• International Journal of Aeronautical and Space Sciences
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• 제14권2호
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• pp.105-111
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• 2013

Radiative heating phenomena occurring in planetary entry flights are reviewed for the purpose of educating those who are not familiar with the problem. How the radiative heat transfer rates to the Apollo entry vehicle were measured and analyzed are first described. Next, the effects of thermo-chemical non-equilibrium on radiation are summarized. Then the radiation problems in entry flights into other planets are reviewed. Finally, unsolved problems are enumerated.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1996년도 제24회 춘계학술대회
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• pp.126-132
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• 1996

A laboratory scale hot strip rolling wear simulator(HRWS) was developed for the purpose of investigating the tribological phenomena occurred in production hot strip rolling mills. The HRWS' main parts are the electric heater, the mechanical descaler, tandem type 2-4Hi rolling mill stands, the cooling chamber, the tension controller and coiler. By simulating the tribelogical phenomena in rolling process at laboratory, wear patterns, cracks, cat-ear wear, black film, effect of hot rolling oil lubrication, etc. were reproduced, and discussed on the performace of simulator.

• 대한기계학회논문집
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• 제12권2호
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• pp.308-318
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• 1988

본 연구에서는 가압된 액체를 가류실에 접선방향으로 도입하게 함으로써 선회운동에 의하여 미립화를 시키도록 스크류형의 선회분사 노즐을 설계제작하였다.

• 대한기계학회논문집
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• 제6권4호
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• pp.331-340
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• 1982

Numerical analysis is made on the turbulent heat transfer with suspension of solid particles in circular tube with constant heat flux. The mean motion of suspending particles in mixture is treated as the secondary gas flow with virtual density and viscosity. Our modeling of turbulent transport phenomena of suspension flow is based on this assumption and conventional mixing length theory. This paper gives the evidence that the mixing length models can be extended to close the governing equations for two phase turbulent flow with solid boundary at a first order level. Results on Nusselt numbers obtained by analytical treatments are compared with available experimental data and discussed. They suggest that the most important parameters of two phase turbulent heat transfer phenomena are relative particle diameter to pipe diameter, gas-solid loading ratio, and specific heat of suspending material.

• 대한기계학회논문집
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• 제18권3호
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• pp.573-583
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• 1994

In this study, the shock characteristics for high velocity impact phenomena during the initial shock state by the long rod penetrator are calculated. From these results we re-analyze the one-dimensional hydrodynamic penetration theory by introducing the effective area ratio calculated from the mushroomed strain which is dependent on impact velocity. Calculated penetration depth and mushroomed strain show good agreement with high velocity impact experimental data. In addition we visualize the shock wave propagation in a transparent acryle block.

• Journal of Advanced Marine Engineering and Technology
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• 제25권5호
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• pp.1065-1075
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• 2001

It is common knowledge amongst electrical and marine engineers that short-circuit in electrical system may cause large mechanical torque on generator and prime mover However, it is not so widely known that the faulty synchronizing of generators may cause even higher torques than that of short-circuit. In this study, the transient phenomena related to the parallel running of synchronous generators are analyzed and the exact computer simulation method is proposed. In result, maximum transient torque and current take place in case of $120^{\circ}$ voltage angle difference between Master and Slave and that may develop higher torque than the short-circuit according to a condition of synchronizing. When synchronizing in power system using only two generators higher torque and current occur Master, but using multimachine system those occur to Slave. The short-circuit of marine generator does not happen frequently but faulty synchronizing sometimes takes place, therefore, it is necessary for designers to consider these phenomena.

• 대한기계학회논문집
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• 제5권2호
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• pp.110-121
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• 1981

In order to study on the fracture behavior and the fracture thoughness of combined structure, the specimens, structural steel (SM28C) and 6:4 brass are annealed for ductility and investigated for the befavior of fracture and the absorbed energy at the variation of the impact velocity. The results obtained by this study are as follows: (1)The maximum load increases with the impact velocity, but in the condition of constant impact velocity it decreases as the ductility increases. (2)The absorbed energy increases with the impact velocity, but in the condition of constant impact velocity it is constant as the ductility increases. (3)In the case of the combined structure of peralite and ferrite, the microcracks initiates and propagates mainly in the ferrite structure intergranular in accompany with the slip, and the slip concentration phenomena occur in the boundary of pearlite structure However, in case of the combined structure of .alpha. and ..betha. phase, the microcracks initiates and propagares mainly in the .alpha. phase intergranularly, and slip concentration phenomena not ocur in the boundary of .betha. phase.

• 대한기계학회논문집B
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• 제22권8호
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• pp.1132-1140
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• 1998

The disintegration process of initial spray from high-pressure swirl injector was investigated at different injection pressures. The transient breakup phenomena that were difficult to observe at high injection pressure were easily observed at the low injection pressure of 0.4MPa. The effect of fuel remained inside a nozzle hole volume on the penetration of initial spray was also investigated. The disintegration process of initial spray could be classified four regions: the formation of mushroom shape, the first collision, the second collision, and the development of spray, The liquid film of cup shape was particularly found in the second collision region, and the growth ratio of its length and width at low and high injection pressures were compared.

• 터널과지하공간
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• 제8권1호
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• pp.17-25
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• 1998

This paper investigates coupled thermal, mechanical and hydraulic phenomena in deep rock mass especially for underground heat storage system. Firstly, concepts of underground heat storage were presented and coupling phenomena in this area were illustrated. In order to understand the basic mechanism of thermal, hydraulic and deformation behavior in rock cavern disturbed by thermal gradient about 10$0^{\circ}C$, various numerical experiments were conducted using several codes. The study involves the behavior of fractured rock mass including rock joint. In spite of the limitation of codes modelling fully coupled effects, these codes could be applied in analysis of underground heat storage. The heat loss in rock mass, which is a major factor in heat storage, is insignificant in all results.

• 대한기계학회논문집B
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• 제33권4호
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• pp.225-234
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• 2009

The present study has been preformed to investigate the effect of obstacles around a cooling tower with air-guide to prevent recirculation. The external region as well as the cooling tower are included in the computational domain to analyze the flow phenomena around a cooling tower accurately. Three-dimensional analysis is performed using the finite volume method with non-orthogonal and unstructured grid system. The standard turbulence model is used to consider the turbulence effect. In order to investigate the recirculation phenomena, flow and temperature fields are calculated with the distance between cooling tower and obstacle, the allocated geometrical type and the air-guide. The moisture fraction rates decrease with increment of the distance between cooling tower and obstacle. The effect of air-guide to reduce the mean recirculation rate is obviously observed.