• Title/Summary/Keyword: Thrust Variation

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Evaluation of Thrust Dynamic Load under Tower Shadow in Wind Turbine below the Rated Wind Speed (정격풍속 이하에서 풍력터빈의 타워 섀도 추력 동하중 개발)

  • Lim, Chae-Wook
    • Journal of the Korean Society of Industry Convergence
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    • v.25 no.6_2
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    • pp.993-1002
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    • 2022
  • This paper relates to a method of modeling the thrust dynamic load caused by the thrust variation occurring on the blade due to the tower shadow below the rated wind speed. A method that uses thrust coefficient is presented by introducing "tower shadow coefficient of thrust variation". For a 2MW wind turbine, the values of "tower shadow coefficient of thrust variation" are calculated and analyzed at wind speeds below the rated. The dynamic load model of thrust under tower shadow is evaluated in Matlab/Simulink using the obtained "tower shadow coefficient of thrust variation" and thrust coefficient. It shows that the thrust variations acting on the three blades by the tower shadow can be expressed using both the thrust coefficient and the introduced "tower shadow coefficient of thrust variation".

Evaluation of Dynamic Thrust Under Wind Shear in Wind Turbine Below Rated Wind Speed (정격풍속 이하에서 풍력터빈의 윈드쉬어 추력 동하중 개발)

  • Lim, Chae-Wook
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.4
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    • pp.407-414
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    • 2016
  • As wind turbines are getting larger in size with multi-MW capacity, the blades are getting longer, over 40 m, and hence the asymmetric loads produced during the rotation of the rotor blades are increasing. Some factors such as wind shear, tower shadow, and turbulence have an effect on the asymmetric loads on the blades. This paper focuses on a method of modeling the dynamic load acting on a blade because of thrust variation under wind shear. A method that uses thrust coefficient is presented. For this purpose, "wind shear coefficient of thrust variation" is defined and introduced. Further, we calculate the values of the "wind shear coefficient of thrust variation" for a 2 MW on-shore wind turbine, and analyze them for speeds below the rated wind speed. Then, we implement a dynamic model that represents the thrust variation under wind shear on a blade, using MATLAB/Simulink. It is shown that it is possible to express thrust variations on three blades under wind shear by using both thrust coefficient and "wind shear coefficient of thrust variation."

An Investigation on Thrust Properties under Wind Shear for an On-Shore 2 MW Wind Turbine (윈드 쉬어에 의한 2MW급 육상용 풍력터빈의 추력 특성 확인)

  • Lim, Chae Wook
    • The KSFM Journal of Fluid Machinery
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    • v.19 no.6
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    • pp.14-18
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    • 2016
  • Multi-MW wind turbines have very large blades over 40~50 m in length. Some factors like wind shear and tower shadow make an effect on asymmetric loads on the blades. Larger asymmetric loads are produced as the length of blade is getting longer. In this paper, a 2 MW on-shore wind turbine is considered and variations of thrust on 3 blades and rotor hub under wind shear are calculated by using a commercial Bladed S/W and dynamic properties of the thrust variations are investigated. It is shown that the amplitude of the asymmetric thrust on each blade under wind shear is getting larger as the wind speed increases, the frequency of the thrust variation on each blade is same as the one of rotor speed, and the frequency of the thrust variation at rotor hub is 3 times as high as the one of rotor speed.

Effect of Mixture Ratio Variation near Chamber Wall in Liquid Rocket Engine

  • Han, Poong-Gyoo;Kim, Kyoung-Ho
    • International Journal of Aeronautical and Space Sciences
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    • v.4 no.2
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    • pp.51-60
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    • 2003
  • An experimental research program is being undertaken to develop a regeneratively-cooled experimental thrust chamber of liquid rocket engine using liquefied natural gas and liquid oxygen as propellants. Prior to firing test using a regenerative cooling with liquefied natural gas in this program, several firing tests were conducted with water as a coolant. Experimental thrust chambers with a thrust of about 10tf were developed and their firing test facility was built up. Injector used in the thrust chamber was of shear-coaxial type appropriate for propellants of gas and liquid phase and cooling channels are of milled rectangular configuration. Periodical variation of the soot deposition and discoloration was observed through an eyes' inspection on the inner wall of a combustion chamber and a nozzle after each firing test, and an intuitive concept of the periodical variation of mixture ratio near the inner wall of a combustion chamber and a nozzle at once was brought about and analyzed quantitatively. Thermal heat flux to the coolant was calculated and modified with the periodical variation model of mixture ratio, and the increment of coolant temperature at cooling channels was compared with measured one.

Fuzzy Robust Control with Constant Thrust Force on Load Variation for Linear Pulse Motor (리니어 펄스모터의 부하변동에 따른 일정추력 퍼지 강인제어)

  • Bae Dong-Kwan;Kim Kwang-Heon;Park Hyun-Soo
    • Proceedings of the KIPE Conference
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    • 2002.11a
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    • pp.40-44
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    • 2002
  • In this paper, robust control method using fuzzy PI parameter tuning is proposed to control constant thrust force on load variation. First, a structure and thrust force equations of the LPM are described. Second, an controller with PI parameter-tuning using a fuzzy theory is proposed to achieve high-precision position with constant thrust force of the LPM. Finally, the effectiveness of an fuzzy PI controller is demonstrated by some simulated and experimental results. Accurate tracking response and superior dynamic performance can be obtained due to the powerful on-line Fuzzy PI gain tuning method with regard parametric variations and load thrust force variations.

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The Improvement of Aerodynamic Performance of Flapping-Airfoil Using Thickness Variation Airfoil (두께 변화가 있는 익형을 이용한 flapping-Airfoil의 공력성능 개선)

  • Lee Jung Sang;Kim Chongam;Rho Oh Hyun
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.787-790
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    • 2002
  • In this work, numerical experiments ave conducted to find out the optimal shape of flapping-airfoil using thickness variation airfoils. In the previous study of flapping-airfoil, we had found that the thrust efficiency of thicker airfoil is better than thinner one, but the latter has higher thrust coefficient. Therefore, we have combined thin(NACA0009) and thick(NACA0015)airfoil to overcome these demerits of each airfoil. Using this combined airfoil, we can achieve acceptable aerodynamic performances from thrust efficiency and coefficient points of view. In order to computational study, we have used parallel-implemented incompressible Wavier-Stokes solver. Computational results show how to design leading and trailing edge shapes.

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Comparative study of prediction methods of power increase and propulsive performances in regular head short waves of KVLCC2 using CFD

  • Lee, Cheol-Min;Seo, Jin-Hyeok;Yu, Jin-Won;Choi, Jung-Eun;Lee, Inwon
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.11 no.2
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    • pp.883-898
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    • 2019
  • This paper employs computational tools to predict power increase (or speed loss) and propulsion performances in waves of KVLCC2. Two-phase unsteady Reynolds averaged Navier-Stokes equations have been solved using finite volume method; and a realizable k-ε model has been applied for the turbulent closure. The free-surface is obtained by solving a VOF equation. Sliding mesh method is applied to simulate the flow around an operating propeller. Towing and self-propulsion computations in calm water are carried out to obtain the towing force, propeller rotating speed, thrust and torque at the self-propulsion point. Towing computations in waves are performed to obtain the added resistance. The regular short head waves of λ/LPP = 0.6 with 4 wave steepness of H/λ = 0.007, 0.017, 0.023 and 0.033 are taken into account. Four methods to predict speed-power relationship in waves are discussed; Taylor expansion, direct powering, load variation, resistance and thrust identity methods. In the load variation method, the revised ITTC-78 method based on the 'thrust identity' is utilized to predict propulsive performances in full scale. The propulsion performances in waves including propeller rotating speed, thrust, torque, thrust deduction and wake fraction, propeller advance coefficient, hull, propeller open water, relative rotative and propulsive efficiencies, and delivered power are investigated.

Development of Iron Core type Linear Motor for Machine Tool (공작기계용 철심형 니니어모터 기술개발)

  • 정재한;박재완
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.10a
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    • pp.33-36
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    • 1997
  • The merits of linear motor are high speed, high acceleration and goad positioning accuracy. In addition, Linear motor for high quality machme tool call for high thrust, high stiffness. In using linear motor we also consider thrust ripple, detent force and thermal behavior. In this research, Iron core type single sided linear DC motor(LDM) is designed which thrust is 6,000 N. To accomplish this design, Various research is hlfilled l~ke the relation of thrust and permanent magnet position angle, the variation of detent force and thrust ripple, dynamic characteristics, and so on.

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Analysis of Primary and Secondary Thrust of a Metal Belt CVT Part I : New Formula for Speed Rtio-Torque-Thrust Relationship Considering Band Tension and Block Compression (금속벨트 CVT 의 구동 및 종동 드러스트 해석 Part I : 밴드 장력과 블록 압축력을 고려한 새로운 변속비-토크-트러스트 관계식)

  • 이희라;김현수
    • Transactions of the Korean Society of Automotive Engineers
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    • v.7 no.8
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    • pp.132-142
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    • 1999
  • In this paper, a new formula for primary and secondary thrust of metal belt CVT is proposed considering variation of band tension, block compression and active arc for each of the primary and secondary pulleys. For the secondary thrust, effective friction coefficient is introduced considering the effect of flange deflection. Nondimensional primary and secondary thrust of the metal belt CVT by the new formula agree well with the experimental results except for low torque range, $0\;<\;{\lambda}\;<\;0.2$ at speed ration i = 1.0. The new formula can be used in design of the primary and secondary thrusts control system for the metal belt CVT.

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A study on the thrust characteristics of three phase linear induction motor by frequency variation (주파수변환에 의한 3상 선형유도전동기의 추력 특성에 관한 연구)

  • Im, Dal-Ho;Kim, Hak-Lyun;Kang, Do-Hyun
    • Proceedings of the KIEE Conference
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    • 1988.07a
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    • pp.73-76
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    • 1988
  • In this paper, the governing equation of the three phase linear induction motor is induced by the method that current in the primary winding is assumed as a current sheet. The steady state flux and the flux that is produced by end effect are mathematically analysed by electromagnetic equation. Each thrust of these flux is respectively induced. So in this paper, it is proved that linear motor is highly affected by end effect at high speed and speed-thrust characteristics of three phase linear induction motor are shown by frequency variation in the actual model.

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