A high temperature furnace temperature measurement system with automatic temperature calibration

Abstract

The present invention discloses a high-temperature furnace temperature measurement system with automatic temperature calibration, comprising a high-temperature furnace unit, which is a closed cavity for placing samples and maintaining a constant environment; an execution unit, which is used to heat the high-temperature furnace body and process the feedback temperature; a temperature-measuring thermocouple, which measures the in-situ temperature of the sample; an infrared temperature measurement system, which measures the temperature of the medium and high temperature sections of the sample; a temperature processing unit, which is used for temperature fitting correction and data output; the temperature data measured by the temperature-measuring thermocouple and the infrared temperature measurement system are processed by the temperature processing unit to feedback the in-situ temperature of the sample in the entire temperature section. The present invention accurately measures the in-situ temperature of the sample in the medium and low temperature sections with the help of thermocouples, and feedbacks the sample temperature in the medium and high temperature sections through the infrared temperature measurement system. The two are subjected to data analysis and correction, and the temperature processing unit fits the relationship curve to finally output the in-situ temperature of the sample in the entire temperature section.

Description

Technical Field

[0001] The invention belongs to the field of high-temperature furnace temperature measurement, and in particular relates to a high-temperature furnace temperature measurement system with automatic temperature calibration. Background Art

[0002] In industrial production, the use of vacuum high-temperature furnaces to create a vacuum and high-temperature environment, or a high-temperature environment filled with inert gas, for heat treatment of materials is becoming increasingly common. Real-time and accurate temperature measurement of metal samples within vacuum high-temperature furnaces is crucial for maintaining stable production activities.

[0003] There are usually two ways to measure the temperature of samples in a vacuum high-temperature furnace:

[0004] One method is contact temperature measurement, which uses thermocouples mounted on the surface of the sample to measure temperature. While this method offers high accuracy, it is subject to the complexities of industrial production environments, including those with rapid temperature fluctuations, high temperatures, and sample movement. In these complex environments, thermocouple installation and measurement are significantly limited, reducing efficiency and potentially preventing stable operation. Failure of the temperature measurement equipment can directly impact normal production activities and even pose safety risks.

[0005] Another method is non-contact temperature measurement. Currently, one method uses an infrared thermal imager to measure the target temperature. This method is not restricted by the target's spatial environment or shape. The temperature measurement device does not require direct contact with the target, but determines the target temperature by measuring the infrared radiation emitted by the sample. However, in the process of using infrared radiation for non-contact temperature measurement, the target's emissivity is an essential condition. Emissivity is a property that indicates an object's ability to radiate radiation. It is the ratio of the radiation emitted by the object at a certain temperature to the radiation emitted by a black body at the same temperature. The emissivity varies from object to object, and the emissivity of the same object also varies under different conditions such as temperature, surface roughness, and wavelength. In addition, during the temperature measurement process, in addition to the target being measured, the inner wall of the vacuum high-temperature furnace also emits radiation, and the inner wall of the vacuum high-temperature furnace and the target being measured can absorb or reflect each other's radiation. Although scholars have conducted extensive research on the emissivity of metals, industrial production environments are complex and diverse. Even the same material can have different emissivities under different conditions. Therefore, for the high-temperature vacuum environment or high-temperature oxygen-free environment in the industrial vacuum high-temperature furnace, how to eliminate the influence of various factors on the temperature measurement results and obtain the accurate target temperature is a problem that must be solved when measuring temperature. Summary of the Invention

[0006] The main technical problem addressed by this invention is to provide a high-temperature furnace temperature measurement system with automatic temperature calibration. This system, through coupled temperature measurement, addresses the issues of thermocouples being unable to measure temperatures at higher temperatures in single temperature measurement methods, as well as the inaccurate temperature measurement caused by infrared temperature measurement being affected by factors such as the environment, sample characteristics, and equipment parameters. During the sample temperature measurement phase, this device simultaneously obtains feedback data from the thermocouple and infrared temperature measurement system, as well as input current data, to calibrate a finite element model. Combining the calibrated finite element model with the current data, it ultimately outputs the in-situ temperature of the sample over the entire temperature range.

[0007] The present invention relates to a high-temperature furnace temperature measurement system with automatic temperature calibration, the basic components of which include the following structure:

[0008] The high-temperature furnace unit is a fully enclosed structural cavity used to place samples and maintain a constant environment. It can also heat the samples. The internal cavity can achieve a vacuum environment or be filled with inert gas to protect the samples.

[0009] The execution unit is a power control system that heats the high-temperature furnace by adjusting numerical parameters such as current and voltage, and leveraging the principle of plasma discharge. The execution unit receives signals from the temperature processing unit and performs corresponding processing based on the temperature value fed back.

[0010] The temperature measuring thermocouple is installed on the side of the furnace body, and the temperature measuring end is in direct contact with the sample mold, which can accurately measure the in-situ temperature of the sample;

[0011] The infrared temperature measurement system irradiates the sample mold through the lens in the furnace structure and directly feedbacks the sample temperature based on the infrared light wave measurement principle. A vacuum environment is maintained between the infrared temperature measurement system and the lens of the furnace structure to prevent outside air or other foreign matter from affecting the infrared temperature measurement system's beam. The data output by the infrared temperature measurement system accurately fits the data output by the temperature measuring thermocouple.

[0012] The temperature processing unit can collect the signals transmitted by the thermocouple and the infrared temperature measurement system respectively, and use the independent temperature signals of the two to calibrate the finite element model. The calibrated finite element model is used to output the data of the entire temperature range, which is infinitely close to the in-situ temperature of the sample. The data is fed back to the execution unit, ultimately realizing the precise temperature measurement and control process.

[0013] Among them, the high-temperature furnace unit includes a furnace body, an upper electrode, a lower electrode and a sample mold. The upper electrode and the lower electrode are respectively connected to the execution unit through wires to form a circuit that can complete current transmission. The sample mold is located between the upper and lower electrodes, and the sample is placed inside the sample mold. With the help of current transmission, the heating process of the sample is realized.

[0014] Furthermore, the wire connecting the execution unit and the high-temperature furnace unit is a copper wire. With the help of the excellent conductivity of the copper wire, the execution unit inputs a stable current to the high-temperature furnace unit, and the current acts on the sample to achieve rapid heating of the sample.

[0015] Furthermore, the temperature measuring thermocouple is an armored thermocouple. The temperature measuring thermocouple passes through the high-temperature furnace body, and the end is located inside the high-temperature furnace unit cavity, in direct contact with the sample mold. It accurately feeds back the in-situ temperature of the sample in the range of 0 to 1500°C, and the measured data within this range is used as basic correction data.

[0016] Among them, the infrared temperature measurement system determines the sample temperature by irradiating the sample with light waves reflected during the heating stage.

[0017] Among them, during the sample heating stage, the temperature processing unit receives the temperature values ​​fed back by the temperature measuring thermocouple and the infrared temperature measuring system respectively, establishes a temperature rise relationship curve between the two, and realizes in-situ temperature measurement of the sample in the entire temperature range. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the appearance structure diagram of this system;

[0019] Figure 2 This is the furnace structure diagram;

[0020] Figure 3 It is the ECR fitting curve graph;

[0021] Figure 4 is the TCR fitting curve;

[0022] Figure 5 A comparison chart of calculated and measured temperatures.

[0023] Figure numerals: 1-high temperature furnace unit, 2-infrared beam, 3-infrared temperature measurement system, 4-vacuum pipe, 5-copper wire, 6-execution unit, 7-temperature measurement thermocouple, 8-feedback signal, 9-temperature processing unit, 10-sample, 101-furnace body, 102-upper electrode, 103-sample mold, 104-lower electrode. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] Example 1:

[0026] The present embodiment relates to a high-temperature furnace temperature measurement system with automatic temperature calibration, and its basic components include the following structure:

[0027] The high-temperature furnace unit 1 is a fully enclosed structural cavity for placing the sample 10 and maintaining a constant environment. The internal cavity can achieve a vacuum environment or be filled with inert gas to protect the sample.

[0028] The execution unit 6 is a power control system that heats the high-temperature furnace body by adjusting numerical parameters such as current and voltage, and utilizing the principle of plasma discharge. The execution unit receives signals from the temperature processing unit and performs corresponding processing based on the temperature value fed back.

[0029] The temperature measuring thermocouple 7 is installed on the side of the furnace body 101, and the temperature measuring end is in direct contact with the sample mold 103, which can accurately measure the in-situ temperature of the sample 10. A vacuum cavity 4 is formed between the infrared temperature measuring system 3 and the lens of the furnace structure. The vacuum cavity can maintain a vacuum environment to prevent external air or other foreign matter from affecting the light beam of the infrared temperature measuring system 3. The data output by the infrared temperature measuring system 3 and the data output by the temperature measuring thermocouple 7 are input into the finite element model, that is, the temperature processing unit 9, and the model is calibrated.

[0030] The infrared temperature measurement system 3 irradiates the sample mold 103 through the lens in the furnace structure and directly feeds back the sample temperature based on the infrared light wave measurement principle;

[0031] The temperature processing unit 9 can collect the signals transmitted by the temperature measuring thermocouple 7 and the infrared temperature measuring system 3 respectively, draw the temperature rise curve of the independent temperature signals of the two, and automatically compare and fit the two curves; synchronously, the temperature processing unit 9 collects current data, and preliminarily constructs a finite element model of the collected current and temperature signals to form an automatic calibration model of current and temperature data in the low temperature stage, and uses the initial model to infinitely advance and output the current and infrared temperature data in the high temperature stage, thereby forming temperature output data of the entire temperature range, which is infinitely close to the original temperature of the sample, and feeds the data back to the execution unit 6, thereby finally realizing the precise temperature measurement and temperature control process.

[0032] Among them, the high-temperature furnace unit 1 includes a furnace body 101, an upper electrode 102, a lower electrode 104 and a sample mold 103. The upper electrode and the lower electrode are respectively connected to the execution unit 6 through a copper wire 5 to form a loop that can complete current transmission. The sample mold 103 is located between the upper and lower electrodes, and the sample 10 is placed inside the sample mold. With the help of current transmission, the heating process of the sample is realized.

[0033] Furthermore, the wire connecting the execution unit 6 and the high-temperature furnace unit 1 is a copper wire. With the help of the excellent conductivity of the copper wire 5, the execution unit 6 inputs a stable current to the high-temperature furnace unit 1, and the current acts on the sample to achieve rapid heating of the sample.

[0034] Furthermore, the temperature measuring thermocouple 7 is an armored thermocouple. The temperature measuring thermocouple 7 passes through the high-temperature furnace body 101, and the end is located inside the high-temperature furnace unit cavity, in direct contact with the sample mold 103. In the range of 0 to 1500°C, it accurately feeds back the in-situ temperature of the sample 10, and the measured data within this range is used as basic correction data.

[0035] The infrared temperature measurement system 3 determines the sample temperature by irradiating the sample with light waves reflected by the sample during the heating stage.

[0036] Among them, during the sample heating stage, the temperature processing unit 9 receives the temperature values ​​fed back by the temperature measuring thermocouple 7 and the infrared temperature measuring system 3, namely the feedback signal 8; establishes a temperature rise relationship curve between the two, and realizes in-situ temperature measurement of the sample in the entire temperature range.

[0037] Example 2:

[0038] The basic working principle of the automatic temperature calibration high-temperature furnace temperature measurement system involved in this embodiment is as follows:

[0039] In the medium and low temperature stage (range of 0 to 1500°C), the end of the temperature measuring thermocouple 7 is located inside the high temperature furnace unit cavity, in direct contact with the sample mold 103, and accurately feeds back the in-situ temperature of the sample 10. The data measured in the range of 0 to 1500°C is used as basic correction data.

[0040] The infrared temperature measurement system 3 determines the sample temperature by irradiating the sample with light waves reflected during the heating stage; the temperature measured by the infrared temperature measurement system 3 and the temperature measured by the thermocouple 7 are used as basic data;

[0041] The temperature measurement data of the thermocouple 7 and the infrared temperature measurement system 3 are input into the packaged finite element model, i.e. the temperature processing unit 9. The model will automatically fit and calibrate the electric and thermal contacts (ECR and TCR) in the mold, as shown in the following example. Figure 3 and 4 As shown. Combining the calibrated ECR and TCR, the model can analyze the input current data and the data measured by the infrared temperature measurement system 3, and output the in-situ temperature and current density of each location in the mold (including sample 10). The solution equation of the model is as follows:

[0042] The current distribution is solved based on the charge conservation equation (1):

[0043]

[0044] Where J is the current density; σ is the conductivity; E is the electric field; and U is the electric potential.

[0045] The temperature distribution inside the mold is solved by the heat conduction partial differential equation (2):

[0046]

[0047] Where ρ is the density; C P is heat capacity; T is temperature; t is time; k is thermal conductivity. Implementing electro-thermal coupling, which describes the Joule heat generated per unit volume per unit time, is expressed as:

[0048]

[0049] The last four terms of formula (2) and They correspond to the heat flows caused by heat conduction, heat convection, heat radiation, and interface Joule heating effect, respectively. In our model, since the experiment is carried out under vacuum conditions, the heat convection on the side surfaces of the system can be ignored. Only the radiation heat dissipation on the side surfaces of the system and the water cooling heat dissipation on the electrode surfaces at both ends need to be considered, which are expressed by (4) and (5) respectively:

[0050]

[0051]

[0052] Where ε is the emissivity; σ is the Stefan-Boltzmann constant; h is the convection coefficient;

[0053] T s is the emitting surface temperature; T amb is the ambient temperature; T e is the electrode surface temperature; T water It's the water temperature.

[0054] The initial temperature of the system is the initial measurement temperature of the thermocouple; the ambient temperature is always the initial measurement temperature of the infrared temperature measurement system; the convection coefficient is set to (200W / (m 2 *K); the water temperature is constant at 25°C; the emissivities of the electrode, graphite mold, and graphite felt are 0.67, 0.8, and 0.3, respectively.

[0055] Due to the incomplete contact between different parts in the system, electrical contact resistance (ECR) and thermal contact resistance (TCR) exist at the contact interface. Experiments have shown that ECR and TCR have a significant impact on temperature and current distribution. Therefore, the influence of ECR ​​and TCR must be considered to obtain a reliable model. During the simulation process, ECR and TCR at the interface are expressed by equations (6) and (7):

[0056]

[0057]

[0058] Where J c and q cis the electric flux and heat flux of the contact surface; V 1，2 and T 1，2 are the voltage and temperature of the contact surface. Therefore, the Joule heat generated at the contact interface can be expressed as:

[0059]

[0060] The temperature processing unit 9 calibrates the ECR and TCR using the data output by the temperature measuring thermocouple 7 and the infrared temperature measuring system 3 at the medium and low temperature stages;

[0061] Calibration process: Based on the current data input by the system, the initial model outputs the calculated temperature data, which is compared with the input measured temperature data to adjust the ECR and TCR. Then, based on the adjusted ECR and TCR, the calculated temperature data is output and compared again. Through repeated experiments and iterations, reliable ECR and TCR curves are obtained through calibration, such as Figure 3 and 4 shown.

[0062] In the high temperature stage, with the help of the calibrated finite element model, the temperature value that is infinitely close to the sample's in-situ temperature can be calculated based on the input current data, such as Figure 5 As shown in the figure, the accurate sample temperature is output during the full temperature stage of the sample.

[0063] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A high temperature furnace temperature measurement system with automatic temperature calibration, characterized in that: include: The high-temperature furnace unit is a closed cavity used to place samples and maintain a constant environment. The high-temperature furnace unit includes a furnace body, an upper electrode, a lower electrode, and a sample mold. The upper electrode and the lower electrode are connected to the execution unit through copper wires. The internal cavity of the high-temperature furnace unit realizes a vacuum environment or is filled with inert gas. The execution unit is a power control system that heats the high-temperature furnace body by adjusting and setting current and voltage numerical parameters based on the principle of plasma discharge. The execution unit can receive signals transmitted by the temperature processing unit and make corresponding processing based on the feedback temperature value; The temperature measuring thermocouple is an armored thermocouple installed on the side of the furnace body. The temperature measuring end is in direct contact with the sample mold to measure the in-situ temperature of the sample in the range of 0 ~ 1500℃; The infrared temperature measurement system irradiates the sample mold through the lens in the furnace structure and directly feedbacks the sample temperature based on the infrared light wave measurement principle. A vacuum environment is maintained between the infrared temperature measurement system and the lens of the furnace structure to prevent external air or other foreign matter from affecting the infrared temperature measurement system's light beam; The temperature processing unit collects the signals transmitted by the thermocouple and the infrared temperature measurement system respectively, and uses the independent temperature signals of the two to calibrate the finite element model. The calibrated finite element model outputs the data of the full temperature range, which is infinitely close to the in-situ temperature of the sample. The data is fed back to the execution unit, ultimately achieving accurate temperature measurement and control. The temperature data from the thermocouple and infrared temperature measurement system are input into the packaged finite element model, i.e., the temperature processing unit. The model will automatically fit and calibrate the electrical contact resistance and contact thermal resistance in the mold. Combining the calibrated electrical contact resistance and contact thermal resistance, the model analyzes the input current data and the data measured by the infrared temperature measurement system, and outputs the in-situ temperature and current density at various locations in the mold. The temperature processing unit calibrates the electrical contact resistance and contact thermal resistance using the data output by the temperature measuring thermocouple and the infrared temperature measuring system at medium and low temperature stages; The calibration process is as follows: based on the current data input by the system, the initial model outputs calculated temperature data, compares it with the input measured temperature data, adjusts the electrical contact resistance and contact thermal resistance, and then outputs calculated temperature data based on the adjusted electrical contact resistance and contact thermal resistance, and compares them again; Through repeated experimental iterations, reliable electrical contact resistance and contact thermal resistance curves are calibrated and obtained; In the high-temperature stage, with the help of the calibrated finite element model, the temperature value that is infinitely close to the sample's in-situ temperature is calculated and output based on the input current data, so as to output accurate sample temperature in the full temperature stage of the sample.

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