• 대한기계학회논문집B
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• 제35권6호
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• pp.641-648
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• 2011

고온 발전용 연료전지인 MCFC의 연료극에서 방출되는 미반응 가스를 촉매연소의 열원으로 사용하고, 촉매연소 반응에 의해 발생한 열을 개질 반응에 필요한 공급열로 이용하는 통합형 촉매연소-개질 반응기에 있어서 MCFC의 운전 조건 변경에 따른 반응기의 열적 거동과 반응 특성을 실험적으로 연구하였다. 특히, 연료극에서 연료 이용률을 변동될 때 슬립가스의 조성이 바뀌는 것을 고려하여 촉매연소측에 공급해줄 혼합가스의 조성을 실험조건으로 설정하였다. 또한 개질측에서는 S/C(수증기/탄소)의 비를 운전조건의 변동 조건으로 설정하였다. 실험적으로 얻어진 데이터는 보다 현실적인 통합형 촉매연소-개질반응기를 설계하고 제작하는데 필요한 기본 자료로 활용될 수 있을 것이다.

• International Journal of Fluid Machinery and Systems
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• 제2권4호
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• pp.286-294
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• 2009

Hydroelectric power plants are known for their ability to cover variations of the consumption in electrical power networks. In order to follow this changing demand, hydraulic machines are subject to off-design operation. In that case, the swirling flow leaving the runner of a Francis turbine may act under given conditions as an excitation source for the whole hydraulic system. In high load operating conditions, vortex rope behaves as an internal energy source which leads to the self excitation of the system. The aim of this paper is to identify the influence of the full load excitation source location with respect to the eigenmodes shapes on the system stability. For this, a new eigenanalysis tool, based on eigenvalues and eigenvectors computation of the nonlinear set of differential equations in SIMSEN, has been developed. First the modal analysis method and linearization of the set of the nonlinear differential equations are fully described. Then, nonlinear hydro-acoustic models of hydraulic components based on electrical equivalent schemes are presented and linearized. Finally, a hydro-acoustic SIMSEN model of a simple hydraulic power plant, is used to apply the modal analysis and to show the influence of the turbine location on system stability. Through this case study, it brings out that modeling of the pipe viscoelastic damping is decisive to find out stability limits and unstable eigenfrequencies.

• 한국항해항만학회지
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• 제36권5호
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• pp.357-361
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• 2012

풍향풍속계는 실시간으로 풍향과 풍속을 측정하는 기상관측기구로서 바람의 영향을 많이 받는 항만, 조선소, 해상구조물, 또는 건설현장에서 사용되는 크레인에 장착되어 작업가능 여부를 알리거나 전도 사고를 예방하기 위한 안전시스템과 연동되어 사용된다. 로드 셀형 풍향풍속계는 로드 셀을 이용하여 풍향 및 풍속을 측정하기 위한 것으로 4개의 날개에 연결된 로드 셀의 하중 합을 이용하여 풍속을, 하중 비를 이용하여 풍향을 측정한다. 본 연구에서는 하중 비와 풍향사이의 관계식을 도출하기 위하여 각각 이론적 접근, 해석적 접근, 실험적 접근 세 가지를 병행하여 결과를 비교 분석한다. 풍향을 설계변수로 설정하며, 해석 시 $0^{\circ}$에서 $90^{\circ}$까지 $11.25^{\circ}$ 간격으로 9가지 풍향조건을, 실험 시 $10^{\circ}$ 간격으로 10가지 풍향조건을 설정한다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.187-194
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• 2008

Because the types and severities of most engine faults are various and complex, it is not easy that the conventional model based fault detection approach like the GPA(Gas Path Analysis) method can monitor all engine fault conditions. Therefore this study proposed newly a diagnostic algorithm for isolating and diagnosing effectively the faulted components of the smart UAV propulsion system, which has been developed by KARI(Korea Aerospace Research Institute), using the fuzzy logic and the neural network algorithms. A precise performance model should be needed to perform the model-based diagnostics. The based engine performance model was developed using SIMULINK. For the work and mass flow matching between components of the steady-state simulation, the state-flow library was applied. The proposed steady-state performance model can simulate off-design point performance at various flight conditions and part loads, and in order to evaluate the steady-state performance model their simulation results were compared with manufacturer's performance deck data. According to comparison results, it was confirm that the steady-state model well agreed with the deck data within 3% in all flight envelop. The diagnosis procedure of the proposed diagnostic system has the following steps. Firstly after obtaining database of fault patterns through performance simulation, then secondly the diagnostic system was trained by the FFBP networks. Thirdly after analyzing the trend of the measuring parameters due to fault patterns, then fourthly faulted components were isolated using the fuzzy logic. Finally magnitudes of the detected faults were obtained by the trained neural networks. Because the detected faults have almost same as degradation values of the implanted fault pattern, it was confirmed that the proposed diagnostic system can detect well the engine faults.

• Wind and Structures
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• 제34권6호
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• pp.483-497
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• 2022

Three-dimensional (3D) computational fluid dynamics (CFD) analysis of flow around a hipped-roof building representative of UK inland conditions are conducted. Unsteady simulations are performed using three variations of the k-ϵ RANS turbulence model namely, the Standard, Realizable, and RNG models, and their predictive capability is measured against current European building standards. External pressure coefficients and wind loading are found through the BS 6399-2:1997 standard (obsolete) and the current European standards (BS EN 1991-1-4:2005 and A1:20101). The current European standard provides a more conservative wind loading estimate compared to its predecessor and the k-ϵ RNG model falls within 15% of the value predicted by the current standard. Surface shear stream-traces and Q-criterion were used to analyze the flow physics for each model. The RNG model predicts immediate flow separation leading to the creation of vortical structures on the hipped-roof along with a larger separation region. It is observed that the Realizable model predicts the side vortex to be a result of both the horseshoe vortex and the flow deflected off it. These model-specific aerodynamic features present the most disparity between building standards at leeward roof locations. Finally, pedestrian comfort and safety criteria are studied where the k-ϵ Standard model predicts the most ideal pedestrian conditions and the Realizable model yields the most conservative levels.

• 한국전산구조공학회논문집
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• 제29권5호
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• pp.447-454
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• 2016

최근에 각광받고 있는 3D BIM기반 철근 물량 산출 현황을 살펴보면 상용 BIM 도구들이 철근 모델링 기능을 제공하지만 그 기능을 이용해서 철근을 모델링하려고 하면 방대한 양의 모델링 시간이 소요가 되어 현재 실용적으로 사용할 수 있는 BIM 소프트웨어는 없다. 본 연구에서는 BIM 기반 설계 현업에서 실용적인 철근 물량 산출 프로세스를 정리 및 제시하고, 초기설계단계의 단면 정보가 없는 상태에서 기존의 2D방식에 비하여 보다 정확하게 기동, 보, 슬래브, 벽체의 철근 단면 정보를 자동으로 배근해주는 프로그램인 Rebar Automatic Arrangement Program(이하 RAAP)을 개발하였다. 본 연구 결과는 건설프로젝트의 초기 설계단계에서 설계 진행상 구조 부재 단면 설계가 완료되지 않은 상태의 골조 물량 산출 시 적은 노력으로 기존의 2D기반 방식보다 신뢰성을 향상시킨 물량을 산출할 수 있는 기술로 발전시키는데 의미가 있으며, 합리적인 초기 설계단계의 물량 산출 프로그램을 구축할 수 있는 기초 연구로서 활용될 수 있을 것으로 기대된다.

• 한국추진공학회지
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• 제13권3호
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• pp.20-26
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• 2009

30톤급 액체로켓엔진용 터보펌프에 대하여 실매질을 사용하여 성능시험이 이루어졌다. 산화제펌프와 연료펌프에는 각각 액체산소, 케로신의 실매질을 사용하고 터빈에는 고압의 상온 수소가스가 사용되었다. 터보펌프는 설계점과 탈설계점의 전 영역에서 안정적으로 작동하였고 요구되는 성능 조건을 만족 시켰으며 이로써 엔진 서브시스템 수준의 터보펌프 개발이 성능 측면에서 검증되었다고 볼 수 있다. 본 논문에서는 단일 운전으로 세 운용점에서 총 75초간 작동된 경우의 시험결과를 소개하였다. 펌프와 터빈의 성능 특성 관점에서 터보펌프 조립체의 실매질 성능시험 결과와 터보펌프 구성품의 상사 성능시험 결과가 양호하게 일치하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제40권3호
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• pp.217-222
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• 2016

본 논문은 수정된 Gram-Schmidt와 결합한 Potter 또는 Carlson 알고리즘을 가지는 제곱근 확장 칼만 필터에 의한 영구자석 동기전동기의 센서리스 속도 제어에 관한 연구이다. 일반적으로 반올림 오차에 기인하는 칼만 필터의 민감도는 잘 알려진 문제이다. 제곱근 개념과 칼만 필터의 결합은 수치적 성능을 향상할 수 있고 발산과 같은 불안전한 문제를 풀 수 있다. 본 논문에서는 제곱근 확장 칼만 필터의 구현을 위한 설계와 분석을 수행하였다. 설계된 제곱근 확장 칼만 필터의 추정 성능을 입증하기 위해, 고속, 저속, 역 회전, 파라미터 변동, 부하 변동 실험 등 여러 운전 조건 아래에서 실험 결과들을 분석하였다. 또한, 프로그램 코드 크기 및 연산 시간을 비교하였다. 실험적 결과들은 제곱근 확장 칼만 필터에 의한 영구자석 동기전동기의 센서리스 속도 제어가 양호함을 보인다.

• 한국패션뷰티학회지
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• 제4권3호
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• pp.13-17
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• 2006

Perm is one the of the most common thing in a beauty salon like hair-cut and hair perm needs processing solutions which is chemical substances. Those chemical substances damage the hair cuticle. Damaged hair cuticles with mistakes of perm will follow with the next performance and it will cause more damage to hair. As damage of hair cuticle become worse, it is harder to recover the hair cuticle like before. Therefore, this study shows that plain rinse is the way to reduce the damage of hair cuticle with perm as much as possible. With experiments, I suggest the right way to do plain rinse to satisfy customers' demand and reduce the damage. During the research, I figured that plain rinse with the knowledge, structure of hair cuticle, principle of perm and plain rinse, is very needed. The hair with plain rinse have more elastic curl and have less scales which came off from hair cuticle than the hair without plain rinse. This experiment concludes that hairdresser has to figure out about the time, temperature and type of water depends on the degree of damaged hair of customers. In order to perm, there is no way to not to use chemical substances to perm. Therefore, hairdresser has to choose suitable processing solutions and right steps, and as this is the age of 'well-being' boom, hairdresser must try to keep the healthy hair. Consequently, in order to meet the demands and conditions of customers, hairdresser needs to find the right method to do plain rinse and use the method in perm.

• International Journal of Automotive Technology
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• 제8권6호
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• pp.761-769
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• 2007

The configuration of the flow channel on a bipolar plate of a proton exchange membrane fuel cell(PEMFC) for efficient reactant supply has great influence on the performance of the fuel cell. Recent demand for higher energy density fuel cells requires an increase in current density at mid voltage range and a decrease in concentration overvoltage at high current density. Therefore, an interdigitated flow channel where mass transfer rate by convection through a gas diffusion layer is greater than the mass transfer by a diffusion mechanism through a gas diffusion layer was recently proposed. This study attempts to analyze the i-V performance, mass transfer and pressure drop in interdigitated flow channels by developing a fully three dimensional simulation model for PEMFC that can deal with anode and cathode flow together. The results indicate that the trade off between performance and pressure loss should be considered for efficient design of flow channels. Although the performance of the fuel cell with interdigitated flow is better than that with conventional flow channels due to a strong mass transfer rate by convection across a gas diffusion layer, there is also an increase in friction due to the strong convection through the porous diffusion layer accompanied by a larger pressure drop along the flow channel. It was evident that the proper selection of the ratio of channel and rib width under counter flow conditions in the fuel cell with interdigitated flow are necessary to optimize the interdigitated flow field design.