A method and system for detecting small leaks in buried pipelines based on resonance cavity modulation

Abstract

The present invention discloses a method and system for detecting tiny leaks in buried pipelines based on resonance cavity modulation, which belongs to the field of detection of tiny leaks in buried pipelines and includes the following steps: S1, sending a sound wave signal with adjustable parameters to the pipeline; S2, using the resonance cavity formed by the tiny leak hole in the pipeline and the soil to perform nonlinear modulation on the sound wave signal; S3, performing decomposition and filtering on the sound wave signal; S4, judging whether there is a tiny leak hole in the pipeline; S5, obtaining the position of the tiny leak hole in the pipeline on the pipeline and visually displaying it. The present invention adopts the above-mentioned method and system for detecting tiny leaks in buried pipelines based on resonance cavity modulation, and nonlinearly modulates the sound wave through the resonance cavity formed by the tiny leak hole in the pipeline and the soil, and amplifies the sound wave, which can greatly improve the detection and identification capabilities of tiny leaks, and has the advantages of anti-noise interference, detection of tiny leaks, and the ability to visualize the position of tiny leaks on the pipeline.

Description

Technical Field

[0001] The present invention relates to the technical field of buried pipeline micro-leakage detection, and in particular to a buried pipeline micro-leakage detection method and system based on resonance cavity modulation. Background Art

[0002] Buried pipelines have the advantages of large transportation volume, low cost, and little impact from external conditions such as weather, so they are often used in the transportation of water, oil, gas and other substances. However, during the long-term operation and service of buried pipelines, they are often affected by factors such as corrosion, vibration, and stress fatigue, and are prone to leakage accidents, resulting in economic losses, environmental pollution, and even casualties. Therefore, the earlier the leakage accident is detected, the smaller the loss will be. Therefore, if effective detection can be carried out at the initial stage of pipeline leakage, the harm and loss of the accident will be effectively reduced, which is of great significance to the normal operation of the pipeline and the safety of the people.

[0003] At present, a variety of pipeline leakage detection methods have been developed, such as tracer method, infrared thermal imaging method, pipeline internal detector method, mass (flow) balance method, pressure point analysis method, optical fiber method and acoustic method, etc. Compared with other methods, the acoustic method is easy to install and maintain, does not require a large amount of excavation of the soil above the pipeline, and has certain advantages in the field of buried pipeline leakage detection.

[0004] The principle of most acoustic methods at present is: regard the leak point on the pipeline as the sound source, install an acoustic sensor on the pipeline, and passively receive the sound emitted by the leak point, and then perform detection. This method is generally suitable for large leaks, that is, it is assumed that the leak point can emit a strong enough sound. However, for some buried pipelines, due to the low gas pressure inside the pipeline or the compact soil above the pipeline, the sound emitted by the initial small leak is very weak and easily disturbed by noise. In this case, it is difficult to detect small leaks in the pipeline. Summary of the invention

[0005] To solve the above problems, the present invention provides a method and system for detecting tiny leaks in buried pipelines based on resonance cavity modulation. The sound waves are nonlinearly modulated and amplified through the resonance cavity formed by the tiny leakage holes in the pipeline and the soil, which can greatly improve the detection and identification capabilities of tiny leaks. The system has the advantages of being able to resist noise interference, detect tiny leaks, and visualize the location of tiny leaks on the pipeline.

[0006] To achieve the above object, the present invention provides a method for detecting small leaks in buried pipelines based on resonance cavity modulation, comprising the following steps:

[0007] S1, send a sound wave signal with adjustable parameters to the pipeline;

[0008] S2, the sound wave signal propagates along the pipeline, and when there is a tiny leak hole in the pipeline, the resonance cavity formed by the tiny leak hole in the pipeline and the soil is used to nonlinearly modulate the sound wave signal to amplify the sound wave signal of the set frequency band, and the resonance cavity then reflects the amplified sound wave signal of the set frequency band back to the pipeline;

[0009] S3, receiving the acoustic wave signal modulated by the resonance cavity and reflected back to the pipeline, and performing acoustic wave signal decomposition and filtering;

[0010] S4. Determine whether there are small leak holes in the pipeline:

[0011] The sound wave signal is subjected to waveform analysis, and whether there is a tiny leak in the pipeline is determined by retrieving the sound wave signal of the set frequency band. That is, when the sound wave signal of the set frequency band is retrieved, it is determined that there is a tiny leak hole in the pipeline, otherwise it is determined that there is no tiny leak hole in the pipeline.

[0012] Preferably, step S2 specifically includes the following steps:

[0013] S21. The relationship between the resonance center frequency, the size of the tiny leak hole in the pipeline, and the resonance cavity volume is set as follows:

[0014]

[0015] Where f1 is the resonance center frequency, c is the propagation speed of the acoustic wave signal in the pipeline transmission medium, S is the cross-sectional area of ​​the tiny leakage hole in the pipeline, V is the volume of the resonance cavity formed by the pipeline and the soil, L is the length of the pipeline leakage hole, and Le is the correction factor;

[0016] S22. Considering the equivalent volume of the debris particles in the resonance cavity, optimize the calculation of the resonance center frequency:

[0017]

[0018] Where f2 is the resonance center frequency when considering the debris particles in the resonance cavity, and W is the equivalent volume of the debris particles;

[0019] S23. Calculate the acoustic signal amplification factor A:

[0020]

[0021] Calculate the acoustic wave signal reflection coefficient Re of the resonant cavity:

[0022]

[0023] In the formula, S p is the cross-sectional area of ​​the pipeline, M is the acoustic mass of the tiny leak hole in the pipeline, C is the acoustic capacity of the resonance cavity, and ω is the angular frequency of the acoustic wave signal;

[0024] in,

[0025]

[0026] Where ρ is the density of the medium inside the pipeline.

[0027] Preferably, in step S21, the correction factor Le is calculated according to the size of the tiny leakage hole in the pipeline and the internal pressure of the pipeline;

[0028] The calculation formula is as follows:

[0029]

[0030] Where r is the radius of the tiny leak hole in the pipeline, P is the internal pressure of the pipeline, and P0 is the reference pressure.

[0031] Preferably, in step S3, the acoustic wave signal propagation process is as follows:

[0032] First, the emitted sound wave signal propagates along the pipeline until it reaches a tiny leak hole on the pipeline, and the sound wave enters the resonance cavity;

[0033] Then the resonance cavity is used to perform nonlinear modulation on the incoming sound wave signal to amplify the sound wave signal of the set frequency band;

[0034] Finally, the resonant cavity reflects the amplified sound wave signal back to the pipeline.

[0035] Preferably, the sound wave signal decomposition formula described in step S3 is as follows:

[0036]

[0037] Where IMF is the intrinsic mode function, which satisfies the following conditions: (1) the number of zero-crossing points and the number of extreme points in the acoustic signal are equal or differ by at most one; (2) the mean of the upper and lower envelopes of the acoustic signal is zero; t is the emission time of the acoustic signal, r is n represents the residual value, n represents the number of intrinsic mode functions obtained by decomposing the acoustic wave signal;

[0038] The sound wave signal filtering step described in step S3 includes: taking the resonance center frequency f2 as a reference, retaining the IMF component of the sound wave signal in a set frequency band, and filtering out the IMF components of the remaining frequency bands.

[0039] Preferably, after step S4, step S5 is also included:

[0040] When there is a tiny leak hole in the pipeline, the sound distance conversion calculation is performed on the sound wave signal of the set frequency band to obtain a visual display of the position of the tiny leak hole on the pipeline.

[0041] Preferably, the sound distance conversion calculation formula is as follows:

[0042]

[0043] Where d is the distance between the speaker and the tiny leak hole in the pipeline, t1 is the time when the sound wave signal is emitted, and t2 is the time when the sound wave signal is received.

[0044] Preferably, the parameters described in step S1 include amplitude and frequency;

[0045] The amplitude adjustment method is: according to the amplitude of the received sound wave signal, the amplitude of the emitted sound wave signal is reversely adjusted to ensure that the amplitude of the received sound wave signal is within the detectable range. The adjustment formula is as follows:

[0046]

[0047] Where A0(ω) represents the amplitude of the emitted sound wave signal; A1(ω,x) represents the amplitude of the received sound wave signal at position x on the pipeline; x represents the distance between the position where the sound wave signal is received and the position where the sound wave signal is emitted; k represents the pipeline complex wave number, and the imaginary part of k contains the attenuation coefficient of the pipeline;

[0048] The frequency adjustment method is: expanding based on the resonance center frequency f2 calculated in step S22.

[0049] A system for detecting small leaks in buried pipelines based on resonance cavity modulation, comprising:

[0050] Active acoustic wave excitation module, used to send acoustic wave signals with adjustable parameters to the pipeline;

[0051] The resonance cavity structure analysis module is used to utilize the resonance cavity formed by the tiny leakage hole in the pipeline and the soil to perform nonlinear modulation on the acoustic wave signal emitted by the active acoustic wave excitation module to amplify the acoustic wave signal of the set frequency band, and the resonance cavity then reflects the amplified acoustic wave signal of the set frequency band back to the pipeline;

[0052] The sound wave receiving module is used to receive the sound wave signal modulated by the resonance cavity and reflected back to the pipeline, and to decompose and filter the sound wave signal;

[0053] The micro-leakage detection module is used to analyze the waveform of the acoustic wave signal and determine whether there is a micro-leakage hole in the pipeline by searching the acoustic wave signal of the set frequency band;

[0054] The leakage position acoustic distance imaging module is used to perform acoustic distance conversion calculation on the sound wave signal of a set frequency band when a tiny leak hole is detected in the pipeline, so as to obtain a visual display of the position of the tiny leak hole on the pipeline;

[0055] Communication and power supply module, used for communication and power supply of the above modules.

[0056] Preferably, the active sound wave excitation module comprises a sound wave generator, a signal amplifier and a speaker connected in sequence, and the speaker is fixed to the end of the pipeline via a connecting flange;

[0057] Among them, the sound wave generator is used to generate a sound wave signal with adjustable parameters, including amplitude, frequency and phase; the signal amplifier is used to amplify the sound wave signal generated by the sound wave generator; and the speaker is used to transmit the amplified sound wave signal into the inside of the pipeline.

[0058] The present invention has the following beneficial effects:

[0059] (1) The special structure of the resonance cavity formed by the tiny leak hole in the pipeline and the soil can be used to perform nonlinear modulation on the sound waves and amplify the sound waves in the set frequency band, which can greatly improve the detection capability of tiny leaks;

[0060] (2) The proposed method is resistant to noise interference and can visualize the location of small leaks on the pipeline.

[0061] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a logic flow chart of a method for detecting small leakage of buried pipelines based on resonance cavity modulation of the present invention;

[0063] Figure 2 A resonant cavity schematic diagram of a method for detecting small leaks in buried pipelines based on resonant cavity modulation according to the present invention

[0064] Figure 3 It is a schematic diagram of the effect of the resonance cavity modulation on the number of sound wave reflections in a method for detecting small leaks in buried pipelines based on the resonance cavity modulation of the present invention;

[0065] Figure 4 Schematic diagram of a method for detecting micro-leakage of buried pipelines based on resonance cavity modulation according to the present invention, (a) there is no micro-leakage in the pipeline, (b) there is a micro-leakage in the pipeline;

[0066] Figure 5 A layout diagram of a system for a method for detecting tiny leaks in buried pipelines based on resonance cavity modulation according to the present invention;

[0067] Figure 6 Another arrangement diagram of a system for a method for detecting tiny leaks in buried pipelines based on resonance cavity modulation according to the present invention;

[0068] Figure 7It is a schematic diagram of the acoustic distance imaging result of an embodiment of the present invention. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical scheme and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions.

[0070] It should be noted that the terms "include", "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or server comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or devices.

[0071] Like reference numerals and letters denote similar items in the following drawings, and thus, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0072] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0073] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "setting", "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0074] like Figure 1-Figure 4 As shown, a method for detecting small leaks in buried pipelines based on resonance cavity modulation comprises the following steps:

[0075] S1, send a sound wave signal with adjustable parameters to the pipeline;

[0076] The parameters described in step S1 include amplitude and frequency;

[0077] The amplitude adjustment method is: according to the amplitude of the received sound wave signal, the amplitude of the emitted sound wave signal is reversely adjusted to ensure that the amplitude of the received sound wave signal is within the detectable range. The adjustment formula is as follows:

[0078]

[0079] Where A0(ω) represents the amplitude of the emitted sound wave signal; A1(ω,x) represents the amplitude of the received sound wave signal at position x on the pipeline; x represents the distance between the position where the sound wave signal is received and the position where the sound wave signal is emitted; k represents the pipeline complex wave number, and the imaginary part of k contains the attenuation coefficient of the pipeline;

[0080] The frequency adjustment method is: expanding based on the resonance center frequency f2 calculated in step S22, such as setting the frequency range to [a*f2, b*f2], a is 0.1 to 0.5, and b is 1.5 to 2.

[0081] In this embodiment, when the waveform is not obvious, the phase of the sound wave signal can be adjusted, that is, based on the first waveform signal, a second sound wave signal is emitted, and there is a phase difference of 90° between the first sound wave signal and the second sound wave signal, which is convenient for observing the waveform.

[0082] S2, the sound wave signal propagates along the pipeline, and when there is a tiny leak hole in the pipeline, the resonance cavity formed by the tiny leak hole in the pipeline and the soil is used to nonlinearly modulate the sound wave signal to amplify the sound wave signal of the set frequency band, and the resonance cavity then reflects the amplified sound wave signal of the set frequency band back to the pipeline;

[0083] Step S2 specifically includes the following steps:

[0084] S21. The relationship between the resonance center frequency, the size of the tiny leak hole in the pipeline, and the resonance cavity volume is set as follows:

[0085]

[0086] Where f1 is the resonance center frequency, c is the propagation speed of the acoustic wave signal in the pipeline transmission medium, S is the cross-sectional area of ​​the tiny leakage hole in the pipeline, V is the volume of the resonance cavity formed by the pipeline and the soil, L is the length of the pipeline leakage hole, and Le is the correction factor;

[0087] In step S21, a correction factor Le is calculated according to the size of the tiny leak hole in the pipeline and the internal pressure of the pipeline;

[0088] The calculation formula is as follows:

[0089]

[0090] Where r is the radius of the tiny leak hole in the pipeline, P is the internal pressure of the pipeline, and P0 is the reference pressure.

[0091] S22. There will be debris such as sand and soil particles in the resonance cavity formed by the pipeline leakage hole and the soil. Therefore, the equivalent volume of the debris particles in the resonance cavity is considered to optimize the calculation of the resonance center frequency:

[0092]

[0093] In the formula, f2 is the resonance center frequency when considering the debris particles in the resonance cavity, and W is the equivalent volume of the debris particles, so as to obtain a more accurate resonance center frequency;

[0094] S23. The resonance cavity will amplify and amplify the sound waves near the resonance frequency. Calculate the amplification factor A of the sound wave signal:

[0095]

[0096] Calculate the acoustic wave signal reflection coefficient Re of the resonant cavity:

[0097]

[0098] In the formula, S p is the cross-sectional area of ​​the pipeline, M is the acoustic mass of the tiny leak hole in the pipeline, C is the acoustic capacity of the resonance cavity, and ω is the angular frequency of the acoustic wave signal;

[0099] in,

[0100]

[0101] Where ρ is the density of the medium inside the pipeline.

[0102] S3, receiving the acoustic wave signal modulated by the resonance cavity and reflected back to the pipeline, and performing acoustic wave signal decomposition and filtering;

[0103] In step S3, the acoustic wave signal propagation process is as follows:

[0104] First, the emitted sound wave signal propagates along the pipeline until it reaches a tiny leak hole on the pipeline, and the sound wave enters the resonance cavity;

[0105] Then the resonance cavity is used to perform nonlinear modulation on the incoming sound wave signal to amplify the sound wave signal of the set frequency band;

[0106] Finally, the resonant cavity reflects the amplified sound wave signal back to the pipeline.

[0107] The acoustic wave signal decomposition formula described in step S3 is as follows:

[0108]

[0109] Where IMF is the intrinsic mode function, which satisfies the following conditions: (1) the number of zero-crossing points and the number of extreme points in the acoustic signal are equal or differ by at most one; (2) the mean of the upper and lower envelopes of the acoustic signal is zero; t is the emission time of the acoustic signal, r is n represents the residual value, n represents the number of intrinsic mode functions obtained by decomposing the acoustic wave signal;

[0110] The sound wave signal filtering step described in step S3 includes: taking the resonance center frequency f2 as a reference, retaining the IMF component of the sound wave signal in a set frequency band, and filtering out the IMF components of the remaining frequency bands.

[0111] S4. Determine whether there are small leak holes in the pipeline:

[0112] The sound wave signal is subjected to waveform analysis, and whether there is a tiny leak in the pipeline is determined by retrieving the sound wave signal of the set frequency band. That is, when the sound wave signal of the set frequency band is retrieved, it is determined that there is a tiny leak hole in the pipeline, otherwise it is determined that there is no tiny leak hole in the pipeline.

[0113] After step S4, the method further includes step S5:

[0114] When there is a tiny leak hole in the pipeline, the sound distance conversion calculation is performed on the sound wave signal of the set frequency band to obtain a visual display of the position of the tiny leak hole on the pipeline.

[0115] Preferably, the sound distance conversion calculation formula is as follows:

[0116]

[0117] Where d is the distance between the speaker and the tiny leak hole in the pipeline, t1 is the time when the sound wave signal is emitted, and t2 is the time when the sound wave signal is received.

[0118] Example: Figure 7 As shown, there is a small leak at the 60-meter position in a 100-meter pipeline.

[0119] like Figure 5 and Figure 6 As shown, a system for detecting small leaks in buried pipelines based on resonance cavity modulation comprises:

[0120] An active acoustic wave excitation module is used to send an acoustic wave signal with adjustable parameters to the pipeline; the active acoustic wave excitation module includes an acoustic wave generator, a signal amplifier and a speaker connected in sequence, and the speaker is fixed to the end of the pipeline through a connecting flange; wherein the acoustic wave generator is used to generate an acoustic wave signal with adjustable parameters, and the parameters include amplitude, frequency and phase; the signal amplifier is used to amplify the acoustic wave signal generated by the acoustic wave generator; and the speaker is used to transmit the amplified acoustic wave signal to the inside of the pipeline.

[0121] The speaker of the active acoustic wave excitation module can be fixed at the pipeline valve or pipeline port position using a connecting flange.

[0122] The resonance cavity structure analysis module is used to utilize the resonance cavity formed by the tiny leakage hole in the pipeline and the soil to perform nonlinear modulation on the acoustic wave signal emitted by the active acoustic wave excitation module to amplify the acoustic wave signal of the set frequency band, and the resonance cavity then reflects the amplified acoustic wave signal of the set frequency band back to the pipeline;

[0123] The sound wave receiving module is used to receive the sound wave signal modulated by the resonance cavity and reflected back to the pipeline, and to decompose and filter the sound wave signal;

[0124] The micro-leakage detection module is used to analyze the waveform of the acoustic wave signal and determine whether there is a micro-leakage hole in the pipeline by searching the acoustic wave signal of the set frequency band;

[0125] The leakage position acoustic distance imaging module is used to perform acoustic distance conversion calculation on the sound wave signal of a set frequency band when a tiny leak hole is detected in the pipeline, and obtain a visual display of the position of the tiny leak hole on the pipeline;

[0126] The communication and power supply module is used for communication and power supply of the above modules. In this embodiment, it is also used to upload the detection results to the dispatching center.

[0127] In this embodiment, the active acoustic wave excitation module, the resonance cavity structure analysis module, the acoustic wave receiving module, the micro-leakage detection module, and the leakage position acoustic distance imaging module are connected in sequence via the communication and power supply module.

[0128] Therefore, the present invention adopts the above-mentioned buried pipeline micro-leakage detection method and system based on resonance cavity modulation, and nonlinearly modulates the sound waves through the resonance cavity formed by the micro-leakage hole of the pipeline and the soil, and amplifies the sound waves, which can greatly improve the detection and identification capabilities of micro-leakages. It has the advantages of resisting noise interference, detecting micro-leakages, and being able to visualize the location of micro-leakages on the pipeline.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for detecting small leaks in buried pipelines based on resonance cavity modulation, characterized in that: The following steps are involved: S1, send a sound wave signal with adjustable parameters to the pipeline; The parameters described in step S1 include amplitude and frequency; The amplitude adjustment method is: according to the amplitude of the received sound wave signal, the amplitude of the emitted sound wave signal is reversely adjusted to ensure that the amplitude of the received sound wave signal is within the detectable range. The adjustment formula is as follows: Where A0(ω) represents the amplitude of the emitted sound wave signal; A1(ω,x) represents the amplitude of the received sound wave signal at position x on the pipeline; x represents the distance between the position where the sound wave signal is received and the position where the sound wave signal is emitted; k represents the pipeline complex wave number, and the imaginary part of k contains the attenuation coefficient of the pipeline; The frequency adjustment method is: expanding based on the resonance center frequency f2 calculated in step S22; S2, the sound wave signal propagates along the pipeline, and when there is a tiny leak hole in the pipeline, the resonance cavity formed by the tiny leak hole in the pipeline and the soil is used to nonlinearly modulate the sound wave signal to amplify the sound wave signal of the set frequency band, and the resonance cavity then reflects the amplified sound wave signal of the set frequency band back to the pipeline; Step S2 specifically includes the following steps: S21. The relationship between the resonance center frequency, the size of the tiny leak hole in the pipeline, and the resonance cavity volume is set as follows: Where f1 is the resonance center frequency, c is the propagation speed of the acoustic wave signal in the pipeline transmission medium, S is the cross-sectional area of ​​the tiny leakage hole in the pipeline, V is the volume of the resonance cavity formed by the pipeline and the soil, L is the length of the pipeline leakage hole, and Le is the correction factor; In step S21, a correction factor Le is calculated according to the size of the tiny leak hole in the pipeline and the internal pressure of the pipeline; The calculation formula is as follows: In the formula, r is the radius of the tiny leak hole in the pipeline, P is the internal pressure of the pipeline, and P0 is the reference pressure; S22. Considering the equivalent volume of the debris particles in the resonance cavity, optimize the calculation of the resonance center frequency: Where f2 is the resonance center frequency when considering the debris particles in the resonance cavity, and W is the equivalent volume of the debris particles; S23. Calculate the acoustic signal amplification factor A: Calculate the acoustic wave signal reflection coefficient Re of the resonant cavity: In the formula, S p is the cross-sectional area of ​​the pipeline, M is the acoustic mass of the tiny leak hole in the pipeline, C is the acoustic capacity of the resonance cavity, and ω is the angular frequency of the acoustic wave signal; in, Where ρ is the density of the medium inside the pipeline; S3, receiving the acoustic wave signal modulated by the resonance cavity and reflected back to the pipeline, and performing acoustic wave signal decomposition and filtering; In step S3, the acoustic wave signal propagation process is as follows: First, the emitted sound wave signal propagates along the pipeline until it reaches a tiny leak hole on the pipeline, and the sound wave enters the resonance cavity; Then the resonance cavity is used to perform nonlinear modulation on the incoming sound wave signal to amplify the sound wave signal of the set frequency band; Finally, the resonant cavity reflects the amplified sound wave signal back to the pipeline; The acoustic wave signal decomposition formula described in step S3 is as follows: Where IMF is the intrinsic mode function, which satisfies the following conditions: (1) the number of zero-crossing points and the number of extreme points in the acoustic signal are equal or differ by at most one; (2) the mean of the upper and lower envelopes of the acoustic signal is zero; t is the emission time of the acoustic signal, r is n represents the residual value, n represents the number of intrinsic mode functions obtained by decomposing the acoustic wave signal; The sound wave signal filtering step described in step S3 includes: taking the resonance center frequency f2 as a reference, retaining the IMF component of the sound wave signal in the set frequency band, and filtering out the IMF components of the remaining frequency bands; S4. Determine whether there are small leak holes in the pipeline: The sound wave signal is subjected to waveform analysis, and whether there is a tiny leak in the pipeline is determined by retrieving the sound wave signal of the set frequency band. That is, when the sound wave signal of the set frequency band is retrieved, it is determined that there is a tiny leak hole in the pipeline, otherwise it is determined that there is no tiny leak hole in the pipeline.

2. The method for detecting small leaks in buried pipelines based on resonance cavity modulation according to claim 1 is characterized in that: After step S4, the method further includes step S5: When there is a tiny leak hole in the pipeline, the sound distance conversion calculation is performed on the sound wave signal of the set frequency band to obtain a visual display of the position of the tiny leak hole on the pipeline.

3. The method for detecting small leaks in buried pipelines based on resonance cavity modulation according to claim 2 is characterized in that: The sound distance conversion calculation formula is as follows: Where d is the distance between the speaker and the tiny leak hole in the pipeline, t1 is the time when the sound wave signal is emitted, and t2 is the time when the sound wave signal is received.

4. A system for detecting small leaks in buried pipelines based on resonance cavity modulation as claimed in any one of claims 1 to 3, characterized in that: include: Active acoustic wave excitation module, used to send acoustic wave signals with adjustable parameters to the pipeline; The resonance cavity structure analysis module is used to utilize the resonance cavity formed by the tiny leakage hole in the pipeline and the soil to perform nonlinear modulation on the acoustic wave signal emitted by the active acoustic wave excitation module to amplify the acoustic wave signal of the set frequency band, and the resonance cavity then reflects the amplified acoustic wave signal of the set frequency band back to the pipeline; The sound wave receiving module is used to receive the sound wave signal modulated by the resonance cavity and reflected back to the pipeline, and to decompose and filter the sound wave signal; The micro-leakage detection module is used to analyze the waveform of the acoustic wave signal and determine whether there is a micro-leakage hole in the pipeline by searching the acoustic wave signal of the set frequency band; The leakage position acoustic distance imaging module is used to perform acoustic distance conversion calculation on the sound wave signal of a set frequency band when a tiny leak hole is detected in the pipeline, so as to obtain a visual display of the position of the tiny leak hole on the pipeline; Communication and power supply module, used for communication and power supply of the above modules.

5. A system for detecting small leaks in buried pipelines based on resonance cavity modulation as claimed in claim 4, characterized in that: The active acoustic wave excitation module includes an acoustic wave generator, a signal amplifier and a speaker connected in sequence, and the speaker is fixed to the end of the pipeline via a connecting flange; Among them, the sound wave generator is used to generate a sound wave signal with adjustable parameters, including amplitude, frequency and phase; the signal amplifier is used to amplify the sound wave signal generated by the sound wave generator; and the speaker is used to transmit the amplified sound wave signal into the inside of the pipeline.

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