Quasi-static pressure evaluation and calculation method for explosion in small-hole cabin in water mist environment

Abstract

The invention discloses a quasi-static pressure evaluation and calculation method for explosion in a small-hole cabin in a water mist environment. The quasi-static pressure evaluation and calculation method comprises the steps that quasi-static pressure of different explosive quantities and different water mist environments is obtained through simulation or testing; deducing a quasi-static pressure theoretical model of the explosion in the small-hole cabin by using an ideal adiabatic gas hypothesis and a Baker formula; verifying whether the cabin meets the condition of small opening; further constructing a quasi-static pressure theoretical model of the internal explosion of the small-hole cabin by combining the water mist implosion and the small-hole condition; fitting an empirical formula of time-varying explosion quasi-static pressure in the small-hole cabin in the water mist environment under different explosive quantity-volume ratios; and fitting an empirical formula of time-varying explosion quasi-static pressure in the small-hole cabin in the water mist environment under different water mist concentrations. According to the method, the quasi-static pressure theoretical model in the small-hole cabin in the water mist environment can be accurately established, and the empirical formula of the quasi-static pressure of the explosion in the small-hole cabin along with the time change under different explosive quantity-volume ratios and different water mist concentrations can be fitted.

Description

Technical Field

[0001] The invention relates to the technical field of explosion response calculation, and in particular to a quasi-static pressure evaluation calculation method for explosion 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 the 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 Ship Research. The quasi-static pressure characteristics of the explosion in a closed cabin under water mist environment were explored. Firstly, 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 value of the 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 and high-pressure detonation products are instantly generated after the explosives are detonated, and the surrounding air is compressed to form a shock wave, which will cause serious damage to the cabin structure. Most cabins have openings such as water holes and through-welding holes, and the 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 under water mist environments, so as to better apply it to quickly grasp the quasi-static pressure of cabin structures with small openings under water mist environments. Therefore, how to quickly and accurately assess the quasi-static pressure of cabin structures with small openings under water mist environments is an urgent problem to be solved. Summary of the invention

[0005] Aiming at the problem that the quasi-static pressure of the explosion in a cabin with a small opening in a water mist environment is different from the quasi-static pressure change in the explosion in a closed cabin due to the influence of the water mist environment and the opening, the present invention provides a quasi-static pressure evaluation and calculation method for the explosion in a cabin with a small opening in a water mist environment, so as to solve the problem that there is a lack of rapid and accurate evaluation of the quasi-static pressure of the cabin with a small opening in a water mist environment in the prior art.

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

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

[0008] S1. Through simulation or experiment, obtain quasi-static pressure curve data of multiple different drug amounts and different water mist environments.

[0009] In order to study the variation law of quasi-static pressure in cabin explosion under different charge amounts and different water mist environments, the main variables considered in the design of working conditions are the explosive mass and water mist concentration. After designing a series of small-opening cabin explosion conditions with different charge-volume ratios and different water mist concentrations, simulation calculations or tests are carried out to obtain a series of quasi-static pressure curves.

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

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

[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 mass conservation, 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 cabin opening area.

[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 With the quasi-static pressure p qs The relationship can be expressed as:

[0030]

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

[0032]

[0033] By 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] Formula (9) is a theoretical model of the quasi-static pressure in the cabin obtained based on the Bernoulli equation, assuming that the gas in the cabin is an ideal adiabatic gas. If you want to solve this differential equation, you also need to know the quasi-static pressure p qs The initial conditions and isentropic index γ s The value of .

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

[0039]

[0040] In the formula, p qs (t) is the quasi-static pressure in the cabin as a function of 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 attenuation 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 the 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. Solve the law of change of gas mass in the cabin with time and verify whether it meets the conditions of small opening.

[0043] It can be seen from equations (9) and (10) that if we want to depict the specific curve of the quasi-static pressure change in the cabin over time, we need the same initial condition: 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 in the short time from the start of the explosion to the quasi-static pressure peak, and the change in the gas mass in the cabin can be ignored. Therefore, the quasi-static pressure peak in the small-opening cabin under the same test conditions can be deduced and calculated to be equal to the quasi-static pressure peak in the closed cabin. In order to verify whether the object of study is a small-opening cabin, it is necessary to study the mass of the exhaust gas in the short time from the start of the explosion to the quasi-static pressure peak, so it is necessary to discuss the change law of the gas mass in the cabin over time.

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

[0045]

[0046] In the above formula, M and p qs They are all functions of time t, and the rest is a constant. Substituting the data obtained by S1 into formula (10) can obtain the function of quasi-static pressure corresponding to different working conditions with respect to time. Then substituting it into formula (11) and solving the differential equation can obtain the functional relationship of the residual mass of the gas in the cabin with time.

[0047] Assume that in a small opening cabin, the time from the explosion to the quasi-static pressure peak is t maxAt about 20ms, draw a vertical line at 20ms on the horizontal axis of the gas residual graph in the cabin under different working conditions to intersect with the residual gas curve. If the vertical axis of the intersection is almost 100% (within 5%), it can be considered that the assumption that the change in the gas mass in the cabin is negligible during the period from the start of the explosion to the quasi-static pressure peak is valid. Based on this assumption, it can be inferred that the quasi-static pressure peak in the small opening cabin is equal to the quasi-static pressure peak in the closed cabin under the same test conditions. Therefore, by studying the mass of the gas discharged from the cabin during the period from the start of the explosion to the quasi-static pressure peak, it can be determined whether the cabin is a small opening cabin.

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

[0049] After proving that the cabin is a cabin with a small opening, the theoretical model of the quasi-static pressure of the explosion in the cabin with a small opening is further derived. Referring to the theoretical model of the quasi-static pressure of the explosion in a completely closed cabin under ideal adiabatic gas, similarly, the quasi-static pressure of the explosion in the cabin with a small opening under water mist environment is pqs It is divided into two parts: (1) Assuming 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 quickly 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 study 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 explosive, 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 explosion heat of explosive, L a is the latent heat of evaporation per unit mass of water mist, and λ is the post-combustion correction term.

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

[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 equation (13), it is also necessary to discuss the isentropic exponent 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 termination time t end .

[0059] S5. Fit the relationship between the attenuation index b and the charge-volume ratio through the simulation or test data obtained in S1, and obtain an empirical formula for the change of the quasi-static pressure of the small-opening cabin in a water mist environment with different charge-volume ratios over time.

[0060] First, according to the attenuation termination time t end The definition of can be obtained as follows:

[0061]

[0062] Taking the logarithm of both sides gives:

[0063]

[0064] According to formula (16), if we want to obtain the attenuation index b of different working conditions under 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 in 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 / 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 in still air c, latent heat of evaporation of droplets Q 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 density of explosive is 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] In the formula, 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, so b and its influencing parameters can be expressed as follows:

[0088]

[0089] It can be seen from formula (30) that the attenuation coefficient of the quasi-static pressure in the open-hole 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 of the change of quasi-static pressure over time in a small opening cabin under water mist environment with different charge-volume ratios, the data was further processed and analyzed. When the opening area and water mist concentration are constants, the attenuation coefficient b can be expressed as:

[0091]

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

[0093] Substituting equation (31) and the quasi-static pressure peak empirical formula (12) into equation (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 index b and the water mist concentration through the simulation or test data obtained in S1, and obtain an empirical formula for the change of the quasi-static pressure in the small opening cabin with different water mist concentrations over time.

[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. 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 is in the pressure relief process after 20ms, with the cabin pressure slowly dropping 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 when 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 w / V functional relationship.

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

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

[0102] The present invention is based on the data and related theoretical formulas of explosions in cabins under water mist environments, and takes the quasi-static pressure evaluation and calculation method of explosions in small opening cabins of ships under water mist environments as the background. The quasi-static pressure theoretical model of explosions in small opening cabins is derived by using the ideal adiabatic gas assumption and the Baker formula, and combined with the existing research results of implosions under water mist environments, the quasi-static pressure peak of implosions in small opening cabins under water mist environments is derived, and the quasi-static pressure theoretical model of implosions in small opening cabins under water mist environments is further constructed. By fitting the relationship between the attenuation index and the amount-volume ratio of data, an empirical formula for the change of the quasi-static pressure of the explosion in a small opening cabin under water mist environments with time under different amount-volume ratios can be obtained; by fitting the relationship between the attenuation index and the water mist concentration of experimental data, an empirical formula for the change of the quasi-static pressure of the explosion in a small opening cabin under different water mist concentrations can be obtained.

[0103] Compared with the prior art, the method for evaluating and calculating the quasi-static pressure of explosion in a small opening cabin under a 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 a small opening cabin under a water mist environment, and fit the empirical formulas for the variation of the quasi-static pressure of the explosion in a small opening cabin under a water mist environment with time under different charge-volume ratios and the empirical formulas for the variation of the quasi-static pressure of the explosion in a small opening cabin 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 a 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 briefly introduces 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 creative work.

[0105] Figure 1 It is the principle diagram of the method of the present invention;

[0106] Figure 2 This is a schematic diagram of a 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 of the amount of residual gas in the cabin over time when determining whether the test is a cabin with a small opening in an embodiment of the present invention;

[0108] Figure 4 It is a fitting curve diagram 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 dosage-volume ratio based on the experimental data fitting in the embodiment of the present invention;

[0110] Figure 6 It is a comparison diagram of the experimental quasi-static pressure variation with time curve in the embodiment of the present invention and the fitted empirical formula of the quasi-static pressure variation with time in a small opening cabin explosion under a water mist environment with different charge amount-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 fitting in an embodiment of the present invention;

[0112] Figure 8 It is a comparison chart of the experimental quasi-static pressure variation with time curve in the embodiment of the present invention and the empirical formula for fitting the variation with time of the quasi-static pressure 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 solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with 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 used 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 20 mm. The exterior is provided with reinforcing ribs in both the longitudinal and transverse directions to ensure that the cabin does not undergo significant deformation under the action of an implosion. A 100 mm diameter opening is provided at the center of the cabin top. Figure 3 As shown, it is equipped with a sealing cover. During the test, it can be adjusted to a completely closed cabin or an open cabin according to the actual working conditions. The test charges are all TNT column charges. During each test, the charge column is hung in the center of the cabin 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 the 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] Using Baker's formula to derive the quasi-static pressure theory model of explosion in a small opening cabin, we can obtain:

[0124]

[0125] (3) Solve the law of change of gas mass in the cabin over time 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 function of quasi-static pressure with respect to time corresponding to different test conditions. Then, substituting into the above formula, 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 experiment t max At about 20ms, a vertical line is drawn at 20ms on the horizontal axis of the figure above to intersect the residual gas volume curve. It can be seen that the vertical axis of the intersection is almost 100%. Therefore, it can be considered that the assumption that the change in the gas mass in the cabin is negligible during the period from the start of the explosion to the peak of the quasi-static pressure is valid, which verifies that it does meet the conditions of a small opening.

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

[0128] First, the afterburning correction term λ is fitted with 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. λ / (m / V) is used as the vertical axis and m / V is used as the horizontal axis. The fitting curve is as follows: Figure 4 As shown. Therefore, the correction term for combustion after internal explosion in water mist environment is expressed as:

[0129]

[0130] Then 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 change of the quasi-static pressure of the small opening cabin in the water mist environment with time under different charge-volume ratios is obtained. The attenuation coefficients corresponding to the charge-volume ratios of each working condition in the test are listed in the following Table 33:

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

[0138]

[0139] According to the data in the above table, the relationship between the attenuation coefficient b and m / V in the water mist environment is obtained by using the Hill function fitting. 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 1:

[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 different charge-volume ratios over time:

[0145]

[0146] Compare the quasi-static pressure variation curve collected in the test with the calculation result 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 change of the quasi-static pressure of the small hole cabin explosion with time under different water mist concentrations is obtained. The relevant data of the pressure characteristics of the hole cabin explosion with different water mist concentrations are listed in the following Table 4:

[0148] Table 4 Data on pressure characteristics of the explosion in the open-hole cabin at 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 small hole cabin explosion, we can obtain the empirical formula 3 of the change of the pressure of the small hole cabin explosion with time under different water mist concentrations:

[0154]

[0155] Or we can get the empirical formula 4 (same as empirical formula 2) of the change of the explosion pressure in 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 explosion over 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, and 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 order of execution of each step in the above embodiment does not mean the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present application.

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

Claims

1. A quasi-static pressure evaluation and calculation method for explosion in a small opening cabin under a water mist environment, characterized in that: include: S1. Obtain quasi-static pressure curve data of multiple different drug amounts and different water mist environments through simulation or experiment; S2. The quasi-static pressure theory model of explosion in a small-opening cabin is derived using the ideal adiabatic gas assumption and Baker's formula respectively; S3. Solve the time-varying law of the gas mass in the cabin to verify whether the cabin meets the conditions of small openings; 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 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 a quasi-static pressure theoretical model of the explosion in a small-opening cabin is further constructed; S5. Fitting the relationship between the attenuation index b and the charge-volume ratio by the simulation or test data obtained in S1, and obtaining an empirical formula for the change of the quasi-static pressure of the explosion in a small opening cabin under a water mist environment with different charge-volume ratios over time; S6. Fit the relationship between the attenuation index b and the water mist concentration through the simulation or test data obtained in S1, and obtain an empirical formula for the change of the quasi-static pressure of the explosion in a small opening cabin under a water mist environment with different water mist concentrations over time.

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 tests are performed to obtain a series of quasi-static pressure curves.

3. 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, when the quasi-static pressure theory model of the explosion in the small opening cabin is derived using the ideal gas hypothesis, it is assumed that the gas in the cabin is an adiabatic ideal gas. During the pressure relief stage, 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 flow; (3) The properties of the gas in the cabin change only with time; The quasi-static pressure theory model of explosion in a small opening cabin based on the Bernoulli equation is: In the formula, p qs is the quasi-static pressure in the cabin as a function of time t, γ s is the isentropic index of the gas during the decompression process, p0 and ρ0 are the initial air pressure and density respectively, A is the cabin opening area, and V 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 quasi-static pressure theoretical model of explosion in a small opening cabin is derived using the Baker formula: In the formula, p qs (t) is the quasi-static pressure in the cabin as a function of 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 in the cabin at time , b is the decay exponent.

5. 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 S3, the change law of the gas quality in the cabin over time is as follows: Where M is the gas mass in the cabin, which is a function of time t; A is the cabin opening area, V is the cabin volume; γ s is the isentropic index of the gas during the pressure release process; p qs is the quasi-static pressure in the cabin, which is a function of time t; p0, ρ0 are the initial air pressure and density, respectively.

6. The quasi-static pressure evaluation calculation method for explosion in a small opening cabin under a water mist environment according to claim 5 is characterized in that: The method for verifying whether the cabin meets the condition of small opening is as follows: substitute the data obtained in S1 into the quasi-static pressure theoretical model of explosion in a cabin with small opening derived by Baker’s formula, and obtain the function of quasi-static pressure corresponding to different working conditions with respect to time; then substitute it into equation (11) and solve the differential equation to obtain the functional relationship of the residual mass of gas in the cabin under different working conditions with time; in the diagram of the residual mass of gas in the cabin under different working conditions, the horizontal coordinate t max Draw a vertical line at the intersection to intersect the residual gas mass curve. If the ordinate 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 peak value of the quasi-static pressure is valid, and the cabin can be judged to be a cabin with a small opening.

7. 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 S4, based on the assumption of ideal adiabatic gas, the quasi-static pressure theory model of explosion in a small opening cabin is further constructed as follows: In the formula, p qs is the quasi-static pressure in the cabin as a function of time t, γ s is the isentropic index of the gas during the decompression process, p0 and ρ0 are the initial air pressure and density, A is the opening area of ​​the cabin, and V is the volume of the cabin; m is the mass of explosive; V0 is the explosive volume; 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 explosion heat of explosive; L a is the latent heat of evaporation per unit mass of water mist; λ is the post-combustion correction term.

8. 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 S4, based on the Baker formula, the quasi-static pressure theory model of the explosion in the small opening cabin is further constructed as follows: Where p(t) is the function of the quasi-static pressure in the cabin with respect to time, p0 is the initial air pressure, and t max is the time when the quasi-static pressure peak reaches, p qs,max t max The quasi-static pressure in the cabin at the time, b is the decay index; m is the mass of explosives; V0 is the explosive volume; V is the volume of the cabin; 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 explosion heat of explosive; L a is the latent heat of evaporation per unit mass of water mist; λ is the post-combustion correction term.

9. 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 S5, the attenuation index b, the drug volume ratio m / V, and the water mist concentration m are determined by dimensional analysis. w The relationship between / V and opening area A is: Where A is the area of ​​the cabin opening, V is the cabin volume, m is the mass of the explosive, and m w is the mass of the initial water mist in the space; When the opening area and the water mist concentration are constants, the attenuation coefficient b can be expressed as: The attenuation coefficient corresponding to the charge-volume ratio of each working condition is calculated, and based on the calculated data, the Hill function is used to fit the relationship between the attenuation coefficient b and m / V in the water mist environment; then it is substituted into the quasi-static pressure theoretical model of the explosion in a small opening cabin further constructed based on the Baker formula to obtain the empirical formula for the change of the quasi-static pressure of the explosion in a small opening cabin with water mist environment under different charge-volume ratios over time.

10. 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 S6, the attenuation index b, the drug volume ratio m / V, and the water mist concentration m are determined by dimensional analysis. w The relationship between / V and opening area A is: Where A is the area of ​​the cabin opening, V is the cabin volume, m is the mass of the explosive, and m w is the mass of the initial water mist in the space; When A / V 2 / 3 When and m / V are constants, the attenuation coefficient b 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 b and m under the water mist environment are obtained by fitting the Hill function. w / V; then substitute it into the theoretical model of quasi-static pressure of explosion in a small opening cabin further constructed based on Baker's formula to obtain the empirical formula for the change of quasi-static pressure of explosion in a small opening cabin with time under water mist environment with different water mist concentrations.

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