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Influence of Exit-Recovery Coefficient on the Leakage and Dynamic Characteristics of Annular Seal

  • Research Article - Mechanical Engineering
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Abstract

In order to study the effect of exit-recovery coefficient on leakage performance and dynamic characteristics of finite-length annular seal, a new boundary condition including exit-recovery coefficient is applied to the solution of the first-order perturbation equations according to bulk-flow model and small disturbance hypothesis. The theoretical results are validated by the experimental results with the minimum and maximum error percentage being 0.22% and 4.33%, respectively. On the basis of the accurate model, the influences of exit-recovery coefficient on leakage performance, dynamic coefficients and stability are investigated in detail. The calculated results imply that the exit-recovery coefficient needs to be considered in the characteristic research of annular seal. The exit-recovery coefficient is proportional to principle stiffness, while it is inversely proportional to leakage, principle damping, cross-coupled stiffness and damping. In addition, the exit-recovery coefficient has little effect on the stability of annular seal. The theoretical model including the exit-recovery coefficient is closer to actual condition and the results can provide references for the design of annular seal and multistage pump rotor system.

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Abbreviations

C :

Principle damping of seal (\(\hbox {N}\,\hbox {s/m}\))

\({\bar{C}}\) :

Dimensionless principle damping of seal

c :

Cross-coupled damping of seal (\(\hbox {N}\,\hbox {s/m}\))

\({\bar{c}}\) :

Dimensionless cross-coupled damping of seal

\(F_{s}\) :

Fluid-induced force (N)

\(H_{0}\) :

Clearance of radial seal (m)

i :

Imaginary unit (\(i^{2} = -1\))

K :

Principal stiffness of seal (\(\hbox {N/m}\))

\({\bar{K}}\) :

Dimensionless principal stiffness of seal

k :

Cross-coupled stiffness of seal (\(\hbox {N/m}\))

\({\bar{k}}\) :

Dimensionless cross-coupled stiffness of seal

\(L_{c}\) :

Length of seal (\(\hbox {m}\))

M :

Principal mass of seal (\(\hbox {kg}\))

\({\bar{M}}\) :

Dimensionless principal mass of seal

\({\bar{p}}\) :

Dimensionless pressure

\(P_\mathrm{in}, p_\mathrm{out}\) :

Inlet and outlet pressure (MPa)

Q :

Leakage flow (\(\hbox {m}^{3}/\hbox {s}\))

R :

Radius of rotor (\(\hbox {m}\))

\({\bar{r_0 }}\) :

Dimensionless whirl amplitude

T :

Time passed through seal (\(\hbox {s}\))

\(\bar{u}_{{\mathrm{z}}0}, {\bar{u}}_{\phi {0}}\) :

Dimensionless zero-order velocity in axial and circumferential direction

V :

Axial velocity (\(\hbox {m/s}\))

v :

Dimensionless pre-whirl velocity

xyz :

Axes (\(\hbox {m}\))

\({\bar{x}},{\bar{y}},{\bar{z}}\) :

Dimensionless axes

\(\Delta {p}\) :

Differential pressure (\(\hbox {MPa}\))

\(\varepsilon \) :

Eccentricity

\(\zeta \) :

Dimensionless eccentricity ratio of seal

\(\xi _{i}\) :

Inlet-loss coefficient

\(\xi _\mathrm{e}\) :

Exit-recovery coefficient

\(\varOmega \) :

Whirl speed (\(\hbox {r/min}\))

\(\omega \) :

Rotating speed (\(\hbox {r/min}\))

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Correspondence to Guangkuan Wu.

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Zhou, W., Wu, G., Qiu, N. et al. Influence of Exit-Recovery Coefficient on the Leakage and Dynamic Characteristics of Annular Seal. Arab J Sci Eng 44, 1293–1303 (2019). https://doi.org/10.1007/s13369-018-3495-5

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  • DOI: https://doi.org/10.1007/s13369-018-3495-5

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