A high-precision control method for an ultra-low temperature test system

Abstract

This invention discloses a high-precision control method for an ultra-low temperature test system. The ultra-low temperature test system includes an ultra-low temperature test chamber, which is equipped with a multi-stage temperature detection system. The ultra-low temperature test chamber is connected to several cold source delivery pipelines, which are connected to a liquid nitrogen storage tank. The liquid nitrogen storage tank is equipped with a stirring device and an evaporation device. The high-precision control method includes steps S1-S8. This scheme is used to finely regulate the ultra-low temperature test system. By collecting temperature and pressure changes in the liquid nitrogen storage tank and the ultra-low temperature test chamber, a temperature correction model is established. During temperature regulation, the actual temperature in the ultra-low temperature test chamber and the pressure changes in the liquid nitrogen storage tank are fully considered. While ensuring that the pressure in the liquid nitrogen storage tank is within a safe range, the temperature in the ultra-low temperature test chamber reaches the conditions required for the test.

Description

Technical Field

[0001] This invention relates to the field of cryogenic testing technology, and more specifically to a high-precision control method for a cryogenic testing system. Background Technology

[0002] The split Hopkinson bar testing system, consisting of a split Hopkinson compression bar (SHPB) and a split Hopkinson tension bar (SHTB), is a typical device for studying the mechanical response of materials at high strain rates, and is of great significance for material structure design and research. Its core idea is to decouple the stress wave effect and strain rate effect in the experiment, thereby establishing the stress-strain relationship of the material under high strain rates.

[0003] While some temperature-holding devices have been reported both domestically and internationally, their temperature ranges are relatively low, making it difficult to meet the needs of engineering applications. With the advancement of engineering projects, the testing of the impact dynamic mechanical properties of low-temperature solid materials urgently needs to be addressed. Existing temperature-holding devices generally directly regulate the temperature within the test chamber, but most only regulate temperatures above 0°C, failing to achieve control over ultra-low temperature testing environments. Furthermore, their temperature control accuracy is low and the range is wide, making it impossible to achieve high-precision ultra-low temperature environment control. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, this invention provides a high-precision control method for an ultra-low temperature test system.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0006] A high-precision control method for an ultra-low temperature test system is provided. The ultra-low temperature test system includes an ultra-low temperature test chamber, which is equipped with a multi-stage temperature detection system. The multi-stage temperature detection system includes temperature sensors that detect the surface temperature of the test piece, the temperature inside the ultra-low temperature test chamber, and the surface temperature of the ultra-low temperature test chamber. The ultra-low temperature test chamber is connected to several cold source delivery pipes, which are evenly distributed on the ultra-low temperature test chamber. Each cold source delivery pipe is equipped with a control valve, a temperature sensor, a temperature controller, and a flow sensor. The cold source delivery pipe is connected to a liquid nitrogen storage tank, which is equipped with a stirring device and an evaporation device. The liquid nitrogen storage tank is equipped with a pressure sensor, a temperature sensor, a liquid level sensor, and a main control valve.

[0007] The high-precision control method includes the following steps:

[0008] S1: Set the required low-temperature environment temperature W for the test, place the test piece into the ultra-low temperature test chamber, seal the test chamber, and connect the cold source delivery pipeline;

[0009] S2: Open the main control valve and the control valve on one of the cold source delivery pipes, turn on the evaporator to heat and evaporate the liquid nitrogen at the bottom, convert the low-temperature liquid nitrogen into a low-temperature gaseous working fluid, and stir the liquid nitrogen with the stirring device to break the large-diameter vapor bubbles into small-diameter vapor bubbles. The small-diameter vapor bubbles are further cooled during the floating process.

[0010] S3: The temperature sensor inside the ultra-low temperature test chamber collects the temperature value T every set time t, collects the flow rate L and temperature T′ on the opened cold source delivery pipeline, and collects the gas pressure value P and temperature T″ on the liquid nitrogen storage tank.

[0011] S4: Adjust the temperature inside the ultra-low temperature test chamber to W;

[0012] S5: Acquire all temperature values ​​(T1, T2, ..., T...) collected during the process of the temperature inside the ultra-low temperature test chamber reaching W. n ), air pressure values ​​(P1, P2, ..., P n The temperature control values ​​(T1″′, T2″′, ..., T) given by the temperature controller during the interval between each temperature acquisition. n "″′), where n is the number of data acquisitions during step S4, and the average value of the temperature gradient during the temperature change from room temperature to W is calculated. Average value of the pressure change gradient Average value of temperature control

[0013]

[0014] S6: Calculate the relationship coefficient k between temperature change and air pressure change, and establish a temperature correction model for the test in the ultra-low temperature chamber:

[0015]

[0016] Where η is the correction factor for temperature change, γ is the correction factor for temperature, and W n To achieve the target temperature required for the experiment, W n-1 The temperature inside the test chamber is denoted as μ, which is a correction factor for temperature control.

[0017] S7: The specimen is tested under temperature W. The temperature sensor continues to collect the temperature value T every set time t. The temperature rise change value ΔT in the ultra-low temperature test chamber is calculated: ΔT = WT.

[0018] S8: Compare the temperature change value ΔT with the allowable temperature change threshold ΔT 阈值 Comparison:

[0019] If ΔT≤ΔT 阈值If the temperature fluctuation inside the ultra-low temperature test chamber is within the allowable range, then the temperature fluctuation is within the allowable range.

[0020] If ΔT>ΔT 阈值 Then, the target temperature value W and the current temperature value T are input into the temperature correction model, and the gas pressure value P required to regulate the temperature is output. After the pressure in the liquid nitrogen storage tank reaches the value P, the control valve and the main control valve are opened to regulate the temperature in the ultra-low temperature test chamber.

[0021] Further, step S3 includes:

[0022] Compare the air pressure value P with the air pressure threshold P 阈值 Comparison: Comparing temperature value T with temperature W:

[0023] If T > W and P > P 阈值 If the evaporator heating and stirring are stopped, and the air pressure in the cold source delivery pipeline has reached its limit, the temperature controller will open to supply hot air into the cold source delivery pipeline until the temperature is satisfied in the next three temperature measurements, where T = W and P ≤ P. 阈值 Close the control valve, main control valve, and temperature controller on the cold source delivery pipeline;

[0024] If T > W and P ≤ P 阈值 Then, the heating of the evaporator and the stirring of the stirring device are stopped, the main control valve is closed, and then the temperature controller opens to supply hot air medium into the cold source delivery pipeline until T = W and P ≤ P are satisfied in the subsequent three temperature acquisitions. 阈值 Close the control valve on the cold source delivery pipeline;

[0025] If T≤W and P>P 阈值 If the air pressure in a single cold source delivery pipe has reached its limit, open the control valve on another cold source delivery pipe. The heating power of the evaporator and the stirring power of the stirring device remain unchanged until T = W and P ≤ P are satisfied in the subsequent three temperature measurements. 阈值 Stop the heating and stirring of the evaporator, and close all control valves and the main control valve;

[0026] If T≤W and P≤P 阈值 Increase the heating power of the evaporator and the stirring power of the stirring device until T = W and P ≤ P are satisfied in the subsequent three temperature acquisitions. 阈值 Stop the heating of the evaporator and the stirring of the stirring device, and close the control valve and the main control valve.

[0027] The beneficial effects of this invention are as follows: This solution is used for precise control of the cryogenic testing system. By collecting temperature and pressure changes within the liquid nitrogen storage tank and the cryogenic test chamber, a temperature correction model is established. During temperature control, the actual temperature within the cryogenic test chamber and the pressure changes within the liquid nitrogen storage tank are fully considered. While ensuring the pressure within the liquid nitrogen storage tank remains within a safe range, the temperature within the cryogenic test chamber reaches the required experimental conditions. Furthermore, if significant temperature fluctuations occur within the cryogenic test chamber during the experiment, the temperature correction model can be used for adaptive control, ensuring the stability of experimental conditions and improving experimental accuracy, thus achieving high-precision temperature control. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the ultra-low temperature test system. Detailed Implementation

[0029] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0030] like Figure 1 As shown, the high-precision control method of the ultra-low temperature test system in this scheme includes an ultra-low temperature test chamber. The ultra-low temperature test chamber is equipped with a multi-stage temperature detection system, which includes temperature sensors that detect the surface temperature of the test piece, the temperature inside the ultra-low temperature test chamber, and the surface temperature of the ultra-low temperature test chamber. The ultra-low temperature test chamber is connected to several cold source delivery pipes, which are evenly distributed on the ultra-low temperature test chamber. Each cold source delivery pipe is equipped with a control valve, a temperature sensor, a temperature controller, and a flow sensor. The cold source delivery pipe is connected to a liquid nitrogen storage tank, which is equipped with a stirring device and an evaporation device. The liquid nitrogen storage tank is equipped with a pressure sensor, a temperature sensor, a liquid level sensor, and a main control valve.

[0031] The high-precision control method for the above-mentioned cryogenic test system includes the following steps:

[0032] S1: Set the required low-temperature environment temperature W for the test, place the test piece into the ultra-low temperature test chamber, seal the test chamber, and connect the cold source delivery pipeline;

[0033] S2: Open the main control valve and the control valve on one of the cold source delivery pipes, turn on the evaporator to heat and evaporate the liquid nitrogen at the bottom, convert the low-temperature liquid nitrogen into a low-temperature gaseous working fluid, and stir the liquid nitrogen with the stirring device to break the large-diameter vapor bubbles into small-diameter vapor bubbles. The small-diameter vapor bubbles are further cooled during the floating process.

[0034] S3: The temperature sensor inside the ultra-low temperature test chamber collects the temperature value T every set time t, collects the flow rate L and temperature T′ on the opened cold source delivery pipeline, and collects the gas pressure value P and temperature T″ on the liquid nitrogen storage tank.

[0035] Step S3 includes:

[0036] Compare the air pressure value P with the air pressure threshold P 阈值 Comparison: Comparing temperature value T with temperature W:

[0037] If T > W and P > P 阈值 If the evaporator heating and stirring are stopped, and the air pressure in the cold source delivery pipeline has reached its limit, the temperature controller will open to supply hot air into the cold source delivery pipeline until the temperature is satisfied in the next three temperature measurements, where T = W and P ≤ P. 阈值 Close the control valve, main control valve, and temperature controller on the cold source delivery pipeline;

[0038] If T > W and P ≤ P 阈值 Then, the heating of the evaporator and the stirring of the stirring device are stopped, the main control valve is closed, and then the temperature controller opens to supply hot air medium into the cold source delivery pipeline until T = W and P ≤ P are satisfied in the subsequent three temperature acquisitions. 阈值 Close the control valve on the cold source delivery pipeline;

[0039] If T≤W and P>P 阈值 If the air pressure in a single cold source delivery pipe has reached its limit, open the control valve on another cold source delivery pipe. The heating power of the evaporator and the stirring power of the stirring device remain unchanged until T = W and P ≤ P are satisfied in the subsequent three temperature measurements. 阈值 Stop the heating and stirring of the evaporator, and close all control valves and the main control valve;

[0040] If T≤W and P≤P 阈值 Increase the heating power of the evaporator and the stirring power of the stirring device until T = W and P ≤ P are satisfied in the subsequent three temperature acquisitions. 阈值 Stop the heating of the evaporator and the stirring of the stirring device, and close the control valve and the main control valve.

[0041] S4: Adjust the temperature inside the ultra-low temperature test chamber to W;

[0042] S5: Acquire all temperature values ​​(T1, T2, ..., T...) collected during the process of the temperature inside the ultra-low temperature test chamber reaching W. n ), air pressure values ​​(P1, P2, ..., P n The temperature control values ​​(T1″′, T2″′, ..., T) given by the temperature controller during the interval between each temperature acquisition. n "″′), where n is the number of data acquisitions during step S4, and the average value of the temperature gradient during the temperature change from room temperature to W is calculated. Average value of the pressure change gradient Average value of temperature control

[0043]

[0044] S6: Calculate the relationship coefficient k between temperature change and air pressure change, and establish a temperature correction model for the test in the ultra-low temperature chamber:

[0045]

[0046] Where η is the correction factor for temperature change, γ is the correction factor for temperature, and W n To achieve the target temperature required for the experiment, W n-1 The temperature inside the test chamber is denoted as μ, which is a correction factor for temperature control.

[0047] S7: The specimen is tested under temperature W. The temperature sensor continues to collect the temperature value T every set time t. The temperature rise change value ΔT in the ultra-low temperature test chamber is calculated: ΔT = WT.

[0048] S8: Compare the temperature change value ΔT with the allowable temperature change threshold ΔT 阈值 Comparison:

[0049] If ΔT≤ΔT 阈值 If the temperature fluctuation inside the ultra-low temperature test chamber is within the allowable range, then the temperature fluctuation is within the allowable range.

[0050] If ΔT>ΔT 阈值 Then, the target temperature value W and the current temperature value T are input into the temperature correction model, and the gas pressure value P required to regulate the temperature is output. After the pressure in the liquid nitrogen storage tank reaches the value P, the control valve and the main control valve are opened to regulate the temperature in the ultra-low temperature test chamber.

[0051] This solution is used for precise control of the cryogenic testing system. By collecting temperature and pressure changes within the liquid nitrogen storage tank and the cryogenic test chamber, a temperature correction model is established. During temperature control, the actual temperature within the cryogenic test chamber and the pressure changes within the liquid nitrogen storage tank are fully considered. While ensuring the pressure within the liquid nitrogen storage tank remains within a safe range, the temperature within the cryogenic test chamber is brought to the required experimental conditions. Furthermore, if significant temperature fluctuations occur within the cryogenic test chamber during the test, the temperature correction model can be used for adaptive adjustments, ensuring the stability of experimental conditions and improving experimental accuracy, thus achieving high-precision temperature control.

Claims

1. A high-precision control method for an ultra-low temperature test system, the ultra-low temperature test system comprising an ultra-low temperature test chamber, wherein the ultra-low temperature test chamber is equipped with a multi-stage temperature detection system, the multi-stage temperature detection system comprising temperature sensors for detecting the surface temperature of the test piece, the temperature inside the ultra-low temperature test chamber, and the surface temperature of the ultra-low temperature test chamber, the ultra-low temperature test chamber being connected to a plurality of cold source delivery pipes, the plurality of cold source delivery pipes being evenly distributed on the ultra-low temperature test chamber, each of the cold source delivery pipes being equipped with a control valve, a temperature sensor, a temperature controller, and a flow sensor, the cold source delivery pipes being connected to a liquid nitrogen storage tank, the liquid nitrogen storage tank being equipped with a stirring device and an evaporation device, and the liquid nitrogen storage tank being equipped with a pressure sensor, a temperature sensor, a liquid level sensor, and a main control valve; Its features are, Includes the following steps: S1: Set the required low-temperature environment temperature for the experiment. W Place the test specimen into the ultra-low temperature test chamber, seal the test chamber, and connect the cold source delivery pipeline; S2: Open the main control valve and the control valve on one of the cold source delivery pipes, turn on the evaporator to heat and evaporate the liquid nitrogen at the bottom, convert the low-temperature liquid nitrogen into a low-temperature gaseous working fluid, and stir the liquid nitrogen with the stirring device to break the large-diameter vapor bubbles into small-diameter vapor bubbles. The small-diameter vapor bubbles are further cooled during the floating process. S3: The temperature sensor inside the ultra-low temperature test chamber operates at set intervals. t Collect temperature value once T Collect the flow rate on the opened cold source delivery pipeline. L ,temperature Collect the gas pressure value on the liquid nitrogen storage tank. P ,temperature ; S4: Adjust the temperature inside the ultra-low temperature test chamber to... W ; S5: Obtain the temperature inside the ultra-low temperature test chamber. W All temperature values ​​collected during the process ( T 1, T 2, ... T n ), air pressure value ( P 1, P 2, ... P n The temperature control value given by the temperature controller during the interval between each temperature acquisition. , , ···, ), n To determine the number of data acquisitions during step S4, calculate the average value of the temperature gradient as the temperature changes from room temperature to W. Average value of the pressure change gradient Average value of temperature control : ， ， ； S6: Calculate the coefficients relating temperature change and air pressure change. k Establish a temperature correction model for testing in an ultra-low temperature test chamber: ； in, η For the correction factor of the temperature change value, γ This is a correction factor for temperature. W n To achieve the target temperature required for the experiment, W n-1 This is the current temperature inside the test chamber. μ This is a correction factor for temperature control; S7: Specimen at temperature W The experiment was conducted under the following conditions, with the temperature sensor set at regular intervals. t Continue collecting temperature values T Calculate the temperature rise change value inside the ultra-low temperature test chamber at this time. : ; S8: Temperature change value With respect to the allowable threshold of temperature change Comparison: like ≤ If the temperature fluctuation inside the ultra-low temperature test chamber is within the allowable range, then the temperature fluctuation is within the allowable range. like > Then the target temperature value W and current temperature value T The input is fed into the temperature correction model, and the output is the air pressure value required to regulate the temperature. P Control the pressure inside the liquid nitrogen storage tank to reach P After setting the value, open the control valve and the main control valve to adjust the temperature inside the ultra-low temperature test chamber.

2. The high-precision control method for the cryogenic testing system according to claim 1, characterized in that, Step S4 includes: air pressure value P With air pressure threshold P 阈值 Comparison, temperature values T With temperature W Comparison ： If T≤ W ,and P > P 阈值 If the evaporator heating and stirring devices stop, and the air pressure in the cold source delivery pipeline has reached its limit, the control valve opens to supply cold air into the cold source delivery pipeline until the temperature meets T= in the subsequent three temperature measurements. W and P ≤ P 阈值 Close the control valve, main control valve, and temperature controller on the cold source delivery pipeline; If T≤ W ,and P ≤ P 阈值 Then, stop the heating of the evaporator and the stirring of the stirring device, close the main control valve, and then open the control valve to supply cold air medium into the cold source delivery pipeline until T= is satisfied in the subsequent three temperature acquisitions. W and P ≤ P 阈值 Close the control valve on the cold source delivery pipeline; If T> W ,and P > P 阈值 If the air pressure in a single cold source delivery pipe has reached its limit, open the control valve on another cold source delivery pipe. The heating power of the evaporator and the stirring power of the stirring device remain unchanged until T= is satisfied in the subsequent three temperature measurements. W and P ≤ P 阈值 Stop the heating and stirring of the evaporator, and close all control valves and the main control valve; If T> W ,and P ≤ P 阈值 Increase the heating power of the evaporator and the stirring power of the stirring device until T= is satisfied in the subsequent three temperature acquisitions. W and P ≤ P 阈值 Stop the heating of the evaporator and the stirring of the stirring device, and close the control valve and the main control valve.

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