One of the merits of a solar thermal utility is that the cost of heat storage is lower than that of an electrical battery. Furthermore, a power generation system using solar thermal energy with heat storage equipment is capable of stabilizing its output. For a parabolic trough solar concentrator, molten salt is adopted as the heat storage material using latent heat. However, molten salt is applicable only up to 600 °C; this temperature is not sufficiently high for adaptation to a solar central receiver system. Therefore, we designed and produced sensible heat storage equipment for a beam down solar concentrator (a central receiver system) to offer higher temperature storage. Heat storage materials in this device are mechanically mixed, and receive the concentrated sunlight on the focal plane of the solar concentrator. First, the radiation flux distribution under CPC (Compound Parabolic Concentrator) was measured using thin film heat flux sensors to obtain the input energy for the storage equipment. Next, an experiment was carried out using the storage equipment and the beam down solar concentrator. The maximum temperature was found to reach 1070 °C at the center of the heat storage tank in this experimental conditions, and the stored energy was approximately 14 % of the incident energy.
This paper describes how to produce a biodiesel from the oil in the waste soup of ramen noodles, and especially clarifies an amount of oil in waste soup, the energy profit ratio (EPR) of the production of biodiesel from the oil in waste soup of ramen noodles and the engine performance of the biodiesel from waste soup of ramen noodles. As a result, from the waste pig bone (ton-kotsu) soup the recovered tri-glyceride was about 11g per a soup. The biodiesel produced from the oil in the waste soup of ramen noodles by using ordinary alkyl catalyst method has low cold flow properties, due to the high content of the saturated fatty acid methyl ester such as C16:0, C18:0 and so on. And it is estimated that the amount of BDF from a ramen noodle restaurant is about 2.4L if the customers are around 300 per day, and this means that the 9.9 kW co-generation system is able to be operated for an hour per day. About energy profit ratio analysis, if the oil separation process is improved, EPR from the waste soup to biodiesel will become higher than 5.0. Furthermore, engine test is performed by using BDF from the waste soup of ramen noodles as B5. As a result, it is shown that fuel consumption rate and emissions are almost the same as the case of using gasoil.
In carbon dioxide capture and storage (CCS), the shift to the dissolution trapping of CO2 in brine from the capillary trapping and physical trapping by caprock depends on the mass transfer associated with density-driven natural convection at a reservoir scale. In this study, natural convection between miscible fluids in a porous medium with layered structure is visualized three-dimensionally by means of an X-ray microtomography. When a finger associated with Rayleigh-Taylor convection passes through the interface of the layered heterogeneous structure with an increasing permeability, because of an increase in the finger extension velocity, the finger diameter and the concentration in the finger decrease. On the other hand, when a finger passes through the interface with a decreasing permeability, the finger diameter increases and the concentration in the finger remains the same, which suggests that the change in the concentration in the finger shows nonlinearity against the permeability. In present study, because the thickness of the initial interface is lower than the thickness of the layer structure, the onset time of convection depends on the property of the porous medium just around the initial interface. In addition to that, the finger extension velocity depends on the local property of the porous medium and the empirical equation derived for the uniform porous medium agrees well with the local finger extension velocity estimated for each layer.
This study investigated pressure drop for gas and non-Newtonian liquid two-phase flows in a horizontal circular microchannel. The microchannel was a fused silica tube with 0.25 mm I.D. Polyacrylamide aqueous solutions with different mass concentration, which exhibit pseudo plastic behavior, were used as non-Newtonian liquid, while the nitrogen gas was used as the test gas. Pressure drop was measured with a calibrated differential pressure transducer. The pressure drop data have been compared with calculations by various correlations, usually used for prediction of the pressure drop in mini/micro channels as well as conventional sized channel. As the comparison results, the data have been correlated with separated flow model by using a newly developed equation of two-phase friction factor as well as homogenous flow model with an effective viscosity accounting for non-Newtonian effects. The Lockhart-Martinelli model also predicted well the present data if an appropriate C-value in two-phase friction multiplier was adopted.
The tri-generation system is the high efficiency of the system which utilizes not only the electricity and heat from an engine co-generation system, but also CO2 in the exhaust gas as a resource for growing plants or micro-algae. In our previous study, we demonstrate the mass production of algal-oil at enriched CO2 aeration under the sunlight condition. In this study, we collected CO2 in the diesel engine exhaust of co-generation system and introduced the enriched CO2 aeration in cultivation of microalgae, Scenedesmus dimorphus, in photo bioreactors. In addition, fuel property of the oil extracted and treated by the super-heated methanol vapor method was analyzed. From the experimental result, it was shown that the aeration of enriched CO2 of diesel engine exhaust is effective to increase algal cell density, and fuel property of FAME produced from microalgae is improved by the super-heated methanol vapor method. Also, it was estimated that the super-heated methanol vapor method is effective to reduce the energy consumption for fuel production.
As the effective utilization method of unused heat energy between 100 and 300 degree-C in the industrial sector, Organic Rankine Cycle (ORC) was selected from the viewpoint of high efficiency. The prototype of air-cooled compact ORC electric power generation system for 1kW class was evaluated in variation of the ambient temperature of condenser and the suction temperature of expander. In the experimental results, at the expander suction temperature of 175°C and the ambient temperature of 20°C for condenser, the generated power by the expander is 1,027W and the gross power generation efficiency is 10.3%. The net power generation efficiency, considering the input power of auxiliary equipment such as pumps and fans, is 9.0%. In the result of energy balance analysis, power consumptions of the pump and the fan are small and almost of the generated power is effectively available.
HCCI combustion is effective for improving thermal efficiency of a gas engine, but it has problems such as control of the ignition and combustion. To solve the problem, availabilities of dedicated EGR technique are considered to control its ignition and combustion. Dedicated EGR involves reforming fuel into H2 or CO by running a single or more cylinder with rich mixture and supplying the exhaust gas directly into other cylinders. In this study, the effect of dedicated EGR on methane HCCI combustion was investigated by experiments. As a result, when equivalence ratio of rich SI combustion or EGR ratios increase, the ignition timing of HCCI advances and combustion becomes steep. The advanced ignition timing is caused by an increase of H2 mole fraction in the intake gas. In addition, the possibility of controlling the ignition timing, which is strongly concerned with the thermal efficiency of a HCCI engine, by dedicated EGR was discussed. It was shown that the ignition timing linearly depends on H2 mole fraction in the intake gas.
The objective of this study is to develop probabilistic risk assessment (PRA) methodology for combination event of low temperature and snow by focusing on decay heat removal system (DHRS) of sodium-cooled fast reactor. For this combination event, annual excess probability depending on the hazard intensity was statistically estimated based on the meteorological data. Event tree was developed by considering the impact of low temperature and snow on DHRS: e.g., plug at the air intake of ultimate heat sink and of emergency diesel generator and unopenable door for access route due to accumulated snow, failure of air intake filter due to deposited snow, possibility of freezing of cooling circuits. Recovery actions (i.e., snow removal and filter replacement) were considered in the event tree. By using annual excess probability and failure probabilities, the event tree was quantified and the quantified event tree showed that dominant core damage sequence is loss of access route for snow removal against the combination event at daily snowfall depth of 3m/day continued during 24h. When the access route is secured for all hazard intensity assumed this paper, it was showed that core damage frequency decreases about 1/10 times and securement of the access route has significant sensitivity to the core damage frequency.
Recently, necessity of energy saving is more increasing in the industrial field with relation to energy cost increase. Measurement of steam flow rate is indispensable for a performance diagnosis and an energy solution in facilities such as factories and power plants. However, a sensor installation for steam flow is generally difficult. Because the industrial facilities needs to be out of operation temporarily, in the case of installation of conventional flowmeter such as orifice type and vortex type. And steam pipes are necessary to be cut for the installation. Accordingly, clamp-on type steam flowmeter, of which installation does not require pipe-cutting, is hoped to be developed. Ultrasonic sensor has certain degree of possibility for steam flow measurement. On the other hand, there are such problems as ultrasonic inlet to a pipe and operational condition of temperature, to be solved. Therefore, we devised “heater method” for steam flow measurement. A circumferential heater is attached to the outside of a tube. Then, axial temperature distribution on the tube outside is measured. Steam velocity is analyzed on the basis of the temperature distribution, considering heat transmission in the pipe and thermal conductivity in steel pipe. The sensor is heat-resistant and possible to measure high temperature fluid, because it is comprised of the heater, thermocouples and insulator. It is necessary to solve physical phenomenon such as temperature boundary layer and thermal conductivity in the pipe in case of thin area heating, to develop the method. This paper reports air and steam flow rate measurements by the heater method, and comparison between analyzed fluid velocity and reference fluid velocity.
A clamp-on ultrasonic gas flowmeter we had developed has been modified to measure steam flow by newly developed damping material endurable to high temperature. As clamp-on flowmeters are widely used for temporally flow measurement because there is no need for plumbing, most of them are for liquid flow measurement because ultrasonic energy wouldn't get into the fluid as acoustic impedance of the pipe and that of the fluid is widely spread. To measure the gas flow by clamp-on flowmeter, damping material is the key of the measurement because it will dampen the propagating ultrasonic wave in the pipe wall and as a result the weak signal go through the fluid can be observed. If the fluid is steam, endurance for high temperature is also required. With the developed flowmeter, the flow of steam at 0.8MPa in the pipe of 50A SGP can be measured up to 30m/s flow rate. This measurement is reproducible. The flowmeter is compatible to both saturated steam and superheated steam. There is no need to alternate the setup when the type of steam change. The key of this success depends on the newly developed damping material. The base material effectively dampen the ultrasonic wave was explored widely from many types of silicone materials. Dense material was added to increase the acoustic impedance of the damping material. We are now trying to lower the measurable steam pressure and widen the types of target pipes. In the process of this trial, we've already found a damping material with which the received ultrasonic signal captured from the clamp-on transducer on the 25A steam pipe could be observed clearly above the noise level. The pressure of the steam was still 0.9MPa but we're trying to lower the measurable pressure limit.
Low temperature thermal energy included in hot spring or waste-heat at factories has been abandoned until now. It is reported that geothermal heat of up to 120 degrees corresponds to the energy of 7.4GW. Among them, a new technology that attempts to recover the thermal energy by driving turbine with two-phase flow which is generated by flashing hot water has been developed. The high momentum and low velocity two-phase flow drives the turbine at synchronous speed to the generator. This eliminates the need for the expensive gearbox required for the conventional steam turbine systems and thereby improves the reliability and reduces the maintenance. However, the improvement of efficiency and stability is required to put to the practical use. Therefore, the basic experiment to understand the performance of two-phase turbine and flashing nozzle was conducted and discussed by using water instead of organic fluid. Water is expected to be used to prevent the environmental destruction. The visualization of two-phase flow at the nozzle exit was conducted and the power output of two-phase turbine was measured. The experimental and analytical results showed that: (1) the non-equilibrium degree changed from nozzle throat to exit.; (2) steel wool in the convergent part of nozzle could effectively reduce the non-equilibrium and suppressed the pulsation of two-phase jet; (3) the practical two-phase jet velocity was obtained from the maximum turbine efficiency and compared with the prediction with non-equilibrium model.
Lead lithium alloy (Pb-17Li) is one of the candidate tritium breeders of fusion reactors. Lead bismuth eutectic alloy (LBE) is one of the candidate materials for the coolant of fast reactors and the target of accelerator driven systems. The functional layers such as an anti-corrosion layer and a tritium permeation barrier have been developed to be applied in these liquid metal systems. Zirconium oxide (ZrO2) are considered to be the candidate material of the functional layers due to its excellent chemical stability. The online monitoring of oxygen potential in the liquid metals is essential technology. The development of in-situ analysis technique for the layer properties in the liquid metals at high temperature is important issue. The purpose of the present study is to develop the on-line monitoring system for the oxygen potential and the layer properties both by the solid electrolyte (SE) oxygen sensor and the electrochemical impedance spectroscopy (EIS). The YSZ type SE sensor and the ZrO2/Zr specimen for the EIS were simultaneously immersed to liquid Pb at 698-898K. The responses of the oxygen sensor and the EIS were successfully obtained, and these signals indicated that the ZrO2 oxide layer is thermodynamically stable in liquid Pb. The EIS response was evaluated based on some equivalent circuit models as the oxide layer had a lot of horizontal cracks in its structure. The influence of the cracks on the capacitance is larger than that on the electrical resistance, when the covering ratio of the cracks in the layer is low. The influence on the electrical resistant becomes larger when the ratio is close to 100%.
Enhancement in performance of heat transfer is one of the most significant issues for a heat exchanger in waste heat recovery systems. In design of the heat exchanger, increases of the heat transfer area and the heat transfer coefficient have been generally considered until now. On the other hand, a practically-designed heat exchanger has not often provided enough performance in terms of the heat transfer due to restrictions of installation space of the system and pressure drop of working fluid. Especially, in the waste heat recovery system for internal combustion engines, it is necessary to pay attention for a design of exhaust system because high-pressure drop of exhaust gas has considerable effect on combustion in the engine. In this study, the mathematical models which can estimate heat transfer rate of the heat exchanger and the pressure drop of exhaust gas has been defined. The mathematical model has roughly validated by comparison with CFD. And then, the optimum design of the heat exchanger has been considered for the solution of a trade-off problem between the heat transfer rate and the pressure drop of exhaust gas based on a genetic algorithm coupled with the mathematical model. Moreover, the benchmark experiment has been carried out with some prototypes of heat exchanger based on the optimum calculations, and the validation study of the mathematical model has presented by the comparison with the experiments. The methodology of the optimum design for the exhaust gas heat exchanger has been mentioned from these results.
It is necessary to evaluate the geometry factor for predicting the flow accelerated corrosion (FAC) in the plant piping. Geometry factor is defined as the ratio of the wall mass transfer coefficient in the piping systems (such as orifices, elbows) to that in a straight pipe. In this study, the mass transfer coefficient is measured experimentally with electrochemical method for fully developed flow, downstream of orifice and 90-degree elbow. The experimental measurement is conducted with the pipe of the test section made of nickel, in which the whole pipe surface acts as electrode (in this paper, referred as ‘overall electrode condition'). In order to clarify the effect of the area of the electrode, obtained results are compared with the other experiments with only point electrode working (referred as ‘point electrode condition'). In addition, geometry factor is calculated with large eddy simulation (LES) and turbulent scalar transport is numerically analyzed. The values of geometry factor for the downstream of the orifice measured with overall electrode condition and point electrode condition are quantitatively different with each other, while those for elbow flow shows qualitative difference between them. Calculated values with LES are good agreement with measured values in overall electrode condition. Analysis of turbulent scalar transport reveals that, at the downstream of the orifice, the sweep component affects more strongly than the ejection component. Near the wall region in the elbow, the ejection component, on the contrary, is found to have a greater contribution than the sweep component.
Improvement of Pressurized Water Reactor (PWR) thermal efficiency has strong effects on the plant economy and uranium resource economy. PWR has two main systems, the primary system including reactor and the secondary system including turbine for generating electricity. Steam Generator (SG) exchanges the heat from the primary system to secondary system. For improving the thermal efficiency, the prediction of heat and mass flux in PWR SG is important. In this study, the simplified prediction method of SG with economizer considering the effects of U-Tubes area has been developed to predict the pressure drop of the secondary system. The developed evaluation model was verified by comparing with the measured value of KWU type SG of Grafenrheinfeld PWR plant in East Germany. In the developed model, SG was divided into nodes along the secondary coolant flow. The total pressure drop of SG was obtained by the sum of static head loss, friction loss, acceleration loss and local loss. The following conclusions were obtained from this study. (1) The simplified prediction method of the pressure drop has been developed. (2) The prediction accuracy with Drift flux model is better than that with homogeneous model. The prediction accuracy for this method with Drift flux model is about 10%. (3) The static head loss is larger than the other pressure drop factors. The prediction accuracy of the void fraction and the heat transfer in SG is needed to be better for evaluating static head loss and total pressure drop more correctly.
There is a CO2 emission reduction method of burning woody biomass and coal, as a technical method to reduce the CO2 emission of the coal fired power plant. But a co-firing woody biomass ratio of the existing coal fired power plants gives only the 2-3% co-firing ratio due to some restrictions, so we have performed studies and examinations for providing the useful technical knowledge. Based on the result, we performed the verification test of 25cal% in a quality of woody pellet with commercial coal fired power plant of 149MW. When the verification test was performed with 25cal% co-firing ratio, this boiler which has 4 mills was operated while three mills pulverized coal and one mill pulverized woody biomass. The boiler had been performing the stable operation during that test. This text introduces the studies, examinations and verification test for high co-firing ratio of woody biomass.
Liquid inlet behavior to a heat surface in micro-bubble emission boiling (MEB) was investigated by flow measurement using particle image velocimetry (PIV). Subcooled pool boiling experiments under atmospheric pressure were carried out using a heat surface with a diameter of 10 mm. An upper end of a heater block made of copper was used as the heat surface. Working fluid was the deionized water and the subcooling was varied from 40 K to 70 K. Three K-type thermocouples were installed in the copper block to measure the temperature gradient, and the heat flux and wall superheat were estimated from these temperature data to make a boiling curve. The flow visualization around the heat surface was carried out using a high-speed video camera and a light sheet. The microbubbles generated in the MEB were used as tracer particles and the velocity field was obtained by PIV analysis of the acquired image sequence. As a result, the higher heat fluxes than the critical heat flux could be obtained in the MEB region. In addition, the distribution characteristics of the velocity in MEB region were studied using the PIV results and the location of the stagnation point in the velocity fields was discussed.
A combined heat and power (CHP), sometimes called cogeneration, is one of the effective technologies for reducing CO2 emission. In the previous research, the authors proposed a concept of “Networked CHP system”, which allows surplus electricity of CHP to be reversed to the power grid and to consume it effectively in the network. Result of the analysis clarified significant CO2 reduction with minimum social cost compared to the non-networked system. The social cost is the amount supplying energy to the area, and it is different from the benefit of individual customer. Customers select the capacity and operation of CHP to have the minimum cost for them, and it is mostly different from the social optimum. This paper analyzes the conditions of energy prices to direct customer selection to the social optimum for cost and CO2 reduction. The results of the analysis show that the electricity/gas price ratio normalized by CO2 emission factor should be unity, and the sell/buy ratio of electricity between the grid for the customer should be larger than 0.6. As an example of measures to keep the profit of electric company for increasing CHP, FIT price of about 1% is enough to be added on the electricity and gas prices. To make customers to select the optimum capacity of the CHP, clear guideline of the optimum kW for unit floor area should be indicated and the CHP price should be in the acceptable range for customers; this is due to the fact that effective subsidy for CHP selection is hardly determined, as the minimum cost for customers does not vary much for the capacity of the CHP.
The requirements for the start-up of gas turbine combined cycle power plants have become more diverse, which include faster start-up, reduced fuel consumption, and less thermal stress (i.e. reduced life consumption). However, these multiple requirements sometimes contradict each other, for example start-up time and thermal stress are in a trade-off relationship. In this paper, a method to solve such multi-objective problems is presented, in which optimized start-up curves are automatically generated. The presented method iterates the search for candidate start-up curves by the NSGA (Non-dominated Sorting Genetic Algorithm)-II and the evaluation of multiple objective functions based on the dynamic simulation of plant transients. To assess the validity of the presented method, case studies were performed, where the steam turbine start-up time and steam turbine rotor thermal stress were employed as the objective functions. As a result, start-up curves were generated on the Pareto-front representing the best trade-off between the start-up time and thermal stress. These Pareto-front curves can be effectively used for interactively selecting an optimum start-up curve. It was also found that the start-up curves on the Pareto-front were classified into three types according to the operating sequences of gas turbine load and steam control valve position, which means that the optimal start-up strategy differs depending on the priority allocation of the fast start-up and reduced thermal stress.
Here, we propose a chemical heat pump chiller with a SrBr2 hydration reaction system for utilization of waste heat. The SrBr2 hydration reaction could recover waste heat in low temperatures ranging from 373 to 353K, and the system showed good potential in terms of the high cooling thermal-storage density. Previous studies have given little information on the reaction characteristics of the SrBr2 hydration reaction. In this paper, we developed a measuring method for the reaction rate based on the volumetric method. We analyzed the hydration reaction rate with an unreacted-core shell model. In the experiments, the reaction fraction of the SrBr2 hydration reached 1.0 within 300 sec. By analyzing the hydration reaction rate with the unreacted-core shell model, the SrBr2 hydration rate was successfully applied to intra particle diffusion controlled. And the activation energy for vapor diffusion in SrBr2 particle value was calculated to be 26.8 (kJ/mol). The calculation results showed good agreement with those of the experiment as the reaction fraction reached 0.8.
Scallop pattern is widely recognized as a typical morphology on the corroded surface by high flow-accelerated corrosion (FAC) rate in single-phase flow. Although turbulence flow condition could be closely related to scalloped appearance, the detailed process of scallop development is not fully known. In this study, detailed characterization of scalloped appearance (scallop size, depth, and density) and oxide layer (nano-void structure, thickness, and compositional profile) on the inner surface of the carbon steel piping elbow used in a fossil power plant have been carried out. The extrados of the piping elbow showed maximum FAC rate (approximately 0.25 mm/year). On the other hand, the intrados of that showed no FAC. The FAC rate lineally decreased from the center of extrados to intrados side, while the scallop patterns were observed in a limited region on the extrados. Approximately half of the maximum FAC rate was shown even on the smooth surface. It has been notable that there was no significant increase of the FAC rate by scallop formation although the local turbulence was increased by hydrodynamic effect due to scallop surface. The relationship among scallop size, depth, and density obtained in this study indicated that the occurrence of overlapping horse-shoe shaped pits that give a scalloped appearance. The surface morphologies under FAC condition is considered to essentially depend on the nucleation density of pits. Nanometer-scaled thin porous oxide layer was formed on both extrados and intrados, and there was no significant difference in nano-void structure, thickness, and crystalline structure obtained by transmission electron microscope characterizations despite a significant difference in the FAC rate. Since no Cr enrichment was observed in the oxide layers formed on the both sides, FAC suppression by Cr content of carbon steels could be negligible in this condition.
In this study, we report the relationship between the mechanical properties and structural defects of multi-walled carbon nanotubes (MWCNTs) synthesized by a chemical vapor deposition (CVD) method. The tensile strength, Young's modulus and Weibull modulus of the individual MWCNTs were determined by conducting uniaxial tensile tests using a manipulator tool operated inside a scanning electron microscope. In addition, the structural defects which induced the failure of the MWCNTs were observed by a transmission electron microscope (TEM). TEM observations revealed that the MWCNTs exhibited several types of structural defects: discontinuous flaws such as holes; kinks and bends; impurities i.e., catalysts even though highly crystalline layers were almost perfectly aligned with the MWCNT axis. The tensile-loading experiments demonstrated that the average tensile strength, Young's modulus and Weibull modulus of the 23 MWCNTs were 5.2 ± 2.1 GPa, 210 ± 140 GPa and 2.7, respectively. The MWCNTs underwent failure leaving either a clean break or a very short sword and sheath failure, suggesting that a significant interwall load transfer might be facilitated by the irregular wall structures as mentioned above. These mechanical characteristics and fracture modes were reasonably consistent with those of previously reported CVD-grown MWCNTs. In order to identify the structural defects controlling the fracture of the MWCNTs, structural analyses were conducted by comparing TEM images captured before and after their breaking. The TEM images of the individual MWCNTs revealed that the defects described above induced the nanotube failure. These suggest that the tensile strength of the CVD-grown MWCNTs used in this study is dominated by the structural defects in particular discontinuous flaws and kinks and bends. The results reported here indicate that improvement and optimization of synthesis methods are needed to prepare stronger MWCNTs with less structural defects reported here.
The effect of specimen size on tensile deformation behavior of the ultrafine-grained ferrite-cementite (FC) steel was studied from the viewpoint of true stress (σ)-true strain (ε) relationship. In this study, we took notice of the estimation of σ-ε relationship up to the plastic deformation limit in order to discuss tensile deformation behavior up to fracture, especially in the local deformation behavior which the size dependence on mechanical properties is large. From the ultrafine-grained FC steel, round tensile test specimens with various sizes of gage length (GL) and gage diameter (φ) were prepared. Static tensile tests and stepwise tensile tests were performed with an initial strain rate of 5.0 × 10-4 s-1 at 296 K using a gear-driven-type machine. In the nominal stress-strain curves, the lower yield strength and total elongation increased with a decrease in the gage length. The σ-ε relationship up to the plastic deformation limit was almost independent of the specimen size, whereas the true strain at the plastic deformation limit and reduction of area decreased when the value of GL/φ became less than 1. The σ-ε relationship up to the plastic deformation limit estimated by Bridgman equation is unique data independent of specimen size and is effective to discuss the effect of specimen size on deformation behavior.
This paper presents the effect of loading rate on relationship between strength and flaw size of ceramics. First, a probabilistic effective inert strength model was proposed on the basis of SCG concept and upper limit flaw size in conjunction with the Weibull distribution. It was derived that the effective inert strength converted using fracture strength which depended on loading rate and effect loading time of ceramics conformed to a three-parameter Weibull distribution. Second, the effect of loading rate on the relationship between fracture strength and flaw size was theoretically derived on the basis of fracture criterion by applying the virtual equivalent crack length and a grain fracture model in conjunction with the probabilistic model. Third, four-point bending test was performed using alumina ceramics (Al2O3) under a wide range of loading rate. The fracture surface was then observed by scanning electron microscope. Fourth, the material constants and the Weibull parameters related to the probabilistic model were determined using the experiment data. Weibull plots of the inert strength calculated from the grain fracture model using the equivalent crack length accorded well with the three-parameter Weibull distribution calculated from the Weibull parameters for the effect inert strength. This result supported the conclusion derived from the probabilistic model. Finally, the validity of the theoretically presented effect of loading rate was confirmed through the comparison of the predicted relationship between fracture strength and flaw size at various loading rates with the experiment data.
The effect of grain boundary character and grain boundary geometrical configuration on nucleation of intergranular fatigue crack in SUS430 ferritic stainless steel was quantitatively investigated to reveal the elementary process of high cycle fatigue fracture. The grain boundary microstructure in the pre- and post-fatigued specimen was evaluated by scanning electron microscopy/ electron backscatter diffraction (SEM/EBSD) technique. Fatigue crack nucleation occurred mainly at grain boundaries at the low stress amplitude level. On the other hand, nucleated fatigue cracks were propagated immediately to perpendicular to the stress direction at the high stress amplitude level, regardless of the grain interior or grain boundaries. In the case of low stress amplitude level, intergranular fatigue cracks preferentially nucleated at high-angle random boundaries, although the fatigue cracks never nucleated at low-angle boundaries. Fatigue cracks nucleated at low-∑ coincidence site lattice (CSL) boundaries only when the trace of grain boundaries on the specimen surface was parallel to persistent slip bands (PSBs), although the fatigue cracking at random boundaries was accelerated even when the trace of grain boundary on the specimen surface was not parallel to PSBs in neighbouring grains. Fatigue crack nucleation was hardly affected by the geometrical arrangements between the trace of grain boundary on the specimen surface and the stress axis. The grain boundary engineering for control of intergranular fatigue cracking was discussed on the basis of the results of the grain boundary character-dependent intergranular fatigue crack nucleation.
In this paper, a new method for scaling the crack tip stress distribution under small scale yielding condition was proposed and named as T-scaling method. This method enables to identify the different stress distributions for materials with different tensile properties but identical load in terms of K or J. Then by assuming that the temperature dependence of a material is represented as the stress-strain relationship temperature dependence, a method to predict the fracture load at an arbitrary temperature from the already known fracture load at a reference temperature was proposed. This method combined the T-scaling method and the knowledge “fracture stress for slip induced cleavage fracture is temperature independent.” Once the fracture load is predicted, fracture toughness Jc at the temperature under consideration can be evaluated by running elastic-plastic finite element analysis. Finally, the above-mentioned framework to predict the Jc temperature dependency of a material in the ductile-to-brittle temperature distribution was validated for 0.55% carbon steel JIS S55C. The proposed framework seems to have a possibility to solve the problem the master curve is facing in the relatively higher temperature region, by requiring only tensile tests.
The effect of test temperature on the fatigue crack propagation behavior was studied with center-notched specimens of PPS (polyphenylene sulfide) reinforced with 30 wt% short carbon fibers. Specimens were cut from injection-molded plates with 1 mm thickness at three angles of the loading axis relative to the molding flow direction, i.e. θ = 0° (MD), 45°, 90° (TD). Crack propagation tests were conducted under the stress ratio of 0.1 at four temperatures below and above the glass transition temperature Tg = 363 K：room temperature (RT = 298 K), 343 K, 373 K and 403 K. The macroscopic crack path was nearly perpendicular to the loading axis for MD and TD at all temperatures. The crack growth direction of 45° plates was inclined against the loading axis, and the inclined angle was decreased with increasing temperature. In the relation between the crack propagation rate, da/dN, and the stress intensity factor range, ΔK, da/dN was slowest for MD, and increased with increasing fiber angle at all temperatures. The crack propagation rate of each fiber angle was nearly the same at RT and 345K, and increased greatly at temperatures of 373 K and 403K above Tg. When da/dN was correlated to the J-integral range, ΔJ, the relations for different fiber angles came closer at each temperature, and also for each fiber angle the influence of test temperature on da/dN was decreased. The inelastic deformation of the matrix was mainly responsible for the acceleration of crack propagation seen in da/dN vs ΔK relation at high temperatures.
Considering the effect of microscopic voids to macroscopic mechanical behavior is important because the fracture of ductile materials occurs through the initiation, the growth and the coalescence of voids. Anisotropy and softening are affected by the voids arrangement, and the growth bahavior of voids depends on not only stress and strain but their histories. The elasto-plastic constitutive equation which can represent anisotropy and compressivility of porous materials at once is presented in order to analyse deformation and damage evolution of the materials including voids to predict these phenomena. Damage tensor is employed to express decrease of effective cross-section area subjected to stress and its evolution equation is also derived to predict three dimensional growth of void. Thermomechanical consideration based on Clausius-Duhem's inequality is used to derive the model. Functional forms of dissipation inequality and dissipation potential are derived so that the anisotropic mechanical responce caused by the arrangement of voids is incorporated. The adequacy of presented model is evaluated through finite element analysis of unit cell assuming grid alignment of spherical voids. Initial and subsequent yield behavior are analysed with triaxial stress conditions. The presented model shows good agreement with finite element model for initial yield condition and relation between stress, strain and damage tensor.
The air speed measurement is important as the quantitative index for the assessment of the building wind-resistance, the indoor thermal environment and the aerodynamic characteristic of high speed vehicles. NMIJ has established the high air speed standard facility and started a calibration service for Pitot-static tubes. This facility covers the air speed range from 40 m/s up to 90 m/s with relative expanded uncertainty (k = 2) of 0.63 %. The reference air speed is derived from the national primary gas flowrate standard. The test section for conversion from flowrate to air speed is installed at the test line of the closed loop gas flowrate calibration facility. The standard air speed at the center of the nozzle exit is obtained by comparing the integral value of the air speed profile and the standard gas flowrate. Against this standard air speed, a dedicated wind tunnel, which serves for daily calibration service, is calibrated by using a total pressure tube as a transfer standard. An internal comparison was carried out between the new wind tunnel and the conventional medium-speed wind tunnel. The comparison result agreed well enough to validate the capability of the new wind tunnel. This paper describes the calibration system, the traceability chain and the uncertainty analysis of the new air speed standard.
At specific velocities, intense noise can be generated by the flow around a cascade of flat plates due to acoustic resonance. To reduce the aerodynamic noise, dielectric barrier discharge (DBD) plasma actuators (PAs) were utilized. The aim of this investigation was to clarify the control effects and the mechanism of noise reduction. To do this, wind tunnel experiments and computations were carried out for three vertically aligned flat plates. The PAs were mounted on both sides near the leading-edge of the vertically central flat plate. Moreover, to optimize the deployment of the operated PAs for control, PAs divided in the spanwise direction were utilized, where the PA was composed of 2 parts on each side. Experiments with various combinations of operated PAs were performed. The noise reduction achieved increases as the applied voltage of PAs increases. The maximum reduction of the tonal noise was 10.8 dB and was achieved by operating the whole array of PAs at a velocity of 13.5 m/s. The velocity profiles downstream of the PAs changed and the frequency of vortex shedding in the wake of the flat plate decreased with control of the PAs. The velocity corresponding to the maximum acoustic resonance was increased by operating the whole array of PAs. When the array of PAs are partially operated with a spanwise asymmetric deployment, it intensifies the three-dimensionality of the flow. Consequently, the acoustic radiation was weakened with a wider range of frequencies compared to the control by operating the whole array of PAs. The present results indicated that spatial asymmetry deployment is preferred to reduce aerodynamic noise.
Generally, industrial vehicles such as agricultural machines and construction machinery use hydraulic systems for heavy-load work. Also the work often continues for a long time in a certain area. Consequently, noise exposure of the surrounding environment is increased. Thus noise regulations are established in several countries. The noise emitted from the hydraulic system has a significant contribution to the over-all of the noise in an industrial vehicle. Recently, the choice of power sources in industrial vehicles has tended to shift from internal combustion engines to electric motors. Consequently, the contribution of noise emitted from the internal combustion engine will decrease and the contribution of noise emitted from a hydraulic system will become relatively prominent in the future. It is, therefore, more than ever important to take care of the noise generated by the hydraulic system of the industrial vehicles. It is known that speed of sound in hydraulic oil has an effect on pressure ripples which can be source of noise. Therefore, it is important to understand behavior of the speed of sound reasonably in design of quiet hydraulic systems. However, relationship between operating conditions and the speed of sound has not been revealed up to now. In this study, the speed of sound has been investigated at the operating conditions that are oil temperature, loading pressure, volume ratio of entrained air to the hydraulic oil and type of the oil for typical agricultural machines and construction machinery.
Measurement of thermal conductivity for anisotropic material is difficult or troublesome for conventional measurement techniques. Then periodic heating method using lock-in thermography was proposed as a convenient measurement technique. In this paper, thermal diffusivity distribution of pitch based carbon fiber reinforced plastics (CFRP) was measured by periodic heating method using lock-in thermography. The results showed that thermal diffusivity of several CFRPs depend on heating frequency. Then CFRPs were made using autoclave in various conditions and thermal diffusivities were measured. The results showed that thickness directional thermal diffusivities of CFRPs which were made at low pressurization are smaller than that of CFRPs which were made at standard pressurization, and in-plane thermal diffusivities of CFRPs which were made at low pressurization depend on heating frequency. It means that thermal contact resistance between prepregs causes heating frequency dependencies. Next, numerical model for pitch based CFRP was constructed using control volume method, and parametric study about thermal contact resistance was carried out in order to find the cause of heating frequency dependencies. Numerical results supported the results of experimental study.
This paper describes about improvement of spray characteristics of the nozzle for a direct injection Diesel nozzle, which excellent spray characteristics is obtained. The purpose of this study is to develop high-dispersion injection nozzle for direct injection Diesel engine that is able to achieve lean combustion based on requirements of some automobile makers. In this study, effects of the pitch circle diameter and existence of inclination of the nozzle hole of the designed atomization enhancement nozzle on atomization characteristics were investigated. It was cleared that in case of the multi-hole nozzle with inclination angle of 45 degrees at the nozzle hole, breakup length becomes short about 20 % and spray angle becomes large about three times compared with the nozzle without inclination angle of the nozzle hole. Moreover, disintegration behavior of spray and atomization characteristics has been considerably improved.
Ammonia is regarded as one of the alternative fuels because the physical properties of Ammonia are suitable for transportation and storage as a “hydrogen carrier”. Also, a large amount of ammonia can be produced easily through the Haber-Bosch process with low price. To use ammonia as a fuel, it is necessary to get the knowledge of fundamental combustibility of ammonia. Flame stability and flame height are important factors when ammonia is used as a fuel in industry. Ammonia laminar diffusion flame is difficult to be stable under atmospheric oxidizer (O2 21%) of room temperature. In this study, therefore, the oxygen-enriched combustion was applied to make the stable ammonia laminar diffusion flame. The burner lip was focused to make the more stable ammonia laminar diffusion flame and the dependences of O2 concentration and burner lip on flame stability were investigated. Flame height was also measured under the conditions that the ammonia laminar diffusion flame were formed stably. The flame height of ammonia laminar diffusion flame was compared with that of methane laminar diffusion flame. Results showed that the stability of the ammonia laminar diffusion flame was improved in thick burner lip condition. Also, the flame height of ammonia laminar diffusion flame was shorter than that of methane laminar diffusion flame.
Due to development of day-to-day remarkable machine technology, people are being released from the extreme hard work and simple work. However, still difficult hard work site and work site which requires unreasonable attitude, such as agriculture and forestry, fishing industry, manufacturing, building industry, transport industry and medical welfare, to mechanize and automate exists. Then, it is low back pain is especially a problem in these field. According to the report of the Ministry of Health, Labour and Welfare, in 2011, low back pain that require four or more days of temporary absence from work accounts for 60 presents of occupation - related disease. So we have developed a wearable power assisting device "Muscle Suit ". In particular, because the waist is easily the most injury in the body, we are promoting the development of "Back support Muscle Suit" specializing in auxiliary of the waist, it was achieved practical use. Evaluation of auxiliary effect is important as well as the development. In this report, by using EMG, we compared the effect on the muscles of the back at the time of lifting and taking down due to the presence or absence of wearing the muscle suit, the difference in load and the difference in the position during operation. In addition, we consider how the EMG outputs by using the correlation coefficient. Furthermore, we investigated the integrated EMG of as divided operations into several, not as a continuous operation. Then, by the above investigation, we showed an auxiliary effect and usefulness of the back support muscle suit.
In industrial scenes, semiconductor exposure apparatuses have pneumatic anti-vibration apparatuses. It can produce high-performance ICs by raising exposure precision by removing vibration. It is known that exposure precision is affected by temperature change. Therefore, the voice coil motors which are large heating element are cooled down by water. Moreover, the sensor and LED which are small heating element are cooled down by air. The temperature of inner air of exposure apparatus is locally managed by means of air condition. However, the temperature in the air springs changes due to pressure change which is caused anti-vibration; it has not been managed in semiconductor industries. On the other hand, it is reported that the pipe connecting to an air spring has condensation in semiconductor industries. Moreover, the temperature changes of air spring affect to precision pressure and position control. For the above reason, the heat radiation from the air spring affects the semiconductor manufacturing probably. Therefore, this paper proposes new method of restraining temperature change of air springs which is based on heat equivalent circuit. At first, it is confirmed that the methods of flow-design and piezo-fan as mechanical technique are effective in temperature change restraint. However, the method of flow-design must have air flow in the air spring at all time. Moreover, that method of piezo-fan needs processing of the metal case of air spring and also generates heat. In order to solve these disadvantages, the method of twin-valves is proposed as fusion of mechanical and electrical methods. This method does not generate heat and it does not need processing of the metal case of air spring. Moreover, twin-valves can generate air flow at all time. Hence, it influences the temperature change suppression of air spring of anti-vibration apparatus at levitation. Furthermore, it achieves a further more temperature change suppressing effect by the method of combination of twin-valves and flow-design.
In general, manual sorting carries out for the quality inspection of corbicula shells prior to shipment. The inspection worker drops each corbicula shells on the concrete floor, and a shell is assessed as good or bad by the sound of collision with floor. The corbicula shell containing mud or nothing is specified as a bad corbicula. This manual sorting process is time consuming and laborious. In addition, this process is often prone to mistakes. In order to overcome the problem of manual sorting, an inspection probe has been developed. The inspection probe assesses a corbicula shell as good or bad by detecting the transmitted light spectra, and it has been tested that the probe can detect good and bad corbicula shells with an accuracy of 100%. Thereafter, a quality sorting device with the inspection probe has been developed for the commercial use. A laboratory based experiments have been conducted first to evaluate the performance of developed quality sorting device. The test results showed that the sorting device can sort shells with an accuracy of about 99%. Subsequently, a comprehensive evaluation experiment have also been carried out, and the experimental results showed that our developed sorting device is able to sort corbicula shells with an accuracy of 98.6%. This results implies that the present quality sorting device is ready to use for commercial sorting of corbicula shells
The purpose of this study is to understand the nature of one of the oldest gears used in traditional Japanese clock. Today's gear manufacturing technology in Japan came mostly from Europe and America, but we do not know exactly, when and how the gears were manufactured for the first time in Japan. It is interesting to search for this history. It is also exciting to study the tooth profile, precision and accuracy of the gears, and materials of the gears at that time. So far, there have been some studies performed for the mechanism of traditional Japanese clocks/watches, but not for gears. Fortunately we have a chance this time to investigate gears for Japanese watch drive that was made in 1688. Tooth profile and pitch error were measured, and transmission error analysis was also performed. It revealed that the precision of the watch was extremely high without any rust for more than 300 years, even though they were all handmade by Japanese mechanism technician named Sukeza-emon Tsuda the III. In the old days, there was no study on conjugate tooth profile theory available, but mysteriously, tooth profile was nearly made in the form of cycloid. Moreover, the gear material investigation was very interesting: The texture of the gear material was very homogeneous and grain size is far smaller than that of today's comparable steel kind. Impurities in it were very small and scattered well in the matrix. The steel was surely made by Japanese sword smith. The ore of the steel was perhaps sand-iron and it was refined with pine charcoal. The steel was forged and forged by hand very hardly. As the result the quality of the steel of 1688 looks far better than today's industrial steel. This research enabled us to discover how Japanese gear technology was born and developed.
This study aimed to measure a viscoelastic property of gelatin gels and porcine liver by the magnetic resonance elastography using micro-magnetic resonance imaging (micro-MRE). In the experiments, gelatin gel specimens (90 × 70 × 50 mm) made of gelatin solution with 5, 7, 10, 12, and 15 wt% concentration were examined under excitation with longitudinal waves in frequency of 50-250 Hz and amplitude of 0.5 mm. The viscoelastic modulus was obtained as storage shear modulus G’ and loss shear modulus G”. As a result, G’ values increased with the concentration and the excitation frequency. G” value was much smaller than G’. Double-layer specimens composed of 5 and 15 wt% gelatin gels were also examined. The average of G’ in each concentration gel in the double-layer specimens showed no significant difference from the single-material specimens with the same concentration. Furthermore, a porcine liver specimen (150 × 50 × 30 mm) were examined; however, the specimen were not vibrated and the displacement distribution in the specimen was not observed. When porcine liver specimens were embedded in the 15 wt% gel (70 × 70 × 50 mm), the specimens were vibrated deeply and G’ and G” of the liver and gel regions were obtained. As a result, G’ of the gel region was almost the same as the value of the gel specimens. G’ of the liver region increased with the excitation frequency as well as the gel specimens. The viscoelastic modulus of the porcine liver could be measured by embedding it inside gelatin gel using the micro-MRE system. This study demonstrated the application of the MRE system as the dynamic viscoelasticity measurements of gelatin gel and liver specimen.
We have devised a steering system in which the magnetic elastomer is used for the elastic members such as rubber bushings in the axle box suspension of railway vehicles. The magnetic elastomer is composed of magnetic particles and the elastomer such as synthetic rubber. This material is characterized by its hardness variation depending on the magnetic field. The axle box suspension using the magnetic elastomer is capable of varying the longitudinal stiffness. In straight sections, the application of this axle box suspension ensures running stability by increasing the longitudinal stiffness by means of applying a magnetic field. On the other hand, in curve sections, it improves curving performance by decreasing the longitudinal stiffness by means of turning off the magnetic field. We made test pieces towards the development of the magnetic elastomer for the steering bogie. In a characteristic test, we confirmed that the Young's modulus of the magnetic elastomer changes in the range of about five times depending on the presence or absence of the magnetic field. In addition, we simulated the vehicle model by applying the longitudinal stiffness change of the magnetic elastomer to the axle box of the bogie. We confirmed that this axle box was capable of reducing the average of the outer wheel lateral force in the circular curve section compared to that of the normal axle box.