﻿ 电容电导传感器油水两相流含率测量
 中国科学院大学学报  2017, Vol. 34 Issue (2): 237-243 PDF

Capacitance-conductance sensor for water holdup measurement in oil-water two-phase flow
WU Hao, TAN Chao, DONG Feng
Tianjin Key Laboratory of Process Measurement and Control, School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072, China
Abstract: In oil-water two-phase flow measurement, a capacitance-conductance sensor has been designed based on the fact that the capacitance sensor and conductance sensor realize the water holdup measurement in different situations with different sensitive ranges. Electrical switches are used to switch the two measurement methods at high speed in order to make them have the same sensitive fields. The disigned sensor realizes the whole fraction measurement in oil-water two-phase flow with low conductivity water (tap water) and the water holdup measurement error is less than 5[WTB4]%[WTBZ].
Key words: oil-water two-phase flow     capacitance-conductance sensor     water holdup measurement     sensor optimization

1 电容电导传感器结构

 Download: JPG larger image 图 1 电容电导传感器结构 Fig. 1 Structure of the capacitance-conductance sensor

2 理论模型

2.1 电导测量模型

 $V = \frac{{{V_{\text{w}}}}}{{{V_{\text{m}}}}},$ (1)

 ${\sigma _{\text{m}}} = \frac{{2{H_t}}}{{3 - {H_t}}}{\sigma _{\text{w}}},$ (2)

 ${H_t} = \frac{{3V}}{{2 + V}}.$ (3)

2.2 电容测量模型

 ${\text{RCD}} = \frac{{{C_{\text{m}}} - {C_{\text{o}}}}}{{{C_{\text{w}}} - {C_{\text{o}}}}} = \frac{{{V_{{\text{cm}}}} - {C_{{\text{co}}}}}}{{{V_{{\text{cw}}}} - {V_{{\text{co}}}}}},$ (4)

(a) 当管道内充满导电水时，可以认为是容性负载和阻性负载并联，设RwCw1分别是导电水的电阻值和电容值，其阻抗可表示为

 ${Z_{{\text{w1}}}} = \frac{2}{{{\text{j}}\omega {C_{\text{p}}}}} + \frac{{{R_{\text{w}}}}}{{1 + j\omega {C_{{\text{w1}}}}{R_{\text{w}}}}}.$ (5)

(b) 当管道内充满非导电水时，可以认为只有容性负载，设Cw2为非导电水的电容值，其阻抗可以表示为

 ${Z_{{\text{w2}}}} = \frac{2}{{{\text{j}}\omega {C_{\text{p}}}}} + \frac{1}{{1 + j\omega {C_{{\text{w2}}}}}}.$ (6)

Vcm与极板之间的电容值大小成正比，定义一个参数γ=|1/Zw1|/|1/Zw2|，代入方程 (4)，得到修正的RCD值

 ${\text{RC}}{{\text{D}}^ * } = \frac{{{V_{{\text{cm}}}} - {C_{{\text{co}}}}}}{{{V_{{\text{cw}}}}/\gamma - {V_{{\text{co}}}}}}.$ (7)

3 电容电导传感器测量系统

 Download: JPG larger image 图 2 电容电导传感器测量系统结构框图 Fig. 2 Structure diagram of the capacitance-conductance sensor measurment system

 Download: JPG larger image 图 3 电容传感器模型与电容电导传感器模型仿真结果 Fig. 3 Simulation results of the capacitance sensor model and the conductance-capacitance sensor model

4 电容电导传感器油水两相流实验 4.1 电容电导传感器层流响应

 Download: JPG larger image 图 4 电容电导传感器层流响应 Fig. 4 Stratified flow response to the capacitance-conductance sensor
4.2 实验装置介绍

 Download: JPG larger image 图 5 油水两相流实验装置结构图及实验点设计 Fig. 5 Structure diagram of the oil-water two-phase flow experimental device and the experimental condition
4.3 电容电导传感器动态标定实验

 ${E_r} = \frac{{{\text{Holdu}}{{\text{p}}_{{\text{meas}}}} - {\text{Holdu}}{{\text{p}}_{{\text{QCV}}}}}}{{{\text{Holdup}}\;{\text{range}}}} \times 100\% ,$ (8)

 Download: JPG larger image 图 6 电容电导传感器测量结果与快关阀结果对比 Fig. 6 Measurement result comparison between the capacitance-conductance sensor and QCV

5 结论

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