Preparation method of T-shaped coaxial thermocouple and T-shaped coaxial thermocouple

Abstract

The invention discloses a T-shaped coaxial thermocouple preparation method and a T-shaped coaxial thermocouple, and the method comprises the steps: S1, enabling a constantan wire to be immersed in and pulled out of an insulating slurry for many times, so as to enable the insulating slurry to be uniformly attached to the surface of the constantan wire; s2, obtaining an insulating layer on the surface of the constantan wire through a preset curing mode; s3, depositing a copper film layer on the insulating layer; s4, a constantan wire is welded to the lower end face of the constantan wire, and electric conduction is formed between the copper wire and the copper thin film in a conductive adhesive bonding mode; and S5, removing the insulating layer formed on the upper end surface of the constantan wire, and coating the outer diameter edge of the constantan wire with a conductive adhesive to enable the constantan wire to be electrically conducted with the copper film, thereby obtaining the T-shaped coaxial thermocouple. According to the preparation method of the T-shaped coaxial thermocouple and the T-shaped coaxial thermocouple provided by the invention, a high transient heat flow sensor which can be used for a shock tunnel heat measurement test is realized by utilizing a relatively low-cost thermocouple material and a mature process, and the consistency and the accuracy of a heat measurement result of the sensor are improved.

Description

Technical Field

[0001] The present invention relates to the field of hypersonic wind tunnel testing technology. More specifically, the present invention relates to a method for preparing a T-type coaxial thermocouple that can be used to test heat flow in pulse-type equipment such as shock wind tunnels, and to the T-type coaxial thermocouple. Background Art

[0002] The effective test time of a shock tunnel is usually less than 10ms, but the ground simulation test of the aerodynamic thermal environment necessary for the development of hypersonic aircraft is mainly carried out in a shock tunnel, and the heat flux distribution test results on the surface of the aircraft test model obtained in the test will provide the calculation input conditions for the prediction of the aircraft's aerodynamic thermal environment. Currently, E-type coaxial thermocouples are mainly used to carry out the corresponding heat flux tests. In the process of experimental data processing, due to the comprehensive thermal physical parameters of the positive and negative dipole materials of the E-type (nickel-chromium-constantan) coaxial thermocouple, the thermal conductivity of the positive and negative dipole materials of the E-type (nickel-chromium-constantan) coaxial thermocouple is less than 10ms. There are obvious differences in (density ρ, specific heat capacity c, thermal conductivity k). In actual use, the average value of the two values ​​is taken as the sensor's own physical parameters to calculate the heat flow, ignoring the impact of the numerical difference on the thermal measurement results, resulting in low accuracy of the thermal measurement results.

[0003] In practical applications, the main reasons why existing E-type coaxial thermocouples have not been migrated to T-type coaxial thermocouples are: first, they do not address the inherent low thermal measurement accuracy of E-type coaxial thermocouples; second, at the same temperature, the thermoelectric output of T-type coaxial thermocouples is lower than that of E-type coaxial thermocouples. Therefore, there is a great need for a high-transient heat flux sensor with fewer factors affecting thermal measurement accuracy, a simpler sensor structure, a feasible preparation method, and controllable costs. Summary of the Invention

[0004] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0005] In order to achieve these objects and other advantages of the present invention, a method for preparing a T-type coaxial thermocouple is provided, comprising:

[0006] S1. Immerse the constantan wire in and out of the insulating slurry multiple times to ensure that the insulating slurry is evenly attached to the surface of the constantan wire;

[0007] S2. Obtain an insulating layer on the surface of the constantan wire by a predetermined curing method, while confirming that the insulating layer does not cover the lower end surface of the constantan wire;

[0008] S3, depositing a copper thin film layer on the insulating layer;

[0009] S4. Weld the constantan wire to the lower end surface of the constantan wire and use conductive adhesive to make the copper wire and the copper film electrically connected, and confirm that the constantan wire and the copper wire are in a non-conductive state;

[0010] S5. Remove the insulating layer formed on the upper end surface of the constantan wire, apply conductive glue to the outer diameter edge of the constantan wire, make the constantan wire and the copper film electrically conductive, confirm that the constantan wire and the copper wire are in a conductive state, and obtain a T-type coaxial thermocouple;

[0011] Wherein, in S1, in a low temperature environment not higher than 200°C, the insulating paste is epoxy resin paste;

[0012] In a high temperature environment of 200° C. to 500° C., the insulating paste is any one of glass paste and ceramic precursor polymer paste.

[0013] Preferably, the constantan wire is made of copper-nickel alloy, with a mass fraction of copper of 60% and a mass fraction of nickel of 40%;

[0014] The diameter of the constantan wire is 1.8 mm, and the thickness of the copper film layer and the insulating layer is 10 μm.

[0015] Preferably, in S2, the predetermined curing method is: when the insulating paste is epoxy resin paste, the curing method is curing in a heating furnace at 100° C.; when the insulating paste is glass paste or ceramic precursor polymer paste, the curing method is laser heating sintering;

[0016] In S3, the copper thin film layer is deposited by electroplating or physical vapor deposition.

[0017] A T-type coaxial thermocouple, comprising:

[0018] Constantan wire;

[0019] The insulating layer and copper film layer are arranged on the surface of the Constantan wire from the inside to the outside;

[0020] A constantan conductor electrically connected to the lower end face of the constantan wire;

[0021] a copper conductor conductively connected to the copper film layer;

[0022] The constantan wire and the copper thin film layer are electrically connected via a conductive layer arranged on the upper end surface of the copper wire.

[0023] A high transient heat flux sensor adopts a T-type coaxial thermocouple when performing heat flux measurement in a hypersonic wind tunnel.

[0024] The present invention has at least the following beneficial effects:

[0025] The present invention utilizes relatively inexpensive thermocouple materials and mature processes to produce a high-transient heat flux sensor suitable for shock tunnel thermal measurement tests, improving the consistency and accuracy of the sensor's thermal measurement results. The sensor can also be widely applied to other hypersonic wind tunnels for heat flux measurements. Specifically, the present invention utilizes a Czochralski sintering method to form a micron-thick insulating layer on the surface of a cylindrical constantan wire and then deposits a micron-thick copper film on the insulating layer to prepare a T-shaped coaxial thermocouple for high-transient heat flux testing. Because the thickness of the insulating layer and the copper film is very small relative to the constantan wire, the corresponding heat capacity is also very limited. Therefore, the impact of the comprehensive thermophysical properties of the insulating layer and the copper film on the heat flux test results is negligible. Furthermore, the use of a T-shaped coaxial thermocouple and constantan wire as the intermediate core has the advantages of relatively low raw material prices and the ability to select pure copper as the target material for physical vapor deposition of the copper film, thus ensuring that the thermocouple type meets the requirements for positive and negative dipole materials. The T-type coaxial thermocouple invented in this way not only improves the consistency of measurement data, but also avoids the influence of the comprehensive thermophysical parameters of different dipole materials on the thermal measurement results, which will improve the accuracy of thermal measurement data of the aerodynamic thermal environment of shock tunnels.

[0026] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the T-type coaxial thermocouple of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be described in further detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0029] The present invention provides a method for preparing a T-type coaxial thermocouple. The method uses a wire-type constantan as a core, forms a micron-thick insulating layer on the surface of a cylindrical constantan wire through a pulling and sintering method, and then deposits a micron-thick copper film on the insulating layer. The T-type coaxial thermocouple thus prepared can ignore the influence of the comprehensive thermophysical parameters of the copper dipole during heat flow testing, and only needs to consider the comprehensive thermophysical parameters of the constantan wire. This method achieves good test data consistency and data accuracy using relatively inexpensive materials.

[0030] Specifically, the preparation process of T-type coaxial thermocouple includes:

[0031] 1. Use a 1.8mm diameter constantan wire as the core. The constantan wire has a nominal composition of an alloy with a mass fraction of 60% copper and 40% nickel. Its diameter is recommended to be 1.8mm and its surface is flat and smooth.

[0032] 2. Immerse the constantan wire in / out of any one of the epoxy resin insulation slurry, glass slurry, and ceramic precursor polymer slurry multiple times to ensure that the slurry is evenly adhered to the surface of the constantan wire. Use a heating furnace curing or laser heating sintering curing method to form a uniform, dense, and flat insulation layer with a thickness of about 10μm on the surface of the constantan wire. In actual applications, different slurries can be selected as needed. Sensors formed under epoxy resin insulation slurry are mainly used in low-temperature environments not exceeding 200℃; sensors formed under glass slurry or ceramic precursor polymer slurry are mainly used in high-temperature environments above 200℃ to 500℃. When epoxy resin slurry is used as the insulation slurry, the curing method is curing in a heating furnace at 100℃; when glass slurry or ceramic precursor polymer slurry is used as the insulation slurry, the curing method is laser heating sintering.

[0033] At the same time, ensure that the insulation layer does not cover the end face of the Constantan wire to facilitate the subsequent welding of the Constantan wire;

[0034] 3. Deposit a uniform, dense, and smooth copper film about 10 μm thick on the insulating layer of the insulating constantan wire by electroplating copper or other methods. At the same time, the insulating layer is exposed on the side of the constantan wire.

[0035] 4. Use spot welding to weld an ordinary copper wire to the lower end face of the constantan wire, and use conductive glue to bond the ordinary wire and the copper film to form electrical conduction. Then check whether the two wires are electrically conductive. If there is no conduction, it is normal. Remove the insulating layer formed on the upper end face of the constantan wire, use conductive glue to apply the outer diameter edge of the constantan wire to make it electrically conductive with the copper film, and check whether the two wires are electrically conductive. If there is conduction, it is normal. When used for temperature measurement, the wire connected to the constantan wire must be constantan, and the wire connected to the copper film must be copper. In this way, a high transient heat flux sensor with high test result accuracy that can be used in shock wave wind tunnels can be realized. The present invention adopts a pulling and sintering method to form a micron-thick insulating layer on the surface of a cylindrical constantan wire, and a method of depositing a micron-thick copper film on the insulating layer to prepare a T-type coaxial thermocouple for high transient heat flux testing. The T-type coaxial thermocouple prepared by the method of the present invention can ignore the thermal physical parameters of the insulating layer and the copper film when performing high transient heat flow testing, and only consider the thermal physical parameters of constantan, thereby achieving the advantage of improving the accuracy of the heat flow test results.

[0036] like Figure 1 As shown, a T-type coaxial thermocouple comprises:

[0037] Constantan wire 1;

[0038] An insulating layer 2 and a copper film layer 3 are provided on the surface of the constantan wire from the inside to the outside;

[0039] A constantan wire 4 electrically connected to the lower end face of the constantan wire;

[0040] A copper conductor 5 electrically connected to the copper film layer;

[0041] Among them, the constantan wire and the copper thin film layer are connected through the conductive layer 6 arranged on the upper end surface of the copper wire. When it is only used for heat flow testing in the shock wave wind tunnel, the wires conductively connected to the lower end surface of the constantan wire and the copper thin film layer do not need to be different materials (that is, as shown in the solution of the present invention, a constantan wire is arranged at the lower end of the constantan wire, and the copper thin film layer is connected to a copper wire, all of which are made of the same material). They can be copper wires or other types of wires at the same time.

[0042] In practical applications, the T-type coaxial thermocouples of this solution can be used in high-transient heat flux sensors for use in heat flux measurements in hypersonic wind tunnels. The T-type coaxial thermocouple preparation method of the present invention utilizes relatively inexpensive thermocouple materials and mature processes to produce a T-type coaxial thermocouple suitable for shock tunnel thermal measurement testing, thereby improving the consistency and accuracy of the sensor's thermal measurement results. The device can also be widely used in other hypersonic wind tunnels for heat flux measurements. Compared to existing E-type coaxial thermocouples, whose dipole materials are both alloys and whose comprehensive thermophysical parameters differ, their thermal measurement results are inherently affected by factors that affect accuracy. Furthermore, the alloy nature of the dipoles makes the method described in the present invention difficult to use. The new T-type coaxial thermocouple formed by the present invention only needs to consider the comprehensive thermophysical parameters of constantan, resulting in fewer factors affecting the accuracy of heat flux test results and the potential for high-precision testing of medium and high heat fluxes.

[0043] Specifically, the T-type coaxial thermocouple prepared using the present invention only considers the comprehensive thermophysical parameters of constantan. Compared to existing E-type coaxial thermocouples, these thermocouples are subject to fewer factors affecting the accuracy of heat flow test results, making them suitable for high-precision heat flow testing in shock tunnels. Furthermore, copper coatings are simple to process and have a high degree of physical purity, meeting the requirements for dipole materials used in T-type thermocouples.

[0044] In the method of calculating the corresponding heat flux from the temperature rise history of the T-type coaxial thermocouple using formula (1), since the thickness of the copper film is very small compared to the constantan wire core, the influence of the comprehensive thermophysical parameters of the copper film on the thermal measurement results can be almost ignored, thereby achieving the advantage of ensuring the consistency and accuracy of the thermal measurement results.

[0045]

[0046] Where α is the Seebeck coefficient of the T-type thermocouple, t is time, V is the thermoelectric potential output by the thermocouple, and the subscript represents the time series. For the currently commonly used E-type coaxial thermocouple, since the nickel-chromium-constantan size is similar, the comprehensive thermal physical parameters in formula (1) are The arithmetic mean of the two is often taken, where the comprehensive thermal physical parameters of nickel and chromium are approximately 7447.2Ws -0.5 / (m 2 .K), the comprehensive thermal physical parameters of constantan are about 8227.1Ws -0.5 / (m 2 .K), the relative difference between the two is obvious; and for the new T-type coaxial thermocouple described in the present invention, the comprehensive thermal physical parameters in formula (1) It is just a single ingredient, Constantan.

[0047] The above solution is only an illustration of a preferred embodiment, but is not limited thereto. When implementing the present invention, appropriate replacements and / or modifications can be made according to user needs.

[0048] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and exemplary embodiments. They can be applied to a variety of fields suitable for the present invention. Further modifications will be readily apparent to those skilled in the art. Therefore, the present invention is not limited to the specific details and illustrations shown and described herein without departing from the general concept defined by the claims and their equivalents.

Claims

1. A method for preparing a T-type coaxial thermocouple, characterized in that: include: S1. Immerse the constantan wire in and out of the insulating slurry multiple times to ensure that the insulating slurry is evenly attached to the surface of the constantan wire; S2. Obtain an insulating layer on the surface of the constantan wire by a predetermined curing method, while confirming that the insulating layer does not cover the lower end surface of the constantan wire; S3, depositing a copper thin film layer on the insulating layer; S4. Weld the constantan wire to the lower end surface of the constantan wire and use conductive adhesive to make the copper wire and the copper film electrically connected, and confirm that the constantan wire and the copper wire are in a non-conductive state; S5. Remove the insulating layer formed on the upper end surface of the constantan wire, apply conductive glue to the outer diameter edge of the constantan wire, make the constantan wire and the copper film electrically conductive, confirm that the constantan wire and the copper wire are in a conductive state, and obtain a T-type coaxial thermocouple; Wherein, in S1, in a low temperature environment not higher than 200°C, the insulating paste is epoxy resin paste; In a high temperature environment of 200° C. to 500° C., the insulating paste is any one of glass paste and ceramic precursor polymer paste.

2. The method for preparing a T-type coaxial thermocouple according to claim 1, wherein: The constantan wire is made of copper-nickel alloy, with a mass fraction of copper of 60% and a mass fraction of nickel of 40%; The diameter of the constantan wire is 1.8 mm, and the thickness of the copper film layer and the insulating layer is 10 μm.

3. The method for preparing a T-type coaxial thermocouple according to claim 1, wherein: In S2, the predetermined curing method is: when the insulating paste is epoxy resin paste, the curing method is curing in a heating furnace at 100° C.; when the insulating paste is glass paste or ceramic precursor polymer paste, the curing method is laser heating sintering; In S3, the copper thin film layer is deposited by electroplating or physical vapor deposition.

4. A T-type coaxial thermocouple, obtained by the preparation method according to any one of claims 1 to 3, characterized in that: include: Constantan wire; The insulating layer and copper film layer are arranged on the surface of the Constantan wire from the inside to the outside; A constantan conductor electrically connected to the lower end face of the constantan conductor; a copper conductor conductively connected to the copper film layer; The constantan wire and the copper thin film layer are electrically connected via a conductive layer arranged on the upper end surface of the copper wire.

5. A high transient heat flow sensor, characterized in that: In the heat flow measurement carried out in the hypersonic wind tunnel, the high transient heat flow sensor adopts the T-type coaxial thermocouple as described in claim 4.

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