A device for measuring the liquid nitrogen wetting contact angle of a cryosolid surface

Abstract

The application provides a liquid nitrogen wetting contact angle measuring device for a super-low-temperature solid surface, comprising a super-low-temperature solid surface cooling assembly, a nitrogen atmosphere protection assembly, a liquid nitrogen titration assembly and a wetting contact angle observation assembly, wherein the super-low-temperature solid surface cooling assembly can make the sample quickly enter and maintain the super-low-temperature state during the test through liquid nitrogen circulation and a silver cooling plate. The nitrogen atmosphere protection assembly discards the commonly used vacuum scheme in engineering and adopts dry nitrogen protection to avoid the rapid gasification of liquid nitrogen under vacuum. The liquid nitrogen titration device realizes the dropping of liquid nitrogen at different heights, supports the related research on wetting contact angle measurement and droplet impact dynamics. The wetting contact angle observation assembly guarantees the observation of the droplet shape under the super-low-temperature environment through a light source plate, a blowing device and the like. The application fills the gap in the research on the wetting and spreading behavior of super-low-temperature fluid on a cooled solid surface and has important value for super-low-temperature fluid lubrication and super-low-temperature fluid transportation.

Description

Technical Field

[0001] This invention relates to the technical field of assessing the wettability of cryogenic fluid media, and specifically to a device for measuring the liquid nitrogen wetting contact angle of an ultra-low temperature solid surface. Background Technology

[0002] The wetting contact angle is one of the important properties of solid surfaces, used to assess the ease with which a liquid wets and spreads on a fixed surface. It is mainly influenced by the surface free energy and microstructure of the solid. Quantitative research on wetting behavior began with T. Young, who introduced the concept of the wetting angle and proposed the famous Young's equation in 1805. According to this equation, Young argued that for an ideal smooth surface, the contact angle of a liquid is only related to the surface tension of the solid-gas, solid-liquid, and liquid-gas interfaces; reducing the surface energy of the solid can improve its hydrophobicity. Because wettability has wide applications in fluid lubrication, self-cleaning, anti-fogging, anti-icing and frosting, corrosion resistance, oil-water separation, non-destructive liquid transfer, and liquid transportation, related research has received widespread attention from scholars both domestically and internationally. Among these, the preparation and application of superhydrophobic surfaces are the most representative.

[0003] There are two main types of methods for measuring wetting contact angle: the weighing method and the shape image method. The former requires a wetting balance or a permeation contact angle meter, but the shape image method is currently the most widely used and accurate. The principle of the shape image analysis method is as follows: a droplet is placed on the surface of a solid sample, and the shape image of the droplet is obtained through a microscope and camera. Then, digital image processing and related algorithms are used to calculate the contact angle of the droplet in the image. It is worth noting that current research on wettability mainly focuses on room temperature and high temperature fields, such as the wetting and spreading characteristics of water on textured solid surfaces and liquid lithium metal on solid surfaces. Researchers have built various room temperature and low temperature wetting contact angle measurement devices for specific working conditions. However, a literature search reveals that research on the wetting behavior of cryogenic fluid media (liquid nitrogen, liquid hydrogen, liquid oxygen, etc.) on solid surfaces is very rare, which greatly limits the progress of technologies such as cryogenic fluid lubrication and cryogenic fluid transport. This is mainly because the development of cryogenic wetting contact angle measurement systems is quite challenging, and water vapor in the ambient atmosphere will quickly condense on the solid surface, interfering with the measurement results. In particular, with the continued advancement of research on reusable rocket turbopumps, the replacement of existing rolling bearings with liquid film bearings has gained attention from major spacefaring nations. The hydrophilicity / hydrophobicity of the cryogenic fluid medium at the bearing interface directly affects the lubrication dynamics performance of liquid film bearings, making related research of significant strategic importance and urgency.

[0004] Therefore, developing a liquid nitrogen wetting contact angle measurement device for ultra-low temperature solid surfaces is of great engineering value for determining their affinity and repulsion properties and thus regulating the dynamic characteristics of low temperature fluid lubricated bearings. It also provides a reference for the study of the wetting behavior of other low temperature fluid media on solid surfaces. Summary of the Invention

[0005] This invention aims to address the current limitations in research on the wetting behavior of cryogenic fluid media on solid surfaces by proposing a device for measuring the contact angle of liquid nitrogen wetting on ultra-low temperature solid surfaces. The device employs a method of filling with dry nitrogen to avoid the influence of vacuum negative pressure, while simultaneously solving the problems of frost formation and vaporization during liquid nitrogen titration. This provides a technical tool for measuring the wetting behavior of cryogenic fluids.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A liquid nitrogen wetting contact angle measuring device for ultra-low temperature solid surfaces includes a base plate. A nitrogen atmosphere protection component is disposed at the middle position of the upper surface of the base plate. The nitrogen atmosphere protection component includes a top plate, a side plate, a transparent observation plate, and a transparent back plate. The top plate, side plate, transparent observation plate, and transparent back plate together with the base plate form a closed cavity. The top plate is fixedly connected to the top of the side plate by fixing bolts, which allows for easy disassembly for sample replacement. An ultra-low temperature solid surface cooling component is disposed inside the closed cavity. A liquid nitrogen titration component is installed on the top plate. A wetting contact angle observation component is disposed on the side of the closed cavity facing the transparent observation plate.

[0008] Preferably, the ultra-low temperature solid surface cooling assembly includes a liquid nitrogen cavity, which is fixedly connected to a base plate. A U-shaped opening is provided at the top of the liquid nitrogen cavity, and a cooling silver plate is connected to the U-shaped opening by ultra-low temperature sealing adhesive. A sample is placed on the horizontal bottom surface of the cooling silver plate.

[0009] Preferably, the cryogenic solid-state surface cooling assembly further includes a liquid nitrogen tank, a liquid nitrogen circulation pump, a liquid nitrogen output pipe, and a liquid nitrogen recovery pipe. The liquid nitrogen tank is placed outside the sealed cavity. The liquid nitrogen circulation pump is fixedly installed at the top of the liquid nitrogen tank, with its pump core extending into the tank. One end of the liquid nitrogen output pipe is fixedly connected to the circulation pump. One end of the liquid nitrogen recovery pipe is fixedly connected to the upper side wall of the liquid nitrogen tank, and the end of the recovery pipe away from the tank penetrates the side plate and communicates with the liquid nitrogen cavity. The pump core of the circulation pump draws liquid nitrogen from the tank, which enters the liquid nitrogen cavity through the output pipe. After filling the cavity, excess liquid nitrogen flows back to the tank through the recovery pipe, achieving liquid nitrogen circulation to enhance the cooling effect. The test sample is rapidly cooled to a cryogenic state through heat conduction from the cooling silver plate and can maintain this state for a relatively long period for wetting contact angle testing.

[0010] Preferably, the nitrogen atmosphere protection assembly further includes a nitrogen tank, a first nitrogen valve, a second nitrogen valve, a liquid nitrogen input pipe, a nitrogen input pipe, and a pressure gauge. The nitrogen tank is placed outside the sealed cavity. A three-way pipe is fixedly connected to the top of the nitrogen tank. The end of the liquid nitrogen output pipe away from the liquid nitrogen circulation pump and the liquid nitrogen input pipe are respectively fixedly connected to the two empty ports on the three-way pipe. The end of the liquid nitrogen input pipe away from the three-way pipe passes through a side plate and communicates with the liquid nitrogen cavity. One end of the nitrogen input pipe is fixedly connected to the upper end of the side wall of the nitrogen tank. The end of the nitrogen input pipe away from the nitrogen tank passes through a side plate and communicates with the sealed cavity. The first nitrogen valve is fixedly installed on the nitrogen input pipe. An exhaust pipe is fixedly connected to the side plate of the sealed cavity away from the nitrogen input pipe, and the second nitrogen valve is fixedly installed on the exhaust pipe; the pressure gauge is fixedly installed on the outer surface of the sealed cavity and connected to the inside of the sealed cavity; before the test, the first nitrogen valve and the second nitrogen valve are opened, and the dry nitrogen stored in the nitrogen tank enters the sealed cavity through the nitrogen input pipe. After the original air inside the sealed cavity is replaced, the first nitrogen valve is closed, and the pressure gauge is observed. After the pressure rises to 2 atmospheres, the second nitrogen valve is closed, and a dry nitrogen protective atmosphere is created; this design abandons the commonly used vacuum scheme in engineering, and the use of dry nitrogen protection can avoid the rapid vaporization of liquid nitrogen under vacuum.

[0011] Preferably, the liquid nitrogen titration assembly includes a liquid nitrogen titration device, a telescopic support, and a dropper. The telescopic support is fixedly connected to the top plate, the liquid nitrogen titration device is fixedly installed at the top of the telescopic support, the liquid nitrogen titration device contains liquid nitrogen, and the dropper is fixedly connected to the bottom of the liquid nitrogen titration device. The end of the dropper penetrates the top plate and is vertically positioned directly above the sample. The position of the liquid nitrogen titration device can be adjusted by the telescopic support, thereby adjusting the liquid nitrogen drop height to support the measurement of wetting contact angle and related research on droplet impact dynamics.

[0012] Preferably, the wetting contact angle observation assembly includes a light source plate, an air blowing device, a high-speed camera, and a camera bracket. The light source plate is vertically fixed behind the transparent back plate, and the air blowing device is fixedly installed on one side of the U-shaped opening on the liquid nitrogen cavity. The camera bracket is placed outside the transparent observation plate and directly in front of the sample, and the high-speed camera is fixedly installed on the top of the camera bracket. The light emitted by the light source plate shines on the sample through the transparent side plate. The camera bracket is adjusted so that the lens of the high-speed camera reaches a suitable height to record the liquid nitrogen droplet and the wetting and spreading process on the ultra-low temperature solid surface. By setting the air blowing device, frost formation in the observation area can be avoided to the greatest extent.

[0013] Beneficial effects:

[0014] (1) Liquid nitrogen is introduced into the heat insulation cavity so that the bottom of the heat-conducting plate is in complete contact with the liquid nitrogen, thereby achieving an ultra-fast cooling effect. At the same time, the liquid nitrogen circulates continuously in one direction to ensure the stability of the surface temperature of the heat-conducting plate after cooling and improve the stability of the ultra-low temperature of the workpiece being measured.

[0015] (2) The method of using inert gas to remove air requires ultra-low temperature and high pressure to produce liquefaction phenomenon, thereby creating a waterless environment. Inert gas can effectively insulate heat transfer, create ultra-low temperature working conditions, and avoid the influence of negative pressure dehydration on titration, which is beneficial to the image acquisition and analysis of the wetting process.

[0016] (3) The ultra-low temperature dripping needle is set inside the observation box to avoid the ultra-low temperature liquid freezing when it comes into contact with air. At the same time, the titration device can adjust the titration height and dripping speed, and can be used for experimental research under different working conditions. The top plate and side plate are fixed and sealed by sealing strips and screw knobs, which facilitates disassembly and replacement of the measuring workpiece and improves the accuracy and practicality of the ultra-low temperature wettability measuring device.

[0017] In summary, this invention, through the aforementioned technical points, constructs a liquid nitrogen wetting contact angle measurement system for ultra-low temperature solid interfaces, effectively solving technical difficulties such as water vapor condensation in ambient atmosphere and ultra-low temperature solid surface cooling, and is of great value for studying the lubrication characteristics of low temperature fluids. Attached Figure Description

[0018] Figure 1 This is a three-dimensional structural diagram of the present invention from a frontal perspective;

[0019] Figure 2 This is a top-view three-dimensional structural diagram of the present invention;

[0020] Figure 3 This is a two-dimensional front view of the present invention;

[0021] Figure 4 This is a two-dimensional side view of the present invention;

[0022] Figure 5 This is a schematic diagram of the ultra-low temperature solid surface cooling component of the present invention;

[0023] Figure 6 This is a schematic diagram of the liquid nitrogen titration component of the present invention.

[0024] Explanation of the labels in the diagram:

[0025] 1. Base plate; 2. Liquid nitrogen tank; 3. First nitrogen valve; 4. Liquid nitrogen recovery pipe; 5. Liquid nitrogen circulation pump; 6. Liquid nitrogen output pipe; 7. Light source plate; 8. Liquid nitrogen titration device; 801. Telescopic bracket; 802. Dropper; 9. Top plate; 10. Fixing bolt; 11. Nitrogen tank; 12. Second nitrogen valve; 13. Nitrogen input pipe; 14. Side plate; 15. Cooling silver plate; 16. High-speed camera; 17. Camera bracket; 18. Liquid nitrogen cavity; 19. Transparent observation plate; 20. Transparent back plate; 21. Pressure gauge; 22. Air blowing device; 23. Sample. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1:

[0028] Please refer to Figure 1-6 A liquid nitrogen wetting contact angle measuring device for ultra-low temperature solid surfaces includes a base plate 1. A nitrogen atmosphere protection component is disposed at the middle position of the upper surface of the base plate 1. The nitrogen atmosphere protection component includes a top plate 9, a side plate 14, a transparent observation plate 19, and a transparent back plate 20. The top plate 9, side plate 14, transparent observation plate 19, and transparent back plate 20 together with the base plate 1 form a closed cavity. The top plate 9 is fixedly connected to the top of the side plate 14 by fixing bolts 10. An ultra-low temperature solid surface cooling component is disposed inside the closed cavity. A liquid nitrogen titration component is installed on the top plate 9. A wetting contact angle observation component is disposed on the side of the closed cavity facing the transparent observation plate 19.

[0029] The ultra-low temperature solid surface cooling assembly includes a liquid nitrogen cavity 18, which is fixedly connected to the base plate 1. A U-shaped opening is provided at the top of the liquid nitrogen cavity 18, and a cooling silver plate 15 is connected to the U-shaped opening by ultra-low temperature sealing adhesive. A sample 23 is placed on the horizontal bottom surface of the cooling silver plate 15.

[0030] The cryogenic solid surface cooling assembly also includes a liquid nitrogen tank 2, a liquid nitrogen circulation pump 5, a liquid nitrogen output pipe 6, and a liquid nitrogen recovery pipe 4. The liquid nitrogen tank 2 is placed outside the closed cavity. The liquid nitrogen circulation pump 5 is fixedly installed on the top of the liquid nitrogen tank 2 and the pump core of the liquid nitrogen circulation pump 5 extends into the liquid nitrogen tank 2. One end of the liquid nitrogen output pipe 6 is fixedly connected to the liquid nitrogen circulation pump 5. One end of the liquid nitrogen recovery pipe 4 is fixedly connected to the upper end of the side wall of the liquid nitrogen tank 2, and the end of the liquid nitrogen recovery pipe 4 away from the liquid nitrogen tank 2 passes through the side plate 14 and is connected to the liquid nitrogen cavity 18.

[0031] The nitrogen atmosphere protection assembly also includes a nitrogen tank 11, a first nitrogen valve 3, a second nitrogen valve 12, a liquid nitrogen input pipe, a nitrogen input pipe 13, and a pressure gauge 21. The nitrogen tank 11 is placed outside the closed cavity. A three-way pipe is fixedly connected to the top of the nitrogen tank 11. The end of the liquid nitrogen output pipe 6 away from the liquid nitrogen circulation pump 5 and the liquid nitrogen input pipe are respectively fixedly connected to the two empty ports on the three-way pipe. The end of the liquid nitrogen input pipe away from the three-way pipe passes through the side plate 14 and is connected to the liquid nitrogen cavity 18. One end of the nitrogen input pipe 13 is fixedly connected to the upper end of the side wall of the nitrogen tank 11. The end of the nitrogen input pipe 13 away from the nitrogen tank 11 passes through the side plate 14 and is connected to the closed cavity. The first nitrogen valve 3 is fixedly installed on the nitrogen input pipe 13. An exhaust pipe is also fixedly connected to the side plate 14 of the closed cavity away from the nitrogen input pipe 13. The second nitrogen valve 12 is fixedly installed on the exhaust pipe. The pressure gauge 21 is fixedly installed on the outer surface of the closed cavity and is connected to the inside of the closed cavity.

[0032] The liquid nitrogen titration assembly includes a liquid nitrogen titration device 8, a telescopic support 801, and a dropper 802. The telescopic support 801 is fixedly connected to the top plate 9. The liquid nitrogen titration device 8 is fixedly installed at the top of the telescopic support 801. Liquid nitrogen is stored inside the liquid nitrogen titration device 8. The dropper 802 is fixedly connected to the bottom of the liquid nitrogen titration device 8. The end of the dropper 802 passes through the top plate 9 and is vertically positioned directly above the sample 23.

[0033] The wetting contact angle observation assembly includes a light source plate 7, an air blowing device 22, a high-speed camera 16, and a camera bracket 17. The light source plate 7 is vertically fixed behind the transparent back plate 20. The air blowing device 22 is fixedly installed on one side of the U-shaped opening on the liquid nitrogen cavity 18. The camera bracket 17 is placed outside the transparent observation plate 19 and located directly in front of the sample 23. The high-speed camera 16 is fixedly installed on the top of the camera bracket 17.

[0034] As described above, in use, liquid nitrogen is introduced into the insulation chamber, ensuring complete contact between the bottom of the heat-conducting plate and the liquid nitrogen, thereby achieving ultra-rapid cooling. Simultaneously, the continuous unidirectional flow of liquid nitrogen ensures the stability of the surface temperature of the heat-conducting plate after cooling, improving the stability of the measured workpiece's ultra-low temperature. Furthermore, the use of inert gas to remove air creates a water-free environment, as inert gas requires ultra-low temperature and high pressure to liquefy. This inert gas effectively insulates against heat transfer, creating ultra-low temperature conditions while avoiding the impact of negative pressure dehydration on titration, which is beneficial for image acquisition and analysis of the wetting process. In addition, the use of an ultra-low temperature dispensing needle within the observation chamber prevents the ultra-low temperature liquid from freezing upon contact with air. The titration device allows for adjustment of the titration height and speed, enabling experimental research under different conditions. The top plate 9 and side plate 14 are sealed together with sealing strips and screw knobs, facilitating disassembly and replacement of the measured workpiece, thus improving the accuracy and practicality of the ultra-low temperature wettability measurement device.

[0035] In summary, this invention, through the aforementioned technical points, constructs a liquid nitrogen wetting contact angle measurement system for ultra-low temperature solid interfaces, effectively solving technical difficulties such as water vapor condensation in ambient atmosphere and ultra-low temperature solid surface cooling, and is of great value for studying the lubrication characteristics of low temperature fluids.

[0036] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concept, should be covered within the scope of protection of the present invention.

Claims

1. A device for measuring the contact angle of liquid nitrogen wetting on a cryogenic solid surface, comprising a base plate (1), characterized in that, A nitrogen atmosphere protection component is provided at the middle position of the upper surface of the base plate (1). The nitrogen atmosphere protection component includes a top plate (9), a side plate (14), a transparent observation plate (19), and a transparent back plate (20). The top plate (9), side plate (14), transparent observation plate (19), and transparent back plate (20) together with the base plate (1) form a closed cavity. The top plate (9) is fixedly connected to the top of the side plate (14) by fixing bolts (10). An ultra-low temperature solid surface cooling component is provided inside the closed cavity. A liquid nitrogen titration component is installed on the top plate (9). A wetting contact angle observation component is provided on the side of the closed cavity facing the transparent observation plate (19). The ultra-low temperature solid surface cooling assembly includes a liquid nitrogen cavity (18), which is fixedly connected to the base plate (1). A U-shaped opening is provided at the top of the liquid nitrogen cavity (18), and a cooling silver plate (15) is connected to the U-shaped opening by ultra-low temperature sealant. A sample (23) is placed on the horizontal bottom surface of the cooling silver plate (15). The nitrogen atmosphere protection assembly also includes a nitrogen tank (11), a first nitrogen valve (3), a second nitrogen valve (12), a liquid nitrogen input pipe, a nitrogen input pipe (13), and a pressure gauge (21). The nitrogen tank (11) is placed outside the closed cavity. A three-way pipe is fixedly connected to the top of the nitrogen tank (11). The end of the liquid nitrogen output pipe (6) away from the liquid nitrogen circulation pump (5) and the liquid nitrogen input pipe are respectively fixedly connected to the two empty ports on the three-way pipe. The end of the liquid nitrogen input pipe away from the three-way pipe passes through the side plate (14) and is connected to the liquid nitrogen cavity (18). The nitrogen input pipe (13) is fixedly connected at one end to the upper side wall of the nitrogen tank (11), and the end of the nitrogen input pipe (13) away from the nitrogen tank (11) passes through the side plate (14) and is connected to the closed cavity. The second nitrogen valve (12) is fixedly installed on the nitrogen input pipe (13). An exhaust pipe is also fixedly connected to the side plate (14) of the closed cavity away from the nitrogen input pipe (13). The first nitrogen valve (3) is fixedly installed on the exhaust pipe. The pressure gauge (21) is fixedly installed on the outer surface of the closed cavity and is connected to the inside of the closed cavity.

2. The device for measuring the liquid nitrogen wetting contact angle of an ultra-low temperature solid surface according to claim 1, characterized in that, The ultra-low temperature solid surface cooling assembly also includes a liquid nitrogen tank (2), a liquid nitrogen circulation pump (5), a liquid nitrogen output pipe (6), and a liquid nitrogen recovery pipe (4). The liquid nitrogen tank (2) is placed outside the closed cavity. The liquid nitrogen circulation pump (5) is fixedly installed on the top of the liquid nitrogen tank (2), and the pump core of the liquid nitrogen circulation pump (5) extends into the liquid nitrogen tank (2). One end of the liquid nitrogen output pipe (6) is fixedly connected to the liquid nitrogen circulation pump (5). One end of the liquid nitrogen recovery pipe (4) is fixedly connected to the upper end of the side wall of the liquid nitrogen tank (2). The end of the liquid nitrogen recovery pipe (4) away from the liquid nitrogen tank (2) passes through the side plate (14) and is connected to the liquid nitrogen cavity (18).

3. The device for measuring the liquid nitrogen wetting contact angle of an ultra-low temperature solid surface according to claim 1, characterized in that, The liquid nitrogen titration assembly includes a liquid nitrogen titration device (8), a telescopic support (801), and a dropper (802). The telescopic support (801) is fixedly connected to the top plate (9). The liquid nitrogen titration device (8) is fixedly installed at the top of the telescopic support (801). Liquid nitrogen is stored inside the liquid nitrogen titration device (8). The dropper (802) is fixedly connected to the bottom of the liquid nitrogen titration device (8). The end of the dropper (802) passes through the top plate (9) and is vertically positioned directly above the sample (23).

4. The device for measuring the liquid nitrogen wetting contact angle of an ultra-low temperature solid surface according to claim 1, characterized in that, The wetting contact angle observation assembly includes a light source plate (7), an air blowing device (22), a high-speed camera (16), and a camera bracket (17). The light source plate (7) is vertically fixed behind the transparent back plate (20). The air blowing device (22) is fixedly installed on one side of the U-shaped opening on the liquid nitrogen cavity (18). The camera bracket (17) is placed outside the transparent observation plate (19) and located directly in front of the sample (23). The high-speed camera (16) is fixedly installed on the top of the camera bracket (17).

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