Explosion pressure load calculation method for charge with shell based on chemical reaction of detonation product

Abstract

The invention discloses a method for calculating explosion pressure load of charge with a shell based on chemical reaction of detonation products, which comprises the following steps of: obtaining detonation energy, detonation products generated by detonation and mass fraction of each detonation product, and determining further chemical reaction in the post-combustion process of the explosive and pre-exponential factors and activation energy of each detonation product; the explosion process is divided into a detonation stage, an adiabatic expansion stage and a post-combustion reaction stage; calculating the initial temperature and the initial pressure of an air mass generated by explosive detonation; constructing a finite element three-dimensional model of a detonation product air mass generated by the shell charge explosion in the closed space, and calculating related parameters of a detonation product at the end of the adiabatic expansion stage; and solving a time-history curve of the shell charging explosion pressure load in the post-combustion reaction stage. The method has the beneficial effects that the limiting effect of the shell on the chemical reaction of the explosive detonation product is introduced, the pressure load of the charge explosion with the shell is calculated, the analysis process does not depend on the specific test calibration working condition, and the universality is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of explosion load calculation, in particular to a shell charge explosion pressure load calculation method based on chemical reaction of detonation products. BACKGROUND

[0002] The warship will be threatened by anti-ship missiles and other attack weapons during service, and the scene of the warship cabin being attacked by the explosion of the warhead appears. Therefore, accurately evaluating the damage state of the warship under the attack of the warhead cabin explosion is a necessary prerequisite for designing the protection system and the post-war repair system of the warship.

[0003] The shell charge explosion pressure load is a parameter for evaluating the damage degree of the warship under the attack of the warhead cabin explosion. However, the method of obtaining the charge explosion pressure load by test has many problems such as high economic cost, high labor cost, high time cost and low repeatability, which leads to the fact that it cannot be carried out in large quantities, so the numerical calculation simulation means for simulating the explosion damage effect of the warhead in the closed space of the shell charge is the current feasible general scheme.

[0004] At present, the mainstream fluid dynamics calculation program which can effectively simulate the initiation of explosive cannot well consider the restriction of the shell structure on the initiation process of the explosive, and the finite element software which can effectively simulate the coupling effect of fluid Euler grid and structure Lagrange grid cannot simulate the chemical reaction and diffusion process of the detonation products during the explosion of the explosive. The inherent defects of the above two calculation methods lead to the difficulty of simulating the initiation process of the warhead which can truly reflect the actual combat environment of the shell charge load. The existing solution is to deduce and equivalent the damage power of the explosive to the structure by the test results, but this not only cannot effectively obtain the actual chemical reaction process and diffusion of the detonation products, but also leads to the fact that the numerical calculation must depend on the specific test results, cannot obtain the damage parameters outside the test conditions, has poor universality, and is difficult to predict other conditions. SUMMARY

[0005] The present application aims at the deficiencies of the prior art, and provides a shell charge explosion pressure load calculation method based on chemical reaction of detonation products, which aims at solving the problem of poor universality in the prior art.

[0006] The technical scheme adopted by the present application is as follows: a shell charge explosion pressure load calculation method based on chemical reaction of detonation products, comprising the following steps: Based on the chemical reaction occurring in the detonation process of the explosive, the detonation energy, the detonation products produced by the detonation, and the mass fraction of each detonation product are obtained; Based on the composition and proportion of detonation products, combined with the temperature and oxygen supply conditions of afterburning, the chemical reactions further occurring in the afterburning process of explosives are judged, and the thermodynamic characteristic parameters of each detonation product, including the pre-exponential factor and activation energy, are calculated; The explosion process of the shell-loaded charge in the closed space is divided into three stages: detonation stage, adiabatic expansion stage, and afterburning reaction stage; Based on the assumption of instantaneous detonation, combined with the detonation products and the mass fraction of each detonation product, the initial temperature of the gas cloud generated by the explosion of the explosive is calculated; The detonation stage of the explosion process of the shell-loaded charge in the closed space is numerically calculated to obtain the initial pressure of the gas cloud; According to the initial radius, initial height and charge quantity of the explosive, as well as the initial temperature and initial pressure of the gas cloud, combined with the structural characteristics of the closed space, a finite element three-dimensional model of the detonation product gas cloud generated by the explosion of the shell-loaded charge in the closed space is constructed in the Eulerian multiphase flow solver. The constraints on the gas cloud flow process during the expansion and fragmentation of the shell, as well as the duration of the constraints, are input into the Eulerian multiphase flow solver to calculate the pressure, temperature, and diffusion velocity of the gas cloud after expansion in the detonation product spray state at the end of the adiabatic expansion stage; The pressure, temperature, and diffusion velocity of the detonation product spray state, as well as the pre-exponential factor and activation energy of each detonation product, are input into the finite element three-dimensional model as input parameters of the afterburning reaction stage to calculate and obtain the time history curve of the shell-loaded charge explosion pressure load in the afterburning reaction stage.

[0007] According to the above scheme, the division method of the explosion process is based on the physical characteristics of each stage: the detonation stage is simplified according to the assumption of instantaneous detonation, which assumes that the detonation process of the explosive is completed instantaneously, and the explosive is completely converted into detonation products at the moment of initiation, and the detonation products are equivalent to a gas cloud; the adiabatic expansion stage is in a limited mixing state and no chemical reaction occurs; the afterburning reaction stage ends the limited mixing state.

[0008] According to the above scheme, the initial temperature of the gas cloud is calculated by formula (1), that is: (1); In the formula, W is the mass of the charge, with the unit of g; Q is the detonation energy per unit mass of the explosive, with the unit of MJ / kg; Δ E is the energy consumed by the fragments, with the unit of MJ; n is the amount of substance of the detonation product mixture gas, with the unit of mol; C vm represents the constant volume specific heat of the substance, with the unit of J / (kg•K); T 0 is the room temperature, with the unit of K; Tm is the initial temperature of the gas mass, in K.

[0009] According to the above scheme, the initial pressure of the gas mass P 0 is calculated by formula (2): (2); In the formula, n is the amount of substance of the gas mass, in mol; R is the universal gas constant, and the value is 8.31 J / (mol•K); T m is the initial temperature of the gas mass, in K; V e is the volume of the gas mass after expansion, in m 3 .

[0010] According to the above scheme, the shell is completely broken, the maximum expansion volume is reached, the maximum expansion radius of the gas mass is read in the Euler-Lagrange coupled solver, and the volume of the gas mass after expansion is calculated according to the maximum expansion radius and the height of the explosive V e .

[0011] According to the above scheme, the duration of the constraint state of the gas mass flow process is from the start of the explosive detonation to the time when the kinetic energy of the fragments reaches stability.

[0012] According to the above scheme, the constraint of the gas mass is a reflective boundary applied to the gas mass by the simulation shell, and the constraint position changes in real time with the expansion and breaking of the shell, and the free flow is maintained in the area without the shell.

[0013] According to the above scheme, the method for modifying the constraint condition of the gas mass is to release the constraint applied to the gas mass by the shell, and to let the gas mass flow freely in the afterburning stage.

[0014] The beneficial effects of the present application are: 1、The present application introduces the limiting effect of the shell on the chemical reaction of the explosive detonation product, so as to accurately calculate the pressure load of the shell charge explosion, solves the defect that the mainstream method of simulating explosive initiation based on the chemical reaction of detonation products cannot consider the influence of the shell structure; at the same time, the analysis process is not dependent on specific test calibration conditions, and the solution and calculation of the shell charge load are suitable for all known detonation products and detonation energy and shell material shell charge explosion problems, which has strong universality, can predict other working conditions, and has great engineering application value.

[0015] 2、The present application considers the influence and limiting effect of the initial temperature, initial pressure and flow state of the detonation product gas mass generated by the shell on the detonation of the explosive, introduces the influence of the shell structure into the chemical reaction of the detonation product, obtains the dispersion state and duration of the high-pressure gas mass of the detonation product through fluid-solid coupling solving, provides support for accurately obtaining the load of the shell-loaded charge and subsequent numerical calculation simulation, and effectively makes up for the defects that the two mainstream solving methods in the prior art cannot realize the load solving of the shell-loaded charge. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The flow schematic diagram of one specific embodiment of the present application.

[0017] Figure 2 The schematic diagram for comparing the pressure load calculation results with the test results in the present embodiment. DETAILED DESCRIPTION

[0018] To make the purposes, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below with reference to the drawings in the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0019] In the description of the embodiments of the present application, it should be noted that the orientations or positional relationships indicated by the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated thereby must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present application. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0020] In the description of the embodiments of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or detachably connected, or integrally connected, it can be mechanically connected, or electrically connected, it can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0021] In the embodiments of this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0022] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the embodiments of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, the term "a plurality of" indicates two or more.

[0023] like Figure 1 The method for calculating the explosion pressure load of a charged explosive device based on the chemical reaction of detonation products, as shown, includes the following steps: S1. Based on the chemical reactions that occur during the detonation process of explosives, obtain the detonation energy, the detonation products produced by the detonation, and the mass fraction of each detonation product.

[0024] In this invention, the chemical reaction formula, detonation energy, and detonation products and their mass fractions in the explosive detonation process are obtained by existing methods; the detonation products generated by the detonation and the mass fractions of each detonation product are used to calculate the initial temperature of the gas mass in S4.

[0025] S2. Based on the composition and proportion of detonation products, combined with the temperature and oxygen supply conditions of post-combustion, determine the further chemical reactions that occur during the post-combustion process of the explosive, and obtain the thermodynamic characteristic parameters of each detonation product, including the pre-exponential factor and activation energy.

[0026] In this invention, based on the composition and proportion of the detonation products obtained in S1, combined with the temperature and oxygen supply conditions of the post-combustion process, the chemical reactions occurring in the post-combustion process are determined. Then, based on the chemical reactions, the chemical equations are derived and balanced, and the thermodynamic characteristic parameters of each detonation product, including the pre-exponential factor and activation energy, are calculated. This is prior art and will not be described in detail here.

[0027] When oxygen is sufficient, the oxidation reaction of H2 and CO occurs preferentially at medium-low temperature (800-1200K), and carbon black is oxidized at high temperature (>1200K); when oxygen is insufficient, the disproportionation reaction (such as the reaction of CO and H2O) occurs easily at medium-low temperature, and the product decomposition reaction may occur at extremely high temperature (>2000K); the accuracy of the chemical equation deduced and balanced according to the type of chemical reaction can be verified by experiment or simulation; this is the prior art, and will not be described here.

[0028] In the present application, the pre-exponential factor is a dimensionless number, which is used to calculate the maximum reaction rate of the post-combustion stage of the detonation products in step S7; the activation energy unit is J / mol, which is used to calculate the heat of combustion released by each detonation product in the post-combustion stage in step S7. Both the pre-exponential factor and the activation energy can be obtained by using the existing method.

[0029] S3, the explosion process of the shell-loaded charge in the closed space is divided into three stages: detonation stage, adiabatic expansion stage and post-combustion reaction stage.

[0030] In the present application, the explosion process of the shell-loaded charge in the closed space is actually the explosion process of the shell-loaded charge in the closed space, and the division method of the explosion process is mainly based on the physical characteristics of each stage. The detonation stage is simplified according to the instantaneous detonation assumption, that is, it is assumed that the explosion process of the explosive is completed instantaneously, the explosive is completely converted into detonation products at the moment of initiation, and the detonation products can be equivalent to a high-temperature and high-pressure gas mass with the same size as the initial size of the charge. In the adiabatic expansion stage, air and detonation products are not fully mixed, that is, they are in a limited mixing state, and the detonation products release very limited energy. It is assumed that no chemical reaction occurs in this process until the limited mixing state ends, and it can be considered that the temperature and pressure of the high-temperature and high-pressure gas mass remain unchanged at the beginning and end of the adiabatic expansion stage. In the post-combustion reaction stage, the reflected shock wave enhances the mixing degree of the detonation products and oxygen, and the limited mixing state ends. The first time when the shock wave contacts the near wall is taken as the starting time of the post-combustion reaction stage in the calculation.

[0031] S4, considering the influence of the shell on the explosion process of the shell-loaded charge in the closed space, based on the instantaneous detonation assumption, combined with the detonation products and the mass fraction of each detonation product obtained in step S1, the initial temperature of the high-temperature and high-pressure gas mass generated by the detonation of the explosive is calculated.

[0032] In the present application, the TNT detonation process is constrained by the shell, and part of the detonation energy is converted into the kinetic energy of the shell fragments, so that the energy carried by the high-temperature and high-pressure gas mass generated when the TNT detonation is completed is equal to the total energy generated during the TNT detonation process minus the kinetic energy of the fragments. The initial temperature of the gas mass is calculated by formula (1), that is: (1); In the formula, WFor the charge quality, the unit is g; Q For the detonation energy of unit mass explosive, the unit is MJ / kg; Δ E For the fragment consumption energy that can be obtained by numerical calculation, the unit is MJ; n For the amount of substance of the detonation product gas mixture, which is calculated according to the mass fraction of each detonation product in S1, the unit is mol; C vm Indicated as the constant volume specific heat of substance, the unit is J / (kg•K); T 0 is the room temperature, the unit is K; T m For the initial temperature of the detonation product to be solved, that is, the initial temperature of the gas cluster, the unit is K.

[0033] S5, using the Euler-Lagrange coupling solver, inputting the initial related parameters of the explosive, carrying out numerical calculation on the detonation stage in the explosion process of the closed space with the shell charge, obtaining the initial pressure of the high-temperature and high-pressure gas cluster at this time by solving the maximum expansion volume of the shell under the driving of the explosive detonation (that is, the volume of the high-temperature and high-pressure gas cluster after expansion V e ).

[0034] In the application, the initial pressure of the high-temperature and high-pressure gas cluster is calculated by formula (2): (2). In the formula, n The amount of substance of the high-temperature and high-pressure gas cluster, the unit is mol ；R The universal gas constant, the value is 8.31 J / (mol•K); V e The volume of the high-temperature and high-pressure gas cluster after expansion, the unit is m 3 .

[0035] In the application, when calculating the expansion radius of the gas cluster, the constraint effect of the shell expansion process on the diffusion characteristics of the detonation product needs to be considered. When the shell expansion process will occur fragmentation phenomenon, the shell is completely broken when it expands to a certain extent, and the gas cluster reaches the maximum expansion volume. The maximum expansion radius of the gas cluster is read in the Euler-Lagrange coupling solver, and the volume of the high-temperature and high-pressure gas cluster after expansion V e is calculated according to the maximum expansion radius and the height of the explosive, and the initial pressure of the high-temperature and high-pressure gas cluster is calculated according to formula (2). The initial related parameters of the explosive, including the initial radius, the initial height and the charge quantity, the initial temperature of the gas cluster calculated in step S4 and the initial pressure of the gas cluster obtained in step S5 are input parameters, which are used for the input of step S6.

[0036] S6, according to the initial relevant parameters of the explosive (including initial radius, initial height and charge quantity), the initial temperature and initial pressure of the gas mass, and the environmental temperature and environmental pressure, and in combination with the structural characteristics of the closed space, a finite element three-dimensional model of the high-temperature and high-pressure gas mass generated by the explosion of the closed space with the shell charge is constructed in the Eulerian multiphase flow solver, and the constraint of the high-temperature and high-pressure gas mass flow process during the expansion and fragmentation of the shell and the constraint duration are input into the Eulerian multiphase flow solver, and the relevant parameters of the detonation product at the end of the adiabatic expansion stage are calculated, including the radius, height, pressure, temperature and diffusion velocity of the expanded gas mass, so as to obtain the dispersion state of the detonation product at the end of the adiabatic expansion stage.

[0037] In the present application, the duration of the constraint state of the high-temperature and high-pressure gas mass flow process is from the start of the explosive detonation to the time when the kinetic energy of the fragments reaches stability. The time when the kinetic energy of the fragments reaches stability can be obtained in step S5. The constraint of the high-temperature and high-pressure gas mass is a reflective boundary applied to the gas mass by the shell, and the constraint position changes in real time with the expansion and fragmentation of the shell, and the shell-free area is kept free flowing.

[0038] S7, after the end of the adiabatic expansion stage, the reaction into the post-combustion reaction stage is solved, the relevant parameters of the detonation product at the end of the adiabatic expansion stage obtained in S6 (including the radius, height, pressure, temperature and diffusion velocity of the expanded gas mass), and the thermodynamic characteristic parameters of each detonation product solved in step S2 (including the pre-exponential factor and activation energy) are input into the finite element three-dimensional model of S6 as input parameters of the post-combustion reaction stage, and the constraint condition of the high-temperature and high-pressure gas mass in the post-combustion reaction stage is modified, at this time the shell is completely expanded and fragmented and no longer produces constraint effect on the high-temperature and high-pressure gas mass, and the Eulerian multiphase flow solver is used to calculate the time history curve of the explosion pressure load of the shell charge in the post-combustion reaction stage.

[0039] In the present application, the specific method for modifying the constraint condition of the high-temperature and high-pressure gas mass is to remove the constraint applied by the shell to the gas mass in S6, and let the high-temperature and high-pressure gas mass flow freely in the post-combustion stage, and the post-combustion reaction stage ends when the explosion pressure load tends to be stable.

[0040] In the present application, the chemical reaction determined by S2 and the pre-exponential factor obtained are used to calculate the maximum reaction rate of each detonation product in the post-combustion stage (obtained by existing conventional technology); when the real-time reaction rate of a certain detonation product reaches the maximum reaction rate, the reaction stops, otherwise the post-combustion reaction of the detonation product continues. The activation energy obtained by S2 in combination with the amount of substance of each detonation product, the real-time reaction rate, etc. can calculate the combustion heat released by each detonation product in the post-combustion stage (obtained by existing technology), so as to solve the explosion pressure load.

[0041] Embodiment This embodiment takes 28g of TNT explosive as an example to specifically illustrate the calculation method of the explosion pressure load of the shell-charge.

[0042] A calculation method of the explosion pressure load of the shell-charge based on the chemical reaction of detonation products, comprising the following steps: S1, based on the chemical reaction occurring in the detonation process of the explosive, the detonation energy, the detonation products produced by the detonation, and the mass fraction of each detonation product are determined.

[0043] In this embodiment, the chemical reaction occurring in the detonation process of TNT explosive is: C7H5N3O6→ 2.2CO+1.6H2O+1.5N2+1.1CO2+0.36H2+0.27CH4+3.43C; The density of TNT explosive is 1.63g / cm 3 From the above formula, the total mass of the detonation products produced by the detonation of 28g of TNT explosive is 1.2895mol, and when T 0=298K (room temperature), the unit mass detonation energy is 4.495MJ / kg. The types of detonation products and their corresponding mass fractions are shown in Table 1.

[0044] Table 1 Mass fraction of detonation product mixture

[0045] S2, based on the composition of the detonation products, the chemical reactions further occurring in the afterburning process of the explosive, and the thermodynamic characteristic parameters of each detonation product, including the pre-exponential factor and the activation energy, are determined.

[0046] In this embodiment, CO, H2, CH4 and C produced by detonation are all combustible products, which will further release energy after mixing with sufficient oxygen in a high temperature environment. The specific chemical reaction related parameters of the detonation products are shown in Table 2.

[0047] S3, the explosion process of the shell-charge in the closed space is divided into three stages: detonation stage, adiabatic expansion stage and afterburning reaction stage.

[0048] Table 2 Chemical reaction related parameters of detonation products

[0049] S4, considering the influence of the shell on the explosion process of the shell-charge in the closed space, based on the instantaneous detonation assumption, the initial temperature of the high temperature and high pressure gas mass produced by the detonation of the explosive is calculated based on the detonation products and the mass fraction of each detonation product obtained in step S1.

[0050] In this embodiment, W The charge mass is 28g; QThe detonation energy of unit mass of explosive is 4.495 MJ / kg; T 0 is the ambient temperature, i.e. room temperature, and is 298 K; the shell fragment material is 235 steel, and the energy is 0.041 MJ. The energy carried by the high-temperature and high-pressure gas mass obtained after calculation is 0.08484 MJ, and the initial temperature T m is 2476 K, as shown in Table 3.

[0051] Table 3 Related parameters of the shell-encased charge working condition

[0052] S5, using an Euler-Lagrange coupling solver, inputting the initial related parameters of the explosive, performing numerical calculation on the detonation stage in the explosion process of the shell-encased charge in the closed space, and obtaining the initial pressure of the high-temperature and high-pressure gas mass by solving the maximum expansion volume of the shell under the driving of the explosive detonation.

[0053] In this embodiment, the TNT explosive is a cylinder with a height of 35.9 mm and a diameter of 25.1 mm, and a 5 mm thick steel shell is attached to the outside of the TNT explosive. The initial related parameters of the explosive include a charge amount of 28.0 g, an initial height of 35.9 mm, and an initial radius of 12.55 mm. When the steel shell expands to 2.5 times, the shell is completely broken, so the radius of the high-temperature and high-pressure gas mass corresponding to the 28 g explosive is expanded to 2.5 times the initial radius of the TNT explosive, and the maximum expansion radius is 31.4 mm. Then, the volume of the high-temperature and high-pressure gas mass after expansion is calculated according to the maximum expansion radius and the height of the explosive V e , and the initial pressure of the high-temperature and high-pressure gas mass is calculated according to formula (2). The initial related parameters of the explosive, including the initial radius, the initial height, and the charge amount, as well as the initial temperature of the gas mass calculated in step S4 and the initial pressure of the gas mass obtained in step S5, are input parameters for step S6, as shown in Table 4.

[0054] Table 4 Related input parameters of S6

[0055] S6, according to the initial related parameters of the explosive, the initial temperature and the initial pressure of the gas mass, and the ambient temperature and the ambient pressure, and combining the structural characteristics of the closed space, a high-temperature and high-pressure gas mass generated by the explosion of the shell-encased charge in the closed space is modeled in an Eulerian multiphase flow solver; then, the constraints on the flow process of the high-temperature and high-pressure gas mass during the expansion and fragmentation process of the shell and the constraint duration are input into the Eulerian multiphase flow solver, and the related parameters of the detonation product at the end of the adiabatic expansion stage are calculated, including the radius, the height, the pressure, the temperature, and the diffusion velocity after expansion of the gas mass, so as to obtain the spray state of the detonation product at the end of the adiabatic expansion stage.

[0056] The example is an explosion environment of a shell-encased charge in a closed space, and the structural characteristics of the closed space include the length, width, and height of the closed space, the wall thickness, material properties, and the like. The structural dimensions of the closed space are 900 mm x 400 mm x 400 mm, the ambient temperature is 298 K (room temperature), and the ambient pressure is 0.101 MPa. The explosion environment of the shell-encased charge in the closed space is modeled and solved, the initial radius of the high-temperature and high-pressure gas mass before expansion is 12.55 mm, the height is 35.9 mm, the initial pressure is 239 MPa, the radius of the gas mass increases from 12.55 mm to 31.4 mm after expansion, and the pressure of the gas mass does not change before and after expansion. The duration of the constraint state is 0.03 mm, and since the shell has no end cap, the high-temperature and high-pressure gas mass is free to flow at the bottom and top surfaces of the shell, and the constraint is only provided in the circumferential direction.

[0057] S7, after the end of the adiabatic expansion stage, the relevant parameters of the detonation product in the dispersion state obtained in S6 and the thermodynamic characteristic parameters of each detonation product solved in step S2 are used as input parameters of the post-combustion reaction stage, at this time the shell is completely expanded and broken and no longer produces a constraint on the high-temperature and high-pressure gas mass, the constraint condition of the high-pressure gas mass of the detonation product in the post-combustion reaction stage is modified, and an Eulerian multiphase flow solver is used to calculate the time history curve of the explosion pressure load of the shell-encased charge in the post-combustion reaction stage.

[0058] In the example, after the duration of the adiabatic expansion stage in S6, the circumferential constraint of the shell on the high-temperature and high-pressure gas mass is removed, and the Eulerian multiphase flow solver is continued to be used to calculate the time history curve of the explosion pressure load (i.e., the curve of the explosion pressure load changing with time), and the solving duration is selected to be 5 mm, at this time the explosion pressure load has stabilized, and the stable pressure is about 0.61 MPa; the explosion pressure load and the impulse (time integral of the pressure) obtained by solving are output, and are compared with the test data (i.e., the test pressure and the test impulse) in Figure 2 , as shown in Figure 2 , it can be found that the pressure change history considering the post-combustion process of the detonation product is in good agreement with the test results, which indicates that the shell-constrained shell-encased charge pressure load calculation method established can well reflect the test pressure change and can be used for the analysis of the explosion load characteristics of the shell-encased charge in a closed space.

[0059] The embodiments of the present application are described above in combination with the drawings, but the present application is not limited to the specific embodiments described above, and the specific embodiments described above are only illustrative and not limiting, and those of ordinary skill in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, which all belong to the protection of the present application.

Claims

1. A method for calculating the explosion pressure load of a charged explosive device based on the chemical reaction of detonation products, characterized in that, Includes the following steps: Based on the chemical reactions that occur during the detonation process of explosives, the detonation energy, the detonation products produced by the detonation, and the mass fraction of each detonation product are obtained. Based on the composition and proportion of detonation products, combined with the temperature and oxygen supply conditions of post-combustion, the chemical reactions that occur further during the post-combustion process of the explosive are determined, and the thermodynamic characteristic parameters of each detonation product, including the pre-exponential factor and activation energy, are determined. The explosion process of a charged explosive in a confined space is divided into three stages: the detonation stage, the adiabatic expansion stage, and the post-combustion reaction stage. Based on the instantaneous detonation assumption, and combining the detonation products and the mass fraction of each detonation product, the initial temperature of the gas cloud generated by the explosive detonation is calculated. Numerical calculations were performed on the detonation stage of a charged explosive device in a confined space to obtain the initial pressure of the gas cloud. Based on the initial radius, initial height, and charge amount of the explosive, as well as the initial temperature and initial pressure of the gas cloud, and combined with the structural characteristics of the enclosed space, a finite element three-dimensional model of the detonation product gas cloud generated by the explosion of the shell-loaded explosive in the enclosed space is constructed in the Euler multiphase flow solver. The constraints on the gas cloud flow process during the shell expansion and breakage process and the duration of the constraints are input into the Euler multiphase flow solver to calculate the pressure, temperature, and diffusion rate of the gas cloud after expansion under the state of detonation product dispersion at the end of the adiabatic expansion stage. The pressure, temperature, and diffusion rate of the detonation products under the dispersion state, as well as the pre-exponential factor and activation energy of each detonation product, are input into the finite element three-dimensional model as input parameters for the post-combustion reaction stage. The time history curve of the explosion pressure load of the charged explosive in the post-combustion reaction stage is calculated and obtained.

2. The method for calculating the explosion pressure load of a charged explosive based on the chemical reaction of detonation products as described in claim 1, characterized in that, The method for dividing the explosion process is based on the physical characteristics of each stage: The detonation stage is simplified according to the instantaneous detonation assumption, which assumes that the explosive detonation process is completed instantaneously, and that the explosive is completely converted into detonation products at the moment of detonation. The detonation products are equivalent to a gas cloud. In the adiabatic expansion stage, the air and detonation products are not fully mixed and are in a restricted mixing state, and no chemical reaction occurs. In the post-combustion reaction stage, the restricted mixing state ends.

3. The method for calculating the explosion pressure load of a charged explosive device based on the chemical reaction of detonation products as described in claim 1, characterized in that, The initial temperature of the air mass is calculated using formula (1), that is: (1)； In the formula, W The mass of the propellant is expressed in grams (g). Q Δ represents the detonation energy per unit mass of explosive, expressed in MJ / kg. E The energy consumed by the fragments is measured in MJ. n This represents the amount of substance of the detonation product mixture, expressed in mol. C vm It is expressed as the specific heat at constant volume of a substance, with units of J / (kg·K); T 0 represents room temperature, expressed in K. T m The initial temperature of the air mass is expressed in Kelvin (K).

4. The method for calculating the explosion pressure load of a charged explosive device based on the chemical reaction of detonation products as described in claim 1, characterized in that, Initial pressure of the air mass P 0 is calculated using formula (2): (2)； In the formula, n The amount of substance of the air mass, expressed in mol. R For universal gas constants, the value is taken as 8.31 J / (mol•K); T m The initial temperature of the air mass, expressed in Kelvin (K). V e The volume of the air mass after expansion, in meters. 3 .

5. The method for calculating the explosion pressure load of a charged explosive based on the chemical reaction of detonation products as described in claim 4, characterized in that, Volume of the gas cloud after expansion V e The calculation method is as follows: the shell is completely broken, reaching the maximum expansion volume. The maximum expansion radius of the gas cloud is read in the Euler-Lagrange coupled solver. The volume of the gas cloud after expansion is calculated based on the maximum expansion radius and the height of the explosive. V e .

6. The method for calculating the explosion pressure load of a charged explosive based on the chemical reaction of detonation products as described in claim 1, characterized in that, The duration of the constrained state during the gas flow process is the time from the start of the explosive detonation to the time when the fragment kinetic energy reaches a stable state.

7. The method for calculating the explosion pressure load of a charged explosive based on the chemical reaction of detonation products as described in claim 1, characterized in that, The constraint on the air mass is a reflective boundary applied to the air mass by a simulated shell, and the position of the constraint changes in real time as the shell expands and breaks, maintaining free flow in the shell-free region.

8. The method for calculating the explosion pressure load of a charged explosive based on the chemical reaction of detonation products as described in claim 1, characterized in that, The method to modify the constraints on the gas mass is to remove the constraints imposed by the shell on the gas mass, allowing the gas mass to flow freely in the post-combustion stage.

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