Experimental device and test method for near-wall cavitation collapse visualization

Abstract

The invention discloses an experimental device and a test method for near-wall cavitation collapse visualization. The system comprises a high-speed camera system, an electric spark generation device, a water area system, a data acquisition system and a wall surface vibration generation device. The high-speed camera system is used for capturing the dynamic behaviors of the near-wall cavitation in each stage of generation and collapse; the electric spark generation device is used for generating low-voltage electric sparks to generate cavitation bubbles; the water area system is used for simulating a liquid environment under actual working conditions; the data acquisition system is used for monitoring key parameters in the experiment process in real time; and the wall surface vibration generation device is used for generating different forms of vibration wall surfaces on the wall surface of the water area system. The cavitation collapse process visualization under different environment temperatures, wall surface types, wall surface temperatures and bubble sizes can be realized through system setting. Furthermore, the near-wall cavitation collapse behavior under the complex wall surface condition is analyzed in detail.

Description

Technical Field

[0001] The invention relates to the field of cavitation testing, and in particular to an experimental device and a testing method for visualizing near-wall cavitation collapse. Background Art

[0002] Cavitation, as a physical process that is common in hydraulic machinery, valves, pumps and nozzles, has long been one of the main causes of structural damage to these devices. Especially during the operation of diesel engines, due to the narrow space of the cylinder water jacket, the vibration and impact of the piston will cause periodic and drastic changes in local pressure.

[0003] With the increasing requirements of environmental protection emissions and economic performance for low-carbon development in recent years, the power of diesel engines has continued to increase. At the same time, in order to meet the needs of compactness, the cylinder center distance and water jacket space have become more urgent, and the thickness of the cylinder liner has been forced to decrease, resulting in its stiffness becoming weaker and the degree of cavitation becoming worse. In this context, it is particularly urgent to conduct in-depth research on the cavitation phenomenon, especially to explore the mechanism of cavitation through cavitation visualization experiments. Understanding the occurrence and development of cavitation phenomena will not only help improve the reliability and durability of diesel engines, but also provide a theoretical basis and technical support for other engineering applications involving cavitation phenomena.

[0004] At present, there are many studies on the free collapse of cavitation and the collapse of cavitation near the wall. However, most of these studies focus on relatively ideal conditions, such as the collapse of a single cavitation bubble, rigid wall conditions or constant temperature, and rarely involve the coupling of multiple factors under complex working conditions.

[0005] As a typical reciprocating internal combustion engine, diesel engines have strong vibration shock and high heat flux coupling in their working process, and the impact of this on the cavitation collapse behavior is still unclear. Therefore, studying the near-wall cavitation collapse behavior under different wall types, different motion forms (such as vibration) and different wall temperature conditions is crucial for a deep understanding of the cavitation mechanism under complex working conditions. This not only helps to reveal the basic laws of cavitation dynamics, but also has great significance for the development of effective cavitation suppression technology and the improvement of the operating stability and life of engineering machinery. Summary of the invention

[0006] In order to solve the above problems, realize the study of the cavitation collapse behavior near different types of vibrating walls, the influence of different liquid temperatures and wall temperatures on the cavitation collapse process, and visualize the entire cavitation collapse process closer to actual working conditions, the present invention provides a near-wall cavitation collapse visualization experimental device and test method.

[0007] The object of the present invention is achieved through the following technical solution: an experimental device for visualizing near-wall cavitation collapse, comprising:

[0008] A high-speed camera system to capture the dynamic behavior of near-wall cavitation at various stages of formation and collapse;

[0009] an electric spark generating device for generating electric sparks to generate cavitation;

[0010] A water system to simulate the liquid environment under actual working conditions;

[0011] A data acquisition system to monitor key parameters during the experiment in real time, such as the temperature of the deionized water in the water area;

[0012] A wall vibration generating device is used to generate two types of vibration walls, namely, a cylindrical vibration wall and a spherical vibration wall, on the wall of a water area system.

[0013] Specifically, in the near-wall cavitation collapse visualization experimental device, the camera frame rate of the high-speed camera system can reach 36,000 frames per second, which can clearly capture the rapid changes of cavitation. In order to obtain clear images, a NIKKOR 200mm macro lens is used to shoot, ensuring accurate recording of the generation, growth, and collapse of cavitation.

[0014] Specifically, in the near-wall cavitation collapse visualization experimental device, the principle of the electric spark generation device is to use a capacitor to generate electric sparks between short-circuited wires to generate cavitation. The low-voltage electric spark generation of cavitation can control the size and position of the cavitation. By keeping the DC power supply voltage consistent, cavitations of similar diameter can be obtained, thereby meeting the experimental consistency requirements.

[0015] Specifically, in the near-wall cavitation collapse visualization experimental device, the water system consists of a 40×20×20 cm acrylic glass box and deionized water. The size of the acrylic glass box is sufficient to accommodate the liquid and experimental device required for the experiment, and the transparent material facilitates the observation of the cavitation generation and collapse process; the deionized water has a high purity and can effectively reduce the impact of impurities on the experimental results.

[0016] Specifically, in the near-wall cavitation collapse visualization experimental device, the data acquisition device includes a thermocouple and a NI board. The thermocouple is used to measure the temperature of deionized water in the water system; the NI board is used to collect the signal of the thermocouple and transmit it to the computer for processing and analysis.

[0017] Specifically, in the near-wall cavitation collapse visualization experimental device, the wall vibration generating device can generate a cylindrical vibration wall surface and a spherical vibration wall surface respectively and heat the wall surface.

[0018] On the other hand, the present invention also provides a method for testing an experimental device for visualizing near-wall cavitation collapse, and the specific steps are as follows:

[0019] Step 1: Build the experimental device and debug it to ensure the normal operation of the system.

[0020] Step 2: Pour deionized water into the acrylic glass box and adjust the water temperature to the set value.

[0021] Step 3: Select the appropriate type of wall according to the experimental requirements. If a cylindrical vibration wall is required, proceed to step 4; if a spherical vibration wall is required, proceed to step 5.

[0022] Step 4: Install the cylindrical vibrating wall in the glass box and start the wall vibration. If the wall needs to be heated, proceed to step 6, otherwise proceed to step 7.

[0023] Step 5: Install the spherical vibrating wall in the glass box and turn on the wall vibration. If the wall needs to be heated, proceed to step 6, otherwise proceed to step 7.

[0024] Step 6: Turn on the wall heating.

[0025] Step 7: Adjust the DC power supply voltage of the electric spark generating device until cavitation of a desired size is generated.

[0026] Step 8: Set up the high-speed camera system and data acquisition system.

[0027] Step 9: Start the high-speed camera system and the electric spark generating device in sequence.

[0028] Step 10: Record and save the images captured by the high-speed camera and the data collected by the data acquisition system.

[0029] Step 11: Extract the cavitation equivalent radius parameters and analyze and interpret the experimental results.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention can be used to study the near-wall cavitation collapse behavior under different wall types, different motion forms (such as vibration) and different wall temperature conditions, which helps to deeply understand the cavitation mechanism under complex working conditions. Further, it helps to develop effective cavitation suppression technology and improve the operating stability and life of engineering machinery.

[0032] (2) In the present invention, the cylindrical wall setting may cause the fluid to generate a large shear stress around it, thereby affecting the generation and collapse process of cavitation; while the spherical wall setting may cause the fluid to form a relatively uniform pressure distribution around it, thereby affecting the behavior of cavitation. The introduction of different working conditions can achieve a study of cavitation generation and collapse behavior that is closer to practical application. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 A schematic diagram of the hardware arrangement of an experimental device for near-wall cavitation collapse visualization according to the present invention;

[0035] In the figure, 1. high-speed camera, 2. light-emitting diode, 3. DC regulated power supply, 4. low-voltage electric spark charging and discharging circuit, 5. copper wire electrode, 6. NI board, 7. thermocouple, 8. computer, 9. acrylic glass box, 10. wall vibration generating device.

[0036] Figure 2 This is a schematic diagram of two types of settings of a cylindrical vibration wall and a spherical vibration wall of a wall vibration generating device according to an embodiment of the present invention and their appearance dimensions.

[0037] In the figure, (a) is a schematic diagram of the overall cylindrical vibration wall and the spherical vibration wall, (b) is a side view of the cylindrical vibration wall, and (c) is a front view of the spherical vibration wall;

[0038] Figure 3 A schematic diagram of a specific process of a test method of an experimental device for near-wall cavitation collapse visualization according to an embodiment of the present invention; DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] like Figure 1 As shown, an experimental device for visualizing near-wall cavitation collapse includes a high-speed camera system, an electric spark generating device, a water area system, a data acquisition system, and a wall vibration generating device.

[0041] The high-speed camera system is used to capture the dynamic behavior of near-wall cavitation at various stages of generation and collapse. The electric spark generating device is used to generate low-voltage electric sparks to produce cavitation. The water area system is used to simulate the liquid environment under actual working conditions. The data acquisition system is used to monitor the key parameters of the experiment in real time. The wall vibration generating device is used to generate different forms of vibrating walls on the wall of the water area system.

[0042] According to one embodiment of the present invention, an experimental device for visualizing near-wall cavitation collapse includes:

[0043] A high-speed camera 1 is connected to a computer 8, and the generation, growth, and collapse of cavitation is accurately recorded through images and uploaded to the computer. The frame rate of the high-speed camera can reach 36,000 frames per second, and the rapid changes of cavitation can be clearly captured. In order to obtain clear images, a NIKKOR 200mm macro lens is used for shooting, which can provide high resolution and high magnification to ensure accurate recording of the generation, growth, and collapse of cavitation.

[0044] A light emitting diode 2 is used as a light source of the high-speed camera system to provide sufficient brightness for the high-speed camera to record images.

[0045] A DC regulated power supply 3 is connected to a low voltage electric spark charging and discharging circuit 4 to charge the charging and discharging circuit until the required voltage is reached.

[0046] A low voltage electric spark charging and discharging circuit 4, including two 1000μF capacitors, one 3300μF capacitor, one 1000Ω resistor, one single-pole double-throw switch and two copper rods, is connected to a DC voltage regulated power supply and a 0.3mm copper wire electrode 5, and discharges through the copper wire electrode.

[0047] A copper wire electrode 5 is connected to a low-voltage electric spark charging and discharging circuit, forming a short-circuited wire between which electric sparks appear, thereby generating cavitation and controlling the location of cavitation generation. The advantages of low-voltage electric spark cavitation are simple operation, low cost, and the size and location of cavitation can be controlled. By keeping the DC power supply voltage consistent, cavitation of similar diameter can be obtained, thereby meeting the experimental consistency requirements.

[0048] A NI board 6 is connected to the thermocouple 7 and the computer, and is used to collect the signal of the thermocouple and transmit it to the computer for processing and analysis.

[0049] A thermocouple 7, connected to the NI board, is used to measure the temperature of the deionized water in the water area.

[0050] A computer 8 is connected to the high-speed camera and the NI board, and is used for receiving and storing the data recorded by the high-speed camera and the signals collected by the NI board and converting them into temperature data, as well as subsequent data processing and analysis.

[0051] An acrylic glass box 9, which contains sufficient deionized water, has a size of 40×20×20 cm, and is used to contain the liquid and experimental equipment required for the experiment. The transparent material facilitates the observation of the generation and collapse process of cavitation, and provides a sufficiently transparent environment for the high-speed camera to record the generation and collapse process of cavitation. Deionized water has a high purity, and providing a sufficiently high purity environment can effectively reduce the influence of impurities on the experimental results.

[0052] A wall vibration generating device 10, such as Figure 2 As shown, it is used to generate two types of vibration walls, namely cylindrical vibration wall and spherical vibration wall, on the wall of the water area system, and can be heated.

[0053] The high-speed camera and the computer are connected in sequence, the thermocouple, the NI board and the computer are connected in sequence, and the DC voltage-stabilized power supply, the low-voltage electric spark charging and discharging circuit and the copper wire electrode are connected in sequence.

[0054] like Figure 3 The system test method shown is as follows:

[0055] The test method of the experimental device for visualizing near-wall cavitation collapse is:

[0056] Step 1: Follow the steps below Figure 1 The experimental setup for visualizing near-wall cavitation collapse is shown in FIG.

[0057] Step 2: inject deionized water into the acrylic glass box 9 and adjust the water temperature to a set value.

[0058] Step 3: Select the appropriate type of wall according to the experimental requirements. If a cylindrical vibration wall is required, proceed to step 4; if a spherical vibration wall is required, proceed to step 5.

[0059] Step 4: Install the cylindrical vibrating wall surface vibration generating device 10 in the glass box. If the wall surface needs to be heated, proceed to step 6, otherwise proceed to step 7.

[0060] Step 5: Install the spherical vibrating wall surface vibration generating device 10 in the glass box. If the wall surface needs to be heated, proceed to step 6; otherwise, proceed to step 7.

[0061] Step 6: Turn on the wall vibration generating device 10 to heat the wall surface.

[0062] Step 7, adjust the voltage of the DC power supply 3 of the electric spark generating device to reach the voltage value corresponding to the required bubble size, use a single-pole double-throw switch to form a loop between the DC power supply 3 and the low-voltage electric spark charging and discharging circuit 4, and wait for the low-voltage electric spark charging and discharging circuit 4 to complete charging.

[0063] Step 8, setting the high-speed camera 1 and the computer 8, ensuring that the high-speed camera 1 can clearly capture the bubbles at the predetermined position and ensuring that the data transmitted by the NI board 6 can be read and recorded on the computer 8.

[0064] Step 9, start the high-speed camera 1 in sequence, use the single-pole double-throw switch to make the low-voltage electric spark charging and discharging circuit 4 and the copper wire electrode 5 form a loop and short-circuit, so that electric sparks appear between the copper wire electrodes 5 and cavitation is generated.

[0065] Step 10: Use the computer 8 to record and save the images captured by the high-speed camera 1 and the data collected by the thermocouple 7.

[0066] Step 11: Use the computer 8 to perform subsequent processing on the obtained results, and extract relevant parameters therein, such as the cavitation equivalent radius, so as to analyze and interpret the experimental results.

[0067] The above embodiments are used to illustrate the present invention rather than to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. An experimental device for visualizing near-wall cavitation collapse, characterized in that: include: A high-speed camera system to capture the dynamic behavior of near-wall cavitation at various stages of formation and collapse; an electric spark generating device for generating electric sparks to generate cavitation; A water system to simulate the liquid environment under actual working conditions; A data acquisition system for real-time monitoring of the temperature parameters of deionized water in the water area during the experiment; A wall vibration generating device is used to generate two types of vibration walls, namely, a cylindrical vibration wall and a spherical vibration wall, on the wall of a water area system.

2. The experimental device for visualizing near-wall cavitation collapse according to claim 1, characterized in that: The camera frame rate of the high-speed camera system can reach 36,000 frames per second, which can clearly capture the rapid changes of cavitation. In order to obtain clear images, a NIKKOR 200mm macro lens is used to shoot, ensuring accurate recording of the generation, growth, and collapse of cavitation.

3. The experimental device for visualizing near-wall cavitation collapse according to claim 1, characterized in that: The principle of the electric spark generating device is to use a capacitor to generate electric sparks between short-circuited wires to generate cavitation. The electric spark generating cavitation can control the size and position of the cavitation; by maintaining a consistent power supply voltage, cavitations of similar diameters are obtained, thereby meeting the experimental consistency requirements.

4. The experimental device for visualizing near-wall cavitation collapse according to claim 1, characterized in that: The water area system consists of an acrylic glass box and deionized water. The size of the acrylic glass box is sufficient to accommodate the liquid and experimental equipment required for the experiment, and the transparent material facilitates the observation of the generation and collapse process of cavitation. Deionized water can reduce the impact of impurities on the experimental results.

5. The experimental device for visualizing near-wall cavitation collapse according to claim 1, characterized in that: The data acquisition device includes a thermocouple and a NI board; wherein the thermocouple is used to measure the temperature of deionized water in the water system; and the NI board is used to collect the signal of the thermocouple and transmit it to a computer for processing and analysis.

6. The experimental device for visualizing near-wall cavitation collapse according to claim 1, characterized in that: The wall vibration generating device is used to generate a cylindrical vibration wall surface and a spherical vibration wall surface respectively and heat the wall surface.

7. A test method of the experimental device for visualizing near-wall cavitation collapse as claimed in claims 1 to 6, characterized in that: include: Step 1: Build the experimental device and debug it to ensure the normal operation of the system; Step 2: Pour deionized water into the acrylic glass box and adjust the water temperature to the set value; Step 3: Select the appropriate type of wall surface according to the experimental requirements. If a cylindrical vibration wall surface is required, proceed to step 4; if a spherical vibration wall surface is required, proceed to step 5; Step 4: Install the cylindrical vibration wall in the glass box and start the wall vibration; if the wall needs to be heated, proceed to step 6, otherwise proceed to step 7; Step 5: Install the spherical vibrating wall in the glass box and start the wall vibration; if the wall needs to be heated, proceed to step 6, otherwise proceed to step 7; Step 6: Turn on the heating wall; Step 7, adjusting the DC power supply voltage of the electric spark generating device until a cavitation bubble of a desired size is generated; Step 8: Setting up a high-speed camera system and a data acquisition system; Step 9, start the high-speed camera system and the electric spark generating device in sequence; Step 10, record and save the images captured by the high-speed camera and the data collected by the data acquisition system; Step 11: Extract the cavitation equivalent radius parameters and analyze and interpret the experimental results.

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