CN114199116A

CN114199116A - Liquid film sensor

Info

Publication number: CN114199116A
Application number: CN202111424417.7A
Authority: CN
Inventors: 肖瑶; 张亨伟; 顾汉洋; 闫旭
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2021-11-26
Filing date: 2021-11-26
Publication date: 2022-03-18
Anticipated expiration: 2041-11-26
Also published as: CN114199116B

Abstract

The invention provides a liquid film sensor which comprises a circular metal wire net rack, wherein the circular metal wire net rack is composed of a plurality of mutually crossed metal wires penetrating through the circle center, the circular metal wire net rack is arranged in a measured pipeline during measurement, and the part of each metal wire, which is far away from the measured wall surface, is covered with an insulating layer; the metal wires are electrically connected with the circuit module, the circuit module sequentially excites the metal wires by using high-frequency pulse square waves during measurement, when one metal wire is excited, the circuit module records a current value received by the metal wire which is adjacent to the metal wire and is not excited, and after all the metal wires are excited, one-frame liquid film thickness measurement is completed.

Description

Liquid film sensor

Technical Field

The invention belongs to the technical field of measuring the thickness of a liquid film, and particularly relates to a liquid film sensor.

Background

The annular flow is a two-phase flow consisting of gas and liquid, and is characterized by that along the inner wall of the tube a liquid film is formed, most of the liquid can be made into film form and can be moved along the tube wall, and the gas can be entrained with entrainment in the central zone of the tube and can be flowed through at high speed. The annular flow is a very common two-phase flow pattern, and widely exists in the fields of nuclear energy, power plants, chemical industry, petroleum and the like, such as a steam-water separator of a nuclear energy system, oil-gas transportation of the petroleum industry and the like.

The basic principle of the conductance method is that the height of the liquid film has a certain relation with the current received by the receiving electrode. The conductance type liquid film sensor is divided into two methods of non-invasive measurement and double parallel conductance probe measurement.

The non-invasive measurement arranges a transmitting electrode and a receiving electrode on the measuring wall surface, and the current flows from the transmitting electrode to the receiving electrode through a liquid film. The thicker the liquid film that is coated on the wall surface, the greater the current received by the receiving electrode. By using the current signal, the liquid film thickness can be obtained. The non-invasive electrodes are arranged in an array, so that the imaging of the instantaneous liquid film thickness distribution can be realized. But the non-invasive measurement method has a limited measuring range on the thickness of the liquid film, and after the thickness of the liquid film exceeds 2mm, the current signal does not change along with the increase of the thickness of the liquid film.

Two parallel metal wires are arranged in the flow channel of the double-parallel conductive probe, one is used as a transmitting electrode, and the other is used as a receiving electrode. The current flows from the transmitting electrode to the receiving electrode through the fluid between the double parallel electrode wires. The current value received by the receiving electrode is proportional to the thickness of the liquid film. The double parallel conductance probes have wide measuring range for measuring the thickness of the liquid film, but only can measure the thickness of the local liquid film, and cannot image the thickness distribution of the liquid film.

Disclosure of Invention

In order to solve the problems, the invention provides a liquid film sensor which comprises a circular metal wire net rack, wherein the circular metal wire net rack is composed of a plurality of metal wires which penetrate through the circle center and are crossed with each other;

the metal wires are electrically connected with the circuit module, the circuit module sequentially excites the metal wires by using high-frequency pulse square waves during measurement, when one metal wire is excited, the circuit module records a current value received by the metal wire which is adjacent to the metal wire and is not excited, and after all the metal wires are excited, one-frame liquid film thickness measurement is completed.

Preferably, a plurality of said wires are uniformly crossed.

Preferably, the diameter of the wire is no more than 0.1 mm.

Preferably, the frequency of the square wave of the high-frequency pulse is not lower than 16000 Hz.

Preferably, the length of the portion of the wire not covered by the insulating layer is not less than 3 mm.

Preferably, during measurement, the circular wire net rack is vertically arranged in the measured pipeline.

Preferably, the portion of the wire not covered by the insulating layer is perpendicular to the tangential direction of the wall surface to be measured.

Preferably, the single-frame liquid film thickness measurement frequency is not lower than 1000 Hz.

Preferably, when one said wire is excited, its adjacent unexcited wire is at a 0 potential with respect to the wire.

Compared with the prior art, the invention has the following technical effects:

the invention provides a liquid film sensor, wherein a circular metal wire net rack is arranged in a measured pipeline, in order to avoid the influence of liquid drops carried by the core of a flow channel of the measured pipeline on a measuring signal, the part of each metal wire far away from the measured wall surface is covered with an insulating layer, the metal wires are excited by using high-frequency pulse square waves in sequence, the potential 0 of the metal wire which is not excited is kept, and the current value received by the adjacent metal wire of an excited electrode is recorded. The average value of the current received by the adjacent wires is proportional to the local liquid film thickness at the location of the excited wire. When all the electrodes are excited, a frame of liquid film thickness measurement is obtained. The invention has simple structure, convenient operation, no limit to the measuring range and area of the liquid film thickness and wide measuring range.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts. In the drawings:

fig. 1 is a schematic structural diagram of a liquid film sensor according to a preferred embodiment of the present invention.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.

Referring to fig. 1, a liquid film sensor includes a circular wire mesh frame 2, and the circular wire mesh frame 2 is composed of a plurality of mutually crossed wires 21 passing through the center of a circle. The number of the metal wires 21 is not limited, and the number can be set according to actual measurement requirements. In the present embodiment, the shape, size and configuration of the wires 21 are the same, the wires 21 are uniformly crossed to form a circle, and the center points of the wires 21 are all overlapped with the center of the circle.

During measurement, the circular wire mesh frame 2 is vertically arranged in the measured pipeline 1, in order to avoid the influence of liquid drops carried by the core of the flow channel 12 of the measured pipeline 1 on a measurement signal, the part of each wire 21 far away from the measured wall surface 12 is covered with an insulating layer 211, that is, the part close to the measured wall surface 12 is a bare wire part 212 (the bare wire part 212 is a part which is not covered by the insulating layer), and the bare wire part 212 is connected with the circuit module 3 through a wire. The material of the insulating layer 211 is not limited in the present invention, such as insulating paint, and the insulating layer 211 is used to ensure that the current does not flow from the place far away from the wall surface 12 to be measured by the metal wire, and ensure that the current value received by the receiving electrode is proportional to the thickness of the liquid film on the wall surface 12 to be measured. The bare wire part 212 of the wire 21, which is not covered by the insulating layer, is perpendicular to the tangential direction of the measured wall surface 12, in this embodiment, the diameter of the wire 21 is not more than 0.1mm, and the length of the bare wire part 212 of the wire 21, which is not covered by the insulating layer, is not less than 3 mm.

The plurality of metal wires 21 are electrically connected to the circuit module 3, during measurement, the circuit module 3 sequentially excites the plurality of metal wires 21 using a high-frequency pulse square wave (the circuit module 3 excites only one metal wire 21 at a time, sequentially excites all the metal wires 21, when a certain metal wire 21 is excited, the metal wire 21 serves as a transmitting electrode, and the other metal wires 21 serve as receiving electrodes), when a metal wire 21 is excited, the adjacent unexcited metal wire 21 is at 0 potential relative to the metal wire 21, the circuit module 3 records the current value received by the adjacent unexcited metal wire 21 of the excited metal wire 21, and when all the metal wires 21 are excited, one frame of liquid film thickness measurement is completed.

In this embodiment, the frequency of the square wave of the high-frequency pulse is not lower than 16000Hz, and the measurement frequency of the thickness of the single-frame liquid film is not lower than 1000 Hz.

The circular wire rack 2 in fig. 1 includes twelve wires 21, the diameter of each wire 21 is 0.08mm, the portion of each wire 21 near the measured wall surface 12 is a bare wire portion 212, the length of the bare wire portion 212 is 4mm, and the surface of the remaining portion of each wire is subjected to insulation treatment. The circuit module 3 sequentially applies square wave excitation with the frequency of 20000Hz to the metal wires 21, the amplitude of the square wave is 1V, the metal wires 21 which are not excited keep 0 potential, and simultaneously the magnitude of the current received by the metal wires 21 adjacent to the excited metal wires 21 is recorded. The average of the magnitudes of the currents received by the adjacent wires 21 is indicative of the local liquid film thickness of the excited wire 21. All wires 21 are excited in sequence to complete one frame of measurement.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims

1. A liquid film sensor is characterized by comprising a circular metal wire net rack, wherein the circular metal wire net rack is composed of a plurality of metal wires which penetrate through the circle center and are mutually crossed;

2. The liquid film sensor according to claim 1, wherein a number of the metal wires are uniformly crossed.

3. The liquid film sensor according to claim 1, wherein the wire has a diameter of no more than 0.1 mm.

4. The liquid film sensor according to claim 1, wherein the frequency of the high frequency pulse square wave is not lower than 16000 Hz.

5. The liquid film sensor according to claim 1, wherein the portion of the wire not covered by the insulating layer has a length of not less than 3 mm.

6. The liquid film sensor according to claim 1, wherein the circular wire mesh frame is vertically disposed in the pipe to be measured at the time of measurement.

7. The liquid film sensor according to claim 6, wherein the portion of the wire not covered by the insulating layer is perpendicular to the tangential direction of the wall surface to be measured.

8. The liquid film sensor according to claim 1, wherein the single frame liquid film thickness measurement frequency is not less than 1000 Hz.

9. The liquid film sensor according to claim 1, wherein when one of the wires is excited, its adjacent non-excited wire is at a potential of 0 with respect to the wire.