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

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.

Radial Thrust of Single-Blade Centrifugal Pump

Nishi, Yasuyuki,Fukutomi, Junichiro,Fujiwara, Ryota Korean Society for Fluid machinery 2011 International journal of fluid machinery and syste Vol.4 No.4

Single-blade centrifugal pumps are widely used as sewage pumps. However, the impeller of a single-blade pump is subjected to strong radial thrust during pump operation because of the geometrical axial asymmetry of the impeller. Therefore, to improve pump reliability, it is necessary to quantitatively understand radial thrust and elucidate the behavior and mechanism of thrust generating. This study investigates the radial thrust acting up on a single-blade centrifugal impeller by conducting experiments and CFD analysis. The results show that the fluctuating component of radial thrust increases as the flow rate deviates from the design flow rate to low or high value. Radial thrust was modeled by a combination of three components, inertia, momentum, and pressure by applying an unsteady conservation of momentum to the impeller. The sum of these components agrees with the radial thrust calculated by integrating the pressure and the shearing stress on the impeller surface. The behavior of each component was shown, and the effects of each component on radial thrust were clarified. The pressure component has the greatest effect on the time-averaged value and the fluctuating component of radial thrust. The time-averaged value of the inertia component is nearly 0, irrespective of the change in the flow rate. However, its fluctuating component has a magnitude nearly comparable with the pressure component at a low flow rate and slightly decreased with the increase in flow rate.

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.

Internal Flow Structure and Hydraulic Loss of Closed-Type Centrifugal Pumps with a Single Blade

Yasuyuki Nishi,Takahiro Noji,Chunqi Wang 한국유체기계학회 2023 International journal of fluid machinery and syste Vol.16 No.4

In the present study, we surveyed the performance of closed-type centrifugal pump with a single blade and its fluctuations through an experiment and a CFD analysis, and comparatively verified the blade outlet flow, with the objective of elucidating the internal flow structure and loss generation mechanism of the pump. Furthermore, we quantitatively evaluated each hydraulic loss on the pump and examined the relationship with the vortex structure in an impeller. The result showed that fluctuations in the impeller loss were notable at any flow rate with the maximum value at a blade phase angle of 133° when the best efficiency point flow rate. It suggests an impact of the vortex generated on the shroud side near the end of the blade outlet winding. While the impeller loss indicates similar behavior to the best efficiency point flow rate at a high flow rate, but its fluctuation was extremely large, and we found that such fluctuations are the behavior at a low flow rate was opposite to other flow rates.

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.

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

A Study of Performance and Internal Flow in a New Type of Sewage Pump

Nishi, Yasuyuki,Fukutomi, Junichiro Korean Society for Fluid machinery 2009 International journal of fluid machinery and syste Vol.2 No.3

Sewage pumps are designed with a wide flow channel by, for example, sacrificing some efficiency and reducing the number of blades, in order to prevent plugging with foreign bodies. However, the behavior of foreign bodies which actually flow into a pump is extremely complex, and there are questions about whether the presumed foreign bodies will actually pass through. This paper proposes a new type of sewage pump impeller designed to further improve pump efficiency and performance in passing foreign bodies. This sewage pump impeller has a structure in which the suction flow channel of a closed type non-clog pump is wound in a helical spiral. The focus of this research was to investigate pump performance and internal flow in this single blade sewage pump impeller. The results clearly indicated the following facts: The developed sewage pump impeller exhibits high efficiency over a wide range of flow rates; internal flow of the pump is very complicated; and the internal flow state varies greatly when the flow rate changes.

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.