基于多变量摄动的超临界CO2干气密封动态特性

doi:10.11949/0438-1157.20201040

摘要/Abstract

摘要：

超临界CO₂压缩机进口端干气密封工况处于临界点附近，强非线性物性及高Reynolds数流动使其密封特性异于常规介质干气密封。在综合考虑四种实际流体效应的稳态膜压求解模型基础上，基于摄动法推导了包括膜压、密度、黏度、Reynolds数、湍流系数和惯性系数在内的多变量摄动干气密封动特性数值模型。对比分析了超临界CO₂和N₂干气密封的动态特性，研究了不同频率比下各实际流体效应和变量摄动形式对超临界CO₂干气密封动特性系数的影响规律，获得了不同条件下动态特性的关键影响因素。结果表明：高频下超临界CO₂干气密封的刚度和阻尼系数较N₂干气密封降幅超过50%，湍流效应和实际气体效应对干气密封动态特性影响显著，低频下采用经典变量摄动和忽略湍流系数摄动会使动特性系数计算偏差很大，而高频下经典变量摄动模型对刚度系数的预测精度可接受。

关键词: 超临界二氧化碳, 干气密封, 动态仿真, 变量摄动, 湍流, 实际效应

Abstract:

The dry gas seal working condition at the inlet of the supercritical CO₂ compressor is near the critical point. The strong nonlinear physical properties and high Reynolds number flow make the sealing characteristics different from conventional dry gas seals. Based on the steady-state film pressure calculation model considering the real gas effect, centrifugal inertia effect, turbulent effect and choked effect, a multi variables perturbation numerical model by considering perturbed film pressure, density, viscosity, Reynolds number, turbulence coefficient and inertia coefficient for calculating dynamic characteristics of dry gas seal is established based on perturbation method. The dynamic characteristics of supercritical CO₂ and N₂ dry gas seals were compared and analyzed. The influences of actual fluid effects and variable perturbation models on the axial and angular dynamic characteristics coefficients of supercritical CO₂ dry gas seals under different conditions were obtained. The results show that the stiffness and damping coefficient of supercritical CO₂ dry gas seal are reduced by more than 50% compared with N₂ dry gas seal under high frequency disturbance. Turbulent effect and real gas effect have significant influence on dynamic characteristics of dry gas seal. The calculation deviations of dynamic characteristics calculated by classical variable perturbation and ignoring turbulence coefficient perturbation are relative large under low frequency disturbance, while the prediction accuracy of the classical variable perturbation model is acceptable under high frequency disturbance.

Key words: supercritical carbon dioxide, dry gas seal, dynamic simulation, variable perturbation, turbulent flow, actual effect

中图分类号:

TH 117.2

江锦波, 滕黎明, 孟祥铠, 李纪云, 彭旭东. 基于多变量摄动的超临界CO₂干气密封动态特性[J]. 化工学报, 2021, 72(4): 2190-2202.

JIANG Jinbo, TENG Liming, MENG Xiangkai, LI Jiyun, PENG Xudong. Dynamic characteristics of supercritical CO₂ dry gas seal based on multi variables perturbation[J]. CIESC Journal, 2021, 72(4): 2190-2202.

图/表 13

图1 超临界CO2旋转设备干气密封结构示意图

Fig.1 Schematic diagram of dry gas seal used in supercritical CO2 rotating equipments

图2 超临界CO2干气密封实际流体效应示意图

Fig.2 The real fluid effects in supercticail CO2 dry gas seal

图3 干气密封动态特性求解中的变量摄动关联关系

Fig.3 The relationship among different perturbed variables on the calculation of dynamic characteristics in dry gas seal

图4 sCO2介质物性参数扰动示意图

Fig.4 Schematic of physical parameters perturbation of supercritical CO2

图5 sCO2干气密封动特性系数计算流程

Fig.5 Solution process of dynamic characteristics calculation for sCO2 dry gas seal

表1 本文干气密封动态特性数值计算初始参数

Table 1 Initial parameters adopted in the calculation of dynamic characteristics of dry gas seal

参数	数值	参数	数值
密封端面内径r_i/mm	58.42	非开槽区气膜厚度h_b/μm	8
密封端面外径r_o/mm	77.78	高压腔介质压力p_o/MPa	8
槽根半径r_g/mm	68.10	低压腔介质压力p_i/MPa	0.1
螺旋角β/(°)	15	介质温度T₀/K	310
螺旋槽深度h_g/μm	5	密封端面平均线速度v/(m·s^-1)	100
螺旋槽数N_g	12	频率比Γ	1.0
周向槽宽堰宽比δ	1

图6 考虑离心惯性和湍流的计算程序正确性验证

Fig.6 Verification of calculated program with consideration of turbulent and inertia

图7 sCO2和N2介质干气密封动态特性系数对比

Fig.7 Comparison on dynamic characteristics of dry gas seals lubricated with sCO2 and N2

图8 实际效应对不同频率比下sCO2密封动特性系数影响

Fig.8 The influence of real effects on dynamic characteristics of sCO2 dry gas seal at different frequency ratio

图9 不同实际效应下sCO2干气密封一阶实部压力差值分布

Fig.9 First-order real pressure differential distribution of sCO2 dry gas seal at different real effects

图10 实际效应对不同线速度下sCO2密封动特性系数影响

Fig.10 The influence of real effect on dynamic characteristics of sCO2 dry gas seal at different seal velocity

图11 变量摄动对不同频率比下sCO2密封动特性系数影响

Fig.11 The influence of variable perturbation on dynamic characteristics of sCO2 dry gas seal at different frequency ratio

图12 变量摄动对不同线速度下sCO2密封动特性系数影响

Fig.12 The influence of variable perturbation on dynamic characteristics of sCO2 dry gas seal at different seal velocity

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基于多变量摄动的超临界CO₂干气密封动态特性

Dynamic characteristics of supercritical CO₂ dry gas seal based on multi variables perturbation

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