Capacitance type sensor with liquid electrode for measuring liquid holdup of multiphase flow

Abstract

The invention discloses a capacitance type sensor with a liquid electrode for measuring the liquid holdup of a multiphase flow, which comprises more than one metal plate with an insulating material coating surface, wherein each metal plate is in contact with the conductive liquid of the measured multiphase flow, and simultaneously, is connected with a measurement circuit by a cathode connector consisting of metal conductors; and the conductive liquid in the multiphase flow serves as the cathode of the capacitance type sensor, and the metal plates with the insulating material coatings form an anode. Therefore, the capacitance and sensitivity of the capacitance type sensor for measuring the liquid holdup of the multiphase flow are greatly improved, the problems of zero drift and ant-interference of the sensor are solved, simultaneously the sensor can be applied to the measurement of the multiphase flows of various flow patterns with flow pattern and size factor-independent measurement results, and is also applied to high-temperature high-pressure occasions.

Description

technical field [0001] The invention belongs to the technical field of sensor equipment for multiphase flow liquid holdup measurement, in particular to a capacitive sensor with liquid electrodes for multiphase flow liquid holdup measurement. Background technique [0002] Liquid holdup refers to the volume fraction occupied by a liquid in a multiphase flow in which at least one phase is a conductive liquid. [0003] Capacitive sensors are the most common among sensor devices currently used in the measurement of multiphase flow parameters. Traditional capacitive sensors are mainly composed of two fixed metal plates, and the multiphase fluid to be measured is used as the dielectric of the capacitor. between the plates. Since each phase in a multiphase fluid has a different dielectric constant, the equivalent dielectric constant depends on the ratio or phase content of each phase. At different phase contents, it has different equivalent dielectric constants and exhibits differ...

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Problems solved by technology

It can be seen from the geometric principle that only when the interface between the oil and water phases is strictly horizontally stratified, there is a definite correspondence between the lateral area and the cross-sectional area, and the volume of the water body can be uniquely determined by measuring the lateral area , that is, the water holdup in the pipe, otherwise the water holdup determined by it will have a large gap with the actual value, but the actual two-phase flow is rarely such an ideal horizontal stratified flow, that is, the oil-water The interface is rarely horizontal, mostly wavy, not only wavy in the axial direction, but also wavy in the lateral direction, and the waves are often very large, so the actual measurement error of the sensor must be very large

In addition, the inner insulating cylinder of the sensor is nested on the inner metal cylinder, which will bring two problems. One is that the thickness of the inner insulating cylinder is too thick, which increases the distance between the two plates of the capacitor. According to the principle of the capacitor , which will reduce the capacitance value and sensitivity of the sensor; the second is that the tightness and integrity between the inner insulating cylinder and the inner metal cylinder are poor, and some uncertain gaps will inevitably occur, which will affect the stability and reliability of the sensor

[0006] Finally, the above two sensors also have a common disadvantage that the insulating materials used are all organic matter, which is difficult to withstand high temperatures and cannot be used in the measurement of high temperature and high pressure multiphase flow

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