In this study, fine particle bombarding treatment (FPB) was applied to A5052 aluminum alloy, the effects of FPB treatment time (5, 10, 20, 40s) on the near-surface microstructure hardness, and fatigue strength was examined. The near-surface microstructure of 20s and 40s FPBed Al-Alloy was nano-crystallized, and lamellar structures were partially formed. The average grain sizes in and around lamellar structure are 65nm and 125nm by TEM observation. The relationship between hardness and grain size indicates Hall-Petch relationship. Moreover, fatigue tests were carried out with cantilever-type rotary bending fatigue test machine. Fatigue strength of 20s-FPBed Al Alloy is highest, the relationship between fatigue strength and grain size indicates linearity. Then 20s-FPBed A5052 had the fatigue strength equivalent to 7000 series aluminum alloys.

By optimize the mixing conditions of powders and the conditions of the spark plasma sintering, dense 20 vol % TiB₂ particle aluminum composites with uniform distribution of particles were obtained. The thermal conductivity and the mechanical properties were estimated. The experimental results were good agreement with the theoretical value based on the rule of mixture which is considering the uniform distribution of particles and without pores. The strength of the composites at room temperature is lower than that of pure aluminum block, but the strength of the composites was improved at higher temperature such as at 100°C compared with the monolithic aluminum.

Ferrite/martensite dual-phase (DP) steels have been used for automobile body parts because of their excellent strength/ductility balance. It is known that damage forms with plastic deformation in the DP steels, and is associated with their microstructure. It is thus possible to control the crack/void growth by designing the distribution and morphology of ferrite/martensite. In this work two types of DP steels, with almost same fraction but different distribution/morphology of martensite, were prepared by changing heat treatment process. Effects of microstructure on the damage evolution behavior during tensile tests at 20, -100, and -180 °C were discussed with quantitative method of damage growth and scanning electron microscopy (SEM). It was found that (1) martensite morphology affected the size of crack/void damage and the mechanism of damage nucleation; (2) nucleated damage was arrested to grow by plastic deformation of ferrite in both DP steels; (3) the arrested damage started to grow again in further deformation, resulting in failure; (4) this restarting of damage growth occurred at a smaller strain at low temperatures of -100 and -180 °C than 20 °C.

When an Al-Al₃Ti composite containing platelet Al₃Ti particles is severely deformed, distribution and size of the Al₃Ti particles are drastically changed. In this study, distribution change of the Al₃Ti particles in the Al-Al₃Ti composite by multi-directional forging (MDF) is investigated. The Al₃Ti particles are fragmented and refined with increasing number of MDF passes. As well as particle size, shape of Al₃Ti particles changes from platelet to granular. Moreover, deviation of Al₃Ti particle-size distribution gets smaller as the number of MDF passes increases. In order to investigate change of the spatial-distribution of the Al₃Ti particles by MDF, the spatial particle distributions of Al₃Ti particles in the Al-Al₃Ti composite deformed by MDF are evaluated by Morisita's index I_δ. As a result, the fragmented Al₃Ti particles form aggregation at 3 passes of MDF. In addition, shape of the aggregation of the Al₃Ti particles is similar with that of the Al₃Ti particles in undeformed Al-Al₃Ti composite. This phenomenon can be explained by plastic flow of matrix during the MDF.

A gas dynamic method, to estimate the mixed-mean gas temperature which is called stagnation temperature, in a stagnation chamber of a cold spray nozzle with a long injection-pipe, is proposed. The method does not use temperature measured by thermocouple but mass flow rate of the process/carrier gases and stagnation pressure upstream of the nozzle. The stagnation temperatures estimated by the present method were validated by comparing them with measured values using a coiled sheath-type φ 0.5mm thermocouple, inserted in the stagnation chamber of the nozzle. The gas flow experiment of cold spray was conducted under the conditions of gas pressure up to 0.96MPa, and heater-exit gas temperature up to 673K. The working gases selected were air and helium. The species of the process gas and the carrier gas was the same. The ratio of the mass flow rate of the carrier gas against that of the total mass flow rate selected was 0.2. The comparison of the estimated and measured stagnation temperatures shows that the estimation error of the present method is less than 4% for air, and less than 5% for helium gas.

Vortex tube (VT) is a simple mechanical device which splits compressed gas of room temperature into cold and hot streams. It can produce cold stream down to around -30°C and hot stream up to around 130°C. However, the detail of its mechanism of energy separation is still unclear. One of the most important parameters of energy separation is the tangential velocity of the working gas at the exit of the tangential nozzle, which is installed in a vortex chamber. In this research, we measured temperature of cold stream using thermocouple probe, then calculated the tangential velocity at the exit of the tangential nozzle and isentropic efficiency. The results indicate that the tangential velocity and the isentropic efficiency increase as the cold fraction decrease, and reach maximum values at the inlet pressure of 0.3 to 0.5MPa and cold fraction less than 0.34.

In this study, we investigated the effect of the angle of air supply θ and the air inlet position x on the ejector performance of air vacuum cleaner. First, as the effect of the angle of air supply, it was found that in the case of θ=16deg, the ejector efficiency increases approximately 23% in comparison with θ=8deg which was a basic form. It is because that in the case of θ=16deg, high speed flow supplied from inlet expands uniformly in the narrow flow passage. Next, as the effect of the air inlet position, it was found that the ejector efficiency increases in the case of x=20mm regardless of the angle of air supply, and it raises approximately 56% at θ=8deg for x=3mm in particular. It is because that in the case of x=20mm, high speed flow which meets main passage at upstream side can be sent to the narrow flow passage independent of the angle of air supply.

As a part of study on the diffusion control of jet flow, the purpose of this study is to control the jet diffusion by using the deforming nozzle. The shape of polypropylene nozzle can change from square shape into cruciform one smoothly. The velocity measurement of the jet flow was performed using a hot-wire sensors, by changing the shape of nozzle exit variously. The basic characteristics of the jet flow, such as velocity distributions and half value widths have been obtained. As a result, it has been clarified that the jet width of the deforming nozzle is suppressed in the downstream location from the nozzle exit to the 8 times the characteristic length. And the jet width of the deforming nozzle in xOy’-plane is small, comparing with that in xOz-plane. Moreover it has been also found that the diffusion of the deforming nozzle is same level in both planes in the downstream location more than 10 times of the characteristic length. Furthermore, in the in the downstream location more than 13 times of the characteristic length, in the case of the shape of the nozzle is a square, the diffusion of the jet is suppressed and the jet diffusion in the case of changing the shape of the nozzle continually periodically is promoted.

When vacuum accidents occur in beam lines in a synchrotron radiation facility, shock waves will be generated with hazard of damaging the experimental apparatus. To protect them from shock waves, acoustic delay lines (ADLs) are installed in the beam lines. In this study, noticing the diverging type, converging type and square type as basic elements of ADLs, we considered three models of single element type (backward slope model, forward slope model, and square model for comparison) and four models of composite type (double backward slope model, double forward slope model, central concave model, and central convex model). Each element consists of wedges, angle of which is 30 °, 45 °, or 60 °. Experiments were carried out using a shock tube with a blast-wave generator. The pressure decay was evaluated by transmissive factor and reflective factor for the incident blast wave. As the results, composite type models showed higher pressure decay than single element types. Above all, the central concave type were best with regard to the transmisssive decay.

With recent increase of cars, the noise problem is caused by the exhaust sounds generated from exhaust pipes, which consist of weak pressure waves called blast waves. To diminish the noise, silencer is installed in front of the exhaust pipe. In the present study reflectors were installed in the high pressure portion of the shock tube to generate blast waves, and as silencer models, three basic types of expansion regions are combined with four types of perforated panels and an acoustic material (glass wool). The pressure decay was investigated by transmitting factor and reflection factor to the incident blast wave, together with pressure sensors and high-speed movies by the shadow graph method. As results, it was confirmed that the perforated panel contributes to weaken the blast wave to some extent, while the acoustic material does greatly: the one-stage expansion model with perforated panel and glass wool shows the highest decay of the peak over pressure for transmission and the two-stage expansion model other models with those shows the second highest. The acoustic material also contributes to decay of reflected shock waves propagating toward an upstream duct.

Numerical simulations of the jet injected into supersonic cross-flow are carried out. In aborting process in liquid rocket flight, the fuel is transversely injected into the supersonic freestream. Developed jet/freestream interaction structure may trigger unexpected auto-ignition or explosion events; thus the understanding of the flow-field of jet-in-supersonic cross-flow is essential to meet the reliability of rocket. The two-dimensional numerical simulations are carried out in a wide-range of jet and freestream conditions: the jet-to-freestream momentum flux ratio and the pressure ratio. Present result shows recirculation regions are formed both at the upstream and downstream of injector with the characteristic vortex structures. With increasing the jet-to-freestream momentum flux ratio, the vortex structures in the recirculation region are largely developed. It is founded that the highest temperature in the separation region depends on the total temperature in the separation region and furthermore, it is the lower temperature than the total temperature of freestream.

Aerodynamic characteristics have great influences on fuel economy and environmental problems nowadays. The aim of this research is to analyze the influence of configurations and diffusers of road vehicles on aerodynamic characteristics. As configuration parameters, the rear window angle and the side window angle are adopted, and together with the diffuser angle, totally 126 patterns of configurations changing from box type through fastback to notchback types are investigated by wind-tunnel experiments using the moving belt. As results, by the rear diffuser, the lift is decreased with the minimum at diffuser angle 15°, but overall the drag is increased except for diffuser angle 5°~10° with the minimum at diffuser angle 5°. The drag is greatly reduced when combined with side angles 30° and diffuser angle 5°. The well-known tendency that the drag increases steeply at rear angle from 20° to 35° appears with side angles 0° and 15° for most diffusers, while this tendency does not with side angle 30°. Visualization by the five-hole Pitot tube suggests that the drag reduction can be obtained by restraining longitudinal vortices.

The formation of deposits on a fuel injector tip is considered a cause of particulate matter (PM) generation. Because wetting by fuel generates the deposits, reducing that adheres to the injector tip is important. In particular, coarse droplets of fuel are generated during the valve opening and closing and cause tip wetting. In this study, we have therefore investigated the effects of valve motion, especially closing and off-axis valve motion, on fuel flow in the injector nozzle by numerical simulations. The results are summarized as follows. (1) The calculated results show that low speed fuel was sprayed during valve closing. (2) Off-axis valve motion decreases the amount of fuel spray in the hole located in the opposite direction to the off-axis valve motion at the valve seating. This is caused by fuel flowing toward the off-axis valve motion in the sac volume. (3) The averaged fuel velocity at the hole outlet located in the off-axis direction with off-axis valve motion is larger than that without off-axis valve motion. During valve bouncing, the averaged fuel velocity at the hole outlet shows little differences in the presence or absence of off-axis valve motion, which indicates that off-axis valve motion for closing barely affects the fuel velocity after the valve seating.

This research deals with improvements of side-wind stability about restraint of yawing and turning sideways under high speed operation of cars. For this purpose a side-jet machinery called aero slit is adopted, which decreases the yawing moment by causing separation in the case of receiving side wind. The Ahmed body is used as a simplified car model with an aero slit on one side. In the slit size the width is 8mm common, the height has three patterns (20 mm, 30 mm, and 40 mm), and the slit position has five patterns (0mm, 25mm, 50 mm, 100 mm, and 150 mm) from the front end of the model. Totally sixteen patterns are manufactured together with a bumper without an aero slit. In the experiments, the wind speed is taken as 20 m/s with yawing angle changing every 10° from 0° up to 60°. As results of yawing, the maximum value of yawing moment was decreased at yawing angle of about 30° by most of slits. The most effective slit is 20 mm in height at 50 mm in position, i.e., smallest height at ending location of edge rounding. Next, the wind speed at overturning limit is estimated by the evaluation method with the overturning moment using lift and side force. Consequently, an overturn of cars with an aero slit can be restrained in angle 0° to 20° and 60°, but slightly in angle 20° to 50°. Thus the effect of the aero slit has been confirmed on yawing and turning sideways.

Dynamic effects on the pressure distributions around a sedan-type simplified automobile model were investigated by conducting forced oscillation tests in a wind tunnel. HEXA, an original 6-DOF parallel-link manipulator was used to impose heaving and pitching motions on the model and unsteady pressure distributions over the model surfaces were measured with the effects of the ground plate. The obtained results show that dynamic effects become prominent mainly on the front side of the model underfloor and change depending on the Strouhal number. The effects were mostly consistent to those predicted by the quasi-steady model, but the pressure ports near the far front side of the model showed different behaviors. It is suggested that these observations are related to the local separation regions found in surface-flow visualization tests.

In order to validate the calibration and measurement capabilities of the high air speed standard, inter-laboratory comparison of air speed calibration facilities was conducted at 40 m/s. From the result, increase of the air speed point on the comparison was needed for the increase the reliability. In this paper, the validation assessment in advance using uncertainty analysis was calculated case of under 40 m/s about the high air speed standard. As the result, the air speed range more 20 m/s has potential the accepted range of the expanded uncertainty (k = 2) under 1.0 %. Besides, uncertainty source of the differential pressure is especially increased at the low air speed.

The thermo-anemometer comprised of the cold-wire thermometer and the hot-wire anemometer is used for the simultaneous measurement of the temperature and the velocity fields. The cold-wire thermometer involves the frequency characteristics due to the heat capacities of the fine sensor and its prongs. In this study, the frequency compensator for the cold-wire thermometer was constructed by adapting the programmable logic device of FPGA. The numerical experiments indicated that the frequency compensator mounted on the FPGA realized the sufficient precision at a higher sampling frequency. In addition, the automatic evaluation system was developed with the monitoring function of the ambient environment.

A large ball prover for hydrocarbon flow measurement has been calibrated over the actual operating flow rate range by using a reference standard flowmeter and a positive displacement flowmeter installed in parallel. The operating flow range of the ball prover is from 100 m³/h to 1800 m³/h, and its volume is 10 m³. The reference standard flowmeter, of which maximum flow rate is 300 m³/h, was calibrated at NMIJ in order to be traceable to national standard. The calibrated flow rates for the ball prover were expanded from 300 m³/h to 1800 m³/h by the reference standard flowmeter and the PD meter installed in parallel. As a results, the calibration factors for the ball prover were obtained at all operating flow range. The deviation of the calibration factors against flow rates was less than 0.05 %, indicating good linearity of the prover. The detailed uncertainty analysis was carried out, resulting the uncertainty of the calibration factors of the ball prover were evaluated to be less than 0.09 %.

The static pressure measurement error at a wall tap of a flow nozzle is examined for a wide range of Reynolds number. The static pressure measurement error is obtained using the measured discharge coefficient for the flow nozzle. The static pressure measurement error is influenced by the diameter of the wall tap and the viscosity of the working fluid. This paper presents several relations between the static pressure measurement error normalized by the wall shear stress and the tap Reynolds number, which is based on the diameter of the wall tap and the friction velocity. The best relation to reasonably explain the static pressure measurement error is proposed in this paper.

The increase on environmental concern has made current water turbine for tidal power generation to become one of the best adapted solutions to the energy needs of society. In this paper, the relationship between the fluid force of blade and flow field around blade with or without the guide was analyzed using CFD method. In this university, it has been reported that the performance could be improved using cylindrical guide inside the wind turbine, but the guide has not been application to tidal current power generation water turbine. It was clarified that the flow around the blades of the water turbine on condition that chord length l_c=50[mm] and number of blades N=3 eased by using the elliptical guide with the long diameter and the short diameter of r_a/l_r=0.5, r_b/l_r =0.25.

We propose a flapping wing type micropump, which is categorized as a velocity pump. The kinematics of the flapping wing consists of heaving and pitching motions like insects. Two dimensional computational fluid dynamics for a flapping wing type micropump is conducted to assess the no load flow velocity as the performance of the pump and optimize the wing kinematics. The numerical results indicate that the flapping type micropump shows high flow rate when the wing motion has larger heaving amplitude. In this case, the flapping type micropump utilizes the interaction between the flapping wing and pipe wall to enhance flow velocity, which is similar to the “clap-and-fling” effect by a pair of flapping wings of an insect.

The purpose of this study is to investigate experimentally and numerically the characteristics of gas flow (single phase flow) in the hemispheric head cyclone separator without flowing particles and to find the flow characteristics contributing into high collection efficiency. It is shown that the numerical results calculated by RIKEN’s computational code and K computer are qualitatively agreement with the experimental results. The numerical results at Re = 2.3 × 10⁵ show the characteristics of the outer spiraling flow, the vortex rope formed at the central core, the longitudinal vortices surrounded the vortex rope, in the hemispherical head cyclone separator, comparing with a conventional flat head cyclone separator.

Micro quad-rotor, which is one of the UAV, has been increasingly developed recently by many researches. We focus on the transverse side wall effects of a hovering quad-rotor. The attitude of the quad-rotor is unstable due to the wall effects including the ground effect, in hovering near the walls by the air-flow through the walls. The objective of this study is to clarify the effects of the transverse side walls exerted on aerodynamic characteristics of a hovering micro quad-rotor. Acted fluid forces on the hovering quad-rotor near the walls are measured by a 6-axis Force-torque sensor. It is shown that the variations in the characteristics with the changes in the distance from the transverse side walls, comparing with the case of straight side wall. The increases of lift and the torque are observed in the specific location where the distance from the wall to the quad-rotor. These variations are similar to the case that the pair of outward rotation rotors faces to the straight side wall. This is, it is considered that the increases of the lift and the torque caused by that the lift of the pair of outward rotation rotors is increased by circulating flow around the outward rotation rotors.

It is well known that necklace vortices are formed in front of a three-dimensional object set on the ground wall. The necklace vortices may be related with various flow fields in mechanical engineering, aeronautical engineering, civil engineering and so on. However, the detail of the structure and the behavior of the necklace vortices for wide range of Reynolds number is not well known yet. For the high Reynolds number, the vortices become unsteady and complicated, and the property depends on various shape of the three-dimensional object. Therefore, in this investigation a thin square flat plate is employed as the basic and simple three-dimensional object. Then, the property of unsteady necklace vortices formed in front of a vertical square plate standing on a ground wall is investigated by using the visualization and PIV measurement with a water channel. As a result, the property of the unsteady necklace vortices is revealed. Necklace vortex pattern can be classified by only the Reynolds number, and does not depend on the boundary layer thickness.

There are two types of square lattice structure, biplane grid and woven screen, in order to control various industrial flow fields. In particular, the square biplane grid which consists of several cylinders arrayed at right angle is often used to make turbulence. In addition, it is proposed to apply the heat transfer enhancement effect to heat exchanger. Accordingly, it is important to reveal the flow characteristics around circular cylinders forming biplane grid. However, the flow characteristics around circular cylinders forming square biplane grid has not been fully examined. Therefore, the aim of this study is to clarify the three-dimensional flow field around the circular cylinder members forming the square biplane grid by means of the measurement of surface pressure distributions, the estimation of local drag coefficients and the visualization of path line. It is known from the previous results of two crossed circular cylinders that the flow over the separation area on the upstream cylinder invades in the vicinity of the contact point between upstream and downstream cylinders. Accordingly, it is supposed that the there-dimensional flow which is similar to the two crossed cylinders is made in the cross region of cylinder members forming the biplane grid. As a result, it was found that the flow invading in the contact region may have produced the longitudinal vortices periodically fluctuating behind the downstream cylinder of the biplane grid.

In order to control various industrial flow fields there are two types of square lattice structure, biplane grid and woven screen. Woven screen which is used as a rectification lattice consists of the alternation of knitted circular crynders. Though the woven screen and the biplane grid have similar shape, the vortex structure behind two types of lattice is though to be different each other. However, the vortex structure formed behind these lattices is not almost known yet. It way leads to the explanation of the straightening effect of woven screen to clarify vortex structure. Therefor, the aim of this investigation is to clarify the vortex structure formed behind woven screen and the growth process in the near wake by means of flow visualization and PIV measurement using the stainless steel large model of woven screen submarged in the water tunnel flow under the low Reynolds number. As a result, two pair of longitudinal vortices behind all downstream cylinders are produced in the cross region of circulare cylinder menbers. The secondary flow which is made by four longitudinal vortices shows a plus or minus vorticity in each mesh. It becomes difficlut to confirm four longitudinal vortices in the wake region of x/d=10.0.

The objective of this study is to experimentally investigate the structure of the boundary layer flow over a rotating disk under orbital motion in order to reveal the generation mechanism and characteristics of disturbances. The disk diameter is 300 mm, and the orbital radius is one third of the disk radius (50mm). The velocity field in the boundary layer flow at high Reynolds number is measured by a hot-wire anemometer (as for the measurement height z = 0.65mm from the disk surface), at a fixed orbital angler portion. The structure of the three-dimensional boundary layer flow is deformed elliptically and flown away to a certain direction which is not orbital radial direction, by orbital motion. The effects on the turbulent region, the fluctuating intensity becomes larger except a certain region, as the orbital speed increases. There are observed independently of the direction of rotation. However the flown direction and the location of expecting region depend on the direction of rotation. In the coinciding orbital and rotational directions, the low frequency disturbances which have high intensity of fluctuating velocity are observed in the upstream region of transition point. The transient vortices which form streaks on the coating film are considered to be destroyed by the low frequency disturbances. However, in the opposite orbital and rotational directions, the low frequency disturbances are not observed at any section.

Leidenfrost effect is a physical phenomenon occurs in liquid droplets which are close to a solid surface heated up to a significantly high temperature compared to the boiling point of the liquid. In the Leidenfrost effect, the vapor layer between the droplet and surface keeps the droplet levitate without touching the surface. Previously, we developed a new technique named Mist CVD, in order to fabricate uniform functional thin films under atmospheric pressure. In Mist CVD, the micro-meter-size mist droplets in the Leidenfrost state play a vital role in the thin film fabrication with atomic-layer-level arrangement and high uniformity on large-scale substrates under atmospheric pressure. However, the properties and behavior of these micro-size droplets are not well understood. It is even not clear which mechanism is responsible for the growth of thin films in Mist CVD. This work studied the relationship between substrate temperature and the evaporation time of pure water millimeter-size droplets in Leidenfrost state. In addition, images of micrometer-size Leidenfrost droplets could be captured using a microscope connected with a digital camera and a nanosecond flash light souse.

We investigated to the evaluation of flowability of cohesive powder using the test of powder discharge from an orifice by air flow. In this study, we used three kinds of Calcium hydroxide which changed the particle diameter. The mean particle diameter of an original powder, Ca(OH)₂ A, is 13.1μm. Other particle diameters, i.e. Ca(OH)₂ B and Ca(OH)₂ C, are 14.1μm and 2.5μm respectively. As The experimental conditions, the initial void fraction and the interstitial air pressure have been changed. The result was obtained that the flowability of Ca(OH)₂ B was the highest flow which was judged from the relation of the mass flow rate and the average interstitial air pressure. Furthermore, the influence of cohesiveness between particles was examined from the relationship between the ration of separation force to gravity force and the initial void fraction. The result indicated that the cohesiveness of Ca(OH)₂ C which has the smallest particle diameter was the strongest.

Microbubbles generated by a pressurized dissolution method and ultrasonic waves are applied to decomposition of organic compounds. Though there has been some reports on such research so far, the relation between microbubbles and ultrasonic waves has not been discussed in detail. In the present study, first, the effects of microbubbles or ultrasonic waves on the decomposition of methylene blue is examined from the comparison of decomposition rates obtained from the experiments under some conditions; at rest, water flow, microbubbles alone, ultrasonic waves alone, and the combination of microbubbles and ultrasonic waves. Next, the influence of the frequency of ultrasonic waves on the decomposition of methylene blue is investigated. A bubble has a natural frequency according to the bubble dynamics, and it oscillates explosively when it is exposed to the ultrasonic wave with the natural frequency. The frequencies 20 kHz, 70 kHz, 100 kHz, 140 kHz, 200 kHz, 250 kHz, and 330 kHz are used in the present experiment. As a result, the combination of microbubbles and ultrasonic could decompose the methylene blue most rapidly. In particular, among the above frequencies, the methylene blue could be hardly decomposed in the case of 70 kHz and 330 kHz, and it could be decomposed in the case of 200 kHz most rapidly. The mean bubble radius measured by laser diffraction-scattering type particle size distribution measuring device is 54 μm and its natural frequency is 123 kHz. Though the discrepancy is small, its cause could not be clearly specified.

A novel droplet generator equipped with flow-control has been developed for the formation of various liquid droplets. Two fast falling droplets with small angle are collided in air and are formed one droplet, which gets out of its shape from various type of oval to ball in falling by convection inside a small droplet. On the other side, two water jets with same speed and same angle are collided. But, one jet cannot be obtained by collision.

The effects of the size and the angle of attack a water droplet on the ice accretion are investigated when spraying liquid-gas flows against a flat plate in a freezer. In the case of a small droplet of which Sauter mean diameter (SMD) is 20.9μm, the graze icing is formed and the thickness and density of the ice accretion on the flat plate is 10.6mm and 213kg/m³. In the case of a large droplet of which SMD is 43.2μm, the rime icing is formed and the thickness and density of the ice accretion on the flat plate is 2.6mm and 617kg/m³. Due to the disturbance caused by the freezer wall, the thickness of the ice accretion in the case of the small droplet is larger than that in the case of the large droplet. A feather shape icing is observed on the bottom of the flat plate. When the angle of attack of the flat plate is changed from -90 to -81 degrees, the angle made by the spraying direction and the flat plate surface changes by 9 degrees, whereas the feather angle change is observed to be 3.1 degrees in the case of the small droplet and 6.0 degrees in the case of the large droplet.

In the present study, the meniscus instability of a viscous fluid film confined into a narrow gap between a circular rigid flat plate and an elastic sheet with uniform thickness was examined theoretically. The Reynolds lubrication equation was solved numerically to obtain axisymmetric flow which occurs when the plate and sheet were separated with constant speed. After that, linear stability analysis was performed to assess the influence of elastic deformation on the instability of free surface. The elastic sheet was modeled by infinite linear elastic plank bonded to rigid substrate. Surface displacement of the sheet was calculated using a Green's function derived from stress function and Hankel transformation. Consequently, it was found that the moving velocity of the fluid radius decreases with increasing elastic compliance of the sheet. This result shows that the deformation of the elastic body contributes to the stabilization of motion of free surface.

The drag coefficient measurements of spherical particles (5.53, 5.88 and 12.68 mm in diameter) in unsteady flows induced by a propagating shock wave were perfomed using a shock tube facility. The Mach number of the shock wave was set to be 1.3. The trajectories of the spherical particles were recorded using the shadowgraphy with a high-speed video camera. Based on the experimental results, the drag coefficients of the spheres were calculated. The drag coefficients of spheres in unsteady flows were found to be larger than the standard drag coefficienets in steady flows.

A swirling flow has a high diffusibility and the high mixed efficiency, so it is used in a combustor, a boiler, a gas turbine and so on. The swirling flow is known that it has various unsteady, and in the case of unstable condition, the swirling flow causes fluid oscillation and it causes a vibration and a noise for fluid machinery. However, there is few reports of the research which is taken account of the high-speed swirling flow, that is, about compressibility flow. In this research, the unsteady behavior of the high-speed swirling flow was experimentally investigated. The high-speed swirl flow was generated by the inlet guide vane and the suction type wind tunnel. The various type of the unsteady flows was found in the large guide vane angles and the lower tank pressures. For 60 and 70 degrees of the inlet guide vane, the peaks near 2000Hz and 5000Hz observed in the large guide vane angles disappeared and the peak near the 3000Hz appeared.

The ability to obtain laser based quantitative temperature measurements is particularly important in high pressure environments. In this study, quantitative temperature measurements using Laser Induced Thermal Grating Spectroscopy (LITGS) were employed for a toluene vapor/air jet varying the toluene concentration and pump laser power. In LITGS, the gas temperature at the crossing point of two pump laser beams can be derived from the oscillation frequency of the LITGS signal and, in principle, the signal at high pressure is larger than that at atmospheric pressure. Thus, LITGS is a promising laser diagnostic method for high pressure environments. LITGS signal was acquired for toluene vapor/air mixtures at atmospheric pressure and room temperature and it was found that the derived temperature is influenced by the energy of incident pump laser, showing an increase with an increase in the pump energy. A semi-empirical equation showing the relationship between the relative temperature rise, pump energy and mole fraction was then derived. The experimental results match the linear semi-empirical equation.

The response characteristics of a lean methane-air premixed flame to equivalence ratio oscillation was investigated experimentally. In order to clarify unsteady flame response from the actual measured values of the burning velocity, we developed a new burner that allowed measurement of the flow field by using particle image velocimetry (PIV). Chemiluminescent emission intensity of CH radical, which is correlated with the combustion intensity of the lean flame, was also measured by using high speed camera with a band pass filter. The equivalence ratio was varied sinusoidally only in the direction of the main flow at burner exit by two speakers. For an oscillation with mean equivalence ratio of 0.85, amplitude of 0.05 and the oscillation frequency ranging from 5 to 10 Hz, following results were obtained: The variation widths of burning velocity and CH radical emission intensity in fluctuating flame are increased as oscillation frequency increases. These variation widths are larger than those of a steady flame in the equivalence ratio range corresponding to the fluctuation. This means that when the flame moves against (along) the fuel flow, the mass flux at the flame front increases (decreases) as compared with that of the steady flame.

An experimental study was performed to investigate the influences of fuel nozzle shape on soot emission from coflow propane-air diffusion flame. Two different fuel nozzles, which have circular and square outlet shape respectively, were used in this study. Excess air ratio was varied by adjusting air flow rate with fuel flow rate kept constant. The soot discharge rate, flame luminosity and flame temperature are measured. Soot was collected by a glass filter and then the filter was weighed to obtain the mass of soot by an electric balance. The soot discharge rate is determined by dividing the mass of soot by suction time. The obtained results are summarized as follows: 1) When the excess air ratio is low, the soot discharge rate of the diffusion flame formed on square nozzle is lower than that formed on circular nozzle. 2) Comparing flame temperature in the upstream of the flame, the temperature of the square nozzle flame is higher than that of the circular nozzle flame. 3) The difference of nozzle shape changes the flame temperature and affects the soot emission.

Influence of turbulence fluctuation of temperature and gas composition was examined based on absorption line database, in relation to the radiative heat transfer toward the wall of large-scale industrial furnaces enveloping a soot hydrocarbon flame. Adding the method to obtain the emissive power by soot to our calculation method, we can evaluate the radiative heat transfer from both of gas and soot in the turbulent luminous flame. As results, though soot radiation leads to obvious changes both in the distribution of radiative heat flux and in the spatial distribution of time-averaged temperature, influence on the total of wall heat flux is not so remarkable. But, the difference appears in the total of wall radiative heat flux estimated according to the band by the difference in the emission spectrum of gas and soot. And, also it was found that influence the turbulent fluctuation of soot on the total of wall heat flux is small relatively.

Interaction between flame-spread and droplet motion has been investigated to have basic understandings of the spray combustion mechanism. New experimental apparatus was developed to measure interactive force acting on n-heptane droplets during droplet pair combustion. A droplet array suspension system consists of two SiC fiber of 8.5 micrometers in diameter and a silver bead. Droplet motion was recorded with a high-speed video camera. The force was calculated from the droplet position history. Initial droplet diameter was set at 1.0 mm. Two droplets were ignited simultaneously by a hot wire. The force acting on the droplet more than 0.1 μN can be measured.

To effectively utilize palm acid oil (PAO), PAO mixed fuel usability was studied by 1. analyzing PAO properties, 2. making PAO-diesel and PAO-fuel oil A mixed fuels using solvent and ultrasonic homogenizer, 3. evaluating stability of PAO-diesel mixed fuel in cool temperature, 4. conducting an experiment in combustion of PAO mixed fuel using diffusion burner, 5. carrying out an experiment in NO reduction caused by thermally decomposed PAO mixed fuel using a plug flow reactor. Main components of PAO used in this study are considered to be palmitic acid and oleic acid. The PAO includes about 80% free fatty acid and a little bit water. Total calorific value of the PAO is less than diesel fuel and fuel oil A. To stabilize PAO-diesel and PAO-fuel oil A in cool temperature, an ultrasonic homogenizing with pulse generation is used and the remarkable effect is presented but prevention of both coagulation and deposition is difficult when the temperature is below about 10°C and PAO is contained over 20%. Diffusion combustion burner using the PAO mixed fuel demonstrates that NOx is reduced within the specific range:1.2~1.6 of air excess ratio in spite of the combustion chamber outlet temperature are high as compare with the temperature of diesel fuel. The cause of NOx reduction was studied by the plug flow reactor that showed both diesel fuel and PAO-diesel fuel are able to reduce NOx, especially at about φ=3.0, NOx is reduced by 55% which suggests a potential of NOx reduction caused by thermally decomposed hydrocarbons.