Dynamic characteristics of smooth annular gas seal

YANG Xingchen1, ZHANG Wanfu1,2, ZHANG Xiaobin3, CHEN Luqi4, GU Chengjing1, LI Chun1,2

Journal of Vibration and Shock ›› 2022, Vol. 41 ›› Issue (1) : 88-97.

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PDF(4544 KB)
Journal of Vibration and Shock ›› 2022, Vol. 41 ›› Issue (1) : 88-97.

Dynamic characteristics of smooth annular gas seal

  • YANG Xingchen1, ZHANG Wanfu1,2, ZHANG Xiaobin3, CHEN Luqi4, GU Chengjing1, LI Chun1,2
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Abstract

The dynamic characteristics of smooth annular gas seals directly affect the system stability of turbomachines. A three-dimensional numerical model of a smooth annular gas seal is established. The identification method based on infinitesimal theory is applied to calculate the flow characteristics under two outlet states (unchoked/choked), five eccentric ratios (ε = 10%, 30%, 50%, 70%, 80%) and three length-diameter ratios (L/D = 0.5, 1.0, 1.5). Results show that the direct stiffness coefficient decreases with the increasing eccentric ratios and whirling frequencies under the unchoked and choked flow conditions (L/D = 1.0). The magnitude of the cross-coupled stiffness coefficient and the direct damping coefficient increase with the increasing eccentric ratios. For the seal working in high eccentric ratios, the influence of eccentric ratios on the dynamic coefficient must be taken into consideration, which cannot be simplified to the conventional four dynamic coefficients. Under different whirling frequencies, the effective damping coefficient shows an opposite trend with the increase of eccentric ratio and length-diameter ratios. The rotor system with low frequency whirling, high eccentric ratio length-diameter ratios is more likely to be unstable.

Key words

smooth annular gas seal / dynamic characteristics / eccentric ratios / stability / computational fluid dynamics (CFD)

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YANG Xingchen1, ZHANG Wanfu1,2, ZHANG Xiaobin3, CHEN Luqi4, GU Chengjing1, LI Chun1,2. Dynamic characteristics of smooth annular gas seal[J]. Journal of Vibration and Shock, 2022, 41(1): 88-97

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