阅读说明：本技术 一种热电偶组合式速度电势探针及测量方法 (Thermocouple combined type speed potential probe and measuring method ) 是由 阳倦成 曹炎武 倪明玖 吕泽 于 2021-10-15 设计创作，主要内容包括：一种热电偶组合式速度电势探针,其探头的整体护壳由黄铜制成,表面涂覆有绝缘层,探头前端护壳是测量电势的部分,包括四根周向均匀分布的铜探针,以及布置在四根铜探针的探点中心的一根T型热电偶,所有铜探针以及T型热电偶超出探头前端护壳10-20mm；本发明组合焊接热电偶和速度测量探针,测量信号统一,仅通过测量电压的方式即可同时得到液态金属任意局部的温度和速度,且与液态金属直接接触,响应较快精度较高。(A thermocouple combined type speed potential probe is characterized in that an integral protective shell of a probe is made of brass, an insulating layer is coated on the surface of the integral protective shell, a front-end protective shell of the probe is a potential measuring part and comprises four copper probes uniformly distributed in the circumferential direction and a T-shaped thermocouple arranged in the center of probe points of the four copper probes, and all the copper probes and the T-shaped thermocouple exceed the front-end protective shell of the probe by 10-20 mm; the combined welding thermocouple and the speed measuring probe have unified measuring signals, can simultaneously obtain the temperature and the speed of any local part of the liquid metal only by measuring the voltage, are in direct contact with the liquid metal, and have quicker response and higher precision.)

1. A thermocouple combined type speed potential probe is characterized in that an integral protective shell of a probe is made of brass, an insulating layer is coated on the surface of the integral protective shell, a front end protective shell (6) of the probe is a potential measuring part and comprises four copper probes (1, 2, 3 and 4) which are uniformly distributed in the circumferential direction and a T-shaped thermocouple (5) which is arranged in the center of a probe point of the four copper probes, and all the copper probes and the T-shaped thermocouple (5) exceed the front end protective shell (6) of the probe by 10-20 mm.

2. The thermocouple combination type speed potential probe according to claim 1, wherein the diameter of each copper probe is 0.1-0.3mm, the diameter of the thermocouple is 0.5mm, the first copper probe (1) and the fourth copper probe (4) have no distance in the horizontal direction, and the distance in the vertical direction is 1.8-2.8 mm; the distance between the second copper probe (2) and the third copper probe (3) in the horizontal direction is 1.8-2.8 mm.

3. A method of measuring a thermocouple combination type velocity potential probe according to any one of claims 1 to 2, comprising the steps of:

potential signals are obtained through measurement of four copper probes, a relation is established between the potential signals and flow velocity, and local velocity distribution of a flow field is obtained based on ohm's law:

whereinFor current density, σ is the liquid metal conductivity,the voltage signal is measured as a potential difference,in order to be the flow rate of the gas,for the intensity of the applied magnetic field, the applied magnetic field is assumedAt a speed ofCurrent densityWhen the magnetic field intensity is large, the current density pole of the main flow areaSmall, i.e. j_x≈0，j_zAnd 0, measuring the potential gradient in each direction in a vertical magnetic field plane at a specific position in the main flow area by the probe, and converting to obtain two velocity components of the position in the plane, namely a main flow velocity u and a velocity w along the z axis:

wherein B is₀In order to homogenize the magnetic field strength,is the voltage signal measured by the probe.

4. A method of measuring a thermocouple combination velocity potential probe according to any one of claims 1 to 2, including temperature measurement:

the local temperature difference potential is directly measured by a T-shaped thermocouple (5) in the probe, and for a single welding thermocouple, because two electrodes of the T-shaped thermocouple (5) are welded without distance, the flowing potential in the liquid metal can not influence the T-shaped thermocouple, and the potential loop of the thermocouple obtains the temperature difference potential:

E_CoCu(T₁，T₀)＝E_CoCu(T₁)+E_Cu(T₁，T₀)+E_CoCu(T₀)+E_Co(T₁，T₀)

E_CoCu(T₁，T₀) Namely, the measured voltage is converted to obtain the temperature according to the calibrated thermocouple coefficient.

Technical Field

The invention relates to the technical field of liquid metal measurement, in particular to a thermocouple combined type speed potential probe and a measurement method.

Background

The liquid metal flow phenomenon can be understood as the combination of electromagnetism and fluid dynamics, and the liquid metal flow phenomenon contains abundant fundamental research significance. In the cladding structure of the magnetic confinement nuclear fusion device, the flow problem of the metal fluid in the magnetic field is a great research direction, and in addition, in some industrial processes, such as metal smelting processes, the flow control of the metal fluid needs to be realized by utilizing an external magnetic field. How to realize accurate measurement on the flow field characteristics of the metal fluid under the condition of high-temperature and strong magnetic fields is always a serious challenge, and because the metal fluid has the characteristics of light impermeability, easy oxidation, high electrical conductivity, high thermal conductivity and the like, the direct measurement on the flow speed becomes more difficult, and meanwhile, because more turbulent heat flux information is needed by applying a semi-empirical turbulence model in the liquid metal flow, the measurement on any local temperature of the liquid metal is also crucial.

The direct contact measurement method for measuring the internal flow field characteristics of the liquid metal flow under the condition of the magnetic field comprises the following steps: direct contact measurement method: (1) potential probe method. The local velocity of the flow field is obtained by measuring the potential difference perpendicular to the direction of the magnetic field generated by the fluid in a constant magnetic field through immersing the probe in the liquid metal and keeping good electrical contact with the fluid. The method has the advantages that the time resolution is high, the probe and the space can be designed to be very small so as to improve the space measurement precision, and the method is conveniently designed into a wall matrix array so as to obtain rich transient flow field information; (2) resistance probe method. The principle is that the resistance measured when the liquid phase passes through the probe region drops significantly, while the resistance rises sharply when the gas phase passes. The method is commonly used for measuring the two-phase flow of the liquid metal, and the electrical contact performance of the probe and the liquid must be carefully regulated; (3) hot wire velocimeter technology. The method is consistent with the principle of the traditional hot wire anemometer, and the temperature of the method is linearly related to the flow velocity of peripheral liquid based on the heat exchange between a resistance wire and a flow field in a heating state; (4) precision optical-mechanical methods. The method is based on the mechanical force of a fluid on an immersed microprobe. However, the mounting accuracy is highly required. The most direct and effective method for measuring the speed and the vorticity of any local part in the metal fluid under the strong magnetic field is a potential probe method.

Each single body of the existing 4-pole immersion type speed potential probe comprises a plurality of copper wires with insulating layers, the diameter of each copper wire is 0.1-0.5mm, the copper wires penetrate through and are fixed in a hollow copper tube body or a stainless steel tube body, the diameter of each copper wire is 2-5mm, the copper wires exceed the tube body by 10-30mm, the surface of the tube body is covered with one insulating layer, the probe is guaranteed not to be in electric contact with liquid after being immersed, only the tips of the copper wires are in electric contact with the liquid metal, the place where each copper wire is in contact with the liquid metal is called an electrode, and the distance between the two electrodes in the same direction is generally 2-5 mm. The 4-pole immersion type speed potential probe can only work in a flow field with uniform temperature, and the 4 copper electrodes cannot measure local temperature difference potential due to the fact that materials are the same, so that the local temperature cannot be obtained, and only the local speed in fluid with uniform temperature can be measured.

If the speed is to be measured, the potential signals between the electrodes need to be measured, the corresponding potential difference is related to the flow speed, the local speed distribution of the flow field is directly obtained, and the applied magnetic field isAt a speed ofCurrent densityAccording to ohm's law, the horizontal velocity u and the vertical velocity w are respectively:

the measuring method only realizes the measurement of the speed and the vorticity of any local part in the liquid metal, and does not provide a measuring method aiming at the temperature of any local part in the liquid metal.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a thermocouple combined type speed potential probe and a measuring method, wherein a thermocouple and a speed measuring probe are combined and welded, measuring signals are unified, the temperature and the speed of any local part of liquid metal can be obtained simultaneously only by measuring voltage, and the thermocouple combined type speed potential probe is in direct contact with the liquid metal, has quick response and high precision.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a thermocouple combined type speed potential probe is characterized in that an integral protective shell of a probe is made of brass, an insulating layer is coated on the surface of the integral protective shell, a protective shell 6 at the front end of the probe is a part for measuring potential and comprises four copper probes 1, 2, 3 and 4 which are uniformly distributed in the circumferential direction and a T-shaped thermocouple 5 which is arranged at the center of a probe point of the four copper probes; all copper probes and T-type thermocouples 5 are extended by 610-20 mm from the front end of the probe.

The diameter of each copper probe is 0.1-0.3mm, the diameter of the thermocouple is 0.5mm, wherein the first copper probe 1 and the fourth copper probe 4 have no distance in the horizontal direction, and the distance in the vertical direction is 1.8-2.8 mm; the distance between the second copper probe 2 and the third copper probe 3 in the horizontal direction is 1.8-2.8 mm.

The thermocouple combined type speed potential probe based measuring method comprises the following steps:

(1) and measuring the speed: potential signals are obtained through measurement of four copper probes, a relation is established between the potential signals and flow velocity, and local velocity distribution of a flow field is obtained based on ohm's law:

whereinFor current density, σ is the liquid metal conductivity,the voltage signal is measured as a potential difference,in order to be the flow rate of the gas,for the intensity of the applied magnetic field, the applied magnetic field is assumedAt a speed ofCurrent densityWhen the magnetic field strength is large, the current density of the main flow region is extremely small, i.e., j_x≈0，j_zAnd 0, measuring the potential gradient in each direction in a vertical magnetic field plane at a specific position in the main flow area by the probe, and converting to obtain two velocity components of the position in the plane, namely a main flow velocity u and a velocity w along the z axis:

wherein B is₀In order to homogenize the magnetic field strength,a voltage signal measured for the probe;

(2) and temperature measurement: the local thermoelectric potential is directly measured by the T-shaped thermocouple 5 in the probe, and for a single welding thermocouple, because two electrodes of the T-shaped thermocouple 5 are welded without distance, the flowing potential in the liquid metal can not influence the T-shaped thermocouple, and the potential loop of the thermocouple can obtain the thermoelectric potential:

E_CoCu(T₁，T₀)＝E_CoCu(T₁)+E_Cu(T₁，T₀)+E_CoCu(T₀)+E_Co(T₁，T₀)

E_CoCu(T₁，T₀) I.e. measuring the resulting voltage, according to calibrated thermocouplesThe coefficient is converted to obtain the temperature.

Compared with the prior art, the method has the advantages that,

1. the T-shaped thermocouple 5 is added on the whole probe, so that the temperature can be measured, the synchronous and unified measurement of the temperature and the speed is realized, and only voltage measurement is needed.

2. The monomer immersion probe for measuring the speed and the temperature in the conductive fluid under the condition of a strong magnetic field has the advantages that the surfaces of the front end protective shell and the rear end protective shell of the probe are coated with insulating layers, so that the probe is ensured not to be in electric contact with liquid after being immersed, and only the probe tip is kept in electric contact with liquid metal.

3. The invention is suitable for the synchronous measurement of the local speed and the temperature in the opaque metal fluid under the condition of a strong magnetic field, and compared with the prior art, the invention increases the independent temperature measurement function of the welding thermocouple, and the advantage of using the independent welding thermocouple is that the local temperature and the speed can be obtained by measuring the voltage, meanwhile, the temperature difference potential and the speed potential are not influenced mutually, and the coupling effect of the two potentials is not required to be considered, so that the temperature and the speed obtained by measurement are more accurate and reliable.

Drawings

Fig. 1 is a schematic structural view of the present invention.

Fig. 2 is a schematic diagram of the internal flat cable of the present invention.

Detailed Description

The present invention will be described in detail with reference to the accompanying drawings.

Referring to fig. 1, a thermocouple-combined velocity potential probe, the integral protective shell of the probe is made of brass, the surface of the integral protective shell is coated with an insulating layer, a front end protective shell 6 of the probe is a potential measuring part and comprises four copper probes 1, 2, 3 and 4 which are uniformly distributed in the circumferential direction, and a T-shaped thermocouple 5 which is arranged in the center of the probe points of the four copper probes, and all the copper probes and the T-shaped thermocouple 5 exceed the front end protective shell 6 of the probe by about 10-20 mm.

The diameter of the shell of the protective shell 7 at the rear end of the probe is 3mm, the diameter of each copper probe is 0.1-0.3mm, the diameter of the thermocouple is 0.5mm, the first copper probe 1 and the fourth copper probe 4 have no distance in the horizontal direction, and the distance in the vertical direction is 1.8-2.8 mm; the distance between the second copper probe 2 and the third copper probe 3 in the horizontal direction is 1.8-2.8mm, the T-shaped thermocouple 5 measures the fluctuation of the temperature at the fixed position, the 4 copper probes can measure accurate flow speed, and the T-shaped thermocouple 5 arranged in the middle measures the fluctuation of the temperature at the fixed position.

The thermocouple combined type speed potential probe based measuring method comprises the following steps:

(1) and measuring the speed: potential signals are obtained through measurement of four copper probes, a relation is established between the potential signals and flow velocity, and local velocity distribution of a flow field is obtained based on ohm's law:

whereinFor current density, σ is the liquid metal conductivity,the voltage signal is measured as a potential difference,in order to be the flow rate of the gas,is the external magnetic field intensity. Referring to FIG. 2, assume an applied magnetic fieldAt a speed ofCurrent densityWhen the magnetic field strength is large, the current density of the main flow region is extremely small, i.e., j_x≈0，j_z0, then measuring the edge at a specific position in the main flow region by a probeThe potential gradient in each direction in the vertical magnetic field plane is converted to obtain two velocity components of the position in the plane, namely a main flow velocity u and a velocity w along the z-axis:

wherein B is₀In order to homogenize the magnetic field strength,is the voltage signal measured by the probe.

(2) And temperature measurement: the local thermoelectric potential is directly measured by the T-shaped thermocouple 5 in the probe, and for a single welding thermocouple, because two electrodes of the T-shaped thermocouple 5 are welded without distance, the flowing potential in the liquid metal can not influence the T-shaped thermocouple, and the potential loop of the thermocouple can obtain the thermoelectric potential:

E_CoCu(T₁，T₀)＝E_CoCu(T₁)+E_Cu(T₁，T₀)+E_CoCu(T₀)+E_Co(T₁，T₀)

E_CoCu(T₁，T₀) Namely, the measured voltage is converted to obtain the temperature according to the calibrated thermocouple coefficient.