CN104458108B - Method for measuring pressure drop of liquid metal pipe flow magnetic fluid under high-intensity magnetic field - Google Patents

Abstract

The invention provides a method for measuring the pressure drop of liquid metal pipe flow magnetic fluid under a high-intensity magnetic field. According to the method, liquid metal flows in a steel pipe, the direction of the magnetic field is perpendicular to the flowing direction, electrodynamic potentials are generated on the two sides of the steel pipe, and measurement can be conducted by installing potential probes on the two sides of the steel pipe. The potential difference obtained through measurement is subjected to theoretical calculation, and then pressure gradient information at the position of the pipe is directly obtained. When neither the magnetic filed in the direction of the pipe nor the pipe changes, the pressure gradient keeps constant, and the pressure drop of an inlet and an outlet of the pipe is directly obtained by multiplying by the pressure gradient by the length of the pipe. For a round pipe, the relational expression of the pressure gradient and the potential difference is independent of physical property parameters and the flow speed of the liquid metal inside the pipe and only dependent on the size of the pipe, the physical property parameters and parameters of the magnetic field, and therefore pressure drop measurement under various flowing conditions can be completed only by measuring the potential difference of the two sides of the wall of the pipe. The method has the advantages that measurement is conducted without invasion into the fluid, flowing of the fluid is not disturbed, superhigh temperature fluid can be borne, and the measurement process is convenient and simple.

Description

A method for measuring pressure drop of magnetic fluid in liquid metal pipeline under strong magnetic field

technical field

The invention relates to the technical field of liquid metal pressure drop measurement, in particular to a method for measuring the pressure drop of magnetic fluid in a liquid metal pipeline under a strong magnetic field.

Background technique

Pressure drop measurement is an important part of thermal hydraulic measurement. In a magnetic confinement fusion reactor, the liquid metal cladding is in a strong magnetic field environment, and its flow presents a special magnetic fluid (MHD) effect, among which the MHD pressure drop is the most important MHD effect. Under the action of a strong magnetic field, the flowing liquid metal cuts the magnetic field and generates an induced current, which forms a Lorentz force under the action of the magnetic field, hindering the fluid flow and forming an MHD pressure drop. According to the strength of the magnetic field, the pressure drop will be 10 to 100 times larger than the flow pressure drop of ordinary pipelines. Its accurate measurement is one of the core contents of the thermal hydraulic research of liquid metal cladding.

The pressure drop measurement technology of liquid metal cladding requires to meet the following three characteristics:

(1) High temperature resistance: measure the temperature of liquid medium >300°C;

(2) Corrosion resistance: the measured medium is a liquid metal alloy, which has certain corrosiveness;

(3) Anti-magnetic field: The working environment of the pressure (differential pressure) gauge is required to be a strong magnetic field>2T;

The conventional high-temperature liquid metal pressure drop measurement technology uses a pressure sensor to measure the pressure difference ΔP between two specific points on the pipeline. The high-temperature liquid metal contacts the high-temperature and corrosion-resistant diaphragm (generally made of steel), and the pressure deforms it. The deformation of the diaphragm transmits the pressure to the pressure sensor through an incompressible medium (such as silicone oil). There are many types of mechanical sensors, such as resistance strain gauge pressure sensors, semiconductor strain gauge pressure sensors, piezoresistive pressure sensors, inductive pressure sensors, capacitive pressure sensors, etc.

The working temperature of this commonly used pressure sensor measurement method is <300°C, so when measuring high-temperature liquid metal, it is necessary to use a pressure induction tube to lead out to cool down and then measure. Using the pressure induction tube, the intrusion into the fluid will disturb the fluid, and there is a current between the static fluid in the pressure induction tube and the flowing fluid in the main pipeline, which will form a local pressure drop difference under the action of the magnetic field, which will bring errors to the pressure drop measurement. When used for a long time, the diaphragm is exposed to high-temperature liquid metal, and its deformation performance and accuracy will decrease after being corroded. And during the shutdown period, part of the liquid metal may solidify on the diaphragm, and a long time will affect its deformation accuracy.

Contents of the invention

In order to make up for the deficiencies of the existing pressure sensor gauges in the high-temperature liquid metal and strong magnetic field environment, the present invention provides a new liquid metal pressure drop measurement technology, specifically a method for measuring the pressure drop of liquid metal pipeline magnetic fluid pressure drop under a strong magnetic field , the method does not invade the fluid for measurement, does not interfere with fluid flow, can withstand ultra-high temperature fluid, and is convenient and simple to measure.

The present invention is realized through the following technical solutions: a method for measuring the pressure drop of magnetic fluid flowing in a liquid metal pipeline under a strong magnetic field, including a magnetic field generator, a pair of potential probes, signal leads, and a voltmeter. The liquid metal flows in the steel pipe, and the direction of the magnetic field is vertical In the flow direction, the induced electromotive force will be generated on both sides of the steel pipe. Potential probes are installed on both sides of the steel pipe to measure the potential difference. The potential difference signal is transmitted to the voltmeter through the potential probe and the signal lead in turn. Calculate and convert the pressure gradient data or other related flow field data of this section of pipeline.

Further, the potential probes are symmetrically welded on the outer walls of the metal pipe on both sides parallel to the magnetic field, and the material of the probes is the same as that of the pipes, so as to avoid the thermoelectric potential between different materials from interfering with the potential difference signal.

Further, the outer end of the potential probe is connected to a signal lead wire, and the material of the signal lead wire is also kept the same as that of the electrode probe, so as to avoid thermoelectric potential interference between different materials.

Further, the ends of the two signal leads are connected to a voltmeter, and the voltmeter is a high-precision voltmeter, and the high-precision voltmeter has a measurement accuracy of millivolt level.

Further, the potential difference data is converted into the pressure gradient signal of the pipeline through theoretical calculation. After the potential difference data is obtained, the pressure gradient information can be obtained according to the relationship between the potential difference and the pressure gradient of the specific pipeline. When the pipeline is a round pipe, the calculation The formula is as follows:

$<span\; class="notranslate">\; \&dtri;</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; BL</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}<span\; class="notranslate">\; \&dtri;</span>\mathrm{<span\; class="notranslate">\; \&phi;</span>}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; )</span>$

In the formula: —— induced electromotive force, V;

K ₁ —— terminal shunt effect, its size is usually taken as 0.33～0.357;

σ _w —— wall conductivity, S/m;

B——magnetic field strength, T;

L——length of straight pipe, m;

d - the inner diameter of the pipe, m;

D——pipe outer diameter, m.

The advantage of the present invention compared with prior art is:

(1), a method for measuring the pressure drop of a magnetic fluid in a liquid metal pipeline under a strong magnetic field of the present invention adopts the above technical scheme, does not invade the fluid for measurement, does not interfere with the fluid flow, can withstand ultra-high temperature fluid, and is convenient and simple to measure;

(2) The method for measuring the pressure drop of the magnetic fluid in a liquid metal pipeline under a strong magnetic field of the present invention is not disturbed by the magnetic field, so it meets the measurement conditions of the fusion reactor liquid metal cladding.

Description of drawings

Fig. 1 is the schematic diagram of potential measurement method in the present invention; Wherein 1 is a voltmeter, 2 is a potential probe 1, 3 is a potential probe 2, 4 is a magnetic field direction, and 5 is a flow direction.

Fig. 2 is a diagram of the installation position of the potential probe of the present invention, wherein (a) is a bottom view, (b) is a right view, and (c) is a front view.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

The invention relates to a method for measuring the pressure drop of liquid metal. The main measurement object is the potential difference on both sides of the pipeline, and the main measurement components include a pair of potential probes, signal lead wires and a high-precision voltmeter. The electrode probes are symmetrically welded on the outer walls of both sides of the metal pipe parallel to the magnetic field, and the material of the probes is the same as that of the pipe, so as to prevent the thermoelectric potential between different materials from interfering with the potential difference signal. The outer end of the probe is connected to the lead wire, and the material of the lead wire is kept the same as that of the probe to avoid thermoelectric potential interference between different materials. The ends of the two lead wires are connected to a high-precision voltmeter, and the measurement accuracy is at the millivolt level.

After the potential difference signal is obtained, the pressure gradient information can be obtained according to the relationship between the potential difference and the pressure gradient of the specific pipeline. The following formula is the relationship between the potential difference and the pressure of the circular pipeline:

$<span\; class="notranslate">\; \&dtri;</span>\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; BL</span>}{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}<span\; class="notranslate">\; \&dtri;</span>\mathrm{<span\; class="notranslate">\; \&phi;</span>}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; )</span>$

In the formula: —— induced electromotive force, V;

K ₁ —— terminal shunt effect, its size is usually taken as 0.33～0.357;

σ _w —— wall conductivity, S/m;

B——magnetic field strength, T;

L——length of straight pipe, m;

d - the inner diameter of the pipe, m;

D——pipe outer diameter, m.

The electrical signal generated by the flowing liquid metal under the strong magnetic field is transmitted to the voltmeter through the potential probe and the lead wire in turn. In order to reduce the interference of the thermoelectric potential on the potential signal, the potential probe and lead wire are made of the same material as the pipeline. The data read by the voltmeter can be converted into the pressure drop signal of the pipeline after being processed by the formula (1).

Due to the adoption of the above technical scheme, the method does not invade the fluid for measurement, does not interfere with the fluid flow, can withstand ultra-high temperature fluid, is convenient and simple to measure, and is not disturbed by the magnetic field, so it meets the measurement conditions of the fusion reactor liquid metal cladding.

Parts not described in detail in the present invention belong to the known techniques of those skilled in the art.

Claims (4)

1. a kind of liquid metal pipeline stream magnetic fluid drop measurement method under high-intensity magnetic field, visits including magnetic field generator, a pair of potential Pin, signal lead, voltammeter it is characterised in that: liquid metal in steel Bottomhole pressure, magnetic direction perpendicular to flow direction, then Induction electromotive force will be produced in the both sides of steel pipe, in steel pipe both sides, potential probe measurement electric potential difference will be installed, potential difference signal is successively By potential probe, signal lead, it is transferred to voltammeter, the potential difference data that voltammeter reads, be converted to through Theoretical Calculation The pressure gradient data of this segment pipe or other related streams field data；

Described potential difference data is converted to the pressure gr. adient signal of this segment pipe through Theoretical Calculation, and potential difference data obtains Afterwards, the electric potential difference according to concrete pipeline and barometric gradient relational expression can obtain barometric gradient information, the meter when pipeline is for pipe Calculate formula as follows:

$\&dtri;p={\mathrm{bl\&sigma;}}_w\&dtri;{\mathrm{\&phi;k}}_1(\frac{d^2}{d}-1)/\left(2d\right)$

In formula:Induction electromotive force, v；

k₁End shunt effect, its size generally takes 0.33～0.357；

σ_wWall conductivity, s/m；

B magnetic field intensity, t；

L straight pipeline length, m；

D internal diameter of the pipeline, m；

D outer diameter tube, m.

2. liquid metal pipeline stream magnetic fluid drop measurement method, its feature under a kind of high-intensity magnetic field according to claim 1 It is: described potential probe is symmetrically welded at steel pipe parallel on the both sides outer wall in magnetic field, and the material of probe and steel tubing Matter is identical, to avoid the thermoelectrical potential interference potential difference signal between unlike material.

3. liquid metal pipeline stream magnetic fluid drop measurement method, its feature under a kind of high-intensity magnetic field according to claim 1 It is: the outer end of described potential probe connects signal lead, signal lead material also keeps and described potential probe material Identical, to avoid the thermoelectrical potential between different materials to disturb.

4. liquid metal pipeline stream magnetic fluid drop measurement method, its feature under a kind of high-intensity magnetic field according to claim 1 It is: two signal lead ends connect voltammeter, and volt is calculated as high accuracy voltammeter, this high accuracy voltammeter certainty of measurement milli Volt level.