著者

金子 康智 今井 貴彦 森 一石 大山 宏治

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.16-00536-16-00536, 2017 (Released:2017-06-25)

参考文献数

9

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A vane used in a low pressure end of steam turbine is usually fixed to an inner shroud and an outer ring by welding both ends. In such a vane structure, the damping in loading operation is comprised of the material damping and the aerodynamic damping, because the structural damping is very small. In addition, steam turbine vanes are sometimes manufactured in a half-ring structure, where all vanes in a upper half and a lower half are connected by the shroud. In such a half-ring structure, the vane exhibits closely spaced natural frequencies of Toop (Tangential out-of-phase) modes, in which each vane in a half-ring vibrates like a fixed-fixed beam in a different phase. In such a steam turbine vane, the forced vibration and the self-excited vibration of Toop modes may become a serious issue. Therefore, in the design of the steam turbine vane, it becomes indispensable to evaluate the resonant response and the stability of Toop modes under the high loading condition. In this study, first, the vibration characteristics of steam turbine vane with a half-ring structure are studied by use of the results of FE analysis. Second, the reduced order model (the equivalent spring-mass model) of a half-ring structure is assembled, based on the results of FE analysis. Finally, the forced response analysis of the mistuned system of a half-ring structure is carried out, using the reduced order model and the Monte Carlo simulation. From these results, the vibration response characteristics of steam turbine vane with a half-ring structure are clarified.

著者

兼森 祐治 半田 康雄

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.16-00513-16-00513, 2017 (Released:2017-06-25)

参考文献数

18

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Axial thrust forces acting on an impeller of a diffuser type mixed flow pump and the behavior of the axial thrust generated by the vortex occurrence in a pump intake sump were studied. The thrust from distinct discontinuities, such as the hysteresis phenomenon, was measured from a pump's hydraulic performance. In pump partial load operation the axial thrust increases discontinuously because of the reverse flow at impeller inlet. Synchronous and non-synchronous components of axial thrust increase during the onset of reverse flow zones. A prediction method for static axial thrust was derived based on Oshima's theory, accounting for the pressure reduction at pump suction bell-mouth caused by a vortex. Qualitative comparison of the predicted results with the actual static axial thrust results measured during the experiment, showed reasonable similarities around pump best efficiency flow rate. The thrust was measured using a pump intake sump test apparatus in which both an air-entrained surface vortex and a submerged vortex could occur. The level of dynamic axial thrust is dependent on the pump intake sump water level and the dynamic axial thrust begins to increase when a full air core vortex occurs at the pump intake. When submerged as well as full air core continuous vortices occur, the axial thrust and the fluctuation of total pump head become abruptly large. The fluctuation of axial thrust becomes the highest when the impeller draws in a large air-drawing vortex, imposing a pressure fluctuation which generates not only a rotational speed but also nZ vane passing and low frequency components.

著者

藤澤 彰宏 千田 有一

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.16-00472-16-00472, 2017 (Released:2017-06-25)

参考文献数

19

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This paper describes about path planning for a root-cutting blade of an automatic spinach harvester. Automatic harvesters for spinach have not been widely used among farmers because mechanical harvesting easily spells bruises to stems and leaves. We have been developing the harvester which successfully harvests spinach without bruising stems and leaves. The path which blade moves in soil is very important in order to attain desired performance and to reduce the amount of soil which is pushed by the blade is the most meaningful factor for successful execution. In this paper, first, we discuss about a method to reduce the amount of soil and proposed a constraint equation for the method. Next, an appropriate path of the blade of the harvester is proposed by using the equation. The effectiveness of the proposed path is verified by numerical simulations based on the Discrete Element Method (DEM).

著者

渡壁 智祥 山本 智彦 深沢 剛司 岡村 茂樹 杣木 孝裕 諸菱 亮太 櫻井 祐 加藤 亨二

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.16-00444-16-00444, 2017 (Released:2017-06-25)

参考文献数

9

被引用文献数

1

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A seismic isolation system composed of a thick rubber bearing and an oil damper has been developed for Sodium-Cooled Fast Reactor. One of the advantages of the isolation system is the use of thick rubber bearings to ensure the longer vertical natural period of a plant, thereby mitigating seismic loads to mechanical components. Characteristics of thick rubber bearings have been confirmed through a series of tests. This paper focused on the aging properties of thick rubber bearings, such as basic mechanical properties and ultimate strength. An aging test of thick rubber bearings was conducted using 1/2-scale (800 mm diameter) and 1/8-scale (200 mm diameter) rubber bearings. Aging of the rubber bearings was reproduced using thermal degradation based on Arrhenius law, in which the target of aging periods was 60 years, plant life time. The hysteresis loops of the thick rubber bearings after aging were obtained through horizontal and vertical static loading tests, and the effects of aging were evaluated by comparison with the initial mechanical properties. In addition, for the purpose of further research, the effect of scale by aging was clarified to compare the mechanical properties between the 1/2-scale and 1/8-scale rubber bearings.

著者

田村 伊知郎 松浦 真一

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.16-00438-16-00438, 2017 (Released:2017-06-25)

参考文献数

11

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For seismic design of components, elastic response spectrum analysis, which is based on linear response using elastic response spectrum, is generally used as a dynamic analysis of multi-degree-of-freedom(MDOF) systems not only elastic response but also elastoplastic response. Elastoplastic response is different from elastic response due to nonlinearity of the system by yielding of components. Several researchers have proposed response spectrum analysis methods of nonlinear MDOF systems using equivalent linearized methods, which replace a nonlinear system to the linear system equivalent to the nonlinear system on the response. We developed a response spectrum analysis method using elastoplastic response spectrum and not replacing a nonlinear system to the linear system as a dynamic analysis method of nonlinear MDOF systems. This method is obtained from exact equations of motions by just two assumptions; no interaction between natural moods and modal combination rules. We verified this method was effective in the calculated 2-DOF systems. This method is also considered of value for interpretation on the response of nonlinear MDOF systems by spectrum modal approaches.

著者

大谷 充人 花島 直彦 吉田 英樹

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.16-00317-16-00317, 2017 (Released:2017-06-25)

参考文献数

24

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In this study, we discuss a problem to collect observation data with one mobile robot in extensive investigation field. When the measurement of observation data is carried out by the mobile robot, the setting of running-path and navigation are important for appropriate measurement. Usually reciprocating straight paths at even interval are employed to collect data with spatially uniform density. However it is possible that some area between the straight paths requires detailed measurement. The method proposed in this paper makes it possible that in ordinary situation the robot follows the straight path, in the proximity of the area with need of observation it leaves the straight path toward the area, after that returns to the preceding straight path. Recently the path-generating regulator (PGR) has been applied to a tracking problem along a straight passage for car-like robots. The PGR is a control method for a vehicle so as to orient its heading toward a tangent to one of the curves belonging to a family of path functions. In this paper, we append a property to the PGR tracking the straight passage to modify the target heading angle in accordance with necessity of observation and to realize the motion toward the area with need of observation. To confirm the efficiency of the proposed method, two types of simulations are performed. The first simulation shows how a level of necessity of observation and a range to the area changes the locus of the mobile robot. In the second simulation, the mobile robot is satisfactorily guided by the level of necessity of observation obtained from actual measured data in a survey site.

著者

大友 光彰 鈴置 哲典 山本 征治 宮川 浩

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.17-00044-17-00044, 2017 (Released:2017-06-25)

参考文献数

5

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This paper studies the condition of reducing knock intensity which is the pressure oscillation initiated by auto-ignition of the end gas. The knock intensity is thought to be decreased by suppressing the reaction rate of auto-ignition. In this study, the effect of the mixture dilution which decreases the reaction rate on the knock intensity was investigated by using a spark ignition engine. In the case of low dilution, knock was observed when the auto-ignition of the end gas occurred. When the dilution ratio was over 30%, there was the condition that the knock did not occur even if the end gas auto-ignited. The combustion with low knock intensity was observed in either case that dilution gas was inert gas or air. The knock intensity was shown as a function of the maximum temperature and the maximum pressure which affected the reaction rate although the knock intensity was affected by the composition of the mixture, load, ignition timing, auto-ignition timing of the end gas and heat release quantity of the auto-ignited mixture.

著者

林 知生 近藤 義広 豊田 浩之 佐藤 重匡 椿 繁裕

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.16-00580-16-00580, 2017 (Released:2017-06-25)

参考文献数

10

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We have developed the evaluation method for two performance factors to design the thermal connector: Insertion force of thermal grease and thermal conductance. The thermal connector was comprised of a thermal plug and a thermal socket, and the thermal grease which was filled into the gap between the thermal plug and the thermal socket connected the thermal plug and the thermal socket thermally. Firstly, the insertion force was theoretically calculated using the Bingham plastic model for rheology characteristics of the thermal grease and the slip model on the surfaces of the thermal plug and the thermal socket. The calculated results were in good agreement with the experimental results. Secondly, the experimental results of the thermal conductance between the thermal plug and the thermal sockets at the first connection to the 20 times connection were -1 to +26 percent greater than the theoretical value. The reason why some experimental results exceed the theoretical results is the eccentricity between the thermal plug and the thermal socket. In addition, the filling status of the thermal grease in the gap was visualized by ultrasonic testing. The results after the 20 times connections showed there were some voids in the thermal grease and the area of voids was 4 percent of the heat transfer area. Therefore, the thermal conductance was mostly not influenced by the voids. Finally, it was found that the proposed methods to predict the insertion force and thermal conductance were reasonable.

著者

多田 宏次郎 師岡 愼一

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.16-00577-16-00577, 2017 (Released:2017-06-25)

参考文献数

18

被引用文献数

1

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This paper presents the pressure drop prediction of BWR fuel assembly without experiment. To evaluate the core performance, pressure drop of fuel assembly is one of the key design parameters. The shape of fuel assembly is complicated and the spacer has a strong effect on pressure drop. Therefore, to obtain the pressure drop of fuel assembly, the experiments are needed. However, the experiments need a lot of time and money. In the authors' previous study, the friction coefficient and spacer loss coefficient under single phase flow condition were evaluated using CFD analysis and total pressure drop under two phase flow condition were predicted using these coefficients and verified by the data of the tight lattice bundle. The purpose of this study is to predict the pressure drop of BWR fuel assembly without experiments. The predicted pressure drop by the previous study's method was compared with the pressure drop data for full-scale high-burnup 8x8 fuel assembly covering the operating BWR conditions. The following conclusions are obtained; (1)The average and standard deviations of prediction accuracy (calculation/experiment) were 1.046 and 0.023, (2)The prediction accuracy of this method is almost same as that of the current BWR design method.

著者

北村 健三 光石 暁彦 鈴木 孝司

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.16-00542-16-00542, 2017 (Released:2017-06-25)

参考文献数

16

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The natural convective flow and heat transfer of air induced around an inclined row of heated horizontal cylinders have been investigated experimentally. The experiments were carried out with the ten-cylinders row placed in the plane of inclination angles θ=0°, 30°, 45°, 60°, 75° and 90° from horizontal. The cylinders in the row were heated with constant heat flux and their diameter d and gap G were varied as d=8.4, 14.4mm and G=3.6 to 20.6mm. The Nusselt numbers Nud from the cylinders in the row were measured. They showed maxima and minima for the horizontal and vertical rows, while intermediate Nusselt numbers were obtained for the inclined rows. Those Nusselt numbers were next converted to the gap-based Nusselt numbers NuG, and, then, rearranged with the non-dimensional parameter RaG*(G/d). The result showed that the Nusselt numbers NuG are predicted well with the parameter RaG*(G/d) for the whole rows of inclination angle from horizontal to vertical.

著者

上杉 康登 山崎 由大 金子 成彦 疋田 孝幸 津村 雄一郎 水野 沙織

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.16-00537-16-00537, 2017 (Released:2017-06-25)

参考文献数

15

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To predict the combustion characteristic of auto ignition combustion in internal combustion engines, it is necessary to consider the inhomogeneity of the fuel, EGR and air in the mixture. In this research, a PDF (Probability Density Function) combustion model considering the influence of the inhomogeneity of mixture on the auto ignition combustion is developed. In our approach, the PDF of the injected fuel and the EGR gas is predicted by two-zone turbulent mixing model and only the PDF at the top dead center of the combustion stroke is used to calculate combustion characteristic to realize the reasonable calculation time for the control system design tool. The prediction model was validated by comparing with the experimental result for various injection timings and EGR ratios. It found that the model can qualitatively predict the combustion characteristics with reasonable calculation time.

著者

栩谷 吉郎 川北 英貴

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.16-00528-16-00528, 2017 (Released:2017-06-25)

参考文献数

8

被引用文献数

1

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An experimental study has been carried out to clarify the effect of quantity of absorbed water on behaviour of single silica-gel particles in oil with dc electric field, as a basic research to augment adsorption. The progress of adsorption changes mass and physical properties of a silica-gel particle, and the change might influence the behaviour of the particle. The experiment is conducted under condition that the adsorbed material is only water, and the quantity of water is adjusted beforehand to prescribed value. Two electrode plates are horizontally set up 40 mm apart in silicone oil. Particle diameter is adopted of 2.7, 4.0 and 5.0 mm, and the range of applied voltage is 0 - 28 kV. The applied voltage is increased at approximately 2kV/min. Observation of behaviour of a silica-gel particle starts from resting condition on a lower electrode. As a result, a dried silica-gel particle does not begin moving even at the maximum voltage. For a silica-gel particle of water adsorbed, following four stages have been observed, excluding a very few exceptions; rise from the upper side of lower electrode to the upper electrode, bound and rest on the lower side of the upper electrode, descent to the lower electrode, and bound and rest on the lower electrode. The rest time on the electrode is not seen to a completely water-absorbed silica-gel particle. It is thought that the particle exchange the electric charge at the rest time. The applied voltage for the leave of a silica-gel particle from the lower electrode, rest time on each electrode, and bound height from each electrode are also shown.

著者

森 賢斗 駒田 佳介 植木 弘信

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.16-00507-16-00507, 2017 (Released:2017-06-25)

参考文献数

20

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A laser 2-focus velocimeter (L2F) was used for measurements of velocity and size of droplets in diesel fuel sprays. Diesel fuel was injected intermittently into the atmosphere by using a 8-hole injector nozzle. The diameter of the nozzle orifice was 0.112mm. The rail pressure was set at 65MPa by using a common rail system. The period of injector solenoid energizing was set at 2.3ms. The L2F had a micro-scale probe which consists of two foci. The focal diameter was about 3μm, and the distance between two foci was 20μm. The data sampling rate of the L2F system was markedly high as 15MHz. L2F measurement was conducted at 10mm downstream from the nozzle exit. Temporal and spatial changes in the velocity, size and number of droplets inside sprays were investigated. Spray images were taken by using a 180ns spark light source, and the scattered light intensity distribution and spray width were estimated. The scattered light intensity, the spray width and the number of droplets were oscillated several times in the injection period. The number of droplets at the inner region of the spray decreased and the one at the outer region of the spray increased, when the spray width increased. That is, many droplets fly to the outer region of the spray at the time when spray width is wide.

著者

玉木 伸茂 室谷 拓也 原田 貴人

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.16-00500-16-00500, 2017 (Released:2017-06-25)

参考文献数

20

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It is important to improve spray characteristics of an energy conversion engine in order to reduce carbon dioxide and exhaust gas emission. The purpose of this study is to design and develop high-dispersion injection nozzle for direct injection Diesel engine. This paper describes about that effects of the measurement and the geometric shapes of nozzles on spray characteristics and design of the nozzle which is obtained more excellent spray characteristics. When the measurement, the geometric shapes and the internal structure of nozzle were designed the most suitable conditions, breakup length becomes approximately 10 % shorter and spread of spray i.e., spray angle becomes large about 30 %. Moreover, Sauter mean diameter obtained is about order of 10 μm which is smaller than that with the nozzle developed in the previous study.

著者

宗意 奎太郎 杉田 勝彦 梅沢 修一 川島 久宜 石間 経章

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.17-00054-17-00054, 2017 (Released:2017-06-25)

参考文献数

13

被引用文献数

1

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Water spray is used for cooling suction air of gas turbine for power augmentation. Cooling efficiency depends on the spraying properties. The aim of this study is to investigate the spray characteristics and the influence of secular change in the spray nozzle. PDA (Phase Doppler Anemometry) measurements are conducted at each cross section in wind tunnel which is scale model of inlet duct. Pin type nozzles and a hole type nozzle are tested. Same type nozzles with different using period are also tested. The nozzles are new one and old one which is used 1750 hours before the spray experiments. The spray properties in high spatial-temporal resolution are provided by the PDA. As a result, the droplet size by a pin type nozzle has no change after 1750 hours. The data rate, velocity and flow rate decrease after 1750 hours due to increase of the passage resistance by filter clogged. Pin type nozzles have asymmetry shape in data rate distribution due to the existence of pin. The SMD distributions by pin type nozzles have flat shape in the measurement region. The SMD distributions gradually increase in the value from the center to outer in hole type nozzle. Droplet size dispersion at each measuring point for all nozzles are also evaluated by the experiment. Dispersion of diameter increase in from the center to outer in a hole type nozzle. Also cooling efficiency and the relations of particle density are evaluated. If the particle density is high, the cooling efficiency become small even if the particles have small diameter and high velocity.

著者

稲垣 大志 中村 暢志 板野 智昭 関 眞佐子 兵頭 仁介

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.17-00042-17-00042, 2017 (Released:2017-06-25)

参考文献数

10

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The water velocity field in a rectangular reservoir driven by a previously unexplored water streamer is investigated experimentally and numerically. Firstly, the velocity field on the water surface induced in a rectangular reservoir is estimated from trajectories of floating passive tracers. Secondly, the velocity at the several fixed points below the surface is directly measured with the aid of an electro-magnetic velocimetry. These measurements elucidate that the streamer activates an underwater circulation between the surface and the bottom in the reservoir. Additionally, a numerical simulation is examined to realise the induced three-dimensional flow below the water surface. The obtained results provide an evidence that the induced flow structure is three-dimensionally spiral, which is distinct from that induced by the water streamers traditionally utilized in aquacultural reservoirs. The investigated streamer may be utilized for the purpose to particularly enhance the underwater vertical mixing in aquacultural reservoir or purification plant.

著者

姜 東赫 佐藤 光太郎 横田 和彦

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.17-00038-17-00038, 2017 (Released:2017-06-25)

参考文献数

15

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The present study investigates a swirl flow instability induced by a rotating cylinder between coaxial two disks as a model of a vaneless diffuser at zero flow rate. To begin with, the experiment and three-dimensional finite volume simulation were performed. The rotating cylinder was used to produce the swirl flow. Small vortices were generated from the cylinder surface. They were combing and forming one croissant-shaped toroidal vortex (CTV), which was rotating around the cylinder. Small vortices were separating from the CTV and flowing away from the cylinder. In order to investigate the cause of the swirl flow instability, a 2D stability analysis for an annular vortex street was performed. The annular vortex street became less unstable for the larger radial location and the fewer number of vortices. This implies that the vortices could be forming into one vortex as their radial locations increased. In order to validate the stability analysis, the vortex simulations were carried out. The vortices generated from the cylinder surface were forming into one cell as their radial locations increased. In order to validate the stability analysis and vortex simulation, the 2D finite volume simulation was performed. The vortices were generated from the cylinder surface. They were combining and forming one cell, which was rotating around the cylinder. The vortices were separating from one cell and flowing away from the cylinder. The frequencies of vortex rotation agreed in the experiment, the two and three-dimensional simulations. Therefore, it is considered that the 2D vortex transforms to the 3D CTV, similarly the Tayler vortex. Furthermore, all the results indicate that the 2D swirl flow instability causes the CTV, and the vortices combining to and separating from the CTV.

著者

高橋 護 岩野 耕治 酒井 康彦 伊藤 靖仁

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.17-00004-17-00004, 2017 (Released:2017-06-25)

参考文献数

26

被引用文献数

1

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Simultaneous measurement of the velocity-gradient and fluctuating static pressure was carried out in a turbulent planar jet. We use a constant-temperature hot-wire anemometry and a miniature pressure probe for velocity measurement and fluctuating static pressure measurement, respectively. Two types of the combined probe are introduced for simultaneous measurement of the velocity-gradient and fluctuating static pressure. One consists of an X-type hot-wire probe and a pressure probe and the other consists of two I-type hot-wire probes arranged in vertical direction and a pressure probe. For improvement of the measurement accuracy, the responsivity of the pressure probe, the time-lag due to the spatial distance between the hot-wire probe and the pressure probe, and the attenuation of the velocity-gradient measurement due to the finite difference method, are corrected. In this paper, we compare the various statistics of the turbulent planar jet acquired using the combined probes and those acquired using hot-wire probe or pressure probe alone. Through the results, it is confirmed that the simultaneous measurements were well-performed in the turbulent planar jet expect for the outside of the velocity half-width. Further, it is revealed that the Pressure Rate-of-Strain Correlation, which appears in the Reynolds stress transport equation, is almost dominated by (p´/ρ)(∂u´2/∂x1) and (p´/ρ)(∂u´1/∂x2) barely contributes to the Reynolds stress transport in the cases of Re ≥ 10,000.

著者

江尻 英治 岩楯 智哉

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.16-00484-16-00484, 2017 (Released:2017-06-25)

参考文献数

16

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The straight-bladed vertical axis wind turbine is one of the promising candidates for next-generation power sources because of its high efficiency, quiet operation and structural simplicity. Fewer wind turbines of this type have been manufactured and used so far compared with other types like the horizontal type. Therefore, further improvement in efficiency is essential in order to promote their widespread use. The purpose of this study is to better understand the influence of the blade profile of the straight-bladed vertical axis wind turbine on flow and aerodynamic performance and to improve wind turbine efficiency. Unsteady two-dimensional flow through a wind turbine with a symmetrical blade profile, the diameter of which was 3 m, was numerically computed with a commercial CFD code and the results were analyzed. A wind turbine with outward-cambered blades was then designed in order to increase the rotational force acting on the blade along with a wind turbine with inward-cambered blades for comparison. The computational results showed that the wind turbine with outward-cambered blades was better in performance than the ones with symmetrical or inward-cambered blades. Experiments using small wind turbine models, the diameter of which was 200 mm, were carried out in order to verify the computational results. The experimental results showed the same tendencies as the computational results in spite of the difference in scale, Reynolds number and blade number. The effects on flow and performance were also analyzed by additional computations performed with the same CFD code.

著者

倉光 貴之 藤井 達也 蓮沼 将太 小川 武史 禹 明勲 高梨 正祐

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.17-00066-17-00066, 2017 (Released:2017-06-25)

参考文献数

12

被引用文献数

1

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The purpose of this study is to investigate low cycle fatigue (LCF) and high cycle fatigue (HCF) strengths, crack initiation and growth behaviors of Ni based castalloy 246. LCF and HCF tests are conducted under load controlled conditions. As the result of the observation of etched specimen, the grain size is from 3 mm to 5 mm. And the microstructure is mainly composed of dendritic structure. Growth orientation of dendritic structure varies in every grain. The result of elemental analysis, Si and Ti are detected at dendritic boundary. The results of LCF test show that small cracks initiate at the first cycle, followed by the crack growth along slip direction. Observation of fracture surface reveals that small cracks originate at casting defect or dendritic boundary. The results of HCF, on the other hand, show that small cracks initiate from subsurface casting defect under Δσ ≦ 600 MPa, while fracture origin becomes surface under Δσ > 600 MPa. The result of HCF test after introducing small crack on the surface shows that small crack on the surface does not affect on the fatigue life and the location of crack initiation. As the result of EBSD, the crack initiation site is near grain boundary and the crack grows along slip plane.