Measurements Versus Predictions for the Dynamic Impedance of Annular Gas Seals—Part II: Smooth and Honeycomb Geometries

Dawson, Matthew P.; Childs, Dara W.

doi:10.1115/1.1478076

Cited by 16 publications

(4 citation statements)

References 5 publications

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“…However, an induced aerodynamic forcing acts on the whirling rotor [1,2]. Various numerical studies [3][4][5][6][7][8][9] and experimental measurements [10][11][12][13][14] have been made to get a school of rotordynamic coefficients which characterized the global influence of the aerodynamic forcing on the rotordynamics.…”

Section: Introductionmentioning

confidence: 99%

Influence of leakage flow through labyrinth seals on rotordynamics: numerical calculations and experimental measurements

et al. 2007

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An extensive investigation of the influence of the leakage flow through a labyrinth seal at supply pressure of 12 bar on the rotordynamics was performed by using numerical calculations and experimental measurements. Toward this end, an experimental rotor setup was established in Shanghai Jiao Tong University. Two labyrinth seals were chosen for comparison, e.g., an interlocking seal and a stepped one. The numerical calculations based on the bulk-flow theory and the perturbation analysis were accomplished. Simultaneous acquisitions of the fluctuating static pressure at the stator wall and the displacement of the whirling rotor were made. The influence of the aerodynamic forcing on the rotor was analyzed in terms of the axial distribution of the mean static pressure, the circumferential distribution of the fluctuating pressure, the fist critical speed and the destabilization rotating speed of the rotor. The experimental results demonstrated that the sinusoidal distribution of the fluctuating static pressure on the stator wall was closely related to the whirling motion of the rotor. The first critical speed of the rotor was reduced by the aerodynamic forcing, resulting in intensified destabilization of the rotor system. Furthermore, the numerical analyses were in good agreement to the experimental measurements. List of symbols AUnsteady cross-sectional area of the cavity (m 2 ) A n Steady annular flow area (m 2 ) [C]Damping matrix C 0Orifice contraction coefficient C 1 Kinetic energy carry-over coefficient C r Steady radial seal clearance (m) C x x , C yy Damping coefficients (N-s/m) C xy , C yx Cross-couple damping coefficients (N-s/m)

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Section: Introductionmentioning

confidence: 99%

Influence of leakage flow through labyrinth seals on rotordynamics: numerical calculations and experimental measurements

et al. 2007

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“…where x  , y  are the Fourier transforms of the lateral displacements in two fixed orthogonal directions and F x  , F y  are the Fourier transforms of the corresponding forces. The frequency-response function H ij is a dynamic stiffness, but is called impedance in this paper, following the use of other authors in the same context [4], [6] and [7]. This choice has some advantage because the term stiffness can be used for the real part, i.e.…”

Section: Dynamic Coefficientsmentioning

confidence: 99%

Review and Upgrade of a Bulk Flow Model for the Analysis of Honeycomb Gas Seals Based on New High Pressure Experimental Data

Diego

Forte

Vannini³

2015

SV-JME

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The design of the gas seals used in centrifugal compressors and axial turbines requires to consider not only their aptitude to reduce leakage, but also their contribution to the overall dynamics of the machine. Honeycomb and hole pattern annular seals are often employed in compressors for the end balance piston seal or as the central balance piston seal in a back-to-back arrangement. In contrast to labyrinth seals, they show a beneficial damping effect.In order to obtain an effective tool for predicting the leakage and the dynamic response of honeycomb seals, a bulk flow model has been devised in the past and, implemented in numerical codes, it is presently used in the design process. This kind of codes, however, require simplifying assumptions: in particular, one reference code available to the authors adopts the hypothesis of isothermal process. As the required level of confidence in seal design is increasing, an experimental validation and possibly some refinement are needed.In this work, the bulk flow model was reviewed and the sensitivity to different hypotheses was explored. New experimental data from a high pressure test rig were compared with the results of simulations.

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“…The effects of the design parameters for conventional seals have been analyzed as suggested in references. 31–33 For the RAS, further research is needed to study the dependency of the seal characteristics on the design parameters.…”

Section: Flow Behavior For the Outward And Inward Flows In The Radial Annular Sealmentioning

confidence: 99%

Research on the leakage and dynamic characteristics of a new kind of radial annular seal and comparisons with labyrinth seals

Zhang

Yang

Tian

et al. 2013

Proceedings of the Institution of Mechanical Engineers, Part A:

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To minimize fluid leakage and improve rotordynamic stability of traditional seals, a new kind of radial annular seal is presented in this article. The structure and the sealing principle are analyzed. Compared to the traditional labyrinth seal, the fluid leakage direction is altered from the axial to radial direction. The flow resistance is increased, and the flowinduced force is reduced greatly. There is also a tremendous improvement in the wear resistance of the seal. Threedimensional numerical models of the traditional labyrinth seal and radial annular seal are set up. Calculated results show that the discharge coefficient of the radial annular seal is about 20% lower than that of the labyrinth seal. Though the rotating speed has a small influence on the radial seal force for both the radial annular seal and labyrinth seal, it has a large effect on the tangential seal force. The tangential seal force increases with the increasing speed, and the destabilizing force in the radial annular seal is reduced greatly when compared to that in the labyrinth seal. The radial seal force of the radial annular seal is about 1.5-2.5 times as strong as that of the labyrinth seal. The tangential seal force is about 30-50% lower than that of the labyrinth seal under the same eccentricity, and this ratio becomes larger and larger with the increasing speed. Finally, the dependency of the seal characteristics on the design parameters is studied. It is shown that the optimum ratios of the clearance s to the tooth thickness b (s/b) for the outward and inward flows are 4.5-5.5 and 11-13, respectively. The flow characteristics perform best with the ratio of the seal chamber width B to the tooth height H (B/H) on the same order of 5.5-7 for the two kinds of flows.

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Measurements Versus Predictions for the Dynamic Impedance of Annular Gas Seals—Part II: Smooth and Honeycomb Geometries

Cited by 16 publications

References 5 publications

Influence of leakage flow through labyrinth seals on rotordynamics: numerical calculations and experimental measurements

Influence of leakage flow through labyrinth seals on rotordynamics: numerical calculations and experimental measurements

Review and Upgrade of a Bulk Flow Model for the Analysis of Honeycomb Gas Seals Based on New High Pressure Experimental Data

Research on the leakage and dynamic characteristics of a new kind of radial annular seal and comparisons with labyrinth seals

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