Dynamic Coefficients of Stepped Labyrinth Gas Seals

Kwanka, K.

doi:10.1115/99-gt-020

Cited by 2 publications

(2 citation statements)

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“…Recently, various seal geometries, e.g., stepped labyrinth seal and honeycomb seal, were numerically investigated by Kleynhans [8], Yucel and Kazakia [9] and Dursun [10]. Cross-coupled stiffness coefficients of stepped labyrinth seal predicted by Yucel [11] showed relatively good agreement with the experimental data [12]. Further more, a set of differential equations were employed to allow the clear flow structure of the leakage air flow through a straight-labyrinth seal [13,14].…”

Section: Introductionmentioning

confidence: 96%

Computation of rotordynamic coefficients associated with leakage steam flow through labyrinth seal

et al. 2007

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A mathematical model of calculating rotordynamic coefficients associated with leakage steam flow through labyrinth seals was presented. Particular attention was given to incorporating thermal properties of the steam fluid into prediction of leakage flow and subsequent derivation of rotordynamic coefficients, which quantitatively characterize influence of aerodynamic forcing of the leakage steam flow on the rotordynamics. By using perturbation analysis, we determined periodic and analytic solutions of the continuity and circumferential momentum equations for the time-dependent flow induced by non-axisymmetric rotation of the rotor encompassed by a labyrinth seal. Pressure distributions along labyrinth seal cavities and rotordynamic coefficients were compared at the same condition for air and steam flows. Influence of steam flow through the labyrinth seal cavities on rotordynamic coefficients was analyzed in terms of inlet pressure, inlet swirl velocity and rotor speed. List of symbolA unsteady cross-sectional area of the cavity [m 2 ] A 0 steady annular flow area [m 2 ] B tooth height [m] C 0 orifice contraction coefficient C 1 kinetic energy carry-over coefficient C r steady radial clearance [m] C x x , C yy damping coefficients [N s/m] C xy , C yx cross-couple damping coefficients [N s/m] Dh 0 , Dh steady and unsteady hydraulic diameter of the cross-sectional area of the cavity [m] F total air reaction force [N] F x , F y annular seal reaction force components [N] h 0 stagnant enthalpy [J/Kg] h iseal enthalpy at the ith orifice [J/Kg] H unsteady labyrinth seal radial clearance [m] H 1 (t, θ) perturbation clearance [m] K x x , K yy direct stiffness coefficients [N/m] K xy , K yx cross-couple stiffness coefficients [N/m] L cavity length [m] N tooth number n specific heat ratio P 0i , P i steady and unsteady pressure at the ith cavity [Pa] P 0iseal , P iseal steady and unsteady pressure at the ith orifice [Pa] P 1i (t, θ) perturbation pressure in the ith cavity [Pa] q 0i ,q i steady and unsteady leakage flow rate per unit length [kg/s m] q 1i (t, θ) perturbation leakage flow rate per unit length [kg/s m] R steam constant [J/kg K] R s rotor radius [m] T i temperature at the ith cavity [K] T iseal temperature at the ith orifice [K] U iseal velocity at the ith orifice [m/s] V 0i , V i steady and unsteady circumferential velocities at the ith cavity [m/s] V 1i (t, θ) perturbation pressure at the ith cavity [m/s] (x, y)x and y coordinates of rotor whirling motionGreek symbols ε eccentricity ratio η imaginary number ρ i , ρ 0i steady and unsteady gas density of the ith cavity [kg/m 3 ] ρ 1 (t, θ) perturbation gas density of the ith cavity [kg/m 3 ] ρ 0iseal , ρ iseal steady and unsteady gas density at the ith clearance [kg/m 3 ] ρ 1iseal (t, θ) perturbation gas density at the ith clearance [kg/m 3 ] τ r 0i , τ ri steady and unsteady shear stresses at the rotor wall [N/m 2 ] τ r 1i (t, θ) perturbation shear stresses at the rotor wall [N/m 2 ] τ s0i , τ si steady and unsteady shear stresses at the stator wall [N/m 2 ] ...

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Section: Introductionmentioning

confidence: 96%

Computation of rotordynamic coefficients associated with leakage steam flow through labyrinth seal

et al. 2007

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“…The presence of rub grooves would deteriorate the sealing performance or even induce the seal failure. Previous studies [2][3][4] have shown that leakage flow through labyrinth seals without rub grooves would give a significant influence on the rotor dynamics. Accordingly, an insight understanding of influence of rub grooves on dynamics of the rotor subjected to aerodynamic forcing of the leakage flow is of essential significance.…”

Section: Introductionmentioning

confidence: 99%

Influence of rub groove on rotordynamics associated with leakage air flow through a labyrinth seal

et al. 2010

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An extensive investigation of influence of rub grooves on dynamics and stability of the rotor, which is subjected to aerodynamic forcing associated with the leakage flow through 44 straight-through seals, was performed by using numerical calculations based on the single control-volume method and the perturbation analysis. Three cases of different groove configurations were chosen for the comparative study, e.g., the seal without rub groove (case1), the seal with upstream shifting of the seal tooth in respect to the rub groove (case2) and the seal with location of the seal tooth in the middle station of the rub groove (case3). The orifice contract coefficient adopted in reduction of rotordynamic coefficients was provided by using Computational Fluid Dynamics (CFD). Influence of rub grooves on the leakage flow was obtained in terms of the close-up view of the flow pattern near the seal tooth, leakage flow rate, distributions of the mean pressure and circumferential velocity in cavities. In comparison to case 1, the leakage flow in case 3 is considerably intensified, while which in case 2 is slightly increased. Dynamics and instability of the rotor in all cases was discussed in terms of the rotordynamic coefficients and the logarithmic decrement, respectively. The results disclosed that the aerodynamic forcing in case 2 intensified the destabilization of the rotor system.

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Dynamic Coefficients of Stepped Labyrinth Gas Seals

Cited by 2 publications

References 0 publications

Computation of rotordynamic coefficients associated with leakage steam flow through labyrinth seal

Computation of rotordynamic coefficients associated with leakage steam flow through labyrinth seal

Influence of rub groove on rotordynamics associated with leakage air flow through a labyrinth seal

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