Aerodynamic suspension nozzle structure and aerodynamic suspension device

Abstract

The application relates to the field of aerodynamic suspension, and particularly provides an aerodynamic suspension nozzle structure and an aerodynamic suspension device. The aerodynamic suspension nozzle structure comprises a nozzle body and a gas flow channel arranged in the nozzle body, the gas flow channel is connected with an air inlet and an outlet, the outlet is arranged on the upper surface of the nozzle body, the gas flow channel comprises a pressure stabilizing chamber, a flow stabilizing zone, an acceleration zone and a lofting zone arranged in sequence, the diameter of the lofting zone changes from small to large from the side of the acceleration zone to the side of the outlet, the diameter of the acceleration zone changes from large to small from the side of the flow stabilizing zone to the side of the lofting zone. According to the application, the flow channel in the nozzle body is designed, the gas flow channel comprises the pressure stabilizing chamber, the flow stabilizing zone, the acceleration zone and the lofting zone; the inlet gas flow is stabilized, stabilized and accelerated, and finally the outlet gas flow has a large and stable flow velocity, so that the nozzle structure of the application has small gas flow disturbance and stable gas flow distribution, and the sample can be stably suspended.

Description

Technical Field

[0001] This application relates to the field of pneumatic suspension, and more specifically, to a pneumatic suspension nozzle structure and a pneumatic suspension device. Background Technology

[0002] Pneumatic suspension is a containerless suspension processing technology that uses airflow to suspend samples, allowing for melting and solidification. It plays a crucial role in research fields such as rapid solidification, new material preparation, and the determination of the thermophysical properties of high-temperature melts. By melting and solidifying samples in a suspended state, accurate detection of thermophysical properties can be achieved, the microstructure of alloys can be improved and optimized, and novel materials with metastable and amorphous phases can be prepared. The performance of samples suspended by a pneumatic suspension device is related to many factors, including the structure of the device, the suspension environment, the type of gas, the flow rate, and airflow disturbance. The nozzle structure plays a key role, determining the gas flow rate and the distribution of airflow disturbance; therefore, the nozzle structure is a critical component for both pneumatic suspension technology and the pneumatic suspension device itself.

[0003] Most existing nozzle structures involve gas flowing in directly from the nozzle inlet into the flow channel and exiting at the other end, forming an airflow to suspend the sample. The nozzle structure is simple, with a cylindrical flow channel combined with a simple conical inlet. The gas velocity at the outlet is adjusted by the velocity at the inlet. As the gas moves within the flow channel, it transmits airflow disturbances, resulting in strong turbulence at the outlet. This leads to significant airflow instability, unstable sample suspension, and particularly pronounced solid-liquid transitions. For example, the paper titled "Aerodynanic levitation of laser-heated solids ingas jets" discloses the aerodynamic levitation of materials such as steel, LaB6, glass, and Al2O3 with a diameter of 3-5 mm using cylindrical single-channel and multi-channel nozzles with conical orifices. The study found that solid samples could be stably suspended for a long time. However, when heated and melted into a liquid state, it was difficult to maintain stable suspension of the sample by adjusting the gas flow rate due to the increased sensitivity of the airflow to disturbances. The stable suspension time of the liquid sample was 5-10 seconds. The papers "Thermophysical property measurement of high-temperature oxide melts based on aerodynamic levitation" and "Aerodynamic levitation, supercooled liquids and glass formation" disclose the use of conical nozzles to aerodynamically levitate high-temperature oxide and glass melts with a sample size between 1-3 mm, with a gas flow rate of 0.2-0.5 L / min. However, the low sample size and gas flow rate severely restrict the development of aerodynamic levitation technology in the preparation of new materials such as large-volume metastable phases and metallic glasses, as well as in the field of rapid solidification.

[0004] In summary, existing pneumatic suspension devices have simple nozzle structures, large airflow disturbances, unstable flow field distribution, and low flow velocity, making it impossible to stably suspend larger samples and molten liquid samples. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by providing a pneumatic suspension nozzle structure and a pneumatic suspension device, thereby solving the problems of existing pneumatic suspension devices having simple nozzle structures, large airflow disturbances, unstable flow field distribution, and low flow velocity, which make it impossible to stably suspend larger-sized samples and molten liquid samples.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This application provides a pneumatic suspension nozzle structure. The nozzle structure includes a nozzle body and a gas flow channel disposed inside the nozzle body. The gas flow channel connects an air inlet and an outlet. The outlet is disposed on the upper surface of the nozzle body. From the air inlet to the outlet, the gas flow channel includes a pressure stabilizing chamber, a flow stabilizing zone, an acceleration zone, and a sampling zone arranged in sequence. From the acceleration zone side to the outlet side, the diameter of the sampling zone increases from small to large. From the flow stabilizing zone side to the sampling zone side, the diameter of the acceleration zone decreases from large to small.

[0008] Furthermore, the steady flow zone includes a transition zone, a damping zone, and a rectification zone arranged in sequence. The transition zone is connected to the voltage stabilizing chamber, and the rectification zone is connected to the acceleration zone. The transition zone, damping zone, and rectification zone are all columnar.

[0009] Furthermore, the central axes of the pressure stabilizing chamber, transition zone, damping zone, rectification zone, acceleration zone, and sampling zone coincide, and the centers of the air inlet and outlet are located on the central axis.

[0010] Furthermore, the stabilizing chamber, transition zone, and rectification zone are cylindrical in shape. The diameter of the stabilizing chamber is D3, and the diameters of the transition zone and rectification zone are the same, D2. The diameter of the acceleration zone to the lofting zone first decreases and then increases again, with the smallest diameter being D1. The diameter of the stabilizing chamber, D3, is 3-4 times the diameter of the rectification zone, D2. The expression for the diameters of the rectification zone, D2 and D1, is D2 = β·D1, where β is the contraction ratio of the acceleration zone.

[0011] Furthermore, the length of the lofting zone is L0, the length of the acceleration zone is L1, the length of the rectification zone is L2, the length of the transition zone is L6, the sum of the lengths of the damping zone and the transition zone is L5, the length of the damping zone is L5-L6, and the length of the stabilizing chamber is L3; the length of the transition zone L6 is more than 0.3 times the diameter D2 of the transition zone, the sum of the lengths of the damping zone and the transition zone L5 is not greater than 1 / 3 times the length of the rectification zone L2, the length of the stabilizing chamber L3 is 1-1.2 times the length of the rectification zone L2, and the length of the rectification zone L2 is 2-3 times the diameter D2 of the rectification zone; the expression for the lengths L1 and D1 of the acceleration zone is: L1=γ·D1, where γ is the aspect ratio of the acceleration zone.

[0012] Furthermore, the damping region consists of a damping module fixedly installed within a cylindrical flow channel. The damping module includes damping plates and damping pads, and the opening ratio of the damping plates is... Represented as: Where b is the spacing between adjacent holes, which is 1 / 100 of D1, and d is the opening width and opening ratio. Greater than 0.56.

[0013] Furthermore, the nozzle body includes a first nozzle mechanism and a second nozzle mechanism, each of which is provided with half of a gas flow channel separated in the vertical direction. The first nozzle mechanism and the second nozzle mechanism together form a gas flow channel.

[0014] Furthermore, the first nozzle mechanism has raised structures on both sides of the flow channel, and the second nozzle mechanism has grooved structures on both sides of the flow channel, with no gap between the raised structures and the grooved structures; the nozzle body is made of copper.

[0015] This application also provides a pneumatic suspension device, including a device body, a support mechanism, and a suspension mechanism. The upper part of the device body is hemispherical and the lower part is cylindrical. The support mechanism includes a support rod and a support plate that are fixedly connected. The support rod is fixed to the bottom wall of the device body, and the suspension mechanism is fixed to the support plate. The suspension mechanism is the aforementioned nozzle structure.

[0016] Furthermore, the pneumatic suspension device has a through hole in the center of the support plate, and the central axis of the through hole is collinear with the central axis of the gas flow channel in the suspension mechanism; the device body is equipped with a laser window, a sampling window, a detection window, an electrostatic flange, a vacuum pump flange, a pressure relief flange, a first air inlet flange, and a second air inlet flange.

[0017] Compared with the prior art, the beneficial effects of this invention are as follows: This application proposes a pneumatic suspension nozzle structure, which designs the internal flow channel of the nozzle body. The gas flow channel includes a pressure stabilizing chamber, a flow stabilizing zone, an acceleration zone, and a sample release zone. This achieves pressure stabilization, flow stabilization, and acceleration of the incoming airflow, resulting in a large and stable airflow velocity at the final outlet. Therefore, the airflow turbulence from the nozzle structure of this application is small, and the airflow distribution is stable, enabling the sample to be stably suspended. This application also provides a pneumatic suspension device utilizing the above-mentioned nozzle structure. The gas film formed by the nozzle structure and pneumatic suspension device of this application is stable and has small disturbances, enabling the sample to be stably suspended, thereby facilitating the detection of corresponding thermophysical properties or the processing of the sample. Attached Figure Description

[0018] Figure 1 A schematic diagram of a pneumatic suspension nozzle structure provided by the present invention;

[0019] Figure 2 A cross-sectional view of a pneumatic suspension nozzle structure provided by the present invention;

[0020] Figure 3 A schematic diagram of another pneumatic suspension nozzle structure provided by the present invention;

[0021] Figure 4 A three-dimensional schematic diagram of another pneumatic suspension nozzle structure provided by the present invention;

[0022] Figure 5 A schematic diagram of a damper in a pneumatic suspension nozzle structure provided by the present invention (the figure shows two layers of dampers);

[0023] Figure 6 A schematic diagram of a pneumatic levitation device provided by the present invention;

[0024] Figure 7 This is a schematic diagram of a support mechanism in a pneumatic suspension device provided by the present invention.

[0025] Icons: 1- Nozzle body; 11- First nozzle mechanism; 12- Second nozzle mechanism; 2- Gas flow channel; 3- Protruding structure; 4- Groove structure; 5- Damping plate; 6- Damping pad; 7- Device body; 8- Support mechanism; 81- Support rod; 82- Support plate. Detailed Implementation

[0026] To make the implementation process of this invention clearer, a detailed description will be provided below in conjunction with the accompanying drawings.

[0027] This invention provides a pneumatic levitation nozzle structure. The nozzle structure includes a nozzle body 1 and a gas flow channel 2 inside the nozzle body. The nozzle body 1 is made of a rigid material. Considering the friction of the high-speed airflow within the gas flow channel 2 and the thermal radiation effects of the suspended melt and laser, the nozzle material must be selected from copper, which has high thermal conductivity and low laser absorption coefficient. The shape of the nozzle structure can be any shape, such as a cuboid or cylinder. The gas flow channel 2 forms an airflow channel inside the nozzle body 1, allowing gas to enter through the inlet, advance within the gas flow channel 2, and finally reach one end of the outlet. The sample to be levied is placed at the outlet, and the gas flows out from the outlet, forming an airflow film that exerts a force on the sample. Under the action of this force and gravity, the sample is stably levied at a certain height. The stability of the levitation is closely related to the distribution and velocity of the airflow film at the outlet, which are strictly dependent on the shape and size of the gas flow channel 2. Therefore, the design of the gas flow channel 2 is crucial for the levitation effect. The air inlet is located on the lower side or all four sides of the nozzle body 1. Preferably, the air inlet is located directly below the gas flow channel 2, which reduces gas loss along the pipeline due to the length and bends of the pipeline. One or more air inlets can be provided. The outlet is located on the upper side of the nozzle body 1. The positions of the air inlet and the outlet correspond to each other. The air inlet and the outlet are connected by the gas flow channel 2.

[0028] The gas flow channel of this application includes, in sequence from the inlet to the outlet, a pressure stabilizing chamber, a flow stabilizing zone, an acceleration zone, and a sampling zone. The central axes of the inlet, pressure stabilizing chamber, flow stabilizing zone, acceleration zone, sampling zone, and outlet may or may not be collinear. Preferably, the central axes of the inlet, pressure stabilizing chamber, flow stabilizing zone, acceleration zone, sampling zone, and outlet are collinear and coincident, perpendicular to the plane containing the upper side surface of the nozzle body 1. Specifically, the inlet is used to connect the gas path pipe, allowing gas to flow into the nozzle structure; the pressure stabilizing chamber is used to provide a stable pressure difference, ensuring the momentum flux required by the jet and reducing downstream pressure fluctuations caused by changes in external factors such as the length, shape, and vibration of the upstream pipe. The shape of the pressure stabilizing chamber can be cylindrical, spherical, etc.; the flow stabilizing zone is used to further stabilize the airflow, providing a stable airflow for the acceleration process; the acceleration zone is used to accelerate the airflow. Based on the principle of Bernoulli's equation, the acceleration of the gas in the flow channel and the transformation to supersonic flow are achieved through a sudden change in the flow channel diameter, thereby increasing the flow velocity when the airflow reaches the outlet, thus increasing the cooling rate of the sample cooling process. The diameter of the acceleration zone gradually decreases; the diameter of the sample placement zone gradually increases from the acceleration zone to the outlet, which facilitates the placement of the sample at the outlet. At the same time, the cone-like shape can form a cone-shaped airflow film at the outlet, making the sample suspension more stable; the outlet is used to discharge the gas that has passed through the gas flow channel. The discharged gas interacts with the sample, suspending the sample.

[0029] Since the gas flow channel 2 is located inside the nozzle body 1, considering the difficulty of processing, the nozzle body 1 of this application includes a first nozzle mechanism 11 and a second nozzle mechanism 12. Both the first nozzle mechanism 11 and the second nozzle mechanism 12 contain half of the gas flow channel 2, with the axis of symmetry along the central axis of the gas flow channel 2. That is, when the first nozzle mechanism 11 and the second nozzle mechanism 12 are closed together, the aforementioned gas flow channel 2 is formed. Half of the cross-section of the gas flow channel 2 is machined symmetrically with equal dimensions on both the first nozzle mechanism 11 and the second nozzle mechanism 12. The roughness Ra<1 of the contact surface of the first nozzle mechanism 11 and the second nozzle mechanism 12 can be achieved by precision milling. This smoothness of the two inner end faces ensures a good air seal after closure and also reduces the friction of the inner wall of the flow channel on the airflow, increasing the airflow velocity. When the first nozzle mechanism 11 and the second nozzle mechanism 12 are closed, the flow channels of the first nozzle mechanism 11 and the second nozzle mechanism 12 are closely fitted together, forming complex flow channel structures such as a pressure stabilizing chamber and a supersonic flow channel, improving the airflow velocity and uniformity. However, deviations during the closing process can significantly reduce the airtightness of the gas flow channel, which will worsen the suspension effect.

[0030] To avoid the aforementioned problems, this application provides a triangular protrusion 3 on each side of the gas flow channel 2 in the first nozzle mechanism 11, and a triangular groove 4 on each side of the gas flow channel 2 in the second nozzle mechanism 12. The protrusion 3 and groove 4 are arranged parallel to the central axis of the gas flow channel 2, and the distance between the two protrusions 3 and the gas flow channel 2 is the same as the distance between the two grooves 4 and the gas flow channel 2. The protrusions 3 and grooves 4 together form a positioning mechanism. The positions of the protrusions 3 and grooves 4 correspond, and the cross-sectional shapes and dimensions of the two structures are exactly the same. In this way, the protrusions 3 can be inserted into the grooves 4, and the apex of the triangular structure is easy to position. Therefore, when the protrusions 3 are inserted into the grooves 4, the gas flow channel 2 in the middle is exactly formed as a complete gas flow channel. Meanwhile, the contact surfaces of the first nozzle mechanism 11 and the second nozzle mechanism 12 are planar, making it easy for airflow to escape along the contact surface at the edge of the gas flow channel 2, thus reducing airtightness. The presence of the positioning mechanism increases the gas escape resistance, as the gas escape process needs to bypass the contact surface between the groove structure and the protrusion structure, which is quite difficult. Therefore, the positioning mechanism not only serves a positioning function but also improves airtightness. A schematic diagram of the nozzle structure is shown below. Figure 1 and Figure 2 As shown.

[0031] Closure can be achieved through various methods, including welding, bonding, screws, and applying force. The split design of the nozzle structure is not a limitation on the nozzle structure; split, single, and even multi-part nozzle structures are all solutions disclosed in this application. The core of this application lies in the design of the gas flow channel 2 inside the nozzle structure, which has a significant impact on the sample suspension effect.

[0032] The sample is placed in the placement area, centered on the central axis of the gas flow channel. Gas introduction is achieved via a quick-connect 2d gas hose, a standard PU material (outer diameters of 6, 8, and 10 mm are available), or other methods can be used. Gas enters through the inlet, enters the pressure stabilization chamber for pressure stabilization, then enters the flow stabilization zone for further stabilization, preparing for the acceleration process. After the flow stabilization zone, it enters the acceleration zone, where the diameter narrows, increasing the gas velocity. Finally, it passes through the placement area and exits through the outlet, suspending the sample at the outlet. The gas used can be argon, nitrogen, helium, oxygen, carbon dioxide, air, or a mixture of multiple gases, such as argon and helium, or oxygen and carbon dioxide, depending on the detection or processing requirements after sample suspension. Compared to a cylindrical flow channel with a fixed diameter, the nozzle structure of this application first stabilizes the inflowing gas, then accelerates it, and finally allows the gas to flow out stably through the sample release zone. The gas film generated by the gas flow is more stable, thus making the suspended sample more stable.

[0033] Furthermore, this application proposes another nozzle structure, which differs from the above-described nozzle structure in that the flow stabilization zone includes a transition zone, a damping zone, and a rectification zone. The transition zone is located near the pressure stabilizing chamber, the rectification zone is located near the acceleration zone, and the damping zone is located between the transition zone and the rectification zone. That is, from the inlet end to the outlet end, the sequence is: pressure stabilizing chamber, transition zone, damping zone, rectification zone, acceleration zone, and discharge zone, as shown below. Figure 3 and Figure 4 As shown, after the gas flows in through the inlet, it passes sequentially through the pressure stabilizing chamber, transition zone, damping zone, rectification zone, acceleration zone, and sample release zone before being ejected and acting on the sample, causing the sample to be suspended at a certain height above the nozzle. The dimensions and shapes of the functional zones, such as the acceleration zone, rectification zone, damping zone, transition zone, and pressure stabilizing chamber, are designed according to the shape and size of the sample. Generally, the sample shape is spherical or near-spherical. The diameter of the suspended sample is typically 2-10 mm.

[0034] The primary function of the sampling zone is to ensure that the sample, after suspension heating and cooling, is accurately positioned directly above the gas flow, meaning the center of gravity of the suspended sample is on the straight line of the central axis of the gas flow channel. This prevents the sample from shifting or falling out of the nozzle outlet, thus affecting the suspension effect. In this application, the sampling zone is a circular cross-section expansion channel, meaning the horizontal cross-section of the channel is circular, with the radius increasing from bottom to top. (Similar to a nozzle structure flow channel.) Figure 3 As shown, the characteristic parameters determining the size and shape of the lofting zone include the expansion angle (θ), which is the angle between the vertical direction and the direction of the inner wall of the lofting zone channel; the outlet diameter D1 of the acceleration zone channel, which is the diameter corresponding to the smallest diameter at the lower end of the lofting zone; and the length L0 of the lofting zone, which is the length of the lofting zone in the vertical direction. Considering that the gas enters the lofting zone through the outlet of the acceleration zone, the expansion of the channel will generate an adverse pressure gradient. The range and magnitude of the adverse pressure gradient increase with the increase of the expansion angle (θ). This leads to flow separation, which has a significant impact on flow loss, the magnitude of suspension force, and suspension stability. Therefore, the expansion angle (θ) must not exceed 10°.

[0035] The gas flow ejected from the nozzle is a circular cross-section turbulent jet. According to the flow characteristics of a circular cross-section jet, the flow is mainly along the jet direction, and the longitudinal velocity component decreases rapidly with increasing distance from the jet axis. Therefore, the jet shape is a conical region originating from the exit port. The shape parameters of the jet are determined by the jet half-width (R). t The jet shape is characterized by the distance from the edge of the upper exit of the layout zone to the central axis of the gas flow channel, i.e., the radius of the uppermost circular cross-section of the layout zone. The half-width of the jet zone is defined by the vertical direction and the line connecting the center of the lowermost circular cross-section of the layout zone and the edge of the uppermost circular cross-section of the layout zone. At a position much larger than the exit, the jet shape is unaffected by the shape and size of the exit. The half-width of the jet zone satisfies:

[0036] R t =x·tanα (1)

[0037] Where α is the semi-cone angle of the jet region, with experimental values ​​of 12.5°-15°; x refers to the vertical distance from the exit nozzle.

[0038] Considering that flow separation occurs at the boundary of the conical region, driving the flow of ambient gas and causing backflow, which affects the stability of the sample suspension, the sample diameter (D0) must not exceed the width of the jet region (2R). t Considering both the characteristics of the jet flow and the constraint of the expansion angle (θ), it can be concluded that the vertex of the semi-cone angle (α) in the jet region must coincide with the origin of the exit circular section of the acceleration zone. Furthermore, as shown in the figure, through geometric conversion, the characteristic parameter equation of the shape of the lofted area is:

[0039]

[0040]

[0041] Where 0°≤θ≤10°, 12.5°≤α≤15°. Therefore, the characteristic parameters θ and L0 of the sampling zone are determined by formulas (2) and (3) based on the sample diameter (D0), semi-cone angle (α), and acceleration zone outlet diameter (D1). The selection of the sample diameter needs to consider the type and properties of the material. If the sample diameter is too large, the surface tension of the molten sample will not be able to constrain the shape of the sample to be spherical or near-spherical, thus affecting the stability of the suspension process. Therefore, the sample diameter (D0) required for the sampling zone size design is the maximum diameter that different material samples can be suspended, preferably 8-10 mm. The semi-cone angle (α) is preferably 15° to prevent the sample from deviating and falling out of the nozzle. The acceleration zone outlet diameter (D1) needs to consider the minimum size of the suspended material sample diameter, because if the sample diameter is smaller than the acceleration zone outlet diameter (D1), it will fall into the nozzle. Preferably, it is 2-3 mm. The expansion angle θ calculated by substituting into formula (2) is about 9°-10°, which meets the requirements. At this time, the diameter range of the suspended sample is 2-10 mm.

[0042] The acceleration zone is designed to maximize gas velocity and levitation force under the same flow conditions, i.e., to maximize gas velocity and levitation force, thereby improving the stability of the sample during suspension and the cooling rate during solidification. The flow channel in the acceleration zone has a contracting shape, meaning that the diameter of the circular cross-section of the flow channel decreases from bottom to top, and the diameter decreases at first and then decreases as the horizontal height increases, forming a "bottleneck" shape.

[0043] Due to the size limitations of the suspended sample, the flow velocity range of aerodynamic suspension is below 20 m / s, and the Mach number (Ma) is much less than 1, belonging to low-speed flow. According to the laws of fluid mechanics, a converging cross-section pipe can accelerate the fluid. The shape and size of the acceleration zone are characterized and controlled by the contraction curve equation. This is because a smooth contraction of the flow channel can increase the flow uniformity at the acceleration zone outlet, thin the boundary layer (suppressing flow separation), and reduce turbulence. The contraction curve equation is:

[0044] D2=β·D1 (4)

[0045] L1=γ·D1 (5)

[0046]

[0047] Where β is the contraction ratio of the acceleration zone, γ is the aspect ratio of the acceleration zone, D2 is the diameter of the rectifier outlet, L1 is the length of the acceleration zone, and l represents the axial distance from the acceleration zone outlet, i.e., the vertical distance from the acceleration zone outlet. Equation (6) is the specific expression of the contraction curve equation.

[0048] Therefore, based on the outlet diameter (D1) of the acceleration zone determined by the layout area, and given the contraction ratio (β) and length-to-diameter ratio (γ) of the acceleration zone, the dimensional characteristic parameters D2 and L1 of the acceleration zone can be obtained by formulas (4), (5), and (6). Although increasing the diameter ratio (β) and length-to-diameter ratio (γ) can significantly improve the gas flow rate, uniformity, and stability, it will also increase the material and processing costs of the nozzle structure. Therefore, the preferred ranges for the diameter ratio (β) and length-to-diameter ratio (γ) are 5-8, and the values ​​of the diameter ratio (β) and length-to-diameter ratio (γ) can be different.

[0049] The rectifying zone serves to dissipate, guide, and homogenize the small-scale vortex structure of the incoming flow, creating a uniform and stable inlet airflow for the acceleration zone. The rectifying zone channel is cylindrical, meaning the rectifying zone inlet diameter is the same as the rectifying zone outlet diameter (D2). The length (L2) of the rectifying zone is preferably 2-3 times the rectifying zone outlet diameter (D2), considering material and processing costs, as well as the guiding, stabilizing, and homogenizing effects of a long straight pipe with a uniform cross-section.

[0050] A damping module is installed on the inner wall of gas flow channel 2 to form a damping zone. This zone is used to break up the large-scale vortex structure of the incoming flow, converting it into a smaller, more easily dissipated vortex structure. The damping module is a damper with a small opening. The damping zone is cylindrical, with a diameter 1.2-1.3 times the diameter of the installed damper and the outlet diameter (D2) of the rectifying zone. The plane containing the damper is perpendicular to the central axis of the gas flow channel.

[0051] The damper consists of a damping plate 5 and a damping pad 6. The damping plate 5 breaks up the vortex structure, while the damping pad 6 acts as a buffer between damping plates 5 or between the damping plate 5 and the nozzle body 1, protecting the damping plate 5 and fixing it in place. Annular grooves are provided around the inner wall of the flow channel in the damping zone for fixing the damping plate 5 and the damping pad 6. The damping plate 5 is preferably made of a material with high stiffness and strength, such as 316L stainless steel; the damping pad 6 is preferably made of a material with high pressure resistance and wear resistance, such as a PU polyurethane rubber sealing ring. The damping plate 5 has a circular cross-section, and the damping pad 6 has an annular cross-section. The outer diameter of the damping pad 6 is equal to the diameter of the damping plate 5, and the inner diameter of the damping pad 6 is greater than or equal to the diameter D2 of the vent mesh section of the damping plate 5 (numerically equal to the diameter of the rectifying zone and transition zone). This ensures that the damping pad fixes the damping plate 5 without affecting the airflow. The thickness of the damping plate 5 should not be too large, as this will increase the congestion of the flow channel; 2mm is preferred. The small circular holes of the damping plate 5 are evenly distributed on a circular cross-section with a diameter of D2, centered on the center of the damping plate 5. The opening ratio is... It needs to be greater than 0.56, otherwise it will lead to gas instability. Open area ratio. The ratio of the opening area to the gas flow cross-sectional area can be represented by the following formula:

[0052]

[0053] Where b is the distance between adjacent holes and d is the opening width.

[0054] The combination of multiple damping plates 5 and damping pads 6 can form a multi-layer damper, which is more effective at breaking up large-scale vortices than a single layer, as shown in the schematic diagram. Figure 5 As shown. The spacing between the layers of damping plate 5 is the thickness of damping pad 6, and its value must be more than 50 times the spacing (b) between adjacent holes. Considering the material and processing costs, the damper can be selected as a 2-layer damper. The opening ratio of damping plate 5 is preferably 0.57. The spacing (b) between adjacent holes of damping plate 5 is 1 / 100 times the outlet diameter D1 of the acceleration zone, that is, 0.02-0.03mm. The purpose is to ensure the size of the vortex after breakup and reduce the influence on the flow field at the outlet. The opening width of damping plate 5 can be obtained according to formula (7). In this example, the opening type is a round hole, but the hole type can be a round hole, a square hole, an elliptical hole, etc., which is not limited here.

[0055] The transition zone connects the damping zone and the stabilizing zone, mitigating the pressure gradient between the stabilizing and damping zones and stabilizing the flow field at the outlet of the stabilizing zone. The length of the transition zone (L6) is at least 0.3 times the diameter of the gas flow cross-section in the damping zone (value D2), ensuring sufficient space and time for the transition zone to mitigate the pressure gradient. Furthermore, to reduce friction loss along the flow path, the distance (L5) between the rectifying zone and the stabilizing zone must not exceed 1 / 3 of the length of the rectifying zone (L2), i.e., the sum of the lengths of the damping and transition zones. Considering material costs in this example, the transition zone is a cylinder with a uniform cross-section, the same as the gas flow cross-section of the damping zone. However, the transition zone can also be conical or a smoothly tapered shape similar to the flow path of the acceleration zone; this is not a limitation.

[0056] The pressure stabilizing chamber is used to reduce downstream pressure fluctuations caused by changes in external factors such as the length, shape, and vibration of the upstream pipe. It provides a stable pressure differential for the circular cross-section jet during the suspension process, ensuring the required momentum flux of the jet. The pressure stabilizing chamber is cylindrical. The length of the pressure stabilizing chamber (L3) is 1-1.2 times the length of the rectifying zone (L2), because the pressure potential energy within the pipe depends on the pipe length; the greater the length, the greater the pressure potential energy stored. The diameter of the pressure stabilizing chamber (D3) is 3-4 times the diameter of the rectifying zone (D2), as this allows for the efficient conversion of the fluid's kinetic energy into pressure potential energy, reducing energy loss and maintaining a high pressure value.

[0057] Additionally, water-cooled chambers can be installed on both sides of the nozzle structure away from the gas flow channel 2 to cool the inner wall of the gas flow channel 2. This provides constant temperature control (20℃-25℃) for the gas in the rectification zone, acceleration zone, and sample release zone of the flow channel, thus achieving cooling. The water inlet of the water-cooled chamber is lower than its outlet, allowing water to flow from bottom to top and fill the entire chamber, ensuring temperature control of the flow channel gas during laser heating, with a temperature control range of 20℃-25℃.

[0058] The nozzle structure of this application stabilizes, breaks up vortices, rectifyes, and accelerates the incoming airflow, resulting in a large and stable airflow velocity at the outlet. Therefore, the airflow turbulence from the nozzle structure of this application is small and the airflow distribution is stable, enabling the sample to remain stably suspended.

[0059] This application also provides a pneumatic levitation device, such as Figure 6As shown, the pneumatic levitation device includes a device body 7, a support mechanism 8, and a levitation mechanism. The levitation mechanism is fixedly mounted inside the device body 7 via the support mechanism 8, and the levitation mechanism is fixedly connected to the support mechanism 8, which in turn is fixedly connected to the device body 7. The device body 7 is made of a rigid material, such as stainless steel. Multiple detection windows and flange interfaces are provided on the side walls of the device body 7. The detection windows are used to install detection devices for the thermophysical properties of the sample, and the flange interfaces are used to provide power or air to the levitation mechanism inside the device body 7. The device body 7 is a sealed cavity, and the internal pressure can be adjusted according to experimental requirements during detection.

[0060] Specifically, the device body 7 is a combination of a hemispherical and a cylindrical shape, with a hemispherical upper part and a cylindrical lower part. The radius of the hemispherical part is the same as the radius of the bottom surface of the cylindrical part, which facilitates assembly. It can be a single structure or a separate structure that is sealed and fixed together. The lower end of the cylindrical part is closed, meaning it has a bottom surface, which is sealed and fixedly connected to the cylindrical part. The hemispherical upper part ensures that the flow field around the suspended sample maintains a symmetrical structure and facilitates the installation of the detector without dead angles. The diameter of the hemispherical part is more than 100 times larger than the diameter of the suspended sample, reducing the interference of the device wall on the flow field of the suspended gas. A laser window is provided on the top of the device body 7. The window is made of transparent material, such as ultraviolet fused silica, and coated with a corresponding laser antireflection film to allow the melting laser to pass through. In use, the laser is positioned directly above the device, the laser source is turned on, and the laser emitted by the source shines through the laser window onto the suspended sample, heating and melting the sample. This allows for the detection of the thermophysical properties of the sample.

[0061] A sample loading and unloading window is set near the target suspension height of the sample to facilitate the removal of the suspended sample and the placement of the sample to be suspended. Multiple detection windows can also be set near the suspension height of the sample, depending on the detection needs. For example, detector windows can be set around the spherical shell for infrared thermometry, high-speed image and video acquisition, indoor pressure measurement, density measurement systems, active light source systems, and the determination of thermophysical properties such as viscosity and surface tension. The setting of detection windows must ensure the airtightness of the device body; specific requirements are not specified for the specific size and location of the detection windows. An electrostatic flange, a vacuum pump flange, a pressure relief flange, a first air inlet flange, and a second air inlet flange are set on the side wall of the device body 7. The electrostatic flange provides power to the internal levitation mechanism or any necessary built-in sensors. The vacuum pump flange connects to the vacuum pump, which controls the internal pressure of the device. The pressure relief flange releases pressure when the sample needs to be removed after levitation, ensuring equal pressure inside and outside the device for easy opening of the sample removal window. The first inlet flange introduces the levitation gas; a flexible hose or rigid stainless steel tubing connects the first inlet flange to the inlet of the levitation nozzle, forming a gas path. The second inlet flange connects to an external gas source to create a specific atmosphere inside the device. The gas source can be argon, helium, carbon dioxide, oxygen, etc.

[0062] The support mechanism 8 consists of a support rod 81 and a support plate 82, such as... Figure 7 As shown. Support rods 81 are symmetrically arranged around the center of the bottom wall of the device body 7, with more than three support rods 81 of equal length. A support plate 82 is fixedly mounted on the upper end of each support rod 81. The length of the support rods 81 is set as needed, ensuring that the sample is stably suspended at the height of a detection window; no specific limitation is imposed. The support rods 81 can be fixed to the bottom wall and support plate 82 using any fixing method, such as screw fixing. A hole is provided in the center of the support plate 82 to facilitate gas path connection to the nozzle structure fixed thereon. The suspension mechanism is the pneumatic suspension nozzle structure described in this application. The nozzle structure is fixedly mounted on the support plate of the support mechanism 8. The center of the support plate 82 is collinear with the central axis of the gas flow channel 2 of the nozzle structure. The flexible hose connecting the gas path passes through the through hole, ultimately connecting the external gas source to the air inlet of the nozzle structure, thus ensuring gas path connectivity.

[0063] In application, open the sampling window and place the sample to be suspended in the center of the conical sampling area of ​​the nozzle structure. Close the sampling window to ensure good airtightness. Determine whether to turn on the vacuum pump to create a negative pressure inside the device body 7, depending on the detection requirements. Sometimes, a positive pressure is required. To create a positive pressure, a specific atmosphere is introduced into the device body through the second inlet flange. After determining the pressure and atmosphere type inside the device body 7, close the vacuum pump and the second inlet flange. Generally, the first and second inlet flanges introduce the same type of gas. Open the first inlet flange to introduce gas into the nozzle structure. The gas enters the gas flow channel 2 inside the nozzle body through the inlet of the nozzle structure. As the gas flows through the gas flow channel 2, the airflow velocity increases and the stability is enhanced. Finally, a stable, high-speed airflow is formed at the outlet to suspend the sample. After the sample is stably suspended, turn on the heating laser to heat the sample. During the melting process, the thermophysical properties of the sample can be detected. After the detection is completed, turn off the laser. The sample cools rapidly under the action of the high-velocity suspended airflow. The thermophysical properties during the cooling process can be detected. During the detection process, the heating laser can be repeatedly switched on and off to perform multiple thermophysical property detections. After the detection is completed, the gas source of the first inlet flange is shut off, the sample falls to the upper side of the nozzle structure, and after depressurization, the sample collection and release window is opened to remove the sample, completing the suspension and detection of the sample. The pneumatic suspension device of this application adopts the above-mentioned nozzle structure, and the airflow ejected from the outlet has strong stability and a high flow velocity, which enables the sample to be stably suspended.

[0064] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pneumatically levitated nozzle structure, the nozzle structure comprising a nozzle body and a gas flow channel disposed inside the nozzle body, the gas flow channel connecting an air inlet and an outlet, the outlet being disposed on the upper surface of the nozzle body, characterized in that, From the air inlet to the outlet, the gas flow channel includes a pressure stabilizing chamber, a flow stabilizing zone, an acceleration zone, and a sampling zone arranged in sequence. From the acceleration zone side towards the outlet side, the diameter of the sampling zone increases; from the flow stabilizing zone side towards the sampling zone side, the diameter of the acceleration zone decreases. The flow stabilizing zone includes a transition zone, a damping zone, and a rectifying zone arranged in sequence. The transition zone communicates with the pressure stabilizing chamber, and the rectifying zone communicates with the acceleration zone. The transition zone, damping zone, and rectifying zone are all cylindrical. The pressure stabilizing chamber, transition zone, and rectifying zone are cylindrical in shape, and the diameter of the pressure stabilizing chamber is... The transition region and the rectifier region have the same diameter. The diameter from the acceleration zone to the lofting zone first decreases and then increases again, with the minimum diameter being... The diameter of the voltage stabilizing chamber The diameter of the rectifier region 3-4 times; the diameter of the rectifier region With the The expression is ,in, The contraction ratio of the acceleration zone is ; the length of the lofting zone is . The length of the acceleration zone is The length of the rectifier region is The length of the transition region is The sum of the lengths of the damping region and the transition region is The length of the damping region is - The length of the voltage stabilizing chamber is The length of the transition region The diameter of the transition region The sum of the lengths of the damping region and the transition region is more than 0.3 times that of the damping region. Not greater than the length of the rectifier region 1 / 3 times the length of the voltage stabilizing chamber The length of the rectifier region The length of the rectifier region is 1-1.2 times that of the rectifier region. The diameter of the rectifier region 2-3 times; the length of the acceleration zone With the The expression is: ,in, The aspect ratio of the acceleration zone is denoted as .

2. The pneumatic suspension nozzle structure according to claim 1, characterized in that, The central axes of the pressure stabilizing chamber, the transition zone, the damping zone, the rectification zone, the acceleration zone, and the sampling zone coincide, and the centers of the air inlet and the outlet are located on the central axis.

3. The pneumatic suspension nozzle structure according to claim 2, characterized in that, The damping region consists of a damping module fixedly installed within a cylindrical flow channel. The damping module includes a damping plate and a damping pad, and the opening ratio of the damping plate is... Greater than 0.

56.

4. The pneumatic suspension nozzle structure according to claim 3, characterized in that, The nozzle body includes a first nozzle mechanism and a second nozzle mechanism. Each of the first nozzle mechanism and the second nozzle mechanism is provided with half of the gas flow channel that is separated in the vertical direction. The first nozzle mechanism and the second nozzle mechanism together form the gas flow channel.

5. The pneumatic suspension nozzle structure according to claim 4, characterized in that, The first nozzle mechanism has raised structures on both sides of the flow channel, and the second nozzle mechanism has groove structures on both sides of the flow channel, with no gap between the raised structures and the groove structures; the nozzle body is made of copper.

6. A pneumatic levitation device, comprising a device body, a support mechanism, and a levitation mechanism, characterized in that, The upper part of the device body is hemispherical and the lower part is cylindrical. The support mechanism includes a support rod and a support plate that are fixedly connected. The support rod is fixed to the bottom wall of the device body. The suspension mechanism is fixed to the support plate. The suspension mechanism is any nozzle structure according to claims 1-5.

7. The pneumatic levitation device according to claim 6, characterized in that, The support plate has a through hole in the center, and the central axis of the through hole is collinear with the central axis of the gas flow channel in the suspension mechanism; the device body is provided with a laser window, a sampling window, a detection window, an electrostatic flange, a vacuum pump flange, a pressure relief flange, a first air inlet flange, and a second air inlet flange.

Images