• Journal of the KSME
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• v.54 no.7
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• pp.34-39
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• 2014

소형 풍력발전시스템(Small wind energy conversion systems)은 대형 풍력발전시스템과 더불어 급격한 성장세를 유지하고 있다. 풍력발전시스템은 다양한 기계적 하부시스템(로터, 허브 및 기어박스 등) 및 전기적 하부시스템(컨버터/인버터, 제어기 등)으로 구성되어 있다. 이와 같이 다양한 하부 시스템의 일부분이 파손될 경우, 이는 전체 시스템의 파손 또는 정지를 야기할 수 있고 막대한 경제적 손실을 발생시킬 수 있다. 이 글에서는 대형 풍력발전시스템과 더불어 급격한 성장세를 유지하고 있으며 인간의 생활 공간에 근접하게 설치되는 소형 풍력발전시스템의 기계적 신뢰성 평가 동향에 대하여 소개하고자 한다.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.3
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• pp.29-38
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• 2015

In this study, 3-dimensional URANS simulation was performed to analyze the effect of the nozzle-rotor axial gap spacing of a supersonic impulse turbine on turbine performance. The computations were conducted for four different axial gap cases corresponding to about 6%, 10%, 20% and 30% of the blade height, respectively. The results show a good agreement with previous studies and the turbine efficiency decreases drastically in certain range. It is examined that the turbine performance characteristics could change depending on the influence of leading edge shock to the nozzle outlet. It is also found that the entropy rise distributions along the span differ from each other.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.7
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• pp.542-550
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• 2018

This paper presents design of a bearingless main rotor of SNUF (Seoul National University Flap) blade equipped with active trailing-edge flap to reduce the hub vibratory loads during helicopter forward flight. For that purpose, sectional design of the flexbeam is carried out using the thin-walled composite material rotating beam vibration analysis program (CORBA77_MEMB) in EDISON. Using the multi-body dynamics analysis program, DYMORE, blade dynamic characteristics and those of the loads control are examined using the active trailing-edge flap in terms of the flexbeam sectional design.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.310-315
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• 2003

This paper described that rotating test and fatigue test of a small-scale hingeless hub system with composite rectangular blades. Generally Rotating stability and fatigue test technique is one of Key-technology on test and evaluation for helicopter rotor system Rotating test of hingeless rotor system was achieved by means of rotor vibration characteristic and aeroelastic stability test GSRTS, equipped with hydraulic actuator and 6-component rotating balance was used to test hingeless rotor system especially for an observation of blade motion including flawing, lagging and feathering. Rotating test was done in hover and forward flight condition. Small-scaled blade fatigue test condition was determined by blade load analysis with the reference table of composite materials(S-N curve). Fatigue test bench was developed for the estimation of blade fatigue life, and tested its characteristic.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.575-580
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• 2004

In this work, the effect of composite couplings and mass distributions on hub loads of a hingeless rotor in forward flight is investigated. 1'he hingeless composite rotor is idealized as a laminated thin-walled box-beam. The nonclassical effects such as transverse shear and torsion warping are considered in the structural formulation. The nonlinear differential equations of motion are obtained by applying Hamilton's principle. The blade responses and hub loads are calculated using a finite element formulation both in space and time. The aerodynamic forces acting on the blade are calculated using the quasi-steady strip theory. The theory includes the effects of reversed flow and compressibility The magnitude of elastic couplings obtained by MSC/NASTRAN is compared with the classical pitch-flap($\delta$$_{3}$) coupling. It is observed that the elastic couplings and mass distributions of the blade have a substantial effect on the behavior of $N_{b/}$rev hub loads. About 40% hub loads is reduced by tailoring or redistributing the structural properties of the blade.f the blade.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.8
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• pp.734-740
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• 2004

In this work, the effect of composite couplings and mass distributions on hub loads of a hingeless rotor in forward flight is investigated. The hingeless composite rotor is idealized as a laminated thin-walled box-beam. The nonclassical effects such as transverse shear and torsion warping are considered In the structural formulation. The nonlinear differential equations of motion are obtained by applying Hamilton’s principle. The blade responses and hub loads are calculated using a finite element formulation both in space and time. The aerodynamic forces acting on the blade are calculated using the quasi-steady strip theory. The theory includes the effects of reversed flow and compressibility. The magnitude of elastic couplings obtained by MSC/NASTRAN is compared with the classical pitch-flap($\delta$$_3$) coupling. It Is observed that the elastic couplings and mass distributions of the blade have a substantial effect on the behavior of $N_{b}$ /rev hub loads. About 40％ hub loads is reduced by tailoring or redistributing the structural properties of the blade.e.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.9
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• pp.9-15
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• 2005

This paper describes the test carried out on an experimental study of fuselage drag and stability characteristics of a helicopter configuration and the test techniques developed for the testing and the lessons learned in the Agency for Defense Development Low Speed Wind Tunnel(ADD-LSWT). The main objective of this test is to determine the drag and stability characteristics of helicopter configurations according to the various configuration changes. The fuselage model with a highly modular structure is a representation of 1:8 scale of the external contour of the conceptual design helicopter configuration with rotating main rotor hub including blade stubs capable of rotating up to 500 rpm. The test results are compared with the available similar data and fair to good agreement is obtained.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.3
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• pp.1-8
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• 2013

In this study, we performed three-dimensional CFD analysis to investigate the effect of the rotor blade sweep of a partial admission supersonic turbine on the stage performance and the flow field. The computations are conducted for three different sweep cases, No sweep(NSW), Backward sweep(BSW), and Forward sweep(FSW), using flow analysis program, FLUENT 6.3 Parallel. The results of the BSW model show reduced mass flow rates of tip leakage and increased total-to-static efficiency. The strength of leading edge bow shock was decreased a little with BSW model. And the BSW model also shows a good performance around the hub region compared to other models.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.117-122
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• 2012

A blisk with rotor shroud is usually adopted in LRE turbine to maximize its performance. However it experiences severe thermal load and resulting damage during engine stating and stop. Shroud splitting is devised to relieve thermal stress on the turbine rotor. Structural analysis confirmed the reduction of plastic strain at the blade hub and tip. However, split gap at the rotor shroud entails additional tip leakage and results performance degradation. In order to assess the effect of shroud split on the turbine performance, tests have been performed for various settings of shroud split. For the maximum number of shroud splitting, measured efficiency reduction ratio was 2.65% to the value of original shape rotor.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.5
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• pp.455-463
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• 2012

In this study, we calculate dynamic constrained force of tower top and blade root of a floating offshore wind turbine. The floating offshore wind turbine is multibody system which consists of a floating platform, a tower, a nacelle, and a hub and three blades. All of these parts are regarded as a rigid body with six degree-of-freedom(DOF). The platform and the tower are connected with fixed joint, and the tower, the nacelle, and the hub are successively connected with revolute joint. The hub and three blades are connected with fixed joint. The recursive formulation is adopted for constructing the equations of motion for the floating wind turbine. The non-linear hydrostatic force, the linear hydrodynamic force, the aerodynamic force, the mooring force, and gravitational forces are considered as external forces. The dynamic load at the tower top, rotor shaft, and blade root of the floating wind turbine are simulated in time domain by solving the equations of motion numerically. From the simulation results, the mutual effects of the dynamic response between the each part of the floating wind turbine are discussed and can be used as input data for the structural analysis of the floating offshore wind turbine.