Safety valve leakage rate calculation method

Abstract

The invention provides a method for calculating the leakage rate of a safety valve. The method comprises the steps that the temperature of a gas storage during operation is measured; measuring the pressure of the gas storage during operation; calculating the effective flow area of the throat of the valve seat when the valve is opened; the leakage rate of the safety valve is calculated according to the following formula: # imgabs0 #, wherein Q is mass flow rate, # imgabs1 # gas theoretical emission capacity, Aeff is effective flow area of a throat part of a valve seat, # imgabs2 # is pressure of a gas storage during gas storage operation, # imgabs3 # is temperature of the gas storage during gas storage operation, # imgabs4 # is an isentropic exponential function, # imgabs5 # is a compression factor, and # imgabs6 # is gas molar mass. According to the invention, the leakage rate can be simply and accurately calculated.

Description

Technical Field

[0001] The present invention relates to the technical field of compressed air energy storage, and in particular to a method for calculating the leakage of a safety valve. Background Art

[0002] Compressed air energy storage is a large-scale energy storage technology with advantages such as large scale, low cost, long life, fast response, and environmental protection. In compressed air energy storage systems, safety valves are key overpressure protection devices with the following main functions: overpressure relief and system protection. Leakage is a key indicator for evaluating the performance of safety valves. Currently, commonly used measurement methods include: (1) Bubble detection method: Apply soapy water to the valve seat sealing surface and observe the bubble generation rate. (2) Pressure drop method: Close the downstream valve, monitor the rate of decrease of system pressure over time, and calculate the leakage. (3) Flow meter direct measurement method: Install a flow meter at the outlet of the safety valve. However, the main disadvantages of the currently commonly used leakage detection methods include: (1) Bubble detection method: It cannot accurately measure the leakage; it relies on manual operation and is highly subjective. (2) Pressure drop method: It is greatly affected by temperature changes and requires a long time to stabilize the environment. (3) Flow meter direct measurement method: The flow meter may interfere with the normal operation of the safety valve.

[0003] Therefore, it is necessary to develop a new method for calculating the leakage of safety valves in order to calculate the leakage simply and accurately. Summary of the Invention

[0004] The present invention aims to provide a method for calculating the leakage of a safety valve, so as to solve the problem that the existing method for calculating the leakage of a safety valve is complex and has low accuracy.

[0005] In order to solve the above technical problems, the present invention provides a method for calculating the leakage of a safety valve, comprising: Measuring the temperature of the gas storage during operation; Measuring the pressure of gas storage during operation; Calculate the effective flow area of ​​the valve seat throat when the safety valve installed in the gas storage is open; The leakage of the safety valve is calculated using the following formula: Where Q is the mass flow rate, Theoretical gas emission capacity, A eff is the effective flow area of ​​the valve seat throat, is the pressure of the gas storage during gas storage operation, is the temperature of the gas storage during gas storage operation, is the isentropic exponential function, is the compression factor, is the molar mass of the gas.

[0006] Optional, yes function, , is the adiabatic index, and the isentropic exponential function is calculated as follows: in, γ 0 : adiabatic index under standard conditions, α : Temperature correction coefficient, β : pressure correction coefficient, T 0 : Reference temperature P 0 : Reference pressure.

[0007] Optionally, the leakage calculation formula of the safety valve after flow compensation is: in, η is the flow compensation coefficient.

[0008] Optionally, in a compressed air storage tank, the air , , substitute into the gas emission capacity calculation formula and mass flow calculation formula to obtain: .

[0009] Alternatively, use the following formula to calculate the effective flow area of ​​the valve seat throat when the valve is open: A eff =π· d f · h =π· d f ·[ λ ·( P ·π· d f 2 / 4- F ) / F ] in, A eff is the effective flow area of ​​the valve seat throat, d f is the valve aperture, F is the total pre-pressure of the safety valve, A is the flow area of ​​the valve seat throat, df is the valve aperture, λ is the proportionality coefficient, P is the gas storage system pressure, h is the valve opening.

[0010] Optionally, the safety valve includes a valve body, a spring, a valve stem, an electromagnet, a valve core, a pressure and temperature sensor and a valve port, the valve stem can be reciprocatingly slidably installed on the valve body, the other end of the valve stem is connected to the valve core, and the valve core can block the valve port, the first end of the spring is installed on the valve body, the second end is installed on the valve core, and the spring is sleeved on the valve stem, the number of the electromagnets is two, and the first electromagnet is installed on the valve body, and the second electromagnet is installed on the valve core, wherein the first electromagnet and the first end of the spring are located at the same position of the valve body, and the second electromagnet and the second end of the spring are located at the same position of the valve stem.

[0011] Optionally, the first electromagnet and the second electromagnet have the same pole, F Calculated by the following formula: in, is the repulsive force between the two electromagnets, is the spring pressure.

[0012] Optional, repulsive force between two electromagnets Calculated by the following formula: , in, N 1 , N 2 : Number of turns of the two coils I 1 , I 2 : Current in the two coils (A) R 1 , R 2 : Radius of the two coils (m) K(r) : The distance between the two electromagnets x The correlation coefficient is approximately 0.158 / x 4 Function μ 0 : Vacuum magnetic permeability.

[0013] Optional, spring pressure Calculated by the following formula: , in, is the deformation of the spring, including extension or compression, is the spring stiffness coefficient, L is the natural length of the spring L 1 , L 2 are the lengths of the two sets of cylindrical electromagnets respectively.

[0014] Optionally, the spring stiffness coefficient is calculated using the following formula: , in: : Shear modulus : Spring wire diameter : Spring middle diameter N 3 : Valid number of circles.

[0015] The present invention provides a method for calculating the leakage of a safety valve, which has the following beneficial effects: First, the present invention installs a pressure and temperature sensor in the safety valve to obtain gas parameters in real time and combines it with the derived mass flow calculation formula to accurately calculate the actual air leakage. This method takes into account the dynamic effects of temperature and pressure on the adiabatic index and introduces a temperature correction coefficient. α and pressure correction factor β , making the calculation results more consistent with actual operating conditions. Traditional measurement methods are often highly subjective, susceptible to environmental influences, or may interfere with normal valve operation. The calculation system of this invention overcomes these shortcomings. It not only accurately assesses leakage volume to provide a basis for economic loss assessment, but also predicts the required leakage time under overpressure conditions, helping to determine whether human intervention is necessary and preventing irreversible damage to the gas storage cavern. This intelligent monitoring and calculation system provides a scientific basis and technical support for the safe operation of compressed air energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 1 is a schematic structural diagram of a safety valve closed in an embodiment of the present invention; Figure 2 This is a schematic structural diagram of the safety valve when it is open in an embodiment of the present invention; Figure 3 This is a diagram showing the motion of the spring and the electromagnet when the safety valve is open in an embodiment of the present invention; Figure 4 Schematic diagram of the structure of the safety valve core and valve port in an embodiment of the present invention.

[0017] Description of reference numerals: 100-valve body; 200-spring; 300-valve stem; 400-electromagnet; 500-valve core; 600-pressure and temperature sensor; 700-valve port. DETAILED DESCRIPTION

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0020] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0021] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" and the like indicate positions or locations based on the positions shown in the accompanying drawings, or the positions or locations in which the inventive product is typically placed when in use. These terms are intended solely to facilitate the description of the present invention and to simplify the description, and are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third," etc., are used solely to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0022] Furthermore, terms such as "horizontal" and "vertical" do not necessarily mean that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.

[0023] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0024] This embodiment provides a method for calculating the leakage of a safety valve, including: Measuring the temperature of the gas storage during operation; Measuring the pressure of gas storage during operation; Calculate the effective flow area of ​​the valve seat throat when the valve is open; The leakage of the safety valve is calculated using the following formula: Where Q is the mass flow rate, Theoretical gas emission capacity, A eff is the effective flow area of ​​the valve seat throat, is the pressure of the gas storage during gas storage operation, is the temperature of the gas storage during gas storage operation, is the isentropic exponential function, is the compression factor, is the molar mass of the gas.

[0025] The flow of gas through the safety valve is an isentropic expansion process (no heat exchange, reversible adiabatic). At critical flow, the pressure ratio is (For air, it is 0.528). When the compressed air storage safety valve leaks, the ratio of the outlet pressure to the inlet pressure is generally less than 0.5, so only sonic flow is considered. According to the standard ISO 4126, the theoretical discharge capacity of gas under critical flow (sonic flow) conditions is It can be expressed as: .

[0026] The adiabatic exponent γ in traditional formulas is usually fixed at 1.4, but in practice γ It changes significantly with temperature and pressure. Therefore, the temperature and pressure correction coefficients are introduced to correct the adiabatic index. The adiabatic index correction formula is: in: γ 0 : Adiabatic index under standard conditions (1.4), α : Temperature correction coefficient (obtained from indoor experiments), β : Pressure correction coefficient (obtained from indoor experiments), T 0 : Reference temperature (293.15 K) P 0 : Reference pressure (101.325 kPa) yes function, , is the adiabatic index, so the calculation formula of the isentropic exponential function C is: .

[0027] Considering the isentropic exponential function , compression factor The data depends on experimental or empirical data, which may have deviations, and the compressed air energy storage is in the process of releasing. and There will be a certain dynamic drop, resulting in the actual flow rate being slightly lower than the theoretical value, so the flow compensation coefficient η (obtained from indoor experiments). The final gas emission capacity is ( ) Calculation formula: therefore, .

[0028] Preload F Determines the opening conditions of the safety valve and affects the opening of the safety valve h , and the opening directly affects the effective flow area in the leakage calculation A eff The following relationship can be established: When the system pressure P > F / A When the valve is open, the valve opening h Calculation formula: h = λ ·( P · A - F ) / F=λ ·( P ·π· d f 2 / 4- F ) / F in: F : Total preload (preload of spring 200 F t With electromagnet 400 repulsion F c sum) A : Valve seat throat flow area d f :Valve aperture λ : Proportional coefficient (related to valve structure) P : Gas storage system pressure.

[0029] Preload F Directly affects the opening h ,and h It also determines the effective flow area in the leakage calculation A eff , effective flow area A eff The calculation formula is: A eff =π· d f · h =π· d f ·[ λ ·( P ·π· d f 2 / 4- F ) / F ] Mass flow calculation formula: .

[0030] In compressed air storage, air , ,Air γ 0 =1.4, reference temperature T 0 =293.15 K, reference pressure P 0 =101.325 kPa, and substituting it into the gas discharge capacity calculation formula and mass flow calculation formula, we get: .

[0031] In this embodiment, the safety valve includes a valve body 100, a spring 200, a valve stem 300, an electromagnet 400, a valve core 500, a pressure and temperature sensor 600 and a valve port 700. The valve stem 300 can be reciprocatingly slidably mounted on the valve body 100. The other end of the valve stem 300 is connected to the valve core 500. The valve core 500 can block the valve port 700. A first end of the spring 200 is mounted on the valve body 100, and a second end is mounted on the valve core 500. The spring 200 is sleeved on the valve stem 300. There are two electromagnets 400, a first electromagnet is mounted on the valve body 100, and a second electromagnet is mounted on the valve core 500. The first electromagnet and the first end of the spring 200 are located at the same position on the valve body 100, and the second electromagnet and the second end of the spring 200 are located at the same position on the valve stem 300. The pressure and temperature sensor 600 is arranged at the valve port 700. In this way, by controlling the magnitude of the electromagnet current, a stable magnetic system is constructed within the safety valve, significantly improving the valve's response speed and service life. Traditional spring 200-type safety valves often experience pre-stress decay due to fatigue of the spring 200 after long-term use. However, the repulsive force provided by the electromagnet 400 in this embodiment does not suffer from material fatigue issues. By complementing the advantages of the electromagnetic force and the spring 200 force, the service life of the safety valve is effectively extended. This system is particularly suitable for high-pressure compressed air energy storage systems, which can avoid the frequency hopping problem of traditional safety valves and provide more reliable safety protection for the energy storage system. In addition, the opening pressure can be adjusted in real time by changing the magnitude of the current to adapt to different working conditions. In addition, this embodiment can generate an opposite-pole attraction by changing the direction of the current to actively open the safety valve for pressure relief. This bidirectional electromagnetic force control mechanism significantly improves the operational flexibility and emergency response capability of the safety valve, providing a more comprehensive safety guarantee and operational adaptability for the compressed air energy storage system.

[0032] The valve body 100 and valve stem 300 are made of stainless steel; the valve core 500 is conical and made of rubber material to ensure airtightness; the spring 200 is made of carbon fiber composite material, which has a high fatigue limit and anti-relaxation performance, and is suitable for dynamic load scenarios; the electromagnet 400 is a nanocrystalline soft magnetic alloy material, which has the advantages of both amorphous and crystalline materials, and has the advantages of high magnetic permeability, high saturation magnetic induction intensity, low coercive force, low iron loss, and low magnetostriction. The pressure and temperature sensor 600 is a miniature sensor installed in the safety valve. The sensor has a diameter of 12 mm and a length of 50 mm. The side of the sensor is attached to the inner side of the valve body 100 and is fixed with epoxy resin glue. The sensor connector faces downward, and a hole is opened on the valve body 100 below the sensor. The gap between the hole and the sensing line is sealed with fluororubber. The applicable pressure range is <60 MPa, which meets the use conditions of compressed air energy storage caverns; the upper electromagnet 400 is fixed to the fixed end of the valve stem 300 with epoxy resin glue and is arranged on both sides of the spring 200. The lower electromagnet 400 is fixed to the movable end of the valve stem 300 with epoxy resin glue. Sealing rubber is pasted on the contact between the valve core 500 and the valve body 100 to ensure air tightness.

[0033] refer to Figure 1 、 Figure 2 、 Figure 3 and Figure 4 , Figure 1 This is a schematic diagram of the structure of the safety valve when it is closed in an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of the safety valve when it is open in an embodiment of the present invention. Figure 3 : is a diagram showing the motion state of the spring 200 and the electromagnet 400 when the safety valve is opened in an embodiment of the present invention. Figure 4 Schematic diagram of the structure of the safety valve core 500 and the valve port 700 in the embodiment of the present invention. When the valve is open, the movement state of the spring 200 and the electromagnet 400 is as follows: Figure 3 As shown, the fixed end electromagnet 400 does not move, the lower electromagnet 400 moves upward with the valve stem 300 platform, and the spring 200 is compressed upward. The cross section of the valve port 700 is circular. When the valve is open, the valve core 500 and the valve port 700 are partially enlarged as shown in FIG. Figure 4 shown.

[0034] Since the temperature and pressure of the gas storage during operation are substantially consistent with the temperature at the valve port of the safety valve, the temperature and pressure of the gas storage can be measured using the pressure-temperature sensor 600 disposed at the valve port of the safety valve.

[0035] For two identical cylindrical electromagnets 400, their repulsive force can be expressed as: in, N 1 , N2 : Number of turns of the two coils I 1 , I 2 : Current in the two coils (A) R 1 , R 2 : Radius of the two coils (m) K(r) : The distance between the two electromagnets 400 x The correlation coefficient is approximately 0.158 / x 4 Function μ 0 : Vacuum magnetic permeability.

[0036] Spring 200 stiffness coefficient formula: in: : Shear modulus : Spring 200 wire diameter : Spring 200 diameter N 3 : Valid number of circles.

[0037] Spring 200 pressure calculation formula: in: : The deformation of the spring 200, including the extension or compression L : The natural length of spring 200 L 1 , L 2 : The length of two sets of cylindrical electromagnets 400.

[0038] Therefore, the pre-pressure of the variable safety valve F The calculation formula is: .

[0039] Specific example: Take a compressed air energy storage power station gas storage as an example, the permissible pressure of the compressed air system is 15MPa (150bar), the gas storage volume is 3000 , air density under standard conditions is 1.225 Assume that the volume needs to be released within 5 minutes (300 ) to reduce pressure: flow rate For high pressure systems, assume the valve aperture (seal surface diameter) is , then the pressure area (the valve is designed in a cylindrical shape, and the valve pressure area is equal to the valve seat throat flow area): , Required preload . Select two pairs of nanocrystalline soft magnetic alloy electromagnets 400, vacuum magnetic permeability μ 0 =4π×10⁻ 7 H / m, number of turns of the coil N 1 = N 2 = 2000 turns, radius of the two coils R 1 = R 2 =30mm, the current in the two coils I 1 = I 2 =1.5A, the distance between the two sets of electromagnets is 400 x =15mm, then the repulsive force between the electromagnets 400 F c =0.0395×(4π×10 -7 / π)×(2000×1.5)×(2000×1.5)×(π×0.03 2 )×(π×0.03 2 ) / 0.015 4 ) = 22.456kN; carbon fiber composite material is selected as spring 200, shear modulus G = 35GPa, wire diameter d =16mm, median diameter D =85mm, effective number of circles N 3 =3, natural length L =120mm, compression of spring 200 △L =15mm, k = (35×10 9 ×0.016 4 ) / (8×0.085 3 ×4)=467.608kN / m, then the spring pressure of 200 F t = 467.608×0.015 =7.014kN; pre-pressure of variable safety valve F=22.456+7.014=29.47kN=29470N, which meets the requirements. P =155bar When the pressure is greater than the allowable pressure of 150bar, the valve opens quickly and the gas is released. The valve structure is a conical valve core 500, and the proportional coefficient λ =0.54, opening h =0.54·(155·π·50 2 / 4-29470) / 29470 = When the diameter is 5mm, the effective flow area is: A eff =π×50×5=785.4mm 2 , reference temperature T 0 = 293.15K, reference pressure P 0 =101.325kPa, α= 0.0002 / K, β =0.0001 / bar, flow compensation coefficient η= 0.8, assuming the safety valve inlet temperature T =323.15K, pressure P =15.5MPa, then the gas discharge capacity , mass flow rate , air density ρ ,flow , meeting the conditions.

[0040] The valve opening time is obtained through the pressure and temperature sensor 600. Assuming the opening time is 20s, the gas leakage Assume that the system is over-pressured at a certain moment, the pressure is 155 bar, the temperature is 323.15 K, and 30% of the volume needs to be released (900 ) to reduce pressure urgently, , , it takes time If special circumstances require that the actual pressure relief time be shorter than the predicted time, human intervention can be used to actively release the pressure to ensure safety.

[0041] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention. Any changes and modifications made by ordinary technicians in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A method for calculating the leakage of a safety valve, characterized in that: include: Measuring the temperature of the gas storage during operation; Measuring the pressure of gas storage during operation; Calculate the effective flow area of ​​the valve seat throat when the safety valve installed in the gas storage is open; The leakage of the safety valve is calculated using the following formula: Where Q is the mass flow rate, Theoretical gas emission capacity, A eff is the effective flow area of ​​the valve seat throat, is the pressure of the gas storage during gas storage operation, is the temperature of the gas storage during gas storage operation, is the isentropic exponential function, is the compression factor, is the molar mass of the gas.

2. The method for calculating the leakage of a safety valve according to claim 1, wherein: yes function, , is the adiabatic index, and the isentropic exponential function is calculated as follows: in, γ 0 : adiabatic index under standard conditions, α : Temperature correction coefficient, β : pressure correction coefficient, T 0 : Reference temperature P 0 : Reference pressure.

3. The method for calculating the leakage of a safety valve according to claim 1, wherein: The formula for calculating the leakage of the safety valve after flow compensation is: in, η is the flow compensation coefficient.

4. The method for calculating the leakage of a safety valve according to claim 3, wherein: In compressed air storage, air , , substitute into the gas emission capacity calculation formula and mass flow calculation formula to obtain: 。 5. The method for calculating the leakage of a safety valve according to claim 1, wherein: Use the following formula to calculate the effective flow area of ​​the valve seat throat when the valve is open: A eff =π· d f · h =π· d f ·[ λ ·( P ·π· d f 2 / 4- F ) / F ] in, A eff is the effective flow area of ​​the valve seat throat, d f is the valve aperture, F is the total pre-pressure of the safety valve, A is the flow area of ​​the valve seat throat, d f is the valve aperture, λ is the proportionality coefficient, P is the gas storage system pressure, h is the valve opening.

6. The method for calculating the leakage of a safety valve according to claim 5, wherein: The safety valve includes a valve body, a spring, a valve stem, an electromagnet, a valve core, a pressure and temperature sensor and a valve port. The valve stem can be reciprocatingly slidably installed on the valve body. The other end of the valve stem is connected to the valve core. The valve core can block the valve port. The first end of the spring is installed on the valve body, and the second end is installed on the valve core. The spring is sleeved on the valve stem. There are two electromagnets, and the first electromagnet is installed on the valve body, and the second electromagnet is installed on the valve core. The first electromagnet and the first end of the spring are located at the same position on the valve body, and the second electromagnet and the second end of the spring are located at the same position on the valve stem.

7. The method for calculating the leakage of a safety valve according to claim 6, wherein: The first electromagnet and the second electromagnet have the same pole, F Calculated by the following formula: in, is the repulsive force between the two electromagnets, is the spring pressure.

8. The method for calculating the leakage of a safety valve according to claim 7, wherein: The repulsive force between two electromagnets Calculated by the following formula: ， in, N 1 , N 2 : Number of turns of the two coils I 1 , I 2 : Current in the two coils (A) R 1 , R 2 : Radius of the two coils (m) K(r) : The distance between the two electromagnets x The correlation coefficient is approximately 0.158 / x 4 Function μ 0 : Vacuum magnetic permeability.

9. The method for calculating the leakage of a safety valve according to claim 7, wherein: Spring pressure Calculated by the following formula: ， in, is the deformation of the spring, including extension or compression, is the spring stiffness coefficient, L is the natural length of the spring L 1 , L 2 are the lengths of the two sets of cylindrical electromagnets respectively.

10. The method for calculating the leakage of a safety valve according to claim 9, wherein: The spring rate is calculated using the following formula: ， in: : Shear modulus : Spring wire diameter : Spring middle diameter N 3 : Valid number of circles.

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