• Journal of the Korean Society for Precision Engineering
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• v.18 no.10
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• pp.61-68
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• 2001

Turbine blade in nuclear plant is subject to cyclic bending fatigue by high steam pressure. Especially, fatigue fracture is caused by low stress below yielding stress. Photograph by SEM doesn't have striation but photograph by AFM has striation on the fatigue fractured surface of 12% Cr steel used in turbine blade. Surface roughness $R_q$ has the linear relation with respect to stress intensity factor range ΔK and is increased linearly according to load amplitude $\textit{\Delta}P$. In this study loading condition applied to turbine blade is predicted by the relation between the gradient of $R_q$ to $\textit{\Delta}K$ and load amplitude $\textit{\Delta}P$.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.893-899
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• 2014

X-band antenna has been widely used to effectively transmit the high resolution image data from the observation satellite to the ground station. To achieve above mission, X-band antenna is mainly composed of the 2-axis gimbal system using stepping motors and gears. However, the micro-vibration induced by the stepping motor actuation and the imperfect gear teeth alignment during this on-orbit operation is the main source of image quality degradation. In this paper, X-band antenna combined with a blade gear for micro-vibration isolation was suggested and investigated. The structural safety of the blade gear with low rotational stiffness was confirmed by structure analysis based on the derived torque budget. The isolation performance of the X-band antenna with the blade gear was verified through micro-vibration measurement test using the dedicated micro-vibration measurement device proposed in this study.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.33.2-33.2
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• 2011

The 'NREL Phase VI' model with a 10.06m diameter was tested in the NASA Ames tunnel to make a reference data of the computational models. The test was conducted at the one rotational speed, blade tip speed 38m/s and the Reynolds number of the sectional airfoils in that test was around 1E6. The 1/5 scale down model of the 'NREL Phase VI' model was used in this paper to study the power characteristics in low Reynolds number region, 0.1E6 ~ 0.4E6 which is achievable range for the conventional wind tunnel facilities. The torque generated by the blade was directly measured by using the torque sensor installed in the rotating axis for a given wind speed and rotational speed. The power characteristics below the stall condition, lambda > 4, was presented in this paper. The power coefficient is very low in the condition below the Re. 0.2E6 and rapidly increases as the Re. increases. And it still increases but the variation is not so big in the condition above the Re. 0.3E6. This results shows that to study the performance of the wind turbine blade by using the scaled down model, the Re. should be larger than the 0.3E6.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.6
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• pp.551-559
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• 2009

In this study, flow-induced vibration(FIV) analyses have been conducted for a 3D compressor blade model. Advanced computational analysis system based on computational fluid dynamics(CFD) and computational structural dynamics(CSD) has been developed in order to investigate detailed dynamic responses of designed compressor blades. Fluid domains are modeled using the computational grid system with local grid deforming and remeshing techniques. Reynolds-averaged Navier-Stokes equations with $\kappa-\epsilon$ turbulence model are solved for unsteady flow problems of the rotating compressor model. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of the 3D compressor blade for fluid-structure interaction(FSI) problems. Detailed dynamic responses and instantaneous pressure contours on the blade surfaces considering flow-separation effects are presented to show the multi-physical phenomenon of the rotating compressor blade.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.452-455
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• 2004

The influence of wake flow on a flat-plate blade having different shapes near the hailing edge has been investigated in this paper. Two different shapes near the trailing edge namely the pressure surface cutting (TP) and the suction surface cutting (TS) have been used. The calculation has been performed for two different angles of attack (a =10 and 15 degree) in both the cases. RANS equations have been solved using SST-model as a turbulence closure. Cp and CL values obtained for TS are higher compared to those obtained for TP. Also, the vorticity distribution obtained in case of TS is stronger as compared to that obtained in the case of TP The Karmann Vortex is observed in both the cases but it is more clear in TS case. It is found that in the case of TS, flow separation does not occur upto the trailing edge on both the suction and the pressure sides of the blade while in the case of TP, the flow separateson the pressure surface near the trailing edge of the flat-plate blade.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.519-522
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• 2010

Flow-induced vibration analyses have been conducted for a 3D compressor blade model. Advanced computational analysis system based on computational fluid dynamics(CFD) and computational structural dynamics has been developed in order to investigate detailed dynamic responses of designed compressor blades. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of the 3D compressor blade for fluid-structure interaction problems. Detailed dynamic responses and instantaneous pressure contours on the blade surfaces considering flow-separation effects are presented to show the multi-physical phenomenon of the rotating compressor blade.

• The KSFM Journal of Fluid Machinery
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• v.18 no.1
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• pp.20-28
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• 2015

The pump-turbine impeller is the key component of pumped storage power plant. Current design methods of pump-turbine impeller are private and protected from public viewing. Generally, the design proceeds in two steps: the initial hydraulic design and optimization design to achieve a balanced performance between pump mode and turbine mode. In this study, the 3D inverse design method is used for the initial hydraulic impeller design. However, due to the special demand of high performance in both pump and reverse mode, the design method is insufficient. This study is carried out by modifying the geometrical parameters of the blade which have great influence and need special consideration in obtaining the high performance on the both modes, such as blade shape type at low pressure side (inlet of pump mode, outlet of turbine mode) and the blade lean at blade high pressure side (outlet of pump mode, inlet of turbine mode). The influence of the geometrical parameters on the performance characteristic is evaluated by CFD analysis which presents the efficiency and internal flow results. After these investigations of the geometrical parameters, the criteria of designing pump-turbine impeller blade low and high sides shape is achieved.

• Advances in Energy Research
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• v.6 no.1
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• pp.35-54
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• 2019

A successful blade design must satisfy some criterions which might be in conflict with maximizing annual energy yield for a specified wind speed distribution. These criterions include maximizing power output, more resistance to fatigue loads, reduction of tip deflection, avoid resonance and minimize weight and cost. These criterions can be satisfied by modifying the geometrical parameters of the blade. This study is dedicated to the aerodynamic assessment of a 20 kW horizontal axis wind turbine operating with two possible airfoils; that is $G{\ddot{o}}ttingen$ 413 and NACA 2415 airfoils (the Gottingen airfoil never been used in wind turbines). For this study parameters such as chord (constant, tapered and elliptic), twist angle (constant and linear) are varied and applied to the two airfoils independently in order to determine the most adequate blade configuration that produce the highest annual energy output. A home built numerical code based on the Blade Element Momentum (BEM) method with both Prandtl tip loss correction and Glauert correction, X-Foil and Weibull distribution is developed in Matlab and validated against available numerical and experimental data. The results of the assessment showed that the NACA 2415 airfoil section with elliptic chord and constant twist angle distributions produced the highest annual energy production.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.100-105
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• 2021

This paper proposes the polydimethylsiloxane (PDMS) blade coating method for fabrication of paper-based analytical device (PAD) that is able to monitor the disease diagnosis and progress without special analytical equipment. The mold that has PAD design is easily modified by using laser cutting technique. And the fabricated mold is used for hydrophobic barrier formation by blade coating. We have optimized the stable formation of PDMS hydrophobic barrier as blade coating condition, which is established by analyzing the structure of the PDMS hydrophobic barrier and change of hydrophilic channel size as thickness of the ink and contact time with the chromatography paper. Based on optimal condition, we demonstrate that PAD as biosensor can apply to detect protein, glucose, and metal ion without special analysis equipment.

• Journal of Sensor Science and Technology
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• v.30 no.1
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• pp.51-55
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• 2021

We demonstrated a polymer dielectric with low leakage characteristics through an optimal blade coating method for low-cost and large-scale fabrication of metal-insulator-metal (MIM) capacitors. Cross-linked poly(4-vinylphenol) (C-PVP), which is a typically used polymer dielectric, was coated on a 10 × 10 cm indium-tin-oxide (ITO) deposited glass substrate by changing the deposition temperature (TD) and coating velocity (VC) in the blade coating. During the blade coating, the thickness of the thin c-PVP varied depending on TD and VC owing to the 'Landau-Levich (LL) regime'. The c-PVP-dielectric-based MIM capacitor fabricated in this study showed the lowest leakage current characteristics (10-6 A/㎠ at 1.2 MV/㎠, annealing at 200 ℃) and uniform electrical characteristics when TD was 30 ℃ and VC was 5 mm/s. In addition, at TD = 30 ℃, stable leakage characteristics were confirmed when a different electric field was applied. These results are expected to positively contribute to applications with next-generation electronic devices.