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Article type: Cover
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Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Article type: Appendix
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App1-
Published: August 05, 2003
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Article type: Index
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Toc1-
Published: August 05, 2003
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Yinchun CAO, Hidetsugu KOBAYASHI, Haruhiko MORIKAWA, Tomokazu FUJITA, ...
Article type: Article
Pages
1-2
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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It is well known that centrifugal pump efficiency becomes worse with the decrease of pump size and specific speed. The small-sized pump with low specific speed, in which the impeller outlet velocity was larger, was designed by an optimum design method combined with blade surface singularity method The results show as follows : The semi-open impeller designed by the optimum design method, yielded the highest efficiency of 61% among test impellers in narrow tip clearance c/b_2. In larger c/b_2,however, the leakage loss becomes dominant and the efficiency of impeller with larger blade outlet angle is higher. This fact implies that the c/b_2 should be considered as an additional factor for optimum design.
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Toshiaki KANEMOTO, Daisuke TANAKA, Toshihisa ITO, Youichi NAKAMURA
Article type: Article
Pages
3-4
Published: August 05, 2003
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The inducer is very effective to suppress the cavitation in the main impeller. The conventional type attached directly to the main impeller, however, not only has a limit of the suppression, but also must be replaced repeatedly because the inducer is in the cavitating flow in general. To overcome these weak points, this paper prepared the two stage impellers driven by the isolated motor. The front impeller works just like the inducer and the speed is actively optimized in response to the suction head and/or the pump discharge so as not to generate the cavity. The pump performances were predicted and discussed accompanying with the internal flow conditions.
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Masamichi IINO, Kazuhiro TANAKA, Kazuyoshi MIYAGAWA, Takeshi OKUBO
Article type: Article
Pages
5-6
Published: August 05, 2003
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In the present study, the effect of volute casing on the head/discharge characteristics with 2-step positive slope of a centrifugal pump has been investigated through calculating internal flow field. Based on the hypothesis of axisymmetric flow field, the numerical simulations on the incompressible turbulent flow have been carried out for partial-blade passages with periodic boundary conditions. As a model of the volute casing, a parallel diffuser or three volute casings with different configuration was prepared in the simulation. The result on each head/discharge characteristic curve has the same tendency as the experiment in the positive slope. At partial flow operation, the pumps with each model have the large backflow and recirculation regions in two locations, one of which is near the casing at the impeller inlet and the other near the central part of the diffuser. The scale of these regions varies steeply under two partial flow operation points as the discharge changes. The results show that the dominant factor of the positive slope is independents of the configuration of volute casing and exists in the upwind of volute casing.
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Toru Shigemitsu, Satoshi WATANABE, Akinori FURUKAWA, Kusuo OKUMA
Article type: Article
Pages
7-8
Published: August 05, 2003
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Higher specific speed of axial flow pump follows a strong demand for more compact structure but yields deterioration of pump efficiency and cavitation performance. One solution might be adoption of contra-rotating pump. The previous experimental results implied its possibility although guideline of rear rotor design was not found because of the complexity of internal flow. Numerical analysis was performed with a method of commercial code to consider the optimum design of rear rotor. Numerical results are compared with experimental ones for two kinds of rear rotors tested. And further improvements of pump performance are considered from numerical results for rear rotors with various design parameters.
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Tsutomu IWAKO, Hiroshi TUKAMOTO, Koji MIYAZAKI
Article type: Article
Pages
9-10
Published: August 05, 2003
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Diffuser pump instability was studied near the rated condition, in which a positive slope appears slightly in the pump characteristic curve, by analyzing the correlation dimension for unsteady pressure in the pump. As a result of the chaotic analysis, the attractor of pressure data was found to extend spatially at the 80% flow rate more than the one at the design point. Moreover, the correlation dimension took the value of 2.2 to 2.3 for unstable flow, and thus may be utilized as a qualitative measure of instability in diffuser pump.
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Jun MATSUI, Juinichi KUROKAWA, Hiroshi IMAMURA
Article type: Article
Pages
11-12
Published: August 05, 2003
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The internal unsteady flow in the variable capacity type fluid coupling is analyzed by CFD, considering the movement of free-surface. The torque curve of CFD shows very good agreement of experimental one. In the area of instability of the fluid coupling, where the torque and rotational speed varies very much in the experiment, the numerical result shows that there are two different flow patterns in this area. In a pattern, most of working fluid is rotating in the rotor area, and it transfers small torque only. In anther pattern, the working fluid rotates around the air area, that is concentrated at the center of fluid coupling, and it can translates large torque. When the flow go around between these two flow pattern, the torque will be varied widely.
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Norio SAKAZUME, Masaharu UCHIUMI, Masayuki UCHIDA, Takuzo IWATSUBO
Article type: Article
Pages
13-14
Published: August 05, 2003
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The fuel (liquid hydrogen) turbo-pump (FIP) of the LE-7A engine, the first stage main engine of H-IIA launch vehicles, has been attended, from the outset of development, with problems of excessive sub-synchronous whirl vibration. Test data indicate system damping of the rotor system becomes nearly zero and actions of the rotor system readily respond to external random force. The outstanding reduction in system damping was shown due primary to Thomas force induced by the high power turbine. It was generated by torque difference, depending on tip clearance distribution of rotating turbine blades. For estimation of blade force, CFD was used to predict flow in the turbine. The present study was conducted so as to find means for augmenting damping. Determination was made of seal characteristics and system damping was evaluated. It was estimated that the rotor system could become sufficiently stable by injecting seal fluid in a counter rotating direction. Hot firing test data indicate the vibration was sufficiently suppressed using this seal.
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Shin OBA, Toshiaki KANEMOTO, Kouji UEMURA
Article type: Article
Pages
15-16
Published: August 05, 2003
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Turbopumps have weak points, such as the pumping operation becomes unstable in the rising portion of the head characteristic and/or the cavitation occurs under the low suction head. To overcome simultaneously the both weak points, the authors have proposed the unique pumping system with counter-rotating mechanism. In this paper, the flow interactions in the counter-rotating impellers are discussed using the experimental results of the wall pressure. The flow at the front impeller inlet fluctuates in response to the front blade number and the flow fluctuation between the front and the rear impellers is affected mainly with the rear blade number.
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Tomoyasu YAMANOKUCHI, Keisuke MURAMAMI, Toshiaki KANEMOTO, Yuji HATTOR ...
Article type: Article
Pages
17-18
Published: August 05, 2003
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It is impossible, in the conventional turbofan engine technology, to make the core engine speed optimize, because the front fan is directly connected to the core turbine shaft. Pratt & Whitney have proposed the geared turbofan engine to reduce the front fan speed at higher core turbine speed. On the contrary, this paper prepare the axial flow type torque converter composed of the driver and the turbine wheels in place of the gearbox, and the characteristics are discussed under unsteady operating conditions. The turbine wheel whose tip ring equips with the front fan works acceptably in response to the driver wheel speed.
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Hirokazu SAKAI, Satoshi TOKUSHIGE, Yoshiaki GOTOU
Article type: Article
Pages
19-20
Published: August 05, 2003
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Front grille of an air conditioner as well as its function to cover the inside of the air conditioner are important components to determine the quality. The draft resistance is determined by this complicated shape. Thanks to the development of Computational Fluid Dynamics (CFD), we have a method to apply CFD to various developments. We studied the porous media for modeling the front grille. Then, we designed a method for analyzing individual draft resistance of the front grille to obtain the relation given to the porous media. Further, we analyzed the influence of design parameters of each front grille upon the draft resistance. Finally, we obtained an ideal shape of the front grille under certain conditions.
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Hoshio Tsujita, Shimpei Mizuki, Atsumasa Yamamoto
Article type: Article
Pages
21-22
Published: August 05, 2003
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In a passage of turbomachinery, the complex secondary flow is produced by the effects of the centrifugal forces induced by the passage curvature as well as its rotation and the Coriolis force. The passage vortex (PV) in the secondary flow generates a major part of the losses. Curved ducts are considered to be fundamental models to clarify the behavior of PV in the present study. The mechanisms of the loss generation caused by PV are analyzed in detail by using the stationary curved square ducts. The analyses are performed with the numerical technique in order to examine the effect of the curvature of the curved duct on the loss generation by PV. The computed results revealed the relationships among the curvature, the loss generation, the strength of PV and the pressure distribution.
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Xiang Yu Qiao, Shinji Fukao, Yoshinobu Tsujimoto, Chisachi Kato
Article type: Article
Pages
23-24
Published: August 05, 2003
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In order to analyze the occurrence mechanism of the backflow at the inlet of inducers, a series of numerical calculations were carried out including the different sizes of the tip clearance and the different geometry of the leading edges. Discussions are made based not only on the flow field at the inlet but also on the on the balance of the flow into/out from control volumes. The results show that the radial direction flow near the blade suction surface plays the main role in the formation of backflow. It is also shown that the leading edge gives an important influence for the backflow region
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Akiko DOSHO, Kazuhiko YOKOTA, Motoyuki ITOH
Article type: Article
Pages
25-26
Published: August 05, 2003
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The present paper describes the experimental results of the influence of a bend type inlet on the swirling backflow by using the backflow model test rig. The backflow is generated by using a propeller with zero stagger blades. The backflow regions were observed by using a taft-stick and air bubbles. The backflow region thickness is not influenced by a bend type inlet so much. On the other hand, its length becomes shorter at the inner side and longer at the outer one. The fluctuation of the backflow region length becomes stronger for the bend type inlet than for the straight type one.
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Takahiro NISHIOKA, Shuuji KURODA, Tadashi KOZU
Article type: Article
Pages
27-28
Published: August 05, 2003
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Inception patterns of rotating stall in a low-speed axial-flow fan have been investigated by measurements of pressure and velocity fluctuations. Experiments have been carried out at two different stagger angle settings for rotor blades. At the design stagger angle, a short length-scale stall cell known as a "spike" and multiple short length-scale stall cells appear first. These stall cells then grow into a long length-scale stall cell as flow rate decrease. The spike and the multiple short length-scale stall cells induce a part-span stall, and the long length-scale stall cell induces a full-span stall. At the small stagger angle, a long length-scale disturbance known as a "modal" is observed first, and the modal and spikes then induces the long length-scale stall cell. It is concluded from these results that the rotating stall inception patterns depend on the rotor stagger angle.
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Masahiro ISHIDA, Taufan SURANA, Takeshi SAKAGUCHI, Daisaku SAKAGUCHI
Article type: Article
Pages
29-30
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In a high specific speed type open shrouded centrifugal impeller, a periodic unstable flow occurs at small flow rates due to both inducer stall and diffuser stall. In the present study, the effect of diffuser width on diffuser stall was analyzed by a numerical simulation, in which the 3-Dturbulent flow in the impeller and vaneless diffuser was calculated by using a commercial CFD code of the CFX-TASCflow together with the κ-ω turbulence model. The numerical simulation shows the reverse flow in the vaneless diffuser disappears significantly by reducing the diffuser width from 15 to 10[mm]. The experimental result shows that, by the reduction of diffuser width, the unstable flow due to diffuser stall was suppressed effectively at small flow rates without deteriorating the diffuser performance.
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Masahiro ISHIDA, Taufan SURANA, Takeshi SAKAGUCHI, Hironobu UEKI
Article type: Article
Pages
31-32
Published: August 05, 2003
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In order to suppress a periodic unstable flow occurring at small flow rates in a high specific speed type open shrouded centrifugal impeller, both effects of inlet recirculation and reduction of diffuser width on suppression of inducer stall and diffuser stall as well were analyzed by a numerical simulation and verified experimentally. The unstable flow range of the test blower was significantly improved by about 45% by adopting the optimum ring groove arrangement in addition to the narrowed diffuser width without deteriorating the blower characteristics even at the design flow rate.
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Yasutomo KANEKO, Kazushi MORI, Masayuki TOMII, Hiroharu OYAMA
Article type: Article
Pages
33-34
Published: August 05, 2003
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The reduction effect on the vibratory stress of the steam turbine blade is studied theoretically for the most probable asymmetric vane, in which the vane count of the upper and lower half is slightly different. The method for predicting the vibratory stress of the blade for the asymmetric spacing vane is proposed. Using the simple model of the asymmetric vane, the parametric study is carried out to clarify the influence of the blade damping, vane count etc. on the reduction effect of blade vibratory stress. The vibratory stresses are analyzed in both case of the symmetric and asymmetric spacing vane by use of the proposed method and the effect of the asymmetric spacing vane on the resonant stress is verified.
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Hiroshi IMAMURA, Junichi KUROKAWA, Jun Matsui, Masashi KIKUCHI
Article type: Article
Pages
35-36
Published: August 05, 2003
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Cavitation is one of the serious problems in the operation of the turbo-pump because it causes the noise, vibration and erosion in the pump. However, the deterministic method to suppress the cavitation in turbo-pump has not yet been established in spite of the many efforts in the past. The purpose of the study is to control and suppress the cavitation caused in the inducer by J-groove. "J-groove" composed of shallow grooves mounted parallel to the pressure gradient on the casing wall is a very simple passive device to suppress several anomalous phenomena in turbomachinery. In this study the effects of J-groove are examined experimentally, where the cavitation performance and pressure fluctuation on the wall are measured. The results showed that the cavitation performance is remarkably improved by J-groove
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Omi KONDO, Hiroshi MAEKAWA
Article type: Article
Pages
37-38
Published: August 05, 2003
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The influence of pair of small plates at several locations downstream the nozzle exit on the development of a round jet mixing layer is investigated by means of hotwire measurements and flow visualization. The results show that the plates put at the shear layer are effective to manipulate the jet vortex development. The spectral measurements indicate that the peak amplitude at the roll-up is greatly reduced or even suppressed. While the plates are put at the center of potential core the jet direction is controlled. The results also suggest that a choice of proper size of plates is significant to get an effective control of jets.
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Kaoru FUKASAWA, Hitoshi KUROYANAGI, Masatoshi SANO
Article type: Article
Pages
39-40
Published: August 05, 2003
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The experimental study has been performed on turbulent channel flow with injection through an inclined slit. The inclined angle is changed 30°, 60° and 90° at the main stream velocity 10m/s. The dimensionless injection flow rate is varied three steps in ranging 0.067∿0.200. The cooling effectiveness, wall static pressure are measured behind the slit. The cooling effectiveness increases with increasing the dimensionless injection flow rate. When the inclined angle is 30°, the effect of injection remains over long distance in the near-wall region, and the highest performance is obtained.
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Masashi HIGASHIURA, Hidetoshi AOKI, Tadashi MORIOKA, Shinji HONAMI
Article type: Article
Pages
41-42
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In order to establish the active control system by using the vortex generator jets (VGJs), it is necessary to understand the detailed suppression mechanism of the flow separation in the diffuser. An opening angle of the diffuser can be changed from 8 to 15 deg corresponding to three flow regimes, "Unstalled", "Appreciable Stall" and "Transitory Stall". A micro wall flow sensor was used for measurement of forward flow fraction. It is found that VGJ makes the local forward flow fraction increase and prevents the stall. Although the effect of separation control is obtained resulting from the higher jet velocity ratio, excessive jet velocity ratio introduces pressure loss due to the lower diffuser effectiveness.
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Kouki Murakami, Takehiko Segawa, Hiroshi Mizunuma
Article type: Article
Pages
43-44
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In order to control the longitudinal vortices in turbulent flow, a suction-blowing actuator array which can produce artificial horseshoe-like vortices by water jets was tested in closed loop water channel. By using a fiber Bragg grating (FBG) system, total skin frictional coefficient of flat plate was also measured to evaluate the effect of the suction-blowing control and detected some drag reduction. The also measured to evaluate the effect of the suction-blowing control and detected some drag reduction. The local shear stress measured using a hot-film probe indicated the cyclic stress change that had the same phase relation as the piston-blowing.
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Takeo KAJISHIMA, Masahiro SHIGEMORI
Article type: Article
Pages
45-46
Published: August 05, 2003
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We applied the direct numerical simulation (DNS) to investigate the particle-laden turbulence in fully-developed upward flow in a vertical channel. In this report, particular attention is focused on the influence of particle rotation. Rotating particles are distributed more uniformly in the channel in comparison with irrotational ones. Flow separation from irrotational spheres develops to hairpin vortices in near-wall region, while flow around rotational ones increases small scale turbulence in the mainstream region.
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Toshihiro TAKAMI, Yoshinori KITA, Shinichiro YANASE, Yoshiyasu ENDOU
Article type: Article
Pages
47-48
Published: August 05, 2003
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An unsteady behavior of wall-drag is experimentally investigated in the unsteady turbulent pipe flow, under several flow conditions with a rapid to slow time-variation and a moderate to large distortion of the flow-rate imposed stepwise.
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Motohiko HASEBE, Hiroshi MAEKAWA, Youichi KAMIKUCHI
Article type: Article
Pages
49-50
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Control of near-wall large-scale vortices is significant for a skin frication reduction in the turbulent boundary layers. From this viewpoint, the mechanism to control hairpin vortices in the transitional boundary layers developing on a flat plate is studied. Using a pair of wings, which is designed so that each wing generates a circulation opposite to longitudinal hairpin vorticity, hairpin vortices have been manipulated. This configuration of the wings results in as much as 35% turbulent fluctuation reduction. This technique will be applied to manipulation of many hairpin vortices generated by acoustic excitation with a loudspeaker.
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Masashi ICHIMIYA, Tomoaki HOSOBE
Article type: Article
Pages
51-52
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Experiments were performed to investigate the effect of a three-dimensional roughness row on boundary-layer transitions on a flat-plate with zero pressure gradient. Each roughness element was a cylinder 2 mm in both diameter and height. Eleven elements formed a row in the spanwise direction. Wedge-shaped turbulent regions ("turbulence wedges") developed downstream from the respective roughnesses. Further downstream, two adjacent wedges merged together and then a two-dimensional turbulent boundary layer was formed. Mean and fluctuating velocities were measured by hot-wire anemometers and an intermittency factor were obtained. The manner how the three-dimensional turbulence wedges change into two-dimensional boundary layer were investigated. The transition was promoted in the region near the spanwise position at which two wedges interact. The promoted turbulence damped before the promotion spread to the wedge centerline.
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Masato HAMADA, Noriaki OHTA, Hiroharu KATO
Article type: Article
Pages
53-54
Published: August 05, 2003
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We measured the reduction of turbulent frictional resistance by microbubbles injected in a two-dimensional water flow channel. We also measured the velocity as well as the turbulent intensity distributions in the boundary layer by LDV. The turbulent intensity was increased with the microbubbles at the buffer layer and the turbulent region. Whereas, the turbulent intensity was decreased with the microbubbles at the region very near to the wall. Further studies are necessary including the measurement of Reynolds stress.
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Yuji Okita, Masashi Ichimiya, Katsutaka Nakamura
Article type: Article
Pages
55-56
Published: August 05, 2003
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The purpose of this paper is to study in detail the flow over an inclined fence in a turbulent boundary layer, as basic research which issues from promoting heat transfer and the decrease of the pressure drop. The fence height h set in a turbulent boundary layer is 1 mm (u_rh/ν ≑ 25,u_r : friction velocity, ν : kinematic viscosity) and setting angle of a fence is 20° in the free stream direction. The velocity profiles in the downstream of the fence were measured by I-shaped hot-wire probe and we investigated turbulence characteristics. Consequently, we clarified the turbulence intensity profiles and probability density functon profiles, and the skewness, flatness.
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Shinya TANIGUCHI, Motoyuki ITOH, Kazuhiko YOKOTA, Shinji TAMANO
Article type: Article
Pages
57-58
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This investigation was done for understanding the effect of the flexibility of the wall on the turbulent boundary layer in a flutter state. A wind tunnel was used for the present experiment. The profiles of the mean flow and turbulence intensity on the flexible sheet were measured with a hot-wire anemometer. In addition, the displacement of the sheet was measured using a laser displacement meter. The velocity defect on the flexible sheet was larger than that on the rigid wall, and the turbulence intensity was larger.
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Yoshifumi NISHIZAWA, Yasuyuki NEMOTO, Yukihiro MAEZAWA, Izumi USHIYAMA
Article type: Article
Pages
59-60
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The drawback of the Darrieus type wind turbines is their low self-starting ability due to small generated torque at start. In the previous study, we have already designed a Helix-Darrieus type wind turbine applying helical twist to the basic straight Darrieus type blades along its circumference and conducted a series of wind tunnel tests. In the present study, we introduced curvature of the blades for swept-back angle to the Helix-Darrieus type blades to improve the self-startability further. The wind tunnel tests are conducted using two improved Helix-Darrieus type wind turbines havning different swept-back angles. The results show that the both torque and power coefficients at low wind speed are improved with the newly proposed Helix-Darrieus type wind turbines.
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Masaki YAMAGISHI
Article type: Article
Pages
61-62
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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To improve the performance of the drag-type vertical-axis windmills, the system using a wake behind a bluff body is proposed. In this study, the model which is constructed with two Savonius rotors placed in parallel behind a circular cylinder is made. In this system, drag which acts on the reversing bucket of Savonius rotor decreases owing to being in the low speed velocity region in a wake. Furthermore, as the flow accelerates beside the circular cylinder, drag which acts on the advancing bucket increases. To compare the revolution of the rotor in this system with that of the single rotor, the wind tunnel experiments were conducted. It is found that the revolution in the system is higher than that of the single rotor. In order to determine the Savonius rotors configuration in the system, the experiments were conducted for various configurations of rotors. The results showed that there is the optimal configuration of the rotors.
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Yan LI, Tsutomu HAYASHI, Yutaka HARA, Katsuya SUZUKI
Article type: Article
Pages
63-64
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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A new three-stage Savonius windmill rotor, buckets of which have 120-degree phase shift between the adjacent stages, was made. The static torque and the dynamic torque characteristics of the different-phase-type rotor and another type rotor with no phase shift (same-phase type) were measured by the wind tunnel experiments and compared. It became clear that the torque variation of the different-phase type rotor was smoothed and the characteristic in starting was improved. The influence of twelve guide vanes that were attached around the rotors was observed in the torque variation. And the influence was remarkable in low wind velocity or high rotation states.
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Yukimaru SHIMIZU, Takao MAEDA, Yasunari KAMADA, Shintaro KAWAGUCHI, Ta ...
Article type: Article
Pages
65-66
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This paper describes the power augmentation of the Orthoptere wind turbine due to several diffusers. The Orthoptere wind turbine is a kind of paddle-type vertical axis wind turbine operated by the effects of both lift and drag forces exerted on the blades. The performance of the Orthoptere wind turbine shows middle characteristics between Sabonius wind turbine and Darius wind turbine. Different from other vertical axis wind turbines, the Orthoptere wind turbine shows directivity respect to wind direction. Using diffuser, power augmentation of the Orthoptere wind turbine could be achieved. The diffuser we used has rectangular cross section. The diffuser is composed of straight duct and divergence part for power augmentation. The experiment was carried out in wind tunnel.
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Kazuki TAKEUCHI, Junichiro FUKUTOMI, Hidetoshi KODANI, Hironori HORIGU ...
Article type: Article
Pages
67-68
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The cross-flow wind turbine has high torque and low speed characteristics and the structure are very simple. However, even if the power coefficient is high, it is about 10%. The purpose of this paper is to show how we can improve the power coefficient by applying a casing, which has a nozzle and a diffuser. In this research, the performance of a cross-flow turbine simple substance and the flow state of the circumference of a rotor, and the internal flow were first cleared up for the purpose of the improvement in a performance of a cross-flow wind turbine. Furthermore, in order to raise a power coefficient, cylindrical casing which has a nozzle and diffuser was installed. And the effect of cylindrical casing was investigated from an experiment and numerical analysis.
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A. Iida, A. Mizuno
Article type: Article
Pages
69-70
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Unsteady flow field and flow induced noise of vertical axis wind turbine are numerically investigated. The flow field is numerically calculated by the vortex method with core-spreading model. This simulation obtains aerodynamic performance and aerodynamic forces. Aerodynamic noise is also simulated by using Ffowcs Williams-Hawkings equation with compact body and low-Mach number assumptions. Tip speeds of rotor blades are not so high, then the contribution of the moving sound source is smaller than that of the dipole sound source. Since the maximum power coefficient of VAWT can be obtained at lower tip-speed ratio compared to the conventional, horizontal axis wind turbines, the aerodynamic noise from vertical axis wind turbine is smaller than that of the conventional wind turbines at the same aerodynamic performance. This result indicates that the vertical axis wind turbines are useful to develop low-noise wind turbines.
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Takayuki Hagiwara, Syo Kamata, Kazuichi Seki
Article type: Article
Pages
71-72
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The basic characteristics of the straight wing type vertical axis wind turbine are presented under some simplifying assumptions and set of weighting functions is order to provide explicit the relationship between wind turbine efficiency and the aerodynamics characteristics of the airfoil. It is shown that pitching moment coefficient as will as minimum drag coefficient and lift coefficient has significant effect both on the starting capability and on the maximum efficiency of a wind turbine. Furthermore, a suggestion is mode with regard to the design of the mean lines to attain a preferable characteristics for the airfoil of the vertical axis wind turbine.
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Kazuichi SEKI, Kenji HORIUCHI, Keita SAGARA
Article type: Article
Pages
73-74
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Researches about the aerodynamics of wind turbine with straight wing vertical axis (SW-VAWT) are very limited, in spite of a number of advantages such as low dependence on wind direction variation and easy constructible straight blades. For these reasons, we are researching the lift type SW-VAWT for many years. The elucidation of the behavior of the flow inside and neighborhood of the wind turbine during the rotation is very important because of the performance improvement of the vertical axis wind turbine. We estimated flow behavior during the wind turbine rotation by using this numerical simulation technique, and evaluated the flow around the wind turbine. This paper presents outline and results of these calculations and evaluations.
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Yoshiaki TANZAWA, Kenzo Cho, Takao SATO, Takumi HASHIZUME
Article type: Article
Pages
75-76
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Many birds increase by flapping the wing and the whole wing is flexibly moved this time. This movement produces a difference in the air resistance. The air is grasped enough, when the wing is moved in the downward direction. The air is released from the clearance of the wing, when the wing is moved upward. It is considered to apply this mechanism to the bird type wing of the wind turbine. In the paper, performance evaluation experiments under the higher wind velocity of a three sheet small type turbine generator system are discussed. A worthwhile knowledge is obtained on operation of the wind turbine.
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Keita SAGARA, Kosuke Nomoto, Kazuichi SEKI
Article type: Article
Pages
77-78
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In this paper we will present some novel results of our research and development in the filed of wind energy utilization. Our effort in this filed is mainly concentrated to the conceptual design of optimum airfoil sections for the blade of straight wing non-articulated vertical axis wind turbine which undergo cross wind motion. This concept was embodied in the design of a family of airfoil sections designated as Tokai Wind Turbine (TWT) sections and a series of wind tunnel testing was conducted to confirm its desired aerodynamic characteristics. Then, we designed an experimental straight wing non-articulated vertical axis wind turbine system with straight blades to evaluate system performance and structural analysis results, and furthermore to collect operating experiences under real fluctuating wind conditions. We are now working for evaluating operational feasibility of five sets different straight wing non-articulated vertical axis wind turbines system, which are partially in service as pilot plants of regional energy development.
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Yukimaru SHIMIZU, Takao MAEDA, Yasunari KAMADA, Kotaro SUGI, Yusaku SA ...
Article type: Article
Pages
79-80
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This paper describes the performance and power augumentation effect of three-bladed wind turbine. Three sets of blade were tested. The blade had the same geometry and configuration, but were different on the way of arranging airfoil sections. One of them is tapered blade which consists 4 kind of aerofoil section and twisted, the others are slant arranged aerofoil of it. The performance data are given and relationship between the performance, and the flow behavior around the blade obtained by use of LDV is investigated.
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Yasuyuki NEMOTO, Izumi USHIYAMA
Article type: Article
Pages
81-82
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The pinwheel type wind turbine has the characteristics between the propeller type, which has a high tip speed ratio and a high power coefficient, and the multi blades type, which has a low tip speed ratio and a high torque coefficient. However until now, there has been little work to determine the optimum design configuration of pinwheel type wind turbines. The purpose of this paper is to clarify the characteristics and to determine the optimum design configuration of pinwheel type wind turbines. The authors fabricated the test rotors with various shapes and carried out the experiment in a wind tunnel. As a result, the high performance, such as power coefficient C_p=0.22,was obtained. Also, the authors examined the performance of the pinwheel type wind turbine generator. High speed type pinwheel wind turbine with diameter of 0.8m was directly connected to a generator and tested. As a result, electricity of 23W was obtained at a wind velocity of 8m/s.
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Tetsuya KOGAKI, Hikaru MATSUMIYA, NAOFUMI Yoshimizu, Eiji KATO
Article type: Article
Pages
83-84
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In this paper, the new modified vortex generator was developed for wind turbine airfoils. The wind tunnel experiments were conducted to examine the effectiveness of the modified vortex generator. The effect of Reynolds number, height and interval of vortex generator were also examined by the wind tunnel experiments. The former vortex generator of which section is flat plate enhances the lift, however, the drag also increase simultaneously. On the other hand, lift to drag ratio considerably increased by means of the modified vortex generator, especially in low Reynolds number Re=100,000-400,000. Therefore, it was verified that the modified vortex generator is suitable especially for airfoil of small wind turbines.
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Ayumu ANZAI, Yasuyuki NEMOTO, Izumi USHIYAMA
Article type: Article
Pages
85-86
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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To improve the performance of wind rotors by increasing an energy density of the wind, various power augmentation systems have been studied. The concentrator (nozzle) augmentation system is one of them. However, until now, the optimum design of concentrator is not revealed. The purpose of this study is to clarity the effect and to decide the optimum design of the concentrator. In conclusion, the effect of power augmentation was increased as following condition. 1. The position of the rotor is backward the outlet of concentrator. 2. The outlet diameter of the concentrator is smaller than the rotor diameter. 3. The inlet diameter is much larger than the rotor diameter.
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Kazumasa KUBOTA, Morihito INAGAKI, Narumi UMEDA, Kazuyoshi MIYAGAWA, T ...
Article type: Article
Pages
87-88
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In order to improve performance of a reversible pump-turbine, individual guide vane control was studied. First, selection of components and layout of these components were discussed, after that each guide vane opening to improve an efficiency and vortex rope in a partial flow were investigated. Servo valve and actuator has to be adopted to decrease the space and force to structures. Hydraulic performance is improved by guide vane individual control.
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Yoichi KINOUE, Toshiaki SETOGUCHI, Mamun MOHAMMAD, Kenji KANEKO, Masah ...
Article type: Article
Pages
89-90
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Monoplane and biplane Wells turbines for wave power conversion have hysteretic characteristics in a reciprocating flow. The mechanisms of the hysteretic behaviors were elucidated based on the unsteady 3-dimensional Navier-Stokes numerical simulations. For the monoplane Wells turbine, the hysteretic loop is opposite to the well-known dynamic stall of an airfoil. It was found that the hysteretic behavior was associated with a streamwise vortical flow appearing near the suction surface. For the biplane Wells turbine, the hysteretic behavior was similar to the monoplane at lower attack angles. But the hysteretic loop similar to the dynamic stall was observed at higher attack angles, which was attributed to the unsteady flow separation near the hub and the trailing edge of the suction surface of the upstream blade.
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Sachiko MIGIWA, Haruo SAKAMOTO, Sinya NOUDA, Toshifumi ASAI
Article type: Article
Pages
91-92
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The wind power generators have been a great concern as one method obtaining clean energy. In order to obtain the wind power generation for the area where wind is not so strong and unidirectional, savonius-type wing which gives the rotation even in a low wind velocity and undirectional condition was applied. The generator combined with savonius-type wings has been studies by wind tunnel experiments and dynamic magnetic field analyses. Herein, the effect of core configuration on power generation is reported.
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Hiroichi WATANABE, Hiroshi NAGAI, Haruo SATOH, Izumi USHIYAMA
Article type: Article
Pages
93-94
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Generally, wind conditions of the middle grade mountain areas are more unstable than the coast parallel. Therefore, it is considered that it should be utilized by combining with other new energy of solar light and rivers, etc., in order to utilize the wind in the inland. Then, this study carried out wind condition investigations of the campus in this department which was just located in the center in Fukushima Prefecture, and it examined solar light and wind force and hybrid power generating system using the river. The solar photovoltaic generation force is the plan that 20kW, wind power generation force hybridize and that the hydraulic power generation force hybridizes at 40kW and about 20kW on the scale of the system.
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