A precise simulation method for oxygen content variation in low-temperature PSP over a wide temperature range

Abstract

The present invention relates to a method for accurately simulating the change of oxygen content in a low-temperature pressure-sensitive paint (PSP) over a wide temperature range, using a low-temperature pressure-sensitive paint static calibration and paint property research experimental device. The method comprises: a control module reads a set of pre-set target temperatures T, a set of nitrogen pressure target values ​​P, and a set of oxygen content change target values ​​O; each target temperature, each nitrogen pressure target value, and each oxygen content change target value are read in sequence, a calibration container is controlled to reach a specified target temperature and nitrogen pressure target, a monotonic control method is used to make the calibration container reach a specified oxygen content target value, an experimental image of a calibration sample coated with pressure-sensitive paint under the specified target temperature, nitrogen pressure target value, and oxygen content target value is obtained, and after traversing the above target values, the experimental image is summarized to analyze the low-temperature PSP paint property.

Description

Technical Field

[0001] The present invention belongs to the technical field of aerodynamics in the aerospace industry, and in particular relates to a method for accurately simulating changes in oxygen content in a low-temperature PSP over a wide temperature range. Background Art

[0002] Measuring model surface pressure has always been a crucial topic in aircraft wind tunnel testing. Measuring model surface pressure distribution in low-temperature, high-Reynolds-number wind tunnels is a crucial tool for studying the influence of Reynolds number on the aerodynamic characteristics of advanced aircraft. By measuring surface pressure distribution, we can determine the aerodynamic loads on the aircraft surface, the separation zone of the flow field, shock waves, and the boundary layer transition location under different test Reynolds numbers, and observe the aerodynamic interference between aircraft components. Furthermore, surface pressure distribution measurement is an important tool for validating numerical calculation methods used in computational fluid dynamics (CFD).

[0003] Since the late 1990s, domestic PSP (Pressure Sensitive Paint) pressure sensitive paint measurement technology has undergone years of basic research and technological accumulation. The China Aerodynamics Research and Development Center, China Aerospace Aerodynamics Research Institute, China Academy of Aerospace Aerodynamics, Northwestern Polytechnical University, Shanghai Jiaotong University and other institutions have mastered key technologies such as room temperature pressure sensitive coating development, static calibration, and image processing. They have successfully applied room temperature PSP measurement technology to engineering application fields such as surface pressure measurement of large-scale low-, cross-, super-, and hypersonic industrial wind tunnel aircraft models, and rotor surface pressure measurement, which has effectively promoted the level of refined design of my country's advanced aircraft and the development of aerodynamics.

[0004] However, unlike conventional wind tunnels, the inlet flow of low-temperature wind tunnels is nitrogen, and the operating temperature is low with a large temperature difference (110-323K). Therefore, a small amount of oxygen (oxygen content less than 3000ppm) needs to be injected into the wind tunnel circuit. The application of room-temperature PSP in low-temperature wind tunnels will encounter many technical difficulties, such as low oxygen content, low oxygen permeability, poor pressure-sensitive properties of coatings in deep-cold environments, and easy cracking. According to publicly published literature, domestic research on low-temperature pressure-sensitive coating measurement technology is still in its infancy. It is urgent to establish a precise simulation method for the wide-temperature range oxygen content change of low-temperature PSP, and to solve the development of pressure-sensitive coatings in low-temperature and low-oxygen environments as soon as possible, as well as the research on the characteristics of low-temperature pressure-sensitive coatings and their influencing factors. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems in the prior art of low oxygen content, low oxygen permeability, poor pressure-sensitive properties of the coating in deep cold environments and easy cracking when used in low-temperature wind tunnels at room temperature PSP, and propose a method for accurately simulating the changes in oxygen content in low-temperature PSP over a wide temperature range.

[0006] To achieve the above objectives, the present invention proposes a method for accurately simulating the change of oxygen content in a low-temperature PSP over a wide temperature range. The method uses a low-temperature pressure-sensitive paint static calibration and coating property research experimental device. The device is based on a light source and a camera and includes: a calibration container, a pressure measurement and control system, an oxygen content measurement and control system, a temperature measurement and control system, and a control module deployed on a host computer; wherein,

[0007] The calibration container is used to provide an environment with controllable temperature, pressure and oxygen concentration for the calibration sample coated with low-temperature pressure-sensitive paint. An external light source is irradiated onto the calibration sample coated with pressure-sensitive paint through a window at the top of the calibration container, and the calibration sample is photographed by a camera to obtain the coating properties.

[0008] The pressure measurement and control system is used to provide a nitrogen source with controllable and measurable pressure for the calibration sample under the control of the control module;

[0009] The oxygen content measurement and control system is used to provide a controllable and measurable ultra-low oxygen content oxygen source for the calibration sample under the control of the control module, while satisfying pressure control. The ultra-low oxygen content is 100ppm to 3000ppm;

[0010] The temperature measurement and control system is used to provide controllable and measurable cooling and heating capacity for the calibration sample under the control of the control module, thereby achieving temperature control;

[0011] The control module is used to control the operating sequence of the pressure measurement and control system, the oxygen content measurement and control system, and the temperature measurement and control system, and is used to control them separately according to the pressure value, oxygen content, and temperature value of the calibration container in combination with the experimental target value; it is also used to trigger the light source and camera to work when the experimental target value is reached, and to collect experimental images of the corresponding state, thereby realizing static calibration of low-temperature pressure-sensitive paint and research on coating properties;

[0012] The method comprises:

[0013] Step s1) The control module reads a set of preset target temperatures T, a set of nitrogen pressure target values ​​P, and a set of oxygen content change target values ​​O; wherein the oxygen content change target values ​​satisfy a range of 100 ppm to 3000 ppm;

[0014] Step s2) When a set of target temperatures T has been traversed, go to step s6), otherwise, read each target temperature in turn, and control the temperature measurement and control system so that the calibration container reaches the specified target temperature;

[0015] Step s3) when a set of nitrogen pressure target values ​​P are traversed at the specified target temperature, go to step s2); otherwise, read each nitrogen pressure target value in turn, and control the pressure measurement and control system so that the calibration container reaches the specified nitrogen pressure target value;

[0016] Step s4) When a set of oxygen content change target values ​​O are traversed under the specified nitrogen pressure target value, go to step s3); otherwise, read the oxygen content target values ​​one by one in sequence, and control the oxygen content measurement and control system using a monotonically increasing or monotonically decreasing control method so that the calibration container reaches the specified oxygen content target value;

[0017] Step s5) triggering the light source and camera to work by the control module to obtain an experimental image of the calibration sample coated with the pressure-sensitive paint at the specified target temperature, nitrogen pressure target value, and oxygen content target value, and then going to step s4);

[0018] Step s6) Summarize the experimental images and analyze the low-temperature PSP coating characteristics.

[0019] As an improvement to the above method, the calibration container is made of 304 stainless steel, can withstand vacuum negative pressure and positive pressure, and has a smooth surface.

[0020] As an improvement to the above method, the outside of the calibration container further includes a heat-insulating layer of a certain thickness.

[0021] As an improvement to the above method, the window on the top of the calibration container is made of 15 mm thick high-strength quartz glass with K9 light transmittance. The window glass is pressed tightly against the calibration container through a flange and sealed with a silicone rubber ring.

[0022] As an improvement to the above method, the pressure measurement and control system includes a nitrogen bottle of set purity, a pressure reducing valve, a needle valve, a vacuum pump and a fast on-off solenoid valve; wherein,

[0023] The nitrogen cylinder with set purity and the pressure reducing valve are used to provide a nitrogen source with stable pressure and purity requirements to the calibration container;

[0024] The needle-tip valve is used to provide a small and adjustable nitrogen flow channel to the calibration container;

[0025] The vacuum pump is used to reduce the pressure in the calibration container;

[0026] The fast on-off solenoid valve is used to control the delivery of nitrogen to the standard container to achieve the target content.

[0027] As an improvement of the above method, the oxygen content measurement and control system includes an electrochemical oxygen concentration analyzer, a zirconium oxide oxygen concentration sensor, an oxygen cylinder, a pressure reducing valve, a micro-regulating valve and a fast on-off solenoid valve; wherein,

[0028] The electrochemical oxygen concentration analyzer is used to measure the oxygen concentration entering the calibration container within a set range;

[0029] The zirconia oxygen concentration sensor is used to measure the oxygen concentration in the calibration container over the entire pressure, temperature and oxygen concentration range;

[0030] The oxygen cylinder is connected to the calibration container through a pressure reducing valve, a micro-regulating valve, and a fast on-off solenoid valve;

[0031] The fast on-off solenoid valve is used to control the delivery of oxygen to the standard container to achieve the target content.

[0032] As an improvement to the above method, the step s4) adopts a monotonically increasing or monotonically decreasing control mode to control the oxygen content measurement and control system so that the calibration container reaches a specified oxygen content target value; specifically comprising:

[0033] When the oxygen content needs to be increased, open the quick-on / off solenoid valve, adjust the micro-regulating valve to control the flow rate and gradually input oxygen into the calibration container. When the target content is approaching, gradually reduce the gas supply until the target content is reached and stop inputting.

[0034] When the oxygen content needs to be reduced, the calibration container is evacuated to reduce the pressure to the set range, and then nitrogen is added to restore the original pressure. Each pumping and filling operation reduces the oxygen content while ensuring the pressure is stable. The operation is repeated until the oxygen content accurately drops to the set value, thereby achieving high-precision control of ultra-low oxygen content values.

[0035] As an improvement of the above method, the temperature measurement and control system includes a refrigeration unit, a chiller, a heater and a temperature-controlled copper block; wherein,

[0036] The refrigeration unit adopts a single compressor for refrigeration. Under the control of the control module, the PLC controls the opening and closing time ratio of the solenoid valve on the refrigerant path, adjusts the refrigerant flow through the temperature-controlled copper block, and realizes the refrigeration control of the standard container;

[0037] The chiller is used to cool the single compressor;

[0038] The heater is used to control the heating amount and achieve heat control of the standard container by inputting a voltage with a certain on-off time ratio determined by PID parameters through a solid-state relay under the control of the control module;

[0039] The temperature-controlled copper block and the heater are both arranged in a calibration container. The temperature-controlled copper block is arranged at the bottom of the calibration sample, and the heater is arranged at the bottom of the temperature-controlled copper block. Accurate temperature control is achieved by balancing the cooling capacity and the heating capacity. The temperature gradient is less than 1K and the temperature control accuracy is less than 0.1K.

[0040] As an improvement of the above method, the temperature-control copper block includes two parts, each of which has four semicircular slots of the same diameter. The upper and lower parts are clamped by screws to form four circular slots as refrigerant channels for the inflow and outflow of refrigerant.

[0041] As an improvement to the above method, the surface of the temperature-control copper block is uniform, the surface area of ​​the four refrigerant channels occupies more than 1 / 2 of the cross-sectional area of ​​the temperature-control copper block, the thickness of the solid part of the upper temperature-control copper block meets the preset value, and the thermal conductivity is not less than 350 W / m·K.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] 1. The method of the present invention fills a domestic gap and provides a high-efficiency and precise adjustment control strategy for multiple temperature, pressure, and oxygen content states during the static calibration of low-temperature pressure-sensitive paint and the coating property experiment;

[0044] 2. The method of the present invention uses a single compressor refrigeration device, which can achieve ultra-low temperature control of a minimum of 110K without the need for liquid nitrogen, and the control accuracy is less than ±0.1K;

[0045] 3. The method of the present invention enables precise control of the ultra-low oxygen content of the calibration container through a monotonic change control mode, with a control error of less than ±10ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a flow chart of the method for accurately simulating changes in oxygen content in a low-temperature PSP over a wide temperature range according to the present invention;

[0047] Figure 2 This is the external schematic diagram of the experimental device for static calibration of low-temperature pressure-sensitive paint and coating characteristics research;

[0048] Figure 3 This is the schematic diagram of the pressure measurement and control system;

[0049] Figure 4 This is the schematic diagram of the oxygen content measurement and control system;

[0050] Figure 5 It is the schematic diagram of temperature measurement and control system;

[0051] Figure 6 Schematic diagram of the temperature-controlled copper block. DETAILED DESCRIPTION

[0052] The present invention provides a method for accurately simulating the change of oxygen content in low-temperature PSP over a wide temperature range. Figure 1 As shown, the method mainly includes the following steps:

[0053] A set of target temperatures (-163°C to 50°C) and oxygen content variations (100ppm to 3000ppm) are set. A low-temperature PSP calibration container provides a temperature- and oxygen-controllable environment for the low-temperature PSP paint calibration samples. The container is connected to a chiller, an ultrapure nitrogen cylinder, and an ultrapure oxygen cylinder. A single compressor provides refrigerant, which flows through the refrigerant channel of a temperature-controlled copper block. The cooling capacity provided by the compressor is equal to the heating capacity provided by the heater, achieving temperature stability and high-precision temperature control over a wide temperature range of ±0.1K. Once the temperature stabilizes, a monotonic incremental control method is used to precisely control the ultra-low oxygen content range from 100ppm to 3000ppm. To increase the oxygen content, a fast-acting solenoid valve gradually introduces oxygen into the calibration container. As the target concentration approaches, the valve gradually reduces the gas flow until the target concentration is reached, at which point the flow is stopped. To reduce the oxygen content, the calibration container is evacuated to slightly reduce the pressure, and then nitrogen is added to restore the original pressure. Each pumping and filling operation, while maintaining stable pressure, slightly reduces the oxygen content. Repeating this process allows the oxygen content to precisely drop to the set value, achieving high-precision control of ultra-low oxygen levels. Simulating all target temperatures and oxygen levels, capturing corresponding paint luminescence images, and evaluating paint properties based on low-temperature PSP images at different temperatures and oxygen levels.

[0054] Based on a highly efficient and precise control strategy for multiple temperature, pressure, and oxygen content states, this invention can achieve ultra-low temperature control down to 110K with a control accuracy of less than ±0.1K. Through a monotonic control method, the ultra-low oxygen content of the calibration container can be precisely controlled with a control error of less than ±10ppm, thus achieving precise simulation.

[0055] This method uses a low-temperature pressure-sensitive paint static calibration and coating property research experimental device, which is based on a light source and a camera and includes: a calibration container, a pressure measurement and control system, an oxygen content measurement and control system, a temperature measurement and control system, and a control module deployed on a host computer; Figure 2 Schematic diagram of the external structure of the experimental device for static calibration of low-temperature pressure-sensitive paint and coating properties research.

[0056] The calibration container is used to provide an environment with controllable temperature, pressure and oxygen concentration for the calibration sample coated with low-temperature pressure-sensitive paint. An external light source is irradiated onto the calibration sample coated with pressure-sensitive paint through a window at the top of the calibration container, and the calibration sample is photographed by a camera to obtain the coating properties.

[0057] The pressure measurement and control system is used to provide a pressure-controllable and measurable nitrogen source for the calibration sample under the control of the control module; the principle is as follows Figure 3 shown.

[0058] The oxygen content measurement and control system is used to provide a controllable and measurable ultra-low oxygen content oxygen source for the calibration sample under the control of the control module under the premise of meeting pressure control. The ultra-low oxygen content is 100ppm to 3000ppm; the principle is as follows Figure 4 shown.

[0059] The temperature measurement and control system is used to provide controllable and measurable cooling and heating capacity for the calibration sample under the control of the control module, thereby achieving temperature control. The principle is as follows: Figure 5 shown.

[0060] The control module is used to control the operating sequence of the pressure measurement and control system, the oxygen content measurement and control system, and the temperature measurement and control system, and is used to control them separately according to the pressure value, oxygen content, and temperature value of the calibration container in combination with the experimental target value; it is also used to trigger the light source and camera to work when the experimental target value is reached, and to collect experimental images of the corresponding state, thereby realizing static calibration of low-temperature pressure-sensitive paint and research on coating properties;

[0061] Methods include:

[0062] Step s1) The control module reads a set of preset target temperatures T, a set of nitrogen pressure target values ​​P, and a set of oxygen content change target values ​​O; wherein the oxygen content change target values ​​satisfy the range of 100 ppm to 3000 ppm;

[0063] Step s2) When a set of target temperatures T has been traversed, go to step s6), otherwise, read each target temperature in turn, and control the temperature measurement and control system so that the calibration container reaches the specified target temperature;

[0064] Step s3) when a set of nitrogen pressure target values ​​P are traversed at the specified target temperature, go to step s2); otherwise, read each nitrogen pressure target value in turn, and control the pressure measurement and control system so that the calibration container reaches the specified nitrogen pressure target value;

[0065] Step s4) When a set of oxygen content change target values ​​O are traversed under the specified nitrogen pressure target value, go to step s3); otherwise, read the oxygen content target values ​​one by one in sequence, and control the oxygen content measurement and control system using a monotonically increasing or monotonically decreasing control method so that the calibration container reaches the specified oxygen content target value;

[0066] Step s5) triggering the light source and camera to work by the control module to obtain an experimental image of the calibration sample coated with the pressure-sensitive paint at the specified target temperature, nitrogen pressure target value, and oxygen content target value, and then going to step s4);

[0067] Step s6) Summarize the experimental images and analyze the low-temperature PSP coating characteristics.

[0068] Specifically, a single compressor refrigeration is used to achieve high-precision temperature regulation in a wide temperature range of -163℃ to 50℃, and precise control of ultra-low oxygen content values ​​of 100ppm-3000ppm is achieved through monotonically increasing or monotonically decreasing control methods, thereby providing a precise simulation platform for wide-temperature range oxygen content changes for the development of low-temperature PSP coatings and research on coating properties.

[0069] The present invention provides a method for accurately simulating the change of oxygen content in a low-temperature PSP over a wide temperature range, comprising the following steps:

[0070] Set a set of target temperature (-163℃~50℃) and oxygen content change (100ppm-3000ppm) target values;

[0071] Provide a temperature and oxygen concentration controlled environment for the low-temperature PSP paint calibration samples through a low-temperature PSP calibration container, which is connected to a chiller, ultra-pure nitrogen cylinder, and ultra-pure oxygen cylinder;

[0072] A single compressor is used to provide refrigerant. The low-temperature refrigerant flows through the refrigerant channel of the temperature-controlled copper block. The cooling capacity provided is equal to the heating capacity of the heater, achieving temperature stability and realizing high-precision temperature control in a wide temperature range of ±0.1K. The temperature-controlled copper block is as follows: Figure 6 shown.

[0073] After the temperature stabilizes, a monotonic incremental control method is used to precisely control ultra-low oxygen levels ranging from 100ppm to 3000ppm. To increase the oxygen content, a rapid on-off solenoid valve gradually introduces oxygen into the calibration container. As the target concentration approaches, the valve gradually reduces the flow until the target concentration is reached, at which point the flow ceases. To decrease the oxygen content, the calibration container is evacuated to slightly reduce the pressure, and then nitrogen is added to restore the original pressure. Each pump-and-fill operation slightly reduces the oxygen content while maintaining stable pressure. Repeated operation allows the oxygen content to accurately drop to the set value, achieving highly precise control of ultra-low oxygen levels.

[0074] Simulate all target temperatures and target oxygen contents, collect corresponding coating luminescence images, and evaluate coating properties based on low-temperature PSP images under different temperature and oxygen content conditions.

[0075] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0076] Example

[0077] like Figure 1 As shown, the embodiment of the present invention provides a method for accurately simulating the change of oxygen content in a low-temperature PSP over a wide temperature range. The specific steps are as follows:

[0078] S101: Set a set of target temperature (-163℃~50℃) and oxygen content change (100ppm-3000ppm) target values. The target temperatures are: -163℃, -100℃, -50℃, 0℃, 50℃; the target oxygen contents are 100ppm, 500ppm, 1000ppm, 2000ppm, 3000ppm.

[0079] S102: Providing a temperature- and oxygen-concentration-controlled environment for the low-temperature PSP paint calibration sample through a low-temperature PSP calibration container, and connecting the calibration container to a chiller, an ultrapure nitrogen cylinder, and an ultrapure oxygen cylinder.

[0080] The calibration container is a 304 stainless steel cylinder that can withstand both negative and positive vacuum pressures. The calibrated container's opening is determined by the size of the camera and light source. To accommodate different cameras and light sources, a viewing window area of ​​Φ150mm is used. The calibration container measures Φ180×150mm, with a smooth surface, a wall thickness of 3mm, and a flange thickness of 10mm. The calibration container weighs less than 20kg and can be moved by a single person. The exterior of the calibration container is insulated with a 50mm layer. The top of the calibration container is a viewing window made of 15mm thick high-strength quartz glass with a K9 light transmittance. The viewing window is pressed against the flange and the calibration container, and a silicone rubber ring is used for sealing.

[0081] After the calibration container is installed, it is connected to the chiller, ultra-pure nitrogen cylinder, ultra-pure oxygen cylinder and other equipment.

[0082] S103: A single compressor is used to provide refrigerant. The low-temperature refrigerant flows through the refrigerant channel of the temperature-controlled copper block. The cooling capacity provided is equal to the heating capacity of the heater, achieving a stable temperature of -163°C and realizing high-precision temperature control of ±0.1K.

[0083] The low-temperature refrigerant generated by a single-compressor refrigeration unit enters a temperature-controlled copper block, cools the block, and then returns to the refrigeration unit. The surface temperature of the copper block must be uniform, with a temperature gradient of less than 1K and a temperature control accuracy of less than 0.1K. The temperature-controlled copper block consists of an upper and lower section, each with four semicircular slots. The upper and lower sections are clamped together by screws to hold four copper tubes. Low-temperature refrigerant flows through the tubes, cooling the block. A heater is installed beneath the block, achieving precise temperature control by balancing cooling and heating. Heat from the heater and cooling from the refrigerant are uniformly transferred to the block through the surfaces of the four copper tubes. The surface area of ​​the four refrigerant channels accounts for more than half of the block's cross-sectional area, ensuring uniform heat transfer across the upper section. The solid portion of the upper copper block is 9 mm thick, with an RRR greater than 80 and a thermal conductivity of approximately 350 W / m·K. This high thermal conductivity ensures high temperature consistency throughout the block.

[0084] Temperature stability is achieved through dual PID control of the heater and refrigerant flow. Heater PID control uses a solid-state relay to input a voltage with a specific on / off time ratio determined by PID parameters to the heater, thereby controlling the heating output. Refrigerant flow PID control uses a PLC to control the on / off time ratio of the solenoid valve in the refrigerant flow path, regulating the refrigerant flow through the copper block and thus controlling the cooling capacity. The solenoid valve uses a fast on / off solenoid valve with a short on / off time (less than 2 seconds), a long life (millions of cycles), and low power consumption (a few watts).

[0085] S104: After the temperature stabilizes at -163°C, a series of ultra-low oxygen content values ​​of 100ppm, 500ppm, 1000ppm, 2000ppm, and 3000ppm are precisely controlled in sequence through monotonically increasing control. After each oxygen content stabilizes, a trigger signal is sent to trigger the camera to capture the luminescent image of the coating under the corresponding temperature and oxygen content conditions.

[0086] In the entire oxygen concentration measurement and control system, a high-purity oxygen cylinder and a pressure reducing valve form a stable, high-purity oxygen source. A needle-tip valve, acting as a small, adjustable flow channel, works in conjunction with a solenoid valve with fast on-off capability (cycle time less than 2 seconds) to control oxygen concentration. When oxygen concentration needs to be increased, the fast-on / off solenoid valve gradually introduces oxygen into the calibration container while simultaneously monitoring the oxygen content. As the target concentration approaches, the fast-on / off solenoid valve gradually reduces the gas flow until the target concentration is reached, at which point the flow ceases.

[0087] S105: Repeat S104 and S105 to simulate the target temperatures of -100°C, -50°C, 0°C, and 50°C and the target oxygen content, collect the corresponding coating luminescence images, and evaluate the coating properties based on the low-temperature PSP images under different temperature and oxygen content conditions.

[0088] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention and are intended to be encompassed by the claims of the present invention.

Claims

1. A method for accurately simulating the change of oxygen content in a low-temperature PSP over a wide temperature range, characterized in that: The method uses a low-temperature pressure-sensitive paint static calibration and coating property research experimental device, which is based on a light source and a camera and includes: a calibration container, a pressure measurement and control system, an oxygen content measurement and control system, a temperature measurement and control system, and a control module deployed on a host computer; wherein, The calibration container is used to provide an environment with controllable temperature, pressure and oxygen concentration for the calibration sample coated with low-temperature pressure-sensitive paint. An external light source is irradiated onto the calibration sample coated with pressure-sensitive paint through a window at the top of the calibration container, and the calibration sample is photographed by a camera to obtain the coating properties. The pressure measurement and control system is used to provide a nitrogen source with controllable and measurable pressure for the calibration sample under the control of the control module; The oxygen content measurement and control system is used to provide a controllable and measurable ultra-low oxygen content oxygen source for the calibration sample under the control of the control module, while satisfying pressure control. The ultra-low oxygen content is 100ppm to 3000ppm; The temperature measurement and control system is used to provide controllable and measurable cooling and heating capacity for the calibration sample under the control of the control module, thereby achieving temperature control; The control module is used to control the operating sequence of the pressure measurement and control system, the oxygen content measurement and control system, and the temperature measurement and control system, and is used to control them separately according to the pressure value, oxygen content, and temperature value of the calibration container in combination with the experimental target value; it is also used to trigger the light source and camera to work when the experimental target value is reached, and to collect experimental images of the corresponding state, thereby realizing static calibration of low-temperature pressure-sensitive paint and research on coating properties; The method comprises: Step s1) The control module reads a set of preset target temperatures T, a set of nitrogen pressure target values ​​P, and a set of oxygen content change target values ​​O; wherein the oxygen content change target values ​​satisfy a range of 100 ppm to 3000 ppm; Step s2) When a set of target temperatures T has been traversed, go to step s6), otherwise, read each target temperature in turn, and control the temperature measurement and control system so that the calibration container reaches the specified target temperature; Step s3) when a set of nitrogen pressure target values ​​P are traversed at the specified target temperature, go to step s2); otherwise, read each nitrogen pressure target value in turn, and control the pressure measurement and control system so that the calibration container reaches the specified nitrogen pressure target value; Step s4) When a set of oxygen content change target values ​​O are traversed under the specified nitrogen pressure target value, go to step s3); otherwise, read the oxygen content target values ​​one by one in sequence, and control the oxygen content measurement and control system using a monotonically increasing or monotonically decreasing control method so that the calibration container reaches the specified oxygen content target value; Step s5) triggering the light source and camera to work by the control module to obtain an experimental image of the calibration sample coated with the pressure-sensitive paint at the specified target temperature, nitrogen pressure target value, and oxygen content target value, and then going to step s4); Step s6) Summarize the experimental images and analyze the low-temperature PSP coating characteristics.

2. The method for accurately simulating the change of oxygen content in a low-temperature PSP over a wide temperature range according to claim 1, characterized in that: The calibration container is made of 304 stainless steel, can withstand vacuum negative pressure and positive pressure, and has a smooth surface.

3. The method for accurately simulating the change of oxygen content in a low-temperature PSP over a wide temperature range according to claim 2, characterized in that: The outside of the calibration container also includes a heat-insulating layer of a certain thickness.

4. The method for accurately simulating the change of oxygen content in a low-temperature PSP over a wide temperature range according to claim 1, characterized in that: The window on the top of the calibration container is made of high-strength quartz glass of a set thickness and has a K9 light transmittance. The window glass is pressed tightly against the calibration container through a flange and sealed with a silicone rubber ring.

5. The method for accurately simulating the change of oxygen content in a low-temperature PSP over a wide temperature range according to claim 1, characterized in that: The pressure measurement and control system includes a nitrogen bottle with set purity, a pressure reducing valve, a needle valve, a vacuum pump and a fast on-off solenoid valve; wherein, The nitrogen cylinder with set purity and the pressure reducing valve are used to provide a nitrogen source with stable pressure and purity requirements to the calibration container; The needle-tip valve is used to provide a small and adjustable nitrogen flow channel to the calibration container; The vacuum pump is used to reduce the pressure in the calibration container; The fast on-off solenoid valve is used to control the delivery of nitrogen to the standard container to achieve the target content.

6. The method for accurately simulating the change of oxygen content in a low-temperature PSP over a wide temperature range according to claim 1, characterized in that: The oxygen content measurement and control system includes an electrochemical oxygen concentration analyzer, a zirconium oxide oxygen concentration sensor, an oxygen cylinder, a pressure reducing valve, a micro-regulating valve and a fast on-off solenoid valve; wherein, The electrochemical oxygen concentration analyzer is used to measure the oxygen concentration entering the calibration container within a set range; The zirconia oxygen concentration sensor is used to measure the oxygen concentration in the calibration container over the entire pressure, temperature and oxygen concentration range; The oxygen cylinder is connected to the calibration container through a pressure reducing valve, a micro-regulating valve, and a fast on-off solenoid valve; The fast on-off solenoid valve is used to control the delivery of oxygen to the standard container to achieve the target content.

7. The method for accurately simulating the change of oxygen content in a low-temperature PSP over a wide temperature range according to claim 6, characterized in that: The step s4) of controlling the oxygen content measurement and control system using a monotonically increasing or monotonically decreasing control method so that the calibration container reaches a specified oxygen content target value specifically includes: When the oxygen content needs to be increased, open the quick-on / off solenoid valve, adjust the micro-regulating valve to control the flow rate and gradually input oxygen into the calibration container. When the target content is approaching, gradually reduce the gas supply until the target content is reached and stop inputting. When the oxygen content needs to be reduced, the calibration container is evacuated to reduce the pressure to the set range, and then nitrogen is added to restore the original pressure. Each pumping and filling operation reduces the oxygen content while ensuring the pressure is stable. The operation is repeated until the oxygen content accurately drops to the set value, thereby achieving high-precision control of ultra-low oxygen content values.

8. The method for accurately simulating the change of oxygen content in a low-temperature PSP over a wide temperature range according to claim 1, characterized in that: The temperature measurement and control system includes a refrigeration unit, a chiller, a heater and a temperature-control copper block; wherein, The refrigeration unit adopts a single compressor for refrigeration. Under the control of the control module, the PLC controls the opening and closing time ratio of the solenoid valve on the refrigerant path, adjusts the refrigerant flow through the temperature-controlled copper block, and realizes the refrigeration control of the standard container; The chiller is used to cool the single compressor; The heater is used to control the heating amount and achieve heat control of the standard container by inputting a voltage with a certain on-off time ratio determined by PID parameters through a solid-state relay under the control of the control module; The temperature-controlled copper block and the heater are both arranged in a calibration container. The temperature-controlled copper block is arranged at the bottom of the calibration sample, and the heater is arranged at the bottom of the temperature-controlled copper block. Accurate temperature control is achieved by balancing the cooling capacity and the heating capacity. The temperature gradient is less than 1K and the temperature control accuracy is less than 0.1K.

9. The method for accurately simulating the change of oxygen content in a low-temperature PSP over a wide temperature range according to claim 8, characterized in that: The temperature-control copper block includes two parts, an upper part and an lower part, each part has four semicircular slots with the same diameter. The upper and lower parts are clamped by screws to form four circular slots as refrigerant channels for the inflow and outflow of refrigerant.

10. The method for accurately simulating the change of oxygen content in a low-temperature PSP over a wide temperature range according to claim 9, characterized in that: The surface of the temperature-control copper block is uniform, the surface area of ​​the four refrigerant channels occupies more than 1 / 2 of the cross-sectional area of ​​the temperature-control copper block, the thickness of the solid part of the upper temperature-control copper block meets the preset value, and the thermal conductivity is not less than 350W / m·K.

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