A simulation method for the dynamic evolution of bubble discharge plasma in ethanol

Abstract

The invention discloses a simulation method for the dynamic evolution of bubble discharge plasma in ethanol. The method first establishes a geometric model of bubble discharge in ethanol, a plasma chemical model describing the electron collision reaction process, and an electrohydrodynamic model describing the discharge physical process, then sets the model boundary conditions and meshes the calculation domain, uses simulation software to solve the model control equation by the finite element method, and obtains the dynamic image of the time and space evolution of the electric field intensity, particle concentration distribution, and plasma channel through post-processing. The invention can simulate the dynamic process of the start and development of the discharge of bubbles containing different gas components in ethanol at different voltage values ​​and the formation process of active particles under room temperature and standard atmospheric pressure conditions, and provides data support for studying the influence of voltage amplitude on the characteristics of discharge plasma, and is simple to operate, convenient and efficient.

Description

Technical Field

[0001] The invention relates to the technical field of plasma discharge physics, and in particular to a method for simulating the dynamic evolution of bubble discharge plasma in ethanol. Background Art

[0002] In the field of low-temperature plasma physics, bubble discharge in ethanol is widely used in nanomaterial preparation and hydrogen production technology because it can produce a variety of active particles. The difficulty of liquid phase discharge can be effectively reduced by introducing bubble discharge into liquid ethanol. In addition, the use of bubbles containing different gas components can control the active substances generated in the plasma and eventually diffused into the surrounding liquid ethanol, thereby achieving different discharge treatment effects. Understanding the basic physical and chemical processes of bubble discharge is crucial to promoting the development of non-equilibrium plasmas. Therefore, a large number of experimental studies have been carried out at home and abroad on the discharge characteristics of bubbles in liquid ethanol. It was found that the gas type, voltage amplitude, and electrode structure affect the discharge start mode, discharge appearance, and breakdown mode in the bubble.

[0003] However, due to the complexity of the discharge system, it is difficult to fully understand the dynamic characteristics of the discharge inside the bubble through the current experimental diagnosis. Therefore, it is necessary to use numerical simulation methods to conduct research to further explain the experimental observation results. For example, Levko D et al. (Non-thermal plasma ethanol reforming in bubbles immersed in liquids, Journal of Physics D: Applied Physics 2017 Vol. 50) used adaptive simulation methods to provide valuable insights into the characteristics of isolated bubble discharge in alcohol solutions, but it is still difficult to study the dynamics of the discharge initiation, propagation in the bubble, and subsequent formation of reactive substances in the bubble attached to the electrode needle tip at room temperature and pressure. Therefore, it is necessary to establish a model of bubble discharge in ethanol, and use simulation methods to study the dynamic characteristics of bubble discharge and the formation process of active particles at room temperature and pressure. This can provide a new perspective for the microscopic process of bubble discharge in ethanol, which has important theoretical value and practical significance. Summary of the invention

[0004] The purpose of the present invention is to propose a simulation method for the dynamic evolution of bubble discharge plasma in ethanol, which can simulate the initiation and development dynamics of the discharge of bubbles containing different gas components in ethanol at different voltage values ​​and the formation process of active particles under room temperature and standard atmospheric pressure conditions, and realize the study of the influence of voltage amplitude on the characteristics of discharge plasma.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] A method for simulating the dynamic evolution of bubble discharge plasma in ethanol is provided. First, a geometric model of bubble discharge in ethanol is established. The model is filled with liquid ethanol and provided with collection electrodes and bubbles. The bubbles are filled with collection gas. The method comprises the following steps:

[0007] Step S1. collecting particle components in bubbles during the bubble discharge process in ethanol and setting the initial concentration of the particle components, and constructing a plasma chemistry model by collecting the rate coefficient, energy threshold and collision cross section data of the reaction between particles to calculate the electron mobility and average electron energy;

[0008] Step S2. constructing an electrohydrodynamic model for describing the discharge physical process based on the particle continuity equation, the electron energy conservation equation and the Poisson equation;

[0009] Step S3. Based on the bubble discharge process in the ethanol, boundary conditions are set to obtain boundary equations, wherein the boundary conditions include electrodes, bubble boundaries, symmetry axes, and dielectric boundaries;

[0010] Step S4. Select a computational domain and perform meshing on the computational domain to construct a computational domain simulation model;

[0011] Step S5. Based on the plasma chemistry model, the electrohydrodynamic model, the boundary equations, and the computational domain simulation model, a two-dimensional axisymmetric geometric model of bubble discharge in ethanol is constructed for numerical simulation of the dynamic evolution of bubble discharge plasma in ethanol.

[0012] The scheme further comprises: the initial concentration of the particle components in step S1 includes setting a first initial density of uniform low-density seed charge and a second initial density of other particles pre-ionized and pre-excited, wherein the first initial density is 10 15 m -3 , the second initial density is 10 8 m -3 ;

[0013] Determine the reaction between particles according to the first initial density and the second initial density, and obtain the rate coefficient, the energy threshold, and the collision cross-section data;

[0014] Based on the collision cross section data, the electron mobility and the average electron energy were calculated by BOLSIG+ software.

[0015] The scheme is further as follows: the equation set of the electrohydrodynamic model in step S2 is:

[0016]

[0017]

[0018]

[0019]

[0020]

[0021] Where: n e 、n i and n m are the number densities of electrons, ions and neutral species, respectively;

[0022] Γ e , Γ i and Γ m are the particle flow densities of electrons, ions and neutral matter, respectively, Where E is the electric field strength, μ e and μ i are the mobility of electrons and ions, respectively, and D e , D i and D m are the diffusion coefficients of electrons, ions and neutral species, respectively, D e =μ e T e , e is the electron charge, k b is the Boltzmann constant, T g is the gas temperature, T e is the electron temperature, is the average electron energy;

[0023] S e , S i and S m are the particle source terms of electrons, ions, and neutral matter, respectively;

[0024] n ε is the electron energy density,

[0025] Γ ε is the electron energy flow density, Among them, μ ε is the electron energy mobility, D ε is the electron energy diffusion coefficient,

[0026] S ε is the electron energy loss;

[0027] ε0 and ε r are the vacuum dielectric constant and relative dielectric constant, respectively;

[0028] V is the electric potential;

[0029] ρ is the space charge density.

[0030] The solution is further as follows: the particle source term S e , S i and S m and the electron energy loss S ε The calculation formula is as follows:

[0031]

[0032]

[0033] Where: X is the number of reactions that lead to a change in particle number density;

[0034] c x is the mole fraction of the target substance of reaction x;

[0035] k x is the rate coefficient of reaction x;

[0036] n N is the total neutral species number density, Where P is the air pressure;

[0037] Y is the number of electron-neutral particle inelastic collision reactions;

[0038] ΔE y is the energy loss caused by the inelastic collision reaction y;

[0039] k y is the rate coefficient of reaction y;

[0040] Z is the number of electron-neutral particle elastic collision reactions;

[0041] m e is the mass of the electron;

[0042] M z is the mass of the neutral reactant in reaction z;

[0043] v n is the effective collision frequency between electrons and neutral particles, Among them, n z is the number density of the neutral reactant in reaction z, N A is Avogadro's constant, k z is the rate coefficient of reaction z.

[0044] The solution is further that the boundary conditions of the electrode are:

[0045]

[0046] Where: V0 represents the voltage applied to the electrode;

[0047] n represents the boundary normal vector;

[0048] The boundary conditions for the bubble are:

[0049]

[0050] Where: (D2-D1)·n represents the difference in electric displacement flux flowing into and out of the boundary, where D is the electric displacement vector, D = ε0ε r E;

[0051] ρ s is the boundary surface charge density, Among them, J i and J e are the total ion current density and the total electron current density on the boundary respectively;

[0052] The boundary conditions for the dielectric are:

[0053]

[0054] The scheme further includes: the simulation model adopts a mixture average diffusion model, and the diffusion coefficients D of ions and neutral substances are i and D m Take 0.01m 2 / s, gas temperature T g Take room temperature 300K, dielectric relative permittivity ε r The relative dielectric constant of ethanol is taken as 25, and the gas pressure P is taken as the standard atmospheric pressure 760 Torr.

[0055] The scheme is further as follows: the geometric model is a 50mm×50mm square, a metal needle electrode is placed in liquid ethanol in the geometric model, the needle tip of the metal needle electrode is a hemispherical shape with a radius of 0.5mm, a bubble with a radius of 0.5mm is attached to the needle tip, and 1 atmosphere of helium and ethanol vapor are filled into the bubble at room temperature, wherein the proportion of ethanol vapor is 5%, and the top and right boundary of the liquid are grounded.

[0056] The solution is further as follows: the mesh division in step S4 adopts free triangle network division to simulate the calculation domain, and the mesh of the simulation area division contains 22957 domains and 694 boundaries in total, and the number of degrees of freedom to be solved is 244897.

[0057] The scheme further includes: the method further includes the following steps:

[0058] Step S6. The direct solver PARDISO of COMSOL Multiphysics software is used to solve the two-dimensional axisymmetric geometric model of bubble discharge in ethanol, wherein the calculation step size is set to 10 -12 s, using the constant Newton method, the tolerance factor and the maximum number of iterations were set to 1% and 25, respectively;

[0059] Step S7. Post-process the results solved in step S6 to obtain the electric field strength, particle concentration distribution characteristics and the spatiotemporal evolution dynamics of the plasma channel, wherein the post-processing includes the two-dimensional intercept points and two-dimensional mirror distribution of the electric field strength at different times, the change of electron density distribution over time, and the dynamic evolution process of the plasma discharge channel.

[0060] The scheme is further that: the simulation method is implemented by a simulation system, and the simulation system comprises:

[0061] Chemical model building module: used to collect the particle components in the bubble during the bubble discharge process in ethanol and set the initial concentration of the particle components. By collecting the rate coefficient, energy threshold and collision cross-section data of the reaction between particles, a plasma chemical model is built to calculate the electron mobility and average electron energy.

[0062] Physical model building module: used to build an electrohydrodynamic model for describing the discharge physical process based on the particle continuity equation, the electron energy conservation equation and the Poisson equation;

[0063] Boundary condition constraint module: used to set boundary conditions based on the bubble discharge process in the ethanol and obtain boundary equations, wherein the boundary conditions include electrodes, bubble boundaries, symmetry axes and dielectric boundaries;

[0064] Computational domain construction module: used to select a computational domain and perform meshing on the computational domain to construct a computational domain simulation model;

[0065] Simulation model construction module: based on the plasma chemical model, the electrohydrodynamic model, the boundary equation, and the computational domain simulation model, a two-dimensional axisymmetric geometric model of bubble discharge in ethanol is constructed for numerical simulation of dynamic evolution of bubble discharge plasma in ethanol;

[0066] Simulation model calculation module: used to solve the two-dimensional axisymmetric geometric model of bubble discharge in ethanol using the direct solver PARDISO of COMSOL Multiphysics software, where the calculation step size is set to 10 -12 s, using the constant Newton method, the tolerance factor and the maximum number of iterations were set to 1% and 25, respectively;

[0067] Data post-processing module: post-process the results solved in the simulation model calculation module to obtain the electric field intensity, particle concentration distribution characteristics and the spatiotemporal evolution dynamics of the plasma channel, wherein the post-processing includes the two-dimensional intercept points and two-dimensional mirror distribution of the electric field intensity at different times, the change of electron density distribution over time, and the dynamic evolution process of the plasma discharge channel.

[0068] The beneficial effects of the present invention are as follows: the method of the present invention establishes a model based on a geometric model of bubble discharge in ethanol, a plasma chemical model, and an electrohydrodynamic model, and solves the model by a finite element method, and can simulate the initiation and development kinetics of bubble discharge in ethanol and the formation process of active particles under room temperature and standard atmospheric pressure conditions. The influence of electrode structure, voltage amplitude, and gas components contained in bubbles on discharge plasma characteristics can be studied by changing model settings and simulation conditions, and the method is simple to operate, convenient and efficient, and has strong applicability.

[0069] The present invention is described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 is a flow chart of the numerical simulation method of the present invention;

[0071] Figure 2 Schematic diagram of the two-dimensional axisymmetric geometric model of bubble discharge in ethanol;

[0072] Figure 3 This is the grid division diagram of the bubble discharge model in ethanol;

[0073] Figure 4 This is a graph showing the evolution of electron density distribution in one embodiment of the present invention. DETAILED DESCRIPTION

[0074] 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. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0075] like Figure 1-4 As shown, the present invention provides a simulation method for the dynamic evolution of bubble discharge plasma in ethanol. First, a geometric model of bubble discharge in ethanol is established. The model is filled with liquid ethanol and a collection electrode and bubbles are set. The bubbles are filled with a collection gas. The method includes the following steps:

[0076] Step S1. collecting particle components in bubbles during the bubble discharge process in ethanol and setting the initial concentration of the particle components, and constructing a plasma chemistry model by collecting the rate coefficient, energy threshold and collision cross section data of the reaction between particles to calculate the electron mobility and average electron energy;

[0077] Step S2. constructing an electrohydrodynamic model for describing the discharge physical process based on the particle continuity equation, the electron energy conservation equation and the Poisson equation;

[0078] Step S3. Based on the bubble discharge process in the ethanol, boundary conditions are set to obtain boundary equations, wherein the boundary conditions include electrodes, bubble boundaries, symmetry axes, and dielectric boundaries;

[0079] Step S4. Select a computational domain and perform meshing on the computational domain to construct a computational domain simulation model;

[0080] Step S5. Based on the plasma chemistry model, the electrohydrodynamic model, the boundary equations, and the computational domain simulation model, a two-dimensional axisymmetric geometric model of bubble discharge in ethanol is constructed for numerical simulation of the dynamic evolution of bubble discharge plasma in ethanol.

[0081] The following is a specific embodiment of the above method:

[0082] 1) Establish Figure 2 The two-dimensional axisymmetric geometric model of bubble discharge in ethanol is shown; Figure 1 As shown, the shape and size of the computational domain, electrode structure, bubble, and different dielectric regions are determined. The complete computational domain is a 50mm×50mm square. The metal needle electrode is placed in the computational domain of the geometric model, which is liquid ethanol (its relative dielectric constant is 25). Its tip is a hemispherical shape with a radius of 0.5mm. A bubble with a radius of 0.5mm is attached to the tip of the needle. At room temperature (300K), 1 atmosphere of helium and ethanol vapor are filled into the bubble, of which the proportion of ethanol vapor is 5%. The top of the liquid and the right boundary are grounded.

[0083] 2) Establishing a plasma chemical model describing the electron collision reaction process: This embodiment determines the particle components contained in the bubble by consulting multidisciplinary data, as shown in Table 1. The initial concentration of the particle components includes setting a first initial density of uniform low-density seed charge and a second initial density of other particles for pre-ionization and pre-excitation, wherein the first initial density is 10 15 m -3 , the second initial density is 10 8 m -3 ; That is, set the density (concentration) in the calculation domain to 10 15 m -3The electrons are used as the initial uniform low-density seed charge, and the initial density of other particles from pre-ionization and pre-excitation is set to 10 8 m -3 ; Then determine the reaction between these particles, as shown in Table 2; According to the first initial density and the second initial density, obtain the rate coefficient, energy threshold and collision cross section of the reaction between the particles, and calculate the electron mobility and average electron energy by BOLSIG+ software according to the collision cross section data of these reactions, as shown in Table 3.

[0084] Table 1

[0085]

[0086] Table 2

[0087]

[0088]

[0089] Table 3

[0090]

[0091]

[0092] 3) An electrohydrodynamic model describing the discharge physical process is constructed by the particle continuity equation, the electron energy conservation equation and the Poisson equation, which is used to solve the evolution of particle density, electron energy density and electric field strength in the model, including the following set of equations:

[0093]

[0094]

[0095]

[0096]

[0097]

[0098] Where: n e 、n i and n m are the number densities of electrons, ions and neutral species, respectively;

[0099] Γ e , Γ i and Γ m are the particle flow densities of electrons, ions and neutral matter, respectively, Where E is the electric field strength, μ e and μ iare the mobility of electrons and ions, respectively, and D e , D i and D m are the diffusion coefficients of electrons, ions and neutral species, respectively, D e =μ e T e , e is the electron charge, k b is the Boltzmann constant, T g is the gas temperature, T e is the electron temperature, is the average electron energy;

[0100] S e , S i and S m are the particle source terms of electrons, ions, and neutral matter, respectively;

[0101] n ε is the electron energy density,

[0102] Γ ε is the electron energy flow density, Among them, μ ε is the electron energy mobility, D ε is the electron energy diffusion coefficient,

[0103] S ε is the electron energy loss;

[0104] ε0 and ε r are the vacuum dielectric constant and relative dielectric constant, respectively;

[0105] V is the electric potential;

[0106] ρ is the space charge density.

[0107] Among them, the particle source term S in formula (1) to formula (3) is e , S i and S m And the electron energy loss S in formula (4) ε The calculation formula is as follows:

[0108]

[0109]

[0110] Where: X is the number of reactions that lead to a change in particle number density;

[0111] c xis the mole fraction of the target substance of reaction x;

[0112] k x is the rate coefficient of reaction x;

[0113] n N is the total neutral species number density, Where P is the air pressure;

[0114] Y is the number of electron-neutral particle inelastic collision reactions;

[0115] ΔE y is the energy loss caused by the inelastic collision reaction y;

[0116] k y is the rate coefficient of reaction y;

[0117] Z is the number of electron-neutral particle elastic collision reactions;

[0118] m e is the mass of the electron;

[0119] M z is the mass of the neutral reactant in reaction z;

[0120] v n is the effective collision frequency between electrons and neutral particles, Among them, n z is the number density of the neutral reactant in reaction z, N A is Avogadro's constant, k z is the rate coefficient of reaction z.

[0121] The simulation model uses a mixture-averaged diffusion model, and the diffusion coefficients of ions and neutral species are D i and D m Take 0.01m 2 / s, gas temperature T g Take room temperature 300K, dielectric relative permittivity ε r The relative dielectric constant of ethanol is taken as 25, and the gas pressure P is taken as the standard atmospheric pressure 760 Torr.

[0122] 4) setting model boundary conditions for the model described in 1) above, including electrodes, bubble boundaries, symmetry axes, and dielectric boundaries;

[0123] a) The boundary conditions of the needle electrode are:

[0124]

[0125] Where: V0 represents the voltage applied to the electrode;

[0126] n represents the boundary normal vector;

[0127] b) The boundary condition of the ground electrode is: V = 0 (V)

[0128] c) The boundary conditions of the bubble are:

[0129]

[0130] Where: (D2-D1)·n represents the difference in electric displacement flux flowing into and out of the boundary, where D is the electric displacement vector, D = ε0ε r E;

[0131] ρ s is the boundary surface charge density, Among them, J i and J e are the total ion current density and the total electron current density on the boundary respectively;

[0132] d) The boundary conditions of the dielectric are:

[0133]

[0134] 5) Mesh the computational domain described in 1) above, and set the maximum cell size, maximum cell growth rate, curvature factor, boundary layer properties, and meshing method for different simulation regions and boundaries. The simulation uses free triangle network meshing. Since the electric field gradient at the interface between the two media is large, the meshing is denser at the electrode and bubble boundary. At the same time, a boundary layer is added to the plasma region to resolve the sheath. The mesh of the simulation model region contains a total of 22,957 domains and 694 boundaries, and the number of degrees of freedom to be solved is 244,897, such as Figure 3 shown.

[0135] 6) Solving the model control equations by finite element method: numerically solving the bubble discharge model in ethanol using simulation software, and setting the transient solver, including the calculation time step, nonlinear method, tolerance factor and maximum number of iterations. Therefore, the method further includes the following steps:

[0136] Step S6. The direct solver PARDISO of COMSOL Multiphysics software is used to solve the two-dimensional axisymmetric geometric model of bubble discharge in ethanol, wherein the calculation step size is set to 10 -12 s, using the constant Newton method, the tolerance factor and the maximum number of iterations were set to 1% and 25, respectively;

[0137] Step S7. Post-process the result obtained in step S6 to obtain the electric field strength, particle concentration distribution characteristics and the spatiotemporal evolution dynamics of the plasma channel, wherein the post-processing includes the two-dimensional intercept point and two-dimensional mirror distribution of the electric field strength at different times, the change of the electron density distribution over time, and the dynamic evolution process of the plasma discharge channel; as shown in the attached Figure 4 The diagram shows the evolution process of an electron density distribution from 1.0 ns to 2.5 ns in this embodiment.

[0138] The above simulation method in the embodiment is implemented by a simulation system, and the simulation system includes:

[0139] Chemical model building module: used to collect the particle components in the bubble during the bubble discharge process in ethanol and set the initial concentration of the particle components. By collecting the rate coefficient, energy threshold and collision cross-section data of the reaction between particles, a plasma chemical model is built to calculate the electron mobility and average electron energy.

[0140] Physical model building module: used to build an electrohydrodynamic model for describing the discharge physical process based on the particle continuity equation, the electron energy conservation equation and the Poisson equation;

[0141] Boundary condition constraint module: used to set boundary conditions based on the bubble discharge process in the ethanol and obtain boundary equations, wherein the boundary conditions include electrodes, bubble boundaries, symmetry axes and dielectric boundaries;

[0142] Computational domain construction module: used to select a computational domain and perform meshing on the computational domain to construct a computational domain simulation model;

[0143] Simulation model construction module: based on the plasma chemical model, the electrohydrodynamic model, the boundary equation, and the computational domain simulation model, a two-dimensional axisymmetric geometric model of bubble discharge in ethanol is constructed for numerical simulation of dynamic evolution of bubble discharge plasma in ethanol;

[0144] Simulation model calculation module: used to solve the two-dimensional axisymmetric geometric model of bubble discharge in ethanol using the direct solver PARDISO of COMSOL Multiphysics software, where the calculation step size is set to 10 -12 s, using the constant Newton method, the tolerance factor and the maximum number of iterations were set to 1% and 25, respectively;

[0145] Data post-processing module: post-process the results solved in the simulation model calculation module to obtain the electric field intensity, particle concentration distribution characteristics and the spatiotemporal evolution dynamics of the plasma channel, wherein the post-processing includes the two-dimensional intercept points and two-dimensional mirror distribution of the electric field intensity at different times, the change of electron density distribution over time, and the dynamic evolution process of the plasma discharge channel.

[0146] It should be noted that similar numbers and letters represent similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description and are not to be understood as indicating or implying relative importance.

[0147] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can still modify the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or perform equivalent replacements on some of the technical features thereof; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention. They should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A simulation method for the dynamic evolution of bubble discharge plasma in ethanol. First, a geometric model of bubble discharge in ethanol is established. The model is filled with liquid ethanol and provided with collection electrodes and bubbles. The bubbles are filled with collection gas. It is characterized in that The method comprises the following steps: Step S1: collecting particle components in bubbles during the bubble discharge process in ethanol and setting the initial concentration of the particle components, and constructing a plasma chemistry model by collecting rate coefficients, energy thresholds, and collision cross-section data of reactions between particles to calculate electron mobility and average electron energy; Step S2: constructing an electrohydrodynamic model for describing the discharge physical process based on the particle continuity equation, the electron energy conservation equation and the Poisson equation; Step S3: Based on the bubble discharge process in the ethanol, boundary conditions are set to obtain boundary equations, wherein the boundary conditions include electrodes, bubble boundaries, symmetry axes, and dielectric boundaries; Step S4: selecting a computational domain and performing meshing on the computational domain to construct a computational domain simulation model; Step S5: constructing a two-dimensional axisymmetric geometric model of bubble discharge in ethanol based on the plasma chemical model, the electrohydrodynamic model, the boundary equation, and the computational domain simulation model, for numerical simulation of dynamic evolution of bubble discharge plasma in ethanol; The equations of the electrohydrodynamic model in step S2 are: Where: n e 、n i and n m are the number densities of electrons, ions and neutral species, respectively; Γ e , Γ i and Γ m are the particle flow densities of electrons, ions and neutral matter, respectively, Where E is the electric field strength, μ e and μ i are the mobility of electrons and ions, respectively, and D e , D i and D m are the diffusion coefficients of electrons, ions and neutral species, respectively, D e =μ e T e , e is the electron charge, k b is the Boltzmann constant, T g is the gas temperature, T e is the electron temperature, is the average electron energy; S e , S i and S m are the particle source terms of electrons, ions, and neutral matter, respectively; n ε is the electron energy density, Γ ε is the electron energy flow density, Among them, μ ε is the electron energy mobility, D ε is the electron energy diffusion coefficient, S ε is the electron energy loss; ε 0 and ε r are the vacuum dielectric constant and relative dielectric constant, respectively; V is the electric potential; ρ is the space charge density.

2. A method for simulating the dynamic evolution of a bubble discharge plasma in ethanol according to claim 1, It is characterized in that The initial concentration of the particle components in step S1 includes setting a first initial density of uniform low-density seed charge and a second initial density of other particles pre-ionized and pre-excited, wherein the first initial density is 10 15 m -3 , the second initial density is 10 8 m -3 ; Determine the reaction between particles according to the first initial density and the second initial density, and obtain the rate coefficient, the energy threshold, and the collision cross-section data; Based on the collision cross section data, the electron mobility and the average electron energy were calculated by BOLSIG+ software.

3. The method for simulating the dynamic evolution of a bubble discharge plasma in ethanol according to claim 1, It is characterized in that The particle source term S e , S i and S m and the electron energy loss S ε The calculation formula is as follows: Where: X is the number of reactions that lead to a change in particle number density; c x is the mole fraction of the target substance of reaction x; k x is the rate coefficient of reaction x; n N is the total neutral species number density, Where P is the air pressure; Y is the number of electron-neutral particle inelastic collision reactions; ΔE y is the energy loss caused by the inelastic collision reaction y; k y is the rate coefficient of reaction y; Z is the number of electron-neutral particle elastic collision reactions; m e is the mass of the electron; M z is the mass of the neutral reactant in reaction z; v z is the effective collision frequency between electrons and neutral particles, Among them, n z is the number density of the neutral reactant in reaction z, N A is Avogadro's constant, k z is the rate coefficient of reaction z.

4. The method for simulating the dynamic evolution of a bubble discharge plasma in ethanol according to claim 1, It is characterized in that The boundary conditions of the electrode are: Where: V 0 represents the voltage applied to the electrode; n represents the boundary normal vector; The boundary conditions for the bubble are: Where: (D 2 -D 1 )·n represents the difference in electric displacement flux flowing into and out of the boundary, where D is the electric displacement vector, D = ε 0 ε r E; ρ s is the boundary surface charge density, Among them, J i and J e are the total ion current density and the total electron current density on the boundary respectively; The boundary conditions for the dielectric are:

5. The method for simulating the dynamic evolution of bubble discharge plasma in ethanol according to claim 1, It is characterized in that The simulation model adopts the mixture average diffusion model, and the diffusion coefficients of ions and neutral species are D i and D m Take 0.01m 2 / s, gas temperature T g Take room temperature 300K, dielectric relative permittivity ε r The relative dielectric constant of ethanol is taken as 25, and the gas pressure P is taken as the standard atmospheric pressure 760 Torr.

6. A method for simulating the dynamic evolution of bubble discharge plasma in ethanol according to claim 1, It is characterized in that The geometric model is a 50 mm × 50 mm square. The metal needle electrode is placed in liquid ethanol in the computational domain geometric model. The needle tip of the metal needle electrode is a hemispherical shape with a radius of 0.5 mm. A bubble with a radius of 0.5 mm is attached to the needle tip. At room temperature, helium and ethanol vapor at 1 atmosphere are filled into the bubble, wherein the proportion of ethanol vapor is 5%. The top and right boundary of the liquid are grounded.

7. The method for simulating the dynamic evolution of bubble discharge plasma in ethanol according to claim 1, It is characterized in that The meshing in step S4 is performed by free triangle network partitioning, which is used to simulate the computational domain. The mesh of the simulation region contains 22957 domains and 694 boundaries, and the number of degrees of freedom to be solved is 244897.

8. The method for simulating the dynamic evolution of bubble discharge plasma in ethanol according to claim 1, It is characterized in that The method further comprises the following steps: Step S6: The direct solver PARDISO of COMSOL Multiphysics software is used to solve the two-dimensional axisymmetric geometric model of bubble discharge in ethanol, wherein the calculation step size is set to 10 -12 s, using the constant Newton method, the tolerance factor and the maximum number of iterations were set to 1% and 25, respectively; Step S7: Post-processing the results solved in step S6 to obtain the electric field strength, particle concentration distribution characteristics and the spatiotemporal evolution dynamics of the plasma channel, wherein the post-processing includes the two-dimensional intercept points and two-dimensional mirror distribution of the electric field strength at different times, the change of electron density distribution over time, and the dynamic evolution process of the plasma discharge channel.

9. A method for simulating the dynamic evolution of bubble discharge plasma in ethanol according to claim 8, It is characterized in that The simulation method is implemented by a simulation system, and the simulation system comprises: Chemical model building module: used to collect the particle components in the bubble during the bubble discharge process in ethanol and set the initial concentration of the particle components. By collecting the rate coefficient, energy threshold and collision cross-section data of the reaction between particles, a plasma chemical model is built to calculate the electron mobility and average electron energy. Physical model building module: used to build an electrohydrodynamic model for describing the discharge physical process based on the particle continuity equation, the electron energy conservation equation and the Poisson equation; Boundary condition constraint module: used to set boundary conditions based on the bubble discharge process in the ethanol and obtain boundary equations, wherein the boundary conditions include electrodes, bubble boundaries, symmetry axes and dielectric boundaries; Computational domain construction module: used to select a computational domain and perform meshing on the computational domain to construct a computational domain simulation model; Simulation model construction module: based on the plasma chemical model, the electrohydrodynamic model, the boundary equation, and the computational domain simulation model, a two-dimensional axisymmetric geometric model of bubble discharge in ethanol is constructed for numerical simulation of dynamic evolution of bubble discharge plasma in ethanol; Simulation model calculation module: used to solve the two-dimensional axisymmetric geometric model of bubble discharge in ethanol using the direct solver PARDISO of COMSOL Multiphysics software, where the calculation step size is set to 10 -12 s, using the constant Newton method, the tolerance factor and the maximum number of iterations were set to 1% and 25, respectively; Data post-processing module: post-process the results solved in the simulation model calculation module to obtain the electric field intensity, particle concentration distribution characteristics and the spatiotemporal evolution dynamics of the plasma channel, wherein the post-processing includes the two-dimensional intercept points and two-dimensional mirror distribution of the electric field intensity at different times, the change of electron density distribution over time, and the dynamic evolution process of the plasma discharge channel.

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