Cavitation erosion measurement simulation system, method and application in solid-liquid two-phase fluid

Abstract

The present invention belongs to the technical field of mechanical material testing, and discloses a system, method and application for measuring cavitation of group cavitation bubbles in solid-liquid two-phase fluids, including a flow circulation water tank for adjusting the characteristics of solid phase particles, a target wall manufacturing and precision adjustment device for manufacturing target wall surfaces, and using a wall surface micro-adjustment control mechanism to realize the characterization of the relative position of the cavitation zone from the target wall surface through the movement of the platform, a multi-beam split laser cavitation zone generation device for controlling the cavitation zone scale and the number of cavitation bubbles, a cavitation and wear multi-means measurement system for inferring the cavitation collapse impact force based on the shock wave, micro-jet velocity and target wall deformation, and a target cavitation / wear data processing and analysis system for evaluating the cavitation resistance and wear resistance of the target material. The present invention can realize a feasible, highly applicable, low-cost, low-consumption, parameter-controllable static laser cavitation verification approach to quantitatively evaluate the cavitation resistance and wear resistance of materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of mechanical material testing, and in particular relates to a system, method and application of cavitation measurement simulation of group cavitation in solid-liquid two-phase fluid based on laser controllable cavitation. Background Art

[0002] At present, when ship propellers, turbines and other equipment rotate at high speed and the local pressure is lower than the saturated steam pressure, a large number of cavitation bubbles will be generated. When the cavitation bubbles encounter high pressure near the impeller surface, the volume will be compressed sharply and collapse near the wall, releasing huge energy to attack the wall, causing cavitation damage to the material, seriously affecting the normal operation law and energy conversion efficiency of the equipment. Cavitation erodes the surface material, thereby destroying the solid boundary of the flow. Cavitation can erode various solids, and all metal and non-metal solids are susceptible to cavitation damage. At the same time, the sediment content in the coastal areas and rivers of the Yellow Sea and Bohai Sea in my country is very high. The sand-containing water flow affects the operation of propellers and turbines with its unique movement law. The cavitation and cavitation phenomenon in the sand-containing water flow changes the cavitation conditions and erosion intensity of the fluid due to the influence of sediment, and has different cavitation laws and erosion mechanisms from general clean water projects. When the sediment particles moving with the water flow come into contact with the solid boundary, friction and impact will inevitably occur, resulting in different degrees of damage to both sides, that is, wear. Wear and erosion on the surface of materials is not only related to the characteristics of the material itself, but also to the sand content, sand particle size, mineral composition and water flow state when the material is certain. Neither its form nor its cause is single. When the two properties of wear and cavitation are intertwined, the mechanism becomes more complicated.

[0003] Under the combined effect of cavitation and sediment wear, the flow parts of the turbine and hydraulic flow structures will be severely damaged in a short period of time, affecting the normal operation of power stations and water discharge structures. Therefore, sediment wear and cavitation (abbreviated as abrasion) of the flow surfaces of hydraulic machinery such as turbines, water pumps, etc. and hydraulic structures such as spillways and water discharge holes are major issues in my country's national economic construction that need to be urgently resolved.

[0004] At present, there are few studies on cavitation in solid-liquid two-phase flow, which are mainly limited to material destruction tests. So far, there are few results on the study of cavitation mechanism and cavitation destruction mechanism in solid-liquid two-phase flow. The key reason for this situation is that the cavitation mechanism in solid-liquid two-phase flow is very complicated, and it is very difficult to conduct theoretical analysis and experimental research on it. When comparing and analyzing the material destruction test results seen so far, it is found that due to different test conditions, test methods, test equipment, measurement methods and sand characteristics, it is difficult to obtain consistent results in experimental research. Sometimes there are even large discrepancies, and a unified and convincing result cannot be obtained. Some scholars believe that the generation of cavitation zones will cause solid particles to impact the material surface at high speed, especially in the process of cavitation collapse, the solid particles will move at high speed with the bubble wall, causing cavitation on the material surface. Some scholars also believe that the narrow sand in the water flow will inhibit the growth of cavitation bubbles, thereby reducing cavitation damage. Some scholars also believe that the influence of sand content on cavitation varies with the sand content in the water and the water flow conditions. In fact, the cavitation and abrasion caused by sand in the water and their interaction involve many aspects and are very complicated: first, the sand in the water may increase the number of air nuclei in the water, leading to the early generation of cavitation; second, the sand in the water flow will also affect the development of cavitation, the growth and collapse of cavitation bubbles, and thus affect the damage of cavitation. In addition, the two destructive effects of cavitation and abrasion may also affect each other: first, the characteristic of cavitation damage is honeycomb pits, so the sand particles may easily knock off the convex body at the edge of the pit, thereby aggravating the damage; second, the sand wear may polish the surface of the material, thereby reducing the amount of cavitation. In addition, sand wear will also destroy the surface finish of the material in the initial stage of cavitation and shorten the incubation period of cavitation damage. The mutual influence of the above factors may depend on factors such as the amount of sand in the water, the characteristics of the sand particles themselves, and the state of the water flow.

[0005] In traditional methods, the study of cavitation characteristics in solid-liquid two-phase fluids is mainly focused on macroscopic methods such as numerical calculations and model tests. The test conditions (water quality parameters, environmental parameters, etc.) are difficult to control and have great randomness. Only the overall evaluation of system performance can be carried out. It is difficult to obtain the quantitative relationship between the wall material characteristics, solid sand characteristics (size, concentration, etc.), cavitation characteristics (size, density, distribution, etc.), water flow characteristics (flow rate, temperature, static pressure, viscosity coefficient, etc.) and cavitation characteristics, which brings great difficulties to the study of cavitation mechanism in solid-liquid two-phase fluids. Therefore, it is of great theoretical significance and engineering practice value to explore new technical means and experimental test methods for the study of cavitation in solid-liquid two-phase fluids, quantitatively study the cavitation movement and collapse impact characteristics near the wall under different solid particles, cavitation characteristics, and water flow characteristics, and establish the mutual influence and action model between cavitation and solid particles.

[0006] Laser cavitation technology refers to the use of high-energy lasers focused on liquids through an optical system to form cavitation zones with different sizes, densities, and distribution characteristics in the liquid. The characteristics of the cavitation zones can be controlled by adjusting laser parameters and liquid parameters. Actual measured data show that laser cavitation technology can generate controllable cavitation zones with size, density, and spatial distribution near the wall in solid-liquid two-phase fluids. High-speed photography technology and pressure sensor measurement can be used to quantitatively test cavitation pulsation, cavitation collapse shock waves, cavitation collapse jets, and the interaction characteristics between solid particles and cavitation. At the same time, by adjusting the solid-phase particle characteristics and water flow characteristics in the solid-liquid two-phase fluid, quantitative testing and analysis of cavitation erosion and wear in the solid-liquid two-phase fluid can be achieved.

[0007] People have been studying the cavitation phenomenon for more than a hundred years, but the mechanism of cavitation is still not fully understood, and no very effective method to inhibit cavitation has been found. The difficulty of cavitation research lies in the fact that it is a complex physical process of multiphase, transient, microscopic and random, involving instantaneous gas-liquid phase change, energy transfer and material response. Therefore, the relevant experimental work is often very difficult, and the theoretical modeling process is also quite complicated. Despite this, due to the important scientific significance and great practical value of cavitation research, scientists and technicians from all over the world are still actively conducting relevant research. At present, the United States, Japan, Russia and other countries have accumulated rich experimental data and practical experience through a lot of research and practice; in China, the Chinese Academy of Sciences, Tsinghua University, Shanghai Jiaotong University, Xi'an Jiaotong University, Sichuan University, Hohai University and other units are also conducting research on cavitation mechanism and anti-cavitation technology.

[0008] The mechanical properties of materials, such as strength, hardness, plasticity, and toughness, are closely related to the cavitation resistance of materials. However, due to the complexity of the cavitation process, the ability of materials to resist cavitation is often determined by the comprehensive mechanical properties of the materials. Therefore, it is difficult to establish a quantitative relationship between the mechanical properties of materials and their cavitation resistance. From a qualitative point of view, materials with good cavitation resistance should have good toughness, elasticity, strength, hardness, work hardening ability, and fatigue limit. The research on cavitation resistance material technology has always attracted a large number of researchers. In the past decade, there have been many related research papers and results. However, due to the complexity of the cavitation phenomenon itself and the fact that people have not yet fully understood the mechanism of cavitation, the research on cavitation resistance material technology has always faced great difficulties. In short, it has become a consensus that the influence of cavitation factors must be considered in high-speed flow machinery and hydraulic structures. From the research progress of various anti-cavitation technologies, the research on surface shape design, aeration cavitation reduction, anti-cavitation materials and other technologies has achieved certain results. However, these technologies themselves have limitations to varying degrees, and cavitation cannot be cured by relying solely on the above technologies. Therefore, the research on anti-cavitation technology needs to be advanced in a broader and deeper direction. Whether it is the development of new methods or the improvement of existing methods, it depends on a further understanding of the cavitation process and mechanism.

[0009] Mechanical action mechanism believes that mechanical action is the main cause of cavitation. The strength of mechanical impact alone is enough to destroy any material. At present, the mechanical action mechanism of cavitation damage mainly includes two theories: microjet and shock wave. For example, Philipp et al. studied the relationship between the morphology of cavitation collapse and the mode of cavitation, and concluded that the shock wave of cavitation collapse is the main cause of cavitation. In 2008, Brujan et al. measured the instantaneous impact of collapse at 68μm from the cavitation bubble wall through experiments to reach about 1GPa. The research of He Mingzhao, Hu Yingying and others from Tsinghua University also believes that the shock wave generated by cavitation collapse is the main cause of cavitation damage. Hu Yingying's calculation shows that when the dimensionless distance between the cavitation bubble and the wall is 1.9, the pressure generated by the high-pressure pulse on the wall is about 26MPa, while the force of the jet on the wall is only about 0.1MPa. Therefore, she inferred that at least when the dimensionless distance is greater than 1, the high-pressure pulse is the main cause of solid wall cavitation. Mechanical action is the conventional action mechanism of cavitation damage. However, there is still some controversy about the specific form of mechanical action. The main points of controversy are: 1. Is the dominant way for the energy generated by the collapse of cavitation to be transferred to the wall and cause cavitation erosion micro-jet or shock wave? 2. Is the surface pitting the result of a single cavitation collapse impact or fatigue damage behavior of multiple impacts? At the same time, cavitation damage is often a complex process involving multiple effects such as mechanics, chemistry, electrochemistry and thermal effects. In a specific environment, chemical corrosion, electrochemical corrosion and thermal effects may play an extremely important role in surface cavitation damage.

[0010] There are few studies on the cavitation mechanism and cavitation destruction mechanism in solid-liquid two-phase flow. As far as the current work is concerned, most of the work is experimental research on the resistance of materials to cavitation and wear. The key reason for this is that the cavitation mechanism in solid-liquid two-phase flow is very complex, and it is very difficult to conduct theoretical analysis and experimental research on it.

[0011] The sediment content in my country's rivers is very high, so cavitation and sediment wear are very prominent. The mechanism of cavitation and wear in sand-laden water has long been controversial. To clarify this issue, in-depth theoretical analysis and meticulous experimental observation are necessary. Over the years, my country's water conservancy and hydropower workers and material researchers have done a lot of work in this field, such as Wang Zhechang from the Institute of Metal Research, Chinese Academy of Sciences (Shenyang), Wu Peihao and Yao Qipeng from China Institute of Water Resources and Hydropower Research (Beijing), Gu Sihang and Wang Zhigao from the National Water Machine Abrasion Test Center (Tianjin), and He Xiaokui from the Institute of Water Resources of the Yellow River Conservancy Commission (Zhengzhou) of the Ministry of Water Resources. They have conducted a lot of research on the causes and influencing factors of this failure form; the Institute of Corrosion and Protection of the Chinese Academy of Sciences and Xi'an Jiaotong University have also jointly conducted research on the corrosion resistance, erosion wear and corrosion fatigue performance of metastable materials, high-strength and toughness stainless steel, superelastic steel, surface engineering materials, wear-resistant high-chromium cast iron materials, etc. under various variable parameters, looking for the interaction between wear and cavitation and corrosion from a microscopic perspective.

[0012] Through the above analysis, the problems and defects of the prior art are as follows:

[0013] In the traditional analysis method of cavitation characteristics in solid-liquid two-phase fluids, the experimental conditions are difficult to control and have a high degree of randomness. Only an overall evaluation of the system performance can be performed. It is difficult to obtain the quantitative relationship between the wall material properties, solid sand properties, cavitation properties, water flow properties and cavitation characteristics, which brings great difficulties to the study of the cavitation mechanism in solid-liquid two-phase fluids. Summary of the invention

[0014] In view of the problems existing in the prior art, the present invention provides a system, method and application for measuring cavitation erosion of group cavitation in a solid-liquid two-phase fluid.

[0015] The present invention is implemented in that a system for measuring cavitation erosion of a group of cavitation bubbles in a solid-liquid two-phase fluid comprises:

[0016] Flow circulation water tank, used to adjust the characteristics of solid particles;

[0017] The target wall manufacturing and precision adjustment device is used to manufacture the target wall and use the wall fine adjustment control mechanism to achieve the relative position of the cavitation area from the target wall by moving the platform;

[0018] A multi-beam splitting laser cavitation zone generation device is used to control the size of the cavitation zone and the number of cavitation bubbles;

[0019] Cavitation and wear multi-measurement system, used to infer the cavitation collapse impact force based on the shock wave, microjet velocity and target wall deformation;

[0020] The target cavitation / wear data processing and analysis system is used to analyze and compile statistics on target cavitation and wear data under different conditions, and combine theoretical analysis and numerical calculation results to reveal the cavitation and wear mechanism and their interaction rules in solid-liquid two-phase fluids, and evaluate the target's anti-cavitation and wear resistance from the aspects of material and surface morphology.

[0021] Furthermore, the flow circulation water tank is composed of a flow rate controllable water pump, a water tank, and a solid phase particle measuring and adjusting device. The two ends of the flow rate controllable water pump are connected to the two sides of the water tank through connecting pipes, and the solid phase particle measuring and adjusting device is arranged inside the water tank.

[0022] Furthermore, the solid phase particles are spherical plastic sands of different sizes.

[0023] Furthermore, the target wall manufacturing and precision adjustment device includes target selection, design, processing and wall fine-adjustment control mechanism. The target material is made of metal and non-metal. The target shape is selected based on the target thickness, appearance shape, surface roughness and surface morphology. The wall fine-adjustment control mechanism is used to perform precise adjustments in three dimensions in space, so as to realize the characterization of the relative spatial position of the cavitation zone from the target wall by moving the platform.

[0024] Furthermore, the multi-beam splitting laser cavitation zone generating device includes multiple lasers, a beam splitting device, a beam focusing device, a timing control device, and a laser power supply. The cavitation zone scale and the bubble quantity characteristics are controlled by adjusting the laser energy, pulse width, pulse waveform structure, and the splitting ratio of the beam splitter group.

[0025] Furthermore, the multi-means measurement system for cavitation and wear includes an imaging illumination optical device, a high-speed photography device, a pressure sensing array, and an optical fiber strain sensing array;

[0026] The illumination optical device is used to realize illumination of the cavitation area, and is used for high-speed camera to image the cavitation with high quality, and involves the intensity of the illumination light source and the selection of the illumination angle;

[0027] The high-speed camera is used to measure the cavitation size, cavitation pulsation characteristics, cavitation collapse shock wave, cavitation collapse microjet, and solid phase particle movement;

[0028] The pressure sensor array is used to measure the shock wave and noise of cavitation collapse radiation;

[0029] The optical fiber strain sensing system measures the transient deformation of the target material wall.

[0030] Furthermore, the different conditions of the target cavitation wear data include targets of different materials / surface morphologies, cavitations of different sizes, solid particles of different sizes / concentrations, and the spatial position of the cavitation area relative to the target wall.

[0031] Another object of the present invention is to provide a method for measuring cavitation erosion of a group of cavitation bubbles in a solid-liquid two-phase fluid. The method for measuring cavitation erosion of a group of cavitation bubbles in a solid-liquid two-phase fluid comprises:

[0032] Step 1: Simulation of cavitation movement and collapse cavitation / abrasion characteristics in solid-liquid two-phase fluid;

[0033] Step 2: High-energy laser cavitation characteristics and cavitation flow field control, high-speed photography, pressure sensor array, and optical fiber strain sensor array to measure the cavitation field change process;

[0034] Step 3: Experimental test and data analysis of the characteristics of cavitation erosion and particle wear in solid-liquid two-phase flow;

[0035] Step 4: Evaluation and analysis of the abrasion resistance of targets with different materials / surface morphologies.

[0036] Furthermore, the experimental test and data analysis of the characteristics of cavitation erosion and particle wear in the solid-liquid two-phase flow in step 3 specifically include:

[0037] (1) Through controllable laser cavitation, the cavitation characteristics of the target wall caused by multiple cavities of different sizes and at different spatial positions relative to the target wall are analyzed;

[0038] (2) By changing the solid phase particle characteristics, water flow parameters, and different water qualities, the interaction between microparticles and cavitation flow field and its effect on cavitation erosion are tested;

[0039] (3) By selecting different target types and changing the target surface morphology through processing methods, the influence of target material and surface morphology on cavitation is tested;

[0040] (4) Use direct and indirect multi-measurement methods to obtain quantitative data on target cavitation and wear.

[0041] Another object of the present invention is to provide a system for testing the cavitation resistance and wear resistance of hydraulic machinery materials, wherein the system for testing the cavitation resistance and wear resistance of hydraulic machinery materials adopts a group cavitation measurement system in a solid-liquid two-phase fluid.

[0042] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0043] First, in view of the technical problems existing in the above-mentioned prior art and the difficulty of solving the problems, the technical solutions to be protected by the present invention and the results and data during the research and development process are closely combined to analyze in detail and deeply how the technical solutions of the present invention solve the technical problems, and some creative technical effects brought about after solving the problems. The specific description is as follows:

[0044] Aiming at the problems of cavitation and wear on the wall of hydraulic machinery in solid-liquid two-phase fluid, the present invention analyzes the multi-phase, transient, microscopic and random complex cavitation physical processes, and invents a controllable generation of laser group cavitation in solid-liquid two-phase fluid as well as high-speed photography, pressure shock array, optical fiber strain sensor array measurement and other technologies, forming a research framework and technical route for the cavitation mechanism of cavitation in solid-liquid two-phase fluid and the quantitative measurement of target cavitation and wear intensity.

[0045] The present invention has the following three meanings:

[0046] (1) The present invention proposes a complete research platform for the laser cavitation flow field and target wall cavitation and wear characteristics in solid-liquid two-phase fluids, breaks through key technologies such as the cavitation / wear mechanism in solid-liquid two-phase fluids, laser cavitation flow field control in solid-liquid two-phase fluids, and quantitative measurement and analysis of cavitation / wear intensity. The controllable laser cavitation technology is applied to the fields of hydraulic machinery cavitation, wear mechanism and material anti-cavitation and wear resistance evaluation and analysis, providing a theoretical and static verification platform for the development of hydraulic machinery anti-abrasion materials and surface morphology design.

[0047] (2) On the scientific level, the present invention belongs to the interdisciplinary field of laser technology, hydraulics, fluid mechanics, optical measurement, etc. By establishing a theoretical model of cavitation pulsation, cavitation collapse shock wave / microjet, and the interaction between solid particles and cavitation pulsation / collapse, it is of great significance to clarify the mechanism of hydraulic mechanical cavitation and wear.

[0048] (3) At the application level, for the development of anti-cavitation materials and surface morphology design of hydraulic machinery, a feasible, highly applicable, low-cost, low-consumption, and parameter-controllable static laser cavitation verification method can be realized to quantitatively evaluate the anti-cavitation and wear resistance of materials.

[0049] Second, considering the technical solution as a whole or from the perspective of the product, the technical effects and advantages of the technical solution to be protected by the present invention are described in detail as follows:

[0050] By applying high-energy laser cavitation to generate cavitation zones with controllable characteristics, and at the same time coordinating the design of solid-liquid two-phase fluid water tanks, target wall micro-adjustment systems, etc., and using high-speed photography, pressure sensor arrays, and fiber optic strain sensor array measurement technologies, the microscopic mechanism of cavitation erosion in solid-liquid two-phase fluids and the quantitative analysis of material cavitation and wear characteristics can be achieved. It has the advantages of controllability, low cost, low consumption, and safety, and can inject new blood into the research on cavitation, wear, and anti-cavitation and wear-resistant materials of hydraulic machinery such as turbines and water pumps in solid-liquid two-phase flow.

[0051] Third, as auxiliary evidence of the inventiveness of the claims of the present invention, it is also reflected in the following important aspects:

[0052] (1) The expected benefits and commercial value of the technical solution of the present invention after transformation are:

[0053] After the technical solution of the present invention is transformed, it can provide a static laser cavitation verification solution and static testing equipment with strong applicability, low cost, low consumption, and controllable parameters for the development of anti-cavitation materials and surface morphology design problems for steam-water turbine hydraulic machinery equipment and ship propellers, quantitatively evaluate the anti-cavitation and wear performance of materials, greatly save the cost of sample design, and have significant economic benefits.

[0054] (2) The technical solution of the present invention fills the technical gap in the industry at home and abroad:

[0055] The sediment content in my country's rivers is very high, so cavitation and sediment wear are very prominent. The cavitation and wear mechanism in sediment-laden water has long been a hot topic of debate. To understand this issue, in-depth theoretical analysis and careful experimental observation are necessary.

[0056] Regarding the cavitation mechanism in solid-liquid two-phase flow and the microscopic quantitative test of cavitation destruction, most of the current work is the experimental study of the material's resistance to cavitation and wear, and the macroscopic result evaluation of the cavitation effect, which cannot achieve the quantitative measurement of the cavitation effect at the cavitation scale. The key reason for this situation is that the cavitation mechanism in solid-liquid two-phase flow is very complex, and it is very difficult to conduct quantitative experimental research on it.

[0057] By applying high-energy laser cavitation to generate cavitation zones with controllable characteristics, and at the same time designing a flowing solid-liquid two-phase fluid water tank, a target wall micro-adjustment system, and using high-speed photography, pressure sensor array, and fiber optic strain sensor array measurement and other technologies, the microscopic mechanism of cavitation erosion in solid-liquid two-phase fluids and quantitative analysis of material cavitation erosion can be realized. It has the advantages of controllability, low cost, low consumption, and safety, and can inject new blood into the research on cavitation erosion, wear and anti-cavitation materials of hydraulic machinery such as turbines and water pumps in solid-liquid two-phase flow.

[0058] The present invention can be used for the development of anti-cavitation materials and surface morphology design of hydraulic machinery, and proposes and constructs a feasible, highly applicable, low-cost, low-consumption, parameter-controllable static laser cavitation verification scheme to quantitatively evaluate the anti-cavitation and wear performance of materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 1 is a schematic diagram of the structure of a system for measuring cavitation erosion in a solid-liquid two-phase fluid provided by an embodiment of the present invention;

[0060] Figure 2 This is a free-field laser cavitation pulsation effect diagram provided by an embodiment of the present invention;

[0061] Figure 3 This is a diagram showing the effect of laser cavitation pulsation near a rigid wall provided by an embodiment of the present invention;

[0062] Figure 4 It is a double-cavitation pulsation interaction image in the horizontal direction provided by an embodiment of the present invention;

[0063] Figure 5 This is a diagram showing the pulsation effect of double cavitation bubbles near a rigid wall provided by an embodiment of the present invention;

[0064] Figure 6 This is a sequence effect diagram of laser cavitation collapse shock waves provided by an embodiment of the present invention;

[0065] Figure 7 This is a sequence effect diagram of laser cavitation collapse shock waves near a rigid wall provided by an embodiment of the present invention;

[0066] Figure 8 It is an effect diagram of a sequence of images of the interaction of double cavitation collapse shock waves in a free field provided by an embodiment of the present invention;

[0067] Fig. 9 It is an image of the shock wave radiated at the instant of double bubble collapse near a rigid wall provided by an embodiment of the present invention;

[0068] Fig.10 This is an image of a single laser cavitation bubble eroding a wall surface provided by an embodiment of the present invention;

[0069] Fig.11 This is a rendering of the cavitation damage morphology provided by an embodiment of the present invention; Fig.11 (a) is the morphology of cavitation damage after a single cavitation bubble was repeated 48,000 times; Fig.11 (b) is the morphology of cavitation damage after 62,000 repetitions of single cavitation. Fig.11 (c) is the morphology of cavitation damage after a single bubble was repeated 78,000 times;

[0070] Fig.12 This is an image of cavitation caused by local shock waves and microjets of the target provided by an embodiment of the present invention;

[0071] In the figure: 1. Solid phase particle parameter adjustment and measurement system; 2. Target wall precision adjustment control mechanism; 3. Fiber optic strain sensor array measurement module implanted in the target; 4. Impact pressure sensor array measurement module; 5. High-speed photography measurement module; 6. Signal acquisition and processing module; 7. Target cavitation and wear characteristics quantitative analysis module; 8. High-speed camera; 9. First laser; 10. Second laser; 11. Spectrometer; 12. Timing controller; 13. Flow rate controllable water pump. DETAILED DESCRIPTION

[0072] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0073] 1. Explanatory Examples In order to enable those skilled in the art to fully understand how to implement the present invention, this section provides an illustrative example that expands and describes the technical solution of the claims.

[0074] like Figure 1 As shown, the group cavitation erosion measurement system in a solid-liquid two-phase fluid provided by an embodiment of the present invention includes a flow circulation water tank with controllable solid phase particle characteristics, a target wall production and precision adjustment device, a multi-path beam splitting laser group cavitation generation device, a cavitation and wear multi-means measurement system, and a target cavitation / wear data processing and analysis system.

[0075] The flow circulation water tank is composed of a flow rate controllable water pump, a water tank, and a solid phase particle measurement and adjustment device. The solid phase particles are initially considered to be spherical plastic sands of different sizes, which can easily change the parameters such as particle size and water content, while avoiding the adverse effects of poor light transmission caused by the use of natural sand on high-speed imaging measurement.

[0076] The target wall production and precision adjustment device mainly includes target selection, design, processing and wall fine-adjustment control mechanism. The choice of target material considers the use of metal and non-metal. The metal is evaluated based on the typical materials of existing hydraulic machinery from the indicators such as material toughness, elasticity, strength, hardness, work hardening ability and fatigue limit. The shape of the target is selected based on the target thickness, appearance shape, surface roughness, surface morphology, etc. The design of the precision fine-adjustment control mechanism must meet the requirements of precise adjustment in three dimensions in space, and at the same time facilitate the installation of the target, so as to realize the characterization of the relative spatial position of the cavitation zone from the target wall through the movement of the platform.

[0077] The multi-beam splitting laser cavitation zone generating device is composed of multiple lasers 9, 10, a beam splitting device, a beam focusing device, a timing controller 12, a laser power supply, etc. The cavitation zone size and the number of cavitation bubbles can be controlled by adjusting the laser energy, pulse width, pulse waveform structure and the splitting ratio of the beam splitter group.

[0078] The multi-means measurement system for cavitation and wear consists of an imaging illumination optical device, a high-speed photography device, a pressure sensor array, and a fiber optic strain sensor array. The illumination optical device realizes the illumination of the cavitation area, which is convenient for the high-speed camera to image the cavitation with high quality, involving issues such as the intensity of the illumination light source and the selection of the illumination angle. The high-speed camera can measure the cavitation size, cavitation pulsation characteristics, cavitation collapse shock wave, cavitation collapse microjet, and solid phase particle movement. The pressure sensor array measures the shock wave and noise of the cavitation collapse radiation, and the fiber optic strain sensor system measures the transient deformation of the target wall. The cavitation collapse impact force can be inferred based on the shock wave, microjet velocity, and target wall deformation.

[0079] The target cavitation / wear data processing and analysis system will analyze and compile statistics on target cavitation and wear data under conditions such as targets of different materials / surface morphologies, cavitations of different sizes, solid particles of different sizes / concentrations, and spatial positions of cavitation areas relative to the target wall. It will also combine theoretical analysis and numerical calculation results to reveal the cavitation and wear mechanisms and their interaction laws in solid-liquid two-phase fluids, and evaluate the target's cavitation and wear resistance from aspects such as material and surface morphology.

[0080] Combining technologies such as micro-adjustment of the target wall in solid-liquid two-phase fluids, controllable laser cavitation flow field generation, high-speed photography, pressure sensing measurement, fiber optic strain measurement of target wall deformation, and flow rate controllable sand-entrained circulating water tank, a comprehensive key technology for quantitative experimental measurement of cavitation and wear characteristics of target materials in solid-liquid two-phase fluids is formed. The experimental data of cavitation collapse shock waves, cavitation collapse jets, and target cavitation wear intensity corresponding to different solid sand particle characteristics (size, concentration, etc.), different wall material types (toughness, elasticity, strength, hardness, work hardening ability and fatigue limit, etc.), cavitation characteristics (size, density, distribution, etc.), and water flow characteristics (flow rate, flow direction, temperature, static pressure, viscosity coefficient, etc.) are analyzed to obtain the experimental model of cavitation and wear characteristics in solid-liquid two-phase fluids near different wall targets, and the numerical calculation results are corrected. Through experiments under multi-parameter conditions, the microscopic mechanism process of cavitation and wear in solid-liquid two-phase fluids, the interaction between cavitation and wear, and the anti-cavitation and wear resistance of the target material wall were accurately described.

[0081] The method for measuring cavitation erosion of cavitation bubbles in a solid-liquid two-phase fluid provided in an embodiment of the present invention adopts laser controllable cavitation technology to realize the research on cavitation erosion of cavitation bubbles in a solid-liquid two-phase fluid, which involves the research on four aspects: cavitation movement and collapse cavitation / abrasion characteristics of cavitation bubbles in solid-liquid two-phase fluid, high-energy laser cavitation characteristics and cavitation flow field control, experimental testing and data analysis of cavitation erosion and particle wear characteristics in solid-liquid two-phase flow, and evaluation and analysis of the anti-abrasion of targets with different materials / surface morphologies.

[0082] (I) Cavitation movement and collapse cavitation and abrasion characteristics in solid-liquid two-phase fluids

[0083] Cavitation damage in solid-liquid two-phase flow is a more complex destruction process, which involves cavitation and wear and the interaction between the two. Factors such as the solid concentration in the liquid and the size of the solid particles will affect the collapse of the cavitation. As the solid concentration in the liquid increases, the cavitation collapse process will slow down. When the solid concentration remains unchanged, the smaller the size of the solid particles, the greater the impact on the cavitation collapse. During the cavitation collapse process, the solid particles will move with the liquid. When the initial position of the particles is at the top of the cavitation bubble and is relatively close to the bubble wall and the particle size is relatively small, the particles will move at high speed. As the distance between the particles and the bubble wall increases, their speed will decrease. In the later stage of cavitation collapse, the particles will slow down.

[0084] The problem of cavitation collapse near the rigid wall in two-phase flow is one of the important topics in studying the cavitation mechanism in two-phase flow. Solving this problem can help us understand the influence of solid particles on the cavitation destruction ability and the influence of cavitation collapse on solid particles, which is of great significance for solving the cavitation damage in the current high-sand content water flow in my country. This section will study this problem based on the two-phase flow model using numerical methods and experimental test verification. The research in this part also provides a basis for the design and parameter selection of the controllable laser cavitation flow field in the subsequent project.

[0085] (II) Characteristics and control of laser cavitation flow field in solid-liquid two-phase fluid

[0086] To apply laser cavitation technology to study cavitation erosion in solid-liquid two-phase fluids, it is first necessary to solve the analogy and similarity problems between the two. At the same time, the laser cavitation flow field with controllable parameters should be constructed by designing and selecting laser cavitation system parameters (laser parameters, optical focusing system parameters), wall parameters (wall material parameters, wall relative cavitation position control system) and solid-liquid two-phase fluid (sand particle characteristics, water quality characteristics), etc., based on the actual hydraulic mechanical cavitation characteristics.

[0087] This part involves the following three aspects: (1) Research on the characteristics of laser cavitation flow field in solid-liquid two-phase fluid; (2) Design and production of target wall surface of different materials (metal (toughness, elasticity, strength, hardness, work hardening ability and fatigue limit, etc.), non-metal (plastic, glass, quartz, concrete, etc.)); (3) Design and production of circulating laser cavitation flow field water tank, which can realize the adjustment of liquid flow rate and solid phase particle parameters.

[0088] (III) Experimental system for cavitation erosion and particle wear characteristics in solid-liquid two-phase fluid

[0089] Based on the established controllable laser cavitation flow field, high-speed photogrammetry, pressure sensor array, fiber optic strain sensor measurement and data correlation technologies are used to measure different solid-phase particle characteristics, different material / surface morphology wall materials, different cavitation characteristics, cavitation pulsation under different water flow characteristics, cavitation collapse shock waves, cavitation collapse microjets, solid-phase particle motion parameters, etc., and cavitation erosion and particle wear characteristic data under multi-parameters are obtained through a variety of technical means. Through statistical analysis of different measurement methods and massive data under multi-parameter conditions, experimental models of cavitation group pulsation in infinite domain free field and cavitation characteristics near the target wall in solid-liquid two-phase fluid are obtained, and the numerical calculation results are corrected.

[0090] (1) Through controllable laser cavitation, the cavitation characteristics of the target wall caused by multiple cavities of different sizes and at different spatial positions relative to the target wall are studied.

[0091] (2) By changing the solid phase particle characteristics (material, size, concentration, etc.), water flow parameters (flow velocity, flow direction, temperature, static pressure, viscosity coefficient, etc.) and different water qualities, the interaction between microparticles and cavitation flow field and its effect on cavitation erosion are studied.

[0092] (3) By selecting different types of targets, such as metal targets with different toughness, elasticity, strength, hardness, work hardening ability and fatigue limit, as well as non-metal targets such as plastic, glass, quartz, concrete, etc., the surface morphology of the target can be changed by processing, and the influence of the target material and surface morphology on cavitation can be studied. This research can provide support for the evaluation of the material's anti-cavitation and wear performance.

[0093] (4) Use direct and indirect multi-methods to obtain quantitative data on target cavitation and wear. Direct measurement of cavitation intensity can be done by using high-speed photography, impact pressure sensor, fiber optic strain sensor and other technologies to directly obtain cavitation collapse shock wave and microjet intensity. Indirect measurement can be done by microscopic analysis of the subsurface of the target material after cavitation and wear to obtain material cavitation and wear intensity parameters.

[0094] (IV) Evaluation and analysis of target material wear resistance of different materials and surface morphologies

[0095] In order to reduce the abrasion of hydraulic machinery and hydraulic structures, in addition to improving the design, manufacturing, installation, construction and operation management, it is also important to provide new materials that are resistant to cavitation and wear through experiments. Due to the many factors that affect material abrasion, and the problems of high-speed water flow of three phases of steam, liquid and solid, the abrasion mechanism has not been fully understood so far, and new anti-abrasion materials need to be studied and developed.

[0096] At present, there are many methods for studying material abrasion tests. These methods all attempt to conduct research under the conditions of simulating actual sand-carrying water flow. Although these simulations are known to have limitations, the essence of sediment wear and cavitation erosion, namely the abrasion mechanism, is common to specific materials. Therefore, the application purpose of the controllable laser cavitation device studied in this project is to explore the abrasion mechanism, compare the anti-abrasion performance of materials, and study the abrasion test of metals, non-metals, and coating materials under variable flow velocity and variable sand content conditions.

[0097] This section will select different types of target materials for a large number of experimental tests through the designed laser cavitation flow field and cavitation quantitative measurement system in solid-liquid two-phase fluids. Through the analysis of experimental data, the cavitation and wear resistance of the material will be evaluated from the aspects of material quality (toughness, elasticity, strength, hardness, work hardening ability and fatigue limit, etc.) and surface morphology. The target materials with cavitation resistance and wear resistance are studied, and the selection basis of target material and surface morphology is given.

[0098] Using solid Q-switched Nd:YAG laser (wavelength 1.06μm, pulse width 8ns, pulse energy 100mj-3000mj adjustable, repetition rate 1Hz), an experimental platform for laser beam splitting three-way laser cavitation bubble generation, high-speed photography, and pressure sensing measurement was established.

[0099] Typical laser cavitation bubble pulsation in free field Figure 2 .

[0100] Typical laser cavitation pulsation near a rigid wall is shown in Figure 3 .

[0101] When the double cavitation is arranged horizontally, the typical motion image is as follows Figure 4 shown.

[0102] The pulsation of double cavitation bubbles near a rigid wall is shown in Figure 5 shown.

[0103] The shock wave sequence emitted by the instantaneous collapse of the laser cavitation bubble in a free field is as follows: Figure 6 shown.

[0104] The shock wave sequence of laser cavitation collapse near a rigid wall is as follows: Figure 7As shown (photographic frequency 360,000 frames / second, frame interval 2.778μs).

[0105] The shock waves and interaction sequences of the instantaneous radiation of double bubble collapse in the free field and near the wall are as follows: Figure 8 , 9 shown.

[0106] When multiple single laser cavitation bubbles collapse near a plane wall, the microscopic image of the damage to the wall is shown in Fig.10 (where γ = L bp / R max , where L bp Refers to the distance from the bubble center to the wall when the cavitation is formed, R max Refers to the maximum radius to which a cavitation bubble can expand in a free field).

[0107] When γ = 0.9, laser cavitation is used to repeatedly generate a single bubble, which pulsates and collapses near the pure aluminum plane wall, causing cavitation on the wall. The cavitation images formed on the plane wall at different cavitation bubble collapse times are shown in Figure 1. Fig.11 , Fig.11 (a) is 48,000 times, Fig.11 (b) is 62,000 times, Fig.11 (c) is 78,000 times.

[0108] The local enlarged image of the target wall cavitation results caused by the different distances between the cavitation bubble and the wall and the different action mechanisms of the cavitation bubble collapse shock wave and microjet is shown in Figure 12.

[0109] 2. Application Examples: In order to prove the creativity and technical value of the technical solution of the present invention, this section provides application examples of the technical solution of the claims on specific products or related technologies.

[0110] The invention can be used for testing cavitation and wear of hydraulic machinery such as turbines and water pumps in solid-liquid two-phase flow, and testing cavitation-resistant and wear-resistant materials.

[0111] The present invention discloses a system for testing the cavitation resistance and wear resistance of hydraulic machinery materials. The system for testing the cavitation resistance and wear resistance of hydraulic machinery materials adopts the system for measuring cavitation of group cavitation in solid-liquid two-phase fluid.

[0112] It should be noted that the embodiments of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware part can be implemented using dedicated logic; the software part can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated design hardware. It can be understood by a person of ordinary skill in the art that the above-mentioned devices and methods can be implemented using computer executable instructions and / or contained in a processor control code, such as a carrier medium such as a disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. Such code is provided on the carrier medium. The device and its modules of the present invention can be implemented by hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., can also be implemented by software executed by various types of processors, and can also be implemented by a combination of the above-mentioned hardware circuits and software, such as firmware.

[0113] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A system for measuring cavitation erosion of cavitation bubbles in a solid-liquid two-phase fluid, characterized in that: The system for measuring cavitation erosion of cavitation bubbles in a solid-liquid two-phase fluid comprises: Flow circulation water tank, used to adjust the characteristics of solid particles; The target wall manufacturing and precision adjustment device is used to manufacture the target wall and use the wall fine adjustment control mechanism to achieve the characterization of the relative position of the cavitation area from the target wall through the movement of the platform; A multi-beam splitting laser cavitation zone generation device is used to control the size of the cavitation zone and the number of cavitation bubbles; Cavitation and wear multi-measurement system, used to infer the cavitation collapse impact force based on the shock wave, microjet velocity and target wall deformation; Target cavitation / wear data processing and analysis system is used to analyze and count the target cavitation wear data under different conditions, and combine theoretical analysis and numerical calculation results to reveal the cavitation and wear mechanism and their interaction rules in solid-liquid two-phase fluids, and evaluate the target cavitation and wear resistance from the aspects of material and surface morphology; The flow circulation water tank is composed of a flow rate controllable water pump, a water tank, and a solid phase particle measuring and adjusting device. The two ends of the flow rate controllable water pump are connected to the two sides of the water tank through connecting pipes, and the solid phase particle measuring and adjusting device is arranged inside the water tank. The solid phase particles are spherical plastic sands of different sizes.

2. The cavitation measurement system for group cavitation in solid-liquid two-phase fluid according to claim 1, characterized in that: The target wall manufacturing and precision adjustment device includes target material selection, design, processing and wall surface fine-adjustment control mechanism. The target material is made of metal and non-metal. The target shape is selected according to the target material thickness, appearance shape, surface roughness and surface morphology. The wall surface fine-adjustment control mechanism is used for precise adjustment in three dimensions in space, so as to realize the characterization of the relative spatial position of the cavitation zone from the target wall by the movement of the platform.

3. The cavitation measurement system for group cavitation in solid-liquid two-phase fluid according to claim 1, characterized in that: The multi-beam splitting laser cavitation zone generating device comprises multiple lasers, a beam splitting device, a beam focusing device, a timing control device, and a laser power supply. The cavitation zone scale and the number characteristics of cavitation bubbles are controlled by adjusting the laser energy, pulse width, pulse waveform structure, and the splitting ratio of the beam splitter group.

4. The cavitation measurement system for group cavitation in solid-liquid two-phase fluid according to claim 1, characterized in that: The multi-means measurement system for cavitation and wear includes an imaging illumination optical device, a high-speed photography device, a pressure sensing array, and an optical fiber strain sensing array; The illumination optical device is used to realize illumination of the cavitation area and is used for high-speed camera to image the cavitation with high quality, which involves the intensity of the illumination light source and the selection of the illumination angle; The high-speed camera is used to measure the cavitation size, cavitation pulsation characteristics, cavitation collapse shock wave, cavitation collapse microjet, and solid phase particle movement; The pressure sensing array is used to measure the shock wave and noise of cavitation collapse radiation; The optical fiber strain sensing system measures the transient deformation of the target material wall.

5. The cavitation measurement system for group cavitation in solid-liquid two-phase fluid according to claim 1, characterized in that: The different conditions of the target cavitation wear data include targets of different materials / surface morphologies, cavitations of different sizes, solid particles of different sizes / concentrations, and the spatial position of the cavitation area relative to the target wall.

6. A method for measuring cavitation group in solid-liquid two-phase fluid for implementing the cavitation group measurement system in solid-liquid two-phase fluid according to any one of claims 1 to 5, characterized in that: The method for measuring cavitation erosion of a group of cavitation bubbles in a solid-liquid two-phase fluid comprises: Step 1: Cavitation movement and collapse cavitation / abrasion characteristics in solid-liquid two-phase fluid; Step 2: High-energy laser cavitation characteristics and cavitation flow field control; Step 3: Experimental test and data analysis of the characteristics of cavitation erosion and particle wear in solid-liquid two-phase flow; Step 4: Evaluation and analysis of the abrasion resistance of targets with different materials / surface morphologies.

7. The method for measuring cavitation erosion of cavitation bubbles in a solid-liquid two-phase fluid according to claim 6, characterized in that: The step 3 of experimental testing and data analysis of cavitation erosion and particle wear characteristics in solid-liquid two-phase flow specifically includes: (1) Through controllable laser cavitation, the cavitation characteristics of the target wall caused by multiple cavities of different sizes and at different spatial positions relative to the target wall are analyzed; (2) By changing the solid phase particle characteristics, water flow parameters, and different water qualities, the interaction between microparticles and cavitation flow field and its effect on cavitation erosion are tested; (3) By selecting different target types and changing the target surface morphology through processing methods, the influence of target material and surface morphology on cavitation is tested; (4) Use direct and indirect multi-measurement methods to obtain quantitative data on target cavitation and wear.

8. A system for testing the cavitation resistance and wear resistance of hydraulic machinery materials, characterized in that: The cavitation resistance and wear resistance testing system for hydraulic machinery materials adopts the cavitation group measurement system in solid-liquid two-phase fluid according to any one of claims 1 to 5.

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