Calculation method for quasi-static pressure assessment of explosion in a small-opening cabin under water mist environment

Abstract

The present invention discloses a method for evaluating and calculating the quasi-static pressure of an explosion in a small-opening cabin under a water mist environment. The method obtains the quasi-static pressure under different charge amounts and different water mist environments through simulation or testing. A theoretical model for the quasi-static pressure of an explosion in a small-opening cabin is derived using the ideal adiabatic gas assumption and the Baker formula. The method verifies whether the cabin meets the small-opening conditions. The method further constructs a theoretical model for the quasi-static pressure of an explosion in a small-opening cabin by combining the water mist implosion and small-opening conditions. The method also fits empirical formulas for the temporal variation of the quasi-static pressure of an explosion in a small-opening cabin under water mist environments with different charge amount-to-volume ratios. The method also fits empirical formulas for the temporal variation of the quasi-static pressure of an explosion in a small-opening cabin under water mist environments with different water mist concentrations. The present invention accurately establishes a theoretical model for the quasi-static pressure of an explosion in a small-opening cabin under a water mist environment and fits empirical formulas for the temporal variation of the quasi-static pressure of an explosion in a small-opening cabin under different charge amount-to-volume ratios and different water mist concentrations.

Description

Technical Field

[0001] The present invention relates to the technical field of explosion response calculation, and in particular to a quasi-static pressure evaluation calculation method for explosions in a small-opening cabin under a water mist environment. Background Art

[0002] The water mist protection method can achieve multi-dimensional protection effects. It can not only directly weaken the explosion shock wave and wall-reflected overpressure, but also slow down or extinguish the subsequent reflections of the initial explosion, becoming a new type of protection technology.

[0003] Xi Xiuyi, Li Jun, Zhang Ya, Wang Zhiping, Chen Wei, Li Ying, Li Xiaobin. Research on the quasi-static pressure characteristics of the explosion in a closed cabin under water mist environment [J / OL]. Chinese Journal of Ship Research. The quasi-static pressure characteristics of the explosion in a closed cabin under water mist environment were explored. First, a theoretical model of the quasi-static pressure of the explosion in a closed cabin under water mist environment was established. Then, an implosion test of the closed cabin under a typical water mist environment was carried out. The results verified the weakening effect of water mist on the quasi-static pressure. Based on the relevant test data, an empirical formula for the peak quasi-static pressure of the implosion under water mist environment was obtained.

[0004] At present, when an explosion in a cabin damages an open cabin, high-temperature, high-pressure detonation products are instantly generated after the explosives are detonated. At the same time, the surrounding air is compressed, forming a shock wave, which will cause serious damage to the cabin structure. Most cabins have openings such as water holes and through-weld holes. These openings will affect the pressure relief process after the explosion, thereby affecting the quasi-static pressure of the cabin after the explosion. Therefore, it is also necessary to establish a quasi-static pressure assessment and calculation method for explosions in cabins with small openings in a water mist environment, so that it can be better applied to quickly grasp the quasi-static pressure of cabin structures with small openings in a water mist environment. Therefore, how to quickly and accurately assess the quasi-static pressure of cabin structures with small openings in a water mist environment is an urgent problem to be solved. Summary of the Invention

[0005] The present invention aims to solve the problem that the quasi-static pressure of an explosion in a cabin with a small opening in a water mist environment is different from the quasi-static pressure change in an explosion in a closed cabin due to the influence of the water mist environment and the opening. A quasi-static pressure evaluation and calculation method for an explosion in a cabin with a small opening in a water mist environment is provided to solve the problem that the existing technology lacks a fast and accurate evaluation method for the quasi-static pressure of a cabin with a small opening in a water mist environment.

[0006] The technical solution adopted in the present invention is:

[0007] A quasi-static pressure assessment calculation method for explosion in a small-opening cabin under a water mist environment is characterized by comprising:

[0008] S1. Obtain quasi-static pressure curve data of multiple different drug dosages and different water mist environments through simulation or experiment.

[0009] To investigate the quasi-static pressure variations associated with cabin explosions under varying charge weights and water mist environments, the primary variables considered during the design of operating conditions were explosive mass and water mist concentration. After designing a series of small-opening cabin explosion conditions with varying charge-volume ratios and water mist concentrations, simulations or tests were performed to generate a series of quasi-static pressure curves.

[0010] S2. The quasi-static pressure theory model of the explosion in a small-opening cabin is derived using the ideal gas hypothesis and Baker's formula respectively.

[0011] First, the ideal adiabatic gas theory is used to deduce the quasi-static pressure variation of a small-opening cabin explosion. During the decompression phase, the following assumptions are made about the cabin gas:

[0012] (1) The detonation products can be regarded as ideal gases with constant specific heat capacity;

[0013] (2) The pressure relief flow is isentropic (reversible and heat transfer is not considered);

[0014] (3) The properties of the gas in the cabin change only with time.

[0015] According to the ideal gas isentropic relationship:

[0016]

[0017] Where: p is the gas pressure in the cabin, ρ is the gas density in the cabin, t represents time, p0, ρ0 are the initial air pressure and density respectively, γ s is the isentropic index of the gas during the pressure release process.

[0018] According to the law of conservation of mass, the differential equation of the mass M(t) of the gas in the cabin can be expressed as:

[0019]

[0020] Where: M is the mass of the gas in the cabin, ρ is the gas density in the cabin; u is the gas outflow velocity at the opening, and A is the area of ​​the cabin opening.

[0021] And the gas in the cabin meets the following initial conditions:

[0022] M t＝0 =ρV (3)

[0023] Where: ρ is the gas density in the cabin, and V is the cabin volume.

[0024] The gas flow satisfies the Bernoulli equation, then:

[0025]

[0026] Where:u is the gas outflow velocity at the opening, p qs is the quasi-static pressure in the cabin, p is the gas pressure in the cabin, ρ( p ) represents the gas density which varies with the cabin pressure.

[0027] Substituting formula (1) into formula (4), we can get the following after integration:

[0028]

[0029] The gas outflow velocity at the opening is u and quasi-static pressure p qs The relationship can be expressed as:

[0030]

[0031] Substituting equations (2) and (3) into equation (6), we can obtain:

[0032]

[0033] Taking the derivative of both sides of equation (1) with respect to time t, we can obtain:

[0034]

[0035] Substituting equation (7) into equation (8), we can obtain the quasi-static pressure p in the cabin: qs The differential equation for time t is:

[0036]

[0037] Equation (9) assumes that the gas in the cabin is an ideal adiabatic gas and is based on the Bernoulli equation to obtain the theoretical model of the quasi-static pressure in the cabin. To solve this differential equation, it is also necessary to know the quasi-static pressure p qs Initial conditions and isentropic index γ s The value of .

[0038] In addition, the quasi-static pressure of an explosion in a cabin with a small opening can also be expressed using the Baker formula:

[0039]

[0040] Where p qs (t) is the function of the quasi-static pressure in the cabin with respect to time, p0 is the initial air pressure, t max is the time when the quasi-static pressure peak reaches, p qs,max t max The quasi-static pressure peak value corresponding to the moment, b is the decay exponent.

[0041] This model is a completely empirical model. After long-term research by scholars, it has been proved that this model can accurately reflect the changing law of the quasi-static pressure in the cabin. From formula (10), it can be seen that the pressure change trend over time described by this quasi-static pressure model is divided into two stages, and the horizontal coordinate of the dividing point is t=t max , from 0 to t max is the linear rising stage, t max The exponential decay phase follows. The decay phase ends at time t end It is defined as the quasi-static pressure decaying from the peak value to p qs,max ×The time corresponding to 1%.

[0042] S3. Determine how the gas mass in the cabin changes over time and verify whether it meets the conditions for a small opening.

[0043] From equations (9) and (10), it can be seen that if we want to depict the specific curve of the quasi-static pressure in the cabin changing with time, we need the same initial condition: at t max The quasi-static pressure peak p corresponding to the moment qs,max In a small-opening cabin, the mass of the exhaust gas is very small during the short period from the onset of the explosion to the peak quasi-static pressure, and the change in the cabin gas mass is negligible. Therefore, under the same test conditions, the peak quasi-static pressure in a small-opening cabin can be equated with the peak quasi-static pressure in a sealed cabin for deduction and calculation. To verify whether the object under study is a small-opening cabin, it is necessary to study the mass of the exhaust gas during the short period from the onset of the explosion to the peak quasi-static pressure. Therefore, it is necessary to discuss the temporal variation of the cabin gas mass.

[0044] To determine whether it is a small-opening cabin, first substitute formula (6) into formula (2) to obtain:

[0045]

[0046] In the above formula, M and p qs All are functions of time t, with the remainder being constant. Substituting the data obtained from S1 into Equation (10) yields the quasi-static pressure function with respect to time for different operating conditions. Substituting this into Equation (11) and solving the differential equation yields the functional relationship between the residual mass of the gas in the cabin and time.

[0047] Assume that in a small opening cabin, the time t from the explosion to the quasi-static pressure peak is maxAt around 20ms, draw a vertical line at the 20ms horizontal axis of the graph of the residual gas volume under different operating conditions, intersecting the residual gas volume curve. If the vertical axis of the intersection is nearly 100% (within 5%), then the assumption that the change in the gas mass in the cabin is negligible from the onset of the explosion to the quasi-static pressure peak is valid. This assumption leads to the conclusion that the quasi-static pressure peak in a small-opening cabin is equal to the quasi-static pressure peak in a sealed cabin under the same test conditions. Therefore, by studying the mass of the exhaust gas from the onset of the explosion to the quasi-static pressure peak, it is possible to determine whether a cabin has a small opening.

[0048] S4. By converting the quasi-static pressure peak of the explosion in a small-opening cabin into the quasi-static pressure peak of the explosion in a closed cabin, based on the ideal adiabatic gas quasi-static pressure model and combining the theoretical formula of the quasi-static pressure peak of the explosion in a closed cabin under water mist environment, the quasi-static pressure peak of the explosion in a small-opening cabin under water mist environment is derived, and the quasi-static pressure theoretical model of the explosion in a small-opening cabin is further constructed.

[0049] After proving that the cabin is a small-opening cabin, the theoretical model of the quasi-static pressure of the explosion in the small-opening cabin is further derived. Referring to the theoretical model of the quasi-static pressure of the explosion in a completely enclosed cabin under ideal adiabatic gas, the quasi-static pressure of the explosion in the small-opening cabin under water mist environment is also derived. pqs It is divided into two parts: (1) Assuming that the temperature remains unchanged, the cold pressure state p1 caused by the explosion gas products and water vapor in the confined space; (2) The energy generated by the explosion causes the water mist to evaporate rapidly and causes the temperature of the gas in the cabin to change, resulting in a hot pressure state p2 caused by the pressure change.

[0050] Referring to the research on the quasi-static pressure characteristics of the closed cabin under water mist environment, the theoretical formula of the quasi-static pressure peak in the cabin under water mist environment with the afterburning correction term introduced is:

[0051]

[0052] Where m is the mass of explosives, V0 is the explosive volume, V is the volume of the cabin, p0 is the initial air pressure, k is the evaporation rate of water mist, m w is the mass of the initial water mist in the space, V e is the specific volume of water vapor, γ is the specific heat ratio of gas, q is the explosive heat, L a is the latent heat of evaporation per unit mass of water mist, and λ is the afterburning correction term.

[0053] Combining Equation (12) with Equation (9) and Equation (10) respectively, we can obtain the theoretical model of quasi-static pressure of explosion in a small opening cabin under water mist environment:

[0054]

[0055] Or:

[0056]

[0057] From the above theoretical model, it can be seen that to describe the change of quasi-static pressure over time under a certain working condition, only three pieces of information need to be extracted from the data measured by the quasi-static pressure sensor: (1) the quasi-static pressure peak value p qs,max ; (2) Time t corresponding to the quasi-static pressure peak max (3) The time t when the pressure drops to 1% of the maximum value end .

[0058] In order to obtain the empirical formula of quasi-static pressure of explosion in a small-opening cabin under water mist environment through formula (13), it is also necessary to discuss the isentropic index γ s For formula (14), it is also necessary to study the attenuation index b of the quasi-static pressure in the cabin under the water mist environment, as well as the quasi-static pressure peak arrival time t max and pressure decay end time t end .

[0059] S5. Fit the relationship between the attenuation exponent b and the charge-volume ratio using the simulation or test data obtained in S1 to obtain an empirical formula for the time-varying quasi-static pressure in a small-opening cabin under a water mist environment with different charge-volume ratios.

[0060] First, according to the decay end time t end The definition of , we can get the following formula:

[0061]

[0062] Taking the logarithm of both sides gives:

[0063]

[0064] According to formula (16), if we want to obtain the attenuation index b under different working conditions in the water mist environment, we only need to extract the time t when the quasi-static pressure peak is reached from the collected data. max The moment t when the quasi-static pressure drops to 1% of the peak value end In order to obtain the empirical formula for the quasi-static pressure of a small-opening cabin explosion under a water mist environment, it is also necessary to obtain the ratio of b to the charge-volume ratio m / V, the water mist concentration m w The relationship between / V and the opening area A. The following uses the method of dimensional analysis to explore the relationship between b and other physical quantities.

[0065] Select the following physical quantities:

[0066] Geometric parameters of the cabin: cabin volume V, opening area A;

[0067] Explosive parameters: Explosive density ρ e , the energy W released by the explosion of explosives;

[0068] Air state parameters: initial air density ρ0, initial air pressure p0, speed of sound c in still air, latent heat of evaporation Q of the droplet v ;

[0069] Time t.

[0070] The physical quantities and dimensions related to the explosion pressure in a small-opening cabin under a water mist environment are shown in Table 1:

[0071] Table 1 Physical quantities and dimensions related to explosion pressure in a small-opening cabin under water mist environment

[0072]

[0073] Select p0, V, and c as the three basic dimensions, p, A, and ρ e ,W,ρ0,t,Q v To derive the dimension. According to the dimensional homogeneity, the physical quantities in Table 1 are dimensionless, and the π item:

[0074]

[0075] according to π Theorem, we can get:

[0076] π1=f(π2,π3,π4,π5,π6,π7) (24)

[0077] Right now:

[0078]

[0079] In formula (25), the explosive density ρ e , initial air density ρ0, initial air pressure p0, the speed of sound c in still air is a constant, and:

[0080] W=mq (26)

[0081] Q v =m w L a (27)

[0082] Where, the explosive heat q and the latent heat of evaporation per unit mass of water mist L a Can be considered as a constant.

[0083] Then formula (25) can be simplified as:

[0084]

[0085] Substituting the pressure decay segment expression in equation (14) into equation (28) yields:

[0086]

[0087] It has been derived According to the physical meaning of the attenuation coefficient b, we know that b is not a function of time t. Therefore, b and its influencing parameters can be expressed as follows:

[0088]

[0089] From formula (30), it can be seen that the attenuation coefficient of the quasi-static pressure in the open cabin is related to the charge-volume ratio m / V and the water mist concentration m w / V and the opening area and the 2 / 3 power of the cabin volume A / V 2 / 3 Closely related.

[0090] In order to fit the empirical formula for the time-varying quasi-static pressure of a small-opening cabin explosion under water mist environment with different charge-volume ratios, the data were further processed and analyzed. When the opening area and water mist concentration are constant, the attenuation coefficient b can be expressed as:

[0091]

[0092] The attenuation coefficient corresponding to the drug amount-volume ratio of each working condition was calculated, and based on the data, the Hill function was used to fit the relationship between the attenuation coefficient b and m / V in the water mist environment.

[0093] Substituting formula (31) and the quasi-static pressure peak empirical formula (12) into formula (14), the quasi-static pressure empirical formula for a small-opening cabin in a water mist environment can be obtained.

[0094] S6. Fit the relationship between the attenuation exponent b and the water mist concentration using the simulation or test data obtained in S1 to obtain an empirical formula for the change of the quasi-static pressure in the small-opening cabin over time under different water mist concentrations.

[0095] First, according to It can be seen that the attenuation coefficient is not only related to the drug-volume ratio m / V, but also to the opening area A and the water mist concentration m w / V. When A / V 2 / 3 When and m / V are constants, the attenuation coefficient b can be expressed as:

[0096]

[0097] The pressure curve of the open-hole cabin explosion under different water mist concentration environments generally shows that the pressure rises rapidly in 0-1ms, stabilizes in 10-20ms, and after 20ms, it is the pressure relief process, and the cabin pressure slowly drops to 0. Therefore, the quasi-static pressure peak p qs,max Take the average pressure of the two measuring points within 10 to 20 ms, and the time t at which the quasi-static pressure is reached max Both are 20ms, and the pressure relief completion time t end The moment when the pressure drops to 1% of the quasi-static pressure peak is taken.

[0098] The attenuation index b is still in accordance with formula (16): calculate.

[0099] According to formula (32), b and m w / V is still fitted according to the Hill function to obtain the relationship between the attenuation coefficient and the water mist concentration. The b and m obtained by the fitting curve are w / V function relationship.

[0100] Substituting formula (32) and the quasi-static pressure peak empirical formula (12) into formula (14), the quasi-static pressure empirical formula for a small-opening cabin in a water mist environment can be obtained.

[0101] The beneficial effects produced by the present invention are:

[0102] This paper, based on data and related theoretical formulas from explosions in cabins under water mist environments, uses the quasi-static pressure assessment and calculation method for explosions in small-opening cabins on ships under water mist environments as the background. Using the ideal adiabatic gas assumption and the Baker formula, a theoretical model for quasi-static pressure of explosions in small-opening cabins is derived. Combining existing research results on explosions in water mist environments, the peak quasi-static pressure of explosions in small-opening cabins under water mist environments is derived, and a further theoretical model for quasi-static pressure of explosions in small-opening cabins is constructed. By fitting the relationship between the attenuation exponent and the charge-volume ratio, empirical formulas for the temporal variation of the quasi-static pressure of explosions in small-opening cabins under water mist environments at different charge-volume ratios can be obtained. By fitting the relationship between the attenuation exponent and the water mist concentration according to experimental data, empirical formulas for the temporal variation of the quasi-static pressure of explosions in small-opening cabins at different water mist concentrations can be obtained.

[0103] Compared with the existing technology, the calculation method for evaluating the quasi-static pressure of explosions in small-opening cabins under water mist environment provided by the present invention, combined with theoretical derivation and data processing, can accurately establish a theoretical model of the quasi-static pressure in small-opening cabins under water mist environment, and fit the empirical formulas for the change of the quasi-static pressure in small-opening cabins under water mist environment with time under different charge-volume ratios and the empirical formula for the change of the quasi-static pressure in small-opening cabins under different water mist concentrations with time. The obtained empirical formulas can quickly and accurately determine the quasi-static pressure in the small-opening cabin of a ship under water mist environment, provide a basis for the study of ship structure damage, and provide theoretical guidance for the development of cabin structure response damage assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0104] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0105] Figure 1 Schematic diagram of the method of the present invention;

[0106] Figure 2 This is a schematic diagram of the small opening at the top of the test chamber in an embodiment of the present invention;

[0107] Figure 3 This is a graph showing the change in the amount of residual gas in the cabin over time when determining whether the test is for a cabin with a small opening in an embodiment of the present invention;

[0108] Figure 4 Graph showing the fitting curve of the afterburning term at the same water mist concentration in the embodiment of the present invention;

[0109] Figure 5 This is a graph showing the relationship between the attenuation index and the drug dose-volume ratio based on the experimental data fitting in an embodiment of the present invention;

[0110] Figure 6 A comparison chart of the experimental quasi-static pressure variation over time curve in an embodiment of the present invention and the fitted empirical formula for the variation of the quasi-static pressure over time in a small-opening cabin explosion under a water mist environment with different charge-volume ratios;

[0111] Figure 7 This is a graph showing the relationship between the attenuation index and the water mist concentration based on the experimental data fitted in an embodiment of the present invention;

[0112] Figure 8 This is a comparison chart of the experimental quasi-static pressure change over time curve in an embodiment of the present invention and the empirical formula for fitting the quasi-static pressure change over time in a small-opening cabin explosion under a water mist environment with different water mist concentrations. DETAILED DESCRIPTION

[0113] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0114] The test model in this embodiment is a closed box-type cabin with an internal space geometric size of 1m×0.75m×0.7m and a cabin volume of 0.525m 3 ,like Figure 2 The cabin model is made of Q235 steel with a thickness of 20mm. The exterior is provided with reinforcement ribs in both longitudinal and transverse directions to ensure that the cabin does not deform significantly under the action of an implosion. There is an opening with a diameter of 100mm in the center of the cabin top. Figure 3 The test chamber is equipped with a sealing cover, which can be adjusted to a completely enclosed chamber or an open chamber according to actual working conditions. The test charges are all TNT cylindrical charges. During each test, the charge column is hung in the center of the chamber and the explosive is detonated with a detonator.

[0115] Taking the data obtained from the experiment as an example, the specific implementation method of the present invention is described, which includes the following steps:

[0116] (1) Through experiments, quasi-static pressure curve data of multiple different drug dosages and different water mist environments were obtained.

[0117] A series of cabin operating conditions with small openings are designed as shown in Table 2. A series of cabin quasi-static pressure data are obtained from the test.

[0118] Table 2. Test conditions for small opening cabins

[0119]

[0120] (2) The quasi-static pressure theoretical model of explosion in a small opening cabin is derived using the ideal adiabatic gas assumption and Baker's formula respectively.

[0121] Assuming that the gas in the cabin is an ideal adiabatic gas, the theoretical model of the quasi-static pressure in the cabin is obtained based on the Bernoulli equation:

[0122]

[0123] The quasi-static pressure model of explosion in a cabin with a small opening can be derived using the Baker formula:

[0124]

[0125] (3) Solve the time-varying law of the gas mass in the cabin to verify whether it meets the conditions of small openings. Take the openings in this test to prove that it is a small opening cabin. In formula (11), M and p qs All are functions of time t, and the rest are constants. The opening area of ​​this experiment is 0.00785m 2 Substituting the test data into the above formula, we can get the quasi-static pressure function with respect to time corresponding to different test conditions. Then, substituting the above formula and solving the differential equation, we can get the functional relationship of the residual mass of the gas in the cabin with time. When solving the differential equation, temporarily take γ s =1.15. The final amount of gas remaining in the cabin under different working conditions is as follows: Figure 3 shown.

[0126] Known t in the experiment max At around 20ms, a vertical line intersecting the residual gas curve at the 20ms horizontal axis in the above figure shows that the vertical axis of the intersection is almost 100%. Therefore, the assumption that the change in gas mass in the chamber is negligible from the onset of the explosion to the peak quasi-static pressure is valid, confirming that the small opening condition is met.

[0127] (4) By converting the quasi-static pressure peak of the explosion in a small-opening cabin into the quasi-static pressure peak of the explosion in a closed cabin, on the basis of the ideal adiabatic gas quasi-static pressure model and combining the theoretical formula of the quasi-static pressure peak of the explosion in a closed cabin under a water mist environment, the quasi-static pressure peak of the explosion in a small-opening cabin under a water mist environment is derived, and the quasi-static pressure theoretical model of the explosion in a small-opening cabin is further constructed.

[0128] First, the afterburning correction term λ is fitted to the test data, and λ is a function of m / V. The difference between the test value and the theoretical value is considered to be the pressure change caused by afterburning in the water mist environment. With λ / (m / V) as the vertical axis and m / V as the horizontal axis, the fitting curve is as follows: Figure 4 As shown. Therefore, the correction term for internal explosion afterburning in water mist environment is expressed as:

[0129]

[0130] The theoretical formula for the quasi-static pressure peak in the cabin under water mist environment with the afterburning correction term introduced is:

[0131]

[0132] Substituting the above equations into the quasi-static pressure theoretical model of a small-opening cabin in (2) can obtain the quasi-static pressure theoretical model of a small-opening cabin in a water mist environment:

[0133]

[0134] Or:

[0135]

[0136] (5) By fitting the relationship between the attenuation index and the charge-volume ratio of the test data, an empirical formula for the time-dependent change of the quasi-static pressure in the small-opening cabin explosion under a water mist environment with different charge-volume ratios was obtained. The attenuation coefficients corresponding to the charge-volume ratios of each working condition in the test are listed in Table 33 below:

[0137] Table 3 Attenuation coefficients corresponding to different drug dose-volume ratios

[0138]

[0139] According to the data in the table above, the relationship between the attenuation coefficient b and m / V in the water mist environment is obtained by fitting the Hill function. The fitting curve is as follows: Figure 5 shown.

[0140]

[0141] Substituting the above formula and the empirical formula of quasi-static pressure peak into the theoretical model of quasi-static pressure of small-opening cabins, the empirical formula of quasi-static pressure of small-opening cabins in water mist environment can be obtained.

[0142] Using the data obtained from this test, the applicable range can be fitted to be 0.015kg / m 3 ≤m / V≤0.476kg / m 3 ;m w / V=0.812kg / m 3 ; A / V=0.015(m -1 The empirical formula for the quasi-static pressure of a small-opening cabin in a water mist environment is:

[0143]

[0144] Take the isentropic index γ s =0.5 to obtain the empirical formula 2 for the change of the explosion pressure in the open cabin with time under different charge-volume ratios:

[0145]

[0146] Compare the quasi-static pressure variation curve collected in the test with the calculation results of the quasi-static empirical formula in the above formula. Figure 6 As can be seen from the figure, the two empirical formula curves are in good agreement with the experimental curve.

[0147] (6) By fitting the relationship between the attenuation index and the water mist concentration with the test data, an empirical formula for the time-varying quasi-static pressure of the small-hole cabin explosion under different water mist concentrations was obtained. The relevant data on the pressure characteristics of the small-hole cabin explosion under different water mist concentrations are listed in Table 4 below:

[0148] Table 4 Pressure characteristics of the open cabin explosion under different water mist concentrations

[0149]

[0150] The attenuation index b is still in accordance with formula (16): calculate.

[0151] b and m w / V is still fitted according to the Hill function to obtain the relationship between the attenuation coefficient and the water mist concentration. The fitting curve is as follows Figure 7 As shown, the obtained b and m w The functional relationship of / V is as follows:

[0152]

[0153] Substituting the above formula into the quasi-static pressure theoretical model of the small-hole cabin explosion, we can obtain the empirical formula 3 of the change of the cabin explosion pressure with time under different water mist concentrations:

[0154]

[0155] Alternatively, we can obtain the empirical formula 4 (same as empirical formula 2) for the change of the explosion pressure inside the open cabin with time under different water mist concentrations:

[0156]

[0157] The quasi-static pressure variation curve collected in the test is compared with the empirical formula calculation results of the explosion pressure variation with time in the open cabin under different water mist concentrations in the above formula. Figure 8 As can be seen from the figure, the two empirical formula curves are in good agreement with the experimental curve.

[0158] Based on the ideal adiabatic gas theory and the characteristics of small-opening cabin explosions in a water mist environment, the present invention combines data fitting with the relationship between the change in quasi-static pressure in the cabin and time to obtain an empirical formula for the change in quasi-static pressure of a small-opening cabin with time under different charge-volume ratios and different water mist concentrations.

[0159] It should be pointed out that, according to the needs of implementation, the various steps / components described in this application can be split into more steps / components, or two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0160] The size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0161] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A quasi-static pressure assessment calculation method for explosions in small-opening cabins under water mist environment, characterized by: include: S1. Obtain quasi-static pressure curve data of multiple different drug dosages and different water mist environments through simulation or experiment; S2. Using the ideal adiabatic gas assumption and Baker's formula, derive the quasi-static pressure theory model for explosions in small-opening cabins. S3. Solve the time-varying law of the gas mass in the cabin to verify whether the cabin meets the small opening conditions; S4. By converting the quasi-static pressure peak of an explosion in a cabin with a small opening into the quasi-static pressure peak of an explosion in a closed cabin, based on the quasi-static pressure model of an ideal adiabatic gas and combining it with the theoretical formula for the quasi-static pressure peak of an explosion in a closed cabin under a water mist environment, the quasi-static pressure peak of an explosion in a cabin with a small opening under a water mist environment is derived, and a theoretical quasi-static pressure model for explosions in cabins with small openings is further constructed. S5. Fit the decay index using the simulation or test data obtained in S1 The empirical formula of the change of quasi-static pressure of explosion in a small opening cabin with water mist environment under different charge-volume ratios is obtained. S6. Fit the decay index using the simulation or test data obtained in S1 The empirical formula for the change of quasi-static pressure with time in a small-opening cabin under water mist environment with different water mist concentrations was obtained.

2. The quasi-static pressure evaluation calculation method for explosion in a small-opening cabin under a water mist environment according to claim 1 is characterized in that: In step S1, after designing a series of small-opening cabin explosion conditions with different charge-volume ratios and different water mist concentrations, simulation calculations or experiments are performed to obtain a series of quasi-static pressure curves.

3. The quasi-static pressure evaluation and calculation method for explosion in a small-opening cabin under a water mist environment according to claim 1 is characterized in that: In step S2, when deriving the quasi-static pressure theory model for explosions in small-opening cabins using the ideal gas hypothesis, it is assumed that the gas in the cabin is an adiabatic ideal gas. During the pressure relief phase, the following assumptions are made for the gas in the cabin: (1) The detonation products can be regarded as ideal gases with constant specific heat capacity; (2) The pressure relief flow is isentropic; (3) The properties of the gas in the cabin change only with time; The quasi-static pressure theoretical model of explosion in a small-opening cabin based on the Bernoulli equation is: Where, p qs is the quasi-static pressure in the cabin, which is the time t function, is the isentropic index of the gas during the pressure release process, , are the initial air pressure and density, A is the cabin opening area, is the cabin volume.

4. The quasi-static pressure evaluation calculation method for explosion in a small-opening cabin under a water mist environment according to claim 1 is characterized in that: In step S2, the Baker formula is used to derive the quasi-static pressure theoretical model for explosions in small-opening cabins: Where, is the quasi-static pressure in the cabin as a function of time t, is the initial air pressure, t max is the time when the quasi-static pressure peak reaches, for t max The quasi-static pressure peak in the cabin at time , b is the decay index.

5. The quasi-static pressure evaluation and calculation method for explosion in a small-opening cabin under a water mist environment according to claim 1 is characterized in that: In step S3, the change pattern of the gas quality in the cabin over time is as follows: Where, M is the gas mass in the cabin, and t function; A is the cabin opening area, is the cabin volume; is the isentropic index of the gas during the pressure release process; p qs is the quasi-static pressure in the cabin, which is the time t function; , are the initial air pressure and density, respectively.

6. The quasi-static pressure evaluation and calculation method for explosion in a small-opening cabin under a water mist environment according to claim 5 is characterized in that: The method to verify whether the cabin meets the small opening condition is as follows: substitute the data obtained in S1 into the quasi-static pressure theoretical model of the explosion in the small opening cabin derived by the Baker formula to obtain the quasi-static pressure function of different working conditions with respect to time; then substitute it into formula (11) and solve the differential equation to obtain the functional relationship between the residual mass of the gas in the cabin under different working conditions and the time; in the diagram of the residual mass of the gas in the cabin under different working conditions, the horizontal coordinate is t max Draw a vertical line at the intersection to intersect the residual gas mass curve. If the vertical coordinate of the intersection is 95%-100% of the initial mass of the gas in the cabin, it is considered that the assumption that the change in the gas mass in the cabin is negligible during the period from the beginning of the explosion to the quasi-static pressure peak is valid, and the cabin can be judged to be a small-opening cabin.

7. The quasi-static pressure evaluation and calculation method for explosion in a small-opening cabin under a water mist environment according to claim 1 is characterized in that: In step S4, based on the ideal adiabatic gas assumption, the quasi-static pressure theoretical model for the explosion in a small-opening cabin is further constructed as follows: Where, p qs is the quasi-static pressure in the cabin, which is the time t function, is the isentropic index of the gas during the pressure release process, , are the initial air pressure and density, A is the cabin opening area, V is the cabin volume; m is the mass of explosives; V 0 is the explosive capacity of explosives; is the water mist evaporation rate, is the mass of the initial water mist in the space, is the specific volume of water vapor, is the gas specific heat ratio, q for the explosive heat; is the latent heat of evaporation per unit mass of water mist; is the afterburning correction term.

8. The quasi-static pressure evaluation and calculation method for explosion in a small-opening cabin under a water mist environment according to claim 1 is characterized in that: In step S4, based on the Baker formula, the quasi-static pressure theoretical model for explosion in a small-opening cabin is further constructed as follows: Where, is the quasi-static pressure in the cabin as a function of time t, is the initial air pressure, t max is the time when the quasi-static pressure peak reaches, for t max The quasi-static pressure in the cabin at time , b is the decay index; m is the mass of explosives; V 0 is the explosive capacity of explosives; V is the cabin volume; is the water mist evaporation rate, is the mass of the initial water mist in the space, is the specific volume of water vapor, is the gas specific heat ratio, q The explosive heat of explosives; is the latent heat of evaporation per unit mass of water mist; is the afterburning correction term.

9. The quasi-static pressure evaluation and calculation method for explosion in a small-opening cabin under a water mist environment according to claim 1 is characterized in that: In step S5, the attenuation index is determined by dimensional analysis. b and dose-volume ratio m / V , water mist concentration m w / V and opening area A The relationship is: Where, A is the cabin opening area, V is the cabin volume, m is the mass of explosives, is the mass of the initial water mist in the space; When the opening area and the water mist concentration are constant, the attenuation coefficient b It can be expressed as: The attenuation coefficient corresponding to the drug dosage-volume ratio of each working condition is calculated, and the attenuation coefficient under water mist environment is obtained by fitting the Hill function based on the calculated data. b and m / V Then, the empirical formula of the quasi-static pressure variation of the explosion in a small-opening cabin under water mist environment with different charge-volume ratios can be obtained by substituting it into the theoretical model of quasi-static pressure of the explosion in a small-opening cabin further constructed based on the Baker formula.

10. The quasi-static pressure evaluation and calculation method for explosion in a small-opening cabin under a water mist environment according to claim 1 is characterized in that: In step S6, the attenuation index is determined by dimensional analysis. b and dose-volume ratio m / V , water mist concentration m w / V and opening area A The relationship is: Where, A is the cabin opening area, V is the cabin volume, m is the mass of explosives, is the mass of the initial water mist in the space; when A / V 2 / 3 and m / V When it is a constant, the attenuation coefficient b It can be expressed as: The attenuation coefficient corresponding to the water mist concentration of each working condition is calculated, and based on the calculated data, the attenuation coefficient under the water mist environment is obtained by fitting the Hill function. b and m w / V Then, the empirical formula of the quasi-static pressure of the explosion in a small-opening cabin under water mist environment with different water mist concentrations can be obtained by substituting it into the theoretical model of quasi-static pressure of the explosion in a small-opening cabin further constructed based on the Baker formula.

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