A labyrinth flow channel type throttling element cavitation intensity characterization device

Abstract

The application provides a labyrinth flow channel type throttling element cavitation intensity characterization device, the throttling element is provided with a throttling element body including a cylinder and a positioning step located at the outer periphery of the throttling element body, and the device comprises: a transparent test section provided with a first through hole and a first counterbore in communication along the axial direction, the first through hole is used for mounting the throttling element body, and the first counterbore is used for mounting the positioning step; a peripheral pipeline connected with the flange of the transparent test section to form a circulating loop; a photographic device used for recording the cavitation bubble image generated by the throttling element; a damage showing member including a surface protective layer, an intermediate layer and a base layer, the surface protective layer adopts a transparent hydrophobic material, the intermediate layer includes a color developing layer containing potassium ferricyanide and an iron source layer used for providing divalent iron ions, and the damage showing member is installed in the first through hole. The labyrinth flow channel type throttling element cavitation intensity characterization device can improve the real-time performance and accuracy of cavitation intensity characterization.

Description

Technical Field

[0001] This invention relates to the field of fluid machinery and valve testing technology, and in particular to a labyrinth flow channel type throttling device for characterizing cavitation intensity. Background Technology

[0002] When a liquid medium flows through a throttling device, the local flow velocity increases and the static pressure decreases. When the local pressure drops to near or below the saturated vapor pressure of the medium at that temperature, cavitation is likely to occur. When cavitation bubbles collapse in the downstream pressure recovery zone, they generate microjets and shock waves, causing noise, vibration, flow pulsation, and fatigue erosion of the wall surface. Under high pressure differential conditions, this may further evolve into stronger wall impact and failure risk. Therefore, characterizing the cavitation intensity of the throttling device is of great significance for evaluating the safety performance of valves.

[0003] In engineering practice, flow parameters such as choke flow curves, critical pressure difference, flow coefficient, and pressure recovery coefficient are usually used to analyze cavitation characteristics. This type of method can reflect the difference in cavitation intensity generated by different throttling devices under the same operating conditions, but it cannot locate the location of cavitation and the local impact area on the wall.

[0004] While numerical simulations can predict the location of cavitation collapse, their damage models generally rely on empirical formulas, leading to discrepancies between simulation results and measured damage distributions. Although microscopes and three-dimensional optical profilometers can accurately characterize the wall morphology damaged by cavitation, measurements need to be taken after the experiment, making it impossible to achieve a simultaneous correlation study between the dynamic process of cavitation and the local damage response.

[0005] Existing visualization solutions using transparent test sections combined with high-speed photography can typically only observe the generation, development, detachment, and collapse of cavitation clusters, but it is difficult to confirm the actual wall impact location corresponding to cavitation collapse. Relying solely on cavitation images cannot reliably determine the location of the dominant structure causing wall damage.

[0006] Traditional methods such as weight loss analysis of metal samples, surface morphology analysis, or statistical analysis of corrosion pits often require long processing times to generate sufficiently obvious damage features, and offline analysis can only be performed after the testing cycle is over, making it difficult to correspond to the transient cavitation behavior during the test frame by frame. Therefore, there is an urgent need for a characterization component that can be placed inside a transparent test section and generate a locally visible response under cavitation impact, in order to improve the real-time performance, spatial positioning capability, and correlation with flow field images of cavitation intensity characterization. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a labyrinth flow channel type throttling device for characterizing cavitation intensity, which can simultaneously characterize the dynamic process of cavitation and damage response, thereby improving the real-time performance and accuracy of cavitation intensity characterization.

[0008] To achieve the above and other related objectives, the present invention provides a labyrinth flow channel type throttling element cavitation intensity characterization device, the labyrinth flow channel type throttling element cavitation intensity characterization device comprising: The transparent test section is provided with a first through hole and a first countersunk hole that are connected along the axial direction. The first through hole is used to install the throttling device body, and the first countersunk hole is used to install the positioning step. The external piping is connected to the flange of the transparent test section to form a circulation loop; A photographic device for recording images of cavitation bubbles generated by the throttling device; The flaw-revealing component includes a surface protective layer, an intermediate layer, and a base layer. The surface protective layer is made of a transparent hydrophobic material. The intermediate layer includes a color-developing layer containing a ferricyanide color-developing agent and an iron source layer for providing ferrous ions. The flaw-revealing component is installed in the first through hole.

[0009] Preferably, the surface protective layer is polymethyl methacrylate with a thickness of less than or equal to 6 μm.

[0010] Preferably, the coloring layer is located close to the surface protective layer, and the iron source layer is located close to the base layer.

[0011] Preferably, the color development layer is a dry gel film in which potassium ferricyanide is embedded in a cross-linked network, and the iron source layer is a dry gel film in which soluble ferrous salt is embedded in a cross-linked network.

[0012] Preferably, the transparent test section is made of acrylic or silicone-modified PC, the transparent test section has a second through hole extending along the axial direction, the two ends of the peripheral pipeline are flanges, and the two flanges clamp and fix the transparent test section by bolts passing through the second through hole.

[0013] Preferably, the positioning step and the first countersunk hole are circular. The labyrinth flow channel type throttling device for characterizing cavitation intensity further includes an annular mounting sleeve. The inner ring of the annular mounting sleeve is in contact with the outer circumferential surface of the throttling device body. The first axial end of the annular mounting sleeve abuts and limits the positioning step, and the second axial end of the annular mounting sleeve abuts and limits the bottom surface of the first countersunk hole.

[0014] Preferably, the second axial end of the annular mounting sleeve is provided with an arc-shaped slot, the base layer is an arc-shaped metal sheet adapted to the shape of the first through hole, and the damage-revealing component is inserted into the arc-shaped slot.

[0015] Preferably, it also includes a sealing gasket installed between the flange and the transparent test section.

[0016] Preferably, the peripheral pipeline includes a water storage tank, a circulation pump, an inlet control valve, an inlet flow meter, an inlet pressure gauge, an outlet pressure gauge, a back pressure regulating valve, and an outlet flow meter along the circulation loop.

[0017] Preferably, the peripheral pipeline further includes a pressure relief valve, one end of which is connected to the outlet of the circulating pump, and the other end of which is connected to the water storage tank.

[0018] In this invention, the damaged component is not observed offline after conventional abrasion accumulation. Instead, it utilizes the localized high-intensity microjets and transient pressure pulses generated near the wall surface during cavitation bubble collapse. This causes microcracks, localized brittle fractures, or micropores to form on the surface protective layer of the component at the impact location. This allows the working medium to locally penetrate the intermediate layer and triggers a colorimetric reaction between ferrous ions and ferricyanide colorimetric agents, resulting in visible colored spots at the impact location. Because the colorimetric reaction only occurs at locations where the protective layer is locally damaged and the working medium can penetrate the intermediate layer, the colorimetric location has good local correspondence, enabling the visual recording of high-incidence areas of cavitation impact, thereby improving the real-time performance and accuracy of cavitation intensity characterization. Attached Figure Description

[0019] Figure 1 The diagram shown is a schematic diagram of a loop structure according to an embodiment of the present invention.

[0020] Figure 2 The diagram shown is a structural schematic of the transparent test section according to an embodiment of the present invention.

[0021] Figure 3 Displayed as Figure 2 A sectional view.

[0022] Figure 4 The diagram shown is a structural schematic of a throttling element according to an embodiment of the present invention.

[0023] Figure 5 The diagram shown is a structural schematic of a transparent test segment according to an embodiment of the present invention.

[0024] Figure 6 The diagram shown is a structural schematic of a damage-revealing component according to an embodiment of the present invention.

[0025] Figure 7 The diagram shown is a structural schematic of an annular mounting sleeve according to an embodiment of the present invention.

[0026] Figure 8 shows a high-speed photographic image of cavitation bubbles at the labyrinth flow channel of the throttling device, used to visually demonstrate the generation, distribution, and collapse location of cavitation bubbles in an embodiment of the present invention.

[0027] Component designation explanation 100. Throttling element; 110. Throttling element body; 120. Positioning step; 200. Transparent test section; 210. First through hole; 220. First countersunk hole; 230. Second through hole; 300. Photographic device; 400. Damage display component; 410. Surface protective layer; 420. Color development layer; 430. Iron source layer; 440. Base layer; 510. Flange; 520. Bolt; 530. Water storage tank; 540. Circulation pump; 550. Inlet control valve; 560. Inlet flow meter; 570. Inlet pressure gauge; 580. Outlet pressure gauge; 590. Back pressure regulating valve; 591. Outlet flow meter; 592. Pressure relief valve; 600. Annular mounting sleeve; 610. Countersunk screw; 700. Sealing gasket. Detailed Implementation

[0028] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0029] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0030] It should be noted that when a component is said to be "connected" to another component, it can be directly connected to the other component or it can be connected to a component in between. When a component is said to be "set on" another component, it can be directly set on the other component or it may be set to a component in between.

[0031] Please refer to Figures 1-8This embodiment provides a labyrinth-flow-channel type cavitation intensity characterization device. The cavitation element 100 includes a cylindrical cavitation element body 110 and a positioning step 120 located on the outer periphery of the cavitation element body 110. The labyrinth-flow-channel type cavitation intensity characterization device includes a transparent test section 200, peripheral piping, a photographic device 300, and a flaw-displaying component 400. The transparent test section 200 has a first through hole 210 and a first countersunk hole 220 that are axially connected. The first through hole 210 is used to install the cavitation element body 110, and the first countersunk hole 220 is used to install the positioning step 120. The peripheral piping is connected to the transparent test section 200 via a flange to form a circulation loop. The photographic device 300 is used to record images of cavitation bubbles generated by the cavitation element 100. The damage-revealing component 400 includes a surface protective layer 410, an intermediate layer, and a base layer 440. The surface protective layer 410 is made of a transparent hydrophobic material. The intermediate layer includes a color-revealing layer 420 containing potassium ferricyanide and an iron source layer 430 for providing ferrous ions. The damage-revealing component 400 is installed in the first through hole 210.

[0032] The cavitation test process in this embodiment is as follows: First, the throttling device 100 to be tested and the flaw-detecting component 400 are inserted axially into the first through hole 210 of the transparent test section 200, and the positioning step 120 is installed into the first countersunk hole 220. Then, the transparent test section 200 and the external pipeline are connected by a flange structure. After connection, the flange structure provides axial preload to the positioning step 120. The base layer 440 of the flaw-detecting component 400 faces the inner wall of the first through hole 210, and the working surface of the flaw-detecting component 400 faces the throttling device 100 to be tested. The imaging device 300 is aligned with the side wall of the transparent test section 200, and the lens focal length is adjusted so that the field of view of the imaging device 300 at least covers the throttling device 100 and the flaw-detecting component 400.

[0033] The peripheral pipeline is opened to form a circulation loop, and its parameters are adjusted to the preset operating conditions. After the flow field stabilizes, the imaging device 300 is activated to record the generation, growth, coalescence, and collapse of cavitation bubbles. Simultaneously, the imaging device 300 records the distribution image of the blue spots on the damaged component 400. One or multiple imaging devices 300 can be used. When multiple imaging devices 300 are used, one device can record the development process of cavitation bubbles, while another device records the development process of the blue spots. Frames in the recorded videos from the two devices are aligned using timestamps. The cavitation bubble images captured by the imaging device 300 are shown below. Figure 8 As shown, the dynamic development process of cavitation bubbles in the flow channel can be clearly observed.

[0034] This embodiment uses a damage-displaying component 400 to convert the local high-intensity microjets and pressure pulses caused by cavitation bubble collapse into visible spots. This allows the wall damage trend, which would normally require a long accumulation period to become apparent, to be quickly indicated by a precursor damage-displaying method. This enables in-situ, synchronous, and visual recording of the cavitation dynamic process and the local impact response.

[0035] Since the formation of cavitation spots depends on the localized damage to the surface protective layer 410 and the subsequent localized color development reaction, the location of the spots can reflect the spatial distribution characteristics of cavitation impact on the wall surface. By aligning the high-speed images acquired by the imaging device 300 with the color development images, a correspondence can be established between local flow channel structures such as maze corners, expansion sections, contraction sections, or recirculation zones and their corresponding impact areas, which is beneficial for identifying the key structural locations that induce cavitation damage. This embodiment not only improves the reliability of cavitation intensity evaluation but also provides guiding experimental basis for the structural optimization direction of the throttling device 100.

[0036] Explanation of the principle of visible damage components: In this invention, the damage-displaying component 400 preferably includes a surface protective layer 410, a color-developing layer 420, an iron source layer 430, and a base layer 440. The surface protective layer 410 is located on the outermost side and faces directly towards the working medium, serving to isolate water, limit flow, reduce background wetting, and maintain the initial colorless state; the color-developing layer 420 is used to contain ferricyanide color-developing agent; the iron source layer 430 is used to contain iron source material that can release divalent iron ions; and the base layer 440 is used to provide mechanical support, installation strength, and curved surface adhesion capability.

[0037] Under normal flow conditions but weak or non-existent cavitation impact, the surface protective layer 410 remains continuous, and the working medium has difficulty entering the intermediate layer over a large area. Although the coloring layer 420 and the iron source layer 430 are arranged in close proximity, due to the lack of effective penetration channels and local dissolution conditions, it is not easy for obvious coloring to occur. Therefore, the damaged component 400 as a whole remains colorless or near-colorless.

[0038] When cavitation bubbles collapse near the throttling element 100, the cavitation bubbles near the wall form microjets pointing towards the wall under the action of an asymmetric pressure field, accompanied by transient high-pressure pulses. This type of local impact is characterized by short action time, small action area, and high peak stress, which can cause brittle fracture, microcrack propagation, or micropore penetration in the surface protective layer 410 at local locations. The working medium then enters the intermediate layer along the microcracks or micropores, causing the ferrous ions in the iron source layer 430 to dissolve and migrate. The migrated ferrous ions and the ferricyanide colorant in the coloring layer 420 form a blue coloring product after local contact, thus forming a high-contrast color spot at the impact location. By comparing the blue spot photograph with multiple cavitation bubble photographs before the appearance of the blue spot, the generation and development process of the cavitation bubbles causing the blue spot can be traced, ultimately relating to the local geometry of the throttling element 100, achieving precise location and structural attribution of the cavitation source.

[0039] Since the color development reaction depends on the local liquid infiltration caused by the local damage to the protective layer, the resulting color spots generally correspond to the effective area of ​​cavitation impact, rather than the uniform discoloration of the entire damaged component 400.

[0040] In this embodiment, the stacking order of the coloring layer 420 and the iron source layer 430 in the damage-revealing component 400 is not limited. Before cavitation occurs, the damage-revealing component 400 in this embodiment is colorless. The peak pressure of the microjets generated by the collapse of cavitation bubbles is 300~800MPa, and the action time is 2~10μs. This impact load can cause the 2~6μm thick PMMA surface protective layer to form penetrating microcracks. The working medium penetrates into the interior through the microcracks. Divalent iron ions or metallic iron particles in the iron source layer 430 enter the coloring layer 420 and react with potassium ferricyanide to develop a color. The color response time is ≤1s, the contrast is high, and it only appears in the cavitation impact area. There is no background color in the non-cavitation area, and a stable, high-contrast blue spot is formed at the corresponding impact position.

[0041] In one embodiment, the surface protective layer is polymethyl methacrylate (PMMA) with a thickness of less than or equal to 6 μm. PMMA is a transparent, brittle polymer material. When cavitation impact does not occur or is weak, the PMMA film layer can remain continuous, reducing the risk of the intermediate layer being exposed to the water environment for a long time. When a localized high-intensity impact occurs, the PMMA film layer can form cracks, holes, or fragmentation edges in the impacted micro-area, allowing the working medium to locally enter the intermediate layer and trigger color development, facilitating the observation and recording of the cavitation results.

[0042] In one embodiment, the colorimetric layer 420 is located near the surface protective layer, and the iron source layer 430 is located near the substrate layer. When the microjets generated by cavitation collapse partially penetrate the surface protective layer 410 to form microporous channels, the working medium, as it permeates inward along these channels, first wets and exposes the colorimetric layer 420 and releases potassium ferricyanide, and then reaches the iron source layer 430 and releases ferrous ions or metallic iron particles. This embodiment ensures that the ferrous ions or metallic iron particles in the iron source layer 430 must pass through the colorimetric layer 420 during their outward diffusion, thereby ensuring that the ferrous ions or metallic iron particles in the iron source layer 430 participate in the colorimetric reaction.

[0043] In one embodiment, the color development layer is a dry gel film in which potassium ferricyanide is embedded in a cross-linked network, and the iron source layer is a dry gel film in which soluble ferrous salts are embedded in a cross-linked network. The polymer matrix in the dry gel film can be polyvinyl alcohol, sodium alginate, polyacrylamide, etc. Potassium ferricyanide is added when preparing the precursor sol, or soluble ferrous salts such as ferrous sulfate and ferrous chloride are added when preparing the precursor sol. The film is then formed by spin coating, blade coating, or dip-coating, and then dried to obtain the corresponding dry gel film.

[0044] In one embodiment, the transparent test section 200 is made of acrylic or siloxane-modified PC. The transparent test section 200 is provided with a second through hole 230 extending along the axial direction. The two ends of the peripheral pipeline are flanges 510. The two flanges 510 clamp and fix the transparent test section 200 by bolts 520 passing through the second through hole 230.

[0045] In one embodiment, the positioning step 120 and the first countersunk hole 220 are circular. The labyrinth flow channel type throttling device for characterizing cavitation intensity also includes an annular mounting sleeve 600. The inner ring of the annular mounting sleeve 600 is in contact with the outer peripheral surface of the throttling device body 110. The first axial end of the annular mounting sleeve 600 is abutted and limited by the positioning step 120, and the second axial end of the annular mounting sleeve 600 is abutted and limited by the bottom surface of the first countersunk hole 220.

[0046] This embodiment, by using the annular mounting sleeve 600, can reduce deformation or damage to the transparent test section 200 when replacing the throttling device 100 to be tested, thus ensuring hydrodynamic stability. Furthermore, the annular mounting sleeve 600 can compensate for the thickness differences of the positioning steps 120 of different throttling devices 100, facilitating comparative studies of different throttling devices 100 under unified geometric and hydrodynamic parameters.

[0047] Please refer to Figure 7 In one embodiment, the second axial end of the annular mounting sleeve 600 is provided with a countersunk screw 610, the base layer 440 is a semi-circular arc-shaped metal sheet adapted to the shape of the first through hole 210, and the damage-revealing component 400 is clamped between the throttling component 100 and the annular mounting sleeve 600 and is connected by the countersunk screw 610.

[0048] In one embodiment, one end of the arc-shaped metal sheet is provided with a flange, and the arc-shaped metal sheet is fixed to the shaft end of the annular mounting sleeve 600 by fasteners passing through the flange, and can be replaced at the same time as the throttling device.

[0049] In one embodiment, the second axial end of the annular mounting sleeve 600 is provided with an arc-shaped slot, the base layer 440 is an arc-shaped metal sheet adapted to the shape of the first through hole 210, and the exposed component 400 is inserted into the arc-shaped slot.

[0050] In one embodiment, one end of the arc-shaped metal sheet is provided with a flange, and the arc-shaped metal sheet is fixed to the axial second end of the annular mounting sleeve 600 by fasteners passing through the flange.

[0051] In one embodiment, one end of the arc-shaped metal sheet is provided with a positioning protrusion, and the sidewall of the arc-shaped slot is provided with a circular positioning groove that conforms to the shape of the positioning protrusion. During installation, the positioning protrusion is engaged into the circular positioning groove by the elastic deformation of the arc-shaped metal sheet, preventing the arc-shaped metal sheet from axially dislodging from the arc-shaped slot. First, a positioning protrusion is formed by pressing a pneumatic punch onto one end of the arc-shaped metal sheet, and then an intermediate layer and a surface protective layer are prepared on the arc-shaped metal sheet.

[0052] In one embodiment, one end of the arc-shaped metal sheet is provided with an axially extending positioning protrusion, and the side wall of the arc-shaped slot is provided with a strip-shaped positioning groove adapted to the shape of the positioning protrusion. During installation, the positioning protrusion is embedded in the strip-shaped positioning groove to prevent the damaged component from rotating circumferentially.

[0053] In one embodiment, the sidewall of the arc-shaped slot is provided with a plurality of strip-shaped positioning grooves, and each strip-shaped positioning groove is arranged circumferentially.

[0054] In one embodiment, the substrate 440 is made of aluminum foil or copper foil with a thickness of 20-80 μm, preferably 80 μm aluminum foil.

[0055] In one embodiment, a sealing gasket 700 is installed between the flange 510 and the transparent test section 200.

[0056] In one embodiment, the sealing gasket 700 is a graphite gasket or a silicone gasket.

[0057] In one embodiment, the end face of the sealing gasket 700 is provided with an annular pressure relief groove to reduce the elastic deformation of the transparent test section and improve the observation accuracy of cavitation bubbles.

[0058] In one embodiment, the peripheral pipeline includes a water storage tank 530, a circulation pump 540, an inlet control valve 550, an inlet flow meter 560, an inlet pressure gauge 570, an outlet pressure gauge 580, a back pressure regulating valve 590, and an outlet flow meter 591, arranged sequentially along the circulation loop.

[0059] In one embodiment, the working medium stored in the water storage tank 530 is room temperature deionized water. The top of the water storage tank 530 is provided with a vent hole to maintain constant pressure on the liquid level. The water storage tank 530 is provided with a level gauge to monitor the remaining amount of the working medium in real time.

[0060] The circulating pump 540 provides the power source for the circulation loop. The circulating pump 540 is a variable frequency centrifugal pump; the total flow rate of the loop is controlled by adjusting the speed of the variable frequency motor, thereby adjusting the cavitation number of the throttling element 100. The inlet control valve 550 is a manual or electric ball valve. During system start-up and shutdown, the flow rate is coarsely adjusted using the inlet control valve 550, and during testing, it works in conjunction with the back pressure regulating valve 590 to achieve flow stabilization. The back pressure regulating valve 590 is an electric needle valve or a proportional valve. By adjusting the opening of the back pressure regulating valve 590, the outlet resistance is changed, thereby precisely controlling the pressure difference across the throttling element 100, and thus regulating the cavitation conditions.

[0061] In one embodiment, the peripheral pipeline also includes a pressure relief valve 592, one end of which is connected to the outlet of the circulating pump 540, and the other end of which is connected to the water storage tank 530.

[0062] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered to be within the scope of this specification. When technical features of different embodiments are embodied in the same drawing, it can be regarded as the drawing also disclosing examples of combinations of the various embodiments involved.

[0063] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A labyrinth-type throttling device for characterizing cavitation intensity, wherein the throttling device comprises a cylindrical throttling device body and a positioning step located on the outer periphery of the throttling device body, characterized in that, include: The transparent test section is provided with a first through hole and a first countersunk hole that are connected along the axial direction. The first through hole is used to install the throttling device body, and the first countersunk hole is used to install the positioning step. The external piping is connected to the flange of the transparent test section to form a circulation loop; A photographic device for recording images of cavitation bubbles generated by the throttling device; The flaw-revealing component includes a surface protective layer, an intermediate layer, and a base layer. The surface protective layer is made of a transparent hydrophobic material. The intermediate layer includes a color-revealing layer containing potassium ferricyanide and an iron source layer for providing ferrous ions. The flaw-revealing component is installed in the first through hole.

2. The labyrinth flow channel type throttling element cavitation intensity characterization device according to claim 1, characterized in that, The surface protective layer is polymethyl methacrylate with a thickness of less than or equal to 6 μm.

3. The labyrinth flow channel type throttling element cavitation intensity characterization device according to claim 1, characterized in that, The coloring layer is located near the surface protective layer, and the iron source layer is located near the base layer.

4. The labyrinth flow channel type throttling element cavitation intensity characterization device according to claim 1, characterized in that, The color-developing layer is a dry gel film in which ferricyanide color-developing agent is embedded in a cross-linked network, and the iron source layer is a dry gel film in which soluble ferrous salt is embedded in a cross-linked network.

5. The labyrinth flow channel type throttling element cavitation intensity characterization device according to claim 1, characterized in that, The transparent test section is made of acrylic or silicone-modified PC. The transparent test section has a second through hole extending along the axial direction. The two ends of the peripheral pipeline are flanges. The two flanges clamp and fix the transparent test section through bolts passing through the second through hole.

6. The labyrinth flow channel type throttling element cavitation intensity characterization device according to claim 5, characterized in that, The positioning step and the first countersunk hole are circular. The labyrinth flow channel type throttling device for cavitation intensity characterization also includes an annular mounting sleeve. The inner ring of the annular mounting sleeve is in contact with the outer circumferential surface of the throttling device body. The first axial end of the annular mounting sleeve abuts and limits the positioning step. The second axial end of the annular mounting sleeve abuts and limits the bottom surface of the first countersunk hole.

7. The labyrinth flow channel type throttling element cavitation intensity characterization device according to claim 6, characterized in that, The second axial end of the annular mounting sleeve is provided with an arc-shaped slot, the base layer is an arc-shaped metal sheet adapted to the shape of the first through hole, and the damage-revealing component is inserted into the arc-shaped slot.

8. The labyrinth flow channel type throttling element cavitation intensity characterization device according to claim 6, characterized in that, It also includes a sealing gasket installed between the flange and the transparent test section.

9. The labyrinth flow channel type throttling element cavitation intensity characterization device according to claim 1, characterized in that, The peripheral pipeline includes a water storage tank, a circulation pump, an inlet control valve, an inlet flow meter, an inlet pressure gauge, an outlet pressure gauge, a back pressure regulating valve, and an outlet flow meter along the circulation loop.

10. The labyrinth flow channel type throttling element cavitation intensity characterization device according to claim 9, characterized in that, The peripheral pipeline also includes a pressure relief valve, one end of which is connected to the outlet of the circulating pump, and the other end of which is connected to the water storage tank.

Images