• Journal of the Society of Naval Architects of Korea
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• v.54 no.3
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• pp.267-273
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• 2017

Pressure hulls of submerged structures are generally designed as circular cylinders, spheres or cones with form of axisymmetric shell of revolution to withstand the high external pressure of deep ocean. The compressive buckling (implosion) due to hydrostatic pressure is the main concern of structural design of pressure hull and many design codes are provided for it. It is well-known that the buckling behavior of thin shell of revolution is very sensitive to the initial geometric imperfections introduced during the construction process of cutting and welding. Hence, the theoretical solutions for thin shells with perfect geometry often provide much higher buckling pressures than the measured data in tests or real structures and more precise structural analysis techniques are prerequisite for the safe design of pressure hulls. So this paper dealt with various buckling pressure estimation techniques for unstiffened circular cylinder under hydrostatic pressure conditions. The empirical design equations, eigenvalue analysis technique for critical pressure and collapse behaviors of thin cylindrical shells by the incremental nonlinear FE analysis were applied. Finally all the obtained results were compared with those of the pressure chamber test for the aluminium models. The pros and cons of each techniques were discussed and the most rational approach for the implosion of circular cylinder was recommended.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2002.05a
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• pp.107-111
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• 2002

A complex valve dynamic analysis has been performed with a high Pressure reciprocating gas compressor. Valve dynamic equations, which take into account the flow continuity and cylinder pressure fluctuation, have been derived. Flow coefficients of valves has been analyzed, using CFD models. Results have shown that both of the suction and discharge values behave favorably without any fluttering motions.

• Korea-Australia Rheology Journal
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• v.20 no.1
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• pp.15-26
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• 2008

It has been known that there is a viscoelastic instability in the channel flow past a cylinder at high Deborah (De) number. Some of our numerical simulations and a boundary layer analysis indicated that this instability is related to the shear flow in the gap between the cylinder and the channel walls in our previous work. The critical condition for instability initiation may be related to an inflection velocity profile generated by the normal stress near the cylinder surface. At high De, the elastic normal stress coupling with the streamline curvature is responsible for the shear instability, which has been recognized by the community. In this study, an instability criterion for the flow problem is proposed based on the analysis on the pressure gradient and some supporting numerical simulations. The critical De number for various model fluids is given. It increases with the geometrical aspect ratio h/R (half channel width/cylinder radius) and depends on a viscosity ratio ${\beta}$(polymer viscosity/total viscosity) of the model. A shear thinning first normal stress coefficient will delay the instability. An excellent agreement between the predicted critical Deborah number and reported experiments is obtained.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.4
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• pp.154-160
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• 2004

Hydraulic breaker of excavator has been used for the destruction and disassembling of buildings, crashing road pavement, breaking rocks at quaky and etc. The performance of breakers is evaluated their own destructive force and the number of impact by input hydraulic flow rate and pressure on the operating conditions. Because hydraulic breakers generate high impact energy, the accurate measurement of the impact force has been facing a technical challenge. In this study, the hydraulic pressure transducer system was developed based on the characteristics of pressure variation in closed vessel fur testing the impact energy. The hydraulic pressure transducer system is consisted with a hydraulic cylinder, main base, pressure & temperature sensors, LVDT, data acquisition system and etc. The developed hydraulic pressure transducer system was applied to measure the impact energy for hydraulic breaker. The measured impact force was 438.8 kgf.m within the designed impact force bounds. The developed hydraulic pressure transducer system as a simple tester could be applied to measure the impact force and the number of impact.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.12 no.1
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• pp.13-18
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• 1979

Volumetric efficiency is a determining factor for tile measurement of compessor capacity, but it is practically hard to take an accurate measurement of capacity characteritics so that most of users trust the data of makers catalogue. We often realized the discrepancy in their data with actual capacity. This study was attemped to establish the basic data of capacity characteristics of compressor by measuring volumetric efficiency of high speed multi-cylinder compressor and rotary compressor. The volumetric efficiency was calculated based on the quantity of the flow of ammonia vapor and pressure difference in suction state of orifice plate and compressor. The volumetric efficiency of high speed multi-cylinder compressor was $37-61\%$ and that of rotary compressor was $57-82\%$ when compression ratio was in the range of 4-12. The discrepancy in volumetric efficiency at an equal evaporating temperature between the makers catalogue and the measured data was $5.5\%$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.7 s.262
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• pp.800-807
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• 2007

Autofrettage process is used for internal forming and sizing of cylinder designed to withstand high internal pressures. Once the tube is autofrettaged, it needs to be machined to its final dimensions both at the bore and its outer surface. This paper presents an analytical analysis and numerical analysis of machined compound cylinder using finite element code, ANSYS10.0. An analytical model for predicting the level of autofrettage following either inner, outer, or combined machining of the compound cylinder is developed for the autofrettage residual stress field is simulated by an autofrettaged pressure. The autofrettaged pressures are obtained by using trying-error method. As autofrettage percentage is 20 % and 40 %, the numerical results are found to be in almost agreement with the analytical ones. However, as autofrettage percentage is 60 %, the numerical results have a little difference with the analytical ones.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.620-625
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• 2007

Autofrettage process is used for internal forming and sizing of cylinder designed to withstand high internal pressures. Once the tube is autofrettaged, it needs to be machined to its final dimensions both at the bore and its outer surface. This paper presents an analytical analysis and numerical analysis of machined compound cylinder using finite element code, ANSYS10.0. An analytical model for predicting the level of autofrettage following either inner, outer, or combined machining of the compound cylinder is developed for the autofrettage residual stress field is simulated by an autofrettaged pressure. The autofrettaged pressures are obtained by using trying-error method. As autofrettage percentage is 20 %, the numerical results are found to be in almost agreement with the analytical ones. However, as autofrettage percentage is 60 %, the numerical results have a little difference with the analytical ones.

• Journal of KSNVE
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• v.7 no.5
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• pp.861-869
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• 1997

An approximate analytical method has been developed for estimating hydrodynamic forces acting on oscillating inner cylinder in concentric annulus. When the rigid inner cylinder executes translational oscillation, fluid inertia and damping forces on the oscillating cylinder are generated by unsteady pressure and viscous skin friction. Considering the dynamic-characteristics of unsteady viscous flow and the added mass coefficient of inviscid fluid, these hydrodynamic forces including viscous effect are dramatically simplified and expressed in terms of oscillatory Reynolds number and the geometry of annular configuration. Thus, the viscous effect on the forces can be estimated very easily compared to an existing theory. The forces are calculated by two models developed for relatively high and low oscillatory Reynolds numbers. The model for low oscillatory Reynolds number is suitable for relatively high ratio of the penetration depth to annular space while the model for high oscillatory Reynolds number is applicable to the case of relatively low ratio. It is found that the transient ratio between two models is approximately 0.2~0.25 and the forcea are expressed in terms of oscillatory Reynolds number, explicity. The present results show good agreements with an existing numerical results, especially for high and low penetration ratios to annular gap.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.2
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• pp.177-186
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• 2002

This paper describes a research work on the development of computer-aided design system far the deep drawing & ironing of high pressure gas cylinder. An approach to the design system is based on the knowledge-based rules. Knowledge for the system is formulated from plasticity theories, handbook, experimental results and the empirical knowledge of field experts. This system has been written in AutoLISP on the AutoCAD Rl4.0 using personal computer. This system is composed of three modules which are input. process design and drawing.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.5
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• pp.670-676
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• 2008

A diesel engine requires a high Performance of lubrication because of the extreme conditions such as high temperature and pressure during combustion process in a cylinder. Many researches to improve the lubrication performance on the extreme condition have been executed. The lubricant oil suspended with nano-metal particles is the one of the measure. In this study, the nano-lubricant oil is applied on a commercial diesel engine, and the engine performance is tested. The results show the increase of maximum torque and the decrease of cylinder pressure, exhaust gas temperature, CO emission.