Forces and Moments Due to Combined Motion of Conical and Cylindrical Whirls for a Long Seal

Abstract

The mutual interaction effects of cylindrical and conical whirl on the dynamic fluid forces and moments, which act on a long annular seal, were studied experimentally. A whirling motion composed of cylindrical and conical whirls is actuated by intentionally giving the phase difference between the seal exit and inlet whirling movements. This whirling motion is believed to generate during actual pump running. The experiment was conducted by changing the phase difference, at various rotor speeds and with a pressure difference between the seal inlet and exit. The result of this study revealed that fluid forces and moments are greatly dependent on the phase difference of the whirl, namely the long seal has a significant coupling between displacements and rotations. Furthermore, dynamic fluid forces and moments were derived theoretically, assuming that total fluid force acting on the rotor could be determined by superposing fluid forces due to conical and cylindrical whirling movements. It was confirmed that the experimental results moderately agree with the theoretical values, if the rotor and seal are set in concentric alignment, the principle of superposition becomes applicable.

Investigations of the static and dynamic performances of an annular seal with a tilted rotor by transient CFD methods with dynamic mesh

“…2 Numerical geometric structure and computational fluid dynamics method 2.1 The numerical information of the annular seal Figure 1A depicts the seal used in the paper, which is based on Kanemori's experimental model (Kanemori and Iwatsubo, 1994). The geometric information and simulation information of the annular seal are shown in Table 1.…”

“…Childs (1982) mentioned the dynamic coefficients due to shaft angular displacements are also crucial in annular seals having characteristics of large length-diameter (L/D) ratio, especially in submerged pumps. The moment coefficients due to shaft misalignment angles were obtained by Askharone and Hensel, (1991) through finite element (Kanemori and Iwatsubo, 1994).…”

Dynamic force and torque characteristic of annular gaps -- Simulation results and evaluation of the relevance of the tilt and torque coefficients

“…It is shown that the phase of the whirl acts either as a stabilising or destabilising force. Kanemori and Iwatsubo (1994a) extend their work to a linear stability analysis using the logarithmic decrement on a real submerged motor pump including hydrodynamic forces and torques when carrying out the stability analysis. The individual contributions of the whirl and concentric motion to the stability of the system is evaluated.…”

On the modelling of aerodynamic force coefficients for over-shroud seals of turbine stages

“…Mutual relationship between pressure force and displacement of rotor against casing is usually described by means of the so called "seal dynamic coeffcients" [1][2][3][4][5][6][7][8][12][13][14] which can be incorporated into whole model of turbine set during its designing process. Three kinds of the dynamic coefficients can be distinguished: stiffness, damping nad inertia ones.…”