• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.1
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• pp.52-58
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• 2018

A Study on the dynamic characteristics of a rotor driven by a tipjet system in hovering condition was carried out. The sectional modeling was performed for the tipjet blade in which the flow path was inserted, and the dynamic characteristics analysis was conducted by modeling the components of the proposed rotor system. The analysis was conducted with respect to the rotational speed and the collective pitch. As a result of the analysis, it was checked that the proposed tipjet rotor did not have aeroelastic instability within the designed operating range. The tipjet test equipment was constructed in order to verify the analysis approach. It was confirmed that the proposed rotor was driven normally by tipjet. The non-rotating eigenmode measurement test and the rotation test were performed, and the validity was proved by comparing the test results and the analysis results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.2
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• pp.159-166
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• 2018

In this study, the internal structural design, dynamic characteristics and load analyses of the small scaled rotor blade required for LCH(Light Civil Helicopter) main rotor wind tunnel test were carried out. The test is performed to evaluate the aerodynamic performance and noise characteristics of the LCH main rotor system. Therefore, the Mach-scale technique was appled to design the small scaled blade to simulate the equivalent aerodynamic characteristics as the full scale rotor system. It is necessary to increase the rotor speed to maintain the same blade tip speed as the full scale blade. In addition, the blade weight, section stiffness, and natural frequency were scaled according to the Mach-type scaling factor(${\lambda}$). For the design of skin, spar, torsion box, which are the main components of the blade, carbon and glass fiber composite materials were adopted, and composite materials are prepreg types that can be supplied domestically. The KSec2D program was used to evaluate the section stiffness of the blade. Also, structural loads and dynamic characteristics of the Mach scale blade were investigated through the comprehensive rotorcraft analysis program CAMRADII.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.3
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• pp.40-46
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• 2011

A velocity-compounded(VC) turbine of the 75ton turbopump was developed as an improved performance backup for a single-rotor base-line turbine. Curvic coupling was used for the connection between rotors and shaft. High temperature torsion test and spin test was performed for the curvic coupling design validation. Aerodynamic performance test revealed that the developed VC turbine can generate 20.5% higher specific power than the base-line turbine. It has been measured that $1^{st}$ rotor of the subject turbine generates 74.1% of total power at design operating condition.

• Current Research on Agriculture and Life Sciences
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• v.32 no.2
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• pp.91-97
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• 2014

In order to analyze the structural factors and milling performance of farmhouse rice milling machines in Korea, this study classified 29 models of the farmhouse rice milling machines sold in Korea into hulling and polishing devices, examined the structural features for each device, and then analyzed the performance factors based on the results. With regard to hulling devices, impeller rotational speed was investigated as a major structural factor. The hulling devices at an impeller rotational speed of 4,800 rpm were most frequently used and accounted for the largest proportion, 65.5%. At this rotational speed, the hulling rate was the highest, 99.45%, and the brown rice cracked rate was the lowest. Thus, the best impeller rotational speed for the hulling performance was analyzed as 4,800 rpm (p<0.05). With regard to polishing devices, rotor speed was investigated as a major structural factor. The polishing devices with a rotor linear velocity of 2 m/s were most commonly used and accounted for the largest proportion, 60.1%. At this linear velocity, the hulling rate was the highest with 75.07%, and the dispassion rate and broken rice rate were the lowest with 0.02 and 7.06%, respectively. Thus, the best rotor linear velocity for the polishing performance was analyzed as 2 m/s (p<0.05).

• The KSFM Journal of Fluid Machinery
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• v.15 no.2
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• pp.30-35
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• 2012

Aerodynamic torque of wind turbine has nonlinear properties. Nonlinearity of aerodynamic torque is very important in wind turbine in the aspect of control. The traditional torque control method using optimal mode gain has been applied in many wind turbines but its response is slower as wind turbine size is larger. In this paper, a torque control method using a nonlinear parameter of rotor speed among nonlinear properties of aerodynamic torque. Simulink model is implemented to obtain the nonlinear parameter of rotor speed and numerical simulations for a 2MW wind turbine are carried out and simulation results for the traditional and proposed torque control methods are compared.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.10
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• pp.575-582
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• 2009

The optimum rotation speed of a desiccant rotor is studied theoretically based on a theoretical solution to the heat and mass transfer processes in the desiccant rotor. A simple correlation equation for the optimum rotation speed is derived to show the effects of various parameters including the thermo-physical properties, the geometric dimension, and the operating condition of the desiccant rotor. The theoretical result is compared with existing experimental data to validate the linearization and simplification included in the solution procedure. Based on the theoretical solution, the effects of major parameters on the optimum rotation speed are studied and the fundamental mechanism of the influences is investigated.

• Current Industrial and Technological Trends in Aerospace
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• v.4 no.1
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• pp.55-60
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• 2006

헬리콥터와 같은 전통적인 수직이착륙항공기는 이착륙시 활주로가 필요로 하지 않는 장점이 있으나 고 속비행 및 고고도 성능에 있어서는 고정익기에 뒤떨어진다. 고효율의 엔진개발에 따라 고정익 항공기가 최 대속도 및 성능이 비약적으로 발전한대 비해, 헬리콥터의 최대속도는 160 ~170 kts (300~315 km/h) 수 준으로 제한되어왔고 장거리 운항에서 필수적인 고고도 운항능력에 있어서도 4km 이상의 고도에서 효율 적인 비행을 수행하는 데에는 한계가 있다. 이를 극복하기 위해 지난 반세기 동안 다양한 신개념 비행체 연 구가 수행되었다. 스마트무인기기술개발사업단에서는 항공선진국의 이러한 연구개발동향 및 그 결과를 종 합하여 미래적 신개념 비행체 대안을 모색하였고, 그 결과 틸트로터 개념을 선정하여 상세설계를 종료한 상태이다. 이러한 경과에 대한 요약과 현재 활발히 진행중인 항공선진국의 미래형 수직이착륙 항공기 개발 기종의 현황, 성능비교를 통해 고속, 고고도 수직이착륙 항공기 개발에 관한 세계적 추세와 본 사업의 연관 성을 고찰해 보았다.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.603-608
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• 2008

A simple equation to find a optimum speed of desiccant rotor is presented in this theoretical study. Usually the determination of optimum speed of desiccant rotor requires tedious and lengthy procedures by solving governing differential equations with many complicated parameters. The determining equation of optimal rotating speed is derivated from governing differential equations with three linearization assumptions, which simplify temperature profile linear along the desiccant rotor depth, psychrometric chart within a proper range, and relative humidity-sorption capacity relation. This study shows that the dominant parameters of optimal rotating speed of desiccant rotor are NTU, flow velocity, desiccant rotor depth, and temperature different between dehumidification and regeneration. The comparison shows the good agreement between complicated calculation results and simple theoretical equation prediction.

• Journal of Ocean Engineering and Technology
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• v.1 no.2
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• pp.83-92
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• 1987

Inorder ot estimate the running life of turbine rotors, fatigue crack propagation low, da/dN = C(${\DELTA}K)^m$, proposed by paris et al. has been widely applied. In this study, fatigue crack propagation rates for 16 samples of 1% Cr-Mo-V rotor steel were measured and statistical characteristics of m and C values in above equation were reviewed. The results are summarized as follows. 1. C and m follow a log-normal distribution and normal distribution, respectively. And the relation of C and shows a strong negative correlation. 2. Fatigue crack propagation equation can be expressed as da/dN=$4.11{\times}10^{-4}({\Delta}K/153.8)^m$, introducing the ralationship C=$C_oK_o^{-m}$. In this case, contribution of $C_o$ distribution to the distribution of log C shows very small compared to degrees of contribution by m.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.805-809
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• 2002

The support bearing requires high DN to raise specific energy efficiency for the state of the art rotating machine with high speed. Especially for the system has a big rotor(670 kgf) with high speed(about one million DNs) such as the pulsed generator, the selection of the bearing and lubrication method are very important. So the study for the critical speed of hollow rotor as well in accordance with high speed rotor and a full analysis are needed for rotor bearing system. This paper describes the analysis for rotor bearing system of pulsed generator compared with experimental data. The bearing and lubrication method are discussed as well with experimental data.