Effects of Wear-reducing Groove Depth on Leakage and Flow Characteristics of Graphite Circumferential Seal

doi:10.3969/j.issn.1004-132X.2026.08.002

Abstract

Abstract:

During the operation of graphite circumferential seals， degradation in tracking performance may cause contact between the inner sealing surface and the rotor runway， leading to wear and subsequent failure of the dynamic-pressure wear-reducing groove. However， a theoretical basis for determining the groove depth in engineering applications remains lacking. In this study， a numerical model of leakage and flow characteristics for the graphite circumferential seal is established and validated through experiments. Based on the validated model， the airflow evolution and leakage variation through the seal clearance are comparatively analyzed under different inlet/outlet pressure differences and groove depths， aiming to reveal the influence mechanism of groove depth on the leakage and flow characteristics. The results indicate that as the groove depth increases to 150 μm， the area of the local high-pressure zone around the groove gradually decreases， suggesting a weakening of the hydrodynamic pressure effect. However， this decreasing trend becomes less pronounced with increasing inlet/outlet pressure difference. The airflow velocity near the groove wall decreases significantly with increasing groove depth. Notably， when the groove depth exceeds 100 μm， a local high-velocity region appears near the groove bottom， and its area expands with both increasing groove depth and increasing pressure difference. When the groove depth exceeds 25 μm， reverse flow is observed at the groove end due to the obstruction of the step wall. Further increase in groove depth intensifies the reverse flow velocity， which consequently reduces the hydrodynamic pressure effect of the graphite circumferential seal.

Key words: graphite circumferential sealing, wear-reducing groove, leakage flow characteristics, hydrodynamic pressure effect, groove depth

摘要：

石墨圆周密封随动性下降引起内表面与转子跑道碰磨，导致动压减磨槽磨损失效，工程应用中槽深设计缺少理论依据。建立动压式石墨圆周密封泄漏流动特性数值求解模型，在实验验证数值模型准确性的基础上，对比分析不同进出口压差下、不同深度减磨槽的石墨圆周密封间隙内气流流动演变的过程和泄漏量的变化规律，揭示减磨槽深度对密封泄漏流动特性的影响机理。研究结果表明：随着减磨槽深度的增加，槽内局部高压区域面积逐渐减小，减磨槽内流体动压效应减弱，进出口压差增大使高压区域面积减小的趋势减弱。气流流经槽内壁面附近流速显著降低，特别是减磨槽深度大于100 μm时，靠近减磨槽底部出现局部增速区，且随着槽深和进出口压差的增加而逐渐增大。减磨槽深度大于25 μm时，由于槽末端台阶壁面阻挡，部分气流发生回转倒流，槽深增加，回转气流流速增加，密封流体动压效应随之减弱。

关键词: 石墨圆周密封, 减磨槽, 泄漏流动特性, 流体动压效应, 槽深

CLC Number:

V232.7

WANG Zhuang, ZHAO Huan, SUN Dan, ZHANG Lijing, WANG Xinyu, WEN Shuaifang, FAN Rufeng. Effects of Wear-reducing Groove Depth on Leakage and Flow Characteristics of Graphite Circumferential Seal[J]. China Mechanical Engineering, 2026, 37(8): 1824-1831.

王壮, 赵欢, 孙丹, 张立静, 王鑫宇, 温帅方, 樊汝凤. 减磨槽深度对石墨圆周密封泄漏流动特性影响研究[J]. 中国机械工程, 2026, 37(8): 1824-1831.

Figures/Tables 22

Fig.1 2-D structure diagram of graphite circumferential seal

Fig.2 Graphite ring three-dimensional structure diagram

Fig.3 Structural diagram of graphite circumferential seal with wear-reducing groove

Tab.1 Structural parameters

环槽深度h_c/mm	0.80	环槽宽度w_c/mm	2.00
横槽深度h_a/mm	0.80	横槽宽度w_a/mm	4.00
横槽长度L_a/mm	5.30	减磨槽深度h_p/μm	15~150
减磨槽宽度w_p/mm	3.50	减磨槽长度L_p/mm	9.00

Fig.4 Fluid domain mesh of graphite circumferential seal

Fig.5 Leakages under different groove depths withnumber of grids

Tab.2 Grid number of fluid domain in graphite segment under different groove depths

槽深/μm	网格节点数/10⁴	网格数/10⁴
15	139.3	123.4
25	155.7	139.1
50	197.2	179.1
75	240.2	220.5
100	280.3	259.0
125	323.5	300.6
150	365.8	341.3

Fig.6 Test piece of graphite circumferential seal

Fig.7 Test equipment of graphite circumferential seal performance under high-temperature and high- speed

Fig.8 Comparison between numerical and experimental results

Fig.9 Pressure distribution of graphite circumferential seal

Fig.10 Schematic diagram of radial cross section of wear-reducing groove

Fig.11 Airflow velocity in radial cross section of wear-reducing groove

Fig.12 Pressure distribution of airflow in radial cross section of wear-reducing groove

Fig.13 Change in pressure distribution of airflow in wear-reducing groove with groove depth

Fig.14 Change of maximum airflow pressure in wear-reducing groove with groove depth

Fig.15 Airflow velocities at end of wear-reducing groove under different groove depths

Fig.16 Airflow velocities at end of wear-reducing groove under different inlet/outlet pressure differences

Fig.17 Leakages of seal with different groove depths under different pressure differences

Fig.18 Fluid film schematic diagram of force on theelement body

Fig.19 Airflow streamline diagram at end of wear-reducing groove under different groove depths

Fig.20 Airflow velocity vector diagram at end of wear-reducing groove under different groove depths

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