• Steel and Composite Structures
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• v.33 no.3
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• pp.463-472
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• 2019

Initial thermo-elastic and steady state creep deformation of a rotating functionally graded simple blade is studied using first-order shear deformation theory. A variable thickness model for cantilever beam has been considered. The blade geometry and loading are defined as functions of length so that one can define his own blade profile and loading using any arbitrary function. The blade is subjected to a transverse distributed load, an inertia body force due to rotation and a distributed temperature field due to a thermal gradient between the tip and the root. All mechanical and thermal properties except Poisson's ratio are assumed to be longitudinally variable based on the volume fraction of reinforcement. The creep behaviour is modelled by Norton's law. Considering creep strains in stress strain relation, Prandtl-Reuss relations, Norton' law and effective stress relation differential equation in term of effective creep strain is established. This differential equation is solved numerically. By effective creep strain, steady state stresses and deflections are obtained. It is concluded that reinforcement particle size and form of distribution of reinforcement has significant effect on the steady state creep behavior of the blade.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.33-36
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• 2005

A critical issue in the field of the rotor aerodynamics is the treatment of the wake. The wake is of primary importance in determining overall aerodynamic behavior, especially, a wind turbine blade includes the unsteady air loads problem. In this study, the wake generated by blades are depicted by a free wake model to analyse unsteady loading on blade and a new free wake model named Finite Vortex Element(FVE hereafter) is devised in order to include a wake-tower interact ion. In this new free wake model, blade-wake-tower interaction is described by cutting a vortex filament when the filament collides with a tower. This FVE model is compared with a conventional free wake model and verified by a comparison with NREL and SNU wind tunnel model. A comparison with NREL and SNU data shows validity and effectiveness of devised FVE free wake model and an efficient.

• 유체기계공업학회:학술대회논문집
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• 1998.12a
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• pp.91-96
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• 1998

The broadband noise generated aerodynamically from a two-bladed axial flow fan has been measured and compared to the result of a self-noise prediction method. The prediction scheme is based on the experimental data set acquired from a series of aerodynamic and acoustic tests of two and three-dimensional airfoil blade sections. For low blade loading case the comparison showed a reasonably good agreement, but as the loading becomes larger the empirical formula overpredict the sound pressure level at high frequency range. This is probably due to the use of stationary wing data for the prediction of rotating blade case, which will be quite different in their vortex strength at the blade tip.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.1
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• pp.76-81
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• 2001

A structural test of the wind turbine rotor blade is to evaluate the uncertainty of design due to selection of material, design concepts, production processes and so on, and their possible impacts on the structural integrity. In the full-scale static strength test, the measuring parameters are strain and displacements vs. loads, weight and the center of gravity. In order to simulate the aerodynamics load, the three-point loading method is applied. There is slight difference between the measured results and the predicted results for the reference fiber volume fraction of 60% . However, the agreement between the measured results and the predicted results with the actual fiber volume fraction of 52.5% is good. Even though a slightly non-linearity from 80% loading to 100% loading exists, a linear static solution is sufficient for the design purpose due to te small amount of non-linearity. Comparison between measured and predicted strain results at the maximum thickness positions of the blade profile for 0.236R(5.56m), 0.493R(11.59m) and 0.574R(13.43m), under 20%, 40%, 60%, 80% and 100% loadings for the upper part of the blade. The predicted values are in good agreement with the measured values.

• Wind and Structures
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• v.16 no.3
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• pp.241-248
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• 2013

The wind turbine blade is a very important part of the rotor. Extraction of energy from wind depends on the design of blade. In this work, the analysis is done on a blade of length 38.95 m which is designed for V82-1.65 MW horizontal axis wind turbine (supplied by Vestas). The airfoil taken for the blade is NACA 634-221 which is same from root to tip. The analysis of designed blade is done in flap-wise loading. Two shapes of the spar are taken, one of them is of square shape and the other one is combination of square and cross shape. The blade and spar are of the same composite material. The Finite element analysis of designed blade is done in ANSYS. This work is focused on the two segments of blade, root segment and transition segment. Result obtained from ANSYS is compared with the experimental work.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.3
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• pp.297-304
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• 2012

For the assessment of the performance of a wind-turbine blade, a simulated loading test may be required. In this study, the blade behavior was investigated through numerical analysis using a dual-axis loading test, closely simulating the real operation conditions. The blade structure for the 100-kW-class wind-turbine system was modeled using the finite element (FE) program ANSYS. The failure criteria and buckling analysis under dual-axis loading were examined. The failure analysis, including fiber failure and inter-fiber failure, was performed with Puck's failure criterion. As the dual-axis load ratio increases, the relatively increased stress occurs at the trailing edge and skin surface 3300-3600 mm away from the root. Furthermore, it is revealed that increasing the dual-axis load ratio makes the location that is weakest against buckling move toward the root part. Thus, it is seen that the dual-axis load test may be an essential requirement for the verification of blade performance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.11
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• pp.1705-1712
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• 2001

Mechanical component has striation with constant width and SEM can estimate fracture type and loading condition. SEM has benefit to fatigue fracture analysis but striation can be observed according to the kind of material and range of crack growth rate and can't. In this case, it needs AFM that can measure 3-dimensional surface profile with resolution of atomic size. In this study. to find fracture reason of torsion-mounted blade in nuclear plant, we estimate the relation between stress intensity factor range and root mean square roughness in 12% Cr steel by AFM and predict in-service loading condition of turbine blade. failure analysis is performed by finite element method and Goodman diagram on torsion-mounted blade.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.4
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• pp.571-580
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• 2015

In this paper, a computational study was conducted in order to investigate the rotor blade sweep effect on the aerodynamics of a small axial supersonic impulse turbine stage. For this purpose, three-dimensional unsteady RANS simulations have been performed with three different rotor blade sweep angles ($-15^{\circ}$, $0^{\circ}$, $+15^{\circ}$) and the results were compared with each other. Both NTG (No tip gap) and WTG (With tip gap) models were applied to examine the effect on tip leakage flow. As a result of the simulation, the positive sweep model ($+15^{\circ}$) showed better performance in relative flow angle, Mach number distribution, entropy rise, and tip leakage mass flow rate compared with no sweep model. With the blade static pressure distribution result, the positive sweep model showed that hub and tip loading was increased and midspan loading was reduced compared with no sweep model while the negative sweep model ($-15^{\circ}$) showed the opposite result. The positive sweep model also showed a good aerodynamic performance around the hub region compared with other models. Overall, the positive sweep angle enhanced the turbine efficiency.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.585-590
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• 2001

Turbine blade is subject to torsional load by torsion-mount, centrifugal load by rotation of rotor and repeated bending load by steam pressure. Turbine with partially cracked blade has normal working condition at initial repair time but vibratory working condition at middle repair time due to crack growth. Finite element analysis on turbine blade indicates that repeated bending load out of all loads is the most important factor on fatigue strength of turbine blade. Therefore, this study shows root mean square roughness has linear relation with stress intensity factor range in 12% Cr steel and can predict loading condition of fractured turbine blade.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.170-177
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• 2001

Turbine blade is subject to torsional load by torsion-mount, centrifugal load by rotation of rotor and repeated bending load by steam pressure. Turbine with partially cracked blade has normal working condition at initial repair time but vibratory working condition at middle repair time due to crack growth. Finite element analysis on turbine blade indicates that repeated bending load out of all loads is the most important factor on fatigue strength of turbine blade. Therefore, this study shows root mean square roughness has linear relation with stress intensity factor range in 12% Cr steel and can predict loading condition of fractured turbine blade.