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Investigations Concerning the Flow through a Face Clearance with a Flexible Slip Ring

Korczak A., Peczkis G.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2005

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nr 128, vol. 2

301-312

EN

Abstract: In these investigations a disk with a flexible slip-ring was applied: a) mounted on an elastomer layer, b) a "floating" ring. The aim of the investigations was to determine the coefficients of the hydraulic resistance, the laminar flow through the face clearing, the walls of which display an axial run-out exceeding the average width of the clearance several times. Thanks to the flexibility of one of the walls the momentum of pressure in the clearance [2] prevents any contact between them.

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The flow through the face clearance of the disk relieving the axial force in multi-stage centrifugal pump

Korczak A., Papierski A.

Transactions of the Institute of Fluid-Flow Machinery

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2004

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nr 115

125-140

EN

The paper deals with the turbulent flow through the face clearance, which is a characteristic element of the flow system of the disk which relieves the axial force in a multi-stage centrifugal pumps. The presented description illustrates the automodelling flow, i.e. the square dependence of hydraulic resistances on the flow rate, applying the model k-... and making use of the Tasc-Flow program of calculations. The essential aim was to compare the pressure fields in both these descriptions. The pressure field decides about the value and direction of the hydrodynamic moment affecting the walls of the clearance. The hydrodynamic forces and moments in the sealing clearances influence essentially the dynamic properties of the rotor of centrifugal pumps. The results of calculations have been compared basing on a numerical example with the same assumed geometry of the clearances, the same flow rate and the same pressure drop. The pressure fields obtained by means of both methods of calculations have been presented graphically, providing numerical values of the calculated axial forces and moments, as well as the direction of their activity. Moreover, for the selected cross-section of the clearance the fields of radial and spherical speeds have been given. The coefficients of the inlet resistance and continous resistance in the clearance, the application of which in the description of the automodelling flow provided the pressure field have been calculated sismilary as in the case of applying the model k-... . As we see, in order to obtain correct results, the description of the automodelling flow ougth to differentiate the coefficient of continuous resistance along the perimeter of the clearance.

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The laminar flow of liquids in a flat-wal face clearence with a variable width between stationary and rotating rings

Korczak A.

Transactions of the Institute of Fluid-Flow Machinery

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2002

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nr 111

89-109

EN

The paper deals with the laminar flow through a flat-wall face clearance with a variable width between the stationary and rotating rings. The flow through such an clearance with immobile walls is described, too. Besides the longitudinal clearence, the face clearence is an essential structural element of hydraulic machines. A characteristic example is the face clereance between the slip and stopper ring the balance disc in a multistage centrifugal pump. In the case of conventional solutions of the balance dosc the structionally required width of the clearance leads to a turbulent flow of the liquid through the clearance [2]. If the outer diameter of the balance disc is reduced, the pressure under the disc increases, the width of the face clearance gets smaller and the flow rate through this clearance become less intensive. In result, the turbulence of the flow drops and it becomes possible to enter the zone of transient and laminar flows [7]. The reduction ot the diameter of the balance disc is connected with a reduction of leakage losses and friction resistance, and thus the pump becomes more efficient. In the case of applying a self-aligning disc, the momentum of the pressure forces may deviate it, preventing a dry friction of the slip-ring against the stopper ring. Such a disc can operate with a considerably narrower clearance than that required by stiff disc. Laboratory-scale investigations carried out on a model of a balance disc with a self-aligning support of the rotating ring have confirmed that in the case of a contrifugal flow the distribution of pressure in the face clearance provents the occurrance of dry friction, i. e. a contact of both rings [7,8]. In convectional structures of balance discs this effect is neutralized by their stiffness, so that the possibility of dry friction cannot be prevented.