• Journal of Biosystems Engineering
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• 제43권2호
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• pp.119-127
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• 2018

Purpose: Fermented feedstuffs have been found to improve productivity, reduce manure odor, and increase immunity. However, because there is not a commercialized pelletizing system for fermented total mixed ration (TMR) for pig feeding in Korea, a pelletizing system using TMR fermented feed was developed. Methods: The particle size, density, and volumetric density of the TMR feeds used in the test were measured. The pellet durability index (PDI, %) value of the pelletized TMR feed based on its moisture content, and the amount of pellet production based on the rotation speed of the compression roller were measured. Results: The test materials, TMR1 and TMR2, were approximately compressed to 387 kg/m3 with 18.2% (w.b.) and 544 kg/m3 with 22.2% (w.b.), respectively. Throughout this pellet molding test, the moisture content from 15 to 20% (w.b.) of mixture feedstuffs, including fermented forage, could be used for pellet molding. Based on the results, a small-scale pellet molding system of fermented TMR was designed and manufactured for pig farms. As rotation speed increased, the throughput increased, whereas the moisture content decreased by approximately 2% (w.b.) because of pellet molding. The best yield of pellets with 94.2% PDI was of 536 kg/h at 135 rpm rotation speed. Conclusions: Although the throughput of the prototype increased as the rotation speed increased, it was difficult to operate because of the greater noise and the lower PDI (%) at the higher rotation speed of the pellet molding rotor. It was found that the best production of pellets using the prototype was 536 kg/h having a PDI of 94.2% or more at a rotation speed of 135 rpm.

• 한국산학기술학회논문지
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• 제12권5호
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• pp.2061-2066
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• 2011

사이클로이드 감속기는 기계의 회전수를 조절하기위한 장치이다. 사이클로이드 감속기는 큰 토크로 변환시킬 수 있는 장점이 있지만 높은 회전수 에는 적합하지 않다. 한편 200톤 하중이 가해지는 수송기기에 있어서 감속기의 사용한계속도를 찾아내기는 불가능하다. 본 연구에서는 LS-DYNA를 이용하여 마찰손실동력을 수치 해석적으로 검토하였다. 최대토크3.5ton-m에 있어서 회전수 60rpm 그리고 162rpm으로 구동하여 해석을 수행한 결과 다음과 같은 결과를 얻었다. 60rpm회전의 경우 최대응력은 RV gear의 경우 463MPa 핀기어의 경우 507MPa이 발생하였다. 마찰손실동력은 50kW이며, 162rpm의 경우 최대응력값은 RV gear와 핀기어 각각 550MPa, 538MPa이 발생하였다. 손실동력은 175kW이 발생하여 사용이 불가능하다는 것을 알 수 있었다.

• 한국터널지하공간학회 논문집
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• 제17권3호
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• pp.403-413
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• 2015

본 논문은 복합지반에서 쉴드 TBM 커터헤드의 회전속도 제어에 관한 실험적 연구이다. 복합지반에서는 암반을 굴착하는 디스크커터와 더불어 커터비트의 절삭 성능이 매우 중요하다. 이 연구에서는 특히 풍화토와 풍화암으로 이루어진 복합지반의 커터비트의 성능평가에 초점을 두었다. 이 연구를 위하여 실험실용으로 개발된 쉴드 TBM 커터비트 평가 장비를 이용하여 실내시험을 실시하였다. 복합지반은 공학적 상사성을 고려하여 조성하였다. 조성된 복합지반에서 쉴드 TBM 커터헤드 회전속도를 2, 3, 4 rpm으로 적용하여 각 커터비트에 작용하는 절삭력을 측정하고 회전에 따른 절삭력의 변화를 분석하였다. 실험결과로 부터 커터비트에 작용하는 절삭력은 지반경계부에서 급상승하는 경향을 보여주었다. 또한 이러한 상승되는 절삭력의 크기는 쉴드 TBM 커터헤드의 회전속도가 클수록 크게 나타났다. 이러한 결과로부터 복합지반에서 쉴드 TBM 커터헤드의 회전속도를 빠르게 할 경우 커터비트에 가해지는 위험요소가 더 크다는 것을 보여주고 있다. 따라서 복합지반조건에 현장 TBM 굴착 시 회전속도의 제어가 필요한 것으로 나타났으며 감속시키는 것이 비트에 가해지는 리스크를 저감시킬 수 있을 것이다.

• Journal of Electrical Engineering and Technology
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• 제12권6호
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• pp.2268-2277
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• 2017

As constantly increasing wind power penetrates power grid, wind power plants (WPPs) are exerting a direct influence on the traditional power system. Most of WPPs are using variable speed constant frequency (VSCF) wind turbines equipped with doubly fed induction generators (DFIGs) due to their high efficiency over other wind turbine generators (WTGs). Therefore, the analysis of DFIG has attracted considerable attention. Precisely measuring optimum reference speed is basis of utilized maximum wind power in electric power generation. If the measurement of wind speed can be easily taken, the reference of rotation speed can be easily calculated by known system's parameters. However, considering the varying wind speed at different locations of blade, the turbulence and tower shadow also increase the difficulty of its measurement. The aim of this study is to design fuzzy controllers to replace the wind speedometer to track the optimum generator speed based on the errors of generator output power and rotation speed in varying wind speed. Besides, this paper proposes the fuzzy adaptive PID control to replace traditional PID control under rated wind speed in variable-pitch wind turbine, which can detect and analyze important aspects, such as unforeseeable conditions, parameters delay and interference in the control process, and conducts online optimal adjustment of PID parameters to fulfill the requirement of variable pitch control system.

• 대한기계학회논문집A
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• 제27권7호
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• pp.1179-1184
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• 2003

The technique for measuring the rotational speed of tappet in direct acting type valve train system has been developed. The optic signal monitoring system with laser and optic fiber was designed to follow the signal of tappet rotation. The system was based on ON/OFF signal generation from the additional encoder teeth under the tappet with optic fibers attached photo transistor. The data showed that tappet rotation was affected by offset, oil temperature and cam shaft operating speed. Also it was found that tappet rotation increases with oil temperature. Tappet spin was delayed 10∼s20$^{\circ}$ cam angle after valve opening. The instantaneous rotational speed of tappet was reciprocal to cam shaft speed and the tappet and the cam angle ratio was located in the range of 0.1∼0.3.

• 조명전기설비학회논문지
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• 제29권3호
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• pp.96-101
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• 2015

Induction machine requires a rotating magnetic field for energy conversion. The current to generate a rotating magnetic field is the magnetization current. This magnetization current corresponds to the reactive power. Reactive power is higher than active power at start-up of induction motor. As the rotation speed is increased, their magnitudes are reversed each other. The active power is higher than the reactive power at near the synchronous speed. This paper is dealing with the analysis result for the changes of the magnetizing current and reactive power when the induction machine is operating as a motor or generator near synchronous speed.

• 한국공작기계학회논문집
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• 제16권6호
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• pp.125-132
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• 2007

Inherent dynamic interaction between flexible disk and workpiece creates partially non-flat surface profile. A flat zone was defined using minimum depth of engagement. Several key parameters were defined to explain the characteristics of the zone. Process conditions including disk rotation speed, initial depth of cut and feed speed were varied to produce product profile database. Correlation between key factors was examined to find the characteristic dependencies. Trends of key parameters were displayed and explained. Higher flat zone ratio was observed for lower depth of cut and higher disk rotation speed. Ratio of minimum depth of cut against target depth of cut increased for higher feed speed and disk rotation speed but was insensitive to the depth of cut variation. The process transition was visualized by continuously displaying instantaneous orientation of the deflected disk and the location of key parameters were clearly marked for comparison.

• 드라이브 ㆍ 컨트롤
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• 제17권2호
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• pp.28-37
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• 2020

It is difficult to analytically derive the relationship among volumetric displacement, flowrate, torque, and rotation speed regarding an instantaneous position of gerotor hydraulic pumps/motors. This can be explained by the geometric shape of the rotors, which is highly complicated. Herein, an analytical method for the instantaneous torque, rotation speed, flowrate, and volumetric displacement of a pump/motor is proposed. The method is based on two physical concepts: energy conservation and torque equilibrium. The instantaneous torque of a pump/motor shaft is determined for the posture of rotors from the torque equilibrium. If the torque equilibrium is combined with the energy conservation between the hydraulic energy of the pump/motor and the mechanical input/output energy, the formula for determining the instantaneous volumetric displacement and flowrate is derived. The numerical values of the instantaneous volumetric displacement, torque, rotation speed, and flowrate are calculated via the MATLAB software programs, and they are illustrated for the case in which inner and outer rotors rotate with respect to fixed axes. The degrees of torque fluctuation, speed fluctuation, and flowrate fluctuation can be observed from their instantaneous values. The proposed formula may provide a better understanding of the design or analysis process of gerotor pumps/motors.

• Tribology and Lubricants
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• 제14권3호
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• pp.81-86
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• 1998

The purpose of this paper is to measure the rotational speed of tappet in OHC valve train system. Tappet has eccentricity about cam center, which induces the tappet rotation and prevents from wear. In this paper, the experimental test rig which composes of one cam system is developed to measure the tappet rotation by using the laser generating system, rotary encoder, optical fiber, and photo transistor. The direction of tappet rotation is judged from the oder of optical signal. As results of experiment, average and instant rotational speed and average rotation angle per one cam revolution are presented. Measured results show that eccentricity ratio is dominant factor for the tappet rotation, and tappet is rotated at the base circle.

• 대한기계학회논문집
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• 제19권5호
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• pp.1308-1318
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• 1995

The influence of varying rotation speed of both crystal and crucible was numerically investigated for the Czochralski silicon-crystal growth. Based on a simplified model assuming flatness of free surfrae, the Navier-Stokes Boussinesq equations were employed to identify the flow pattern, temperature distribution as well as the shape of the melt/crystal interface. The present results showed that the interface shape was relatively convex with respect to the melt at lower pulling rate and tended to be concave as the pulling rate increased. In particular, the experimentally observed gull-winged shape of the interface was qualitatively in agreement with the predicted shape. The rotation of crystal alone little affected the growth system. When the rotation speed of the crucible was increased, there occurred inversion of the interface shape from convex to concave pattern. At rapid rotation of the crucible, an interesting channel formation was predictied primarily due to the assumption of laminar flow.