• Tribology and Lubricants
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• v.36 no.2
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• pp.105-115
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• 2020

This paper presents a numerical study on the rotordynamic analysis of a dual-spool turbofan engine in the context of blade defect events. The blades of an axial-type aeroengine are typically well aligned during the compressor and turbine stages. However, they are sometimes exposed to damage, partially or entirely, for several operational reasons, such as cracks due to foreign objects, burns from the combustion gas, and corrosion due to oxygen in the air. Herein, we designed a dual-spool rotor using the commercial 3D modeling software CATIA to simulate blade defects in the turbofan engine. We utilized the rotordynamic parameters to create two finite element Euler-Bernoulli beam models connected by means of an inter-rotor bearing. We then applied the unbalanced forces induced by the mass eccentricities of the blades to the following selected scenarios: 1) fully balanced, 2) crack in the low-pressure compressor (LPC) and high pressure compressor (HPC), 3) burn on the high-pressure turbine (HPT) and low pressure compressor, 4) corrosion of the LPC, and 5) corrosion of the HPC. Additionally, we obtained the transient and steady-state responses of the overall rotor nodes using the Runge-Kutta numerical integration method, and employed model reduction techniques such as component mode synthesis to enhance the computational efficiency of the process. The simulation results indicate that the high-vibration status of the rotor commences beyond 10,000 rpm, which is identified as the first critical speed of the lower speed rotor. Moreover, we monitored the unbalanced stages near the inter-rotor bearing, which prominently influences the overall rotordynamic status, and the corrosion of the HPC to prevent further instability. The high-speed range operation (>13,000 rpm) coupled with HPC/HPT blade defects possibly presents a rotor-case contact problem that can lead to catastrophic failure.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.4
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• pp.19-26
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• 2003

In this paper, the result of the conceptual study of a tipjet driven propulsion system is presented. The concept of a tipjet driven propulsion system is to employ tipjet as power source to drive a rotor Because the vehicle is supposed to takeoff and land vertically, a rotor system, which has tipjet nozzles, is adopted to fly like a helicopter. Exhaust gas, which is generated by an engine, Passes through an internal duct system and divided into four blade ducts. The design code is consists of two parts, engine model and internal duct model. Inside a rotating duct, compressible flow is affected by two additional force terms, centrifugal force and coriolis force and they govern the performance in rotary mode, The intention of this paper is to address the issues associated with sizing and optimizing configurations of a tipjet driven propulsion system especially in rotary wing mode.

• Journal of Drive and Control
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• v.21 no.1
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• pp.16-21
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• 2024

The yaw gearbox is a key device in a wind power generator that improves power generation efficiency by rotating hundreds of tons (400 to 600 tons) of nacelle so that the blade reaches 90 degrees in the wind direction. Recently, installation sites have been advancing from land to sea as they have become super-large at (8-12) MW to increase the economic feasibility of wind power generators and utilize excellent wind resources, and the target life of large wind power generators is 25 to 30 years. The yaw gearbox of 6 to 12 sets is installed in a very complex place inside the nacelle on the tower with parallels, and it is important to secure the reliability of the yaw gearbox because if a failure occurs after installation, it costs tens to hundreds of times the price of a new product to restore. In this study, equivalent loads were calculated by analyzing failure mode and field data, accelerated life test conditions were established, and a test device was constructed to perform the accelerated life tests and performance tests to ensure the reliability of the gearbox.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.183.1-183.1
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• 2010

Recently, the increased interest in environmental issues has led to extensive research for development of green energy generation systems. However, only one type of generation system may not be sufficient for stand-alone mode because it cannot cope with the irregularity of weather condition. A hybrid generation system is able to make up for the weakness of each system. In this paper, a stand-alone hybrid wind/PV system is developed that can guarantee the stable energy supply. The system is suitable for power supply under 50W, and a vertical savonius type of blade was designed and applied for the wind generation system.

• Journal of the Korean Society of Costume
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• v.48
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• pp.133-150
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• 1999

In future what kind of costume do we wear\ulcorner We can guess it is in advance through movie. Movie is a comnipresent medium and a mode of expression that reflect a distintive feature of the times like fashion. In many case costume design which belongs to a special era is based on the historic costumes but ostume design for future movie depends on the creativity of costume designer and director. Therefore it is interesting to research how costume designer get his/her design concept for future ccostume in movie how he/hse express his/her design concept through his/her costume and can we convince the design comes true practically in future. In this study I analyze the costume design of masterpieces among SF Film: (Metropolis/1926) (2001: A Space Odyssey/1968) (Star Wars/1977) (Blade Runner/1982) (The 5th Element/1977) Because this study is analyzed not through the original article but just through movie it has some limitation in exact materials or color.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.415-421
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• 2006

The unsteady flow calculation around the proprotor of Smart UAV was conducted. Using the flight scenario of SUAV which composed of hover, transition, and airplane mode, the aerodynamic analysis of proprotor were performed for the variation of collective pitch, rpm, forward speed, and tilt angle. The unsteady compressible Navier-Stokes equations were used for the calculation and the dynamic overset grid technique was applied for the rotating proprotor. The aerodynamic performance of proprotor calculated in this way were validated by comparing with the performance data obtained from the blade element momentum method.

• Journal of Mechanical Science and Technology
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• v.20 no.11
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• pp.1790-1800
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• 2006

Dynamic behavior of flexural-torsional coupled vibration of rotating beams using the Rayleigh-Ritz method with orthogonal polynomials as basis functions is studied. Performance of various orthogonal polynomials is compared to each other in terms of their efficiency and accuracy in determining the required natural frequencies. Orthogonal polynomials and functions studied in the present work are: Legendre, Chebyshev, integrated Legendre, modified Duncan polynomials, the special trigonometric functions used in conjunction with Hermite cubics, and beam characteristic orthogonal polynomials. A total of 5 cases of beam boundary conditions and rotation are studied for their natural frequencies. The obtained natural frequencies and mode shapes are compared to those available in various references and the results for coupled flexural-torsional vibrations are especially compared to both previously available references and with those obtained using NASTRAN finite element package. Among all the examined orthogonal functions, Legendre orthogonal polynomials are the most efficient in overall CPU time, mainly because of ease in performing the integration required for determining the stiffness and mass matrices.

• Journal of Power System Engineering
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• v.14 no.6
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• pp.20-28
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• 2010

The computational flow analysis using LES technique was carried out to investigate the flow characteristics of a RAC chassis consisting of a rear-guider, a stabilizer and a cross-flow fan. The commercial SC/Tetra software was used in this analysis. In view of the results so far achieved, the distribution trends of static pressure and velocity vector of central region except the edges of a CFFan are similar regardless of the number of revolution, and an eccentric vortex exists around the bottom blade of a CFFan. Also, a reverse flow is found in the region between stabilizer and CFFan. Moreover, near the edges of a CFFan, an eccentric vortex is separated to two vortexes. Also these vortexes increase the velocity near a rear-guider, and guide the flow near a rear-guider into stabilizer inlet. Therefore, the reverse flow region is formed in the bottom of a CFFan.

• Bulletin of the Society of Naval Architects of Korea
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• v.18 no.3
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• pp.11-27
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• 1981

This paper is prepared to solve the problem of two-dimensional sinusoidal motion of hydrofoil, which can be related not only to the prediction of unsteady forces acting on the marine propeller blade but to the study of aquatic animal's undulatory mode of propulsion. For convenience's shake, this manuscript can be devided into two parts. In the first part, the lift and moment coefficients have been calculated by the method of conformal transformation. In the other part, the thrust and the hydromechanical efficiency have been evaluated, using Lagally's technique having extended to the unsteady case, they also have been compared with the results, which had been obtained by Lighthill[6] and Wu[7] using Prandtl's acceleration potential.

• Journal of Korean Vacuum Science & Technology
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• v.5 no.1
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• pp.25-32
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• 2001

Baffles have been used in cryopumps to prevent 300 K thermal radiation from reaching freely cryopanels whose temperature must be kept steadily below certain levels(4 K, 20 K or something) depending on the gas to be pumped. There are two conflicting requirements in designing a baffle such that the transmission of particles(gas molecules) should be maximized, while that of the thermal radiation(photons) minimized. The transmission probability of gas molecules or photons through chevron type baffles, influenced by the detailed geometry of blades, the reflection mode, and the absorption property of the surface, was analyzed parametrically. The effects of geometrical discrepancy between the fabricated baffle and the designed one, resulting in unexpected deterioration in the performance of the baffle, were also investigated by taking into account the gaps(or overlaps) between the baffle blades and the asymmetry in the blade arms.