• Title/Summary/Keyword: rotors

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Design and Performance Evaluation of a 10kW Scale Counter-Rotating Wind Turbine Rotor (10kW급 상반전 풍력터빈 로터의 설계와 성능 평가에 관한 연구)

  • Hoang, Anh Dung;Yang, Chang-Jo
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.20 no.1
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    • pp.104-112
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    • 2014
  • The counter-rotating approach on wind turbine has been recently put in interest for its certain advantages in both design and performance. This paper introduces a study on a counter-rotating wind turbine designed and modeled using NREL airfoils S822 and S823. The aims of the study is to evaluate and discover the performance of the counter-rotating system, and compares to that of single rotor turbine of same design using numerical simulation. The results show higher performance of the counter-rotating system compared with single rotor case at TSR 3 to 5 but lower performance at higher TSR. This is due to the interaction between upstream and downstream rotors. Thus, the counter-rotating turbine is more efficient at low rotor rotational speed.

Subsynchronous Vibration Behavior of Turbocharger Supported by Semi Floating Ring Bearing (세미 플로팅 링 베어링으로 지지된 터보차저의 Subsynchronous 진동 특성)

  • Lee, Donghyun;Kim, Youngcheol;Kim, Byungok;Ahn, Kookyoung;Lee, Youngduk
    • The KSFM Journal of Fluid Machinery
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    • v.20 no.1
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    • pp.15-20
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    • 2017
  • The small turbocharger for the automotive application is designed to operate up to 200,000 rpm to increase system efficiency. Because of high rotation speed of turbocharger, floating ring bearing are widely adopted due to its low friction loss and high rotordynamic stability. This paper presents a linear and nonlinear analysis model for a turbocharger rotor supported by a semi-floating ring bearing. The rotordynamic model for the turbocharger rotor was constructed based on the finite element method and fluid film forces were calculated based on the infinitely short bearing assumption. In linear analysis, we considered fluid film force as stiffness and damping element and in nonlinear analysis, the fluid film force was calculated by solving the time dependent Reynolds equation. We verified the developed theoretical model by comparing to modal test results of test rotors. The analysis results show that there are two unstable modes, which are conical and cylindrical modes. These unstable modes appear as sub-synchronous vibrations in nonlinear analysis. In nonlinear analysis, frequency jump phenomenon demonstrated when vibration mode is changed from conical mode to cylindrical one. This jump phenomenon was also demonstrated in the test. However, the natural frequency measured in the test differs from those obtained using nonlinear analysis.

An Analysis on Volumetric Displacement of Gerotor Hydraulic Motor using Energy Conservation and Torque Equilibrium - Second Report: The Case of a Revolving and Rotating Inner Rotor - (에너지보존과 토크평형을 이용한 제로터 유압모터의 배제용적 해석 - 내부로터 공·자전 경우 -)

  • Kim, S.D.;Kim, D.M.;Ham, Y.B.
    • Journal of Drive and Control
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    • v.11 no.4
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    • pp.15-24
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    • 2014
  • It is difficult to analytically derive a volumetric displacement formula for a gerotor hydraulic motor due to the complexity of the geometric shape of its gear lobes. This work proposes an analytical method for the volumetric displacement, a relatively easy method based upon two physical concepts: conservation between hydraulic energy and mechanical shaft energy, and torque equilibrium for the rotor's motion. The first research using these concepts was conducted on inner and outer rotors rotating with respect to each rotor axis. This work represents the second report conducted on an inner rotor revolving as a planetary motion on the stationary outer rotor. The formula equations regarding the volumetric displacement and flow rate are derived, and the proposed formula about the volumetric displacement is proven to be the same as another analytical displacement formula: the so-called vane length method. From the formula, volumetric displacement is calculated for an example geometry of the gear lobes. The resultant displacement is confirmed to be the same as the value calculated from the chamber volume method. The proposed analytical formula can be utilized in the analysis and design of gerotor hydraulic motors. Because it is based on torque equilibrium, this formula can provide a better understanding of torque performance, such as torque ripple, in designing a gerotor type motor.

An Study on Pole Piece Shape for Improving Torque Ripple of Magnetic Gears (마그네틱 기어의 토크리플 개선을 위한 폴피스 형상 연구)

  • Kim, Chan-Seung;Park, Eui-Jong;Kim, Sung-Jin;Kim, Yong-Jae
    • The Journal of the Korea institute of electronic communication sciences
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    • v.12 no.6
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    • pp.1065-1070
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    • 2017
  • Magnetic gears are magnetically coupled to the input side and the output side of the rotary machine to transmit power without mechanical contact. The magnetic gear consists of an inner rotor, an outer rotor and pole pieces. Torque ripple occurs due to the difference in reluctance between the two rotors and the pole pieces during power transmission. Torque ripple is a cause of the noise and vibration of the rotary machine, so it is necessary to minimize it. In this paper, we propose a shape that cuts the corner of the pole piece and apply a fillet to reduce torque ripple. We used a two-dimensional finite element analysis method to compare and analyze the torque ripple of the magnetic gears according to the change of the fillet parameters and to find the pole piece shape with excellent torque ripple.

Effects of Rotational Velocity on Weld Character of Inertia-Welded IN713C-SAE8630 (관성용접(慣性熔接)된 이종재질(異種材質) IN713C-SAE8630의 용접성능(熔接性能)에 회전속도(回轉速度)가 미치는 영향(影響))

  • Sae-Kyoo,Oh
    • Bulletin of the Society of Naval Architects of Korea
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    • v.9 no.2
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    • pp.43-48
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    • 1972
  • Inertia friction welding, a relatively recent innovation in the art of joining materials, is a forge-welding process that releases kinetic energy stored in the flywheel as frictional heat when two parts are rubbed together under the right conditions. In a comparatively short time, the process has become a reliable method for joining ferrous, and dissimilar metals. The process is based on thrusting one part, attached to a flywheel and rotating at a relatively high speed, against a stationary part. The contacting surfaces, heated to plastic temperatures, are forged together to produce a reliable, high-strength weld. Welds are made with little or no workpiece preparation and without filler metal or fluxes. However, In order to obtain a good weld, the determination of the optimum weld parameters is an important problem. Especially, because the amount of the flywheel mass will be determined according to the initial rotating velocity values at the constant thrust load, the initial rotating velocity is an important factor to affect a weld character of the inertia-welded IN713C-SAE8630, which is used for the wheel-shafts of turbine rotors or turbochargers, exhausting valves, etc. In this paper, the effects of initial rotational velocity on a weld character of inertia-welded IN713C-SAE8630 was studied through considerations of weld parameters determination, micro-structural observations and tensile tests. The results are as the following: 1) As initial rotating velocity was reduced to 267 FPM, cracks and carbide stringers were completely eliminated in the micro-structure of welded zone. 2) As initial rotating velocity was reduced and flywheel mass was increased correspondingly, the maximum welding temperatures were decreased and the plastic working in the weld zone was increased. 3) As initial rotating velocity was progressively decreased and carbides were decreased, the tensile strengths were increased. 4) And also the fracture location moved out of the weld zone and the tensile tests produced, the failures only in the cast superalloy IN713C which do not extend into the weld area. 5) The proper initial rotating velocity could be determined as about 250 thru 350 FPM for the better weld character.

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Analysis of Flight Test Result for Control Performance of Smart UAV (스마트무인기의 비행제어 성능관련 비행시험 결과분석)

  • Kang, Young-Shin;Park, Bun-Jin;Cho, Am;Yoo, Chang-Sun;Koo, Sam-Ok
    • Aerospace Engineering and Technology
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    • v.12 no.1
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    • pp.22-31
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    • 2013
  • Flight tests on flight control performance of helicopter, conversion and airplane mode for the Smart UAV were completed. Automatic take-off and landing, automatic return home as well as automatic approach to hover were performed in helicopter mode. Climb/descent, left/right turn using speed and altitude hold mode were performed in each 10 tilt angle in conversion mode. The rotor speed in airplane mode was reduced to 82% from 98% RPM in order to increase rotor efficiency with reducing Mach number at tip of rotors. It reached to the designed maximum speed, VTAS=440 km/h at 3 km altitude. This paper presents the flight test result on full envelopment of Smart UAV. Detailed test plan and test data on control performance were also presented to prove that all data meets the flying qualities requirement.

Design and Fabrication of a small Coaxial Rotorcraft UAV (동축반전 헬리콥터형 소형 무인항공기 설계 및 제작)

  • Kim, Sang-Deok;Byun, Young-Seop;Song, Jun-Beom;Lee, Byoung-Eon;Song, Woo-Jin;Kim, Jeong;Kang, Beom-Soo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.37 no.3
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    • pp.293-300
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    • 2009
  • The rotorcraft-based unmanned aerial vehicle(UAV) capable of performing close-range surveillance and reconnaissance has been developed. Trade studies on mission feasibility led to the adoption of a coaxial rotorcraft with twin rotors counter-rotating in one axis and driven by electric motors. A commercial off-the-shelf flight control computer(FCC) and a radio frequency modem were adopted for autonomous navigation. In order to achieve an aerial view, commercial charge-coupled device camera was also integrated into the vehicle. The performance of the completed vehicle was proved with manual flight test, and mission capability was verified through waypoint navigation flight after being equipped with FCC. This paper treats the whole process of design and system integration for development of the coaxial rotorcraft UAV.

Numerical Analysis of the Turbine Rotor Flow with the Unsteady Passing Wake from a Stator (정익에서 발생한 비정상 후류를 지나는 터빈 동익 유동장 수치해석)

  • Lee, Eun-Seok
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.4
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    • pp.275-280
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    • 2007
  • A turbine stage consists of stators and rotors. The stator provides the required inlet flow conditions so that the rotor can produce the necessary power. Passing wakes generated from the trailing edge of the stator make an interaction with the rotor. In the present study, this flow mechanism is investigated using the numerical analysis. In case of a large gap distance between the stator and rotor, the flow can be solved independently. First, only the stator flow field is solved. Second, the rotor flow field is solved including the passing wake characteristics obtained from the stator analysis. The passing wake experiences the shearing as it approaches to the rotor blade leading edge. And it is chopped when it strikes the rotor blade. After that, the chopped wakes becomes the prolongation as it travels downstream. The flow according to the variation of the gap distance is also studied. Pressure jumps due to the passing wakes result in the pressure and lift loss and it gets stronger with the closer gap distance.

A Study on Correlation of Microstructural Degradation and Mechanical Properties of 9-12%Cr-Steel for Ultra-Super Critical Power Generation (초초임계압 발전용 소재의 장시간 열처리에 따른 미세조직 변화와 기계적 특성의 상관관계 연구)

  • Joo Sungwook;Yoo Junghoon;Shin Keesam;Hur Sung Kang;Lee Je-Hyun;Suk Jin Ik;Kim Jeong Tae;Kim Byung Hoon
    • Korean Journal of Materials Research
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    • v.15 no.1
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    • pp.19-24
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    • 2005
  • For the good combination of high-temperature strength, toughness and creep property, 912% chromium steels are often used for gas turbine compressors, steam turbine rotors, blade and casing. In this study, the correlation of microstructural evolution and mechanical properties was investigated fur the specimens heat-treated at 600, 650 and 700C for 1000, 3000 and 5000 hrs. The microstructure of as-received specimen was tempered martensite with a high dislocation density, small sub-grains and fine secondary phase such as M23C6. Aging for long-time at high temperature caused the growth of martensite lath and the decrease of dislocation density resulting in the decrease in strength. However, the evolution of secondary phases had influence on hardness, yield strength and impact property. In the group A specimen aged at 600Cand650C, Laves phase was observed. The Laves phase caused the increase of the hardness and the decrease of the impact property. In addition, the abrupt growth of secondary phases caused decrease of the impact property in both A and B group specimens.

The Numerical Analysis of the Aeroacoustic Characteristics for the Coaxial Rotor in Hovering Condition (동축반전 로터의 제자리 비행 공력소음 특성에 관한 수치 해석적 연구)

  • So, Seo-Bin;Lee, Kyung-Tae
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.49 no.8
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    • pp.699-708
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    • 2021
  • In this paper, the aerodynamic and aeroacoustic characteristics that vary depending on the rotation axial distance between the upper and lower rotor, which is one of the design parameters of the coaxial rotor, is analyzed in the hovering condition using the computational fluid dynamics. Aerodynamic analysis using the Reynolds Averaged Navier Stokes equation and the aeroacoustic analysis using the Ffowcs Williams ans Hawkings equation is performed and the results were compared. The upper and lower rotor of the coaxial rotor have different phase angle which changes periodically by rotation and have unsteady characteristics. As the distance between the upper and lower rotors increased, the aerodynamic efficiency of the thrust and the torque was increased as the flow interaction decreased. In the aeroacoustic viewpoint, the noise characteristics radiated in the direction of the rotational plane showed little effect by axis spacing. In the vertical downward direction of the axis increased, the SPL maintains its size as the frequency increases, which affects the increase in the OASPL. As the axial distance of the coaxial rotor increased, the noise characteristics of a coaxial rotor were similar with the single rotor and the SPL decreased significantly.