The result of scale analysis showed that the thermal-regime, in which the flame became most robust, located in low ambient flow condition. This predicted that the robust flame could exist in microgravity with a mild flow even if the oxygen concentration was below the limiting oxygen index (LOT). The result of the flight experiment agreed with the prediction; the flame spread in mild flow environment was observed even at 15.3% oxygen level in microgravity whereas the downward spread was not observed at the same oxygen level.

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This paper presents a simplest model that describes the smoldering propagation over a thin solid in a narrow space. A two-equation model is derived based on phenomenological arguments. The Lewis number, defined as the ratio of the solid thermal diffusivity to the oxygen diffusion coefficient, is identified as an important parameter. Numerical solutions of the basic equations exhibit similar finger-like patterns to those observed by previous experiments. The Lewis number effects on smoldering behaviors are discussed.

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Ignition tests of overloaded electric wire were carried out in microgravity provided by airplane parabolic flight. Polyethylene insulated NiCr core wire (inner core diameter 0.5 and outer diameter 0.8 mm) was used as a test sample. The results showed that the ignition limit in terms of supplied electric power dramatically decreased with increase in microgravity time. It was suggested that the total electric energy supplied to the wire gave the primary criteria for ignition, which was consistent with experimental findings. Further, the importance of conductive heat loss to the surroundings was pointed out for very low electric current condition according to the simple one-dimensional numerical calculation.

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Liquid pool fires in low gravity environment have been performed by using the drop tower. The gravitational acceleration was changed from 1G to 0.55G. To clarify the factor of puffing occurrence, experiments were performed for the eleven different size of fuel pan with three different kinds of fuels. It is found that the fuel pan size occurring puffing increases with decreasing gravity due to decreasing the flame height with decreasing gravity.

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This research conducted microgravity experiments to investigate flame-spread characteristics of droplet-cloud element. The results show that the flame-spread rate to the droplet in the perpendicular direction to the axis of two droplet interaction was greater than that to the droplet in the same direction to the axis of two droplet interaction. The flame-spread-limit distance also increased with the perpendicular direction to the axis of two droplet interaction. The temperature distribution around burning droplets was measured by Thin Filament Pyrometry (TFP) method based on visible light radiation from SiC fibers suspending droplets.

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Blowout experiments of a methane-air diffusion flame have been performed by using water vapor. The water vapor is produced due to the impact of a water droplet onto a heated wall. The water droplet diameter is varied from 3.4 mm to 10.4 mm and the temperature of the heated plate, from 100℃ to 430℃. The formation probability of the water vapor vortex ring and the blowout probability were measured. From the experimental results, the maps of the formation condition of the water vapor vortex ring and the blowout condition are made.

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Using FDS (Fire Dynamics Simulator), a tunnel fire was simulated. On the ceiling of tunnel, six sprinklers were lined, and these water sprays made a water screen in order to interrupt a thermal flow and a smoke flow. The author's previous study showed that the smaller the particle size of water droplets, the shorter traveling distance of a thermal flow and a smoke flow. This article shows the effect of evaporation of water droplet. Volume fraction of water vapor and velocity field near the sprinklers were investigated in different water droplet size conditions.

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This paper describes the experimentally results of extinguishment performance change by fuel type of plant biomass extinguishment form. This extinguishing method is assumed to be used for small packaged extinguishing systems for installation in general residential. In this study, extinguishing experiment was conducted to clarify extinguishing performance of fire by common fuel in the home. In previous studies, n-heptane was used as fuel that simulates gasoline. In this study, vegetable oil and kerosene was used. These fuels are further high boiling point. In a high boiling point fuel case, much foam was collapsed. Because the radiation intensity from high boiling fuel flame to foam is higher than n-heptane flame.

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Flame extinction limit of Ethyl Methyl Carbonate (EMC) often used for Li-ion Batteries has been measured when Trimethyl Phosphate (TMP) is added to EMC. The wick flame was used to determine the extinction limit in terms of oxygen concentration. The results showed that extinction limit much increased when the first 5wt% TMP was added to EMC. The change of extinction limit, when another 5wt% TMP was added, was not so large, while the increasing trend was kept. On the other hand, addition of TMP caused increase in flame temperature. From these results, it was suggested that chemical effect, capturing of H and OH radicals by TMP and organophosphorus compounds, is more important than promotion effect with the flame temperature increase.

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In order to clarify the characteristics and mechanism of fire extinguishment with blast wave, the blowout experiments of methane-air jet diffusion flame have been performed by using a laser-induced breakdown. The blast wave extinguishment can be used as a firefighting technique to post-disaster fires. In this study,the blowout process has been visualized by using schlieren technique. And the probability profile has been measured by varying the distance from the breakdown point to the flame base.

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We have experimentally investigated a ventilation-controlled and medium-size pool fire (fuel: ethanol). Special attention was paid to meandering processes with the low frequency velocity fluctuations in the vicinity of a pool, which were revealed by our previous study. The velocity vectors were measured by using a PIV technique with spores of lycopodium clavatum as tracer particles (the diameter becomes several μm in flame). The dominant flow structures, which were obtained by the proper orthogonal decomposition with measured velocity vectors, clearly show the impacts of under ventilation conditions: the deficient O2 supply yields suppression of puffing motions and activation of leisured fluid motions in horizontal direction.

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It is important to investigate the flammability of circuit subjected to arc discharge in terms of fire safety. In this research, the flammability of electric wire was investigated as a most simplified circuit. Furthermore, stable arc discharge is assumed by using TIG arc welding machine. The electric wire subjected to arc discharge is ignited in any arc energy, however, the probability that the electric wire burns independently after arc discharge varies with arc energy. Finally, the result was summarized by introducing a dimensionless number that shows the energy balance between arc energy and latent heat energy of insulator of electric wire.

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The objective of this study is to predict the flame spread probability over urban fire by the ratio of non-combustible area to combustible area (porosity). This paper described the experimental results of flame spread experiments along randomly arranged combustible cubes. Flame spread experiments conducted with changing porosity and size of experiment region. Porosity of flame spread probability set to 0 increased with the increase of experiment region. Subjected to finite size scaling in experimental results and examined the influence of number of grid on flame spread probability.

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This work is devoted to examine the effect of ambient temperature on limiting oxygen index (LOI), whose concept will be utilized to evaluate the safeness of the material bringing into the space environment, currently based on NASA-STD-6001 (TEST 1). For LOI test (= ISO 4589-2), flame spreads toward the downward, whereas for TEST1, flame spreads toward upward, therefore, the criterion for burning for both tests is not identical. Considering the fact that the upward spread is more preferable than downward spread, limiting oxygen concentration given by LOI test method may always over-predict the limiting oxygen concentration for TEST 1 configuration. To cover this discrepancy, the concept of Temperature Oxygen Index (TOI) based on ISO 4589-34) is newly demonstrated to elucidate the applicability to fulfill the current demand. As increase the field temperature, test material might be easy to burn so that limiting oxygen concentration would decrease even in downward spread test method (namely, LOI test method). It is found that increasing temperature results in linear decrease of LOT (minimum oxygen concentration to burn). More importantly, ABS, PC and PMMA shows almost the same decrease rate of LOI against the temperature increase. Further analyses are underway to explain this observed trend.

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In this study, the temperature distribution inside PMMA with 5 mm thickness during the flame spread was measured experimentally and the feature of heat transfer was discussed. The temperature measurement was conducted by a novel method that is phosphor thermometry based on the two-color photoluminescence intensity ratio obtained from up-conversion phosphors. The temperature measured by this phosphor thermometry showed a good agreement with that measured by the thermocouple, so that this method gave a non-contact and fine measurement of the temperature distribution inside PMMA. The heat flux analysis with the measured temperature distribution revealed that the heat transfer from the flame to PMMA governed the flame propagation.

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The characteristics of mezo-scale combustors having characteristics of high speed flame propagation in a vortex flow and method of heat recirculation combustion were examined. The limits of flame stabilization in the mezo-scale combustors did not approach the lower limits of flammability under the conditions of preheated temperatures of the unburned gas. The characteristics of the space heating rate (SHR) of the combustor were similar to those of combustors of various sizes using various kind of fuels.

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A non-scanning 3D-CT technique using a multi-directional quantitative schlieren system, is proposed to obtain instantaneous density distributions of unsteady premixed flames. This "schlieren 3D-CT" is based on (i) simultaneous acquisition of schlieren images taken from numerous directions, (ii) reproduction of projection images from the schlieren images, and (iii) 3D-CT reconstruction of the projections by an appropriate algorithm. In this paper, 3D-CT reconstruction of a non-axisymmetric steady flame is made with a single-directional quantitative schlieren system. This investigation is conducted as a preliminary research relevant to a massive system having 20 schlieren systems, suitable for the observation of high speed flames.

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This paper reports the basic experimental result of counterflow diffusion flame in the microwave. Since flames contain ions and charged particles represented by soot, the flame interacts with microwave. The methane-air counter diffusion flame was formed in waveguide of microwave and effect of microwave on the flames was observed. Frequency of microwave is 2.45GHz and output of microwave generator ranges from 0 to 250 W. Application of microwave makes the flame intensity increase and the flame color change. These experimental results indicate that flame temperature increase with the application of the microwave.

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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 reduction of structural strength for attaching of fins on the heat transfer surface. In this study, the effect of heat transfer enhancement by inserting porous metal (metallic wire , foam metal) intermittently was studied and the pressure drop by using porous material was also evaluated.

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A numerical study has been done for natural convection heat transfer in the joint part of a cylindrical thermal insulation structure with a metallic outer shell. If the joint is relatively narrow, the effect of natural convection which occurs inside the joint on the thermal insulation performance is small. Although the heat transfer rate increases as joint width becomes large, the increase in the heat transfer rate is less than 10 percent, even when the joint width is 10mm.

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A numerical study has been made on combined forced and natural convection around a porous square cylinder which is heated uniformly. Buoyancy caused by the heating induces a significant change in the flow pattern. With increase in the amount of heating, the structure of the vortex in the wake is changed to a steady twin vortex from unsteady Karman vortex and the 'oscillatory motion is suppressed. A further increase in the amount of heating reduces the length of the twin vortex. Moreover, the drag coefficient of the porous square cylinder increases with the increases of the amount of heating.

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In this paper, the flow field near the ground surface in an urban area is numerically investigated using a porous media approach. Three-dimensional numerical simulations of turbulent flows through a collection of vertical rods are conducted using the standard two equation model. These microscopic results are integrated over a structural unit to investigate the volume averaged flow field near the ground surface in an urban area.

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From the viewpoint of safety design of nuclear reactor and economic terms, for PWR, It is important to clear the mechanism of DNB and predict accurately the critical heat flux under subcooled boiling condition. So, in this research, we proposed a calculated model of the CHF phenomena and developed a method to predict the CHF under subcooled boiling condition. Furthermore, we evaluated the prediction accuracy and validity of this prediction method by comparing the prediction results with experimental data for a circular tube under high pressure and subcooled boiling condition. From the results, for uniform power distribution data, the method developed in this research was able to predict accurately, but for non-uniform power distribution data, we have to improve its accuracy and develop a new prediction model of CHF point.

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In evaluation of cooling performance for Passive Corium Cooling System, Heat removal capability depends on natural circulation flow rate. Proper selection of void fraction and two phase multiplier correlations is important to predict two phase natural circulation flow rate accurately. Evaluation method with void fraction using Ishii model and two phase multiplier using Chisholm model is developed. Predicted natural circulation flow rate compared with test results. Evaluation results with Ishii model and Chisholm model can predict accurate natural circulation flow rate in high pressure range. But natural circulation flow rate is overestimated in low pressure range. It is found from examination results that this overestimation is caused by underestimation of two phase multiplier. Change of two phase multiplier from Chisholm model to Nakazatomi model enabled accurate prediction of natural circulation flow rate in low pressure.

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Nonlinear trend of subcooled water flow boiling CHFs versus outlet subcooling for flow velocities at outlet pressures in tubes flowing subcooled water was studied using existing database based on the corresponding correlations extending the new correlations with different mechanisms recently developed for the nonlinear trend of CHF in through tubes with wide ranges of inside diameter, and length-to-diameter ratio for wide ranges of flow velocities, outlet pressure and outlet subcooling. The object of this paper is to clarify if the CHF correlation mentioned above can be extended to apply to the previously existing flow boiling CHF data obtained for the test sections such as a heated metal strip in a channel with rectangular cross section, and heated tubes with various diameters and lengths under wide ranges of conditions.

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This paper presents experimental study of the effects of the surface angles on the cooling rate in water spray cooling using a micro jet dispenser. The sample surface used is SUS304 cylinder with different roughness, Ra0.04 (Mirror) and 10 and is inclined at 15°, 30° and 45°. The droplet diameter and velocity are independently controlled in 500μm and 2.5m/s. The cooling curve is drawn in the range of 500℃ to 100℃ from the temperature data of the sample. The inclination of the surface decreases the cooling time both at the roughness Ra0.04 and Ra10. The increase of the cooling rate is observed at the region of transition boiling and nucleate boiling.

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Boiling heat transfer from a hydrophilic/hydrophobic combined surface was studied to examine the effect of the subcooling. The experiment was conducted at the subcooling of 30 K and its results were compared with previous data of the subcooling of 0, 10, 20 K. In subcooled conditions, boiling incipient superheat turns to a negative value and becomes lower with an increase in subcooling. The bubbles stay on the PTFE coating area without departure and maintain the hemispherical shape while oscillating up and down.

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This study was searched for the possibility of high deposition rate by the gas jet stream in the non-equilibrium plasma CVD with little power consumption. On high pressure and narrow gap conditions, it has checked obtaining a high deposition rate (several μm/s) locally using a single axial symmetry nozzle. Well, the dynamic deposition method was adopted using a high deposition rate for large area-deposition. And the possibility of uniformity of the film thickness in the direction of movement was found out. In order to enlarge the uniform deposition area to a meter scale thin film, we have started the experimental study by a two-dimensional slit nozzle (3×0.3mm^2) instead of 0.5mmφ single nozzle. In this paper, we report the experimental study result.

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Solar energy is capturing the spotlight as clean energy replaced with atomic energy. Then, we paid attention to the thin film silicon solar cell with low manufacture cost. It is usually manufactured by PECVD under low back pressure. We found that high-speed film deposition was enabled by increasing back pressure. However, high back pressure is put into the domain of a viscous flow, and produces involvement of clusters. The film quality will be worsened if a cluster adheres to a substrate. In order to attain a high quality and high deposition rate, it is necessary to investigate the dependence between the back pressure and deposition quality, and the relation between the back pressure and deposition rate. This paper reports the experimental results.

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The purpose of this study is to produce hydrogen gas from saccharide efficiently using 27.12 MHz radio-frequency (RF) in-liquid plasma. In order to enhance the production rate of hydrogen gas, ultrasonic irradiation was added to the plasma. The experiments were conducted adopting two different ultrasonic frequencies, 29 kHz using a horn-type transducer and 1.6 MHz using a piezoelectric transducer. When 29 kHz ultrasonic irradiation was added to the RF plasma in 0 to 10wt% glucose solution, the hydrogen production rate increased 4-17% from that without ultrasonic irradiation. When 1.6 MHz ultrasonic irradiation was applied to the RF plasma in 5wt% glucose solution, the gas production rate increased 90-150% from that without ultrasonic irradiation. The effects of ultrasonic atomization and agitation in the solution of nonvolatile glucose enhance a chemical reaction of the in-liquid plasma.

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The influence of non-equilibrium Ar plasma on the composition of tar obtained by cellulose pyrolysis was investigated. When Ar plasma is given to the cellulose pyrolysis from the beginning of the experiments (from room temperature), the collected tar composition is almost the same with no plasma condition. In the case plasma is given after furnace temperature becomes higher than 300℃, the rate of furfural in the collected tar increases and the rate of levoglucosan decreases. From the results, it is suggested that decrease in decomposition temperature or increase in pyrolysis rate is caused by applying non-equilibrium Ar plasma to the cellulose pyrolysis.

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We performed three-dimensional unsteady calculations of reactive flows, based on the compressible N-S equation, to investigate the hydrodynamic instability of premixed flames under the low temperature environment. As the unburned-gas temperature became lower, the growth rate decreased and the unstable range narrowed. This was due mainly to the reduction of the burning velocity of a planar flame. The normalized growth rate increased with a decrease of the unburned-gas temperature. This was because that the thermal-expansion effects became stronger owing to the increase of the temperature ratio of burned and unburned gases. In addition, we compared with the results of asymptotic analysis and confirmed that both results were almost the same at sufficiently small wave numbers.

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This study investigates the suitability of lower fatty-acid methyl esters from plants oils in port-injected SI engines. Caprylic acid (C8:0) methyl ester (CaME) that is the lowest fatty acid in a palm kernel oil was selected as a test fuel. CaME was blended into ethanol to obtain the adequate vaporability for SI engines. The experiments were conducted for various fuel blend-ratios, engine loads, and ignition timings under the stoichiometric condition. The results show that the engine performance and exhaust emissions with CaME blend up to 40vol% are almost equivalent to those with ethanol fuel.

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Bio-oil/char slurry from wood biomass is an attractive and novel fuel with advantages in energy density, storage and transportation. In this paper, fundamental characteristics of fluidized bed system for fast pyrolysis is presented as improved pyrolysis reactor of our earlier system. This system shows good performance for short residence time close to a few seconds. Influences of the location of biomass supply in a fluidized bed and the resident time on yields quantity and quality are clarified. The property of the yields is shown that the high quality (high-heating value) of bio-oil is obtained under the short residence time.

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This study presents an experimental investigation of adsorption kinetics of ethanol onto a highly porous activated carbon powder namely Maxsorb III. Instantaneous adsorption uptake of ethanol is measured using magnetic suspension adsorption measurement unit (MSB-VG-S2). Experiments have been carried out at different adsorption temperatures ranging from 30℃ to 60℃. The Dubinin-Radushkevich (D-R) equation has been used to correlate the experimental data. Experimental results show that Maxsorb III can adsorb up to 1.24 kg of ethanol per kg of adsorbent. The diffusion time constant and overall mass transfer coefficient are also estimated using the semi-infinite model. The result shows that these values increase with adsorption temperature.

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The purpose of this study is to establish the basic technology to achieve CO_2 reduction and hydrogen production by using exhaust gas, waste steam, and chaffs. We used the chaffs with mean particle diameter of 20 and 100μm, and applied shock heating technique by the shock wave driven by high pressure helium. The experimental apparatus is a standard shock tube having inner diameter of 100mm. We found that hydrogen concentration increases gradually with increase of temperature. The highest hydrogen concentration was about 30%. The shock heating temperature for acquiring the value of high hydrogen concentration was about 1000〜1300K. By using the mixing chaffs(average particle diameter of 20μm and 100μm), hydrogen concentration higher than the case where average particle diameter is 20μm was obtained.

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Understanding of natural convection of miscible two phases in porous media is of great importance to problems of geological storage of carbon dioxide. We consider saltwater-freshwater fingering instabilities in a saturated porous medium. Plastic resin particles with an average diameter of 320μm or 440μm were packed 50 mm in height in a tube with the inter diameter of 32 mm. Development of the fingering due to instabilities and natural convection of freshwater and saltwater in porous media have been imaged by means of micro-focused X-ray computer tomography (CT) every three minutes. At early stages of convective mixing, ripples appear on the contour surface of the concentration of sodium iodine and grow to be fingers which extend vertically downwards with time. As fingers proceed downwards, the concentration of sodium iodine in fingers are reduced. As a result the convective mixing is rapidly suppressed. With an increase in the density difference and the permeability, the development of the natural convection occurs more quickly. The standard deviation of CT values in the particle pack was used to evaluate the critical time and the mixing time of natural convection.

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We have investigated fluid flow characteristics of liquid film flow and mist flow rising along the outer surface of the rotating cone. It is important to know the power consumption necessary for the generation of mist flow and rising film flow along the rotating conical outer surface. Therefore, we measured the torque acting on the rotating cone by using the torque sensor. However, the values of torque depend on the mist flow quantity. So, we clarified the relationship between the mist flow quantity and power consumption necessary to pump up the liquid film flow and make the mist flow.

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Diesel engine is lifted in terms of high thermal efficiency, reduction of carbon dioxide. The purpose of this study is to improve spray and flow characteristics of nozzle for direct injection Diesel engine by using cavitation phenomena in the nozzle hole, which is considerably affected to atomization of spray. As a result, it was obtained the results that when the atomization enhancement nozzle with round inlet cutting was used, spray characteristics was improved, spray angle becomes large about two times, Sauter mean diameter was obtained 20μm order and volumetric flow rate was large about 40 % compared with the nozzle invented in the previous this study. Moreover, when the each nozzle holes of the multi-hole nozzle were inclined at 45 deg., spray angle becomes considerably large about over 100 deg., and high-dispersion spray was obtained.

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Recently, micro-combustors which combust hydrocarbon fuels at micro scale are expected to be used as a small energy source. Since fast evaporation of liquid fuel is required, electrospray techniques, which can generate small droplets, have been employed. We focus on the multi-jet-mode electrospray, which produces many jets from a single capillary. We investigate effect of applied voltage to the capillary and fuel flow rate on the jet characteristics by visualization using a laser light sheet and nano flash shadow graph system. The investigation was conducted for some different diameters of capillaries and distance between the capillary grounded mesh.

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Butanol aqueous solution is a promising useful liquid of boiling for the application of micro thermal devices because of high critical heat flux and small generating bubbles. In the past studies of the authors, boiling heat transfer has been investigated in various modes of boiling. Namely, fundamental features were studied by using horizontal heated wires and as for the application, flow boiling heat transfer was studied by using a mini-tube. The heat transfer on a flat surface has been also investigated in both steady and unsteady quench tests. In the present report, all the results are summarized and remaining problems are described.

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This paper discusses a relation between the microlayer model for the critical heat flux and the micro-bubble emission boiling, MEB. Based on the microlayer model, the mean heat flux of nucleate boiling is expressed by a quintic equation of superheat, which gives different critical point from the CHF on the boiling curve. It depends on a period of bubble departure as well as a density of nucleation site. In the MEB situation, the size of the emission bubble is very small and the site density is so high due to the large superheat. We consider that there is a possibility to express the heat transfer of MEB by the microlayer model.

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