• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.4
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• pp.795-802
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• 1992

A numerical analysis is performed on the turbulent flow in the plain seal with injection. The parameters used in this study are as follows : Reynolds number, rotation speed, injection speed, clearance ratio, injection angle, and axial injection location. Flow pattern and leakage performance due to the variation of parameters are investigated. SIMPLER algorithm is used to solve the Navier-Stokes equation governing steady, incompressible turbulent flow and standard K- .epsilon. turbulent model is used to consider the turbulence effects. The leakage performance is significantly enhanced with injection. The increases of the injection flow rate and be rotation speed of the shaft cause the leakage performance to the increased. With the increase of the Reynolds number the leakage performance is diminished. At the injection angle of 90deg, the leakage coefficient has a minimum value. The pressure drop has a maximum value at axial center location but the injection location has little effect on the pressure drop. Clearance ratio has a significant effect on the pressure drop.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.3
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• pp.55-61
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• 2000

In this paper we have discussed on the characteristics and modeling of machined geometry which was established for the case of round shape machining also the effects of externally machined profile are analyzed and its modeling realia-bility was verified by the experiments of roundness testing especially in lathe operation. In this study we established a harmonic geometric model with the parameter harmonic function. In general we can calculate the theoretical roundness profile with an arbitrary multilobe parameter. But in real experiments only 2-5 lobe profile was frequently measured, The most frequently measured ones are 3 and 5 lobe profile in experiments. With these results we can predict that these results may be applied to round shape machining such as turning drilling boring ball screw and cylindrical grinding operation in bearing and shaft making operation with the same method. in this study simulation and experimental work were performed to show the profile behaviors. we can apply these new modeling methods in real process for the predic-tion of part profile behaviors machined such as in round shape machining operation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2001.04a
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• pp.54-58
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• 2001

In order to Improve the performance of a free power turbine type gas turbine engine by injecting the atomized water into a compressor inlet., a study on Moisture Air Turbine (MAT) cycle was proposed. Compressor work by air-water mixtures in phase change was theoretically considered, and it was found that the water evaporation might reduce the compressor work. Cycle model calculations predicted that power increments of 21.7%, 20.2% and 18.4% by 1.5% water to the air flow rate at the compressor intake with rotational shaft speeds of 1000, 1210, 1350 rps were obtained, and also thermal efficiency due to the reduction of compressor work was improved.

• Nuclear Engineering and Technology
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• v.49 no.2
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• pp.450-457
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• 2017

Waste Isolation Pilot Plant repository releases are evaluated through the application of modified parameters to simulate accelerated creep closure, include capillary pressure effects on relative permeability, and increase brine and gas saturation in the operations and experimental (OPS/EXP) areas. The modifications to the repository model result in increased pressures and decreased brine saturations in waste areas and increased pressures and brine saturations in the OPS/EXP areas. Brine flows up the borehole during a hypothetical drilling intrusion are nearly identical and brine flows up the shaft are decreased. The modified parameters essentially halt the flow of gas from the southern waste areas to the northern nonwaste areas, except as transported through the marker beds and anhydrite layers. The combination of slightly increased waste region pressures and very slightly decreased brine saturations result in a modest increase in spallings and no significant effect on direct brine releases, with total releases from the Culebra and cutting and caving releases unaffected. Overall, the effects on total high-probability mean releases from the repository are insignificant, with total low-probability mean releases minimally increased. It is concluded that the modified OPS/EXP area parameters have an insignificant effect on the prediction of total releases.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.11 s.176
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• pp.111-117
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• 2005

The vibration problems associated with gear coupled rotors have been the focus of much engineering work. These systems are complex and difficult to analyze in that they have the problems associated with conventional rotors plus those additional problems associated with the gear couplings. This paper examines the problems peculiar to the gear mesh. Because of the meshing action of gears, the elasticity of the gear teeth introduces time-varying stiffness coefficients into the governing equations of motion. This means that system response must be thought of in terms of Mathieu-type equations, where multiple-frequency response occur due to the periodic coefficients. The meshing action of the gears also couples the lateral and torsional gear motions. Gear errors, such as tooth profile and spacing errors, produce forces and torque that excite the system at multiple frequencies, some of which are much higher than shaft rotational speed. To investigate how to the time-varying stiffness in the gear teeth and the gear errors act one the dynamic response of the gear coupled rotors, a three-dimensional dynamic model with lateral-tortional oscillation is developed. The harmonic balance technique is employed to solve this mathieu-type problem.

• Journal of the Korean Society of Safety
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• v.12 no.4
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• pp.114-121
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• 1997

Helical anchors are foundation structure that designed to resist uplift loads are installed by applying in load to shaft while rotating it into the ground. These can be a cost effective means of proving tension anchorage for foundation where soil conditions permit their installation because of ease of installation. At present time, tapered helical anchors are commonly used to carry uplift loads. The uplift capacity includes the following factors : the height of overburden above the top helix, the resistant along a cylinder, the weight of the soil in the cylinder and suction force. In order to make clear behavior characteristics of helical anchors with pullout, model tests were conducted with respect to various embedment depth, space of helix, shape of helix. Based on the experimental study, the following conclusions are drawn. 1) The uplift capacity of multi helical anchors increase with embedment ratio of anchors The increase is smooth after critical uplift capacity. 2) Critical breakout factors and critical embedment ratio of multi helical anchor exist 7∼8, 4∼6 respectively. 3) Variation of uplift capacity with helix spaces show down after S/D=5. 4) Critical breakout factors of helical anchor in the laboratory test are similar to Das's theory.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.659-664
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• 2000

In this paper, We have discussed on the modeling of machined outer geometry which was established for the case of round shape machining, also the effects of externally machined profile are analyzed and its modeling realiability was verified by the experiments of roundness testing, especially in lathe operation. In this study, we established harmonic geometric model with the parameter harmonic function. In general, we can calculate the theoretical roundness profile with arbitrary multilobe parameter. But in real experiments, only 2-5 lobe profile was frequently measured. the most frequently ones are 3 and 5 lobe profile in experiments. With this results, we can predict that these results may be applies to round shape machining such as turning, drilling, boring, ball screw and cylindrical grinding operation in bearing and shaft making operation with the same method. In this study, simulation and experimental work were performed to show the profile behaviors. we can apply these new modeling method in real process for the prediction of part profile behaviors machined such as in round shape machining operation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.7
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• pp.621-627
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• 2008

Aerodynamic data measured in a wind tunnel has inevitable errors due to the presence of the wind tunnel walls. These unwanted interference effects must be corrected for the wall interference free aerodynamic data. Streamline curvature effects are caused by straightening of streamlines due to wind tunnel walls. Classical Glauert's correction method that is a standard method for fixed wing aircraft is not suitable for rotary wing aircraft. In this paper, Heyson's correction method of which wake model is compatible with rotors is used to correct the rotor shaft angle as well as the dynamic pressure. The results of Heyson's method are compared with Glauert's correction method.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1548-1553
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• 2003

The design of a high speed axial piston pump for hydrostatic transmission systems requires specific understanding on where and how much its internal frictional and flow losses are generated. In this study, the frictional loss of a bentaxis type hydraulic piston pump was analyzed in order to find out which design factors influence the mechanical efficiency most significantly. To this end, the friction coefficients of the sliding components were experimentally identified by a specially constructed tribometer. Applying them to the three-dimensional dynamic model of the pump presented by Doh and Hong [1], the friction torques generated by the sliding components such as piston head , bearing and valve plate were theoretically computed. The accuracy of the computed results was confirmed by the comparison with the experimentally measured mechanical efficiency. In this paper, it is shown that the viscous friction on the valve plate and the drive shaft bearing is the primary sources of the frictional losses of the bent-axis type pump, while the friction forces on the piston contribute to them only slightly.

• Tribology and Lubricants
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• v.28 no.6
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• pp.278-282
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• 2012

Various bearings such as deep-groove ball bearings, angular-contact ball bearings, and roller bearings are used to support the load and to lubricate between the shaft and the housing. The bearings of potential rolling systems in a turbo pump are the deep-groove ball bearings as comparing with the bearings with rolling elements such as cylindrical rollers, tapered cylindrical rollers, and needle rollers. The deep-groove ball bearings consist of rolling elements, an inner raceway, an outer raceway and a retainer that maintain separation and help to lubricate the rolling element that is rotating in the raceways. In the case of water-lubricated ball bearings, however, fluid friction between the ball and raceways is affected by the entry direction of flow, rotation speed, and flow rate. In addition, this friction is the key factor affecting the bearing life cycles and reliability. In this paper, the characteristics of flow conditions corresponding to a deep-groove ball bearing are investigated numerically, with particular focus on the friction distribution on the rolling element, in order to extend the analysis to the area that experiences solid friction. A simple analysis model of fluid flow inside the water-lubricated ball bearing is analyzed with CFD, and the flow characteristics at high rotation speeds are presented.