• Title/Summary/Keyword: Off-design performance

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Baffle design and test for wide-field off-axis telescopes

  • Kim, Sanghyuk;Pak, Soojong;Chang, Seunghyuk;Kim, Geon Hee;Yang, Sun Choel;Lee, Sang Yong;Huh, Myung Sang;Im, Myungshin
    • The Bulletin of The Korean Astronomical Society
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    • v.38 no.1
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    • pp.72.2-72.2
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    • 2013
  • An off-axis telescope has several advantages in optical performance comparing with a conventional on-axis telescope. However, in general, an off-axis telescope has a narrow field of view due to the linear astigmatism caused by the asymmetric structure. It was shown in the previous work that the linear astigmatism can be eliminated by properly configuring parameters in a confocal off-axis reflector system. Furthermore, the third order aberrations of a confocal off-axis telescope can be minimized by optimizing the shape of the mirrors. Despite many advantages, the confocal off-axis telescopes have been evaded because of difficulties of off-axis mirror fabrication, alignment process and unaccustomed off-axis baffle design. The baffle for the off-axis telescope should be designed considering that the effects of stray lights are different because of the asymmetry of off-axis system. In this poster, the design, manufacturing, and test for the baffle and housing of an off-axis telescope are presented.

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Numerical Prediction of Performance and Acoustic Instability in KSR-III Liquid Rocket Engine (KSR-III 액체 로켓엔진의 성능예측과 음향 불안정성 해석)

  • 문윤완;손채훈;김영목
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2001.04a
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    • pp.17-20
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    • 2001
  • Combustion characteristics of KSR-III liquid rocket engine are investigated numerically in the standpoints of engine performance and acoustic instability. In the present calculation, engine performance for design and off-design conditions is estimated effectively with reasonable error. Numerical results of acoustic instability show that engine operation for the design condition has sufficient stability margin, but for a certain off-design condition, acoustic instability can be triggered by artificial pressure perturbation. The present results are in a good agreement with the available experimental results and can be adopted for the prediction of engine performance and stability, depending on the specific operating condition.

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Sensitivity Analysis on Off-Design Performance of Centrifugal Compressor Due to the Parameters of Two-zone Model and TEIS Model (두영역 모델과 직렬두요소 모델의 변수에 의한 원심 압축기 탈설계 성능의 민감도 분석)

  • Yoon, Sung-Ho;Baek, Je-Hyun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.6
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    • pp.834-844
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    • 2000
  • In this study, an off-design performance analysis procedure is developed based on Two-zone model and TEIS model. In Two-zone model, there are both primary zone and secondary zone for an isentropic core flow and an average of all non-isentropic streamtubes respectively. The level of the core flow diffusion in an impeller is calculated by using TEIS model which regards the impeller as two successive rotating elements in series. At impeller exit, the mixing process occurs with an increase in entropy, that is to say, a decrease in total pressure. In loss models including Two-zone and TEIS model, some empirical parameters have a great influence on overall performance curve. So these parameters' influences on the overall performance curve are investigated and compared with experimental data.

Performance Prediction of Centrifugal Compressors (원심 압축기의 성능 예측)

  • 오형우;정명균
    • Transactions of the Korean Society of Automotive Engineers
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    • v.5 no.2
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    • pp.136-148
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    • 1997
  • The present study has been carried out to develop a computational procedure for the analysis of the off-design performance in centrifugal compressors with vaneless diffusers by integrating empirical loss models and analytical equations. Losses in centrifugal compressors stem from a number of sources and their exact calculation is not yet possible. This study investigates several modeling schemes and shows that a fairly good prediction can be achieved by a proper selection of the most important flow parameters resulting form a meanline one-dimensional analysis. The performance maps for compressors are calculated and compared with measured performance maps. The off-design performance characteristics in terms of the pressure ratio vs. mass flow produced have generally correct forms. However, no universal means have been found to predict accurately the onset of surge. The prediction method developed through this study can serve as a tool to ensure good matching between parts and it can assist the understanding of the operational characteristics of general purpose centrifugal compressors.

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Integrated Optimal Design for Suspension to Improve Load/unload Performance (로드/언로드 성능향상을 위한 서스팬션의 구조최적화)

  • Kim Ki-Hoon;Son Suk-Ho;Park Kyoung-Su;Yoon Sang-Joon;Park No-Cheol;Yang Hyun-Seok;Choi Dong-Hoon;Park Young-pil
    • 정보저장시스템학회:학술대회논문집
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    • 2005.10a
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    • pp.204-209
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    • 2005
  • Load/Unload(L/UL) technology includes the benefits, that is, increased areal density, reduced power consumption and improved shock resistance contrary to contact-start-stop(CSS). It has been widely used in portable hard disk drive and will become the key technology far developing the small form factor hard disk drive. The main object of L/UL is no slider-disk contact or no media damage. For realizing those, we must consider many design parameters in L/UL system. In this paper, we focus on lift-off force. The 'lift-off' force, defined as the minimum air bearing force, is another very important indicator of unloading performance. A large amplitude of lift-off force increases the ramp force, the unloading time, the slider oscillation and contact-possibility. To minimize 'lift-off' force we optimizes the slider and suspension using the integrated optimization frame, which automatically integrates the analysis with the optimization and effectively implements the repetitive works between them. In particular, this study is carried out the optimal design considering the process of modes tracking through the entire optimization processes. As a result, we yield the equation which can easily find a lift-off force and structural optimization for suspension.

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Design of a Steering Control Mechanism for a Skateboard on Off-road Driving (비포장 노면 주행을 위한 스케이트보드의 조향제어기구 설계)

  • Sim Hansub
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.14 no.3
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    • pp.110-115
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    • 2005
  • Driving performance is affected by a steering mechanism and characteristics of the ground at off-road skateboarding. In order to drive on off-road, it is necessary off-road wheel and high performance steering mechanism to adapt on various configuration of the ground. In this paper, design factors are studied to affect to steering radius such as inclination angle of a king-bolt, distance of a wheel axle, and rolling angle of a deck plate. A steering system is adhered to inclination face of the deck plate. And, inclination angle is existed between the king-bolt and the flat face of the deck plate. Therefore, the wheel axle of the steering system can be steered by control of the rolling angle of the deck plate.

A Passive Multiple Trailer System with Off-axle Hitching

  • Lee, Jae-Hyoung;Woojin Chung;Kim, Munsnng;Song, Jae-Bok
    • International Journal of Control, Automation, and Systems
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    • v.2 no.3
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    • pp.289-297
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    • 2004
  • This paper deals with the design and control of passive multiple trailer systems for practical applications. Due to the cost and complexity of the trailer mechanism, passive systems are preferred to active systems in this research. The design and control objective is to minimize the trajectory tracking errors occurring in passive multiple trailers. Three sorts of passive trailer systems, off-hooked, direct-hooked, and three-point, are discussed in this paper. Trajectory tracking performance and stability issues under constant curvature reference trajectories are investigated for these three types. As well, various simulations and experiments have been performed for each type. It is shown that the proposed off-hooked trailer system produces a tracking performance that is superior to the others.

Steady-state Performance Simulation and Operation Diagnosis of a 2-spool Separate Flow Type Turbofan Engine (2스풀 분리 배기 방식 엔진의 정상상태 성능모사 및 작동 진단)

  • Choo, KyoSeung;Sung, Hong-Gye
    • Journal of Aerospace System Engineering
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    • v.13 no.1
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    • pp.38-46
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    • 2019
  • There is a growing interest in engine diagnostic technology for gas turbine engines. An engine simulation program, precisely simulating the engine performance, is required in order to apply it to the engine diagnosis technology for engine health monitoring. In particular, the simulation program can predict not only design point performance but also off-design point and partial load performance in accurate. So the engine simulation program for the 2-spool separate flow type turbofan engine was developed and the JT9D-7R4G engine of PW(Pratt & Whitney) was analyzed. The steady-sate performance analysis is conducted at both design and off-design points in flight path and the differences between analysis results of takeoff and cruise conditions are compared. The effect of Reynold's correction method was analyzed as a scaling method of the engine component performance. The simulation results was compared with NPSS.

The influence of guide vane opening on the internal flow of a francis turbine

  • Wei, Qingsheng;Choi, Young-Do
    • Journal of Advanced Marine Engineering and Technology
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    • v.37 no.3
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    • pp.274-281
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    • 2013
  • The variable demand on the energy market requires a great flexibility in operating hydro turbines. However, Francis turbine operated at off-design conditions poses technical challenges related to large unsteady forces given by residual swirl and angular momentum. In order to improve the performance of a Francis turbine, the paper presents a numerical investigation of the 3D flow in the turbine at off-design conditions and discusses the influence of variable guide vane openings on the internal flow of a Francis turbine with the help of computational fluid dynamics. First, the internal flow characteristics of Francis turbine operated by varied guide vane angle at off design condition are computed and the optimal guide vane angle is obtained. Secondly, the Francis turbine is operated with guide vane number varies at the optimal guide vane angle. Finally, pressure contours and velocity distributions in the distributor are discussed and compared.

Subsonic Performance Analysis of Air Turbo-Ramjet Engine (에어터보램제트 엔진의 아음속 성능 해석)

  • Lee Yangji;Yang Sooseok;Yang Inyoung
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.10a
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    • pp.62-67
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    • 2004
  • This paper investigates the off-design performance of methane-fueled air turbo ramjet(ATR) engine in subsonic flight speed range. The ATR engine was modeled and simulated numerically. Each component was modeled to enable their off-design calculation. Compressor operating point was determined by flow matching with nozzle, and turbine by work matching. The ATR engine exhibited quite different off-design behavior compared to the conventional gas turbine engine.

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