A low temperature pressure sensitive paint static calibration and paint property research experimental device

Abstract

The present application relates to a kind of low-temperature pressure-sensitive paint static calibration and coating characteristic research experimental device, based on light source and camera realization, the device includes: calibration container, pressure measurement and control system, oxygen content measurement and control system, temperature measurement and control system and the control module deployed in host computer;Wherein, calibration container, for the calibration sample coated with low-temperature pressure-sensitive paint provides test environment, obtains coating characteristic by camera shooting;Pressure measurement and control system and oxygen content measurement and control system, respectively, provide pressure controllable measurable nitrogen source and ultra-low oxygen content oxygen source for calibration sample;Temperature measurement and control system, for realizing temperature controllable;Control module, for controlling working time sequence, for controlling according to the pressure value of calibration container, oxygen content and temperature value;Also for reaching experimental target value, trigger light source and camera work, gather experimental image and realize low-temperature pressure-sensitive paint static calibration and coating characteristic research.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of aerodynamics in the aerospace industry, and particularly relates to a low-temperature pressure-sensitive paint static calibration and coating characteristic research experimental device. BACKGROUND

[0002] Pressure sensitive paint measurement technology (PSP) is a new optical non-contact pressure measurement method based on the photoluminescence process of high molecular polymer and the dynamic oxygen quenching effect. Since the 1980s, with its technical advantages and great development prospects, it has received extensive attention and in-depth research in the aerospace field of countries around the world. At present, aerospace powers such as the United States, Russia and Europe have been very mature in the application research of PSP measurement technology, and have established advanced PSP measurement systems in various large-scale production wind tunnels.

[0003] Since 2000, aerodynamic research institutions and related universities such as the German Aerospace Institute DLR, the NASA Langley Center in the United States, and the Japanese Aerospace Research Center JAXA have widely carried out basic and experimental research on low-temperature PSP pressure measurement technology on the basis of successfully developing conventional PSP technology, and have made it into engineering application, developing into one of the important experimental technologies of low-temperature high Reynolds number wind tunnels. At present, the research foundation in the field of low-temperature PSP is relatively weak in China, and it is still in the initial stage. The low-temperature wind tunnel is a continuous closed-loop return flow transonic wind tunnel with low-temperature nitrogen as the operating medium, and the low-temperature pressure sensitive coating measurement based on the photoluminescence oxygen quenching principle of organic high molecular requires that the flow must have a certain concentration of oxygen. In order to realize the PSP measurement of the low-temperature wind tunnel, dry air or oxygen needs to be injected at a proper position of the wind tunnel. In order to control the test cost and not affect the control of the wind tunnel flow parameters, the oxygen content of the wind tunnel flow is generally less than 3000ppm. In order to verify the low-temperature PSP coating characteristics under different oxygen contents and flow temperatures, a static calibration device is urgently needed. SUMMARY

[0004] The application proposes a low-temperature pressure-sensitive paint static calibration and coating characteristic research experimental device to realize the PSP measurement of the low-temperature wind tunnel.

[0005] In order to achieve the above purpose, the application proposes a low-temperature pressure-sensitive paint static calibration and coating characteristic research experimental device, which is realized based on a light source and a camera, and comprises 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,

[0006] The calibration container is used for providing a calibration sample coated with a low-temperature pressure-sensitive paint with a controllable environment of temperature, pressure and oxygen concentration, an external light source irradiates on the calibration sample coated with the pressure-sensitive paint through a view window on the top of the calibration container, the calibration sample is photographed by a camera, and paint characteristics are obtained.

[0007] The pressure measurement and control system is used for providing the calibration sample with a controllable and measurable nitrogen source under the control of the control module.

[0008] The oxygen content measurement and control system is used for providing the calibration sample with a controllable and measurable oxygen source with ultra-low oxygen content under the control of the control module under the premise of meeting the pressure control, and the ultra-low oxygen content is 100 ppm to 3000 ppm.

[0009] The temperature measurement and control system is used for providing the calibration sample with controllable and measurable refrigeration and heating capacity respectively under the control of the control module, and realizing temperature control.

[0010] The control module is used for controlling the working time 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 for controlling according to the pressure value, the oxygen content and the temperature value of the calibration container in combination with experimental target values respectively, and is further used for triggering the light source and the camera to work and collecting experimental images in a corresponding state when the experimental target values are reached, so as to realize static calibration of the low-temperature pressure-sensitive paint and paint characteristic research.

[0011] As an improvement of the above device, the calibration container is made of 304 stainless steel material, can withstand vacuum negative pressure and positive pressure, and has a smooth surface.

[0012] As an improvement of the above device, the calibration container further includes a certain thickness of a heat preservation layer.

[0013] As an improvement of the above device, the view window on the top of the calibration container is made of high-strength quartz glass with a set thickness, has K9 light transmittance, the view window glass is compressed through a flange and the calibration container, and is sealed by a silicone rubber ring.

[0014] As an improvement of the above device, the pressure measurement and control system includes a nitrogen cylinder with a set purity, a pressure reducing valve, a needle valve, a vacuum pump and a quick on-off electromagnetic valve; wherein,

[0015] The nitrogen cylinder with a set purity and the pressure reducing valve are used for providing the calibration container with a nitrogen source with stable pressure and meeting purity requirements;

[0016] The needle valve is used for providing the calibration container with a small and adjustable nitrogen flow channel;

[0017] The vacuum pump is used for reducing the pressure in the calibration container.

[0018] The fast on-off electromagnetic valve is used for controlling the delivery of nitrogen to the standard container to reach the target content.

[0019] As an improvement of the above device, the oxygen content measuring and controlling system comprises an electrochemical oxygen concentration analyzer, a zirconia oxygen concentration sensor, an oxygen cylinder, a pressure reducing valve, a micro regulating valve and a fast on-off electromagnetic valve; wherein,

[0020] The electrochemical oxygen concentration analyzer is used for measuring the oxygen concentration in the calibration container within a set range.

[0021] The zirconia oxygen concentration sensor is used for measuring the oxygen concentration in the calibration container within the whole pressure, temperature and oxygen concentration range.

[0022] The oxygen cylinder is connected with the calibration container through the pressure reducing valve, the micro regulating valve and the fast on-off electromagnetic valve.

[0023] The fast on-off electromagnetic valve is used for controlling the delivery of oxygen to the standard container to reach the target content.

[0024] As an improvement of the above device, the temperature measuring and controlling system comprises a refrigeration unit, a water chiller, a heater and a temperature control copper block; wherein,

[0025] The refrigeration unit adopts single compressor refrigeration, and under the control of the control module, the opening and closing time ratio of the electromagnetic valve on the refrigerant passage is controlled by the PLC to adjust the refrigerant flow through the temperature control copper block, so as to realize the refrigeration control of the standard container.

[0026] The water chiller is used for cooling the single compressor.

[0027] The heater is used for controlling the heating amount by inputting the voltage determined by the PID parameters through the solid-state relay under the control of the control module, so as to realize the heat control of the standard container.

[0028] The temperature control copper block and the heater are both arranged in the calibration container, the temperature control copper block is arranged at the lower part of the calibration sample, and the heater is arranged at the lower part of the temperature control copper block, so as to realize the accurate temperature control through the balance of the refrigeration amount and the heating amount, the temperature gradient is less than 1K, and the temperature control precision is less than 0.1K.

[0029] As an improvement of the above device, the temperature control copper block comprises two upper and lower parts, each part has four semicircular grooves with the same caliber, the upper and lower parts are clamped by screws to form four circular grooves as the refrigerant passages for the inflow and outflow of the refrigerant.

[0030] As an improvement of the above device, the surface of the temperature control copper block is uniform, the surface area of the four refrigerant channels accounts for more than 1 / 2 of the cross-sectional area of the temperature control copper block, and 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.

[0031] Compared with the prior art, the application has the advantages of:

[0032] 1. The device fills the domestic blank and provides the measurement conditions such as deep low temperature and ultra-low oxygen content required by low-temperature pressure-sensitive paint measurement technology.

[0033] 2. The device adopts single-compressor refrigeration, and can realize ultra-low temperature control of 110K without liquid nitrogen, and the control precision is less than ±0.1K.

[0034] 3. The device realizes accurate control of the ultra-low oxygen content of the calibration container through single monotonic change control mode, and the control error is less than ±10ppm. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is an external schematic view of the low-temperature pressure-sensitive paint static calibration and paint property research experimental device.

[0036] Figure 2 It is a principle diagram of the pressure measurement and control system.

[0037] Figure 3 It is a principle diagram of the oxygen content measurement and control system.

[0038] Figure 4 It is a principle diagram of the temperature measurement and control system.

[0039] Figure 5 It is a schematic view of the temperature control copper block. DETAILED DESCRIPTION

[0040] The application provides a low-temperature pressure-sensitive paint static calibration and coating characteristic research experimental device. The device mainly comprises 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 system, and is composed of five components. The calibration container provides a temperature, oxygen concentration and pressure controllable environment for the calibration sample; the pressure control system is composed of a high-purity nitrogen cylinder, a pressure reducing valve, a fast on-off electromagnetic valve, a needle valve and a vacuum pump, and realizes accurate control of the interior of the calibration container; the oxygen content measurement is completed by an electrochemical oxygen concentration sensor and a zirconia oxygen concentration sensor, and realizes accurate measurement of the ultra-low oxygen content (100ppm-3000ppm) of the gas in the calibration container; the oxygen content control system is composed of a high-purity oxygen cylinder, a pressure reducing valve, a needle valve and a fast on-off electromagnetic valve, and realizes accurate control of the ultra-low oxygen content value (100ppm-3000ppm) of the gas in the calibration container; the temperature control adopts a refrigeration capacity and heating capacity balanced temperature control mode, the low-temperature refrigerant flows through the refrigerant channel of the temperature control copper block, the refrigeration capacity provided by the low-temperature refrigerant and the heating capacity of the heater are equal, and the temperature is stable; after the target values of temperature, oxygen content and pressure are reached, a TTL signal is sent to the synchronous controller to trigger the light source and the camera to work, and the experimental images of the corresponding state are collected, so that the low-temperature pressure-sensitive paint static calibration and coating characteristic research are realized. The control system is deployed in the upper computer.

[0041] The technical solutions provided by the application are further illustrated below in combination with the embodiments.

[0042] Embodiment

[0043] Embodiment 1 of the application provides a low-temperature pressure-sensitive paint static calibration and coating characteristic research experimental device; as shown in Figure 1 , it is an appearance schematic diagram of the device. As shown in Figure 2 , it is a schematic diagram of the device of embodiment 1 of the application; mainly comprising:

[0044] The device is realized based on a light source and a camera, and the device comprises 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 in an upper computer; wherein,

[0045] The calibration container is used for providing a temperature, pressure and oxygen concentration controllable environment for the calibration sample coated with low-temperature pressure-sensitive paint, an external light source irradiates on the calibration sample coated with pressure-sensitive paint through the window on the top of the calibration container, the calibration sample is photographed by the camera, and the coating characteristics are obtained;

[0046] The pressure measurement and control system is used for providing a pressure controllable and measurable nitrogen source for the calibration sample under the control of the control module;

[0047] An oxygen content measurement and control system is used to provide a controllable and measurable ultra-low oxygen content oxygen source for a calibration sample under the control of a control module, the ultra-low oxygen content being 100 ppm to 3000 ppm, under the premise of meeting pressure control.

[0048] A temperature measurement and control system is used to provide controllable and measurable refrigeration and heating for a calibration sample under the control of a control module, to achieve controllable temperature.

[0049] A control module is used to control the working timing of the pressure measurement and control system, the oxygen content measurement and control system, and the temperature measurement and control system, to control according to the pressure value, oxygen content, and temperature value of the calibration container, in combination with experimental target values; and is further used to trigger the light source and camera to work when the experimental target values are reached, to collect experimental images of the corresponding state, thereby realizing low-temperature pressure-sensitive paint static calibration and paint property research.

[0050] Specifically:

[0051] The calibration container provides a controllable temperature, pressure, and oxygen concentration environment for the calibration sample. The calibration container is a 304 stainless steel cylinder that can withstand vacuum negative pressure and positive pressure.

[0052] To adapt to different cameras and light sources, a Φ150mm view window area is used. The size of the calibration container is Φ180x150mm, the surface is smooth, the wall thickness is 3mm, and the flange thickness is 10mm. The weight of the calibration container is less than 20kg, and a single person can move it. The calibration container has a 50mm insulation layer on the outside. The top of the calibration container is a view window glass made of 15mm thick high-strength quartz glass with K9 light transmittance. The view window glass is pressed against the calibration container through a flange and sealed with a silicone rubber ring.

[0053] The pressure measurement and control system: The pressure control system is composed of a high-purity nitrogen cylinder, a pressure reducing valve, a fast on-off electromagnetic valve, a needle valve, and a vacuum pump. The high-purity nitrogen cylinder and the pressure reducing valve form a pressure-stable, high-purity nitrogen source. The needle valve serves as a small, adjustable flow channel. The vacuum pump is used to reduce the pressure in the calibration container. The nitrogen source, needle valve, vacuum pump, and fast on-off electromagnetic valve (with a cycle of less than 2s) can achieve pressure control. The principle diagram is shown in Figure 2 .

[0054] Oxygen content measurement and control system: Oxygen content measurement is completed by electrochemical oxygen concentration analyzer and zirconia oxygen concentration sensor. The advantage of electrochemical oxygen concentration tester is that the precision is less than 10 ppm, and the range can be lower than 100 ppm. The advantage of zirconia oxygen concentration sensor is that it has a heating element, the sensor is resistant to low temperature, and can work in vacuum and high pressure. Zirconia oxygen concentration sensor works in the whole pressure, temperature and oxygen concentration range, and electrochemical oxygen concentration tester is used as the comparison of oxygen concentration at normal pressure and temperature. The two kinds of oxygen concentration sensors are mutually checked, which can effectively verify the accuracy of oxygen content measurement. How to realize the trace and controllable oxygen gas intake is the difficulty of precise control of ultra-low oxygen content. Filling appropriate trace oxygen into the calibration container is realized by the joint control of multiple valves. The oxygen cylinder is connected with the calibration container through the pressure reducing valve, trace regulating valve and fast on-off electromagnetic valve. Because the target oxygen content value is very low, the step change is usually less than 100 ppm, and it is difficult to achieve high precision control or the required control time is longer according to the conventional PID control mode. The device adopts the oxygen content single change control mode: the principle diagram is shown in Figure 3

[0055] When the oxygen content needs to be increased, the fast on-off electromagnetic valve is opened, the trace regulating valve controls the flow to input oxygen into the calibration container gradually, and when the target content is approached, the gas input is gradually reduced until the target content is reached, and the input is stopped.

[0056] When the oxygen content needs to be reduced, the calibration container is pumped to increase the vacuum, so that the pressure slightly decreases, and then nitrogen is supplemented to restore the original pressure. Each pumping operation ensures that the pressure is stable, so that the oxygen content slightly decreases, and the operation is repeated to accurately reduce the oxygen content to the set value, so as to realize the high precision control of ultra-low oxygen content value.

[0057] ​Temperature measurement and control system: single compressor refrigeration is used to provide refrigerant, and the low-temperature refrigerant generated by the single compressor refrigeration unit enters the temperature control copper block to cool the copper block and then returns to the refrigeration unit. The temperature of the copper surface should be uniform, and the temperature gradient should be less than 1K, and the temperature control accuracy should be less than 0.1K. The temperature control copper block is composed of upper and lower parts, and both have four semicircular grooves. The upper and lower copper blocks are clamped by four copper pipes through screws. The low-temperature refrigerant flows in the copper pipe to cool the copper block. The temperature control copper block is equipped with a heater, and the precise temperature control is realized by balancing the refrigeration capacity and the heating capacity. The heat of the heater and the cold of the refrigerant are uniformly transmitted to the copper block through the surface of the four copper pipes. The surface area of the four refrigerant channels accounts for more than 1 / 2 of the cross-sectional area of the copper block, ensuring uniform heat transfer of the upper half of the copper block. The solid part of the upper half of the copper block is 9mm thick, the copper block RRR>80, and the thermal conductivity is about 350W / m·K. The higher thermal conductivity ensures that the whole has higher temperature consistency. The stability of the temperature is controlled by double PID control of the heater and the refrigerant flow. The heater PID control is realized by a solid-state relay, which inputs a certain on / off time ratio voltage to the heater determined by the PID parameters, so as to control the heating capacity. The refrigerant flow PID control is realized by adjusting the opening / closing time ratio of the electromagnetic valve in the refrigerant passage controlled by the PLC (Programmable Logic Controller), so as to adjust the refrigerant flow through the copper block and control the refrigeration capacity. The schematic diagram is shown in Figure 4 , Figure 5 The schematic diagram of the temperature control copper block is shown in

[0058] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the examples, those skilled in the art should understand that modifications or equivalent replacements of the technical solutions of the present application do not deviate from the spirit and scope of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. An experimental device for static calibration and coating characteristic research of low-temperature pressure-sensitive paint, based on a light source and a camera, characterized in that, The device 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 a controllable environment of temperature, pressure and oxygen concentration for the calibration sample coated with low-temperature pressure-sensitive paint. Through the viewing window on the top of the calibration container, an external light source shines on the calibration sample coated with pressure-sensitive paint, and a camera takes a picture of the calibration sample to obtain the characteristics of the paint. 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 oxygen content measurement and control system is used to provide a controllable and measurable ultra-low oxygen content source for the calibration sample under the control of the control module, provided that pressure control is met. 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 to the calibration sample under the control of the control module, so as to achieve temperature controllability. The control module is used to control the working sequence of the pressure measurement and control system, the oxygen content measurement and control system, and the temperature measurement and control system. It is used to control the pressure, oxygen content, and temperature values ​​of the calibration container in combination with the experimental target values. It is also used to trigger the light source and camera to work when the experimental target values ​​are reached, and to collect experimental images of the corresponding state, thereby realizing the static calibration of low-temperature pressure-sensitive paint and the study of coating characteristics. The pressure measurement and control system includes a nitrogen cylinder with a set purity, a first pressure reducing valve, a needle valve, a vacuum pump, and a first fast-on / off solenoid valve; wherein, The nitrogen cylinder with the set purity and the first pressure reducing valve are used to provide a nitrogen source with stable pressure and meeting the 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 inside the calibration container; The first fast-on / off solenoid valve is used to control the delivery of nitrogen gas to a standard container to achieve the target content.

2. The experimental apparatus for static calibration and coating characteristic research of low-temperature pressure-sensitive paint according to claim 1, characterized in that, The calibration container is made of 304 stainless steel, which can withstand vacuum negative pressure and positive pressure, and has a smooth surface.

3. The experimental apparatus for static calibration and coating characteristic research of low-temperature pressure-sensitive paint according to claim 2, characterized in that, The calibration container also includes an insulation layer of a certain thickness.

4. The experimental apparatus for static calibration and coating characteristic research of low-temperature pressure-sensitive paint according to claim 1, characterized in that, The viewing window on top of the calibration container is made of high-strength quartz glass of a set thickness with K9 light transmittance. The viewing window glass is pressed against the calibration container by a flange and sealed with a silicone rubber ring.

5. The experimental apparatus for static calibration and coating characteristic research of low-temperature pressure-sensitive paint according to claim 1, characterized in that, The oxygen content measurement and control system includes an electrochemical oxygen concentration analyzer, a zirconia oxygen concentration sensor, an oxygen cylinder, a second pressure reducing valve, a micro-adjustment valve, and a second rapid 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 across the entire pressure, temperature, and oxygen concentration range. The oxygen cylinder is connected to the calibration container via a second pressure reducing valve, a micro-adjustment valve, and a second fast on / off solenoid valve. The second fast-on / off solenoid valve is used to control the delivery of oxygen to a standard container to achieve the target concentration.

6. The experimental apparatus for static calibration and coating characteristic research of low-temperature pressure-sensitive paint according to claim 1, characterized in that, The temperature measurement and control system includes a refrigeration unit, a chiller unit, a heater, and a temperature-controlling copper block; wherein, The refrigeration unit uses a single compressor for refrigeration. Under the control of the control module, the PLC controls the opening and closing time ratio of the solenoid valves in the refrigerant passage to adjust the refrigerant flow through the temperature control copper block, thereby realizing the refrigeration control of the standard container. The chiller unit is used to cool the single compressor; The heater is used to control the heating amount 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, thereby realizing the heat control of the standard container. Both the temperature-controlling copper block and the heater are placed inside the calibration container. The temperature-controlling copper block is placed below the calibration sample, and the heater is placed below the temperature-controlling copper block. Precise temperature control is achieved by balancing the cooling and heating capacity, with a temperature gradient of less than 1K and a temperature control accuracy of less than 0.1K.

7. The experimental apparatus for static calibration and coating characteristic research of low-temperature pressure-sensitive paint according to claim 6, characterized in that, The temperature-controlling copper block consists of upper and lower parts, each with four semi-circular slots of the same diameter. The upper and lower parts are clamped together by screws to form four circular slots as refrigerant channels for the inflow and outflow of refrigerant.

8. The experimental apparatus for static calibration and coating characteristic research of low-temperature pressure-sensitive paint according to claim 7, characterized in that, The surface of the temperature-controlling 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-controlling copper block, the thickness of the solid part of the upper part of the temperature-controlling copper block meets the preset value, and the thermal conductivity is not less than 350W / m·K.

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