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Experimental identification of the force and moment characteristic of symmetrically and non-symmetrically profiled annular seals

Kuhr Maximilian M. G., Pelz Peter F.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 6

art. no. e147062

EN

In modern turbomachinery, the performance and reliability is often limited by shaft vibrations induced by fluid film forces and moments of (i) plain or (ii) profiled annular seals. Therefore, these narrow annuli are mainly responsible for the overall system behaviour, i.e. safe operation and maintenance intervals. However, many studies focus only on the characteristics from the forces due to the translational motion, although the influence of the rotordynamic tilt and moment coefficients is well known. Therefore, these additional coefficients are much less researched. Especially, for profiled seals, the availability of reliable experimental data for validation purpose is rare. To overcome this fact, a test rig is operated at the Chair of Fluid Systems at the Technische Universität Darmstadt. The generic experiments presented here investigate the force and moment characteristic of plain, symmetrically profiled and non-symmetrically profiled annular seals within the relevant parameter range for turbulent flows in pumps. The investigations focus on the influence of the annulus length as well as the pressure difference across the annulus.

2

Determination of critical speeds of a centrifugal pump impeller in annular seals

Kundera C., Marcinkowski W. A.

International Journal of Applied Mechanics and Engineering

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2012

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Vol. 17, no. 3

873-883

EN

The paper deals with combined transverse and angular vibrations of a single-disc impeller in annular seals. The formulated equations of vibrations include additional (i.e., inertia, damping, potential, gyroscopic and circular) hydrodynamic forces and moments occurring in clearances of non-contact seals. The study involved performing digital calculations to determine the natural frequencies in two models of the rotor, both for constant pressure drops in seals and for a square relationship between the pressure drops and the rotational frequency of the impeller. It was also necessary to estimate the influence of the conicity of the annular clearance gaps in non-contacting seals on the natural and critical frequencies of the rotor.

3

The effect of annular seal parameters on the dynamics of a rotor system

Kundera C., Marcinkowski W. A.

International Journal of Applied Mechanics and Engineering

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2010

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Vol. 15, no 3

719-730

EN

The paper analyzes the influence of annular seal parameters on the critical angular velocity and the dynamic stability of rotor system consisting of a shaft and a symmetrical impeller rotating in two seals. The equations of motion of the rotor system were formulated. The special model developed to describe the seal fluid forces takes into account not only the stiffness and damping forces but also the inertial, gyroscopic and circulatory forces. The calculation results show that the clearance shape has a considerable effect on the critical velocity of the rotor. The greater the pressure drop in the seal, the greater the influence of the clearance conicity.