Measurements or PvTx (pressure-volume-temperature-composition) properties and saturated densities near the critical point for ternary 54 mass% R-1234ze(E) + 43 mass% R-32 + 3 mass% CO_2 refrigerant mixture were made by the isochoric method and by the direct observation of meniscus disappearance. One hundred and two PvTx property data for this ternary systems were obtained in the temperature range from 310 K to 385 K, and pressure up to 6.9MPa along six isochores. Moreover thirteen saturated vapor and liquid densities near the critical point for ternary 54 mass% R-1234ze(E) + 43 mass% R-32 + 3 mass% CO_2 refrigerant mixture were obtained in the temperature range from 345.9 K to 363.2 K, and densities from 240.6 kg/m^3 to 807.5 kg/m^3. The critical temperature T_c and critical density p_c were directly determined by the visual observation of meniscus disappearance.

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In order to clarify the possibility of measuring an oil circulation ratio (OCR), the speed of sound in a mixture of refrigerant/PAG oil has been measured in an HF01234yf refrigeration cycle. As the result, it is found that the speed of sound of the mixture depends on the value of OCR, although it is also affected by temperature and pressure. We think that it is possible for measuring OCR by means of measuring the speed of sound by taking into account the effected of temperature and pressure. In the case of immiscible oil, on the other hand, the measured value of the speed of sound changes significantly when oil drops pass through the sound velocity sensor. By using a mixing chamber, the variation of the speed of sound becomes small.

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in this study, the possibility or introducing R1234ze(E) and Rl/34ze(Z) as a low-GWP refrigerant ror high temperature heat pumps is investigated. As the first trial, their cycle performances were thermodnamically analized. Next, the drop-in experiments of R1234ze(E) and R1234ze(Z), using a compressor developed for R410A were carried out. As a result, in the range of test conditions, volumetric capacity of R1234ze(E) is enough large for 2 kW class applications at the condensation temperature ranging 75℃. Volumetric capacity of R1234ze(Z) seems to be enough at codensation temperatures over 100℃. These results suggest that R1234ze(E) and R1234ze(Z) can be strong candidate as low-GWP refrigerant for nigh temperature applications.

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There are numerous examples of electric heaters used in drying processes in factories. These heaters' capacities are small but energy consumption of them is large because of continuous operation, hence the development of highly efficient heat pump is expected. In our previous study, it was confirmed that a C0_2 heat pump can heat air up to 80℃ with heating capacity of 6 kW and COP of 4 under the condition that air inlet temperature is 25℃ and water mlet temperature is 30℃. In this study, efficiency improvement using with intermediate heat exchanger (IHX) and stability operation investigation in low heat source temperature were studied. It was found that IHX have limited effectiveness against COP improvement and that the heat pump can operate well in water inlet temperature of 5℃.

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This paper deals with decompression flashing flows through an adiabatic capillary tube with inlet subcooling and supercritical conditions. Blowdown experiments were carried out for a horizontal copper straight tube with the inner diameter of 0.7 mm and the length of 1000 mm. Boiling inception points were measured form wall temperature profiles, and critical mass flow rates were measured. The condition when a flow became to critical flow was specified by changing the exit pressure. As the results, for the inlet subcooling conditions, a boiling delay with thermal non-equilibrium around the boiling inception point was not observed. In this case, measured temperature profiles agreed well with numerical calculation results based on homogenous model.

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Recently, CO_2 heat pump water heaters have already been developed and commercialized from the viewpoint of energy-saving. However, further improvement on heat transfer performance is needed because the water side tends to be laminar flow in the gas-coolers of CO_2 heat pump water heaters. In this study, two kinds of heat transfer tubes are tested to clarify the effects of the tube geometries on the heat exchange performance and the pressure drop. The tested tube geometries are as follows:(1)twisted smooth (TS) and (2) twisted dimple (TD). In the C02 flow passages, the heat transfer performance though of twisted dimple tube is nearly equivalent to that of the TS tube although the pressure drop of the TD tube is higher than that of TS tube.

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In order to reduce the weight of air-conditioner, a new type micro-channel heat exchanger is applied for heat pump system. The micro-channel heat exchanger has high performance compared with a conventional fin and tube type heat exchanger due to its characteristic configuration. However, there are some challenges, when the micro-channel heat exchanger is applied for heat pump system. One of the most difficult problems is to improve the drainage of condensed water when it is used as an evaporator. To solve this problem, a new shape fin named "Insertion waffle louver fin" is proposed. In addition, the specifications of the heat exchanger, such as louver configurations and tube arrangement, are optimized for heat pump system. As a result, the micro-channel heat exchanger can reduce the weight about one third and the amount of containing remgerant about one fourth compared with a conventional fin and tube type heat exchanger

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Adsorption heat pump can cool with effective use of low-temperature waste heat, and can heat up as a thermally driven heat pump. Therefore, it is the useful technology for saving energy, and it has already been commercialized. However, Adsorption heat pump isn't popular because it is large and expensive in current technology level, this study deals with an adsorption equipment which has become a bottleneck of downsizing and cost reduction in adsorption heat pump. We significantly improve performance by applying "micro-fin" technology to the adsorption equipment.

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In this study, the flow boiling heat transfer characteristics of R1234ze(E) and R32 in a horizontal two rectangular multi-port tubes are investigated experimentally. The hydraulic diameters of tested tube are 0.85 and 1.13 mm, respectively. The effect of refrigerants and hydraulic diameters on the heat transfer characteristics are clarified. Heat transfer characteristics in the horizontal multi-port tubes are strongly influenced by forced convective evaporation especially in the region where the liquid film is thinner. The heat transfer coefficient of 0.85mm is higher than 1.13 mm. The heat transfer coefficient of R32 is higher than that of R1234ze(E) at entire the test range.

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In the present study, the characteristics of heat transfer and flow patterns are investigated experimentally for the falling film evaporation of pure refrigerant HCFC123 in a vertical rectangular channel with a serrated-fin surface. A transparent vinyl chloride resin plate is placed as the front wall for direct flow observation. The experiments are performed with the ranges of mass velocity G = 28〜70kg/(m^2s), the heat flux q = 20〜50kW/m^2 and the pressure P ≪ lOOkPa. It is clarified that the heat transfer coefficient a depends on G and q in the region of vapor quality x > 0.3 and the relation between heat transfer and flow pattern. Taking fin efficiency into consideration, heat transfer coefricient af is calculated.

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Experiments on the flow boiling heat transrer or HCFC123 and ammonia inside a internallv spirally grooved horizontal steel tube with a 12mm average inner diameter were performed. Experimental conditions of ammonia are 30 to 100 kg/(m^2.s) in mass velocity about 0.7 MPa in pressure, and () to 20 kW/m^2 in heat flux. The correlation for heat transfer coefficients from both fluids in the annular flow regime were developed based on the assumption that the heat transfer enhancement by the inner grooves on the heat transfer surface varies by mass velocity. Also the results in the separated flow regime could be correlated well using the present equation for the well wetted surface at bottom and the previously proposed correlation for the fluorocarbons on the thin liquid meniscus.

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In this study, we carried out experiments or three types or low-tinned tubes and externallv microscopic-grooved tubes using two fluorocarbon refrigerants: R123, which has a small ozone depletion potential (ODP); and R245fa, which has a zero ODP and a global-warming potential smaller than that of R134a. Both refrigerants are currently used in shell-and-tube condensers of turbo-refrigerators. The verified results, which are fundamental performances of condensation heat transfer, flow pattern of condensation liquid film, heat transfer enhancement effects and other related factors experimentally for those tubes and refrigerants, were reported in this paper.

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Numerical simulations of heat exchange at the regenerator ot thermoacoustic remgerator have been performed to estimate the heat transfer coefficient between the working gas and wall of remgerator. Simple heat conduction model is proposed in order to simulate the heat exchange between the working gas and refrigerator because the heat exchange phenomenon with sound wave and refrigerator is complex. As a result, average Nusselt number <Nu>^^^→ shows about 8.0 under the dimensionless parameter A { = ωd^2_0 / a) is less than 10, and it is found that the average Nusselt number is approximately expressed as <Nu>^^^→ = 8.0 + 0.07A^<0'8>. Furthermore, one dimensional simulation of thermoacoustic refrigerator is performed using above <Nu>^^^→. The simulation results agree qualitatively with previously reported feature of thermoacoustic refrigerator. However, obtained optimum operating point ω τ shift a bit toward higher value.

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Thermoacoustic cooler is one of promising technique for utilization of unused thermal energy. The object of this paper is to study acoustic field and temperature field in looped-tube-type thermoacoustic cooler. Using finite-difference time-domain (FDTD) method and energy equations, pressure, particle velocity and temperature were numerically simulated for various stack structure. By propagating sound in the stack, the temperature gradient was generated. It was also found that the effect of thermoacoustic cooling depends on mesh size in the stack. Summarizing these results, the mechanism of thermoacoustic cooling was discussed in relation to thermal response of stack and phase difference.

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Thermoacoustic cooling is one of promising technique tor utilization of unused thermal energy. The object of this paper is to stuay perrormance improvement of a loop-tube-type thermoacoustic cooler with branch resonator by optimization of the stack structure. In experiments, the cooling performance was measured by varying porosity of mesh in the stack and inner diameter of a phase adjuster. Firstly, the optimum thermal responsibility of stacks was determined in relation to phase difference between pressure and velocity of sound wave. Secondly, the structure of multi-mesh stack was designed to realizing local optimum thermal responsibility for distribution of phase difference in the stack. High performance of the proposed multi-mesh stack was indicated experimentally in comparison to single-mesh stack.

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A magnetic refrigerator system without a refrigerant in which heat is transported from the cold to the hot side through well-controlled thermal switches is proposed. For the purpose of fast heat transfer between neighboring magnetocaloric material slabs, the effect of configuration of magnetocaloric material slab comprised of high thermal conductivity material and magnetocaloric material on apparent thermal conductivity is evaluated under ideal condition by numerical simulation. It is clarified that the configuration affects the apparent thermal conductivity. The specifications to enhance thermal conductivity are also shown.

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The classical molecular dynamics simulation was carried out to study the effects of the strong magnetic field on the phonon transport properties of ionic crystals. Heat transport analysis for the alkali halide thin film model is conducted using nonequilibrium direct method. Strong magnetic flux density (〜10^6T) is applied perpendicularly to the direction of temperature bias. Thermal conductivity in the thickness direction decreases with increasing the magnetic flux density at low-temperature region (15K and 115K). In order to reveal the mechanism of change in thermal conductivity, spectral energy density (SED) is calculated and discussed.

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In this study we try to build a framework for phonon calculation. There are several steps to obtain thermal properties of nanostructure material: first step is force constants (FCs) calculation, after that we can calculate phonon properties with those FCs (LD calculation), and finally phonon dynamics can be simulated with the Boltzmann transport equation (BTE) for phonons. We introduce a LD and BTE calculation scheme in the LJ FCC crystal.

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We have developed numerical simulation tools for thermal analysis of solids with microscale structure, based on Boltzmann-type transport equations (BTE) lor phonons and electrons. In this paper, the basic concepts and models are described, the features of the simulators are given, and some results of test calculations with the prototype code are shown. First, general descriptions and comparisons are given on the BTEs of phonons and electrons. Based on simple models, we have developed test codes for both carriers. Simulations for two-dimensional solid systems was carried out as demonstration; one-dimensional energy transport in thin solid films to show the size dependence of thermal conductivity.

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Mass transport in liquids contacting solid surfaces exhibits complicated characteristics and an essential understanding of their mechanism is of critical importance. The interfaces between Si0_2 and water or IP A (iso-propyl alcohol) are typical system in the semiconductor industry, and the molecular-scale mass transport is being required to improve the lithography and cleaning process. In the present study, molecular dynamics simulations of Si0_2-water and Si0_2-IPA interfaces have been performed in order to investigate molecular-scale structure of the adsorption layers of liquid molecules and molecular transport characteristics.As typical terminations of Si0_2 surfaces, H- and OH-terminated ones were used and behaviors of liquid water and IPA molecules in the vicinity of these surfaces were analyzed.

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The nonequilibrium molecular dynamics simulations are conducted for the liquid wetting phenomena on a solid surface with a nanometer scale slit pore using SPC/E potential. The results show that the wetting phenomena of the slit pore depend on the liquid molecule-solid atoms interaction intensity and the width of the slit pore. There was a critical value of the liquid-solid interaction intensity which determines the wetting phenomena of the slit pore, and the critical value was changeable depending on the slit pore width. The calculation results didn't show pronounced differences qualitatively under the present simulation condition compared with the previous results obtained using Lennard-Jones(LJ) potential for liquid molecules.

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Carbon nanotubes (CNTs) have high intrinsic thermal conductivity and high surface-to-volume ratio, thus CNT-based fins is considered to be promising for hign performance device cooling. In addition, exploring the heat transfer between a CNT and gases is important not only for CNT-based gas sensors but also for scientific interest oi mterfacial heat transport. In this work, we have developed novel technique for measuring heat transfer coefficients between an individual carbon nanotube and surrounding gases (Air, N_2, Ar, He) using platinum hot film sensor. Measured heat transfer coefficients quantitatively show good agreement with estimated values by kinetic gas theory at atmospheric pressure but do not match with theoretical prediction at low pressure regime.

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Numerical simulations have been conducted to explore thermally and hyarodynamicallv developing forced convective heat transfer or nanofluids in a circular tube subject to a uniform wall heat flux. From the results, it has been concluded that, for certain cases of both alumina-water nanofluids and titania-water nanofluids, the anomalous heat transfer enhancement (i.e. the heat transfer enhancement exceeding the rate expected from the increase in thermal conductivity) is possible in most part of the entrance region except the region close to the leading edge.

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With the aim of enhancing the heat transfer in a heat exchanger made or silicon carbide (SiC),nanostructure formed by carbon nano tubes (CNT) were produced on SiC substrate by surface decomposition of SiC. The CNT nanostructure suriaces or hydrophobicity and hyarophilicitv were made to investigate the surface wettability. Their heat transfer characteristics were evaluated. Although the CNT nanostructure surfaces of hydrophilicity showed the heat transfer enhancement, it was much smaller than previous reports. It is thought that representative length of nanostructure influenced the heat transfer enhancement.

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We have proposed a "micro-beam" MEMS sensor for measuring thermal conductivity of fluids, The principle of the measurement is to determine the thermal conductivity from the temperature rise of the sensor at a steady state, which is achieved within a millisecond. Promising application of the sensor includes the thermal conductivity detector (TCD) for gas detectors and gas chromatographs. However, these applications require the sensor to be used in the flow. We therefore placed the sensor in the core of the air flow from a nozzle,and examined the effect of air velocity on the temperature rise of the sensor.

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Both n- and p-type bismuth telluride (Bi<_>2Te<_>3) thermoelectric thin films were prepared by coaxial type vacuum arc evaporation method. The atomic compositions of the as-deposited thin films and several annealed thin films were comparable to that of bulk Bi<_>2i'e<_>3. Their thermoelectric properties were measured. The Seebeck coefficient and electrical conductivity of the as-deposited thin films were improved by the annealing process. The measured figure of merits (ZT) of the n- and p-type Bi<_>2Te<_>3 thin films were 0.86 and 0.41 at 300 K when the annealing temperatures were 573 K and 523 K respectively. The in-plane thermoelectric generators were fabricated on a glass substrate through shadow masks. The output power was 0.9 μW at 77 K temperature difference.

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We investigated the effects of nano-structure (pore size and depth) on the thermoelectric properties of porous p-Bi_<0.4>Te_3Sb_<1.6> and n-Bi_<2.0>Te_<2.7>Se_<0.3> thin films.The cross-plane thermal conductivity of the porous p-Bi_<0.4>Te_3Sb_<1.6> and n-Bi_<2.0>Te_<2.7>Se_<0.3> thin films is 0.26 and 0.22 W m^<-1> K^<-1>, respectively. The value was significantly reduced from that of standard p- and n-type flush evaporated bismuth telluride films. The figure of merit (ZT) of the porous p-Bi_<0.4>Te_3Sb_<1.6> and n-Bi_<2.0>Te_<2.7>Se_<0.3> thin films is estimated to be ZT = 1.30, 1.47, respectively. We evaluated the thermoelectric power generation of porous and flat p-Bi_<0.4>Te_3Sb_<1.6> single cell. The output power is improved 25 % by nano porous structure.

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In this study, we clarified the effect of dip-coating rates on the film thickness and pore alignment of SBA-15 mesoporous silica thin films. It is known that film thickness increases with increasing the dip-coating rate, and film thickness also increases with decreasing the dip-coating rate to the ultraslow region where the capillary rise of the solution occurs on the dried film. Detail analysis of the synthesized thin films clarified that the pore diameter and interpore distance also depended on the dip-coating rate. This result suggests that the film thickness and pore alignment can be controlled without changing the physical-chemical properties of silica solutions and the size of template molecules, and thus the heterogeneous thin films can be synthesized by a dip-coating method with variable withdraw speeds.

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The adsorption-desorption isotherm of water on mesoporous silicas with pore diameters of 3.8 nm was measured at 298 K using a gravitational method. Type V adsorption-desorption isotherm with significant hysteresis was obtained. Capillary condensation was initiated around 0.4 - 0.6 relative pressure and complete pore filling with water occurred near the saturated vapor pressure. The kinetics of water adsorption-desorption was also investigated. The relaxation rate of water uptake in the capillary condensation state was much smaller than that in the layer adsorption or pore filling state. However, he relaxation rate increased with increasing the amount of stepwise change in relative humidity. This result suggests that, in the capillary condensation state, water transport mechanism in mesopores should be different from simple diffusion. Similar trend could also be observed in the desorption process.

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The evaporation behavior of a sessile droplet on the nano/microstructured surfaces is investigated experimentally in this paper. Three typical modes of evaporation of water droplets on surfaces are observed: one at constant contact radius (CCR), one at constant contact angle (CCA) and a mix of CCR and CCA. The CCR mode is the dominating evaporation mode for water droplet on the nano/microstructures surfaces even if the initial contact angle is larger than 90 degree. The pinning of the three-phase contact line is significant and large spreading coefficient is obtained at the nano/microstructured surfaces.

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We synthesized mesoporous silica SBA-16 thin films via evaporation induced self assembly by dip-coating method using F127 triblock copolymer to investigate proton transport phenomena in mesopores with highly ordered 3D cubic structures. Using the electrochemical measurements of ionic current under DC electric fields, we elucidated proton transport phenomena flowing through the mesopores of SBA-16 thin film. At low concentrations, unlike nonlinear behaviors of I-Vcurves of KCl aqueous solutions, those of HCl aqueous solutions were almost linear. These linear behaviors can be attributed to a decrease in electric potential barrier due to drop in surface charge density caused by active protonation with silanol groups on the inner surface of mesopores.

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The membrane electrode assembly (MEA) is the heart of a proton-exchange membrane fuel cell and the contact surface of MEA components plays an important role in the cell performance. In this paper, the effect of the contact surface structure of porous Si based MEA on the performance of the micro fuel cell is discussed. The porous Si substrate is fabricated by the anodic etching to the n type silicon substrate. It is found that the porous Si based MEA works well and a higher power density has been achieved than that of Nafion^R 212 membrane. Also, we find that the nano/microstructures of the porous Si have the advantage of reducing activation over voltage to improve the cell performance.

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The objective of the present study is to establish a versatile optimal control methodology for achieving desired spatio-temporal temperature distribution in various micro devices. Here we formulate the adjoint-based optimization scheme, which provides the optimal heat input so as to minimize the temperature variation in the active region of modeled vertical-cavity surface-emitting lasers (VCSELs). Surface heat flux from ring-type heater on the top surface is assumed as the control input. It is shown that the present control is effective for temperature control in VCSELs. The heat input from the ring heater is applied prior to the onset of the laser emission, which significantly suppresses the temperature variation.

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A novel rotational internal combustion engine is invented and investigated. No eccentric rotational component is used in this engine, resulting in vibration-free operation. The engine consists of rotor casing and two types of rotor; cycloid rotor and trochoid rotor. The shape of the cycloid rotor is characterized by epicycloid surface, and the trochoid rotor also superior-epitrochoid surface. In this paper, first, the typical configuration is shown, next, two procedure for designing the rotors are described in detail. Furthermore the design drawing of the prototype engine is given and its cyclic behaivior, the time variations of the chamber volume and the estimated pressure are indicated. The result of detail investigation for geometry of the engine configuration shows that the most appropriate combination of numbers of cycloid tooth and trochoid cavity is Nc:Nt=2:3 for engine compactness and compression ratio.

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To improve internal combustion engines, it is critical to measure the temperature distribution of their walls. Lifetime-based temperature imaging was performed in this study. The uncertainty was ±2.0℃ for measurements of uniform temperature fields in the range 40-250℃. Single-shot measurements enabled inhomogeneous temperature distributions in the engine with or without flames to be visualized. Even under motoring conditions, there was a large temperature gradient across the side window at the highest position of the piston. The side window temperature decreased near the intake valve. The intake gas flow had a cooling effect and the intake pressure affected the temperature distribution. The engine speed and the coolant temperature increased the temperature but they did not affect the overall temperature distribution. The instantaneous temperature of the top of the piston was visualized in the transient process after firing had commenced. Single-shot imaging was able to identify hot spots, which may generate soot and cause knocking.

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This study deals with the development of controlled-ignition technology for high performance compression ignition alcohol engines. The objective of this study is to make clear the main factors that govern auto-ignition phenomenon of an alcohol spray. Spray mixture formation and auto-ignition phenomena of ethanol-diethyl ether blended fuels were visualized by shadowgraph method and images were recorded with high-speed camera (8213 fps). Effects of surrounding gas conditions such as oxygen concentration on spray mixture formation up to auto-ignition were experimentally investigated by the use of a large constant volume electrical heating chamber. Result showed that the controlled ignition was possible by the control of surrounding gas oxygen concentration for spray of ethanol and diethyl ether blended fuels.

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The chemical quenching effect of metal wall surface on a methane-air premixed flame formed in narrow quartz channel is investigated. In order to eliminate oxidation of the metal surface and to establish equivalent thermal boundary condition with different wall materials, SUS321 and inconel600 thin films are deposited on the quartz plates by using vacuum arc plasma gun. OH-PLIF and numerical simulation are employed to examine the near-wall flame structure. It is found that OH concentration near the metal surface is significantly lower than that near the quartz surface. The initial sticking coefficients associated with radical adsorption for the metal and the quartz surfaces are estimated to be 0.1 and 0.01, respectively.

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Various turbulent combustion models are currently used with RANS (Reynolds-Averaged Navier-Stokes Simulation) or LES (Large Eddy Simulation) for the analyses and developments of IC (internal combustion) engines. Their models are, however, insufficient for their analyses and developments because the models are constructed by considering only the combustion in the gas phase without considering the chemical process on the internal surface of engine cylinder. In actual IC engines, the effects of chemical process on solid surfaces on the combustion should not be negligible because the combustion takes place in a very small volume surrounded by cylinder liner, cylinder head and piston. In this study, DNS (Direct Numerical Simulation) of premixed flames with a detailed chemical kinetics of hydrogen/air including the chemical processes in the bulk and on the solid surface were implemented. It was found that heat release rate near the wall increased temporally in the case of both a turbulent flame and a planar flame. This may be due to the Lewis number effect or adiabatic wall condition.

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A dry non-slug process by fluidized bed was proposed to gasify coal whose ash fusion temperature is higher than 1500℃ with high efficiency. A lab-scale of hot model examination was performed to evaluate the performance of coal decomposition gasification in fluidized bed under a higher temperature level than 800℃. The gasification could take place successfully without forming clinker in the bed. The knowledge on the gas yield and the composition was studied, and tar emission was decreased with rise in bed temperature.

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This paper presents hydrogen sulfide (H_2S) formation characteristics on the pulverized coal combustion of two bituminous coals with different sulfur release. The sulfur released from coal to the gaseous phase in the near-burner region is affected by the forms of sulfur. The organic sulfur is readily released compared to the other forms of sulfur. When the blends of two bituminous coals with different sulfur release are fired, H_2S concentration in the near-burner region coincide with the value estimated by the blending ratio, and concentrations of H_2S and SO_2 in the upstream region of the two-stage combustion air ports are in the chemical equilibrium.

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The temperature from the tip of the methane premixed flame along the flow direction decreased dramatically at low mass flow rate of the Hexamethyldisiloxane (HMDSO) vapor while the temperature was almost constant along the flow direction at high mass flow rate of the HMDSO vapor. From the SEM images, the size of the agglomerates of silica nanoparticles had a maximum at a certain mass flow rate of the HMDSO vapor due to not only the temperature distribution along the flow direction from the tip of the premixed flame but also the temperature. Furthermore, when the concentration of the oxygen in the premixed flame increased, the size of the agglomerates decreased.

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Fuel-NOx concentrations under the conditions of high CO_2 concentration have been experimentally investigated with a tubular flame burner. At first, flame stability limits are examined for CH_4/O_2/CO_2 mixture with a flat flame burner as well as a tubular flame burner. Results show that, for CO_2-dilution mixture, a flame can be established on a flat flame burner when O_2 concentration in oxidizer is greater than 26%. On the other hand, a tubular flame can be established in wide range of φ even O_2 concentration in oxidizer is 21% O_2. The results of NOx measurement showed that the Fuel-NOx concentration large for lean to stoichiometric condition. The results also showed that the Fuel-NOx concentration of 32% O_2 CO_2-diluted mixture is almost identical with that of air combustion, and NOx concentration drastically decreases with decreasing oxygen concentration in oxidizer.

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To clarify the behavior of soot within a diffusion flame, measurements of soot, its precursors and oxidant were carried out. Laser spectroscopy was applied to obtain a fuel, PAHs, soot and OH concentration distribution in the propane diffusion flame, and carbon nanostructure of soot such as crystallite size and amorphous carbon content was also investigated. Obtained results suggest that formation and growth of PAHs arise from chemical reactions beginning with pyrolysis of fuel, and then inception of soot particles occurs by coagulation of grown PAHs. OH was distributed around the outer edge of the flame, and was oxidizing the soot particles. Furthermore, the soot underwent a change in the nanostructure within the flame.

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