment, molten material is injected into water to experimentally obtain fragments and the visualized information of the fragmentation. The distributed particle behaviour of the molten material jet is observed with high-speed video camera. The distributions of the fragmented droplet diameter from the molten material jet are evaluated by correcting the solidified particles. The experimental results of the mean fragmented droplet diameter are compared with the existing theories. Consequently, the fragmented droplet diameter is close to the value estimated based on the Kelvin-Helmholtz instability. Once the particle diameter of the fragmented molten material could be known from a hydrodynamic model, it becomes possible to estimate the mass ratio of the molten particle to the total injected mass by combining an appropriate heat transfer model The mass ratio of the molten fragment to total mass of the melted mixed oxide fuel in sodium coolant estimated in the present study is very small. The result means that most of the molten mixed oxide fuel material injected into the sodium coolant can be cooled down under the solidified temperature, if the amount of the coolant is sufficient.

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In a branch pipe with closed end, the cavity flow penetrates into the branch pipe from the main loop and the thermal boundary layer occurs because the cavity flow is a hot fluid, but the heat removal causes the colder fluid in the branch pipe. It is possible for the thermal stratification to affect the structural integrity. Therefore, it is necessary to establish the pipe design standard to suppress thermal fatigue. The pipe design standard consists of the maximum penetration depth L_sv and the minimum penetration depth L_sh. In orde to establish the evaluation method for L_sh, the visualization test and the temperature fluctuation test were carried out. Theoretical formula of thermal stratification was introduced from the heat balance model. Using this model, the empirical equation was obtained from the map of fluid temperature fluctuation. The method can predict the vortex penetration depth by cavity flow in the horizontal branch pipe.

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The combustion characteristics of a prototype micro-gasturbine combustor fueled by kerosene were investigated. In order to enhance the recirculation in a primary combustion zone, a swirler was set between the primary and secondary combustion zones. Primary combustion air was introduced through the swirler and forced to flow upward to the combustor bottom, from where the fuel spray was supplied through a nozzle. The fundamental combustion characteristics such as lean combustion limit, flame luminosity etc. showed that this prototype combustor had a high potential for lean combustion and wide flame holding. Since a strong forced recirculation flow was induced by the upward swirl, lean and non-luminous flame was maintained in the primary combustion zone. Further, burned gas recirculation and highly turbulent shear flow in the primary combustion zone, both of which were caused by the upward swirl, resulted the low NO_x emission characteristics.

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The effect of wall temperature on soot deposition from a diffusion flame placed near the wall has been investigated by utilizing microgravity environment, which can attain very stable flame along the wall. Cylindrical burner with fuel injection was adopted to obtain two dimensional soot distributions by laser extinction method. In the experiment three different wall temperatures, T_w=300, 600, 800 K, were selected as test conditions. The results showed that the soot distribution between flame and burner wall was strongly affected by the wall temperature and soot deposition increases with decrease in wall temperature. According to the numerical calculation both convective motion and thermophoretic effect are important to explain the transfer of soot toward the burner wall. Then, “soot deposition length” defined as the relevant approach distance to the wall per a given axial distance is newly introduced as a better parameter to evaluate the soot deposition tendency to the wall. The comparison among the values for three different wall temperatures suggested that the change in thermophoretic effect is the most dominant factor to give the change in soot deposition characteristics.

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Atomization characteristics of a liquid film were investigated, experimentally. A liquid jet emerging from a straight-type hole nozzle is impinged onto a solid wall, forming a liquid film. Effects of three independent parameters were investigated, namely, injection pressure P₀, impingement angle α and impingement wall diameter d. The liquid film velocity V₂ was measured with a PDPA. The SMD of the droplets was measured with an LDSA. It is shown that the SMD decreases linearly with the increase in the liquid film velocity V₂, and that the gradient of the line decreases with the increase in the impingement angle α. For the case that the impingement angle α is 30 deg, the SMD of the droplets is proportional to V₂^-0.63. For the case that the impingement angle α is 90 deg, the SMD of the droplets is proportional to V₂^-0.51. For the case that V₂<300m/s, the SMD of the droplets is smaller than that for a liquid jet. It is shown that by use of a liquid film, atomization is enhanced compared with a liquid jet.

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A unique solar thermal electric system was proposed and tested in the present study. In this system, an organic working fluid, which is suitable for a temperature range fitted for solar energy, is adopted. We call this system “Solar Organic Rankine Cycle System (SORCS)”. To improve the thermal efficiency by using solar energy, the displacement type scroll expander and CPC (Compound Parabolic Concentrator) solar collector are used. This system consists of very simple components similar to the air conditioner and is very cost effective. The present paper reports experimental results of the scroll expander test and the practical operation of the proposed SORCS under the actual solar radiation input. Total thermal efficiency of the present SORCS reached to 7% (42% when cooling water is used for the cogeneration system).

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Decreasing the compression ratio improves thermal efficiency in a premixed charge compression ignition engine for the range of investigated octane numbers up to the limit of stable ignition. This is because improvement in the degree of constant volume combustion and decreased cooling loss as the ignition timing approached TDC outweigh reductions in combustion efficiency and theoretical efficiency. The indicated thermal efficiency with different octane number fuels is almost unchanged if the compression ratio is optimized. The thermal efficiency benefits of lower compression ratios decreased with higher homogeneity achieved by advancing the injection timing due to a corresponding deterioration in combustion efficiency. However, the fuel ignitability and compression ration dependence of the indicated thermal efficiency and the exhaust gas emissions are nearly unaffected by changes in the mixture homogeneity. In addition, EGR efficiently suppresses premature ignition and reduces cooling losses without deteriorating combustion efficiency.

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