Numerical calculation method for spatial flow diffusion characteristics of high-boiling-point chemical gas extinguishing agent

Abstract

The invention provides a numerical calculation method for spatial flow diffusion characteristics of a high-boiling-point chemical gas extinguishing agent, and relates to the field of correlation research of gas-liquid two-phase flow characteristics of extinguishing agents and the field of CFD numerical simulation calculation. According to the method, numerical calculation is carried out on the high-boiling-point chemical gas extinguishing agent, and the method comprises the steps that physical and mathematical models of flowing diffusion of the high-boiling-point chemical gas extinguishing agent are built, calculation boundary conditions and physical property parameters are set, and numerical calculation is carried out by optimizing a phase change model. According to the method, Fluent commercial software is adopted, the space flow diffusion process of the fire extinguishing agent is calculated based on a pressure base solver under an Euler-Lagrange model, and a change cloud chart of the steam mass fraction, the space temperature and the like of the fire extinguishing agent is obtained; the influence rules of different influence factors on the gasification characteristics of the fire extinguishing agent are compared according to the difference between the steam quality gasification ratio and the steam quality gasification increasing ratio. The method can provide theoretical guidance for related research and application of the flow diffusion characteristics of the high-boiling-point gas extinguishing agent.

Description

Technical Field

[0001] The invention relates to the research field related to the gas-liquid two-phase flow characteristics of fire extinguishing agents and the CFD numerical simulation calculation field, and specifically to a numerical calculation method for the spatial flow diffusion characteristics of a high-boiling-point chemical gas fire extinguishing agent. Background Art

[0002] High boiling point gas fire extinguishing agent refers to a fire extinguishing agent that is liquid at room temperature and can be quickly vaporized and extinguish fire in the form of full flooding after release; it has low ODP, GWP and ALT values, and has high fire extinguishing efficiency. However, due to the high boiling point of the fire extinguishing agent, it is liquid at room temperature and is not easy to vaporize, which seriously affects its full fire extinguishing ability. At present, domestic and foreign scholars mainly use experiments to study the flow and fire extinguishing performance of this type of fire extinguishing agent, but due to the limitation of measurement methods, it is difficult to carry out very precise measurement and analysis of the dynamic process of its flow and diffusion, and numerical simulation methods can make up for the shortcomings of experimental research in this regard. Therefore, the study of simulation calculation methods for the spatial flow and diffusion characteristics of high boiling point chemical gas fire extinguishing agents has important theoretical significance for guiding the research and application of high boiling point gas fire extinguishing agents. Summary of the invention

[0003] The present invention is based on the discrete phase (DPM) model, constructs a flow diffusion model of the fire extinguishing agent in the fluid domain, selects the RNGk-ε turbulence model and the component transport model, and opens the energy equation; uses the evaporation boiling model to calculate the phase change process of the droplet, uses the TAB breakup model to calculate the breakup process of the droplet, and uses the UDF function to define the change function of the droplet saturated vapor pressure with temperature and the binary diffusion coefficient between the fire extinguishing agent vapor and the air. The simulation calculation method of the spatial flow diffusion characteristics of the high boiling point chemical gas fire extinguishing agent provided by the present invention can simulate and calculate the flow diffusion characteristics of the high boiling point chemical gas fire extinguishing agent under different operating conditions.

[0004] At the same time, the present invention designs an evaluation method for the spatial flow and diffusion characteristics of high-boiling-point chemical gas fire extinguishing agents. By analyzing parameters such as the fire extinguishing agent vapor and temperature distribution cloud map in the fluid domain and the rate of change of vapor mass, the spatial flow and diffusion characteristics of the fire extinguishing agent under different operating conditions are evaluated. The correlation between the effects of different operating conditions on the flow and diffusion of the fire extinguishing agent is analyzed through numerical fitting. This can provide certain theoretical guidance for the study of the spatial flow and diffusion characteristics of the fire extinguishing agent.

[0005] The object of the present invention is to provide a numerical calculation method for the spatial flow diffusion characteristics of a high boiling point chemical gas fire extinguishing agent, comprising the following steps:

[0006] S1: According to the characteristics of the full flooding fire extinguishing form of gas fire extinguishing agent, the corresponding flow field area geometric model is constructed, and the mesh is divided, and the mesh file is imported into the Fluent software;

[0007] S2: Establish a mathematical model based on the flow characteristics of high boiling point chemical gas fire extinguishing agents;

[0008] S3: Specify the corresponding boundary conditions according to the spatial flow characteristics of the high boiling point chemical gas extinguishing agent;

[0009] S4: setting the physical property parameters of the high boiling point chemical gas fire extinguishing agent liquid and its vapor, setting the discretized droplets, and assigning initial state information to the droplets;

[0010] S5: Calculate the resultant force on the discretized droplets of high-boiling-point chemical gas extinguishing agent, set the droplet phase change model, breakup model and resistance coefficient, and use UDF to set the change function of the droplet saturated vapor pressure with temperature and the binary diffusion coefficient between the extinguishing agent vapor and air.

[0011] S6: Carry out simulation calculation of the spatial flow of high-boiling-point chemical gas fire extinguishing agents to study the spatial release flow and diffusion characteristics of high-boiling-point chemical gas fire extinguishing agents.

[0012] Preferably, in S1, the geometric model of the fluid domain is a cylinder with a diameter of 1m and a height of 4m, structured meshing is performed, and O-shaped segmentation is performed, the middle area is locally encrypted, the corresponding number of nodes is set, and the final number of calculated meshes is 180,000.

[0013] Preferably, in S2, the RNG k-ε model is selected. The flow speed of the fire extinguishing agent in the fluid domain is relatively fast, which will produce certain turbulent disturbances. Compared with the standard k-ε turbulence model used by predecessors, the RNG k-ε turbulence model corrects the turbulent viscosity and takes into account the swirl flow in the average flow, so that the model can more accurately describe the complex shear flow. Compared with the SST k-ω turbulence model used by predecessors, it is more suitable for the flow of high Reynolds number fluids and more in line with the actual flow of fire extinguishing agents. The DPM model can consider the interaction between particles and the continuous phase, and better calculate the flow trajectory of particles and other information; in addition, the DPM model provides 5 types of particles, among which Droplet can well simulate the gasification process of droplets. The component transport model can model the mixing of chemical components by solving the convection and diffusion conservation equations of each component. In the process of calculating the flow of the fire extinguishing agent, the vapor mass fraction of the fire extinguishing agent in the fluid domain can be calculated by the component transport model.

[0014] Preferably, in S3, the present invention studies the flow and diffusion characteristics of fire extinguishing agent droplets in space. After studying the influence of environmental factors on the flow and diffusion of the fire extinguishing agent, the inlet boundary condition is set as the velocity inlet, and the remaining boundaries are set as the pressure outlet. The discrete phase and its interaction form are of the escape type, and a pressure-based solver and a SIMPLE algorithm are used. The discrete method adopts a second-order upwind scheme to perform transient calculations.

[0015] Preferably, in S4, the particle size of the droplets can adopt uniform distribution, double R distribution, etc. The particle size is set according to actual conditions, and the physical properties of the fire extinguishing agent droplets, vapor and air can be obtained through the National Institute of Standards and Technology (NIST) database.

[0016] Preferably, in S5, gravity, temperature-related latent heat and crushing force are considered to more accurately describe the spatial flow and diffusion process of the fire extinguishing agent. To accurately calculate the motion trajectory of the droplet, the resultant force on the droplet is calculated by the following formula: Where m p is the droplet mass, is the continuous phase velocity, is the droplet velocity, ρ is the continuous phase density, ρ p is the droplet density, is the additional force, is the resistance; τ r is the relaxation time of the droplet, calculated as Where μ is the viscosity of the continuous phase, d p is the droplet size, Re 1 is the relative Reynolds number, calculated as:

[0017] In addition, in order to accurately simulate the droplet vaporization process, the evaporation boiling model is used to calculate the phase change of the droplets, and the heat balance equation is as follows:

[0018] Among them, c p is the specific heat capacity of the droplet, T p is the droplet temperature, h is the convective heat transfer coefficient, T ∞ is the continuous phase temperature, is the latent heat of vaporization. The vaporization process involves three different stages: inert heat transfer, evaporation, and boiling. The droplets are vaporized at the corresponding stage according to the conditions met. The driving force in the droplet vaporization process comes from the saturated vapor pressure. The UDF function is used to define the saturated vapor pressure within the temperature range of the fire extinguishing agent calculation. The binary diffusion coefficient between gases is also one of the factors that affect the gas dispersion. The UDF function is used to define the binary diffusion coefficient related to the continuous phase temperature.

[0019] Considering the secondary fragmentation during the gasification process of the extinguishing agent, the fragmentation control equation under the TAB model is used

[0020]

[0021] In the formula, y 0 =y(0), The particle size and velocity of the daughter droplets after fragmentation are determined by the energy of the mother droplet, and the particle size and velocity of the daughter droplets are calculated by the following formula:

[0022] Among them, ρ g and ρ l are the densities of the continuous and discrete phases, u is the relative velocity of the droplet, r is the undisturbed droplet radius, σ is the droplet surface tension, and u l is the droplet viscosity, C k , C b and C F are dimensionless constants, taking values ​​of 8, 5, and K is the ratio of the total oscillation energy to the fundamental mode energy, and y is the critical ratio of the distortion growth to the droplet radius.

[0023] The accuracy of the droplet drag coefficient determines the accuracy of the droplet flow model. The drag coefficient selects the Dynamic drag model, which is compatible with the TAB model for the breakup process. In this model, the droplet is assumed to be spherical, and the specific value is related to the Reynolds number (Re). The drag coefficient of this model (C D )for

[0024]

[0025] Preferably, in S6, during the flow of the fire extinguishing agent, as the heat between the gas and liquid phases is transferred, the phase change continues, and Fluent is used to monitor the vapor mass flow rate in the fluid domain; the results of the simulation calculation are data processed, and the spatial flow diffusion characteristics of the high-boiling-point chemical gas fire extinguishing agent under different operating conditions are evaluated by the vapor mass flow rate change rate of the fire extinguishing agent in the fluid domain and the droplet vaporization mass ratio, and the correlation between the influencing factors and the flow diffusion characteristics of the high-boiling-point chemical gas fire extinguishing agent is analyzed by numerical fitting.

[0026] The numerical calculation method of the spatial flow diffusion characteristics of a high boiling point chemical gas fire extinguishing agent of the present invention has the following beneficial effects:

[0027] The present invention performs numerical simulation calculations by model construction, setting calculation parameters, and optimizing the phase change model, calculates the vapor mass change rate and vapor gasification mass ratio of the fire extinguishing agent under different influencing factors, and obtains the influence law of the influencing factors on the gasification of the high-boiling-point chemical gas fire extinguishing agent;

[0028] The numerical calculation results of the present invention show that the numerical calculation method of the high-boiling-point gas fire extinguishing agent can better calculate the flow trajectory of the fire extinguishing agent after it is released, and environmental factors and physical and chemical properties have an important influence on the flow and diffusion of the fire extinguishing agent. When gasified at the boiling rate, the vapor mass flow rate and the droplet gasification mass ratio of the fire extinguishing agent are greatly improved compared with the evaporation gasification; the present invention can effectively calculate the flow and diffusion process of the high-boiling-point chemical gas fire extinguishing agent, can more accurately react to the flow and diffusion characteristics of the fire extinguishing agent, and can provide certain theoretical guidance for the spatial flow and diffusion characteristics of the fire extinguishing agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A flow chart of the present invention is given.

[0030] Figure 2 A geometrical model diagram of an embodiment is given.

[0031] Figure 3 The variation process of the vapor mass fraction cloud diagram during the flow of fire extinguishing agent is given.

[0032] Figure 4 The temperature cloud diagram variation process during the flow of fire extinguishing agent is given.

[0033] Figure 5 The curves of steam mass flow rate changing with time at different boiling point temperatures are given.

[0034] Figure 6 The variation curves of droplet vaporization mass ratio and vapor mass increase ratio at different boiling point temperatures are given.

[0035] Figure 7 The curves of steam mass flow rate changing with time under different latent heat of vaporization are given.

[0036] Figure 8 The numerical fitting curves of the droplet vaporization mass ratio and the vapor mass increase ratio under different latent heats of vaporization are given.

[0037] Appendix 1 Related UDF functions of saturated vapor pressure. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention; it is obvious that the described examples are only part of the example diagrams of the present invention, rather than all of the example diagrams. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In this embodiment, except that the parameters of steps S1, S3, and S4 are set according to the actual geometric model and the parameters to be measured, the parameters of the remaining steps can be set to the parameters in the following embodiments.

[0039] Example 1

[0040] The present invention provides a technical solution: a numerical calculation method for the spatial flow diffusion characteristics of a high boiling point chemical gas fire extinguishing agent, taking perfluorohexanone, a typical high boiling point chemical gas fire extinguishing agent, as an example, combined with the attached Figure 1 The present invention is further described, comprising the following steps:

[0041] S1: According to the characteristics of the full flooding fire extinguishing form of gas fire extinguishing agent, the geometric model of the solution area is established. The geometric model of the fluid domain is a cylinder with a diameter of 1m and a height of 4m. Structured grid division is performed and O-shaped division is performed. The middle area is locally encrypted and the corresponding number of nodes is set. The final calculation grid number is 180,000, as shown in the attached figure. Figure 2 shown.

[0042] S2: The RNG k-ε model is used. The flow speed of perfluorohexanone in space is relatively fast, which will produce certain turbulent disturbances. Compared with the standard k-ε turbulence model used by predecessors, the RNG k-ε turbulence model corrects the turbulent viscosity and takes into account the swirl flow in the average flow, so that the model can more accurately describe the complex shear flow. Compared with the SST k-ω turbulence model used by predecessors, it is more suitable for the flow of high Reynolds number fluids and more in line with the actual flow of perfluorohexanone. The k and ε equations are as follows:

[0043] The conservation equation of turbulent kinetic energy k is:

[0044]

[0045] Conservation equation of turbulent dissipation rate ε:

[0046]

[0047] Among them, G k is the turbulent kinetic energy due to the mean velocity, G b is the turbulent kinetic energy generated by buoyancy, is the turbulent Prandtl number for energy, Y m represents the contribution of wave expansion to the total dissipation rate in compressible turbulence, S k and S ε is a user-defined source term.

[0048] The DPM model is selected as the discrete phase model. The DPM model can better calculate information such as the flow trajectory of particles by considering the interaction between particles and the continuous phase. In addition, the DPM model provides 5 types of particles. The Droplet type selected in the present invention can well simulate the vaporization process of droplets.

[0049] The energy conservation equation followed by the DPM model can be found in the description of the phase change model, and the mass conservation equation is:

[0050]

[0051] Among them, S m is the mass transferred from the discrete phase to the continuous phase, and also includes other user-defined source terms.

[0052] Momentum conservation equation:

[0053]

[0054] Where p is the static pressure, is the stress tensor, is the gravitational body force, is the external volume force (such as the force caused by the interaction with the dispersed phase).

[0055] The component transport model is used to calculate the convection diffusion process between gases. The component transport model can model the mixing of chemical components by solving the conservation equations of convection and diffusion of each component. In the process of calculating the flow of perfluorohexanone, the component transport model can be used to calculate the mass fraction of perfluorohexanone vapor in the fluid domain. The conservation equation of the component transport model is as follows:

[0056]

[0057] Where Y i represents the mass percentage of component i in the mixed gas, represents the convective diffusion coefficient of component i, R i It represents the pure output rate of component transport per unit time, S i Represents the discrete phase with additional velocities set by the user through custom source terms.

[0058] S3: The present invention specifically studies the flow and diffusion characteristics of a single perfluorohexanone droplet in space. After studying the influence of environmental factors on the flow and diffusion of perfluorohexanone, the boundary conditions set the particle velocity inlet, taking the inlet velocity as 5m / s, the injection type as single, the mass flow rate as 0.235kg / s, and the injection time as 0.001s. The remaining boundaries are set as pressure outlets, and the discrete phase and its interaction form are of escape type. To ensure that the ambient temperature of the calculation domain is 328K, the ambient temperatures of the inlet and outlet are set to 328K. A pressure-based solver is used, the SIMPLE algorithm is used, and the discrete method uses a second-order upwind format for transient calculations. The time step is 0.001s, the number of iterations is 1000 steps, and the physical calculation time is 1s.

[0059] S4: For the particle size of a single droplet, a uniform distribution is used, and the particle size is 450um. The physical properties of perfluorohexanone droplets, vapor and air are shown in the following table:

[0060]

[0061] S5: In order to better describe the spatial flow and diffusion process of perfluorohexanone, gravity, temperature-related latent heat and breaking force are considered. In order to accurately calculate the motion trajectory of the droplet, the resultant force on the droplet is calculated by the following formula: Where m p is the droplet mass, is the continuous phase velocity, is the droplet velocity, ρ is the continuous phase density, ρ p is the droplet density, is the additional force, is the resistance; τ r is the relaxation time of the droplet, calculated as Where μ is the viscosity of the continuous phase, d p is the droplet size, Re 1 is the relative Reynolds number, calculated as:

[0062] The vaporization phase change process of perfluorohexanone droplets uses the evaporation boiling model, and the heat balance equation is:

[0063] Among them, c p is the specific heat capacity of the droplet, T p is the droplet temperature, h is the convective heat transfer coefficient, T ∞ is the continuous phase temperature, It is the latent heat of vaporization. The vaporization process involves three different stages: inert heat transfer, evaporation and boiling. The droplets vaporize at the corresponding stage according to the conditions met. The judgment conditions are as follows:

[0064] When the droplets only perform inert heat transfer:

[0065] T p <T vap

[0066] m p ≤(1-f v，0 )m p,0

[0067] When the droplet temperature reaches the temperature at which the droplet begins to evaporate, it vaporizes by evaporation:

[0068] T vap ≤T p <T bp

[0069] m p >(1-f v，0 )m p,0

[0070] When the droplet temperature reaches the boiling point, it vaporizes by boiling:

[0071] T p ≥T bp

[0072] m p >(1-f v，0 )m p,0

[0073] Where, T p is the droplet temperature, T vap It is the temperature at which the droplets begin to evaporate and has no practical meaning. bp is the boiling point temperature of the droplet, m p is the droplet mass, m p，0 is the mass of non-volatile matter, f v，0 is the proportion of non-volatile matter.

[0074] In addition, the driving force in the droplet vaporization process comes from the saturated vapor pressure. The UDF (Appendix 1) function is used to define the saturated vapor pressure within the calculation temperature range. The binary diffusion coefficient between gases is also one of the factors affecting gas dispersion. The UDF function is used to set the binary diffusion coefficient related to the temperature of the continuous phase. Considering the secondary breakage in the perfluorohexanone gasification process, the breakage control equation under the TAB model is used.

[0075]

[0076] In the formula, y0=y(0), The particle size and velocity of the daughter droplets after fragmentation are determined by the energy of the mother droplet, and the particle size and velocity of the daughter droplets are calculated by the following formula:

[0077] Among them, ρ g and ρ l are the densities of the continuous and discrete phases, u is the relative velocity of the droplet, r is the undisturbed droplet radius, σ is the droplet surface tension, and u l is the droplet viscosity, C k , C b and C F are dimensionless constants, taking values ​​of 8, 5, and K is the ratio of the total oscillation energy to the fundamental mode energy, and y is the critical ratio of the distortion growth to the droplet radius.

[0078] The accuracy of the droplet drag coefficient determines the accuracy of the droplet flow model. The drag coefficient selects the Dynamic drag model, which is compatible with the TAB model for the breakup process. In this model, the droplet is assumed to be spherical, and the specific value is related to the Reynolds number (Re). The drag coefficient (C D )for

[0079]

[0080] S6: During the flow of perfluorohexanone, as the heat between the gas and liquid phases is transferred, the phase change continues, and Fluent is used to monitor the vapor mass flow rate in the fluid domain. The results of the simulation calculation are processed, and the spatial flow and diffusion characteristics of perfluorohexanone under different physical and chemical properties are evaluated by the vapor mass flow rate change rate of perfluorohexanone in the fluid domain and the droplet vaporization mass ratio. The correlation between the physical and chemical properties and the flow and diffusion of perfluorohexanone is analyzed by numerical fitting. Figure 3 The variation of the vapor mass fraction cloud diagram during the flow of the fire extinguishing agent is given; Figure 4 The temperature cloud diagram change process during the flow of fire extinguishing agent is given; Figure 5 The curves of the steam mass flow rate changing with time at different boiling point temperatures are given; Figure 6 The variation curves of droplet vaporization mass ratio and vapor mass increase ratio at different boiling point temperatures are given; Figure 7 The curves of the change of steam mass flow rate with time under different latent heat of vaporization are given; Figure 8 The numerical fitting curves of the droplet vaporization mass ratio and the vapor mass increase ratio under different latent heats of vaporization are given. It can be found that the physical and chemical properties have a certain influence on the vaporization process of perfluorohexanone. The effect of boiling point on the vaporization of perfluorohexanone has a sudden change value, while the effect of latent heat of vaporization on the vaporization of perfluorohexanone is a linear negative correlation; Appendix 1 is the related UDF function of saturated vapor pressure.

[0081] The present invention is based on the commercial software ANSYS Fluent, takes the spatial flow and diffusion characteristics of perfluorohexanone fire extinguishing agent as the research background, constructs the geometric model of the corresponding fluid domain according to the characteristics of the spatial flow of perfluorohexanone, imports the grid into the Fluent software, selects the RNG k-ε turbulence model, the DPM model and the component transport model, adopts the evaporation boiling model to simulate the phase change process of the droplet, and uses the UDF function to define the change function of the saturated vapor pressure of the droplet with the temperature and the change function of the binary diffusion coefficient with the temperature of the continuous phase; uses the TAB fragmentation model to track the secondary fragmentation process of the droplet. Combined with post-processing for analysis, the flow and diffusion characteristics of the perfluorohexanone fire extinguishing agent can be more accurately reflected, and the influence of the physical and chemical properties on the flow and diffusion characteristics of the perfluorohexanone can be evaluated accordingly, providing certain theoretical guidance for the modification experiment of the perfluorohexanone fire extinguishing agent.

[0082] Appendix 1 UDF functions related to saturated vapor pressure

[0083]

[0084] if(Tk<=323.15)

[0085] s_t=4000*(Tk-273.15)-110000;

[0086] else if(Tk<=333.15)

[0087] s_t=540000-19000*(Tk-273.15)+200*pow(Tk-273.15,2);

[0088] else

[0089] s_t=524047.6-15857.4*(Tk-273.15)+152.4*pow(Tk-273.15,2);

[0090] return s_t;

[0091] }

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limited thereto. Although the technical solutions of the present invention are described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the present invention, which should be included in the protection scope of the present invention.

Claims

1. A numerical calculation method for the spatial flow diffusion characteristics of a high boiling point chemical gas fire extinguishing agent, characterized in that: The following steps are involved: S1: According to the characteristics of the full flooding fire extinguishing form of gas fire extinguishing agent, the corresponding flow field area geometric model is constructed, and the mesh is divided, and the mesh file is imported into the Fluent software; S2: Establish a mathematical model based on the flow characteristics of high boiling point chemical gas fire extinguishing agents; S3: Specify the corresponding boundary conditions according to the spatial flow characteristics of the high boiling point chemical gas extinguishing agent; S4: setting the physical property parameters of the high boiling point chemical gas fire extinguishing agent liquid and its vapor, setting the discretized droplets, and assigning initial state information to the droplets; S5: Calculate the resultant force on the discretized droplets of high-boiling-point chemical gas extinguishing agent, set the droplet phase change model, breakup model and resistance coefficient, and use UDF to set the change function of the droplet saturated vapor pressure with temperature and the binary diffusion coefficient between the extinguishing agent vapor and air; S6: Carry out simulation calculation of the spatial flow of high-boiling-point chemical gas fire extinguishing agents to study the spatial release flow and diffusion characteristics of high-boiling-point chemical gas fire extinguishing agents.

2. The numerical calculation method for spatial flow diffusion characteristics of a high boiling point chemical gas fire extinguishing agent according to claim 1 is characterized in that: In S2, considering that the extinguishing agent will produce certain turbulent disturbances during high-speed flow, the RNGk-ε turbulence model is specially selected. Compared with the standard k-ε turbulence model, the turbulent viscosity is corrected. At the same time, compared with the k-ω turbulence model, this model is more suitable for the flow of high Reynolds number fluids and more in line with the spray flow process of high boiling point chemical gas extinguishing agents in space.

3. The numerical calculation method for spatial flow diffusion characteristics of a high boiling point chemical gas fire extinguishing agent according to claim 1 is characterized in that: In S2, considering that the gasification process of the extinguishing agent involves phase change, the Droplet particle type in the discrete phase DPM model is selected to consider the heat and mass transfer between the droplets and the continuous phase.

4. The numerical calculation method for spatial flow diffusion characteristics of a high boiling point chemical gas fire extinguishing agent according to claim 1 is characterized in that: In S2, considering the interaction between the fire extinguishing agent vapor and air, the component transport model is selected to calculate the mass fraction of the fire extinguishing agent vapor in the fluid domain.

5. The numerical calculation method for spatial flow diffusion characteristics of a high boiling point chemical gas fire extinguishing agent according to claim 1 is characterized in that: In S5, in order to better calculate the motion trajectory of the droplet, the resultant force on the droplet is calculated by the following formula: Where m p is the droplet mass; is the continuous phase velocity; is the droplet velocity; ρ is the continuous phase density; ρ p is the droplet density; It is an additional force; is the resistance; τ r is the relaxation time of the droplet, calculated as Where μ is the viscosity of the continuous phase, d p is the droplet size, Re1 is the relative Reynolds number, calculated by the following formula:

6. The numerical calculation method for spatial flow diffusion characteristics of a high boiling point chemical gas fire extinguishing agent according to claim 1 is characterized in that: In S5, in order to better calculate the transformation process of the fire extinguishing agent from liquid to gas, the evaporation boiling model is used to calculate the phase change process of the droplets; since the phase change process is closely related to the saturated vapor pressure of the fire extinguishing agent; in order to accurately calculate the phase change process of the fire extinguishing agent, UDF is used to set the change function of the saturated vapor pressure of the fire extinguishing agent droplets with temperature and the binary diffusion coefficient between the fire extinguishing agent vapor and air.

7. The numerical calculation method for spatial flow diffusion characteristics of a high boiling point chemical gas fire extinguishing agent according to claim 1 is characterized in that: In S5, the secondary breakup of the extinguishing agent droplets uses the TAB breakup model suitable for low Weber number We. The control equation in the breakup process is: In the formula, The particle size and velocity of the daughter droplets after fragmentation are determined by the energy of the mother droplet. The particle size and velocity of the daughter droplets are Among them, ρ g and ρ l are the densities of the continuous and discrete phases, u is the relative velocity of the droplet, r is the undisturbed droplet radius, σ is the droplet surface tension, and u l is the droplet viscosity, C k , C b and C F are dimensionless constants, taking values ​​of 8, 5, and K is the ratio of the total oscillation energy to the fundamental mode energy, and y is the critical ratio of the distortion growth to the droplet radius.

8. The numerical calculation method for spatial flow diffusion characteristics of a high boiling point chemical gas fire extinguishing agent according to claim 1 is characterized in that: In S5, the accuracy of the droplet drag coefficient determines the accuracy of the droplet flow model. The dynamic drag model is selected for the droplet drag coefficient, which is compatible with the TAB model for the breakup process. In this model, the droplet is assumed to be spherical, and the specific value is related to the Reynolds number Re. The drag coefficient C of this model is D for 9. The numerical calculation method for spatial flow diffusion characteristics of a high boiling point chemical gas fire extinguishing agent according to claim 1 is characterized in that: In S6, the results of the simulation calculation are processed, and the flow and diffusion process of the fire extinguishing agent is displayed through cloud maps of vapor mass fraction and spatial temperature, or the influence of influencing factors on the high-boiling point chemical gas fire extinguishing agent is evaluated through the change rate of vapor mass flow rate of the fire extinguishing agent in the fluid domain and the droplet vaporization mass ratio, and the correlation between the influence of influencing factors on the flow and diffusion characteristics of the high-boiling point chemical gas fire extinguishing agent is analyzed through numerical fitting.

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