Cross-flow Water Turbine Research Articles

315 下掛け式クロスフロー水車の性能と流れ場に及ぼす羽根枚数の影響(OS3-(4),OS3 オーガナイズドセッション《熱・流体・エネルギー変換工学の進展》)

315 下掛け式クロスフロー水車の性能と流れ場に及ぼす羽根枚数の影響(OS3-(4),OS3 オーガナイズドセッション《熱・流体・エネルギー変換工学の進展》)

0708 PIV計測と数値解析による下掛け式クロスフロー水車の流れ場

The final purpose of this study is to develop a water turbine appropriate for low-head open channels in order to effectively utilize the unused hydropower energy. The application of the cross-flow runner to open channels as an undershot water turbine has come under consideration. However, the flow field of undershot cross-flow water turbines possesses free surfaces. This means that with the variation in the rotational speed, the water depth around the runner will change and flow field itself is significantly altered. Thus it is necessary to clearly understand the flow fields with free surfaces in order to improve the performance of this turbine. In this study, the performance of this turbine and the flow field were studied through experiments and numerical analysis. The particle image velocimetry (PIV) technique was used for flow measurement. The experimental results on the performance of this turbine and the flow field were consistent with the numerical analysis.

20509 下掛け式クロスフロー水車の性能に及ぼす羽根枚数の影響

An undershot type cross-flow water turbine does not require a casing for open channels and hence considerable simplification is attained. However, because this water turbine does not have a casing and has a free surface, it is believed that the internal flow considerably changes with the number of blades and the rotational speed. In this study, the effects of number of blades on performance of undershot type cross-flow water turbine at a constant flow rate are investigated by an experiment and numerical analysis, and the following facts are clarified. The torque and power of the runner with 8 blades are lower than them of the runner with 24 blades, but the efficiency of the runner with 8 blades is higher.

1019 貫流水車に関する数値的試作(OS10-4 再生可能流体エネルギーの利用技術,OS10 再生可能流体エネルギーの利用技術)

Some foil sections of ducted cross flow water turbines were simulated by LES analysis. The equations are discretized by Finite volume method for space and Fractional step method for time. In this study, blade number is 16 and chord length is 15.5% of diameter. Important parameters are thickness and the edge shape of blade. The following are results of analysis. Best shape was outer-wedge type and round edge was not good in the standpoint of efficiency. Gap width between duct and blade increase the difference of efficiency by edge shape.

Numerical Investigation of a Darrieus Rotor for Low-head Hydropower Generation

The aim of this paper is to numerically investigate the performance of a cross-flow water turbine of the Darrieus type for very low head hydropower applications. The interest for this kind of vertical axis turbine relies on its versa- tility. For instance, in the field of renewable energy, this kind of turbine may be considered for different applications, such as: tidal power, run-of-the-river hydroelectricity, wave energy conversion. Until now, low head hydropower, with heads less than 2 meters, has remained scarcely developed due to the relatively low energy density, which makes the cost of generation higher than traditional hydropower applications. However, in the spirit of distributed generation, the use of low head hydropower can be reconsidered, having the advantage of lower electricity transmission losses due to the localization near the consuming area. Nonetheless, it is fundamental to improve the turbine performance and to decrease the equipment costs for achievement of “environmental friendly” solutions and maximization of the “cost-advantage”. In the present work, the commercial CFD code Fluent is used to perform 2D simulations, solving the incompressible Unsteady Reynolds-Averaged Navier-Stokes (U-RANS) equations discretized by means of a fi- nite volume approach. The implicit segregated version of the solver is employed. The pressure-velocity coupling is achieved by means of the SIMPLE algorithm. The convective terms are discretized using a second order accurate up- wind scheme, and pressure and viscous terms are discretized by a second-order-accurate centered scheme. A second order implicit time formulation is also used. Turbulence closure is provided by the realizable k− [turbulence model. The model has been validated, comparing numerical results with available experimental data.

311 直線羽根を用いた下掛け式クロスフロー水車に関する研究(OS9 オーガナイズドセッション《熱・流体・エネルギー変換工学の進展》)

The aim of this study is to develop an ultralow-head water turbine for an open channel, such as an irrigation channel, in order to effectively use hitherto unused hydropower energies. By focusing on a cross-flow runner, we eliminated the casing and used the application as a water turbine undershot-type cross-flow water turbine) for an open channel. We investigated the performance and internal flow of the water turbine with straight blades through an experiment and numerical analysis. As a result, the following facts became clear. At the turbine with straight blades, water area is narrowed at the outer and inner circumference of the runner, and torque and power are bigger.

J056051 直線羽根を用いた下掛け式クロスフロー水車の性能と内部流れ(〔J056-05〕再生可能エネルギー(水力・太陽光)(5))

J056051 直線羽根を用いた下掛け式クロスフロー水車の性能と内部流れ(〔J056-05〕再生可能エネルギー(水力・太陽光)(5))

Performance and Internal Flow of an Undershot-Type Cross-Flow Water Turbine

An undershot-type cross-flow water turbine does not require a casing for open channels and hence considerable simplification is attained. However, because this water turbine does not have a casing and has a free surface, it is believed that the internal flow considerably changes with the rotational speed. In this study, the performance and internal flow of the undershot-type cross-flow water turbine at a constant flow rate were investigated by an experiment and numerical analysis, and the following facts were clarified. The first-stage inlet area and the second-stage inlet and outlet areas are reduced with increase in rotational speed. Shock loss at the second- and first-stage areas is dominant in low- and high-rotational-speed regions, respectively. Moreover, shock loss has a considerable influence on the performance of this water turbine in low- and high-rotational-speed regions.

Study on Internal Flow of an Undershot-Type Cross-Flow Water Turbine

Study on Internal Flow of an Undershot-Type Cross-Flow Water Turbine

1017 直線羽根を用いた下掛け式クロスフロー水車の性能に及ぼす流量の影響(OS10-4 再生可能流体エネルギーの利用技術,OS10 再生可能流体エネルギーの利用技術)

An undershot-type cross-flow water turbine does not require a casing for open channels and hence considerable simplification is attained. However, because this water turbine does not have a casing and has a free surface, it is believed that the internal flow considerably changes with the flow rate. We investigated the effect of flow rate on the performance of this water turbine with straight blades by an experiment and numerical analysis. As a result, the following facts became clear. When a flow rate is small, the power becomes small, but turbine efficiency becomes large. This is because the first-stage shock loss becomes small in a low rotational speed region and the second-stage shock loss becomes small in a high rotational speed region.

Simulating variable pitch crossflow water turbines: A coupled unsteady ONERA-EDLIN model and streamtube model

This article describes a new method for simulating unsteady hydrodynamics forces and moments on the blades of a crossflow ‘Darrieus’ turbine with active pitch variation. This method is based on the ONERA-EDLIN dynamic stall model, coupled with a momentum streamtube model to take into account the turbine interference on the flow. Both models are presented, and compared separately with experimental results for a pitching airfoil for the ONERA-EDLIN model; and for Darrieus turbine for the momentum theory. The model coupling is then detailed and compared with experimental data taken from the open literature [1] The turbine has 2 straight blades with a NACA 0012 section operating in water at a mean chord Reynolds number of 4 × 104 for tip speed ratio λ = 2.5, 5 and 7.5. Good agreement was found for average λ = 5, and qualitative agreement could be obtained at low and high λ, where dynamic stall effects and interference effects respectively are predominant. This is positive because λ = 5 is the closest value from the optimal power production point. Variable pitch is finally introduced in the model and several functions are tested in order to increase efficiency. A maximum increase of 53% on the power coefficient was found to occur with a sinusoidal law.

Synchronized control of cross-flow-water-turbine-based twin towers

This paper deals with a renewable energy conversion system based on cross-flow water turbines operating in a river stream. Two twin vertical towers, each of which is composed of four such turbines, need to meet an imposed restriction between their angular positions (synchronization) in order to achieve improved hydrodynamic performances. The synchronization is achieved by a control approach, without using any power coupling (mechanical or electrical) between the two towers. As each tower is equipped with a permanent-magnet synchronous generator which delivers electrical power to the grid through a back-to-back power electronics converter, their rotational speeds can be controlled such that to achieve angular position synchronization. Being similar to the phase-locked loop devices used in electronics, the proposed method has been tested on a power hardware-in-the-loop simulator dedicated to cross-flow water turbines and proved good potential for being easily and effectively used in practice due to its simplicity and reliability.

403 下掛け式クロスフロー水車の非設計点における内部流れ(OS3-5 オーガナイズドセッション《熱・流体・エネルギー変換工学の進展》)

403 下掛け式クロスフロー水車の非設計点における内部流れ(OS3-5 オーガナイズドセッション《熱・流体・エネルギー変換工学の進展》)

1929 下掛け式クロスフロー水車の内部流れに関する研究(OS7-6 流れの計測と制御VI,OS7 流れの計測と制御)

This study is aimed at development of the extra-low head water turbine for an open channel from a viewpoint of using effectively unused hydropower energies, such as an irrigation channel Then, paying attention to the cross-flow runner, authors eliminated the casing and tried the application as a water turbine for an open channel (Undershot Type Cross-Flow Water Turbine) In this paper, water turbine performance and internal flow of water turbine were investigated by experiments and a CFD analysis in constant flow rate The results showed that the position of inflow and outflow in the runner from volume fraction and radial velocity distributions

0912 下掛け式クロスフロー水車の内部流れに及ぼす流量の影響(OS9 再生可能流体エネルギーの利用技術,オーガナイズドセッション)

The aim of this study is to develop an ultralow-head water turbine for an open channel,such as an irrigation channel,in order to effectively use hitherto unused hydropower energies.By focusing on a cross-flow runner,we eliminated the casing and used the application as a water turbine(undershot-type cross-flow water turbine) for an open channel.We investigated the effect of flow rate on the internal flow of the water turbine by an experiment and a CFD analysis.As a result,the following facts became clear.At a large flow rate,water region is wide at the outer and inner circumference of a runner.Moreover,the influence that a shock loss gives to water turbine efficiency is large.

Management and Control of Operating Regimes of Cross-Flow Water Turbines

This paper deals with a generation system based on cross-flow water turbines (CFWTs) operating in a river stream. It is equipped with a permanent-magnet synchronous generator and can feed a power grid or an insulated load through a back-to-back power electronics converter. This paper concerns the control of these two operating regimes with focus on the manner of achieving a soft switching between them, in order to ensure the balance between the generated and the provided power and to alleviate transients. The control laws and the switching sequences have been experimentally validated on a real-time CFWT simulator equipped with the same type of generator and power electronics converter. This paper aims at offering a synthetic vision of how the CFWT-based generation system should be controlled across the main operating regimes in order to preserve its continuity of service.

Operation of Grid-Connected Cross-Flow Water Turbines in the Stall Region by Direct Power Control

This paper proposes a new method of controlling cross-flow-water-turbine (CFWT)-based generation systems, having fixed pitch, by power regulation. The method consists of directly controlling the electrical generator power, as imposed by a dispatcher, without employing an inner rotational speed control loop. The proposed control approach represents the base for the operation framework (i.e., output power and rotational speed limitations, start-up, and stopping) for the entire operating range up to the cut-out water flow speed. A permanent-magnet synchronous generator is used in this paper. The system is operated at low rotational speed values, i.e., in the so-called hydrodynamic stall region, where mechanical and hydrodynamic stresses are lower. Given that this region corresponds to an unstable dynamic behavior, the power regulation relies upon an inner loop of rotational-speed stabilization. Consequently, the innermost (electrical machine current) control loop is fed by a reference having two components, namely, the driving and stabilization currents. The embodied control laws and the output power and rotational speed limitation sequences have been experimentally validated on a real-time simulator of CFWT-based generation systems.

Study on a Cross-Flow Water Turbine Installed in an Open Channel

Study on a Cross-Flow Water Turbine Installed in an Open Channel

Cavitating behaviour analysis of Darrieus-type cross flow water turbines

The aim of this paper is to study the cavitating behaviour of bare Darrieus-type turbines. For that, the RANS code CAVKA, has been used. Under non-cavitating conditions, the power coefficient and the thrusts calculated with CAVKA are compared to experimental values obtained in the LEGI hydrodynamic tunnel. Under cavitating conditions, for several cavitation numbers, the numerical power coefficients and vapour structures are compared to experimental ones. Different blade profiles and camber lines are also studied for non-cavitating and cavitating conditions.

Numerical and experimental analysis of a darrieus-type cross flow water turbine in bare and shrouded configurations

The aim of this paper is to present the results of the analysis of a Darrieus-type cross flow water turbine in bare and shrouded configurations. Numerical results are compared to experimental data and differences found in values are also highlighted. The benefit of the introduction of a channelling device, which generates an efficiency increment factor varying from 2 to 5, depending on the configuration, is discussed.