Method for making a flammability map for backflash phenomenon and application thereof

Abstract

This invention provides a method for creating a flammability map for indoor fire flashback phenomena, characterized by the following steps: S1. Sampling flue gas to obtain raw data: oxygen volume fraction, carbon dioxide volume fraction, carbon monoxide volume fraction, total hydrocarbon volume fraction (represented by methane concentration), and hydrogen gas integral (for underground coal fires). The excess nitrogen gas integral is obtained by subtracting the sum of the above gases from 100% (i.e., the remaining nitrogen portion after air removal in the full gas analysis); S2. Generating de-air-removed derived data based on the raw data: total nuclear flue gas volume, total nuclear flue gas volume, and normalized data; constructing the flammability zone of the core flue gas (pseudo-fuel) using thermal fingerprint parameters formed by weighted averaging; S3. Based on the proportion of the core flue gas, the position of the state point can be plotted, which, together with the core flammable zone, forms a gas flammability map (flame map); S4. Calculating the comprehensive index of the flue gas: combustion flow, directly determining the combustion and explosion potential of the flue gas. The combustion chart (flame diagram) displays the combustion and explosion potential of the flue gas mixture and can be used to diagnose the ignition potential (nose point) and explosion potential (state point) of the flue gas; the flow chart (flow diagram) directly generates the combustion and explosion potential of the flue gas. Therefore, both can be used to predict and display the flashback phenomenon in a fire, which has important risk indication value for firefighters' fire safety and is a brand-new means of fire safety diagnosis.

Description

Technical Field

[0001] This invention relates to the field of disaster early warning and prevention, specifically to a method for creating a flammability map for predicting indoor fire backfire and its application. Background Technology

[0002] In recent years, numerous major building fire accidents have demonstrated that indoor fire fighting involves significant high risks and complex decision-making processes.

[0003] The aforementioned accidents demonstrate that extreme fire behaviors such as flashover, backdraft, and smoke explosion have become key risk factors threatening the lives of firefighters. However, due to the high uncertainty of the fire environment, the complexity and variability of fuel types and combustion stages, and the invisible, high-density, and rapidly evolving characteristics of high-temperature smoke, current fire command and operations lack effective technical means to quantitatively assess smoke conditions and their potential hazard thresholds. This leads to tactical decisions relying primarily on experience-based judgment, increasing the risk of casualties and disaster escalation.

[0004] Statistical analysis shows that in firefighting operations, the fatality rate among Chinese firefighters is approximately 65%, significantly higher than the US rate of about 45%, and this casualty rate has remained persistently high. This comparison indicates that existing technological systems still have significant shortcomings in the dynamic perception of fire situations and the identification and prediction of extreme fire behaviors, and that the command and decision-making levels need to further improve their quantitative understanding of the fire's evolution. This issue also highlights the real need to enhance fire risk identification and decision support capabilities through technological means.

[0005] It should be noted that objective descriptions of phenomena such as flashback are not a modern invention. As early as the Song Dynasty (988 AD), there were records of intense combustion occurring after a sudden change in ventilation conditions during confined space fires (salt well gas outbursts), reflecting a clear increase in exothermic heat between oxygen-deficient combustion and sudden oxygen supply. However, for a long time, such phenomena remained mainly at the level of empirical description, lacking quantitative criteria that could be used for engineering practice.

[0006] In modern urban building fire response, firefighters often face situations where opening doors and windows or breaking structures allows fresh air to enter rapidly, accelerating the combustion reaction or even causing it to spiral out of control. In the high-rise building fire on Longwu Road in Xuhui District, Shanghai on May 1, 2014, the instantaneous high-pressure impact generated by backfire exceeded the protective capabilities of personnel, resulting in serious consequences. Despite numerous similar incidents, current methods for quantitatively assessing the risk of combustion and explosion of combustible gases or flue gas mixtures in industrial applications remain relatively rudimentary. At the academic research level, various theoretical models exist for determining the conditions for combustion and explosion of gaseous mixtures, but their applicable boundaries and engineering consistency are still unclear.

[0007] In summary, existing technologies for identifying and assessing smoke and explosion risks in fire scenes generally suffer from problems such as inconsistent quantitative models, ambiguous criteria boundaries, difficulty in real-time application, and difficulty in post-event reconstruction. This lack of systematic and engineering-based assessment methods not only hinders the further development of basic research related to fire dynamics but also directly limits the practical application of real-time fire risk monitoring and early warning technologies. Summary of the Invention

[0008] This invention aims to overcome the above-mentioned defects by deriving the flammability diagram of flue gas through a self-developed heat balance method and flame resistance theorem. While integrating fuel gas, oxygen and inert gas, it separately displays the dangers of fuel and oxygen, and provides a visual flammability diagram of the smoke hazards of indoor fires. It introduces a complete evaluation system and a unified prediction system and method in the field of smoke hazard analysis (ignition and explosion).

[0009] The flammability diagrams covered by this invention can address three scenarios: pure fuel (methane), experimentally simulated diluted flue gas, and real-collected re-ignition flue gas, each solving problems with different properties.

[0010] The present invention provides a method for creating a flammability map, characterized by comprising the following steps:

[0011] S1. Key parameters for collecting smoke from the fire scene: oxygen volume concentration carbon dioxide volume concentration Unburned hydrocarbon fuel volume concentration carbon monoxide volume concentration and hydrogen volume concentration (Optional, hydrogen measurement only for underground coal fires).

[0012] S2. Generate de-aired derived data based on the raw data from S1: excess nitrogen concentration and total amount of nuclear flue gas (including three fuel gas components and two inert gases).

[0013] The excess nitrogen concentration is:

[0014] The total amount of nuclear flue gas is:

[0015] S3. Based on the original data and / or derived data, draw the combustible zone and add state points dominated by the ambient oxygen concentration, which represent the combustion and explosion potential of the flue gas mixture, to form a combustibility map of the gas (i.e., a combustion map).

[0016] S4. Separate the contributions of the core flue gas and the background air, calculate their ignitable combustion flow (IFF) and explosive combustion flow (EFF) respectively, comprehensively evaluate the combustion and explosion potential of the flue gas, and construct a combustion flow diagram (i.e., flow diagram).

[0017] Furthermore, the method for creating flow graphs provided by the present invention is further characterized in that:

[0018] The calculation method for ignitable flame flow (IFF) is as follows:

[0019] ;

[0020] Among them, the thermal fingerprints of inert gases are the endothermic potentials of CO2 and N2, respectively, which are constants.

[0021] The calculation method for the explosive flow EFF is as follows:

[0022] .

[0023] Furthermore, the present invention also provides the application of the combustion flow index obtained by the above method in demonstrating ignition and explosion potential.

[0024] That is, the above-mentioned flammability diagram is used to create a flammability diagram that demonstrates ignition potential;

[0025] The process of creating a flammability diagram demonstrating ignition potential includes the following steps:

[0026] S3A1. The concentrations of various components in the flue gas obtained from the flue gas sampling are as follows:

[0027] , .

[0028] A pseudo-fuel is created by combining three fuels (CH4, CO, and H2) and two inert gases (N2 and CO2) in a flue gas mixture.

[0029]

[0030] Will

[0031] The normalized volume concentration composition is defined as X1, X2, X3, X4, and X5, and the thermal fingerprint of the pseudo-fuel is calculated. , , ;

[0032] = ;

[0033] = ;

[0034] = ;

[0035] The thermal fingerprints of various fuels are as follows:

[0036] Methane: =2; =13.807; =16.404;

[0037] Carbon monoxide: =0.5; =0.796; =15.593;

[0038] hydrogen: =2; =3.509; =55.017.

[0039] S3A2. Set the initial variable for inert gas as follows:

[0040] And environmental oxygen level parameters: =0.2095, plotted based on the following governing equations:

[0041] For low fuel consumption limits The governing equations are: ;

[0042] The governing equations are: ;

[0043] It is known that the two intersect at Point (i.e., nose point): .

[0044] in , is the main independent variable.

[0045] S3A3. Mark the state point in the diagram, with coordinates R=0. .

[0046] Furthermore, the present invention also provides the application of flammability diagrams produced using the above-described method in illustrating the air dilution process, characterized in that:

[0047] A flammability diagram was created to illustrate the air dilution process.

[0048] Its production process includes the following steps:

[0049] The energy density of the fuel in the mixture is obtained by using the nose point on the flammability diagram of the air dilution process, and this is used to determine the degree of danger at the scene.

[0050] Furthermore, the application of the above-mentioned flammability diagram may also include at least one of the following uses:

[0051] A. Evaluate critical phenomena in the fire scene (such as flashover, fireback, and smoke explosion);

[0052] B. Evaluate the potential for other ignition scenarios using flue gas or pyrolysis products;

[0053] C. The possibility that the combustible material in the fire forecast may ignite if it exceeds the low flammability limit;

[0054] D. Estimating the ignition potential of lean flue gas;

[0055] E. The potential for smoldering to turn into an open flame at the smoldering point;

[0056] F. Assess / predict the combustion and explosion potential of gas mixtures;

[0057] G. Determine / predict the combustion products and state of the fire source;

[0058] H. To manufacture products / tools for any of the purposes described in the AG above.

[0059] Furthermore, this invention also provides the application of the above-mentioned flammability diagram in evaluating critical phenomena in fire scenes, characterized by the following evaluation method:

[0060] If IFF < 1, the current state is determined to be: insufficient fuel, unable to ignite (non-explosive).

[0061] If IFF > 1 and EFF < 1, then the current state is determined to be: fuel and air support ignition, and it can be ignited (explosive).

[0062] If EFF>1, the current state is determined as: insufficient oxygen, cannot explode; but can explode upon contact with oxygen (potentially-explosive). Attached Figure Description

[0063] Figure 1 A diagram of the core flammability of methane diluted with air; it is a derivation of the physical properties of pure methane by the process of dilution with air, and the results help to understand the changes in the core flue gas flammability caused by air dilution.

[0064] Figure 2 The core flammability diagram shows the change in the ignition potential of flue gas as it is diluted with air. It is a diagram of the flammability of flue gas generated at different stoichiometric ratios for the combustion reaction of butane. Combining the above diagram with the ignition potential of flue gas after being diluted with air can be understood.

[0065] Figure 3 A combustibility diagram (flame diagram) of actual backfire; it displays the combustibility of real flue gas during backfire, highlighting the impact of background oxygen supply on the explosion potential of the flue gas. The proportion of core flue gas (or flue gas dummy fuel) must exceed the combustible range (i.e., the mixture is fuel-rich and oxygen-deficient); only the difference can combine with oxygen to ignite or produce a fireball. This diagram effectively demonstrates the effectiveness of core combustibility diagrams in illustrating and predicting backfire phenomena, thus possessing significant value in predicting backfire occurrences.

[0066] Figure 4 The combustibility diagram of core flue gas as a pseudo-fuel is... Figure 3 The superposition of the combustible zones (therefore no additional formula). This figure shows the energy density information of the combustion reaction source flue gas without air dilution, and is therefore source information unaffected by the sampling point location, which is of great significance for diagnosing the hazard of the source.

[0067] Figure 3 Expressing the local danger, Figure 4 This demonstrates the danger at the source. Therefore, in Figure 3 In this method, the nose point represents the source, and the state point represents the local area; the nose point represents the fuel gas, and the state point represents the oxygen. This method successfully separates the effects of oxygen and fuel gas, as well as the contributions of the local area and the source, and has a unique effect on demonstrating the hazards of flue gas.

[0068] Figure 5 The actual combustion flow index (flow diagram) of backfire; its function is to condense the flue gas around the fuel and oxygen into a macroscopic index called combustion flow or energy density. If the ignitability flow (IFF) is greater than 1, it means ignitable; if the explosiveness flow (EFF) is less than 1, it means explosive. Observing these two macroscopic indices, we can quickly diagnose the current combustion and explosion potential of the flue gas, thus aiding in understanding... Figure 3 It is of great help in the flue gas diagnostic process.

[0069] The combustibility diagrams shown above are essentially designed to separate the contributions of fuel and oxygen in flue gas. The hazard of fuel is determined by the nose point of the combustible zone (or whether the ignitable flow (IFF) is greater than 1), while the hazard of oxygen is determined by the position of the state point (i.e., whether the state point is within the combustible zone, or whether the explosive flow (EFF) is less than 1). The combination of these two factors together demonstrates the hazard of the mixture and effectively predicts the potential for critical fire phenomena (such as flashback). Detailed Implementation

[0070] This invention is capable of various modifications and embodiments, and therefore specific embodiments are illustrated and described in the accompanying drawings. However, this is not intended to limit the invention to specific implementations, but should be understood to include all modifications, equivalents, and even substitutions that fall within the spirit and scope of this invention.

[0071] This embodiment provides a method for creating a flammability map, which includes the following steps:

[0072] S1. Important parameters of flue gas collected from the fire site: oxygen volume concentration, carbon dioxide volume concentration, unburned hydrocarbon fuel volume concentration, carbon monoxide volume concentration and hydrogen volume concentration (optional, specific to underground coal fires).

[0073] S2. Generate normalized derived data after air removal based on the raw data in S1: total amount of nuclear flue gas, volume concentration of carbon dioxide, volume concentration of unburned hydrocarbon fuel, and concentration of excess nitrogen; and plot the combustible zone based on the raw data and / or derived data.

[0074] S3. Add state points representing the combustion and explosion potential of flue gas to form a complete gas combustibility diagram (combustion diagram).

[0075] S4. Separate the contributions of the core flue gas and the background air, calculate their ignitable combustion flow (IFF) and explosive combustion flow (EFF) separately, and comprehensively evaluate the combustion and explosion potential of the flue gas.

[0076] The calculation method for ignitable flame flow (IFF) is as follows:

[0077] ;

[0078] The calculation method for the explosive flow EFF is as follows:

[0079] .

[0080] Example 1. Combustibility diagrams at different methane concentrations

[0081] Using methane as pure fuel and diluting it with air, flammability diagrams were obtained at different methane concentrations, i.e. Figure 1This is a virtual experiment based on the manipulation and derivation of methane's physical properties. The specific method is as follows:

[0082] S1A1. Let methane burn in air (hypothetical scenario, construct flammability diagram based on methane properties), introduce inert gas (nitrogen) into methane for dilution, and define each set of data as variables X1 (oxygen volume concentration), X2 (methane volume concentration), and X3 (methane concentration after dilution with air).

[0083] S1A2. Set the initial variables as follows: C0=2; QF=13.79; H0=16.39; QD=1.75;

[0084] S1A3. Set the parameters for the diluted mixture as follows:

[0085] ; ;

[0086] S1B4. Graphing is based on the following governing equations:

[0087] For low fuel consumption limits The governing equations are: ;

[0088] The governing equations are: ;

[0089] It is known that the two intersect at point: .

[0090] Based on different X3 values, we obtain different flammability curves, such as... Figure 1 As shown in the figure. This figure illustrates the effect of air dilution on fuel ignition capability. When the nose point position shifts to the left of the coordinate axis R=0 (i.e., The "nose point" (or "nose point") indicates that the fuel is too lean to support ignition, thus representing the critical point for a safe state after the combustible gas has been diluted, and also the critical point for the combustible portion of the flue gas to reach intrinsic safety. This figure illustrates that the nose point represents the energy density of the fuel in the mixture, and is therefore a visual representation of the fuel characteristics of the mixture.

[0091] Example 2. Graph showing the change in flue gas ignitability with air dilution on the core combustibility map.

[0092] Table 1 below lists the sampling results of flue gas generated after the proportional feeding of butane and air into the Purser combustion furnace. The first column is the stoichiometric ratio, the result of the mixture. Columns 2-4 are the sampling results, and column 5 is the nitrogen remaining after deducting the nitrogen (which makes up the air) corresponding to the oxygen in columns 2-4. Therefore, columns 3 / 4 / 5 constitute the core fuel gas, and their algebraic sum is shown in column 6. The results in column 6 are used for normalization. It must be less than 1. Normalization turns it into 1, while the relative proportions of each component remain unchanged. ) Columns 3 / 4 / 5 give us the normalized columns 7 / 8 / 9, which represent the composition of the core flue gas.

[0093] Table 1. Simulated flue gas dataset generated by the combustion furnace

[0094]

[0095] *All units above refer to volume concentration;

[0096] **THC stands for total hydrocarbons. Since it is similar to methane, it must be measured with a methane probe. Therefore, in this embodiment, it is equivalent to methane.

[0097] The core flammability map is obtained from the raw data in the table above (columns 2 / 3 / 4). Figure 2 The specific process is as follows:

[0098] Butane and air in a specified ratio are fed into a Purser combustion furnace. The resulting flue gas is sampled and analyzed to obtain four raw concentration data points: oxygen volume fraction, carbon dioxide volume fraction, total hydrocarbon volume fraction, and nitrogen volume fraction. Typically, flue gas sampling cannot be conducted at the source; the outdoor sampling process dictates that the sample obtained in this embodiment must be a diluted sample far from the source. To avoid uncertainties arising from the sampling point, this embodiment performs air removal treatment, and then treats the remaining components (including three fuels and two inert gases) as a pseudo-fuel, integrating them into the three fuel characteristic parameters required for the combustibility diagram. This represents the characteristics of the core flue gas. To construct a combustibility diagram, two more parameters are needed: one is the ambient oxygen concentration (the reverse of the degassing process, meaning an oxygen concentration of 0.2095 or 0.21), and the other is the characteristics of the inert gas, typically nitrogen.

[0099] It can also be carbon dioxide ( ). With these five parameters, we can construct a variable combustibility diagram based on the flue gas core.

[0100] In this embodiment, the parameters represent the following: The amount of oxygen (in moles) required for the complete combustion of one mole of fuel. The heat release potential of oxygen per unit of fuel; The heat absorption potential of a unit of gas; : The heat absorption potential of a unit of inert gas.

[0101] The basic steps for constructing a heat map are as follows:

[0102] S2A1, Constructs a thermal fingerprint calculation table for fuel gas based on various gas compositions;

[0103] Formula 1

[0104] Formula 2

[0105] S2A2 is used to remove air from the flue gas components to obtain an excess nitrogen concentration (the nitrogen concentration remaining after air removal).

[0106]

[0107] S2A3, the composition of the resulting pseudo-fuel or core combustion gas is as follows:

[0108]

[0109] The core fuel gas contains three fuels (carbon monoxide, methane, and hydrogen) and two inert gases (carbon dioxide and nitrogen), which can be treated as a pseudo-fuel, meaning their thermal fingerprints can be accumulated.

[0110] S2A4, based on the thermal fingerprint calculation table, the thermal fingerprint of the pseudo-fuel is obtained by normalizing and weighting the pseudo-fuel.

[0111]

[0112] S2A5 combines the thermal fingerprint of pseudo-fuels with environmental variables.

[0113] and Substituting these values ​​into the governing equations below, we can obtain the combustible range of the pseudo-fuel. The combustible range can be obtained from the governing equations below.

[0114] Formula 4

[0115] Formula 5

[0116] S2A6, the effective flammability zone is typically distributed in (-1, ...). )between. The coordinates of the nose point are obtained by solving the two governing equations above.

[0117] Formula 6

[0118] A core flammability diagram of a variable oxygen environment was drawn based on the raw data, representing the current combustion and explosion state of the gas mixture (see...). Figure 2 ).

[0119] This core flammability diagram uses stoichiometry as the primary variable. By changing the stoichiometry, the flammability range can be significantly narrowed. On the other hand, the air portion of the flue gas effectively dilutes the fuel, causing the nose point to gradually shift to the left due to this dilution. Therefore, observing the position of the nose point on the core flammability diagram can conveniently demonstrate the ignition potential of the flue gas, thus enabling the prediction of its combustion and explosion potential.

[0120] Example 3. Combustibility diagram of gas that actually experienced flashback.

[0121] This embodiment uses a flashback experiment conducted at the State Key Laboratory of Fire Science, University of Science and Technology of China (Weng, WG, Fan, WC "Critical condition of backdraft in compartment fires: a reduced-scale experimental study." Journal of Loss Prevention in the Process Industries 16.1(2003):19-26.) as a reference. This experiment aims to accurately determine the critical conditions for flashback in compartment fires through a series of scaled-down tests, thus verifying the diagnostic effectiveness of flammability parameters. The experiment used a scaled-down compartment with dimensions of 1.2 m long, 0.6 m wide, and 0.6 m high, approximately one-quarter the volume of a typical residential room. To ensure experimental safety and accurately simulate the overpressure conditions during flashback, both the inner and outer surfaces of the compartment were covered with 2 mm thick welded stainless steel, with a 200 mm thick fire-resistant insulation material filling the space between. This robust structural design effectively withstood the overpressure generated by flashback while minimizing heat loss.

[0122] In the center of the short end wall of the compartment, there is an opening 0.2m wide and 0.6m high. This opening is equipped with a computer-controlled hatch that can open rapidly at a predetermined time to simulate a sudden influx of fresh air. The experiment uses 99.8% pure methane as fuel. The methane is released through a square burner installed in the compartment, and its flow rate is precisely measured and controlled by a high-precision rotor flow meter. In addition, a 1200W electric heating wire is installed in the compartment as a continuous ignition source, positioned above the burner to ensure timely ignition when the gas in the compartment reaches the critical mixing conditions for backfire.

[0123] The experimental data in Table 2 are primarily used to determine the critical conditions for flashback and to quantify its intensity. This table records the results of eight scaled-down compartment fire experiments conducted under strictly controlled conditions to systematically examine the impact of different preset conditions on flashback. Since this method is based on volume concentration, while the other method's data is based on mass concentration, a concentration conversion is necessary. As shown in the table, the five components on the left are mass concentrations (represented by y), and the five components on the right are volume concentrations converted from the left (represented by x).

[0124] Table 2. Results of eight flashback experiments converting mass concentration to volume concentration.

[0125]

[0126] The treatment of real flue gas also needs to consider the portion of air that has been removed. Since this removal is proportional to the amount of air, it's reasonable to assume that the background gas is air, and the diluent for the pseudo-fuel is virtual (because all inert gases become part of the pseudo-fuel), which can be assumed to be nitrogen. In addition to the combustible range mentioned above, the combustibility diagram of real flue gas requires obtaining the state point based on the total amount of pseudo-fuel. The specific method is as follows:

[0127] S3A1-S3A6 are the same as S2A1-S2A6.

[0128] For S3A7, the state point requires two parameters. The first parameter is R=0 (because the core flue gas is not diluted by any inert gas, so R=0), and the second parameter is the total content of the core flue gas (or pseudo-fuel, represented by the subscript core) (i.e. (Contains all three fuels plus carbon dioxide and excess nitrogen), or This means that after 100% of the flue gas has had its air removed, the remaining portion is core flue gas. In other words, this state point must lie on the line where R=0, containing all components of core oxygen (three fuel gases and two inert gases); this is the state point on the combustion chart. The intersection of R=0 and UFL is the critical point where the flue gas sample cannot ignite due to lack of oxygen. The difference between the two represents the margin for backfire. A larger margin means a greater likelihood of a fireball forming during a flashback, which is more dangerous (see...). Figure 3 ).

[0129] from Figure 3 As can be seen, all eight symptomatic experiments resulted in a state of fuel abundance and oxygen deficiency, therefore the state point was always above the flammable zone. Furthermore, the fuel abundance margin in the graph...

[0130] This comes from two factors. First, the state point represents the energy density of oxygen in the mixture, and the core flue gas volume (…). A high percentage of oxygen (i.e., a high state point) means insufficient oxygen concentration, because On the other hand, the nose point position represents the fuel's heat release capacity. If the degree of dilution by air is low (i.e., the fuel content is high), then the further to the right the nose point is, the higher the fuel's flammability limit. The value decreases. Combining these two characteristics, the larger the dx, the greater the potential for backfire. Figure 3 The results were in line with our expectations (the mixture in all eight states was ignitable upon contact with air, and the last two formed significant fireballs, indicating that a flashback occurred).

[0131] Figure 4 yes Figure 3 A comparison of the flammable zone portions. From Figure 4 It can be seen from this that there is a rich fuel margin. The changes are primarily caused by variations in the nose point location or the energy density of the fuel, rather than by air dilution. This aligns with our expectation that the increased hazard is mainly due to incomplete combustion at the source, rather than insufficient local ventilation, although insufficient ventilation at the source can lead to incomplete combustion. This allows us to assess the hazard at the fire source even when detecting smoke far from it.

[0132] The four figures above demonstrate the results of interpreting the combustion and explosion potential of smoke using the core combustibility diagram. They reveal the current state and dilution process of the smoke as it is diluted by air, providing intuitive assistance in diagnosing the critical combustion state and process in a fire. This result is derived from the principle of energy conservation and has been verified in multiple experiments (i.e., Figure 2-4 Therefore, it is a fairly reliable forecast and is an important part and core algorithm of the fire smoke disaster analyzer.

[0133] Example 4. Burn Flow Diagram

[0134] The flue gas data from Example 3 above can also be distilled into two macroscopic indicators to visually represent the combustion and explosion risks of the flue gas. If we represent the ignition potential and explosion potential of the flue gas using two macroscopic indicators, it is also called a combustion flow diagram (or flow diagram). Its production process is as follows.

[0135] In S4A1, each component of the core flue gas can individually generate an ignitability flammable flux (IFF) for the flue gas ignition process, as shown in the following formula:

[0136]

[0137] It is divided into two parts: the first part is combustible material (gas), and the second part is non-combustible material (inert gas). For conventional flue gas (which contains three types of combustible material and two types of inert gas generated in a fire), we can further refine it as follows.

[0138]

[0139] In S4A2, each component of the core flue gas can individually generate an explosive flammable flux (EFF) during the flue gas explosion process, the general expression of which is:

[0140]

[0141] The core flue gas composition can be divided into two parts: the former is combustible material, and the latter is non-combustible material (inert gas). For conventional flue gas (which contains three types of combustible materials and two types of inert gas fire products), we can further refine it as follows.

[0142]

[0143] After the above two steps, we can obtain Figure 3 The experimental results are displayed in a flow graph, as follows: Figure 5 As shown.

[0144] There are three possibilities for any smoke:

[0145] If IFF < 1, then there is insufficient fuel and the fuel cannot be used to ignite (non-explosive).

[0146] If IFF > 1 and EFF < 1, then the fuel and oxygen support ignition and the fuel can be explosive.

[0147] If EFF>1, there is insufficient oxygen and it cannot explode; however, it can explode upon contact with oxygen, and is therefore called a potentially-explosive.

[0148] In other experimental cases, this method also applies to hydrogen (which is generally found in the flue gas of underground coal fires). Hydrogen acts in the same way as methane or carbon monoxide, altering the flammability profile by changing the nose point of the dummy fuel.

[0149] The function and effect of this embodiment:

[0150] 1) This solution is developed for fire scene smoke analysis technology to demonstrate the combustion and explosion potential of smoke after it has been diluted with air;

[0151] 2) The core flammability map separates the contributions of fuel and oxygen, showing both the fuel hazard at the source and the local oxygen risk;

[0152] 3) The combustible zone prominently displays the ignition risk of the core flue gas, which is of particular use in preventing backfire;

[0153] 4) The state point still represents the contribution of oxygen, highlighting the explosion risk brought about by oxygen (or lack of oxygen), and has indicative value for preventing local explosion potential.

[0154] 5) The results of the flammability diagram can be concisely expressed using two macroscopic indicators: IFF > 1, meaning the mixture is ignitable; EFF < 1, meaning the mixture is explosive. This is the flammability diagram mentioned above (i.e., Figure 3 Another way to express ( ) is to help interpret the results on the fire chart.

[0155] While the foregoing has focused on embodiments, these are merely illustrative and do not limit the invention. Those skilled in the art will understand that various modifications and applications not illustrated above can be made without departing from the essential characteristics of these embodiments. For example, the constituent elements specifically shown in the embodiments can be implemented through modifications. Furthermore, various differences related to such modifications and applications should be interpreted as being included within the scope of the invention as defined in the appended claims.

Claims

1. A method for preparing a flammability map, wherein the flammability map is designed to address flashback phenomena, characterized in that, It includes the following steps: S1. Important parameters for collecting smoke from the fire scene: oxygen volume concentration carbon dioxide volume concentration Unburned hydrocarbon fuel volume concentration carbon monoxide volume concentration and hydrogen volume concentration ; S2. Generate derived data after air removal based on the raw data from S1: excess nitrogen concentration and total amount of nuclear flue gas; S3. Based on the original data and / or derived data, draw the combustible zone and add state points dominated by the ambient oxygen concentration to represent the combustion and explosion potential of the flue gas, which together constitute the combustibility map of the gas. S4. Separate the contributions of the core flue gas and the background air, calculate their ignitable combustion flow (IFF) and explosive combustion flow (EFF) respectively, comprehensively evaluate the combustion and explosion potential of the flue gas, and construct a combustion flow diagram.

2. The method for generating a flammability diagram as described in claim 1, characterized in that: In the process of constructing the combustion flow diagram, The calculation method for the ignitable flame flow (IFF) is as follows: ； The calculation method for the explosive flow EFF is as follows: 。 3. The application of the combustion flow index obtained by the method as described in claim 1 in demonstrating ignition potential.

4. The application as described in claim 3, characterized in that: The flammability diagram is used to create a flammability diagram that demonstrates ignition potential; The process of creating the flammability map demonstrating ignition potential includes the following steps: S3A1. The concentrations of each component of the flue gas obtained from the flue gas sampling are as follows: , ,Will The core flue gas is defined by its normalized volumetric concentration composition as X1, X2, X3, X4, and X5, and the thermal fingerprint of the pseudo-fuel is calculated. , , ;in, = ; = ; = The thermal fingerprints of various fuels are as follows: Methane: =2; =13.807; =16.404 carbon monoxide: =0.5; =0.796; =15.593 hydrogen: =2; =3.509; =55.017; S3A2. Set the initial variable for inert gas to And environmental oxygen level parameters: =0.2095, plotted based on the following governing equations: For low fuel consumption limits The governing equations are: ; The governing equations are: ; It is known that the two intersect at point: ;in , is the main independent variable; S3A3. Mark the state point in the diagram, with coordinates R=0. .

5. The application of a flammability map produced by the method described in claim 1 in illustrating the air dilution process, characterized in that: A flammability diagram illustrating the air dilution process is created using the aforementioned flammability diagram; Its production process includes the following steps: The energy density of the fuel in the mixture is obtained by using the nose point on the flammability diagram of the air dilution process, and this is used to determine the degree of danger at the scene.

6. The application of the flammability diagram as described in any one of claims 1-5, characterized in that, Includes at least one of the following uses: A. Evaluate the potential for fire criticality phenomena, flashover, backfire, and smoke explosion by examining flue gas or pyrolysis products; B. Evaluate the ignition potential in other situations using flue gas or pyrolysis products; C. The possibility that the combustible material in the fire forecast may ignite if it exceeds the low flammability limit; D. Estimating the ignition potential of lean flue gas; E. The potential for smoldering to turn into an open flame at the smoldering point; F. Assess / predict the combustion and explosion potential of gas mixtures; G. Determine / predict the combustion products and state of the fire source; H. To manufacture products / tools for any of the purposes described in the AG above.

7. The application of the flow map as described in any one of claims 1-6 in evaluating critical phenomena in a fire scene, characterized in that, The evaluation method is as follows: If IFF < 1, the current state is determined to be: insufficient fuel, unable to ignite (non-explosive). If IFF>1 and EFF<1, then the current state is determined to be: the fuel and air are just right to support ignition, and it can be ignited (explosive). If EFF>1, the current state is determined as: insufficient oxygen, cannot explode; but can explode upon contact with oxygen (potentially-explosive).

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