• Title/Summary/Keyword: Blade Parameters

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Cost-efficient Fabrication of Colorless and Optically Transparent Polyimide Film for Flexible Displays (비용 효율적인 유연 디스플레이용 무색 투명 폴리이미드 필름 제작)

  • Dawoon Jo;Ji-Ho Kim;Chung-Seog Oh
    • Journal of the Semiconductor & Display Technology
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    • v.22 no.1
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    • pp.33-38
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    • 2023
  • As the demand for large flexible displays such as tablet computers continues to rise, there is an increasing need for cost-efficient colorless and optically transparent polyimide film that can meet the desired performance, particularly optical transmittance. In this study, we investigated a detailed procedure for achieving optimal optical transmittance using two different combinations of monomers: 6FDA+BAPB and 6FDA+BPA+TFDB. We employed a design of experiment method to systematically synthesize polymers, allowing for the optimization of optical transmittance. In addition, we were able to achieve uniform thickness in the films by using a doctor blade. By comparing the price and optical transmittance of four different monomer combinations, we obtained fundamental data on the production of polyimide films that can be customized to meet the specific price and performance requirements of manufacturers. This approach enables users to select the most suitable polyimide film based on their desired price and performance parameters while achieving optimal optical transmittance.

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The development and the magnetic properties of sheet hexaferrite magnets (Hexaferrite 쉬트자석의 개발과 자기적 성질에 관한 연구)

  • 김철성;박승일;오영제
    • Journal of the Korean Magnetics Society
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    • v.5 no.4
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    • pp.281-286
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    • 1995
  • In order to study the effect of additives $SiO_{2}$ on the magnetic properties of hexaferrite sheet magnet, we used X-ray diffractometer, Mossbauer spectrometer, and VSM magnetometer. We have prepared $Ba_{0.25}Sr_{0.75}Fe_{12}O_{19}$ green sheets by the Dr. Blade method. Most of samples have a magnetoplurnbite crystal structure of typical M-type hexaferrite. The lattice parameters are found not to be affected by the addition of $SiO_{2}$. ${\alpha}-Fe_{2}O_{3}$ phase develops above $SiO_{2}$ 2.0 wt.%. Isomer shifts indicate that the valence of Fe ions is trivalent. Curie temperatures decrease slightly with increasing $SiO_{2}$ concentrations. It means that the $Si^{4+}$ subsitution for 12k-site $Fe^{3+}$ has an effect on the superexchange interactions Fe-O-Fe, which change the distance and the angle between cations and anions. It was suggested that ${\alpha}-Fe_{2}O_{3}$ phase results from the excessive Fe produced by subsituting $Si^{4+}$ for $Fe^{3+}$. Based upon the results of $Ba_{0.25}Sr_{0.75}Fe_{12}O_{19}$ added with $SiO_{2}$, we concluded that $H_{c}$, $M_{s}$ and $M_{r}$ depend more strongly on the microstructure chracteristics than on the cation substitution.

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Development of a new lifetime prediction method for gas turbine core parts by digital image analysis of precipitates morphology (석출물 형상의 디지털 이미지 분석에 의한 가스터빈 핵심부품의 새로운 수명평가기술 개발)

  • Chang, Moon Soo;An, Seong Uk
    • Analytical Science and Technology
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    • v.21 no.2
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    • pp.148-157
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    • 2008
  • To describe the lifetime prediction of gas turbine core parts serviced in some ten thousands rpms at over $1,000^{\circ}C$, the Larson-Miller Creep Curves, which are formed by creep rupture tests as the destructive experiment with parameters of stress and temperature, are used often, but not exact and reliable with errors of over some tens. On the other hand, this study shows a non-destructive method with increased accuracy and reliability. The SEM and TEM specimens were extracted by replica after polishing the local airfoil and root surfaces of the first stage scraped blade (bucket), serviced for 18,000 hours at $1,280^{\circ}C$ in Gas Turbines of Boryong. The observed TEM and SEM precipitates were digitalized for calculation of the average size. Here we could find the precipitate size grown from $0.45{\mu}m$ to $0.6{\mu}m$ during service and the grown precipitates to be still sound. From these results we could conclude that the scraped balde can be used for ten thous and hours additionally and for twenty thousand hours by additional heat treatments on the scraped blade.

Development of KD- Propeller Series using a New Blade Section (새로운 날개단면을 이용한 KD-프로펠러 씨리즈 개발)

  • J.T. Lee;M.C. Kim;J.W. Ahn;H.C. Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.28 no.2
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    • pp.52-68
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    • 1991
  • A new propeller series is developed using the newly developed blade section(KH18 section) which behaves better cavitation characteristics and higher lift-drag ratio at wide range of angle-of-attack. The pitch and camber distributions are disigned in order to have the same radial and chordwise loading distribution with the selected circumferentially averaged wake input. Since the geometries of the series propeller, such as chord length, thickness, skew and rate distribations, are selected by regression of the recent full scale propeller geometric data, the performance prediction of a propeller at preliminary design stage can be mure realistic. Number of blades of the series propellers is 4 and the expanded blade area ratios are 0.3, 0.45, 0.6 and 0.75. Mean pitch ratios are selected as 0.5, 0.65, 0.8, 0.75 and 1.1 for each expanded area ratio. The new propeller series is composed of 20 propellers and is named as KD(KRISO-DAEWOO) propeller series. Propeller open water tests are performed at the experimental towing tank, and the cavitation observation tests and fluctuating pressure measurements are carried out at the cavitation tunnel of KRISO. $B_{P}-\delta$ curves, which can be used to select the optimum propeller diameter at the preliminary design stage, are derived from a regression analysis of the propeller often water test results. The KD-cavitation chart is derived from the cavitation observation test results by choosing the local maximum lift coefficient and the local cavitation number as parameters. The caviy extent of a propeller can be predicted more accurately by using the KD-cavitation chart at a preliminary design stage, since it is derived from the results of the cavitation observation tests in the selected ship's wake, whereas the existing cavitation charts, such as the Burrill's cavitation chart, are derived from the test results in uniform flow.

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Fatigue life prediction based on Bayesian approach to incorporate field data into probability model

  • An, Dawn;Choi, Joo-Ho;Kim, Nam H.;Pattabhiraman, Sriram
    • Structural Engineering and Mechanics
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    • v.37 no.4
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    • pp.427-442
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    • 2011
  • In fatigue life design of mechanical components, uncertainties arising from materials and manufacturing processes should be taken into account for ensuring reliability. A common practice is to apply a safety factor in conjunction with a physics model for evaluating the lifecycle, which most likely relies on the designer's experience. Due to conservative design, predictions are often in disagreement with field observations, which makes it difficult to schedule maintenance. In this paper, the Bayesian technique, which incorporates the field failure data into prior knowledge, is used to obtain a more dependable prediction of fatigue life. The effects of prior knowledge, noise in data, and bias in measurements on the distribution of fatigue life are discussed in detail. By assuming a distribution type of fatigue life, its parameters are identified first, followed by estimating the distribution of fatigue life, which represents the degree of belief of the fatigue life conditional to the observed data. As more data are provided, the values will be updated to reduce the credible interval. The results can be used in various needs such as a risk analysis, reliability based design optimization, maintenance scheduling, or validation of reliability analysis codes. In order to obtain the posterior distribution, the Markov Chain Monte Carlo technique is employed, which is a modern statistical computational method which effectively draws the samples of the given distribution. Field data of turbine components are exploited to illustrate our approach, which counts as a regular inspection of the number of failed blades in a turbine disk.

Numerical Analyses and Wind Tunnel Tests of a Propeller for the MAV Propulsion (초소형 무인기 추진용 프로펠러의 전산해석 및 풍동시험)

  • Cho, Lee-Sang;Lee, Sea-Wook;Cho, Jin-Soo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.10
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    • pp.955-965
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    • 2010
  • The MH-75 propeller for the MAV propulsion is designed using a free vortex design method which considers design parameters such as the hub-tip ratio, the twist angle distribution, the maximum camber location and the chord length of the propeller blade. Aerodynamic characteristics of the MH-75 propeller are predicted by changing the flight speed using the frequency domain panel method. And, the thrust characteristics of the MH-75 propeller are measured using the balance system of the subsonic wind tunnel for the validation of numerical results. The performance characteristics of the MH-75 propeller satisfied with design requirements. Numerical results of the MH-75, which are predicted by the frequency domain panel method, are more agree with experimental results compare with XFOIL.

Development of Multiphase Pump for Offshore Plant (해양플랜트용 다상유동 펌프 개발)

  • Kim, Joonhyung;Choi, Youngseok;Yoon, Joonyong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.2
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    • pp.183-190
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    • 2014
  • A multiphase pump was developed in this study. The optimum multiphase pump design was arrived at, and the interactions among the different geometric configurations were explained by applying numerical analysis and the DOE (design of experiments) method. First, we designed the base model to meet the specifications. Then, we defined the design parameters related to the meridional plane and the blade angle. Each design parameter was used for generating experiment sets, and numerical analyses were performed on these sets. Finally, the optimized design was selected based on the results of the DOE analysis. The numerical optimization resulted in the optimum model having higher efficiency than the base model. In addition, performance degradation due to changes in the GVF (gas volume fraction) is discussed.

Fabrication of Transparent Electrode Film for Organic Photovoltaic using Ag grid and Conductive Polymer (Ag grid와 전도성 고분자를 이용한 인쇄기반 OPV용 투명전극 형성)

  • Yu, Jongsu;Kim, Jungsu;Yoon, Sungman;Kim, Dongsoo;Kim, Dojin;Jo, Jeongdai
    • 한국신재생에너지학회:학술대회논문집
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    • 2011.05a
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    • pp.116.1-116.1
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    • 2011
  • Materials with a combination of high electrical conductivity and optical transparency are important components of many electronic and optoelectronic devices such as liquid crystal displays, solar cells, and light emitting diodes. In this study, to fabricate a low-resistance and high optical transparent electrode film for organic photovoltaic, the following steps were performed: the design and manufacture of an electroforming stamp mold, the fabrication of thermal roll imprinted (TRI) poly-carbonate (PC) patterned films, the manufacture of high-conductivity and low-resistance Ag paste which was filled into patterned PC film using a doctor blade process and then coated with a thin film layer of conductive polymer by a spin coating process. As a result of these imprinting processes the PC films obtained a line width of $10{\pm}0.5{\mu}m$, a channel length of $500{\pm}2{\mu}m$, and a pattern depth of $7.34{\pm}0.5{\mu}m$. After the Ag paste was used to fill part of the patterned film with conductive polymer coating, the following parameters were obtained: a sheet resistance of $9.65{\Omega}$/sq, optical transparency values were 83.69 % at a wavelength of 550 nm.

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Flow Evaluation and Hemolysis Analysis of BVAD Centrifugal Blood Pump by Computational Fluids Dynamics

  • Bumrungpetch, Jeerasit;Tan, Andy Chit;Liu, Shu-Hong;Luo, Xian-Wu;Wu, Qing-Yu;Yuan, Jian-Ping;Zhang, Ming-Kui
    • International Journal of Fluid Machinery and Systems
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    • v.7 no.1
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    • pp.34-41
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    • 2014
  • Computational fluid dynamics (CFD) and particle image velocimetry (PIV) are commonly used techniques to evaluate the flow characteristics in the development stage of blood pumps. CFD technique allows rapid change to pump parameters to optimize the pump performance without having to construct a costly prototype model. These techniques are used in the construction of a bi-ventricular assist device (BVAD) which combines the functions of LVAD and RVAD in a compact unit. The BVAD construction consists of two separate chambers with similar impellers, volutes, inlet and output sections. To achieve the required flow characteristics of an average flow rate of 5 l/min and different pressure heads (left - 100mmHg and right - 20mmHg), the impellers were set at different rotating speeds. From the CFD results, a six-blade impeller design was adopted for the development of the BVAD. It was also observed that the fluid can flow smoothly through the pump with minimum shear stress and area of stagnation which are related to haemolysis and thrombosis. Based on the compatible Reynolds number the flow through the model was calculated for the left and the right pumps. As it was not possible to have both the left and right chambers in the experimental model, the left and right pumps were tested separately.

Experimental Study on Efficiency of Floating Vertical Axis Wind Turbine with Variable-Pitch (부유식 가변 피치형 수직축 풍력발전기의 발전효율에 관한 실험 연구)

  • Kim, Jae-Heui;Jo, Hyo-Jae;Hwang, Jae-Hyuk;Jang, Min-Suk;Lee, Byeong-Seong
    • Journal of Ocean Engineering and Technology
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    • v.32 no.3
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    • pp.202-207
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    • 2018
  • This paper presents the efficiency of a floating vertical axis wind turbine with variable-pitch. A model was designed to use the lift force and drag force for blades with various pitch angles. The blade's pitch angle is controlled by the stopper. To validate the efficiency of the wind turbine discussed in this paper, a model test was carried out through a single model efficiency experiment and wave tank experiment. The parameters of the single model efficiency experiment were the wind speed, electronic load, and pitch angle. The wave tank experiment was performed using the most efficient pitch angle from the results of the single model efficiency experiment. According to the results of the wave tank experiment, the surge and pitch motion of a structure slightly affect the efficiency of a wind turbine, but the heave motion has a large effect because the heights of the wind turbine and wind generator are almost the same.