A schlieren observation device and method for supercritical fluid shock wave

Abstract

The present application belongs to the technical field of supercritical fluid observation, and relates to a schlieren observation device and method for supercritical fluid shock waves. The device includes: an observation cabin, a laser, and a heater; the observation cabin includes a spherical hollow tank body, and a supercritical fluid is arranged inside the tank body; at least one pair of connection ports are arranged in the horizontal direction and the vertical direction passing through the center of the tank body, and each connection port is provided with a connection cover covering the corresponding connection port; at least two pairs of connection covers are provided with observation ports, and the observation ports are provided with transparent observation windows; the laser is arranged above the top observation window, and a focusing lens is arranged between the laser and the top observation window, and the focus of the focusing lens coincides with the center of the observation cabin; the heater is arranged at intervals at the bottom and / or side of the observation cabin to provide heating conditions for the observation cabin. The present application can perform accurate static schlieren measurement observations from different angles, and can generate supercritical fluid shock waves.

Description

Technical Field

[0001] The present application relates to the technical field of supercritical fluid observation, and in particular to a schlieren observation device and method for supercritical fluid shock waves. Background Art

[0002] When the temperature and pressure of a fluid are higher than the critical point, it is called a supercritical fluid. For example, the critical point of carbon dioxide is 7.37MPa, 304K, and the critical density is 467Kg / m3.

[0003] Supercritical fluids have high pressures, reaching tens or even hundreds of atmospheres, so they must be stored and transported in high-pressure steel containers, which makes direct observation extremely difficult.

[0004] In the prior art, a supercritical fluid observation container is usually in a cylindrical shape, with glass installed on the flange end faces at both ends of the cylinder, and only one or two viewing windows.

[0005] However, the above scheme can only be used for simple and rough observation with the naked eye, and cannot perform precise schlieren measurement observation; moreover, supercritical fluid has high density and pressure, making it difficult to achieve supersonic flow, and even more difficult to observe various types of shock waves in supercritical fluid. Summary of the invention

[0006] Based on this, it is necessary to provide a schlieren observation device and method for supercritical fluid shock waves in response to the above-mentioned technical problems, which can perform accurate static schlieren measurement and observation from different angles, and can generate supercritical fluid shock waves in the absence of supersonic flow, thereby realizing dynamic observation of supercritical fluid shock waves.

[0007] A schlieren observation device for supercritical fluid shock waves, comprising: an observation cabin, a laser and a heater;

[0008] The observation cabin comprises a spherical hollow tank body, and a supercritical fluid is arranged inside the tank body; at least one pair of connection ports are arranged on the tank body in a horizontal direction corresponding to the center of the tank body, and a pair of connection ports are arranged on the tank body in a vertical direction corresponding to the center of the tank body, and each connection port is provided with a connection cover covering the corresponding connection port; at least two pairs of connection covers are provided with observation ports, and the observation ports are provided with transparent observation windows;

[0009] The laser is arranged above the top observation window, and a focusing lens is arranged between the laser and the top observation window, and the focus of the focusing lens coincides with the spherical center of the observation cabin;

[0010] The heater is arranged at intervals on the bottom and / or the side of the observation cabin to heat the observation cabin.

[0011] In one embodiment, it also includes: a schlieren light source, a knife edge, and a camera;

[0012] The Schlieren light source and the knife edge are respectively arranged at intervals on the sides of a pair of connecting ports located in the horizontal direction, a focusing lens is provided between the Schlieren light source and the adjacent connecting ports and between the knife edge and the adjacent connecting ports, and the distance between the Schlieren light source and the adjacent connecting ports and the distance between the knife edge and the adjacent connecting ports are both the focal lengths of the focusing lens;

[0013] The camera is arranged in a horizontal direction to collect data of imaging through the knife edge.

[0014] In one embodiment, it further includes: a synchronizer;

[0015] The synchronizer is electrically connected to the laser and the camera respectively, so that the camera can collect data instantly when the laser is emitted into the observation cabin.

[0016] In one embodiment, the connection cover is a hollow rotating body structure;

[0017] An installation groove for embedding the observation window is provided on the inner wall of the connection cover.

[0018] In one embodiment, the mounting groove is a flared structure from outside to inside.

[0019] In one embodiment, washers are provided between the observation window and the side wall of the mounting groove and between the observation window and the bottom wall of the mounting groove.

[0020] In one embodiment, a connection position is provided on the inner wall of a connection cover without an observation port in the horizontal direction, which is used for detachably installing various models.

[0021] In one embodiment, the model includes: a plane model or an inclined plane model;

[0022] The plane model has a surface perpendicular to the laser direction to generate a reflected shock wave;

[0023] The inclined surface pattern has a surface that is angled with respect to the laser direction to generate a propagating oblique shock wave.

[0024] A schlieren observation method of a supercritical fluid shock wave, using a schlieren observation device of a supercritical fluid shock wave, comprising:

[0025] Adding supercritical fluid into the observation chamber;

[0026] Using a heater to heat the observation cabin until the temperature and pressure of the supercritical fluid inside the observation cabin reach above the critical point;

[0027] A laser is used to generate a focused laser through a focusing lens, which is shot into the observation cabin through the top observation window, penetrates the supercritical fluid at the center of the observation cabin, and generates an induced shock wave;

[0028] Observe the schlieren of supercritical fluid shock wave through the observation window on the observation port.

[0029] In one embodiment, it further includes:

[0030] The Schlieren light source generates horizontal light through a focusing lens; the light enters from one connection port, is emitted from a corresponding connection port, and forms an image through a knife edge after passing through the focusing lens;

[0031] A camera is used to collect data formed by imaging the knife edge.

[0032] The above-mentioned schlieren observation device and method for supercritical fluid shock waves are provided with a spherical hollow tank body, and multiple pairs of connecting ports are provided on the tank body to connect multiple connecting covers, thereby forming a multi-window structure, realizing the functions of multi-angle observation and multi-directional fill light, facilitating direct and accurate optical observation and schlieren measurement, and facilitating laser entry; the observation cabin, the connecting cover and the observation window together form a sealed structure, so that the fluid in the observation cabin reaches a supercritical state when the heater heats the tank body, and the pulsed laser as an energy source is shot into the observation cabin, instantly heating and breaking down the supercritical fluid at the center of the sphere into plasma, and the rapidly increased temperature and volume have no time to be transmitted to the outside, resulting in an instantaneous detonation, inducing a moving shock wave under high density conditions, so that the supersonic characteristic phenomenon of the supercritical fluid can be observed; the present application generates a supercritical fluid moving shock wave phenomenon equivalent to supersonic flow without generating supersonic flow, overcoming the difficulty of accelerating the supercritical fluid to supersonic speed in the prior art to generate supersonic flow field characteristics and perform visual observation, and filling the gap in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic diagram of a schlieren observation device for supercritical fluid shock waves in one embodiment;

[0034] Figure 2 is a three-dimensional schematic diagram of an observation cabin in one embodiment;

[0035] Figure 3 is a front view of an observation cabin in one embodiment;

[0036] Figure 4 A schematic diagram of a tank body of an observation cabin in one embodiment;

[0037] Figure 5 A schematic diagram of the assembly of a connection cover of an observation cabin in one embodiment;

[0038] Figure 6The figure is a schematic diagram of the assembly of a model cover of an observation cabin in one embodiment.

[0039] Figure 7 Schematic diagram of inducing double shock waves in one embodiment, wherein (a) is shock wave interfering with shock wave, and (b) is shock wave interfering with acoustic wave;

[0040] Figure 8 Schematic diagram of a shock wave hitting a flat plate model in one embodiment, wherein (a) is a single shock wave generating regular reflection, (b) is a single shock wave generating Mach reflection, and (c) is a double shock wave generating interference and reflection;

[0041] Fig. 9 A schematic flow chart of a method for observing schlieren of a supercritical fluid shock wave in one embodiment;

[0042] Fig.10 A schematic flow chart of a method for observing schlieren of a supercritical fluid shock wave in another embodiment;

[0043] Fig.11 1 is a diagram showing the effect of laser breakdown of carbon dioxide in one embodiment, wherein (a) is a gaseous state at 1 MPa, (b) is a gaseous state at 3 MPa, (c) is a gaseous state at 5 MPa, and (d) is a supercritical state at 7.3 MPa;

[0044] Fig.12 1 is a diagram of the evolution of the induced shock wave at different times when the laser breaks down carbon dioxide in one embodiment, wherein (a) is 0 μs, (b) is 2 μs, (c) is 5 μs, (d) is 10 μs, (e) is 20 μs, (f) is 40 μs, (g) is 80 μs, and (h) is 120 μs;

[0045] Fig.13 1 is a diagram of the evolution process of the induced shock wave at different times when the laser breaks down supercritical argon in one embodiment, wherein (a) is 0 μs, (b) is 2 μs, (c) is 5 μs, (d) is 10 μs, (e) is 20 μs, (f) is 40 μs, (g) is 60 μs, (h) is 80 μs, (i) is 100 μs, and (j) is 120 μs;

[0046] Fig.14 1 is a diagram of the induced shock wave reflection process of laser breakdown of supercritical argon at different times in an embodiment, wherein (a) is 0μs, (b) is 2μs, (c) is 5μs, (d) is 10μs, (e) is 20μs, (f) is 40μs, (g) is 60μs, (h) is 80μs, and (i) is 100μs.

[0047] Reference numerals:

[0048] Observation cabin 101, laser 102, focusing lens 103, Schlieren light source 104, knife edge 105, camera 106, synchronizer 107;

[0049] Tank body 1, connection port 2, connection cover 3, observation port 31, installation groove 32, observation window 33, model cover 4, connection position 41, connecting rod 42, model 43, gasket 5, temperature gauge 6, pressure gauge 7, needle valve 8, safety valve 9, installation port 10;

[0050] Reflected shock wave A, interfering shock wave B, Mach rod C, flat plate model D. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0052] It should be noted that all directional indications in the embodiments of the present application (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0053] In addition, the descriptions of "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "multiple groups" means at least two groups, such as two groups, three groups, etc., unless otherwise clearly and specifically defined.

[0054] In this application, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0055] In addition, the technical solutions between the various embodiments of the present application can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0056] The present application provides a schlieren observation device for supercritical fluid shock waves, such as Figure 1 As shown, in one embodiment, it includes: an observation cabin 101, a laser 102 and a heater, and the observation cabin 101 includes a tank body 1 and a connecting cover 3.

[0057] The tank body 1 is a spherical hollow structure, and a supercritical fluid is arranged inside; the supercritical fluid can be a solid, liquid or gaseous substance, such as carbon dioxide, argon, water, ammonia, methane, etc. The tank body 1 is provided with openings, and each opening extends a skirt outside the tank body 1 to serve as a connection port 2; the connection port 2 can be circular or square, preferably circular, and is integrally formed with the tank body 1 to provide a relatively large connection area and ensure the strength of the tank body 1; at least one pair of connection ports is arranged on the tank body corresponding to the horizontal direction passing through the center of the tank body, and a pair of connection ports is arranged on the tank body corresponding to the vertical direction passing through the center of the tank body, each pair of connection ports 2 includes two connection ports 2, and the center of each pair of connection ports 2 is collinear with the center of the tank body 1; among the paired connection ports 2 arranged in the horizontal direction, at least one pair is used to observe the supercritical fluid; all the connection ports 2 can be used for light transmission to provide a fill light function, and in particular, the paired connection ports 2 arranged in the vertical direction are used to pass pulsed lasers to allow the laser to enter the observation cabin.

[0058] A connection cover 3 is provided on each connection port 2 of the tank body 1, and each connection cover 3 covers the corresponding connection port 2; the connection cover 3 and the connection port 2 are fixed by flange connection. Specifically, the inner wall of the connection cover 3 and the outer wall of the connection port 2 are provided with flush end faces to provide a flange surface respectively. After the fixing holes on the two flange surfaces are aligned, they are fixed by screw connection; preferably, a sealing gasket is provided between the two contact surfaces of the connection cover 3 and the connection port 2 to further achieve the sealing of the observation cabin. At least two pairs of connection covers 3 are provided with observation ports 31, and the observation ports 31 are provided with transparent observation windows 33, so that the supercritical fluid in the tank body 1 can be observed through the observation windows 33; the observation windows 33 are made of quartz glass, which has a high light transmittance and is convenient for Schlieren test; the observation windows 33 and the corresponding observation ports 31 are fixed and sealed by modified silicone as sealing gaskets.

[0059] The laser is arranged above the top observation window, and a focusing lens 103 is arranged between the laser and the top observation window, and the focus of the focusing lens 103 coincides with the center of the observation cabin 101, that is, the distance between the focusing lens and the center of the observation cabin is equal to the focal length of the focusing lens.

[0060] Heaters are spaced apart at the bottom and / or sides of the viewing chamber to heat the viewing chamber.

[0061] The working process of this embodiment is: open one of the connection covers, add supercritical fluid (for example: high-purity dry ice, that is, solid carbon dioxide) and then seal the observation cabin through a flange connection; the carbon dioxide absorbs heat from the environment to liquefy and vaporize, and the internal pressure gradually increases, and then the tank body is externally heated by a heater, so that the temperature and pressure inside the observation cabin are constant and slowly increase and reach a critical state; then a laser is used to emit laser, and the laser is focused on the center of the observation cabin after passing through a focusing lens; in this process, visual observation is performed through the observation window, and both the static supercritical fluid and the supersonic flow field phenomena such as induced shock waves can be generated inside the observation cabin, thereby observing the dynamic supercritical fluid.

[0062] The above-mentioned schlieren observation device for supercritical fluid shock wave is provided with a spherical hollow tank body, and a plurality of pairs of connecting ports are provided on the tank body to connect a plurality of connecting covers, thereby forming a multi-window structure, realizing the functions of multi-angle observation and multi-directional fill light, facilitating direct and accurate optical observation and schlieren measurement, and facilitating laser entry; the observation cabin, the connecting cover and the observation window together form a sealed structure, so that the fluid in the observation cabin reaches a supercritical state when the heater heats the tank body, and the pulsed laser as an energy source is shot into the observation cabin, instantly heating and breaking down the supercritical fluid at the center of the sphere into plasma, and the rapidly increased temperature and volume have no time to be transmitted to the outside, resulting in an instantaneous detonation, inducing a moving shock wave under instantaneous high temperature and high pressure conditions, thereby being able to observe the supersonic phenomenon of the supercritical fluid; the present application generates a supercritical fluid moving shock wave phenomenon equivalent to supersonic flow without generating supersonic flow, overcoming the difficulty of accelerating the supercritical fluid to supersonic speed in the prior art to generate supersonic flow field characteristics and perform visual observation, and filling the gap in the prior art.

[0063] In one embodiment, it further includes: a Schlieren light source 104, a knife edge 105, and a camera 106. The Schlieren light source 104 and the knife edge 105 are respectively arranged at intervals on the sides of a pair of connection ports located in the horizontal direction, and a focusing lens is provided between the Schlieren light source 104 and the adjacent connection port and between the knife edge 105 and the adjacent connection port to form a Schlieren light path between the two focusing lenses 103, and the distance between the Schlieren light source 104 and the adjacent connection port and the distance between the knife edge 105 and the adjacent connection port are both the focal length of the focusing lens 103. The camera 106 is arranged in the horizontal direction to collect data imaged by the knife edge.

[0064] The above setup is based on the observation of supercritical fluid, and a schlieren light source and a knife edge are set to image the shock wave inside the observation cabin, and a camera is used to collect imaging data, thereby forming complete and reliable data for subsequent research.

[0065] In one embodiment, it also includes: a synchronizer 107; the synchronizer 107 is electrically connected to the laser 102 and the camera 106 respectively, so that the camera 106 can collect data instantly when the laser 102 enters the observation cabin 101.

[0066] The above arrangement is based on observing and recording the supercritical fluid, and a synchronizer is set to synchronize the laser emission time of the laser and the acquisition time of the camera to ensure that relevant data can be collected in time when the transient shock wave is generated, thereby achieving real-time and integrity of the data.

[0067] like Figures 2 to 6 As shown, preferably, three pairs of connection ports 2 are provided on the observation cabin, and the normals of any two adjacent connection ports 2 are perpendicular to each other, so that the number of connection ports 2 can be minimized on the basis of ensuring multiple viewing angles, so as to ensure the strength and sealing of the observation cabin. Specifically, two first connection ports are provided in opposite directions in the front and rear directions of the center of the observation cabin (i.e. parallel to the horizontal direction), two second connection ports are provided in opposite directions in the left and right directions of the center of the observation cabin (i.e. parallel to the horizontal direction), and two third connection ports are provided in opposite directions in the upper and lower directions of the center of the observation cabin (i.e. perpendicular to the horizontal direction, that is, the vertical direction). It can also be considered that a three-dimensional rectangular coordinate system is established with the center of the tank as the coordinate origin O, two symmetrical first connection ports are provided in the X and -X directions, two symmetrical second connection ports are provided in the Y and -Y directions, and two symmetrical third connection ports are provided in the Z and -Z directions.

[0068] A first connection port is connected to a model cover 4; the model cover 4 is a solid rotating body structure, and a connection position 41 is provided on the inner wall for detachably installing various models 43 to meet the needs of different tests. Specifically, a connecting rod 42 with threads at both ends is provided on the model cover 4, one end of the connecting rod 42 is fixed on the connection position 41, and the other end is connected to different models 43, so that the supercritical fluid impacts on the model to produce supercritical fluid shock waves of different shapes and types, such as: point shock waves, needle shock waves. Preferably, the model includes: a plane model or an inclined model; the plane model has a surface perpendicular to the laser direction, so that the supercritical fluid impacts on the surface and reflects under the action of the laser to generate a reflected shock wave; the inclined model has a surface at an angle to the laser direction, so that the supercritical fluid impacts on the surface under the action of the laser and continues to propagate, generating a propagating shock wave inclined relative to the model surface. For example, the plane model is a rectangular parallelepiped structure, and a connecting thread is provided at one end; the inclined model is a conical structure, and a connecting thread is provided at the flat end.

[0069] Another first connection port, two second connection ports and two third connection ports are all connected to a connection cover 3; the connection cover 3 is a hollow rotating body structure, that is, a cylindrical structure, and each connection cover 3 is provided with a mounting groove 32 on the inner wall to embed the observation window 33. Preferably, the mounting groove 32 is a flaring structure from outside to inside, that is, the cross section of the mounting groove 32 gradually increases in the direction toward the outside of the tank body 1, that is, the part where the observation window 33 and the mounting groove 32 cooperate has a trapezoidal slope, so that when the pressure in the tank body 1 gradually increases, the internal pressure squeezes the observation window 33 and causes the quartz glass to cooperate more closely with the mounting groove 32, thereby realizing automatic pre-tightening, self-sealing and self-locking functions through pressurization. Further preferably, a gasket 5 is provided between the side wall of the observation window 33 and the mounting groove 32 and between the observation window 33 and the bottom wall of the mounting groove 32 to buffer the impact when the internal pressure of the tank body 1 squeezes the observation window 33 and further ensure the sealing of the observation cabin. Preferably, the gasket 5 is selected from modified silicone or rubber sealants.

[0070] The first connection port connected to the model cover is used as the model port, another first connection port is used as the observation port, the two second connection ports are used as the light source ports, the third connection port arranged on the top of the observation cabin is used as the laser port, and another third connection port is used as the spare port.

[0071] The tank body 1 is also provided with an installation port 10 for installing a temperature gauge 6 and a pressure gauge 7, so as to judge the different states of the supercritical fluid and provide accurate data support for the observation of the supercritical fluid; the specific structure of the installation port 10 can adopt existing technology, such as: threaded connection. The tank body 1 is also provided with a needle valve 8 to connect an external pipeline, so as to inject liquid or gaseous fluid into the tank body 1 through the external pipeline; preferably, the number of needle valves 8 is two, so as to open and release the pressure when the pressure in the tank body 1 exceeds expectations. The tank body 1 is also provided with a safety valve 9 to open and release the pressure when the temperature and pressure in the tank body 1 reach a preset threshold.

[0072] The laser is arranged just above the laser port, the heater is arranged just below the spare port, the Schlieren light source is arranged just to the left of one light source port, the knife edge is arranged just to the right of another light source port, and the camera is arranged just to the right of the knife edge.

[0073] It should be noted that in this application, the direction toward the inside of the tank body is the inner side, and the direction away from the inside of the tank body is the outer side. The structures of the thermometer, pressure gauge, needle valve, and safety valve, as well as the connection methods with the tank body, are all prior art. The tank body, the connecting cover, and the model cover are all made of metal, preferably stainless steel, which can provide a sealed high temperature and high pressure resistant environment together with quartz glass. There is no limit on the number and size of the connection ports, and they can be specifically set according to actual observation needs.

[0074] Further preferably, the two second connection ports and the two third connection ports are all connected to a connection cover, wherein the two second connection ports serve as observation ports and / or light source ports, the third connection port located on the top of the observation cabin serves as a laser port, and the other third connection port serves as a spare port; the two first connection ports are all connected to a model cover, one is used to install the model as a model port, and the other is used to install a metal electrode as an electrode port, and the metal electrode induces shock waves through pulse discharge, that is, electrically induced shock waves.

[0075] Alternatively, a first connection port is connected to a model cover for mounting the model, serving as a model port, and another first connection port is connected to a connection cover for passing a laser, serving as a laser port, for laser-induced shock waves.

[0076] By using laser focusing + pulse discharge to induce shock waves and dual laser focusing to induce shock waves, the supercritical fluid can be broken down simultaneously (using a synchronizer to control the laser and the metal electrode, or controlling dual lasers) or successively at different positions (laser focus and electrode tip, or two laser focuses), thereby inducing dual shock waves (spherical shock waves or oblique shock waves).

[0077] like Figure 7As shown in the figure, when double shock waves are induced simultaneously, the two spherical shock waves interfere with each other, that is, the shock waves interfere with each other; when double shock waves are induced successively, the first induced detonation wave has propagated far and decayed into a sound wave, and there is no jump in the fluid physical parameters (such as pressure, temperature, and density) before and after the wave front, and the shock waves interfere with each other.

[0078] The shape and propagation speed of the shock wave front of the supercritical fluid after being disturbed change. The speed of the double shock waves induced successively decreases more slowly than that of the double shock waves induced simultaneously. The closer to the critical point, the smaller the flow loss and the higher the efficiency. Since supercritical fluid is used as a circulating medium in power generation equipment such as the Brayton cycle and the organic Rankine cycle containing turbines, multiple unsteady motion oblique shock waves will be generated on the turbine blades. Therefore, the above characteristics of shock wave interference with sound waves can be applied to turbine research to design the shape, number, spacing and layout of turbine blades, thereby breaking through the limitations of the existing technology in studying the turbine shock wave mechanism and improving the working efficiency of the turbine. It is worth noting that there is no technical means in the existing technology that can directly visualize the flow conditions inside a high-speed turbine.

[0079] It should also be noted that due to the different supercritical fluid states or different laser energy release conditions, the generated shock wave propagation Mach numbers are different. Therefore, when a single shock wave hits the flat plate model, different reflection states will occur, generating different reflected shock waves, namely regular reflection (without Mach rod structure) or Mach reflection (with Mach rod structure, which is actually a normal shock wave). When double shock waves or multiple shock waves hit the flat plate model, the dual effects of shock wave reflection and shock wave interference occur, generating reflected shock waves and interference shock waves, such as Figure 8 As shown, A is the reflected shock wave, B is the interference shock wave, C is the Mach rod, and D is the flat plate model. Studying the propagation evolution mechanisms of different shock waves and their interactions has great practical significance for the application of shock waves in engineering.

[0080] The present application also provides a method for observing the schlieren of supercritical fluid shock waves, such as Fig. 9 As shown, in one embodiment, a schlieren observation device using supercritical fluid shock wave includes the following steps:

[0081] Step 901: Add supercritical fluid into the observation chamber.

[0082] Specifically, any connection cover can be opened to add solid carbon dioxide (high-purity dry ice) according to the amount calculated in advance; or the needle valve can be opened to add liquid or gaseous carbon dioxide through an external pipeline.

[0083] Carbon dioxide absorbs heat from the environment to liquefy and vaporize, and the internal pressure gradually increases, usually from atmospheric pressure to 3-5MPa. The final pressure in the tank can be controlled by controlling the amount of dry ice added (the specific corresponding relationship and control process are existing technologies), thereby achieving initial pressurization.

[0084] Step 902: Use a heater to heat the observation cabin until the temperature and pressure of the supercritical fluid inside the observation cabin reach above the critical point.

[0085] Specifically, the tank body is heated by external heating (for example, a hot air bath is provided by an industrial hot air blower), and the internal temperature and pressure are increased slowly and steadily, thereby achieving secondary pressurization and causing the supercritical fluid inside to reach a critical state.

[0086] Note: Avoid using heating wires or water baths, which can cause rapid temperature rise and fall inside the chamber and cause stress on gaskets and glass.

[0087] Step 903: Use a laser to generate a focused laser through a focusing lens, and inject it into the observation cabin through the top observation window, penetrate the supercritical fluid at the center of the observation cabin, and generate an induced shock wave.

[0088] Specifically, the focusing lens may be a convex lens.

[0089] Step 904: Observe the schlieren of the supercritical fluid shock wave through the observation window on the observation port.

[0090] The above-mentioned schlieren observation method of supercritical fluid shock waves has designed a variety of filling methods to add supercritical fluids in different forms; the supercritical fluid in the observation cabin is pierced by pulsed laser focusing, and induced shock waves are generated in the supercritical fluid. Shock waves are a typical phenomenon of supersonic flow. Therefore, the supersonic phenomenon, namely the shock wave evolution, in the high-pressure supercritical fluid can be directly optically observed and schlieren measured through schlieren.

[0091] like Fig.10 As shown, preferably, the following steps are included:

[0092] Step 1001: Add supercritical fluid into the observation chamber and install the model as needed.

[0093] Specifically, whether to install a model and what type of model to install depends on the test needs.

[0094] It should be noted that all flange screws should be tightened to ensure good airtightness; if liquid carbon dioxide is added by injection, it should be injected after the flange screws are pre-tightened.

[0095] Step 1002: Use a heater to heat the observation cabin until the temperature and pressure of the supercritical fluid inside the observation cabin reach above the critical point.

[0096] Step 1003: A laser is used to generate a focused laser through a focusing lens, which is shot into the observation cabin through the top observation window, penetrates the supercritical fluid at the center of the observation cabin, and generates an induced shock wave.

[0097] Specifically, the laser may be a Nd:YAG 532nm laser.

[0098] Step 1004: Observe the schlieren of the supercritical fluid shock wave through the observation window on the observation port.

[0099] Step 1005: The Schlieren light source generates horizontal light through a focusing lens; the light enters from one connection port, is emitted from the corresponding connection port, and is imaged through the knife edge after passing through the focusing lens.

[0100] Specifically, the Schlieren light source may be a Schlieren LED lamp.

[0101] The focusing lens can be a convex lens. The light emitted by the light source generates parallel light after passing through the convex lens and enters the observation cabin, and is finally focused at the knife edge.

[0102] Step 1006: Use a camera to collect data of knife-edge imaging, and use a synchronizer to synchronize the laser emission process and the camera acquisition process.

[0103] Specifically, the synchronizer may be a DG645 digital synchronizer.

[0104] The above method penetrates the supercritical fluid in the observation cabin through pulsed laser focusing and generates induced shock waves in the supercritical fluid. Shock waves are a typical feature in supersonic flow fields. The supersonic phenomenon of supercritical fluid is realized by inducing shock waves, so that the shock wave evolution phenomenon can be directly optically observed and measured through schlieren. At the same time, experimental models can be easily added to generate different types of shock waves, such as evolving shock waves and reflected shock waves. Moreover, the imaging spot can be captured by a high-speed camera to obtain a supercritical fluid shock wave ripple image. Recording the schlieren of the supercritical fluid through the equipment can retain objective data, which is accurate and intuitive, and provides data support for subsequent research and experiments, which has strong practical significance.

[0105] It should be understood that although Fig. 9 and Fig.10 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Fig. 9 and Fig.10At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0106] like Figures 11 to 14 As shown, in a specific embodiment, the schlieren observation device of the supercritical fluid shock wave of the present application is used, and the schlieren observation method of the supercritical fluid shock wave of the present application is adopted to test and record the process of laser breakdown of carbon dioxide (7.37MPa, 304K) and argon (5MPa, 300K), measure the propagation distance of the shock wave boundary in the schlieren image, and combine with the propagation time to calculate the shock wave propagation speed.

[0107] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0108] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A schlieren observation device for supercritical fluid shock waves, characterized in that: include: observation pods, lasers, and heaters; The observation cabin comprises a spherical hollow tank body, and a supercritical fluid is arranged inside the tank body; at least one pair of connection ports are arranged on the tank body in a horizontal direction corresponding to the center of the tank body, and a pair of connection ports are arranged on the tank body in a vertical direction corresponding to the center of the tank body, and each connection port is provided with a connection cover covering the corresponding connection port; at least two pairs of connection covers are provided with observation ports, and the observation ports are provided with transparent observation windows; The laser is arranged above the top observation window, and a focusing lens is arranged between the laser and the top observation window, and the focus of the focusing lens coincides with the spherical center of the observation cabin; The heater is arranged at intervals on the bottom and / or the side of the observation cabin to heat the observation cabin.

2. The schlieren observation device of supercritical fluid shock wave according to claim 1, characterized in that: Also includes: Schlieren light source, knife edge and camera; The Schlieren light source and the knife edge are respectively arranged at intervals on the sides of a pair of connecting ports located in the horizontal direction, a focusing lens is provided between the Schlieren light source and the adjacent connecting ports and between the knife edge and the adjacent connecting ports, and the distance between the Schlieren light source and the adjacent connecting ports and the distance between the knife edge and the adjacent connecting ports are both the focal lengths of the focusing lens; The camera is arranged in a horizontal direction to collect data of imaging through the knife edge.

3. The schlieren observation device of supercritical fluid shock wave according to claim 2, characterized in that: Also includes: Synchronizer; The synchronizer is electrically connected to the laser and the camera respectively, so that the camera can collect data instantly when the laser is emitted into the observation cabin.

4. The schlieren observation device for supercritical fluid shock waves according to any one of claims 1 to 3, characterized in that: The connecting cover is a hollow rotating body structure; An installation groove for embedding the observation window is provided on the inner wall of the connection cover.

5. The schlieren observation device of supercritical fluid shock wave according to claim 4, characterized in that: The installation groove is a flared structure from outside to inside.

6. The schlieren observation device of supercritical fluid shock wave according to claim 5, characterized in that: Gaskets are provided between the observation window and the side wall of the mounting groove and between the observation window and the bottom wall of the mounting groove.

7. The schlieren observation device for supercritical fluid shock waves according to any one of claims 1 to 3, characterized in that: A connecting position is provided on the inner wall of a connecting cover without an observation port in the horizontal direction, and is used for detachably installing various models.

8. The schlieren observation device of supercritical fluid shock wave according to claim 7, characterized in that: The model includes: a plane model or an inclined plane model; The plane model has a surface perpendicular to the laser direction to generate a reflected shock wave; The inclined surface pattern has a surface that is angled with respect to the laser direction to generate a propagating oblique shock wave.

9. A method for observing the schlieren of supercritical fluid shock waves, characterized in that: A schlieren observation device for supercritical fluid shock waves according to any one of claims 1 to 8, comprising: Adding supercritical fluid into the observation chamber; Using a heater to heat the observation cabin until the temperature and pressure of the supercritical fluid inside the observation cabin reach above the critical point; A laser is used to generate a focused laser through a focusing lens, which is shot into the observation cabin through the top observation window, penetrates the supercritical fluid at the center of the observation cabin, and generates an induced shock wave; Observe the schlieren of supercritical fluid shock wave through the observation window on the observation port.

10. The schlieren observation method of supercritical fluid shock wave according to claim 9, characterized in that: Also includes: The Schlieren light source generates horizontal light through a focusing lens; the light enters from one connection port, is emitted from a corresponding connection port, and forms an image through a knife edge after passing through the focusing lens; A camera is used to collect data formed by imaging the knife edge.

Images