A method and apparatus for measuring the thickness of hydrate deposition in pipes based on ultrasonic transit time.

Abstract

A method and apparatus for measuring the thickness of hydrate deposits in pipelines based on ultrasonic transit time. The method includes: S1. Installing and fixing an ultrasonic transducer to the outer wall of a pipeline, making it perpendicular to the pipeline axis and pointing towards the center, and placing a coupling agent between the transducer and the pipeline wall; S2. Emitting an ultrasonic signal through the ultrasonic transducer, which is received by the transducer after being reflected by the coupling agent, the pipeline wall, and the hydrate deposit layer; S3. Performing noise reduction and feature extraction processing on the received echo signal to extract the pulse signal entering the hydrate deposit layer and its echo signal, and calculating the transit time between them; S4. Calculating the thickness of the hydrate deposit layer based on the transit time and the propagation speed of the ultrasonic wave in the hydrate deposit layer. This invention enables non-invasive online monitoring of hydrate deposits in pipelines, does not affect normal pipeline production, can provide early warning of hydrate blockage risks, is suitable for non-waterlogged terrestrial environments, and has small measurement errors.

Description

Technical Field

[0001] This invention relates to the measurement of hydrate deposition thickness in pipelines, and particularly to a method and apparatus for measuring hydrate deposition thickness in pipelines based on ultrasonic transit time. Background Technology

[0002] During natural gas development and pipeline transportation, the formation and deposition of natural gas hydrates can cause pipeline blockages, equipment damage, and even safety accidents. Therefore, monitoring and measurement technologies for hydrates have become a research focus. Currently, researchers both domestically and internationally have developed various related technical solutions, as detailed below:

[0003] One widely used technical approach involves monitoring changes in temperature and pressure, combined with a high-speed camera to construct a measurement system. The core principle of this system is to indirectly calculate the amount of hydrates formed by measuring water consumption. However, the experimental scenarios for this method are usually limited to reactors, making it only suitable for studying the formation of hydrates in a laboratory environment. It cannot be adapted to the actual operating conditions of natural gas transmission pipelines, and it is difficult to directly calculate and measure the thickness of hydrate deposits inside the pipeline.

[0004] In addition to the above-mentioned solutions, existing technologies also include capacitive probe sensor solutions, microwave sensing imaging non-invasive detection methods, and non-invasive pressure wave methods. However, these technologies and related derivative solutions still have significant limitations in the practical application of natural gas transmission pipelines, specifically:

[0005] Firstly, some measurement methods for hydrate deposition in pipelines (such as acoustic reflection-based detection techniques) are limited by the flow characteristics within the pipeline. When gas passes through a blockage, a clear interface cannot be formed between the gas and the blockage, resulting in a lack of clear reflection signals under fluid flow conditions. This problem prevents such methods from being tested in the normal flow environment of the pipeline, necessitating a halt to production for monitoring operations, severely impacting natural gas production efficiency.

[0006] Secondly, although the acoustic active excitation method has certain advantages and can accurately locate the location of hydrate blockage in the pipeline, this method can only roughly estimate the profile shape of the hydrate and cannot accurately measure the thickness of the hydrate deposition. It is difficult to meet the precise requirement of the key parameter "thickness" in the early warning work of pipeline hydrate blockage.

[0007] Third, fiber optic sensor technology has two shortcomings in application: on the one hand, the equipment and deployment costs of this technology are high, which is not conducive to large-scale engineering applications; on the other hand, its function is limited to determining the growth location of hydrates in the pipeline, and it cannot further obtain core monitoring parameters such as hydrate deposition thickness, making it difficult to support subsequent blockage risk assessment and intervention decisions.

[0008] It should be noted that the information disclosed in the background section above is only for understanding the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0009] The main objective of this invention is to overcome the deficiencies in the aforementioned background technology and provide a method and apparatus for measuring the thickness of hydrate deposits in pipelines based on ultrasonic transit time. This method enables non-invasive, online, quantitative, and accurate measurement of the thickness of hydrate deposits in pipelines under normal natural gas pipeline transportation conditions, thereby meeting the needs for early warning.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A method for measuring the thickness of hydrate deposits in a pipe based on ultrasonic transit time includes the following steps:

[0012] S1. Install and fix the ultrasonic transducer to the outer wall of the pipe, making it perpendicular to the pipe axis and pointing towards the center, and place a coupling agent between the transducer and the pipe wall;

[0013] S2. An ultrasonic signal is emitted through the ultrasonic transducer, and the signal is received by the transducer after being reflected by the coupling agent, the pipe wall and the hydrate deposit layer.

[0014] S3. Perform noise reduction and feature extraction on the received echo signal, extract the pulse signal entering the hydrate deposition layer and its echo signal, and calculate the transit time between the two;

[0015] S4. Calculate the thickness of the hydrate deposition layer based on the transit time and the propagation speed of the ultrasonic wave in the hydrate deposition layer.

[0016] Furthermore, in step S1, the coupling agent is a hydrogel or petroleum jelly. Alternatively, hydrogel may not be used as the coupling agent; other coupling agents such as petroleum jelly can be used.

[0017] Furthermore, in step S2, the frequency of the ultrasonic signal is 10MHz, and a transceiver-integrated ultrasonic transducer is used for transmission and reception. Alternatively, a similar frequency ultrasonic wave can be used instead of a 10MHz ultrasonic wave.

[0018] Furthermore, in step S3, the echo signal is denoised using a higher-order cumulant denoising method based on Wiener inverse filtering. The higher-order cumulant method suppresses Gaussian noise by calculating higher-order statistics of the signal to obtain the denoised signal.

[0019] Noise reduction using higher-order cumulants specifically includes: from the original echo signal... y(t)The signal is changed to the noisy channel spectrum H(ω) after Wiener inverse filtering; the channel characteristics in the frequency domain are denoised using a fourth-order cumulant algorithm. The higher-order cumulant function eliminates Gaussian noise in H(ω) by calculating the difference between the joint moments of the random variables and the combination of the lower-order moments. The result is then subjected to an inverse spectral transform to obtain the time-domain signal.

[0020] Further, in step S3, the feature extraction process includes:

[0021] The noise-reduced signal is decomposed using a matching pursuit sparse decomposition method. In this method, the characteristic atoms representing the pulse signal entering the hydrate deposition layer and the echo signal of the deposition layer are extracted by iteratively selecting the atom with the largest inner product with the signal residual from an overcomplete atom dictionary.

[0022] Based on the extracted feature atoms, the time-domain positions of the pulse signal and the echo signal are determined, and the time difference between them is calculated as the transit time.

[0023] Furthermore, the matching pursuit sparse decomposition method includes:

[0024] The initial residual signal is the denoised signal;

[0025] In each iteration, the inner product of the current residual signal and all atoms in the overcomplete atom dictionary is calculated, and the atom with the largest absolute value of the inner product is selected.

[0026] The selected atom is weighted according to its projection coefficient with the current residual, and the projection component of the atom is subtracted from the current residual to update the residual;

[0027] Repeat the above iterative process until the preset residual energy threshold or number of iterations is met. The selected atoms and their coefficients constitute a sparse representation of the signal, and the atomic components corresponding to the pulse signal and the echo signal are identified accordingly.

[0028] A device for measuring the thickness of hydrate deposition in a pipe based on ultrasonic transit time, comprising:

[0029] An ultrasonic transducer is used to transmit ultrasonic signals and receive echo signals reflected from the pipe wall and hydrate deposits.

[0030] A clamp is used to fix the ultrasonic transducer to the outer wall of the pipe and ensure that it is perpendicular to the pipe axis and points to the center of the circle.

[0031] A coupling agent is placed between the ultrasonic transducer and the outer wall of the pipe to enhance sound wave transmission;

[0032] The processing unit is used to perform noise reduction processing, feature extraction and transit time calculation on the echo signal, and to calculate the thickness of the hydrate deposition layer based on the transit time.

[0033] Furthermore, the clamp includes an arc-shaped portion that fits against the outer wall of the pipe and a vertical portion for fixing the ultrasonic transducer. The end of the vertical portion is provided with a clamp portion parallel to the pipe axis, and the clamp portion is provided with a hole for inserting and fixing the ultrasonic transducer.

[0034] Furthermore, the coupling agent is a hydrogel or petrolatum.

[0035] Furthermore, the processing unit is configured to perform noise reduction processing and a matching pursuit sparse decomposition algorithm to extract echo signal features and calculate transit time.

[0036] The present invention has the following beneficial effects:

[0037] This invention provides a method and apparatus for measuring the thickness of hydrate deposition in natural gas pipelines based on ultrasonic transit time. By fixing an ultrasonic transducer to the outside of the pipeline and calculating the hydrate thickness using ultrasonic transit time, non-invasive online monitoring is achieved. This eliminates the need to interfere with the normal transport operation of the natural gas pipeline, avoiding the drawbacks of traditional partial measurement methods that require production shutdowns. Furthermore, this method can detect hydrate growth signs early, before blockage occurs, providing timely warnings of pipeline blockage risks. This not only guides staff to take preventative measures without interrupting production, effectively avoiding production losses and ecological disasters caused by blockages, but also significantly reduces potential equipment repair costs, effectively filling the gaps in existing pipeline hydrate thickness measurement technologies.

[0038] From a technical perspective, the travel speed of ultrasound varies in different material structures, and the dispersion characteristics and modes of its reflected and transmitted waves are also different. Moreover, the signal intensity is proportional to the density difference of the medium. The method of this invention can not only meet the material compatibility requirements of stainless steel pipes, but also realize the quantitative measurement of the thickness of hydrate deposits in the pipe.

[0039] Furthermore, this invention addresses the environmental limitations of existing technologies. Compared to existing methods that can only be used for measurements in water-immersed environments, this invention can meet the in-situ measurement requirements in non-water-immersed terrestrial environments and enables remote online monitoring. The measurement results have a smaller error compared to the actual thickness of the hydrate deposit layer, further enhancing the engineering applicability of the technology.

[0040] This invention is based on acoustic principles, preferably using 10MHz frequency ultrasound and hydrogel as the coupling agent, and is accompanied by a targeted signal processing method. Regarding data accuracy, the preferred solution of this invention processes the received ultrasonic echo data using specific noise reduction techniques (such as higher-order cumulant methods) and feature extraction techniques (such as MP sparse decomposition methods). This successfully solves the waveform aliasing problem caused by multiple reflections of ultrasonic signals between different media such as coupling agents, pipe walls, and hydrate deposits, ensuring the accuracy and reliability of thickness calculations.

[0041] In summary, this method for measuring the thickness of hydrate deposits in natural gas pipelines is accurate, reliable, real-time, and has minimal impact on the production process. It can not only accurately monitor the hydrate formation state but also assist in subsequent operations to remove hydrate deposits. This is of great significance for improving the production efficiency and operational safety of natural gas pipeline transportation, and effectively safeguards the two core requirements of efficiency and safety in industrial production.

[0042] Other beneficial effects of the embodiments of the present invention will be further described below. Attached Figure Description

[0043] Figure 1 This is the overall flowchart of the pipe hydrate deposition thickness measurement method based on ultrasonic transit time of the present invention.

[0044] Figure 2 This is a schematic diagram of a pipeline hydrate deposition thickness measurement system based on ultrasonic transit time, according to an embodiment of the present invention.

[0045] Figure 3 This is a schematic diagram of the thickness of the hydrate deposit layer inside the pipeline detected by ultrasonic testing according to an embodiment of the present invention. Detailed Implementation

[0046] The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope and application of the present invention.

[0047] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as "connected to" another component, it can be directly connected to or indirectly connected to that other component. Furthermore, a connection can be used for fixing, coupling, or communication.

[0048] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0050] This invention aims to address the limitations of existing methods for measuring the thickness of hydrate deposits in natural gas pipelines, such as their reliance on laboratory settings, the need to halt production, or the inability to quantitatively measure thickness. It proposes a non-invasive measurement scheme based on ultrasonic transit time. This scheme enables remote online monitoring in non-water-immersed terrestrial environments, provides early warning of hydrate blockage risks without affecting normal pipeline production, exhibits minimal measurement error, and combines accuracy, real-time performance, and strong engineering applicability.

[0051] See Figures 1 to 3 This invention provides a method for measuring the thickness of hydrate deposition in a pipe based on ultrasonic transit time, comprising the following steps:

[0052] S1. Install and fix the ultrasonic transducer 1 to the outer wall of the pipe 8, making it perpendicular to the axis of the pipe 8 and pointing towards the center, and place the coupling agent 2 between the ultrasonic transducer 1 and the outer wall of the pipe 8.

[0053] S2. An ultrasonic signal is emitted through the ultrasonic transducer 1, and the signal is received by the transducer after being reflected by the coupling agent 2, the pipe wall and the hydrate deposition layer 9.

[0054] S3. Perform noise reduction and feature extraction processing on the received echo signal, extract the pulse signal entering the hydrate deposition layer 9 and its echo signal, and calculate the transit time between the two;

[0055] S4. Calculate the thickness of the hydrate deposition layer 9 based on the transit time and the propagation speed of the ultrasonic wave in the hydrate deposition layer 9.

[0056] In some embodiments, the speed at which ultrasound propagates in ice (e.g., around 3480 m / s) can be used as the propagation speed in hydrates. It is understood that because natural gas hydrates and ice have similar cage-like crystal structures and physical parameters such as density and elastic modulus, the range of ultrasound propagation speeds in both overlaps. This approximate ultrasound speed in ice can meet the needs of this invention for measuring hydrate deposition thickness and providing early warning of blockages. Alternatively, an ultrasound propagation experiment can be conducted on a hydrate sample with conditions consistent with hydrate formation in the pipeline (e.g., the same pressure, temperature, and natural gas composition) using a transceiver-integrated ultrasonic transducer. The transit time of the ultrasound in the sample and the known thickness of the sample can be measured, and the measured ultrasound propagation speed data can be used as the propagation speed in hydrates for calculation.

[0057] In some embodiments, the speed at which ultrasound propagates in ice (e.g., around 3480 m / s) can be used as the propagation speed in hydrates. It is understood that because natural gas hydrates and ice have similar cage-like crystal structures and physical parameters such as density and elastic modulus, the range of ultrasound propagation speeds in both overlaps. This approximate ultrasound speed in ice can meet the needs of this invention for measuring hydrate deposition thickness and providing early warning of blockages. Alternatively, an ultrasound propagation experiment can be conducted on a hydrate sample with conditions consistent with hydrate formation in the pipeline (e.g., the same pressure, temperature, and natural gas composition) using a transceiver-integrated ultrasonic transducer. The transit time of the ultrasound in the sample and the known thickness of the sample can be measured, and the measured ultrasound propagation speed data can be used as the propagation speed in hydrates for calculation.

[0058] In some embodiments, in step S1, the coupling agent 2 is a hydrogel or petroleum jelly. Alternatively, other coupling agents such as petroleum jelly may also be used.

[0059] In some embodiments, in step S2, the frequency of the ultrasonic signal is 10MHz, and it is transmitted and received using a transceiver-type ultrasonic transducer 1. Other embodiments may use ultrasonic waves of similar frequencies.

[0060] In some embodiments, in step S3, the echo signal is denoised using a higher-order cumulant denoising method based on Wiener inverse filtering. The higher-order cumulant method suppresses Gaussian noise by calculating higher-order statistics of the signal to obtain a denoised signal.

[0061] Noise reduction using higher-order cumulants specifically includes: from the original echo signal... y(t)The signal is changed to the noisy channel spectrum H(ω) after Wiener inverse filtering; the channel characteristics in the frequency domain are denoised using a fourth-order cumulant algorithm. The higher-order cumulant function eliminates Gaussian noise in H(ω) by calculating the difference between the joint moments of the random variables and the combination of the lower-order moments. The result is then subjected to an inverse spectral transform to obtain the time-domain signal.

[0062] In some embodiments, step S3, the feature extraction process includes:

[0063] The noise-reduced signal is decomposed using a matching pursuit sparse decomposition method. In this method, the characteristic atoms representing the pulse signal entering the hydrate deposition layer 9 and the echo signal of the deposition layer are extracted by iteratively selecting the atom with the largest inner product with the signal residual from the overcomplete atom dictionary.

[0064] Based on the extracted feature atoms, the time-domain positions of the pulse signal and the echo signal are determined, and the time difference between them is calculated as the transit time.

[0065] In some embodiments, the matching pursuit sparse decomposition method includes:

[0066] The initial residual signal is the denoised signal;

[0067] In each iteration, the inner product of the current residual signal and all atoms in the overcomplete atom dictionary is calculated, and the atom with the largest absolute value of the inner product is selected.

[0068] The selected atom is weighted according to its projection coefficient with the current residual, and the projection component of the atom is subtracted from the current residual to update the residual;

[0069] Repeat the above iterative process until the preset residual energy threshold or number of iterations is met. The selected atoms and their coefficients constitute a sparse representation of the signal, and the atomic components corresponding to the pulse signal and the echo signal are identified accordingly.

[0070] See Figure 2 and Figure 3 This invention also provides a device for measuring the thickness of hydrate deposits in a pipe based on ultrasonic transit time, comprising: an ultrasonic transducer 1 for emitting ultrasonic signals and receiving echo signals reflected from the wall of the pipe 8 and the hydrate deposit layer 9; a clamp 6 for fixing the ultrasonic transducer 1 to the outer wall of the pipe 8 and ensuring that it is perpendicular to the pipe axis and points towards the center; a coupling agent 2 disposed between the ultrasonic transducer 1 and the outer wall of the pipe 8 for enhancing sound wave transmission; and a processing unit (not shown) for performing noise reduction processing, feature extraction, and transit time calculation on the echo signals, and calculating the thickness of the hydrate deposit layer 9 based on the transit time.

[0071] like Figure 2 As shown, in some embodiments, the clamp 6 includes an arc-shaped portion that conforms to the outer wall of the pipe 8 and a vertical portion for fixing the ultrasonic transducer 1. The end of the vertical portion has a clamping part parallel to the axial direction of the pipe 8, and the clamping part has a hole for inserting and fixing the ultrasonic transducer 1. The ultrasonic probe of the ultrasonic transducer 1 can be fixed with screws.

[0072] In some embodiments, the coupling agent 2 is a hydrogel or petroleum jelly.

[0073] In some embodiments, the processing unit is configured to perform noise reduction processing and a matching pursuit sparse decomposition algorithm to extract echo signal features and calculate transit time.

[0074] The present invention provides a method and apparatus for measuring the thickness of hydrate deposition in pipelines based on ultrasonic transit time. It possesses the core advantage of non-invasive online measurement, enabling continuous monitoring of hydrate deposition during normal natural gas pipeline operation. This effectively avoids the problem of traditional methods such as acoustic reflection requiring shutdown for inspection due to unclear interfaces under flow conditions, overcoming the interference with production efficiency caused by existing technologies. Furthermore, this invention breaks through the limitations of existing technologies, which are mostly confined to water-immersed environments, and is applicable to non-water-immersed terrestrial environments. It supports remote online monitoring and early warning, enabling timely detection of deposition signs before hydrate blockage formation, guiding preventative measures without interrupting production. This significantly reduces the risk of pipeline blockage accidents, minimizes production losses and ecological damage, and saves on high equipment repair costs, providing a reliable technical guarantee for the safe and efficient operation of natural gas pipeline transportation.

[0075] In the preferred embodiment, a specific frequency ultrasonic wave and a hydrogel coupling agent are selected to match the material properties of stainless steel pipes. The echo signal is processed by a high-order cumulative noise reduction and matched pursuit sparse decomposition algorithm, which significantly improves the signal-to-noise ratio and feature extraction accuracy. This successfully solves the waveform aliasing problem caused by multiple reflections between multilayer media, and realizes accurate and quantitative measurement of hydrate deposition thickness with small measurement error and high reliability.

[0076] The following further describes the implementation process, features, and advantages of specific embodiments of the present invention.

[0077] Figure 2 A pipe hydrate deposition thickness measurement system based on ultrasonic transit time is demonstrated. Ultrasonic waves are used to detect the thickness of the hydrate deposition layer inside the pipe, as shown in the diagram. Figure 3 As shown.

[0078] A method for measuring the thickness of hydrate deposits in a pipe based on ultrasonic transit time includes the following steps:

[0079] Transducer Installation and Fixing: The ultrasonic transducer is secured using clamps to ensure it remains centered. The clamp's internal design matches the pipe's outer diameter to ensure close contact between the clamp and the pipe surface. The clamp material is selected to provide sufficient rigidity and corrosion resistance, such as stainless steel or aluminum alloy. The clamp has a small thickness to minimize its impact on the ultrasonic waves. The clamping plates allow for flexible adjustment of the clamping force to ensure the probe is positioned as close as possible to the pipe's central axis. The curved portion of the clamp fully conforms to the pipe's exterior, while the vertical portion extends upwards, with a circular hole at its end parallel to the pipe's axis. The ultrasonic probe is inserted through this circular hole and secured by screws within it, ensuring the probe is perpendicular to the pipe's axis and points towards the center. A hydrogel pad is added between the transducer and the pipe wall as a coupling agent.

[0080] Ultrasonic measurement: A transceiver-integrated ultrasonic transducer is used. The ultrasonic transducer emits a 10MHz ultrasonic signal, which is reflected after passing through the coupling agent, the pipe wall, and the hydrate deposit layer in the pipe, and is then received by the ultrasonic transducer.

[0081] Data Analysis: After receiving the reflected ultrasonic signal, the received data was denoised and feature extracted using a high-order cumulative MP sparse decomposition method, and the transit time of the ultrasonic wave was measured. The hydrate thickness was then calculated using the following formula:

[0082]

[0083] in The speed at which ultrasound propagates. To transcend time.

[0084] When sound waves propagate in different media, reflection occurs. The transit time can be obtained by observing the time difference between the incident wave and the reflected wave. The propagation time of ultrasound in the hydrate layer is calculated using the time difference of ultrasound transit, and then combined with... Calculate the thickness of the hydrate layer.

[0085] Research revealed that a 10MHz frequency probe exhibits low energy loss, high echo amplitude, and a relatively complete, smooth waveform with minimal distortion, making it a superior choice within a given range. A comparison of echo amplitudes using various materials as coupling agents, as well as hydrogel pads of varying thicknesses, showed that the hydrogel pad exhibits lower energy loss and has less impact on the application scenarios and echo quality of this solution. Therefore, hydrogel is the preferred coupling material.

[0086] Furthermore, an echo signal processing method for ultrasonic echo measurement of hydrate deposition layer thickness is proposed. The thickness of hydrate layers in ice layers and loops is then measured and verified.

[0087] Specifically, such as Figure 1 and Figure 2 As shown, the ultrasonic transducer 1 converts electrical signals into acoustic signals and emits ultrasonic waves. The hydrogel 2 acts as a coupling agent, resulting in minimal energy loss in the echo amplitude, thus having little impact on the application scenario and echo of this invention. The ultrasonic transducer 1 is connected to the power supply 7 via power cable 3 and to the host computer 5 via data cable 4. The clamp 6 secures the ultrasonic transducer 1 to the outer wall of the natural gas pipeline (pipeline 8).

[0088] According to different pipeline specifications, a matching clamp 6 is designed. The ultrasonic probe is inserted into the circular hole and fixed by the screw in the circular hole, thereby ensuring that the probe is perpendicular to the axis of the natural gas pipeline and points to the center. The ultrasonic transducer 1 is connected to the power supply 7 using the power cable 3, and the ultrasonic transducer 1 is connected to the host computer 5 using the data cable 4.

[0089] The ultrasonic measurement uses an integrated transceiver ultrasonic transducer 1. The ultrasonic transducer emits a 10MHz ultrasonic signal, which is reflected after passing through the coupling agent, the pipe wall, and the hydrate deposit layer in the pipe, and is then received by the ultrasonic transducer.

[0090] The ultrasonic signal was subjected to noise reduction and feature extraction. For the echo signal, a higher-order cumulant denoising method based on Wiener inverse filtering was first used for noise reduction. The denoised signal was then subjected to MP sparse decomposition to extract features to distinguish the pulse signal entering the hydrate deposition layer and the echo signal from the hydrate deposition layer, and the time difference between the two signals was calculated. Δt That is, the transit time of the ultrasound, combined with the formula The thickness of the hydrate deposition layer was obtained.

[0091] Specifically, after receiving the echo signal, the signal... y(t) Processing is performed first using a Wiener inverse filter. y(t) The noisy channel spectrum H(ω) is obtained. The channel characteristics in the frequency domain are denoised using a fourth-order cumulant algorithm to eliminate noise in H(ω). Finally, an inverse spectral transform is performed on the result to obtain the denoised signal. x(t) Then use MP sparse decomposition on the pair x(t) Feature extraction is performed, and this method first creates a complete atomic dictionary. D Using the matching pursuit method in an incomplete atomic library D The atom that best matches the signal x to be processed is the atom library. D With signal x The atom with the largest inner product. k forM The set of best-matching atoms is extracted using the second sparse extraction method. R M For the remaining part of the signal after feature extraction, if R M Small enough to stop decomposition. x The sparse representation can be approximated as the original signal. Finally, spectral peak search is used to find the pulse signal entering the hydrate deposition layer and the echo signal of the hydrate deposition layer, and the transit time is obtained by calculating the time difference between the two signals. The thickness of the hydrate deposition layer is then calculated.

[0092] The specific calculation process is as follows:

[0093] First, regarding the echo signal

[0094]

[0095] in It is the total echo signal. It is an ultrasonic emission signal. It is the impulse response function of the ultrasonic wave propagation channel characteristics. It's white noise. The frequency domain expression is:

[0096]

[0097] In order to estimate Construct Wiener inverse filter Make:

[0098]

[0099] Obtaining noise Then use fourth-order cumulants Noise reduction:

[0100]

[0101] in The frequency domain response is noise-free. For noise, cum4 represents the calculation of the fourth-order cumulant.

[0102]

[0103] Since the self-accumulators of third-order and higher orders of colored noise and white noise are zero, we can obtain

[0104]

[0105] right Perform inverse spectral transform to obtain the time-domain signal ,

[0106] For the time-domain signal of noise reduction The specific process of performing MP sparse decomposition is as follows:

[0107] First, a complete dictionary D was created;

[0108] In each iteration, the inner product of the current residual signal and all atoms in the overcomplete atom dictionary is calculated, and the atom with the largest absolute value of the inner product is selected.

[0109] The selected atom is weighted according to its projection coefficient with the current residual, and the projection component of the atom is subtracted from the current residual to update the residual;

[0110] Repeat the above iterative process until the preset residual energy threshold or number of iterations is met. The selected atoms and their coefficients constitute a sparse representation of the signal, and the atomic components corresponding to the pulse signal and the echo signal are identified accordingly.

[0111] The processed signal contains a pulse signal and an echo signal. A peak search algorithm is used to find the spectral peaks between the pulse and echo signals, and the time difference Δt between the two peaks is calculated.

[0112]

[0113] Calculate the thickness r of the hydrate layer, where c is the propagation speed of sound waves in the hydrate layer.

[0114] In summary, this invention proposes a method and apparatus for measuring the thickness of hydrate deposits in natural gas pipelines based on ultrasonic transit time. This method allows for the measurement of hydrate deposits within natural gas pipelines without disrupting normal operations, thereby monitoring for pipeline blockages. This invention can detect the early growth of hydrates in natural gas pipelines, providing an early warning system for hydrate-induced pipeline blockages.

[0115] A preferred embodiment of this invention proposes using a 10MHz ultrasonic transducer as the measuring instrument. Using this frequency results in low energy loss, high amplitude, and a relatively complete, smooth waveform with minimal distortion in the received echo. A coupling method using a hydrogel pad suitable for 360° terrestrial environments as the coupling material is proposed. This method overcomes the limitation of most studies that can only be performed in water-immersed environments, enabling in-situ, non-invasive measurements in non-water-immersed terrestrial environments, facilitating remote online monitoring, and minimizing the error between the measured hydrate deposition layer thickness and the actual value. A method based on high-order cumulative MP sparse decomposition is proposed to denoise the received data and extract features, solving the waveform aliasing problem caused by multiple reflections of ultrasonic signals between different media.

[0116] This invention can also be applied in fields such as early warning of oil and gas pipeline blockages.

[0117] The above description provides a further detailed explanation of the present invention in conjunction with specific / preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made to the present invention without departing from the scope of protection of the patent application.

Claims

1. A method for measuring hydrate deposit thickness in a pipeline based on ultrasonic transit time, characterized by, The method comprises the following steps: S1. installing and fixing an ultrasonic transducer on the outer wall of the pipeline, so that it is perpendicular to the axial direction of the pipeline and points to the center, and a coupling agent is arranged between the ultrasonic transducer and the outer wall of the pipeline; the coupling agent is a hydrogel or vaseline; S2. transmitting an ultrasonic signal by the ultrasonic transducer, and receiving the signal reflected by the coupling agent, the pipeline wall and the hydrate deposit layer; S3. performing noise reduction and feature extraction processing on the received echo signal, extracting the pulse signal entering the hydrate deposit layer and the echo signal thereof, and calculating the time of flight between the two; The feature extraction processing comprises: decomposing the signal after noise reduction processing by a matching pursuit sparse decomposition method, wherein the feature atoms representing the pulse signal entering the hydrate deposit layer and the deposit layer echo signal are extracted by iteratively selecting the atom with the maximum inner product with the signal residual in the overcomplete atom dictionary; the time domain positions of the pulse signal and the echo signal are determined according to the extracted feature atoms, and the time difference between the two is calculated as the time of flight; S4. calculating the thickness of the hydrate deposit layer according to the time of flight and the propagation speed of the ultrasonic wave in the hydrate deposit layer.

2. The ultrasonic transit time based method of pipeline hydrate deposit thickness measurement as claimed in claim 1, wherein, In step S2, the frequency of the ultrasonic signal is 10 MHz, and a transceiving integrated ultrasonic transducer is used for transmission and reception.

3. The ultrasonic transit time based method of pipeline hydrate deposit thickness measurement as claimed in claim 1, wherein, In step S3, the echo signal is subjected to the noise reduction by using a high-order cumulant noise reduction method based on Wiener inverse filtering, which calculates the high-order statistics of the signal to suppress Gaussian noise to obtain the denoised signal; The high-order cumulant method for noise reduction specifically includes: using the original echo signal y(t) containing noise after Wiener inverse filtering; using a fourth-order cumulant algorithm to reduce noise of the channel characteristics in the frequency domain, a high-order cumulant function is calculated by combining the difference between joint moments and low-order moments of random variables to eliminate Gaussian noise in H(ω), and then performing inverse spectrum transform on the result to obtain a time-domain signal.

4. The ultrasonic transit time based method of pipeline hydrate deposit thickness measurement as claimed in claim 1, wherein, The matching pursuit sparse decomposition method further comprises: initializing the residual signal as the denoised signal; in each iteration, calculating the inner product of the current residual signal with all atoms in the overcomplete atom dictionary, and selecting the atom with the maximum absolute value of the inner product; weighting the selected atom according to its projection coefficient with the current residual, and subtracting the projection component of the atom from the current residual to update the residual; repeating the above iteration process until a preset residual energy threshold or the number of iterations is met, and the sparse representation of the signal is composed of the selected atom and its coefficient, and the atom components corresponding to the pulse signal and the echo signal are identified accordingly.

5. An ultrasonic transit time based method of measuring the thickness of hydrate deposits in a pipeline for use in implementing an ultrasonic transit time based method of measuring the thickness of hydrate deposits in a pipeline as claimed in any one of claims 1 to 4 characterised in that, It comprises: an ultrasonic transducer for transmitting an ultrasonic signal and receiving an echo signal reflected by the pipeline wall and the hydrate deposit layer; a clamp for fixing the ultrasonic transducer on the outer wall of the pipeline and ensuring that it is perpendicular to the axial direction of the pipeline and points to the center; a coupling agent arranged between the ultrasonic transducer and the outer wall of the pipeline for enhancing sound conduction; the coupling agent is a hydrogel or vaseline; a processing unit for performing noise reduction processing, feature extraction and time of flight calculation on the echo signal, and calculating the thickness of the hydrate deposit layer according to the time of flight; the processing unit is configured to perform noise reduction processing and a matching pursuit sparse decomposition algorithm to extract the features of the echo signal and calculate the time of flight.

6. The ultrasonic transit time based pipe hydrate deposit thickness measurement apparatus of claim 5, wherein, The clamp comprises an arc-shaped part abutting with the outer wall of the pipeline and a vertical part for fixing the ultrasonic transducer, and an end of the vertical part is provided with a clamp part parallel to the pipeline axis, and the clamp part is provided with a hole for inserting and fixing the ultrasonic transducer.

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