• Journal of the Korean institute of surface engineering
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• v.48 no.5
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• pp.194-198
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• 2015

A blade-abrading method was newly developed for the preparation of clean Mg alloy surface and reported for the first time in detail in this paper. The blade-abrading method includes abrading of the Mg alloy surface with a sharp blade or knife to remove the surface oxide and contaminants on the skin of Mg alloys mechanically, thereby providing very clean surface of Mg alloys. The clean surface prepared by the blade-abrading method in the air was found to be covered with thin and dense air-formed oxide films. Based on the experimental results obtained in this work, it is concluded that the newly developed blade-abrading technique is a very simple and useful pretreatment method which can provide clean and well-defined surface for the following surface treatments.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.140-150
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• 2004

In this study, the effect of relative position of the blade for the fixed vane has been investigated on blade surface heat transfer. The experiments were conducted in a low speed stationary annular cascade, and heat transfer of blade was examined for six positions within a pitch. Turbine test section has one stage composed of sixteen guide vanes and blades. The chord length of the tested blade is 150 mm and the mean tip clearance of the blade having flat tip is about $2.5\%$ of the blade chord. For the detailed mass transfer measurements on the blade surfaces, a naphthalene sublimation technique was used. The inlet flow Reynolds number is fixed to $1.5{\times}10^5$. Complex heat transfer characteristics are observed on the blade surface due to various flow characteristics, such as separation bubble, relaminarization, transition to turbulence and leakage vortices. The distributions of velocity and turbulence intensity change significantly with the relative position due to the blockage effect of the blade. This causes the variation of heat transfer patterns on the blade surface. The results show that the flow near the leading edge get highly disturbed and deflected toward the either side of the blade when the blade leading edge is positioned close to the trailing edge of the vane. Therefore, separation bubble disappears on the pressure side and overall heat transfer on the relaminarization region is increased. But, due to reduced tip gap flow at the upstream region, the effect of leakage flow on the upstream region of the blade surface is weakened. Thus, the heat transfer characteristics significantly change with the blade positions.

• Smart Structures and Systems
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• v.34 no.2
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• pp.129-143
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• 2024

In recent years, with the vigorous development of visual algorithms, a large amount of research has been conducted on blade surface defect detection methods represented by deep learning. Detection methods based on deep learning models must rely on a large and rich dataset. However, the geographical location and working environment of wind turbines makes it difficult to effectively capture images of blade surface defects, which inevitably hinders visual detection. In response to the challenge of collecting a dataset for surface defects that are difficult to obtain, a multi-class blade surface defect generation method based on the StyleGAN3 (Style Generative Adversarial Networks 3) deep learning model and PBGMs (Physics-Based Graphics Models) method has been proposed. Firstly, a small number of real blade surface defect datasets are trained using the adversarial neural network of the StyleGAN3 deep learning model to generate a large number of high-resolution blade surface defect images. Secondly, the generated images are processed through Matting and Resize operations to create defect foreground images. The blade background images produced using PBGM technology are randomly fused, resulting in a diverse and high-resolution blade surface defect dataset with multiple types of backgrounds. Finally, experimental validation has proven that the adoption of this method can generate images with defect characteristics and high resolution, achieving a proportion of over 98.5%. Additionally, utilizing the EISeg annotation method significantly reduces the annotation time to just 1/7 of the time required for traditional methods. These generated images and annotated data of blade surface defects provide robust support for the detection of blade surface defects.

• The KSFM Journal of Fluid Machinery
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• v.10 no.3 s.42
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• pp.9-16
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• 2007

Deterioration of surface of turbomachinery blades occurs in course of time due to many factors and hence reduces the performance of the machine. In this paper, the effects of surface roughness of transonic axial compressor blade on performance are studied considering a reference blade and a shape distorted (optimized) blade. Optimal blade is designed considering sweep and lean. Baldwin-Lomax turbulence model is used for flow field analysis and Cebeci-Smith roughness model is formulated for roughness modeling. It is found that, as the surface roughness increases, adiabatic efficiency, total temperature ratio and total pressure ratio decrease while Mach number increases. Performance deterioration is more severe in case of distorted blade as compared to reference blade.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.4 s.235
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• pp.485-494
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• 2005

For the extensive investigation of local heat/mass transfer on the near-tip surface of turbine blade, experiments were conducted in a low speed stationary annular cascade. The turbine test section has a single stage composed of sixteen guide vanes and blades. The chord length and the height of the tested blade are 150 mm and about 125 mm, respectively. The blade has flat tip geometry and the mean tip clearance is about $2.5{\%}$ of the blade chord. Detailed mass transfer coefficient on the blade near-tip surface was obtained using a naphthalene sublimation technique. The inlet flow Reynolds number based on chord length and incoming flow velocity is changed from $1.0{\times}10^{5}\;to\;2.3{\times}10^{5}.$ Extremely complex heat transfer characteristics are observed on the blade surface due, to complicated flow patterns, such as flow acceleration, laminarization, transition, separation bubble and tip leakage flow. Especially, the suction side surface of the blade has higher heat/mass transfer coefficients and more complex distribution than the pressure side surface, which is related to the leakage flow. For all the tested Reynolds numbers, the heat/mass transfer characteristics on the turbine blade are the similar. The overall averaged $Sh_{c}$ values are proportional to $Re_{c}^{0.5}$ on the stagnation region and the laminar flow region such as the pressure side surface. However, since the flow is fully turbulent in the near-tip region, the heat/mass transfer coefficients are proportional to $Re_{c}^{0.8}.$

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.7 s.250
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• pp.622-629
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• 2006

The shape optimization of blade sweep in a transonic axial compressor rotor of NASA Rotor 37 has been performed using response surface method and the three-dimensional Wavier-Stokes analysis. Two shape variables of the rotor blade, which are used to define the rotor sweep, are introduced to increase the adiabatic efficiency of the compressor. Throughout the optimization, optimal shape having a backward sweep is obtained. Adiabatic efficiency, which is the objective function of the present optimization, is successfully increased. Separation line due to the interference between a shock and surface boundary layer on the blade suction surface is moved downstream for the optimized blade compared to the reference one. The increase in adiabatic efficiency for the optimized blade is caused by suppression of the separation due to a shock on the blade suction surface.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.11
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• pp.41-46
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• 2019

The purpose of this study is to examine and propose a high quality blade manufacturing method by applying ELID grinding technology to machining the tungsten carbide blade edge for MLCC sheet cutting. In this study, experiments are performed according to the abrasive type of grinding wheel, grinding method and grinding direction using the non-stop continuous dressing ELID grinding technology. By comparing and analyzing the chipping phenomena and surface roughness of both the blade grinding surface and the processed surface, a method for machining the tungsten carbide blade for cutting MLCC sheet is proposed. From the analysis of the surface roughness and chipping phenomena, it is confirmed that the use of diamond abrasive is advantageous for the blade machining. In addition, it succeeds in the machining of $6{\mu}m$ fine blade without any chipping, by using the grinding wheel #4000 with the diamond abrasive.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.5 s.236
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• pp.625-632
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• 2005

This paper describes the shape optimization of a stator blade in a single-stage transonic axial compressor. The blade optimization has been performed using response surface method and three-dimensional Navier-Stokes analysis. Two shape variables of the stator blade, which are used to define a stacking line, are introduced to increase an adiabatic efficiency. Data points for response evaluations have been selected by D-optimal design, and linear programming method has been used for an optimization on a response surface. Throughout the shape optimization of a stator blade, the adiabatic efficiency is increased to 5.8 percent compared to that of the reference shape of the stator. The increase of the efficiency is mainly caused by the pressure enhancement in the stator blade. Flow separation on the blade suction surface of the stator is also improved by optimizing the stator blade. It is noted that the optimization of the stator blade is also useful method to increase the adiabatic efficiency in the axial compressor as well as the optimization of a rotor blade, which is widely used now.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.4
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• pp.357-366
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• 2007

The present study investigated local heat/mass transfer characteristics on the surface of the rotating turbine blade with various incidence angles. The experiments are conducted in a low speed annular cascade with a single stage turbine. The blade has a flat tip with the mean tip clearance of 2.5% of the blade chord. A naphthalene sublimation method is used to measure detailed mass transfer coefficient on the blade. At design condition, the inlet Reynolds number is $Re_c=1.5{\times}10^5$ which results in the blade rotation speed of 255.8 rpm. Also, the effect of off-design condition is examined with various incidence angles between $-15^{\circ}$ and $+7{\circ}$. The results indicated that the incidence angle has significant effects on the blade surface heat transfer. In mid-span region, the laminar separation region on the pressure side is reduced and the laminar flow region on the suction side shrinks with increasing incidence angle. Near the tip, the effect of tip leakage flow increases in span wise and axial directions as the incidence angle decreases because the tip leakage flow is formed near the suction side surface. However, the effect of tip leakage flow is reduced with positive incidence angle.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.10
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• pp.110-115
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• 2019

Stationary and rotating blades can be found in a steam turbine generator and the airfoil shapes of these blades can be defined by point data from an aerodynamic design system. The main design process of blades is composed of two steps: first, the blade surface is modeled with the point data; and then, the section data is generated which contains composite curves with line segments and arcs for CAE of the blade. The surface is modeled by a curve-net defined by the point data, which may be extended to obtain the section data to model the blade. This paper presents methods for automating the above-mentioned steps, which have been implemented in the commercial CAD/CAM system, Unigraphics, with API functions written in C-language. Finally, the proposed methods have been applied to model the blade of a steam turbine generator.