Heat transport characteristics of liquid column oscillated forcedly in a straight channel with square cross section have been investigated experimentally. The channel was initially evacuated, and ethanol was charged to form a liquid column, which is called single component system. In addition, the ethanol was charged in the channel with air in the gas phase at atmospheric pressure, which is called two components system. The fluctuations of vapor pressure and wall temperature with liquid column oscillation were measured at high-speed sampling rate. The mechanism of heat transport is discussed on the basis of these measurements.

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This paper focused on thermosyphon heat pipe as a cooling of high heat density by high performance electronic devices. The flat-plate type was determined from the relationship between the installation and space. The purpose of the present work was the design of high performance heat pipe to understand the heat transfer characteristics of flat-plate thermosyphon. The effect of the channel which was designed in the thermosyphon, working filling ratio and thermosyphon configuration were examined on the thermosyphon performance. As the result, the thermosyphon performance was improved by the design of channel in high heat input. The influence of cooling section's configuration on thermosyphon performance was examined.

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A mathematical model of Oscillating Heat Pipes (OHPs) with check valves has been constructed. The mathematical model was a one-dimensional slug flow model. Movement of liquid slugs was governed by pressure differences among vapor plugs and by pressure drops in the tubes. Check valves were reproduced by change of liquid slug's momentum. As a result, check valves caused the circulation flow in OHP.

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Vapor pressure and saturated liquid density for HFE7100 were measured in the temperature range from 300 K to 400 K at intervals of 10 K by using the extraction method. Experimental uncertainties are estimated to be 0.028 K for temperature, 0.4 kPa for pressure and 0.8 kg/m^3 for density. Vapor pressure is obtained in the pressure range from 28 kPa to 629 kPa. Saturated liquid density is obtained in the pressure range from 1203 kg/m^3 to 1516 kg/m^3. On a basis of the present data, correlations of vapor pressure and saturated liquid density were formulated using fourth-order polynomial equation. The maximum deviations from correlations were 1.1 kPa for vapor pressure and 1.2 kg/m^3 for saturated liquid density, respectively. The standard deviations from correlations were 0.6 kPa for vapor pressure and 0.4 kg/m^3 for saturated liquid density, respectively.

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The apparatus for measuring saturated vapor density of working fluids was constructed. Extraction method was adopted as a principle. The apparatus has two cells whose both volume is about 50 cm^3. These are called main cell and sub cell which are immersed in a thermostat. The sub cell with a pressure sensor is located above the main cell and valve is connected between the main cell and the sub cell. After the sample filled in the both cell, sample in the main cell is filled at a state of vapor-liquid equilibrium, and sample in the sub cell is filled at a state of saturated vapor. And then, the sample in the sub cell was recovered to the recovery cell using liquid nitrogen and its mass was measured. Saturated liquid density was obtained from the mass of recovered sample and inner volume of the sub cell. The apparatus is designed for measurement in the temperature range from 323 K to 473 K.

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This paper reviews the recent trend in the developments of Helmholtz energy equations of state. In I990s the equations were developed mainly using a linear least square method, and a step wise regression analysis was employed to select an optimum set of terms from a large bank of terms. This method is fast, but requires a large amount of experimental data. Equations obtained from this method consist of 25-50 terms. Recent approaches are based on a nonlinear least square algorithm, where not only deviations in calculated values but departures from thermodynamic requirements are included in the sum of square. These approaches are very time consuming, but can result in equations with 15-20 terms.

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Within a few years, definintion of thermodynamic temperature T may be replaced by a definition, E = kT, using the Boltzmann constant, k, or the universal gas constant, R(= kN_A), where N_A is the Avogadro constant. A gaseous speed-of-sound measurement (AGT, acoustic gas thermometry) reported by Moldover et al. in 1988 is the most promising approach to determine R within a relative uncertainty beging 1.8 ppm. Other experimental approaches such by a dielectric constant or refractive index, uncertainties are still several times larger than AGT. Gas density thermometry (GDT) is also a possible experimental approach, due to an improving measurement performance realized by a silicon single-crystal sphere as a solid density standard. In this paper, feasibility of the GDT using a silicon single-crystal was examined and concluded that it is possible to determine the universal gas constant with a relative uncertainty of 3.5 ppm by pressures, densities, temperatures and molar mass of argon.

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Hydrogen has attracted attention as an energy carrier, and the development of hydrogen refueling stations is an urgent issue to promote the diffusion of fuel cell vehicles. Accurate thermophysical properties of hydrogen over a wide temperature and pressure range are essential for the design of safe and efficient hydrogen refueling stations. In this study, PVT properties of hydrogen have been measured by a magnetic suspension densimeter with an uncertainty of 0.05 % at 100 MPa. In addition, the vibrating wire method was adopted to measure the viscosities of hydrogen using a semi-circular tungsten wire, and the viscosities from 296 K to 573 K and up to 0.7 MPa were measured.

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A decision at the 24th General Conference on Weights and Measures (CGPM) has been made to adopt a dramatic change of the International System of the Units (SI). The unit of thermodynamic temperature, kelvin, is likely to be redefined based upon the fundamental constant k_B, the Boltzmann constant. To this concern, leading national metrology institutes are developing thermodynamic thermometry systems to acquire reliable data for the Boltzmann constant to ensure this redefinition to take place smoothly. Another issue following the redefinition of kelvin is the deviation between the thermodynamic temperature and the temperature scale. This paper describes the background, the aim and the progress of the development of acoustic gas thermometry (AGT) at the National Institute of Advanced Industrial Science and Technology (AIST).

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The Scanning Thermal Microscope (SThM) which can measure temperature in micro to nanoscale has been studied. Previously, it was demonstrated that active thermometry with an analog feedback system can measure quantitative temperature. To reduce time and effort for preparation and operation of the SThM, we started to develop a digital system and an auto tuning sequence, which easily adjust feedback parameters for each individual probe and quickly evaluate probe property. The test of the auto-tuning sequence with a chip calorimeter showed a quick calibration of a temperature sensitivity of a thermopile sensor and determination of thermal resistance and heat capacity through a frequency response sequence. The test of the active thermometry operation showed that the system can control probe temperature similar to sample temperature with proper feedback parameters.

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We have been developing a bent-tip type multifunctional cantilever probe for the purpose of improving a shape measurement performance in SThM. Firstly, a fabrication process of the bent-tip probe was studied by making a prototype probe with the MEMS techniques. Additionally, the bent-tip probe was tested in a topography performance by measuring a blind angle showing a blind region below a step and a probe tip radius of the curvature. As a result, it was shown that the blind angle of the bent-tip type reduced to half of that of a straight tip type cantilever previously used. Shape measurement performance at a step was improved. The tip radius of curvature was also evaluated to be similar to that of the straight tip type. It means that the bent-tip type will have the spatial resolution of several tens nanometer for flat surface sample as well as the straight tip type probe.

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In order to obtain the exact value of the latent heat of sodium alginate solution envisaged the use as a cooling-lubricant of grinding, we were examined for the effects of various factor in the latent heat measurement. The sodium alginate solution is structure deformation by keeping a long period of time at 50℃ or excess. So we propose a new method for measuring latent heat. However, it occurs error in the latent heat measurement. The error cause was examined in detail.

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Diffusion coefficient and Soret coefficient are important for understanding mass transfer in fluid mixtures. In the present study, we have developed the theory for measurement of cross diffusion coefficient and Soret coefficient in ternary fluid mixtures by Soret Forced Rayleigh Scattering (SFRS) method. In this measuring principle, two probing lasers of different wavelength are used. Difference of compositional dependence of the refractive index (∂n/∂c_i) by wavelength causes two different signals. This enables analysis for obtaining four diffusion coefficients and two Soret coefficients in ternary solution. ∂n/∂c_i and ∂n/∂T of mixture with n-Dodecane, Isobutylbenzene, and 1,2,3,4-Tetrahydronaphthalene (equal mass fraction) have been measured.

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This study is intended to measure the humidity into the space that it is hard to measure with the existing humidity sensor. The humidity sensor is the tip of 1mm. This sensor is made of T-type thermocouple and polymers. Finally, there polymers are two kinds of epoxy resin and diamine. This sensor is very influenced by ambient environment. The thing to affect in particular is air temperature and size of the measurement space and velocity of feed air. Therefore we checked influence of the temperature and size of the measurement space. As a result we understood that psychrometer coefficients increased if ambient temperature was high.

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We have developed Micro Optical Diffusion Sensor (MODS) based on a laser-induced dielectrophoresis (LIDEP), enabling high-speed measurement with a small sample volume. The diffusion coefficient is measured by observing a diffusion process of the samples. A sinusoidal concentration distribution induced by LIDEP is formed in microchannel, and the mass diffusion is observed by the First-order diffracted beam. The formation of the concentration distribution is a key of high-sensitive detection because it influence diffraction efficiency of the probing laser. In order to gain the measurement sensitivity, the numerical analysis of the DEP force distribution is required. In this paper, a new design of cell that can achieve the high-sensitive is presented.

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Many researchers have investigated the optical properties of human skin in vitro and in vivo. The optical properties in vivo provide critical information for the medical, cosmetics and computer graphics fields. Some authors have proposed a method for estimating the optical properties in vivo. In these methods, the skin was assumed to be homogeneous. However, human skin has nonhomogeneous optical properties. Therefore, in this study, we proposed a method for estimating the distribution of optical properties in plane direction in vivo by using square patterned irradiation. And we succeeded to estimate the distribution of optical properties of human skin including a freckle by using the present method.

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We have measured the out-of-plane thermal conductivity of YBCO thin film (1.0μm in thickness) in the temperature range from 5 K to 300 K by photothermal reflectance method as preliminary measurement. Measured value exhibits temperature dependence of same tendency as bulk value, but the absolute value is smaller. Subsequently, we have performed measurement under high magnetic field up to 7 T below critical temperature (90 K). By changing the intensity of magnetic field, phase lags of temperature response are changed. This indicates existence of magnetic field dependence of the out-of-plane thermal conductivity for YBCO thin films.

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The great advantage of the aqueous Li-air battery is that the discharge reaction product LiOH is soluble in H_2O; however, LiOHH2_O precipitates in the air-electrode when concentration excesses the solubility. It is considered to cause cell performance degradation, and its mechanism needs to be clarified. In this study, we succeeded to observe precipitation of solid phase on carbon fibers after discharge process and charge/discharge cycle by using a soft X-ray inclined CT. Then, the charge/discharge characteristics suggested that the solid phases degraded cell performance due to the concentration overpotential of O_2. The solid phases did not disappear despite charging because OFT was provided from the bulk before they dissolved.

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An anode-supported honeycomb SOFC can achieve high volumetric power density and improve thermo-mechanical durability at high temperatures. We have so far fabricated the honeycomb cell with a cathode layer of LSM and an electrolyte layer of 8YSZ on a porous anode honeycomb substrate of Ni/8YSZ. The anode-supported honeycomb cell exhibited promising volumetric power densities. In the present study, current-voltage and current-power density characteristics of the cells having different porous substrate thicknesses and anode/cathode flow channel configurations are studied under different flow rates and partial pressures of fed hydrogen to clarify the effect of fuel transport in the anode porous substrate.

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One of the problems of solid oxide fuel cells is current distribution since it decays total cell performance and efficiency. Current and temperature distributions also cause the electrode degradation thermo-mechanically and chemically. In particular, this behavior is complicated in the case of the hydrocarbon fuel. Elucidation of those distributions is therefore required to optimize the gas flow condition under operation, and to develop new cell design with higher performance and durability, and diagnosis method for the distribution. The aim of this work is thus to measure the current distribution in an anode-supported microtubular cell having segmented cathodes, comparing with the measured surface temperature at each segmented cathode caused by the current distribution.

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Numerical investigation on two-dimensional flow fields and reaction distributions in a Vanadium redox flow battery with single and double fiber electrode geometry has been performed. Simulation results in a single fiber geometry showed cell performance deteriorated by less electrolyte flow velocity and formation of concentration boundary layer around the fiber electrode in high current density operation. In a double (tandem) fiber geometry, local depletion of reactive species around a 2nd fiber electrode was observed, resulting in inhomogeneous current distribution on the surface of electrodes that caused excess overpotential.

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Proton exchange membrane fuel cell (PEMFC) is comparatively efficient, environment friendly and suitable to a wide range of applications. For further high performance, water management is needed. The management system has not been completed because of not elucidated transport phenomena inside PEMFC. So we approach numerical analysis to clear phenomena. Water, heat, and chemical species transport are included in the phenomena. Two-dimensional, two-phase unsteady-state PEMFC model was developed to investigate the effect of the chemical species transport and temperature distribution on the electrochemical reaction kinetics in catalyst layer. In this time, we compared Non-Isothermal and Isothermal system to investigate how the distribution of temperature affects power generation performance.

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Microporous layer (MPL) has a dramatic effect on water management in polymer electrolyte fuel cells (PEFCs), because its microstructure reduces liquid water accumulation at cathode CL/GDL interface. In this paper, the microstructure of MPLs fabricated from different carbon black (CB) loadings was observed using scanning electron microscope (SEM). Furthermore, the effect of CB loading of MPL on the liquid water transport and performance characteristics in a PEFC was experimentally investigated. It was found that several particle agglomerates are formed in the MPL with high CB loading of 4.0 mg/cm^2, and effective in alleviating water flooding in the cathode electrode.

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Water management in polymer electrolyte fuel cell (PEFC) is closely related to cell performance. At high current density, the excessive water obstructs oxygen transport, and the cell performance greatly decreases. In order to improve the cell performance, it is necessary to remove effectively the generated water. In this study, to improve the water management in gas channels, novel gas channel with micro-grooves is adopted. The micro-grooves are manufactured inside gas channel walls. The generated water from gas diffusion layer is removed through the micro-grooves to upper-side of gas channel by surface tension and shearing force that is generated by air flow. The performance of the PEFC with micro-grooves was examined in various experimental conditions. As the result, the PEFC with micro-grooves showed high performance.

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We report the effect of improving the indoor thermal environment by the case, which was adopted in the leading projects adopted by promotion program for CO_2 emission reduction projects MLIT (Ministry of Land, Infrastructure, Transport and Tourism) to implement. This case is the external insulation refurbishment on the existing apartment buildings whole less example. We confirmed that the indoor thermal environment of non-room as well as room was improved by the refurbishment. In addition, in comparison of the changes in the thermal performance, it was found that the effect of improving the airtightness performance by installation refurbishment was great.

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The aim of this study is to make clear that hygrothermal characteristic inside the wall in the well-sealed and high-insulated dwellings in hot and humid areas by transient simulation. Thus we simulated the cases with three kinds of damp-proof membranes. The materials of membranes were polyethylene, polyamide and copolymer resin on polypropylene. Concurrently, we investigated the effects of the membrane on the wall's hygrothermal aspect. In the case without membrane, relative humidity at inside wall was higher than the other cases. If the polyetylene membrane was put on, humidity was higher than 80%RH outside the membranes in summer. When the other two membranes were put on, the humidity inside wall kept lower than 80%RH. Therefore, in hot and humid area, the wall must have the damp proof membrane and pay attention to the humid outside the membrane in summer.

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This paper quantifies whole-tree transpiration rates for urban tree species using a weighing machine. A novel weighing system was developed for measuring the whole-tree transpiration rate with a high degree of accuracy. The daily transpiration amounts of the eleven urban trees, whose heights ranged from 3 m to 7 m, varied from 10 kg to 30 kg under clear skies and water supply conditions during the summer season. The ratio of the daily transpiration amount to potential evaporation was 0.6 ± 0.3 when using the standard of crown projection area. The peak values of transpiration rates for tree species that showed large transpiration amounts were over 3 kg/h. This value is equivalent to more than 2 kW of latent heat flux.

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Tall buildings often have various troubles during winter caused by the stack effect. The stack effect is a kind of natural convection. Warmer indoor air than outdoor obtains the buoyancy and it brings vertical pressure difference in the building. This pressure difference causes draft, sound, and door problems. It is sometimes quite difficult to solve these problems, especially when the building is already used. These problems becomes more severe when the building height is taller. Recently, similar problems caused by other factors, such as solar heat through glass walls, are also increasing. In this paper, various problems caused by the stack effect are shown and the countermeasures against these problems which the authors have tried are described.

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To investigate the thermal environment in railway tunnels, temperature predictions by simulation are necessary. The authors made an acrylic model tunnel, sent the heated air inside of the model tunnel and measured the temperatures of the outer surface of the model tunnel and the air in the model tunnel. As a result, we found that it is possible to assume the outer surface temperatures to be isothermic. And, the analytical predictions of the steady state air temperature in the model tunnel showed good agreement with the measured values.

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It was shown by theoretical and experimental studies that high temperature and high pressure state is provided in the converging center by converging shock wave or imploding detonation. In particular, the imploding detonation can implode more effectively than the case of the shock wave. The authors examined the microorganism treatment technique using ultra-high pressure underwater shock waves in a steel pipe by the gas imploding detonation until now. The authors tried to confirm the effect of underwater shock wave generation by change minimum converging radial distance of imploding detonation, equivalence ratio and concentration of the nitrogen as diluent. As a result, effect of the equivalence ratio was small in comparison with the change in the minimum converging radial distance. Therefore, influence of diluent addition was different each minimum converging radial distance.

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Underwater shock wave, generated by the imploding detonation of propane-oxygen mixture, was applied for extinction processing of Water-bloom. We filled the water containing Water-bloom into a stainless steel pipe having inner diameter of 10.9 mm, and transmitted the underwater shock waves which have the maximum pressure of about 100MPa. As Water-bloom of the treatment experiments, Chlorella and Chlamydomonas were used. We found that the destruction rates of Chlorella and Chlamydomonas increase gradually with the increase in the number of times of shock processing. Although the maximum destruction rates of Chlorella and Chlamydomonas were, respectively, about 80% and 60% after 5 times processing, it turned out that the mortality rates of Chlorella and Chlamydomonas become 100% in one week later after shock processing.

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The effect of design parameters on natural convection heat transfer from horizontal heated surface with a heated cylindrical pipe is estimated experimentally. The heat transfer increased with increasing the heat flux of the horizontal heater. In the case of no flow reversal and flow reversal occurred in the heated cylinder, the heat transfer was affected by the aspect ratio and the heat flux of the heated cylinder, and the distance of the heaters. On the other hand, when flow reversal reached to the horizontal heater, the heat transfer had a little influence on the heated cylinder conditions. Nusselt number was expressed as a function of the modified Rayleigh number of heaters and the nondimensional height.

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The problem of forced convective laminar boundary layer flow of alumina water nanofluid over a flat plate is investigated in the present paper. Both analytical solution (i.e. the local similarity solution) and numerical solution based on finite difference method are obtained for the boundary layer problem in nanofluid convection. The results generated from the local similarity method are compared against those from the finite difference method. Comparison reveals that there is only minor difference between the local similarity solution and numerical solution of finite difference method. Thus, the local similarity method can be directly extended to the boundary layer flow of nanofluid convection over a flat plate.

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This paper describes the effect of the ration of the diameter and the length for thermal performance on natural convection in circle tube using numerical analysis. The velocity, pressure and temperature distributions are obtained by SIMPLE algorithm. The buoyant term is applied by Boussinesq approximations. The numerical conditions of tube diameter are 10, 15, 20 and 25mm, and tube length is L=1500mm. The inclined angle of the tube is 30 degree. The working fluid is water. Results show that the average velocity along the flow direction increases linearly with Grashof number Gr. However, the pressure drop decreases with Gr increasing. Also, the amount of heat removable increases with Gr.

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A numerical simulation of the T-junction channel flow with heat transfer has been carried out in order to investigate and observe a phenomenon of turbulent heat transfer and a turbulent mixing of temperature, in which a numerical simulation is conducted by using DNS method. In results of DNS, the detailed turbulent heat transfer and a turbulent mixing of temperature in T-junction are clearly given. Also, two conditions of thermal field at inlet channels are given in order to observe the influences of thermal inlet condition, i.e., a uniform temperature without temperature fluctuation or a non-uniform temperature with temperature fluctuation is given at the inlet channel. In the results, differences of heat-transfer and turbulent mixing of temperature at the separation region of T-junction are revealed. On the other hand, a large eddy simulation of T-junction channel is also carried out in order to evaluate predictions of LES and investigate a T-junction flow with higher Reynolds number.

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This paper describes the onset of free convection around a 1 mm diameter steel sphere heated inductively in water using a light absorption imaging method with a wavelength of 1150 nm. Since the concentric absorbance distributions formed by pure thermal conduction are distorted by free convection, the onsets of free convection are determined by measuring the position of a centroid of a region with a certain absorbance and compared to Rayleigh number.

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Intensive cooling of combustor liner is essential for high-temperature gas of gas turbines, and film cooling is adopted as its cooling method. In this study, both film cooling effectiveness and heat transfer coefficient were experimentally measured in one run of experiment using two different thermal-conductivity materials as liner wall. Three-dimensional heat conduction was taken into account in the data reduction. Four different wavy liner-walls were examined in which three geometric parameters were varied: cooling-hole diameter (d), wave half amplitude (δ), and shift of trough location (S). The present results using the orthogonal table showed that small d and large o and S were preferable for effective film cooling.

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Photo-rheological fluids(PRFs), which have light-tunable rheological properties, have interesting potential in miniaturized channel devices due to a high affinity for light converging. To provide a high miniaturized efficiency heat exchanger, the authors are aiming at controlling the heat transfer rate actively with PRFs as a working fluid. In this study, PRFs consist of cationic surfactant(cetyl-tri-methyl-ammonium bromide (CTAB)), sodium salicylate (Nasal), and ortho-methoxy-cinnamic acid (OMCA). OMCA is photoisomerized from a trans-form to a cis-form upon exposure to UV light. As a result of the experiment, both mean heat transfer coefficient and pressure loss penalty were decreased with an increase in the exposure time, which leads to actively control heat transfer performance with UV light.

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There are several methods for heat transfer enhancement. For example, one can attach various fins on the heat transfer surface, process the surface roughly, insert twisted tape, and so on. These methods increase the heat transfer coefficient or area by manufacturing changes to the heat transfer surface. However it is necessary to consider the problem on account of processing heat transfer area. In this study, the repeatability of heat transfer enhancement effect by under the condition inserting metallic wire was evaluated. It was found that an amount of removed heat was stable bur a pressure drop changed widely under the same Reynolds number.

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Airfoil heat exchangers realize a light and compact intercooled and recuperated aviation gas turbine. In order to clarify the effect of airflow velocity on heat transfer performance of the airfoil heat exchanger, a cascade of three airfoil heat exchangers were installed in a subsonic wind tunnel. Further, an inverse heat transfer method and a least square method were applied to the experimental results to estimate air Nusselt number. In the case that airflow is heated by the airfoil heat exchangers, with increase of air Reynolds number, the average air Nusselt number increases because the heat transfer rate increases and because the average temperature difference between airfoil temperature and air adiabatic temperature decreases.

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Heat transfer experiments were carried out for viscoelastic fluid flow in a serpentine channel under low Reynolds number conditions (Re=0.32〜1.6). Local heat transfer characteristics were measured from the entrance to the developed region. Water solution of polyacrylamide was used as viscoelastic fluid. Nusselt number increased markedly in the viscoelastic fluid case compared with the Newtonian fluid case. This was attributed to the single longitudinal-vortex-like secondary flow generated in the channel. In the downstream region, the flow core region was located adjacent to the channel top and bottom walls. This position fluctuated largely particularly when passing the inflection point. This led to an additional low-frequency fluctuation of the Nusselt number, and heat transfer enhancement.

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Premixed combustion is one of the most efficient techniques to reduce NOx emission. But it is necessary to mix gaseous fuel with air sufficiently before the mixture burns. In this study, we present an instantaneous measurement of 2-D mixing behavior in a closed cylindrical burner by acetone-LIE in the both cases of unburned and burned conditions. It was clarified the relationship between acetone concentration and acetone-LIF intensity in a cylindrical glass using high-quality quartz cylindrical glass and a polarizing filter. The mixing and flame characteristics using various fuel nozzles are discussed based on instantaneous fuel profiles in unburned and burned conditions.

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Effect of flame stretch on CH_4/air ultra lean co-rotation counter flow premixed flame was investigated by numerical simulation. Counterflow twin flame and co-rotating counterflow twin flame were compared. The result shows that the flame stretch under ultra lean conditions is very small. In the case of ultra lean conditions of co-rotation counterflow twin flames, local burning velocity and radial velocity gradient at the flame front are very small. They are extremely small compared to those of non-rotating counterflow twin flames and ordinary lean co-rotating counterflow twin flames. In addition, the flow velocity at the flame front is also small. We could not determine whether co-rotating counterflow twin flame suffers the effects of flame stretch or not, since the flow fields of these flames are different significantly.

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Flame-wall interaction is an important phenomenon on combustors. Especially, the influence of wall on the flame characteristics in small scale combustors becomes larger than that in normal scale ones because of their large stuface-to-volume ratio. In this study, the influence of stuface reaction and heat-loss on reactant consumption and heat release rate of propane-air mixture is investigated using numerical simulation. As a result, it is found that reactant consumption rate is the same value for active or inert wall and for all wall temperature conditions. On the other hand, heat release rate for the active wall condition is smaller than that for inert wall condition.

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In this study, the mechanism of high speed flame propagation in narrow combustion chamber have been experimentally investigated with a high speed video camera. The combustion chamber has a narrow channel of which width are variable ranging L=1-2mm was used. The propane / air and methane / air mixture were ignited at the large cavity which was equipped at the one end of the narrow channel. Results showed that, the flame could be propagated through the L=1 and 2mm channel for the both of CH4 / air and C3H3 / air mixture although the channel width was less than those quenching distance. Moreover, it was found that the maximum flame speed in the combustion chamber was over 1.5 times higher than the laminar burning velocity.

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This study is performed to examine experimentally the effects of dilation gas types (N_2, Ar and CO_2) and dilution rates of N_2 on the burning velocity of the stoichiometric methane-oxygen-dilution gas premixed meso-scale spherical laminar flames with the flame radius r_f < approximately 5mm. The radius and the burning velocity of meso-scale flames are obtained by using sequential schlieren images recorded under appropriate ignition conditions. It is found that the burning velocity at the same r_f has tendency to increase not only with the mixture diluted with CO_2 at the same laminar burning velocity, but also with decreasing the dilution rate at the stoichiometric mixture.

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Turbulent burning velocity of spherically propagating premixed flame continues increasing during flame propagation. The flame front area is considered to be the most dominant factor for turbulent burning velocity. In this study, fractal analysis was conducted for stoichiometric spherically propagating premixed turbulent H_2/CO/O_2/CO_2 flames. Variations of fractal characteristics, such as fractal dimension, inner-cutoff and outer-cutoff scales with flame radius were investigated. Then, the correlation between turbulent burning velocity and flame front area estimated by fractal analysis was investigated.

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To investigate fractal characteristics of turbulent premixed flames with mean shear, direct numerical simulations of hydrogen-air turbulent jet and V-shape premixed flames are conducted. From fractal analysis with box-counting methods, it is revealed that fractal dimensions of flame surfaces of jet and V-shape flames increase in streamwise direction. The fractal dimensions calculated with a three dimensional box-counting method reach about 2.52-2.57 in downstream region where turbulence is fully developed by mean shear. An expression proposed by Shim et al. gives good predictions for inner cutoffs of turbulent premixed flames with mean shear and in a high pressure condition when flame surfaces are sufficiently distorted by turbulence.

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Three-dimensional direct numerical simulation of methane-air turbulent premixed planar flame propagating in homogenous isotropic turbulence is conducted to investigate local flame structure in thin reaction zones. GRI-Mech 3.0 is used to represent methane-air reactions. For a better understanding of the local flame structure in thin reaction zones, distributions of mass fractions of major species, heat release rate and temperature are investigated. To clarify effects of turbulence on the local flame structure, the statistical characteristics of flame elements are also revealed. In the thin reaction zones, the mean flame thickness increases about 3% that of laminar flame, although most of the flame elements are stretched in the tangential direction. An asymmetrical dependence of flame thickness on flame front curvature is observed.

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Ammonia is expected as a hydrogen energy carrier and a carbon-free fuel. Because the combustion intensity of ammonia is weaker than that of hydrocarbon fuels, improvement of combustion intensity is required. In this study, combustion characteristics of ammonia/hydrogen/air flames were investigated using a constant volume combustion chamber and a nozzle-type burner. The laminar burning velocity monotonically increases with hydrogen addition. The Markstein length varies non-monotonically with hydrogen addition. The scale of turbulent flame front wrinkles of smaller hydrogen concentration flames are larger than that of higher ones because of thicker flame thickness of smaller hydrogen concentration flame.

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