Hydrogen seal leakage amount prediction method and detection device

Abstract

The application discloses a hydrogen sealing leakage amount prediction method and detection device, which comprises an extrusion mechanism, a hydrogen supply circuit, a cone and a cone seat. The extrusion mechanism comprises a motor, a screw rod, a first piston, a spring, a spring seat, a tension and pressure sensor and a second piston. The motor drives the screw rod to rotate. One end of the screw rod abuts against one end of the first piston. The other end of the first piston abuts against the spring. The spring is located in the spring seat. The spring seat is connected with one end of the second piston through the tension and pressure sensor. The other end of the second piston abuts against the cone. The cone is provided with a sealing rubber ring on one side. The cone extrudes the cone seat through the sealing rubber ring. The other side of the cone seat is connected with a hydrogen concentration detection sensor. The hydrogen supply circuit is connected with the position where the cone is located. The application can accurately obtain the numerical relationship between the hydrogen leakage amount and different gas pressures and screw extrusion forces, obtain an optimal solution, provide a basis for optimizing the hydrogen sealing system, effectively reduce the leakage amount and avoid the fatigue deformation of the cone.

Description

Technical Field

[0001] This invention relates to the field of hydrogen sealing technology, and in particular to a method and device for predicting and detecting hydrogen sealing leakage. Background Technology

[0002] Hydrogen, due to its high combustion efficiency and pollution-free byproducts, is considered one of the three major new energy sources, along with solar and nuclear energy. As a new energy source, hydrogen is widely used in aviation, power, and fuel cells for vehicles. However, hydrogen molecules are very small, making them prone to leakage during storage and use. Because hydrogen is inhalable, colorless, odorless, and undetectable by the human nose, and has an ignition point of only 585°C, it will explode upon contact with an open flame if its concentration in the air is between 4% and 75%. Therefore, the sealing of hydrogen is crucial. Even minor hydrogen leaks not only waste resources but can also pose safety hazards. Therefore, leakage monitoring is essential during the use of hydrogen.

[0003] In hydrogen transmission, sealing is achieved through a compression contact surface formed between the cone and the valve seat. This component is widely used in hydrogen sealing systems, such as check valves in hydrogen circuits, where the sealing method is a compression seal between the cone and the valve seat. The reliability of this seal directly determines the safety of the hydrogen circuit system. However, prolonged opening and closing of the sealing interface causes frequent reciprocating impacts between the cone and the valve seat, which can easily lead to seal fatigue failure. Therefore, selecting an appropriate compression force between the cone and the valve seat based on the pressure of the hydrogen system is an effective means to achieve a long-term seal between the cone and the valve seat.

[0004] The selection of the extrusion pressure between the cone and its seat requires exploring the relationship between leakage and extrusion pressure to determine the optimal extrusion pressure corresponding to the critical leakage rate. Currently, there are limited testing methods and mathematical models for verifying the hydrogen sealing performance between the cone and its seat. Existing testing devices are neither able to accurately measure hydrogen leakage nor effectively reveal the relationship between gas pressure and leakage. Therefore, a testing device is needed that can accurately and effectively detect hydrogen leakage between the cone and its seat and help understand the relationship between gas pressure and leakage, thus providing support for the rational selection of the extrusion pressure. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and device for predicting hydrogen seal leakage. By combining experiments and mathematical model verification, the numerical relationship between hydrogen leakage and different gas pressures and screw extrusion forces can be accurately obtained, and the optimal solution can be obtained. This provides a basis for optimizing the hydrogen sealing system, effectively reducing leakage and avoiding cone fatigue deformation.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A hydrogen leak detection device includes a compression mechanism, a gas supply circuit, a cone, and a cone seat. The compression mechanism includes a motor, a screw, a first piston, a spring, a spring seat, a tension / compression sensor, and a second piston. The motor drives the screw to rotate. One end of the screw abuts against one end of the first piston, and the other end of the first piston abuts against the spring. The spring is located inside the spring seat. The spring seat is connected to one end of the second piston via the tension / compression sensor. The other end of the second piston abuts against the cone. A sealing rubber ring is installed on one side of the cone, and the cone compresses the cone seat through the sealing rubber ring. A hydrogen concentration detection sensor is connected to the other side of the cone seat. The gas supply circuit is connected to the location of the cone, and a gas pressure sensor is installed in the channel at the location of the cone.

[0008] The gas supply circuit includes a compressor, a hydrogen storage tank, a filter, a pressure relay, a dryer, and a shut-off valve. The compressor compresses the externally input hydrogen and delivers it to the hydrogen storage tank. The hydrogen storage tank is connected to the dryer through the filter. The other side of the dryer is connected to the cone location through the shut-off valve. The start and stop of the compressor are controlled by the pressure relay.

[0009] The gas supply circuit includes a cooler and an automatic drainer. The cooler is connected between the compressor and the hydrogen storage tank, and the automatic drainer is connected to the bottom of the hydrogen storage tank.

[0010] A method for predicting hydrogen seal leakage includes a leakage calculation model and a fatigue life calculation model. The leakage calculation model calculates the leakage by inputting the screw extrusion pressure and the gas pressure inside the cavity measured by the sensor into a mathematical model, thus verifying the theory and the experiment. The fatigue life calculation model obtains the fatigue life of the sealing cone under alternating load conditions by constructing a fatigue failure model of the rubber sealing ring. Finally, based on the dual constraints of leakage and fatigue life, the optimal design range of the extrusion pressure between the sealing cone and the valve seat is obtained.

[0011] The calculation process of the leakage calculation model is as follows: based on the measured screw extrusion pressure. F Intracavitary gas pressure p Surface roughness power spectral density C ( q ), calculate the contact area ratio A ( x c ) / A 0, yielding the critical magnification factor. x c Overall average height Height of the critical contraction section u 1( x ),pass u 1( x Calculate the leakage rate for each square. Q0, yielding the total leakage rate. Q = Ly / LxQ 0.

[0012] The entire nominal contact area between the cone and the cone base is rectangular, with an area of ​​[area missing]. L x × L y Divide it into L y / L x The side length is L x Area is A 0= L x 2 A square, when the magnification reaches the critical magnification. x c At this point, a seepage channel will appear that runs through the entire contact area. Assuming all leaks occur within this seepage channel, and the pressure drop Δ... p If it occurs in the critical contraction region, then the leakage rate of each square... Q 0 can be calculated using formula (1).

[0013] (1)

[0014] in, m It is the dynamic viscosity of the fluid. α It is a correction factor. α Equal to 1, along the circumference, the circumference is Ly Then the number of squares on the contact surface is Ly / Lx The total leakage rate can be obtained through Q = Ly / LxQ 0 is calculated.

[0015] At a magnification of x At that time, the contact area is greater than A ( x ) / A 0 can be obtained through formula (2):

[0016] (2)

[0017] in, To add external pressure, Let be the error function. Effective stiffness, representing surface roughness, at a magnification of 10 ... x Time can be represented as:

[0018] (3)

[0019] in, q It is a wave vector. It is the reference wave vector. It is the equivalent elastic modulus, which can be obtained through formula (4). C ( q ) is the power spectral density (PSD) of isotropic surface roughness, which can be expressed by a one-dimensional PSD function. The result is shown in formula (5).

[0020] (4)

[0021] in, n It is Poisson's ratio. E 1 and E 2 are the elastic moduli of the contacting objects;

[0022] (5)

[0023] Height of the critical contraction portion u 1( x This is considered to be the distance between the two surfaces when the first channel penetrates the contact area. u 1( x It can be calculated using the following formula:

[0024] (6)

[0025] in, Are two surfaces at a magnification of x The overall average height at that time and They are u ( x ) and contact area A ( x )right x The derivative, It can be obtained from equations (7)-(9).

[0026] (7)

[0027] (8)

[0028] (9)

[0029] in, As the reference wave vector, For the maximum wave vector, It is a power spectrum related to surface roughness Related weighting functions, The nominal pressure at the current magnification factor, , A function related to local contact stiffness. It is a function related to local pressure and elastic deformation, and , P ( q,p,ξ ) is an error function representing a specific magnification. Sum of wave vectors q Below, local contact pressure p The impact on the probability of elastic contact is addressed by introducing a correction factor, since the elastic energy stored in the contact region is less than that in the fully contact region. c 0, c 0 is taken as 0.4.

[0030] The calculation process of the fatigue life calculation model is as follows: Based on the parameters of the rubber material and the length of the initial crack c0, the elastic strain energy U is obtained, the strain energy release rate G and the crack propagation rate dc / dN are calculated, and then the number of cycles N and the fatigue life T are obtained.

[0031] According to the energy method, the released elastic strain energy U drives crack propagation.

[0032] (10)

[0033] σ1, σ2, and σ3 are the principal stresses in the x, y, and z directions, respectively, and ε1, ε2, and ε3 are the strains in the three directions, respectively.

[0034] Introducing the strain energy release rate G, representing the energy released when the initial crack increases by a unit area, G is defined as the negative partial derivative of the strain energy U with respect to the crack area C, i.e., the energy released when the initial crack increases by a unit area, which can be expressed by equation (11):

[0035] (11)

[0036] During crack propagation, the release mechanism of strain energy U is divided into two parts: one part originates from the redistribution of elastic strain energy generated by crack propagation within the material, and the elastic strain energy originally stored around the crack is released with the newly added crack surface; the other part is related to the work W done by the external force. Under the continuous action of the external force, the structural deformation mode changes during crack propagation, and the work done by the external force affects the change of strain energy. The calculation method of strain energy release rate is shown in Equation (12):

[0037] (12)

[0038] In the formula: G Indicates the strain energy release rate; W Indicates the work done by external forces; U Indicates strain energy;B This represents a material constant, which is related to factors such as the material's geometry and dimensions. k ( l ) indicates the stretch ratio l Relevant proportionality coefficients; c Indicates the crack length; w 0 represents strain energy density, which is the strain energy stored in a unit volume of material. It is related to the material's elastic modulus, Poisson's ratio, and other mechanical property parameters, as well as the stress state it is subjected to.

[0039] (13)

[0040] ε represents engineering strain;

[0041] Substituting equation (11) into equation (12), we obtain the expression for the number of cycles N required for the initial crack length to expand from c0 to c:

[0042] (14)

[0043] In the formula: c0 represents the crack propagation parameter and can be determined experimentally.

[0044] The expression for the number of cycles required for the initial crack length to expand from c0 to the final fracture failure crack length c is shown in equation (15):

[0045] (15)

[0046] The fatigue life T is obtained by multiplying the number of cycles by the cycle time t.

[0047] (16)

[0048] The beneficial effects of this invention are:

[0049] The leakage calculation model calculates leakage by inputting the screw extrusion pressure and internal gas pressure measured by sensors into a mathematical model, thus verifying the theory with experiments. The fatigue life calculation model derives the fatigue life of the sealing cone under alternating load conditions by constructing a fatigue failure model for the rubber seal ring. Finally, based on the dual constraints of leakage and fatigue life, the optimal design range of the extrusion pressure between the sealing cone and the valve seat is obtained. Attached Figure Description

[0050] Figure 1 This is a cross-sectional view of a hydrogen gas leak detection device.

[0051] Figure 2 This is a pneumatic circuit diagram for a hydrogen gas seal leakage detection device.

[0052] Figure 3Flowchart for calculating leakage.

[0053] Figure 4 This is a flowchart for fatigue life calculation.

[0054] Figure 5 This is a graph showing the relationship between maximum cyclic stress and fatigue life.

[0055] Figure 6 This is a graph showing the relationship between screw extrusion pressure and leakage.

[0056] Figure 7 This is a graph showing the relationship between gas pressure and leakage in the sealed cavity.

[0057] In the diagram: Motor 101, Screw 102, Sealing Ring 103, First Piston 104, Hydrogen Concentration Alarm Sensor 105, Spring 106, Spring Seat 107, Tension / Compression Sensor 108, Second Piston 109, Tension / Compression Sensor Display 110, Cone 201, Gas Supply Circuit 202, Gas Pressure Sensor 203, Sealing Rubber Ring 204, Cone Seat 205, Hydrogen Concentration Detection Sensor 206, Compressor 301, Cooler 302, Hydrogen Storage Tank 303, Overflow Valve 304, Automatic Drainer 305, Filter 306, Pressure Relay 307, Dryer 308, Shut-off Valve 309. Detailed Implementation

[0058] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0059] like Figure 1-Figure 2 As shown, this embodiment discloses a hydrogen gas leak detection device, including a compression mechanism, a gas supply circuit 202, a cone 201, and a cone seat 205. The compression mechanism includes a motor 101, a screw 102, a first piston 104, a spring 106, a spring seat 107, a tension / compression sensor 108, and a second piston 109. The motor 101 drives the screw 102 to rotate, thereby compressing the spring 106 through the first piston 104. A sealing ring 103 is installed on the outer wall of the first piston 104. One end of the screw 102 abuts against one end of the first piston 104, and the other end of the first piston 104 abuts against the spring 106. The spring 106 is located inside the spring seat 107. The spring seat 107 is connected to one end of the second piston 109 through the tension / compression sensor 108, and the other end of the second piston 109 abuts against the cone 201.

[0060] According to Hooke's Law (in The force acting on the spring. Let be the spring constant. The spring 106, after being compressed by the screw 102, generates a spring force proportional to its deformation. This spring force is transmitted to the tension / compression sensor 108 via the spring seat 107. The tension / compression sensor 108 has high precision and can convert the received force signal into an electrical signal, which is then displayed on the tension / compression sensor display 110 as the compressive force of the second piston 109 on the cone 201. The deformation of the spring 106 is measured... (The force applied by the spring 106 can be calculated by means of the number of rotations of the screw 102, etc.) This force is then calibrated and verified in conjunction with the measurement value of the tension / compression sensor 108, thereby ensuring accurate measurement of the compressive force and reducing measurement errors. The spring seat 107 drives the second piston 109 to compress the cone 201 through the tension / compression sensor 108, generating a large compressive force between the cone 201 and the cone seat 205, thus achieving a good seal and preventing hydrogen leakage from the cavity. A sealing rubber ring 204 is installed on one side of the cone 201, which compresses the cone seat 205 to ensure a seal. The other side of the cone seat 205 is connected to a hydrogen concentration detection sensor 206, which has high sensitivity and can accurately measure the hydrogen content in a small volume, thus providing accurate data for analyzing the sealing performance. A gas pressure sensor 203 is installed in the channel where the cone 201 is located. The gas pressure sensor 203 can detect and record the gas pressure in the sealed cavity in real time, investigate changes in system pressure, and, combined with hydrogen concentration measurement, obtain the correlation between changes in gas leakage and pressure in the cavity. A hydrogen concentration alarm sensor 105 is installed in the channel where the first piston 104 is located. This sensor has high sensitivity and can issue an alarm signal at the first moment of hydrogen leakage, promptly reminding operators to take measures.

[0061] Because both the first piston 104 and the spring seat 107 have rubber rings with good sealing effect, an effective sealing effect can be achieved. Therefore, hydrogen leakage to the left side can be ignored. Other channel joints and sensor joints also have good sealing rings. Therefore, the entire hydrogen leakage path is along the metal mating interface between the cone 201 and the cone seat 205. To accurately detect the amount of hydrogen leakage between the cone 201 and the cone seat 205, a hydrogen concentration detection sensor 206 is installed at the right outlet. The leakage amount is calculated by detecting the outlet hydrogen concentration and combining it with the outlet cavity volume. At the same time, to prevent hydrogen leakage caused by the failure of the sealing rings of the first piston 104 and the spring seat 107 on the left side or installation problems, a hydrogen concentration alarm sensor 105 is added at the corresponding position of the groove opened in the first piston 10. If hydrogen is detected at this position, an alarm is issued, indicating that hydrogen is leaking from the left side, and the entire test must be stopped, thus ensuring the accuracy of the amount of hydrogen leakage between the right cone 201 and the cone seat 205.

[0062] To simulate the fatigue load experienced by the cone seat 205 during repeated opening and closing in actual operation, the force applied to the cone seat 205 is varied by adjusting the forward and reverse rotation of the motor 101. The number of rotations of the screw 102 driven by the motor 101 in the same direction determines the forward displacement of the screw 102, which in turn determines the amount of compression between the cone 201 and the cone seat 205. The frequency of the forward and reverse rotation of the motor 101 determines the frequency of the alternating load on the cone 201, thereby completing the alternating loading of the load between the cone and the cone seat, providing experimental support for predicting the performance and lifespan of the seal under alternating load.

[0063] The gas supply circuit 202 is connected to the cone 201. The gas supply circuit 202 includes a compressor 301, a hydrogen storage tank 303, an overflow valve 304, a dryer 308, and a shut-off valve 309. The compressor 301 compresses the externally input hydrogen. If the compressed hydrogen contains moisture, it can be cooled by the cooler 302 to separate condensate. The condensate accumulates at the bottom of the hydrogen storage tank 303 and is discharged by an automatic drain 305. The compressed hydrogen from the hydrogen storage tank 303 passes through a filter 306 and then enters the dryer 308 for dehydration. Afterward, it enters the sealed cavity through the shut-off valve 309. The pressure control of the gas supply circuit 202 is achieved using a pressure relay 307. The pressure relay 307 controls the start and stop of the compressor 301, maintaining the pressure in the sealed cavity and the hydrogen storage tank 303 at the required pressure value, thus allowing the investigation of hydrogen leakage under constant gas pressure. When the gas pressure in the sealed cavity reaches a certain value, the shut-off valve 309 can be closed, thus forming a closed space in the sealed cavity, further allowing the investigation of the relationship between leakage and changes in the gas pressure within the cavity. After the test, the shut-off valve 309 is opened to release the hydrogen gas in the sealed cavity.

[0064] The detection device is used as follows: Motor 101 drives screw 102 to compress spring 106, sealing cone 201 and cone seat 205 simultaneously. The sealing pressure is recorded. Hydrogen gas is introduced into the cavity through gas supply circuit 202 until a certain pressure is reached, then shut-off valve 309 is closed to seal the cavity. Leakage is detected by hydrogen concentration sensor 206, and abnormal leakage is monitored by hydrogen concentration alarm sensor 105. After the test, hydrogen gas is discharged from the cavity. This device uses gas pressure sensor 203 to investigate system pressure changes, combined with leakage hydrogen content measurement, to help understand the correlation between gas leakage changes and cavity pressure, providing support for the research and optimization of the cone valve's hydrogen sealing performance. Simultaneously, the reciprocating motion of screw 102 driven by motor 101 simulates the repeated opening and closing of cone seat 205 under actual working conditions, thus subjecting sealing rubber ring 204 to alternating conditions. The forward and reverse rotation frequency of motor 101 determines the frequency of the alternating load, and the displacement range of screw 102 determines the pressure change between cone 201 and cone seat 205. The compressive force is monitored in real time by a tensile / compressive force sensor 108, the gas pressure sensor 203 records the changes in gas pressure inside the sealed cavity, and the hydrogen concentration detection sensor 206 detects the leakage. During the test, the number of cycles of alternating load is recorded. The test is stopped when the hydrogen leakage exceeds a set threshold to evaluate the fatigue life of the sealing system.

[0065] The testing process of the detection device is divided into two parts:

[0066] Initial pressure constant test: Hydrogen gas is introduced into the sealed cavity through the gas supply circuit 202. The hydrogen pressure in the cavity is monitored in real time by the gas pressure sensor 203. When the hydrogen pressure reaches the set value, the shut-off valve 309 is closed, forming a sealed space. The hydrogen leakage is monitored in real time by the hydrogen concentration detection sensor 206, and the change in gas pressure in the cavity is monitored in real time by the gas pressure sensor 203. A correlation between the leakage of compressed hydrogen and the pressure drop is established. By obtaining the relationship between the leakage of compressed hydrogen in the sealed container and the pressure change, the leakage amount can be predicted by detecting the pressure change of the sealed container without the need for a hydrogen concentration sensor in subsequent tests.

[0067] Constant pressure test throughout the process: Hydrogen gas is continuously supplied to the cavity through the gas supply circuit 202, and the shut-off valve 309 is always open. The pressure of the system is controlled by the overflow valve 304. If the set pressure is reached, the pressure relay 307 is disconnected and the compressor 301 stops working. If the pressure is detected to be lower than the set pressure, the pressure relay 307 sends a signal to the compressor 301 to continue working. Through this method, even if there is a leak, the hydrogen pressure in the cavity can be kept at a constant value, thereby obtaining the hydrogen leakage amount under constant gas pressure. By moving the first piston 104 with the screw 102, different extrusion pressures between the cone 201 and the cone seat 205 can be obtained, thereby obtaining the relationship between the hydrogen leakage rate and the extrusion pressure between the cone 201 and the cone seat 205 under constant pressure. Similarly, by keeping the position of the screw 102 constant (i.e., the extrusion pressure between the cone 201 and the cone seat 205 remains unchanged) and changing the pressure setting value of the pressure relay 307 of the gas supply circuit 202, different hydrogen pressures can be obtained, thereby obtaining the relationship between the hydrogen leakage rate and the gas pressure in the cavity under constant extrusion pressure.

[0068] While conducting experiments, a mathematical model for predicting hydrogen leakage was used. Substituting the compressive force applied by screw 102 to cone 201 and the pressure value within the sealing cavity, the model's formula algorithm was used to calculate parameters such as contact area, leakage, and critical contraction thickness under different magnifications. This predicted the changes in gas pressure and hydrogen leakage under the current compressive force of screw 102, thus calculating the leakage under those conditions. The model's accuracy was corrected using leakage data obtained from experiments, yielding a leakage correction coefficient. By analyzing leakage under different compressive forces and gas pressures, an accurate hydrogen leakage model for the cone-seat seal was finally obtained, enabling precise prediction of hydrogen leakage and providing support for setting the compressive force between the cone and cone seat in the hydrogen sealing system.

[0069] This experiment provides measured data to support model correction and optimization, continuously improving the fatigue life prediction model to better reflect actual working conditions. It effectively detects hydrogen leakage between cone 201 and cone seat 205 and obtains the fatigue life of the sealing rubber under alternating conditions. Combining measurement and mathematical prediction models, it accurately obtains the relationship between leakage and extrusion pressure / gas pressure fatigue life, helping to understand its patterns. Therefore, for the hydrogen system pressure, appropriate extrusion pressure and extrusion frequency between cone 201 and cone seat 205 can be selected, ensuring that the leakage meets safety limits while enabling the cone valve seal to operate stably and effectively for extended periods, thus guaranteeing the safety of the hydrogen sealing system. This experiment has promising application prospects.

[0070] The method for predicting hydrogen seal leakage includes a leakage calculation model and a fatigue life calculation model. The leakage calculation model calculates the leakage by inputting the screw extrusion pressure and internal gas pressure measured by sensors into a mathematical model, thus verifying the theory with experiments. The fatigue life calculation model derives the fatigue life of the sealing cone under alternating load conditions by constructing a fatigue failure model for the rubber sealing ring. Finally, based on the dual constraints of leakage and fatigue life, the optimal design range of the extrusion pressure between the sealing cone and the valve seat is obtained.

[0071] The theoretical basis of the leakage calculation model is to establish the relationship between hydrogen leakage Q and screw extrusion pressure through a combination of experiments and mathematical models. F Gas pressure in the sealed cavity p The quantitative relationship reveals the influence of sealing interface morphology and material parameters on leakage.

[0072] Based on the magnification contact model, the entire nominal contact area between the cone and its seat is rectangular, with an area of... L x × L y It can be divided into L y / L x The side length is L x Area is A 0= L x 2 A square. Magnification. x This is a key parameter in the theory. At the minimum magnification ( x When =1), the two surfaces are in complete contact with each other, that is... A (1)= A 0. As the magnification increases, the details of surface roughness become more apparent, and some areas become non-contact areas, reducing the actual contact area. A ( x (Decreases.) When the magnification reaches the critical magnification. x c At this time, a seepage path will appear that runs through the entire contact area, and the thickness (spacing) of the contraction portion is defined as u 1( x c ).

[0073] Leakage calculation: Assuming all leaks occur in the seepage channels, and the pressure drop Δ p If it occurs in the critical contraction region, then each square ( L x × L x The fluid transfer rate (leakage)Q 0 can be calculated using formula (1).

[0074] (1)

[0075] in, m It is the dynamic viscosity of the fluid. α This is a correction factor used to account for the shape of the contraction section and the effect of smaller channels at higher magnifications. Since the critical contraction section is simplified to a rectangular aperture, and the actual shape of the contraction section is unavailable, therefore... α The expected value is 1. The circumference along the circumference is... L y Then the number of squares on the contact surface is L y / L x The total leakage rate can be measured by... Q = L y / L x Q 0 is calculated.

[0076] Relationship between contact area and magnification: The ratio of non-contact area is... As the magnification increases, the contact area decreases. Although the actual contact area is difficult to define and obtain, the theory based on magnification combines the contact area with seepage theory to obtain information about the seepage channels. According to seepage theory, for isotropic surfaces, when the non-contact area is greater than the area of ​​the seepage channel... When the value reaches approximately 0.6, a channel will appear connecting the two ends of the contact area. At this point, the corresponding contact area is greater than... A ( x c ) / A 0 is 0.4, which is used as the standard for determining the critical magnification factor.

[0077] At a magnification of x At that time, the contact area is greater than A ( x ) / A 0 can be obtained through formula (2):

[0078] (2)

[0079] in, External pressure, amplification factor x The contact pressure at point 1 Let be the error function. Effective stiffness, representing surface roughness, at a magnification of 10 ... x Time can be represented as:

[0080] (3)

[0081] in, q It is a wave vector. It is the reference wave vector. It is the equivalent elastic modulus, which can be obtained through formula (4). C ( q ) is the power spectral density (PSD) of isotropic surface roughness, which can be expressed by a one-dimensional PSD function. The result is shown in formula (5).

[0082] (4)

[0083] in, n It is Poisson's ratio. E 1 and E 2 represents the elastic modulus of the contacting objects (i.e., the sealing rubber ring and the cone seat).

[0084] (5)

[0085] Calculation of the thickness of the critical contraction region: Height of the critical contraction region u 1( x This is considered to be the distance between the two surfaces when the first channel penetrates the contact area. Therefore, u 1( x ) is defined as the change in magnification by an infinitesimally small amount (Δ) x When ), the height at which the two surfaces that originally appear to be in contact will separate. u 1( x It can be calculated using the following formula:

[0086] (6)

[0087] in, Are two surfaces at a magnification of x The overall average height at that time and They are u ( x ) and contact area A ( x )right x The derivative, It can be obtained from equations (7)-(9).

[0088] (7)

[0089] (8)

[0090] (9)

[0091] in, As the reference wave vector, For the maximum wave vector, It is a power spectrum related to surface roughness Related weighting functions, The nominal pressure at the current magnification factor, .

[0092] A function related to local contact stiffness. It is a function related to local pressure and elastic deformation, and , P ( q,p,ξ ) is an error function representing a specific magnification. Sum of wave vectors q Below, local contact pressure p The impact on the probability of elastic contact. Since the elastic energy stored in the contact region is less than that in the fully contacted region, a correction factor is introduced. c 0, c 0 is less than 1, here c 0 is taken as 0.4.

[0093] The entire leakage calculation process is as follows: Figure 3 As shown, based on the measured screw extrusion pressure F Intracavitary gas pressure p Surface roughness power spectral density C ( q ), calculate the contact area ratio A ( x c ) / A 0, yielding the critical magnification factor. x c Overall average height Height of the critical contraction section u 1( x ),pass u 1( x Calculate the leakage rate for each square. Q 0, yielding the total leakage rate. Q = Ly / LxQ 0. The key parameter is the critical magnification factor. x 0. Average spacing and the thickness of the critical contraction portion u 1.

[0094] Fatigue life calculation of sealing rubber: revealing the relationship between alternating load frequency, amplitude and life. The load frequency and amplitude are set by motor 101, and the load magnitude can be measured by tensile / compressive sensor 108.

[0095] Fracture mechanics was used to study the fracture characteristics of sealing rubber under cyclic alternating loads. Finite element analysis was employed to obtain the internal stress and strain changes during extrusion, and fracture mechanics theory was used to determine the fatigue life of the rubber seal under alternating loads. Fracture mechanics posits that all materials possess naturally occurring micron-level defects (such as bubbles, impurities, and processing damage). These defects originate from inherent defects in the material preparation process (such as micropores caused by uneven mixing, residual vulcanization bubbles, or filler agglomeration) or microcracks that initiate during fatigue / aging, serving as the starting point for crack propagation.

[0096] The fatigue life calculation process is as follows: Figure 4 As shown, based on the parameters of the rubber material and the length of the initial crack c0, the elastic strain energy U is obtained, the strain energy release rate G and the crack propagation rate dc / dN are calculated, and then the number of cycles N and fatigue life T are obtained.

[0097] First, stress simulation is performed using finite element simulation software to determine the strain state of the sealing rubber under alternating loads at the specified load amplitude. Mesh generation software is then used to create a finite element model of the seal. Based on the alternating load conditions experienced by the rubber ring, and combined with the finite element analysis software, the nominal strain results, strain amplitudes, and critical element numbers in each direction are extracted. The nominal strain values ​​are then input into the fatigue analysis file according to the load history to calculate the equivalent stress.

[0098] According to the energy method, the released elastic strain energy U drives crack propagation.

[0099] (10)

[0100] σ1, σ2, and σ3 are the principal stresses in the x, y, and z directions, respectively, and ε1, ε2, and ε3 are the strains in the three directions, respectively.

[0101] Introducing the strain energy release rate G, representing the energy released when the initial crack increases by a unit area, G is defined as the negative partial derivative of the strain energy U with respect to the crack area C, i.e., the energy released when the initial crack increases by a unit area, which can be expressed by equation (11):

[0102] (11)

[0103] During crack propagation, the release mechanism of strain energy U is divided into two parts: one part is the redistribution of elastic strain energy generated by crack propagation within the material, where the elastic strain energy originally stored around the crack is released with the newly added crack surface; the other part is related to the work done by external force W. Under the continuous action of external force, the structural deformation mode changes during crack propagation, and the work done by external force affects the change of strain energy.

[0104] Therefore, the method for calculating the strain energy release rate is shown in equation (12):

[0105] (12)

[0106] In the formula: G It represents the strain energy release rate, reflecting the driving force for crack propagation; W It represents the work done by external forces, and the unit is joule (J). U This represents strain energy, measured in joules (J). B This represents a material constant, which is related to factors such as the material's geometry and dimensions. k ( l ) indicates the stretch ratio l The relevant proportionality coefficients describe the mechanical behavior of materials under different tensile conditions; c This indicates the crack length, in meters (m). w 0 represents strain energy density, which is the strain energy stored in a unit volume of material. It is related to the material's elastic modulus, Poisson's ratio, and other mechanical property parameters, as well as the stress state it is subjected to. The unit is joules per cubic meter (J / m³).

[0107] (13)

[0108] ε represents engineering strain.

[0109] Substituting equation (11) into equation (12), we obtain the expression for the number of cycles N required for the initial crack length to expand from c0 to c:

[0110] (14)

[0111] In the formula: The crack propagation parameter c0 can be determined experimentally: by directly measuring surface microcracks using a scanning electron microscope (SEM) or a laser confocal microscope (with an accuracy of up to [insert accuracy here]). ).

[0112] Therefore, the expression for the number of cycles required to expand the initial crack length from c0 to the final fracture failure crack length c is shown in equation (15):

[0113] (15)

[0114] The fatigue life T is obtained by multiplying the number of cycles by the cycle time t.

[0115] (16)

[0116] During the seal test, the pressure exerted on the sealing ring by the screw during its reciprocating motion changes repeatedly. Figure 6 The leakage rate under different screw extrusion pressures can provide a data basis for subsequent fatigue analysis of maximum cyclic stress, where maximum cyclic stress is the maximum extrusion pressure exerted by the screw on the seal ring during reciprocating cycles, i.e., the peak value.

[0117] Combination Figure 5-Figure 7 Based on the dual constraints of leakage and fatigue life, the optimal design range of the extrusion pressure between the sealing cone and the valve seat is derived.

[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A hydrogen seal leakage amount prediction method applied to a hydrogen seal leakage amount detection device, characterized by, The hydrogen seal leakage detection device comprises a pressing mechanism, a hydrogen supply circuit (202), a cone (201), and a cone seat (205). The pressing mechanism comprises a motor (101), a screw rod (102), a first piston (104), a spring (106), a spring seat (107), a tension and pressure sensor (108), and a second piston (109). The motor (101) drives the screw rod (102) to rotate. One end of the screw rod (102) abuts against one end of the first piston (104). The other end of the first piston (104) abuts against the spring (106). The spring (106) is located in the spring seat (107). The spring seat (107) is connected to one end of the second piston (109) through the tension and pressure sensor (108). The other end of the second piston (109) abuts against the cone (201). One side of the cone (201) is provided with a sealing rubber ring (204). The cone (201) presses the cone seat (205) through the sealing rubber ring (204). The other side of the cone seat (205) is connected to a hydrogen concentration detection sensor (206). The hydrogen supply circuit (202) is connected to the position where the cone (201) is located. A gas pressure sensor (203) is installed in the channel at the position where the cone (201) is located. The hydrogen seal leakage prediction method comprises a leakage calculation model and a fatigue life calculation model. The leakage calculation model calculates the leakage by inputting the screw rod pressing force and the cavity gas pressure measured by the sensor into a mathematical model, so as to verify the theory and the test. The fatigue life calculation model obtains the fatigue life of the sealing cone under alternating load conditions by constructing a rubber sealing ring fatigue failure model. Finally, based on the double constraints of leakage and fatigue life, the optimal design interval of the pressing force of the sealing cone and the valve seat is obtained. The calculation process of the leakage calculation model is as follows: according to the measured screw rod pressing force F, cavity gas pressure p, and surface roughness power spectral density C(q), the contact area ratio A(ξc) / A0 is calculated, the critical magnification ξc, the overall average height u(ξ), and the height u1(ξ) of the critical contraction part are obtained, the leakage rate Q0 of each square is calculated through u1(ξ), and the total leakage rate Q=Ly / LxQ0 is obtained. The entire nominal contact area between the cone (201) and the cone seat (205) is a rectangle with an area of Lx×Ly. It is divided into Ly / Lx squares with a side length of Lx and an area of A0=Lx2. When the magnification reaches the critical magnification ξc, a seepage channel will appear through the entire contact area. It is assumed that all the leakage occurs in the seepage channel, and the pressure drop Δp occurs in the critical contraction part. Therefore, the leakage rate Q0 of each square is calculated through formula (1), （1） wherein μ is the dynamic viscosity of the fluid, and α is a correction coefficient, α is equal to 1. Along the circumferential direction, the length is Ly. Therefore, the number of squares of the contact surface is Ly / Lx. The total leakage rate is calculated through Q=Ly / LxQ0.

2. The hydrogen seal leak rate prediction method of claim 1, wherein The hydrogen supply circuit (202) comprises a compressor (301), a hydrogen storage tank (303), a filter (306), a pressure relay (307), a dryer (308), a stop valve (309), the compressor (301) compresses and delivers hydrogen input from the outside to the hydrogen storage tank (303), the hydrogen storage tank (303) is connected to the dryer (308) through the filter (306), the other side of the dryer (308) is connected to the place where the cone (201) is located through the stop valve (309), and the start and stop of the compressor (301) are controlled by the pressure relay (307).

3. The hydrogen seal leak rate prediction method of claim 2, wherein, The hydrogen supply circuit (202) comprises a cooler (302) and an automatic water drain (305), the cooler (302) is connected between the compressor (301) and the hydrogen storage tank (303), and the automatic water drain (305) is communicated with the bottom of the hydrogen storage tank (303).

4. The hydrogen seal leak rate prediction method of claim 1, wherein The calculation process of the fatigue life calculation model: according to the parameters of the rubber material, the length c0 of the initial crack, the elastic strain energy U is obtained, the strain energy release rate G and the crack propagation rate dc / dN are calculated, and then the cycle number N and the fatigue life T are obtained.

5. The hydrogen seal leak rate prediction method of claim 4, wherein, According to the energy method, the released elastic strain energy U drives the crack propagation, （10） σ1, σ2, σ3 are the principal stresses in x, y, z directions respectively, and ε1, ε2, ε3 are the strains in three directions respectively; The strain energy release rate G is introduced, which represents the energy released when the initial crack increases per unit area, and the definition of G is the negative partial derivative of strain energy U to crack area C, that is, the energy released when the initial crack increases per unit area, which is represented by formula (11): （11） During the crack propagation process, the release mechanism of strain energy U is divided into two parts: one part is the elastic strain energy redistribution caused by crack propagation in the material, and the elastic strain energy stored around the crack is released with the new crack surface; the other part is related to the work done by the external force W. Under the action of external force, the deformation mode of the structure changes when the crack propagates, and the work done by the external force affects the change of strain energy. The calculation method of strain energy release rate is shown in formula (12): （12） In the formula: G represents the strain energy release rate; W represents the work done by the external force; U represents the strain energy; B represents the material constant, which is related to the geometry and size of the material; k(λ) represents the proportional coefficient related to the tensile ratio λ; c represents the crack length; w0 represents the strain energy density, which is the strain energy stored in unit volume of material, and is related to the elastic modulus, Poisson's ratio and stress state of the material; （13） ε represents the engineering strain; Substitute formula (11) into (12) to get the expression of cycle number N required for the initial crack length to expand from c0 to c: （14） wherein: represents the crack propagation parameter, c0is determined by an experimental method; The expression of cycle number required for the initial crack length to expand from c0 to the final crack length c of failure is shown in formula (15): （15） The cycle number multiplied by the cycle time t per cycle gives the fatigue life T: （16）。

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