CN110487163B - Instantaneous conductance measurement system for thickness of gas-liquid two-phase annular flow liquid film in local area of rod bundle channel - Google Patents
Instantaneous conductance measurement system for thickness of gas-liquid two-phase annular flow liquid film in local area of rod bundle channel Download PDFInfo
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- CN110487163B CN110487163B CN201910597809.XA CN201910597809A CN110487163B CN 110487163 B CN110487163 B CN 110487163B CN 201910597809 A CN201910597809 A CN 201910597809A CN 110487163 B CN110487163 B CN 110487163B
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- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
- G01B7/06—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/041—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body
Abstract
The invention discloses a system for measuring instantaneous conductance of the thickness of a gas-liquid two-phase annular flow liquid film in a local area of a rod bundle channel. The method can accurately measure the thickness of the annular flow liquid film in the local area of the rod bundle channel, determine the uneven distribution characteristic of the thickness of the liquid film in the circumferential direction of the rod wall and the circumferential cooperative propagation mechanism of the liquid film, and accurately predict the Dryout type critical heat flux density triggering condition, thereby ensuring the normal use of related elements of a nuclear reactor system and the safety of the reactor under the accident condition.
Description
Technical Field
The invention relates to the field of industry, in particular to a system for measuring instantaneous conductance of a liquid film thickness of a gas-liquid two-phase annular flow in a local area of a rod bundle channel.
Background
The annular flow is an important flow pattern in the gas-liquid two-phase flow, is commonly used in related elements and equipment of a nuclear reactor, such as a boiling water reactor core under a normal working condition, a pressurized water reactor core under an accident working condition and a steam generator, and the research on the annular flow is the basis of the reliable operation of the equipment and the safety analysis of the reactor under the accident working condition. The annular flow is typically characterized by a portion of the liquid phase flowing adherently as a liquid film and the remainder being entrained by the high velocity gas flow. The annular fluid film consists of a smooth film base and a perturbation wave of about four times the film base thickness, which is closely related to the critical heat flux density triggering mechanism of the Dryout type, i.e. the partial evaporation of the annular fluid film is the triggering condition of the critical heat flux density of the Dryout type. Due to the complexity of the flow cross-sectional geometry of the steam generator shell side and core bundle channels, the non-uniform distribution of liquid film circumferentially in the outer rod wall local regions will affect the accuracy of the critical heat flux density triggering condition of the Dryout type. Therefore, accurately obtaining the gas-liquid two-phase annular flow liquid film behavior in the local area of the complex rod bundle channel has important significance on related elements of a nuclear reactor system and the safety of the reactor under the accident condition.
At present, the measurement of the thickness of the annular flow liquid film mainly comprises a conductance method, an acoustic method, a high-speed image pickup method, an optical method and a ray method. The acoustic method is used for determining the thickness of a liquid film based on the attenuation and reflection propagation time of ultrasonic waves at a gas-liquid interface, and the uncertainty of the wavelength of the ultrasonic waves limits the application of the acoustic method in the measurement of the thin liquid film; the optical and ray method utilizes different characteristics of light rays emitted from different phases and obtains the thickness of an interface liquid film by performing spectral analysis on refracted light. The optical and ray method has high precision in measuring the thickness of the liquid film, but the operation is complex, and the method is difficult to be applied to liquid film measurement in the local area of a complex rod bundle structure. In addition, the high-speed photography method uses a high-speed photography or high-speed dynamic analysis device to track, photograph and record a gas-liquid two-phase interface in real time, and then analyzes the obtained image and signal, thereby obtaining the liquid film thickness. The high-speed photography method can dynamically record a gas-liquid interface at a high speed, and although a fine structure of a liquid film interface can be obtained, the high-speed photography method is severely limited by a shooting area. The conductance method is a high-precision and fast-response liquid film thickness real-time contact type measuring method, the flat-embedding contact of the electrode does not influence the liquid film behavior, the surface tension of the working medium is not changed by adding a trace amount of dielectric medium, and the electrode size can provide enough space resolution when being controlled to be a certain size. The existing conductance measurement liquid film thickness method mainly adopts a double-ring flat embedded simple geometric structure, is limited to the measurement of the average liquid film thickness of an axial section, and cannot obtain the behavior characteristic of an annular flowing liquid film in a local area of a complex rod bundle channel.
Disclosure of Invention
The present invention is directed to solving the problems of the prior art.
The technical scheme adopted for achieving the purpose of the invention is that the instantaneous conductance measuring system for the thickness of the gas-liquid two-phase annular flow liquid film in the local area of the rod bundle channel mainly comprises a rod electrode unit, a plurality of electrode pairs, a signal generating module, a signal acquisition module, a data processing module, a liquid film calibration device and an impedance adjusting circuit.
The rod electrode unit is a hollow cavity with the upper end and the lower end both open.
And two ends of the rod electrode unit are respectively sleeved with a pipe rod forming an annular flow channel.
The annular flow liquid phase working medium is a conductive medium.
The outer side wall of the rod electrode unit is provided with n clamping grooves. The clamping groove is provided with an opening for the signal input transmission line and the signal output transmission line to penetrate through.
The electrode pair is arranged in the rod electrode unit clamping groove.
The pair of electrodes includes a receiving electrode and an excitation electrode.
The electrode pairs are printed on a PCB board.
Several electrode pairs are arranged circumferentially of the rod electrode units at an azimuthal angle of 45 deg..
Wherein the size of the receiving electrode is 4 x0.8mm. The size of the excitation electrode was 2 x0.8mm. The loading frequency of an excitation signal of the excitation electrode is 10KHz, and the loading current is alternating current.
The axial spacing of the receiving electrode and the excitation electrode was 2 mm.
One end of the signal output transmission line is welded with the receiving electrode, and the other end of the signal output transmission line is connected with the signal acquisition and processing module through an opening on the clamping groove.
And one end of the signal input transmission line is welded with the excitation electrode, and the other end of the signal input transmission line is connected with the signal generation module through an opening on the clamping groove.
The signal generating module sends an excitation signal to the excitation electrode through a signal input transmission line.
The signal acquisition module acquires the alternating current output signal of the receiving electrode through the signal output transmission line, converts the alternating current output signal into a direct current output signal and sends the direct current output signal to the data processing module.
And after receiving the direct current output signal, the data processing module preprocesses the direct current output signal and inputs the preprocessed direct current output signal into a liquid film thickness calibration function model, so that the thickness of the liquid film is calculated.
The preprocessing is denoising.
The liquid film thickness calibration function model is as follows:
＝aV4+bV3-cV2+dV-f。 (1)
wherein the thickness of the liquid film is shown. V is the voltage value of the direct current output signal. And the calculation parameter a, the calculation parameter b, the calculation parameter c, the calculation parameter d and the calculation parameter f are obtained by calculating the measurement result of the liquid film calibration device.
The liquid film thickness calibration model is established by the measurement result of the liquid film calibration device.
The impedance adjusting circuit is connected in parallel with the electrode pair to adjust the impedance between the receiving electrode and the exciting electrode.
The main steps for establishing the liquid film thickness calibration model are as follows:
1) and (5) building a liquid film calibration device.
2) The stepping motor control system sends a driving signal to the stepping motor so as to drive the stepping motor to move.
3) The stepping motor drives the moving block II to move along the direction of the guide rail.
And the moving block II drives the moving block I to move along the direction of the guide rail.
The moving block I moves along the guide rail direction together with the rod electrode unit, so that the gap distance between the rod electrode unit and the semi-cylindrical groove, namely the thickness h of the liquid film, is changedi。i＝1,2，…n。
4) In the working process of the liquid film measuring system, an excitation electric signal is loaded by the excitation electrode, and a liquid film outside the rod wall is used as a conductive medium to enable the excitation electrode end and the receiving electrode end to form a closed circuit.
5) The signal acquisition module acquires the alternating current output signal of the receiving electrode through the signal output transmission line, converts the alternating current output signal into a direct current output signal and sends the direct current output signal to the data processing module. 6) After the data processing module receives the direct current output signal, the direct current output signal is preprocessed to obtain the thickness h of the liquid filmiVoltage value V of time-lapse output signali。
7) Repeating the steps 3 to 6 every T periods to obtain n groups of liquid film thicknesses hiAnd the voltage value V of the output signali。
8) Based on n groups of liquid film thickness hiAnd the voltage value V of the output signaliCalculating the calculation parameter a and the calculation parameter in the liquid film thickness calibration function modelCounting b, calculating parameter c, calculating parameter d and calculating parameter f, thereby establishing a liquid film thickness calibration function model.
The liquid film calibration device mainly comprises an auxiliary support, a micro-motion platform, a stepping motor and a stepping motor control system.
The auxiliary support mainly comprises a base, a fixing block, a supporting rod I, a supporting rod II, a moving block I, a moving block II, a guide rail, a connecting rod and a connecting piece.
The base supports an auxiliary support.
And a fixed block is fixed on the base.
And a support rod is welded on the base.
The fixing block is provided with a semi-cylindrical groove. The support rod is sleeved with a guide rail.
The moving block II moves along the direction of the guide rail.
The side wall of the moving block II is provided with two through grooves.
The moving block I is embedded into the through groove of the moving block II.
One end of the connecting rod is fixed at the bottom of the moving block I, and the other end of the connecting rod is fixed at the top of the micro-motion platform.
One end of the connecting piece is connected with the side wall of the moving block II, and the other end of the connecting piece is connected with the stepping motor.
And a rod electrode unit is fixed at the bottom of the micro-motion platform.
The rod electrode unit is placed in the semi-cylindrical groove. Gaps are formed between the rod electrode units and the semi-cylindrical grooves, conductive working media are filled in the gaps, and the size of the gaps is recorded as the thickness of a liquid film. The conductivity of the conductive working medium is the same as that of the working water in the rod bundle channel.
The stepping motor control system sends a driving signal to the stepping motor so as to drive the stepping motor to move.
The method has the advantages that on the basis of a conductance method, the instantaneous liquid film thickness of the local area of the rod beam channel with the spatial resolution is obtained by utilizing the calibration function relation between the thickness of the conductive liquid film and the output signal of the local electrode; through the correlation analysis of the output signals of the local electrodes, the circumferential propagation mechanism of the rod wall of the annular flow liquid film of the rod bundle channel can be obtained. The method can accurately measure the thickness of the annular flow liquid film in the local area of the rod bundle channel, determine the uneven distribution characteristic of the thickness of the liquid film in the circumferential direction of the rod wall and the circumferential cooperative propagation mechanism of the liquid film, and accurately predict the Dryout type critical heat flux density triggering condition, thereby ensuring the normal use of related elements of a nuclear reactor system and the safety of the reactor under the accident condition.
Therefore, the invention has the following advantages:
1) the method has enough spatial resolution to measure the thickness of the gas-liquid two-phase annular flow liquid film in the local area of the complex rod bundle channel, and the sampling frequency of 10KHz is enough to obtain the transient characteristic of the annular flow liquid film interface fluctuation in the local area.
2) Through the calibration device with the continuously-changed liquid film thickness, the calibration function between the liquid film thickness and the output signal of the receiving electrode does not need interpolation fitting, and the calibration function relation is mapped into an actual rod beam channel local area annular flow liquid film thickness measurement system more accurately.
3) The low impedance design between the input circuit and the output circuit of the circuit board ensures that the resistance between the input circuit and the output circuit is far lower than the resistance of the conductive working medium, and reduces the influence of parasitic current generated by other excitation electrodes on output signals.
Drawings
FIG. 1 is a schematic view of a system for measuring the thickness of an annular flow film in a local area of a bundle channel;
FIG. 2 is a schematic diagram of the arrangement of the liquid film measuring electrode bundle channels;
FIG. 3 is a schematic diagram of a Maxwell simulation model of the rod electrode unit;
FIG. 4 is a graph of field intensity transients near the receiving electrode;
FIG. 5 is a schematic view of a liquid film calibration apparatus;
FIG. 6 is a diagram of liquid film thickness-output signal calibration curves and functions;
FIG. 7 is a schematic view of a transient characteristic curve of liquid film thickness;
FIG. 8 is a schematic diagram of correlation analysis of local area liquid film characteristics.
In the figure: the device comprises a base 101, a fixed block 102, a support rod I103, a support rod II104, a moving block I105, a moving block II106, a guide rail 107, a connecting rod 108, a connecting piece 109, a micro-motion platform 2, a receiving electrode 3 and an exciting electrode 4.
Detailed Description
The present invention is further illustrated by the following examples, but it should not be construed that the scope of the above-described subject matter is limited to the following examples. Various substitutions and alterations can be made without departing from the technical idea of the invention and the scope of the invention is covered by the present invention according to the common technical knowledge and the conventional means in the field.
Example 1:
referring to fig. 1 to 5, the instantaneous conductance measurement system for the thickness of a gas-liquid two-phase annular flow liquid film in a local area of a rod bundle channel mainly comprises a rod electrode unit, a plurality of electrode pairs, a signal generation module, a signal acquisition module, a data processing module, a liquid film calibration device and an impedance adjustment circuit.
Further, according to the characteristics of the square array rod bundle channel, that is, the geometric structures of the central area and the rod gap area of the rod bundle sub-channel are symmetrical, and the gas-liquid two-phase hydrodynamic characteristics are obviously different, the central area and the rod gap area of the rod bundle sub-channel are selected as the arrangement positions of the electrodes for measuring the thickness of the annular flow liquid film in the local area.
The rod electrode unit is a hollow cavity with the upper end and the lower end both open.
Two ends of the rod electrode unit are respectively sleeved with a rod bundle forming an annular flow channel.
The annular flow liquid phase working medium is a conductive medium.
The outer side wall of the rod electrode unit is provided with n clamping grooves. The clamping groove is provided with an opening for the signal input transmission line and the signal output transmission line to penetrate through.
Further, the rod electrode unit is made of PMMA (polymethyl methacrylate) acrylic materials and is completed through 3D printing. The inner diameter of the rod is reserved at two ends of the rod electrode unit, so that the rod electrode unit is conveniently embedded and connected with the rod and is fixed and sealed by glue; the rod electrode unit is hollow and guides an input and output signal wire, and the input and output signal wire is respectively welded with the excitation electrode and the receiving electrode; the rod electrode units are respectively reserved with channels for measuring the sizes of the electrode pairs by the liquid film at the positions with the circumferential interval of 45 degrees, and the channels are connected with the hollow through holes so as to be convenient for leading out signal wires. The rod circumferential spacing 45 deg. positions are the rod gap and rod center local area in the square array bundle, respectively.
The electrode pair is arranged in the rod electrode unit clamping groove.
The electrode pair comprises a receiving electrode 3 and an excitation electrode 4.
The electrode pairs are printed on a PCB board.
The electrode pair is matched with the reserved size of the rod electrode unit, so that the PCB can be conveniently embedded into the rod electrode unit. The electrode pair PCB is embedded with the rod electrode unit, fixed and sealed by AB glue.
Several electrode pairs are arranged circumferentially of the rod electrode units at an azimuthal angle of 45 deg..
Parameters such as electrode size, axial spacing, excitation signal potential, working medium conductivity and the like are optimized through simulation, under the condition of the optimal field intensity-parasitic current ratio, the sizes (length x width) of an excitation electrode and a receiving electrode are respectively determined to be 2x0.8mm and 4x0.8mm, and the axial spacing is 2 mm.
Further, the method for determining data such as electrode size comprises the following steps: a rod electrode unit simulation model is established through Maxwell software, a solving domain is set to be sodium sulfate-containing conducting medium working medium water, alternating current is loaded on an exciting electrode, a Maxwell equation set is solved, and an instantaneous electric field and a magnetic field near a liquid film measuring electrode are obtained. By controlling a variable method, parameters such as electrode size, axial spacing, excitation signal potential and frequency, working medium conductivity and the like are optimized, and the size and the axial spacing of the excitation electrode and the receiving electrode under the condition of the optimal external field intensity-parasitic current ratio of the receiving electrode are obtained.
The exciting signal loading frequency of the exciting electrode 4 is 10KHz, and the loading current is alternating current.
One end of the signal output transmission line is welded with the receiving electrode 3, and the other end of the signal output transmission line is connected with the signal acquisition and processing module through an opening on the clamping groove.
One end of the signal input transmission line is welded with the excitation electrode 4, and the other end of the signal input transmission line is connected with the signal generation module through an opening on the clamping groove.
The signal input transmission line and the signal output transmission line adopt a shielding twisted pair, and the signal interface of the circuit board adopts a shielding interference plug, so that the interference of noise to the output signal is reduced.
The signal generation module sends an excitation signal to the excitation electrode 4 through a signal input transmission line.
The signal acquisition module acquires the alternating current output signal of the receiving electrode 3 through the signal output transmission line, converts the alternating current output signal into a direct current output signal and sends the direct current output signal to the data processing module.
And after receiving the direct current output signal, the data processing module preprocesses the direct current output signal and inputs the preprocessed direct current output signal into a liquid film thickness calibration function model, so that the thickness of the liquid film is calculated.
Furthermore, the data processing module is placed in the signal shielding box, and a signal interface of the data processing module adopts a switch plug for shielding interference, so that the interference of noise on an output signal is reduced; the signal wire adopts a shielding twisted pair, and a plurality of layers of tinfoil paper are wrapped outside the superfine signal wire led out by the shielding twisted pair and the liquid film measuring electrode so as to achieve the function of signal shielding.
The preprocessing is denoising in the following mode: and filtering the interference of the high-frequency noise to the signal by using an RC low-pass filter of an input signal port of the circuit board.
The liquid film thickness calibration function model is as follows:
＝aV4+bV3-cV2+dV-f。 (1)
wherein the thickness of the liquid film is shown. V is the voltage value of the direct current output signal. And the calculation parameter a, the calculation parameter b, the calculation parameter c, the calculation parameter d and the calculation parameter f are obtained by calculating the measurement result of the liquid film calibration device.
The liquid film thickness calibration model is established by the measurement result of the liquid film calibration device.
The impedance adjusting circuit is connected in parallel with the electrode pair to adjust the impedance between the receiving electrode 3 and the exciting electrode 4. The impedance adjusting circuit reduces the impedance between the input circuit and the output circuit of the circuit board, ensures that the resistance between the input circuit and the output circuit is far lower than the resistance of the conductive working medium, and reduces the influence of parasitic current generated by other excitation electrodes on output signals.
The main steps for establishing the liquid film thickness calibration model are as follows:
1) and (5) building a liquid film calibration device.
2) The stepping motor control system sends a driving signal to the stepping motor so as to drive the stepping motor to move.
3) The stepper motor drives the moving block II106 to move along the direction of the guide rail 107.
The moving block II106 drives the moving block I105 to move along the direction of the guide rail 107.
The moving block I105 moves together with the rod electrode unit in the direction of the guide rail 107, thereby changing the gap distance between the rod electrode unit and the semi-cylindrical groove, that is, the liquid film thickness hi。i＝1,2，…n。
4) The signal generation module sends an excitation signal to the excitation electrode 4 through a signal input transmission line. The alternating current signal is converted into a direct current signal and transmitted to the signal acquisition module and the NI signal acquisition card, finally the direct current signal is transmitted to an upper computer through NI data, the output electric signal is converted into the thickness of a liquid film through a calibration function, and the sampling frequency is 10 KHz.
5) The signal acquisition module acquires the alternating current output signal of the receiving electrode 3 through the signal output transmission line, converts the alternating current output signal into a direct current output signal and sends the direct current output signal to the data processing module. The alternating current signal is converted into a direct current signal and transmitted to the signal acquisition module and the NI signal acquisition card, finally the direct current signal is transmitted to an upper computer through NI data, the output electric signal is converted into the thickness of a liquid film through a calibration function, and the sampling frequency is 10 KHz.
6) After the data processing module receives the direct current output signal, the direct current output signal is preprocessed to obtain the thickness h of the liquid filmiVoltage value V of time-lapse output signali。
7) Repeating the steps 3 to 6 every T periods to obtain n groups of liquid film thicknesses hiAnd the voltage value V of the output signali。
8) Based on n groups of liquid film thickness hiAnd the voltage value V of the output signaliAnd calculating values of a calculation parameter a, a calculation parameter b, a calculation parameter c, a calculation parameter d and a calculation parameter f in the liquid film thickness calibration function model, thereby establishing the liquid film thickness calibration function model.
The liquid film calibration device mainly comprises an auxiliary support, a micro-motion platform 2, a stepping motor and a stepping motor control system.
The auxiliary support mainly comprises a base 101, a fixed block 102, a support rod I103, a support rod II104, a moving block I105, a moving block II106, a guide rail 107, a connecting rod 108 and a connecting piece 109.
The base 101 supports an auxiliary stand.
A fixed block 102 is fixed on the base 101.
The base 101 is welded with a support rod 103.
The fixing block 102 has a semi-cylindrical groove. The support rod 103 is sleeved with a guide rail 107.
The moving block II106 moves along the guide rail 107.
The moving block II106 slides on a guide rail 107.
The guide rail 107 is a vertical guide rail.
The side wall of the moving block II106 is provided with two through grooves.
The moving block I105 is embedded into a through groove of the moving block II 106.
One end of the connecting rod 108 is fixed at the bottom of the moving block I105, and the other end is fixed at the top of the micro-motion platform 2.
One end of the connecting piece 109 is connected with the side wall of the moving block II106, and the other end is connected with the stepping motor.
The bottom of the micro-motion platform 2 is fixed with a rod electrode unit.
Furthermore, the distance of each movement of the micro-motion platform is 0.1 mm-1.2 mm.
The rod electrode unit is placed in the semi-cylindrical groove. Gaps are formed between the rod electrode units and the semi-cylindrical grooves, conductive working media are filled in the gaps, and the size of the gaps is recorded as the thickness of a liquid film. The conductivity of the conductive working medium is the same as that of the working water in the rod bundle channel.
The different rod circumferential electrode pairs can be respectively calibrated by adjusting the angles of the rod electrode units.
The stepping motor control system sends a driving signal to the stepping motor so as to drive the stepping motor to move.
Further, the stepping motor control system controls the action of the stepping motor according to input instructions such as parameters of up-down moving speed, data acquisition time and the like of the micro-motion platform.
The measurement principle of the liquid film calibration device is as follows: the step motor control system controls the step motor to rotate to drive the micro-motion platform to move up and down, the micro-motion platform moves to cause the thickness of a liquid film in the space between the semi-cylindrical groove and the rod electrode unit to change, a functional relation exists between the thickness of the liquid film and an output signal of the data acquisition system, and the functional relation is a calibration function between the thickness of the liquid film and the output signal.
Example 2:
the instantaneous conductance measuring system for the thickness of a gas-liquid two-phase annular flow liquid film in a local area of a rod bundle channel mainly comprises a rod electrode unit, a plurality of electrode pairs, a signal generating module, a signal acquisition module, a data processing module and a liquid film calibration device.
The rod electrode unit is a hollow cavity with the upper end and the lower end both open.
Two ends of the rod electrode unit are respectively sleeved with a rod bundle forming an annular flow channel.
The outer side wall of the rod electrode unit is provided with n clamping grooves. The clamping groove is provided with an opening for the signal input transmission line and the signal output transmission line to penetrate through.
The electrode pair is arranged in the rod electrode unit clamping groove.
The pair of electrodes includes a receiving electrode and an excitation electrode.
The signal generating module sends an excitation signal to the excitation electrode through a signal input transmission line.
The signal acquisition module acquires the alternating current output signal of the receiving electrode through the signal output transmission line, converts the alternating current output signal into a direct current output signal and sends the direct current output signal to the data processing module.
And after receiving the direct current output signal, the data processing module preprocesses the direct current output signal and inputs the preprocessed direct current output signal into a liquid film thickness calibration function model, so that the thickness of the liquid film is calculated.
The liquid film thickness calibration function model is as follows:
＝aV4+bV3-cV2+dV-f。 (1)
wherein the thickness of the liquid film is shown. V is the voltage value of the direct current output signal. And the calculation parameter a, the calculation parameter b, the calculation parameter c, the calculation parameter d and the calculation parameter f are obtained by calculating the measurement result of the liquid film calibration device.
The liquid film thickness calibration model is established by the measurement result of the liquid film calibration device.
Example 3:
the instantaneous conductance measurement system for the thickness of the liquid film in the gas-liquid two-phase annular flow in the local area of the rod bundle channel has the main structure shown in the embodiment 2, wherein a plurality of electrode pairs are arranged on the circumference of a rod electrode unit at intervals of 45 degrees in azimuth angle.
The size of the receiving electrode 3 was 4 x0.8mm. The excitation electrode 4 has a size of 2 x0.8mm. The exciting signal loading frequency of the exciting electrode 4 is 10KHz, and the loading current is alternating current.
The axial spacing of the receiving electrode 3 and the excitation electrode 4 is 2 mm.
Example 4:
the instantaneous conductance measurement system for the thickness of the liquid film of the gas-liquid two-phase annular flow in the local area of the rod bundle channel has the main structure shown in the embodiment 2, wherein the main steps for establishing the liquid film thickness calibration model are as follows:
1) and (5) building a liquid film calibration device.
2) The stepping motor control system sends a driving signal to the stepping motor so as to drive the stepping motor to move.
3) The stepper motor drives the moving block II106 to move along the direction of the guide rail 107.
The moving block II106 drives the moving block I105 to move along the direction of the guide rail 107.
The moving block I105 moves in the vertical direction together with the rod electrode unit, thereby changing the rod electrode unit andthe gap distance between the semi-cylindrical grooves, i.e. the liquid film thickness hi. i is 1,2, … n. n is the total number of experimental measurements.
4) The signal generation module sends an excitation signal to the excitation electrode 4 through a signal input transmission line.
5) The signal acquisition module acquires the alternating current output signal of the receiving electrode 3 through the signal output transmission line, converts the alternating current output signal into a direct current output signal and sends the direct current output signal to the data processing module.
6) After the data processing module receives the direct current output signal, the direct current output signal is preprocessed to obtain the thickness h of the liquid filmiVoltage value V of time-lapse output signali。
7) Repeating the steps 3 to 6 every T periods to obtain n groups of liquid film thicknesses hiAnd the voltage value V of the output signali。
8) Based on n groups of liquid film thickness hiAnd the voltage value V of the output signaliAnd calculating values of a calculation parameter a, a calculation parameter b, a calculation parameter c, a calculation parameter d and a calculation parameter f in the liquid film thickness calibration function model, thereby establishing the liquid film thickness calibration function model.
Example 5:
the instantaneous conductance measuring system for the thickness of a gas-liquid two-phase annular flow liquid film in a local area of a rod bundle channel is mainly structurally shown in an embodiment 2, wherein the liquid film calibration device mainly comprises an auxiliary support, a micro-motion platform 2, a stepping motor and a stepping motor control system.
The auxiliary bracket 1 mainly comprises a base 101, a fixed block 102, a support rod I103, a support rod II104, a moving block I105, a moving block II106, a guide rail 107, a connecting rod 108 and a connecting piece 109.
The base 101 supports the auxiliary stand 1.
A fixed block 102 is fixed on the base 101.
The base 101 is welded with a support rod 103.
The fixing block 102 has a semi-cylindrical groove. The support rod 103 is sleeved with a guide rail 107.
The fixed block 102, the moving block II106 and the moving block I105 may be a cube, such as a rectangular parallelepiped.
The moving block II106 moves along the guide rail 107.
The side wall of the moving block II106 is provided with two through grooves.
The moving block I105 is embedded into a through groove of the moving block II 106.
One end of the connecting rod 108 is fixed at the bottom of the moving block I105, and the other end is fixed at the top of the micro-motion platform 2.
One end of the connecting piece 109 is connected with the side wall of the moving block II106, and the other end is connected with the stepping motor.
The bottom of the micro-motion platform 2 is fixed with a rod electrode unit.
The rod electrode unit is placed in the semi-cylindrical groove. Gaps are formed between the rod electrode units and the semi-cylindrical grooves, conductive working media are filled in the gaps, and the size of the gaps is recorded as the thickness of a liquid film. The conductivity of the conductive working medium is the same as that of the working water in the rod bundle channel.
The stepping motor control system sends a driving signal to the stepping motor so as to drive the stepping motor to move.
Example 6:
an experiment based on a rod bundle channel local area gas-liquid two-phase annular flow liquid film thickness instantaneous conductance measurement system mainly comprises the following steps:
1) prototype Pressurized Water Reactor (PWR) bundle fuel assemblies, as shown in fig. 2, using a 3x3 array bundle configuration with 9.5mm rod diameter and 12.6mm rod spacing. The 3x3 bundle channel configuration ensures that the outer liquid film properties of the center rod wall are not affected by the thimble or side wall effects. The liquid film measuring electrode pairs are arranged on the periphery of the central rod wall, and three pairs of local electrodes are spaced at intervals of a circumferential azimuth angle of 45 degrees and correspond to local areas such as rod bundle channel gaps and centers. Due to the symmetry of the array rod bundle structure and the difference of two-phase hydrodynamic characteristics of annular flow in the two local areas, the measurement of the thickness of the liquid film outside the rod wall corresponding to the two local areas has a typical meaning. In addition, the liquid film measuring system is only provided with a pair of liquid film measuring electrodes at the axial position of the rod, the thickness of the liquid film needs to be fully developed at the axial position, and the electrode pairs are arranged at the axial position of the whole rod bundle channelIs downstream of the inlet and downstream of the gridinlet/Dh126.5 and Lspacer/Dh＝50。
2) After the arrangement position of the liquid film measuring electrode is determined, the sizes and the intervals of the exciting electrode pairs and the receiving electrode pairs need to be determined, and the electrode pairs are ensured not to be interfered with each other. The smaller the size and the interval of the exciting and receiving electrode pairs, the higher the spatial resolution of the liquid film measurement in the local area, the smaller the interference between the local electrode pairs, and conversely, the weaker the output acquisition signal. Therefore, the resolution design of the liquid film thickness measuring electrode is a comprehensive parameter optimization process of electrode size, axial interval, signal-to-noise ratio and the like. Rod electrode unit simulation models were built using Maxwell software, as shown in fig. 3. The rod electrode unit is 9.5mm in diameter and 30mm long. The electrode pairs are embedded in the rod wall in a flat mode, and circumferential azimuth angles between the electrode pairs are 45 degrees. The solution domain is set to the subchannel size, 30mm long. And (3) loading 10KHz alternating current on the exciting electrode and 5V alternating current on the electrode, solving Maxwell equations to obtain an instantaneous electric field and a magnetic field near the receiving electrode. By controlling a variable method, the size of the electrode is optimized, the length x width of the exciting electrode is 1-5 mm x 0.5-1.0 mm, the axial distance is 1 mm-5 mm, and the conductivity of the working medium in the solution domain is respectively set to be pure water, the working medium water with the conductivity of 400 mu S/cm and seawater. Fig. 4 shows the instantaneous field strength near the receiving electrode, and the magnitude of the field strength near the receiving electrode represents the strength of the output signal of the receiving electrode. The excitation and receiving electrode sizes under the condition of the optimal external field intensity-parasitic current ratio of the receiving electrode are respectively 2x0.8mm and 4x0.8mm, and the axial distance is 2 mm. In addition, only the potential of the exciting electrode in the central area is loaded, the field intensity near the receiving electrodes in the two gap areas can be ignored, the fact that the local electrode pairs have no mutual interference is shown, and the local liquid film measuring electrode has good spatial resolution.
3) The electrode designed above was used on a 3x3 rod bundle channel center rod, and the completed rod electrode unit was printed in 3D. The rod electrode unit is made of PMMA acrylic material, the outer diameter of two ends of the rod electrode unit is 6mm, the length of the two ends of the rod electrode unit is 10mm, the outer diameter of the two ends of the rod electrode unit is matched with the inner diameter of the central rod, the rod electrode unit is conveniently connected with the rod in an embedded mode, and the rod electrode unit is fixed and sealed by AB glue; the rod electrode unit is hollow, has an inner diameter of 3mm and guides an input signal wire and an output signal wire; the rod electrode unit is provided with 3 channels at the positions of circumferential spacing of 45 degrees, namely two rod gap areas and a rod bundle sub-channel central area, and the length x width of each channel is 10 x1.5mm. The channel is connected with the hollow through hole of the rod electrode unit, so that a signal wire can be conveniently led out.
4) The exciting electrode and the receiving electrode pairs are printed on the PCB in a printed circuit board mode, and the length x width of each electrode pair on the PCB is 10x1.5mm and is the same as the size of the rod electrode unit groove. The PCB plate is embedded into the rod electrode unit and fixed and sealed by AB glue. The exciting electrode and the receiving electrode are connected with the input and output signal wires through tin soldering and are respectively led out from the holes and the rod electrodes in a hollow mode. The superfine signal wire led out from the electrode pair is connected with the shielding twisted pair, the connection part is wrapped with a plurality of layers of tin foil paper to achieve the function of signal shielding, the switch plug with the end of the shielding twisted pair for shielding interference is connected with the signal processing circuit board, and the whole signal processing circuit board is placed in the signal shielding box to reduce the interference of noise to output signals. The input signal port of the signal processing circuit board is designed with an RC low-pass filter for filtering the interference of high-frequency noise to signals. The low impedance between the input and output circuits of the circuit board ensures the influence of the parasitic current generated by other exciting electrodes on the output signal.
5) In the working process of the liquid film measuring system, an excitation electric signal is loaded by the excitation electrode, and the liquid film outside the wall of the central rod is used as a conductive medium to enable the excitation electrode end and the receiving electrode end to form a closed circuit. The receiving electrode is connected with the signal processing circuit board, alternating current signals are converted into direct current signals and transmitted to the signal acquisition module and the NI signal acquisition card, and finally transmitted to the upper computer through NI data, and the signal sampling frequency is 10 KHz.
The collected output electrical signal needs to be converted into the liquid film thickness through a calibration function, and fig. 5 shows a liquid film thickness-collected signal calibration device. The calibration device consists of a micro-motion platform, a stepping motor control system and an auxiliary support. Fixing the rod electrode unit on the micro-motion platform, adjusting the angle of the rod electrode unit on the micro-motion platform to 45 degrees, and calibrating electrode pairs in different local areas. The micro-motion platform is connected with a stepping motor, and the stepping motor is driven by a single chip microcomputer controller. The micro-motion platform moves up and down continuously with a stroke of 0.1 mm-1.2 mm. The stepping motor control drive unit is connected with the upper computer and controls the action of the stepping motor according to input instructions such as parameters of up-down moving speed, data acquisition time and the like of the micro-motion platform. In the calibration process, the descending speed of the micro-motion platform is 0.3667mm/mins, and the acquisition time is three minutes. The calibration device is characterized in that a semi-cylindrical groove matched with the rod electrode unit is formed in the supporting base of the calibration device, the diameter of the semi-cylindrical groove is 11mm, conducting working medium water added with sodium sulfate is filled between the semi-cylindrical groove and the rod electrode unit at intervals, the conductivity is 400 mu S/cm, and the interval size between the semi-cylindrical groove and the rod electrode unit is the known liquid film thickness. The working principle of the whole liquid film thickness-collected signal calibration is as follows: the initial size of the gap between the semi-cylindrical groove and the rod electrode unit is 1.2mm, the stepping motor control system controls the stepping motor to rotate and drives the micro-motion platform to move, the descending speed is 0.3667mm/mins, the thickness of a liquid film in the gap between the semi-cylindrical groove and the rod electrode unit is changed from 1.2mm to 0.1mm, a functional relation exists between the thickness of the liquid film and an output signal of the data acquisition system, the functional relation is a calibration function between the thickness of the liquid film and the output signal, namely a liquid film thickness calibration function model, and the liquid film thickness calibration function model is shown in figure 6.
The liquid film thickness calibration function model is as follows:
＝10.58V4+33.63V3-27.64V2+8.53V-0.48。
wherein, a is 10.58, b is 33.63, c is 27.64, d is 8.53, f is 0.48, which are obtained by simultaneous solving of multiple sets of measurement data.
6) The functional relationship between the liquid film thickness and the output signal is mapped to an actual measurement system for the thickness of the annular flow liquid film in the local area of the rod bundle channel, and the transient characteristic of the thickness of the annular flow liquid film as shown in fig. 7 can be obtained. The transient characteristic curves of the liquid film thickness in the rod gap and the rod central local area are subjected to correlation analysis, and the circumferential propagation mechanism of the rod wall of the rod bundle channel annular flow liquid film can be obtained, as shown in fig. 8.
Claims (7)
1. The instantaneous conductance measurement system for the thickness of a gas-liquid two-phase annular flow liquid film in a local area of a rod bundle channel is characterized by comprising a rod electrode unit, a plurality of electrode pairs, a signal generation module, a signal acquisition module, a data processing module and a liquid film calibration device;
the rod electrode unit is a hollow cavity with the upper end and the lower end being open;
two ends of the rod electrode unit are respectively sleeved with a pipe rod forming an annular flow channel;
the side wall of the rod electrode unit is provided with n clamping grooves; the clamping groove is provided with an opening through which a signal input transmission line and a signal output transmission line penetrate;
the electrode pair is arranged in the rod electrode unit clamping groove;
the electrode pair comprises a receiving electrode (3) and an exciting electrode (4);
the signal generation module sends an excitation signal to an excitation electrode (4) through a signal input transmission line;
the signal acquisition module acquires an alternating current output signal of the receiving electrode (3) through a signal output transmission line, converts the alternating current output signal into a direct current output signal and sends the direct current output signal to the data processing module;
after the data processing module receives the direct current output signal, preprocessing the direct current output signal, and inputting the preprocessed direct current output signal into a liquid film thickness calibration function model, so that the thickness of the liquid film is calculated;
the liquid film thickness calibration function model is as follows:
in the formula (I), the compound is shown in the specification,
is the thickness of the liquid film; v is the voltage value of the direct current output signal; the calculation parameter a, the calculation parameter b, the calculation parameter c, the calculation parameter d and the calculation parameter f are obtained by calculating the measurement result of the liquid film calibration device;
the liquid film thickness calibration function model is established by the measurement result of the liquid film calibration device;
the steps of establishing a liquid film thickness calibration function model are as follows:
1) building a liquid film calibration device; the liquid film calibration device comprises an auxiliary support, a micro-motion platform (2), a stepping motor and a stepping motor control system;
the auxiliary support comprises a base (101), a fixing block (102), a supporting rod I (103), a supporting rod II (104), a moving block I (105), a moving block II (106), a guide rail (107), a connecting rod (108) and a connecting piece (109);
the base (101) supports an auxiliary support;
a fixed block (102) is fixed on the base (101);
a support rod I (103) is welded on the base (101);
the fixing block (102) is provided with a semi-cylindrical groove; a guide rail (107) is sleeved on the support rod I (103);
the moving block II (106) moves along the direction of a guide rail (107);
the side wall of the moving block II (106) is provided with two through grooves;
the moving block I (105) is embedded into a through groove of the moving block II (106);
one end of the connecting rod (108) is fixed at the bottom of the moving block I (105), and the other end of the connecting rod is fixed at the top of the micro-motion platform (2);
one end of the connecting piece (109) is connected with the side wall of the moving block II (106), and the other end of the connecting piece is connected with the stepping motor;
a rod electrode unit is fixed at the bottom of the micro-motion platform (2);
the rod electrode unit is placed in the semi-cylindrical groove; gaps are formed between the rod electrode units and the semi-cylindrical grooves, conductive working media are filled in the gaps, and the size of the gaps is recorded as the thickness of a liquid film; the conductivity of the conductive working medium is the same as that of the working water in the rod bundle channel;
the stepping motor control system sends a driving signal to the stepping motor so as to drive the stepping motor to move;
2) the stepping motor control system sends a driving signal to the stepping motor so as to drive the stepping motor to move;
3) the step motor drives the moving block II (106) to move along the direction of the guide rail (107);
the moving block II (106) drives the moving block I (105) to move along the direction of the guide rail (107);
the moving block I (105) moves along the direction of the guide rail (107) together with the rod electrode unit, so that the gap distance between the rod electrode unit and the semi-cylindrical groove, namely the thickness h of the liquid film, is changedi；i=1,2，…n；
4) The signal generation module sends an excitation signal to an excitation electrode (4) through a signal input transmission line;
5) the signal acquisition module acquires an alternating current output signal of the receiving electrode (3) through a signal output transmission line, converts the alternating current output signal into a direct current output signal and sends the direct current output signal to the data processing module;
6) after the data processing module receives the direct current output signal, the direct current output signal is preprocessed to obtain the thickness h of the liquid filmiVoltage value V of time-lapse output signali；
7) Repeating the steps 3) to 6) every T periods to obtain n groups of liquid film thicknesses hiAnd the voltage value V of the output signali；
8) Based on n groups of liquid film thickness hiAnd the voltage value V of the output signaliAnd calculating values of a calculation parameter a, a calculation parameter b, a calculation parameter c, a calculation parameter d and a calculation parameter f in the liquid film thickness calibration function model, thereby establishing the liquid film thickness calibration function model.
2. The system for measuring instantaneous conductance of a liquid film thickness of a gas-liquid two-phase annular flow in a local area of a rod bundle channel according to claim 1, wherein: the electrode pairs are printed on a PCB board.
3. The system for measuring instantaneous conductance of a liquid film thickness of a gas-liquid two-phase annular flow in a local area of a rod bundle channel according to claim 1, wherein: the conductive working medium is a liquid working medium of annular flow.
4. The system for measuring instantaneous conductance of a liquid film thickness of a gas-liquid two-phase annular flow in a local area of a rod bundle channel according to claim 1, wherein: the device also comprises an impedance adjusting circuit;
the impedance adjusting circuit is connected in parallel with the electrode pair and adjusts the impedance between the receiving electrode (3) and the exciting electrode (4).
5. The system for measuring instantaneous conductance of a liquid film thickness of a gas-liquid two-phase annular flow in a local area of a rod bundle channel according to claim 1, wherein: the preprocessing is denoising.
6. The system for measuring instantaneous conductance of a liquid film thickness of a gas-liquid two-phase annular flow in a local area of a rod bundle channel according to claim 1, wherein: the electrode pairs are arranged on the circumference of the rod electrode unit at intervals of 45 degrees in azimuth angle;
wherein the size of the receiving electrode (3) is 4x0.8 mm; the size of the exciting electrode (4) is 2x0.8 mm; the loading frequency of an excitation signal of the excitation electrode (4) is 10KHz, and the loading current is alternating current;
the axial distance between the receiving electrode (3) and the exciting electrode (4) is 2 mm.
7. The system for measuring instantaneous conductance of a liquid film thickness of a gas-liquid two-phase annular flow in a local area of a rod bundle channel according to claim 1, wherein: one end of the signal output transmission line is welded with the receiving electrode (3), and the other end of the signal output transmission line is sequentially connected with the signal acquisition module and the data processing module through the opening on the clamping groove;
one end of the signal input transmission line is welded with the excitation electrode (4), and the other end of the signal input transmission line is connected with the signal generation module through an opening on the clamping groove.
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| CN111750769B (en) * | 2020-06-18 | 2022-04-05 | 哈尔滨工程大学 | Determinant conductivity probe system suitable for measuring thickness of annular flow liquid film in narrow rectangular channel and liquid film thickness measuring method |
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