A method for predicting the ignition conditions of metal combustion

Abstract

The present application provides a method for predicting the ignition conditions of metal combustion, including: establishing a metal combustion mathematical model based on the energy change during the metal ignition process; obtaining the test results of the characteristic parameters of the metal sample under different combustion test factors based on the combustion experiment on the metal sample; obtaining the corresponding relationship between the total gas pressure and the ignition temperature of the metal sample based on the test results of the characteristic parameters and the metal combustion mathematical model; using the corresponding relationship between the total gas pressure and the ignition temperature, predicting the ignition temperature of the metal to be tested under a predetermined total gas pressure. The present application improves the rationality and accuracy of the combustion characteristic parameters, and the reliability of the established metal combustion mathematical equation is higher, which can more accurately predict the ignition conditions of metal combustion.

Description

Technical Field

[0001] The present application relates to the technical field of metal combustion, and in particular to a method for predicting metal combustion ignition conditions. Background Art

[0002] When metals are exposed to high temperature, oxygen-rich, high-speed impact and friction, they ignite and burn at temperatures far below their melting points, similar to the ignition and combustion of wood and nylon, which is called metal combustion.

[0003] The essence of metal combustion is a violent physical and chemical reaction after the system energy reaches a threshold value under the combined effects of material factors, operating conditions and ignition factors. Metal combustion is different from general oxidation and melting. Once it occurs, it releases heat rapidly and can easily lead to major catastrophic accidents. Therefore, how to establish a theory to describe metal combustion behavior in order to achieve scientific prediction of ignition conditions is the key to metal combustion and protection. Summary of the invention

[0004] The purpose of this application is to provide a method for predicting metal combustion ignition conditions, so as to achieve the prediction of metal combustion ignition conditions. The specific technical solution is as follows:

[0005] The present application provides a method for predicting metal combustion ignition conditions, comprising the following steps:

[0006] Based on the energy change during the metal ignition process, a mathematical model of metal combustion is established, which is used to represent the relationship between the energy accumulated during the metal ignition process and the heat generated by the metal combustion, the heat released by convection heat dissipation during the metal combustion process, and the heat released by heat conduction heat release during the metal combustion process;

[0007] According to the metal combustion mathematical model, determining characteristic parameters affecting metal combustion, the characteristic parameters including reaction order, pre-exponential factor, combustion activation energy and adsorption coefficient;

[0008] Based on a combustion experiment on the metal sample, obtaining test results of the characteristic parameters of the metal sample under different combustion experiment factors;

[0009] Based on the test results of the characteristic parameters and the metal combustion mathematical model, the corresponding relationship between the total gas pressure and the ignition temperature of the metal sample is obtained;

[0010] The corresponding relationship between the total gas pressure and the ignition temperature is used to predict the ignition temperature of the metal to be tested under a predetermined total gas pressure.

[0011] In one embodiment of the present application, the obtaining of the test results of the characteristic parameters of the metal sample under different combustion test factors based on the combustion test of the metal sample includes:

[0012] Under pure oxygen conditions, a first experimental result obtained after a combustion experiment is performed on a plurality of metal samples with different diameters, a first corresponding relationship between the diameter and a critical total pressure of combustion gas is determined, and the reaction order is determined based on the first corresponding relationship, wherein the critical total pressure of combustion gas is the total pressure of gas when the metal sample is ignited;

[0013] Obtain second experimental results after the same metal sample is subjected to combustion experiments under different total gas pressures, determine a second corresponding relationship between the total gas pressure and the ignition temperature, and determine the combustion activation energy and the pre-exponential factor based on the second corresponding relationship.

[0014] In one embodiment of the present application, the obtaining of the test results of the characteristic parameters of the metal sample under different combustion test factors based on the combustion test of the metal sample includes:

[0015] For non-pure oxygen conditions, the third experimental results of the same metal sample after the combustion experiment under different oxygen concentrations are obtained, the third corresponding relationship between the oxygen concentration and the total pressure of the critical combustion gas is determined, and the adsorption coefficient is determined based on the third corresponding relationship.

[0016] In one embodiment of the present application, the corresponding relationship between the total gas pressure and the ignition temperature of the metal sample obtained based on the test results of the characteristic parameters and the metal combustion mathematical model includes:

[0017] For pure oxygen conditions, the corresponding relationship between the total gas pressure and the ignition temperature of the metal sample is determined by using the test results of the reaction order, the combustion activation energy, the pre-exponential factor and the metal combustion mathematical model.

[0018] In one embodiment of the present application, the corresponding relationship between the total gas pressure and the ignition temperature of the metal sample obtained based on the test results of the characteristic parameters and the metal combustion mathematical model includes:

[0019] For non-pure oxygen conditions, the corresponding relationship between the critical total pressure of the combustion gas and the ignition temperature is determined using the test results of the reaction order, the combustion activation energy, the pre-exponential factor, the adsorption coefficient and the metal combustion mathematical model.

[0020] In one embodiment of the present application, the predicting of the ignition temperature of the metal to be tested under a predetermined total gas pressure by using the corresponding relationship between the total gas pressure and the ignition temperature includes:

[0021] The ignition temperature of the metal to be tested under a predetermined total gas pressure is calculated using the following expression:

[0022]

[0023] In the formula, P represents the total gas pressure, T represents the ignition temperature, T0 represents the room temperature, and A2, B2, and C2 are constants.

[0024] In one embodiment of the present application, the metal combustion mathematical model is expressed as:

[0025]

[0026] In the formula, c represents specific heat capacity; m represents the mass of the burning metal; dT / dt represents the change in temperature per unit time; k represents the pre-exponential factor; E a represents combustion activation energy; R represents the ideal gas constant; T represents the ignition temperature; C i represents the oxygen concentration of the premixed gas; P represents the total gas pressure; n represents the reaction order; a represents the adsorption coefficient; H represents the reaction heat; S1 represents the reaction area; h represents the reaction area; B represents the interface heat transfer rate; T0 represents room temperature; S2 represents the bottom area of ​​the metal sample; λ represents the thermal conductivity coefficient; l represents the heating length, that is, the length of the copper wire binding sample during combustion; dT / dl represents the temperature change within a unit heating length.

[0027] In one embodiment of the present application, the metal includes titanium and titanium alloys, iron and iron alloys, nickel and nickel alloys.

[0028] In one embodiment of the present application, the titanium alloy includes at least one of TC4, TC11 and TC17.

[0029] The present application provides a method for predicting metal combustion ignition conditions. After establishing a mathematical model of metal combustion based on the energy changes during the metal ignition process, characteristic parameters that affect metal combustion are determined. Based on a combustion experiment on the metal sample, the test results of the characteristic parameters of the metal sample under different combustion experiment factors are obtained. Then, based on the test results and the mathematical model of metal combustion, the corresponding relationship between the total gas pressure and the ignition temperature of the metal sample is obtained, and the ignition temperature of the metal to be tested under a predetermined total gas pressure is predicted using the corresponding relationship. The method for predicting metal combustion ignition conditions of the present application improves the rationality and accuracy of the combustion characteristic parameters, and the established mathematical model of metal combustion has a higher reliability and can more accurately predict the ignition temperature of the metal. Of course, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0031] Figure 1 A flowchart of a method for predicting metal combustion ignition conditions provided in this application;

[0032] Figure 2 It is a fitting curve diagram of the total pressure P0 of the critical combustion gas corresponding to different diameters d in Example 1 of the present application;

[0033] Figure 3 It is a fitting curve diagram of the ignition temperature T corresponding to different gas total pressures P in Example 1 of the present application;

[0034] Figure 4 The different oxygen concentrations C in Example 2 of this application i The corresponding fitting curve of the critical combustion gas total pressure P0.

[0035] Figure 5 This is a curve diagram showing the relationship between the critical ignition temperature and pressure of the titanium alloy in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0037] In the prior art, a theoretical combustion model of metals is established from the perspective of energy conservation of endothermic-exothermic combustion. However, the prior art usually uses non-isothermal oxidation tests to measure relevant parameters in the model. Since the non-isothermal oxidation test is a slow process, which is different from the nature of metal combustion, the relevant parameters measured are difficult to reflect the combustion characteristics, and therefore it is difficult to accurately predict the ignition temperature of the metal.

[0038] In view of this, the present application provides a method for predicting metal combustion ignition conditions, such as Figure 1 As shown, the following steps are included:

[0039] S1, based on the energy changes during metal ignition, a mathematical model of metal combustion is established.

[0040] The metal combustion mathematical model of the present application is used to represent the relationship between the energy accumulated during the metal ignition process and the heat generated by the metal combustion, the heat released by convection heat dissipation during the metal combustion process, and the heat released by heat conduction heat release during the metal combustion process. Specifically, the energy change during the metal ignition process of the present application is established based on the law of conservation of energy as follows:

[0041] Q i =Q O -Q c -Q λ (1)

[0042] In the formula, Q i Q is the energy accumulated during the combustion of metal. O is the heat generated by the combustion of the metal, Q c Q is the heat released by convection heat dissipation during metal combustion. λ It is the heat released by heat conduction during the combustion of metals.

[0043] In this application, during the metal ignition process, the energy Q accumulated by the metal i Q is the heat generated by the combustion of metal O The total heat dissipated Q L The difference, Q i =Q O -Q L The total heat dissipated is Q L Including the heat Q released by convection heat dissipation during metal combustion c , the heat released by heat conduction during metal combustion Q λ , the heat released by radiation during metal combustion Q r However, since the temperature of the metal during ignition is lower than 1200°C, the heat released by radiation is much less than the heat released by convection, so Q r Can be ignored.

[0044] From the above expression (1), we can see that Q i It is the energy accumulated during the combustion of metals. The heat transferred to the metal through contact with the outside world and acting on the metal causes the metal to rise from room temperature to the critical ignition temperature. Q O The heat generated by metal combustion is related to the degree of oxidation reaction, that is, it depends on the reaction heat H during metal combustion and the oxygen absorption rate. The oxygen absorption rate is related to the surface area S1 of the reaction zone and the oxygen absorption rate per unit area. related, therefore Q cIt is the heat released by convection heat dissipation during the combustion of metal. During the combustion of metal sample, the part with high temperature transfers heat to the part with low temperature by convection. This application only considers the temperature change of metal sample at the moment of ignition, so Q c =S1h B (T-T0); Q λ It is the heat released by heat conduction during the combustion of metal. During the ignition of metal, the heat is conducted from the high temperature area of ​​the ignition point to the low temperature area of ​​the metal. Therefore, Q λ =S2λdT / dl.

[0045] In this application, It can be considered as the accumulated energy change per unit time. Considering that the combustion reaction occurs instantaneously, dt is taken as the unit time, which can be considered as 1s when performing calculations. When performing energy calculations based on the expression (1) established by the law of conservation of energy, considering that 1J / s=1W, when expressing Q O , Q c and Q λ When the energy changes, the energy change per unit time is used as the calculation standard.

[0046] Based on the above analysis, in one embodiment of the present application, the metal combustion mathematical model can be expressed as:

[0047]

[0048] In the formula, c represents specific heat capacity; m represents the mass of the burning metal; dT / dt represents the change in temperature per unit time; k represents the pre-exponential factor; E a represents combustion activation energy; R represents the ideal gas constant; T represents the ignition temperature; C i represents the oxygen concentration of the premixed gas; P represents the total gas pressure; n represents the reaction order; a represents the adsorption coefficient; H represents the reaction heat; S1 represents the reaction area; h represents the reaction area; B represents the interface heat transfer rate; T0 represents the room temperature; S2 represents the bottom area of ​​the metal sample; λ represents the thermal conductivity coefficient; l represents the heating length, that is, the total length of the copper wire when the heating copper wire is wrapped around the metal sample for heating; dT / dl represents the temperature change within the unit heating length. In this application, the total gas pressure P can be considered as the oxygen pressure under pure oxygen conditions and as the total pressure of the mixed gas under non-pure oxygen conditions. For example, if the non-pure oxygen condition is a mixture of oxygen and nitrogen, the total gas pressure can be considered as the sum of the pressures of oxygen and nitrogen.

[0049] S2. Determine the characteristic parameters that affect metal combustion based on the mathematical model of metal combustion.

[0050] After the mathematical model of metal combustion is established, since the mathematical model of metal combustion is used to represent the relationship between the energy accumulated by the metal during the ignition process and the heat generated by the metal combustion, the heat released by convection heat dissipation during the metal combustion process, and the heat released by heat conduction heat release during the metal combustion process, the characteristic parameters that affect the metal combustion can be determined according to the mathematical model of metal combustion. The characteristic parameters of this application include but are not limited to and adsorption coefficients, and the above characteristic parameters refer to parameters that can reflect the essential characteristics of metal combustion. Among them, the reaction order refers to the sum of the reactant concentration exponents during the combustion process, the pre-exponential factor is a constant determined by the nature of the reaction, the combustion activation energy refers to the minimum energy that a molecule must reach for a combustion reaction to occur, and the adsorption coefficient refers to the adsorption rate of oxygen molecules on the combustion surface.

[0051] S3, based on a combustion experiment on the metal sample, obtain test results of characteristic parameters of the metal sample under different combustion experiment factors.

[0052] The inventors have found that the metal combustion phenomenon is usually caused by the combined effects of material factors, operating factors and ignition factors, which lead to a violent physical and chemical reaction after the system energy reaches a threshold value. During the combustion experiment of the metal sample, the material factors include the size of the metal sample, such as the heated length of the metal sample and the diameter of the metal sample; the operating factors and ignition factors include the room temperature, the combustion atmosphere and the ignition temperature, and the combustion atmosphere includes the total gas pressure and oxygen concentration. In the combustion experiment of this application, the metal sample usually produces different ignition temperatures as the diameter of the metal sample and the combustion atmosphere change.

[0053] When conducting a combustion experiment on a metal sample, the present application fixes the metal sample on a combustion device, adjusts the combustion atmosphere, and heats the metal sample until the metal sample is ignited. The present application has no particular restrictions on the method of heating the metal sample, as long as the purpose of the invention of the present application can be achieved. For example, the heating method is resistance wire heating, flame heating, high-temperature plasma spray gun, etc. The present application has no particular restrictions on the heating rate of the metal sample, as long as the purpose of the invention of the present application can be achieved. For example, the heating rate is 200℃ / min-600℃ / min.

[0054] S4, based on the test results of characteristic parameters and the mathematical model of metal combustion, the corresponding relationship between the total gas pressure and the ignition temperature of the metal sample is obtained.

[0055] The inventors found that metal samples of the same material and size have the same reaction order n, pre-exponential factor k, and combustion activation energy E. a, and the same metal sample has the same oxygen adsorption at the moment of ignition. Based on this, after obtaining the test results of the characteristic parameters, based on the mathematical model of metal combustion, the factors affecting metal combustion include combustion atmosphere (total gas pressure and oxygen concentration) and ignition temperature. Therefore, the application can determine the corresponding relationship between total gas pressure and ignition temperature based on the test results of the characteristic parameters and the mathematical model of metal combustion.

[0056] S5, predicting the ignition temperature of the metal to be tested under a predetermined total gas pressure by using the corresponding relationship between the total gas pressure and the ignition temperature.

[0057] After obtaining the corresponding relationship between the total gas pressure and the ignition temperature of the metal sample, the ignition temperature of the metal to be tested under a predetermined total gas pressure can be predicted using the corresponding relationship.

[0058] In one embodiment of the present application, for pure oxygen conditions, step S3 comprises:

[0059] Obtaining a first experimental result obtained after a combustion experiment on a plurality of metal samples with different diameters, determining a first corresponding relationship between the diameter and the critical total pressure of the combustion gas, and determining a reaction order based on the first corresponding relationship, wherein the critical total pressure of the combustion gas is the total pressure of the gas when the metal sample is ignited;

[0060] Obtain the second experimental results of the combustion experiment of the same metal sample under different total gas pressures, determine the second corresponding relationship between the total gas pressure and the ignition temperature, and determine the combustion activation energy and the pre-exponential factor based on the second corresponding relationship.

[0061] In this application, according to expression (2), m is the mass of the metal sample, Where ρ is the density of the metal sample, V is the volume of the metal sample, d is the diameter of the metal sample, and l is the heating length; S1 is the reaction area, S1 = πdl, where d is the diameter of the metal sample, and l is the heating length; S2 is the bottom area of ​​the cylindrical metal test rod, then Where d is the diameter of the metal sample, dT / dt can be expressed as the change in temperature per unit time, dT / dt = (T-T0) / t, and dT / dl can be expressed as the change in temperature per unit heating length, dT / dl = (T-T0) / l.

[0062] Under pure oxygen conditions, the oxygen concentration c i The value of is 1, so expression (2) can be expressed as:

[0063]

[0064] According to expression (3), determine the reaction order n and combustion activation energy E a , pre-factor k:

[0065] Step A1: Determine the reaction order n according to expression (3):

[0066] According to the reaction order n to be determined, the part related to the reaction order n in expression (3) is separately expressed, and expression (3) is simplified to obtain the following expression:

[0067]

[0068] The diameter d of the metal sample is used as an independent variable, and a combustion experiment is carried out on a metal combustion device to obtain the critical total gas pressure P0 corresponding to different metal sample diameters d, that is, the first experimental result. According to the relationship in expression (4), the first experimental result is linearly fitted to obtain the first corresponding relationship between the diameter and the critical total gas pressure, and the characteristic parameter reaction order n is determined based on the first corresponding relationship between the diameter and the critical total gas pressure. The present application has no particular restrictions on the linear fitting method, as long as the purpose of the invention of the present application can be achieved, the linear fitting method known in the art can be used to linearly fit the first experimental result.

[0069] Step A2: Determine the combustion activation energy E according to expression (3): a And the pre-exponential factor k:

[0070] Considering that metals of the same size should have the same combustion activation energy E a and the pre-exponential factor k, therefore, the size-related factors in expression (3) are combined and expression (3) is simplified to obtain the following expression:

[0071]

[0072] In the present application, the total gas pressure P can be used as an independent variable to conduct a combustion experiment on a metal combustion device to obtain the ignition temperature T corresponding to different total gas pressures P, i.e., the second experimental result. According to the relationship in expression (5) and the second experimental result, the second corresponding relationship between the total gas pressure and the ignition temperature is determined, and according to the second corresponding relationship between the total gas pressure and the ignition temperature, the combustion activation energy E is determined. a and the pre-exponential factor k.

[0073] In one embodiment of the present application, for non-pure oxygen conditions, the above step S3 includes:

[0074] Obtain the third experimental results of the combustion experiment of the same metal sample under different oxygen concentrations, determine the third corresponding relationship between the oxygen concentration and the total pressure of the critical combustion gas, and determine the adsorption coefficient based on the third corresponding relationship.

[0075] In the metal combustion process of this application, when the metal combustion environment is not pure oxygen, the influence of the mixed gas needs to be considered. The oxygen concentration C i is the oxygen concentration in the mixed gas. In this application, considering that the oxygen adsorption amount of the same metal material at the moment of ignition should be consistent, only the part containing the adsorption coefficient is considered when simplifying expression (2), and it is considered that is a constant, expressed as:

[0076]

[0077] Where A3 is a constant.

[0078] By rearranging expression (6), we obtain the following relationship:

[0079] (C i P0) n =aA3P0 n (1-C i ) n +A3 (7)

[0080] According to expression (7), the adsorption coefficient a is determined.

[0081] In this application, the oxygen concentration of the metal sample C i As the independent variable, a combustion experiment was carried out on a metal combustion device to obtain different oxygen concentrations C i The corresponding critical combustion gas total pressure P0 is the third experimental result. Based on expression (7) and the third experimental result, the third corresponding relationship between oxygen concentration and critical combustion gas total pressure is obtained, and the adsorption coefficient a is obtained according to the third corresponding relationship between oxygen concentration and critical combustion gas total pressure. The mixed gas in the present application is a mixed gas of oxygen and other gases. There is no special limitation on other gases as long as the purpose of the present invention can be achieved. For example, the other gas is at least one of nitrogen and air.

[0082] In one embodiment of the present application, for pure oxygen conditions, the above step S4 comprises:

[0083] Using the reaction order n, pre-exponential factor k, combustion activation energy E a The corresponding relationship between the total gas pressure and the ignition temperature of the metal sample is determined based on the test results and the mathematical model of metal combustion.

[0084] In the process of metal combustion in this application, under pure oxygen conditions, the oxygen concentration C i The value is 1, which can convert the above reaction order n, pre-exponential factor k, combustion activation energy E a Substitute the test results into expression (2), and combine and simplify the size-related factors in expression (2) to obtain the following expression:

[0085]

[0086] The corresponding relationship between the total gas pressure and the ignition temperature of the metal sample can be determined using expression (5).

[0087] In one embodiment of the present application, for non-pure oxygen conditions, the above step S4 includes:

[0088] Using the reaction order n, pre-exponential factor k, combustion activation energy E a , the test results of the adsorption coefficient a and the mathematical model of metal combustion are used to determine the corresponding relationship between the total pressure of the critical combustion gas and the ignition temperature.

[0089] In the process of metal combustion in this application, under non-pure oxygen conditions, the oxygen concentration C i The value is not 1, and the above reaction order n, pre-exponential factor k, combustion activation energy E a Substitute the test results of the adsorption coefficient a into expression (2), and combine and simplify the size-related factors in expression (2) to obtain the following expression:

[0090]

[0091] The corresponding relationship between the total gas pressure and the ignition temperature can be determined according to expression (8).

[0092] In one embodiment of the present application, the above step S5 includes:

[0093] The ignition temperature of the metal to be tested under a predetermined total gas pressure is calculated using the following expression:

[0094]

[0095] In the formula, P represents the total gas pressure, T represents the ignition temperature, T0 represents the room temperature, and A2, B2, and C2 are constants.

[0096] In the process of metal combustion in this application, under pure oxygen conditions, the oxygen concentration C i The value of is 1, based on expression (2) and the above reaction order n, pre-exponential factor k, combustion activation energy E a The test results show the following relationship:

[0097]

[0098] Simplifying expression (5), we get the following relationship:

[0099]

[0100] In the formula, P represents the total gas pressure, T represents the ignition temperature, T0 represents the room temperature, A2, B2, and C2 are constants, respectively. According to the corresponding relationship between the ignition temperature and the total gas pressure in expression (9), the ignition temperature of the metal to be tested under a predetermined total gas pressure is predicted. In this application, the metal sample has a certain density ρ, specific heat capacity c, reaction heat H, and interface heat transfer rate h B , thermal conductivity λ, in the combustion test of metal samples, the diameter d and heating length l of the metal sample are fixed values. Considering that metal samples of the same size and the same material have the same reaction order n, pre-exponential factor k, combustion activation energy E a , and the same metal sample has the same oxygen adsorption amount at the moment of ignition, that is, the same adsorption constant a. Therefore, A2, B2, and C2 in equation (9) can be treated as constants respectively.

[0101] In one embodiment of the present application, the metal includes titanium and titanium alloys, iron and iron alloys, nickel and nickel alloys.

[0102] The metal in the present application is not particularly limited, as long as the purpose of the present application can be achieved. For example, the metal is selected from any one of titanium and titanium alloys, iron and iron alloys, nickel and nickel alloys. As long as the metal combustion can be achieved, the prediction method of the metal combustion ignition condition provided in the present application can be used for prediction.

[0103] In one embodiment of the present application, the titanium alloy includes at least one of TC4, TC11 and TC17, the iron alloy includes at least one of SS304, stainless steel S03 and 1Cr18Ni9Ti, and the nickel alloy includes at least one of NiCr20Al5Ti2 alloy, GH4169 and GH4202.

[0104] In one embodiment of the present application, there is no limitation on the equipment of the combustion experiment, as long as the purpose of the present application can be achieved. For example, the equipment of the combustion experiment includes an infrared thermal imaging precise temperature measurement device, wherein the infrared thermal imaging precise temperature measurement device can be a commercially available device.

[0105] The infrared thermal imaging precise temperature measurement equipment is a device that uses infrared thermal imaging coupled with Raman spectroscopy to achieve high-precision quantitative testing of the ignition temperature. The infrared thermal imaging precise temperature measurement equipment is used to measure the actual measured value of the ignition temperature during the metal combustion process.

[0106] The present application provides a method for predicting metal combustion ignition conditions. After establishing a metal combustion mathematical model based on the energy changes during the metal ignition process, characteristic parameters that affect metal combustion are determined. Based on a combustion experiment on a metal sample, test results of the characteristic parameters of the metal sample under different combustion experiment factors are obtained. Then, based on the test results and the metal combustion mathematical model, the corresponding relationship between the total gas pressure and the ignition temperature of the metal sample is obtained, and the ignition temperature of the metal to be tested under a predetermined total gas pressure is predicted using the corresponding relationship. The metal combustion ignition condition prediction method of the present application improves the rationality and accuracy of the combustion characteristic parameters, and the established metal combustion mathematical model has higher reliability and can more accurately predict the metal ignition temperature.

[0107] Example

[0108] Hereinafter, the embodiments of the present application will be described in more detail with reference to Examples and Comparative Examples. Various tests and evaluations were performed according to the following methods.

[0109] Example 1

[0110] Prediction of the ignition conditions of metal combustion under pure oxygen conditions

[0111] <Reaction order n, combustion activation energy E a and determination of the pre-exponential factor k>

[0112] Under pure oxygen conditions, the device in the combustion system structure diagram in the "A method and system for temperature-controlled testing of the combustion behavior of metal materials" disclosed in publication number CN107144663A is used to conduct metal combustion experiments in accordance with the ASTM-G124 test standard to determine the reaction order n and the combustion activation energy E. a and the value of the pre-exponential factor k.

[0113] The specific steps of the metal combustion experiment are as follows:

[0114] (1) Wrap 5 turns of 1 mm diameter copper wire around the bottom of the sample and fix the sample with the copper wire;

[0115] (2) Close the combustion environment, evacuate the air and fill it with oxygen to reach the required total gas pressure;

[0116] (3) Turn on the power, heat up, and use an infrared thermal imaging precision temperature measurement device (model MCS640, LUMASENSE MIKRON) to measure the ignition temperature;

[0117] (4) After the combustion reaction is completed, turn off the power supply and remove the sample residue;

[0118] (5) By changing the diameter, total gas pressure and oxygen-nitrogen ratio of the sample, the critical total gas pressure at different diameters, the ignition temperature at different total gas pressures and the critical total gas pressure at different oxygen-nitrogen ratios are obtained, and then the reaction order n and the combustion activation energy E are determined. a and the value of the pre-exponential factor k.

[0119] Experimental material: TC17 titanium alloy. The main known parameters of TC17 titanium alloy are listed in Table 1.

[0120] Table 1 List of main combustion parameters of TC17 titanium alloy

[0121] Specific heat capacity C 0.52J / (kg·K) Density ρ <![CDATA[4770kg / m 3 ]]> <![CDATA[Interface heat transfer coefficient h B > <![CDATA[11W / (m 2 ·K)]]> Reaction heat H 12MJ / kg Thermal conductivity λ 15W / (m·K) Heating length l 5mm

[0122] Determine the reaction order n according to expression (4):

[0123] A metal combustion experiment was conducted on TC17 titanium alloy. According to the parameter list of TC17 titanium alloy during the experiment, the following calculation was performed to determine The critical combustion gas total pressure P0 corresponding to different metal sample diameters d is tested, as shown in Table 2.

[0124] Table 2 Comparison table of different metal sample diameters d and critical combustion gas total pressure P0

[0125]

[0126]

[0127] According to the experimental data in Table 2, a linear fit is performed on the experimental data according to expression (4) to obtain a fitting curve, such as Figure 2 As shown. From the fitting curve, we can get the slope of the curve to be 1.18, that is Thus, the reaction order n is 0.85.

[0128] According to expression (3), the combustion activation energy E is determined a And the pre-exponential factor k:

[0129] right The combustion experiment was carried out on a TC17 titanium alloy metal rod (i.e., a diameter of 3.2 mm and a length of 70 mm). The ignition temperature T corresponding to different gas total pressures P was tested using an infrared thermal imaging precise temperature measurement device. The test results are shown in Table 3.

[0130] Table 3 Comparison of different gas total pressure P and ignition temperature T

[0131] Total gas pressure P(MPa) 0.13 0.21 0.31 0.41 0.51 0.59 Ignition temperature T(K) 1315.9 1188.1 1102 1010.6 986.2 967.3

[0132] According to the simplification of expression (3) under pure oxygen conditions, the corresponding relationship expression (9) between the ignition temperature and the total gas pressure is obtained. According to expression (9), the experimental data in Table 3 are nonlinearly fitted to obtain the following: Figure 3 The nonlinear curve in .

[0133] according to Figure 3 The nonlinear curve in the following results is obtained: The combustion activation energy E can be calculated a =50.01 kJ / mol, pre-exponential factor k = 101.35 kg / (m 2 ·s).

[0134] <Determination of the Correspondence between Total Pressure of Different Gases and Ignition Temperature>

[0135] The determined reaction order n, combustion activation energy E a , the pre-exponential factor k is substituted back into expression (5). When the room temperature is 25°C and the heating length is 5mm, the corresponding relationship between the total gas pressure and the ignition temperature of the TC17 titanium alloy with a diameter of 3.2mm, 5mm and 8mm is obtained. Among them, the corresponding relationship between the total gas pressure and the ignition temperature of the TC17 titanium alloy with a diameter of 3.2mm is expression (10), the corresponding relationship between the total gas pressure and the ignition temperature of the TC17 titanium alloy with a diameter of 5mm is expression (11), and the corresponding relationship between the total gas pressure and the ignition temperature of the TC17 titanium alloy with a diameter of 8mm is expression (12).

[0136]

[0137]

[0138]

[0139] <Prediction of ignition temperature>

[0140] According to expression (10), The ignition temperature of TC17 titanium alloy when the total gas pressure is 0.21MPa, 0.31MPa, 0.41MPa, and 0.47MPa is used as the predicted ignition temperature; The TC17 titanium alloy was subjected to a metal combustion experiment. The infrared thermal imaging precise temperature measuring equipment was equipped to test the ignition temperature of the titanium alloy when the total gas pressure was 0.21MPa, 0.31MPa, 0.41MPa, and 0.47MPa. The ignition temperature was taken as the actual measured ignition temperature. The experimental results are shown in Table 4.

[0141] According to expression (11), The ignition temperature of TC17 titanium alloy at a total gas pressure of 0.45 MPa is used as the predicted ignition temperature; The TC17 titanium alloy was subjected to a metal combustion experiment. The infrared thermal imaging precise temperature measuring equipment was equipped to test the ignition temperature of the titanium alloy at a total gas pressure of 0.45 MPa. The ignition temperature was taken as the actual measured ignition temperature. The results are shown in Table 4.

[0142] (3) Calculate according to expression (12) The ignition temperature of TC17 titanium alloy at a total gas pressure of 0.81 MPa is used as the predicted ignition temperature; The TC17 titanium alloy was subjected to a metal combustion experiment. The infrared thermal imaging precise temperature measuring equipment was equipped to test the ignition temperature of the titanium alloy at a total gas pressure of 0.81 MPa. The ignition temperature was taken as the actual measured ignition temperature. The results are shown in Table 4.

[0143] Table 4 Ignition temperature of TC17 titanium alloy at different diameters and total gas pressures

[0144]

[0145] Example 2

[0146] Prediction of the ignition conditions of metal combustion under non-pure oxygen conditions

[0147] <Reaction order n, combustion activation energy E a and determination of the pre-exponential factor k>

[0148] Under non-pure oxygen conditions, the reaction order n and the combustion activation energy E a The determination of the pre-exponential factor k is the same as the calculation process in Example 1, and the obtained reaction order n and combustion activation energy E a The values ​​of the pre-exponential factor k are the same as those in Example 1, i.e., the reaction order n=0.85, the pre-exponential factor k=101.35 kg / (m 2 ·s), combustion activation energy E a =50.01 kJ / mol.

[0149] <Determination of adsorption coefficient constant a>

[0150] The metal combustion experiment was carried out using the same experimental equipment as in Example 1 to determine the value of the adsorption coefficient a.

[0151] Experimental Materials: TC17 titanium alloy, the main known parameters of TC17 titanium alloy are listed in Table 1.

[0152] Combustion environment: The gas during combustion is a mixture of nitrogen and oxygen with an oxygen concentration of 50%.

[0153] right TC17 titanium alloy metal combustion experiment, testing different oxygen concentrations C i The critical total pressure of the combustion gas P0 under the condition of C is calculated by combining the value of the reaction order n obtained in Example 1. i n P0 n and P0 n (1-C i ) n , as shown in Table 5.

[0154] Table 5 Different oxygen concentrations C i Comparison table of total pressure P0 of critical combustion gas

[0155]

[0156] The above experimental data are converted into C according to expression (7) i n P0 n =aA3P0 n (1-C i ) n +A3 form for linear fitting, and obtain Figure 4 The fitting curve is shown.

[0157] according to Figure 4 The fitting curve in is obtained: intercept A3 = 0.26, thus calculating the characteristic parameter adsorption coefficient a = 1.92.

[0158] <Determination of the Correspondence between Total Gas Pressure and Ignition Temperature under Non-Pure Oxygen Conditions>

[0159] The obtained adsorption coefficient a, characteristic parameter reaction order n, pre-exponential factor k and combustion activation energy E a Substitute the experimental data into expression (8) and use TC17 titanium alloy, at room temperature of 25℃ and heating length l of 5mm, obtain The corresponding relationship between different gas total pressure P and ignition temperature T of TC17 titanium alloy when the oxygen concentration is 50%, 75% and 86% respectively. When the oxygen concentration of TC17 titanium alloy is 50%, the corresponding relationship between different gas total pressures P and the ignition temperature T is expression (13); when the oxygen concentration is 75%, the corresponding relationship between different gas total pressures P and the ignition temperature T is expression (14); when the oxygen concentration is 86%, the corresponding relationship between different gas total pressures P and the ignition temperature T is expression (15).

[0160]

[0161]

[0162]

[0163] <Predict the ignition temperature based on the corresponding relationship between the total pressure of different gases and the ignition temperature>

[0164] According to expression (13), The ignition temperature of the metal when the oxygen concentration of TC17 titanium alloy is 50% (oxygen-nitrogen ratio is 1:1) and the total gas pressure is 1.2MPa, 1.4MPa, and 1.8MPa is used as the predicted ignition temperature; and the same experimental equipment as in Example 1 is used to perform The combustion experiment of TC17 titanium alloy at an oxygen concentration of 50% (oxygen-nitrogen ratio of 1:1) was equipped with infrared thermal imaging precise temperature measurement equipment to test the ignition temperature of the titanium alloy at a total gas pressure of 1.2MPa, 1.4MPa, and 1.8MPa. The ignition temperature was taken as the actual measured ignition temperature. The experimental results are shown in Table 6.

[0165] According to expression (14), The ignition temperature of the metal of TC17 titanium alloy at an oxygen concentration of 75% (oxygen-nitrogen ratio of 3:1) and a total gas pressure of 1.2 MPa is used as the predicted ignition temperature; and the same experimental equipment as in Example 1 is used for The combustion experiment of TC17 titanium alloy at an oxygen concentration of 75% (oxygen-nitrogen ratio of 3:1) was equipped with infrared thermal imaging precise temperature measurement equipment to test the ignition temperature of the titanium alloy at a total gas pressure of 1.2MPa. The ignition temperature was taken as the actual measured ignition temperature. The experimental results are shown in Table 6.

[0166] According to expression (15), The ignition temperature of the metal of TC17 titanium alloy at an oxygen concentration of 86% (oxygen-nitrogen ratio of 6:1) and a total gas pressure of 1.2 MPa is used as the predicted ignition temperature; and the same experimental equipment as in Example 1 is used for The combustion experiment of TC17 titanium alloy at an oxygen concentration of 86% (oxygen-nitrogen ratio of 6:1) was equipped with infrared thermal imaging precise temperature measurement equipment to test the ignition temperature of the titanium alloy at a total gas pressure of 1.2MPa. The ignition temperature was taken as the actual measured ignition temperature. The experimental results are shown in Table 6.

[0167] Table 6 Ignition temperature of TC17 titanium alloy at different oxygen concentrations and total gas pressures

[0168]

[0169] Comparative Example 1

[0170] Mi et al. (Mi Guangbao, Huang Xu, Cao Jingxia, et al. Anti-ignition properties and theoretical analysis of Ti-V-Cr flame-retardant titanium alloys [J]. Acta Metallurgica Sinica, 2014, 50(5): 575-586) measured the critical ignition temperature of a 2 mm thick Ti40 titanium alloy sample. By analyzing the energy change during the combustion of the titanium alloy, the relationship between the critical ignition temperature of the titanium alloy and the total gas pressure was obtained, as shown in equation (16). The relationship curve between the critical ignition temperature of the titanium alloy and the total gas pressure was also plotted, as shown in equation (16). Figure 5 shown.

[0171]

[0172] According to the relationship curve between the critical ignition temperature of titanium alloy and the total gas pressure, the ignition temperature when the total gas pressure is 0.21MPa, 0.31MPa, 0.41MPa, and 0.47MPa, that is, the predicted temperature, is obtained; the same experimental equipment as in Example 1 is used to carry out a combustion experiment of a 2mm thick Ti40 titanium alloy sample, and an infrared thermal imaging precise temperature measuring equipment is used to test the ignition temperature of the 2mm thick Ti40 titanium alloy sample when the total gas pressure is 0.21MPa, 0.31MPa, 0.41MPa, and 0.47MPa, as the measured ignition temperature. The experimental results are shown in Table 7.

[0173] Table 7 Ignition temperature of titanium alloy at different gas total pressures

[0174]

[0175]

[0176] It can be seen from Example 1 that under pure oxygen conditions, the reaction order n and combustion activation energy E determined based on TC17 titanium alloy are a The corresponding relationship between the total pressure of different gases and the ignition temperature of TC17 titanium alloy at a diameter of 3.2 mm was obtained by using the pre-exponential factor k. The error between the predicted value and the actual measured value of the ignition temperature of TC17 titanium alloy at other gas total pressures was small, and the relative error was within 1.65%. The reaction order n and combustion activation energy E calculated under the condition of 3.2 mm diameter were a The expression between the total pressure of different gases and the ignition temperature of TC17 titanium alloy with diameters of 5mm and 8mm was obtained by using the pre-exponential factor k and the mathematical model of metal combustion, and the combustion temperature of TC17 titanium alloy was predicted. The relative error between the predicted value and the measured value of the ignition temperature was controlled within 2.87%. It can be seen that the prediction method of the metal combustion ignition conditions of the present application is highly reliable and can make a relatively accurate prediction of the metal ignition temperature.

[0177] It can be seen from Example 2 that under non-pure oxygen conditions, the reaction order n and combustion activation energy E determined based on TC17 titanium alloy are a , pre-exponential factor k and adsorption coefficient a, when the diameter of TC17 titanium alloy is 3.2mm, the corresponding relationship between different gas total pressures and ignition temperatures of TC17 titanium alloy when the oxygen concentration is 50%, 75% and 86% are obtained respectively. When the oxygen concentration is 50%, the ignition temperature of TC17 titanium alloy is predicted when the total gas pressure is 1.2MPa, 1.4MPa and 1.8MPa respectively. The error between the predicted value and the actual measured value is small, and the relative error is within 1.71%; the error between the predicted value and the measured value is small when the ignition temperature of TC17 titanium alloy is predicted when the oxygen concentration is 75% and 86% under the total gas pressure of 1.2MPa, and the relative error is within 2.33%. Therefore, it can be seen that the prediction method of the metal combustion ignition conditions of the present application is highly reliable and can accurately predict the metal ignition temperature.

[0178] It can be seen from Example 1 and Comparative Example 1 of the present application that the reaction order n and the combustion activation energy E determined by the present application are a When the pre-exponential factor k predicts the ignition temperature during metal combustion, the ignition temperature prediction accuracy is high, and the relative error is within 2.87%. In comparative example 1, according to the relationship curve between the critical ignition temperature of titanium alloy and the total gas pressure, the relative error of the prediction of the ignition temperature of titanium alloy under different total gas pressures is relatively large, ranging from 5.92% to 12.15%. Therefore, it can be seen that the prediction method of the metal combustion ignition conditions of the present application is highly reliable and can make a relatively accurate prediction of the metal ignition temperature.

[0179] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0180] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0181] The above description is only a preferred embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims

1. A method for predicting metal combustion ignition conditions, characterized in that: The following steps are involved: Based on the energy change during the metal ignition process, a mathematical model of metal combustion is established, wherein the mathematical model of metal combustion is used to represent the relationship between the energy accumulated by the metal during the ignition process and the heat generated by the metal combustion, the heat released by convection heat dissipation during the metal combustion process, and the heat released by heat conduction heat release during the metal combustion process; According to the metal combustion mathematical model, determining characteristic parameters affecting metal combustion, the characteristic parameters including reaction order, pre-exponential factor, combustion activation energy and adsorption coefficient; Based on a combustion experiment on the metal sample, obtaining test results of the characteristic parameters of the metal sample under different combustion experiment factors; Based on the test results of the characteristic parameters and the metal combustion mathematical model, the corresponding relationship between the total gas pressure and the ignition temperature of the metal sample is obtained; the metal combustion mathematical model is expressed as: In the formula, c represents specific heat capacity; m represents the mass of the burning metal; dT / dt represents the change in temperature per unit time; k represents the pre-exponential factor; E a represents combustion activation energy; R represents the ideal gas constant; T represents the ignition temperature; C i represents the oxygen concentration of the premixed gas; P represents the total gas pressure; n represents the reaction order; a represents the adsorption coefficient; H represents the reaction heat; S1 represents the reaction area; h B represents the interface heat transfer rate; T0 represents the room temperature; S2 represents the bottom area of ​​the metal sample; λ represents the thermal conductivity; l represents the heating length; dT / dl represents the temperature change per unit heating length; Using the corresponding relationship between the total gas pressure and the ignition temperature, the ignition temperature of the metal to be tested under a predetermined total gas pressure is predicted, including: The ignition temperature of the metal to be tested under a predetermined total gas pressure is calculated using the following expression: In the formula, P represents the total gas pressure, T represents the ignition temperature, T0 represents the room temperature, and A2, B2, and C2 are constants.

2. The prediction method according to claim 1, characterized in that: The method of obtaining the test results of the characteristic parameters of the metal sample under different combustion test factors based on the combustion test of the metal sample includes: Under pure oxygen conditions, a first experimental result obtained after a combustion experiment is performed on a plurality of metal samples with different diameters, a first corresponding relationship between the diameter and a critical total pressure of combustion gas is determined, and the reaction order is determined based on the first corresponding relationship, wherein the critical total pressure of combustion gas is the total pressure of gas when the metal sample is ignited; Obtain second experimental results after the same metal sample is subjected to combustion experiments under different total gas pressures, determine a second corresponding relationship between the total gas pressure and the ignition temperature, and determine the combustion activation energy and the pre-exponential factor based on the second corresponding relationship.

3. The prediction method according to claim 1, characterized in that: The method of obtaining the test results of the characteristic parameters of the metal sample under different combustion test factors based on the combustion test of the metal sample includes: For non-pure oxygen conditions, the third experimental results of the same metal sample after the combustion experiment under different oxygen concentrations are obtained, the third corresponding relationship between the oxygen concentration and the total pressure of the critical combustion gas is determined, and the adsorption coefficient is determined based on the third corresponding relationship.

4. The prediction method according to claim 1, characterized in that: The corresponding relationship between the total gas pressure and the ignition temperature of the metal sample obtained based on the test results of the characteristic parameters and the metal combustion mathematical model includes: For pure oxygen conditions, the corresponding relationship between the total gas pressure and the ignition temperature of the metal sample is determined by using the test results of the reaction order, the combustion activation energy, the pre-exponential factor and the metal combustion mathematical model.

5. The prediction method according to claim 1, characterized in that: The corresponding relationship between the total gas pressure and the ignition temperature of the metal sample obtained based on the test results of the characteristic parameters and the metal combustion mathematical model includes: For non-pure oxygen conditions, the corresponding relationship between the critical total pressure of combustion gas and the ignition temperature is determined using the test results of the reaction order, the combustion activation energy, the pre-exponential factor, the adsorption coefficient and the metal combustion mathematical model.

6. The prediction method according to claim 1, characterized in that: The metals include titanium and titanium alloys, iron and iron alloys, nickel and nickel alloys.

7. The prediction method according to claim 6, characterized in that: The titanium alloy includes at least one of TC4, TC11 and TC17.

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