System and method for testing sealing performance of hydrogen-doped natural gas pipeline connecting piece

Abstract

The invention relates to the technical field of sealing test devices, in particular to a hydrogen-doped natural gas pipeline connecting piece sealing performance test system which comprises a gas source subsystem and a connecting piece subsystem. The dynamic load simulation subsystem is used for simulating the pressure pulsation inside the pipeline and the mechanical vibration environment outside the pipeline under the actual dynamic working condition for the connecting piece subsystem; the connection subsystem is arranged in the environment simulation subsystem; the sensor subsystem is used for monitoring gas pressure and temperature in the test cavity; the sampling subsystem is used for collecting gas leaked from the test cavity so as to carry out component analysis on the leaked gas; and the control subsystem is used for receiving and processing the monitoring data and controlling the test system. By simulating the dynamic working condition of the pipeline connecting piece, the pipeline connecting piece can be subjected to the sealing performance test under the combined action of the set pressure pulsation and / or mechanical vibration and / or temperature, and the accuracy and reliability of the sealing performance test structure are ensured. The invention also correspondingly discloses a test method.

Description

Technical Field

[0001] This invention relates to the field of sealing testing equipment technology, and in particular to a system and method for testing the sealing performance of hydrogen-blended natural gas pipeline connectors. Background Technology

[0002] Under the "dual carbon" goal, blending hydrogen into natural gas pipelines (hereinafter referred to as "hydrogen-blended natural gas") has become an important energy transition strategy. However, hydrogen molecules are extremely small and more prone to seepage and leakage than methane, posing a serious challenge to the safety and sealing integrity of existing natural gas pipeline systems. In particular, the gasket sealing performance of bolted flange connections, which are commonly found in pipeline systems, is at risk of accelerated failure under complex dynamic conditions such as hydrogen blending, high pressure, pressure pulsation, mechanical vibration, and changes in ambient temperature.

[0003] Currently, research on pipeline connection sealing mainly focuses on static performance testing under natural gas or pure hydrogen conditions. However, this type of hydrogen-blended natural gas pipeline connection sealing performance testing device has the following drawbacks:

[0004] (1) The existing hydrogen-blended natural gas pipeline connection sealing test device is in a non-flowing state when the gas is under the test state, while the gas is in a flowing state when the actual pipeline is running.

[0005] (2) There are no dynamic loads that exist under multiple actual working conditions such as pressure pulsation, mechanical vibration and temperature change at the same time;

[0006] (3) It is impossible to perform high-precision quantitative measurement of extremely small leakage amounts;

[0007] (4) The proportion of hydrogen in the leaked gas was not analyzed, so the hypothesis of "hydrogen preferential leakage" of hydrogen-blended natural gas could not be verified. Summary of the Invention

[0008] To address at least one of the aforementioned technical problems, this invention proposes a testing system and method for the sealing performance of hydrogen-blended natural gas pipeline connectors. This addresses the issue in existing technologies where it is impossible to comprehensively simulate the real dynamic operating conditions (including pressure, pressure pulsation, mechanical vibration, and temperature) of hydrogen-blended natural gas pipelines on a single testing platform, and to perform high-precision, multi-dimensional testing and analysis of the leakage performance of connectors.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] The first aspect of this invention provides a system for testing the sealing performance of hydrogen-blended natural gas pipeline connectors, comprising:

[0011] The gas source subsystem is used to provide hydrogen-blended natural gas in a set proportion and in a uniformly mixed manner;

[0012] A connector subsystem is used to connect the inflow pipe to be tested and the outflow pipe to be tested. The inflow pipe to be tested is connected to the gas source subsystem. The connector subsystem has a test chamber for accommodating hydrogen-blended natural gas.

[0013] The dynamic load simulation subsystem is used to simulate the pressure pulsation inside the hydrogen-blended natural gas pipeline and the external mechanical vibration environment under actual dynamic working conditions for the connecting component subsystem.

[0014] An environmental simulation subsystem is used to simulate the temperature environment of a hydrogen-blended natural gas pipeline for the connection subsystem, and the connection subsystem is located within the environmental simulation subsystem.

[0015] The sensor subsystem is used to monitor the gas pressure and temperature inside the test chamber, and calculate the gas mass leakage rate inside the test chamber based on the pressure and temperature using the real gas mass equation.

[0016] A sampling subsystem is used to collect the gas leaking from the test chamber for component analysis of the leaked gas;

[0017] The control subsystem is used to receive and process monitoring data and control the test system.

[0018] Preferably, the dynamic load simulation subsystem includes:

[0019] The pressure pulsation unit is connected to the air inlet of the measured inflow pipe. The pressure pulsation unit is a pressure wave generator used to generate pressure pulsations with controllable frequency and amplitude.

[0020] A mechanical vibration unit is disposed at the lower part of the connecting subsystem and is used to apply sinusoidal sweep frequency or random vibration to the mechanical vibration unit.

[0021] Preferably, the connector subsystem includes:

[0022] A flange end cap is connected to the inflow pipe to be tested. The flange end cap has a first mounting hole in the center to facilitate fixing the inflow pipe to be tested. The air outlet of the inflow pipe to be tested is flush with the lower surface of the flange end cap.

[0023] The flange base is connected to the outlet pipe to be tested. The flange base has a second mounting hole at its center that corresponds to the first mounting hole. The outlet pipe to be tested is fixed in the second mounting hole, and the outlet is flush with the upper surface of the flange base.

[0024] A test gasket is placed between the flange end cap and the flange base;

[0025] A axial force bolt is used to fix the flange end cover and the flange base so that the lower surface of the flange end cover, the upper surface of the flange base and the test gasket surround the test cavity. The axial force bolt is embedded with a strain gauge for measuring the axial preload.

[0026] Preferably, the sensor subsystem includes:

[0027] A pressure sensor is installed in the inflow pipe being tested and near the test chamber.

[0028] The first temperature sensor is located in the inflow pipe being tested and near the test chamber.

[0029] Preferably, the environment simulation subsystem includes:

[0030] The test chamber has an internal cavity for accommodating the connector subsystem.

[0031] A heating unit, located inside or connected to the test chamber, is used to heat the accommodating cavity;

[0032] A refrigeration unit, located inside or connected to the test chamber, is used to cool the accommodating cavity;

[0033] An air circulation unit is installed inside the test chamber to circulate the air within the accommodating cavity;

[0034] A temperature monitoring unit is installed inside the test chamber to monitor the actual temperature inside the accommodating cavity in real time.

[0035] The control unit is communicatively connected to the heating unit, cooling unit, air circulation unit, and temperature monitoring unit. Based on the difference between the actual temperature fed back by the temperature monitoring unit and the preset target temperature, it controls the heating system and / or cooling system to dynamically adjust the temperature inside the test chamber.

[0036] Preferably, the sampling subsystem is a portable gas chromatograph, which includes a gas chromatograph body and a gas collection tube connected to the gas chromatograph body. The sampling head of the gas collection tube extends into the accommodating cavity of the test chamber and is close to the test pad.

[0037] Preferably, the gas source subsystem includes:

[0038] A hydrogen unit for supplying hydrogen includes a hydrogen cylinder and a hydrogen pipeline connected to the outlet of the hydrogen cylinder. The hydrogen pipeline is provided with a first check valve, a first pressure regulating valve and a first flow controller in sequence along the direction of hydrogen flow.

[0039] A natural gas unit for supplying natural gas includes a natural gas cylinder and a natural gas pipeline connected to the outlet of the natural gas cylinder. The natural gas pipeline is provided with a second check valve, a second pressure regulating valve and a second flow controller in sequence along the natural gas flow direction.

[0040] A blending unit is used to uniformly blend the hydrogen and natural gas. The outlets of the hydrogen pipeline and the natural gas pipeline are respectively connected to the two inlets of the blending unit. The outlet of the blending unit is connected to a blending pipeline, which is provided with a third check valve, a first flow meter, a circulating compressor and a first pressure flow meter in sequence along the flow direction of the hydrogen-blended natural gas.

[0041] A buffer unit is used to buffer the hydrogen-blended natural gas after it has been uniformly blended by the blending unit. The outlet of the blending pipeline is connected to the inlet of the buffer unit. The outlet of the buffer unit is connected to the pipeline to be measured through a buffer pipeline. The buffer pipeline is provided with a fourth check valve, a second pressure measuring device, a fifth check valve, and a third pressure measuring device in sequence along the gas flow direction. The pressure wave generator is connected to the pipeline between the second pressure measuring device and the fifth check valve.

[0042] The circulation unit includes a fourth pressure measuring device, a second flow meter, and a sixth check valve arranged sequentially along the gas flow direction on the circulation pipeline; the inlet of the circulation pipeline is connected to the measured outflow pipeline, and the outlet of the circulation pipeline is connected to the pipeline between the third check valve and the first flow meter.

[0043] Preferably, the blending unit includes:

[0044] A Venturi mixer for achieving preliminary mixing of natural gas and hydrogen, the Venturi mixer comprising:

[0045] The intake section includes a first intake section coaxially arranged and connected to the outlet of the natural gas pipeline, and a second intake section located inside the first intake section and connected to the hydrogen pipeline.

[0046] The nozzle section is connected to the outlet of the second air inlet section and located within the first air inlet section. The cross-section of the nozzle section is a tapered cone, which is used to increase the hydrogen flow rate.

[0047] A mixing section is used to provide an initial mixing space for hydrogen and natural gas, and the mixing section is connected to the outlet of the first inlet section;

[0048] The throat section is used to provide a stable flow field for hydrogen and natural gas to achieve momentum exchange. The throat section is connected to the outlet of the mixing section. The throat section is a cylindrical straight pipe with an inner diameter smaller than that of the mixing section.

[0049] The diffuser section is used to convert the kinetic energy of hydrogen and natural gas into pressure energy. The diffuser section is connected to the outlet of the throat section, and the cross-section of the diffuser section is a gradually expanding cone.

[0050] The outflow section is connected to the air outlet of the diffuser section. The outflow section is a cylindrical straight pipe with an inner diameter equal to the inner diameter of the large end of the diffuser section. The central axes of the inlet section, nozzle section, mixing section, throat section, diffuser section, and outflow section coincide.

[0051] A static mixer is coaxially connected to the outlet of the Venturi mixer. The interior of the static mixer is provided with a microporous annular structure for mixing hydrogen and natural gas and a spiral structure for cutting and recombining the micron-sized bubbles along the gas flow direction.

[0052] The microporous ring structure is a metal microporous ring, which is made of sintered metal powder or sintered metal fiber and has several interconnected pores.

[0053] The spiral structure includes several alternating Kenics spiral blades with opposite twisting directions, and the angle between the tail end and the front end of adjacent Kenics spiral blades is 90°. The pitch angle of the Kenics spiral blades located at the front section of the static mixer along the airflow direction is greater than the pitch angle of the Kenics spiral blades located at the rear section of the static mixer.

[0054] The second aspect of this invention provides a test method for the sealing performance testing system of hydrogen-blended natural gas pipeline connectors as described in the first aspect, comprising the following steps:

[0055] S1, activate the gas source subsystem, environmental simulation subsystem, and sensor subsystem. The gas source subsystem adjusts the ratio of hydrogen to natural gas, the environmental simulation subsystem adjusts the temperature of the connection subsystem, and the sensor subsystem monitors the pressure and temperature of the test chamber. When the rate of change of pressure and temperature is lower than a set threshold, the gas source subsystem is determined to have reached an initial stable state, and the initial time is recorded as t0, and the initial pressure as P(t). 0） and initial temperature T(t0);

[0056] S2, activate the dynamic load simulation subsystem and sampling subsystem to simulate the actual dynamic working conditions of the pipe connection and collect data on the t inside the test cavity. i The pressure of time P(t) i ) and temperature T(t) i );

[0057] S3, based on pressure P(t) i ) and temperature T(t) i ), using the real gas law to calculate t in real time iThe mass m(t) of the gas inside the chamber is measured at constant intervals. i );

[0058] S4, calculate the gas mass loss at each time point relative to the initial time. According to the gas mass loss Δm(t) i Calculate t i The average mass leakage rate at any given time is ;

[0059] S5. Based on the leaked gas collected by the sampling subsystem from the periphery of the test chamber, the ratio of methane to hydrogen in the leaked gas is analyzed by a gas chromatograph and compared with the ratio of methane to hydrogen in the gas source subsystem loop to verify the hydrogen preferential leakage effect.

[0060] S6. After the test is completed, shut down the dynamic load simulation subsystem and the gas source subsystem, and use the venting pipeline to vent the gas in the pipeline.

[0061] Preferably, in S3, the mass m(t) of the gas in the test chamber at time ti is... i The calculation formula is as follows:

[0062]

[0063] In the formula, for Pressure at any given time; V is the volume of the test chamber; M is the molar mass of the gas; and Under the given conditions, the compressibility factor of the test gas is calculated in real time based on the real gas law. This is the universal gas constant.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] This invention simulates the dynamic operating conditions of pipeline connections using a dynamic load simulation subsystem and an environmental simulation subsystem. This allows the pipeline connections to undergo sealing tests under the combined effects of set pressure pulsations and / or mechanical vibrations and / or temperatures. This ensures a high degree of consistency between the multi-physics coupled environment and the actual operating conditions of hydrogen-blended natural gas, guaranteeing the accuracy and reliability of the sealing test structure. Simultaneously, a sensor subsystem, combined with the real gas law, calculates the macroscopic mass leakage rate, enabling high-precision, quantitative measurement of even minute leaks. A sampling subsystem analyzes the components of the leaked gas, allowing for composition determination and direct verification of the hydrogen preferential leakage effect. Attached Figure Description

[0066] Figure 1 A schematic diagram of a system for testing the sealing performance of hydrogen-blended natural gas pipeline connectors;

[0067] Figure 2 This is a schematic diagram of the connector subsystem in this invention;

[0068] Figure 3 This is a schematic diagram of the mixing device in this invention;

[0069] Figure 4 This is a perspective view of the mixing device in this invention;

[0070] Figure 5 This is an exploded view of the mixing device in this invention;

[0071] Figure 6 This is a perspective view of the mixing device in this invention;

[0072] Figure 7 This is a flowchart of a method for testing the sealing performance of hydrogen-blended natural gas pipeline connectors.

[0073] In the diagram: 10. Gas source subsystem; 101. Hydrogen unit; 1011. Hydrogen cylinder; 1012. First check valve; 1013. First pressure regulating valve; 1014. First flow controller;

[0074] 102. Natural gas unit; 1021. Natural gas cylinder; 1022. Second check valve; 1023. Second pressure regulating valve; 1024. Second flow controller;

[0075] 103. Blending unit; 1031. Venturi mixer; 10311. Inlet section; 10312. Nozzle section; 10313. Mixing section; 10314. Throat section; 10315. Diffusion section; 10316. Outlet section; 1032. Static mixer; 10321. Microporous annular structure; 10322. Spiral structure; 1032. Third check valve; 1034. First flow meter; 1035. Circulating compressor; 1036. First pressure flow meter;

[0076] 104. Buffer unit; 1041. Buffer tank; 1042. Fourth check valve; 1043. Second pressure gauge; 1044. Fifth check valve; 1045. Third pressure gauge;

[0077] 105. Circulation unit; 1051. Fourth pressure measuring device; 1052. Second flow meter; 1053. Sixth check valve;

[0078] 20. Connecting components subsystem; 201. Flange end cover; 202. Flange base; 203. Test gasket; 204. Axial bolt; 205. Test chamber;

[0079] 30. Dynamic load simulation subsystem; 301. Pressure pulsation unit; 302. Mechanical vibration unit;

[0080] 40. Environmental simulation subsystem; 50. Sensor subsystem; 501. Pressure sensor; 502. First temperature sensor; 60. Sampling subsystem;

[0081] 70. Venting subsystem; 701. Fifth pressure gauge; 702. First vent valve; 703. Venting torch; 704. Sixth pressure gauge; 705. Second vent valve. Detailed Implementation

[0082] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments of the present invention.

[0083] Example 1

[0084] Please refer to Figure 1 A system for testing the sealing performance of hydrogen-blended natural gas pipeline connectors, comprising:

[0085] Gas source subsystem 10 is used to provide hydrogen-blended natural gas in a set proportion and uniformly mixed;

[0086] The connector subsystem 20 is used to connect the inflow pipe and the outflow pipe to be tested. The inflow pipe is connected to the gas source subsystem 10. The connector subsystem 20 has a test chamber 205 for accommodating hydrogen-blended natural gas.

[0087] The dynamic load simulation subsystem 30 is used to simulate the pressure pulsation inside the hydrogen-blended natural gas pipeline and the external mechanical vibration environment under actual dynamic working conditions for the connection subsystem 20.

[0088] The environmental simulation subsystem 40 is used to simulate the temperature environment of a hydrogen-blended natural gas pipeline for the connection subsystem 20. The connection subsystem is located within the environmental simulation subsystem 40.

[0089] The sensor subsystem 50 is used to monitor the gas pressure and temperature inside the test chamber 205, and calculate the gas mass leakage rate inside the test chamber 205 based on the pressure and temperature using the real gas mass equation.

[0090] The sampling subsystem 60 is used to collect the gas leaking from the test chamber 205 for component analysis of the leaked gas.

[0091] The control subsystem is used to receive and process monitoring data and control the test system.

[0092] This embodiment simulates the dynamic operating conditions of pipeline connections using a dynamic load simulation subsystem and an environmental simulation subsystem 40. This allows the pipeline connections to undergo sealing tests under the combined effects of set pressure pulsations and / or mechanical vibrations and / or temperatures. This ensures that the multi-physics coupled environment closely matches the actual operating conditions of hydrogen-blended natural gas, guaranteeing the accuracy and reliability of the sealing test structure. Simultaneously, the sensor subsystem 50 calculates the macroscopic mass leakage rate using the real gas state equation, achieving high-precision, quantitative measurement of even minute leaks. The sampling subsystem 60 analyzes the components of the leaked gas, enabling composition determination and directly verifying the hydrogen preferential leakage effect.

[0093] Please refer to Figure 1 In this embodiment, the dynamic load simulation subsystem 30 includes:

[0094] The pressure pulsation unit 301 is connected to the air inlet of the pipeline being measured. The pressure pulsation unit 301 is a pressure wave generator used to generate pressure pulsations with controllable frequency and amplitude.

[0095] The mechanical vibration unit 302 is disposed at the lower part of the connecting component subsystem 20 and is used to apply sinusoidal sweep frequency or random vibration to the mechanical vibration unit 302.

[0096] Specifically, the core principle of the pressure wave generator in this embodiment is to periodically change the volume of the closed flow channel, thereby generating pressure pulsations with a controllable frequency (0.1-10Hz) and amplitude (average pressure ±5%) within the pipe.

[0097] In this embodiment, the main function of the pressure wave generator is to superimpose a periodically fluctuating pressure component on top of the stable average pressure, thereby simulating the pressure pulsation caused by compressor start-up and shutdown, valve operation, and changes in user gas consumption during the operation of a real hydrogen-blended natural gas pipeline.

[0098] Pressure wave generators mainly come in various structural forms, including reciprocating piston type, diaphragm type, and bellows type. Considering the pressure pulsation of a certain amplitude in the simulated pipeline in this embodiment, a reciprocating piston type or a long-stroke diaphragm type is preferred. The structure and working principle of the pressure wave generator are prior art and will not be described in detail here.

[0099] In this embodiment, the mechanical vibration unit 302 mainly functions to simulate the vibration of a real pipeline from various sources, including but not limited to: soil settlement and ground pulsation, traffic loads from nearby highways and railways, and the operation of nearby heavy machinery (such as pumps and compressors).

[0100] The mechanical vibration unit 302 in this embodiment can be an electrically driven vibration table. Its main structure includes a platform for mounting the connector subsystem 20 and the environmental simulation subsystem 40, a moving coil fixed below the platform, a magnetic circuit system providing a high-intensity magnetic field to the moving coil, a support system for supporting the weight of the components, and sensors (displacement sensors and accelerometers) for detecting the actual movement of the platform. The electrically driven vibration table can simulate the vibration environment of common pipe structures with frequencies of 0-500 Hz and accelerations of 0-10g.

[0101] It should be noted that in this embodiment, the pressure pulsation unit 301 and the mechanical vibration unit 302 are both independent control units. Therefore, this embodiment can be used to study the influence of pressure pulsation or vibration on the sealing performance of the connector separately, or it can be used to study the synergistic or antagonistic effects of pressure pulsation and vibration on the sealing performance of the connector at the same time, so as to accurately quantify the contribution of different dynamic loads.

[0102] Specifically, pressure pulsation applies an alternating mechanical stress to the connector, accelerating the creep and stress relaxation of the gasket material, leading to a decrease in bolt preload. By simulating pressure pulsation, fatigue failure of the sealing system can be quickly induced and assessed. At the same time, pressure pulsation can stimulate tiny leakage channels, enabling earlier and more sensitive detection of minute gas leaks compared to static testing.

[0103] Simulation of mechanical vibration can be used to study the effects of vibration on bolt loosening and preload decay, as well as the physical effects of gasket materials (such as fatigue damage leading to decreased compression and rebound performance) on sealing performance.

[0104] In actual pipeline operating environments, pressure pulsation and mechanical vibration often coexist. The simultaneous operation of the two can be used to study the dynamic effects of the coupling between the phase and frequency relationship of vibration and pressure pulsation, such as resonance or beat vibration, and their impact on the sealing system.

[0105] Please refer to Figure 1 In this embodiment, the above-mentioned environmental simulation subsystem 40 includes: a test chamber, the interior of which forms a accommodating cavity for accommodating the connector subsystem 20.

[0106] The heating unit, located inside or connected to the test chamber, is used to heat the cavity; the cooling unit, located inside or connected to the test chamber, is used to cool the cavity.

[0107] Specifically, the heating unit can use a resistance heater, and the cooling unit can use a mechanical compression refrigeration unit.

[0108] An air circulation unit 105, located inside the test chamber, circulates air within the chamber. Specifically, the air circulation unit 105 can consist of a centrifugal fan and a guide vane. This forces airflow within the test chamber, promoting natural convection by causing hot air to rise and cold air to sink. This ensures that the heat or cold generated by the heating / cooling unit is rapidly and evenly distributed throughout the chamber. This guarantees that the tested connectors are at a uniform temperature, preventing uneven expansion or stress caused by temperature variations.

[0109] The temperature monitoring unit, located inside the test chamber, is used to monitor the actual temperature within the containment cavity in real time. Specifically, it can consist of one or more high-precision platinum resistance temperature sensors (Pt100).

[0110] The control unit is connected in communication with the heating unit, cooling unit, air circulation unit 105 and temperature monitoring unit. Based on the difference between the actual temperature fed back by the temperature monitoring unit and the preset target temperature, it controls the heating system and / or cooling system and dynamically adjusts the temperature in the test chamber 205.

[0111] Specifically, the control unit can use a PID controller. When the actual temperature is lower than the preset target temperature, the heating unit is activated; conversely, when the actual temperature is higher than the preset target temperature, the cooling unit is activated, so that the temperature inside the test chamber can be stabilized at the preset temperature value or smoothly follow the preset temperature change curve.

[0112] It should be noted that the environmental simulation subsystem 40 in this embodiment forms a temperature-controlled chamber with cooling, heating, circulation, and control functions, thereby simulating the temperature environment required for active testing with a wide temperature range and high precision. Furthermore, together with pressure pulsation and mechanical vibration, it constitutes a multi-dimensional realistic working condition simulation environment for testing the sealing performance of connectors. The structure of the environmental simulation subsystem 40 described above is only one possible structural form; those skilled in the art can select a suitable temperature-controlled chamber as needed.

[0113] Please refer to Figure 1 and Figure 2 As shown, the connector subsystem 20 in this embodiment includes:

[0114] The flange end cap 201 is connected to the inflow pipe to be tested. The flange end cap 201 has a first mounting hole in the center to facilitate the fixing of the inflow pipe to be tested. The air outlet of the inflow pipe to be tested is flush with the lower surface of the flange end cap 201. The flange base 202 is connected to the outflow pipe to be tested. The flange base 202 has a second mounting hole in the center corresponding to the first mounting hole. The outflow pipe to be tested is fixed in the second mounting hole, and the air outlet is flush with the upper surface of the flange base 202. The test gasket 203 is set between the flange end cap 201 and the flange base 202. The axial force bolt 204 is used to fix the flange end cap 201 and the flange base 202 so that the lower surface of the flange end cap 201, the upper surface of the flange base 202 and the test gasket 203 form a test cavity 205. The axial force bolt 204 is embedded with a strain gauge for measuring the axial preload.

[0115] It should be noted that the flange structure facilitates the replacement of test gaskets 203 with different materials, sizes, and surface structures, thereby enabling a systematic study of the sealing performance of various gaskets under hydrogen-blended natural gas and dynamic loads.

[0116] Meanwhile, by monitoring the preload variation curves under dynamic loads such as vibration and temperature cycling, we can understand the relaxation law of preload caused by vibration, the effect of thermal expansion and contraction caused by temperature changes on preload, and the rate of stress relaxation caused by gasket creep. Furthermore, by analyzing the relationship between preload attenuation and leakage rate, we can identify the critical preload for connection seal failure.

[0117] Please refer to Figure 2 As shown, the sensor subsystem 50 in this embodiment includes:

[0118] Pressure sensor 501 is installed in the inflow pipe being measured and near the test chamber 205;

[0119] The first temperature sensor 502 is located in the inflow pipe being measured and near the test chamber 205.

[0120] It should be noted that the pressure sensor 501 and the first temperature sensor 502 are installed near the test chamber 205, which can accurately reflect the real pressure and temperature of the gas in the test chamber 205, thereby ensuring the accuracy of the measurement data under dynamic load conditions.

[0121] Please refer to Figure 1 As shown, the sampling subsystem 60 is a portable gas chromatograph. The portable gas chromatograph includes a gas chromatograph body and a gas collection tube connected to the gas chromatograph body. The sampling head of the gas collection tube extends into the accommodating cavity of the test chamber and is close to the test pad 203.

[0122] It should be noted that, in order to ensure the accuracy and comprehensiveness of sampling, multiple gas collection tubes are provided around the gasket in this embodiment. By analyzing the collected data, it can be determined whether the gasket is leaking as a whole or in a localized manner. It also facilitates the collection of the original leaked gas with the highest concentration and without dilution, thereby improving the analytical sensitivity and accuracy of the gas chromatograph and helping to verify whether there is a trace hydrogen preferential leakage effect.

[0123] Please refer to Figure 1 As shown, the gas source subsystem 10 in this embodiment includes:

[0124] The hydrogen unit 101 is used to supply hydrogen. The hydrogen unit 101 includes a hydrogen cylinder 1011 and a hydrogen pipeline connected to the outlet of the hydrogen cylinder 1011. The hydrogen pipeline is provided with a first check valve 1012, a first pressure regulating valve 1013 and a first flow controller 1014 in sequence along the direction of hydrogen flow.

[0125] Natural gas unit 102 is used to supply natural gas. Natural gas unit 102 includes natural gas cylinder 1021 and natural gas pipeline connected to the outlet of natural gas cylinder 1021. Natural gas pipeline is provided with a second check valve 1022, a second pressure regulating valve 1023 and a second flow controller 1024 in sequence along the natural gas flow direction.

[0126] Specifically, the instantaneous flow rates of hydrogen and natural gas can be precisely controlled by the first flow controller 1014 and the second flow controller 1024 to ensure the accuracy of the blending ratio.

[0127] To improve the uniformity of the hydrogen and natural gas mixture, a blending unit 103 is provided in this embodiment. The outlets of the hydrogen pipeline and the natural gas pipeline are respectively connected to the two inlets of the blending unit 103. The outlet of the blending unit 103 is connected to a blending pipeline. The blending pipeline is provided with a third check valve 1032, a first flow meter 1034, a circulating compressor 1035 and a first pressure flow meter 1036 in sequence along the flow direction of the hydrogen-blended natural gas.

[0128] Specifically, please refer to Figures 3-6 As shown, in this embodiment, the mixing unit 103 includes:

[0129] Venturi mixer 1031, used for preliminary mixing of natural gas and hydrogen, includes:

[0130] The intake section 10311 includes a first intake section 10311 coaxially arranged and connected to the outlet of the natural gas pipeline, and a second intake section 10311 located inside the first intake section 10311 and connected to the hydrogen pipeline.

[0131] Nozzle section 10312 is connected to the outlet of the second air inlet section 10311 and is located inside the first air inlet section 10311. The cross-section of nozzle section 10312 is a tapered cone, which is used to increase the hydrogen flow rate.

[0132] Specifically, in this embodiment, the inlet section 10311 adopts a ring-shaft design to provide a stable flow field for pre-separation of hydrogen and natural gas; utilizing Bernoulli's principle, when hydrogen passes through the tapered nozzle, the flow velocity increases sharply and the pressure decreases significantly, forming a low-pressure zone required for ejection at the nozzle outlet.

[0133] The mixing section 10313 is used to provide an initial mixing space for hydrogen and natural gas, and the mixing section 10313 is connected to the outlet of the first inlet section 10311.

[0134] Specifically, in this embodiment, the above-mentioned mixing section 10313 includes a first mixing section 10313 that is connected to the first intake section 10311 and has a tapered cross section, and a second mixing section 10313 that is smoothly connected to the first mixing section 10313 and has a tapered cross section. The inner diameter of the second mixing section 10313 is larger than the inner diameter of the throat section 10314.

[0135] Understandably, the tapered first mixing section 10313 brings the natural gas flow rate close to that of the central hydrogen jet, reducing severe shearing and energy loss caused by excessive velocity difference. At the same time, the further contraction strengthens the effect of the low-pressure zone, ensuring that the natural gas can be more stably and continuously low-pressure ejected, thus improving the ejection stability.

[0136] The gradually expanding conical second mixing section 10313 provides a pressure and velocity buffer zone for the mixed airflow that has completed its initial convergence and whose flow state is still unstable. This helps to reduce the initial vortices and disturbances caused by the convergence, making the flow field more uniform and stable before entering the throat section 10314, which is conducive to the formation of effective turbulent mixing in the throat section 10314.

[0137] The throat section 10314 is used to provide a stable flow field for hydrogen and natural gas to achieve momentum exchange. The throat section 10314 is connected to the outlet of the mixing section 10313. The throat section 10314 is a cylindrical straight pipe with an inner diameter smaller than that of the mixing section 10313.

[0138] Specifically, the cylindrical throat section 10314 eliminates potential flow field disturbances at the front end through a constant cross-sectional area, and the small inner diameter ensures that the high-speed mixed airflow can maintain a stable high-speed flow field, thereby maintaining the turbulent mixing intensity and shearing, stretching and folding the hydrogen and natural gas to complete most of the momentum exchange and mixing.

[0139] The diffuser section 10315 is used to convert the kinetic energy of hydrogen and natural gas into pressure energy. The diffuser section 10315 is connected to the outlet of the throat section 10314, and the cross-section of the diffuser section 10315 is a gradually expanding cone.

[0140] Specifically, based on Bernoulli's principle, due to the increased cross-sectional area of ​​the diffuser section 10315, the fluid velocity decreases, and the fluid kinetic energy is converted back into pressure energy, effectively reducing the total pressure loss of the Venturi mixer 1031.

[0141] The outlet section 10316 is connected to the outlet of the diffuser section 10315. The outlet section 10316 is a cylindrical straight pipe with an inner diameter equal to that of the larger end of the diffuser section 10315. The central axes of the inlet section 10311, nozzle section 10312, mixing section 10313, throat section 10314, diffuser section 10315, and outlet section 10316 coincide. Specifically, the uniform diameter of the outlet section 10316 ensures a uniform velocity and pressure distribution of the pressurized mixed airflow.

[0142] In this embodiment, the central axes of the inlet section 10311, nozzle section 10312, mixing section 10313, throat section 10314, diffuser section 10315, and outlet section 10316 of the Venturi mixer 1031 coincide. In this embodiment, the Venturi mixer 1031 achieves efficient ejection, preliminary mixing, and energy recovery without the need for external power.

[0143] Please refer to Figures 4-6 As shown, in this embodiment, the static mixer 1032 is coaxially connected to the outlet of the Venturi mixer 1031. The static mixer 1032 is provided with a microporous annular structure 10321 for mixing hydrogen and natural gas and a spiral structure 10322 for cutting and recombining micron-sized bubbles in sequence along the gas flow direction.

[0144] It should be noted that the microporous ring structure 10321 is a metal microporous ring, which is made of sintered metal powder or sintered metal fiber and has several interconnected pores.

[0145] In this embodiment, the metal microporous ring can be fixed to the front section of the static mixer 1032 by embedding. It should be noted that the gas seeping out from the outer wall of the microporous ring has a slower velocity, while the gas flow rate at the center is very high, forming a strong "shear layer" between the outer wall of the microporous ring and the main gas flow. This high-speed shear layer is unstable and breaks into vortices, thereby entraining and mixing the two gases, increasing the mixing uniformity. Simultaneously, the fluid velocity near the pore wall is slower than the fluid velocity at the center of the pore, creating a strong velocity gradient (shear). The sintered metal microporous ring has a unique three-dimensional network microporous structure, generating shear forces on the gas flow that act on the hydrogen dispersion phase. These microscopic shear forces further "stretch" and "thin" the tiny fluid clumps, increasing the contact area between different component gases, accelerating molecular diffusion, and making the mixing more thorough and uniform.

[0146] Understandably, compared to other porous materials (such as ceramics and plastics), sintered metal materials possess excellent mechanical strength and toughness, enabling them to withstand pressure fluctuations, fluid erosion, and cyclic impacts in pipelines without easily breaking. Furthermore, their superior corrosion resistance ensures long-term stable operation in hydrogen and natural gas environments, resulting in a long lifespan and maintenance-free operation.

[0147] Please refer to Figure 4 and Figure 6 As shown, the spiral structure 10322 includes several alternating Kenics spiral blades with opposite twisting directions and the angle between the tail end and the front end of adjacent Kenics spiral blades is 90°. The pitch angle of the Kenics spiral blades located at the front end of the static mixer 1032 along the airflow direction is greater than the pitch angle of the Kenics spiral blades located at the rear end of the static mixer 1032.

[0148] Understandably, the alternating reverse flow path forces the fluid to generate a strong radial secondary flow. This not only stretches the fluid axially but also continuously flips and displaces it across the cross-section. That is, it pushes the fluid in the center of the pipe towards the outer wall and pulls the fluid on the pipe wall back to the center, in order to eliminate radial concentration and temperature gradients. The 90° angle between the tail and the front ensures that the fluid can enter the next spiral blade at the most ideal angle when leaving the previous spiral blade, achieving effective separation and recombination of the fluid.

[0149] It should be noted that in this embodiment, the number of Kenics spiral blades is 1. The pitch angle refers to the angle between the spiral line and the axis. That is, a larger pitch angle means a smaller pitch, the spiral blades are steeper, the disturbance to the fluid is stronger, the segmentation effect is stronger, and the resulting flow resistance (pressure drop) is also greater. A smaller pitch angle means a larger pitch, the spiral blades are smoother, the effect on the fluid is more consistent, and the pressure drop is relatively smaller.

[0150] Specifically, the front section uses large-pitch helical blades with a shortened axial length. Utilizing strong segmentation and radial mixing capabilities, it quickly eliminates macroscopic non-uniformity, completing the majority of the mixing within the shortest possible flow path. Although this section has a higher pressure drop, its mixing efficiency is extremely high. The rear section uses small-pitch helical blades with an extended axial length, enabling more uniform fluid distribution, improving fluid homogeneity, and providing a more stable and predictable flow path. Simultaneously, the lower pressure drop caused by the rear helical blades helps control the overall pressure loss of the static mixer 1032, avoiding the excessive energy consumption associated with using only large-pitch helical blades.

[0151] In this embodiment, the Kenics spiral blades are designed with asymmetrical blade cross-sectional shape changes along the flow direction, which significantly optimizes the ratio of mixing efficiency to pressure drop and reduces the operating cost of the entire mixing device.

[0152] This embodiment integrates a Venturi mixer 1031, a metal microporous ring, and a Kenics static mixer 1032 to form a multi-stage mixing structure from macroscopic ejection and microscopic atomization to homogenization. This achieves uniform mixing of hydrogen and natural gas with different physical properties, ensures the consistency of gas composition, and eliminates test errors caused by uneven mixing.

[0153] Please refer to Figure 1 As shown, in this embodiment, the buffer unit 104 is used to buffer the hydrogen-blended natural gas after it has been uniformly blended by the blending unit 103. The outlet of the blending pipeline is connected to the inlet of the buffer unit 104. The outlet of the buffer unit 104 is connected to the pipeline to be tested through the buffer pipeline. The buffer pipeline is provided with a fourth check valve 1042, a second pressure measuring device 1043, a fifth check valve 1044, and a third pressure measuring device 1045 in sequence along the gas flow direction. The pressure wave generator is connected to the pipeline between the second pressure measuring device 1043 and the fifth check valve 1044.

[0154] Specifically, in this embodiment, the buffer unit 104 adopts a large buffer tank 1041. Its large volume can absorb and suppress the inherent pressure fluctuations at the outlet of the circulating compressor 1035 and the upstream transmission of pulsations generated by the pressure wave generator, providing a stable working environment for the upstream components. At the same time, as the main gas storage device, it provides a sufficient total gas volume for long-term testing.

[0155] The second pressure gauge 1043 and the third pressure gauge 1045 can accurately monitor pressure changes before and after the test section at the pressure wave generator access point. Simultaneously, the fourth check valve 1042 and the fifth check valve 1044 isolate the area where the pressure wave generator generates pulsations from the upstream buffer tank 1041 and the downstream test section, helping to control the shape of the pressure pulsations and preventing their spread throughout the system.

[0156] Please refer to Figure 1 As shown, the circulation unit 105 includes a fourth pressure measuring device 1051, a second flow meter 1052 and a sixth check valve 1053 arranged sequentially along the gas flow direction on the circulation pipeline; the air inlet of the circulation pipeline is connected to the measured outflow pipeline, and the air outlet of the circulation pipeline is connected to the third check valve 1032 and the first flow meter 1034 via a pipeline.

[0157] Specifically, the function of the circulation unit 105 is to form a closed loop, specifically by guiding the gas flowing out of the measured pipe back to the compressor inlet, forming a closed loop. This saves expensive high-pressure hydrogen-blended gas and also simulates the flow state. Simultaneously, the pressure and flow rate of the return gas are detected by the fourth pressure gauge 1051 and the second flow meter 1052. Comparing this data with upstream data allows for the calculation of the pressure drop across the entire loop and verification of the system's mass balance.

[0158] Please refer to Figure 1 As shown, in order to provide a safe venting channel, the test system in this embodiment also includes a venting subsystem 70, including:

[0159] The first venting unit is connected to the outlet of the buffer unit 104. The first venting unit includes a fifth pressure measuring device 701, a first venting valve 702 and a venting torch 703, which are arranged sequentially along the airflow direction on the first venting pipeline.

[0160] The second venting unit includes a sixth pressure measuring device 704 and a second venting valve 705. The sixth pressure measuring device 704 is connected to the pipeline between the pressure wave generator and the fifth check valve 1044, and the second venting valve 705 is connected to the pipeline between the first venting valve 702 and the venting torch 703.

[0161] Specifically, the first venting unit is mainly used to vent the gas in the large buffer tank 1041, while the second venting unit is responsible for venting the gas in the test pipeline. Additionally, placing the second venting unit after the pressure wave generator allows for timely gas venting in case of generator malfunction or accidental excessive pressure, thus reducing safety hazards.

[0162] Furthermore, the two venting units provide redundant safety discharge paths. If one venting unit fails, the other can serve as a backup discharge path under specific isolation conditions. Simultaneously, sharing the venting flare 703 avoids the duplication of building two separate flare systems, saving costs and space.

[0163] It should be noted that the pressure measuring device described above in this embodiment can be a high-precision silicon piezoresistive pressure transmitter, and a hydrogen-compatible model and compatible materials can be selected.

[0164] Example 2

[0165] Please refer to Figure 7 As shown, a method for testing the sealing performance of hydrogen-blended natural gas pipeline connectors includes the following steps:

[0166] S1. Start the gas source subsystem, environmental simulation subsystem, and sensor subsystem. Adjust the ratio of hydrogen and natural gas through the gas source subsystem, adjust the temperature of the connection subsystem through the environmental simulation subsystem, and monitor the pressure and temperature of the test chamber through the sensor subsystem. When the rate of change of pressure and temperature is lower than the set threshold, it is determined that the gas source subsystem has reached the initial steady state, and the initial time is t0, the initial pressure is P(t0), and the initial temperature is T(t0).

[0167] Specifically, the first check valve, the first pressure regulating valve, the second check valve, and the second pressure regulating valve are opened, the first flow controller and the second flow controller are opened, and the first flow controller and the second flow controller are adjusted according to the blending ratio of hydrogen and natural gas.

[0168] Open the third check valve and the circulating compressor, and control the amount of gas entering the buffer tank through the first flow meter.

[0169] Open the fourth, fifth, and sixth check valves to allow hydrogen-blended natural gas to enter the test circuit.

[0170] It should be noted that the aforementioned set threshold values ​​can be the accuracy thresholds corresponding to the pressure and temperature sensors. The purpose of bringing the gas source subsystem to its initial stable state is to eliminate inherent system noise and short-term thermodynamic fluctuations.

[0171] S2, activate the dynamic load simulation subsystem and sampling subsystem to simulate the actual dynamic working conditions of the pipe connection and collect data on the t inside the test cavity. i The pressure of time P(t) i ) and temperature T(t) i ).

[0172] It should be noted that, in order to reflect the stress changes of axial bolts, preload variation curves can be plotted by collecting preload signals under dynamic loads such as vibration and temperature cycling. This can reflect the relaxation law of preload caused by vibration, the effect of thermal expansion and contraction caused by temperature changes on preload, and the rate of stress relaxation caused by gasket creep. Alternatively, the critical preload for connection seal failure can be determined by analyzing the relationship between preload attenuation and leakage rate.

[0173] S3, based on pressure P(t) i ) and temperature T(t) i ), using the real gas law to calculate t in real time i The mass m(t) of the gas inside the chamber is measured at constant intervals. i).

[0174] Specifically, in S3, t i The mass m(t) of the gas inside the chamber is measured at constant intervals. i The calculation formula is as follows:

[0175]

[0176] In the formula, for Pressure at any given time; V is the volume of the test chamber; M is the molar mass of the gas; and Under the given conditions, the compressibility factor of the test gas is calculated in real time based on the real gas law. This is the universal gas constant.

[0177] It should be noted that the real gas equation of state in this embodiment introduces a compressibility factor (correction factor) to describe the degree of deviation between the real gas and the ideal gas, and the system automatically corrects for calculation errors caused by the non-ideal nature of the gas. The compressibility factor is not a constant; its value depends on the type of gas, temperature, and pressure, and can be calculated in real time through a preset algorithm or database.

[0178] S4, calculate the gas mass loss at each time point relative to the initial time. According to the gas mass loss Δm(t) i Calculate t i The average mass leakage rate at any given time is .

[0179] Specifically, this embodiment can quantify the degree of leakage by calculating the average mass leakage rate, thereby achieving the purpose of monitoring even the smallest leakage of the sealing performance of the connector.

[0180] S5. Based on the leaked gas collected by the sampling subsystem from the periphery of the test chamber, the ratio of methane to hydrogen in the leaked gas is analyzed by a gas chromatograph and compared with the ratio of methane to hydrogen in the gas source subsystem loop to verify the hydrogen preferential leakage effect.

[0181] S6. After the test is completed, shut down the dynamic load simulation subsystem and the gas source subsystem, and use the venting pipeline to vent the gas in the pipeline.

[0182] The above description is a specific implementation of the embodiments of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A system for testing the sealing performance of hydrogen-blended natural gas pipeline connectors, characterized in that, include: Gas source subsystem (10) is used to provide hydrogen-blended natural gas in a set proportion and uniformly mixed; The connector subsystem (20) is used to connect the inflow pipe to be tested and the outflow pipe to be tested. The inflow pipe to be tested is connected to the gas source subsystem (10). The connector subsystem (20) has a test chamber (205) for accommodating hydrogen-blended natural gas. The dynamic load simulation subsystem (30) is used to simulate the pressure pulsation inside the hydrogen-blended natural gas pipeline and the external mechanical vibration environment under actual dynamic working conditions for the connecting component subsystem (20); An environmental simulation subsystem (40) is used to simulate the temperature environment of a hydrogen-blended natural gas pipeline for the connection subsystem (20), and the connection subsystem is located within the environmental simulation subsystem (40). The sensor subsystem (50) is used to monitor the gas pressure and temperature in the test chamber (205) and calculate the gas mass leakage rate in the test chamber (205) based on the pressure and temperature using the real gas mass equation. A sampling subsystem (60) is used to collect the gas leaking from the test chamber (205) for component analysis of the leaked gas; The control subsystem is used to receive and process monitoring data and control the test system.

2. The sealing performance testing system for hydrogen-blended natural gas pipeline connectors according to claim 1, characterized in that, The dynamic load simulation subsystem (30) includes: The pressure pulsation unit (301) is connected to the air inlet of the measured inflow pipe. The pressure pulsation unit (301) is a pressure wave generator used to generate pressure pulsations with controllable frequency and amplitude. A mechanical vibration unit (302) is disposed at the lower part of the connecting subsystem (20) and is used to apply sinusoidal sweep frequency or random vibration to the mechanical vibration unit (302).

3. The hydrogen-blended natural gas pipeline connector sealing performance testing system according to claim 2, characterized in that, The connector subsystem (20) includes: The flange end cap (201) is connected to the inflow pipe to be tested. The flange end cap (201) has a first mounting hole in the center to facilitate fixing of the inflow pipe to be tested. The air outlet of the inflow pipe to be tested is flush with the lower surface of the flange end cap (201). The flange base (202) is connected to the outlet pipe to be tested. The flange base (202) has a second mounting hole at its center that corresponds to the first mounting hole. The outlet pipe to be tested is fixed in the second mounting hole, and the outlet is flush with the upper surface of the flange base (202). A test gasket (203) is disposed between the flange end cap (201) and the flange base (202); A axial force bolt (204) is used to fix the flange end cover (201) and the flange base (202) so that the lower surface of the flange end cover (201), the upper surface of the flange base (202) and the test gasket (203) surround to form the test cavity (205). The axial force bolt (204) is embedded with a strain gauge for measuring the axial preload.

4. The sealing performance testing system for hydrogen-blended natural gas pipeline connectors according to claim 1, characterized in that, The sensor subsystem (50) includes: A pressure sensor (501) is disposed in the inflow pipe to be tested and near the test chamber (205); The first temperature sensor (502) is located in the inflow pipe to be measured and near the test chamber (205).

5. The sealing performance testing system for hydrogen-blended natural gas pipeline connectors according to claim 1, characterized in that, The environment simulation subsystem (40) includes: The test chamber has an internal cavity for accommodating the connector subsystem (20); A heating unit, located inside or connected to the test chamber, is used to heat the accommodating cavity; A refrigeration unit, located inside or connected to the test chamber, is used to cool the accommodating cavity; An air circulation unit (105) is disposed inside the test chamber to circulate the air within the accommodating cavity; A temperature monitoring unit is installed inside the test chamber to monitor the actual temperature inside the accommodating cavity in real time. The control unit is communicatively connected to the heating unit, cooling unit, air circulation unit (105) and temperature monitoring unit. Based on the difference between the actual temperature fed back by the temperature monitoring unit and the preset target temperature, it controls the heating system and / or cooling system and dynamically adjusts the temperature inside the test chamber (205).

6. The sealing performance testing system for hydrogen-blended natural gas pipeline connectors according to claim 5, characterized in that, The sampling subsystem (60) is a portable gas chromatograph, which includes a gas chromatograph body and a gas collection tube connected to the gas chromatograph body. The sampling head of the gas collection tube extends into the accommodating cavity of the test chamber and is close to the test pad (203).

7. The sealing performance testing system for hydrogen-blended natural gas pipeline connectors according to claim 2, characterized in that, The gas source subsystem (10) includes: A hydrogen unit (101) is used to provide hydrogen. The hydrogen unit (101) includes a hydrogen cylinder (1011) and a hydrogen pipeline connected to the outlet of the hydrogen cylinder (1011). The hydrogen pipeline is provided with a first check valve (1012), a first pressure regulating valve (1013) and a first flow controller (1014) in sequence along the direction of hydrogen flow. Natural gas unit (102) is used to provide natural gas. The natural gas unit (102) includes a natural gas cylinder (1021) and a natural gas pipeline connected to the outlet of the natural gas cylinder (1021). The natural gas pipeline is provided with a second check valve (1022), a second pressure regulating valve (1023) and a second flow controller (1024) in sequence along the natural gas flow direction. A blending unit (103) is used to uniformly blend the hydrogen and natural gas. The outlets of the hydrogen pipeline and the natural gas pipeline are respectively connected to the two inlets of the blending unit (103). The outlet of the blending unit (103) is connected to a blending pipeline. The blending pipeline is provided with a third check valve (1032), a first flow meter (1034), a circulating compressor (1035), and a first pressure flow meter (1036) in sequence along the flow direction of the hydrogen-blended natural gas. A buffer unit (104) is used to buffer hydrogen-blended natural gas after uniform blending by a blending unit (103). The outlet of the blending pipeline is connected to the inlet of the buffer unit (104). The outlet of the buffer unit (104) is connected to the measured inflow pipeline through a buffer pipeline. The buffer pipeline is provided with a fourth check valve (1042), a second pressure measuring device (1043), a fifth check valve (1044), and a third pressure measuring device (1045) in sequence along the gas flow direction. The pressure wave generator is connected to the pipeline between the second pressure measuring device (1043) and the fifth check valve (1044). The circulation unit (105) includes a fourth pressure measuring device (1051), a second flow meter (1052) and a sixth check valve (1053) arranged sequentially along the gas flow direction on the circulation pipeline; the air inlet of the circulation pipeline is connected to the measured outflow pipeline, and the air outlet of the circulation pipeline is connected to the pipeline between the third check valve (1032) and the first flow meter (1034).

8. The sealing performance testing system for hydrogen-blended natural gas pipeline connectors according to claim 7, characterized in that, The mixing unit (103) includes: A Venturi mixer (1031) for achieving preliminary mixing of natural gas and hydrogen, said Venturi mixer (1031) comprising: The intake section (10311) includes a first intake section (10311) coaxially arranged and connected to the outlet of the natural gas pipeline, and a second intake section (10311) located inside the first intake section (10311) and connected to the hydrogen pipeline. The nozzle section (10312) is connected to the outlet of the second air inlet section (10311) and located within the first air inlet section (10311). The nozzle section (10312) has a tapered cross section to increase the hydrogen flow rate. A mixing section (10313) is used to provide an initial mixing space for hydrogen and natural gas, and the mixing section (10313) is connected to the outlet of the first inlet section (10311); The throat section (10314) is used to provide a stable flow field for hydrogen and natural gas to achieve momentum exchange. The throat section (10314) is connected to the outlet of the mixing section (10313). The throat section (10314) is a cylindrical straight pipe with an inner diameter smaller than that of the mixing section (10313). The diffuser section (10315) is used to convert the kinetic energy of hydrogen and natural gas into pressure energy. The diffuser section (10315) is connected to the outlet of the throat section (10314), and the cross-section of the diffuser section (10315) is a gradually expanding cone. The outflow section (10316) is connected to the air outlet of the diffuser section (10315). The outflow section (10316) is a cylindrical straight pipe with an inner diameter equal to the inner diameter of the large end of the diffuser section (10315). The central axes of the inlet section (10311), nozzle section (10312), mixing section (10313), throat section (10314), diffuser section (10315), and outflow section (10316) coincide. A static mixer (1032) is coaxially connected to the outlet of the Venturi mixer (1031). The interior of the static mixer (1032) is provided with a microporous annular structure (10321) for mixing hydrogen and natural gas and a spiral structure (10322) for cutting and recombining the micron-sized bubbles in sequence along the gas flow direction. The microporous ring structure (10321) is a metal microporous ring, which is made of sintered metal powder or sintered metal fiber and has a number of interconnected pores. The spiral structure (10322) includes several alternating Kenics spiral blades with opposite twisting directions and the angle between the tail end and the front end of adjacent Kenics spiral blades is 90°. The pitch angle of the Kenics spiral blades located at the front end of the static mixer (1032) along the airflow direction is greater than the pitch angle of the Kenics spiral blades located at the rear end of the static mixer (1032).

9. A test method for a hydrogen-blended natural gas pipeline connector sealing performance testing system as described in any one of claims 1-8, characterized in that, Includes the following steps: S1, start the gas source subsystem (10), environmental simulation subsystem (40) and sensor subsystem (50), adjust the ratio of hydrogen and natural gas through the gas source subsystem (10), adjust the temperature of the connection subsystem (20) through the environmental simulation subsystem (40), and monitor the pressure and temperature of the test chamber through the sensor subsystem (50). When the rate of change of pressure and temperature is lower than the set threshold, it is determined that the gas source subsystem (10) has reached the initial stable state, and the initial time is t0, the initial pressure is P(t0) and the initial temperature is T(t0). S2, activate the dynamic load simulation subsystem (30) and sampling subsystem (60) to simulate the actual dynamic working conditions of the pipe connection and collect the t inside the test cavity. i The pressure of time P(t) i ) and temperature T(t) i ); S3, based on pressure P(t) i ) and temperature T(t) i ), using the real gas law to calculate t in real time i The mass m(t) of the gas inside the chamber is measured at constant intervals. i ); S4, calculate the gas mass loss at each time point relative to the initial time. According to the gas mass loss Δm(t) i Calculate t i The average mass leakage rate at any given time is ; S5. Based on the leaked gas collected by the sampling subsystem from the periphery of the test chamber, the ratio of methane to hydrogen in the leaked gas is analyzed by a gas chromatograph and compared with the ratio of methane to hydrogen in the gas source subsystem loop to verify the hydrogen preferential leakage effect. S6. After the test is completed, shut down the dynamic load simulation subsystem and the gas source subsystem, and use the venting pipeline to vent the gas in the pipeline.

10. The method for testing the sealing performance of hydrogen-blended natural gas pipeline connectors according to claim 9, characterized in that, The mass m(t) of the gas in the test chamber at time ti in S3 i The calculation formula is as follows: ； In the formula, for Pressure at any given time; V is the volume of the test chamber; M is the molar mass of the gas; and Under the given conditions, the compressibility factor of the test gas is calculated in real time based on the real gas law. This is the universal gas constant.

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