• Proceedings of the KSME Conference
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• 2004.11a
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• pp.980-985
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• 2004

This paper shows a performance analysis for conical type sealless cylinders and rod bearings. The pistons without seal have partly cylindrical and conical shapes. 2 dimensional Reynolds equation and FD(finite differential) numerical techniques are utilized for the performance analysis. The relationship among self-centering forces and leakage flows are investigated. Also, optimal design values for a sealless cylinder are presented. A prototype of sealless cylinder which had rod bearing with four pockets, five pockets, and six pockets was manufactured respectively. Leakage flow test is conducted to evaluate performance of piston and rod bearing in sealless cylinder.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1911-1915
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• 2003

The study of Sealless Cylinder is presented. The cylinder has a piston with air bearing. The piston has a partly cylindrical and partly conical shape. The description of system geometry is follows by the flow rate equations. Then pressure distribution and Bearing force equations are derived. Several non dimensional parameters are suggested. The relationship among bearing force, leakage flow and geometry of the bearing is investigated by simulation. And determination method for optimal design of sealless cylinder is given. A prototype of sealless cylinder which had rod bearing with four pockets, five pockets, and six pockets was built respectively.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.961-966
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• 2004

The cylinder without seal has a piston with air bearing which is partly cylindrical and conical shape. The description of system geometry is deviation by the flow rate equation. Then pressure distribution and bearing force equations are derived. Several non-dimensional parameters are suggested. The relationship among bearing force, leakage flow and geometry of the bearing is investigated by simulation. And determination method for optimal design of sealless cylinder is given. A prototype of sealless cylinder which had rod bearing with four pockets, five pockets, and six pockets was built respectively. As a result of leakage flow test, it is evaluation to air bearing in sealless cylinder.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.824-827
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• 2003

The study of Sealless Cylinder is presented. The cylinder has a piston with air bearing. The piston has a partly cylindrical and partly conical shape. The description of system geometry is follows by the flow rate equations. Then pressure distribution and Bearing force equations are derived. Several non dimensional parameters are suggested. The relationship among bearing force, leakage flow and geometry of the bearing is investigated by simulation. And determination method for optimal design of sealless cylinder is given. A prototype of seatless cylinder which had rod bearing with four pockets, five pockets, and six pockets was built respectively.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.76.1-76.1
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• 2005

• Transactions of The Korea Fluid Power Systems Society
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• v.3 no.3
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• pp.1-7
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• 2006

In this paper, a theoretical analysis is carried out to study the lubrication characteristics of sealless piston for hydraulic cylinders. The analytical pressure distributions are obtained solving one-dimensional Reynolds equation with partially tapered moving piston. Nearly analytical expressions for lateral forces acting on the piston and leakage flow rate through the clearance are also presented. Using the analytical expressions, the influence of design parameters on lubrication characteristics can be easily evaluated without numerical analysis. Composite-shaped piston which minimizes the leakage flow rate is the optimum in sealless piston for hydraulic cylinder.

• International Journal of Fluid Machinery and Systems
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• v.3 no.2
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• pp.102-112
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• 2010

Artificial heart pumps have attracted the attention of researchers around the world as an alternative to the organ used in cardiac transplantation. Conventional centrifugal pumps are no longer considered suitable for long-term application because of the possibility of occurrence of blood leakage and thrombus formation around the shaft seal. To overcome this problem posed by the shaft seal in conventional centrifugal pumps, the magnetically suspended centrifugal pump has been developed; this is a sealless rotor pump, which can provide contact-free rotation of the impeller without leading to material wear. In Europe, clinical trials of this pump have been successfully performed, and these pumps are commercially available. One of the aims of our study is to numerically examine the internal flow and the effect of leakage flow through the gap between the impeller and the pump casing on the performance of the pump. The results show that the pressure head increases compared with the pump without a gap for all flow rates because of the leakage of the fluid through the gap. It was observed that the leakage flow rate in the pump is sufficiently large; further, no stagnant fluid or dead flow regions were observed in the pump. Therefore, the present pump can efficiently enhance the washout effect.