Monitoring device and monitoring method for the frequency and amplitude of pressure fluctuations during cavitation collapse processes

Abstract

The application discloses a kind of monitoring devices of pressure fluctuation frequency and amplitude in cavitation collapse process, including water tank, cavitation generator, magnetic fluid, magnetic field device, laser generator, optical splitter, laser probe and receiver;Optical splitter is emitted by single beam laser of laser generator and is divided into two beams, one is emitted as laser, frequency is f ;Another is as reference laser, frequency is f + f r ;Laser probe exports and irradiates on the tip of magnetic fluid by emitting laser, and reflection is formed to form reflected laser, and its frequency is f + f D ;Receiver, accept reflected laser, and it has reference laser inside by optical splitter, and its frequency is f + f r The application can master the whole dynamic data of quantized cavitation collapse by monitoring the frequency and amplitude of whole process pressure fluctuation caused by cavitation collapse in liquid environment through magnetic fluid magneto-rheological effect, tip surface effect and Doppler effect, which provides important technical means for single-cavity theory development and hydraulic machinery cavitation flow research.

Description

Technical Field

[0001] This invention relates to the field of cavitation dynamics technology, specifically to a device and method for monitoring the frequency and amplitude of pressure fluctuations during cavitation collapse. Background Technology

[0002] Cavitation is a widespread phenomenon in various engineering fields, including power, chemical, military, and biological engineering, particularly in rotating hydraulic machinery such as pumps, turbines, and propellers. It has long been a focus of attention primarily because it significantly impacts flow components and the internal fluid flow, altering the dynamic relationship between the fluid and its boundaries. Cavitation also causes cavitation erosion damage to the surface of flow component walls. In the field of hydraulic machinery, cavitation is generally undesirable, except in rare cases. Uncontrolled cavitation can lead to severe or even catastrophic consequences, resulting in substantial economic losses. The need to prevent or control cavitation has severely limited the design of many hydraulic machines, a situation increasingly contradicting the development of current industrial and agricultural production and the progress of science and technology.

[0003] Fundamental theoretical research on cavitation is typically based on single-cavitation or multi-cavitation physical models. However, due to limitations in measurement technology, the shock waves generated by cavitation collapse and their impact on the surrounding liquid flow field are difficult to quantify. Currently, numerical simulation methods are commonly used to approximate the actual physical phenomena and laws. Furthermore, the data obtained through numerical calculations can only be validated through a phenomenological perspective of cavitation morphology changes, confirming the reliability of the simulation data. To date, in-depth quantitative research on the cavitation collapse process has been hampered by the short collapse time and strong destructive force, placing higher demands on sensors. Additionally, placing sensors in water typically affects the cavitation morphology, leading to deviations from actual engineering conditions. This paper proposes a novel, non-intrusive monitoring method, which is of great significance for the development of cavitation dynamics systems and even the hydraulic machinery industry.

[0004] Magnetofluid is a smart liquid obtained by uniformly dispersing nanoscale magnetic particles with surfactants in water. It can be positioned and moved by a magnetic field. At the same time, because the particle size is nanoscale, its response time is very short, almost 10^6 seconds. -7 The magnitude is on the order of s. Furthermore, under the influence of the field, the surface of the magnetic fluid will exhibit unusual and unusual phenomena such as spikes. Under the action of an external force, the spikes on the surface of the magnetic fluid will shorten, and after the external force is removed, they will return to their original length. When there is a pulsating force, the magnetic fluid spikes will undergo a reciprocating motion of "shaking".

[0005] Based on the peak characteristics of magnetohydrodynamics and the Doppler principle, this application proposes a novel monitoring device and method for monitoring the frequency and amplitude of pressure fluctuations during cavitation collapse, combining magnetohydrodynamic properties and laser vibration measurement principles, providing technical support for the quantitative study of cavitation dynamics. Summary of the Invention

[0006] The purpose of this invention is to provide a device and method for monitoring the frequency and amplitude of pressure fluctuations during the cavitation collapse process.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A device for monitoring the frequency and amplitude of pressure fluctuations during cavitation collapse, including:

[0009] The water tank provides a liquid environment for cavitation.

[0010] A cavitation generator has a cavitation generating part located in the liquid in the water tank for generating cavitation.

[0011] Magnetofluid, located in the liquid in the water tank, produces a spike-like shape under the influence of a magnetic field;

[0012] A magnetic field device that provides the required magnetic field for magnetohydrodynamic fluid;

[0013] A laser generator is a laser source.

[0014] A beam splitter divides the single laser beam emitted by the laser generator into two beams of similar color but different frequencies. One beam is used as the emitted laser beam with a frequency of [missing value]. f The other beam serves as a reference laser with a frequency of [frequency value missing]. f + f r ;

[0015] The laser probe will have a frequency of f The emitted laser light is directed and illuminates the spikes of the magnetofluid; the emitted laser light illuminating the magnetofluid is reflected to form reflected laser light with a frequency of [frequency missing]. f + f D ;

[0016] The receiver receives reflected laser light and has an internal frequency formed by a beam splitter. f + f r The reference laser.

[0017] Furthermore, the magnetic field device is located inside or outside the water tank.

[0018] Furthermore, the magnetic field device is a magnet.

[0019] Furthermore, the cavitation generator is an electric spark cavitation generator, and the copper wire end of the electric spark cavitation generator extends into the liquid in the water tank.

[0020] Furthermore, the magnetofluid is located around the cavitation bubble.

[0021] Furthermore, the receiver is a photodetector.

[0022] This invention also discloses a method for monitoring the frequency and amplitude of pressure fluctuations during cavitation collapse, using the aforementioned monitoring device for the frequency and amplitude of pressure fluctuations during cavitation collapse, comprising the following steps:

[0023] Cavitation bubbles are generated in the water tank using a cavitation generator; a laser generator is turned on, and a beam splitter is used to divide a laser beam into beams with frequencies of [frequency value missing]. f The emitted laser and its frequency are f + f r The reference laser is emitted and irradiated onto the surface of the magnetohydrodynamic peak by the laser probe.

[0024] When a cavitation bubble collapses, it generates a shock wave, which is transmitted to the surface of the magnetohydrodynamic (MHD) peak via water. The MHD peak surface, subjected to force, will retract. Because the pressure during cavitation collapse is pulsating, the MHD peak surface exhibits a contraction and rebound process in response to changes in external pressure. Therefore, the reflected laser light from the MHD peak surface exhibits Doppler frequency shift. f D Reflected laser f + f D The signal is transmitted to the receiver and, in conjunction with the reference laser, forms a beat frequency signal internally. By processing the beat frequency signal, the vibration amplitude and frequency of the magnetohydrodynamic peak surface can be obtained, and thus the frequency and amplitude of the pressure wave generated by the cavitation bubble can be obtained.

[0025] The beneficial effects of this invention are:

[0026] 1. This invention monitors the frequency and amplitude of pressure fluctuations throughout the entire process caused by cavitation collapse in a liquid environment through magnetorheological effects, peak surface effects, and Doppler effects. It can obtain quantitative dynamic data on cavitation collapse, providing an important technical means for the development of single cavitation theory and the study of hydraulic mechanical cavitation flow.

[0027] This invention does not require inserting a solid-state probe into the environment under test, and features non-interference, non-destructive monitoring, and high frequency.

[0028] 2. Because the magnetic response relaxation time of a magnetohydrodynamic fluid is 10... -7 s, and the speed of light is 10 8 m / s, while the entire cavitation collapse period is 10 m / s.-4 Since the system relaxation time is much shorter than the cavitation collapse period, the entire process is instantaneous and can fully capture the pressure state of the entire cavitation collapse process.

[0029] 3. When the position of the magnetohydrodynamic (MHD) peak changes, its slope (the peak is generally conical, and the slope is the angle between the top and bottom of the peak) also changes. When laser light is shone on different peak slopes, the intensity of the reflected light will change. Based on the frequency of the change in reflected light intensity, the frequency of the MHD peak change can be monitored, and thus the frequency of the pressure change generated during cavitation collapse can be calculated. The pressure frequency obtained by the light intensity can be cross-corrected with the pressure frequency obtained by the Doppler beat frequency signal, improving the accuracy of this monitoring device.

[0030] 4. This invention can be used not only to monitor the frequency and amplitude of pressure fluctuations during the cavitation collapse process, but also to monitor the frequency and amplitude of pressure fluctuations in other gases and liquids caused by certain factors. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the monitoring device of the present invention;

[0032] Figure 2 This is a schematic diagram of the present invention;

[0033] Figure 3 This is a schematic diagram of the peak morphology changes of the magnetofluid in this invention.

[0034] In the diagram: 101: Laser generator; 102: Beam splitter; 103: Laser probe; 104: Laser emitter; 105: Cavitation generator; 106: Water tank; 107: Cavitation; 108: Magnetorheological fluid spike surface; 109: Magnet; 110: Reflected laser; 111: Receiver; 112: Reflected laser.

[0035] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent. To better illustrate this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0037] Example 1:

[0038] like Figures 1 to 3As shown, this embodiment discloses a monitoring device for the frequency and amplitude of pressure fluctuations during cavitation collapse, including a laser generator 101, a beam splitter 102, a laser probe 103, an emitting laser 104, a cavitation generator 105, a water tank 106; a cavitation bubble 107, a magnetohydrodynamic peak surface 108, a magnet 109, a reflected laser 110, a photodetector 111, and a reflected laser 112. Specifically:

[0039] Laser generator 101: is a laser source.

[0040] Optical splitter 102: Optical splitter 102 has frequency shifting capabilities. f r ， The single laser beam emitted by the laser generator is split into two beams of similar color but different frequencies. One beam is used as the emitted laser 104, with a frequency of... f The other beam, used as a reference laser 112, has a frequency of... f + f r .

[0041] Laser probe 103: The frequency is... f The emitted laser light is directed out and irradiates the magnetohydrodynamic peak surface 108.

[0042] Laser 104 is emitted: it is guided out by laser probe 103 and irradiates the surface 108 of magnetohydrodynamic peak.

[0043] Cavitation generator 105: Cavitation generator 105 has a cavitation generating part located in the liquid in water tank 106, and is used for cavitation generation.

[0044] In this embodiment, the cavitation generator 105 is an electric spark cavitation generator 105. The copper wire end of the electric spark cavitation generator extends into the liquid in the water tank, and the copper wire generates cavitation bubbles in the water tank 106 in the form of electric sparks.

[0045] In his embodiment, other types of cavitation generators may also be used.

[0046] Water tank 106: Experimental environment, providing a liquid environment for cavitation.

[0047] Cavitation 107: Caused by cavitation generator 105 and appears in water tank 106.

[0048] Magnetofluid: Located in the liquid within water tank 106, and positioned around cavitation bubbles. The magnetofluid generates a peak shape (with a magnetofluid peak surface 108) under the influence of a magnetic field, and the peak shape will change under the influence of external forces.

[0049] Magnetic field device 109 provides the required magnetic field for the magnetofluid. In this embodiment, the magnetic field device 109 is a magnet, which can be located inside or outside the water tank 106 as needed.

[0050] Reflected laser 110: A laser formed by the reflection of laser 104 emitted from a magnetofluid, with a frequency of [frequency missing]. f + f D .

[0051] Receiver 111: Receiver 111 selects a photodetector for receiving reflected laser light, and its internal components have a frequency formed by the beam splitter 102. f + f r The reference laser.

[0052] Reference laser 112: An internal laser formed by a beam splitter, with a frequency of [frequency value missing]. f + f r .

[0053] This embodiment also provides a method for monitoring the frequency and amplitude of pressure fluctuations during cavitation collapse, using a device for monitoring the frequency and amplitude of pressure fluctuations during cavitation collapse, including the following steps:

[0054] A cavitation bubble 107 is generated in the water tank 106 by the cavitation generator 105; the laser generator 101 is turned on, and the laser beam is split into two parts with a frequency of [frequency value missing] by the beam splitter 102. f The emitted laser is 104 and the frequency is f + f r The reference laser 112 emits a laser 104 which is irradiated onto the magnetohydrodynamic peak surface 108 by the laser probe 103.

[0055] When the cavitation bubble 107 collapses, it generates a shock wave, which is transmitted to the magnetofluid tip surface 108 via water. The magnetofluid tip surface 108, under the influence of force, will retract. Since the pressure during the cavitation collapse process is pulsating, the magnetofluid tip surface 108 exhibits a contraction and rebound process following changes in external pressure. Therefore, the reflected laser 110 reflected from the magnetofluid tip surface 108 exhibits Doppler frequency shift. f D Reflected laser f + f D The signal is transmitted to receiver 111 and combined with reference laser 112 to form a beat frequency signal inside. By processing the beat frequency signal, the vibration amplitude and frequency of the magnetohydrodynamic peak surface can be obtained, that is, the frequency and amplitude of the pressure wave generated by the cavitation.

[0056] The working principle of this invention is as follows:

[0057] This invention is based on the magnetorheological effect and spike effect of magnetofluids. When a magnetic field is present, the magnetofluid will produce a spike effect; the spike is due to the balance between the magnetic force and external forces. When the external force changes, the magnetofluid at the spike will change position, moving towards a magnetic field gradient range that can resist the external force. The method for calculating the resistance to external pressure generated by the magnetofluid within the magnetic field gradient range is as follows:

[0058]

[0059] In the formula, p is the force generated by the magnetohydrodynamic fluid to resist external pressure, and μ0 is the free permeability. H 1. H 2 represents the magnetic field value at the location. M s is the saturation magnetization of the magnetohydrodynamic fluid.

[0060] The distribution of the magnetic field generated by a uniform magnet can be determined through numerical calculation or magnetic field camera. Therefore, in the test, it is only necessary to know the positional changes of the magnetohydrodynamic peak.

[0061] The present invention can obtain the peak jitter frequency and amplitude of the magnetofluid through the above monitoring method, and then obtain the frequency and amplitude of the pressure wave generated by the cavitation.

[0062] Since the magnetic response relaxation time of the magnetic fluid is 10 -7 s, and the speed of light is 10 8 m / s, while the entire cavitation collapse period is 10 m / s. -4 Since the system relaxation time is much shorter than the cavitation collapse period, the entire process is instantaneous and can fully capture the pressure state of the entire cavitation collapse process.

[0063] Furthermore, when the position of the magnetohydrodynamic peak changes, its slope (the peak is generally conical, and the slope is the angle between the top and bottom of the peak) also changes. When laser light is shone on different peak slopes, the intensity of the reflected light will change. Based on the frequency of the change in reflected light intensity, the frequency of the magnetohydrodynamic peak change can be monitored, and thus the frequency of the pressure change generated during cavitation collapse can be calculated. The pressure frequency obtained by the light intensity can be cross-corrected with the pressure frequency obtained by the Doppler beat frequency signal, improving the accuracy of this monitoring device.

[0064] This invention utilizes the magnetorheological effect of magnetohydrodynamics, the peak surface effect, and the Doppler effect (extremely short relaxation time) to identify the dynamic pressure changes during the cavitation collapse process. It monitors the frequency and amplitude of pressure fluctuations caused by cavitation collapse in liquid environments, enabling the acquisition of quantified dynamic data on cavitation collapse. It features non-interference, non-destructive monitoring, and high frequency, providing crucial support for research on hydraulic mechanical cavitation flow and fundamental experimental studies of single cavitation collapse processes.

[0065] Example 2:

[0066] This embodiment can be used to monitor the frequency and amplitude of pressure fluctuations in other gases and liquids caused by a certain origin.

[0067] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

[0068] If the terms "first" or "second" are used in this document to define components, those skilled in the art should know that the use of "first" or "second" is merely for the convenience of describing the invention and simplifying the description, and unless otherwise stated, the above terms have no special meaning.

[0069] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0070] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

Claims

1. A device for monitoring the frequency and amplitude of pressure fluctuations during cavitation collapse, characterized in that: include: The water tank provides a liquid environment for cavitation. A cavitation generator has a cavitation generating part located in the liquid in the water tank for generating cavitation. Magnetofluid, located in the liquid in the water tank, produces a spike-like shape under the influence of a magnetic field; A magnetic field device that provides the required magnetic field for magnetohydrodynamic fluid; A laser generator is a laser source. A beam splitter divides the single laser beam emitted by the laser generator into two beams of similar color but different frequencies. One beam is used as the emitted laser beam with a frequency of [missing value]. f The other beam serves as a reference laser with a frequency of [frequency value missing]. f + f r ; The laser probe will have a frequency of f The emitted laser light is directed and illuminates the spikes of the magnetofluid; the emitted laser light illuminating the magnetofluid is reflected to form reflected laser light with a frequency of [frequency missing]. f + f D ; The receiver receives reflected laser light and has an internal frequency formed by a beam splitter. f + f r The reference laser.

2. The monitoring device for the frequency and amplitude of pressure fluctuations during the cavitation collapse process according to claim 1, characterized in that: The magnetic field device is located inside or outside the water tank.

3. The monitoring device for the frequency and amplitude of pressure fluctuations during the cavitation collapse process according to claim 2, characterized in that: The magnetic field device is a magnet.

4. The monitoring device for the frequency and amplitude of pressure fluctuations during the cavitation collapse process according to claim 1, characterized in that: The cavitation generator is an electric spark cavitation generator, and the copper wire end of the electric spark cavitation generator extends into the liquid in the water tank.

5. The monitoring device for the frequency and amplitude of pressure fluctuations during the cavitation collapse process according to claim 1, characterized in that: The magnetofluid is located around the cavitation bubble.

6. The monitoring device for the frequency and amplitude of pressure fluctuations during the cavitation collapse process according to claim 1, characterized in that: The receiver is a photodetector.

7. A method for monitoring the frequency and amplitude of pressure fluctuations during cavitation collapse, using the monitoring device for monitoring the frequency and amplitude of pressure fluctuations during cavitation collapse as described in any one of claims 1-6, characterized in that... Includes the following steps: Cavitation bubbles are generated in the water tank using a cavitation generator; a laser generator is turned on, and a beam splitter is used to divide a laser beam into beams with frequencies of [frequency value missing]. f The emitted laser and its frequency are f + f r The reference laser is emitted and irradiated onto the surface of the magnetohydrodynamic peak by the laser probe. When a cavitation bubble collapses, it generates a shock wave, which is transmitted to the surface of the magnetohydrodynamic (MHD) peak via water. The MHD peak surface, subjected to force, will retract. Because the pressure during cavitation collapse is pulsating, the MHD peak surface exhibits a contraction and rebound process in response to changes in external pressure. Therefore, the reflected laser light from the MHD peak surface exhibits Doppler frequency shift. f D Reflected laser f + f D The signal is transmitted to the receiver and, in conjunction with the reference laser, forms a beat frequency signal internally. By processing the beat frequency signal, the vibration amplitude and frequency of the magnetohydrodynamic peak surface can be obtained, and thus the frequency and amplitude of the pressure wave generated by the cavitation bubble can be obtained.

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