• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2002년도 춘계공동학술발표회요약집
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• pp.171.1-171
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• 2002

• 대한기계학회논문집A
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• 제41권9호
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• pp.845-851
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• 2017

외경에 홈이 존재하는 자긴가공된 압력용기의 피로 파손은 외경 홈에서의 피로균열 발생과 전파에 의해 발생한다. 자긴가공된 압력용기의 피로수명을 예측하기 위하여 유한요소법을 이용하여 자긴가공에 의한 잔류응력해석을 수행하였으며, 피로시험을 통하여 재료의 피로특성을 구하였다. 압력용기의 수명은 압력용기 외경 홈 모서리에서 응력 및 변형률 집중에 의한 피로균열의 생성수명과 전파수명의 합으로 총 수명이 계산되었다. 본 연구에서 80 % 자긴도의 압력용기가 424 MPa의 반복적인 내압을 받을 때 압력용기의 수명은 2,598 사이클로 예측되었다.

• 한국가스학회지
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• 제11권2호통권35호
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• pp.65-70
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• 2007

LP 가스의 폭발현상 및 위험성을 평가하기 위하여, 산소농도변화와 LP 가스의 농도에 따른 혼합가스 조성을 변화시켜 실험을 행하였다. 산소농도 21%에서 LP 가스의 농도가 증가할수록 폭발하한계는 낮아졌으며, 최소산소농도(MOC, Minimum Oxygen Concentration)는 1.0 bar, 1.5 bar, 2.0 bar에서 각각 14.5%, 12.0%, 11.5%로 낮아졌다. 최대폭발압력은 압력이 증가할 경우 $6.46kg/cm^2,\;9.41kg/cm^2,\;13.49kg/cm^2$로 증가하였으며, LP 가스의 초기압력이 클수록 화염의 전파속도가 증가하였다.

• 대한기계학회논문집B
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• 제20권2호
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• pp.659-669
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• 1996

To clarify the effects of equivalence ratio, initial pressure and temperature on the flame propagation and radicals characteristics, a series of the experimental study were conducted in a quiescent methane-air premixture using a constant volume chamber. The development of the flame was visualized following the start of ignition using high speed schlieren photo and radical images by intensified CCD camera. Combustion pressure and ion current were recorded simultaneously according to the experimental conditions which were equivalence ratio with 0.7 to 1.2, initial pressure with 0.08 MPa to 0.40 MPa and initial premixture temperature with 3l3.2K to 403.2K. The results showed that the flame speed by ion current and mass fraction burned by combustion pressure characterized the effects of flame propagation very well. And increased combustion duration due to lean combustion condition that was below equivalence ratio, 0.8 caused cycle variation and decreasing the power of engine.

• 한국가스학회지
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• 제7권4호
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• pp.24-29
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• 2003

실내에서 가스 폭발시 피해를 예측하기 위해서 폭발 화염면의 전파를 수치해석을 통해 해석했다. 확산방정식에 의해 가스누출에 의한 실내의 가스확산분포를 구했으며, 문헌에서 선택한 누출의 초기조건을 사용했다. 화염온도를 계산하기 위해 각 가스 혼합비에 따른 엔탈피와 화학식에 대한 reduced mechanism을 사용했으며 문헌에서 찾은 각 가스의 농도 별 층류 연소속도를 혼합가스의 층류연소속도에 적용시켰다. k-$\epsilon$ 모델에서 난류 에너지를 층류연소속도와 결합시켜 난류화염 전파속도를 모델링 했다. 화염면의 전파를 분석하기 위해 실내의 위치에는 직각, 화염면의 전파에는 원통좌표계를 사용했다. 유리창의 파손에 의한 화염전파면의 변화에 따른 압력상승 요인을 해석하였으며, 창문의 크기에 따라서 점화위치에 따른 실내 압력상승의 영향이 서로 다르게 나타나는 결과를 얻었다.

• Journal of Mechanical Science and Technology
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• 제16권4호
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• pp.564-571
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• 2002

Three-dimensional numerical analysis of the turbulent premixed flame propagation in a constant volume combustion chamber is performed using the KIVA-3V code (Amsden et. al. 1997) by the flame surface density (FSD) model. A simple near-wall boundary condition is eaployed to describe the interaction between turbulent premixed flame and the wall. A mean stretch factor is introduced to include the stretch and curvature effects of turbulence. The results from the FSD model are compared with the experimental results of schlieren photos and pressure measurements. It is found that the burned mass rate and flame propagation by the FSD model are in reasonable agreement with the experimental results. The FSD combustion model proved to be effective for description of turbulent premixed flames.

• 한국자동차공학회논문집
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• 제3권2호
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• pp.136-145
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• 1995

The aim of this study is to gain a better understanding of the effect of a flow motion on the flame development by means of an optically-accessible constant-volume combustion chamber and the visualization technique of a combustion flame. At first, the characteristics of a flame propagation are investigated in the combustion field of the two kinds of flow conditions such as a quiescent and a flowing condition, and methane-air mixture is used as fuel. Then the same investigation is performed in two flow configurations : bulk flow motion type and turbulence generating type. In this study, the combustion phenomena are analyzed by measuring the combustion pressure, flame propagation speed, mean velocity, turbulent intensity, and mass fraction burned.

• Geomechanics and Engineering
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• 제14권4호
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• pp.325-336
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• 2018

Deformation of rock masses is not only related to rock itself, but also related to discontinuities, the latter maybe greater. Study on crack propagation at discontinuities is important to reveal the damage law of rock masses. DDARF is a discontinuous deformation analysis method for rock failure and some modified algorithms are proposed in this study. Firstly, coupled modeling methods of AutoCAD-DDARF and ANSYS-DDARF are introduced, which could improve the modeling efficiency of DDARF compared to its original program. Secondly, a convergence criterion for automatically judging the computation equilibrium is established, it could overcome subjective drawbacks of ending one calculation by time steps. Lastly but not the least, relationship between the super relaxation factor and the calculation convergence is analyzed, and reasonable value range of the super relaxation factor is obtained. Based on these above modified programs, influences on crack propagation of joint angle, joint parameters and geo-stresses' side pressure are studied.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 추계학술대회 논문집
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• pp.379-387
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• 1998

HVAC systems are used to maintain comfort conditions in occupied spaces. Like rolling noise and aerodynamic noise, noise from the HVAC system of train increases interior noise level. For an appropriate interior noise level, it is necessary not to find noise sources and their propagation paths. Noise emission from the sources and propagation through the propagation paths should be regulated in order to reduce their effect to the interior noise level. In general, the main noise source in the HVAC system is blower which operates at high static pressure. This noise propagates through ducts which are directly connected to the residential area. Since the blower noise can be reduced only to some degree, it is necessary for the propagation paths to have enough noise attenuation. Acoustic properties of ducts are usually found by experimental methods but it is rather difficult and expensive to set up such test equipments. In this thesis, the design and the noise characteristics of TGV-K HVAC system are studied. Finite element method in accordance with experimental method is used to study the acoustic properties of TGV-K duct system.

• 한국안전학회지
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• 제7권3호
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• pp.66-72
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• 1992

An experimental study was carried out to analyse the explosion characteristics of flammable gas-air mixtures. Used flammable gases were hydrogen, methane, acethylene, ethylene and pro-pane, explosion Pressure, explosoin pressure rising rate, and flame propagation velocity were measured experimentaly. The maximum explosion pressure and rising rate of flammmalbe gas air mixtures were appeared at the range of slightly higher concentration than the stoichiometric concentration. Initial pressure before explosion was controlled from 0.6 to 2.0kg/cm absolutly. Explosion pressure was increased with increment of the initial pressure, and the relationship between initial pressure and explosion pressure was Pe = KPi. The effect of vessel size on explosion characteristics was also analysed In this experiment. Explosion pressure was increased with in-creasing the vessel size, otherwise explosion pressure rising rate was decreased. When we locate a dummy material in vessel explosion pressure was decreased with increasing the dummy volume but exlosion pressure rising rate was increased.