• Tribology and Lubricants
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• v.12 no.4
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• pp.35-42
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• 1996

The labyrinth seal is one of the widely used non-contact type mechanical seal. Current work was emphasized on the investigation of the air jet effect on the labyrinth seal. To improve the sealing capability of conventional labyrinth seal, air jet was injected against through the leakage flow. In this study, both of the numerical analysis by CFD (Computational Fluid Dynamics) and the experimental measurement were carried out. Both of the turbulence aad the compressible flow model were introduced in CFD analysis. The sealing effect of the leakage clearance and the air jet magnitude were studied in the experiment. The reason of the enhanced sealing was explained as a reduction of effective clearance by jetting air. As a result, the air jet could reduce the effective clearance with a wide range of leakage clearance.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.10
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• pp.477-482
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• 2002

One of the key technologic requirements for rotary blood pumps is the sealing of the motor shaft. A mechanical seal, a journal bearing, magnetic coupling, and magnetic suspension have been developed, but they have drawbacks such as wear, thrombus formation, and power consumption. A magnetic fluid seal is durable, simple, and non power consumptive. Long-term experiments confirmed these advantages. The seal body was composed of a Nd-Fe-B magnet and two pole pieces; the seal was formed by injecting magnetic fluid into the gap (50${\mu}m$) between the pole pieces and the motor shaft. To contain the ferro-fluid in the seal and to minimize the possibility of magnetic fluid making contact with blood, a shield with a small cavity was attached to the pole piece. While submerged in blood, the sealing pressure of the seal was measured and found to be 31kPa with magnetic fluid LS-40 (saturated magnetization, 24.3 KA/m) at a motor speed of 10,000 rpm and 53kPa under static conditions(0mmHg). The specially designed magnetic fluid seal for keeping liquids out is useful for axial flow blood pumps. The magnetic fluid seal was incorporated into an intra-cardiac axial flow blood pump.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1149-1149
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• 2006

The leakage characteristic is an important factor in power plant. However, most of power plant have efficiency problem which is occurred leaking between high pressure steam turbine axle and stator. The labyrinth seal which is used between the main turbine axle and stator in the power plant. Because it is able to be non-contact seal and it is minimize clearance to decrease the leakage. But its actual system is too huge to experiment. Therefore, most steam turbine seal performance tests were conducted by air similarity test. This paper described a test facility and program for air similarity test of high pressure steam turbine seal. A test facility has been designed and built to evaluate leakage verification of labyrinth seal. The test facility consist of air compressor, anti-swirl labyrinth seal for 1/3 air similarity model, pressure transducer, air flow measure system, instrumentation and auxiliary system. For evaluation of steam turbine seal performance, the air similarity test of labyrinth seal leakage verification was conducted and we compared experiment data and analysis result.

• Proceedings of the Korean Reliability Society Conference
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• 2006.05a
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• pp.40-47
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• 2006

Rail car axles are very important parts for safety of passengers and structural integrity of vehicles. The axles are supported by bearings. To seal grease lubricating the bearings of freight cars, a non-contact oil seal has been developed. The developed oil seal is composed of inner plate, outer plate and seal rubber. The friction between axle and housing with the developed oil seal is very low. The seals are designed for a minimum life expectancy of 800,000 kilometers service. In this study, an accelerated durability tests according to AAR Specification M-934-82 were carried out. Developed products satisfy the AAR Specifications.

• Journal of Magnetics
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• v.22 no.2
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• pp.299-305
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• 2017

Magnetic fluid, a new type of magnetic material, is a colloidal liquid constituted of nano-scale ferromagnetic particles suspended in carrier fluid. Magnetic fluid sealing is one of the most successful applications of magnetic fluid. As a new type of seal offering the advantages of no leakage, long life and high reliability, the magnetic fluid seal has been widely utilized under vacuum- and low-pressure-differential conditions. In practical applications, for improved pressure capacity, a multistage sealing structure is always used. However, in engineering applications, a uniform distribution of magnetic fluid under each tooth often cannot be achieved, which problem weakens the overall pressure capacity of the seals. In order to improve the pressure capacity of magnetic fluid seals and broaden their applications, the present study theoretically and experimentally analyzed the degree of non-uniform distribution of multistage magnetic fluid seals. A mathematical model reflecting the relationship between the pressure capacity and the distribution of magnetic fluid under a single tooth was constructed, and a formula showing the relationship between the volume of magnetic fluid and its contact width with the shaft was derived. Furthermore, the relationship of magnetic fluid volume to capacity was analyzed. Thereby, the causes of non-uniform distribution could be verified: injection of magnetic fluid; the assembly of magnetic fluid seals; the change of magnetic fluid silhouette under pressure loading; the magnetic fluid sealing mechanism of pressure transmission, and seal failure. In consideration of these causes, methods to improve the pressure capacity of magnetic fluid seals was devised (and is herein proposed).

• Tribology and Lubricants
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• v.28 no.2
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• pp.70-80
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• 2012

Non-contact type mechanical face seals installed in mechanical systems prevent leakage of working fluid using thin working fluid film between stator and rotor. For that purpose, various kinds of surface profiles, grooves and conings have been applied on seal surfaces of stator and rotor to generate hydrodynamic and hydrostatic pressure. The thickness distribution of working fluid film is one of important factors which affect the working performances of mechanical face seal, and it is strongly affected by the surface height profiles of stator and rotor. Therefore, appropriate design of surface height profiles of stator and rotor is necessary to optimize the working performances and life of mechanical face seal. In this study, numerical analysis using finite volume method was conducted to estimate the working performances of wavy mechanical face seals which have 36 coning combinations. As results, minimum thickness of working fluid film, leakage volume of working fluid and friction torque in static equilibrium condition of mechanical face seal, and stiffness of working fluid film were obtained. The results show that the working performances of mechanical face seal were affected by the coning combinations which can change the thickness distribution of working fluid film and pressure distribution in sealing region of mechanical face seal.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.3
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• pp.285-291
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• 2014

This paper is related to the improvement of efficiency for high performance centrifugal pumps by reducing leakage loss, which is achieved by applying the grooved seal as a non-contact seal to the pumps. Various combinations of grooved seal types, including the spiral and the parallel groove in the rotor and/or in the stator, were tested by the experiment. And the corresponding hydraulic performance and the magnitude of axial thrust were measured and calculated for ten cases. From the results, the type with the spiral groove(spiral angle : $0.98^{\circ}$) in both the rotor and the stator was found to be most effective. In this case, the head and the efficiency were improved from the original design by 2.1% and 2.3% respectively at design capacity($340m^3/h$), and the axial thrust was decreased by 10%.

• Tribology and Lubricants
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• v.21 no.4
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• pp.171-176
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• 2005

O-ring seal is an essential component in various mechanical apparatuses for a sealing of oil container and pressure vessels. This paper presents the sealing pressure and compressive contact behaviors of hi-polymer O-rings, which is made by an outer shell of FFKM material and an inner solid ring of FKM one. The contact normal pressure and its ratios are measured by experimental method with an automatic control system of the working temperature and analyzed numerically by using the non-linear Marc FEM program. The results show reasonably good agreements between the computed FEM results and measured ones when the operating temperature is kom normal temperature of $18^{\circ}C$ and a high temperature of $300^{\circ}C$ But the compared values between the computed and tested results show a little difference because of the increased temperature, which is related to the non-linear parameter of the O-ring material. Bi-polymer 0-ring shows a good contact normal stress and compression behavior for a given operation temperature and compression ratio.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.241-247
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• 2003

The sealing performance of O-ring is effected in environments of the O-ring seal, like that applied pressure, working temperature, pre-compressed ratio and materials. In this paper, design of composite O-ring under pressurized, compressed was optimized based on Taguchi experimental design method. and it analysed numerically using non-linear finite element method. Ogden model in which is developed based on the experimental data is used for simulating the contact stress and strain in NBR and PTFE materials. Sensitivity analysis was performed with FEM results, which are contact stress, strain and temperature as variable.

• Tribology and Lubricants
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• v.35 no.2
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• pp.99-105
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• 2019

This study presents an experimental investigation of the wear and oxidation of the bristles of a brush seal in a super-heated steam environment. We construct a model reflecting normal force and radial interference to predict the amount of wear. To monitor the volume loss of the bristle induced by the swirl phenomenon of the rotor, we measure the clearance between the rotor and the brush seal by using a non-contact 3-D device. We calculate the area by using the area-wise measurement method. Considering the obvious brush seal wear variables, we use two disks with different roughness($Ra=0.1{\mu}m$ and $100{\mu}m$) to determine the effect of roughness on wear. Considering an actual steam turbine, we utilize a steam generator and super-heater to generate a working fluid (0.95MPa, 523.15K) that has high kinetic energy. We observe the abrasion of the bristles in the hot steam environment through a scanning electron microscope image. This study also conducted energy dispersive X-ray (EDX) analysis for a qualitative evaluation of local chemistry. The results indicate that the wear and elimination of bristles occur on the disk with high roughness, and the weight increases due to oxidation. Furthermore these results, reveal that the bristle oxidation is accelerated more under super-heated steam conditions than under conditions without steam.