Square closed space combustible gas explosion overpressure prediction method and processor

Abstract

The invention discloses a square closed space combustible gas explosion overpressure prediction method and a processor, and relates to the technical field of combustible gas explosion overpressure prediction. The method comprises the following steps: firstly, assuming relevant parameters in the explosion process of the square closed space; establishing a simplified physical model according to flames development characteristics of combustible gas explosion in an experiment; then, according to the simplified physical model, combining with a control equation to obtain an explosion pressure prediction mathematical model; and finally, the engineering actual prediction initial parameters are substituted into the explosion pressure prediction mathematical model for calculation, and prediction values of the square confined space explosion overpressure in different explosion stages can be obtained. According to the invention, the explosion overpressure prediction model established by using the segmentation method has high conformity with an experimental result; according to the method, the explosion overpressure of the square closed space can be quickly predicted, and reliable reference basis is provided for combustible gas explosion disaster effect and consequence evaluation.

Description

Technical Field

[0001] The present invention relates to the technical field of combustible gas explosion overpressure prediction, and in particular to a combustible gas explosion overpressure prediction method and a processor applied to a square enclosed space. Background Art

[0002] Currently, combustible gases such as natural gas and hydrogen are widely used due to their high thermal energy, wide availability, and low pollution. They are both industrial raw materials and can be used as fuel to provide energy for people's production and life. During their use, storage, and transportation, if these combustible gases leak, the explosive premixed gas formed after mixing with air is very likely to cause an explosion accident when it encounters a heat source or spark. This is especially true in confined spaces. Due to the constraints of the walls, the pressure in the confined space rises rapidly after the explosion, forming a shock wave, leading to structural damage, fragment scattering, and thermal radiation, resulting in serious property damage and casualties. To avoid the occurrence or expansion of accidents, improving the accuracy of explosion overpressure prediction is key to structural explosion-resistant design and daily safety management. In particular, the peak overpressure generated by a confined space explosion is one of the most important parameters in explosion-resistant design and daily safety management.

[0003] Currently, researchers in this field have conducted research on explosive overpressure in confined spaces, achieving a comprehensive understanding of overpressure and its influencing factors. Due to experimental safety and economic constraints, current research on explosive flame propagation and overpressure primarily utilizes a combination of small-scale experiments, theoretical analysis, and numerical simulations. The most extensive research on explosive flame propagation and overpressure in pipelines is currently underway. This research focuses on the acceleration mechanisms and overpressures affected by obstacles, pipe shape, and aspect ratio within the pipeline. For analysis of explosive flame propagation and overpressure in other vessels, a 20L sphere was used as a background to investigate the effects of different gases, concentrations, ignition methods, and ignition energies on overpressure and pressure rise rates. Theoretical analysis focuses on the acceleration mechanisms of explosive flames, instabilities during flame propagation, and the critical conditions for the transition from deflagration to detonation. Combustible gas explosions occur frequently in both industry and daily life, often occurring within buildings such as factories, warehouses, and residential buildings. The consequences of these explosions are severe. Existing research mainly focuses on pipelines and spherical containers, but the research on the explosion characteristics of combustible gases occurring in square spaces is not sufficient. Once an explosion occurs in a square space such as a factory building or warehouse, the consequences are very serious. Therefore, research on square space explosions is particularly important.

[0004] Guo Qiang et al. proposed the “Study on Experimental and Three-dimensional Numerical Simulation of Combustible Gas Deflagration in Square Space”. 3The effect of the pressure relief area and gas volume fraction on the explosion relief pressure within a square space is not discussed. The parameter time t is not mentioned, and the main focus is on calculating the value of the explosion relief pressure. There is a lack of prediction of the pressure change at a certain time during the explosion of the square confined space. The time-pressure prediction can provide a valuable reference for the selection of the explosion relief pressure. The lack of prediction of the pressure change at a certain time during the explosion of the square confined space makes it difficult to quickly and efficiently develop an explosion relief design plan for the square confined space. Hu Sheng et al. proposed the "Review of Research on Combustible Gas Explosion Hazards and Pressure Relief Dimensions in Class A Warehouses." The article mainly used numerical simulation software to build models, set conditions, and perform calculations using simulation software. No innovation or derivation was made to the formula itself. The calculation formula in the simulation software is not applicable to square confined spaces.

[0005] It can be seen that the research on the prediction of combustible gas explosion in square confined spaces needs further improvement. Summary of the Invention

[0006] One of the purposes of the present invention is to provide a method for predicting the overpressure of combustible gas explosion in a square confined space. The method is suitable for studying the explosion of combustible gas in a square confined space. The method is simple to operate and can be promoted for use in engineering applications. The prediction method of the present invention provides a reliable reference basis for evaluating the hazard effects and consequences of combustible gas explosions.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for predicting overpressure of combustible gas explosion in a square confined space comprises the following steps:

[0009] a. Assume the relevant parameters during the explosion of a square confined space;

[0010] b. Establish a simplified physical model based on the flame development characteristics of combustible gas explosions in the experiment. Assume that the length, width, and height of the square enclosed space are x, y, and z, respectively, where x = a, y = b, and z = c. The explosion of the square enclosed space is divided into three stages:

[0011] b1. Stage I: The reaction time is 0→t1. Assuming that the flame development in this stage expands as a spherical laminar flame, the flame radius r1 in this stage satisfies 0 <r1≤a / 2;

[0012] b2. Stage II: The reaction time is t1→t2. Assuming that the flame in this stage is cylindrical, the flame radius r2 in this stage satisfies a / 2 <r2≤b / 2;

[0013] b3. Stage III: The reaction time is t2→t3. Assuming that the flame shape in this stage is rectangular, the flame radius r3 in this stage satisfies b / 2. <r3≤c / 2;

[0014] c. Based on the simplified physical model established in step b, a mathematical model for explosion pressure prediction is derived in combination with the control equation;

[0015] The explosion pressure calculation formula in the first stage of the combustible gas reaction process in the explosion pressure prediction mathematical model is shown in formula (1):

[0016]

[0017] In formula (1), P1 is the explosion pressure of the combustible gas in stage I when it reaches the corresponding flame area; P0 is the initial pressure of the square enclosed space; α is the turbulence factor; K r is the combustion rate measured at a certain reference temperature and reference pressure; t1 is the reaction time of the first stage; V is the total volume of the square enclosed space; P m is the final pressure of the square enclosed space;

[0018] The explosion pressure calculation formula in the combustible gas reaction process in the second stage of the explosion pressure prediction mathematical model is shown in formula (2):

[0019]

[0020] In formula (2): P2 is the explosion pressure of the combustible gas reaction process in stage II; C1 is the constant coefficient; e is the natural constant; r2 is the flame radius in stage II; t2 is the reaction time in stage II;

[0021] The explosion pressure calculation formula in the combustible gas reaction process in the third stage in the explosion pressure prediction mathematical model is shown in formula (3):

[0022]

[0023] In formula (3), P3 is the explosion pressure during the combustible gas reaction in stage III; C2 is the constant coefficient; r3 is the flame radius in stage III; R2 is the maximum flame radius in stage II; t3 is the reaction time in stage III;

[0024] d. Substituting the parameters obtained from actual measurements into equations (1), (2), and (3) can yield the explosion pressures of the explosion gas in the square enclosed space at different stages.

[0025] In the above-mentioned method for predicting overpressure of combustible gas explosion in a square confined space, in formula (2), the calculation of C1 is shown in formula (4):

[0026]

[0027] In formula (4), P1 is the explosion pressure of the combustible gas in stage I when it reaches the corresponding flame area; P0 is the initial pressure of the square enclosed space; e is a natural constant; α is the turbulence factor; K r P is the burning rate measured at a certain reference temperature and reference pressure; m is the final pressure of the square enclosed space; r2 is the flame radius of stage II; t1 is the reaction time of stage I.

[0028] The above-mentioned method for predicting overpressure of combustible gas explosion in a square confined space is characterized in that: in formula (3), the calculation formula of C2 is shown in formula (5):

[0029]

[0030] In formula (5), P3 is the explosion pressure during the combustible gas reaction in stage III; P0 is the initial pressure of the square enclosed space; α is the turbulence factor; K r P is the burning rate measured at a certain reference temperature and reference pressure; m is the final pressure of the square enclosed space; R2 is the maximum flame radius of stage II; t2 is the reaction time of stage II.

[0031] In the above-mentioned method for predicting overpressure of combustible gas explosion in a square confined space, in step a, the assumptions of the relevant parameters are as follows: the explosion process is assumed to be carried out under adiabatic wall conditions; the combustible gas is evenly distributed in the square confined space and ignites at the exact center of the square confined space; in the initial reaction, the temperature of the combustible gas and the temperature of the combustion products remain unchanged during the development of the explosion; in the initial reaction, the combustible gas and the combustion products both conform to the ideal gas state equation; and the effect of pressure rise on the flame propagation speed in the square confined space is negligible.

[0032] In the above-mentioned method for predicting overpressure of combustible gas explosion in a square enclosed space, in step b, r1 is the distance from the explosion center to the spherical flame surface; r2 is the distance from the explosion center to the side of the cylindrical flame; and r3 is the distance from the explosion center to the side of the rectangular flame where the area no longer changes.

[0033] In the above-mentioned method for predicting overpressure of combustible gas explosion in a square confined space, in step c, during the explosion of combustible gas in the square confined space, it is assumed that the square confined space is an isothermal system and the combustible gas satisfies the law of conservation of mass during the explosion; the equations of state and mass conservation equations of unreacted and reacted substances are obtained;

[0034] According to the state equation and mass conservation equation, the mass change rate of the burned gas per unit time is converted into the pressure rise rate equation, as shown in formula (6):

[0035]

[0036] In formula (6): α is the turbulence factor; K r is the combustion velocity measured at a certain reference temperature and reference pressure; A is the flame front area; V is the volume of the square enclosed space; P m is the final pressure of the square enclosed space; P0 is the initial pressure of the square enclosed space; P is the explosion pressure;

[0037] For stage I, according to formulas (7), (8) and (9), combined with formula (6), the explosion pressure calculation formula for the combustible gas reaction process in stage I is derived;

[0038]

[0039] In formula (7): V b1 is the volume occupied by the reactants in stage I; r1 is the distance from the explosion center to the spherical flame surface;

[0040]

[0041] In formula (8): A1 is the area of the flame front in stage I; r1 is the distance from the explosion center to the spherical flame surface;

[0042]

[0043] In formula (9): A1 is the area of the flame front in the first stage; V is the volume of the square enclosed space; P m is the final pressure of the square enclosed space; P0 is the initial pressure of the square enclosed space; P1 is the explosion pressure when the combustible gas in stage I reaches the corresponding flame area.

[0044] In the above-mentioned method for predicting overpressure of combustible gas explosion in a square confined space, in step c, for stage II, formulas (10), (11), and (12) are combined to derive a calculation formula for the explosion pressure during the combustible gas reaction process in stage II;

[0045]

[0046] In formula (10): V b2 is the volume occupied by the reactants in stage II; r2 is the distance from the explosion center to the side of the cylindrical flame; R1 is the maximum radius of the flame in stage I;

[0047] A2=4πR1r2 (11);

[0048] In formula (11), A2 is the flame front area of stage II; R1 is the maximum flame radius of stage I; r2 is the distance from the explosion center to the side of the cylindrical flame;

[0049]

[0050] In formula (12), A2 is the area of the flame front in stage II; V is the volume of the square enclosed space; r2 is the distance from the explosion center to the side of the cylindrical flame; P m is the final pressure of the square enclosed space; P0 is the initial pressure of the square enclosed space; P2 is the explosion pressure when the combustible gas in stage II reaches the corresponding flame area; R1 is the maximum flame radius in stage I.

[0051] In the above-mentioned method for predicting overpressure of combustible gas explosion in a square confined space, in step c, for stage III, formulas (13), (14), and (15) are combined to derive the calculation formula for the explosion pressure during the combustible gas reaction process in stage III:

[0052] V b3 =8R1R2(r3-r i3 ) (13);

[0053] In formula (13): V b3 is the volume of the reactants in stage III; R1 is the maximum radius of the flame in stage I; R2 is the maximum radius of the flame in stage II; r3 is the radius of the flame in stage III; r i3 is the initial flame radius of stage III;

[0054] A3=8R1R2 (14);

[0055] In formula (14), A3 is the flame front area of stage III; R1 is the maximum flame radius of stage I; R2 is the maximum flame radius of stage II;

[0056]

[0057] In formula (15), A3 is the flame front area of stage III; V is the volume of the square enclosed space; r3 is the flame radius of stage III; r i3 is the initial flame radius of stage III; P m is the final pressure of the square enclosed space; P0 is the initial pressure of the square enclosed space; P3 is the explosion pressure when the combustible gas in stage III reaches the corresponding flame area.

[0058] Another object of the present invention is to provide a processor configured to execute the above-mentioned method for predicting overpressure of combustible gas explosion in a square enclosed space.

[0059] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0060] The present invention studies the prediction of combustible gas explosion in a square confined space, and makes it match the square confined space by deriving and innovating the formula. In the square confined space, x=a, y=b, z=c, The explosion overpressure prediction model is divided into three stages under the conditions of , in which the flame radius of each stage is limited. By assuming multiple conditions, limiting the aspect ratio of the square space, and using the segmentation method, the explosion overpressure prediction model is highly consistent with the experimental results.

[0061] This method uses simplified mathematical models and rapid calculations to approximate some parameters in a complex explosion process. A simplified physical model is established based on the flame development characteristics of combustible gas explosions in experiments. Based on this simplified physical model, the governing equations derive a mathematical model for predicting explosion pressure. By substituting the actual predicted initial parameters for the project into the mathematical model, the predicted values for the explosion overpressure in a square confined space at different stages of the explosion are obtained. This enables rapid and accurate prediction and assessment of the overpressure in a square confined space, filling the gap in traditional simulations that rely solely on spherical and various pipe models. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The present invention will be further described below with reference to the accompanying drawings.

[0063] Figure 1 This is a flow chart for predicting overpressure of combustible gas explosion in a square enclosed space according to the present invention;

[0064] Figure 2 The three stages of the physical model are simplified for this invention. Figure 2 (a) is stage I, (b) is stage II, and (c) is stage III;

[0065] Figure 3 This is a time history graph of acetylene explosion overpressure in a square enclosed space according to the present invention;

[0066] Figure 4 This is a graph showing the overpressure history of hydrogen and methane explosions in a square enclosed space according to the present invention;

[0067] Figure 5 This is a time history graph of overpressure caused by oil and gas explosion in a square enclosed space according to the present invention. DETAILED DESCRIPTION

[0068] The present invention proposes a method and processor for predicting overpressure of combustible gas explosion in a square confined space. In order to make the advantages and technical solutions of the present invention clearer and more specific, the present invention is further described below with reference to specific embodiments.

[0069] The equation of state and mass conservation equation described in the present invention are the basic equations for solving such problems, but the basic equations are not applicable to square confined spaces. Therefore, the present invention innovates the derivation of the existing equations on the basis of the existing equations to make them more compatible with square confined spaces. After verification by the examples, the method of the present invention realizes the rapid and accurate prediction of the overpressure of combustible gas explosion in square confined spaces.

[0070] In addition, for faster calculation, the prediction method proposed in the present invention can be imported into a processor to make its calculation speed faster, and is suitable for quickly evaluating the explosion pressure range and pressure changes in a square enclosed space.

[0071] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application.

[0072] The flow chart of the present invention for predicting overpressure of combustible gas explosion in a square confined space is as follows: Figure 1 As shown, the operation process is:

[0073] The first step is to make approximate assumptions about some parameters in the complex explosion process. The specific assumptions are: the explosion process occurs under adiabatic wall conditions; the combustible gas is evenly distributed in the square enclosed space and ignites at the center of the square enclosed space;

[0074] Initial reaction combustible gas temperature (T u ) and combustion product temperature (T b ) remains unchanged during the explosion, that is, T u =T i = constant, T b =T f = constant; the initial reaction combustible gas and combustion products all conform to the ideal gas state equation; the effect of pressure increase on flame propagation speed is ignored.

[0075] The second step is to establish a simplified physical model based on the flame development characteristics of the combustible gas explosion in the experiment.

[0076] like Figure 2 As shown, a physical model is established. Assume that the length, width, and height of the rectangular enclosed space are x, y, and z, respectively, where x = a, y = b, and z = c, and a ≤ 1 / 3 b ≤ 1 / 3 c. Then the explosion of this square enclosed space can be divided into three stages:

[0077] like Figure 2 As shown in (a), stage I: the reaction time is 0→t1. Assuming that the flame development in this stage is almost a spherical laminar flame expansion, the flame radius at this time satisfies 0 <r1≤a / 2。

[0078] like Figure 2As shown in (b), stage II: the reaction time is t1→t2. When the spherical flame develops to a certain stage, the flame front encounters the narrow xy wall and cannot continue to develop and is continuously compressed, which makes the flame continue to develop evenly in the direction of the wider wall. In order to simplify the calculation process, the flame development shape of this stage is approximated as a cylinder. The flame radius at this time satisfies a / 2 <r2≤b / 2。

[0079] like Figure 2 As shown in (c), stage III: the reaction time is t2→t3. At this time, the cylindrical flame cannot continue to develop after the side contacts the xz wall and is continuously compressed, which makes the flame continue to develop evenly in the direction of the wider wall. In order to simplify the calculation process, the flame development shape of this stage is approximated as a rectangle. At this time, the flame radius satisfies b / 2 <r3≤c / 2。

[0080] The flame radius in the simplified physical model is defined as the distance from the explosion center to the interface between the unburned and burned areas of the flame. The flame radius r1 in stage I specifically refers to the distance from the explosion center to the spherical flame surface; the flame radius r2 in stage II specifically refers to the distance from the explosion center to the side of the cylindrical flame. The flame radius r3 in stage III specifically refers to the distance from the explosion center to the side of the rectangular flame with an unchanged area. The unchanged side here can be further understood as the side of the rectangular flame with an unchanged area.

[0081] The third step is to establish a simplified physical model and combine it with the control equation to derive a mathematical model for explosion pressure prediction.

[0082] Establish the governing equation, assuming an isothermal system and that the combustible gas always satisfies the conservation of mass during the explosion:

[0083] For an isothermal system, the equations of state for the unreacted and reacted species are:

[0084]

[0085] The mass conservation equation is:

[0086] m=m u +m b =n u M u +n b M b (3);

[0087] V=V u +V b (4); In formulas (1), (2), (3), and (4), m is the total mass of the initial premixed gas; m b is the mass of the burned premixed gas; m u is the mass of unburned premixed gas; n uis the number of moles of unburned premixed gas; n b is the number of moles of burned products; M u is the molar mass of the unburned premixed gas; M b is the molar mass of the combustion products; V u is the volume of unburned premixed gas; V b is the volume of combustion products; V is the total volume of the square enclosed space; P is the explosion pressure; R is the ideal gas constant; T u is the initial reaction combustible gas temperature; T b is the combustion product temperature;

[0088] During the entire explosion process, for an isothermal system:

[0089]

[0090] In formula (5), P0 is the initial pressure; P m is the final pressure, i.e. the maximum pressure; n i and n f are the masses of the initial and final states, n i ≈n f ; V0 is the initial gas volume;

[0091] After the combustible gas in the confined space is ignited, the reaction gas flows into the flame surface at a speed v without turbulence. The mass flowing into the flame surface per unit time is:

[0092]

[0093] In formula (6), ρ u is the density of combustible gas; A is the flame front area; v is the reaction gas velocity;

[0094] If expressed in moles, we have:

[0095]

[0096] Using formula (1), the combustion mass change rate is expressed as the burned gas, and then substituted into formula (7), the burnt gas mass change rate per unit time can be expressed as:

[0097]

[0098] Where K r It is the combustion velocity measured at a certain reference temperature and reference pressure; α is the turbulence factor, and in the case of laminar flow, α = 1.

[0099] Combining the equation of state and mass conservation equations (2) to (5), the mass change rate form of equation (8) can be converted into the pressure rise rate form:

[0100]

[0101] The mathematical model of overpressure in a square confined space explosion also corresponds to the physical model, which is divided into three stages. If the heat loss of the container is ignored, the maximum pressure of the gas explosion in the closed container is P m It has nothing to do with the size and shape of the container, but only with the final state of the reaction. Therefore, it is assumed here that the maximum pressure P of the combustible gas reaction is m The reaction state equation (1) and equation (5) show that the volumes of reactants in stage I, stage II, and stage III are:

[0102]

[0103] Where, P1, P2 and P3 are the explosion pressures when reaching the corresponding flame area in stage I, stage II and stage III respectively; V b1 、V b2 and V b3 are the volumes occupied by the reactants in stage I, stage II and stage III respectively; n1, n2 and n2 are the molar numbers of the burned products in stage I, stage II and stage III respectively.

[0104] According to the flame volume and flame front area formulas of the explosion model at different stages, combined with formulas (13)-(15), the formulas for the pressure rise rate in the three stages of explosion in a square closed container can be obtained as follows:

[0105] For Phase I: Then, combining formula (13), we can get:

[0106]

[0107] Substituting this formula into formula (9), we can obtain the formula for the pressure rise rate during the explosion in the closed container in stage I:

[0108]

[0109] make Formula (17) can be written as:

[0110]

[0111] The explosion pressure during the combustible gas explosion reaction in stage I is obtained:

[0112]

[0113] For Phase II: A2=4πR1r2, when the flame in stage I develops to the shortest wall, the flame volume V e1 for:

[0114]

[0115] Flame volume V at the beginning of flame development in stage II i2 It can be calculated that:

[0116]

[0117] Assume that the flame volumes at the end of stage I and the beginning of stage II are approximately equal:

[0118] V e1 ≈V i2 (twenty two);

[0119] Combining equations (20-22), we can calculate the initial radius r of the cylindrical flame at the beginning of stage II: i2 :

[0120]

[0121] Then, combined with formula (13), we can get:

[0122]

[0123] Similarly, the formula for the pressure rise rate during the explosion in the closed container in stage II is:

[0124]

[0125] The flame radius r2 in this stage shows a certain functional change with the reaction time t2. The derivative of formula (14) with respect to t2 is obtained as

[0126]

[0127] and

[0128]

[0129] This gives the flame speed:

[0130]

[0131] Integrate both sides of equation (29) and solve the equation to obtain the relationship between r2 and t2 in this stage.

[0132] Afterwards, the explosion pressure of the combustible gas explosion reaction in the second stage is obtained by rearranging and transforming Equation (25):

[0133]

[0134] In the formula, the C1 value here is a constant coefficient. The coefficient is different under different reaction gas and reaction vessel conditions. It can be obtained by substituting the explosion pressure value P1 and reaction time t1 obtained in stage I and then reversely calculating it.

[0135]

[0136] For Phase III: V b3 =8R1R2(r3-r i3 ), A3=8R1R2, when the flame in stage II develops to the shortest wall, the flame volume V e2 for:

[0137]

[0138] The flame volume V at the initial moment of flame development in stage III i3 It can be calculated that:

[0139]

[0140] Similarly, assuming that the flame volumes at the end of stage II and the beginning of stage III are approximately equal,

[0141] V e2 ≈V i3 (34);

[0142] Combined with formula (32-34), the initial radius r of the cylindrical flame shape at the beginning of stage II is calculated: i3 :

[0143]

[0144] Then, combined with formula (13), we can get:

[0145]

[0146] The flame radius r3 in this stage also shows a certain functional change with the reaction time t3. Similarly, the derivative of formula (15) with respect to t3 can be obtained.

[0147] Similarly, the formula for the pressure rise rate during the explosion in the closed container in stage III is:

[0148]

[0149] The explosion pressure of the combustible gas explosion reaction in stage III is obtained by rearranging and transforming formula (37):

[0150]

[0151] Here, the C2 value is a constant coefficient. It varies under different reaction gas and reaction vessel conditions. C2 can be obtained by substituting the explosion pressure value P2 and reaction time t2 obtained in stage I into the equation and then reversely calculating:

[0152]

[0153] Determine the initial parameter K r 、P m , P0 and the lengths of the flame radii r1, r2, and r3 at each stage are determined according to the size of the square enclosed space. By substituting them into equations (19), (30), and (37), the predicted values of the explosion overpressure in the square enclosed space at different stages of the explosion can be obtained.

[0154] It can be seen from the above explosion pressure model that for a container in a cubic space, that is, when min(x,y,z)=mid(x,y,z)=max(x,y,z), the model of stage I can directly realize the calculation. For mid(x,y,z)=max(x,y,z)>min(x,y,z), the calculation can be realized by the models of stage I and stage II respectively. In other cases, the explosion pressure of each stage needs to be solved according to the models of stage I, stage II and stage III.

[0155] Step 4: Substitute the actual predicted initial parameters of the project into the mathematical model obtained in step 4 to calculate the predicted values of the square confined space explosion overpressure at different stages of the explosion.

[0156] In order to make the calculation of the method of the present invention faster, a corresponding processor can also be configured. The processor is configured to execute the method of predicting overpressure of combustible gas explosion in a square enclosed space of the present invention. The specific configuration method can be implemented by those skilled in the art by referring to the existing technology.

[0157] Example 1:

[0158] The above-mentioned method for predicting the overpressure of combustible gas explosion in a square enclosed space is verified by combining specific examples. The relevant experiments in which the reaction containers are all square containers and the aspect ratio max(x,y,z) / min(x,y,z)≤3 are selected, and the pressure data are compared with the above-mentioned model for verification. The experimental conditions are shown in Table 1. The combustible gas explosion overpressure results obtained from the experiment are compared with the explosion overpressure results calculated using formulas (19), (30), and (37). The results are as follows: Figure 3 、 Figure 4 、 Figure 5 shown.

[0159] Table 1

[0160]

[0161] from Figure 3 It can be seen that when the square enclosed space max(x,y,z) / min(x,y,z)=1, for the combustible gas acetylene, the explosion overpressure calculated by the model theory is basically consistent with the experimental result. Figure 4 and Figure 5 It can be seen that when max(x,y,z) / min(x,y,z)=2 and max(x,y,z) / min(x,y,z)=2.5, for combustible gas, in the early stage of the explosion, the explosion overpressure calculated by using this model is basically consistent with the change trend obtained by experiment; in the following period of time, the results obtained by theoretical calculation deviate slightly from the experimental changes.

[0162] Therefore, when the major diameter of the square confined space is relatively small, the mathematical model for predicting explosion pressure established using the segmentation method has a higher degree of agreement with the experimental results. The main reason for this is that when the major diameter of the confined space is relatively small, the explosion flame begins to develop from the ignition center and, as the flame radius continues to expand, it almost always develops as a spherical smooth laminar flame. In contrast, in confined spaces with a relatively large major diameter, the combustion and explosion reaction develops as a spherical smooth laminar flame in the early stages. In the middle stages, the spherical flame is gradually compressed, accelerating the time of flame instability and eventually evolving into a wrinkled or even turbulent flame that propagates outward.

[0163] At this time, the flame front will be transferred to the unburned area faster to promote new combustion reactions, thereby reducing the mass of combustible premixed gas per unit time more than that of smooth laminar flames, resulting in significant changes in the explosion overpressure process.

[0164] By comparison, it was found that when the ratio of the maximum to minimum side length of the confined space was 1, 2, and 2.5, respectively, the relative errors between the experimental results under the three working conditions and the theoretical calculation results of the explosion pressure prediction mathematical model established using the theory were 6.09%, 8.7%, and 9.75%, respectively. The relative errors in these three cases were all less than 10%, especially under conditions with small aspect ratios, where the relative errors were even smaller. Therefore, when the aspect ratio of the confined space is max(x,y,z) / min(x,y,z) ≤ 3, the established explosion pressure prediction mathematical model can provide support for the explosion-resistant design and daily safety management of confined spaces to a certain extent.

[0165] In summary, the method of the present invention can realize the rapid and accurate prediction and evaluation of the overpressure of combustible gas explosion in a square confined space, filling the gap in the traditional simulation method that only has spherical and various pipeline models, and improving the prevention and control capabilities of indoor gas explosion disasters.

[0166] Parts not described in the present invention can be implemented by referring to the existing technology.

[0167] It should be noted that those skilled in the art should recognize that the above embodiments are only used to illustrate the present application and are not intended to limit the present application. As long as they are within the spirit of the present application, appropriate changes and modifications to the above embodiments should fall within the scope of protection of the claims of the present application.

Claims

1. A method for predicting overpressure of combustible gas explosion in a square confined space, characterized in that: The following steps are involved: a. Assume the relevant parameters during the explosion of a square confined space; b. Establish a simplified physical model based on the flame development characteristics of combustible gas explosions in the experiment. Assume that the length, width, and height of the square enclosed space are x, y, and z, respectively, where x = a, y = b, and z = c. The explosion of the square enclosed space is divided into three stages: b1. Stage I: The reaction time is 0→t1. Assuming that the flame development in this stage expands as a spherical laminar flame, the flame radius r1 in this stage satisfies 0 <r1≤a / 2; b2. Stage II: The reaction time is t1→t2. Assuming that the flame in this stage is cylindrical, the flame radius r2 in this stage satisfies a / 2 <r2≤b / 2 b3. Stage III: The reaction time is t2→t3. Assuming that the flame shape in this stage is rectangular, the flame radius r3 in this stage satisfies b / 2. <r3≤c / 2; c. Based on the simplified physical model established in step b, a mathematical model for explosion pressure prediction is derived in combination with the control equation; The explosion pressure calculation formula in the first stage of the combustible gas reaction process in the explosion pressure prediction mathematical model is shown in formula (1): In formula (1), P1 is the explosion pressure of the combustible gas in stage I when it reaches the corresponding flame area; P0 is the initial pressure of the square enclosed space; α is the turbulence factor; K r is the combustion rate measured at a certain reference temperature and reference pressure; t1 is the reaction time of the first stage; V is the total volume of the square enclosed space; P m is the final pressure of the square enclosed space; The explosion pressure calculation formula in the combustible gas reaction process in the second stage of the explosion pressure prediction mathematical model is shown in formula (2): In formula (2): P2 is the explosion pressure of the combustible gas reaction process in stage II; C1 is the constant coefficient; e is the natural constant; r2 is the flame radius in stage II; t2 is the reaction time in stage II; The explosion pressure calculation formula in the combustible gas reaction process in the third stage in the explosion pressure prediction mathematical model is shown in formula (3): In formula (3), P3 is the explosion pressure during the combustible gas reaction in stage III; C2 is the constant coefficient; r3 is the flame radius in stage III; R2 is the maximum flame radius in stage II; t3 is the reaction time in stage III; d. Substituting the parameters obtained from actual measurements into equations (1), (2), and (3) can yield the explosion pressures of the explosion gas in the square enclosed space at different stages.

2. The method for predicting overpressure of combustible gas explosion in a square confined space according to claim 1, characterized in that: In formula (2), the calculation of C1 is shown in formula (4): In formula (4), P1 is the explosion pressure of the combustible gas in stage I when it reaches the corresponding flame area; P0 is the initial pressure of the square enclosed space; e is a natural constant; α is the turbulence factor; K r P is the burning rate measured at a certain reference temperature and reference pressure; m is the final pressure of the square enclosed space; r2 is the flame radius of stage II; t1 is the reaction time of stage I.

3. The method for predicting overpressure of combustible gas explosion in a square enclosed space according to claim 2, characterized in that: In formula (3), the calculation formula of C2 is shown in formula (5): In formula (5), P3 is the explosion pressure during the combustible gas reaction in stage III; P0 is the initial pressure of the square enclosed space; α is the turbulence factor; K r P is the burning rate measured at a certain reference temperature and reference pressure; m is the final pressure of the square enclosed space; R2 is the maximum flame radius of stage II; t2 is the reaction time of stage II.

4. The method for predicting overpressure of combustible gas explosion in a square enclosed space according to claim 1, characterized in that: In step a, the assumptions about the relevant parameters are as follows: the explosion process is assumed to be carried out under adiabatic wall conditions; the combustible gas is evenly distributed in the square enclosed space and ignites at the exact center of the square enclosed space; in the initial reaction, the temperature of the combustible gas and the temperature of the combustion products remain unchanged during the development of the explosion; in the initial reaction, the combustible gas and the combustion products both conform to the ideal gas state equation; and the effect of the pressure increase in the square enclosed space on the flame propagation speed is negligible.

5. The method for predicting overpressure of combustible gas explosion in a square enclosed space according to claim 1, characterized in that: In step b, r1 is the distance from the explosion center to the spherical flame surface; r2 is the distance from the explosion center to the side of the cylindrical flame; and r3 is the distance from the explosion center to the side of the rectangular flame where the area no longer changes.

6. The method for predicting overpressure of combustible gas explosion in a square enclosed space according to claim 1, characterized in that: In step c, during the explosion of the combustible gas in the square enclosed space, assuming that the square enclosed space is an isothermal system and that the combustible gas satisfies the law of conservation of mass during the explosion, the equations of state and mass conservation equations of the unreacted and reacted substances are obtained; According to the state equation and mass conservation equation, the mass change rate of the burned gas per unit time is converted into the pressure rise rate equation, as shown in formula (6): In formula (6): α is the turbulence factor; K r is the combustion velocity measured at a certain reference temperature and reference pressure; A is the flame front area; V is the volume of the square enclosed space; P m is the final pressure of the square enclosed space; P0 is the initial pressure of the square enclosed space; P is the explosion pressure; For stage I, according to formulas (7), (8) and (9), combined with formula (6), the explosion pressure calculation formula for the combustible gas reaction process in stage I is derived; In formula (7): V b1 is the volume occupied by the reactants in stage I; r1 is the distance from the explosion center to the spherical flame surface; In formula (8): A1 is the area of the flame front in stage I; r1 is the distance from the explosion center to the spherical flame surface; In formula (9): A1 is the area of the flame front in the first stage; V is the volume of the square enclosed space; P m is the final pressure of the square enclosed space; P0 is the initial pressure of the square enclosed space; P1 is the explosion pressure when the combustible gas in stage I reaches the corresponding flame area.

7. The method for predicting overpressure of combustible gas explosion in a square enclosed space according to claim 6, characterized in that: In step c, for stage II, the explosion pressure calculation formula during the combustible gas reaction process in stage II is derived by combining formulas (10), (11), and (12); In formula (10): V b2 is the volume occupied by the reactants in stage II; r2 is the distance from the explosion center to the side of the cylindrical flame; R1 is the maximum radius of the flame in stage I; A2=4πR1r2 (11); In formula (11), A2 is the flame front area of stage II; R1 is the maximum flame radius of stage I; r2 is the distance from the explosion center to the side of the cylindrical flame; In formula (12), A2 is the area of the flame front in stage II; V is the volume of the square enclosed space; r2 is the distance from the explosion center to the side of the cylindrical flame; P m is the final pressure of the square enclosed space; P0 is the initial pressure of the square enclosed space; P2 is the explosion pressure when the combustible gas in stage II reaches the corresponding flame area; R1 is the maximum flame radius in stage I.

8. The method for predicting overpressure of combustible gas explosion in a square enclosed space according to claim 6, characterized in that: In step c, for stage III, the explosion pressure calculation formula during the combustible gas reaction process in stage III is derived by combining formulas (13), (14), and (15): In b3 =8R1R2(r3-r i3 ) (13); In formula (13): V b3 is the volume of the reactants in stage III; R1 is the maximum radius of the flame in stage I; R2 is the maximum radius of the flame in stage II; r3 is the radius of the flame in stage III; r i3 is the initial flame radius of stage III; A3=8R1R2 (14); In formula (14), A3 is the flame front area of stage III; R1 is the maximum flame radius of stage I; R2 is the maximum flame radius of stage II; In formula (15), A3 is the flame front area of stage III; V is the volume of the square enclosed space; r3 is the flame radius of stage III; r i3 is the initial flame radius of stage III; P m is the final pressure of the square enclosed space; P0 is the initial pressure of the square enclosed space; P3 is the explosion pressure when the combustible gas in stage III reaches the corresponding flame area.

9. A processor, characterized in that: The method is configured to execute a method for predicting overpressure of combustible gas explosion in a square enclosed space according to any one of claims 1 to 8.

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