Study on startup operation of dry gas seal with steam lubrication

doi:10.11949/0438-1157.20200134

Abstract

Abstract:

Steam is an actual gas, so it is of great significance to study the starting process of steam-lubricated dry gas seals for the start-up and operation of steam turbine seals. The GW contact model is used whose contact model parameters are determined by experiments. The results show that the contact model parameters determined by way of experiment: asperity curvature radius R=3.7310 μm, asperity area density η=0.1458 μm^-2. During the opening process, as the rotating speed increases, the gas film bearing capacity continues to increase, and the closing force remains unchanged, but the contact force rapidly decreases to zero. When the rotating speed reaches certain value, the bearing capacity of the gas film is equal to the closing force, and the sealing end face is completely separated from each other. When the curvature radius R of the micro-convex body is used as a variable, the gas film bearing capacity increases, and the contact force decreases with R decreasing. With micro-convex body area density η being a variable, the contact force increases, the gas film bearing capacity reduces. By comparing the contact model data of this paper with the model data of Etsion et al., the influence of contact model parameters on the opening performance is analyzed. It is found that based on the contact model data obtained in this paper, the contact force is slightly smaller, and both the opening force and the pressure at the groove root are mildly larger. The leakage rate is slightly smaller, and the ratio of the opening force to the leakage is lightly larger at low speed.

Key words: dry gas seal, contact force, contour instrument, root mean square, root mean square slope

摘要：

水蒸气为实际气体，研究水蒸气润滑干气密封的启动过程，对汽轮机密封的启动、运行有重要意义。选用GW模型，由实验确定接触模型参数。经实验确定的接触模型参数为：微凸体曲率半径R=3.7310 μm，微凸体面积密度η=0.1458 μm^-2。在开启过程中，随着转速增加，气膜承载力持续增加，闭合力保持不变，接触力迅速减小至零。当转速达到一定值时，气膜承载力与闭合力相等，此时，密封端面完全脱开。以微凸体曲率半径R为变量时，R增大，接触力增加、气膜承载力减小；以微凸体面积密度η为变量时，η增加，接触力增加、气膜承载力减小。将本文接触模型数据和Etsion等的模型数据对比，分析接触模型参数对开启性能的影响。发现依据本文接触模型数据计算的接触力稍小、开启力稍大、槽根压力稍大，在低转速时，泄漏率稍小、开漏比稍大。

关键词: 干气密封, 接触力, 轮廓仪, 均方根, 均方根斜率

CLC Number:

S 277.9

Yu FAN, Pengyun SONG, Hengjie XU. Study on startup operation of dry gas seal with steam lubrication[J]. CIESC Journal, 2020, 71(8): 3671-3680.

范瑜, 宋鹏云, 许恒杰. 水蒸气润滑干气密封启动过程研究[J]. 化工学报, 2020, 71(8): 3671-3680.

Figures/Tables 17

Fig.1 Single end face dry gas seal

Fig.2 Rotating ring of a dry gas seal

Table 1 Experimental data of Carbon

Case	R_qs/μm	R_dqs
Case 1	0.0600	0.0633
Case 2	0.0600	0.0619
Case 3	0.0700	0.0616
Case 4	0.0600	0.0633
Case 5	0.0700	0.0640
average	0.0640	0.0628

Table 2 Experimental data of SiC

Case	R_qr /μm	R_dqr
Case 1	0.0700	0.0538
Case 2	0.0600	0.0492
Case 3	0.0800	0.0531
Case 4	0.0800	0.0546
Case 5	0.0700	0.0504
average	0.0700	0.0522

Fig.3 Graph of stationary ring test data

Fig.4 Graph of rotating ring test data

Table 3 Comparison of experimental data with data of Etsion et al.

Data	R/μm	η/μm^-2
experimental	3.7310	0.1458
Etsion et al.^[19]	1.7071	0.4161

Table 4 Comparison of speitral moment between experimental data and literature data

Data	m₀/μm²	m₂	m₄/μm^-2	α	y_s/μm	σ/μm	$σ s$ /μm
experimental	0.008996	0.006669	0.031737	6.4194	0.0845	0.0948	0.0909
Etsion et al.^[19]	0.010650	0.011160	0.151600	12.9634	0.0647	0.1032	0.0996

Table 4 Comparison of speitral moment between experimental data and literature data

Data	m₀/μm²	m₂	m₄/μm^-2	α	y_s/μm	σ/μm	$σ s$ /μm
experimental	0.008996	0.006669	0.031737	6.4194	0.0845	0.0948	0.0909
Etsion et al.^[19]	0.010650	0.011160	0.151600	12.9634	0.0647	0.1032	0.0996

Fig.5 Compression factor of steam gas

Fig.6 The influence of peak radius of curvature on axial force of micro-convex body

Fig.7 Influence of area density on axial force of micro-convex body

Fig.8 The change law of equilibrium speed with film thickness

Fig.9 The law of contact force changing with rotation speed

Fig.10 The change rule of axial force with rotation speed

Fig.11 The variation of root pressure with rotation speed

Fig.12 Variation rule of leakage rate with rotation speed

Fig.13 Change law of the opening-leakage ratio with rotation speed

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