Extra-low Head Research Articles

Comparison of Energy Performance of Shaft Tubular Pump Device at Two Guide Vane Inlet Angles

In order to improve the pump device efficiency of the frequent operating condition of the extra-low head pumping station, the energy performance of the front-positioned shaft tubular pump device at two guide vane inlet angles has been researched. Based on the function of the guide vane in the pump device, the guide vane blades are divided into three parts: the inlet section, the middle section, and the outlet section. Combining numerical simulation and model tests, the energy performance of the pump device with the inlet section angle adjusted to 0° and −12° were studied and compared, respectively. The research results indicate that the inlet section angle of the guide vane has a significant effect on the energy performance of the pump device. When the guide vane inlet section is adjusted clockwise, the pump device efficiency of the optimal operating point—while the efficiency of the pump device at a low head and large discharge that deviate from the optimal operating point—will be improved. The farther the working condition deviates from the optimal operating point, the greater the influence. Within the scope of the working conditions studied in this paper, the pump device efficiency of the optimal operating point is reduced by about 2%, and the pump device efficiency in the low head and high flow conditions is increased by 5% at the maximum. Adjusting the inlet section angle of the guide vane, the flow pattern in the guide vane will be improved, and the hydraulic loss of the guide vane will be decreased, thus the pump device efficiency is increased. The numerical calculation results of the energy performance agree with the model test results; the maximum error of the pump device efficiency is less than 7%. Adjusting the angle of the inlet section of the guide vane has great significance to the hydraulic design and engineering application of the extra-low head pump device.

Improvement of compact Darrieus-type hydraulic turbine for extra low head by changing inlet shape

Hydraulic power generation has a potential as an environmental friendly energy, which is not discharging a carbon dioxide gas during operation. Currently, high and middle water head turbine has been fully developed in practical use. However, extra low head hydraulic turbine has not been developed yet as a commercial utilization. Compact Darrieus-type hydraulic turbine has been focused on for small waterway. The purpose of this study is to improve the performance of the compact Darrieus-type hydraulic turbine, by changing inlet shape. In our previous study, the blade shape, the number of blades, the water wheel diameter ratio of chord length and pitch circle radius are optimized. The purpose of the present study is to further improve the performance of the compact Darrieus-type water turbine based on former results. In this study, the inlet shapes were changed to increase inflow velocity and to contribute improvement of efficiency. As a result, the efficiency of the turbine with using only half side counterpart nozzle was increased compared to the other settings.

Study on Output Characteristics of an Undershot Water Turbine for Extra-Low Head

Study on Output Characteristics of an Undershot Water Turbine for Extra-Low Head

Effect of Runner Position on Performance for Open Type Cross-Flow Turbine Utilizing Waterfalls

The aim of this investigation is to develop an open type cross-flow turbine for environmental friendly nano-hydraulic turbine utilizing extra-low head waterfall. A relative position between the runner and the waterfall is one of the important factors for turbine efficiency. More often, it is necessary to precisely adjust this distance according to changes of the flow rate. In this study, we focused on the influence of the horizontal and vertical position of the runner on performance. First, the effect on the performance of the horizontal relative position between the runner and the falling water is verified. Next, two condition of the vertical relative position are concerned; one is the clearance between the runner and the water surface of the pool, the other is that between the runner and the solid surface as the runner placed closer to the ground or the riverbed. The result highlights that the horizontal relative position was an effect on the power performance. When the solid surface is presented under the runner, the performance is not effected when the water thickness is equivalent to 7.5% or more. On the other hand, when water surface is presented below the runner, the clearance between them has insignificant effect on the performance even though the runner underside is partly submerged.

Darrieus Turbine with Controlled Blades : The Perspective Converter of Hydrokinetic Energy

There is a growing demand for the use of renewable energy technologies to generate electricity due to concerns over climate change. The oceans and rivers currents provide a huge potential resource of energy. Since extra-low head sites of rivers are available near urban-sides, where there is a demand for electricity, an appearance of suitable turbine, which has high costeffectiveness, easy maintenance and little environmental impact, is required. The paper deals with determining the effect of periodic variation of blade pitch angle of vertical axis water turbine (VAWT) model with straight blades on its performance. The model experiment has been carried out in a hydrotray for small VAWT models. Performance of VAWT models with rigidly fixed blades to crosspieces of turbine model and with two various control mechanism of blades on trajectory of their circular movement are determined. The ability of VAWT with controlled blades to self-starting at quite slow incoming flow is shown. The possibility of a significant increase of power coefficient and torque coefficient are shown.

Tentative Study on Performance of Darriues-Type Hydroturbine Operated in Small Open Water Channel

The development of small hydropower is one of the realistic and preferable utilizations of renewable energy, but the extra-low head hydropower less than 2 m is almost undeveloped yet for some reasons. The authors have developed several types of Darrieus-type hydro-turbine system, and among them, the Darrieus-turbine with a wear and a nozzle installed upstream of turbine is so far in success to obtain more output power, i.e. more shaft torque, by gathering all water into the turbine. However, there can several cases exist, in which installing the wear covering all the flow channel width is unrealistic. Then, in the present study, the hydraulic performances of Darrieus-type hydro-turbine with the inlet nozzle is investigated, putting alone in a small open channel without upstream wear. In the experiment, the five-bladed Darrieus-type runner with the pitch-circle diameter of 300 mm and the blade span of 300 mm is vertically installed in the open channel with the width of 1,200 mm. The effectiveness of the shape of the inlet nozzle is also examined using two types of two-dimensional symmetric nozzle, the straight line nozzle (SL nozzle) with the converging angle of 45 degrees and the half diameter curved nozzle (HD nozzle) whose radius is a half diameter of runner pitch circle. Inlet and outlet nozzle widths are in common for the both nozzles, which are 540 mm and 240 mm respectively. All the experiments are carried out under the conditions with constant flow rate and downstream water level, and performances are evaluated by measured output torque and the measured head difference between the water levels upstream and downstream of the turbine. As a result, it is found that the output power is remarkably increased by installing the inlet nozzle, and the turbine with SL nozzle produces larger power than that with HD nozzle. However, the peak efficiency is deteriorated in both cases. The speed ratio defined by the rotor speed divided by the downstream water velocity at the peak efficiency is larger in both cases with the inlet nozzle, partly due to the increase of inflow velocity into the turbine. In order to understand the cause of the differences of power, i.e. torque characteristics of the turbine with SL and HD nozzles, twodimensional CFD simulation is carried out. It is found that the instantaneous torque variation is important for the overall turbine performances, indicating the possibility of further performance improvement through the optimization of nozzle geometry.

A Study on Darrieus-type Hydroturbine toward Utilization of Extra-Low Head Natural Flow Streams

Abstract A two-dimensional Darrieus-type hydroturbine system, installed with a wear for flow streams such as small rivers and waterways, has been developed for hydropower utilization of extra-low head less than 2m. There are several problems such as flow rate change and flowing wastes to be solved for its practical use in natural flow streams. In the present study, at first, a design guideline in the case of overflow or bypass flow is shown by using simple flow model. Next, in order to avoid the unexpected obstacles flowing into the hydroturbine, an installation of waste screening system is examined. It is confirmed that the screen is effective with some amount of bypass flow rate, however the output power is remarkably deteriorated. Keywords : low head hydropower, Darrieus turbine, bypass flow, waste screening system 1. Introduction In recent years, fossil fuel exhaustions and greenhouse gas emissions are becoming severe global issues. The most preferable solution for them is to utilize renewable energies. Hydropower is one of the most popular renewable energies since ancient times and is able to control the output power connected to the grid widely in response to electricity demand [1]. High head hydropower generation plants, installed with large scale structures like dams, however are difficult to be newly constructed for the extensive impacts on ecological system. On the other hand, the low head hydropower, especially extralow head less than 2m, has been -almost undeveloped yet for several reasons. There are many sites of low head hydropower near urban areas and there are reused type small hydroturbine which had operated in past [2]. They are expected therefore as local energy resources as well as photovoltaic and wind power generations.

Numerical Simulation of Water Flow through a Nano-Hydraulic Turbine of Waterfall-Type by Particle Method

This study simulates the flow through an impulse-type small-scale hydraulic turbine utilizing a waterfall of extra-low head. The two-dimensional Moving Particle Semi-implicit (MPS) method is employed for the simulation. The fluid is discretized by particles, and the flow is computed by the Lagrangian calculation for the particle motion. When the distance between the particles discretizing the waterfall of a width , , is set at , the flow can be simulated with the sufficiently high spatial resolution, and the rotor performance can also be favorably predicted. The present simulation also successfully analyzes the effect of the rotational speed of rotor on the flow and the turbine performance.

1016 入口ノズル付ダリウス形水車のトルク特性のCFD 解析による考察(OS10-3 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)

A Darrieus-type hydro-turbine system has been developed for hydropower utilization of extra-low head less than 2m. When the Darrieus-type hydro-turbine was installed in open channel, an increase of torque coefficient was observed with installing inlet nozzle. Especially, an installation of two-dimensional symmetric Straight Line Nozzle (SL Nozzle) with the converging angle of 45°produced larger torque than that of two-dimensional symmetric Half Diameter curved Nozzle (HD Nozzle). In the present study, in order to understand a cause of the difference of torque characteristic between SL Nozzle and HD Nozzle, two-dimensional numerical simulation is carried out. The relation between torque characteristics and the flow around rotating Darrieus blade is discussed.

Research on Darrieus-type hydraulic turbine for extra-low head hydropower utilization

A Darrieus-type turbine has been investigated for extra-low head hydropower utilization. In the present paper, authors'research on Darrieus-type hydraulic turbine is briefly reviewed. The working principle of Darrieus turbine is explained with advantage of its simple structure, at first. Then the fluid-dynamic difference between rotating and linear motions of a blade in a uniform flow is clarified with guiding principle of high performance design of Darrieus turbine. Cavitation problem is also described. Next, effects of duct-casing, consisting of an intake, runner section and draft tube, are discussed and a simplified structure of Darrieus turbine is shown by installing the inlet nozzle. Finally, in the practical use, an adjustment of inlet nozzle section by lowering the inlet nozzle height is proposed when flow rate is varied temporally and seasonally.

Experimental Study on Adjustment of Inlet Nozzle Section to Flow Rate Variation for Darrieus-type Hydro-Turbine

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.

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

Experimental study on simplification of Darrieus-type hydro turbine with inlet nozzle for extra-low head hydropower utilization

A ducted Darrieus-type hydro turbine has been proposed for utilization of extra-low head hydropower less than 2 m. In general, the low head hydro turbine system demands the simple structure to reduce the cost of power generation. The Darrieus-type hydro turbine is cross flow type and takes larger values of generated torque with higher efficiency on the upstream path of the Darrieus blades passing in one revolution. Based on this reason, when a narrow intake at the upstream of the runner, called as “inlet nozzle”, is installed, the performance of Darrieus-type hydro turbine becomes higher than that without one. In addition, it is possible to remove the draft tube and side-walls of the runner casing keeping the turbine efficiency high. In the present paper, more simplified runner casing, composed of only the inlet nozzle and the small upper-casing, is proposed and the experimental results are shown.

106 せきを用いた極低落差水力利用方法に関する研究(OS7自然と生物の流れ現象とその有効利用)

106 せきを用いた極低落差水力利用方法に関する研究(OS7自然と生物の流れ現象とその有効利用)

Inlet Nozzle Effect on Turbine Performance and Self-Starting Characteristics of Darrieus-Type Hydro Turbine for Extra-Low Head Hydropower Utilization

Inlet Nozzle Effect on Turbine Performance and Self-Starting Characteristics of Darrieus-Type Hydro Turbine for Extra-Low Head Hydropower Utilization

Side-wall effect of runner casing on performance of Darrieus-type hydro turbine with inlet nozzle for extra-low head utilization

A ducted Darrieus-type turbine has been proposed for hydropower utilization of extra-low head less than 2 m. Though the hydro turbine system, in general, might consist of an intake, runner casing section and a draft tube for higher efficiency operation, it was clarified in previous experiment that there was no need of the side-walls of runner casing section and a draft-tube for keeping the efficiency high in the case of duct with an inlet nozzle. This would yield a simplification of the structure of the turbine system. In order to reconfirm this result for large-sized turbine with 560 mm×300 mm duct, instead of small-sized one with 400 mm×200 mm duct, the side-wall effect on turbine performance was experimentally investigated for three- or four-bladed runner. In the present paper, the experimental results are shown with considering flow behaviors in the runner section.

1405 入口絞り付ダリウス水車の簡易構造化に関する実験的研究(OS14-2 再生可能流体エネルギー,オーガナイズドセッション)

A ducted Darrieus-type turbine has been proposed for extra-low head hydropower utilization of total head less than 2m. Though the hydro turbine system, in general, consists of an intake, runner section and draft tube for higher efficiency operation, it was clarified in previous experiment that there was no need of a draft-tube and the side-walls of runner section for keeping the performance high, provided with nozzle at the inlet, which yields a simplification of the structure of the turbine system. In order to further simplify the structure, the effects of upper-wall of runner section and water levels of downstream pond on turbine performance were experimentally investigated. In the present paper, the experimental results are shown with various water levels of downstream pond.

Development of ducted Darrieus turbine for low head hydropower utilization

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 .

1202 入口絞りを持つダリウス形水車の側壁開放化による性能変化(OS12-1 再生可能流体エネルギー,オーガナイズドセッション)

A ducted Darrieus-type turbine has been proposed for extra-low head hydropower utilization of total head less than 2m. Though the hydro turbine system, in general, might consist of an intake, runner section and the draft tube for higher efficiency operation, it was clarified in previous experiment that there was no need of the side-walls of runner section and a draft-tube for keeping the performance high, in the case of duct with an inlet nozzle, which yields a simplification of the structure of the turbine system. In order to reconfirm this result for large-sized turbine with 500×300mm duct, instead of small-sized one with 400×200mm, the side-wall effect on turbine performance was experimentally investigated for three- or four-bladed runner. In the present paper, the experimental results are shown with considering flow behaviors in the runner section.

Simplified Structure of Ducted Darrieus-Type Hydro Turbine with Narrow Intake for Extra-low Head Hydropower Utilization

A ducted Darrieus-type hydro turbine has been proposed for extra-low head hydropower utilization of total head less than 2m, where development is almost not done in the commercial base. Though the efficiency of Darrieus-type turbine, which is cross flow type, is not so high as conventional type, the Darrieus-type has a cost-advantage due to the simple structure. By installing a narrow intake at upstream of the runner, the efficiency becomes higher than normal intake that a width of which is the same as one of runner section. In the case of normal intake, the casing clearance between the runner pitch circle and the side-wall at the runner section becomes the influential factor which deteriorates the efficiency. On the other hand, in the case of narrow intake, it is possible to keep efficiency high, based on the fact that the distorting flow to the clearance is prevented. In the present paper, the effects of narrow intake and draft tube on turbine performance are experimentally examined and the design guideline of simplified structure for ducted Darrieus-type turbine with narrow intake is proposed.