Study on influence of operating conditions on thermodynamic process and steady state performance of supercritical CO2 dry gas seal

doi:10.11949/0438-1157.20241240

Abstract

Abstract:

The dry gas seal of a supercritical CO₂ compressor exhibits unique properties and high parameterization near the critical point. The medium flow demonstrates characteristics of multiphase flow, intense turbulence, and property distortion in the sealing gap. Focusing on a segmented micro-grooved dry gas seal, a thermo-hydrodynamic lubrication phase-change simulation model is constructed for supercritical CO₂ dry gas seals, considering real fluid effects under axial force equilibrium. A method to characterize the thermodynamic processes on the seal face is proposed, and the effects of operating conditions, including rotating speed, inlet pressure, and inlet temperature, on the thermodynamic processes, flow field parameters, and steady-state performance of the seal are analyzed. The results indicate that increasing the inlet temperature significantly suppresses liquid-phase condensation on the seal face, while increasing the rotating speed and inlet pressure can only inhibit liquid-phase condensation in the groove region and increase the area of non-liquid phase area on the end face, but has little effect on the gas-liquid two-phase area of the sealing dam. When the inlet temperature reaches 320 K and 340 K, the pure liquid phase area and gas-liquid two-phase area on the end face disappear successively. Expanding the non-liquid phase area benefits the enhancement of the gas film stiffness of the seal.

Key words: supercritical CO₂, dry gas seal, phase transformation, operating parameters, thermodynamic process

摘要：

超临界CO₂压缩机干气密封因密封介质在临界点工况附近的物性特殊性和高参数化，密封间隙内介质流动呈现出多相流动、高度湍流化和物性畸变特征。以微段组合型槽干气密封为研究对象构建了轴向力平衡条件下考虑实际流体效应的超临界CO₂干气密封热动力润滑相变仿真模型，提出了密封端面热力学过程表征方法，研究了转速、进气压力和进气温度等运行工况参数对超临界CO₂干气密封端面热力学过程、流场参数和稳态性能的影响。结果表明：进气温度的提高对于抑制密封端面液相凝析效果显著；转速和进气压力的增大只能抑制槽区液相凝析，增大端面非液相区面积，但对密封坝气液混相区影响不大，当进气温度达到320 K和340 K时，端面纯液相区和气液混相区先后消失；提高非液相区面积，对于增大密封气膜刚度是有利的。

关键词: 超临界CO₂, 干气密封, 相变, 工况参数, 热力学过程

CLC Number:

TH 117.2

Jinbo JIANG, Zhuxin CHEN, Yangyi XIAO, Xin PENG, Yuan CHEN, Chen YU, Xiangkai MENG, Xudong PENG. Study on influence of operating conditions on thermodynamic process and steady state performance of supercritical CO₂ dry gas seal[J]. CIESC Journal, 2025, 76(6): 2913-2928.

江锦波, 陈竹鑫, 肖洋溢, 彭新, 陈源, 于辰, 孟祥铠, 彭旭东. 运行工况对超临界CO₂干气密封端面热力学过程及稳态性能影响研究[J]. 化工学报, 2025, 76(6): 2913-2928.

Figures/Tables 21

Fig.1 Schematic diagram of sCO2 dry gas seal structure and intake system

Fig.2 Geometrical parameter definition of surface groove of dry gas seal

Fig.3 Axial force analysis of floating stationary ring

Fig.4 Schematic diagram of calculation domains of rotating ring and stationary ring and their heat transfer boundary conditions

Fig.5 Calculation flow chart of coupled program of flow and heat transfer considering axial force balance

Table 1 Default values of working conditions and structural parameters of sCO2 dry gas seal

参数	数值
密封端面内径r_i/mm	58.42
密封端面外径r_o/mm	77.78
槽数N_g	12
周向槽宽比δ	0.5
径向槽长比α	0.6
槽深h_g/μm	5
进口螺旋角β₁/(°)	50
中间螺旋角β₂/(°)	30
出口螺旋角β₃/(°)	30
转速n/(r·min^-1)	10000
进气温度T_in/K	305.0
进气压力p_in/MPa	10
弹簧比压p_sp/MPa	0.05
平衡比B	0.80

Fig.6 Influence of grid number on sealing performance of sCO2 dry gas seal

Fig.7 Comparison of film pressure, temperature and mass fraction distribution of dry gas seal between calculated values and literature values

Fig.8 Three important parts of grooved surface in dry gas seal

Fig.9 Thermodynamic process of dry gas seal showed in p-H diagram and p-T diagram

Fig.10 Thermodynamic process of dry gas seal in p-H diagram at different inlet temperature

Fig.11 Effect of inlet temperature on radial average density and viscosity of CO2

Fig.12 Distribution of film pressure, temperature and phase-state in surface at different inlet tempeature

Fig.13 Steady-state performance and phase region area of sCO2 dry gas seal at different outer temperature

Fig.14 Thermodynamic process of dry gas seal in p-H diagram under different rotating speed

Fig.15 Distribution of film pressure, temperature and phase-state in seal face at different rotating speed

Fig.16 Steady-state performance and phase region area of sCO2 dry gas seal at different rotating speed

Fig.17 Thermodynamic process of dry gas seal in p-H diagram at different inlet pressure

Fig.18 Effect of inlet pressure on radial average density and viscosity of CO2

Fig.19 Distribution of film pressure, temperature and phase-state in seal face at different inlet pressure

Fig.20 Steady-state performance and phase region area of sCO2 dry gas seal at different inlet pressure

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Study on influence of operating conditions on thermodynamic process and steady state performance of supercritical CO₂ dry gas seal

运行工况对超临界CO₂干气密封端面热力学过程及稳态性能影响研究

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Figures/Tables 21

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