Recently food transportation by the frozen cargo vehicles has been increasing. By opening and closing of the door in the case of carrying-in, taking-out or delivery, the super saturation moisture within high temperature and high relative humidity open air generates mist inside of the frozen space. This phenomenon influences the performance of heat exchangers. In this study, the mechanism of the mist deposition was investigated numerically. A concept of finless tube heat exchanger, which is composed of flat tubes, is proposed for achieving high performance under refrigeration frosting conditions. Several geometrical parameters based on the specifications of the trial product, such as spanwise tube pitch and longitudinal tube interval, were changed. Furthermore the trajectory of the particles was obtained and compared with the two cases, i.e. the case where no frost exists on the heat transfer surface and the case where frosts exist on it. The result showed the heat transfer characteristic of the heat exchanger and the tendency of mist deposition.

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It is known that small quantities of surfactant additives can greatly reduce the friction factors. This is because the generation of turbulent vortices is suppressed by the formation of rod-like micelles, and the flow remains laminar. However, the heat transfer coefficients decrease during flow laminarization. The research objective is to examine heat transfer enhancement effects by air injection. This paper presents an experimental investigation on the heat transfer characteristics in an air-surfactant solution two-phase flow through a vertical tube. Heat transfer coefficients and friction factors were much larger for the air-surfactant solution two-phase flow than for surfactant solution. However, they were smaller than an air-water. It seems to be due to drag reduction effects of micelle structure. The flow patterns were investigated by visualization. The flow pattern of air-surfactant solution two-phase flow changed from a slug flow to a churn flow or from a churn flow to a bubbly flow at low liquid phase Reynolds number compared with the case of air-water two-phase flow on fixed air flow rate.

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The effects of micro-bubble injection on the forced convection heat transfer of laminar duct flow are experimentally investigated with the temperature measurements using the thermocouples. Hydrogen bubbles generated with electrolysis are adopted as the micro-bubbles. The bubble diameter ranges from 200μm to 500μm. The experimental results shows that the heat transfer coefficient with the micro-bubble injection is up to 1.6 times higher than that without the injection and that the heat transfer coefficient increases with the bubble flow rate and the stream wise direction.

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Experimental study has been carried out to investigate the heat transfer characteristics of emulsion, which consists of silicone oil and water with a trace of surfactant. Heat transfer of an electrically heated horizontal Pt wire was measured for ambient emulsion temperatures and stir conditions. The results show that the heat transfer mode change of the boiling point of emulsified water in oil emulsions. It is observed that the enhancement of heat transfer in the limited temperature region appears under weak stir conditions. It is also obvious that the above enhancement was hidden under strong stir conditions.

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A numerical model for the natural convection phenomena of the suspension accompanied by particle sedimentation was constructed. In this analysis, particle size distribution can be taken into consideration by distributing virtual particles and tracking each particle. This natural convection was divided into two convection layers. One layer hardly contains particles and the other contains particles. This phenomenon was explained by the numerical model. The mean Nusselt number of the natural convection of the suspension was compared with that of water. Inhibitive effect of the heat transfer by particles was obtained with the same tendency as the experiment.

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A study on the visualization of the absorption process in the vicinity of the gas-liquid interface was performed. The system in which CO_2 was absorbed into amine solvents and diffused toward the interior of liquid phase was visualized. The interferogram pattern obtained by phase shifting interferometer showed that the increasing of concentration field instability in liquid phase was observed as time advanced or pressure of the gas phase was increased. This was caused by the density increase of the amine absorbing CO_2 and the liquid was affected by the negative buoyant force which generated natural convection locally. Therefore, pseudo diffusion coefficient in this system was determined larger than that of the molecular diffusion system. It was considered that the self-generated instability enhanced the mass transfer of CO_2 in the vicinity of interface and liquid phase.

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It is well known that particles remaining on silicon wafer form a streak line in cleansing and drying process. To clarify the reason for this and to obtain new findings for the remaining particles, liquid film behavior in the vicinity of three phase contact line in cleansing and drying process has been observed using a CCD camera. The results show that there are two patterns of liquid film appearing just above the three phase contact line; streak-like liquid film and sawtooth one. The streak-like liquid film frequently appears when a comparatively small wave hits on the wafer surface. When a wave hits on the wafer surface, a crest of the wave runs along the surface lifting up the three phase contact line, and when the lifted contact line goes down, the liquid close to the contact line is expanded and drawn away from the bulk liquid. If the remaining liquid film includes particles, it is considered that the particles remain streaked after evaporation of the liquid film.

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In this study, we develop a theoretical model with which we can predict spatial and temporal spectra of the surface divergence at a contaminated turbulent air-water interface. In the present model, the flow field close to a contaminated interface is approximated as superposition of a free-surface flow at a clean interface and a surfactant-induced flow. As a result, the damping factor, which represents the ratio between the intensity of the surface divergence at a contaminated interface and that at a clean interface, is analytically derived as a function of spatial wavenumber k, frequency ω and Marangoni number Ma. The present predictions agree well with the results of direct numerical simulation at a wide range of Marangoni number.

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When DC electric field is applied perpendicularly to silicone oil-water interface, the interface becomes unstable and conic waves are generated. This type of wave is called Taylor cone, and there are features in conical shape and the angle of vertex of the cone. The conic wave, generated in the mesh of a metal net set up on the interface, is taken of a picture with the high-speed video camera, and analyzed on the monitor. As a result, change of the height of conic wave and the angle with time is clarified.

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We investigated a method for reducing work damage in micro-drilling of metals (SUS304, copper, titanium, and aluminum) using a nano-second pulsed Bessel laser beam. Work damage (discoloration and concentric circular marks) due to the side lobs of the Bessel beam are seen on the irradiated surface of SUS304 and copper. On the other hand, in aluminum and titanium, there is little discoloration area on sample surface. In the cases of SUS304 and copper, the absorptivity increases as a result of discoloration due to surface oxidization, and damage is generated. In contrast, for the case of aluminum and titanium, even if the oxide is formed on the surface, neither discoloration nor the changes in absorptivity are remarkable.

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This study concerns with the viscosity for the mixtures of R134a and Lubricant. The emphasis is placed on investigating the oil-concentration dependence on the viscosity for R134a/PAG oil. The measurement was conducted for oil-concentrations up to 32 mass% and temperatures of 278, 283 and 288K. For this measurement the oscillating-cup viscometer making use of polarizer was used. The uncertainty in viscosity was estimated to be less than ±3.5%. The mixture viscosity was found to be nine times greater than that of pure R134a at an oil-concentration of 32 mass%.

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In the present study, we have developed a new miniaturized optical viscometer, namely MOVS (Micro Optical Viscosity Sensor), which is applicable to the noninvasive, high speed, small sample volume, in situ and in vivo measurement of a liquid sample based on laser-induced capillary wave (LiCW) technique in both medical and industrial fields. In this paper, the fabrication of prototype MOVS chip for the first time and the discussion of the validity of the viscosity measurement were reported. Preliminary measurement using distilled water and sulfuric acid were demonstrated, and nanosecond order high speed damping oscillation signals were successfully observed.

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An anisotropic material by molecular alignment has been attracted for its wide applicability. Molecular alignment control and immobilization techniques enable us to design new anisotropic materials. In order to promote and realize the anisotropic material processing, development of the real-time measuring technique as a feedback sensor is inevitable. Forced Rayleigh scattering method (FRSM) is a measurement technique for in-plane thermal diffusivity, and some characteristics (noncontact, high-speed and micro-scale) indicate the ability for a real-time sensing of anisotropic heat conduction. In this study, we controlled molecular alignment of "UV curable liquid crystal" by electric field and immobilization by UV light. Then we measured anisotropic thermal diffusivity by FRSM.

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Thermal conductivity measurement of individual silicon carbide (SiC) nanowire is conducted by using T-type nanosensor. Two kinds of SiC nanowires are measured with simple modeling of thermal contact resistance. One has SiC core of 126nm diameter and surrounding amorphous silicon-dioxide layer of 7nm thickness. Its thermal conductivity shows over 100W/mK at room temperature and has maximum conductivity at higher temperature than pure bulk SiC, whose phonon scattering mechanism is also discussed. The other has two bundled SiC cores of 64nm and 58nm diameter in amorphous layer and shows unusual temperature dependence of thermal conductivity.

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In this paper, we develop a measuring method of nano thermal diode device using Pt nano sensors fabricated by NEMS (Nano electro mechanical systems) technology. Because the thermal conductivity of nano thermal diode has direction dependency, two-way temperature gradient and sensing are needed. So two suspended Pt nano sensors are fabricated, nano thermal diode is bridged between these sensors. One of these Pt nano sensors is electrically heated and temperature gradient is provided to the nano thermal diode. The thermal conductivity is analytically derived and measurement errors are estimated.

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Behavior of bubbles in Gas-liquid two-phase mixing section of microchannel flow system are visualized with microscope and high speed video camera. Several two-phase mixing section are manufactured experimentally and investigated on its performance. Venturi-typed mixing section of less 1mm scale can produce uniformly-sized micro-bubbles of less 100μm in diameter at more than 50,000 times per second. Prototype of multi-orifice typed mixing section are also investigated. Conditions and demands on the structure of micro mixing system for generation of bubbly flow in microchannel are disucussed.

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Carbon Dioxide is one of the most hopeful refrigerants because it has lesser greenhouse effect than all fluorocarbon refrigeration. But when CO2 is used in a refrigeration cycle, the compressor work needed is high and the energy loss at the expansion valve is four times that of the same cycle using refrigerant R-134a. Therefore, this high energy loss diminishes the coefficient of performance of the CO2 refrigeration cycle. We have been researching about a two-phase ejector that recovers expansion work so as it increases the compressor inlet pressure. Consequently, it reduces the compression work and finally it increases the COP of the cycle. This report discusses the mixing Characteristics of two-phase ejector and the performance of CO2 ejector cycle through experiments.

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In the present paper, a chain-shape mixer, which is composed of bifurcated passages and jet injections, is proposed and examined as a new passive-type micro-mixer. The mixing performance, flow characteristics and effects of the size of the jet outlet were evaluated using three-dimensional numerical simulation and μ-PIV measurements. Under small jet-size conditions, a poor mixing performance was obtained. However, by increasing the width of the jet outlet, a marked enhancement effect was achieved. This was due to the generation of multiple layers of the two fluids to be mixed, which was produced by the strong jet distorting the interfaces of the fluids. Furthermore, an optimum size of the jet was found in producing an effective mixing.

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The two-stage High Velocity Oxy-Fuel (HVOF) thermal spray gun has a mixing chamber between a combustion chamber and a supersonic nozzle followed by a straight barrel. The combustion gas is discharged into the mixing chamber, then the gas temperature is lowered in the chamber by injecting nitrogen gas at room temperature. The lowered gas temperature is beneficial from the view point of less oxidation of the spray particle accelerated and heated by the mixed gas. In this paper, the characteristics of the gas in the mixture chamber are clarified by the comparison between the cold-flow experiment and theoretical calculation.

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Two-phase flow nozzles are used in the total flow system for geothermal power plants and in the ejector of the refrigeration cycle, etc. There exist shock waves or rarefaction waves at the outlet of a supersonic nozzle of the ejector in the case of non-best fitting expansion conditions when the operation conditions of the nozzle are widely chosen. The purpose of the present study is to elucidate the character of the rarefaction waves and the shock waves at the outlet of the supersonic two-phase flow nozzle. In particular, this research treats only shock waves. Two-dimensional basic equations for the compressible two-phase flow are introduced considering the inter-phase momentum transfer. Two-dimensional oblique shock waves occurred in the high speed two-phase flows are calculated by the CIP method. Although the basic equations are controlled by the frozen Mach number, shock waves appear even for a frozen Mach number less than one. Angle of the oblique shock wave of two-phase flow can be calculated from the gas dynamic oblique shock wave relation, if sound speeds of two-phase flow may be used instead of that of gases.

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Experiments on the flow boiling of refrigerants inside a horizontal, spirally grooved steel tube with the 12mm average inner diameter were performed using a fluorocarbon refrigerant HCFC123. Experimental conditions were 50 to 150kg/(m^2s) in mass velocity, 0.2MPa in pressure, and nearly 0 to 5kW/m^2 in heat flux. The method to decide the flow pattern based on the condition of the liquid film on the tube surface was described using the circumstantial distribution of the wall temperatures, and the flow pattern maps were presented in the form of mass velocity versus vapor quality.

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This paper is an experimental investigation on forced convective boiling in a mini-tube. First, frictional pressure drops were measured in adiabatic condition. Next, heat transfer coefficients were measured in condition of constant heat fluxes. These data were compared with those in conventional tubes. The inner diameter of test tube is 0.51mm, and the test fluid is HCFC123. Ranges of the experimental parameters are as follows: the pressure P=0.1 - 0.3MPa, the mass flux G=150 - 500kg/m^2s, the heat flux q=10 - 30 kW/m^2, the vapor quality x=0.06-1.0. The pressure drops and heat transfer coefficients were lower than those in conventional tubes.

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Increasing attention has been given to carbon dioxide as an alternative substance in refrigeration and air conditioning from a framework of global environment. The refrigerating cycle with carbon dioxide becomes trans-critical cycle because of low critical temperature (31.06℃), and the operating pressure becomes essentially higher compared with other refrigerants. This paper describes boiling heat transfer and critical heat flux of carbon dioxide near critical pressure in horizontal tubes of 1.0 and 2.0mm in diameter, and observed flow patterns in 2.0mm-diameter tube are presented.

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For the detail study on forced convective boiling heat transfer in mini- and micro-tube, we developed the transparent heated mini- and micro-tube by electroless deposition. The inner wall of the tube is coated with the thin gold film, which allows the visualization of fluid motion. At the same time, the film resistance derives the temperature measurement of the inner wall of the tube. As a result of forced convective boiling experiments by using the tube with 1mm of inner diameter, the fluctuation of the inner wall temperature was caused by the boiling bubble departure from the tube wall, and its frequency was increased with heat flux increasing.

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It is requested to develop a small and high performance heat exchanger for small size energy equipments such as fuel cells and CO_2 heat pumps, and so on. In author's previous studies, a high pressure resistant microchannel layers stacked heat exchanger has been developed. The device is manufactured by diffusion bond technique. It can be used under high pressure condition larger than 15MPa. Due to the high pressure resistance, the heat exchanger can be applied for high flow rate condition with boiling and condensation. The objectives of the present study are to estimate the heat transfer performance of the heat exchanger and to investigate the thermal hydraulic behavior in the microchannel. The flow pattern is observed by fabricating visualization system for one channel to observe the flow condensation behavior in microchannel. In the experiment, the microchannel of Pyrex glass is surrounded by the subcooling water. The flow patterns can visualized from the side of the microchannel. Flow patterns observations are conducted for various diameters of the maicrochannel, flow rates and temperatures of the subclooled water. It is observed that the continuous flow transition from annular and injection flow to slug-bubble flow in the microchannel.

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The influence of a number of particles in molecular dynamics (MD) system on an entropy of liquid made of L-J particles is studied by two dimensional MD method, because the liquid has various micro structures. It was found that more than 200 particles are required for the entropy. They are also necessary for the entropy of "open region" in or from which L-J particles move. The entropy on nonequilibrium system is also discussed.

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Heat flux equations in molecular dynamics have been applied almost for the evaluation of thermal diffusion. However, the equations have never been applied for condition of propagation of the heat wave. In this study, we discuss that two heat flux equations can be applied for heat wave. The solid model is assumed to consist of particles with Lennard-Jones potential. Internal and external heat flux evaluations at heat wave were different from ones at thermal diffusion. It was found that heat flux including absolute velocity represents behavior that is different from the internal and external heat flux for condition of propagation of the heat wave. In order to analyze heat flux at heat wave with time average, we must have the model which has larger sub regions than width of heat wave.

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Molecular dynamics (MD) is one of the computer simulation methods to observe the microscopic state of materials. It was reported that the diffusion coefficient, which is obtained from MD simulation, increased with the increasing of the system size for 128-2,048 water molecules and 128-1,000 Lennard-Jones (LJ) particles fluid. We have performed the large scale MD simulations to study for the system size effect on the diffusion coefficient. The number of molecules for LJ is 1,000-100,000, and for water is 1,000-50,000. MDGRAPE-3, which is the special purpose computer for molecular dynamics simulations, has been employed for water simulation. A crossover from the system-size-dependent to the system-size-independent effects is observed for both LJ and water.

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In this study, molecular dynamics simulations have been performed on single (CO_2)_N (N=1-20) cluster impacts onto a graphite HOPG surface in order to investigate the size and energy dependence on the sputtering effect. Small clusters at high collision velocity easily induced collision cascade in the target leading to non-thermal energy dissipation and that resulted in the saturation of the sputtering yield at higher collision energies while larger clusters showed energy concentration in a small area explained as the group effect. The sputtering yield corresponded well with the experimental results.

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The quantum molecular dynamics method was applied to a simple system composed of an electron, ions and surface molecules in order to investigate an energy transfer process to a thermo or secondary electron in surface collision process of an ion or an atom. A time dependent Schrodinger equation for a thermo or secondary electron was solved by the splitting operator method and Newton's equations for ions and surface molecules were solved by the molecular dynamics method. With the increase of interaction between the observed electron and the colliding ion the energy transfer to the electron during ionic collision process increased. Energy transfer to the observed electron through the potential energy term between the colliding ion and the observed electron and through the potential energy term between the surface molecules and the observed electron were dependent on the colliding energy of an ion.

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In this paper, Dissipative particle dynamics (DPD) simulation is performed for fluid argon. Real argon atom is prepared as a dissipative particle and the validity of model equation of DPD method is examined. Conservative force that is derived from Lennard-Jones potential is applied. Equilibrium DPD simulation was conducted for 864 argon atoms system at 100K and 200K. Thermal conductivities were calculated with Green-Kubo formulae. The simulation results of the thermal conductivity by DPD method are compared with molecular dynamics (MD) simulation results. The simulation results of DPD method agree well with that of MD method independently of random force parameter and nondimensional number density and temperature. This result means that the validity of model equation of DPD simulation.

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Condensation coefficients were obtained experimentally through dropwise condensation on the silicon surface with hydrophobic coating. The experiments were conducted in a vacuum chamber at low pressure around 3kPa in order to reduce the accumulation of non-condensable on the liquid-vapor interface. Experimental results of heat transfer coefficient show good agreements with previous studies. Also, the condensation coefficients were estimated in the range of 0.2-1.0 if we consider the constriction resistance of dropwise condensation.

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We have developed hybrid numerical simulation codes to investigate the dynamics of nanobubbles. The idea is based on a combination of a molecular dynamics (MD) technique and a computational fluid dynamics (CFD) scheme with the Lattice Boltzmann method. In the hybrid simulation, the simulation cell is divided into two parts. The inner region containing a bubble (or bubbles) consists of sufficiently large number of particles and is treated with the MD method. The outer region is treated with CFD scheme. The boundary between the inner and outer regions is movable and driven with the pressure difference between the two regions. To deal with the moving boundary, we adopt the level set method. We will show non-spherical deformation of a bubble and investigate dynamic properties of nanobubbles, e.g., pressure and shape change.

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A micelle is the self-assembly of surfactant molecules formed in surfactant aqueous solution. The micelle has various forms such as a threadlike, spherical, discoid, and bilayer. Particularly, the threadlike micelle has the great possibility of the application in the industry, utilizing the uniqueness in its formation. However, an overall understanding of the formation dynamics of the threadlike micelle has not been accomplished, because of the so-called 'mesoscopic problem' in dynamics. In this paper to clarify the multiscale dynamics in the threadlike micelles we adopted the Dissipative Particle Dynamics (DPD) simulations. Moreover, the shear stress was put on a similar system, and it comnpared it without shear stress.)

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In this paper, molecular structure and heat transfer properties at the interface of alkanethiol SAMs (self-assembled monolayers) adsorbed on Au surface and toluene solvent are investigated by using molecular dynamics simulations. Heat transfer properties at the solid-liquid interface have not fully been understood as compared to the solid-solid interface because the phonon-based theoretical framework breaks down. In this study, we focus on the SAM-solvent interfaces on the solid substrate which are widely used not only in the industrial devices, but also in the biomaterials and biodevices. By molecular dynamics simulations of SAM-solvent systems, the molecular structures of toluene and SAM molecules are obtained and the difference of the heat transfer property between the SAM-modified interface and the bare solid-lquid interface (Au-toluene) is discussed.

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This paper describes how to calculate a volumetric solar heat collection with our-own separation method of direct-scattered component of solar radiation measured by a proving test at experimental site. In the case of calculation, using a simple model for real transparent hot house, firstly solar radiation incident on an each surface which consists of surfaces of the hot house was calculated, next the solar heat collected on the surface was calculated producing 0.6 times of collection rate of the house surfaces. Consequently, the calculations were well applied to the experimental results when proving test on a fully passive solar lumber drying house was executed, it was made clearly the rate of volumetric solar heat collection to the horizontal solar radiation incident on a floor reached to 2.2〜3.5 which corresponds to the collection efficiency of 130%〜210%.

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The purpose of this study is to create an environmental cleanup material at low cost and low loading. In this report, wood chip with cellulose and lignin was crushed to the wood powder state. By two step processes of oxygen plasma irradiation and sodium amide gas plasma irradiation, sodium was adsorbed by the ionic bond on the surface of the wood powder. Sodium ion appeared when the created sodium carrier was put into the water, and the adsorption effect of the chlorine by the carrier was confirmed.

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This paper reports on the pyrolysis and gasification behavior of biomass and the relationship between biomass-char property and gasification rate. The effect of pyrolysis conditions on the product yield has been studied, and the gasification kinetics of biomass-char has been revealed by measuring the rate of weight loss during reaction with CO_2, as a function of temperature. First-order kinetic rate constants are determined by fitting the weight loss data using a random pore model. The relationship between char structure and CO_2 gasification reactivity and pyrolysis product were investigated in the range of 15 to 600℃/min (heating rate) at 0.1Mpa, and 0.1 to 3Mpa (pyrolysis pressure) at 15℃/min. The experimental results indicate that the yields of total volatile matter decrease as pressure increases and the reactivity of the biomass-char is determined by pyrolysis condition. The CO_2 gasification rates in char generated at 0.1MPa exhibited approximately twice values compared to those at 3MPa. This is because the uniformity of carbonaceous structure rises with increasing pyrolysis pressure. The uniformity of carbonaceous structure would affect CO_2 gasification reactivity.

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This paper refers to the experimental performance evaluation of a tubular type steam reformer for indirect internal reforming in solid oxide fuel cell power generation systems. In the experiment, the spherical ruthenium catalysts were filled inside the reactor. Methane and steam mixture was supplied into the reactor, which was set inside the electric furnace. The composition of dry gas after reforming was measured with a gaschromatographequipment. Throughouttheexperiments, weobtainedtherelationshipbetween the methane conversion ratio to the space velocity. It was clarified that the reforming temperature, the steam to carbon ratio and the fuel flow rate affected the methane conversion ratio, especially the conversion ratio was strongly influenced with the fuel flow rate. In the case of the smaller fuel flow rate, whole reforming reaction reached an equilibrium state. However, the excess fuel lead to the lower conversion ratio.

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The flame reactors have been suitable to produce a large quantity of the TiO_2 fine particles with having the photo-catalytic ability. In attendant to the flame temperature, which decides the formation of the TiO_2 fine particles, the temperature measurement has been studied using laser speckle method. From the results, double flames are formed both for the diffusion combustion and the premixed combustion. Furthermore, the movement of speckle pattern, which means the change of temperature, decreases with the equivalence ratio for the diffusion combustion. On the other hand, the movement increases with the equivalence ratio for the premixed combustion.

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Fuel-rich solid propellants have been studied to use them for hybrid rocket motors. In this paper, the combustion characteristics of the propellants were investigated. A one-dimensional flame model was developed for the solid-propellant combustion. The gaseous flame was assumed to be quasisteady, premixed, and laminar with a one-step overall chemical reaction. The steady burning rate of fuel-rich solid propellants was calucultaed by the flame model. As a result, the effect of the mixture ratio on the steady-state combustion was revealed theoretically. In order to compare with the result, the linear burning rate of the propellants was measured at subatmospheric pressures.

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This study investigates low temperature startability of dimethyl-ether (DME) catalytic combustor as a small size heat generator. A procedure of DME pre-supply followed by mixture supply into the reactor shows great improvement of startability. With this procedure catalyst surface temperature increases caused by DME adsorption heat at the period of DME pre-supply and increased temperature promote catalytic reaction. When the period of DME pre-supply is excess, the reactor temperature turns decrease by increased heat loss in comparison with adsorption heat. Consequently, it is suggested that the optimum condition for DME pre-supply exists to give best startability of DME catalytic combustor with this procedure.

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To elucidate characteristics of a droplet flame as an elementary process of turbulent spray combustion, droplet combustion experiments in varying forced convection at high pressure were performed in microgravity. 1-butanole was used as a fuel and the maximum pressure was 1.0MPa. High-speed back lit images of burning droplet were obtained and time history of the droplet diameter was measured using image processing. Results showed that maximum velocity in oscillating flow is predominant for the burning rate constant, meaning that the classical quasi-steady assumption is not valid. Mechanism of this droplet combustion characteristic was discussed based on the ratio of characteristic time scales of flow oscillation and gas diffusion.

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It is planned to launch Orion Crew Vehicle to International Space Station, Moon and Mars by NASA. The fire protection is the most important problem in the cabin of low pressure, high Oxygen mass fraction and low gravity conditions. The experimental test of flame spread over flammable material in low gravity requires huge cost and it is actually unacceptable. This study tested upward flame spread over PMMA in different conditions of pressure, Oxygen mass fraction and gravity by numerical simulations. The flame spread speed and peak heat release fell as gravity was dropped at same pressure and Oxygen mass fraction conditions.

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The effects of pressure on outwardly propagating laminar and turbulent flames were studied for Iso-octane-air mixtures at the equivalence ratios from 0.8 to 1.4 and the initial pressures from 0.10 to 0.50MPa. Turbulence intensity, u' was set to 0.80 and 1.59m/s. The Lewis number of the mixture, Le was employed to quantify the thermo-diffusive effects on turbulent burning velocities. The ratios of the turbulent burning velocities at 30mm flame radius to laminar ones, U_<tn>(30mm)/U_n (30mm) increased as the turbulence Reynolds number, Re_<Lf> increased. And U_<tn>(30mm)/U_n(30mm) increased with the decrease in the Lewis number. Possible correlations of U_<tn>(30mm)/U_n(30mm) were developed in terms of U'/U_n (30mm) and Re_<Lf>/Le^2.

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The influence of the addition of hydrogen to propane mixtures on its local burning velocity is investigated directly. Hydrogen added propane mixtures having nearly the same laminar burning velocity with different rates of addition of hydrogen and equivalence ratios are prepared. A two-dimensional sequential laser tomography technique is used to obtain the temporal statistical relationship between the flame shape and the flame displacement. The local flame displacement velocity S_F is quantitatively obtained as the key parameters of the turbulent combustion. The obtained S_F is also discussed by the concept of Markstein number.

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A comparative study of stochastic modeling of turbulent combustion has been conducted in the configuration of jet diffusion flame. Flamelet model, multivariate presumed probability density function (PDF) model, and PDF model are evaluated in terms of numerical accuracy. Fuel is a mixture of hydrogen and nitrogen. A fast chemistry is assumed in the flamelet model, a one-step irreversible reaction in the multivariate presumed PDF, and a detailed chemistry in the PDF model. The flamelet model overestimates the reaction than the others but shows an agreement with experiment results. This is attributable to turbulent models employed here. Therefore, the accuracy of combustion modeling strongly depends on the turbulent model of the flow field.

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Direct numerical simulations of ignition and propagating of n-heptane/air premixed flame in two-dimensional homogeneous isotropic turbulence are conducted to investigate the effects of turbulence and fuel species on ignition and propagation process. In the ignition process, eddies stretch the high temperature region and disturb its evolution. Compared with hydrogen/air mixture, the influence of turbulence on ignition is weak for n-heptane/air mixture. In the propagation process, strong eddies prevent propagating of the flame, and the flame propagates along the edge of eddies. The shape of flame in n-heptane/air mixture is more complex compared with that in hydrogen/air mixture. The heat release rate of n-heptane/air turbulent premixed flame is several times of that of one-dimensional laminar flame.

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The new turbulent combustion model, which is applicable to the premixed and diffusion flame was proposed. The model includes the laminar flame speed and the gradient of mixing fraction. Through the laminar flame speed, the effect of pressure in the combustor and the temperature of unburned gas were considered. To verify the model, two dimensional numerical simulation of the laminar counterflow diffusion flame was performed. The predicted distribution of the temperature was in good agreement with experimental data.

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This paper treats the fluctuation of methane-air premixed flames formed on multiple small tubes. Premixed flames were formed on individual tubes when the equivalence ratio was around unity. We measured the fluctuation of brightness intensity of premixed flames and obtained the RMS and power spectrum density of the brightness fluctuation. The obtained RMS was considerably small because premixed flames were stable. The RMS slightly increased by increasing the equivalence ratio. The 1/f spectrum appeared in low frequency range, and the sharp peak in the power spectrum density was found at sufficiently large equivalence ratios. The present results suggest that the analysis of the brightness fluctuation is applicable to the diagnostics of premixed flames.

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