• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.9
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• pp.837-845
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• 2013

An airlift pump can be used to pump liquids and sediments within itself, which cannot easily be pumped up by a conventional method, by using the airlift effect. This characteristic of the airlift pump can be exploited in a DCFC (Direct Carbon Fuel Cell) so that molten fuel with high temperature may be carried or transported. The basic characteristics of airlift are investigated. A simple system is constructed, where the reservoir is filled with water, a tube is inserted, and air is supplied from the bottom of the tube. Then, water is lifted and its flow rate is measured. Bubble patterns in the tube are observed in a range of air flow rates with the parameters of the tube diameter and submergence ratio, leading to four distinct regimes. The pumping performance is predicted, and the correlation between the supplied gas flow rate and the induced flow rate of water is found.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.56.1-56.1
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• 2005

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.11-11
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• 1998

최적의 액체 램제트 연소기 설계를 위하여 흡입공기와 분무, 혼합 그리고 이에 따른 연소의 일련의 과정이 일어나는 램제트 연소기의 유동해석을 2차원 및 3차원으로 수행하였다. 격자구성은 연소기에 공기를 공급하고 연료를 분무하는 공기 유입관 영역과 연소실 및 노즐 영역, 그리고 출구 대기 영역으로 나누어 독자적으로 격자를 생성시켰다. 연소실 내의 유동 특성에 있어서 2차원과 3차원의 유동해석 결과는 선회영역 유동특성이 크게 차이가 남을 알 수 있었다. 따라서 실제 액체 램제트 연소기의 설계를 위해서는 3차원 유동해석과 실험이 반드시 필요하다.

• Journal of the Korean Geosynthetics Society
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• v.15 no.3
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• pp.57-66
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• 2016

In this study, to prevent possible collapse caused by hydraulic or mechanical instability, liquid nitrogen injection method is developed and implemented at the tip of drilling auger of steel pipe propulsion tunneling. In this study, 1/5-scale model auger and sand chamber were manufactured. The prototype diameter of steel pile (or casing) is assumed about 1,000 mm. For the frictional sandy soils and plastic weathered soils, liquid nitrogen injection methods were tested varying water contents of the soils. For the induced hydraulic instability, the ground near the drilling auger was frozen within approximately 5 minutes preventing mechanical collapse and water infiltration. Securing stability of steel pile propulsion tunneling using liquid nitrogen was much more effective for which the water content of the soil somewhat exceeds the optimum water content.

• Journal of Power System Engineering
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• v.12 no.1
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• pp.28-34
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• 2008

가스-액체 이젝터에 관한 수치해석은 3차원 CFD 모델로 수행하였다. 본 논문에서는 이젝터의 유동특성과 질량전달특성에 대한 작동조건과 이젝터의 기하학적 모형의 영향에 관한 연구를 수행하고자 한다. CFD 결과 실험 데이터에 의하여 검증되었으며, 유동 분석과 이젝터 성능의 예측 또한 실행되었다. 작동상태의 변화는 0.2 $\sim$ 1.2 범위에서 가스-액체 유량비를 변화시킴으로서 주어진다. 혼합관의 $L_M/D_M$이 4 $\sim$ 10의 범위에서 변화를 주었다. CFD 연구는 길이와 직경비가 5.5일 때 체적 유량전달계수는 가스 유량이 증가함에 따라 증가한다는 것을 나타낸다. 동시에 $L_M/D_M$가 4일 때 체적유량전달계수는 기체-액체 유량비가 0.6에서 최대치에 도달한다. 또한, 체적 유량전달계수는 혼합 튜브길이가 증가함에 따라 감소한다.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.165.2-165
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• 2002

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.477-480
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• 2011

The stress analyses of the 'U'-shaped multi-ply reinforced gimbal bellows under high pressure and rotational displacement loadings are performed at the room and cryogenic temperatures. The bellows are used for the Lox pipe line which connects the combustion chamber with the turbopump of a liquid rocket engine. The distributions of the stress, the strains and the contact pressures are obtained from the finite element analysis considering the geometric non-linearities of the contacts between the plies and the material one of the isotropic plasticity. Those are compared with the stress results from EJMA (Expansion Joint Manufacturing Association) standard. Also, the effects of the operating temperature and the reinforcing ring on the stresses are investigated.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.2
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• pp.29-37
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• 2015

This paper presents a numerical investigation on detonation of a kerosene-air mixture in the copper tube and the structural response associated with combustion instability in liquid rocket engine. A single step Arrehnius rate law and Johnson-Cook strength model are used to describe the chemical reaction of kerosene-air mixture detonation and the plastic deformation of the copper tube. The changes of flow field and tube stress which are induced by plastic deformation, are investigated on the different tube thicknesses and nozzle configurations.

• Applied Chemistry for Engineering
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• v.8 no.5
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• pp.816-821
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• 1997

The hydrodynamics and the liquid flow characteristics were investigated in an internal circulation airlift reactor with a single nozzle as a gas distributor. In an air-water system, the gas holdup in the individual flow zone and the impulse-response curve of tracer were measured at various gas velocities and reactor heights. Experimental results showed that for the higher gas velocity(>about 8 cm/s), the flow behavior of bubbles in the riser was turbulent flow due to strong bubble coalescences and the axial height of dispersion zone of large bubbles having uniform sizes in the downcomer was decreased with increasing gas velocity. And mean gas holdups in the individual flow zone and the reactor were increased with increasing gas velocities and were decreased with increasing heights of the top section of the reactor and it was decreased with increasing the height of the top section and gas velocity. Flow characteristics of liquid in the riser and the downcomer was tend to access to plug flow and the overall flow behavior of liquid was mainly varied with the size of the top section which it was assumed to be perfect mixing zone. In these conditions, liquid circulation velocities were increased with increasing gas velocities and they were higher than those by using other gas distributors.

• Fire Science and Engineering
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• v.28 no.4
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• pp.64-72
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• 2014

Flammable liquids residues in fire debris and pyrolysis products of flammable materials were analyzed by using Gas detecting tube, Gas Chromatograph/Mass Spectrometers (GC/MS), and Pyrolyzer. Comparison studies between chemical components detected in debris fired with and without Flammable liquids were performed. Though Flammable liquids were not present in debris, Gas detecting tube colors were also changed. Chemical components produced from conventional combustions were different from those produced from pyrolysis. Due to the difference of the reaction conditions between combustions and pyrolysis, different chemical products were produced. Petrochemical products of PVC wood-linoleum block could produce ignitable chemicals, such as toluene, ethylbenzene, undecane, and dodecane. So, for better fire investigation more consideration of those chemicals will be porformed.