A newly developed 1M fps video camera was applied to the observation of drop impacts onto water surfaces. It captured the detailed mechanism of air sheet entrapment when a water drop is impacting onto water surfaces. Instability is newly found on the edge of the entrapped air sheet. The 100 consecutive images are enough to form a short movie, which is suitable for dynamic recognition

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A combined technique of simultaneous measurements of size and 3D velocity components of droplets in a spray has been proposed. This technique is based on the optical technique of glare points observation and stereoscopic PIV (SPIV). The size of droplet is obtained by the interval of the glare points generated by the direct reflection and the 1st refraction from the droplet illuminated by Nd : YAG laser (532nm). The 3D velocity components of droplets are measured by using SPIV based on the images of distribution of the glare points. The optical arrangement for this simultaneous measurements has been devised and the feasibility and capability of the technique was confirmed by applying to size and velocity field measurements of a spray issuing from a swirl fuel nozzle being used in a gas turbine.

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Many of unintrusive velocimetry techniques measure the velocity of tracer particles mixed in fluid. In gas-liquid two-phase bubbly flow, the tracer particles accumulate on the gas-liquid interface and therefore the flow around a bubble might be affected by a possible change of the boundary condition on the interface. To avoid the influence of the tracer particles on the flow, molecular tagging velocimetry is one of the preferable methods because it tracks moleculartags and does not require the tracer particles to measure the fluid velocity. In the present study, we developed a molecular tagging velocimetry using photobleaching which is a photodegradation of fluorescent dye induced by intense illumination. The regions in which photobleaching took place were visualized by a laser sheet and the liquid velocity was measured by tracking the region. The method was applied to laminar pipe flows and the flows around single bubbles. As a result, we confirmed that (1) the measured liquid velocity in a laminar pipe flow agrees well with the analytical value, (2) the present method enables us to measure the velocity in the vicinity of bubbles and (3) the shear stress can be evaluated by measuring the deformation rate of the tags.

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This paper reports a new technique for measuring surface velocities of Marangoni convections in liquid bridges. The technique is based on the use of micro-fluorescent particles and microscopic imaging so that it can achieve spatial resolution high enough to extract velocity information from a thin velocity boundary layer near the air-liquid interface. This technique is combined with the microscopic imaging displacement meter developed by the authors for measuring dynamic surface deformations of the liquid bridge. The surface velocities measured under laminar-flow conditions compare well with those calculated numerically. Some behaviors of surface velocities under oscillatory-flow conditions are revealed experimentally for the first time.

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For understanding such dispersed two-pjase flow as spray and bubbly flow, not only the size and velocity distribution of particles but those simultaneous properties of individual particles are required to understand the unsteady behavior of flow fields. The improved interferometric imaging technique has been developed by the authors that can measure the planar or even volumetric distribution of diameter and velocity vector of particles instantaneously. The accurate diameter determination by the optical compression and subpixel frequency estimation by a Gaussian interpolation technique enables the accurate determination of the droplet correspondence between two successive images and consequently the velocity vectors of each droplet can be measured even from the image of denser spray. The results showed the significant difference of particle behavior depending on the group of diameters in the unsteady flow.

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Measurements of the turbulent properties and local void fraction distribution for bubbly channel flow are reported. Liquid phase velocities and local void fraction are measured using Laser Doppler Velocimetry (LDV) and Image Processing respectively. In bubbly flow, addition of a small amount of 3-pentanol behaving as surfactant changes its flow structure drastically. Absorption of surfactants on the bubble surface prevents bubble coalescence and keeps bubbles smalland mono-disparsed size. So we used two types of bubbles selectively, one has mono-dispersed 1mm diameter under the condition of "with 3-pentanol" and the other has wide spread 1-4mm diameter under the condition of "without 3-pentanol". It is shown that depending on their diameter, tendency of bubble migration toward the wall varies. This tendency links to a deformation of bubble. In the case of "with 3-pentanol", bubbles highly accumulate in the vicinity of the wall. Then the features of bubbly channel flow such as steeper velocity gradient near the wall and flattened turbulent properties in the center of the channel become increasingly prominent.

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This paper describes about the characteristics in the particle laden water jet flow. The experiments are carried out in a particle-laden jet where the mean center velocity of the jet is about 1.9m/s, the particle mean diameter is 389μm and volume flux is 0.25%. In the experiments, the authors propose a new method for measuring the both phase velocities in simultaneously. The technique is based on the PIV. The intensity of the scattering light is used for discriminating the phase of water or particle. The results show the mean velocity of the water-phase has no change with laden particles under the dilute concentration. The fluctuation velocity in the vertical direction is not changed however that of lateral direction is decreased. The Reynolds stress is also decreased when adding the particle, The new experimental method can be presented these features in two-phase flow.

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The particle image velocimetry (PIV) can capture velocity vector fields with high spatial developed with combining the high-speed camera and high speed laser with double pulse option. The 1024×1024 pixel images with frame straddling were captured in 2kHz. Also, PIV data were measured in 512×256 pixel in 10kHz. The system had been applied to capture the water droplet flow. The transient characteristics of the droplet flow can be clearly captured using the developed Dynamic PIV System.

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Ultra micro turbine concept based upon MEMS technology was proposed by MIT in 1997,since then several projects have been initiated and sponsored by DARPA for its development throughout the universities and research institutions in the US. The present authors, who belong to Gas Turbine Society of Japan, regard such ultra micro gas turbine engine systems to be crucial for the future mobile and friendly energy utilization technology that anyone can enjoy at any place on the globe. In this paper, our palm top gas turbine (2-3kW, dry weight 14.3kg included generator, rotational speed 235000rpm, outer diameter 180mm, length 335mm) and finger top gas turbine test model (tens of W, rotational speed 1170000rpm, outer diameter 23mm, length 32mm) are described, which is the two-years research outcome of international cooperation amongst the Japanese universities, institutions and companies, ONERA, CIAM and VKI, under the NEDO financial support International Joint Research Project from FY2001 to FY2003.

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Development of a micro-scale gas turbine power generator is underway at Tohoku University, Tohoku-Gakuin University, Sankyo Seiki Co., Ltd, and Ishikawajima-Harima Heavy Industries Co., Ltd. (IHI). The gas turbine has a centrifugal compressor and a centrifugal turbine of diameter 10mm. The impellers have fully 3-dimensional geometry machined by micro 5-axis end-mill. The objective of developing the micro-turbo charger is to confirm the possibility to realize the compressor efficiency over 62.5% at pressure ratio 3 and at design rotational speed of 870000 rpm. The mechanical design of the micro-turbocharger has been completed, and tested up to 500,000rpm. The compressor performance has been measured at 450,000rpm (52% of design speed).

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This paper describes the design, fabrication and test of a MEMS-based micro turbo machinery. In this device, a compressor and a turbine are formed on the same side of the rotor to escape miss-alignment during bonding process. The rotor is supported by hydrostatic journal and thrust bearings. The device rotated only at low rotation speed up to 2500 rpm, and the rotation speed did not remarkably changed by adjusting air supplies to the hydrostatic bearings. From the test results, we found important problems to be solved for high speed rotation. Concerning to fabrication, flat and smooth bearing surfaces is difficult to fabricate, and a bearing gap is difficult to precisely control due to spikes on etched surfaces and the warp of the devices induced by anodic bonding. The other concerning is bearing design. The journal bearing has a very low L/D number(length divided by diameter). As a result, the journal bearing has a small journal surface, and it is difficult to install the restriction on the journal bearing. Additionally, there is interference between the journal and thrust bearing due to air leakage.

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A prototype Flat-Flame micro-combustor based on the considerations of the problems due to downsizing a combustor has been built and stable flat-flames of premixed hydrogen/air formed within the combustion chamber volume of 0.067 [(cm)^3]. Its stable flame region was enough wide to satisfy the design operation region of power-output of 16 [W]. Flame behavior was observed with an image intensifier and temperature distributions were measured in detail with a fine thermocouple. Although heat losses were remarkable, at the equivalence ratios of over 0.4,the maximum temperatures achieved the adiabatic flame temperatures and the combustion efficiencies achieved more than 99.2[%].

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We have investigated the flame stability of a can-type propane-fueled combustor with a diameter of 50mm for a kW-class micro-gas turbine. The effects of the diameter and number of the fuel injection holes and the position of the fuel injector on flame stability and the temperature distribution near the injector rim were studied experimentally. When a strong re-circulation zone developed near the injector exit, the flame stability satisfied the design point of the combustor, and mcreased with a decrease of the hole diameter and hole number. The stability mechanism was discussed, and the role of high temperature gas passing through the intervals of injection holes was clarified.

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A micro channel device is a device with many narrow passages. It is expected that the micro channel device is high performance heat exchanger device in various fields. In the present study, a high pressure resistant micro channel device is developed. And the heat exchanger with the micro channel device is newly manufactured. Experiment and numerical analysis are performed to investigate the heat transfer characteristic of the flow through the micro channel heat exchanger. It turns out that the overall heat transfer coefficient becomes high with increasing the Reynolds number of heating gas and a coolant gas. The maximum value of the overall heat transfer coefficient for gases is 180 (W/m^2K) in present experimental range.

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In order to establish the design methodology of ultra micro centrifugal compressor, which is the most important component of ultra micro gas turbine unit, a 10 times of the final target model size was designed, prototyped and tested. The problems to be solved for downsizing were examined and 2-dimensional impeller was chosen as the first model due to its productivity. The conventional 1-dimensional prediction method was used for the impeller design. The prototyped compressor was driven by using a turbocharger and the performance characteristics were measured and compared with the prediction. The stress and the vibration analysis in the operating condition were also performed.

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Small-scale radial gas turbincs that are composed of a two-dimensional vaned nozzle and a two-dimensional impeller with tip diameter of 40 mm have been designed, fabricated and experimented. The designed pressure ratio, turbine inlet temperature, and mass flow rate are, respectively 2.91,1223K and 30g/s (in one case 19g/s). These turbines are expected to generate an output power approximately of 7 kW at a rotational speed of 2.4-(10)^5rpm and in one case 4 kW at a rotational speed of 1.89×(10)^5rpm. Aerodynamic-performance measurements revealed that a maximum adiabatic-efficiency of over 65% on the total-to-static basis is about 15% lower than that of a conventional three-dimensional radial turbine. From three-dimensional Navier-Stokes computations with Baldwin-Lomax turbulence model, major sources have been quantified from the entropy generation, and therefore they give room for performance improvement; about halves of loss-generation occur at the exducers, and around 40% of losses occur at nozzle trailing edges and suction side of blades.

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Recently, much attention is paid to foil bearings for micro gas turbine use because these bearings are indispensable elements for realizing maintenance free small size gas turbines. We designed and manufactured a small size radial and thrust foil bearing for the shaft the size of which is 20mm in diameter. In this test apparaturs, the shaft is equipped with radial turbine blades and is driven by compressed air. As a result, we succeeded to operate it at the speed of 60000rpm and measured vibration characteristics.

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