Measurements Versus Predictions for the Dynamic Impedance of Annular Gas Seals: Part 1 — Test Facility and Apparatus

Dawson, Matthew P.; Childs, Dara W.; Holt, Christopher G.; Phillips, Stephen

doi:10.1115/2001-gt-0237

Cited by 4 publications

(2 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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

View full text Add to dashboard Cite

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)

show abstract

Section: Introductionmentioning

confidence: 99%

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

et al. 2007

View full text Add to dashboard Cite

show abstract

“…It was later altered to test annular gas seals. Dawson et al [8] describe how the test rig was altered to test at an inlet pressure up to 17.2 bars (250 psi). Weatherwax and Childs [9] explain how the rig was modified for testing at inlet pressures to 84 bars (absolute) (1235 psi (absolute)).…”

Section: Test-rig Descriptionmentioning

confidence: 99%

Measurement Versus Predictions of Rotordynamic Coefficients of a Hole-Pattern Gas Seal With Negative Preswirl

Brown¹,

Childs

2012

Journal of Engineering for Gas Turbines and Power

Self Cite

View full text Add to dashboard Cite

Test results are presented for the rotordynamic coefficients of a hole-pattern annular gas seal at supply pressures to 84 bar and running speeds to 20200 rpm. The principal test variable of interest was negative preswirl. Preswirl signifies the circumferential fluid flow entering a seal and negative preswirl indicates a fluid swirl in a direction opposite to rotor rotation. The influences of the pressure ratio and rotor speed were also investigated. The measured results produce direct and cross-coupled stiffness and damping coefficients that are a function of the excitation frequency Í2. Changes in the pressure ratio had only small effects on most rotordynamic coefficients. Cross-coupled stiffness showed slightly different profiles through the midrange of Q. values. Increasing rotor speed significantly increased the cross-coupled stiffness and cross-coupled damping. At 10,200 RPM, high negative inlet preswirl produced negative cross-coupled stiffness over an excitation frequency range of 200-250 Hz. Negative preswirl did not affect the direct stiffness and damping coefficients. Effective damping combines the stabilizing effect of direct damping and the destabilizing effect of cross-coupled stiffness. The crossover frequency is the precession frequency where effective damping transitions from a negative value to a positive value with increasing frequency. At 20,200 rpm with a pressure ratio of 50%, the peak effective damping was increased by 50%, and the crossover frequency was reduced by 50% for high-negative preswirl versus zero preswirl. Hence, reverse swirl can greatly enhance the stabilizing capacity of a hole-pattern balance-piston or division-wall seals for compressors. A two-control-volume model that uses the ideal gas law at constant temperature was used to predict rotordynamic coefficients. The model predicted direct rotordynamic coefficients well, however, substantially underpredicted cross-coupled rotordynamic coefficients, especially at high negative preswirls.

show abstract

Theory Versus Experiment for the Rotordynamic Characteristics of a High Pressure Honeycomb Annular Gas Seal at Eccentric Positions

Weatherwax

Childs

2003

Journal of Tribology

View full text Add to dashboard Cite

Test results for leakage and rotordynamic coefficients are presented for a honeycomb-stator/smooth-rotor annular seal for eccentricity ratios out to 0.5 using air as the test fluid. Tests were conducted at supply pressures up to 70 bars and running speeds up to 20200 rpm. The seal has a diameter of 115 mm, a cell width of 0.79 mm, and a cell depth of 3.10 mm. Tests were conducted for the back-pressure ratios of 0.35, and 0.5. Comparisons are made to predictions from an analysis due to San Andres. The test results show a minimal sensitivity of either leakage or rotordynamic coefficients to changes in the eccentricity ratio. The predictions generally agree well with measurements.

show abstract

Measurements Versus Predictions for the Dynamic Impedance of Annular Gas Seals: Part 1 — Test Facility and Apparatus

Cited by 4 publications

References 0 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

Measurement Versus Predictions of Rotordynamic Coefficients of a Hole-Pattern Gas Seal With Negative Preswirl

Theory Versus Experiment for the Rotordynamic Characteristics of a High Pressure Honeycomb Annular Gas Seal at Eccentric Positions

Contact Info

Product

Resources

About