Experimental device and experimental method for measuring heat conductivity coefficient of metal material

Abstract

The invention discloses an experimental device and an experimental method for measuring the heat conductivity coefficient of a metal material, the experimental device comprises a tube furnace, an adjustable voltage-stabilized source, a cooler, a data acquisition instrument and a computer, the adjustable voltage-stabilized source, the cooler and the data acquisition instrument are all connected with the tube furnace, the computer is connected with the data acquisition instrument, and the data acquisition instrument is connected with the cooler. The adjustable voltage-stabilized source is used for providing current for the sample, and the cooler is used for cooling the tubular furnace and adjusting the temperature gradient of the sample; the data acquisition instrument is used for acquiring sample and environment temperature data, and the computer is used for collecting and processing the data acquired by the data acquisition instrument. The method is high in measurement accuracy, can be used for researching the change rule of the heat conductivity coefficient of the motor metal material under the high-temperature condition, solves the problems that the heat conductivity coefficient of the metal material of the aero-engine motor is not clear along with the temperature change characteristic and is not accurate in setting, and lays a foundation for the development of the aero-engine motor and green aviation.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-electric engines, and in particular to an experimental device and an experimental method for measuring the thermal conductivity of metal materials. Background Art

[0002] Aviation electrification is an important measure to develop green aviation. In the future, large electrified passenger aircraft will have an increasingly higher demand for the power level of electric propulsion systems. The key to realizing more electric / all-electric aircraft is to embed the motor into the high-pressure shaft of the aircraft engine, thereby eliminating the auxiliary gearbox, which can not only significantly improve the performance of the aircraft, but also provide considerable economic benefits. However, the high temperature environment of the high-pressure shaft of the engine and the high integration of the motor have put forward strict requirements on the starter / generator. In an environment with a temperature of up to 300°C, the starter / generator must have excellent heat resistance and safety, that is, it must have high efficiency (more than 90%), light weight, compactness, and stable operation under high-intensity mechanical, thermal, electromagnetic loads and overload conditions. In addition, since the starter / generator rotates coaxially with the high-pressure rotor, such as the CFM56-7B engine high-pressure rotor speed of the Boeing 737-800 is 15183r / min. Therefore, the motor must also have applicability and reliability under high-speed conditions. The current motor technology is difficult to meet the requirements under the above extreme conditions, and it is necessary to develop high-temperature, high-speed and high-power density high-temperature high-speed motors.

[0003] During the design stage of high-temperature and high-speed motors, researchers usually use simulation software such as Motor-CAD and Ansys Fluent to perform thermal analysis of motors. When setting the thermal conductivity of motor materials, they usually directly use the values ​​under normal temperature conditions provided by the software. For example, the thermal conductivity of silicon steel in the Motor-CAD software database is set to 30W / (m·℃). However, the temperature variation characteristics of the thermal conductivity of high-temperature and high-speed motor materials are still unclear. The thermal conductivity is actually a physical parameter that varies with temperature, and its value is closely related to the intrinsic properties and thermodynamic state (such as temperature and pressure) of the material. Therefore, correctly understanding the temperature variation characteristics of the thermal conductivity of high-temperature and high-speed motor metal materials is the key and basis for the thermal analysis of high-temperature and high-speed motors. In summary, the existing research has obvious deficiencies in the thermal analysis of high-temperature and high-speed motors, especially the inaccurate setting of the thermal conductivity of the metal materials of the motor at high temperatures, which leads to a large deviation between the simulation results and the actual situation. Therefore, there is an urgent need for a measurement experiment and experimental method that can be used to study the thermal conductivity of motor metal materials under high temperature conditions to solve the problem that the temperature variation characteristics of the thermal conductivity of the metal materials of the aero-engine motor are unclear and the setting is inaccurate. Summary of the invention

[0004] Purpose of the invention: In view of the above shortcomings, the present invention provides an experimental device and an experimental method for measuring the thermal conductivity of metal materials.

[0005] Technical solution: To solve the above problems, the present invention adopts an experimental device for measuring the thermal conductivity of metal materials, including a tubular furnace, an adjustable voltage-regulated power supply, a cooler, a data acquisition instrument, and a computer. The adjustable voltage-regulated power supply, the cooler, and the data acquisition instrument are all connected to the tubular furnace, and the computer is connected to the data acquisition instrument. The adjustable voltage-regulated power supply is used to provide current for the sample, and the cooler is used to cool the tubular furnace and adjust the temperature gradient of the sample; the data acquisition instrument is used to collect sample and ambient temperature data, and the computer is used to collect and process the data collected by the data acquisition instrument.

[0006] Furthermore, the cooler is installed at both ends of the tubular furnace, and the cooler is connected to a water circulation pipeline. A flow sensor, a valve, a high-pressure pump, and a water storage tank are arranged in series on the water circulation pipeline. The temperature gradient of the sample is adjusted by adjusting the water flow in the water circulation pipeline.

[0007] Furthermore, a filter is provided at the water outlet of the water storage tank.

[0008] Furthermore, the cooler is connected to both ends of the tubular furnace, the positive and negative electrodes of the adjustable voltage-stabilized power supply are connected to both ends of the cooler, and the tubular furnace and the adjustable voltage-stabilized power supply are powered by a 380V AC power supply.

[0009] Furthermore, a shunt is provided between one of the electrodes of the adjustable voltage-stabilized power supply and the cooler, and the shunt adopts a 0.0005Ω standard alloy resistor.

[0010] Furthermore, the adjustable regulated power supply is also connected to a voltage regulator.

[0011] Furthermore, the data acquisition instrument and computer are powered by a 220V AC power supply.

[0012] The present invention also provides an experimental method for the experimental device for measuring the thermal conductivity of metal materials, comprising the following steps:

[0013] Step 1: Place the sample in a tube furnace and fill the gap between the sample and the furnace tube with high temperature resistant asbestos;

[0014] Step 2: Place the thermocouples used by the data acquisition instrument to collect temperature data on the sample surface and the inside of the furnace tube, respectively, and set the sampling interval and total sampling time of the data acquisition instrument;

[0015] Step 3, turn on the cooler, set the heating temperature, heating time and insulation time of the tube furnace, and then turn on the tube furnace to start heating;

[0016] Step 4: After the temperature of the tube furnace is stable, turn on the data acquisition instrument to collect the sample temperature and the ambient temperature of the tube furnace. According to the temperature data, adjust the cooler so that the temperature gradient of the sample is 5-50°C when the sample is powered on; when the sample temperature is stable, collect the sample temperature data;

[0017] Step 5: Turn on the adjustable voltage-stabilized power supply and adjust the current to make the sample temperature consistent with the ambient temperature of the tube furnace. When the sample temperature is stable, collect the sample temperature data;

[0018] Step 6, swap the positive and negative poles of the adjustable voltage-stabilized power supply, repeat step 5, and collect another set of sample temperature data;

[0019] Step 7, disconnect the adjustable voltage-stabilized power supply and collect the sample temperature data again;

[0020] Step 8, gradually increase the heating temperature of the tube furnace with the same temperature gradient, and repeat steps 3 to 6 to collect sample temperature data at different heating temperatures;

[0021] Step 9: After the test, turn off the power of the tube furnace, wait for the furnace temperature to cool to room temperature, disconnect the thermocouple, and take out the sample;

[0022] Step 10: The computer collects and processes the temperature data and outputs the thermal conductivity of the sample at different temperatures.

[0023] Furthermore, in step 2, a thermocouple is arranged at both ends and the middle of the sample surface and at both ends and the middle of the inner side of the furnace tube.

[0024] Furthermore, when the collected temperature changes within the range of 0.5°C, it is judged that the furnace temperature and the sample temperature have reached stability.

[0025] Beneficial effect: Compared with the prior art, the significant advantage of the present invention is that it provides an experimental device and an experimental method for measuring the thermal conductivity of metal materials, which has high measurement accuracy and can be used to study the changing law of the thermal conductivity of motor metal materials under high temperature conditions, solve the problem that the thermal conductivity of metal materials of aircraft engine motors changes with temperature and the setting is inaccurate, and lay the foundation for the development of aircraft engine motors and green aviation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The figure is a schematic diagram of the overall structure of the experimental device for measuring the thermal conductivity of metal materials according to the present invention;

[0027] Figure 2 This is a schematic diagram of the measurement method of the direct current longitudinal heat flow method;

[0028] Figure 3 The thermal conductivity of three silicon steel samples measured for the present invention varies with temperature. DETAILED DESCRIPTION

[0029] like Figure 1 As shown, an experimental device for measuring the thermal conductivity of metal materials in this embodiment includes a tube furnace 19, an adjustable voltage-stabilized power supply 8, a cooler 11, a data acquisition instrument 3, and a computer 1. The adjustable voltage-stabilized power supply 8, the cooler 11, and the data acquisition instrument 3 are all connected to the tube furnace 19, and the computer 1 is connected to the data acquisition instrument 3. The data acquisition instrument 3 and the computer 1 are powered by a 220V AC power supply 2. The data acquisition instrument 3 is used to collect sample and ambient temperature data. The model of the Agilent data acquisition instrument used in this embodiment is Agilent 34972A. The computer 1 is used to collect and process the data collected by the data acquisition instrument 3.

[0030] The cooler 11 is connected to both ends of the tube furnace 19, and the cooler 11 is externally connected to a water circulation pipeline 14, and the tube furnace is cooled by circulating water. The water circulation pipeline 14 is provided with a flow sensor 13, a valve 15, a high-pressure pump 16, and a water storage tank 18 in series, and a filter 17 is provided at the water outlet of the water storage tank 18. The temperature gradient of the sample is adjusted by adjusting the water flow of the water circulation pipeline 14.

[0031] The positive and negative electrodes of the adjustable voltage-stabilized power supply 8 are connected to both ends of the cooler 11. The adjustable voltage-stabilized power supply 8 is used to provide current for the sample. The tube furnace 19 and the adjustable voltage-stabilized power supply 8 are powered by a 380V AC power supply 6. Switches (4, 7) are provided between the power supply and the tube furnace 19 and the adjustable voltage-stabilized power supply 8. A shunt 5 is provided between one of the electrodes of the adjustable voltage-stabilized power supply 8 and the cooler 11. The shunt adopts a 0.0005Ω standard alloy resistor. A voltage regulator 12 is also connected to the adjustable voltage-stabilized power supply 8.

[0032] This embodiment also provides an experimental method for the above experimental device for measuring the thermal conductivity of metal materials, comprising the following steps:

[0033] Step 1: Place the sample 10 in a tube furnace 19 and fill the gap between the sample 10 and the furnace tube 20 with high temperature resistant asbestos 9. The sample 10 of this embodiment has a density of 7755 kg / m 3 The silicon steel material is processed into a cylindrical shape with a diameter of 3mm and a length of 220mm, and the two ends of the silicon steel sample are welded with an iron alloy with a diameter of 10mm and a high thermal conductivity. During the furnace loading process, relative movement and twisting between the high-temperature resistant asbestos layer 9 and the sample 10 should be avoided, and the center of the sample should be placed at the center of the heating section of the tube furnace.

[0034] Step 2: Place the thermocouples used by the data acquisition instrument 3 to collect temperature data on the sample surface and the inner side of the furnace tube, respectively. Set the sample temperature thermocouples 31 at both ends and the middle of the sample surface, and set the ambient temperature thermocouples 32 at both ends and the middle of the inner side of the furnace tube 20. Set the sampling interval of the data acquisition instrument 3 to 3s, the total sampling time to 10min, and each sampling can collect 200 sets of temperature data.

[0035] Step 3, open the cooler 11, set the heating temperature of the tube furnace 19 to 100°C, the heating time to 30 minutes, the heat preservation time to 3 hours, and then open the tube furnace 19 to start heating.

[0036] Step 4: After the temperature of the tube furnace 19 is stable, turn on the data acquisition instrument 3 to collect the sample temperature and the ambient temperature of the tube furnace. According to the temperature data, adjust the water flow of the cooler 11 so that the temperature gradient Δ1 is 5-50°C when the sample is powered on. When the sample temperature is stable, collect the sample temperature data. When the collected temperature changes within the range of 0.5°C, it is judged that the furnace temperature and the sample temperature are stable.

[0037] Step 5, turn on the adjustable voltage-stabilized power supply 8, adjust the current to make the sample temperature consistent with the ambient temperature of the tube furnace, and collect the sample temperature data when the sample temperature is stable.

[0038] Step 6: swap the positive and negative poles of the adjustable voltage-stabilized power supply 8, repeat step 5, collect another set of sample temperature data, and take the average of the two sets of data as the final temperature data. By swapping the motors connected at both ends of the sample, the measurement error caused by the asymmetry of the sample can be reduced, and the data accuracy can be improved.

[0039] Step 7, disconnect the adjustable voltage-stabilized power supply 8, and collect the sample temperature data again. To further improve the data accuracy, repeat steps 4-6 three times at the same tube furnace temperature, and take the average of the three data as the final data.

[0040] Step 8, gradually increase the heating temperature of the tube furnace 19 with a temperature gradient of 50°C, that is, set the temperature of the tube furnace 19 to 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C and 1000°C respectively and repeat steps 3 to 6 to collect sample temperature data at different heating temperatures. When the furnace temperature rises to 800°C, disconnect the cooling device and stop cooling the tube furnace.

[0041] Step 9: After the test is completed, turn off the power supply of the tube furnace 19, wait for the furnace temperature to cool to room temperature, disconnect the thermocouple, and take out the sample. Continue to measure the temperature data of the samples with diameters of 4 mm and 5 mm using this method.

[0042] Step 10: Computer 1 collects and processes temperature data, and outputs thermal conductivity of the sample at different temperatures.

[0043] The experiment was designed and implemented according to GB / T 3651-2008, which specifies the method for measuring the thermal conductivity of metals at high temperatures. The national standard requires that the experimental data should be processed within the range of ε<<1( Where α is the heat dissipation coefficient, which represents the heat dissipation rate per unit surface area when the temperature difference between the sample and the environment is 1K; P is the circumference of the sample cross section; λ is the thermal conductivity of the metal, in W / (m·℃); A is the cross-sectional area of ​​the sample, in m 2 ; L is the length of the sample, unit is m), |N|<5( Where Δ1 is the temperature gradient on the sample when power is on; Δ2 is the temperature difference corresponding to the environment when power is on. T1′, T′2 and T′3 are the temperatures of the center and two ends of the environment when power is turned on, respectively) and 5<Δ1<50. The data processing of this experiment meets the above conditions.

[0044] like Figure 2 As shown, the present invention adopts the measurement method of the direct energization longitudinal heat flow method. The sample is in the shape of a slender rod and is placed on the central axis of the tubular heat-proof furnace. During the test, a certain current is passed through the sample, and the generated Joule heat is mainly conducted along the longitudinal ends of the sample. After a period of time, after reaching a thermally stable state, it can be considered that the sample is one-dimensionally conductive. From the thermal effect of the current, it can be known that when the current passing through the conductor is constant, the Joule heat generated by the conductor per unit time is a constant. Therefore, for metal materials, the heat generated by the metal conductor can be equal to the longitudinal heat dissipation of the metal sample by passing electricity through the metal sample.

[0045] The thermal conductivity measurement results are as follows Figure 3As shown in the figure, samples 1-3 are the thermal conductivity of three silicon steel samples with diameters of 3mm, 4mm and 5mm respectively. The results show that the thermal conductivity of the three silicon steel samples has the same law of temperature change (100℃~1000℃), and the numerical difference is small. The average thermal conductivity of silicon steel samples at high temperatures of 100℃, 150℃, 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 95℃ and 1000℃ are 32.320W / (m·℃), 40.793W / (m·℃), 42.689W / (m·℃), 42.929W / (m·℃), 42.797W / (m·℃), respectively. W / (m·℃) and 39.545W / (m·℃), 38.384W / (m·℃), 36.958W / (m·℃), 35.873W / (m·℃), 31.362W / (m·℃), 34.316W / (m·℃), 33. 660W / (m·℃), 33.061W / (m·℃), 32.559W / (m·℃), 30.793W / (m·℃), 21.567W / (m·℃), 14.748W / (m·℃) and 15.524W / (m·℃).

[0046] The average thermal conductivity of silicon steel samples increases first, then decreases, and then increases slightly with increasing temperature, with the highest and lowest average thermal conductivity values ​​being obtained at 250°C and 950°C, respectively. Among them, the average thermal conductivity value of silicon steel samples at a high temperature of 300°C is 42.009W / (m·℃), which is 1.4 times the thermal conductivity value of silicon steel at room temperature [30W / (m·℃)].

[0047] The present invention provides an experimental device and an experimental method for measuring the thermal conductivity of metal materials. The device and the method have high measurement accuracy and can be used to study the variation law of the thermal conductivity of motor metal materials under high temperature conditions, solve the problem that the thermal conductivity of metal materials of aircraft engine motors varies with temperature and the setting is inaccurate, and lay the foundation for the development of aircraft engine motors and green aviation.

Claims

1. An experimental device for measuring the thermal conductivity of metal materials, characterized in that: The invention comprises a tube furnace (19), an adjustable voltage-stabilized power supply (8), a cooler (11), a data acquisition instrument (3), and a computer (1). The adjustable voltage-stabilized power supply (8), the cooler (11), and the data acquisition instrument (3) are all connected to the tube furnace (19). The computer (1) is connected to the data acquisition instrument (3). The adjustable voltage-stabilized power supply (8) is used to provide current for the sample. The cooler (11) is used to cool the tube furnace (19) and adjust the temperature gradient of the sample. The data acquisition instrument (3) is used to collect sample and environmental temperature data. The computer (1) is used to collect and process the data collected by the data acquisition instrument (3).

2. The experimental device for measuring the thermal conductivity of metal materials according to claim 1, characterized in that: The cooler (11) is installed at both ends of the tube furnace (19). The cooler (11) is externally connected to a water circulation pipeline (14). A flow sensor (13), a valve (15), a high-pressure pump (16), and a water storage tank (18) are arranged in series on the water circulation pipeline (14). The temperature gradient of the sample is adjusted by adjusting the water flow in the water circulation pipeline (14).

3. The experimental device for measuring thermal conductivity of metal materials according to claim 2, characterized in that: The water outlet of the water storage tank (18) is provided with a filter (17).

4. The experimental device for measuring thermal conductivity of metal materials according to claim 1, characterized in that: The cooler (11) is connected to both ends of the tubular furnace (19), the positive and negative electrodes of the adjustable voltage-stabilized power supply (8) are connected to both ends of the cooler (11), and the tubular furnace (19) and the adjustable voltage-stabilized power supply (8) are powered by a 380V AC power supply (6).

5. The experimental device for measuring thermal conductivity of metal materials according to claim 4, characterized in that: A shunt (5) is provided between one of the electrodes of the adjustable voltage-stabilized power supply (8) and the cooler (11), and the shunt adopts a 0.0005Ω standard alloy resistor.

6. The experimental device for measuring thermal conductivity of metal materials according to claim 4, characterized in that: The adjustable voltage-stabilized power supply (8) is also connected to a voltage regulator (12).

7. The experimental device for measuring thermal conductivity of metal materials according to claim 1, characterized in that: The data acquisition instrument (3) and the computer (1) are powered by a 220V AC power supply (2).

8. An experimental method for the experimental device for measuring thermal conductivity of metal materials according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1, placing a sample (10) into a tube furnace (19), and filling the gap between the sample (10) and the furnace tube (20) with high temperature resistant asbestos (9); Step 2, placing the thermocouples used by the data acquisition instrument (3) to collect temperature data on the surface of the sample and the inner side of the furnace tube (20), respectively, and setting the sampling interval time and the total sampling time of the data acquisition instrument (3); Step 3, opening the cooler (11), setting the heating temperature, heating time and holding time of the tube furnace (19), and then opening the tube furnace (19) to start heating; Step 4: After the temperature of the tube furnace (19) is stable, the data acquisition instrument (3) is turned on to collect the sample temperature and the ambient temperature of the tube furnace. The cooler (11) is adjusted according to the temperature data so that the temperature gradient of the sample is 5-50° C. when the sample is powered on; when the sample temperature is stable, the sample temperature data is collected; Step 5, turn on the adjustable voltage-stabilized power supply (8), adjust the current so that the sample temperature is consistent with the ambient temperature of the tube furnace, and collect the sample temperature data when the sample temperature is stable; Step 6, swap the positive and negative poles of the adjustable voltage-stabilized power supply (8), repeat step 5, and collect another set of sample temperature data; Step 7, disconnect the adjustable voltage-stabilized power supply (8), and collect the sample temperature data again; Step 8, gradually increasing the heating temperature of the tube furnace (19) with the same temperature gradient, and repeating steps 3 to 6 to collect temperature data of the samples at different heating temperatures; Step 9: After the test is completed, turn off the power of the tube furnace (19), wait for the furnace temperature to cool to room temperature, disconnect the thermocouple, and take out the sample; Step 10: The computer (1) collects and processes the temperature data and outputs the thermal conductivity of the sample at different temperatures.

9. The experimental method according to claim 8, characterized in that In step 2, a thermocouple is arranged at both ends and the middle of the sample surface and at both ends and the middle of the inner side of the furnace tube.

10. The experimental method according to claim 8, characterized in that When the collected temperature changes within the range of 0.5°C, it is judged that the furnace temperature and the sample temperature have reached stability.

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