A multi-physical field coupling simulation method for direct current gap under vegetation flame condition

Abstract

A vegetation flame condition direct current gap multi-physical field coupling simulation method, determines the physical quantity required for simulation of charged particle motion, distribution and electric field distribution in the air gap under the condition of applying direct current voltage under the condition of typical vegetation flame, the connection between each physical field; determine the control equation of each physical field; determine the simulation method of multi-physical field coupling; determine the chemical reaction equation corresponding to the vegetation and the pyrolysis material coefficient; measure the vegetation flame temperature distribution and leakage current data by combustion test; compare the simulation obtained flame temperature distribution and leakage current with the test obtained temperature distribution and leakage current data, determine the vegetation pyrolysis reaction equation and chemical reaction rate parameter; simulation calculation obtains the charged particle concentration distribution characteristics and the space electric field distribution characteristics affected by the charged particles generated by the flame combustion. The present application can obtain the charged particle motion, distribution characteristics and electric field distortion of the direct current gap under the condition of typical vegetation flame.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of the insulation characteristics of power transmission lines to the ground under vegetation fire conditions, and particularly relates to a DC gap multi-physical field coupling simulation method under vegetation fire conditions considering strong coupling of chemical reactions. BACKGROUND

[0002] In recent years, affected by extreme weather, forest fires occur frequently, and the power transmission line corridor is increasingly tight. The UHV DC transmission channel inevitably passes through the high forest fire risk area with lush vegetation. Forest fires can cause the insulation strength of power transmission lines to the ground and between phases to decrease and cause tripping accidents, which has become the second largest disaster among all line tripping disasters. The particulate matter and ash in the flame are charged under the influence of ions in the flame and enter the gap below the power transmission line under the action of air flow, electric field force, etc. and form a particle chain, which distorts the space electric field and causes partial discharge, further causing the entire gap to break down. At present, the research on the discharge mechanism and breakdown characteristics of the gap under forest fire conditions is not perfect at home and abroad, and there is a lack of basic basis for risk assessment, early warning and protection of power transmission lines tripping due to forest fires.

[0003] At present, domestic and foreign experiments mainly measure the ion concentration, temperature and breakdown voltage of different vegetation flames, but due to differences in vegetation types, simulation test scales, test methods, etc., the breakdown characteristics obtained are quite different. There is also a lack of test data on the breakdown characteristics of large-scale gaps under different vegetation conditions. At the same time, due to the limitations of experimental conditions, it is difficult to measure the movement and distribution of charged particles in the flame gap and the effect of charged particles on the electric field of the gap, and the distortion of the electric field of the gap directly affects the breakdown characteristics of the flame gap, which needs to be combined with experiments to establish a reasonable simulation model for analysis. As for the simulation model, although some documents or patents consider the multi-physical field coupling model of fluid field, temperature field, electric field and particle motion to analyze the particle motion and distribution, few of them analyze the chemical reaction together. The literature that only considers chemical reactions also only considers a single chemical reaction, which cannot simulate the differences of different vegetation, and does not consider the influence of charged particles in chemical reactions on the electric field. The simulation results have certain differences with the actual chemical reaction of charged particles under different vegetation burning conditions.

[0004] For example: Most existing simulation models only consider the influence of the electric field on the charged particles, but do not consider the influence of the background electric field on the large number of charged particles produced by combustion, and the mutual influence of charged particles, combustion chemical reactions and heat production is also not considered. SUMMARY

[0005] To solve the above problems, the application provides a DC gap multi-physical field coupling simulation method under vegetation flame conditions considering strong chemical reaction coupling, fully considers the interaction of combustion chemical reaction and electric field and temperature field and the like, establishes a multi-physical field simulation model of vegetation combustion under DC voltage with strong chemical reaction coupling, sets key parameters of the simulation model in combination with typical vegetation combustion test results, and improves the accuracy of simulation and simulation; the corrected model can obtain the charged particle motion, distribution characteristics and electric field distortion of the DC gap under the typical vegetation flame conditions, and provides a data basis for the prediction of the insulation withstand voltage characteristics of the gap.

[0006] The technical scheme adopted by the application is as follows:

[0007] A DC gap multi-physical field coupling simulation method under vegetation flame conditions considering strong chemical reaction coupling, comprising the following steps:

[0008] Step 1: considering strong chemical reaction coupling, determining the required physical fields and the physical quantities related to each other in the simulation of the charged particle motion, distribution and electric field distribution in the air gap under the typical vegetation flame conditions with applied DC voltage;

[0009] Step 2: determining the control equations of each physical field according to the relationship of each physical quantity in simulation and simulation;

[0010] Step 3: determining the simulation and simulation method of multi-physical field coupling according to the relationship of each physical field and the transferred physical quantity;

[0011] Step 4: carrying out pyrolysis product analysis test on typical vegetation, determining the chemical reaction equation and pyrolysis material coefficient of the corresponding vegetation according to the proportion of different pyrolysis products;

[0012] Step 5: carrying out combustion test under DC voltage on typical vegetation, measuring vegetation flame temperature distribution and leakage current data; Step 6: setting different pyrolysis reaction equations and chemical reaction rates, comparing the obtained flame temperature distribution and leakage current in simulation with the obtained temperature distribution and leakage current data in test, and determining the parameters of vegetation pyrolysis reaction equation and chemical reaction rate; Step 7: after the parameter optimization setting of steps 4-6, the multi-physical field coupling model is used for simulation calculation, and the charged particle concentration distribution characteristics and the spatial electric field distribution characteristics affected by the charged particles generated by the flame combustion are obtained. In the step 1, the physical fields include: chemical reaction field, material transfer field, fluid field, temperature field and electric field. The coupling relationship between each physical field is as shown in Figure 1

[0013] The physical quantity relationship between the chemical reaction field and the temperature field is that the heat Q generated or absorbed by the chemical reaction affects the temperature distribution, and the temperature T of the temperature field affects the chemical reaction rate;

[0014] ​The physical quantity connection between the chemical reaction field and the mass transfer field is that the reactant concentration c at each position in the mass transfer process r is the basis for generating chemical reactions, and the product concentration c p of the chemical reaction also affects the mass transfer process;

[0015] The physical quantity connection between the mass transfer field and the electric field is that the electric field acts on the charged particles in the mass transfer field through the electric field force F E , and the electric field E formed by the distribution of the charged particles in the mass transfer field will superimpose the overall electric field;

[0016] The physical quantity connection between the mass transfer field and the fluid field is that the mass transfer motion of the mass transfer field affects the density p of the particles in the fluid field, and the mass motion velocity u of the fluid field affects the position change of each particle in the mass transfer field;

[0017] The physical quantity connection between the mass transfer field and the temperature field is that the temperature T of the temperature field affects the diffusion coefficient of the particles in the mass transfer field, thereby affecting the position distribution of the particles in the mass transfer field;

[0018] The physical quantity connection between the temperature field and the fluid field is that the temperature T of the temperature field affects the density of the fluid field, and the fluid field affects the distribution of the temperature through the energy transfer brought by the fluid motion.

[0019] In step 2, the control equations of each physical field include the following:

[0020] The control equation of the chemical reaction field is:

[0021]

[0022]

[0023] k = AT n exp(-E a / RT) (3)

[0024]

[0025]

[0026] Q c = -rH (6)

[0027] In the formula, A and B are reactants; C and D are products; a, b, c, and d are the respective substances; here A, B, C, and D represent reactants and products, respectively, because the reaction equation needs to be based on the specific vegetation, so the letters are used to represent it. The molar proportion number consumed or generated in the reaction; Q cR is the heat source for the reaction; r is the reaction rate; c is the molar concentration; t is the reaction time; k is the reaction rate constant; R i v is the conversion rate; j is the stoichiometric coefficient; A is the apparent pre-exponential factor of the substance, T is the temperature, and n is the reaction order; T n E represents the correction coefficients for the Arrhenius equation. a v is the apparent activation energy, where R is the gas constant; ij r is the stoichiometric coefficient of substance i; i H is the reaction rate of substance i; H is the enthalpy of reaction; h i Let be the enthalpy of substance i.

[0028] The governing equation for the temperature field is:

[0029]

[0030]

[0031]

[0032] In the formula, ρ is the density; C p ρ is the specific heat capacity; u is the specific thermodynamic energy; For Hamiltonian operators; Let T be the temperature gradient; q be the heat transfer rate; Q be the amount of heat; k be the heat transfer coefficient; and p be the pressure.

[0033] The governing equations for the mass transfer field are:

[0034]

[0035]

[0036]

[0037]

[0038] In the formula, c i Let be the molar concentration of substance i; J represents the gradient of molar concentrations of substance i; i For flow rate; D i z is the diffusion coefficient; i U is the charge number of substance i; m,i For mobility; F i V is the net force acting on substance i; V is the electric potential; A and B are the components participating in diffusion; v A v B M represents the diffusion volume of molecules A and B; A M B Let A and B be the molar masses of components A and B.

[0039] The flame combustion gas flow is turbulent flow, and the RNG k-ε turbulent model considering the influence of vortex is used to simulate the fluid field, and the control equation is:

[0040]

[0041]

[0042]

[0043] In the formula, k is the turbulent kinetic energy; x i is the spatial coordinate; α k is the Prandtl number of the turbulent kinetic energy k; μ eff is the equivalent viscosity coefficient; G k is the generation term of the turbulent kinetic energy k; ε is the turbulent dissipation rate; u i is the instantaneous velocity in the i direction; α ε is the Prandtl number of the turbulent dissipation rate ε; C 1ε , C 2ε are both calculation constants.

[0044] The control equation of the electric field is:

[0045]

[0046]

[0047]

[0048]

[0049]

[0050] In the formula, E is the electric field intensity; is the gradient of the electric potential V; D is the electric displacement; is the gradient of the electric displacement D; ρ V is the charge density; F Ei is the component of the electric field force in the i direction; E i is the component of the electric field intensity in the i direction; c + , c - is the concentration of the charged substance; e represents the electron charge; ε0 is the vacuum dielectric constant.

[0051] The step 3 comprises the following steps:

[0052] S3.1: Establish a geometric model according to the size of the vegetation, the size of the electrode and the spatial position, and set the related reaction formula, reaction thermodynamic parameter, initial reaction heat source, electrode applied voltage and boundary condition of the vegetation fuel pyrolysis and combustion process in the geometric model;

[0053] S3.2: The vegetation fuel starts chemical reaction according to the reaction kinetics equation under the action of the initial heat source of the temperature field. The reaction rate is related to the changes of temperature and substance concentration during the reaction process. According to the control equations (1)-(6), i.e., the control equations of the chemical reaction field, which have been represented in the form of numbers in the paper, the calculation is obtained. The chemical reaction process releases or absorbs heat under the action of the reaction enthalpy, generates heat as a heat source to be introduced into the temperature field for calculation. By solving the control equations (7)-(9) of the heat transfer and conversion of the temperature field, the temperature of each point in the space can be obtained, so that the temperature distribution of the whole space as shown in FIG. 2 can be obtained. Figure 4

[0054] S3.3: The transport movement of the reactants and products in the chemical reaction field is realized through the material transfer field and the fluid field. The diffusion movement in the space is carried out at the same time as the reaction. After the control equations (10)-(16) of the material transfer field and the fluid field are solved by the finite volume method, the speed and direction of each substance at each position in the space can be obtained, so that the diffusion speed and position distribution of each substance in the whole space as shown in FIG. 3 can be obtained. Figure 5

[0055] S3.4: The particle concentration at different positions will affect the progress of the reaction process. The diffusion coefficient of the material diffusion is positively related to the temperature and negatively related to the pressure of the fluid field. A large number of charged particles are generated after the chemical reaction. The charged particles are constantly moving under the action of gravity, fluid drag force, electric field force and other forces in the space. The change of the distribution position of the charged particles leads to the change of the distribution of the electric field in the space. By solving the control equations (17)-(21) of the electric field by the finite element method, the potential and electric field distribution at different positions in the space as shown in FIG. 4 can be obtained. Figure 6

[0056] In the step 4, the vegetation combustion test is carried out. The slice with a length of L q corresponding to the type of vegetation is taken. The combustion test is carried out by using the cone calorimeter. At the same time, the cone calorimeter is equipped with CO and CO2 analyzers, carbon black testers and CH4, H2 and water vapor testers. The generation ratios of the combustion products of the vegetation, such as CO2, CO, CH4, H2, H2O and C, can be measured and analyzed. According to the pyrolysis product analysis, the vegetation fuel as a whole is equivalent to C x H y O z , wherein x, y and z are the atomic coefficients of the molecular formula. The main components of the volatile products generated by the pyrolysis of the vegetation are combustible CO, CH4 and H2 and non-combustible CO2 and H2O. The general chemical reaction formula of the overall combustion is:

[0057] C x H y ​​​O z → aC + bH2O + cCO2 + eCO + fCH4 + gH2 (22)

[0058] In the formula, a, b, c, e, f, g are the chemical molecular formula coefficients of the reactants, the product coefficients a, b, c, e, f, g of the chemical equation can be derived from the contents of CO2, CO, CH4, H2, H2O, C measured in the previous vegetation combustion test, and the atomic coefficients x, y, z of the molecular formula can be obtained by balancing the chemical reaction equation, thereby obtaining the overall equivalent expression and pyrolysis chemical reaction equation of different vegetation.

[0059] In step 5, a combustion test under direct voltage is carried out on a typical vegetation to establish a vegetation combustion test platform, which mainly consists of a power supply part, an electrode, and a measurement part. The power supply part mainly consists of a direct current power supply, a voltage divider, and a protection resistor, which is used to adjust the voltage applied to the electrode. The measurement part includes a scale, a thermocouple, a leakage current measuring device, and a visible light camera, etc.

[0060] The temperature data collection procedure is as follows:

[0061] (1) As Figure 2 The vegetation combustion test platform is set up, and according to the dynamic characteristics of the flame body, the flame body can be divided into continuous zone, intermittent zone and smoke plume zone. n hot spot pairs are arranged in each zone at an interval of x cm to record the temperature distribution of the flame body.

[0062] (2) The vegetation is arranged into an approximate circular pile with a diameter of d and a height of h s , and placed at the center of the metal support. The angle of the visible light camera is adjusted to record the test process.

[0063] (3) After preparation, use a watering can to evenly spray alcohol with a concentration of 95% on the circular pile, so that the vegetation fuel can be quickly ignited and fully burned.

[0064] (4) Ignite the vegetation, and the test personnel retreat to a safe area. After the alcohol flame disappears, it is considered that the combustion test has officially started. Turn on the visible light camera and start collecting temperature data. At the same time, start the stopwatch and record the entire test duration.

[0065] (5) After the flame is extinguished, stop data collection.

[0066] The leakage current collection procedure is as follows:

[0067] (1) As Figure 2Build vegetation combustion test platform, check the power supply device and electrode wiring, adjust the electrode height to H, confirm the good grounding of the power supply, capacitor, voltage divider, leakage current acquisition device and other equipment. Each device has a high voltage end and a grounding end, and both are well grounded. Capacitors are used to maintain DC voltage and filtering, and are one of the essential devices in DC testing.

[0068] (2) The vegetation is arranged into an approximate circular pile with a diameter of d and a height of h s , and placed in the center of the metal support; adjust the angle of the visible light camera to record the test results.

[0069] (3) After preparation, use a watering can to evenly spray alcohol with a concentration of 95% on the circular pile, so that the vegetation fuel can be quickly ignited and fully burned.

[0070] (4) Ignite the vegetation, and the test personnel retreat to a safe area. After the alcohol flame disappears, the combustion test is considered to have officially started. Turn on the visible light camera and the leakage current measurement device, and start the stopwatch to record the entire test duration.

[0071] (5) Slowly increase the voltage from 0kV to U n , record the leakage current under the vegetation combustion condition, and slowly reduce the voltage to 0kV after the flame is low enough.

[0072] (6) Use the grounding rod to ground and turn off the test power supply, and stop data collection.

[0073] In step 6, use the temperature distribution and leakage current measured in step 5 as reference values, and bring the vegetation pyrolysis reaction rate interval Q1-Q2 and the different combustion chemical reaction equations obtained in step 4 into the finite element model established in step 3 for simulation calculation. Compare the results of finite element calculation with the results in the test platform. The comparison method is as follows:

[0074] Determine the time period t1-t2 of stable flame combustion, and take the temperature values T w of m time points in the time period of stable flame combustion as references to calculate the average temperature and compare it with the temperature obtained in step 5;

[0075] Statistical the charge density, mobility and electric field strength of charged particles in the area near the electrode, and calculate the ion current and leakage current through formula 23. The size of the ion current can be represented as:

[0076]

[0077] In the formula, I is the ionic current, V is the volume of the reaction region between the measuring electrodes, and r is the distance between the measuring electrodes. When both errors are less than 10%, it is considered to meet the requirements. Finally, the combustion chemical reaction equation and the pyrolysis reaction rate Qr suitable for the model are determined r .

[0078] In step 7, after the parameter optimization setting of steps 4-6, the combustion chemical reaction equation and the pyrolysis reaction rate Qr finally determined in step 6 are brought into the parameter setting of step 3, and the control equation of each physical field in step 3 is solved and calculated, to obtain the charged particle concentration distribution characteristics and the spatial electric field distribution characteristics affected by the charged particles generated by the flame combustion.

[0079] A vegetation combustion test platform under direct current voltage, comprising:

[0080] A power supply part for adjusting the voltage applied to the electrode, the power supply part comprising a test power supply, a voltage divider and a protection resistor;

[0081] The measurement part comprises a thermocouple, a leakage current measuring device and a visible light camera;

[0082] The electrode is mounted on an insulating support, and the height of the electrode is adjustable. The electrode is connected to the test power supply, the capacitor and the voltage divider through wires, and the wires are connected with the protection resistor;

[0083] The leakage current measuring device is placed on an insulating refractory material, and a metal support is arranged on the leakage current measuring device. The vegetation is placed on the metal support,

[0084] A plurality of thermocouples are arranged above the vegetation, and the thermocouples are used to measure the temperature at each temperature measuring point in the vegetation combustion stage;

[0085] The visible light camera is used to record the test results.

[0086] The vegetation flame condition direct current gap multi-physical field coupling simulation method considering chemical reaction strong coupling has the following technical effects:

[0087] 1) The present application fully considers the interaction of combustion reaction and electric field and temperature field, establishes a multi-physical field simulation model of vegetation combustion under direct current voltage with strong coupling of chemical reaction, fully considers the influence of a large number of charged particles in the flame body, which can react on the motion of the charged particles, and fully considers the possible products and combustion rate of the combustion chemical reaction, so as to better simulate the vegetation pyrolysis combustion under the action of the electric field.

[0088] 2) The model constructed in the application actually comprehensively considers that different vegetation combustion will have different combustion products and pyrolysis reaction rates in finite element calculation, therefore, the test is designed to comprehensively consider actual experiment and simulation parameters, set key parameters of the model by combining vegetation combustion test results, and the model after correction can simulate and analyze motion distribution law of charged particles in air gap and effect of charged particles on background electric field under different working conditions.

[0089] 3) Different combustion reaction equations and pyrolysis reaction rates can be set for combustion of different vegetation, and the calculation result of the simulation model of the application is more in line with actual combustion result of vegetation. BRIEF DESCRIPTION OF DRAWINGS

[0090] The application will be further described below in combination with the drawings and examples:

[0091] Figure 1 It is a multi-physical field coupling relationship diagram.

[0092] Figure 2 It is a test platform layout diagram.

[0093] Figure 2 In the figure, 1 is a direct current power supply, 2 is a capacitor, 3 is a voltage divider, 4 is a protection resistor, 5 is a wire, 6 is an insulating support, 7 is an electrode, 8 is a scale, 9 is a visible light camera, 10 is a thermocouple, 11 is a metal support, 12 is a leakage current measuring device, 13 is an insulating refractory material, and 14 is a circular pile composed of vegetation.

[0094] Figure 3 It is a geometric structure diagram of the simulation model.

[0095] Figure 4 It is a temperature distribution diagram of the temperature field.

[0096] Figure 5 It is a diffusion velocity and position distribution diagram.

[0097] Figure 6 It is an electric field distribution diagram.

[0098] Figure 7 It is a temperature measurement point layout diagram.

[0099] Figure 8 It is a test and simulation temperature result comparison diagram. DETAILED DESCRIPTION

[0100] A method for multi-physical field coupling simulation of a direct current gap under vegetation flame conditions considering strong coupling of chemical reactions, first, considering strong coupling of chemical reactions, determining the physical fields and linkage quantities required for simulation of charged particle motion, distribution and electric field distribution in the air gap under typical vegetation flame conditions, then determining the relationship between each physical quantity in the simulation, then determining the simulation method of each physical field coupling according to each physical quantity and control equation, then analyzing the vegetation to determine the reaction equation, then carrying out a burning test under a direct current voltage, measuring the temperature distribution and leakage current of the vegetation flame, then determining the optimal chemical reaction equation and chemical reaction rate parameters according to the measured data, and finally using the multi-physical field coupling model to calculate to obtain the concentration distribution characteristics of the charged particles and the spatial electric field distribution characteristics affected by the charged particles generated by the flame burning. The specific steps are as follows:

[0101] Step 1: The physical fields required for simulation of charged particle motion, distribution and electric field distribution in the air gap under typical vegetation flame conditions include: chemical reaction field, mass transfer field, fluid field, temperature field and electric field. The coupling relationship between each physical field is as shown in Figure 1 .

[0102] The physical quantity relationship between the chemical reaction field and the temperature field is that the heat Q generated (or absorbed) by the chemical reaction affects the temperature distribution, and the temperature T of the temperature field affects the chemical reaction rate.

[0103] The physical quantity relationship between the chemical reaction field and the mass transfer field is that the reactant concentration c r at each position in the mass transfer process is the basis for generating chemical reactions, and the product concentration c p of the chemical reaction also affects the mass transfer process.

[0104] The physical quantity relationship between the mass transfer field and the electric field is that the electric field affects the charged particles in the mass transfer field through the electric field force F E , and the electric field E formed by the distribution of charged particles in the mass transfer field will superimpose the overall electric field.

[0105] The physical quantity relationship between the mass transfer field and the fluid field is that the mass transfer motion of the mass transfer field affects the particle density p in the fluid field, and the mass motion velocity u of the fluid field affects the position change of each particle in the mass transfer field.

[0106] The physical quantity relationship between the mass transfer field and the temperature field is that the temperature T of the temperature field affects the diffusion coefficient of the particles in the mass transfer field, thereby affecting the position distribution of the particles in the mass transfer field.

[0107] The physical quantity relationship between the temperature field and the fluid field is that the temperature T of the temperature field affects the density of the fluid field, and the fluid field affects the distribution of the temperature through energy transfer caused by fluid motion.

[0108] The control equations of each physical field are mainly as follows:

[0109] The control equation of chemical reaction field is:

[0110]

[0111]

[0112]

[0113]

[0114]

[0115]

[0116] In the formula, A and B are reactants; C and D are products; a, b, c and d are respectively the molar proportion numbers of substances A, B, C and D consumed or generated in the reaction; Q c is the reaction heat source; r is the reaction rate; c is the molar concentration; t is the reaction time; k is the reaction rate constant; R i is the conversion rate; v j is the stoichiometric coefficient; A is the apparent pre-exponential factor of the substance, T is the temperature, and n is the reaction order; T n is the Arrhenius equation correction coefficient; E a is the apparent activation energy of R, R is the gas constant; v ij is the stoichiometric coefficient of substance i; r i is the reaction rate of substance i; H is the reaction enthalpy; h i is the enthalpy of substance i.

[0117] The control equation of temperature field is:

[0118]

[0119]

[0120]

[0121] In the formula, ρ is the density; C p is the specific heat capacity; u is the specific thermodynamic energy; is the Hamiltonian operator; is the gradient of temperature T; q is the heat transfer rate; Q is the heat; k is the heat transfer coefficient; p is the pressure.

[0122] The control equation of mass transfer field is:

[0123]

[0124]

[0125]

[0126]

[0127] where c i is the molar concentration of species i; is the gradient of the molar concentration of species i; J i is the flux; D i is the diffusion coefficient; z i is the charge number of species i; u m,i is the mobility; F i is the resultant force on species i; V is the electric potential; A, B are the components involved in diffusion; v A , v B are the molecular diffusion volumes of components A, B; M A , M B are the molar masses of components A, B.

[0128] The flame combustion gas flow is turbulent flow, and the RNG k-ε turbulent model considering the influence of vortex is used to simulate the fluid field. Its control equation is:

[0129]

[0130]

[0131]

[0132] where: k is the turbulent kinetic energy; x i is the spatial coordinate; α k is the Prandtl number of turbulent kinetic energy k; μ eff is the equivalent viscosity coefficient; G k is the generation term of turbulent kinetic energy k; ε is the turbulent dissipation rate; u i is the instantaneous velocity in i direction; α ε is the Prandtl number of turbulent dissipation rate ε; C 1ε and C 2ε are both calculation constants.

[0133] The control equation of the electric field is:

[0134]

[0135]

[0136]

[0137]

[0138]

[0139] E is the electric field intensity; is the gradient of the electric potential V; D is the electric displacement; is the gradient of the electric displacement D; p V is the charge density; F Ei is the component of the electric field force in the i direction; E i is the component of the electric field intensity in the i direction; c + , c - is the concentration of the charged substance; e represents the electronic charge; e0 is the vacuum permittivity.

[0140] Step 3: Establish a simulation geometric model, simplify the model to a two-dimensional axisymmetric model, and simplify the vegetation fuel to a cylinder with a radius of 10 cm and a height of 6 cm. The distance H between the rod electrode and the wood pile is set for testing, the rod electrode has a radius of 1.5 cm and a length of 9.5 cm. Set the air bag with a radius of 50 cm and a height of 250 cm as the outer boundary, and set the boundary condition as an open boundary. The simulation model geometric structure is shown in Figure 3 .

[0141] Set the related reaction formula, reaction thermodynamic parameters, initial reaction heat source, and electrode applied voltage of the vegetation fuel pyrolysis and combustion process. The chemical reaction of vegetation pyrolysis can be expressed as follows:

[0142] C x H y O z →C,H2O,CO2,CO,CH4,H2,etc. (22)

[0143] The global reaction equation of the combustible pyrolysis gas and oxygen is as follows:

[0144] CH4+2O2→CO2+2H2O(g) (23)

[0145] CO+0.5O2→CO2 (24)

[0146] H2+0.5O2→H2O(g) (25)

[0147] At the same time, the carbon-hydrogen fuel (such as CH4) generated in the pyrolysis process and the alkali metals and alkaline earth metals contained in the vegetation will undergo ionization reactions in the combustion process, generating a large number of electrons and ions. The main ion reactions are as follows:

[0148] CH+O→HCO + +e - (26)

[0149] HCO+ + H2O → CO + H3O + (27)

[0150]

[0151]

[0152] The Arrhenius coefficients of the combustible gas oxidation combustion reaction and the ionization reaction in the vegetation combustion process are shown in Table 1 and Table 2, respectively.

[0153] Table 1 Arrhenius coefficients of the combustible pyrolysis gas combustion reaction

[0154]

[0155] Table 2 Arrhenius coefficients of the main ionization reactions in the vegetation combustion process

[0156]

[0157]

[0158] The vegetation fuel starts chemical reaction according to the reaction kinetics equation under the action of the initial reaction heat source of the temperature field, and the reaction rate changes constantly in the reaction process due to the changes of temperature and substance concentration; the chemical reaction process releases (or absorbs) heat under the action of the reaction enthalpy, and the heat source and release are both realized through the temperature field, and the temperature distribution of the temperature field can be obtained by solving the partial differential equation of heat transfer and conversion of the temperature field. The transport movement of the reactants and products in the chemical reaction field is realized through the material transfer field and the fluid field, and the diffusion movement in space is carried out at the same time, and the control equations of the material transfer field and the fluid field are solved by the finite volume method to obtain the diffusion speed and position distribution of each substance, and the particle concentration at different positions will affect the progress of the reaction; the diffusion coefficient of material diffusion is positively correlated with temperature and negatively correlated with the pressure of the fluid field. A large number of charged particles are produced after chemical reaction, and the charged particles constantly move under the action of gravity, fluid drag, electric field force and other forces in space, and the change of the distribution position of the charged particles leads to the change of the distribution of the electric field in space, and the electric potential and electric field distribution at different positions in space can be obtained by solving the control equation of the electric field through the finite element method.

[0159] Step 4: According to the pyrolysis combustion pyrolysis test, the mass ratio of the remaining carbon after the completion of the pine pyrolysis is 13-25% of the raw material, and the volume ratio of the gas product generated by the combustion of the pine used in this test is measured:

[0160] Table 3 Volume ratio of pine pyrolysis gas product

[0161]

[0162] The thermal decomposition rate of the combustible in the experiment was determined by the oxygen consumption method test, and the combustion test of the pine on the support was determined by using a propane burner. The thermal decomposition rate of the used vegetation was 10 -9 ~10 -7 mol / (m 3 ·s) measured by the oxygen consumption calorimeter. The C in the chemical equation of the vegetation mainly comes from the carbon monoxide, carbon dioxide and methane of the pyrolysis decomposition complete carbon substance and gas volatiles; the H mainly comes from the methane, hydrogen and water vapor in the gas volatiles; and the O mainly comes from the carbon monoxide, carbon dioxide and water vapor in the gas volatiles.

[0163] According to the proportion analysis of various substances obtained by the pyrolysis test in step 3, the three chemical equations in table 4 can be obtained by bringing them into equation (9).

[0164] Table 4 Pyrolysis reaction equation corresponding to the proportion of different pyrolysis products

[0165]

[0166]

[0167] Step 5: carry out the combustion test of the typical vegetation under the direct current voltage, establish a vegetation combustion test platform, and the test platform mainly consists of power supply, electrode and measuring device. The power supply part is mainly composed of test power supply, voltage divider and protection resistor, which is used to adjust the voltage applied on the electrode; the measuring part includes scale, thermocouple, leakage current measuring device and visible light camera, etc.

[0168] The temperature data acquisition steps are as follows:

[0169] (1) As Figure 2 shown in the test platform is built, according to the preliminary test, the continuous zone of the vegetation flame is about 40 cm, the intermittent zone is about 15 cm, and the smoke plume zone is about 20 cm. Therefore, 4 temperature measuring points are set at intervals of 15 cm from the starting point of 15 cm on the surface of the wood pile to measure the temperature, and the temperature measuring point setting is shown in Figure 7 .

[0170] (2) the vegetation is placed into an approximate circular pile with a diameter of d and a height of h s , and placed in the center of the metal support; adjust the angle of the visible light camera to record the test process.

[0171] (3) after preparation, use a watering can to quantitatively and uniformly spray alcohol with a concentration of 95% on the wood pile, so that the vegetation fuel can be quickly ignited and fully burned.

[0172] (4) Ignite the vegetation, the test personnel retreat to the safety area, and after the alcohol flame disappears, it is considered that the burning test is formally started, the video camera is turned on, and the temperature collection is started, at the same time, the stopwatch is started, and the whole test duration is recorded.

[0173] (5) After the flame is extinguished, stop the data collection.

[0174] The leakage current collection steps are as follows:

[0175] (1) As Figure 2 The test platform is built, the power supply device and the electrode wiring are checked, the electrode height is adjusted to H, and the grounding device is confirmed to be grounded.

[0176] (2) The vegetation is placed into an approximate circular pile with a diameter of d and a height of h s , and is placed in the center of the metal support; the angle of the visible light video camera is adjusted to record the test results.

[0177] (3) After preparation, the alcohol with a concentration of 95% is quantitatively and uniformly sprayed on the wood pile by a watering can, so that the vegetation fuel can be quickly ignited and fully burned.

[0178] (4) Ignite the vegetation, the test personnel retreat to the safety area, and after the alcohol flame disappears, it is considered that the burning test is formally started, the video camera and the leakage current measuring device are turned on, at the same time, the stopwatch is started, and the whole test duration is recorded.

[0179] (5) The voltage is slowly increased from 0 kV to U n , the leakage current under the vegetation burning condition is recorded, and after the flame is low enough, the voltage is slowly decreased to 0 kV.

[0180] (6) After the grounding rod is grounded and the test power supply is turned off, the data collection is stopped.

[0181] It is found through the test that the vegetation flame height changes in the range of 50-65 cm in the stable stage, the stable burning time is about 200 s, and the temperature at each temperature measuring point in the stable vegetation burning stage gradually decreases from bottom to top. The temperature at measuring point 1 changes in the range of 680-750℃; the temperature at point 2 changes in the range of 400-550℃; the temperature at point 3 changes in the range of 230-400℃; and the temperature at point 4 changes in the range of 130-220℃.

[0182] The gap leakage currents under different direct current voltages and different electrode heights are shown in Table 5.

[0183] Table 5 Gap leakage currents under different direct current voltages and different electrode heights

[0184]

[0185] Under the same voltage level, the leakage current under positive polarity DC voltage is greater than that under negative polarity voltage. The leakage current under 10 kV DC voltage is 3.8-7.9 times that under -10 kV; the leakage current under 20 kV and 30 kV DC voltage is about 1.7-3.2 times that under -20 kV and -30 kV DC voltage. Moreover, the amplitude of the leakage current gradually increases as the gap distance decreases. When the gap distance changes between 40-70 cm, the leakage current increases by about 1.3-2.0 times for each 15 cm decrease in the gap distance; when the gap distance decreases from 40 cm to 25 cm, the leakage current increases by 1.8-2.6 times.

[0186] Step 6: The three pyrolysis reaction equations calculated in Step 4 are brought into the finite element model for calculation, and three different temperature change curves are obtained. Temperature measuring points are set at the same positions as in the test, and the temperature distribution during different pyrolysis reactions is measured. Through comparison, it is found that when the pyrolysis reaction equation of the vegetation is Formula 1, the temperature at measuring point 1 is stable at 700-800℃ for 100-300 s, and the average temperature of 10 points in this time period is 768℃, 787℃, 796℃, 781℃, 776℃, 759℃, 764℃, 743℃, 735℃ and 724℃, the average temperature at this time is 763.3℃, compared with the average temperature of measuring point 1 in the test, which is 715℃, the error is 6.7%; when the pyrolysis reaction equation is Formula 2, the temperature at measuring point 1 is stable at 500-600℃ for 90-320 s, and the average temperature of 10 points in this time period is 515℃, 556℃, 587℃, 601℃, 582℃, 573℃, 553℃, 534℃, 545℃ and 531℃, the average temperature at this time is 557.7℃, compared with the average temperature of measuring point 1 in the test, which is 715℃, the error is 22%; when the pyrolysis reaction equation is Formula 3, the temperature at measuring point 1 is stable at 950-1050℃ for 150-275 s, and the average temperature of 10 points in this time period is 951℃, 991℃, 1003℃, 1016℃, 1035℃, 1021℃, 1025℃, 1014℃, 1004℃ and 998℃, the average temperature at this time is 1005.8℃, compared with the average temperature of measuring point 1 in the test, which is 715℃, the error is 40.7%. Comparison shows that the error is the lowest when Formula 1 is used and is within 10% error range. Similarly, the temperature comparison results at measuring points 2-4 are the same as those at measuring point 1, and the temperature when the pyrolysis reaction of the vegetation is represented by Formula 1 is close to the test results.

[0187] Therefore, the final pyrolysis reaction equation is determined as follows:

[0188] C6H 10O5→4C+1H2O+CO2+3CO+2CH4+2H2

[0189] Using the final determined pyrolysis reaction equation 1, the reaction rate was calculated to be 1.0 × 10⁻⁶. -9 1.0×10 -8 1.0×10 -7 mol / (m 3 The stable burning time of vegetation at ·s). The pyrolysis reaction rate is 1.0×10 s. -9 mol / (m 3 At ·s), the temperature rise time during vegetation combustion is long, and a large amount of combustible volatiles diffuse and are lost during combustion, resulting in a shorter stable combustion time and a lower flame temperature compared to the experimental results; the pyrolysis reaction rate is 1.0×10 -8 mol / (m 3 At ·s), the stable burning time and temperature distribution of vegetation were similar to the experimental results; the reaction rate was 1.0×10 -7 mol / (m 3 At a temperature of 1.0 × 10⁻⁶ s, the rate of volatile matter release from vegetation during pyrolysis is relatively fast, resulting in a faster heat release rate. However, the fuel consumption rate is also faster, and the time to maintain stable combustion is less than 200 s. The final determination of the pyrolysis rate of pine wood is 1.0 × 10⁻⁶ s. -8 mol / (m 3 (approximately ·s)

[0190] The pyrolysis reaction equation in the model is represented as 1, and the pyrolysis reaction rate is set at 1.0 × 10⁻⁶. -8 mol / (m 3 The pyrolysis rate of pine wood was approximately 2.4 × 10⁻⁶ s. Further calculations of the pyrolysis rate yielded a target pyrolysis rate of 2.4 × 10⁻⁶ s. -8 mol / (m 3 The simulation results at time ·s) show that, within the stable time period, the temperature values ​​at 10 time points at temperature measurement point 1 are: 748℃, 782℃, 787℃, 776℃, 768℃, 747℃, 758℃, 734℃, 725℃, and 716℃. The average temperature at this time is 754.1℃, and the error value is 5.4%, which is within the acceptable range. Similarly, the temperature comparison results at temperature measurement points 2 to 4 are the same as those at temperature measurement point 1, all showing a vegetation pyrolysis reaction rate of 2.4 × 10⁻⁶. -8 mol / (m 3 The temperature at ·s) is similar to the experimental results. A comparison of simulation and experimental temperatures is shown below. Figure 8 As shown.

[0191] The pyrolysis reaction equation in the model is expressed as Equation 1, and the pyrolysis reaction rate is set at 2.4 × 10⁻⁶. -8 mol / (m 3• s), the electrode height is set to 70 cm, the ion current in the vicinity of the electrode during the stable combustion stage is calculated when 10 kV, 20 kV and 30 kV direct current voltages are applied respectively, and the ion currents under each voltage are calculated to be 0.56 mA, 6.37 mA and 21.78 mA respectively. By comparing the test values, it can be seen that the error values under the simulation conditions are all within 10%. Therefore, the final pine pyrolysis reaction equation is determined to be formula 1, and the pyrolysis reaction rate Q r = 2.4 x 10 -8 mol / (m 3 · s).

[0192] Step 7: The pine combustion reaction equation determined in step 6:

[0193] C6H 10 O5→4C+1H2O+CO2+3CO+2CH4+2H2

[0194] and the pine pyrolysis reaction rate Q r = 2.4 x 10 -8 mol / (m 3 · s) determined in step 6 are brought into the parameter settings in step 3, and the control equations of each physical field are calculated to obtain the charged particle concentration distribution characteristics:

[0195] The negative electric particle concentration near the positive electrode is 1.2-1.7 times that of the positive electric particle concentration near the negative electrode. With the decrease of the electrode height, the concentration of charged particles near the electrode with different polarity gradually increases. Moreover, the growth of the charged particle concentration near the electrode is similar to the trend of the increase of the leakage current.

[0196] The spatial electric field distribution characteristics affected by the charged particles generated by flame combustion:

[0197] The charged particles generated by vegetation combustion have a great impact on the background electric field. Under the action of the charged particles generated by vegetation combustion, the background electric field near the positive electrode increases to 1.7-2.1 times of the original, and the background electric field near the negative electrode increases to 1.4-1.8 times of the original.

Claims

1. A method for simulating DC gap multiphysics coupling under vegetation-flame conditions considering strong chemical reaction coupling, characterized in that... Includes the following steps: Step 1: Considering the strong coupling of chemical reactions, determine the physical fields and the physical quantities related to each other required for simulating the motion, distribution and electric field distribution of charged particles in the air gap under the condition of applied DC voltage in vegetation flame. Step 2: Determine the governing equations for each physical field based on the relationships between the physical quantities simulated in the simulation. Step 3: Determine the simulation method for multiphysics coupling based on the relationships between the various physical fields and the transmitted physical quantities; Step 4: Conduct pyrolysis product analysis experiments on vegetation, and determine the corresponding chemical reaction equations and pyrolysis coefficients of vegetation based on different proportions of pyrolysis products; Step 5: Conduct a combustion test on the vegetation under DC voltage to measure the vegetation flame temperature distribution and leakage current data; Step 6: Set different pyrolysis reaction equations and chemical reaction rates, compare the simulated flame temperature distribution and leakage current with the experimental temperature distribution and leakage current data, and determine the vegetation pyrolysis reaction equation and chemical reaction rate parameters. Step 7: After optimizing the parameters in steps 4 to 6, use a multiphysics coupling model to perform simulation calculations to obtain the characteristics of charged particle concentration distribution and the characteristics of spatial electric field distribution affected by charged particles generated by flame combustion. In step 1, the physical field includes: chemical reaction field, mass transfer field, fluid field, temperature field, and electric field; The physical quantity relationship between the chemical reaction field and the temperature field is as follows: a chemical reaction generates or absorbs heat. Q Temperature affects temperature distribution and the temperature field. T Affects the rate of chemical reactions; The physical quantity relationship between the chemical reaction field and the mass transfer field is: the reactant concentration at each location during mass transfer. c r It is the basis for chemical reactions, and the concentration of the products of chemical reactions. c p It will also affect the process of mass transfer; The physical quantity relationship between the matter transfer field and the electric field is as follows: the electric field passes through the electric force. F E The electric field formed by the distribution of charged particles in the mass transfer field affects the charged particles in the mass transfer field. E This will have a cumulative effect on the overall electric field; The physical quantity relationship between the mass transfer field and the fluid field is as follows: the mass transfer motion in the mass transfer field affects the particle density in the fluid field. ρ The velocity of matter in the fluid field u The changes in the positions of each particle that affect the matter transfer field; The physical quantity relationship between the mass transfer field and the temperature field is: the temperature of the temperature field T It affects the diffusion coefficient of particles in the mass transfer field, and thus affects the positional distribution of particles in the mass transfer field; The physical quantity relationship between the temperature field and the fluid field is: the temperature of the temperature field T The density of the fluid field is affected, and the fluid field affects the temperature distribution through energy transfer caused by fluid motion.

2. The DC gap multiphysics coupling simulation method for vegetation-flame conditions considering strong chemical reaction coupling as described in claim 1, characterized in that: In step 2, the governing equations for each physical field include the following: The governing equation for the chemical reaction field is: （1）； （2）； （3）； （4）； （5）； （6）； In the formula, A and B are reactants; C and D are products; a, b, c, and d are the molar proportions of the corresponding substances consumed or generated in the reaction; Q c As a heat source for the reaction; r The reaction rate; c Molar concentration; t Reaction time; k The reaction rate constant; R i The conversion rate; v j For measurement coefficients; A The apparent pre-exponential factor of matter, T For temperature, n The reaction order is [number]. T n These are the correction coefficients for the Arrhenius equation; E a For the apparent activation energy, R It is the gas constant; v ij For matter i The measurement coefficients; r i For matter i The reaction rate; H For reaction enthalpy; h i For matter i enthalpy; The governing equation for the temperature field is: （7）； （8）； （9）； In the formula, ρ Density; C p ρ is the specific heat capacity; u is the specific thermodynamic energy; For Hamiltonian operators; For temperature T The gradient; q The heat transfer rate; Q For heat; k The heat transfer coefficient; p Pressure; The governing equations for the mass transfer field are: （10）； （11）； （12）； （13）； In the formula, c i For matter i molar concentration; for i The gradient of molar concentration of a substance; J i For traffic; D i The diffusion coefficient is denoted as . z i For matter i The number of charges; u m,i For mobility; F i For matter i The combined force received; V is the electric potential; A and B are the components participating in the diffusion; v A , v B The diffusion volumes of components A and B molecules; M A , M B Let A and B be the molar masses of components A and B. The combustion airflow of the flame is turbulent, and the influence of vortices is considered in the RNG. k-ε The turbulence model is used to simulate the fluid field, and its governing equations are: （14）； （15）； （16）； In the formula: k is the turbulent kinetic energy; x i Spatial coordinates; α k It is the Prandtl number of the turbulent kinetic energy k; μ eff It is the equivalent viscosity coefficient; G k This is the term that generates turbulent kinetic energy k; ε The turbulent dissipation rate; u i for i Instantaneous velocity in the direction; α ε Turbulent dissipation rate ε Prandt number; C 1ε , C 2ε All are calculation constants; The governing equations of the electric field are: （17）； （18）； （19）； （20）； （21）； In the formula, E Electric field strength; electric potential V The gradient; D It is the electric displacement; electric displacement D The gradient; ρ V Charge density; F Ei For the electric field force in i Component of direction; E i For the electric field strength at i Component of direction; c + , c - Concentration of charged substances; e Indicates electron charge; 0 is the vacuum permittivity.

3. The DC gap multiphysics coupling simulation method for vegetation-flame conditions considering strong chemical reaction coupling as described in claim 1, characterized in that: Step 3 includes the following steps: S3.1: Establish a geometric model based on vegetation size, electrode size and spatial location, and set the relevant reaction formulas, reaction thermodynamic parameters, initial reaction heat source, electrode applied voltage and boundary conditions in the geometric model for vegetation fuel pyrolysis and combustion process; S3.2: Under the initial reaction heat source of the temperature field, the vegetation fuel begins a chemical reaction according to the reaction kinetic equation. During the reaction process, the reaction rate is related to the changes in temperature and substance concentration. According to the control equations (1) to (6), the reaction rate is calculated. The chemical reaction process will release or absorb heat under the action of reaction enthalpy. The heat generated is introduced into the temperature field for calculation. The temperature of each point in space is obtained by solving the control equations (7) to (9) for heat transfer and conversion in the temperature field. S3.3: The transport of reactants and products in the chemical reaction field is realized through the material transfer field and the fluid field. They react while diffusing in space. The control equations (10) to (16) of the material transfer field and the fluid field are solved by the finite volume method to obtain the speed and direction of each substance at each position in space, thereby obtaining the diffusion speed and position distribution of each substance in the whole space. S3.4: The particle concentration at different locations will affect the reaction process. The diffusion coefficient of the substance is positively correlated with temperature and negatively correlated with the pressure of the fluid field. After the chemical reaction, a large number of charged particles will be generated. The charged particles are constantly moving in space under the action of gravity, fluid drag and electric field force. The change in the distribution of charged particles will cause the distribution of the electric field in space to change accordingly. The control equations (17)~(21) of the electric field can be solved by the finite element method to obtain the potential and electric field distribution at different locations in space.

4. The DC gap multiphysics coupling simulation method for vegetation-flame conditions considering strong chemical reaction coupling as described in claim 1, characterized in that: In step 4, a vegetation combustion test is conducted. The volatile products generated by vegetation pyrolysis include combustible CO, CH4, and H2, and non-combustible CO2 and H2O. The general chemical reaction formula for the overall combustion is: （22）； In the formula, a, b, c, e, f, g These are the chemical formula coefficients of each reactant and the product coefficients of the chemical equation. a, b, c, e, f, g Based on the CO2, CO, CH4, H2, H2O, and C contents measured in the previous vegetation combustion experiment, the atomic coefficients of the molecular formula can be deduced. x, y, z By balancing the chemical reaction equations, we can obtain the overall equivalent expressions and pyrolysis chemical reaction equations for different vegetation types.

5. The DC gap multiphysics coupling simulation method for vegetation-flame conditions considering strong chemical reaction coupling as described in claim 1, characterized in that: In step 5, a combustion test of vegetation under DC voltage is conducted, and a vegetation combustion test platform is established. The temperature data acquisition steps are as follows: (1) Based on the dynamic characteristics of the flame body, the flame body is divided into a continuous zone, an intermittent zone, and a plume zone; x The spacing is cm, and the zones are evenly distributed longitudinally within each zone. n A hotspot couple is used to record the temperature distribution of the flame body; (2) Arrange the vegetation in a circle with a diameter of d Gao Wei h s An approximately circular stack was placed in the center of a metal support; the angle of the visible light camera was adjusted to record the experimental process. (3) After preparation, spray alcohol evenly and quantitatively on the circular stack so that the vegetation fuel can be quickly ignited and fully burned. (4) Ignite the vegetation, and the test personnel evacuate to a safe area. The combustion test is considered to have officially started after the alcohol flame disappears. Turn on the visible light camera and start temperature acquisition. At the same time, turn on the stopwatch to record the duration of the entire test. (5) Stop data acquisition after the flame is extinguished.

6. The DC gap multiphysics coupling simulation method for vegetation-flame conditions considering strong chemical reaction coupling as described in claim 5, characterized in that: In step 5, the leakage current acquisition steps are as follows: (1) Check the wiring of the power supply and electrodes, and adjust the electrode height to the specified position. H Confirm that the grounding terminals of the power supply, capacitors, voltage dividers, and leakage current acquisition device are in good condition; (2) Arrange the vegetation in a circle with a diameter of d Gao Wei h s An approximately circular stack was placed at the center of a metal support (11); the angle of the visible light camera (9) was adjusted to record the test results; (3) After preparation, spray alcohol evenly and quantitatively on the circular stack so that the vegetation fuel can be quickly ignited and fully burned. (4) Ignite the vegetation, and the test personnel evacuate to a safe area. The combustion test is considered to have officially started after the alcohol flame disappears. Turn on the visible light camera (9) and the leakage current measuring device (12), and turn on the stopwatch at the same time to record the duration of the entire test. (5) Slowly increase the voltage from 0kV to U n Record the leakage current under vegetation burning conditions, and after the flame drops low enough, slowly reduce the voltage until 0kV. (6) After grounding with a grounding rod and turning off the test power supply (1), stop data acquisition.

7. The DC gap multiphysics coupling simulation method for vegetation-flame conditions considering strong chemical reaction coupling as described in claim 6, characterized in that: In step 6, the temperature distribution and leakage current measured in step 5 are used as reference values ​​to define the vegetation pyrolysis reaction rate range. Q 1~ Q The different combustion chemical reaction equations obtained in steps 2 and 4 are substituted into the finite element model established in step 3 for simulation calculation. The results of the finite element calculation are compared with the results from the experimental platform. The comparison method is as follows: Determine the time period of stable flame combustion t 1~ t 2. Take samples from the period when the flame is burning stably. m Temperature value T at each time point w For reference, the average temperature is calculated and compared with the temperature obtained in step 5; The charge density, mobility, and electric field strength of charged particles in the region near the electrode were statistically analyzed, and the ion current was calculated using Equation 23 and compared with the leakage current; the magnitude of the ion current is expressed as: （23）； In the formula, I It is the ion current. V To measure the volume of the reaction region between the electrodes, r The distance between the measuring electrodes is used; when the error between both is less than 10%, it is considered to meet the requirements; finally, the combustion chemical reaction equation and pyrolysis reaction rate suitable for this model are determined. Q r .

8. The DC gap multiphysics coupling simulation method for vegetation-flame conditions considering strong chemical reaction coupling as described in claim 6, characterized in that: In step 7, after optimizing the parameters in steps 4 to 6, the combustion chemical reaction equation and pyrolysis reaction rate finally determined in step 6 are... Qr The parameters are then input into the parameter settings of step 3, and the control equations of each physical field are solved according to step 3 to obtain the characteristics of charged particle concentration distribution and the characteristics of spatial electric field distribution affected by charged particles generated by flame combustion.

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