A new type of wind turbine system with wind power enhancement technology, named "Wind Lens", has been developed and reported in various publications, showing power augmentation by a factor of 2-5 compared with conventional turbines. This study reports further development of the system and its application including floating off-shore integrated energy farm experiment in Hztkata Bay, Japan. The experiment is a mile stone leading to next generation meaawatt-scale floating off-shore integrated energy farm. The scope of this paper also includes a brief discussion of a road map to the next generation floating energy farm

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The authors conduct subsonic wind-tunnel experiments, in order to investigate the basic characteristics of an autorotating plate in uniform mainstream, which has a potential for new windmills and waterwheels with very simple structures in addition to mixers/diffusers. The present study focuses on both the effects of an aspect ratio AR and a tip-speed ratio Ω° upon the tumbling of a flat plate with a low depth-to-width ratio λ=0.02-0.08. The authors carry out measurements using a torquemeter together with the synchronised measurements of a plate's attack angle a for the analyses with a phase-averaging technique, in addition to measurements using a hot-wire anemometer and flow visualisations. As a result, we confirm that there are two torque modes T-modes I and II, as well as two flow-velocity modes V-modes I and II. This gives us more useful information for efficient renewable-energy resources.

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This paper describes results of a numerical study on the performance of a vertical axis wind turbine (VAWT) with variable-pitch straight blades. Two-dimensional numerical simulation of a VAWT was performed using the commercial CFD software ANSYS FLUENT 13.0. The effects of the amplitude of variable-pitch angle and the tip speed ratio on the performance of VAWT were investigated. As a result, differences between the variable-pitch angle type VAWT and fixed-pitch one regarding torque variation and flow field were revealed. For the low tip speed ratio, the torque of the VAWT with the variable-pitch angle increased in all area of the turbine with increasing amplitude of variable-pitch angle. However, for the high tip speed ratio, the torque of the VAWT increased in the downwind area of the turbine with increasing amplitude of variable-pitch angle.

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In this paper we will present some novel results of our research and development in the field of wind energy utilization. Our effort in this filed is mainly concentrated to the conceptual design of optimum airfoil sections for the blade of straight wing non-articulated vertical axis wind turbine which undergo cross wind motion. This concept was embodied in the design of a family of airfoil sections designated as TWT sections and a series of wind tunnel testing was conducted to confirm its desired aerodynamic characteristics. Then, we designed an experimental straight wing non-articulated vertical axis wind turbine system with straight blades to evaluate system performance and structural analysis results, and furthermore to collect operating experiences under real, fluctuating wind conditions.

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We have started the research of application for comprehensive wind energy since 1976. The research has continued for more than thirty years. The topics of the research include the design of best suitable turbines, wind characteristics, wind energy density and reserve, the efficiency of the wind power system, etc. Both the Straight Win Fixed Pitch Vertical Axis and the Horizontal Axis wind power systems have done the wind tunnel experiments and field tests. The research results also cover the relevant running tests, determination of the boundaries, stress tests in limits, etc. This report is the summarized statement for the most up-to-date experimental results of the Straight Wing Vertical Axis Wind Turbine power system.

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In this paper, further evaluations of performances of prototype Mg-alloy micro vertical axis wind turbine were conducted. In addition, a comparative study of airfoils for vertical wind turbine was conducted; they are a prototyped airfoil based on the Clark-Y airfoil, a numerically optimized airfoil; NUT airfoil, and NACA0018 airfoil. At first, aerodynamics coefficients of lift, drag and momentum centered at the quarter of chord length at various angles of attack were clarified for those airfoils by 2-D steady CFD analysis. Typical Reynolds number were set around 3.3×10^4 for a portable-type micro VAWT system. We also examined a torque variation generated from wings with these airfoils using 3-D unsteady CFD analysis. The optimized airfoil; NUT airfoil has higher torque than NACA0018 airfoil, thus it will bring a promising improvement of power of micro VAWT.

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Vertical axis wind turbine generator is mainly used for small size wind turbine generator, and is independent on wind direction. Its rotating part (shaft unit) should be rotated by extremely small torque so as to increase generation efficiency. But commercially available bearing is not necessarily suitable for the shaft unit because its both static and dynamic load rating are frequently larger than those demanded for the vertical axis wind turbine. As a result, the frictional force and the rotating torque of the commercially available bearing is too large for the shaft unit to rotate lightly. In this study, through the experiment of actual vertical axis wind turbine, the bearings used for the shaft unit are reviewed in accordance with "IEC61400-2". The design of the shaft unit with the bearings having the most suitable load rating and the frictional force for the vertical axis wind turbine is tried. The newly designed shaft unit will be applied to the vertical axis wind turbine and will be tested.

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In this paper, the efficiency improvement in power generation of vertical-axis wind turbine is examined. For the efficiency improvement of power generation in vertical-axis wind turbine, the wind collection equipment and the introduction of the winglet is proposed. The effectiveness of this proposed method is shown by the experiment on 2kW-type small wind turbine system. In this paper, the following is compared :1) The case of the wind collection equipment. 2) The case of the winglet type wing. 3) The case of the collection wind equipment and the winglet type wing. As the results, in this study, they is good characteristics in case of wind collection equipment and the winglet.

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In the current expansion of wind turbine generation, we propose the new wind turbine generator system (hereafter refer to as CC-less) optimized to the wind turbine. The CC-less consists of: the permanent magnet synchronous generator (PMG) which has several windings, reactor, and rectifier. In this paper, a new CC-less with the over speed brake function is proposed. The new CC-less consists of: PMG which has one winding, reactor, condenser, and rectifier. Currently, it was directly coupled with the straight wing non-articulated vertical axis wind turbine (SW-VAWT) and is examined in the roof of our company building. From the field test result and view, it has been confirmed that the new CC-less restrains the over speed of wind turbine.

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The function of yaw driving system which is mounted to the horizontal axis wind turbine is the device to accord the direction of wind and nussel, and gear drive is main drive method in the past. But the generation of failure which is followed gear surface friction by receiving the upwash wind and shock by receiving the side direction wind is reported. And at the time of swivel part exchanging, a large amount of maintenance cost occurs by using large size construction equipment. Under such circumstance, I suggest the gearless Yaw Axis Swivel Driving System as a new and effective mechanical element. I manufactured and installed this system on an actual wind turbine and examined its performance. In this paper, the result of experimental proof is described.

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Recently, new wind turbine generator optimized for the wind turbine output is proposed. This wind turbine generator is made of PM generator and is using neither control circuit nor PWM converter. From the experiment result and review, it has been confirmed that the matching of the wind turbine and new generator. This time, the electrical characteristic examination in combination with the new generator and the interconnection inverter was tested. In the result, it has been confirmed that the efficiency of the new generator is better than the interconnection inverter.

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If tidal and ocean current power system can be installed in site where the flow velocity is fast, it may be able to reduce the power generation cost compared with other power generation system. However, suitable sites like this in shallow water around the coast of Japan are restricted. In this study, we investigate a high power tidal and ocean current power system with a multi rotor system. It is important for the tidal and ocean current power generation system to utilize widely in the coastal area of Japan in order to ensure a certain amount of power generated at about 1.0m/s flow velocity. For the multi-rotor system, the back rotor can be collected the flow energy passed from the front rotor. We report the result of a fundamental study and concept design for multi rotor system.

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Micro hydro power is suitable for Japan, which has many rivers, but it is not sufficiently spread in present. In this study, the authors set to work to develop the micro hydro turbine generator which can be used at low head condition without major construction for installation. In this paper, the authors report the performance tests and their results of a spiral waterwheel. Moreover, the authors tested effects of power augmentation unit such as a confuser and a diffuser.

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An experimental study has been done to elucidate effects of mass flux G, degree of subcooling ΔT_<sub>, initial solid temperature T_<b0> and thermal properties of test liquid and hot block on wetting temperature during spray cooling of a hot block. Wetting and quenching temperatures which correspond to the MHF point and sudden drop in surface temperature during transient transition boiling region were evaluated and categorized with GΔT_<sub>.

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Pool boiling heat transfer experiments for micro heat transfer surfaces were performed by using ethanol as test fluid. The experiments were conducted at 0.101 MPa. The test heat transfer surfaces were 20, 10, 7, 5, 3, 2 and 1 mm in diameter. The test heat transfer surfaces were made of copper. Electric heaters were attached at the back end of the test heat transfer surface. Boiling behavior was also recorded with a high speed video camera. The overall trend of the boiling heat transfer was well expressed with the Rohsenow correlation. As the diameter of the boiling surface became smaller, the boiling heat transfer was enhanced and the critical heat flux increased.

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Flow boiling and evaporation heat transfer in mini-channels was examined by using water. The cross-sections tested were in a range of 0.163 mm × 3 mm〜1.25 mm × 3 mm. The length of the flow channel was 260 mm. When the flow channel gap became smaller than 0.273 mm, the single-phase flow pressure drop coefficient maintained the characteristics of laminar flow in the turbulent flow region. The single-phase flow heat transfer coefficient was smaller than the value predicted with the correlation for the usual size and the trend itself was also different in the turbulent flow region. In forced flow boiling and evaporation, the evaporation was dominant. The flow channel was filled with a large-long bubble. The critical heat flux condition was triggered by the formation of dry areas in the film under the large-long bubble. When the channel gap became smaller than 0.327 mm, the evaporation heat transfer coefficient became smaller than the value predicted with the usual correlation. The provable reason was the use of the usual turbulent flow heat transfer correlation to correlate the results. The effect of narrowing the channel gap on the thermal-hydraulics seemed to appear as the channel gap became smaller than 0.35 mm.

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The wall superheats at the lower limit of film boiling were measured by quenching method for three types of silver cylinder with flat, convex-hemishperical and convex-conical bottoms which were immersed in a saturated or subcooled water at atmospheric pressure. The wall superheats at the lower limit of film boiling for the test cylinders are independent of the bottom configuration for saturated water and increased almost lineary with an increase in liquid subcooling for subcooled water. This dependence of the wall superheat at the lower limit of film boiling on liquid subcooling is similar to the experimental results obtained by Dhir-Purohit for a sphere and by Nishio-Uemura for a horizontal cylinder, respectively.

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It is suggested that a steam injector (SI) is adjusted to heat pump systems for the battle against global warming to downscale them. SI which consists of a compact structure has high heat transfer performance due to the direct contact condensation. Thus, the downsizing of a condenser is expected. And it is expected that the feature to drive without any rotating power source and act as a static jet pump may enable to downscale a compactor. The objective of the present study is to develop the further small SI. In particular the flow observation of an ultra micro steam injector whose throat diameter is 600 μm is consulted on to investigate the internal flow mechanism. As the results, the formation of a water jet and the negative pressure state in the mixing nozzle which are the operating characteristics of SI is confirmed from the flow observation.

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Improvement of steam separators in ABWR is required to decrease pressure drops at high steam qualities without degrading the separation performance. In this study, shapes of the swirler and 1^<st> pick-off ring (POR) were modified to reduce the pressure drop, and experiments using a one-fifth scale model of the separator were carried out to evaluate its performance. Experimental data showed that the modifications successfully reduce the pressure drop and carry-under (CU) in the separator without degrading the separation performance.

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Welding of structures such as pressure vessels is carried out for maintenance of nuclear power plants. For shortening the work process and reducing exposure radiation, development of a technique to weld is carried out without discharging the water from the pressure vessel. However, the welding must be done in an inert gas condition, and therefore it is necessary to remove the water around the welding point. We developed the air jet curtain technology which made possible the removal of water by feeding gas to keep the welding point in the gas phase.

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This paper describes a gas turbine inlet air cooling system using high pressure spray nozzle. Thermal characteristics and fluid properties were studied by performing the wind tunnel test that simulated an actual gas turbine intake cooling duct part. A result of examining the cooling performance due to differences in the inlet relative humidity 30〜50%RH, the cooling performance was the same. Furthermore, as a result of investigating the cooling performance due to the difference in a spray nozzle number, in one case, it became clear from 33 ℃ that it is possible for 28 ℃ to cool ,and in three case, it became clear from 33 ℃ that it is possible for 23 ℃ to cool. The result of obtaining with the relative humidity and temperature sensor was plotted on the psychrometric chart and the air humidifying cooling process of an actual gas turbine inlet duct part was clarified.

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Although area-averaged void fractions in subchannels have been measured frequently in literatures, distribution of local void fraction in a rod bundle have been rarely reported. Little is also known on bubble motion in a rod bundle. Distributions of local void fraction and bubble velocity in a 4x4 rod bundle were, therefore, measured using a conductance probe in this study. Liquid velocity was also measured using LDV. Experimental results showed that the distributions of the void fractions in the inner and side subchannels depend not only on lift force acting on bubbles but also on geometrical interaction between the bubble and the rod wall. The relative velocity between bubbles and liquid phase in the subchannel possesses non-uniform distribution over the cross-section. This is caused by increase in drag force acting on bubbles due to bubble deformation induced by interaction between the bubbles and the rod wall.

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It is important to know the flow structure in industrial products using gas-liquid two-phase flow. Gas-liquid density ratio is one of the most important parameter to simulate flow structure. This research performs two-phase flow measurement in horizontal tube bundle. This test facility can simulate behaviors of water-vapor two-phase flow at high pressure (5.6MPaabs) by using sulfur hexafluoride (SF6) gas for gas-phase and water for liquid-phase at ambient temperature and low pressure (0.6MPaabs). These results were compared to the values by previous empirical equation to verify soundness of this facility and measurement method.

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The void fraction in a forced convective flow boiling is very important information for understanding the characteristics of the boiling two-phase flow. Consequently, many experimental investigations have been carried out to obtain the local void fraction so far, but the detail data among the whole of the test-section has not been enough. Especially, the data under subcooled condition are quite limited. In this study, the void fraction distribution in a forced convective boiling was quantitatively measured by using the thermal neutron radiography. These results were compared with several existing void fraction correlations. Although these correlations show a good agreements with experimental results under low heat flux condition, there is no suitable correlation to estimate the void fraction under non-thermal equilibrium condition.

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Critical Heat Flux (CHF) is a very important designing factor of boiling systems, such as boiler and so on. Under flow instabilities condition, such as density wave oscillation, the CHF value is drastically decreased with an increase of oscillatory amplitude and oscillatory period, and the wall heat capacity becomes a very important parameter. In order to clarify this phenomenon, it is important to understand the void wave propagation under oscillatory flow conditions. In this investigation, the quantitative measurement of the void fraction in boiling two-phase flow under oscillatory flow condition was conducted by using the neutron radiography. The measurement results of the void fraction have been evaluated by the comparing with the calculation results of the lumped parameter model.

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To clarify the sintering property of porous nickel, we simulated the porous nickel models by using molecular dynamics and constructed master sintering curve (MSC) based on the combined stage sintering model to obtain the sintering properties, such as sintering activation energy, dominant sintering mechanisms, and sintering behavior. To construct MSC, we simulated various porous models with changing the initial porosity and synthesized the simulation results. From analysis of constructed MSC, we found that apparent sintering activation energy increased with temperature. This increment of sintering activation energy indicates that dominant sintering mechanism changes with temperature. By using molecular dynamics sintering simulation, we can compare experimental MSC based on thermal history with theoretical MSC based on sintering mechanism and material property.

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Direct internal reforming (DIR) can be applied to solid oxide fuel cells (SOFCs) because the anode of SOFC usually contains Ni which can act as steam reforming catalyst. One drawback is that the endothermic nature of the steam reforming reaction may cause a steep temperature gradient in the cells. In this study, we seek a possibility to control the reaction rate of DIR by tuning the microstructure of the porous anode. As a first step, experiments of steam methane reforming on Ni-YSZ cermet were conducted varying the composition of Ni and YSZ in the test cermets. The performance of the test cermets as a reforming catalyst was evaluated as a reaction rate equation. 3D microstructure quantification was performed to the test cermets after the reforming experiments. The relationship between the microstructure of porous cermet and its reforming performance is discussed.

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The authors try to reveal the dominant chemical reactions and the optimum conditions, supposing the design of ethanol steam-reforming reactors for hydrogen production. Experiments are conducted for Cu/ZnO/Al_2O_3 catalyst. Using a household-use-scale reactor with well-controlled temperature distributions, we specify the effect of liquid-hourly space velocity LHSV upon the ethanol conversion X_<C2H5OH> and upon various concentrations. Furthermore, we compare experimental results with chemical-equilibrium theories. As a result, the obtained concentrations suggest that the dominant chemical reactions at LHSV < 0.2h^<-1> are different from those at LHSV &ge; 0.2h^<-1>.

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The authors develop a small and simple steam-reforming reactor in a home-use size for n-dodecane as a heavy-hydrocarbons fuel. Under the thermal condition controlled by electric heaters and a gas burner with a thermal diffuser, the authors measure the inside-temperature profile and the hydrogen molar fraction (concentration) C_<H2>, together with the molar fractions C_<CH4>, C_<CO> and C_<CO2> of other main gas components such as CH_4, CO and CO_2, respectively. As a result, the authors successfully achieve suitable inside-temperature profiles. And, the effects of the liquid-hourly space velocity LHSV upon the molar fractions and a conversion ratio X_<C12H26>, experimentally. Furthermore, the authors reveal the effects of the temperature T inside the reactor upon them molar fractions, comparing with the thermal-equilibrium theory in a wide range of LHSV.

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Effects of distribution of fuel gas velocity on performance of SOFC were investigated by numerical analysis. The fuel gas was supplied to anode-supported cells by two different methods: jet flow and parallel flow, and cell performance was analyzed at 1000℃ as changing H_2 flow rate in each method. In the case of the jet flow, the fuel gas jetted out a blow port and impinged on the fuel electrode surface. On the other hand, in the case of the parallel flow, the fuel gas flowed parallel to the fuel electrode surface. Activation overpotential, concentration overpotential and electromotive force were calculated by using gas concentrations obtained by numerical analysis. As a result, the terminal voltages were most affected by the electromotive force. Also, it was found that the jet structure could improve the performance of SOFCs.

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The present paper discusses the dynamic behavior of a tubular solid oxide fuel cell (SOFC). The paper focuses on the transient response of voltage to the current change assuming load-following operation. The simulation models of the mass transfer in the gas flow channel and the porous electrodes of the single tubular cell were developed. It was assumed that hydrogen, nitrogen and steam mixture was supplied to the anode channel and air was supplied to the cathode channel. The unsteady diffusion equations were solved under isothermal condition. The steady-state performance of the cell was evaluated, and the good agreement between the simulation results and the previously reported experimental data was found. Based on the transient responses of the voltage to the current change, it was found that the transient time of the diffusion in the electrode was negligible contrary to the diffusion in the gas flow channel. In addition, it was found that the presented results on the dynamic behavior agreed qualitatively with the experimental data.

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The present paper shows the discussion on the experimental investigation conducted with 300W class planar type solid oxide fuel cell (SOFC) cell stacks. The experimental investigation focuses on transient characteristics of the cell performance to the current manipulation, being assumed that the manipulation is appropriate methodology for power control policy in the practical SOFC use under the load-following operation. The stack was forcibly heated by the external sources to keep the cell operating temperature. The dynamic experiment was demonstrated under the constant operating temperature while being purely fueled by hydrogen. The fuel flow rate was manipulated to level the fuel utilization factor under the current change operation. The voltage deterioration was found on the manipulation with higher fuel utilization, though the achieved DC efficiency was contrary higher. Obtained experimental result shows the reasonability of the fuel utilization factor as an operative reference of the control scheme.

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Electrochemical Partial Oxidation (EPOx) of methane can convert exhaust heat into electricity as much as difference between change of Gibbs free energy and change of enthalpy by using Solid Oxide Fuel Cell (SOFC). Gadolinium Doped Ceria (GDC) is used as the electrolyte that has high oxide ion conductivity at the operation temperatures below 600℃. In this work, fabrication process for the micro-tubular SOFC was established through the characterization of the electrode and electrolyte. The SOFC performed the peak power of 147mW/cm^2 and 220mW/cm^2 at 470℃ and 500℃, respectively, and optimizing the porosity and pore size of the anode is estimated to improve the peak power at 550℃.

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Proton exchange membrane (PEM) has been used in electrochemical systems such as fuel cells and water electrolysis. For the practical use of PEM, crossover is a significant issue. The crossover is a permeation of hydrogen gas through PEM, and it causes the decrease of current efficiency. Therefore, it is important to figure out the permeation mechanism and to develop a superior PEM that has a lower permeability. In this study, we developed a new measurement system for hydrogen solubility and diffusivity in PEM based on NMR technique. The system can detect hydrogen molecules in PEM through NMR signal and obtain directly both the solubility and diffusivity. We measured these properties in Nafion^[○!R]112 and 117. The hydrogen solubility showed a proportional relationship to ambient pressure, and its representative value was approximately 1.4×10^<-5>mol/cm^3 at 1.0MPa. The hydrogen diffusivity in Nafion^[○!R] was 2×10^<-10>m^2/s, which did not show pressure dependence up to 1.0MPa.

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Femtosecond laser pulses (fs pulses) cause very interesting phenomena due to their extremely high energy density. The effects on substances are not thermal, but are multi-photon absorption. When this multi-photon absorption of fs pulses operates on water, extraordinary phenomena different from laser-induced cavitation by a usual laser such as nano- or pico-pulse laser are induced. In this study, fs pulses were focused on purified water in a glass cell through several types of lens. Some fs pulses split from original beams through a beam splitter were used as probing light of femtosecond order. Femtosecond-order time-resolved optical measurement was realized by adjusting a light path length of the probing light. We found out strange time-series process of refraction index changes of the water irradiated by the fs pulses, and the bubble nucleation and bubble growth, and the interesting bubble properties. Based on these results, we discuss a relation between those and fs-pulse peak intensity. Further, in particular, we discuss the nucleation and growth process from femtoseconds to picoseconds.

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Solid oxide electrolyte cells are expected to apply for a hydrogen generator as SOECs (Solid Oxide Electrolysis Cells). In this study, we carried out the cycle analysis for SOEC systems. The cycle analysis was carried out by the two following processes. First, we constructed the system models for SOEC systems considering not only SOEC stacks but Balance of Plant (BOP). Next, we calculated for system efficiency based on heat and mass balance. According to the processes, we calculated the SOEC systems by two operating temperatures, 650 and 850℃. As a result, we obtained the high hydrogen energy conversion efficiency (η_<total> =98.4% HHV) of SOEC systems.

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This paper shows an analysis of water transport phenomena in MEA in PEM electrolysis cell. In previous study, it was shown that the change of water transport pattern in diffusion layer and catalyst layer doesn't affect performance and Nafion membrane may be directly related to performance. In this study, a numerical analysis to clarify the water transport phenomena in MEA based on the experimental data (the amount of discharged water from the cathode and the impedance) was developed. The result showed that the effect of osmotic force on the water transport through the MEA is far larger than that of diffusion force and water content in Nafion membrane may increase as current density increases.

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Thermoacoustic refrigeration is a very attractive method of temperature control due to its environment friendliness. The thermoacoustic heat pumping occurs within a regenerator positioned in the thermoacoustic device. The acoustic field within the device consists of acoustic travelling waves propagating in positive and negative directions and as such, the regenerator temperature gradient will be influenced by both. To investigate the effect of these individual travelling waves, we constructed a thermoacoustic device consisting using two opposite facing speakers thus enabling manipulation of positive and negative direction travelling waves. By decomposing the measured acoustic field into its positive and negative propagating components and calculating the acoustic power using the two sensor method, the effect of the individual travelling waves on the direction of acoustic power and regenerator temperature gradient was observed.

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The present paper describes experimental results of the behavior of a small water droplet impinging onto a hot surface and the water spray cooling. The effects of impinging velocity and diameter of droplet on the solid-liquid contact time, maximum spreading ratio on a hot surface and cooling time until the surface temperature drops to 100℃ from 500℃ are examined. The surface used here is SUS304 steel cylinder with the value of roughness, Ra 0.04. The length of contact time decreases as the impinging velocity decreases and increases as the droplet diameter increases. The maximum spread ratio gets bigger with increase in impinging velocity and droplet diameter. The cooling rate increases with increase in impinging velocity. The cooling rate also increases with decrease in droplet diameter when the flow rate of water is constant.

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Thermophotovoltaic generation of electricity in ranges of far-field and near-field radiation was investigated through experiment by making use of a schottoky diode and a p-n junction cells made of GaSb semiconductor. The maximum power for the far-field was not dependent on a gap between the cell and an emitter surfaces, provided that its view factor was almost unity. On further decrease in gap, the output powers for the schottoky and the p-n junction cells became 4.4 and 3.6 times higher than those for the far-field radiation, respectively. The increase in output power might be originated from a near-field radiation effect, that is, an evanescent wave effect.

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Encouraged by the recent progress in nanostructuring techniques to enhance efficiency of thermoelectrics by reduction of lattice thermal conductivity, we attempt to develop a numerical tool that predicts and evaluates the reduction through characterization of microscopic heat conduction, namely phonon transport properties, based on first-principles. The capabilities and limits of the new framework are discussed, with particular emphasis on effects of alloying and interfaces.

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Some cracks were found at the first stage discs of gas turbine rotors made of Ni-base super-alloy. There were inter-granular cracking and observed to be highly stressed and damage sensitive locations with less potential for oxidation, which is thought to occur due to hold-time cracking. In this study, laser peening technology was developed to improve fatigue properties of Ni-base super-alloy Alloy 706, and the effects on the material properties were examined. Laser peening is a novel process to induce compressive residual stress on material surface by irradiating focused high-power laser pulses. Several durability tests, such as thermal aging treatment test and stress aging test, were performed under thermal power plant operation conditions, and the effectiveness of laser peening treatment was confirmed.

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Fatigue crack propagation rate of Co-base superalloys (Co-22Cr-23Ni-14W-0.1C[mass%]) for gas turbine combustion parts have been investigated using the electron back-scattering diffraction pattern (EBSP) method. The damage caused by fatigue clack propagation test at high temperature is detected as misorientation, and localize at the clack tip. The value of misorientation tends to increase with increasing the propagation rate. Orientation distribution (OD), kernel average misorientation(KAM) and grain average misorientation(GAM) show good sensitivity and it is possible to evaluate fatigue clack propagation rate using these misorientation parameters at clack tip.

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