Human respiratory system exposure simulation and injury risk assessment method under toxic gas leakage scene in closed space

Abstract

The invention relates to the technical field of risk assessment of sudden gas material leakage in a closed space to the health state of people, in particular to a human respiratory system injury simulation and risk assessment method based on a toxic gas leakage scene. The method specifically comprises the following steps in sequence: S1, establishing a geometric model of a closed space; s2, simulating a toxic gas leakage diffusion scene and setting toxic gas monitoring points; s3, selecting a proper turbulence model and calculating boundary conditions; s4, obtaining a toxic gas leakage concentration spatio-temporal evolution law through simulation; s5, carrying out numerical analysis on the height plane concentration of the human body breathing area and the concentration of each part of the human body breathing system; s6, human body inhalation injury risk assessment is obtained by combining the dose-reaction relation of the human body to the toxic gas.

Description

Technical Field

[0001] The present invention relates to the technical field of risk assessment of the health status of personnel due to sudden material leakage in a closed space, and in particular to a method for simulating and risk assessing damage to the human respiratory system based on a toxic gas leakage scenario. Background Art

[0002] There are sudden material leakage incidents in various closed spaces, such as production workshops in chemical plants and various laboratories. The leakage of toxic gases is an important type with high frequency, great harm and wide impact range. Especially in recent years, the widespread use of materials involving common laboratory gases such as chlorine, carbon monoxide and ammonia has caused the number of this type of accidents to remain high.

[0003] In response to the diffusion laws of toxic gas leakage and its inhalation damage to the human body, scholars at home and abroad have conducted research through various methods such as theoretical analysis, numerical simulation, and field experiments, and have achieved certain results, mainly including proposing a theoretical calculation model, establishing a rapid estimation method for the concentration distribution of toxic gas leakage, leakage source inversion analysis, concentration field simulation and other tools.

[0004] In general, the existing experimental technology cannot effectively, at low cost and with high precision, quantify the exposure simulation and injury risk of the human respiratory system in the closed space toxic gas leakage scenario, and the theoretical calculation method still has deficiencies in the authenticity and dynamics of the laboratory toxic gas leakage scenario model, and the accuracy of the human body model including the coupling model of the human body and the respiratory system. In addition, most of the existing studies have selected simplified scenario models and human body models, and failed to establish an accurate connection between the real scenario and the numerical model. Their real-time and precision are poor, and they cannot simulate the exposure characteristics of the human respiratory system and make more accurate risk assessments; therefore, it is necessary to design a new solution to meet actual needs. Summary of the invention

[0005] To this end, the present invention combines the computational fluid dynamics (CFD) numerical simulation technology with the toxic gas exposure-dose-response relationship in medical statistical data, and proposes a human respiratory system exposure simulation and injury risk assessment method in a toxic gas leakage scenario in a closed space. This method can establish a more accurate connection between the real scene of toxic gas leakage in the laboratory and the numerical model, and use the human-respiratory tract coupling numerical model with real physiological characteristics to improve the accuracy of risk assessment, which is then used to guide protection and risk control to better ensure the safety of laboratory personnel.

[0006] The present invention is a method for simulating human respiratory system exposure and assessing injury risk in a toxic gas leakage scenario in a closed space, which specifically includes:

[0007] S1. Establishment of closed space geometric model;

[0008] S2. Simulate the scene of toxic gas leakage and diffusion and set up toxic gas monitoring points;

[0009] S3. Select appropriate turbulence model and calculation boundary conditions;

[0010] S4. The temporal and spatial evolution of the concentration of toxic gas leakage is obtained through simulation;

[0011] S5. Conduct numerical analysis of the concentration in the plane at the height of the human respiratory area and the concentration in various parts of the human respiratory system;

[0012] S6. Based on the dose-response relationship of the human body to toxic gases, a risk assessment of human inhalation injury is derived.

[0013] Specifically, in step S1, the geometric model of the closed space is established, the size and space of the closed space, as well as the objects built in the closed space, a three-dimensional numerical model is constructed, and a human-respiratory system coupling numerical model is introduced. The human-respiratory system coupling numerical model simulates a person, and the height of the breathing area of ​​the simulated person's face is set;

[0014] Divide the above closed space into computational grids and build a computational model.

[0015] The height of the simulated person's facial breathing zone is set to 1.5-1.7m, preferably 1.6m or 1.7m. The average height of the facial breathing zone of adult males in East Asia is about 1.6m, and the average height of the facial breathing zone of adult Caucasians in Europe and America is about 1.7m.

[0016] In step S2, a toxic gas leakage and diffusion scenario is simulated, and different types of toxic gases are selected for leakage and diffusion simulation, taking into account the physical and chemical properties and typicality of the gas.

[0017] According to the Abel-Nobel state equation, energy conservation equation and isentropic process assumption, the leakage velocity u0 of the toxic gas at the leak hole is:

[0018]

[0019] Where κ is the adiabatic index, J / (kg·K); υ1 is the specific volume, m 3 / kg; P1 and P a are the pressure at the leakage hole and the surrounding gas pressure, Pa respectively; b is the specific volume correction term.

[0020] The toxic gases include but are not limited to carbon monoxide and / or chlorine; wherein the density of carbon monoxide is lower than that of air, and is used to analyze and evaluate the conditions of toxic gases with a density lower than that of air; wherein the density of chlorine is higher than that of air, and is used to analyze and evaluate the conditions of toxic gases with a density higher than that of air.

[0021] In step S3, in order to explore the spatiotemporal evolution of the leakage and diffusion of toxic gas in the laboratory after leakage, monitoring points and monitoring planes are set at different positions in the closed space, the concentration of toxic gas at corresponding positions at different times is monitored and calculated, and a suitable turbulence model such as the RNG k-ε turbulence model and calculation boundary conditions are selected.

[0022] By expressing the solution variables appearing in the transient Navier-Stokes equations as the sum of an average component and a pulsating component; the average component is an ensemble average or a time average;

[0023]

[0024]

[0025] Where u i is the average axial velocity, m / s; u j is the radial average velocity, m / s; x i is the axial coordinate; x j is the radial coordinate; p is the pressure, Pa; t is the time, s; ρ is the fluid density, kg / m 3 . Where i and j represent the components in the i-th and j-th directions respectively.

[0026] Furthermore, in order to keep the above equations closed, it is necessary to establish a Reynolds stress model and make assumptions about the Reynolds stress. The eddy viscosity hypothesis proposed by Boussinesq is widely used, in which the Reynolds stress is expressed as

[0027]

[0028] Where u i is the average axial velocity, m / s; u j is the radial average velocity, m / s; δ ij is the Kronecker function. When i=j, δ ij =1, otherwise δ ij =0;v T is the eddy viscosity coefficient, which can be used to calculate the Reynolds stress and can be written as

[0029] v T =C μ k 2 / ε

[0030] Where k is the turbulent kinetic energy, m 2 / s 2 ; ε is the turbulent dissipation rate, m 2 / s 3 ; C μ is a constant. The closed Reynolds stress model can achieve a more accurate solution of turbulence statistics with less calculation. The continuity equation and momentum equation of the RNG k-ε turbulence model are as follows

[0031]

[0032]

[0033] Where G k and G b are the turbulent kinetic energy due to the average velocity gradient and buoyancy, J / kg; Y m represents the contribution of wave expansion in compressible turbulence to the total dissipation rate; α k and α ε are the reciprocals of the turbulent Prandtl numbers of k and ε respectively; S k and S ε is a user-defined source term; C 1ε , C 2ε , C 3ε is a constant; eff stands for "effective" and is used to indicate the effective viscosity coefficient.

[0034] The Reynolds stress constant k and ε The calculation method is as follows

[0035]

[0036]

[0037]

[0038] Where u is the average velocity, m / s; I is the turbulence intensity; Re is the Reynolds number; C ε is a constant; l is the characteristic length, m.

[0039] The closed space has doors and windows, where the door is set as an exit (i.e., vent), the ambient wind speed is set, and the window is set as a free outflow boundary condition. The SIMPLEC algorithm is used to achieve the coupling between pressure and velocity, and transient calculations are used to simulate the diffusion law of toxic gas leakage in the closed space and the exposure law of the human respiratory system.

[0040] The ambient wind speed is the annual average wind speed at the location of the enclosed space.

[0041] In step S4, the temporal and spatial evolution law of the toxic gas leakage concentration is obtained through simulation. The initial leakage time is taken as the starting point, the leakage duration is set, and the leakage duration is divided into several stages. The spatial distribution of the gas in each stage is analyzed to explore the propagation law after the leakage occurs. By comparing and analyzing the volume rendering images of gas leakage fractions at different times, it is analyzed that the diffusion path of toxic gas leakage will be affected by factors such as density and obstacles.

[0042] The leakage duration is 90S-360S, which is divided into 3-6 stages; further, the leakage duration is set to 180S, which is divided into 4 stages.

[0043] In step S5, the planar concentration numerical analysis at the human breathing zone height is combined with the height of the simulated person's facial breathing zone, and the planar concentration at that height is analyzed and displayed, which can be used to determine the concentration of toxic gases that people are exposed to in this environment and the possible damage they may suffer. The results are obtained by comparing and analyzing the gas mass fraction distribution at different times within the predetermined leakage time of the toxic gas at a predetermined height plane.

[0044] In step S6, the risk of human inhalation injury is assessed by analyzing multiple monitoring points at different locations in the numerical model to obtain the change of respiratory system risk over time, and calculate the damage suffered by personnel at different exposure times in the toxic gas leakage scenario and the reasonable evacuation time.

[0045] The present invention simulates the change of toxic gas concentration in various areas inside the respiratory system of personnel over time when toxic gas leakage occurs, and can more accurately simulate and analyze in real time, and display the risk change pattern of personnel, thereby providing a reference for key indicators such as safe evacuation time, and guiding their evacuation at the specified time.

[0046] In summary, the present invention uses CFD technology to simulate and analyze the leakage and diffusion process of toxic gases (such as carbon monoxide and chlorine) in a typical closed space, and establishes a technical method to quantify the diffusion behavior after the toxic gas leak, the distribution change of concentration over time and space, and the human inhalation exposure. By combining the relationship between the human body's dose-response to toxic gases, the degree of injury that people may suffer and the safe evacuation time in the scenario of toxic gas leakage in a closed space are evaluated, and a reference is provided for the selection of the alarm setting location.

[0047] The present invention integrates CFD technology simulation and can be used to quantify the exposure simulation and injury risk of the human respiratory system in the scenario of toxic gas leakage in a closed space at low cost and high precision. The present invention can analyze the leakage and diffusion process of toxic gases such as carbon monoxide and chlorine in a closed space environment, and quantify the distribution changes of concentrations over time and space after the toxic gas leakage, simulate the exposure characteristics of the human respiratory system and predict the risk of injury. Establish an accurate connection between the real scene and the numerical model, and by combining the dose-response relationship of the human body to the toxic gas, evaluate the degree of injury and safe evacuation time that people may suffer in the scenario of toxic gas leakage in a closed space, and provide a reference for the selection of the alarm setting location. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The figure is a risk assessment flow chart according to an embodiment of the present invention.

[0049] Figure 2 The figure is a laboratory scene diagram according to an embodiment of the present invention.

[0050] Figure 3 A human body-respiratory system coupling numerical model according to an embodiment of the present invention.

[0051] Figure 4 The figure is a location diagram of monitoring points and a monitoring plane according to an embodiment of the present invention.

[0052] Figure 5 FIG. 1 is a diagram showing the spatial distribution of carbon monoxide leakage and diffusion at different moments according to an embodiment of the present invention.

[0053] Figure 6 FIG. 1 is the spatial distribution of leakage and diffusion of chlorine gas at different moments according to an embodiment of the present invention.

[0054] Figure 7 The figure shows the evolution law of carbon monoxide mass concentration distribution at the human breathing zone height according to one embodiment of the present invention.

[0055] Figure 8 The figure shows the evolution law of the chlorine mass concentration distribution in the human breathing area according to one embodiment of the present invention.

[0056] Fig. 9 The figure shows the evolution law of carbon monoxide mass concentration distribution inside the human respiratory system according to one embodiment of the present invention.

[0057] Fig.10 The figure shows the evolution law of chlorine gas mass concentration distribution inside the human respiratory system according to one embodiment of the present invention.

[0058] Fig.11 The figure shows the evolution law of carbon monoxide mass concentration distribution inside the human respiratory system according to one embodiment of the present invention.

[0059] Fig.12 The figure shows the evolution law of chlorine gas mass concentration distribution inside the human respiratory system according to one embodiment of the present invention.

[0060] Fig.13 Graph showing the variation pattern of carbon monoxide mass concentration at each monitoring point at different times according to an embodiment of the present invention.

[0061] Fig.14 The figure shows the variation pattern of chlorine gas mass concentration at each monitoring point at different times according to an embodiment of the present invention.

[0062] Fig.15 The risk of injury to a human body due to inhalation of carbon monoxide is predicted according to an embodiment of the present invention.

[0063] Fig.16 The risk of injury to the human body caused by inhalation of chlorine gas is predicted according to one embodiment of the present invention. DETAILED DESCRIPTION

[0064] The embodiments of the present application are described in detail below. Examples of the embodiments are shown in the attached Figure 1-16 , wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0065] The following describes, with reference to the accompanying drawings, a method for simulating human respiratory system exposure and assessing injury risk in a toxic gas leakage scenario in a closed space proposed according to an embodiment of the present invention. First, the method for assessing human respiratory system injury risk in a toxic gas leakage scenario proposed according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0066] Figure 1 The figure is a flow chart of a method for assessing the risk of human respiratory system damage in a toxic gas leakage scenario in a closed space according to the present invention.

[0067] The establishment of the closed space geometric model took a certain laboratory as the prototype, constructed a three-dimensional numerical model of this scene, and introduced the human body-respiratory system coupling numerical model, and then divided the above-mentioned area into computational grids to build the computational model; the human body-respiratory system coupling numerical model uses a laser three-dimensional scanner to repeatedly scan a warm-body mannequin fixed in different postures to obtain the torso shape, and embeds the real human respiratory system geometric structure obtained by CT scanning, and finally post-processes it through supporting software to obtain an accurate three-dimensional model.

[0068] To simulate the leakage and diffusion scenario of toxic gas and set up toxic gas monitoring points, taking into account the physical and chemical properties and typicality of the gas, carbon monoxide and chlorine, two toxic gases with density less than and greater than air, were selected for leakage and diffusion simulation.

[0069] In order to explore the spatiotemporal evolution of the diffusion of toxic gas in the laboratory after leakage, monitoring points and monitoring planes were set up at different locations in the closed space to monitor and calculate the concentration and other parameters of toxic gas at the corresponding locations at different times.

[0070] Select appropriate turbulence model and calculation boundary conditions. The flow field area discussed in this invention is indoor space. The flow field in this area is usually dominated by turbulence. The calculation efficiency of RNG k–ε turbulence model is high and accurate.

[0071] The temporal and spatial evolution of the concentration of toxic gas leakage was obtained through simulation, and the leakage time was divided into four stages from 0 to 180 seconds. The distribution of the two gases in space in these four stages was compared and analyzed to explore the propagation law after the leakage occurred. By comparing and analyzing the volume rendering images of gas leakage fractions at different times, it was found that the diffusion path of toxic gas leakage would be affected by factors such as density and obstacles.

[0072] The numerical analysis of the concentration of the human respiratory area and the concentration of each part of the human respiratory system, the 1.6m height plane is selected for analysis and display in the simulation of the present invention, which can be used to judge the concentration of toxic gases and possible damage to the test personnel exposed to the environment. On this basis, combined with the change law of the exposure dose of toxic gases in various areas of the human respiratory system, the gas mass fraction distribution cloud diagram of the 1.6m height plane at different times within 180s after the leakage of carbon monoxide and chlorine is compared and analyzed to obtain the conclusion.

[0073] The human body has a dose-response relationship to toxic gases. Different carbon monoxide gas concentrations and different chlorine gas concentrations have different effects on the human body. Generally speaking, the higher the concentration, the greater the damage.

[0074] For the risk assessment of human inhalation injury, nine monitoring points at different locations in the numerical model were analyzed to obtain the changes in the risk of the respiratory system of personnel over time, and the damage suffered by the test personnel at different exposure times in the toxic gas leakage scenario and the reasonable evacuation time were calculated.

[0075] The evaluation system of the embodiment of the present invention can solve the demand for low-cost and high-precision quantification of human respiratory system exposure simulation and injury risks in laboratory toxic gas leakage scenarios, and can be applied to the design of laboratory protection measures and emergency plans to improve the accuracy of risk assessment and better ensure personnel safety.

[0076] Embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0077] The following describes a method for assessing the risk of human respiratory system damage in a laboratory toxic gas leakage scenario according to an embodiment of the present invention with reference to the accompanying drawings.

[0078] Figure 1 Schematic diagram of the flow structure of an embodiment of the present invention; Figure 1 As shown in the figure, the risk assessment method for human respiratory system injury in the toxic gas leakage scenario in the laboratory includes: establishing a closed space geometric model; simulating the toxic gas leakage and diffusion scenario and setting up toxic gas monitoring points; selecting a suitable turbulence model and calculating boundary conditions; deriving the spatiotemporal evolution law of the toxic gas leakage concentration through simulation and conducting numerical analysis of the height plane concentration in the human respiratory area and the concentration in various parts of the human respiratory system, and then combining the dose-response relationship of the human body to toxic gases to derive the risk assessment of human inhalation injury.

[0079] Establishment of closed space geometric model:

[0080] like Figure 2 As shown, the present invention constructs a three-dimensional numerical model. The dimensions of the laboratory are 8.0m×7.8m×3.5m (length×width×height), with a total volume of 218.4m 3 The laboratory interior includes facilities such as fume hoods, lockers, air conditioners, reagent tables, laboratory tables, wash basins, freezers and gas cylinders.

[0081] ANSYS 2022R1 series software was used to build the numerical model, and Space Claim software was used to build the geometric model. In order to more accurately monitor the value of human inhalation exposure and take into account the impact of human factors on the diffusion pattern of toxic gas leakage, a numerical human model was introduced into the simulation scenario. The height of the human model was 1.7m and the height of the breathing area was 1.6m.

[0082] When using ICEM-CFD software to divide the unstructured tetrahedral mesh, local encryption was performed on the leakage source, doors, windows and other vents to ensure the accuracy of the simulation results. The number of mesh elements used for formal calculations was finally determined through mesh independence test.

[0083] Simulate the toxic gas leakage and diffusion scenario and set up toxic gas monitoring points:

[0084] Taking into account the physical and chemical properties and typicality of the gas, carbon monoxide and chlorine, two toxic gases with density less than and greater than air, were selected for leakage and diffusion simulation. The toxic gas leaked through the test instrument in the fume hood, and the leakage source was located at the 25mm circular hole on the top of the test instrument. According to the Abel-Nobel state equation, energy conservation equation and isentropic process hypothesis, the leakage rate u0 of the toxic gas at the leakage hole is

[0085]

[0086] Where K is the adiabatic index, J / (kg·K); u1 is the specific volume, m 3 / kg; P1 and P a are the pressure at the leakage hole and the surrounding gas pressure, Pa respectively; b is the specific volume correction term.

[0087] The above formula is used to calculate the leakage rate of different gases when the leakage aperture is 25mm. Considering the control of variables when simulating different gases, 100m / s is set as the leakage rate of toxic gases. In order to explore the spatiotemporal evolution of the leakage and diffusion of toxic gases in the laboratory after leakage, monitoring points and monitoring planes are set at different locations in the closed space to monitor and calculate the concentration of toxic gases at corresponding locations at different times and other parameters, such as Figure 3 , Figure 4 shown.

[0088] Select appropriate turbulence model and calculation boundary conditions:

[0089] The flow field area discussed in the present invention is an indoor space, where the flow field is usually dominated by turbulence. The RNG k-ε turbulence model in the Reynolds-averaged Navier-Stokes equations (RANS) performs well in simulating indoor turbulence. The basis of the RANS method is the application of Reynolds decomposition, which expresses the solution variables appearing in the transient Navier-Stokes equations as the sum of an average component (ensemble average or time average) and a pulsating component.

[0090]

[0091]

[0092] Where u i is the average axial velocity, m / s; u j is the radial average velocity, m / s; x i is the axial coordinate; x i is the radial coordinate; p is the pressure, Pa; t is the time, s; ρ is the fluid density, kg / m 3; j, j represent the components in the i-th and j-th directions respectively.

[0093] In order to keep the above equation closed, it is necessary to establish a Reynolds stress model and make assumptions about the Reynolds stress. The eddy viscosity hypothesis proposed by Boussinesq is widely used, in which the Reynolds stress is expressed as

[0094]

[0095] Where u i is the average axial velocity, m / s; u j is the radial average velocity, m / s; δ ij is the Kronecker function. When i=j, δ ij =1, otherwise δ ij =0;v T is the eddy viscosity coefficient, which can be used to calculate the Reynolds stress and can be written as

[0096] v T =C μ k 2 / ε

[0097] Where k is the turbulent kinetic energy, m 2 / s 2 ; ε is the turbulent dissipation rate, m 2 / s 3 ; C μ is a constant. The closed Reynolds stress model can achieve a more accurate solution of turbulence statistics with less calculation. The continuity equation and momentum equation of the RNG k-ε turbulence model are as follows

[0098]

[0099]

[0100] Where G k and G b are the turbulent kinetic energy due to the average velocity gradient and buoyancy, J / kg; Y m represents the contribution of wave expansion in compressible turbulence to the total dissipation rate; α k and α ε are the reciprocals of the turbulent Prandtl numbers of k and ε respectively; S k and S ε is a user-defined source term; C 1ε , C 2ε , C 3ε is a constant; eff stands for "effective" and is used to indicate the effective viscosity coefficient.

[0101] The Reynolds stress constants k and ε in the RNG k-ε turbulence model are calculated as follows

[0102]

[0103]

[0104]

[0105] Where u is the average velocity, m / s; I is the turbulence intensity; Re is the Reynolds number; C3 is a constant; l is the characteristic length, m.

[0106] The door of the laboratory was set as a ventilation outlet, the ambient wind speed was set to the annual average wind speed of 2.61 m / s in Nanjing, where the laboratory is located, and the windows were set to free outflow boundary conditions. The SIMPLEC algorithm was used to achieve the coupling between pressure and velocity, and transient calculations were used to simulate the diffusion law of toxic gas in the laboratory within 180 seconds after the leakage. The initial ambient temperature was set to 25°C and the atmospheric pressure was 1.01×10 5 Pa.

[0107] The simulation results show the temporal and spatial evolution of the concentration of toxic gas leakage and the numerical analysis of the concentration in the human respiratory area and in various parts of the human respiratory system:

[0108] Figure 5 , 6 Figures 7 and 8 show the mass concentration distribution of carbon monoxide and chlorine in the spatial range at different times. The leakage time 0-10s is the initial stage, 10-30s is the warning stage, 30-60s is the emergency stage, and 60-180s is the evacuation stage. By comparing and analyzing the distribution of the two gases in space in these four stages, the purpose is to explore the propagation law after the leakage occurs. By comparing and analyzing the volume rendering images of gas leakage fractions at different times, it is analyzed that the diffusion path of toxic gas leakage will be affected by factors such as density and obstacles. Fig. 9 , 10 Figures 11 and 12 show the evolution of the concentration distribution of carbon monoxide and chlorine in various areas of the respiratory system at different times. By comparing the changes in concentrations in various areas of the respiratory system at different times, the risk changes of test personnel after the leak occurred were explored.

[0109] like Fig.13 , 14As shown in the figure, with air density as the dividing line, gases with a density less than air diffuse to the upper half of the laboratory model after leakage, while gases with a density greater than air diffuse to the lower half of the laboratory model after leakage. When there are obstacles in the propagation path of toxic gases, their diffusion path will be significantly changed, tending to diffuse in the direction without obstacles. Since the density of carbon monoxide is less than that of air, its diffusion is mainly distributed in the upper half of the laboratory. Indoor facility obstacles are limited by height factors and are mostly present in the lower half of the laboratory model. Therefore, in theory, toxic gases with a density less than that of air are relatively less affected by obstacles when leaking and diffusing.

[0110] Under the same initial boundary conditions, chlorine gas can basically cover the laboratory space after 30 seconds of leakage, while carbon monoxide leakage takes 90 seconds to cover the same space. This shows that in the process of toxic gas leakage and diffusion, the influence of obstacles may not significantly reduce the speed of toxic gas diffusion along the straight line in the space.

[0111] The present invention sets a total of 7 monitoring planes for analysis, among which the plane at a height of 1.6m above the breathing area of ​​the test personnel's face is the most representative and can be used to determine the concentration of toxic gases that the test personnel are exposed to in this environment and the possible damage they may suffer. Figure 7 , 8 The mass concentration distribution of carbon monoxide and chlorine gases in the height plane of the human breathing area at different times is shown.

[0112] By comparing and analyzing the gas mass fraction distribution cloud diagrams at different time points within 180s after the leakage of carbon monoxide and chlorine at a height of 1.60m, the following conclusions were found:

[0113] After carbon monoxide and chlorine leak, both gases will gather near the wall. Within the space, the degree of aggregation of chlorine is generally higher than that of carbon monoxide. In addition, the aggregation of carbon monoxide shows obvious spatial differences, which is specifically manifested in that the gas concentration on the left side of the leakage source is higher than that on the right side. At the height of the human breathing area, the diffusion trends of the two gases show certain similarities. The gas begins to diffuse from the leakage source, first gathering on the left and right walls, and then gradually diffuses to the entire plane. According to the mass fraction distribution cloud map, it can be judged that when the leakage diffuses at the same height, the propagation trend of the two gases is not significantly different. The density of toxic gases may have a significant effect on the diffusion rate. The density of carbon monoxide is 1.25kg / m 3 , and the density of chlorine is 3.21kg / m 3 Due to the large difference in density between the two, the diffusion rate of chlorine is significantly faster than that of carbon monoxide in the same height plane and space range due to the influence of density.

[0114] Dose-response relationship of human body to toxic gases:

[0115] Table 1 and Table 2 are the dose-response relationships of the human body to toxic gases according to an embodiment of the present invention, reflecting the effects of different concentrations of carbon monoxide and chlorine on the human body. Carbon monoxide is very stable in the atmosphere, easy to diffuse and migrate, and due to the numerous sources of carbon monoxide pollution, the public is at high risk of being exposed to medium and low mass concentrations of carbon monoxide. In addition, carbon monoxide is colorless and odorless, and leakage is not easy to be detected in time. Acute carbon monoxide poisoning is currently the disease with the highest morbidity and mortality among acute occupational poisoning in my country. In contrast, chlorine is a yellow-green irritating gas with a density 2.5 times that of air. It can cause severe damage to the respiratory tract and has a strong irritating effect on the eye mucosa and skin. Chlorine poisoning usually occurs in the workplace and is a systemic disease mainly characterized by acute respiratory damage due to the inhalation of a large amount of chlorine in a short period of time.

[0116] Table 1 Effects of different carbon monoxide concentrations on the human body

[0117] <![CDATA[Carbon monoxide mass concentration / (mg·m -3 )]]> Effects on the human body 62.5 Permissible exposure concentration, exposure for 8 hours 250 Causes a mild frontal headache within 2 to 3 hours 500 Headache and vomiting after 1 to 2 hours, dizziness after 2.5 to 3.5 hours 1000 Headache, dizziness, vomiting within 45 minutes, coma or death within 2 hours 2000 Headache, dizziness, vomiting within 20 minutes, coma and death within 1 hour 4000 Headache and vomiting within 5 to 10 minutes, unconsciousness within 30 minutes, and risk of death 8000 Headache and dizziness within 1 to 2 minutes, unconsciousness within 10 to 15 minutes, and risk of death 16000 Immediate loss of consciousness, risk of death within 1 to 3 minutes

[0118] Table 2 Effects of different chlorine concentrations on human body

[0119] <![CDATA[Chlorine mass concentration / (mg·m -3 )]]> Effects on the human body 0.06 Human olfactory threshold concentration for chlorine 3 The human sense of smell is obviously stimulated 11.6 The human body cannot tolerate it and causes delayed damage to the human body 120～180 30-60 minutes can cause toxic pneumonia and pulmonary edema 3000 Inhaling a few puffs can be life-threatening. Extremely high concentrations can stimulate the vagus nerve and cause reflex respiratory and cardiac arrest. 30000 General filter-type gas masks have no protective effect, and exposure to this environment is life-threatening

[0120] Human inhalation injury risk assessment:

[0121] Fig.15 , 16 This figure is a prediction of the risk of respiratory damage to the human body to toxic gases according to an embodiment of the present invention. The figure reflects the change of personnel risk over time at the leakage site such as a laboratory. The present invention sets a total of 9 monitoring points at different positions in the numerical model for analysis. According to the architectural layout of the laboratory, these 9 monitoring points are divided into two groups. The first group consists of monitoring points 1, 2, 3, 4, and 9, representing the two main planes that cross at the center of the laboratory; the second group consists of monitoring points 5, 6, 7, and 8, representing the 4 corners of the laboratory. By comparing and analyzing the mass concentration of toxic gases at each monitoring point at different times, and combining the dose-response relationship data of the human body to toxic gases, the damage suffered by the test personnel at different exposure times in the toxic gas leakage scenario and the reasonable evacuation time can be calculated.

[0122] By comparing and analyzing the average mass concentration curves of the two gases at the z = 1.6m plane during leakage and diffusion, it is found that under the same boundary conditions, the leakage of the two gases is significantly different, and the leakage of chlorine is much greater than that of carbon monoxide. According to the dose-response relationship, the mass concentration of chlorine reaches 3000mg / m 3 When the test personnel inhale a few breaths, their lives will be endangered; and the mass concentration of carbon monoxide reaches 4000mg / m 3When the concentration reaches 8000mg / m 3 When exposed to chlorine, headache and dizziness will occur within 1 to 2 minutes, and unconsciousness may occur within 10 to 15 minutes, which also poses a risk of death. Given the high toxicity and rapid leakage characteristics of chlorine, if there are both leakage sources in the laboratory, its protective equipment should meet the protection standards for chlorine leakage. Wearing a filter-type gas mask can reduce the risk of death.

[0123] Further, the reasons for the fluctuation of gas mass concentration at each monitoring point are analyzed. Taking carbon monoxide as an example, monitoring point 5 is located on the left side of the leakage source, close to the leakage source. At the same time, after the toxic gas leaks, it is hindered by the human body and diffuses to both sides. The diffusion trend of the two gases when they leak can be intuitively obtained. According to the simulation results, 10s after the leakage, the toxic gas mainly gathers around the leakage source and on both sides of the human body, and the gas concentration near the monitoring point 5 is more obvious. Since the leakage source is set as a continuous and uniform leakage, the concentration at monitoring point 5 continues to increase, showing a fluctuating rise. Within a few seconds after the leakage, a small amount of toxic gas diffuses to monitoring point 9; at 30s, a large amount of toxic gas diffuses to monitoring point 9, and the mass concentration there suddenly increases. Subsequently, affected by the indoor airflow, the gas mass concentration at monitoring point 9 shows a large fluctuation; after 90s, its mass concentration change is basically consistent with the other monitoring points in the space, indicating that the toxic gas has diffused to the entire laboratory at this time, and its mass concentration change is affected by the wind speed of the ventilation outlet. For chlorine, the reason for the fluctuation of mass concentration at monitoring point 9 is the same as that of carbon monoxide, and the two can mutually support the relative consistency of the spread of toxic gases in the laboratory space. In addition, the changes in mass concentration of chlorine at each monitoring point tend to be consistent, indicating that under the same leakage conditions, the diffusion rate of chlorine may be faster.

[0124] Based on the simulation results of the present invention, it is recommended to set concentration alarms in representative areas such as near the test instrument (i.e., monitoring points 1, 5, and 6), the center of the laboratory (i.e., monitoring point 9), the laboratory exit (i.e., monitoring point 7), and the laboratory vent (i.e., monitoring point 4). The lower limit parameter of the concentration alarm can be set based on the dose-response relationship after the two gases. In similar scenarios, it is recommended to set the lower limit of the carbon monoxide concentration alarm to 500 mg / m3 and the lower limit of the chlorine concentration alarm to 120 mg / m3. The specific installation also needs to be combined with the relevant standards such as the "Petrochemical Combustible Gas and Toxic Gas Detection Alarm Design Standard" (GB / T50493-2019), and comprehensively detect the actual gas density, environmental wind direction and other factors to determine the installation location of the alarm.

[0125] For the transport and deposition of toxic gases in the human respiratory system, regional exposure dose data can also be obtained through simulation results.

[0126] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0127] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0128] For those skilled in the art, the specific meanings of the terms in the present invention can be understood according to specific circumstances.

[0129] In the description of this specification, reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention.

[0130] In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0131] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for simulating human respiratory system exposure and assessing injury risk in a toxic gas leakage scenario in a closed space, characterized in that: Including in order: S1. Establishment of closed space geometric model; S2. Simulate the scene of toxic gas leakage and diffusion and set up toxic gas monitoring points; S3. Select appropriate turbulence model and calculation boundary conditions; S4. The temporal and spatial evolution of the concentration of toxic gas leakage is obtained through simulation; S5. Conduct numerical analysis of the concentration in the plane at the height of the human respiratory area and the concentration in various parts of the human respiratory system; S6. Based on the dose-response relationship of the human body to toxic gases, a risk assessment of human inhalation injury is derived.

2. The method for simulating human respiratory system exposure and assessing injury risk in a toxic gas leakage scenario in a closed space according to claim 1, characterized in that: In step S1, the closed space geometric model is established by setting the size and space of the closed space, as well as the objects built in the closed space, constructing a three-dimensional numerical model, and introducing a human-respiratory system coupling numerical model. The human-respiratory system coupling numerical model is a simulated test person, and the height of the simulated test person's facial breathing area is set; Divide the above enclosed space into computational grids and build a computational model; Set the height of the simulated test personnel's facial breathing area to 1.5-1.7m.

3. The method for simulating human respiratory system exposure and assessing injury risk in a toxic gas leakage scenario in a closed space according to claim 1, characterized in that: In step S2, a toxic gas leakage and diffusion scenario is simulated, and different types of toxic gases are selected for leakage and diffusion simulation by comprehensively considering the physical and chemical properties and typicality of the gas; According to the Abel-Nobel state equation, energy conservation equation and isentropic process assumption, the leakage velocity u0 of the toxic gas at the leak hole is: Where κ is the adiabatic index, J / (kg·K); υ1 is the specific volume, m 3 / kg; P1 and P a are the pressure at the leakage hole and the surrounding gas pressure, Pa respectively; b is the specific volume correction term.

4. The method for simulating human respiratory system exposure and assessing injury risk in a toxic gas leakage scenario in a closed space according to claim 1, characterized in that: The toxic gas is carbon monoxide and / or chlorine.

5. The method for simulating human respiratory system exposure and assessing injury risk in a toxic gas leakage scenario in a closed space according to claim 1, characterized in that: In step S3, in order to explore the spatiotemporal evolution of the leakage and diffusion of toxic gas in the laboratory after leakage, monitoring points and monitoring planes are set at different positions in the closed space, the concentration of toxic gas at the corresponding positions at different times is monitored and calculated, and the RNG k–ε turbulence model of the appropriate turbulence model and the calculation boundary conditions are selected; By expressing the solution variables appearing in the transient Navier-Stokes equations as the sum of an average component and a pulsating component; the average component is an ensemble average or a time average; Where u i is the average axial velocity, m / s; u j is the radial average velocity, m / s; x i is the axial coordinate; x j is the radial coordinate; p is the pressure, Pa; t is the time, s; ρ is the fluid density, kg / m 3 ; i and j represent the components in the i-th and j-th directions respectively.

6. The method for simulating human respiratory system exposure and assessing injury risk in a toxic gas leakage scenario in a closed space according to claim 5, characterized in that: In order to keep the above equation closed, it is necessary to establish a Reynolds stress model and make assumptions about the Reynolds stress; the Reynolds stress is expressed as Where u i is the average axial velocity, m / s; u j is the radial average velocity, m / s; δ ij is the Kronecker function. When i=j, δ ij =1, otherwise δ ij =0; ν T is the eddy viscosity coefficient, which is used to calculate the Reynolds stress and is ν in the k–ε model T =C μ k 2 / ε Where k is the turbulent kinetic energy, m 2 / s 2 ; ε is the turbulent dissipation rate, m 2 / s 3 ; C μ is a constant; the closed Reynolds stress model can achieve accurate solution of turbulence statistics with less calculation. The continuity equation and momentum equation of the RNG k–ε turbulence model are as follows Where G k and G b are the turbulent kinetic energy due to the average velocity gradient and buoyancy, J / kg; Y m represents the contribution of wave expansion in compressible turbulence to the total dissipation rate; α k and α ε are the reciprocals of the turbulent Prandtl numbers of k and ε respectively; S k and S ε is a user-defined source term; C 1ε , C 2ε , C 3ε is a constant; eff stands for "effective" and is used to indicate the effective viscosity coefficient; The Reynolds stress constants k and ε in the RNG k–ε turbulence model are calculated as follows Where u is the average velocity, m / s; I is the turbulence intensity; Re is the Reynolds number; C ε is a constant; l is the characteristic length, m; The closed space has doors and windows, where the door is set as the exit, i.e., the vent, and the ambient wind speed is set, and the window is set as the free outflow boundary condition; the SIMPLEC algorithm is used to achieve the coupling between pressure and velocity, and transient calculation is used to simulate the diffusion law of toxic gas leakage in the closed space and the exposure law of the human respiratory system; The ambient wind speed is the annual average wind speed at the location of the enclosed space.

7. The method for simulating human respiratory system exposure and assessing injury risk in a toxic gas leakage scenario in a closed space according to claim 1, characterized in that: In step S4, the spatiotemporal evolution law of the toxic gas leakage concentration is obtained through simulation. The initial leakage time is taken as the starting point, the leakage duration is set, and the leakage duration is divided into several stages. The spatial distribution of the gas in each stage is analyzed to explore the propagation law after the leakage occurs; by comparing and analyzing the volume rendering images of the gas leakage fractions at different times, it is analyzed that the diffusion path of the toxic gas leakage will be affected by the factors of density and obstacles; The leakage duration is set to 180s, which is divided into 4 stages.

8. The method for simulating human respiratory system exposure and assessing injury risk in a toxic gas leakage scenario in a closed space according to claim 1, characterized in that: In step S5, the planar concentration at the height of the human breathing zone is numerically analyzed, and the planar concentration at the height is analyzed and displayed in combination with the height of the simulated test personnel's facial breathing zone, which can be used to determine the concentration of toxic gases to which the test personnel are exposed in the environment and the possible injuries they may suffer; the results are obtained by comparing and analyzing the gas mass fraction distribution at different times within the predetermined leakage time of the toxic gas in the predetermined height plane.

9. The method for simulating human respiratory system exposure and assessing injury risk in a toxic gas leakage scenario in a closed space according to claim 1, characterized in that: In step S6, the risk of human inhalation injury is assessed by analyzing multiple monitoring points at different locations in the numerical model to obtain the change of respiratory system risk over time, and calculate the damage suffered by the test personnel at different exposure times in the toxic gas leakage scenario and the reasonable evacuation time.

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