2022/05/17 更新

写真a

リ ナクジュン
李 洛中
所属
理工学術院 基幹理工学部
職名
講師(任期付)
 

論文

  • Design Optimization of High Specific Speed Prototype Francis Turbine by Design of Experiments

    Nak Joong Lee, Young Cheol Hwang, Morihito Inagaki, Kazuyoshi Miyagawa

    Journal of Physics: Conference Series   1909 ( 1 )  2021年05月

     概要を見る

    In general, Francis turbines are known to last for 40 to 50 years of use. However, exchanging an old turbine for a new is expensive because of modernization costs. Therefore, many modernization projects will take place through new runner changes. The Francis turbine in this paper has a high specific speed of about 330m-kW and a runner diameter of about 4.3m. The new runner can be expected to have a more stable flow and improved performance by flow analysis. In this paper, the performance analysis of the runner was performed using the CFD by Design Of Experiments (DOE). The sensitivity of variables was examined using L18 method. Numerical analysis was performed via BladeGen, Turbogrid, ICEM CFD, and CFX, which are commercial CFD codes. The design goal is to enable not only the best efficiency point but also a more stable operation than before even at partial load conditions. Find out how to find the shape of a runner blade by searching for design points that maximize annual power generation according to newly selected operating conditions.

    DOI

  • Performance of counter-rotating tandem propellers at oblique flow conditions

    Nak Joong Lee, Morihito Inagaki, Toshiaki Kanemoto

    IOP Conference Series: Earth and Environmental Science   240 ( 5 )  2019年03月  [査読有り]

     概要を見る

    © Published under licence by IOP Publishing Ltd. Tidal currents are a potential source of reliable and renewable energy. Various power generation systems have been proposed. The authors developed a counter-rotating type tidal stream power unit in which the tandem runners make the inner and the outer armatures counter-rotate. The unit is composed of tandem propellers with 3 front and 5 rear blades and has a promising advantage that the rotational torque between the front runner and the rear propellers, namely the inner and the outer armatures, is balanced in the unit. That is, this tidal stream power unit can be moored with only one cable and then its nose and tail will naturally line up in response to the tidal stream by yawing. In this paper, the performance of the propellers in oblique flow conditions were investigated experimentally and numerically. When the coming flow obliquely to the propeller by 30 degrees, the performance deteriorates by 20%.

    DOI

  • Performance of tandem propellers counter-rotating obliquely to tidal stream

    Nak Joong Lee, Toshiaki Kanemoto, Kazuo Kuwano, Isao Samura

    Proceedings of the International Offshore and Polar Engineering Conference     253 - 256  2017年  [査読有り]

     概要を見る

    Copyright © 2017 by the International Society of Offshore and Polar Engineers (ISOPE). The authors have developed a counter-rotating type hydroelectric unit where tandem runners counter-rotate inner and outer armatures in a peculiar generator, and the unit has penetrated into the market in the small/micro hydropower. The unit has promising advantages such as the rotational torque is counter-balanced itself between the front and the rear runners, namely the inner and the outer armatures. Such technology has been provided for the tidal power unit moored to the seabed with one cable. Tidal stream is abundant and clean energy resource whose power is predictable and sustainable. To generate power effectively from the stream, the unit must effectively work in response to change of the flow direction not only in day cycle but also in unsteady condition with turbulent fluctuation. This paper discusses the effects of the flow direction on the output of the tandem propellers by commercial Computational Fluid Dynamics (CFD) code.

  • Experiments on the magnetic coupling in a small scale counter rotating marine current turbine

    I. C. Kim, N. J. Lee, J. Wata, B. S. Hyun, Y. H. Lee

    IOP Conference Series: Materials Science and Engineering   129 ( 1 )  2016年05月  [査読有り]

     概要を見る

    Modern economies are dependent on energy consumption to ensure growth or sustainable development. Renewable energy sources provide a source of energy that can provide energy security and is renewable. Tidal energy is more predictable than other sources or renewable energy like the sun or wind. Horizontal axis marine current turbines are currently the most advanced and commercially feasible option for tidal current convertors. A dual rotor turbine is theoretically able to produce more power than a single rotor turbine at the same fluid velocity. Previous experiments for a counter rotating dual rotor horizontal axis marine current turbine used a mechanical oil seal coupling that caused mechanical losses when water entered through small gaps at the shaft. A new magnetic coupling assembly eliminates the need for a shaft to connect physically with the internal mechanisms and is water tight. This reduces mechanical losses in the system and the effect on the dual rotor performance is presented in this paper.

    DOI

  • Performance investigation of a counter-rotating tidal current turbine by CFD and model experimentation

    Nak Joong Lee, In Chul Kim, Beom Soo Hyun, Young Ho Lee

    Journal of Mechanical Science and Technology   30 ( 2 ) 519 - 524  2016年02月  [査読有り]

     概要を見る

    © 2016, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg. Global warming is one of the issues in the world, which is mainly due to the burning of fossil fuels. Thus, alternative energy is now paramount in the 21st century. In Korea, the tidal currents in the southwestern sea have a wide range of currents that are available for tidal current power generation. Single rotor turbines can obtain a theoretical maximum power coefficient of 59.3%, whereas dual rotor turbines can attain a maximum of 64%. In this study, the performance and efficiency of a counter-rotating tidal current turbine is investigated when changing the front and rear blade angles at different water velocities. The investigation was conducted by using Computational fluid dynamics (CFD) and experimental methods highlighted in this study. When varying these parameters, changes in the streamlines were observed in the CFD results. The changes in flow stability over the blade surfaces observed in the numerical results were reflected in the power and power coefficient graphs presented in this study. The results obtained by the experiments were also shown to be in good agreement with the CFD results.

    DOI

  • Counter-rotating turbine in unique power unit provided for bidirectional tidal streams

    Toshiaki Kanemoto, Nak Joong Lee, Man Woong Heo, Bin Huang, Yuji Nakanishi, Yuki Funami

    Proceedings of the 12th ISOPE Pacific-Asia Offshore Mechanics Symposium, PACOMS 2016     254 - 258  2016年  [査読有り]

     概要を見る

    Copyright © 2016 by the International Society of Offshore and Polar Engineers. The energy from a tidal stream is abundant and renewable resource whose power is predictable and sustainable. To generate power effectively from the stream a unique counter rotating type tidal stream power unit, whose tandem rotors drive inner and outer armatures in a generator, has been provided by the authors. At the tidal power station located in narrow straits, the unit needs to be reoriented so that useful output power can be obtained from both flood and ebbing tides. In this paper, the counter rotating tandem rotor turbine was designed for operation in a bidirectional tidal stream and the performance was analyzed. The maximum output power is somewhat lower than that of the rotors designed exclusively for a unidirectional stream. The relative flow has a positive angle of attack at the leading edge and discharges from the trailing edge along the blade camber. The angular momentum change, namely the rotor work, is seen to always be accompanied with a shock loss at the leading edge.

  • Experimental and numerical investigation of blade angle variation on a counter-rotating tidal current turbine

    Lee Nak-Joong, Kim In-Chul, Hyun Beom-Soo, Lee Young-Ho

    Renewable Energy in the Service of Mankind   1   305 - 316  2015年09月  [査読有り]

     概要を見る

    © Springer International Publishing Switzerland 2015. Importance of renewable energy has become paramount due to its perennial source and no adverse environmental impact. Ocean is one of the major source of renewable energy where the sun's energy is converted into various natural phenomenon. Southwestern sea in particular, in Korea, has large range of tidal currents with potential for tidal current power generation. Tidal power has great potential for future power and electricity generation because of the massive size of the oceans. The major benefit of tidal power and difference from most renewable energy sources is that it is independent of seasons and weather, that is, it is always constant which makes power generation predictable and makes tidal power a reliable energy source. Horizontal-axis-type turbine appears to be the most technologically and economically viable option for the generation of tidal power. Several studies have shown that single-rotor turbines can obtain a theoretical maximum power coefficient of 59.3 %, whereas dual rotor can obtain a maximum of 64? %. Hence, with the optimization of counter-rotating turbines, more power can be obtained than the single-rotor turbines. Previous studies focus on the performance analysis of the turbine with the variation of distance between the blades. This chapter primarily concentrates on the investigation of the performance analysis and power output of a counter-rotating current turbine by the variation of blade angles by both computational fluid dynamics (CFD) simulation and experiments. Numerical simulations were performed using a commercial finite volume method solver, ANSYS CFX ver.13.0. Experiments were conducted in the water tank with a vertically circulating water channel in the laboratory of Korea Maritime and Ocean University (KMOU) to validate the numerical results. Several experiments were conducted with the fixed front blade angle and varying the rear blade angle and vice versa at various water flow rate. Surface streamlines, torque, total power output, power coefficient ( Cp) etc., were characterized and compared for CFD and experimental cases. The results obtained find good agreement with each other.

    DOI

  • Performance study on a counter-rotating tidal current turbine by CFD and model experimentation

    Nak Joong Lee, In Chul Kim, Chang Goo Kim, Beom Soo Hyun, Young Ho Lee

    Renewable Energy   79 ( 1 ) 122 - 126  2015年  [査読有り]

     概要を見る

    © 2014 Elsevier Ltd. Among the various ocean energy resources in Korea, the tidal currents in the South western sea have a large potential for development tidal current power generation. The biggest advantage of tidal power is that it is not dependent on seasons or weather and is always constant. This makes power generation predictable and makes tidal power a more reliable energy source than other renewable energy sources. Marine current turbines convert the kinetic energy in tidal currents for power production. Single rotor turbines can obtain a theoretical maximum power coefficient of 59.3%, whereas dual rotor can obtain a maximum of 64%. Therefore by optimizing the counter rotating turbines, more power can be obtained than the single rotor turbines. In this study, we investigated the effect of varying the distance between the dual rotors on the performance and efficiency of a counter-rotating current turbine by using computational fluid dynamics (CFD) and experimental methods. It was found that the dual rotor produced more power than the single rotor. In addition, the blade gap distance affects the flow on the rear rotor blades as well as power output and performance of the turbine. The distance can be used a parameter for counter rotating turbine design. Finally, the numerical setup used for this study can be further used to evaluate the design of larger counter rotating blade designs.

    DOI

  • Performance investigation of a counter-rotating tidal current turbine by front and rear blade angle by CFD and model experimentation

    Nak Joong Lee, In Chul Kim, Beom Soo Hyun, Young Ho Lee

    Proceedings of the International Offshore and Polar Engineering Conference     575 - 579  2014年  [査読有り]

     概要を見る

    Global warming is one of the issues in the world mainly due to the burning of fossil fuels and so alternative energy is now paramount in the 21st century. In Korea, the tidal currents in the South western sea has a large range of currents that are available for tidal current power generation. Single rotor turbines can obtain a theoretical maximum power coefficient of 59.3%, whereas dual rotor can obtain a maximum of 64%. In this study, we investigated the performance and efficiency of a Counter-rotating current turbine by different front and rear blade angle by water velocity by using CFD and experimental methods. Copyright © 2014 by the International Society of Offshore and Polar Engineers (ISOPE).

  • Numerical analysis on the closed tank of energy storage system during discharge using CFD

    Ji Hoon Park, Byeong Jun Kim, Nak Joong Lee, Young Ho Lee

    IET Conference Publications   2014 ( CP658 )  2014年  [査読有り]

     概要を見る

    Renewable energy sources which are gaining popularity over conventional resources mostly produce intermittent power as they fall under the influence of natural phenomena as daily cycle or weather conditions. However, worldwide remarkable growth of electricity generation from renewable resources in the recent years has resulted in the decentralized production posing network load stability problems, which requires proper energy storage. Therefore, energy storage system can make more efficient utilization of renewable energies available and hence it will be more practical in application. This research work discusses about the energy storage system which comprises the concepts of combined pumped-storage hydro electricity and compressed air energy storage. The system consists of two tanks, one open tank to the air and one closed tank which stores water and compressed air using multistage pump. The energy of compressed air will be released to drive water which passes through the hydro turbine resulting in the generation of electricity when the grid power is insufficient. This study focuses on the CFD analysis on the closed tank of energy storage system during discharge.

    DOI

  • Analysis of a pico tubular-type hydro turbine performance by runner blade shape using CFD

    J. H. Park, N. J. Lee, J. V. Wata, Y. C. Hwang, Y. T. Kim, Y. H. Lee

    IOP Conference Series: Earth and Environmental Science   15 ( PART 4 )  2012年  [査読有り]

     概要を見る

    There has been a considerable interest recently in the topic of renewable energy. This is primarily due to concerns about environmental impacts of fossil fuels. Moreover, fluctuating and rising oil prices, increase in demand, supply uncertainties and other factors have led to increased calls for alternative energy sources. Small hydropower, among other renewable energy sources, has been evaluated to have adequate development value because it is a clean, renewable and abundant energy resource. In addition, small hydropower has the advantage of low cost development by using rivers, agricultural reservoirs, sewage treatment plants, waterworks and water resources. The main concept of the tubular-type hydro turbine is based on the difference in water pressure levels in pipe lines, where the energy which was initially wasted by using a reducing valve at the pipeline of waterworks, is collected by turbine in the hydro power generator. In this study, in order to acquire the performance data of a pico tubular-type hydro turbine, the output power, head and efficiency characteristics by different runner blade shapes are examined. The pressure and velocity distributions with the variation of guide vane and runner vane angle on turbine performance are investigated by using a commercial CFD code. © Published under licence by IOP Publishing Ltd.

    DOI

  • Performance analysis of a counter-rotating tubular type micro-turbine by experiment and CFD

    N. J. Lee, J. W. Choi, Y. H. Hwang, Y. T. Kim, Y. H. Lee

    IOP Conference Series: Earth and Environmental Science   15 ( PART 4 )  2012年  [査読有り]

     概要を見る

    Micro hydraulic turbines have a growing interest because of its small and simple structure, as well as a high possibility of using in micro and small hydropower applications. The differential pressure existing in city water pipelines can be used efficiently to generate electricity in a way similar to that of energy being generated through gravitational potential energy in dams. The pressure energy in the city pipelines is often wasted by using pressure reducing valves at the inlet of water cleaning centers. Instead of using the pressure reducing valves, a micro counter-rotating hydraulic turbine can be used to make use of the pressure energy. In the present paper, a counter-rotating tubular type micro-turbine is studied, with the front runner connected to the generator stator and the rear runner connected to the generator rotor. The performance of the turbine is investigated experimentally and numerically. A commercial ANSYS CFD code was used for numerical analysis. © Published under licence by IOP Publishing Ltd.

    DOI

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