Method and device for accurately identifying gas-containing vortex of hydraulic machinery

Abstract

The application provides a method and device for accurately identifying gas-containing vortex of a hydraulic machine, and the specific steps of the method include: arranging a pressure pulsation measuring point on a water inlet pipeline of the hydraulic machine, collecting a time domain signal of the pressure pulsation; performing continuous wavelet transform on the time domain signal to obtain a time-frequency diagram of the pressure pulsation; extracting an energy amplitude of a characteristic frequency band in the time-frequency diagram and comparing the energy amplitude with a preset threshold value to determine whether the gas-containing vortex appears; and analyzing a characteristic of the gas-containing vortex based on a time-space distribution characteristic of the energy of the characteristic frequency band. Compared with the prior art, the above scheme can determine whether the gas-containing vortex appears by only monitoring and analyzing the pressure pulsation of the water inlet pipeline, realizes non-contact real-time monitoring of a flow field of the hydraulic machine, provides a reliable early warning means for improving a water inlet flow state, and improves the operation efficiency and stability of the hydraulic machine. The method has low cost, is easy to popularize, and has a wide engineering application prospect.

Description

Technical Field

[0001] This invention relates to the field of hydraulic machinery operation monitoring, and in particular to a method and apparatus for accurately identifying air-containing vortices in hydraulic machinery. Background Technology

[0002] In recent years, my country's water conservancy and hydropower industry has developed rapidly. The total installed capacity of hydraulic machinery and equipment, represented by pumping stations, conventional hydropower stations and pumped storage power stations, has ranked first in the world.

[0003] However, in engineering scenarios such as the intake pool of large-scale water diversion pumping stations, the pressure forebay of hydropower stations, and the inlet and outlet of pumped storage power stations, complex inflow conditions, unreasonable design, and low operating submersion depths can easily induce difficult-to-observe air-containing vortices such as surface vortices and underwater vortices within the intake channel. Once these air-containing vortices are drawn into core flow components such as the turbine impeller, they will not only reduce the unit's operating efficiency and cause cavitation damage to the impeller blades, but also trigger strong pressure pulsations and noise. When the pulsation frequency coincides with the unit's natural frequency, it can even induce unit resonance, seriously threatening the safe and stable operation of the unit.

[0004] Currently, there is a lack of precise methods for identifying and monitoring air-containing vortices inside hydraulic machinery. In engineering practice, passive physical vortex-eliminating measures are mainly adopted to improve the inlet flow pattern. For example, vortex-eliminating cones or plates are installed below the inlet pipe, but such methods are difficult to adapt to horizontally arranged inlets; or the geometry of the inlet pool is modified, such as by adding guide platforms or guide piers, but this method has high requirements for the structure of the inlet pool, is complex to construct, and has high maintenance costs.

[0005] In summary, there is a lack of a simple, low-cost, and easily scalable method for accurately identifying air-bearing vortices in hydraulic machinery, so as to achieve active monitoring of air-bearing vortices. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problems of existing technologies, such as difficult operation, complex structure, and lack of active recognition capability.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for accurately identifying air-bearing vortices in hydraulic machinery, comprising the following steps:

[0008] Step 1: Install pressure pulsation measuring points on the inlet pipe of the hydraulic machinery and collect the time-domain signal of pressure pulsation;

[0009] Step 2: Perform continuous wavelet transform on the time-domain signal to obtain the pressure pulsation time-frequency diagram;

[0010] Step 3: Extract the characteristic frequency band energy amplitude from the pressure pulsation time-frequency map and compare it with the preset threshold to determine whether gas-containing vortices have appeared.

[0011] Step 4: Analyze the characteristics of gas-bearing vortices based on the spatiotemporal distribution characteristics of characteristic frequency band energy.

[0012] Preferably, in step 1, the acquired pressure pulsation time-domain signal is processed using dimensionless processing. The formula for dimensionless processing is: ;

[0013] In the formula, This is a dimensionless pressure pulsation coefficient; The instantaneous pressure at the measuring point; The average pressure at the measuring point; The density of the liquid; This refers to the circumferential speed at the outlet of the hydraulic impeller.

[0014] Preferably, in step 3, a dimensionless intensity factor is introduced. The characteristic frequency band is quantitatively defined, and the intensity factor is calculated using the following formula: ;

[0015] In the formula, Let f be the dimensionless intensity factor of frequency f at time t; Let f be the magnitude of the frequency f at time t; To monitor the average amplitude of frequency f within the specified time period. The characteristic frequency band is: in the pressure pulsation time-frequency diagram, satisfying... The set of frequencies consisting of frequencies f, where The preset threshold for identifying gas-bearing vortices is set to 1.8.

[0016] Preferably, the intensity factor extracted within the characteristic frequency band satisfies Given the given data points, count the envelope regions formed by these data points, and record the number of envelope regions. ,when If the flow field contains an air-containing vortex, then it is determined that an air-containing vortex has appeared.

[0017] Preferably, a device for accurately identifying air-containing vortices in hydraulic machinery is also provided to implement the above-mentioned identification method. The device includes a liquid-filled inlet tank with an inlet pipe. The inlet pipe includes a horizontal section and a vertical section. A pressure measuring hole is opened on the center line of the cross-section of the horizontal section, and a pressure pulsation sensor is installed inside the pressure measuring hole. The pressure pulsation sensor is communicatively connected to an air-containing vortex identification system. This device has a simple structure and is convenient for practical testing and identification work.

[0018] Preferably, the lower end of the vertical section of the inlet pipe is provided with an inlet bell mouth, which helps to suppress small-scale, non-air-containing vortex disturbances induced by abrupt changes in the shape of the inlet.

[0019] Preferably, the horizontal section of the inlet pipe and the vertical section of the inlet pipe are connected by flanges. The flange connection avoids structural deformation caused by welding and also improves the overall modularity of the device.

[0020] Preferably, the gas vortex identification system includes a data acquisition device and a computer that are interconnected, and the data acquisition device and the computer are used to process and output identification data.

[0021] Preferably, the liquid has a free surface, which is higher than the inlet bell mouth, so that the liquid can smoothly enter the inlet pipe.

[0022] Preferably, the liquid includes, but is not limited to, water, salt water, water containing sand, etc., and this device is adaptable to a variety of testing conditions.

[0023] Compared with existing technologies, the advantages of this invention are as follows: 1. This invention achieves non-contact real-time monitoring of the flow field in hydraulic machinery, avoiding interference from traditional testing methods. This invention only needs to analyze the time-frequency characteristics of pressure pulsations to determine whether air-bearing vortices occur, providing a reliable real-time early warning method for improving the influent flow pattern and effectively improving the operating efficiency and stability of hydraulic machinery; 2. This invention has strong environmental adaptability. Even under harsh inflow conditions such as turbid water and high sediment content, this invention still has high accuracy in identifying air-bearing vortices; 3. This invention has low cost and is easy to promote. Compared with existing non-contact flow field measurement technologies (such as laser Doppler velocimetry and particle image velocimetry), this invention greatly reduces engineering application costs, and the measurement point layout is simple and easy to operate, showing broad engineering application prospects. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a system for accurately identifying air-containing vortices in hydraulic machinery according to the present invention;

[0025] Figure 2 This is a time-domain diagram of pressure pulsation provided in Embodiment 1 of the present invention;

[0026] Figure 3 This is the time-frequency diagram of pressure pulsation under experimental condition A (N=0) of the present invention, which is free of gas vortices.

[0027] Figure 4 This is a time-frequency diagram of pressure pulsation in experimental case B of the present invention, which involves the generation of gas vortices (N=1).

[0028] Figure 5 This is a time-frequency diagram of pressure pulsation in experimental case C of the present invention, which involves frequent gas vortex occurrence (N=4).

[0029] The components include: 1. Inlet pipe; 11. Horizontal section of inlet pipe; 12. Vertical section of inlet pipe; 2. Pressure measuring hole; 3. Pressure pulsation sensor; 4. Inlet pool; 5. Free liquid surface; 6. Inlet bell mouth; 7. Flange; 8. Data acquisition system; 9. Computer. Detailed Implementation

[0030] To enable those skilled in the art to clearly and completely understand the technical solution of the present invention, the present invention will be further described in detail below with reference to embodiments. Obviously, the embodiments described herein are only for explaining the present invention and are not intended to limit the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0031] Example 1: A method for accurately identifying air-bearing vortices in hydraulic machinery, comprising the following steps:

[0032] Step 1: Install pressure pulsation measuring points on the inlet pipe of the hydraulic machinery and collect the time-domain signal of pressure pulsation;

[0033] Step 2: Perform continuous wavelet transform on the time-domain signal to obtain the pressure pulsation time-frequency diagram;

[0034] Step 3: Extract the characteristic frequency band energy amplitude from the pressure pulsation time-frequency map and compare it with the preset threshold to determine whether gas-containing vortices have appeared.

[0035] Step 4: Analyze the characteristics of gas-bearing vortices based on the spatiotemporal distribution characteristics of characteristic frequency band energy.

[0036] The method provided in this embodiment can be used to achieve active and accurate identification of air-bearing vortices in hydraulic machinery.

[0037] Furthermore, in step 1, the acquired pressure pulsation time-domain signal is subjected to dimensionless processing. The formula for dimensionless processing is: ;

[0038] In the formula, This is a dimensionless pressure pulsation coefficient; The instantaneous pressure at the measuring point; The average pressure at the measuring point; The density of the liquid; This refers to the circumferential speed at the outlet of the hydraulic impeller.

[0039] The collected pressure pulsation time-domain signal is as follows Figure 2 As shown, in this step, the continuous wavelet transform of the pressure pulsation time-domain signal is performed synchronously with the signal acquisition process.

[0040] In the inlet pipeline of hydraulic machinery, the background flow field and the inherent vibration of the system will generate continuous basic pulsations. When the air-containing vortex is drawn in, the distortion, violent rotation and collapse of the air nuclei will cause high instability of the flow in the channel, thereby triggering a surge in local pressure pulsation energy.

[0041] Furthermore, in step 3, a dimensionless intensity factor is introduced. The characteristic frequency band is quantitatively defined, and the intensity factor is calculated using the following formula: ;

[0042] In the formula, Let f be the dimensionless intensity factor of frequency f at time t; Let f be the magnitude of the frequency f at time t; To monitor the average amplitude of frequency f within the specified time period. The characteristic frequency band is: in the pressure pulsation time-frequency diagram, satisfying... The set of frequencies consisting of frequencies f, where Using the preset threshold for identifying air-bearing vortices, the results of actual measurements of pressure pulsation data under vortex conditions combined with high-speed photography show that when no air-bearing vortices appear and the flow field has only weak disturbances, The calculated results are all less than 1.6; while when gaseous vortices occur, the characteristic frequency f is... The values ​​are all consistently greater than 1.8, therefore A value of 1.8 can accurately distinguish between gas vortex disturbances and background noise interference.

[0043] By comparing the transient pulsation amplitude at a specific moment and frequency with the average amplitude of that frequency band over the entire monitoring period, this dynamic ratio calculation can accurately extract the surge in local pulsation energy caused by gas-bearing vortices, thereby enabling precise identification of the unsteady characteristic signals of gas-bearing vortices.

[0044] Furthermore, the intensity factor extracted within the characteristic frequency band satisfies Given the given data points, count the envelope regions formed by these data points, and record the number of envelope regions. , The value of represents the number of cycles of the gas-bearing vortex; the projection length of the envelope region on the time axis represents the duration of the gas-bearing vortex, and the projection length on the frequency axis represents the bandwidth of the gas-bearing vortex.

[0045] when At that time, because there are no frequency components throughout the entire time period The value can exceed the preset recognition threshold. The inability to extract feature data points that meet the conditions means that an effective connected region cannot be formed on the time-frequency surface, indicating that the flow field is in a vortex-free steady state.

[0046] when When N=1, it indicates the presence of an air-containing vortex in the flow field. More specifically, when N=1, it indicates the existence of an isolated vortex disturbance in the flow field.

[0047] when When this occurs, it indicates that there are multiple, intermittent disturbances of air-containing vortices in the flow field.

[0048] Based on the above embodiment 1, the following specific scheme is provided for model experiments to demonstrate the feasibility of the present invention:

[0049] Experimental Example A:

[0050] In this experimental example, the flow rate of inlet tank 4 is set to Q = 16.69 m³ / s. 3 / h, water depth h=191mm, the liquid in the inlet pool is water.

[0051] A continuous wavelet transform is performed on the acquired pressure pulsation time-domain signal to obtain the pressure pulsation time-frequency graph. In the time-frequency graph, the horizontal axis represents time, the vertical axis represents frequency, and the intensity of the spectrum color represents the magnitude of the pressure pulsation. Any point in the graph can represent the intensity of a specific frequency component at a given moment.

[0052] like Figure 3 The figure shows the time-frequency diagram of pressure fluctuations under the condition of no gas vortex (marked as N=0 in the figure). Under this condition, the energy in the time-frequency diagram is mainly concentrated in the 25Hz and 50Hz frequency components, but the energy amplitude in this frequency band is uniformly distributed along the time axis, and the signal is stable. The calculated dimensionless intensity factor of the entire frequency band is shown. All values ​​fluctuated around 1.0, failing to reach the preset threshold for identifying gas-bearing vortices. Therefore, no conditions were met in the time-frequency plot. The number of envelope regions obtained from the data points is N=0, indicating that the flow field at the suction pipe is relatively stable under this working condition, and no air-containing vortices appear.

[0053] Experimental Example B:

[0054] Unlike Experiment A, in Experiment B, the water depth h = 165 mm; other parameters are the same as in Experiment A.

[0055] like Figure 4 The figure shows the time-frequency diagram of pressure fluctuations under the condition of gas vortex generation (marked as N=1 in the figure). Under this condition, a distinct local high-energy region appears on the time-frequency diagram during the period of approximately 5s to 12s. Unlike the steady-state condition, the frequency components in this region are no longer limited to specific low frequencies, but exhibit obvious broadband characteristics. The dimensionless intensity factor of the frequency in the 20Hz to 80Hz frequency band during this period is calculated. All are greater than the preset threshold, and extraction is satisfied. The data points were connected and formed into a connected envelope (white dashed line in the figure). The number of envelope regions, N=1, indicates that an air-bearing vortex evolution process occurred within the suction pipe at this time. Furthermore, the projection length of this envelope region on the time axis (lasting approximately 7 seconds) precisely pinpointed the complete evolution time of the air-bearing vortex from its inception to its collapse, and its evolution period coincided with the time period recorded by high-speed photography when the vortex entered the suction pipe; its projection length on the frequency axis defined the characteristic frequency range of the air-bearing vortex. From the above results, it can be seen that the method provided by this invention can accurately identify the occurrence of air-bearing vortices. This method can not only pinpoint the specific occurrence time of air-bearing vortices but also define the characteristic frequency range (20Hz~80Hz) that induces unsteady pulsations.

[0056] Experimental Example C:

[0057] Unlike Experiment A, in Experiment C, the water depth h = 110 mm; other parameters are the same as in Experiment A.

[0058] like Figure 5 The figure shows the time-frequency diagram of pressure fluctuations under the condition of frequent gas vortex occurrence (marked as N=4 in the figure). Under this condition, four distinct local high-energy regions intermittently appear on the time-frequency diagram throughout the monitoring period. The frequency components in these regions not only break the limitation of the characteristic low frequency, but also exhibit more obvious broadband characteristics. The dimensionless intensity factor of the frequency in the 10Hz~90Hz frequency band within the corresponding period is calculated. All are greater than the preset threshold, and extraction is satisfied. The data points were connected and formed into a connected envelope (white dashed line in the figure). The number of envelope regions obtained was N=4, indicating that there were four gas-bearing vortex evolution processes within the suction pipe at this time. Projecting the envelope region onto the time axis, the corresponding occurrence periods of these four gas-bearing vortices were 3.5s~6s, 10.5s~13s, 17s~25s, and 27s~30s, which are consistent with the time periods when the vortices entered the suction pipe recorded by high-speed photography. Projecting the envelope region onto the frequency axis, the corresponding characteristic frequencies of the four vortices were 15Hz~60Hz, 25Hz~55Hz, 10Hz~90Hz, and 10Hz~65Hz, respectively. It can be seen that the third gas-bearing vortex lasted the longest and had the widest characteristic frequency band, indicating that its disturbance to the internal flow field of the inlet pipe was also the most intense. As can be seen from the above results, the method provided by the present invention can not only identify single gas-containing vortex conditions, but also has the ability to continuously and accurately monitor intermittent and frequent occurrences of gas-containing vortices under complex flow field conditions.

[0059] Example 2: This application also provides a device for accurately identifying air-containing vortices in hydraulic machinery, used to implement the identification method described above, such as... Figure 1As shown, it includes a water inlet tank 4 containing liquid, and a water inlet pipe 1 is provided in the water inlet tank 4. The water inlet pipe 1 includes a horizontal section 11 and a vertical section 12. A pressure measuring hole 2 is opened on the center line of the cross section of the horizontal section 11. A pressure pulsation sensor 3 is installed in the pressure measuring hole 2. The pressure pulsation sensor 3 is communicatively connected to a gas vortex identification system.

[0060] In this embodiment, the pressure measuring hole 2 is located on the center line of the cross-section of the horizontal section 11 of the inlet pipe. This location effectively captures the main frequency energy of pressure pulsations caused by air vortices, while avoiding interference from the pipe wall boundary layer and the secondary flow at bends, thus improving the signal-to-noise ratio. The pressure pulsation sensor 3 is an HBM-P8AP sensor. It is flush with the pipe wall and does not protrude from the inner wall, avoiding additional disturbance to the inlet flow field and ensuring that the measurement results reflect the true flow field state. The air vortex identification system, wirelessly connected to the pressure pulsation sensor 3, can incorporate the aforementioned algorithm modules such as continuous wavelet transform, intensity factor calculation, and envelope region statistics to output the final identification result. The device provided in this embodiment only requires a small hole to be opened in the existing inlet pipe 1 and the pressure pulsation sensor 3 to be installed. No large-scale modifications to the structure of the inlet pool 4 are required. Compared to optical devices such as LDV (Laser Doppler Velocimetry) or PIV (Particle Image Velocimetry), the pressure pulsation sensor 3 used in this device is unaffected by water turbidity or sediment content, exhibiting strong environmental adaptability.

[0061] Furthermore, the lower end of the vertical section 12 of the water inlet pipe is provided with a water inlet bell 6.

[0062] The inlet bell-shaped design 6 guides water flow smoothly and evenly from the inlet pool 4 into the inlet pipe 1, effectively suppressing small-scale, non-air-containing vortex disturbances induced by abrupt changes in the inlet shape. This significantly reduces background noise in the signal collected by the pressure pulsation sensor 3, highlighting the characteristic pulsation signals caused by air-containing vortices. Without the inlet bell-shaped design 6, continuous attachment or separation vortices may be generated at the edge of the inlet pipe 1, whose pressure pulsation characteristics partially overlap with the frequency band of air-containing vortices, easily leading to misjudgments. The streamlined inlet design of the inlet bell-shaped design 6 eliminates such interference sources, making characteristic frequency band extraction and envelope region statistics more reliable. The inlet bell-shaped design 6 can preferably be connected to the lower end of the vertical section 12 of the inlet pipe via a slot.

[0063] Furthermore, the horizontal section 11 of the water inlet pipe and the vertical section 12 of the water inlet pipe are connected by flange 7.

[0064] If welding is used, the high temperature of welding will cause local thermal stress deformation in the inlet pipe 1, altering its roundness or inner wall flatness. Flange connections are cold mechanical connections, free from thermal effects, ensuring the original accuracy of the sensor mounting reference surface. Flange connections allow the horizontal section 11 or the vertical section 12 of the inlet pipe to be prefabricated as independent components, ensuring the critical position of the pressure measuring hole 2 at the cross-sectional centerline. During on-site assembly, flange positioning ensures the coaxiality of the horizontal and vertical sections 12, preventing the pressure measuring hole 2 from deviating from the predetermined circumferential angle due to pipe misalignment. If future expansion of monitoring functions is needed, the horizontal section 11 of the flange-connected inlet pipe can be removed as an independent module, and additional sensor interfaces can be created on its wall before reinstallation, demonstrating good scalability.

[0065] Furthermore, the gas vortex identification system includes a data acquisition device 8 and a computer 9 that are interconnected.

[0066] In this embodiment, the data acquisition device 8 adopts an HBM integrated data acquisition system. The data acquisition device 8 is responsible for high-precision, synchronous acquisition of pressure pulsation time-domain signals, avoiding signal attenuation or delay. The computer 9 is responsible for performing continuous wavelet transform, dimensionless intensity factor calculation, and envelope region statistics, realizing online real-time monitoring with "acquisition and calculation simultaneously," resulting in low output latency. The computer 9 can be equipped with a graphical interface to display pressure pulsation time-domain graphs, time-frequency graphs, envelope region (N value), vortex duration, bandwidth, and other parameters in real time. An automatic alarm is triggered when N≥1, facilitating rapid assessment of the flow field state and implementation of control measures by maintenance personnel.

[0067] Furthermore, the liquid has a free surface 5, which is higher than the inlet bell mouth 6.

[0068] During the operation of this embodiment, the free liquid level 5 needs to always be higher than the inlet bell mouth 6 so that the liquid in the inlet pool 4 can smoothly enter the vertical section 12 of the inlet pipe and then flow to the horizontal section 11 of the inlet pipe.

[0069] Furthermore, the liquid includes, but is not limited to, water, salt water, water containing sand, etc.

[0070] In this embodiment, the selected test liquid includes, but is not limited to, water, salt water, water containing sand, etc. The device provided in this embodiment can be adapted to most real-world working conditions and has good application scenarios.

[0071] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A method of accurately identifying gas-containing vortices in a hydraulic machine, characterized by, Includes the following steps: Step 1: Install pressure pulsation measuring points on the inlet pipe of the hydraulic machinery and collect the time-domain signal of pressure pulsation; Step 2: Perform continuous wavelet transform on the time-domain signal to obtain the pressure pulsation time-frequency diagram; Step 3: Extract the characteristic frequency band energy amplitude from the pressure pulsation time-frequency graph and compare it with a preset threshold to determine whether an air-containing vortex has appeared. Step 4: Analyze the characteristics of gas-bearing vortices based on the spatiotemporal distribution characteristics of the energy in the characteristic frequency band.

2. A method of accurately identifying a gas core of a hydraulic machine according to claim 1, characterized in that, In step 1, the acquired pressure pulsation time-domain signal is processed using a dimensionless method. The formula for this dimensionless processing is as follows: ； In the formula, This is a dimensionless pressure pulsation coefficient; The instantaneous pressure at the measuring point; The average pressure at the measuring point; The density of the liquid; This refers to the circumferential speed at the outlet of the hydraulic impeller.

3. The method for accurately identifying air-bearing vortices in hydraulic machinery according to claim 1, characterized in that, In step 3, a dimensionless intensity factor is introduced. The characteristic frequency band is quantitatively defined, and the intensity factor is calculated using the following formula: ； In the formula, Let f be the dimensionless intensity factor of frequency f at time t; Let f be the magnitude of the frequency f at time t; This represents the average amplitude of frequency f during the monitoring period.

4. The method for accurately identifying air-bearing vortices in hydraulic machinery according to claim 3, characterized in that, Extract the intensity factor within the characteristic frequency band to satisfy Given the given data points, count the envelope regions formed by these data points, and record the number of such envelope regions. ,when If the flow field contains an air-containing vortex, then it is determined that an air-containing vortex has appeared.

5. A device for accurately identifying air-bearing vortices in hydraulic machinery, used to implement the method for accurately identifying air-bearing vortices in hydraulic machinery as described in any one of claims 1 to 4, characterized in that, It includes a water inlet tank containing liquid, and a water inlet pipe is provided in the water inlet tank. The water inlet pipe includes a horizontal section and a vertical section. A pressure measuring hole is opened on the center line of the cross-section of the horizontal section of the water inlet pipe. A pressure pulsation sensor is installed in the pressure measuring hole. The pressure pulsation sensor is communicatively connected to a gas vortex identification system.

6. The device for accurately identifying air-containing vortices in hydraulic machinery according to claim 5, characterized in that, The lower end of the vertical section of the water inlet pipe is equipped with a water inlet bell.

7. The device for accurately identifying air-containing vortices in hydraulic machinery according to claim 5, characterized in that, The horizontal section of the water inlet pipe is connected to the vertical section of the water inlet pipe via flanges.

8. The device for accurately identifying air-containing vortices in hydraulic machinery according to claim 5, characterized in that, The gas vortex identification system includes data acquisition devices and a computer that are interconnected.

9. The device for accurately identifying air-containing vortices in hydraulic machinery according to claim 5, characterized in that, The liquid has a free surface, which is higher than the inlet bell mouth.

10. The device for accurately identifying air-containing vortices in hydraulic machinery according to claim 5, characterized in that, The liquid is water, salt water, or water containing sand.

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