• Ocean Systems Engineering
• /
• v.14 no.2
• /
• pp.141-156
• /
• 2024

The turbine system converts the kinetic energy of water flow to electricity by rotating the rotor in a restricted waterway between the seabed and free surface. A turbine system's immersion depth and rotation direction are significantly critical in the turbine's performance along with the shape of the rotor. This study has investigated the hydrodynamic performance of the Savonius hydrokinetic turbine (SHT) according to the immersion depth and rotation direction using computational fluid dynamics (CFD) simulations. The instantaneous torque, torque coefficient, and power coefficients are calculated for the immersion ratios Z/D ranging [0.25, 3.0] and both clockwise (CW) and counterclockwise (CCW) rotations. A flow visualization around the rotor is shown to clarify the correlation between the turbine's performance and the flow field. The CFD simulations show that the CCW rotation produces a higher power at shallow immersion, while the CW rotation performs better at deeper immersion. The immersion ratio should be greater than the minimum of Z/D=1.0 to obtain the maximum power production regardless of the rotation direction.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.11a
• /
• pp.165.2-165.2
• /
• 2011

Flow with suction to water turbine must be in stable state at small hydraulic power plant. But because of water level fluctuation and water gate effect according to irregular supply of cooling water, it would happen to produce bubble and vortex and finally lead to problems in power-plant system. With utilizing the concept design of double size gate, surface water overflowed the overhead of gate for stable flow at suction. We developed the overflow condition and analyzed the design factor with existed one such as water level(overflow amount) and overhead of water gate(overflow figure). Flow test and CFD simulation say that flow have stable state around suction and 20% of wave reduction effect at surface layer after surface water overflow.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.1338-1339
• /
• 2011

Recently the wind turbine generating systems are increasing world widely. This type of systems will change the nation's energy environment which largely depends on the fossil fuels. It will also bring new problems to the power industry and the customers. The expected problem is the voltage and frequency stability of the power distribution network, when a wind turbine generating system is connected to the line. It becomes necessary and important to evaluate their impact on the electrical network stability. This paper shows the electrical data measurement and analysis of a inductive wind turbine generator affecting the power quality problem of the distribution line.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.11 no.2
• /
• pp.980-992
• /
• 2019

This paper describes a model test and numerical simulation of a 750-kW-semi-submersible platform wind turbine under several wind and wave conditions for validation of the numerical simulation model. The semi-submersible platform was designed to support the 750-kW-wind turbine class and operate at a water depth of 50 m. The model tests were performed to estimate the performance characteristics of the wind turbine system in the wide tank of the University of Ulsan. Motions and loads of the wind turbine system under the wind and wave conditions were measured and analyzed. The NREL-FAST code was used to simulate the wind turbine system, and the results were compared with those of the test model. The results demonstrate that the numerical simulation captures noticeably the fully coupled floating wind turbine dynamic responses. Also, the model shows a good stability and small responses during waves, wind, and operation of the 750-kW-floating offshore wind turbine.

• Journal of Wetlands Research
• /
• v.25 no.3
• /
• pp.176-183
• /
• 2023

The aim of this paper is to understand the blade number effect on vortex turbine performance in the cylindrical vortex chamber below the free water surface. Using the same blade profile, the performance of gravitational vortex turbine is tested each with 2, 3, 4, 5 and 6 blades installed at the relative vortex height (y/h_v) ranging from 0.065 to 0.417. The obtained results indicate that the rotation, voltage, current and power increase in the relative vortex height of 0.065 and 0.111 when increasing the number of blades at flow velocity of less than 0.7 m/s. The average power of the 5-blade turbine is more than others. The performance of the 4-blade turbine with a 130 mm diameter installed near the orifice is higher than that of the same number of blades with a 220 mm diameter in the vortex chamber.

• New & Renewable Energy
• /
• v.6 no.2
• /
• pp.27-32
• /
• 2010

Low Calorific Gas Turbine (LCGT) has been developed as a next generation power system using landfill gas (LFG) and biogas made from various organic wastes, food Waste, waste water and Livestock biogas. Low calorific fuel purification by pretreatment system and carbon dioxide fixation by green house system are very important design target for the optimum applications of LCGT. Main troubles of Low Calorific Gas Turbine system was derived from the impurities such as hydro sulfide, siloxane, water contained in biogas. Even if the quality of the bio fuel is not better than natural gas, LCGT may take low quality gas fuel and environmental friendly power system. The mechanical characterisitics of LCGT system is a high energy efficiency (>70%), wide range of output power (30 kW - 30 MW class) and very clean emission from power system (low NOx). A green house has been designed for four different carbon dioxide concentration from ambient air to 2000 ppm by utilizing the exhaust gas and hot water from LCGT system. LCGT is expected to contribute achieving the target of Renewable Portfolio Standards (RPS).

• Agricultural and Biosystems Engineering
• /
• v.6 no.2
• /
• pp.65-69
• /
• 2005

A windheat generation system with a Savonius windturbine was developed and the performance was evaluated through field tests. The system consisted of a heat generation drum, heat exchanger, water storage tank, and two circulation pumps. Frictional heat is created by rotation of a rotor inside the drum containing thermo oil, and was used to heat water. In order to estimate the capacity of this windheat generation system, weather data was collected for one year at the site near the windheat generation system. Wind Power from the savonius wind turbine mill was transmitted to the heat generation system with an one-to-three gear system. Starting force to rotate the savonius wind turbine and the whole system including the windheat generation system were 1.0 and 2.5 kg, respectively. Under the outdoor wind condition, maximum speed of the rotor in the drum was 75rpm at wind speed 6.5 m/sec, which was not fast enough to produce heat for greenhouse heating. Annual cumulative hours for wind speeds greater than 5 m/sec at height of 10, 20, 30 m were 190, 300 and 1020 hrs, respectively. A $5^{\circ}C$ increase in water temperature was achieved by the windheat generation system under the tested wind environment.

• The KSFM Journal of Fluid Machinery
• /
• v.17 no.4
• /
• pp.30-39
• /
• 2014

The cross flow turbine is economical because of its simple structure. For remote rural region, there are needs for a more simple structure and very low head cross flow turbines. However, in this kind of locations, the water from upstream always flows into the turbine with some other materials such as sand and pebble. These materials will be damage to the runner blade and shorten the turbine lifespan. Therefore, there is a need to develop a new type of cross flow turbine for the remote rural region where there is availability of abundant resources. The new design of the cross flow turbine has an inlet open duct, without guide vane and nozzle to simplify the structure. However, the turbine with inlet open duct and very low head shows relatively low efficiency. Therefore, the purpose of this study is to optimize the shape of the turbine inlet to improve the efficiency, and investigate the internal flow of a very low head cross flow turbine. There are two steps to optimize the turbine inlet shape. Firstly, by changing the turbine open angle along with changing the turbine inlet open duct bottom line (IODBL) location to investigate the internal flow. Secondly, keeping the turbine IODBL location at the maximum efficiency achieved at the first step, and changing the turbine IODBL angle to improve the performance. The result shows that there is a 7.4% of efficiency improvement by optimizing turbine IODBL location (open angle), and there is 0.3% of efficiency improvement by optimizing the turbine IODBL angle.

• New & Renewable Energy
• /
• v.8 no.1
• /
• pp.44-51
• /
• 2012

Due to a high tidal range of up to 10 m on the west coast of Korea, numerous tidal current projects are being planned and constructed. The turbine, which initially converts the tidal energy, is an important component because it affects the efficiency of the entire system. Its performance is determined by design variables such as the number of blades, the shape of foils, and the size of a hub. To design a turbine that can extract the maximum power on the site, the depth and duration of current velocity with respect to direction should be considered. Verifying the performance of a designed turbine is important, and requires a circulating water channel (CWC) facility. A physical model for the performance test of the turbine should be carefully designed and compared to results from computational fluid dynamics (CFD) analysis. In this study, a horizontal axis tidal current turbine is designed based on the blade element theory. The proposed turbine's performance is evaluated using both CFD and a CWC experiment. The sealing system, power train, measuring devices, and generator are arranged in a nacelle, and the complete TCP system is demonstrated in a laboratory scale.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.4
• /
• pp.325-331
• /
• 2016

Computational fluid numerical analysis using the commercial code CFX was performed to develop a Pelton turbine for a pico hydro power generator using the circulating water of a cooling tower in a large building. The performance of the Pelton turbine was examined for different design factors, such as the bucket shape, in which the Pelton wheel was connected in an appropriate manner to the pipe section, and the number of buckets in order to find the optimal design of Pelton turbine for a pico hydro power using surplus water. A benchmark test was carried out on the manufactured small scale Pelton turbine to validate the design method of the Pelton turbine by numerical analysis. The results obtained by comparing the flow characteristics and power output measured using the ultrasonic flowmeter, the pressure transducer and the oscilloscope with the numerical results confirmed the validity of the analytical design method. The possibility of developing Pelton turbines for kW class pico hydro power generators using surplus water with an average circulation velocity of 1.2 m/s for the chosen bucket shape and number of buckets in a 30 m high building was confirmed.