To improve the reliability and the thermal efficiency of LP (Low Pressure) end blades of steam turbine, new standard series of LP end blades have been developed. The new LP end blades are characterized by the ISB (Integral Shroud Blade) structure. In the ISB structure, blades are continuously coupled by blade untwist due to centrifugal force when the blades rotate at high speed. One of the probable failure modes of the ISB structure seems to be fretting fatigue, because the ISB utilizes friction damping between adjacent shrouds and stubs. Therefore, in order to design a blade with high reliability, the design procedure for evaluating the fretting fatigue strength was established by the model test and the nonlinear contact analysis. This paper presents the practical design method for predicting the fretting fatigue strength of the ISB structure, and the some applications are explained.

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The small annular combustor of a micro gas turbine fueled with methane is investigated experimentally and numerically in order to improve the overall efficiency of the small engine. The CFD analysis of the tiny combustor relies on a low Reynolds number turbulence model coupled to the Eddy Dissipation Concept (EDC) and provides important insight about the turbulent flow pattern, flame shape, position and optimal flame anchoring. For the experimental observation, a model combustor, representing 120 degrees of the original annular combustor, is fabricated, which enables us to visualize internal flow. The burning area in the combustion chamber moves to downstream with increase of air flow rate. At full-load, some fuel remains at the combustion chamber exit. Moreover, temperatures are measured and compared with the numerical simulations. The results shown here will form the basis for future optimization of the micro gas turbine with minimal or no increase in combustor pressure loss.

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A methodology to give an optimal layout of a group of heliostats has been developed for beam-down concentrating solar tower systems. Given the maximum solar power together with optical parameters, the method determines an optimal configuration of a heliostat field around a tower. Various optical losses such as cosine factor, shadowing and blocking at heliostats are considered in the calculation. Furthermore, spillage at the receiver is taken into account due to the spread of light caused by the effects of a finite solar disk, flat facet and various stochastic errors in optical hardware and control. It is found the effect of spillage becomes significant at heliostats from the tower at the distance farther than four times of upper focus height of the reflector when receiver diameter is one fifteenth of the height and dominates the configuration of the optimal heliostat layout.

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This paper describes the evaluation of unstable vibration caused by the seal force, which is known as "Steam Whirl" in a steam turbine. Stability of a steam turbine is evaluated by complex eigenvalue analysis of rotordynamics model considering the dynamics of seals, rotor, bearings and pedestals. A commercial CFD program is employed to estimate the dynamic coefficients of labyrinth seal. The labyrinth seal of a large scales steam turbine is taken as an object of analysis and a 3D model with eccentric rotor is solved to obtain the rotordynamic force components. The rotordynamic force is derived by integrating the pressure on the rotor surface. Evaluation formula is formed from the results of numerical calculation, which is used to predict the dynamic coefficient of each seal in a steam turbine. Then rotordynamics model of total system including seal is constructed and stability is evaluated by complex eigenvalue analysis. This procedure is applied to the design of steam turbines and enables the optimization of the turbine structure considering the efficiency and stability.

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A newly developed optical torque sensor was applied to select a steam supply plant among advanced combined cycle, i.e. ACC, power plants of the Tokyo Electric Power Company. The sensor uses laser beams focused on small stainless steel reflectors having bar-code patterns attached on the surface of the rotating shaft, and a technique of signal processing using a correlation function featuring high frequency. The plant that supplied steam was selected on the basis of diagnosis of each steam turbine performance of the plants. Heat balance program was developed to analyze steam turbine performance using data of turbine output measured by the torque sensor and data measured by existing instruments of the power station. The steam turbine that supplied steam was determined by the present method using the optical torque sensor. The accuracy of the method to determine the steam supply plant was analyzed. It was then confirmed that the accuracy was greatly improved as compared with that of existing method.

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A computational method for compressible flows with condensation was developed. Condensation was formulated by two thermodynamic equations of state for pressure and energy. These equations of state were simultaneously solved with the Euler equation and heat transfer equations. A finite volume method based on an approximate Riemann solver was adopted to solve the Euler equation. The computational method was applied to compressible flows in a condenser and a turbine exhaust hood. The flow regime changed widely from subsonic flow to transonic flow during a small decrease of cooling water temperature. Subcooling temperature from the annulus of the turbine blades to the condensate in the hot well was investigated. Results showed the subcooling temperature could be reduced by using an advanced steam guide which was designed to improve diffuser performance under widely changing conditions.

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A significant number of hydraulic turbines operated in Japan were installed in the first half of the 20th century. Today, aging degradation and flaws are observed in these turbine equipments. So far, Japanese engineers have applied NDI technology of Ultrasonic Testing (UT) to detect the flaws, and after empirical evaluation of the remaining life they decided an adequate moment to replace the equipments. Since the replacement requires a large-scale field site works and high-cost, one of the solutions for life-extension of the equipments is introduction of repair services. We have been working in order to enhance the accuracy of results during the detection of flaws and flaws dimensioning, in particular focusing on the techniques of Tip-echo, TOFD and Phased-Array UT, accompanied by the conventional UT. These NDI methods made possible to recognize the entire image of surface and embedded flaws with complicated geometry. Then, we have developed an evaluation system of these flaws based on the theory of crack propagation, of the logic of crack growth driven by the stress-intensity factor of the crack tip front. The sophisticated evaluation system is constituted by a hand-made software and database of stress-intensity factor. Based on these elemental technologies, we propose a technique of repair welding to provide a life-extension of hydraulic turbine components.

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The unsteady flow field of an axial-flow turbine rotor was investigated experimentally using an LDV system. Detailed measurements of the time-averaged and time-dependent distributions of the velocity, the flow angle, and the turbulence intensity were carried out. The obtained data was analyzed from the viewpoints of both absolute (stationary) frame of reference and relative (rotating) frame of reference. This paper focuses on the effect of the turbine nozzle secondary vortices (passage vortices combined with trailing edge vortices) near the hub endwall on the flow field inside the rotor passage. The nozzle passage vortex are accumulated on the rotor suction surface because of both the negative jet effect of the nozzle passage vortex itself and the formation of the rotor passage vortex. The nozzle passage vortex induces large fluctuations of velocity and turbulence intensity inside the rotor. On the rotor suction surface, the maximum value of the turbulence intensity at the nozzle passage vortex region is as much as 18%.

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Visualization of water behavior in a polymer electrolyte fuel cell was conducted by neutron radiography. Real-time video images and high-resolution still images were photographed with measurement of fuel cell performance. It was clearly visualized by real time imaging that water condensed in an air supply line was coming into a fuel cell. In this case the cell voltage decreased when water flowed into the cathode side. On the other hand, no effect of condensed water into the anode side was observed on the cell performance. In the high resolution still imaging, water amount was measured quantitatively. The water thickness was evaluated for the gas diffusion layer (GDL) covered by ribs and channel part with GDL separately. It was shown that the higher oxygen utilization, i.e. lower air flow rate, caused an increase of water amount and lowering of cell voltage. It can be said that water amount in the PEFC might strongly depend on airflow rate, and the cell voltage might be affected by the water amount.

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While significant efforts to prevent further Climate Change have been put into practice, coal is, and coal will always be, playing the major role in global energy supply in next decades. To use coal with minimal environmental impact, one of the practical solutions that are available today is the Ultra-Supercritical (USC) technology which is a well-established technology with high steam conditions took place predominantly in Europe and Japan. This led to construction of many USC power plants in recent years, and Electric Power Development Co., Ltd. (EPDC) in Japan has been one of the most experienced USC operators in the world. Further development of the technology is being carried out in Europe, the USA and Japan.

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The advantages of coal are the largest reserves among any other fossil fuels, and can be found in many places including some developed countries. Due to the weak energy security of Japan, it is necessary to use coal as an energy source. We have designed the detailed energy model of electricity sector in which we take both energy conversion efficiency and economic aspects into consideration. The Japan model means an energy-economic model focusing on the structure of the energy supply and demand in Japan. Furthermore, the most suitable carbon capture and storage (CCS) system consisting of CO₂ collection, transportation, storages are assumed. This paper examines the introduction of clean coal technologies (CCT's) with CCS into the electricity market in Japan, and explores policy options for the promotion of CCT's combined with CCS. We have analyzed the impacts of carbon tax where each fossil technology, combined with CCS, becomes competitive in possible market. CO₂ mitigation costs for all plants with CCS are detailed and compared.

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Environmental concerns are causing commonly used chlorofluorocarbon (CFC) refrigerants to be phased out of production. The less ozone-depleting HCFC's are regulating. The green house effecting HFC's are also likely to be regulated and banned in the next period. Accordingly, attention is drawn to the Stirling refrigerator, which is a perfect Freon free refrigerator. Moreover, The Stirling cycle has the highest theoretical cycle efficiency corresponding to the value of the Carnot cycle among the proposed thermodynamic cycles. The green house effect by carbon dioxide issue would make better recognizing the importance of efficient use of energy in terms of high energy conservation measures. The authors have designed and developed a 100 W class Stirling refrigerator for household use. And the prototype machine has been integrated with a 100 litter class refrigerator. The operating characteristics of this Stirling unit or the prototype machine have been evaluated. Moreover, the authors evaluated the machine driving engine mode using ultra-low temperature media. As a result, the operational characteristics of the Stirling cycle machine have been clarified with respect to design factors. These results demonstrate that the Stirling cycle machine is one of the promising candidates as a new refrigeration system or a new generation system.

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In order to construct a control system for flow separation around an airfoil, continuous jet type vortex generator and optical cantilever sensor for discriminating flow condition were developed. Blowing jet apertures of the vortex generator are placed in airfoil surface at 0 and 30% chord. The jet apertures were aligned span-wise on the suction surface. Locations and interval of the apertures were decided according to the previous data on the flow separation at low and high attack angles of the MEL001 airfoil. Most distinctive feature of the present jet vortex generator is that it can produce single, longitudinal vortex with arbitrary strength and extent by controlling the jet velocity distribution across the aperture. The optical cantilever sensor was developed. It was installed at the trailing edge. The sensor has two functions: discrimination of flow direction and compensation of temperature fluctuation of flow. The flow around the airfoil is controlled by actuating of the vortex generator and information from the optical cantilever sensor. The vortex generator can be used not only as an actuator but also sounding flow condition. The longitudinal vortices are discharged as tracer for the flow monitoring. The discharged tracer vortices accumulate information on the flow around the airfoil as they travel downstream. Thus the flow condition is monitored by the sensor at the trailing edge. The monitored signals were sent to the computer and analyzed and then feedback control signal is sent to the actuator.

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In this work, we developed a Web system for designing constitution and structure of a composite and predicting its thermal conductivity. Two simulation methods, analytical method and finite element method, are available fitting for different requirements on computational efficiency and accuracy. This system has been used to predict the thermal conductivity of composites such as Mo/Al₂O₃, SiC/Al alloy, YSZ thermal barrier coatings, etc. The results are in good agreement with the experimental data, so the reliability and effectiveness of the system has been proved.

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A supercritical CO₂ turbine cycle can achieve a considerably high cycle thermal efficiency at medium turbine inlet temperatures of 500-650°C at high pressure such as 20 MPa, which is too high to produce a reactor pressure vessel within the existing fabrication limits. To solve this problem, a dual expansion turbine cycle is effective; its application was examined for both the fast reactor (FR) of 527°C and 12.5 MPa and a high-temperature gas-cooled reactor (HTGR) of 650°C and 8 MPa. Results showed that, in the case of FR, the cycle thermal efficiency became 42.6%, 44.0%, and 45.1%, respectively, for the 12.5 MPa cycle, the dual expansion cycle, and the 20 MPa cycle. Therefore, the dual expansion cycle is effective. On the other hand, for HTGR, the cycle thermal efficiency became 47.5%, 48.5%, and 50.3%, respectively, for the 8 MPa cycle, the dual expansion cycle, and 20 MPa cycle. In this case, the cycle efficiency advantage becomes smaller than that for the FR, but a 1.0% advantage is obtainable.

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This study focuses on the fundamental characteristics of DME (Dimethyl Ether) combustion aiming at development of low-NOx combustion technology with flue gas recirculation, FGR. The flue gas is recirculated into the combustion chamber to reduce the oxygen concentration and to suppress the combustion gas temperature, so that NOx emission is significantly reduced. The fuel gas recirculation at high mixing ratio, however, may lead to unstable combustion of conventional fuels, methane or city gas. On the other hand, DME has very high potential of applicability for the flue gas recirculation even at high mixing ratio because of its high burning velocity and low ignition temperature. Combustion tests were conducted with laboratory-scale 11kW combustor. The maximum FGR ratio is 85% at the initial air ratio of 1.5 with preheated diluted air about 600K. The NOx emission reduced to 13ppm at 0%-O₂, which corresponds to about 9% of NOx emission at FGR=0%. The stable combustion is sustained even in the low oxygen concentration by preheating diluted-air up to near the auto-ignition temperature of DME. Finally, the effect of the flue gas recirculation on the NOx and CO emission is discussed with reference to the industrial-scale water-tube boilers.

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In order for economically viable distributed generation systems for local communities to be widely accepted, it is essential to develop an efficient and low-cost heat supply system. For this purpose, we propose a new heat supply system which we already presented at the ICOPE-05 Chicago. The key technology for the system is to connect compact heat supply units with a heat storage function installed in all the households of the local community, such as condominiums, by a single-loop of hot water pipe. A phase change material was used for the heat supply unit as the heat storage material. However, for easier handling and reducing the cost of the unit, we have developed a new heat supply unit whose heat storage tank is made of plastic. Hot water for space heating is used as the heat storage material. Further we constructed a heat supply system for 7 lived-in households with a 5 kW gas engine and a 42 kW boiler as the heat sources.
Some experiments with a heat supply unit and a heat supply system, such as for heat storage and heat supply for peak demand were conducted. Additionally, dynamic simulations of heat demand by 50 households and a COP evaluation of a new CO₂ heat pump system using low-temperature exhaust gas from the gas engine were also conducted.

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With regard to the high pressure (HP) feed water heater of thermal power plant at Tokyo Electric Power Company (TEPCO) sites, inspection of feed water (FW) tubes wall thickness are conducted whenever required such that frequent tube leak occurs. As a standard inspection methodology, FW heater is disassembled during planned outage, tube wall thickness is measured by the ultrasonic pulse techique (UT), then plugs are installed at the both ends of FW tube if its measured wall thickness is found below calculated threshold. However, the root causes of wall thinning of FW tube are various such as erosion and corrosion, based on wall thinning condition, the above threshold is not applied but utilizing the other technically well-grounded evaluation method is sometimes more rational. Therefore, TEPCO classified wall-thinning condition based on inspection data and established technically well-grounded and rational evaluation methodologies of FW tube wall thickness to suite each wall thinning condition. Moreover, with recent improvement of inspection technique, technology enabled faster, larger amount, and more accurate data acquisition, TEPCO has developed the systematized evaluation methodology that can transact data acquisition and evaluation simultaneously. This article introduces the logic of evaluation methods and examined algorithms to make them systematized.

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