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Watanabe, Satoshi,Momosaki, Shimpei,Usami, Satoshi,Furukawa, Akinori Korean Society for Fluid machinery 2011 International journal of fluid machinery and syste Vol.4 No.2
An application of contra-rotating rotors, in which a rear rotor is in tandem with a front one and these rotors rotate in the opposite direction each other, has been proposed against a demand for developing higher specific speed axial flow pump. One prototype rotors, which we have designed with a conventional method, has given the positive slope of head characteristic curve especially in the rear rotor. It is necessary to understand the internal flow behavior in the rear rotor to establish the design guideline for achieving higher and more reliable performance. In the present study, we carried out the experimental investigations of the internal flow field of the rear rotor, especially at the partial flow rate, by Laser Doppler Velocimetry (LDV) for the main flow and the limiting streamlines observation on rotor surfaces for the boundary layer flows.
Development of ducted Darrieus turbine for low head hydropower utilization
Akinori Furukawa,Satoshi Watanabe,Daisuke Matsushita,Kusuo Okuma 한국물리학회 2010 Current Applied Physics Vol.10 No.2
It is mentioned in front part of the present paper that how to extract an extra-low head power is one of key-solutions for problems on exhaustion of fossil fuels and greenhouse gas emissions, after explaining the present situation of micro-hydropower utilization in Japan. Since extra-low head sites of rivers are available near urban-sides with high population, where there is a demand for electricity, an appearance of suitable turbine, which has high cost-effectiveness, maximum reliability, easy maintenance and little environmental impact, is required. In rear part of the present paper, a guiding principle of design parameters of a ducted Darrieus-type water turbine for high performance is shown, based on authors’ experimental results. Then the advantage and disadvantage of Darrieus turbine are reviewed and the key problems, which are settled as urgent works in future in order to diffuse the utilization of extra-low head hydropower, are finally suggested.
Watanabe, Satoshi,Shimokawa, Kai,Furukawa, Akinori,Okuma, Kusuo,Matsushita, Daisuke Korean Society for Fluid machinery 2012 International journal of fluid machinery and syste Vol.5 No.1
A two dimensional Darrieus-type turbine has been proposed for the hydropower utilization of extra-low head less than 2m. In a practical use of Darrieus-type hydro-turbine, head and flow rate may be varied temporally and seasonally. Considering that the cost advantage is required for the low head hydro turbine system, the Darrieus turbine should be operated with high efficiency in the wider range of flow rate possibly by using an additional device with simpler mechanism. In the present paper, an adjustment of inlet nozzle section by lowering the inlet nozzle height is proposed to obtain the preferable inlet velocity in low flow rate conditions. Effects of resulting spanwise partial inlet flow are investigated. Finally, an effective modification of inlet nozzle height over flow rate variation is shown.
Internal Flow of a Two-Bladed Helical Inducer at an Extremely Low Flow Rate
Watanabe, Satoshi,Inoue, Naoki,Ishizaka, Koichi,Furukawa, Akinori,Kim, Jun-Ho Korean Society for Fluid machinery 2010 International journal of fluid machinery and syste Vol.3 No.2
The attachment of inducer upstream of main impeller is an effective method to improve the suction performance of turbopump. However, various types of cavitation instabilities are known to occur even at the designed flow rate as well as in the partial flow rate region. The cavitation surge occurring at partial flow rates is known to be strongly associated with the inlet back flow. In the present study, in order to understand the detailed structure of internal flow of inducer, we firstly carried out the experimental and numerical studies of non-cavitating flow, focusing on the flow field near the inlet throat section and inside the blade passage of a two bladed inducer at a partial flow rate. The steady flow simulation with cavitation model was also made to investigate the difference of flow field between in the cavitating and no-cavitating conditions.
Satoshi Watanabe,Kai Shimokawa,Akinori Furukawa,Kusuo Okuma,Daisuke Matsushita 한국유체기계학회 2012 International journal of fluid machinery and syste Vol.5 No.1
A two dimensional Darrieus-type turbine has been proposed for the hydropower utilization of extra-low head less than 2m. In a practical use of Darrieus-type hydro-turbine, head and flow rate may be varied temporally and seasonally. Considering that the cost advantage is required for the low head hydro turbine system, the Darrieus turbine should be operated with high efficiency in the wider range of flow rate possibly by using an additional device with simpler mechanism. In the present paper, an adjustment of inlet nozzle section by lowering the inlet nozzle height is proposed to obtain the preferable inlet velocity in low flow rate conditions. Effects of resulting spanwise partial inlet flow are investigated. Finally, an effective modification of inlet nozzle height over flow rate variation is shown.
Low Speed Design of Rear Rotor in Contra-Rotating Axial Flow Pump
Cao, Linlin,Watanabe, Satoshi,Momosaki, Simpei,Imanishi, Toshiki,Furukawa, Akinori Korean Society for Fluid machinery 2013 International journal of fluid machinery and syste Vol.6 No.2
The application of contra-rotating rotors for higher specific speed pump has been proposed in our studies, which is in principle effective for reducing the rotational speed and/or the pump size under the same specification of conventional axial flow pump. In the previous experiments of our prototype, the cavitation inception at the tip region of the rear rotor rather than that of the front rotor and the strong potential interaction from the suction surface of the rear rotor blade to the pressure surface of the front one were observed, indicating the possibility to further improve the pump performance by optimizing rotational speed combination between the two rotors. The present research aims at the design of rear rotor with lower rotational speed. Considering the fact that the incoming flow velocity defects at the tip region of the rear rotor, an integrated inflow model of 'forced vortex' and 'free vortex' is employed. The variation of maximum camber location from hub to tip as well as other related considerations are also taken into account for further performance improvement. The ideas cited above are separately or comprehensively applied in the design of three types of rear rotor, which are subsequently simulated in ANSYS CFX to evaluate the related pump performance and therefore the whole low speed design idea. Finally, the experimental validation is carried out on one type to offer further proofs for the availability of the whole design method.
Cao, Linlin,Watanabe, Satoshi,Honda, Hironori,Yoshimura, Hiroaki,Furukawa, Akinori Korean Society for Fluid machinery 2014 International journal of fluid machinery and syste Vol.7 No.4
As a high specific speed pump, the contra-rotating axial flow pump with two rotors rotating reversely has been proved with higher hydraulic and cavitation performance, while in our previous researches, the potential interaction between two blade rows was distinctly observed for our prototype rotors designed with equal rotational speed for both front and rear rotors. Based on the theoretical and experimental evidences, a rotational speed optimization methodology was proposed and applied in the design of a new combination of contra-rotating rotors, primarily in expectation of the optimized blade pressure distributions as well as pertinently improved hydraulic performances including cavitation performance. In the present study, given one stationary and two rotating frames in the contra-rotating rotors case, a pressure measurement concept taking account of the revolutions of both front and rear rotors simultaneously was adopted. The casing wall pressure data sampled in time domain was successfully transferred into space domain, by which the ensemble averaged blade-to-blade pressure distributions at the blade tip of two contra-rotating rotors under different operation conditions were studied. It could be seen that the rotor pair with the optimized rotational speed combination as well as work division, shows more reasonable blade-to-blade pressure distribution and well weakened potential interaction. Moreover, combining the loading curves estimated by the measured casing wall pressure, the cavitation performance of the rotor pairs with new rotational speed combination were proved to be superior to those of the prototype pairs.
Linlin Cao,Satoshi Watanabe,Hironori Honda,Hiroaki Yoshimura,Akinori Furukawa 한국유체기계학회 2014 International journal of fluid machinery and syste Vol.7 No.4
As a high specific speed pump, the contra-rotating axial flow pump with two rotors rotating reversely has been proved with higher hydraulic and cavitation performance, while in our previous researches, the potential interaction between two blade rows was distinctly observed for our prototype rotors designed with equal rotational speed for both front and rear rotors. Based on the theoretical and experimental evidences, a rotational speed optimization methodology was proposed and applied in the design of a new combination of contra-rotating rotors, primarily in expectation of the optimized blade pressure distributions as well as pertinently improved hydraulic performances including cavitation performance. In the present study, given one stationary and two rotating frames in the contra-rotating rotors case, a pressure measurement concept taking account of the revolutions of both front and rear rotors simultaneously was adopted. The casing wall pressure data sampled in time domain was successfully transferred into space domain, by which the ensemble averaged blade-to-blade pressure distributions at the blade tip of two contra-rotating rotors under different operation conditions were studied. It could be seen that the rotor pair with the optimized rotational speed combination as well as work division, shows more reasonable blade-to-blade pressure distribution and well weakened potential interaction. Moreover, combining the loading curves estimated by the measured casing wall pressure, the cavitation performance of the rotor pairs with new rotational speed combination were proved to be superior to those of the prototype pairs.