A gas accumulation detection device and method based on the rate of change of acoustic resonant cavity frequency

Abstract

The present application belongs to the technical field of mine safety monitoring and gas sensing, and particularly relates to a gas accumulation detection device and method based on the frequency change rate of an acoustic resonant cavity, comprising an open straight-through acoustic resonant cavity module, a signal generation and driving module, and a signal acquisition and processing module; the open straight-through acoustic resonant cavity module comprises a resonant cavity body, a loudspeaker, and a microphone; the signal generation and driving module comprises a microprocessor, a D / A converter, a signal generator, a power amplifier, and a loudspeaker which are electrically connected in sequence; the signal acquisition and processing module comprises the microphone, a signal amplifier, a band-pass filter, and an A / D converter which are electrically connected in sequence; the microprocessor is used to solve the change rate of the resonant frequency in real time, and compare it with a preset threshold value, so as to realize dynamic and rapid sensing of the change of the gas concentration and graded early warning. The present application solves the problem that the traditional static concentration measurement method is difficult to alarm in time due to response lag when the gas concentration changes rapidly.

Description

Technical Field

[0001] This invention relates to a gas accumulation detection device and method based on the frequency change rate of an acoustic resonant cavity, belonging to the fields of mine safety monitoring technology and gas sensing. Background Technology

[0002] In my country, approximately 60% of coal seams are soft, low-permeability, and high-gas. Gas (mainly methane CH4) hazards endanger most mining areas, and gas accumulation is one of the major safety hazards in underground coal mines. When the gas concentration reaches a certain threshold, it can trigger an explosion upon contact with an open flame, seriously threatening the lives of miners and the safety of mine production. Abnormal gas outbursts or eruptions are characterized by their suddenness, short duration, and high intensity. Therefore, more effective safety monitoring and early warning systems are needed in coal mine production to reduce gas hazards and prevent them from occurring. This places extremely high demands on the rapid and accurate detection of gas accumulation processes.

[0003] Currently, commonly used gas detection technologies in coal mines mainly include catalytic combustion, infrared absorption, thermal conductivity, and optical interferometry. These technologies, which primarily measure gas concentration statically, have certain drawbacks: catalytic combustion detection typically has a response time of ≥5s and is easily affected by high humidity, dust, and sulfides underground, making it unable to quickly capture transient gas outbursts; infrared absorption detection offers high accuracy but also incurs high equipment costs, as optical lenses are susceptible to dust contamination leading to performance degradation, resulting in weak absorption and requiring expensive light source modulation, making the equipment complex; thermal conductivity gas detection is only suitable for high-concentration gas areas, with low output at low concentrations, difficult zero-point drift control, and significant influence from water vapor and carbon dioxide, failing to meet the detection requirements for transient outbursts of low-concentration gas. Numerous historical gas accident data have repeatedly demonstrated that existing instruments and technologies struggle to detect abnormal outbursts or gas surges caused by gas accumulation in a timely manner, often arriving too late when an alarm is triggered. Therefore, developing dynamic, rapid-response gas accumulation detection devices and methods has significant scientific importance and economic application prospects.

[0004] Acoustic resonance sensing technology has been gradually applied to the field of gas detection due to its advantages such as fast response speed, high sensitivity and strong anti-interference ability. Compared with traditional gas detection methods, acoustic resonance method has the potential for millisecond-level response and is especially suitable for capturing transient gas release and dynamic change processes.

[0005] Therefore, developing a gas accumulation detection device and method with rapid response, strong dynamic measurement capability, and high accuracy has broad application prospects in gas disaster prevention and control. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the prior art by providing a gas accumulation detection device and method based on the frequency change rate of an acoustic resonant cavity. This method is applicable to real-time monitoring and rapid early warning of gas outbursts, abnormal outbursts, and eruptions in underground coal mine working faces, roadways, and goaf areas. It can be widely used in safety production monitoring in various high-gas and outburst mines, and is especially suitable for the rapid capture of transient and sudden gas outburst events.

[0007] The technical solution provided by this invention to solve the above-mentioned technical problems is: a gas accumulation detection device based on the frequency change rate of an acoustic resonant cavity, comprising an open direct-through acoustic resonant cavity module, a signal generation and driving module, and a signal acquisition and processing module; It includes an open, through-type acoustic resonant cavity module, a signal generation and driving module, and a signal acquisition and processing module; The open, direct-flow acoustic resonant cavity module includes a resonant cavity, a loudspeaker, and a microphone. The microphone is installed at the center of the resonant cavity, and the loudspeaker is installed at the axisymmetric location of the microphone. It is used to establish a standing wave field and detect acoustic resonant signals within the cavity. The signal generation and driving module includes a microprocessor, a D / A converter, a signal generator, and a power amplifier connected in sequence; the speaker is electrically connected to the power amplifier. The signal acquisition and processing module includes a signal amplifier, a bandpass filter, and an A / D converter connected in sequence. The A / D converter is electrically connected to a microprocessor, and the signal amplifier is electrically connected to a microphone. The microprocessor is used to control the transmission of acoustic signals, acquire and receive signals, perform fast Fourier transform, calculate the real-time resonant frequency, and execute the frequency change rate algorithm. It calls the pre-established characterization relationship between gas accumulation and resonant frequency change rate to realize dynamic monitoring of gas accumulation.

[0008] A further technical solution is that the resonant cavity is a cylindrical tubular straight-through cavity, which is made of one of the following materials: stainless steel, pure copper, or polytetrafluoroethylene.

[0009] A further technical solution is that the inner wall of the resonant cavity is provided with a composite coating that prevents dust accumulation and adsorption. A further technical solution is that the device also includes an alarm and output unit electrically connected to the microprocessor.

[0010] A method for detecting gas accumulation based on the frequency change rate of an acoustic resonant cavity specifically includes the following steps: S1. Excitation Signal Generation and Driving: The signal generation and driving module generates the resonant frequency covering the resonant cavity. The wideband excitation signal drives the loudspeaker in the resonant cavity to generate sound waves, causing the cavity to be in a resonant state; S2. Signal Acquisition and Processing: The signal acquisition and processing module acquires the resonant response signal in the resonant cavity through a microphone, and performs amplification, filtering and analog-to-digital conversion. S3. Resonance Frequency Calculation: The microprocessor sequentially performs Fast Fourier Transform (FFT) and 3rd-order phase difference algorithm on the resonance response signal to calculate the resonance frequency at the current moment. S4. Construct time series data: Calculate the rate of change of resonance frequency over time; S5. Dynamic frequency change rate acquisition: The rate of change of the resonant frequency over time is subjected to high-pass filtering to filter out low-frequency components below the preset cutoff frequency, and the denoised dynamic frequency change rate is obtained. S6. Gas accumulation trend determination: The microprocessor compares the dynamic frequency change rate with the preset gas accumulation change rate threshold, determines the occurrence of a gas accumulation trend, and triggers early warning signals in stages. S7, Output graded alarm: Based on the different states of normal gas outburst, abnormal gas outburst or jet, and protrusion, graded alarms are generated.

[0011] A further technical solution is that the process of extracting the resonant frequency in step S3 is as follows: based on the spectrum obtained by FFT transformation, the resonant frequency is extracted from the resonant cavity's intrinsic resonant frequency. The maximum spectral peak is searched within a certain range, and the peak frequency and phase are output. Then, the initial estimated resonant frequency is finely corrected using a third-order phase difference algorithm and spectral phase difference information, thereby improving the measurement accuracy of the resonant frequency and providing a more accurate frequency sequence for subsequent rate of change calculation.

[0012] A further technical solution is that the formula for calculating the rate of change in S4 is:

[0013] In the formula: The sampling time interval; The resonant frequency at the current moment; The resonant frequency of the previous moment; is the rate of change of the resonant frequency over time.

[0014] A further technical solution is that the sampling time interval The value ranges from 0.01s to 1s.

[0015] A further technical solution is that the cutoff frequency setting in step S5 is based on the bandwidth between the highest frequency component of the natural drift of mine ambient temperature and interference noise and the characteristic frequency component of the gas accumulation event.

[0016] A further technical solution is that the logical criterion used in step S6 is: When the dynamic frequency change rate is less than or equal to the gas accumulation change rate threshold, maintain the normal alarm or reduce the alarm priority. When the gas accumulation change rate threshold is ≥ 2 times the dynamic frequency change rate threshold and > the gas accumulation change rate threshold, a gas accumulation trend warning is issued, indicating that the gas concentration is rising rapidly; When the gas accumulation change rate threshold of 3 times is greater than or equal to the dynamic frequency change rate threshold of 2 times, an emergency over-limit alarm is issued, indicating that gas is rapidly surging out; When the dynamic frequency change rate is ≥3 times the gas accumulation change rate threshold, an emergency over-limit alarm is issued, indicating abnormal gas outburst, spray, or protrusion.

[0017] A further technical solution is that the method also includes a step of real-time calibration of the characterization relationship model: periodically collecting gas concentration data from the coal mine site, and combining the corresponding resonance frequency and its rate of change to correct the characterization relationship model pre-stored in the microprocessor control module, thereby further improving the accuracy of gas accumulation detection and ensuring long-term stable operation of the device.

[0018] A further technical solution is that the method also includes the elimination of environmental sudden noise: when the received signal is much larger than a preset value, it is determined whether it is an interference signal according to the preset threshold of the system, and then eliminated to prevent misjudgment caused by sudden noise.

[0019] A further technical solution is that the method also includes gas cross-sensitivity judgment: when carbon dioxide or other gases are rapidly released, it will cause a negative correlation change in the fundamental frequency of the resonance frequency. Based on the positive correlation change in the methane frequency, gas cross-sensitivity is judged and interference is eliminated.

[0020] The present invention has the following beneficial effects: 1. Simple structure: It adopts an open resonant cavity design with a straight-through type and an inner wall sprayed with a non-stick layer, allowing airflow to enter and exit freely, and gas renewal to be fast. It has no complicated sealing structure, is impact-resistant and vibration-resistant, is suitable for harsh downhole environments, and is not prone to failure due to dust accumulation and blockage. It is inherently safe and simple to operate and maintain for a long time.

[0021] 2. Fast response: By utilizing the instantaneous response characteristics of acoustic resonance, and through FFT, spectrum fitting and high-order phase difference algorithms, combined with the fast computing power of embedded microprocessors, millisecond-level measurement of resonance frequency and its rate of change is achieved. Compared with existing catalytic combustion and infrared absorption detection technologies, the response speed is improved by at least one order of magnitude.

[0022] 3. Dynamic real-time sensing: Compared with existing technologies for measuring static gas concentration, this invention focuses on the dynamic trend of gas change, and can capture dynamic information on gas accumulation in real time to achieve dynamic measurement.

[0023] 4. Strong anti-interference capability: Utilizing the time differential algorithm of the resonant frequency change rate, it can filter out the effects of temperature and pressure drift and slow air pressure fluctuations, without the need for complex constant temperature control or additional compensation air chambers. Combined with the physical isolation of the resonant frequency and the threshold elimination algorithm, it achieves integrated hardware and software anti-interference.

[0024] 5. Intelligent scene recognition: The logical criteria can effectively distinguish between high background concentration (frequency change rate of 0, no trend alarm triggered) and sudden gas concentration change (frequency change rate of large, alarm triggered), solving the problem that traditional static concentration measurement methods are difficult to alarm in time when gas concentration changes rapidly due to response lag. Attached Figure Description

[0025] Figure 1 This is an overall structural block diagram of the detection device of the present invention; Figure 2 This is a flowchart of the rapid detection method of the present invention; Figure 3 This is a schematic diagram of the change rate threshold setting corresponding to the logical criteria of the present invention.

[0026] The diagram shows: 1-Resonant cavity; 2-Speaker; 3-Microphone; 4-Signal amplifier; 5-Bandpass filter; 6-A / D converter; 7-Microprocessor; 8-D / A converter; 9-Signal generator; 10-Power amplifier; 11-Alarm and output unit. Detailed Implementation

[0027] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] It should be noted that the term "gas accumulation" in this invention refers broadly to the dynamic change process of gas concentration in mines, including but not limited to: slow gas accumulation at mining faces, gas outbursts, abnormal outbursts, gas accumulation in roadways, and the instantaneous release of gas before a coal and gas outburst—all phenomena that lead to a rapid increase in gas concentration. This invention identifies rapid changes in gas concentration by monitoring the rate of change of resonant frequency, and therefore can be widely applied to the early warning of various gas anomalies.

[0029] like Figure 1 As shown, the present invention provides a gas accumulation detection device based on the frequency change rate of an acoustic resonant cavity, comprising an open direct-through acoustic resonant cavity module, a signal generation and driving module, a signal acquisition and processing module, and an alarm and output unit 11. The open, direct-flow acoustic resonant cavity module includes a resonant cavity 1, a loudspeaker 2 (such as a piezoelectric ceramic loudspeaker), and a microphone 3 (such as an electret microphone with a frequency response range of 50Hz to 20kHz and a sensitivity of -40dB). The microphone 3 is installed at the center of the inner cavity of the resonant cavity 1, and the loudspeaker 2 is installed at the axis symmetrical position of the microphone 3. It is used to establish a standing wave field and detect acoustic resonant signals within the cavity. The signal generation and driving module is used to generate an excitation signal covering the inherent resonant frequency range of the resonant cavity and drive the loudspeaker to generate corresponding sound waves. Specifically, it includes a microprocessor 7, a D / A converter 8, a signal generator 9, and a power amplifier 10 connected in sequence; the loudspeaker 2 is electrically connected to the power amplifier 10. Signal generator 9 can generate wideband sine, square wave, or sawtooth wave excitation signals, with a range that precisely covers the inherent resonant frequency of the resonant cavity components and the 100% methane frequency range, ensuring that the measuring cavity and the reference resonant cavity can be excited to produce a stable resonant response; preferably, the signal generator is a function signal generator that generates a wideband sine excitation signal in the range of 8kHz to 16kHz (which basically physically isolates the sound wave frequencies of underground coal mine noise sources). The power amplifier 10 amplifies the excitation signal to enhance its driving capability and ensure that the loudspeaker can generate sound waves with stable and controllable intensity and accurate frequency that are transmitted into the resonant cavity. The power amplifier 10 can be a high-frequency power amplifier with an adjustable amplification factor (10 to 100 times) to drive the sound waves generated by the loudspeaker. The signal acquisition and processing module includes a signal amplifier 4, a bandpass filter 5, and an A / D converter 6 connected in sequence. The A / D converter 6 is electrically connected to the microprocessor 7, and the signal amplifier 4 is electrically connected to the microphone 3. The alarm and output unit 11 is also electrically connected to the microprocessor 7.

[0030] The signal amplifier 4 and bandpass filter 5 filter, amplify, and reduce noise in the electrical signal collected by the microphone 3, filtering out interference signals, amplifying the effective signal, and ensuring signal integrity. The A / D converter 6 transmits the analog-to-digital conversion signal to the microprocessor control and calculation module for further processing.

[0031] The microprocessor 7 is used to control the signal generation and driving module to output the speaker sound signal as specified, forming a resonant response in the cavity; receive the response signal from the signal acquisition and processing module, execute FFT and spectrum search algorithms to extract the resonant frequency and phase information, and then use the third-order phase difference algorithm and spectrum phase difference information to finely correct the initially estimated resonant frequency, improve the measurement accuracy of the resonant frequency, and provide a higher-precision frequency sequence for subsequent rate of change calculation. The resonant frequency rate of change over time is calculated based on the obtained resonant frequency value; the pre-stored quantitative characterization relationship model of gas concentration change rate and resonant frequency change rate is called to realize gas accumulation detection and judgment, and the detection results are transmitted to the alarm and output unit 11; the alarm and output unit 11 issues an alarm signal when it detects an abnormal rate of change in real time, and displays different states of gas accumulation.

[0032] In this embodiment, the microprocessor 7 is preferably a single-chip microcomputer, DSP, or FPGA embedded processing module, which has the characteristics of fast operation speed, low power consumption, and strong anti-interference ability, and is suitable for the harsh working conditions in coal mines; its internal pre-stores a quantitative characterization relationship model between the real-time gas concentration change rate and the resonant frequency change rate. This model is a fitting curve or multiple regression model obtained through laboratory calibration and coal mine field tests, which can accurately solve for the real-time gas concentration change rate based on the frequency change rate and determine the corresponding alarm threshold. In this embodiment, the resonant cavity 1 is a cylindrical tubular straight-through cavity, wherein both ends (i.e., the inlet end and the outlet end) of the cylindrical tubular straight-through cavity are directly connected to the gas in the environment to be tested, allowing the gas to flow freely. Its inner cavity is an open straight-through resonant cavity, and its length and radius are designed according to the target resonant frequency and downhole noise spectrum data. The cylindrical tubular straight-through cavity is made of one of the following materials: stainless steel, pure copper, or polytetrafluoroethylene.

[0033] For example, the main body of the resonant cavity is a cylindrical stainless steel tubular structure with a cavity length of 40mm and an inner diameter of 5mm. Both ends are directly open to allow free flow of gas.

[0034] In this embodiment, the inner wall of the resonant cavity 1 is provided with a composite coating to prevent dust accumulation and adsorption, which is used to reduce the adsorption of coal dust entering the cavity.

[0035] In this embodiment, the alarm and output unit 11 includes an audible and visual alarm and an underground ring network communication interface, which displays the gas concentration, concentration change rate and accumulation status in real time; preferably, it integrates an audible and visual alarm and display module. When the detected gas concentration or concentration change rate exceeds a preset threshold, the data is displayed and the audible and visual alarm module triggers a graded alarm, which promptly reminds on-site personnel to take emergency measures and improves the safety of coal mine production.

[0036] In this embodiment, the device also includes a temperature and humidity sensor electrically connected to the microprocessor 7. The temperature and humidity sensor will collect the temperature and humidity of the environment in real time and input it into the microprocessor 7. The microprocessor 7 will perform sound speed compensation correction on the real-time resonant frequency based on the real-time temperature and humidity. The temperature and humidity data are only used for static correction and do not participate in differential calculation.

[0037] like Figure 2 As shown, the present invention provides a method for detecting gas accumulation based on the frequency change rate of an acoustic resonant cavity, which specifically includes the following steps: S1. Excitation Signal Generation and Driving: The signal generation and driving module generates the resonant frequency covering the resonant cavity. A wideband excitation signal (composed of multiple single-frequency signals with controllable amplitude, phase, and frequency, continuously scanned or superimposed, with a frequency range covering the resonant frequency range corresponding to 0 to 100% gas concentration, such as a wideband sinusoidal excitation signal of 8kHz to 16kHz) drives the loudspeaker in the resonant cavity to generate sound waves, causing the cavity to be in a resonant state. S2. Signal Acquisition and Processing: The signal acquisition and processing module acquires the resonant response signal in the resonant cavity through a microphone, and performs amplification (e.g., signal amplification by 50 times), filtering (e.g., filtering out noise above 10kHz), and analog-to-digital (A / D) conversion. S3. Resonance Frequency Calculation: The microprocessor preprocesses the digital signal using a window function (preferably Hanning, Hamming, or Blackman window), and then performs a Fast Fourier Transform (FFT) and a third-order phase difference algorithm on the resonance response signal to calculate the resonance frequency at the current moment. ; The process of extracting the resonant frequency is as follows: based on the spectrum obtained by FFT transformation, the resonant frequencies of the cavity are then extracted. The maximum spectral peak is searched within a certain range, and the peak frequency and phase are output. Then, the initial estimated resonance frequency is finely corrected using the third-order phase difference algorithm and the spectral phase difference information, thereby improving the measurement accuracy of the resonance frequency and providing a higher-precision frequency sequence for subsequent rate of change calculation. S4. Constructing time series data: Calculating the rate of change of resonant frequency over time. ; Resonance frequency The relationship between the gas composition, temperature, pressure, and humidity inside the cavity and the sound wave propagation formula is satisfied. Taking the derivative with respect to time, we can obtain:

[0038] in The rate of change in gas concentration, i.e., the accumulation rate. , and These represent the rates of change of temperature, pressure, and humidity, respectively. Because changes in ambient temperature and pressure are slow processes, within a short time window ≈0、 ≈0 and ≈0, therefore ≈ · Since the rate of change of frequency directly reflects the accumulation rate of gas concentration, the following formula applies:

[0039] In the formula: The sampling time interval ranges from 0.01s to 1s. The resonant frequency at the current moment; The resonant frequency of the previous moment; The rate of change of the resonant frequency over time; For example, suppose the system samples the resonant frequency at a sampling frequency of 100Hz. Assume the natural frequency of the resonant cavity is 10000Hz; where the sampling time interval Δt = 0.01s, and substitute the specific values:

[0040] For example, if the resonant frequency at the current moment is =10001Hz, the previous moment =10000.9Hz.

[0041] Then the rate of change =(10001-10000.9)×100=10(Hz / s).

[0042] S5. Acquisition of dynamic frequency change rate: The rate of change of resonant frequency over time. High-pass filtering is performed to remove low-frequency components below a preset cutoff frequency, resulting in the denoised dynamic frequency change rate. ; A high-pass filter with a preset cutoff frequency of 0.05 Hz is used to filter the rate of change. Filtering is performed to obtain the dynamic frequency change rate. The cutoff frequency is set based on the following: Since the temperature and humidity change cycle in mines is usually on the order of minutes or more, the highest frequency component of the natural drift of temperature and humidity in the mine environment (about 0.02Hz) and the pressure change cycle are also on the order of minutes or more (≤0.01Hz), while the characteristic frequency of gas accumulation events is above 0.1Hz. There is a frequency gap between them, and a cutoff frequency of 0.05Hz can effectively separate the frequency components of temperature and pressure. S6. Gas Accumulation Trend Determination: Establish a characterization model of the relationship between the real-time gas concentration change rate and the resonant frequency change rate. Regularly collect gas concentration data from the coal mine site, and combine this with the corresponding resonant frequency and its change rate to correct the characterization model, further improving the accuracy of gas accumulation detection and ensuring long-term stable operation of the device. The established characterization model is pre-stored in the microprocessor. The microprocessor calls the pre-established characterization model of the real-time gas concentration change rate and the resonant frequency change rate, and then... Compared with the preset threshold for the rate of change of gas accumulation (For example, when the gas concentration changes from 0 to 0.5%, the corresponding resonant frequency change rate is 200 Hz / s) This is compared to determine the gas accumulation trend and triggers early warning signals in stages. Figure 3 ); When the dynamic frequency change rate ≤ Gas accumulation change rate threshold Maintain regular alarms or reduce alarm priority; When the gas accumulation change rate threshold is 2 times ≥ Dynamic frequency change rate > Gas accumulation change rate threshold The system issued a warning about the gas accumulation trend, indicating that the gas concentration was rising rapidly. When the gas accumulation change rate threshold is 3 times ≥ Dynamic frequency change rate >2 times the threshold of gas accumulation change rate An emergency over-limit alarm was issued, indicating that gas was rapidly gushing out; When the dynamic frequency change rate ≥3 times the threshold of gas accumulation change rate It will issue an emergency over-limit alarm, indicating abnormal gas outburst, spray, or protrusion.

[0043] The above description is merely an embodiment of the present invention and is not intended to limit the present invention in any way. Any modifications, equivalent substitutions, structural improvements, etc., made based on the technical essence of the present invention and within the scope of the technical solution and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A gas accumulation detection device based on the frequency change rate of an acoustic resonant cavity, characterized in that, It includes an open, through-type acoustic resonant cavity module, a signal generation and driving module, and a signal acquisition and processing module; The open, direct-flow acoustic resonant cavity module includes a resonant cavity, a loudspeaker, and a microphone. The microphone is installed at the center of the resonant cavity, and the loudspeaker is installed at the axisymmetric location of the microphone. It is used to establish a standing wave field and detect acoustic resonant signals within the cavity. The signal generation and driving module includes a microprocessor, a D / A converter, a signal generator, and a power amplifier connected in sequence; the speaker is electrically connected to the power amplifier. The signal acquisition and processing module includes a signal amplifier, a bandpass filter, and an A / D converter connected in sequence. The A / D converter is electrically connected to a microprocessor, and the signal amplifier is electrically connected to a microphone. The microprocessor is used to control the transmission of acoustic signals, acquire and receive signals, perform fast Fourier transform, calculate the real-time resonant frequency, and execute the frequency change rate algorithm. It calls the pre-established characterization relationship between gas accumulation and resonant frequency change rate to realize dynamic monitoring of gas accumulation.

2. The gas accumulation detection device based on the frequency change rate of an acoustic resonant cavity according to claim 1, characterized in that, The resonant cavity is a cylindrical tubular straight-through cavity, which is made of one of the following materials: stainless steel, pure copper, or polytetrafluoroethylene.

3. The gas accumulation detection device based on the frequency change rate of an acoustic resonant cavity according to claim 1, characterized in that, The inner wall of the resonant cavity is provided with a composite coating that prevents dust accumulation and adsorption.

4. The gas accumulation detection device based on the frequency change rate of an acoustic resonant cavity according to claim 1, characterized in that, The device also includes an alarm and output unit electrically connected to the microprocessor.

5. A method for detecting gas accumulation based on the frequency change rate of an acoustic resonant cavity, characterized in that, This method uses a gas accumulation detection device based on the frequency change rate of an acoustic resonant cavity as described in any one of claims 1-4 for detection, and specifically includes the following steps: S1. Excitation Signal Generation and Driving: The signal generation and driving module generates the resonant frequency covering the resonant cavity. The wideband excitation signal drives the loudspeaker in the resonant cavity to generate sound waves, causing the cavity to be in a resonant state; S2. Signal Acquisition and Processing: The signal acquisition and processing module acquires the resonant response signal in the resonant cavity through a microphone, and performs amplification, filtering and analog-to-digital conversion. S3. Resonance frequency calculation: The microprocessor performs a fast Fourier transform and a third-order phase difference algorithm on the resonance response signal to calculate the resonance frequency at the current moment. S4. Construct time series data: Calculate the rate of change of resonance frequency over time; S5. Dynamic frequency change rate acquisition: The rate of change of the resonant frequency over time is subjected to high-pass filtering to filter out low-frequency components below the preset cutoff frequency, and the denoised dynamic frequency change rate is obtained. S6. Gas accumulation trend determination: The microprocessor compares the dynamic frequency change rate with the preset gas accumulation change rate threshold, determines the occurrence of a gas accumulation trend, and triggers early warning signals in stages. S7, Output graded alarm: Based on the different states of normal gas outburst, abnormal gas outburst or jet, and protrusion, graded alarms are generated.

6. The gas accumulation detection method based on the frequency change rate of an acoustic resonant cavity according to claim 5, characterized in that, The process of extracting the resonant frequency in step S3 is as follows: based on the spectrum obtained by FFT transformation, the intrinsic resonant frequencies of the covering resonant cavity are extracted. The maximum spectral peak is searched within a certain range, and the peak frequency and phase are output. Then, the initial estimated resonant frequency is finely corrected using a third-order phase difference algorithm and spectral phase difference information, thereby improving the measurement accuracy of the resonant frequency and providing a more accurate frequency sequence for subsequent rate of change calculation.

7. The gas accumulation detection method based on the frequency change rate of an acoustic resonant cavity according to claim 5, characterized in that, The formula for calculating the rate of change in S4 is: In the formula: The sampling time interval; The resonant frequency at the current moment; The resonant frequency of the previous moment; is the rate of change of the resonant frequency over time.

8. The gas accumulation detection method based on the frequency change rate of an acoustic resonant cavity according to claim 7, characterized in that, The sampling time interval The value ranges from 0.01s to 1s.

9. The gas accumulation detection method based on the frequency change rate of an acoustic resonant cavity according to claim 5, characterized in that, The cutoff frequency setting in step S5 is based on the bandwidth between the highest frequency component of the mine environment temperature natural drift and interference noise and the characteristic frequency component of the gas accumulation event.

10. The gas accumulation detection method based on the frequency change rate of an acoustic resonant cavity according to claim 5, characterized in that, The logical criterion used in step S6 is: When the dynamic frequency change rate is less than or equal to the gas accumulation change rate threshold, maintain the normal alarm or reduce the alarm priority. When the gas accumulation change rate threshold is ≥ 2 times the dynamic frequency change rate threshold and > the gas accumulation change rate threshold, a gas accumulation trend warning is issued, indicating that the gas concentration is rising rapidly; When the gas accumulation change rate threshold of 3 times is greater than or equal to the dynamic frequency change rate threshold of 2 times, an emergency over-limit alarm is issued, indicating that gas is rapidly surging out; When the dynamic frequency change rate is ≥3 times the gas accumulation change rate threshold, an emergency over-limit alarm is issued, indicating abnormal gas outburst, spray, or protrusion.

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