• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.853-861
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• 2007

To understand the concept of dynamic motion in two degree nonlinear coupled system, free vibration not including damping and excitation is investigated with the concept of nonlinear normal mode. Stability analysis of a coupled system is conducted, and the theoretical analysis performed for the bifurcation phenomenon in the system. Bifurcation point is estimated using harmonic balance method. When the bifurcation occurs, the saddle point is always found on Poincare's map. Nonlinear phenomenon result in amplitude modulation near the saddle point and the internal resonance in the system making continuous interchange of energy. If the bifurcation in the normal mode is local, the motion remains stable for a long time even when the total energy is increased in the system. On the other hand, if the bifurcation is global, the motion in the normal mode disappears into the chaos range as the range becomes gradually large.

• 항공우주기술
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• 제4권2호
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• pp.135-141
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• 2005

본 논문에서는 와류형 및 충돌형 분사기를 가진 액체로켓엔진용 축소형 연소기의 기본 설계 및 상세설계에 대해 기술하였다. 와류분사기는 내부에 액체산소 외부에 케로신을 공급하여 노즐 내부 또는 외부에서 혼합하는 구조를 가지고 있다. 축소형 연소기는 분사기 헤드, 삭마 냉각방식의 내열재 연소실 그리고 물냉각 노즐로 구성되어 있다. 분사기 헤드는 18개의 주 분사기, 하나의 중앙 분사기, 연료 메니폴드, 산화제 매니폴드 그리고 추진제 분배기 등으로 구성되어 있다.

• Journal of Advanced Marine Engineering and Technology
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• 제25권3호
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• pp.605-616
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• 2001

Generally, there are two methods in researching internal combustion engines. One is by experimental research and the other is by computer simulation. The experimental research has many merits that researchers can get data for engine performance, but it has also some demerit of cost and time. If there is an engine simulation code with accuracy for the solution, it is very convenient to predict the performance and optimum design value of the engine. In this study, engine performance simulation program has been improved to predict the transient variation of properties of gas in cylinder, intake and exhaust manifolds, There total program code was developed to calculate the pressure, flame factor and turbulent intensity, As a result of present study, the authors could predicted the in-cylinder pressure, intake manifold pressure and the engine performance in various conditions. The authors also could easily prepare the tool if optimum design of manifold and in-cylinder geometry.

• Korean Chemical Engineering Research
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• 제49권3호
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• pp.314-319
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• 2011

본 연구에서는 전산유체모사기인 Fluent를 활용하여 slot 다이 내부에서 Newtonian과 non-Newtonian 코팅액의 동적 거동을 고찰함으로써 최적 다이 설계를 위한 방법론을 구축하고자 하였다. 다이 출구에서 코팅액의 속도분포를 일정하게 하기 위해 chamber 구조를 변화시킴으로써 최적 하이브리드 다이의 설계가 가능하였다. 특히, non-Newtonian 유체의 경우, 전단담화 정도와 chamber의 coat-hanger 최적 길이의 상관관계를 도출하였다.

• 한국수소및신에너지학회논문집
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• 제34권2호
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• pp.196-204
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• 2023

This study performed the numerical analysis of the internal flow phenomena of 1 kWe-class solid oxide fuel cell (SOFC) stacks with internal manifold type and planar cells using commercial computational fluid dynamics (CFD) software, Star-CCM+. In particular, the locations where the turbulent phenomena occur inside the SOFC stack were investigated. In addition, the laminar flow model and the standard k-ε turbulent model were used to calculate the SOFC stack, separately. And, the calculation results of both laminar and turbulent models were compared. The calculation results showed that turbulent phenomena occurred mainly in the cathode flow. Especially, the turbulent phenomena were found in the cathode inlet/outlet region, and local turbulence occurred in the end plate near the inlet pipe.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.273-275
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• 2014

An ammonia fuel system is developed and applied to both a spark ignition engine and a compression ignition engine to use ammonia as primary fuel in this study. Ammonia is injected separately into the intake manifold in liquid phase while gasoline or diesel is also injected as secondary fuel. As ammonia burns 1/6 time slower than gasoline or diesel, the spark or diesel injection timing is needed to be advanced to have better combustion phasing. The test engine showed quite high variation in the power output with large amount of ammonia. The final goal of the study is to implement a methodology to ignite ammonia-air mixture and have complete combustion without any use of the conventional fuels.

• 약학회지
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• 제37권4호
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• pp.356-361
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• 1993

A sensitive method for the determination of methamphetamine(MA) and amphetamine(AM) in hair was developed by gas chromatography/mass spectrometry using stable isotope-labeled internal standards, amphetamine-d$_{5}$ and methamphetamine-d$_{5}$. Hair sample was washed with MeOH, incubated with MeOH(I% HCI) overnight at $37^{\circ}C$ while stirring and extracted using solid phase extraction column on a vacuum manifold. The extract obtained was pentafluoropropionated, and applied to GC/MS. The calibration curves of MA and AM were linear from 2.5 to 250 ng (r>0.99 for both). The limit of detection was 0.1 ng/mg in hair and cut-off level was set at 0.25 ng/mg for both. Hair samples of 27 MA abusers showed positive results in the range 0.7 to 106.8 ng/mg. AM, its metabolite, was detected in 20 out of 27 samples. The ratio of MA versus AM was 4.6~38.3 in specimens. Hair analysis for methamphetamine by GC/MS is an effective method for identifying long-term drug abusers.

• 열처리공학회지
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• 제18권4호
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• pp.223-228
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• 2005

Tube hydroforming provides a number of advantages over conventional stamping process, including fewer secondary operation, weight reduction, assembly simplification, adaptability to forming of complex structural components and improved structural strength and stiffness. It can produce wide range of products such as subframe, engine cradle, and exhaust manifold. In this study, the effect of the heat treatment conditions such as post seam annealing (PSA) and bright annealing (BA) on the ovality and hydro-formability of steel tubes has been investigated. Hydroformabilities have been estimated by the bulging heights obtained at various processing parameters such as internal pressure, axial feeding and heat treatment conditions. The ovality and forming height are strongly influenced by material properties after heat treatments.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.427-430
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• 2008

Electroforming is one of the key technologies for the regenerative thrust chamber of the rocket engine. To use nickel electroforming method for the thrust chamber, direct electroforming of nickel on cupper and the welding method between different materials are needed. Minimizing the internal stress is one of the important factor for making thick electroforming,. Also minimizing contamination(ex. Sulfur containing compound) is another important factor for the stability of quality. This paper includes advanced methods for thick nickel electroforming, those of strength test results and EDS/EPMA inspection results. Advanced for electroforming process makes the achievement of Electro-beam welding between Inconel718(Manifold) and Nickel Electroforming. This paper also includes the influence of the electroforming precipitation angle on strength. Thus advanced electroforming improvement processes and the test results make achievement for manufacturing of the regenerative thrust chamber with direct nickel thick electroforming on cupper materials.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.230-231
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• 2005

As environmental problems are important, automotive industries are developing various techniques to prevent air pollution. One of these is Positive Crankcase Ventilation (PCV) system. It removes blowby gas which includes about 30% hydrocarbon of total generated quantity. In this system, a PCV valve is attached in a manifold suction tube to control the flow rate of blowby gas which generates differently according to various operating conditions of an automotive engine. As this valve is very important, designers are feeling to design it because of both small size and high velocity. For this reason, we numerically investigated to understand both spool dynamic motion and internal fluid flow characteristics. As the results, spool dynamic characteristics, i.e. displacement, velocity, acting force, increase in direct proportion to the magnitude of differential pressure and indicate periodic oscillating motions. And, the velocity at the orifice region decreases according to the increase of differential pressure because of energy loss which is caused by the sudden decrease of flow area at the orifice region and the increase of flow volume in the front of spool head. Finally, the mass flow rate at the outlet decreases with the increase of spool displacement. We expect that PCV valve designers can easily understand fluid flow inside a PCV valve with our visual information for their help.