Method and system for determining gas cloud state of leakage pressure container

Abstract

The invention discloses a method and system for determining the gas cloud state of a leakage pressure container, and the method comprises the steps: determining the physical property parameters of leakage gas at a leakage port according to the flowing characteristics of gas in a target container, and further determining the gas cloud state of the leakage port based on the temperature and pressure change characteristics of the leakage gas in a dynamic diffusion process; the method comprises the following steps: obtaining a jet flow structure and a flow velocity of leakage gas at a leakage port and gas in a core area under a first shock wave structure, and further obtaining a distribution characteristic of gas in a mixed boundary layer area under each shock wave structure; according to the method, motion parameters of gas in a core area and gas in a mixed boundary layer area under each shock wave structure are calculated, so that the gas cloud state in the dynamic diffusion process is obtained, and the flow velocity of leaked gas at a leakage opening is further combined to obtain corresponding gas motion parameters to characterize the gas cloud state at the end of dynamic diffusion. According to the invention, the structure change of the leakage pressure vessel jet diffusion gas cloud flow field can be accurately obtained.

Description

Technical Field

[0001] This invention belongs to the field of leak gas monitoring technology, and in particular relates to a method and system for determining the state of a gas cloud in a leaking pressure vessel. Background Technology

[0002] Pressure vessels are essential infrastructure in fields such as petrochemicals, food processing, fire protection, transportation, and metallurgy. Various hazardous substances (flammable, explosive, and toxic) are generally stored within them. Flammable, explosive, and toxic gases are typically stored at higher pressures and lower temperatures. However, defects are unavoidable in the manufacturing and installation of high-pressure gas storage tanks and similar equipment. Common causes include corrosion perforation, valve failure, and fatigue cracks, leading to compressed gas leaks. Once leaked gas enters the production area or the atmosphere, it typically drifts due to airflow and mixes with air during diffusion. When the mixture reaches certain conditions, it can ignite upon contact with an ignition source, causing a fire or explosion, or poisoning personnel in the affected area. With the widespread use of natural gas and the increasing demand from chemical production, oil and gas storage is gradually increasing. In the event of a gas leak, the pressurized release source will exacerbate the threat to the safety of nearby equipment, facilities, chemical production, and the safety of people and property. Therefore, studying the jet mechanism formed after a high-pressure-ratio gas leak, as well as the near-field and far-field trajectories of the diffuse cloud after the jet, is of great significance for obtaining the flow field characteristics formed after a high-pressure gas leak, and for predicting the influence range, leakage amount, and flow velocity of the gas cloud. This is crucial for rescue operations and reducing on-site losses.

[0003] In the process of developing this invention, the inventors discovered that current research on near-field shock wave structures in the petrochemical safety field is limited, and the focus of research on underexpanded jets is primarily on the passive diffusion cloud properties that occur when the gas cloud expands to zero kinetic energy after the jet's virtual nozzle. Furthermore, with the increasing number of historical engineering cases using machine learning to acquire the diffusion characteristics of leaked gases, the drawbacks of discrepancies in diffusion results (especially the source term outlet flow field structure distribution and near-field concentration distribution) caused by differences in technical approaches and model designs within the same device have gradually become apparent. This problem directly affects the analysis of the consequences of high-pressure leak accidents and the determination of safe distances. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for determining the gas cloud state of a leaking pressure vessel, comprising: determining the physical property parameters of the leaking gas at the leak outlet based on the gas flow characteristics within the target vessel; using the physical property parameters, based on the temperature and pressure change characteristics of the leaking gas during dynamic diffusion, obtaining the jet structure and velocity of the leaking gas at the leak outlet, as well as the jet structure and velocity of the core region gas under the first shock wave structure, thereby obtaining the distribution characteristics of the gas in the mixing boundary layer region under each shock wave structure; based on this, combined with the Mach number before and after the Mach disk under the first shock wave structure, calculating the motion parameters of the core region gas and the motion parameters of the mixing boundary layer region gas under each shock wave structure, thereby obtaining the gas cloud state during dynamic diffusion; and obtaining corresponding gas motion parameters based on the current motion parameters and the velocity of the leaking gas at the leak outlet to characterize the gas cloud state at the end of dynamic diffusion.

[0005] Preferably, the physical properties of the leaking gas at the leak outlet include, but are not limited to, density, temperature, and pressure. The step of determining the physical properties of the leaking gas at the leak outlet includes: analyzing the energy change characteristics of the gas in the stagnant zone within the target container during its migration to the leak outlet to obtain the gas flow characteristics; establishing a correlation between the density of the gas in the stagnant zone and the density of the leaking gas at the leak outlet based on the gas flow characteristics to obtain the density; and then using the density to obtain the temperature and pressure.

[0006] Preferably, the step of obtaining the jet structure and velocity of the gas in the core region under the first shock wave structure includes: based on the temperature and pressure change characteristics of the leaked gas during the dynamic diffusion process, taking the ambient gas temperature and pressure outside the target container as the leaked gas temperature and pressure at the end of the dynamic diffusion, thereby establishing the correlation between the jet structure and velocity of the leaked gas at the leak outlet and the jet structure and velocity of the gas in the core region under the first shock wave structure, and based on this, obtaining the jet structure and velocity of the gas in the core region under the first shock wave structure.

[0007] Preferably, the correlation between the jet structure and velocity of the leaking gas at the leak outlet and the jet structure and velocity of the gas in the core region under the first shock wave structure is expressed by the following expression:

[0008]

[0009] Where u1 represents the flow velocity of the leaking gas at the leak point, A1 represents the cross-sectional area of ​​the Mach disk of the leaking gas at the leak point, and V1 represents the volume of the leaking gas at the leak point. (2,1)A1 represents the flow velocity of the gas in the core region under the first shock structure in front of the Mach disk, A2 represents the cross-sectional area of ​​the gas in the core region under the first shock structure, V2 represents the gas cloud expansion volume of the gas in the core region under the first shock structure, P2 represents the pressure of the gas in the core region under the first shock structure, and P1 represents the pressure of the leaking gas at the leak point.

[0010] Preferably, the step of obtaining the distribution characteristics of the gas in the mixed boundary layer region under each shock structure includes: based on the jet structure of the leaking gas at the leak outlet and the ambient gas pressure inside and outside the target container, first obtaining the Mach disk cross-sectional diameter and thickness of the gas in the core region under the first shock structure, and then, in combination with the Mach disk cross-sectional area of ​​the gas in the core region under the corresponding shock structure, calculating the cross-sectional area of ​​the gas in the mixed boundary layer region that represents the gas distribution characteristics in the mixed boundary layer region.

[0011] Preferably, the Mach disk cross-section diameter and thickness of the gas in the core region under the first shock structure are obtained using the following expression:

[0012]

[0013] Where, d m d1 represents the diameter of the Mach disk cross-section of the gas in the core region under the first shock structure, d1 represents the diameter of the Mach disk cross-section of the leaking gas at the leak point, P0 represents the ambient gas pressure inside the target container, and P ∞ The pressure of the ambient gas outside the target container is represented by α, γ represents the specific heat ratio of the gas, and B represents the ambient gas pressure. s This represents the Mach disk cross-sectional thickness of the gas in the core region under the first shock structure.

[0014] Preferably, the gas cross-sectional area representing the gas distribution characteristics of the mixing boundary layer region under the first shock wave structure is calculated using the following expression:

[0015]

[0016] Where A3 represents the cross-sectional area of ​​the gas in the mixed boundary layer region under the first shock structure, and A2 represents the cross-sectional area of ​​the Mach disk of the gas in the core region under the first shock structure.

[0017] Preferably, the method further includes: using the ambient gas pressure inside and outside the target container and the gas pressure in the core region under each shock structure to calculate the Mach number before and after the Mach disk under the first shock structure.

[0018] Preferably, the Mach number before and after the Mach disk under the first shock structure is calculated using the following expression:

[0019]

[0020]

[0021] Where P0 represents the ambient gas pressure inside the target container, P ∞ Ma represents the ambient gas pressure outside the target container, γ represents the specific heat ratio of the gas, and Ma represents the specific gas pressure. (2,1) Ma represents the Mach number before the Mach disk in the first shock structure. (2,2) This indicates the Mach number after the Mach disk in the first shock structure.

[0022] Preferably, the step of calculating the gas motion parameters in the core region and the gas motion parameters in the mixed boundary layer region under each shock structure to obtain the gas cloud state during the dynamic diffusion process includes: firstly, based on the ideal gas sound speed, using the Mach number after the Mach disk under the first shock structure, obtaining the mass flow rate of the gas in the core region under the first shock structure, and further calculating the flow velocity and mass flow rate of the gas in the core region and the gas in the mixed boundary layer region under each of the remaining shock structures based on the corresponding conservation equations, thereby obtaining the gas motion parameters in the core region and the gas motion parameters in the mixed boundary layer region under each shock structure.

[0023] Preferably, the gas motion parameters in the mixed boundary layer region are calculated using the following expression:

[0024]

[0025] in, This indicates the mass flow rate of the leaking gas at the leak point. Y3 represents the mass flow rate of the gas in the core region under the first shock structure, Y3 represents the mass fraction of the gas in the mixed boundary layer region under the first shock structure, ρ3 represents the density of the gas in the mixed boundary layer region under the first shock structure, u3 represents the velocity of the gas in the mixed boundary layer region under the first shock structure, A3 represents the cross-sectional area of ​​the gas in the mixed boundary layer region under the first shock structure, P1 represents the pressure of the leaking gas at the leak outlet, A1 represents the Mach disk cross-sectional area of ​​the leaking gas at the leak outlet, u1 represents the velocity of the leaking gas at the leak outlet, P ∞ u represents the ambient gas pressure outside the target container. (2,2) C represents the gas velocity in the core region behind the Mach disk under the first shock structure. (p，air) R represents the specific heat capacity at constant pressure of the environment outside the target container. (g，3) R represents the gas constant of the gas in the mixed boundary layer region under the first shock structure. (g，leak) C represents the gas constant of the leaking gas at the leak point. (p，3) C represents the isobaric specific heat capacity of the gas in the mixed boundary layer region under the first shock structure. (p，leak) T represents the isobaric specific heat capacity of the leaking gas at the leak point, T1 represents the temperature of the leaking gas at the leak point, T2 represents the temperature of the gas in the core region under the first shock structure, P3 represents the pressure of the gas in the mixed boundary layer region under the first shock structure, and T...∞ This indicates the ambient gas temperature outside the target container.

[0026] Preferably, the gas cloud state at the end of dynamic diffusion is characterized by obtaining the corresponding gas motion parameters using the following expression:

[0027]

[0028] in, This indicates the mass flow rate of the leaking gas at the leak point. Y represents the mass flow rate of the core gas under the first shock structure, Y3 represents the mass fraction of the gas in the mixed boundary layer region under the first shock structure, and m3 represents the mass flow rate of the gas in the mixed boundary layer region under the first shock structure. n The mass ratio coefficient of the gas end in the core region under the last shock structure, u1 represents the flow velocity of the leaking gas at the leak point, and m n u represents the mass flow rate of the gas at the core region end under the last shock structure. (2,2) u3 represents the gas velocity in the core region behind the Mach disk under the first shock structure, and u3 represents the gas velocity in the mixed boundary layer region under the first shock structure. n ρ represents the flow velocity at the end of the core region of the last shock structure. n P represents the density of the gas at the core region end under the last shock structure. ∞ R represents the ambient gas pressure outside the target container. (g，n) T represents the gas constant at the end of the core region under the last shock structure. ∞ This indicates the ambient gas temperature outside the target container.

[0029] Preferably, the gas constant at the gas end of the core region under the last shock structure is calculated using the following expression:

[0030] R (g , n) =(1-Y n )R (g , air) +Y n R (g , leak )

[0031] Among them, R (g，air) R represents the ambient gas constant outside the target container. (g，leak) This represents the gas constant of the leaking gas at the leak point.

[0032] On the other hand, the present invention also provides a system for determining the gas cloud state of a leaking pressure vessel. The system includes the following modules: a parameter acquisition module, which is used to determine the physical property parameters of the leaking gas at the leak outlet based on the gas flow characteristics within the target vessel; a first gas cloud acquisition module, which is used to obtain the jet structure and velocity of the leaking gas at the leak outlet, as well as the jet structure and velocity of the core region gas under the first shock wave structure, based on the temperature and pressure change characteristics of the leaking gas during dynamic diffusion and using the physical property parameters, thereby obtaining the distribution characteristics of the gas in the mixing boundary layer region under each shock wave structure. Based on this, and combined with the Mach number before and after the Mach disk under the first shock wave structure, the motion parameters of the core region gas and the motion parameters of the mixing boundary layer gas under each shock wave structure are calculated respectively, thereby obtaining the gas cloud state during dynamic diffusion; and a second gas cloud acquisition module, which is used to obtain the corresponding gas motion parameters based on the current motion parameters and the velocity of the leaking gas at the leak outlet to characterize the gas cloud state at the end of dynamic diffusion.

[0033] Compared with the prior art, one or more embodiments of the above solutions may have the following advantages or beneficial effects:

[0034] This invention proposes a method and system for determining the gas cloud state of a leaking pressure vessel. Based on the physical properties of stagnant gas within the high-pressure vessel and combined with the temperature and pressure changes of the leaking gas during dynamic diffusion, the method accurately calculates the gas parameters of the diffusion cloud formed after the leaking gas expands, consisting of core region gas and mixed boundary layer gas. This yields the gas cloud state of the leaking gas throughout the entire dynamic diffusion process. This invention achieves accurate acquisition of the flow field structure changes of the jet diffusion gas cloud in a leaking pressure vessel, providing technical support for accurately predicting the gas cloud state of a leaking pressure vessel under accident conditions in petrochemical high-pressure equipment and its long-range concentration influence range.

[0035] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims and drawings. Attached Figure Description

[0036] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0037] Figure 1 This is a step diagram of a method for determining the gas cloud state of a leaking pressure vessel according to an embodiment of this application.

[0038] Figure 2This is a schematic diagram of gas distribution in an embodiment of the present application for a method of determining the gas cloud state of a leaking pressure vessel.

[0039] Figure 3 This is a block diagram of a system for determining the gas cloud state of a leaking pressure vessel, according to an embodiment of this application. Detailed Implementation

[0040] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that, as long as there is no conflict, the various embodiments and features in the various embodiments of the present invention can be combined with each other, and the resulting technical solutions are all within the protection scope of the present invention.

[0041] Furthermore, the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0042] Pressure vessels are essential infrastructure in fields such as petrochemicals, food processing, fire protection, transportation, and metallurgy. Various hazardous substances (flammable, explosive, and toxic) are generally stored within them. Flammable, explosive, and toxic gases are typically stored at higher pressures and lower temperatures. However, defects are unavoidable in the manufacturing and installation of high-pressure gas storage tanks and similar equipment. Common causes include corrosion perforation, valve failure, and fatigue cracks, leading to compressed gas leaks. Once leaked gas enters the production area or the atmosphere, it typically drifts due to airflow and mixes with air during diffusion. When the mixture reaches certain conditions, it can ignite upon contact with an ignition source, causing a fire or explosion, or poisoning personnel in the affected area. With the widespread use of natural gas and the increasing demand from chemical production, oil and gas storage is gradually increasing. In the event of a gas leak, the pressurized release source will exacerbate the threat to the safety of nearby equipment, facilities, chemical production, and the safety of people and property. Therefore, studying the jet mechanism formed after a high-pressure-ratio gas leak, as well as the near-field and far-field trajectories of the diffuse cloud after the jet, is of great significance for obtaining the flow field characteristics formed after a high-pressure gas leak, and for predicting the influence range, leakage amount, and flow velocity of the gas cloud. This is crucial for rescue operations and reducing on-site losses.

[0043] In the process of developing this invention, the inventors discovered that current research on near-field shock wave structures in the petrochemical safety field is limited, and the focus of research on underexpanded jets is primarily on the passive diffusion cloud properties that occur when the gas cloud expands to zero kinetic energy after the jet's virtual nozzle. Furthermore, with the increasing number of historical engineering cases using machine learning to acquire the diffusion characteristics of leaked gases, the drawbacks of discrepancies in diffusion results (especially the source term outlet flow field structure distribution and near-field concentration distribution) caused by differences in technical approaches and model designs within the same device have gradually become apparent. This problem directly affects the analysis of the consequences of high-pressure leak accidents and the determination of safe distances.

[0044] Therefore, to address the aforementioned problems, this invention proposes a method and system for determining the gas cloud state of a leaking pressure vessel. This method, based on the physical properties of stagnant gas within the high-pressure vessel and combined with the temperature and pressure changes of the leaking gas during dynamic diffusion, accurately calculates the gas parameters of the diffusion cloud formed after the leaking gas expands, consisting of core region gas and mixed boundary layer gas. This yields the gas cloud state of the leaking gas throughout the entire dynamic diffusion process. This invention achieves accurate acquisition of the flow field structure changes of the jet diffusion gas cloud in a leaking pressure vessel, providing technical support for accurately predicting the gas cloud state of a leaking pressure vessel and its long-range concentration influence range under accident conditions in petrochemical high-pressure equipment.

[0045] Example 1

[0046] Figure 1 This is a step diagram illustrating a method for determining the gas cloud state of a leaking pressure vessel according to an embodiment of this application. The following refers to... Figure 1 This will explain each step of the method.

[0047] like Figure 1 As shown, in step S110, the physical property parameters of the leaking gas at the leak outlet are determined based on the gas flow characteristics inside the target container. Figure 2 This is a schematic diagram of gas distribution in an embodiment of the method for determining the gas cloud state of a leaking pressure vessel according to this application. In this embodiment, the leaking gas in the target vessel is a high-pressure-ratio gas. Figure 2 As shown, when a gas leak occurs, the gas in the stagnant zone (gas at region 0) within the target container migrates towards the leak outlet to region 1, and then continues to migrate until it is ejected into the air from the leak outlet at the end of region 1, thus forming a leak gas cloud through a jet diffusion process in the air. Since the diffusion state of the leaked gas in the air mainly depends on the physical properties of the leaked gas at the leak outlet, which in turn are determined by the gas flow state within the target container, this embodiment determines the physical properties of the leaked gas at the leak outlet based on the gas flow characteristics within the target container.

[0048] The physical properties of the leaking gas at the leak point include, but are not limited to, density, temperature, and pressure. In the steps of determining the physical properties of the leaking gas at the leak point, the energy change characteristics of the gas in the stagnant zone within the target container during its migration to the leak point are first analyzed to obtain the gas flow characteristics. Then, based on the gas flow characteristics, the correlation between the density of the gas in the stagnant zone and the density of the leaking gas at the leak point is established to obtain the density. Finally, the temperature and pressure are obtained using the density.

[0049] Specifically, this embodiment first analyzes the energy change characteristics of the gas moving from the stagnant zone to the leak point within the target container, determining that the flow process is isentropic, and thus obtaining the gas flow characteristics. Then, based on this isentropic flow characteristic, and combining the adiabatic expansion relationship and the corresponding gas state equation, a correlation is established between the density of the gas in the stagnant zone and the density of the leaking gas at the leak point. After establishing this correlation, the measured density of the gas in the stagnant zone is substituted to calculate the density of the leaking gas at the leak point. Finally, using the calculated density of the leaking gas at the leak point, the temperature and pressure of the leaking gas at the leak point are further calculated.

[0050] In this embodiment, the relationship between the gas density in the stagnation zone and the density of the leaking gas at the leak outlet is expressed by the following expression:

[0051]

[0052] Where ρ0 represents the gas density in the stagnation zone, b represents the specific volume coefficient, ρ1 represents the density of the leaking gas at the leak point, and γ represents the specific heat ratio of the gas.

[0053] Next, the temperature and pressure are obtained using the following expressions:

[0054]

[0055] Where T1 represents the temperature of the leaking gas at the leak point, T0 represents the ambient gas temperature inside the target container, P1 represents the pressure of the leaking gas at the leak point, and R... (g，leak) This represents the gas constant of the leaking gas at the leak point.

[0056] In practical applications, the leaked gas diffuses in the air into core region gas (regions 2, 4 to n) and mixed boundary layer gas (region 3). The gas in region 2,1 is formed by the rapid expansion of the leaked gas, with a Mach number much greater than 1, making it a hypersonic flow. After reaching the first Mach disk and undergoing recompression, the gas in region 2,2 drops sharply to a subsonic flow. The mixed boundary layer gas (region 3) is formed by the rapid expansion of the leaked gas under air entrainment.

[0057] Next, in step S120, based on the temperature and pressure change characteristics of the leaked gas during the dynamic diffusion process, the jet structure and velocity of the leaked gas at the leak outlet are obtained using physical property parameters, as well as the jet structure and velocity of the gas in the core region under the first shock structure. Then, the distribution characteristics of the gas in the mixed boundary layer region under each shock structure are obtained. Based on this, combined with the Mach number before and after the Mach disk under the first shock structure, the motion parameters of the gas in the core region and the motion parameters of the gas in the mixed boundary layer region under each shock structure are calculated respectively, thereby obtaining the gas cloud state during the dynamic diffusion process.

[0058] Specifically, the gas migrates from inside the target container until it completes dynamic diffusion outside the target container, always satisfying the conservation of mass and momentum. Therefore, this embodiment constructs the correlation between the flow velocity, Mach disk cross-sectional area, and pressure of the leaked gas in each continuous dynamic diffusion stage containing different shock wave structures, based on the temperature and pressure change characteristics of the leaked gas during dynamic diffusion. Then, the physical property parameters determined in step S110 are substituted into the aforementioned correlation. First, the jet structure and flow velocity of the core region gas under the first shock wave structure are calculated. Then, the currently calculated jet structure and flow velocity of the leaked gas are used to calculate the jet structure and flow velocity of the core region gas under the next shock wave structure. Based on this, calculations are further performed for each subsequent shock wave structure until the jet structure and flow velocity of the core region gas under each shock wave structure are obtained. Next, based on the jet structure and flow velocity of the core region gas under each shock wave structure, the distribution characteristics of the gas in the mixing boundary layer region under each shock wave structure are calculated. Finally, using the Mach numbers before and after the Mach disk under the first shock structure, the gas velocity and mass flow rate representing the gas cloud state in the core region during the first dynamic diffusion stage (or under the first shock structure) are obtained. Based on this, the gas velocity and mass flow rate for the core region gas cloud state under each subsequent shock structure are calculated. Finally, by integrating the gas velocity and mass flow rate representing the core region gas cloud state from all dynamic diffusion stages, the gas cloud state during the dynamic diffusion process is obtained. Furthermore, based on the formation principle of the mixed boundary layer gas, the physical properties of the mixed boundary layer gas are calculated according to the mixing law to obtain the gas velocity representing the gas cloud state in the mixed boundary layer gas at each dynamic diffusion stage (or under each shock structure). Finally, by integrating the gas velocity representing the mixed boundary layer gas cloud state from all dynamic diffusion stages, the gas cloud state during the dynamic diffusion process is obtained.

[0059] In the step of obtaining the jet structure and velocity of the gas in the core region under the first shock structure, based on the temperature and pressure change characteristics of the leaked gas during the dynamic diffusion process, the ambient gas temperature and pressure outside the target container are taken as the leaked gas temperature and pressure at the end of the dynamic diffusion. This establishes a correlation between the jet structure and velocity of the leaked gas at the leak outlet and the jet structure and velocity of the gas in the core region under the first shock structure. Based on this, the jet structure and velocity of the gas in the core region under the first shock structure are obtained. In this embodiment, the temperature and pressure of the leaked gas at the leak outlet are taken as the gas temperature and pressure at the beginning of the dynamic diffusion process, and the ambient gas temperature and pressure outside the target container are taken as the gas temperature and pressure at the end of the dynamic diffusion. Based on this, a correlation is established between the jet structure and velocity of the leaked gas at the leak outlet and the jet structure and velocity of the gas in the core region under the first shock structure. Further, the correlation between the jet structure and velocity of the gas in the core region between each group of adjacent shock structures is obtained. Finally, the established correlations are used to calculate the jet structure and velocity of the gas in the core region under each shock structure.

[0060] In this embodiment, the correlation between the jet structure and velocity of the leaking gas at the leak outlet and the jet structure and velocity of the gas in the core region under the first shock wave structure is expressed by the following expression:

[0061]

[0062] Where u1 represents the flow velocity of the leaking gas at the leak point, A1 represents the cross-sectional area of ​​the Mach disk of the leaking gas at the leak point, and V1 represents the volume of the leaking gas at the leak point. (2,1) A1 represents the velocity of the gas in the core region in front of the Mach disk under the first shock structure, A2 represents the cross-sectional area of ​​the Mach disk of the gas in the core region under the first shock structure, V2 represents the gas cloud expansion volume of the gas in the core region under the first shock structure, and P2 represents the pressure of the gas in the core region under the first shock structure.

[0063] In this embodiment, the jet structure and velocity of the leaking gas at the leak outlet are obtained using the following expression:

[0064]

[0065] Where d1 represents the diameter of the Mach disk section of the leaking gas at the leak point.

[0066] Furthermore, this invention also utilizes the ambient gas pressure inside and outside the target container to calculate the Mach number before and after the Mach disk under the first shock wave structure. (Continue to refer to...) Figure 2In practical applications, the gas velocity in the core area is the highest on the left side of the first shock wave structure. Therefore, this embodiment uses the adiabatic expansion equation and the pressure change formula before and after the normal shock wave to obtain the Mach number on the left side of the Mach disk boundary of the first shock wave structure using the ambient gas pressure inside and outside the target container. This Mach number is then used as the Mach number before the Mach disk of the first shock wave structure (i.e., the Mach number between the leak and the Mach disk of the first shock wave structure). Furthermore, based on the normal shock wave relationship, the Mach number on the right side of the Mach disk boundary of the first shock wave structure is obtained using the currently calculated Mach number before the Mach disk of the first shock wave structure. This Mach number is then used as the Mach number after the Mach disk of the first shock wave structure (i.e., the Mach number between the Mach disk of the first and second shock wave structures).

[0067] In this embodiment of the application, the Mach number before and after the Mach disk under the first shock structure is calculated using the following expression:

[0068]

[0069] Where P0 represents the ambient gas pressure inside the target container, P ∞ Ma represents the ambient gas pressure outside the target container. (2,1) Ma represents the Mach number before the Mach disk in the first shock structure. (2,2) This indicates the Mach number after the Mach disk in the first shock structure.

[0070] In this embodiment, the flow velocity of the core gas behind the Mach disk under the first shock structure and the mass flow rate of the core gas under the first shock structure are obtained using the following expressions:

[0071]

[0072] Among them, u (2,2) T represents the gas velocity in the core region behind the Mach disk under the first shock structure. ∞ Indicates the ambient gas temperature outside the target container. ρ represents the mass flow rate of the gas in the core region under the first shock structure, and ρ2 represents the density of the gas in the core region under the first shock structure.

[0073] Next, in the step of obtaining the distribution characteristics of the gas in the mixed boundary layer region under each shock structure, based on the jet structure of the leaking gas at the leak outlet and the ambient gas pressure inside and outside the target container, the Mach disk cross-sectional diameter and thickness of the gas in the core region under the first shock structure are first obtained. Then, combined with the Mach disk cross-sectional area of ​​the gas in the core region under the corresponding shock structure, the cross-sectional area of ​​the gas in the mixed boundary layer region, representing the gas distribution characteristics, is calculated. In practical applications, based on the relationship between the Mach disk diameter and the specific heat ratio of the gas, the cross-sectional area of ​​the gas in the mixed boundary layer region formed under air entrainment can be obtained through coupled calculations. Therefore, this embodiment utilizes the jet structure of the leaking gas at the leak point, as well as the ambient gas pressure inside and outside the target container, to first calculate the Mach disk cross-sectional diameter and thickness of the gas in the core region under the first shock structure. Then, using the Mach disk cross-sectional diameter of the gas in the core region under the first shock structure, the Mach disk cross-sectional diameter and thickness of the gas in the core region under the second shock structure are obtained. This process is repeated for each subsequent shock structure until the Mach disk cross-sectional diameter and thickness of the gas in the core region under each shock structure are obtained, thus yielding the cross-sectional area of ​​the gas in the mixed boundary layer region under each shock structure. Finally, by summarizing the calculations, the cross-sectional area of ​​the entire mixed boundary layer region is obtained, thereby characterizing the distribution characteristics of the gas in the mixed boundary layer region during the dynamic diffusion process using the cross-sectional area of ​​the entire mixed boundary layer region.

[0074] In this embodiment, the Mach disk cross-sectional diameter and thickness of the gas in the core region under the first shock structure are obtained using the following expression:

[0075]

[0076] Where, d m d1 represents the Mach disk cross-sectional diameter of the gas in the core region under the first shock structure, d1 represents the Mach disk cross-sectional diameter of the leaking gas at the leak point, α represents the empirical coefficient, and B s This represents the Mach disk cross-sectional thickness of the gas in the core region under the first shock structure.

[0077] In one specific embodiment of this application, the empirical coefficient α is obtained based on relevant gas diffusion experiments and has a value of 0.954.

[0078] In this embodiment, the cross-sectional area of ​​the gas in the first mixed boundary layer region, which represents the distribution characteristics of the gas in the first shock wave structure, is calculated using the following expression:

[0079]

[0080] Where A3 represents the cross-sectional area of ​​the gas in the mixed boundary layer region under the first shock structure.

[0081] Next, in the step of calculating the gas motion parameters in the core region and the gas motion parameters in the mixed boundary layer region under each shock structure to obtain the gas cloud state during dynamic diffusion, the mass flow rate of the gas in the core region under the first shock structure is first obtained based on the ideal gas velocity and the Mach number after the Mach disk under the first shock structure. Then, based on the corresponding conservation equations, the velocity and mass flow rate of the gas in the core region and the mixed boundary layer region under each of the remaining shock structures are calculated, thereby obtaining the gas motion parameters in the core region and the mixed boundary layer region under each shock structure. Specifically, in this embodiment, based on the ideal gas velocity calculation formula, the mass flow rate of the gas in the core region under the first shock structure is calculated using the Mach number after the Mach disk under the first shock structure. Then, using the velocity and mass flow rate of the gas in the core region under the previous shock structure, the velocity and mass flow rate of the gas in the core region under subsequent shock structures, as well as the velocity and mass flow rate of the gas in the mixed boundary layer region under each shock structure, are calculated. In calculating the gas velocity and mass flow rate in the core region under the post-shock structure, as well as the gas velocity and mass flow rate in the mixed boundary layer region under each shock structure, based on the mixing law of the gas in the mixed boundary layer region, several conservation equations are established regarding the correlation between the gas velocity and mass flow rate (gas in the core region and gas in the mixed boundary layer region) under different shock structures. This enables the calculation of the motion parameters of the gas in the core region and the gas motion parameters in the mixed boundary layer region under different shock structures.

[0082] In this embodiment of the application, assuming the mass fraction of the gas in the mixed boundary layer region under the first shock structure is Y3, the established conservation equation is expressed by the following expression:

[0083]

[0084] in, ρ3 represents the mass flow rate of the leaking gas at the leak point, and C represents the density of the gas in the mixed boundary layer region under the first shock structure. (p，air) R represents the specific heat capacity at constant pressure of the environment outside the target container. (g，3) C represents the gas constant of the gas in the mixed boundary layer region under the first shock structure. (p，3) C represents the isobaric specific heat capacity of the gas in the mixed boundary layer region under the first shock structure. (p，leak) Y3 represents the isobaric specific heat capacity of the leaking gas at the leak point, Y3 represents the mass fraction of the gas in the mixed boundary layer region under the first shock structure, u3 represents the flow velocity of the gas in the mixed boundary layer region under the first shock structure, and P3 represents the pressure of the gas in the mixed boundary layer region under the first shock structure.

[0085] Furthermore, in step S130, based on the current motion parameters and the flow velocity of the leaking gas at the leak outlet, corresponding gas motion parameters are obtained to characterize the gas cloud state at the end of dynamic diffusion. After the leaking gas is fully mixed with the surrounding air, the shock wave structure eventually disappears. At this point, all kinetic energy is converted into potential energy. The mixed cloud, including the core region gas and the mixed boundary layer region gas, will initiate the buoyancy diffusion process under the action of buoyancy. That is, the starting node of buoyancy diffusion is the ending node of dynamic diffusion. The buoyancy diffusion process still satisfies the conservation of mass, momentum, and energy, and still has the isentropic adiabatic expansion characteristics. Therefore, this embodiment establishes conservation equations for the aforementioned conservation relationships, and substitutes the various gas motion parameters obtained in step S120, as well as the flow velocity of the leaking gas at the leak outlet, into the conservation equations, thereby realizing the calculation of gas motion parameters characterizing the gas cloud state at the end of dynamic diffusion.

[0086] In this embodiment, the conservation equation is expressed using the following expression:

[0087]

[0088] Where m3 represents the mass flow rate of the gas in the mixed boundary layer region under the first shock structure, and Y n m represents the mass proportion factor of the gas end in the core region under the last shock structure. n u represents the mass flow rate of the gas at the core region end under the last shock structure. n ρ represents the flow velocity at the end of the core region of the last shock structure. n R represents the density of the gas at the core region end under the last shock structure. (g，n) This represents the gas constant at the end of the core region under the last shock structure.

[0089] In this embodiment, the gas constant at the gas end of the core region under the last shock structure is calculated using the following expression:

[0090] R (g，n) =(1-Y n )R (g，air) +Y n R (g，leak) (twenty one)

[0091] Among them, R (g，air) This represents the ambient gas constant outside the target container.

[0092] Example 2

[0093] Based on the method for determining the gas cloud state of a leaking pressure vessel as described in Embodiment 1 above, this embodiment of the invention also provides a system for determining the gas cloud state of a leaking pressure vessel (hereinafter referred to as the "gas cloud state determination system"). Figure 3 This is a block diagram of a system for determining the gas cloud state of a leaking pressure vessel, according to an embodiment of this application.

[0094] like Figure 3 As shown, the cloud state determination system in this embodiment of the invention includes: a parameter acquisition module 31, a first cloud acquisition module 32, and a second cloud acquisition module 33. The parameter acquisition module 31 is implemented according to the method described in step S110 above, and is configured to determine the physical property parameters of the leaking gas at the leak outlet based on the gas flow characteristics in the target container; the first gas cloud acquisition module 32 is implemented according to the method described in step S120 above, and is configured to obtain the jet structure and velocity of the leaking gas at the leak outlet, as well as the jet structure and velocity of the core gas under the first shock structure, based on the temperature and pressure change characteristics of the leaking gas during the dynamic diffusion process and using the physical property parameters, thereby obtaining the distribution characteristics of the gas in the mixing boundary layer region under each shock structure. Based on this, combined with the Mach number before and after the Mach disk under the first shock structure, the motion parameters of the core gas and the motion parameters of the mixing boundary layer gas under each shock structure are calculated respectively, thereby obtaining the gas cloud state during the dynamic diffusion process; the second gas cloud acquisition module 33 is implemented according to the method described in step S130 above, and is configured to obtain the corresponding gas motion parameters based on the current motion parameters and the velocity of the leaking gas at the leak outlet to characterize the gas cloud state at the end of the dynamic diffusion.

[0095] This invention discloses a method and system for determining the gas cloud state of a leaking pressure vessel. Based on the physical properties of stagnant gas within the high-pressure vessel and combined with the temperature and pressure changes of the leaking gas during dynamic diffusion, the method accurately calculates the gas parameters of the diffusion cloud formed after the leaking gas expands, consisting of core region gas and mixed boundary layer gas. This yields the gas cloud state of the leaking gas throughout the entire dynamic diffusion process. This invention solves the current problem in the petrochemical safety field of lacking a rapid calculation method for equivalent diffusion surface sources under high-pressure vessel leakage conditions. It achieves accurate acquisition of the flow field structure changes of the jet diffusion gas cloud in a leaking pressure vessel, providing technical support for accurately predicting the gas cloud state of a leaking pressure vessel and its long-range concentration influence range under accident conditions in petrochemical high-pressure equipment. Furthermore, this invention establishes an equivalent virtual nozzle analysis scheme for highly underexpanded jets with high injection pressure ratio gas (NPR > 2) for high-pressure vessel leakage conditions in the petrochemical industry. This scheme can quickly calculate the key physical parameters of the equivalent cloud formed by air entrainment, providing guidance for numerical calculation engineering applications for rapidly calculating jets in high-pressure environments.

[0096] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0097] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

[0098] Those skilled in the art will understand that the modules or steps of the present invention described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Optionally, they can be implemented using computer-executable program code, thereby storing them in a storage device for execution by a computing device, or fabricating them separately as individual integrated circuit modules, or fabricating multiple modules or steps as a single integrated circuit module. Thus, the present invention is not limited to any particular hardware and software combination.

[0099] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and variations in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection for this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method for determining the gas cloud state of a leaking pressure vessel, characterized in that, include: Based on the gas flow characteristics inside the target container, determine the physical property parameters of the leaking gas at the leak point; Based on the temperature and pressure change characteristics of the leaked gas during dynamic diffusion, the jet structure and velocity of the leaked gas at the leak outlet, as well as the jet structure and velocity of the gas in the core region under the first shock structure, are obtained using the aforementioned physical property parameters. This allows for the acquisition of the gas distribution characteristics in the mixed boundary layer region under each shock structure. Based on this, and combined with the Mach number before and after the Mach disk under the first shock structure, the motion parameters of the gas in the core region and the motion parameters of the gas in the mixed boundary layer region under each shock structure are calculated, thereby obtaining the gas cloud state during dynamic diffusion. Based on the current motion parameters and the flow rate of the leaking gas at the leak outlet, corresponding gas motion parameters are obtained to characterize the gas cloud state at the end of dynamic diffusion.

2. The method according to claim 1, characterized in that, The physical properties of the leaking gas at the leak outlet include, but are not limited to, density, temperature, and pressure. The step of determining the physical properties of the leaking gas at the leak outlet includes: The energy change characteristics of the gas in the stagnant zone within the target container during its migration to the leak point are analyzed to obtain the gas flow characteristics. Based on the gas flow characteristics, a correlation is established between the gas density in the stagnation zone and the density of the leaking gas at the leak outlet to obtain the density, and then the temperature and pressure are obtained using the density.

3. The method according to claim 1 or 2, characterized in that, The steps for obtaining the jet structure and velocity of the gas in the core region under the first shock structure include: Based on the temperature and pressure change characteristics of the leaked gas during the dynamic diffusion process, the ambient gas temperature and pressure outside the target container are taken as the leaked gas temperature and pressure at the end of the dynamic diffusion. This establishes the correlation between the jet structure and velocity of the leaked gas at the leak outlet and the jet structure and velocity of the gas in the core region under the first shock wave structure. Based on this, the jet structure and velocity of the gas in the core region under the first shock wave structure are obtained.

4. The method according to claim 3, characterized in that, The correlation between the jet structure and velocity of the leaking gas at the leak point and the jet structure and velocity of the gas in the core region under the first shock wave structure is expressed by the following expression: Where u1 represents the flow velocity of the leaking gas at the leak point, A1 represents the cross-sectional area of ​​the Mach disk of the leaking gas at the leak point, and V1 represents the volume of the leaking gas at the leak point. (2,1) A1 represents the flow velocity of the gas in the core region under the first shock structure in front of the Mach disk, A2 represents the cross-sectional area of ​​the gas in the core region under the first shock structure, V2 represents the gas cloud expansion volume of the gas in the core region under the first shock structure, P2 represents the pressure of the gas in the core region under the first shock structure, and P1 represents the pressure of the leaking gas at the leak point.

5. The method according to any one of claims 1 to 4, characterized in that, The step of obtaining the distribution characteristics of the gas in the mixed boundary layer region under each shock structure includes: Based on the jet structure of the leaking gas at the leak outlet and the ambient gas pressure inside and outside the target container, the diameter and thickness of the Mach disk cross-section of the gas in the core region under the first shock structure are first obtained. Then, combined with the cross-sectional area of ​​the Mach disk of the gas in the core region under the corresponding shock structure, the cross-sectional area of ​​the gas in the mixed boundary layer region, which represents the gas distribution characteristics of the mixed boundary layer region, is calculated.

6. The method according to claim 5, characterized in that, The diameter and thickness of the Mach disk cross-section of the gas in the core region under the first shock structure are obtained using the following expression: Where, d m d1 represents the diameter of the Mach disk cross-section of the gas in the core region under the first shock structure, d1 represents the diameter of the Mach disk cross-section of the leaking gas at the leak point, P0 represents the ambient gas pressure inside the target container, and P ∞ The pressure of the ambient gas outside the target container is represented by α, γ represents the specific heat ratio of the gas, and B represents the ambient gas pressure. s This represents the Mach disk cross-sectional thickness of the gas in the core region under the first shock structure.

7. The method according to claim 6, characterized in that, The gas cross-sectional area representing the gas distribution characteristics in the mixing boundary layer region under the first shock structure is calculated using the following expression: Where A3 represents the cross-sectional area of ​​the gas in the mixed boundary layer region under the first shock structure, and A2 represents the cross-sectional area of ​​the Mach disk of the gas in the core region under the first shock structure.

8. The method according to any one of claims 1 to 7, characterized in that, The method further includes: Using the ambient gas pressure inside and outside the target container, the Mach number before and after the Mach disk under the first shock structure is calculated.

9. The method according to claim 8, characterized in that, The Mach number before and after the Mach disk under the first shock structure is calculated using the following expression: Where P0 represents the ambient gas pressure inside the target container, P ∞ Ma represents the ambient gas pressure outside the target container, γ represents the specific heat ratio of the gas, and Ma represents the specific gas pressure. (2,1) Ma represents the Mach number before the Mach disk in the first shock structure. (2,2) This indicates the Mach number after the Mach disk in the first shock structure.

10. The method according to any one of claims 1 to 9, characterized in that, The steps of calculating the gas motion parameters in the core region and the gas motion parameters in the mixed boundary layer region under each shock wave structure to obtain the gas cloud state during dynamic diffusion include: First, based on the ideal gas velocity, the mass flow rate of the gas in the core region under the first shock structure is obtained using the Mach number after the Mach disk under the first shock structure. Then, based on the corresponding conservation equations, the flow velocity and mass flow rate of the gas in the core region and the gas in the mixed boundary layer region under each of the remaining shock structures are calculated, thereby obtaining the motion parameters of the gas in the core region and the gas in the mixed boundary layer region under each shock structure.

11. The method according to any one of claims 1 to 10, characterized in that, The gas motion parameters in the mixed boundary layer region are calculated using the following expression: in, This indicates the mass flow rate of the leaking gas at the leak point. Y3 represents the mass flow rate of the gas in the core region under the first shock structure, Y3 represents the mass fraction of the gas in the mixed boundary layer region under the first shock structure, ρ3 represents the density of the gas in the mixed boundary layer region under the first shock structure, u3 represents the velocity of the gas in the mixed boundary layer region under the first shock structure, A3 represents the cross-sectional area of ​​the gas in the mixed boundary layer region under the first shock structure, P1 represents the pressure of the leaking gas at the leak outlet, A1 represents the Mach disk cross-sectional area of ​​the leaking gas at the leak outlet, u1 represents the velocity of the leaking gas at the leak outlet, P ∞ u represents the ambient gas pressure outside the target container. (2,2) C represents the gas velocity in the core region behind the Mach disk under the first shock structure. (p，air) R represents the specific heat capacity at constant pressure of the environment outside the target container. (g，3) R represents the gas constant of the gas in the mixed boundary layer region under the first shock structure. (g，leak) C represents the gas constant of the leaking gas at the leak point. (p，3) C represents the isobaric specific heat capacity of the gas in the mixed boundary layer region under the first shock structure. (p，leak) T represents the isobaric specific heat capacity of the leaking gas at the leak point, T1 represents the temperature of the leaking gas at the leak point, T2 represents the temperature of the gas in the core region under the first shock structure, P3 represents the pressure of the gas in the mixed boundary layer region under the first shock structure, and T... ∞ This indicates the ambient gas temperature outside the target container.

12. The method according to any one of claims 1 to 11, characterized in that, The gas motion parameters at the end of dynamic diffusion are obtained using the following expressions to characterize the gas cloud state: in, This indicates the mass flow rate of the leaking gas at the leak point. Y represents the mass flow rate of the core gas under the first shock structure, Y3 represents the mass fraction of the gas in the mixed boundary layer region under the first shock structure, and m3 represents the mass flow rate of the gas in the mixed boundary layer region under the first shock structure. n The mass ratio coefficient of the gas at the core region under the last shock structure is represented by u1, and the flow velocity of the leaking gas at the leak point is m. n u represents the mass flow rate of the gas at the core region end under the last shock structure. (2,2) u3 represents the gas velocity in the core region behind the Mach disk under the first shock structure, and u3 represents the gas velocity in the mixed boundary layer region under the first shock structure. n ρ represents the flow velocity at the end of the core region of the last shock structure. n P represents the density of the gas at the core region end under the last shock structure. ∞ R represents the ambient gas pressure outside the target container. (g，n) T represents the gas constant at the end of the core region under the last shock structure. ∞ This indicates the ambient gas temperature outside the target container.

13. The method according to claim 12, characterized in that, The gas constant at the gas end of the core region under the last shock structure is calculated using the following expression: R (g，n) =(1-Y n )R (g，air) +Y n R (g，leak) Among them, R (g，air) R represents the ambient gas constant outside the target container. (g，leak) This represents the gas constant of the leaking gas at the leak point.

14. A system for determining the state of a gas cloud in a leaking pressure vessel, characterized in that, The system includes the following modules: The parameter acquisition module is used to determine the physical property parameters of the leaking gas at the leak point based on the gas flow characteristics inside the target container. The first gas cloud acquisition module is used to obtain the jet structure and velocity of the leaking gas at the leak outlet, as well as the jet structure and velocity of the core gas under the first shock structure, based on the temperature and pressure change characteristics of the leaking gas during the dynamic diffusion process and the physical property parameters. Then, it obtains the distribution characteristics of the gas in the mixed boundary layer region under each shock structure. Based on this, combined with the Mach number before and after the Mach disk under the first shock structure, it calculates the motion parameters of the core gas and the motion parameters of the mixed boundary layer gas under each shock structure, thereby obtaining the gas cloud state during the dynamic diffusion process. The second gas cloud acquisition module is used to characterize the gas cloud state at the end of dynamic diffusion by obtaining corresponding gas motion parameters based on the current motion parameters and the flow rate of the leaking gas at the leak outlet.

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