• Tribology and Lubricants
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• v.34 no.2
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• pp.49-54
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• 2018

Hydraulic reciprocating seal has been widely used to prevent fluid leakage in hydraulic systems. Also, hydraulic reciprocating seal plays a significant role to provide lubricant film at contacting interface to minimize tribological problems due to sliding with counter material. To predict lifetime of hydraulic reciprocating seal, quantitative understanding of wear characteristics with respect to operating conditions such as normal force and sliding speed is needed. In this work, effect of sliding speed on wear of polyurethane (PU) hydraulic reciprocating seal were experimentally investigated using a pin-on-disk tribo-tester. The wear characteristics of PU specimens were quantitatively determined by comparing the confocal microscope data before and after test. It was found that the wear rate of PU specimens decreased from $4.9{\times}10^{-11}mm^3$ to $1.1{\times}10^{-11}mm^3/Nm$ as sliding speed increased from 120 mm/s to 940 mm/s. Also, it was observed that the friction decreased slightly as the sliding speed increased. Improvement of lubrication state with increasing sliding speed was likely to be responsible for this enhanced friction and wear characteristics. This result also suggests that decrease in sliding distance between PU elastomer and counter materials at lower sliding speed is preferred. Furthermore, the quantitative assessment of wear characteristics of PU specimen may be useful in prediction of lifetime of PU hydraulic reciprocating seal if the allowed degree of wear for failure of the seal is provided.

• Tribology and Lubricants
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• v.20 no.2
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• pp.68-76
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• 2004

Applying a general Galerkin FE lubrication analysis method to spiral groove dry gas seals, this study intends to analyze in detail the effects of groove design parameters, such as a spiral angle, groove width ratio, groove radius ratio, groove depth ratio, and groove taper ratio, on the lubrication performances of an opening force, leakage, axial stiffness and damping, and angular stiffness and damping at low and high rotating speeds: 3,600 and 15,000 nm. Results show that, for the primary design consideration performances such as the opening force and axial and angular stiffnesses, a spiral angle of $25^{\circ}$, a groove width ratio of 0.46, a groove radius ratio of 1.1, a groove depth ratio of 1.0, and a groove taper ratio of 0.0 are preferred. Where the recommended relatively low values of groove depth and taper ratios are to keep the axial and angular dampings positive or higher than 0 particularly at the high rotating speed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.421-422
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• 2002

The purpose of this paper is to investigate the leakage characteristics of the valve stem in the gasoline engines. Especially, three factors affecting oil leakage are the power cylinder, engine head system, and the positive crankcase ventilation system. Which is the most variables, analysis difficulty is the valve stem seal characteristics. The testing system is used with oil motoring system. The leakage of an engine is analyzed for the cylinder temperature, atmosphere pressure, positive pressure, negative pressure, revolution of the camshaft and the surface roughness of the valve stem.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.209-212
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• 2004

The O-ring seal is a usual component part in various mechanical apparatuses for sealing that makes efficient performance of the equipments. The sealing performance of 0-ring is effected in environments of the O-ring seal, like that applied pressures, working temperatures, interferences and materials. In this paper, an pressurized, NBR O-ring is calculated by experimental methods and analysed numerically using the MARC finite element program. The calculated experimental and FEM results showed that the Contact force O-ring decreases as a function of temperature.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1996.10a
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• pp.158-162
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• 1996

A split shaft device is commonly used to measure the radial force of lip seals. The radial force measured with this device includes some inevitable error. This error is caused by the fact that the split shafts cannot maintain a perfect circle when the interference becomes larger or smaller than some initial interference. In this study, a theoretical model for the calculation of the radial contact force has been carried out, and an explicit equation for the measurement error as a function of the initial interference and the interference to be measured has been obtained. The error when the interference is small is not dependent upon the material properties and the shape of the lip seal, but rather upon the amplitude of the initial interference and the interference to be measured. When the interference is larger or smaller than the initial interference, the measured contact force is always underestimated or overestimated.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.273-279
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• 2000

Until recently performance requirements for automatic transmission fluids have continued to change to reflect the design changes of automatic transmission. The major purpose for these design changes is to improve the fuel economy and easy driving. To meet recent performance requirements fur automatic transmission the needs for special base oils Bike API Group III and IV base oils become larger. In this paper to evaluate the effects of base oils on performance of automatic transmission fluids formulated with API Group I,II,III and IV and Dexron III and Hereon Type additive package, Brookfield viscosity, oxidation test, SAE No.2 friction test and seal compatibility test were examined. From the test we knew that the use of Croup III and IV base oils in ATF has several benefits in low temperature viscosity, oxidation stability and SAE No.2 friction characteristics.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.4
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• pp.76-82
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• 1998

Sealing an oil-air mixture plays important roles to have an enhanced lubrication for high speed spindle. Current work is emphasized on the investigation of the air jet effect on the protective collar type labyrinth seal. To improve the sealing capability of conventional labyrinth seal, air jet is injected against through the leakage flow. It has a combined geometry of a protective collar type and an air jet type. In this study, both of a numerical analysis by CFD(Computational Fluid Dynamics) and experimental measurements are carried out to verify sealing improvement. Both of the turbulence and the compressible flow model are introduced in CFD analysis. The sealing effect of the leakage clearance and the air jet magnitude are studied for various parameter in the experiment. The results of pressure drop in the experiment match reasonably to those of the simulation by introducing a flow coefficient. Effects of sealing improvement are explained as decreasing of effective leakage clearance by air jetting. Thus, sealing effect is improved by amount of air jetting even though clearance becomes larger.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1989.06b
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• pp.35-47
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• 1989

누설방지를 목적으로 산업용 기계에서 많이 사용되고 있는 기계평면시일(mechanical face seal)은 기능상 높은 신뢰도를 요구하고 있다. 이를 위하여 동적 안정성이 커야되고, 밀봉된 유체의 누설을 최소화시킬 수 있는 정도에서 시일의 수명을 결정해야 한다. 이와같이 상반된 성질을 동시에 만족시키기 위하여 시일 성능에 영향을 미칠 수 있는 기하학적 요인들을 고려하여 해석해야 한다. 일반적으로 미끄럼 접촉운동을 하고 있는 시일에서 시일링 간극(sealing gap)이 수 micron 단위라는 점을 고려할때 시일 조립시 중심맞추기(alignnment) 정미\ulcorner 결여 및 회전축의 자중량 등에 의한 기계적 변형(mechanical distortion), 특히 고온의 분위기에서 작동되고 있는 시일의 열변형(thermal distortion)은 시일의 경사집에 커다란 영햐을 주고 있다. 또한 누설을 최소화시킬 목적으로 시일 링(seal ring) 을 시일의 경사짐에 커다란 영향을 주고 있는 스프링의 강성도를 증가시키면 상대 미끄럼 운동을 하고 있는 접촉명이 건조마찰에 의한 마멸이 진행되어 코닝(coning)현상이 생긴다. 시일 평면에서 코닝 현상은 시일의 축방향 분리력(axial separtating force)과 경사 모우면트(tilting moment)에 커다란 영향을 주고 있는 것으로 알여졌다. 이들의 연구는 주로 경사진 시일평판에 시일근사치이논(seal approximation bhoryl)을 이용하여 1차원 비압축성에 관한 시월 성능을 해석하였다. 본 연구에서는 비압축성 유체의 점성이 온도에 의하여 변화를 일으키는 조건하에서 경사진 회전시일에 코닝이 발생되었을때 시일링 각극에서의 압력분포를 ㅈ차원인 경우에 대하여 수치적으로 해석을 하였다.

• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.2173-2187
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• 2022

A 3D thermo-elasto-hydrodynamic model is developed to analyze the sealing performance of a notched mechanical seal applied in the reactor coolant pump. In the model, the generalized Reynolds equation, the energy equation coupled with notch heat balance equation, the heat conduction equations, and the deformation equations of the sealing rings are iteratively solved by the finite element method. The film pressure and temperature distribution are obtained, and the deformation of the sealing rings is revealed to study the mechanism of the notched mechanical seals. A parameterized study is conducted to analyze the sealing performance under different operating conditions. As a comparison, the sealing performance of non-notched seals is also studied. The results show that the hydrostatic effect is dominant in the load-carrying capacity of the fluid film due to the radial mechanical and thermal deformations. The notch can cool the fluid film and influence the thermal deformation of seal rings. The sealing performance is sensitive to the pressure difference, ambient temperature, and rotational speed. It is suggested to set the notches on the softer sealing rings to acquire the greater hydrodynamic effect. Compared with the non-notched, the notched end face holds a better lubrication performance, especially under lower rotational speed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1993.12a
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• pp.35-38
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• 1993

질화규소는 고온에서 고강도, 고경도, 내열성, 내식성 등의 우수한 성질을 가지고 있기 때문에 열교환기, 공구, 기계밀봉(mechanical seal), 자동차용 엔진부품중의 피스톤 및 실린더 링 등의 중요한 부품의 재료로 크게 부목받고 있다. 이러한 질화 규소의 고온에서의 마모, 마찰거동이 중요한 부품으로의 활용범위를 넓히고 또한 기능성을 향상시키기 위해서 고온에서의 마모, 마찰거동에 대한 연구 및 이해가 절대적으로 필요하다. 공유결합성이 강한 질화규소의 소결시에 첨가되는 첨가제나 제조공정에서 들어갈 수 있는 불순물들은 소결체의 입자모양이나 입계에 존재하는 상의 점도를 변화시켜 고온에서의 기계적성질을 저하시키는 것으로 알려졌다.