• Journal of Mechanical Science and Technology
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• 제17권10호
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• pp.1572-1582
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• 2003

Hybrid rocket combustion has a manifestation of stable response to the perturbations compared to solid propellant combustion. Recently, it has revealed that the low frequency combustion instability about 10 Hz was occurred mainly due to thermal inertia of solid fuel. In this paper, the combustion response function was theoretically derived by use of ZN (Zeldovich-Novozhilov) method. The result with HTPB/LOX combination showed a quite good agreement in response function with previous works and could predict the low frequency oscillations with a peak around 10 Hz which was observed experimentally. Also, it was found that the amplification region in the frequency domain is independent of the regression rate exponent n but showed the dependence of activation energy. Moreover, the response function has shown that the hybrid combustion system was stable due to negative heat release of solid fuel for vaporization, even though the addition of energetic ingredients such as AP and Al could lead to increase heat release at the fuel surface.

• 대한기계학회논문집A
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• 제25권11호
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• pp.1767-1776
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• 2001

For the stable operation of high speed air spindle, the low rotational inertia and high damping ratio of spindle shafts as well as high fundamental natural frequency are indispensable. Conventional steel spindles are net appropriate for very high speed operation because of their high rotational inertia and low damping ratio. In this study, a high speed spindle composed of carbon fiber epoxy composite shaft and steel flange was designed for maximum critical speed considering minimum static deflection and radial expansion due to bending load and centrifugal force during high speed relation. The stacking angle and the stacking thickness of the composite shaft and the adhesive bonding length of the 7teel flange were selected through vibrational analysis considering static and thermal loads due to temperature rise.

• 대한조선학회 특별논문집
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• 대한조선학회 2007년도 특별논문집
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• pp.7-13
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• 2007

The purpose of this study is to develop a structural analysis system of LNG pump tower structure. The system affords to build optimized finite element model and analysis procedure of the pump tower structure. The pump tower structure is one of the most important components of LNG (liquefied natural gas) carriers. The pump tower structure is subject to sloshing load of LNG induced by ship motion depending on filling ratio. Three types of loading components, which are thermal, inertia and self-gravity are considered in the system. All these design and analysis procedures are embedded in to the analysis system successfully.

• 대한기계학회논문집B
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• 제24권7호
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• pp.967-975
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• 2000

Transient characteristics of a boiler and turbine system for a steam power plant are simulated. One-dimensional unsteady models are introduced for each component. An interaction between boiler and turbine and a control of the water level in the drum are taken into account. Transient responses of the system to the variations of main system variables such as fuel and air flow rate, cooling water injection rate at the attemperator, gas recirculation rate at the furnace and opening of the turbine control valve are examined. Effect of fluid inertia and tube wall thermal inertia on predicted dynamic behavior is investigated.

• 대한기계학회논문집B
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• 제38권11호
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• pp.881-887
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• 2014

본 연구에서는 micro-gap 판형 열교환기 내부의 열유동 특성에 대한 수치해석을 수행하였다. 특히 유량 조건에 따라 열교환기의 주 채널로부터 각 micro-gap 으로의 유동분배에 대한 유동관성의 영향에 대하여 조사하였다. 열교환기 주 채널의 유동을 레이놀즈 수 100 부터 10000 까지 변화시키며 그에 따른 각 micro-gap 으로의 유동분배와 온도분포의 불균일 정도를 평가하였다. 수치해석 결과 유동분배는 유동관성에 의해 크게 영향을 받는 것으로 나타났으며, 관성 효과를 감소시킬 수 있는 헤더 설계를 통해 유동분배 불균일 정도를 줄일 수 있었다. 또한 micro-gap 을 통과한 유체의 온도분포의 불균일 정도는 주유량이 증가함에 따라 증가 후 감소 추세를 나타냈다.

• 설비공학논문집
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• 제28권5호
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• pp.178-185
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• 2016

This study describes the analysis of a 20 MW chilled water plant used for the IT cooling of a recently constructed data center in Korea. The CFD model was developed with the aim of evaluating the impact of problems such as chiller failure on the water and air temperatures in the cooling system. The numerical model includes the chilled water hydraulic network and individual water-to-air CRAC units. The coupling between the IT server room air temperature levels and the cooling plant has enabled a full assessment of the cooling system design in response to system fault conditions to be performed. The paper examines an emergency situation involving the failure of the cooling plant, and shows how the inherent thermal inertia of the system along with additional inertia achieved through buffer systems allowed a suitable design to be achieved.

• 대한기계학회논문집A
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• 제20권5호
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• pp.1562-1572
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• 1996

The rigid-plastic finite element formulation including the inertia force is derived and then the rigid-plastic finite elemnt program considering the inertia effect is developed. In order to consider the strain hardening, strain rate hardening and thermal softening effects which are frequentrly observed in high-velocity deformation phenomena, the Johnson-Cook constitutive odel is applied. The developed program is used to simulate two high-velocity deformation problemss ; rod impact test and hdigh-velocity compression precess. As a result of rod impact test simulation, it is found that the siulated result has a good agreement with the experimental observation. Through the high-velocity compression process simulation. it is also found that the accuracy of the simulated results is dependent upon the time increment size and mesh size.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2018년도 공동국제학술발표회
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• pp.82-82
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• 2018

• 방재기술
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• 통권24호
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• pp.32-39
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• 1998

A room-corner fire scenario of ISO 9705 with flame spread model developed by Quintiere is applied to the interior finish materials to show the sensitivity of properties derived from AST, E-1321 and ASTM E-1354 is investigated and various range of thermal properties by the author were analyzed in the model. There are including flame heat flux and thermal inertia, lateral flame spread parameter, heat of combustion and effective heat of gasfication. The time for total energy release rate to reach 1MW is examined. Though some areas are neede for improvements, The model appears to predict good results with all the range of input properties and could be

• Journal of Advanced Marine Engineering and Technology
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• 제29권8호
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• pp.891-898
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• 2005

Inertia welding is a solid-state welding process in which butt welds in materials are made in bar and in ring form at the joint race, and energy required lot welding is obtained from a rotating flywheel. The stored energy is converted to frictional heat at the interface under axial load. The quality of the welded joint depends on many parameters, including axial force, initial revolution speed and energy amount of upset. working time, and residual stresses in the joint. Inertia welding was conducted to make the large exhaust valve spindle for low speed marine diesel engine. superalloy Nimonic 80A for valve head of 540mm and high alloy SNCrW for valve stem of 115mm. Due to different material characteristics such as, thermal conductivity and flow stress. on the two sides of the weld interface, modeling is crucial in determining the optimal weld geometry and Parameters. FE simulation was performed by the commercial code DEFORM-2D. A good agreement between the Predicted and actual welded shape is observed. It is expected that modeling will significantly reduce the number of experimental trials needed to determine the weld parameters. especially for welds for which are very expensive materials or large shaft. Many kinds of tests, including macro and microstructure observation, chemical composition tensile , hardness and fatigue test , are conducted to evaluate the qualify of welded joints. Based on the results of the tests it can be concluded that the inertia welding joints of the superalloy exhaust valve spindle are better properties than the material specification of SNCrW.