Simulation system and method for internal leakage of ball valve of natural gas pipeline

Abstract

The invention discloses a simulation system and method for internal leakage of a natural gas pipeline ball valve. The method specifically comprises the following steps: S1, constructing a natural gas pipeline ball valve simulation platform by using three-dimensional software; s2, first pressure and first flow entering the ball valve are set in the natural gas pipeline ball valve simulation platform, second pressure and second flow passing through the ball valve are obtained, a gas flow field and a speed field of the ball valve are constructed, and the generation mechanism of inner leakage of the ball valve is analyzed; s3, the sound wave signals passing through the ball valve are obtained, and the characteristics, responding to the leakage rate in the pipeline, in the sound wave signals are determined; and S4, an acoustic emission sensor is arranged at the downstream of the ball valve, then multiple groups of experiments are carried out under different environmental conditions, corresponding acoustic signals are collected, features, responding to the inner leakage rate of the pipeline, in the acoustic signals are extracted, the features and the inner leakage rate of the ball valve are fitted, and the mapping relation between the acoustic signals and the inner leakage rate of the ball valve is determined.

Description

Technical Field

[0001] The present invention relates to the technical field of pipelines, and particularly to a simulation system and method for internal leakage of a natural gas pipeline ball valve. Background Art

[0002] When there is a small amount of internal leakage during the use of valves in natural gas stations, there is a lack of effective means for detection and evaluation, and it is impossible to identify and take control measures in a timely manner.

[0003] At present, on-site production often uses methods such as middle cavity discharge, manual identification, and pressure observation to identify internal leakage of pipeline ball valves. These methods require certain experience, have low identification accuracy, and cannot effectively quantify the leakage amount.

[0004] During the natural gas production process, there is an urgent need for a detection and evaluation method that can effectively identify and quantify valve internal leakage. Identifying internal leakage and predicting flow rate of pipeline ball valves helps to quickly evaluate the current status of valves, analyze and identify valve failure types, and provide technical support for valve leakage maintenance and integrity management of in-service valves.

[0005] However, in domestic and foreign research results, the test environment is mostly an indoor environment or a noise-free environment. The experimental conditions artificially reduce the proportion of noise, making it difficult to reflect the fit with actual projects, and thus the detection accuracy of internal leakage is relatively low. Summary of the Invention

[0006] Aiming at the technical problem of low detection accuracy of internal leakage in the prior art, the present invention discloses a simulation system and method for internal leakage of a natural gas pipeline ball valve.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] Perform internal leakage flow field analysis, internal leakage sound field analysis, and flowing medium replaceability analysis on the simulated internal leakage ball valve respectively to obtain a first analysis result;

[0009] Based on the first analysis result, build a natural gas pipeline ball valve internal leakage identification and flow rate prediction system, and conduct valve internal leakage experiments under different pressure ratios and different internal leakage clearances to obtain experimental data;

[0010] Process and analyze the experimental data to obtain a second analysis result;

[0011] Based on the second analysis result, conduct a quantitative study on the internal leakage rate of natural gas pipeline valves to obtain a research result.

[0012] Wherein, the performing internal leakage flow field analysis, internal leakage sound field analysis, and flowing medium replaceability analysis on the simulated internal leakage ball valve respectively to obtain a first analysis result includes:

[0013] Set the inlet pressure of the simulated internal leakage ball valve to 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, and the outlet pressure to atmospheric pressure. Calculate the pressure field and velocity field respectively to obtain the calculation results, and analyze the calculation results to obtain the analysis results of the internal leakage flow field;

[0014] Set the inlet pressure of the simulated internal leakage ball valve to 0.3 MPa, 0.4 MPa, 0.5 MPa, and set two sound source monitoring points. Monitoring point 1 is the pipe wall 30 cm downstream of the simulated internal leakage ball valve, and monitoring point 2 is the surface of the simulated internal leakage ball valve body. Obtain the simulation results, and analyze the acoustic spectrum and acoustic power spectrum of the simulation results to obtain the analysis results of the internal leakage sound field;

[0015] Select the wall surface of the simulated internal leakage ball valve as the detection point, and simulate the power spectral density characterizing the acoustic characteristics under three different inlet pressure conditions of 0.3 MPa, 0.4 MPa, and 0.5 MPa to obtain the analysis results of the replaceability of the flowing medium;

[0016] Sort out the analysis results of the internal leakage flow field, the analysis results of the internal leakage sound field, and the analysis results of the replaceability of the flowing medium to obtain the first analysis result.

[0017] Among them, based on the first analysis result, build a natural gas pipeline ball valve internal leakage identification and flow prediction system, and conduct valve internal leakage experiments under different pressure ratios and different internal leakage clearances to obtain experimental data, including:

[0018] Place the acoustic emission sensor at different positions under the same working conditions to detect the amplitude and signal intensity, and based on the first analysis result, consider simulating the unevenness of the body of the simulated internal leakage ball valve, as well as the influence of the acoustic emission sensor falling off or the contact surface changing during the experiment. Stick the acoustic emission sensor 30 cm downstream of the simulated internal leakage ball valve to obtain the natural gas pipeline ball valve internal leakage identification and flow prediction system;

[0019] Consider the influence of environmental noise factors, and collect acoustic signals under four environmental conditions: no noise on sunny days, no noise on light rain days, construction noise within 100 m nearby, and construction noise within 100 m - 500 m in the distance;

[0020] Based on the natural gas pipeline ball valve internal leakage identification and flow prediction system, establish experimental conditions with two ball valve specifications of DN50 and DN100, five pressure levels of 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, and valve opening changes increasing by 0.5 degrees from 11° to 16° to obtain an experimental plan;

[0021] Collect and analyze the characteristic parameter data of valves with different pressure levels and different specifications based on the experimental scheme and the acoustic signals; collect and analyze the acoustic signal data at different valve openings under the same pressure; collect and analyze the acoustic signal data at different pressures under the same valve opening to obtain experimental data.

[0022] Among them, the processing and analysis of the experimental data to obtain the second analysis result includes:

[0023] Use EMD to denoise the original acoustic emission signal of the experimental data and then obtain the frequency-domain signal through fast Fourier transform;

[0024] Analyze the internal leakage acoustic experiment results of the simulated internal leakage ball valve based on the frequency-domain signal, and analyze the acoustic emission characteristic parameters of the simulated internal leakage ball valve to obtain the second analysis result.

[0025] Among them, the emission characteristic parameters include amplitude, total sound pressure level, effective value voltage value, and average signal level.

[0026] Among them, the quantitative research on the internal leakage rate of natural gas pipeline valves based on the second analysis result to obtain the research result includes:

[0027] Based on the regression fitting of time-domain energy and leakage rate using the regress method and improving it using the neural network algorithm to obtain a prediction model;

[0028] Based on the second analysis result, use the prediction model to perform error prediction to obtain a prediction result;

[0029] Based on the prediction result, conduct quantitative research on the internal leakage rate of natural gas pipeline valves to obtain the research result.

[0030] In a second aspect, the present invention provides a natural gas pipeline ball valve internal leakage identification and flow prediction system, including a natural gas pipeline, a ball valve 1 installed on the natural gas pipeline, a first flowmeter 2, a first pressure gauge 3, a second flowmeter 4, a second pressure gauge 5, an acoustic emission sensor 6, a collection device 7, and a host computer 8;

[0031] The first flowmeter 2 and the first pressure gauge 3 are installed upstream of the ball valve, and the second flowmeter 4, the second pressure gauge 5, and the acoustic emission sensor 6 are installed downstream of the ball valve. The input end of the collection device 7 is respectively connected to the first flowmeter 2, the first pressure gauge 3, the second flowmeter 4, the second pressure gauge 5, and the acoustic emission sensor 6, and the output end of the collection device 7 is connected to the input end of the host computer 8

[0032] A natural gas pipeline ball valve internal leakage identification and flow prediction system and its design method according to the present invention analyze the internal leakage flow field, internal leakage sound field, and flow medium substitutability of a simulated internal leakage ball valve respectively to obtain a first analysis result; build a natural gas pipeline ball valve internal leakage identification and flow prediction system based on the first analysis result, conduct valve internal leakage experiments under different pressure ratios and different internal leakage clearances to obtain experimental data; process and analyze the experimental data to obtain a second analysis result; conduct a quantitative study on the internal leakage rate of natural gas pipeline valves based on the second analysis result to obtain a research result. In order to fit the actual project, after analyzing the influencing factors of environmental noise, experiments are carried out on the outdoor site. To reduce the external interference and human error caused by outdoor experiments, some identical experimental groups are experimented multiple times.

[0033] In summary, due to the adoption of the above technical solutions, compared with the prior art, the present invention has at least the following beneficial effects:

[0034] The present invention builds a ball valve internal leakage fault simulation experimental platform, selects the pressure range according to the specification, and conducts experimental studies on the valve leakage rate and acoustic characteristic information under different internal leakage clearances and pressure ratio conditions, realizing the diagnosis of internal leakage of natural gas pipeline ball valves under multiple working conditions, thereby improving the diagnosis accuracy.

[0035] Compared with this technical method, in order to fit the actual project, after analyzing the influencing factors of environmental noise, experiments are carried out on the outdoor site. To reduce the external interference and human error caused by outdoor experiments, some identical experimental groups are experimented multiple times. During signal acquisition, acoustic signals are collected under four environmental conditions: sunny day without noise, light rain day without noise, construction noise within 100m nearby, and construction noise within 100m - 500m in the distance. Description of the drawings:

[0036] Figure 1 It is a schematic diagram of a simulation system for internal leakage of a natural gas pipeline ball valve according to an exemplary embodiment of the present invention.

[0037] Figure 2 It is a schematic diagram of a simulation method for internal leakage of a natural gas pipeline ball valve according to an exemplary embodiment of the present invention.

[0038] Figure 3 It is a schematic diagram of the initial natural gas pipe valve flow channel model according to an exemplary embodiment of the present invention.

[0039] Figure 4 It is a schematic diagram of a simplified pipe valve flow channel model according to an exemplary embodiment of the present invention.

[0040] Figure 5 It is a schematic diagram of the pipe valve meshing according to an exemplary embodiment of the present invention.

[0041] Figure 6 Schematic diagram of the gas flow field of a ball valve according to an exemplary embodiment of the present invention.

[0042] Figure 7 Schematic diagram of the velocity flow field of a ball valve according to an exemplary embodiment of the present invention.

[0043] Figure 8 Schematic diagram of the sound pressure level spectrum of a ball valve when the medium is gas according to an exemplary embodiment of the present invention.

[0044] Figure 9 Schematic diagram of the power spectral density of a ball valve when the medium is gas according to an exemplary embodiment of the present invention.

[0045] Figure 10 Schematic diagram of the power spectral density of a ball valve when the medium is air according to an exemplary embodiment of the present invention. Detailed implementation manners

[0046] The present invention will be further described in detail below in conjunction with embodiments and specific implementation manners. However, it should not be understood that the scope of the above-mentioned subject matter of the present invention is limited to the following embodiments. Any technology implemented based on the content of the present invention belongs to the scope of the present invention.

[0047] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0048] As Figure 1 shown, the present invention provides a simulation system for internal leakage of a ball valve in a natural gas pipeline, including a natural gas pipeline ball valve simulation platform, a collection device 7 and a host computer 8.

[0049] In this embodiment, the natural gas pipeline ball valve simulation platform includes a natural gas pipeline, on which a ball valve 1, a first flowmeter 2, a first pressure gauge 3, a second flowmeter 4, a second pressure gauge 5 and an acoustic emission sensor 6 are installed.

[0050] The first flowmeter 2 and the first pressure gauge 3 are installed upstream of the ball valve 1 (the gas / liquid inlet end), and the second flowmeter 4, the second pressure gauge 5 and the acoustic emission sensor 6 are installed downstream of the ball valve 1 (the gas / liquid outlet end).

[0051] The first flow meter 2, the first pressure gauge 3, the second flow meter 4, the second pressure gauge 5 and the acoustic emission sensor 6 are respectively connected to the collection device 7, and the collection device 7 is connected to the host computer 8 via wired / wireless communication.

[0052] Among them, the first flow meter 2 and the first pressure gauge 3 upload the first flow and the first pressure entering the ball valve 1 to the host computer 8 respectively, and the second flow meter 4 and the second pressure gauge 5 upload the second flow and the second pressure after passing through the ball valve 1 to the host computer 8 respectively. The host computer 8 calculates the internal leakage rate of the ball valve 1 according to the first flow, the first pressure, the second flow and the second pressure.

[0053] An acoustic emission sensor 6 is used to collect sound signals leaking from the pipeline and transmit them to a host computer 8 through a collection device 7;

[0054] The host computer 8 extracts a characteristic vector (amplitude, total sound pressure level, effective voltage value, average signal level) from the sound signal, and establishes a mapping between the characteristic vector and the internal leakage rate, thereby realizing the simulation of the internal leakage of the ball valve.

[0055] Based on the above system, Figure 2 As shown, the present invention also provides a method for simulating the internal leakage of a ball valve in a natural gas pipeline, comprising performing internal leakage flow field analysis, internal leakage acoustic field analysis and flow medium replaceability analysis on a simulated internal leakage ball valve to obtain a first analysis result; building a natural gas pipeline ball valve internal leakage identification and flow prediction system based on the first analysis result, performing valve internal leakage experiments under different pressure ratios and different internal leakage gaps to obtain experimental data; processing and analyzing the experimental data to obtain a second analysis result; and conducting a quantitative study on the internal leakage rate of natural gas pipeline valves based on the second analysis result to obtain a research result. Specifically comprising the following steps:

[0056] S1: Use 3D software to build a natural gas pipeline ball valve simulation platform.

[0057] S1-1: In this embodiment, Solidwords2020 3D modeling software can be used to establish an initial natural gas pipe valve flow channel model, such as Figure 3 As shown, the pipe diameter is DN50, the ball valve is Q41f-16c cast steel flange ball valve, the ball valve specification is DN50, and the ball valve opening is set to 15°. According to the valve flow coefficient and flow resistance coefficient test method, the upstream section of the ball valve is 250mm long and the downstream section is 500mm long.

[0058] S1-2: Considering that the structure of the initially established simulation platform for natural gas pipeline ball valves is relatively complex, and devices such as valve stems and handwheels carried by the ball valves have no practical significance for the flow field simulation, the Design Modeler model preprocessing software is used for simplification. By selecting the fluid inlet and outlet boundary surfaces, extracting the internal flow channels of the model, deleting unnecessary components and ensuring that the number of sharp points is minimized, a simplified pipe-valve flow channel model is obtained, as Figure 4 shown.

[0059] S1-3: Mesh encryption is performed on the ball valve. Considering the subsequent calculation accuracy, hexahedral structured meshes are used, as Figure 5 shown. After simulation, it is determined that the number of meshes of the ball valve is 1,861,793, the number of nodes is 459,686, the MinOrthogonal Quality is 0.22, the maximum aspect ratio is 12.183, the maximum slope is 0.78, and the number of meshes exceeding 0.7 is no more than 20.

[0060] S2: Set the first pressure and the first flow rate entering the ball valve in the natural gas pipeline ball valve simulation platform, and then obtain the second pressure and the second flow rate after passing through the ball valve to determine the generation mechanism of internal leakage of the ball valve.

[0061] S2-1: Set the first pressures entering the ball valve to be 0.3 MPa, 0.4 MPa, 0.5 MPa, and 0.6 MPa respectively to obtain the gas flow fields of the ball valve, as Figure 6 shown, Figure 6 where the inlet pressure in (a) is 0.3 MPa, Figure 6 the inlet pressure in (b) is 0.4 MPa, Figure 6 the inlet pressure in (c) is 0.5 MPa, Figure 6 and the inlet pressure in (d) is 0.6 MPa.

[0062] The gas flow field formed by the internal leakage of the ball valve is a secondary throttling flow field. Taking Figure 6 (a) as an example, the pressure entering the ball valve is 0.3 MPa. When the gas enters the ball valve, the pressure decreases due to the reduction of the flow area. During the first throttling, the pressure drops to 0.21 MPa. When the gas flows out of the ball valve, the second throttling occurs, and the pressure drops from 0.2 MPa to 0.14 MPa and then gradually stabilizes. At the same time, a small low-pressure area is formed at the outlet of the ball valve. The formation of the low-pressure area is due to the expansion and compression of the gas in the pipe-valve system, and this pressure characteristic is a necessary condition for the formation of shock waves.

[0063] From Figure 6It can be seen that the higher the pressure entering the ball valve, the greater the throttling pressure drop. When the inlet pressure is 0.3 MPa, the primary throttling pressure drop is 0.09 MPa and the secondary throttling pressure drop is 0.06 MPa; when the inlet pressure is 0.6 MPa, the primary throttling pressure drop is 0.28 MPa and the secondary throttling pressure drop is 0.15 MPa. Therefore, as the pressure entering the ball valve increases, the compression and expansion of the gas caused by throttling become more significant, the area of the low-pressure zone becomes larger, and the output pressure decreases.

[0064] S2-2: Set the first pressures entering the ball valve to be 0.3 MPa, 0.4 MPa, 0.5 MPa, and 0.6 MPa respectively to obtain the velocity flow field of the ball valve, as Figure 7 shown, Figure 7 in which the inlet pressure in (a) is 0.3 MPa, Figure 7 in which the inlet pressure in (b) is 0.4 MPa, Figure 7 in which the inlet pressure in (c) is 0.5 MPa, Figure 7 in which the inlet pressure in (d) is 0.6 MPa.

[0065] When gas enters the ball valve, due to the reduction of the flow area, the throttling effect causes the pressure energy of the gas to be converted into kinetic energy, and the flow velocity increases. When flowing out of the ball valve, due to the secondary throttling effect, the acceleration effect occurs again, and then it gradually decreases. Taking the pressure entering the ball valve as 0.5 MPa as an example, after the gas enters the ball valve, the maximum flow velocity is 550 m / s, and the maximum flow velocity after leaving the ball valve increases to 650 m / s, forming a high-speed jet, that is, a shock jet. Due to the shock jet, a turbulent zone is formed in the outlet area of the ball valve, and the noise generated by the turbulence is the main sound source of the internal leakage noise of the ball valve gas.

[0066] It can be Figure 7 seen that as the pressure entering the ball valve increases, the gas undergoes compression and expansion through throttling, more pressure energy is converted into kinetic energy, the flow velocity of the shock jet generated is higher, and thus the intensity of the sound source signal generated by the shock turbulence is stronger.

[0067] S3: Set the first pressure and the first flow rate entering the ball valve, obtain the acoustic wave signal of the ball valve, and determine the characteristics in the acoustic wave signal that respond to the internal leakage rate of the pipeline.

[0068] S3-1: Set the first pressures of the gas entering the ball valve to be 0.3 MPa, 0.4 MPa, and 0.5 MPa, set two sound source monitoring points. The first monitoring point is the pipe wall 30 cm downstream of the ball valve, and the second monitoring point is the surface of the ball valve body. By collecting and analyzing the acoustic wave signals obtained at the two places, the sound pressure level frequency spectrum diagram of the monitoring points can be obtained (the sound pressure level frequency spectrum represents the frequency band in which the internal leakage noise of the ball valve can generate a response within a certain frequency band and can reflect the magnitude of the response energy), and the relationship between the sound pressure level and the internal leakage of the ball valve can be determined.

[0069] As Figure 8 shown, Figure 8 in (a), the first pressure entering the ball valve is 0.3 MPa, Figure 8 in (b), the first pressure entering the ball valve is 0.4 MPa, Figure 8 in (c), the first pressure entering the ball valve is 0.5 MPa.

[0070] From Figure 8 the analysis, it can be seen that:

[0071] ① In the range of 0 - 100 KHz, there are two obvious peak frequency bands at both the first monitoring point and the second monitoring point of the internal leakage of the ball valve. For example, Figure 8 in (c), when the first pressure entering the ball valve is 0.5 MPa, the two main peak frequency bands of the signal measured at the first monitoring point are at 18.8 KHz - 20.1 KHz and 56.8 KHz - 68 KHz, and the corresponding sound pressure levels are 105.5 dB and 111 dB respectively; the two main peak frequency bands of the signal measured at the second monitoring point are at 4.8 KHz - 13.5 KHz and 61 KHz - 68.3 KHz, and the corresponding sound pressure levels are 140.2 dB and 144.7 dB respectively.

[0072] ② As the distance between the monitoring point and the sound source signal increases, the noise response frequency band changes little, the peak frequencies are relatively concentrated, and the corresponding sound pressure level attenuates with the increase of the distance, but still has obvious characteristics. This shows that when the ball valve has gas internal leakage, the turbulent noise generated by the shock jet has certain characteristic frequencies, and based on this, the sound pressure level peak can be used as an effective basis for judging the internal leakage condition of the ball.

[0073] ③ As the inlet pressure increases, the overall response trend of the total sound pressure level of the noise is the same, and the main peak frequency band remains within 0 - 70 KHz, and the highest peak frequency increases slightly. This shows that when the pressure increases, that is, the leakage amount increases, although the energy of the corresponding sound pressure level peak increases, the increase amplitude is not significant, which can be used as an effective basis for judging the internal leakage condition of the ball.

[0074] S3 - 2: According to the acquired acoustic wave signal, obtain the power spectral density diagram of the monitoring point and determine the relationship between the power spectral density and the internal leakage of the ball valve.

[0075] The power spectral density represents the power signal of the signal in the unit frequency band, reflecting the distribution of the signal power in the frequency domain, and can effectively characterize the intensity and center frequency of the signal, providing a judgment basis for the identification of the internal leakage condition of the ball valve and the quantitative research of the internal leakage. As Figure 9 shown, Figure 9 in (a), the first pressure entering the ball valve is 0.3 MPa, Figure 9 in (b), the first pressure entering the ball valve is 0.4 MPa, Figure 9In (c), it indicates that the first pressure entering the ball valve is 0.5 MPa.

[0076] From Figure 9 analysis, it can be known that:

[0077] ① The signal power of the first monitoring point is mainly concentrated in the range of 48 KHz to 75 KHz, and the signal power of the second monitoring point is mainly concentrated in the ranges of 6 KHz to 30 KHz and 48 KHz to 75 KHz. From this, it is judged that the central frequency of the internal leakage noise of the ball valve mainly remains between 48 KHz and 75 KHz, and the highest peak point basically remains at 55 KHz. Moreover, with the increase of the inlet pressure of the ball valve, the central frequency does not change significantly.

[0078] ② Comparing the situations of the two monitoring points under the same working conditions, as the distance between the monitoring point and the sound source point increases, the power spectral density of the acoustic wave signal shows an obvious attenuation, but the power spectral density after attenuation still has obvious characteristics; this indicates that the power spectral density can be used to effectively identify the occurrence of the internal leakage condition of the ball valve.

[0079] ③ As the inlet pressure of the ball valve increases, that is, the leakage amount increases, the power spectral density value corresponding to the central frequency is higher, and the noise energy is stronger. It shows that different leakage amounts produce different noise levels, and thus the power spectral density can be correlated with the leakage amount.

[0080] S3-3: Set the first pressure of the air entering the ball valve, obtain the acoustic wave signal after passing through the ball valve, obtain the power spectral density diagram of the air, and determine the relationship between the power spectral density of the air and the internal leakage of the ball valve.

[0081] In this embodiment, the first pressures of the air entering the ball valve are set to 0.3 MPa, 0.4 MPa, and 0.5 MPa. Then, by analyzing the obtained acoustic wave signals, the power spectral density diagrams of the air are obtained, as Figure 10 shown, Figure 10 In (a), it indicates that the first pressure entering the ball valve is 0.3 MPa, Figure 10 In (b), it indicates that the first pressure entering the ball valve is 0.4 MPa, Figure 10 In (c), it indicates that the first pressure entering the ball valve is 0.5 MPa.

[0082] From Figure 10 it can be known that when air is used as the flowing medium, the peak point of the central frequency of the internal leakage noise of the ball valve is about 50 KHz. Comparing Figure 9 , it can be considered that using gas (methane) and air as the flowing media respectively has very similar acoustic laws, and the power corresponding to the peak frequency of the central frequency is not much different, that is, using compressed air can characterize the acoustic characteristics of the internal leakage of the natural gas pipeline ball valve.

[0083] In this embodiment, through the analysis of acoustic wave signals, it can be obtained that: by the sound pressure level frequency and power spectral density, the main frequency of the internal leakage sound signal of the ball valve is determined to be in the range of 48KHz to 75KHz, and as the inlet pressure of the ball valve increases, the noise energy becomes stronger; when air is used as the flowing medium, the internal leakage model has the same acoustic characteristics as gas (methane).

[0084] S4: Set an acoustic emission sensor downstream of the ball valve, and then conduct multiple groups of experiments under different environmental conditions, collect the corresponding acoustic wave signals and extract the features therein (such as sound pressure level, power spectral density, etc.), and fit them with the leakage rate of the ball valve to determine the mapping relationship between the acoustic wave signal and the leakage rate of the ball valve.

[0085] In this embodiment, considering the unevenness of the ball valve body and the possible problems such as the sensor falling off or the contact surface changing during the experiment, which may affect the result accuracy, it is finally determined to install the acoustic emission sensor 30 cm downstream of the ball valve.

[0086] In this embodiment, the environmental conditions include environments such as sunny days without noise, light rainy days without noise, construction noise within 100 m nearby, and construction noise within 100 m to 500 m in the distance.

[0087] In this embodiment, the scheme of multiple groups of experiments is as follows:

[0088] (1) Acquisition of acoustic wave signals at different ball valve orifice openings under the same pressure;

[0089] (2) Acquisition of acoustic wave signals at different pressures under the same ball valve orifice opening;

[0090] (3) Acquisition of acoustic wave signals of different specifications of ball valves (ball valve inner diameters are DN50 and DN100) under different pressures.

[0091] In this embodiment, the pressures include five pressure levels of 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, and 0.7MPa; the ball valve orifice openings include valve orifice opening changes increasing by 0.5 degrees from 11° to 16°; different specifications of ball valves include DN50 and DN100.

[0092] In this embodiment, it can be seen from S2 that the leakage rate of the ball valve is associated with the sound pressure level and power spectral density in the acoustic wave signal. Therefore, after the experiment scheme is carried out, the corresponding acoustic wave signals are collected, the acoustic wave signals are denoised and then the frequency domain signals are obtained through fast Fourier transform, the features such as sound pressure level and power spectral density in the frequency domain signals are extracted, and then the neural network algorithm is used to perform regress regression fitting on this feature and the leakage rate (which can be calculated according to the input pressure, input flow rate, output pressure, and output flow rate and is an existing technology) to obtain the mapping relationship, that is, the internal leakage rate (leakage rate) of the ball valve can be fitted only according to the detected input pressure and acoustic wave signal (sound pressure level, power spectral density).

[0093] Analysis shows that when the pressure is constant and the opening of the ball valve is changed, the center frequency of the DN50 ball valve is about 42 KHz, and the center frequency of the DN100 ball valve is 43 KHz - 61 KHz. Moreover, as the opening increases, the amplitude corresponding to the peak frequency increases, the waveform density increases, and the signal intensity increases. By demonstrating the variation laws of the ball valve opening, leakage rate, pressure, amplitude, total sound pressure level, RMS value, and ASL value, it shows that as the variable value increases, the acoustic emission characteristic parameters show a trend of rapid growth in the early stage and then tend to be stable, and different working conditions have obvious distinguishing characteristics.

[0094] In this embodiment, to verify the method of the present invention, verification analysis was carried out:

[0095] Medium-pressure steel natural gas pipelines with DN100 and DN50 were laid on-site, with a pressure of about 0.3 MPa. There were ball valves for cutting, which were installed in valve wells for practical training operations. A turbine flowmeter and a pressure gauge were installed at the upstream end of the ball valve, and a pressure gauge and an acoustic emission sensor (30 cm from the outlet end) were installed at the outlet end of the ball valve; the environmental noise was detected, and the maximum amplitude of the noise was about 35 dB. The DN100 ball valve was detected without a filter, and the leakage amplitude was about 94 dB. The filter threshold was set at 35 dB.

[0096] The inlet flow rates of the DN50 ball valve on the natural gas pipeline were adjusted to 0.001 m3 / s, 0.0045 m3 / s, and 0.0055 m3 / s respectively, and 9 groups of detection data were collected. The inlet flow rates of the DN100 ball valve on the natural gas pipeline were adjusted to 0.0015 m3 / s, 0.0020 m3 / s, and 0.0065 m3 / s respectively, and 9 groups of detection data were collected.

[0097] By analyzing the detection data, on-site detection results and fitting detection results were obtained, as shown in Table 1 and Table 2.

[0098] Table 1. On-site detection results

[0099]

[0100] Table 2. Fitting detection results

[0101]

[0102]

[0103] As can be seen from the analysis of Table 1 and Table 2, after applying the present invention, the prediction error of the DN50 ball valve is within 6%, and the average error is 2.91%. The prediction error of the DN100 ball valve is within 15%, and the average error is 6.71%. It can be seen that this method has high accuracy and has practical value for the internal leakage detection of ball valves in natural gas pipelines.

[0104] Those of ordinary skill in the art can understand that the above embodiments are specific embodiments for implementing the present invention, and in actual applications, various changes can be made in form and details without departing from the spirit and scope of the present invention.

Claims

1. A simulation system for internal leakage of a ball valve in a natural gas pipeline, characterized in that, including a simulation platform for natural gas pipeline ball valves; The simulation platform for natural gas pipeline ball valves includes a natural gas pipeline, on which a ball valve (1), a first flowmeter (2), a first pressure gauge (3), a second flowmeter (4), a second pressure gauge (5) and an acoustic emission sensor (6) are installed; The first flowmeter (2) and the first pressure gauge (3) are installed upstream of the ball valve (1), and the second flowmeter (4), the second pressure gauge (5) and the acoustic emission sensor (6) are installed downstream of the ball valve (1).

2. The simulation system for internal leakage of a ball valve in a natural gas pipeline according to claim 1, characterized in that, It also includes a collection device (7) and a host computer (8); the input end of the collection device (7) is respectively connected to the first flowmeter (2), the first pressure gauge (3), the second flowmeter (4), the second pressure gauge (5) and the acoustic emission sensor (6), and the output end of the collection device (7) is connected to the input end of the host computer (8).

3. The simulation system for internal leakage of a ball valve in a natural gas pipeline according to claim 2, characterized in that, The host computer (8) calculates the internal leakage rate of the ball valve (1) according to the data collected by the first flowmeter (2), the first pressure gauge (3), the second flowmeter (4) and the second pressure gauge (5); at the same time, the host computer (8) also establishes a mapping relationship between the acoustic wave signal collected by the acoustic emission sensor (6) and the internal leakage rate.

4. A simulation method for internal leakage of a ball valve in a natural gas pipeline for the system according to any one of claims 1-3, characterized in that, Specifically, it includes the following steps: S1: Use 3D software to construct a simulation platform for natural gas pipeline ball valves; S2: Set the first pressure and the first flow rate entering the ball valve in the simulation platform for natural gas pipeline ball valves, then obtain the second pressure and the second flow rate after passing through the ball valve, construct the gas flow field and velocity field of the ball valve, and analyze the generation mechanism of internal leakage of the ball valve; S3: Obtain the acoustic wave signal after passing through the ball valve, and determine the characteristics in the acoustic wave signal that respond to the internal leakage rate of the pipeline; S4: Set an acoustic emission sensor downstream of the ball valve, then conduct multiple groups of experiments under different environmental conditions, collect the corresponding acoustic wave signals, extract the characteristics in the acoustic wave signals that respond to the internal leakage rate of the pipeline, and then fit the characteristics with the internal leakage rate of the ball valve to determine the mapping relationship between the acoustic wave signal and the internal leakage rate of the ball valve.

5. The simulation method for internal leakage of a ball valve in a natural gas pipeline according to claim 4, characterized in that, The S1 includes: S1-1: Use Solidwords2020 3D modeling software to establish an initial simulation platform for natural gas pipeline ball valves. The pipe diameter of the pipeline is DN50. The ball valve selects a Q41f-16c cast steel flange ball valve with a specification of DN50. Set the opening of the ball valve to 15°. The length of the pipeline upstream of the ball valve is 250mm, and the length of the pipeline downstream is 500mm; S1-2: Use Design Modeler model preprocessing software to select the fluid inlet and outlet boundary surfaces in the initial simulation platform for natural gas pipeline ball valves, extract the internal flow channel of the model, delete useless components and reduce the sharp points to obtain a simplified pipe-valve flow channel model; S1-3: Use hexahedral structured grids to mesh the ball valve.

6. The simulation method for internal leakage of a ball valve in a natural gas pipeline according to claim 4, characterized in that, In the S2, the generation mechanism of internal leakage of the ball valve is: S2-1: When the gas enters the ball valve, the pressure decreases due to the reduced flow area. When the gas flows out of the ball valve, a second throttling occurs, and a low-pressure area is formed at the outlet of the ball valve; S2-2: When gas enters the ball valve, due to the reduced flow area, the throttling effect causes the pressure energy of the gas to be converted into kinetic energy, increasing the flow velocity. When it flows out of the ball valve again, due to the secondary throttling effect, the velocity increasing effect occurs again, forming a high-speed jet in the low-pressure area, that is, a shock jet. Due to the shock jet, a turbulent area is formed in the outlet area of the ball valve, and the noise formed by the turbulence is the sound source of the internal leakage noise of the ball valve for gas.

7. The simulation method for internal leakage of a ball valve in a natural gas pipeline according to claim 4, characterized in that, The said S3 includes: S3-1: Set two sound source monitoring points. The first monitoring point is the pipe wall 30 cm downstream of the ball valve, and the second monitoring point is the surface of the ball valve body. By collecting and analyzing the acoustic signals obtained at the two places, a sound pressure level spectrogram is obtained; as the inlet pressure of the ball valve increases, the overall response trend of the total sound pressure level at the two sound source monitoring points is the same. Therefore, the sound pressure level is used as the basis for judging the internal leakage condition of the ball. S3-2: By collecting and analyzing the acoustic signals obtained at the two places, a power spectral density diagram is obtained; as the inlet pressure of the ball valve increases, that is, the leakage amount increases, the higher the power spectral density value corresponding to the center frequency, the stronger the noise energy. Therefore, the power spectral density is used as the basis for judging the internal leakage condition of the ball.

8. The simulation method for internal leakage of a ball valve in a natural gas pipeline according to claim 4, characterized in that, The said S3 also includes S3-3: Replace the medium in the pipeline with air, and obtain the sound pressure level spectrogram of the monitoring point. The power spectral density corresponding to the peak frequency of the center frequency is the same as that when the medium is methane, that is, using air can characterize the simulation of internal leakage of the ball valve in the natural gas pipeline.

9. The simulation method for internal leakage of a ball valve in a natural gas pipeline according to claim 4, characterized in that, In the said S4, different environmental conditions include no noise on sunny days, no noise on light rainy days, construction noise within 100 m nearby, and construction noise within 100 m - 500 m in the distance.

10. The simulation method for internal leakage of a ball valve in a natural gas pipeline according to claim 4, characterized in that, In the said S4, the scheme of multiple groups of experiments is: (1) Collect acoustic signals at the same pressure with different ball valve opening degrees. (2) Collect acoustic signals at the same ball valve opening degree with different pressures. (3) Collect acoustic signals of different specifications of ball valves at different pressures.

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