Phase-distribution regularity and sealing performance of supercritical carbon dioxide dry gas seal

doi:10.11949/0438-1157.20200376

Abstract

Abstract:

Taking the supercritical carbon dioxide dry gas seal as the research object, the real gas effect and viscosity change of carbon dioxide are described by the Viri equation and Lucas equation. While considering the choked flow effect, the finite difference method was used to solve the Reynolds equation considering centrifugal inertia force effect and the energy control equation, and the influence of operating condition parameters and groove structure parameters on the phase distribution and sealing performance was analyzed and discussed. The research shows that in the flow process of S-CO₂ from the inlet of the seal end face to the outlet, if the operating condition parameters are set properly, it will gradually change from supercritical state to gaseous state without liquid state. Low inlet pressure, inlet temperature and rotation speed will easily lead to potential condensation flow. Compared with the influence of operating condition parameters on the phase distribution, the influence of groove parameters on the phase distribution is small and almost negligible. Except that the opening force decreases with the increase of inlet temperature, it increases with the increase of inlet pressure, rotation speed, groove depth and spiral angle. The leakage rate decreases with the increase of inlet temperature and rotation speed, but it increases with the increase of inlet pressure, groove depth and spiral angle. These results provide some support for the further study of supercritical carbon dioxide dry gas seal.

Key words: supercritical carbon dioxide, dry gas seal, centrifugal inertia force effect, real gas effect, choked flow, phase distribution

摘要：

以超临界二氧化碳干气密封为研究对象，分别以维里方程、Lucas方程描述二氧化碳真实气体效应、黏度的变化，在考虑阻塞流效应的同时，采用有限差分法对考虑离心惯性力效应的Reynolds方程与能量控制方程进行耦合求解，分析讨论了工况参数与槽形结构参数对其相态分布规律与密封性能的影响。研究表明：S-CO₂从密封端面进口至出口的流动过程中，如果工况参数设置合理，将由超临界态逐渐转变为气态，并不会出现液态；较低的进口压力、进口温度以及转速，均会容易导致潜在的凝结流动发生；相比于工况参数对相态分布的影响，槽形参数对相态分布的影响较小，近乎可以忽略；开启力除了随进口温度的升高而减小外，均随进口压力、转速、槽深、螺旋角的增大而增大；泄漏率随进口温度和转速的增大而减小，但其随进口压力、槽深、螺旋角的增大而增大。这些结果为进一步研究超临界二氧化碳干气密封提供了一定的支撑。

关键词: 超临界二氧化碳, 干气密封, 离心惯性力效应, 真实气体效应, 阻塞流, 相态分布

CLC Number:

TH 136

Ruqi YAN, Xianzhi HONG, Xin BAO, Jie XU, Xuexing DING. Phase-distribution regularity and sealing performance of supercritical carbon dioxide dry gas seal[J]. CIESC Journal, 2020, 71(8): 3681-3690.

严如奇, 洪先志, 包鑫, 徐洁, 丁雪兴. 超临界二氧化碳干气密封相态分布规律与密封性能研究[J]. 化工学报, 2020, 71(8): 3681-3690.

Figures/Tables 11

Fig.1 Schematic diagram of spiral groove dry gas seal

Table 1 Geometric parameter of spiral dry gas seal

参数	N₂^[31]	S-CO₂
内径r_i/ mm	70	25
外径r_o/ mm	90	35.5
根径r_g/ mm	0	29.35
槽数N_g	0	12
螺旋角 $α$ /rad	0	15π/180
槽坝比 $β$	0	1
槽深h_g/μm	0	5
非槽区膜厚h₀/μm	5	3

Table 1 Geometric parameter of spiral dry gas seal

参数	N₂^[31]	S-CO₂
内径r_i/ mm	70	25
外径r_o/ mm	90	35.5
根径r_g/ mm	0	29.35
槽数N_g	0	12
螺旋角 $α$ /rad	0	15π/180
槽坝比 $β$	0	1
槽深h_g/μm	0	5
非槽区膜厚h₀/μm	5	3

Table 2 Operation conditions of spiral dry gas seal

参数	N₂^[31]	S-CO₂
转速n/(r/min)	0	15000
进口压力p_i/MPa	20	12
出口压力p_o/MPa	0.1	0.1
进口温度T_i/K	300	400

Fig.2 Flow chart of numerical calculation

Fig.3 Pressure validation of the calculation program

Fig.4 Distribution of pressure, temperature, and Mach number under different outlet pressure boundary conditions

Fig. 5 Phase distribution in the gas film (a), opening force and leakage rate(b) under different inlet pressure

Fig. 6 Phase distribution in the gas film(a), opening force and leakage rate(b) under different inlet temperature

Fig. 7 Phase distribution in the gas film(a) , opening force and leakage rate(b) under different rotation speed

Fig. 8 Phase distribution in the gas film(a), opening force and leakage rate(b) under different groove depth

Fig. 9 Phase distribution in the gas film(a), opening force and leakage rate (b) under different spiral angle

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