Micro centrifugal pumps with impeller diameter was 5.6mm were experimentally manufactured and their performances were measured. In order to find the optimum design of impeller centrifugal pump operated at low-Reynolds number (≈10^4), four types of impellers were tested and the the effect of Reynolds number on the pump performance was investigated.

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This paper deals with pressure-flow rate, p-Q, characteristic of an ion drag pump. Using two-dimensional electrodes and several types of liquids like insulating oil, functional liquid and refrigerant, the effects of the number of electrode pairs, the distance between electrode pairs and of the temperature on the p-Q characteristic are experimentally investigated. It is shown that the shape of the p-Q characteristic curve is significantly influenced by the type of liquid, and that the degree of the effect of the number of electrode pairs on the p-Q characteristic is also different from one liquid to another. It is also shown that the distance between the electrode pairs affects the pressure generated to some degree.

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This paper deals with an experimental study on the fluid around two circular cylinders in various arrangements. The surface roughness of the cylinders were smooth and rough respectively. The experiments were carried out in a wind-tunnel with a working section 300mm×50mm×500mm, the ratio L/d of the spacing L between the center of two cylinders to outer diameter d of the cylinder was 1.75 constant and the rotation ratio R_n of the cylinder A to the cylinder B used is 1.0 and 2.0. The surface-pressure distributions on the circular cylinders were measured in the range of Re=4.92×10^4〜8.11×10^4 and the drag and lift coefficients were determined from these measurements. The velocities in the wake were measured with a hot-wire anemometer. The flow patterns around the circular cylinders were visualized by a smoke tunnel. As a result, it was found that the drag and lift of circular cylinders were decreased in smooth case.

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When a thin flat plate is released in still air, the plate automatically sets into a rotational motion. This phenomenon is called autorotation. In this state, it is supposed that vortex shedding and unsteady fluid-dynamic forces interact each other. In this study, we carried out the numerical simulation of flow around a rotating elliptic cylinder in a uniform flow by discrete vortex method and comparison with the drag and lift coefficients calculated by finite-volume method and complex potential theory. The results show that the vortex shedding effect on the fluid-dynamic forces at the region between -50 degree phase and -180 degree phase for drag coefficient and at the region between -15 degree phase and -140 degree phase for lift coefficient.

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In the present study, a computational procedure is developed to simulate motion of microorganism such as bacteria. The resistance force theory which can calculate bacterial motion for short time is employed to determine the locomotion and the slender body theory as well as the boundary element method is applied to correct flowfield induced around the microorganism.

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In fluid-solid interaction problems, the virtual-mass force, or added-mass force, plays an important role. For viscous fluid and infinitesimal amplitude, Chen's linear theory and our computation method are effective. In the present study, in order to specify such limit of the infinitesimal-amplitude approximation, the authors conduct full Navier-Stokes analysis by finite difference method (FDM). The authors examine a circular cylinder which oscillates with finite amplitude in viscous. Tested parameter ranges are Keulegan-Carpenter number KC=0.01〜10 and Stokes number β=1,10,100.

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This paper reports the technique of digital holographic particle image velocimetry (DHPIV) with a gradient-based method for 3D flow measurement. In this technique, hologram pattern are observed as a digital image by electric camera and image reconstruction is carried out on a personal computer. Gradient-based method is employed to detect particle displacement in depth direction with high accuracy in the order of one tenth of image reconstruction interval. In numerical simulation, measurement accuracy is evaluated for cubic cavity flow model. In experiment, the present method is applied to the flow measurement of the rotating flow in a cavity.

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Measurement of mass emission of exhaust gas needs measurement of flow rate and concentration. In case, exhaust gas flow rate and concentration of gasoline-fueled vehicle is measured directly at tail pipe, concentration can be measured accuracy. But it is known that while in the measurement of flow rate, the error arises in pulsating flow with reverse flow at idling condition. By the research of last year, it has been understood that the error of measurement doesn't depend on a size of the amplitude alone by flow rate measurement of air pulsating flow using pitot tube flowmeter. In this study, Flow rate of air pulsating flow is measured with changing connecting pipe length of differential presser transmitter, and comparison of flow rate with flow behavior of detector surroundings by visualization.

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Spectroscopic measurements of electron temperatures(T_e) were carried out for the shock wave plasmas, generated in a electromagnetic shock tube, with low pressure argon as the test gas. The T_e's were estimated by the Boltzmann plot method with six spectral lines of singly-ionized argon, for every 0.2μsec after the arrival of plasma to the observation port. Typically, the T_e rises to the peak value of 〜4×10^4K in 〜10μsec, after the arrival of plasma, then rapidly decreases to the steady value of 〜1.5×10^4K during observation period. The rapid decrease of T_e seems to correspond to the rapid increase of electron number density.

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The temporal variation of electron density of shock-produced Ar plasmas was measured by a CO_2 laser heterodyne interferometer. The interference signal was detected by a HgCdTe detector. The extractions of the phase data were performed by simultaneously applying two methods, i.e. the quadrature detection method and the Fourier analysis method for each shot and yielded electron density of fast moving plasma. The results by both methods show good agreement.

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Bronchial asthma is a kind of chronic bronchitis. It causes the airway narrowing happen and so makes breathing difficult. It is important to clarify its mechanism. The characteristic of asthmatic airway is that its buckling consists of some folds into the airway lumen. It is considered to be caused by rapid constriction of smooth muscle. We paid attention to a rapid change in the transmural pressure as a model of the constriction of smooth muscle. In this study, to clarify the mechanism for buckling, we used collapsible tubes as a model of the airway and made apparatus which gave a sudden decrease in the pressure inside the collapsible tube by using a shock tube. The shape of the cross-section on the tube was visualized by a laser sheet method and its behavior during the buckling was photographed by using a high speed video camera. Besides, to use the expanding model, we could derive similarity rule in our experiments.

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Numerical calculations have been performed in order to predict the mixing behavior obtained from basic experiments in which high-density solution was injected horizontally into vertically upward water flow. In the calculations, a continuity equation and momentum equations for total fluid together with a mass transfer equation for solute have been solved by the finite difference method. The numerical calculations have predicted well the mixing efficiency, the fraction of injected solute mass that actually leaves the test section, observed in the experiments.

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Passive and active scalar fluxes in unsteady stratified turbulence are analyzed using the rapid distortion theory (RDT) with the diffusion effects of density and passive scalar. Analytical solutions of the RDT equations show that the passive scalar transiently gives a stronger counter gradient flux than the density flux as demonstrated in the previous experiments. However, long time development shows that, in many cases, the difference reduces again if the initial potential energy is small. The results show the importance of 'unsteady' analysis in the diffusion problems in stratified turbulence.

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The linear stability of finite amplitude internal solitary wave propagating in a two- layer fluid is studied. We try to reveal the critical amplitude that divided the region of stability and instability in a parameter space of solitary waves. The set of equations construct eigen value problem. As a first step, We seek a numerical solution of these problems. As a second step we seek asymptotic solution by asymptotic analysis. Both analyses of them derived the stability criterion that can prescribe which sides of critical surface area stable or unstable.

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Particle clusters formed in gas-solid two-phase flows in risers of circulation fluidized beds or pipes of pneumatic transport systems have much influence on various kinds of transport phenomena. In the present study, effects of particle size distribution on the gas-solid two-phase flow are studied empirically. Especially the effects of inter-particle collision are focused. The Stokes Number about inter-particle collision is defined and the correlation between the fluctuation velocity arised from the inter-particle collision and the Stokes Number is obtained.

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Atomization phenomena of W/O (Water in Oil) system in microchannel were analyzed experimentally and theoretically. To investigate the breakup motion of cylindrical liquid in microchannel, a light emitting diode system was developed for the function of the strobe light We observed cylindrical liquid size at various velocity conditions. Furthermore, theoretical analysis was carried out to predict the size of cylindrical liquids In our theoretical analysis, we calculated liquid flow around the cylindrical liquid and obtained drag coefficient with numerical solver which was developed with stream function vorticity method. The effects of continuous phase velocity and mierochannel wall on the diameter of cylindrical liquids were clarified numerically. The numerical results of cylindrical liquid diameter quantitatively agreed with the experimental results.

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This paper presents the performance test results for the digital holographic measurement of micro-particles which diameter mainly range from 1 to 10μm. In the measurement, the inline hologram patterns for the micro-particles are captured with a single electronic camera and they are numerically analyzed on a personal computer to obtain the particle information, such as their diameter, shape and number density. The present technique enables to numerically reconstruct enlarged particle images for highly accurate particle measurement, whereas the standard size of one pixel in a digial image is about 10μm and the corresponding spatial resolution is not enough for the taget micro-particles. The performance of the technique is evaluated in numerical simulation and the test results show that the present technique successfully measure the particle diameter with higher accuracy.

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Particle collision growth is significantly promoted by flow turbulence. We proposed new collision kernel models which can describe the turbulence effect. By comparing the model predictions with the predictions by direct numerical simulations (DNS), we could confirm the reliability of our model. We also developed a large-eddy simulation (LES) method involving our new model. Then we performed the LES for the particle growth in a turbulent flow. Our LES prediction was compared to the DNS prediction. The comparison showed that our LES can well predict the particle growth in turbulence.

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When water-ferromagnetic particles dispersion flows in a magnetic field gradient, the ferromagnetic particles are attracted toward the direction of high magnetic field. The separation of ferromagnetic particles from water-ferromagnetic particles dispersion flow was calculated by a thermal-hydraulic computer code including a simple two-phase flow model. Calculated results shows that the separation is possible for ferromagnetic particles with diameters greater than 〜1μm. The separation of ferromagnetic particles from water-ferromagnetic particles dispersion flow was also attempted by experiments using cobalt particles with a diameter of 2μm. However, experimental results shows that improvement should be made on the measurement of particles volume fraction in the dispersion in the top and bottom region of test section.

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In this study, in order to understand soot formation characteristics in diesel jet flame on various combustion conditions, effects of experimental parameters (such as ambient gas temperature, ambient oxygen concentration, and injection pressure) on soot volume fraction and particle diameter distribution in diesel jet flame was investigated using Time-Resolved Laser-induced incandescence. The experiments were conducted using constant combustion vessel which simulated diesel engine conditions. The experimental results show that the small soot particles generated at upstream of the jet was carried to downstream and grow to the large soot particles by aggregation or surface growth. And soot volume fraction was reduced by ambient gas temperature and oxygen concentration decrease, injection pressure increase.

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The effects of benzene addition on PAHs formation are studied in a stabilized laminar low-temperature flame under an atmospheric pressure, to understand the processes of soot formation in the internal combustion engines. The burner was operated with a diethyl-ether/air mixture at an equivalence ratio of 3.0, containing 1.6-ppm benzene. Single-ring aromatics and PAH ranging from two- to four-fused aromatic rings were identified by microprobe sampling and a liquid chromatograph with a fluorescence detector. Both the cool- and blue-flame appearance were advanced with the benzene addition. The benzene addition suppressed the growth of PAH, contrary to the more production of single-ring aromatic hydrocarbons, such as, phenylacetylene and styrene. The phenol formation was detected at the time when a cool flame appeared. It is presumed that the benzene-origin HO_2 and OH formed during the low-temperature oxidation have enhanced the cool-flame reaction, even if the amount of benzene addition was not high.

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Unsteady jets with different density are calculated by a large eddy simulation (LES) to investigate the effect of density on flows and the volume of gas entrained into the jet. The results show that the jet with a lower density reduces tip velocity, then suppressing the entrained air and turbulent mixing.

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The sound development of knowledge for generalized saturated and subcooled pool boiling CHF mechanisms and those correlations for test heater surface conditions in water and wetting liquid such as Fluorinert etc. are becoming increasingly important as the fundamental database for not only the design of high heat flux cooling system recently needed but also the derivation of subcooled flow boiling CHF correlations based on the pool boiling ones. Recently the saturated and subcooled pool boiling CHF for a horizontal cylinder in water and wetting liquids such as liquid nitrogen, liquid helium etc. were measured for comparatively wide ranges of pressure and subcooling. It was clarified that the CHFs measured were mainly divided into two groups for lower and higher subcooling at a pressure as a typical case. It was assumed that the former and latter CHFs occur due to hydrodynamic instability (HI) and explosive-like heterogeneous spontaneous nucleation (HSN) on the cylinder surface respectively. This paper suggests that more study on the effect of the cylinder surface condition on the transient CHF is necessary.

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Many researchers have studied about spray coolings and obtained the results of measurement. In this research, the purpose is to improve the performance of cooling in low temperature regime, and to obtain the fundamental database for the highly precision control of heat transfer surface temperature. The experiments on steady cooling on downward horizontal ribbon were performed. The heat transfer process and cooling limitation heat flux of spray were investigated. The experimental results for two kind of spray nozzles were obtained for flow rates and subcoolings. The correlation of cooling limitation heat flux was presented.

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It is important to clarify the transient forced convection heat transfer process under an exponentially increasing heat input, which is expected in an accident of high temperature gas cooled reactor (HTGR) due to excess reactivity. The transient forced convection heat transfer in the flow of helium gas parallel to a horizontal cylinder was experimentally studied, and the effects of the velocity and period of heat generation rate were previously reported by the authors. In this paper, numerical solution on the transient forced convection heat transfer of helium gas was carried out. The changes of surface superheat and heat flux with time, obtained by numerical solution, were compared with author s experimental data. The effect of diameter of cylinder heater on the heat transfer coefficient was also investigated.

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CO_2 as a natural refrigerant is proposed for one of alternatives and recommended in car-conditioners and heat pumps for hot-water supply system. However, unsolved problems are remained to develop the optimum designing method of heat exchanger. In this study, in order to reveal the pressure drop and boiling heat transfer of CO_2 flowing through the micro channel, the test channel was used stainless steel tube with 400mm and 800mm in length and the inner diameter of 1mm and horizontally placed. We investigated the flow and the heat transfer characteristics in the micro channel and compared experimental results with the correlation formulas for the conventional scale channels.

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Heat generation from CPU of personal computer has increased, so more efficient cooling system is needed. This paper presents the result on performance of cooling system using two-phase natural circulation loop as a candidate for this purpose. Boiling on a finned surface that simulates CPU caused two-phase natural circulation. Results of boiling heat transfer showed higher value than Rohsenow-Clark correlation as the system pressure decreases. Also, this might be attributable to the effect of the finned surface. Possibility of cooling system by two-phase natural circulation loop was confirmed. By improving the condenser performances, the system can be applicable to the actual personal computer.

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The understanding of the two-phase flow characteristics in a very narrow annulus with rotating inner cylinder is very important in the development of turbine pump for liquid-propellant rockets. In this investigating the characteristics of the air-water two phase flow in an narrow annular gap of 0.75mm with rotating inner cylinder were conducted. Experimental conditions were as follows; revolution of inner cylinder 0-3100rpm, volumetric gas and liquid fluxes J_G=0.014-0.526m/s, J_L=0.0121-0.2384m/s. The influence of the revolution on the void fraction and friction were experimental confirmed.

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Many of the thermosyphons are of geostationary type, and a lot of researches are going on. On the other hand, there seem to be no reports concerned with accelerating thermosyphons. In this study, by the calculation, we examined the heat transfer characteristics of the thermosyphon with dropwise condensation in the condenser section which was given sinusoidal vibration in the vertical direction. As a result, we expected that the heat transfer of the thermosyphon was enhanced by the vibration.

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Antifreeze proteins have been discovered from vacterias, insects, plants and fish. It is possible for the AFP to reduce the freezing point of aqueous solution without increasing the osmotic pressure. Since it was confirmed by a scanning tunneling microscope that the quenched AFP type 1 (HPLC6) absorbed on the surface of an ice crystal, it has been considered that the HPLC6 keep water molecules away from the ice crystal. However the interaction between the HPLC6 and the ice surface in the care of gradually freezing not has yet been clarified. In the present study, we have carried out detailed measurements on HPLC6 in aqueous solution, which is gradually freezing, with total internal reflection fluorescence microscopy. The observation results show that the HPLC6 is possibly concentrated at the ice-solution interface.

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Thermal radiation reflected by a diffraction grating is characterized by the wave interference, while radiation emitted by the grating at high temperatures is not always interfered well. On the other hand, a film-substrate system with the simplest microstructure emits thermal radiation which is characterized well by the interference. We discuss this subject to suggest a possibility of new thermal radiation energy technology.

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Functionally Graded Material (FGM) has been developed as the element that can stand at high temperatures. FGM is a non-homogeneous material and information about distribution of thermo-physical properties is demanded to evaluate its heat resistance. So we develop a new method to measure thermo-physical properties using induction heating. Changing a depth of that will be possible to have large effect of internal properties on temperature profile at surface with this technique. The method uses an approximate solution for the data reduction on the assumption that FGM is a multi-layers material composed of various substances differing in property. A single layer material is studied as fundamentals of multi-layers material. This report describes accuracy of the method by comparison between analyses in the case that sample heated by internal production and experiments of that.

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Functionally Graded Material (FGM) has been developed as the element that can stand at high temperatures. FGM is a non-homogeneous material and information about distribution of thermo-physical properties is demanded to evaluate its heat resistance. So we develop a new method to measure thermo-physical properties using induction heating. However distribution of electric conductivity in the material must be estimated so that a depth of induction heating is dependent upon the conductivity. Then a method to measure the distribution is investigated by detecting intensity of electromagnetic field and phase difference of that at induction heating. The method uses a theoretical solution for the data reduction on the assumption that FGM is a multi-layers material composed of various substances differing in property. A single layer material is studied as fundamentals of multi-layers material. This report describes a comparison between analyses of electromagnetic field and experiments of that.

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Photoacoustic measurements were performed for metallic foils and human skin. Opened type cell was newly developed for on-site measurement instead of a past closed cell. The thermal diffusivity of titanium foil was measured by using these cells. The measurement results observed good coincidence. Photoacoustic method using the developed opened cell was applied to the measurement of thermophysical properties on human skin.

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In recent years, the heat island phenomena become a social problem in urban area. One of the causes is the increase in the rate of the sensible heat transfer to the latent heat transfer. A scintillation method is given as the way of mesuring the spatial averaged sensible heat tansfer. In the present study, a new measurement system was designed based on the scintillation method. In order to verify the performance, the field tests were carried out in open space. The mesured results were compared with those by using commercial system and those based on an eddy correlation method. As a result of the field measurement, the average difference of sensible heat flux obtained with our system and commercial system was small. In addition the correlation of the both value was high.

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Improvement of the efficiency of passive-type polymer electrolyte fuel cells (passive-type PEFCs) which use hydrogen is one of important subjects for practical use. The authors conceived that it might be possible to improve the efficiency of passive-type PEFCs using the authors' original power control method named Time-Splitting Method (TSM). Using an equivalent circuit model which represents an actual current-voltage curve reasonably well for a passive-type PEFC unit, characteristics of the efficiency of a passive-type PEFC controlled by the TSM have been investigated under various conditions (pulse frequency, external load resistance, duty ratio etc.) and improvement of the efficiency of this PEFC has been confirmed.

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Recently, various mobile devices are widespread. However, these devices consume a lot of electric power. From the problem of short duration of batteries, it is required to develop small-size and light-weight fuel cells as the electric power source for them. In this study, in order to improve the performance of hydrogen-fuelled polymer electrolyte fuel cells (PEFCs) of passive type, the authors investigated the effects of the material and structure of the diffusion layer and current collector on the performance of them, and then attempted to make small-size and light-weight passive-type PEFCs on the basis of these results.

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The direct ethanol polymer electrolyte fuel cell (DEFC) is a suitable energy conversion system for recycle-oriented society on the point that it uses the safe bio-fuel, but there exists a problem that its power generation performance is low. One of the causes is the generation and stagnation of by-products in the anode-side passage. In this study, the authors have carried out the numerical analysis of aqueous solution flow and the measurements of its flow and by-product concentrations for investigating the behavior of by-products.

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In the present study, two types of plasma supplies, the direct plasma oxidation method and the indirect plasma oxidation (air radical injection) method, were evaluated with regard to NO oxidation rate, NOx removal efficiency and applied power. The air radical injection method showed that both NO oxidation rate and NOx removal efficiency were better than those of the direct oxidation method. Furthermore, performance parameters of NO oxidation were investigated. As a result, more than 80% of NO oxidation rate was achieved when air radical flow rate was in the range of 20%.

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Effect of gas humidity and high voltage electrical field (HVEF) on evaporation rate were investigated. A pin type electrode was fixed above the water surface. Mass and temperature changes of water were measured under a continuous current electrical field and with parallel gas flow to the water surface. The experimental results showed that evaporation was enhanced with HVEF, gas humidity increased, evaporation rate was decreased but rate of evaporation acceleration by HVEF was increased. Water temperature reached a level approximate to wet-bulb temperature when HVEF wasn't used. Using HVEF, water temperature reached a lower than that without HVEF reading in the low humidity test, and reached a higher reading in the high humidity test.

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Recently, there has been a need for effective use of low temperature exhaust heat. So, we have suggested the intermittent suction dryer which can use low temperature exhaust heat (steam of latm or water of less than 100℃) as a heat source and use steam condensation in an auxiliary vacuum tank for reducing chamber pressure intermittently. Heat and mass transport mechanism in material to be dried under intermittently reducing pressure, and the utility of intermittent suction effect were investigated experimentally. Used coffee grounds were used as the material to be dried, both the temperature and moisture content distributions were measured. The heat flux from heat source to sample was also measured. From these results, it was shown that water in the area of greater than saturation temperature evaporated rapidly under intermittently reducing pressure and some vapor condensed in the area of less than saturation temperature. Evaporation became rapid at intermittent reducing pressure.

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A better understanding of the formation of polycyclic aromatic hydrocarbons (PAH) is of great practical interest because of their potential hazardous health effects and their role as intermediates in soot and fullerene formation. In this work, a new PAH growth path, the addition of phenylacetyrlne (C_6H_4C_2H*2) to PAH, is suggested. The reaction rate constants were calculated as functions of pressure through the RRKM theory, using the molecular and transition-state parameters computed through the molecular orbital theory at the B3LYP/6-311G (d, p) or 6-31G (d, p) level.

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Molecular behavior of a nano cluster in a nano scale flow field was investigated by the classical molecular dynamics method. A tiny butane molecular cluster and an aluminium surface were employed to simulate the interaction processes of a nano cluster and a metallic filter. The velocity of the butane molecules affected their behavior of passage or adhesion to the filter. The butane molecules adhered to the upper layer of the filter in the cases of small velocity and they adhered to the bottom of the filter in the cases of large velocity. The cluster passed though the flow of the filter in the cases of very large velocity.

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NO formation process on diesel combustion under supercharged conditions was investigated using a spray combustion model. The spray combustion model was developed by adding NO formation scheme to a stochastic mixing model. The calculated results indicate that in the early stage of combustion, rich mixtures are diluted with air and fall into the equivalence-ratio range with high NO formation rate. Then the mixtures are further diluted and shift to the state of frozen NO.

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Our recent results on a new aftertreatment system of diesel emission using nonthermal plasma, especially on the removal of soot and NOx are reported. The nonthermal plasma regeneration of DPF is an important result in this paper. It was possible at the low temperature of 240℃ for a small diesel engine generator. Further, recent results on NOx removal using nonthermal plasma desorption is also reported.

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This paper describes the results of on-board measurement of engine performance and emissions in D.I. diesel vehicle operated with waste-cooking oil bio-fuel. Here, two waste-cooking oils were investigated. One fuel is the waste-cooking oil methyl esters. This fuel is actually applied to the garbage collection vehicle with D.I. diesel engine (B100) and the city bus (B20; B100 is mixed 20 vol.% in gas oil) as an alternative fuel of gas oil in Kyoto City. Another one is the raw waste-cooking oils removed impurities. Here, in order to improve the fuel properties, kerosene is mixed 70% volume in this fuel. This mixing fuel (i-BDF) is applied into several tracks and buses in Wakayama City. It is confirmed that PM emission of biodiesel fuel is remarkably lower than that of gas oil. And PM emission in summer increases comparing with that in autumn. On the contrary, NOx emission in summer is lower than that in autumn.

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Distributions of local flame temperature and chemiluminescence of OH*, CH* and C_2* radicals were simultaneously measured in laminar premixed flames. The temperature measurement is based on the Rayliegh scattering method. The Cassegrain optics was used to measure the chemiluminescence and Rayleigh scattering with high spatial resolution. Relationships between the local flame temperature and chemiluminescence intensities were examined. As a result, it became clear that there was a close relation between temperature and the ratio of OH* and CH* chemiluminescence intensity.

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In this study, 3-Dementional flame flow interaction was experimentally investigated in turbulent premixed Bunsen flame in a reaction sheet regime. It examined the changes of gas vector when flame front passes from unburnt to burnt. It changed more widely the radial direction of the gas velocity than the tangential direction. There is burnt gas between reaction zones closely on the tangential direction, so gas expansions of tangential component of burnt gas velocity are canceled. Therefore it changed more widely the radial direction of the gas velocity than the tangential direction.

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The flame stability limits essentially define the fundamental operation of the combustion system. The critical conditions at the stability limits are highly dependent on flow configurations and some species of fuels. For fuel (Hydrogen), the flame-base stability mechanism for flame holding has been studied. In this study, the transition behavior from the stable flame attached to nozzle rim to lifting and blow off is observed experimentally in unconfined, quiescent atmosphere air. Experiments were conducted to investigate the stability minimum limits and flame behaviors for various nozzle diameters from 0.14 to 6.1 mm. The results obtained are as follows. It turns out that the minimum limit of a stable flame is not dependent on average jet speed, but it is dependent on fuel flow rate. Regarding to the micro scale nozzle, the flame length of the laminar flow is decided by fuel flow rate.

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