Erratum: The Flow Field of Undershot Cross-Flow Water Turbines Based on PIV Measurements and Numerical Analysis

Nishi, Yasuyuki,Inagaki, Terumi,Li, Yanrong,Omiya, Ryota,Hatano, Kentaro Korean Society for Fluid machinery 2016 International journal of fluid machinery and syste Vol.9 No.1

The Flow Field of Undershot Cross-Flow Water Turbines Based on PIV Measurements and Numerical Analysis

Nishi, Yasuyuki,Inagaki, Terumi,Li, Yanrong,Omiya, Ryota,Hatano, Kentaro Korean Society for Fluid machinery 2014 International journal of fluid machinery and syste Vol.7 No.4

The ultimate objective of this study is to develop a water turbine appropriate for low-head open channels to effectively utilize the unused hydropower energy of rivers and agricultural waterways. The application of a cross-flow runner to open channels as an undershot water turbine has been considered and, to this end, a significant simplification was attained by removing the turbine casing. However, the flow field of an undershot cross-flow water turbine possesses free surfaces, and, as a result, the water depth around the runner changes with variation in the rotational speed such that the flow field itself is significantly altered. Thus, clear understanding of the flow fields observed with free surfaces to improve the performance of this turbine is necessary. In this study, the performance of this turbine and the flow field were evaluated through experiments and numerical analysis. The particle image velocimetry technique was used for flow measurements. The experimental results reflecting the performance of this turbine and the flow field were consistent with numerical analysis. In addition, the flow fields at the inlet and outlet regions at the first and second stages of this water turbine were clarified.

The Flow Field of Undershot Cross-Flow Water Turbines Based on PIV Measurements and Numerical Analysis

Yasuyuki Nishi,Terumi Inagaki,Yanrong Li,Ryota Omiya,Kentaro Hatano 한국유체기계학회 2014 International journal of fluid machinery and syste Vol.7 No.4

The ultimate objective of this study is to develop a water turbine appropriate for low-head open channels to effectively utilize the unused hydropower energy of rivers and agricultural waterways. The application of a cross-flow runner to open channels as an undershot water turbine has been considered and, to this end, a significant simplification was attained by removing the turbine casing. However, the flow field of an undershot cross-flow water turbine possesses free surfaces, and, as a result, the water depth around the runner changes with variation in the rotational speed such that the flow field itself is significantly altered. Thus, clear understanding of the flow fields observed with free surfaces to improve the performance of this turbine is necessary. In this study, the performance of this turbine and the flow field were evaluated through experiments and numerical analysis. The particle image velocimetry technique was used for flow measurements. The experimental results reflecting the performance of this turbine and the flow field were consistent with numerical analysis. In addition, the flow fields at the inlet and outlet regions at the first and second stages of this water turbine were clarified.

Study on Performance Improvement of an Axial Flow Hydraulic Turbine with a Collection Device

Nishi, Yasuyuki,Inagaki, Terumi,Li, Yanrong,Hirama, Sou,Kikuchi, Norio Korean Society for Fluid machinery 2016 International journal of fluid machinery and syste Vol.9 No.1

The portable hydraulic turbine we previously developed for open channels comprises an axial flow runner with an appended collection device and a diffuser section. The output power of this hydraulic turbine was improved by catching and accelerating an open-channel water flow using the kinetic energy of the water. This study aimed to further improve the performance of the hydraulic turbine. Using numerical analysis, we examined the performances and flow fields of a single runner and a composite body consisting of the runner and collection device by varying the airfoil and number of blades. Consequently, the maximum values of input power coefficient of the Runner D composite body with two blades (which adopts the MEL031 airfoil and alters the blade angle) are equivalent to those of the composite body with two blades (MEL021 airfoil). We found that the Runner D composite body has the highest turbine efficiency and thus the largest power coefficient. Furthermore, the performance of the Runner D composite body calculated from the numerical analysis was verified experimentally in an open-channel water flow test.

Study on Performance Improvement of an Axial Flow Hydraulic Turbine with a Collection Device

Yasuyuki Nishi,Terumi Inagaki,Yanrong Li,Sou Hirama,Norio Kikuchi 한국유체기계학회 2016 International journal of fluid machinery and syste Vol.9 No.1

The portable hydraulic turbine we previously developed for open channels comprises an axial flow runner with an appended collection device and a diffuser section. The output power of this hydraulic turbine was improved by catching and accelerating an open-channel water flow using the kinetic energy of the water. This study aimed to further improve the performance of the hydraulic turbine. Using numerical analysis, we examined the performances and flow fields of a single runner and a composite body consisting of the runner and collection device by varying the airfoil and number of blades. Consequently, the maximum values of input power coefficient of the Runner D composite body with two blades (which adopts the MEL031 airfoil and alters the blade angle) are equivalent to those of the composite body with two blades (MEL021 airfoil). We found that the Runner D composite body has the highest turbine efficiency and thus the largest power coefficient. Furthermore, the performance of the Runner D composite body calculated from the numerical analysis was verified experimentally in an open-channel water flow test.

Rotor Design Method for a Propeller-Type Wind Turbine that Combines Optimization Method with the Blade Element Momentum Theory

Yasuyuki Nishi,Nozomi Mori,Terumi Inagaki 한국유체기계학회 2023 International journal of fluid machinery and syste Vol.16 No.1

In this study, we created an optimization design method for a rotor of propeller-type wind turbine that combined design of experiments, response surface method, and optimization method with the blade element momentum theory. This design method was applied to a small propeller-type wind turbine. We then examined the performance of an obtained rotor using a three-dimensional computational fluid dynamics analysis and a wind tunnel experiment and examined the relationship between local torque and pressure distribution on the blade surface to investigate the mechanism to improve power output. Our findings showed that the experimental value of power coefficient of optimized rotor designed with our design method was approximately 6.9% higher than that of an original rotor designed with the blade element momentum theory only. This was because the optimized rotor had similar pressure difference between the pressure surface and the suction surface to that of the original rotor as the separation at the leading edge side were decreased on the tip side, and because its local torque increased as the pressure difference increased due to a longer chord length. Thus, the effectiveness of our design method was demonstrated

Multi-Objective Optimization of the Collection Device Shape of an Axial Flow Hydraulic Turbine with a Collection Device

Yasuyuki Nishi,Hiromichi Koga,Terumi Inagaki 한국유체기계학회 2023 International journal of fluid machinery and syste Vol.16 No.1

In this study, a multi-objective optimization design method, combining a design of experiments, single-phase flow analysis, response surface method and a multi-objective optimization method was developed to optimize the collection device shape of an axial flow hydraulic turbine with a collection device to achieve high power and low axial thrust. In addition, the effectiveness of this design method was validated through verification experiments in an open channel with shallow water depth and multiphase flow analysis considering a free surface, and the differences from the single-phase flow analysis results were also discussed. As a result, the optimized collection device obtained by this design method showed the same axial thrust coefficient and improved power coefficient compared with the original collection device in the single-phase flow analysis. In the open channel, the power coefficient of the optimized collection device was significantly higher than that of the original collection device, but unlike the results of the single-phase flow analysis, the axial thrust coefficient of the diffuser was significantly increased, resulting in a significant increase in total axial thrust coefficient.

Flow Structure and Slipstream Characteristics of an Axial Flow Hydraulic Turbine with a Collection Device in a n Open Channel

Yasuyuki Nishi,Hiroto Sasashita,Terumi Inagaki 한국유체기계학회 2022 International journal of fluid machinery and syste Vol.15 No.2

The axial flow hydraulic turbine with a collection device can be simply installed in the flowing water of an open channel with shallow water depth to generate electricity, and the power outp ut is increased by collecting and increasing the veloci ty of th e flow. When the power output of th i s hydraulic turbine is insufficient, it is necessary to install several turbines in series with the flow in narrow channels, and it is necessary to estab lish a guideline for appropriate installation intervals. In thi s st udy, the relationship between the velocity distribution and the vortex structure inside and outside the hydraulic turbine was investigated by experiments and multiphase flow analysis consid ering free surface in order to clarify the slipstream chara cter is ti cs of th is hydraulic turbine in an open channel with shallow water depth. As a result, it was clarified that the axial flow velocity behind the brim recovered rapidly due to the momentum exc hange between the flow passing through the outside of the hydra ul i c turbine and the flow passing through the inside of the hydraulic turbine. It was also discovered that all the major vortices disappeared at a position 9 times the runner diameter in the do wnstream direction from the runner center, and more than 7 0% of t h e axial flow velocity was recovered in the entire width direction

Performance and Flow Field of Gravitation Vortex Type Water Turbine using Volute Tank

Yasuyuki Nishi,Daichi Sukemori,Terumi Inagaki 한국유체기계학회 2021 International journal of fluid machinery and syste Vol.14 No.3

Gravitation vortex-type water turbines use gravitational vortex generated when water is guided into the tank and drained from the hole at the bottom of the tank. When a circular tank is used, a runner inlet flow becomes uneven circumferentially, resulting in poor performance. To control the flow in the tank and make it uniform in the circumferential direction, we used a volute tank to elucidate the impact of tank geometry on the performance and flow field of the gravitation vortex type water turbines. We further investigated the performance and flow field of the water turbine using volute and circular tanks through experiments and free surface flow analysis. We compare the performance and flow field of the volute tank to those of the circular tank. We found that the effective head and turbine output of the volute tank decreased more than those of the circular tank, whereas the water turbine efficiency of the volute tank improved more than that of the circular tank at low to medium rotational speeds. This is because the theoretical head of the volute tank was smaller than that of the circular tank, but the runner inlet flow was uniform in the circumferential direction, and the loss in the tank, which is the dominant loss in the circular tank, was greatly reduced.

Study on Foreign Body Passage in an Ultra-Small Axial Flow Hydraulic Turbine

Yasuyuki Nishi,Tomoyuki Kobori,Yutaka Kobayashi,Terumi Inagaki,Norio Kikuchi 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.1

Ultra-small axial flow hydraulic turbines, which are of the size of your palm, are a type of turbine that can be applied to the low heads of existing pipelines and open channels. However, due to their compact size, they are more likely to malfunction in case of foreign body contamination. In our study, we observed the passage of foreign bodies through an ultra-small axial flow hydraulic turbine and their encounter with the blocking mechanism of the turbine. We selected polyethylene ropes of varying lengths with a wire diameter of 5 mm to serve as foreign bodies. By varying the length of the rope, we were able to visually observe the movement of the foreign body. The turbine’s blocking mechanism can be broadly classified as guide vanes or runners. In the case of runner, blocking occurs when foreign bodies are bent and are caught at the leading edge of the blade. The passage rate through the hydraulic turbine is largely dependent on the passage rate at the runner section, which decreases proportionally with the length of the foreign body and the rotational speed of the blades.