Fire plume characteristic parameter calculation method, evolution experiment device and use method
Through experimental devices and models, the problem of calculating the characteristic parameters of fire plumes under vertical shaft structures in fires has been solved in existing technologies, thereby improving the accuracy and efficiency of fire rescue.
Patent Information
- Application Number
- CN202411772353.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-04
- Publication Date
- 2025-11-07
- Estimated Expiration
- 2044-12-04
AI Technical Summary
In high-rise building fires, vertical shafts become the main pathway for the spread of flames and smoke. Existing technologies struggle to effectively calculate the characteristic parameters of fire plumes, impacting fire rescue efficiency.
By establishing the relationship between flame characteristic parameters and influencing factors, fire plume evolution experiments were conducted. Simulation experiments were performed using a fire plume evolution experimental device. Scatter plots were drawn and nonlinear fitting was performed to establish a fire plume characterization model and calculate the fire plume characteristic parameters.
It improves the efficiency of fire rescue, accurately calculates flame height and temperature rise inside shafts, and provides guidance for fire rescue.
Smart Images
Figure CN119849119B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of fire safety, in particular to a fire plume characteristic parameter calculation method, an evolution experiment device and a use method. BACKGROUND
[0002] In high-rise building fires, there are many accidents of personnel casualties caused by fires in building internal cable shafts, pipe shafts, elevator shafts and other parts. The "vertical shaft" type vertical structure often appears in high-rise buildings, which is usually used for exhaust, smoke exhaust, water pipe and cable erection or lighting, including cable shafts, pipe shafts, ventilation shafts and other vertical structures. The building vertical shaft is the main channel for fire development and spread in high-rise buildings, and its danger mainly manifests in two aspects: first, the building vertical shaft itself has fire hazard with flammable materials and flammable components, such as the use of ordinary wooden doors and other flammable materials for the inspection door of the vertical shaft, which reduces the fire resistance rating of the building vertical shaft and increases the fire hazard of the building vertical shaft; second, the building vertical shaft is the main channel for smoke diffusion, which often causes serious harm to personnel. Experiments have shown that in a 30-story building about 100 meters high, the smoke can reach from the first floor to the top floor in 30 seconds without obstruction. That is, the vertical shaft of the whole building is a "smoke stack" that can blow wind, and once the bottom floor catches fire, it will be accompanied by a large amount of smoke, and the smoke in the smoke stack will form a strong convection with the air at the top of the building, thereby intensifying the fire, which is called "chimney effect".
[0003] Due to the "chimney effect", the stairwell, elevator room and various pipe vertical shafts of high-rise buildings often become the main way for fire spread and expansion when a fire occurs. When the bottom floor and lower floors of a high-rise building catch fire, the smoke can spread up to dozens of floors in tens of seconds through various vertical shafts, making it more difficult to extinguish the fire and endangering the lives of people escaping to the roof. Therefore, under the current circumstances, it is urgent to develop more effective technology to characterize the fire plume evolution process under the vertical shaft structure, so as to calculate the fire plume characteristic parameters (such as the average flame height of the fire plume, the temperature rise in the vertical direction inside the vertical shaft, etc.) for fire rescue and improve the efficiency of disaster relief. SUMMARY
[0004] The main purpose of the present application is to provide a fire plume characteristic parameter calculation method, an evolution experiment device and a use method, which aims to solve the above problems.
[0005] To achieve the above purpose, the present application provides a fire plume characteristic parameter calculation method, which is suitable for vertical shaft structure, comprising the following steps:
[0006] Step S100, determining factors influencing flame characteristics under a shaft structure, and establishing a relationship between flame characteristic parameters and the factors, wherein the flame characteristic parameters include average flame height of a fire plume and temperature rise in the shaft in the vertical direction;
[0007] Step S200, performing simulation experiments through a fire plume evolution experimental device to obtain simulation results under different working conditions, drawing the simulation results into a scatter plot to determine the influence of the factors on the flame characteristic parameters;
[0008] Step S300, determining basic physical quantities of the factors, and converting the relationship between the flame characteristic parameters and the factors into a dimensionless relationship;
[0009] Step S400, performing nonlinear fitting on the results of the scatter plot, and establishing a fire plume representation model based on the dimensionless relationship to calculate the fire plume characteristic parameters.
[0010] Further, the factors include shaft height H, shaft top opening size l, fire source characteristic length D, vertical height Z of a flame to a certain position in the shaft, fire source heat release rate Q, environmental density ρ ∞ , constant-pressure specific heat C p , environmental temperature T ∞ , and gravitational acceleration g.
[0011] Further, the relationship between the flame characteristic parameters and the factors is as follows:
[0012]
[0013] In the formula, L f is the average flame height of a fire plume under a shaft structure;
[0014] ΔT z is the temperature rise at a certain height position in the shaft;
[0015] T z is the temperature at a certain height position in the shaft.
[0016] Further, the basic physical quantities are the fire source characteristic length D, the environmental density ρ ∞ , the constant-pressure specific heat C p , the environmental temperature T ∞ , and the gravitational acceleration g.
[0017] The dimensionless relationship is as follows:
[0018]
[0019] In the formula,
[0020] Furthermore, the fire plume characterization model is as follows:
[0021]
[0022] This invention also provides an experimental apparatus for fire plume evolution, applicable to methods for calculating fire plume characteristic parameters. The experimental apparatus for fire plume evolution includes:
[0023] Multiple shaft models are provided, each shaft model is arranged in the shape of a cuboid and extends in the vertical direction. Each shaft model is formed by a fireproof glass and three fireproof boards enclosing it in sequence along its circumference. The multiple shaft models have different sizes, and one of them is set as a shaft experimental model.
[0024] The fire source simulation component includes a burner, which is located inside the vertical shaft experimental model;
[0025] A temperature measurement component is installed inside the vertical shaft experimental model and includes multiple temperature detection elements. The multiple temperature detection elements are distributed at intervals along the vertical direction, and each temperature detection element is used to detect the temperature at a certain height position inside the vertical shaft experimental model.
[0026] A camera, positioned outside the vertical shaft experimental model and corresponding to the fireproof glass of the vertical shaft experimental model, is used to capture flame images; and,
[0027] A control processing terminal, electrically connected to the temperature measurement component and the imaging device, is used to receive and process information transmitted by the temperature measurement component and the imaging device to characterize the evolution process of the fire plume under the shaft structure.
[0028] Furthermore, the fire source simulation component also includes a gas cylinder and a gas flow meter. The gas cylinder and the gas flow meter are located outside the vertical shaft experimental model. The gas cylinder is connected to the burner through a gas supply pipe, and the gas flow meter is located on the gas supply pipe.
[0029] Furthermore, the burner is a porous gas burner;
[0030] The temperature sensing element is a thermocouple;
[0031] The camera being filmed is a CCD camera.
[0032] Furthermore, the fireproof glass is high-temperature resistant fireproof glass;
[0033] The fireproof board is a strong silicate fireproof board.
[0034] The present invention also provides a method for using a fire plume evolution experimental apparatus, applicable to fire plume evolution experimental apparatus, the method of using the fire plume evolution experimental apparatus includes the following steps:
[0035] Step S1, selecting one of multiple different size shaft models as a shaft experimental model for experiment;
[0036] Step S2, placing a burner and a temperature measuring assembly in the shaft experimental model, and setting a camera assembly corresponding to the shaft experimental model outside the shaft experimental model, wherein the temperature measuring assembly comprises multiple temperature detecting pieces, and the multiple temperature detecting pieces are distributed in an up-down direction;
[0037] Step S3, starting the burner for simulation experiment, and adjusting the output power of the burner multiple times, obtaining multiple sets of temperature data through the temperature measuring assembly, and obtaining multiple sets of flame images through the camera assembly, and transmitting to the control processing terminal for processing;
[0038] Step S4, repeatedly performing the steps S2-S3 for experiment by replacing the shaft experimental model with different size shaft models multiple times, and obtaining simulation results under different working conditions.
[0039] In the technical scheme of the present application, the fire plume characteristic model is obtained by nonlinear fitting of simulation data obtained through a fire plume evolution experiment device, and has high accuracy; when performing prediction calculation, the influence factors are determined according to the actual situation of the fire, and the average flame height of the fire plume under the shaft structure and the temperature rise in the vertical direction inside the shaft are calculated based on the fire plume characteristic model, which can provide guidance for fire rescue and improve the efficiency of disaster relief. BRIEF DESCRIPTION OF DRAWINGS
[0040] In order to more clearly illustrate the technical scheme in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor based on the drawings shown.
[0041] Figure 1 The flowchart of the fire plume characteristic parameter calculation method provided by the present application;
[0042] Figure 2 The structural schematic diagram of an embodiment of the fire plume evolution experiment device provided by the present application;
[0043] Figure 3 The flowchart of the use method of the fire plume evolution experiment device provided by the present application;
[0044] Figure 4 The change diagram of the fire plume under different fire source heat release rates in the shaft structure and the free space, respectively;
[0045] Figure 5 Figure 6 is a graph of the average flame height of the fire plume versus the heat release rate of the fire source for different opening sizes at the top of the shaft;
[0046] Figure 6 Figure 7 is a graph of the average flame height of the fire plume versus the opening size at the top of the shaft for a constant heat release rate of the fire source;
[0047] Figure 7 Figure 8 is a graph of the average flame height of the fire plume versus the opening size at the top of the shaft for different heat release rates of the fire source;
[0048] Figure 8 Figure 9 is a graph of the fire plume characterization model;
[0049] Figure 9 Figure 10 is a graph of the average flame height of the fire plume calculated based on the fire plume characterization model and a graph of the average flame height of the fire plume calculated based on other models;
[0050] Figure 10 Figure 11 is a graph of the vertical temperature in the shaft for different heat release rates of the fire source;
[0051] Figure 11 Figure 12 is a graph of the temperature at a certain height in the shaft versus the vertical height of the flame to the height for different opening sizes at the top of the shaft for a constant heat release rate of the fire source;
[0052] Figure 12 Figure 13 is a graph of the temperature at a certain height in the shaft versus the vertical height of the flame to the height for different opening sizes at the top of the shaft for a constant heat release rate of the fire source;
[0053] Figure 13 Figure 14 is a graph of the temperature at a certain height in the shaft versus the vertical height of the flame to the height for different opening sizes at the top of the shaft for a constant heat release rate of the fire source;
[0054] Figure 14 Figure 15 is a graph of the temperature at a certain height in the shaft versus the vertical height of the flame to the height for different opening sizes at the top of the shaft for a constant heat release rate of the fire source;
[0055] Figure 15 Figure 16 is a graph of the dimensionless temperature rise ΔT z / T ∞ versus Z / H for a constant opening size at the top of the shaft;
[0056] Figure 16 Figure 17 is a graph of the dimensionless temperature rise ΔT z / T ∞ versus Z / H for a constant opening size at the top of the shaft;
[0057] Figure 17 Dimensionless temperature rise ΔT for a certain shaft top opening size z / T ∞ Graph of relationship with Z / H;
[0058] Figure 18 Dimensionless temperature rise ΔT for a certain shaft top opening size z / T ∞ Graph of relationship with Z / H;
[0059] Figure 19 Dimensionless temperature rise ΔT for a certain shaft top opening size z / T ∞ Graph of relationship with Z / H;
[0060] Figure 20 Dimensionless temperature rise ΔT for a certain shaft top opening size z / T ∞ Graph of relationship with Z / H;
[0061] Figure 21 Dimensionless temperature rise ΔT for a certain shaft top opening size z / T ∞ Graph of relationship with Z / H;
[0062] Figure 22 Dimensionless temperature rise ΔT for a certain shaft top opening size z / T ∞ Graph of relationship with Z / H;
[0063] Figure 23 Dimensionless temperature rise ΔT for a certain shaft top opening size z / T ∞ Graph of relationship with Z / H;
[0064] Figure 24 Graph of fitting of relationship between χ / χ0 and l / D;
[0065] Figure 25 Graph of fitting of relationship between λ / λ0 and l / D;
[0066] Figure 26 Graph of comparison between experimental and calculated theoretical values of temperature rise simulation.
[0067] BRIEF DESCRIPTION OF THE DRAWINGS
[0068] Reference Name Reference Name 100 Fire plume evolution experimental set-up 22 Gas bottle 1 Shaft model 23 Gas flow meter 11 Fire resistant glass 24 Gas supply pipe 12 Fire resistant panel 3 Temperature measurement assembly 2 Fire source simulation assembly 31 Temperature detection piece 21 Burner 4 Shutter assembly
[0069] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION
[0070] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below, obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.
[0071] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, motion condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications also change accordingly.
[0072] In addition, if the embodiments of the present application involve descriptions such as "first", "second", etc., the descriptions of "first", "second", etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing throughout the text includes three parallel solutions, for example, "A and / or B" includes A solution, or B solution, or A and B solutions. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of ordinary skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the protection scope required by the present application.
[0073] Due to the effect of "chimney effect", the stairwell, elevator room and various pipe shafts of high-rise buildings often become the main way of fire spread when a fire occurs. When a fire occurs at the bottom and lower floors of a high-rise building, smoke can spread up to dozens of floors in tens of seconds through various shafts, causing fire spread, making it more difficult to extinguish, and endangering the lives of people escaping to the roof. Therefore, under the current circumstances, more effective technology is urgently needed to characterize the fire plume evolution process under the shaft structure, so as to calculate the flame characteristic parameters (such as the average flame height of the fire plume, the temperature rise in the vertical direction inside the shaft, etc.) for fire rescue and improve the efficiency of disaster relief.
[0074] In view of this, the present application provides a fire plume characteristic parameter calculation method, Figure 1 The flowchart of the fire plume characteristic parameter calculation method provided by the present application.
[0075] Please refer to Figure 1 The fire plume characteristic parameter calculation method comprises the following steps:
[0076] Step S100, determining factors influencing flame characteristics under a shaft structure, and establishing a relationship between flame characteristic parameters and the factors, wherein the flame characteristic parameters include average flame height of a fire plume and temperature rise in the shaft in the vertical direction.
[0077] Specifically, the factors include shaft height H, opening size l at the top end of the shaft, fire source characteristic length D, vertical height Z of the flame to a certain position in the shaft, heat release rate Q of the fire source, environmental density p ∞ , constant-pressure specific heat C p , environmental temperature T ∞ , and gravitational acceleration g.
[0078] The relationship between the flame characteristic parameters and the factors is:
[0079]
[0080] In formula (1), L f is the average flame height of the fire plume under the shaft structure;
[0081] Delta T z is the temperature rise at a certain height position in the shaft;
[0082] T z is the temperature at a certain height position in the shaft.
[0083] It should be noted that in formula (1), Delta T z = T z -T ∞ =fcn(Q, Z, l, D, p ∞ , C p , T ∞ , g, H) is obtained according to the McCaffrey model and the Heskestad model.
[0084] Step S200, performing simulation experiments through a fire plume evolution experimental device to obtain simulation results under different working conditions, drawing the simulation results into a scatter plot, and determining the influence of the factors on the flame characteristic parameters.
[0085] Further, please refer to Figure 2 , Figure 2 An embodiment of the fire plume evolution experimental device 100 provided by the present application is suitable for the above-mentioned calculation method of fire plume characteristic parameters.
[0086] The fire plume evolution experiment device 100 comprises a plurality of vertical shaft models 1, a fire source simulation assembly 2, a temperature measurement assembly 3, a photographing assembly 4 and a control processing terminal, each of the vertical shaft models 1 is arranged in the shape of a cuboid and extends along the up-down direction, each of the vertical shaft models 1 is enclosed along the circumferential direction by a fireproof glass 11 and three fireproof plates 12 in sequence, the plurality of vertical shaft models 1 are different in size, and one of them is arranged as a vertical shaft experiment model; the fire source simulation assembly 2 comprises a burner 21, and the burner 21 is arranged in the vertical shaft experiment model; the temperature measurement assembly 3 is arranged in the vertical shaft experiment model and comprises a plurality of temperature detection pieces 31, the plurality of temperature detection pieces 31 are distributed along the up-down direction at intervals, and each of the temperature detection pieces is used for detecting the temperature at a certain height position in the vertical shaft experiment model; the photographing assembly 4 is arranged outside the vertical shaft experiment model and corresponds to the fireproof glass 11 of the vertical shaft experiment model, and is used for shooting a flame image; and the control processing terminal is electrically connected with the temperature measurement assembly 3 and the photographing assembly 4, is used for receiving and processing the information transmitted by the temperature measurement assembly 3 and the photographing assembly 4, so as to characterize the fire plume evolution process under the vertical shaft structure.
[0087] In this way, the vertical shaft model 1 is used for experiment, in the experiment process, the temperature detection pieces 31 are used for measuring the real-time temperature at a plurality of height positions in the well, then the photographing assembly 4 is used for shooting a flame image, the temperature information and the image information are processed by the control processing terminal to obtain the behavior characteristics of the fire plume, then a plurality of vertical shaft models 1 of different sizes are selected as the vertical shaft experiment model for experiment, and the output power of the burner 21 is adjusted, that is, the opening size at the top of the vertical shaft, the power of the fire source and other parameters are adjusted, a plurality of groups of temperature information and image information are obtained, that is, the simulation results under different working conditions are obtained, so as to characterize the fire plume evolution process under the vertical shaft structure, and the influence of the influence factors on the flame characteristic parameters is determined through the scatter diagram drawn according to the simulation results.
[0088] It should be noted that, in an embodiment of the present application, the OTSU method is used to process the flame image shot by the photographing assembly 4.
[0089] It should be further noted that, in the present application, the characteristic length D of the fire source is determined according to the selection of the burner 21. Specifically, in an embodiment of the present application, the burner 21 is a 0.3m*0.3m porous gas burner, therefore, the characteristic length D of the fire source is 0.3m.
[0090] Further, please refer to Figure 2The fire source simulation assembly 2 further comprises a gas cylinder 22 and a gas flow meter 23, the gas cylinder 22 and the gas flow meter 23 are arranged outside the vertical shaft experiment model, the gas cylinder 22 is connected with the burner 21 through a gas supply pipe 24, and the gas flow meter 23 is arranged on the gas supply pipe 24. In this way, the fuel supply rate can be monitored and controlled through the gas flow meter 23, that is, the fire source power can be adjusted, different fire source heat release rates are provided, and then the relationship between the flame height and the fire source heat release rate is obtained.
[0091] Specifically, in an embodiment of the present application, the temperature measurement assembly 3 is arranged on the center line of the vertical shaft experiment model.
[0092] Specifically, in an embodiment of the present application, the distance between the temperature detection piece 31 at the bottom end of the plurality of temperature detection pieces 31 and the bottom end of the vertical shaft experiment model is 30 cm.
[0093] Specifically, in an embodiment of the present application, the distance between any two adjacent temperature detection pieces 31 of the plurality of temperature detection pieces 31 is 10 cm.
[0094] Specifically, in an embodiment of the present application, the sampling time interval of any two adjacent temperature detection pieces 31 of the plurality of temperature detection pieces 31 is 1 s.
[0095] Specifically, in an embodiment of the present application, the temperature detection piece 31 is a thermocouple.
[0096] Specifically, in an embodiment of the present application, the photographing assembly 4 is a CCD camera.
[0097] Specifically, in an embodiment of the present application, the fireproof glass 11 is a high-temperature-resistant fireproof glass 11. Further, the thickness of the fireproof glass 11 is 10 mm.
[0098] Specifically, in an embodiment of the present application, the fireproof plate 12 is a strong silicate fireproof plate 12. Further, the thickness of the fireproof plate 12 is 12 mm.
[0099] Specifically, in an embodiment of the present application, the burner 21 is arranged on the center line of the vertical shaft experiment model.
[0100] Further, referring to Figure 3 The present application also provides a use method of the fire plume evolution experiment device, which is suitable for the fire plume evolution experiment device described above, and comprises the following steps:
[0101] Step S1, selecting one of a plurality of vertical shaft models with different sizes as a vertical shaft experiment model for experiment.
[0102] Step S2, placing a burner and a temperature measuring assembly in the shaft experimental model, and setting a camera assembly corresponding to the fireproof glass of the shaft experimental model outside the shaft experimental model, wherein the temperature measuring assembly comprises a plurality of temperature detecting pieces, and the plurality of temperature detecting pieces are spaced apart in the up-down direction.
[0103] Specifically, in an embodiment of the present application, the burner is a 0.3m*0.3m porous gas burner, which is arranged at the bottom center of the shaft experimental model, the temperature detecting piece is a thermocouple, and a plurality of thermocouples are arranged on the center line of the shaft experimental model, and the camera assembly is a CCD camera.
[0104] Step S3, starting the burner to perform simulation experiments, and adjusting the output power of the burner multiple times, obtaining a plurality of groups of temperature data through the temperature measuring assembly, and a plurality of groups of flame images through the camera assembly, and transmitting to the control processing terminal for processing.
[0105] In this step, the fuel supply rate is monitored and controlled through a gas flow meter, that is, the output power of the burner is adjusted to provide different fire source heat release rates, so as to realize the adjustment of the fire source power.
[0106] Step S4, repeatedly replacing shaft models of different sizes as shaft experimental models to repeat the steps S2-S3 to perform experiments, and obtaining simulation results under different working conditions.
[0107] It should be noted that, in the entire experimental process, there will be a special shaft model, that is, a shaft model with a top opening size l=0.3m, which is used for experiments, that is, experiments in free space, that is, experiments without setting a shaft model.
[0108] Specifically, multiple experiments are performed by adjusting the size of the shaft model, that is, the top opening size of the shaft, and the output power of the burner, and the specific experimental conditions are shown in Table 1:
[0109] Table 1
[0110]
[0111] Step S5, processing the temperature data and the flame images through the control processing terminal to obtain the fire plume evolution process under the shaft structure, and fitting a fire plume representation model in combination with the size of the shaft model and the output power of the burner.
[0112] In this step, the OTSU method is used to process the flame images taken by the camera assembly.
[0113] Specifically, based on the above experimental conditions (see Table 1), experiments are carried out, the temperature data and flame images are processed, and combined with the size of the shaft model and the output power of the burner, a plurality of scatter plots (as shown in Figures 4-7 , and Figures 10-14 ) are drawn to clearly show the influence of the influencing factors on the flame characteristic parameters.
[0114] First, refer to Figure 4 , Figure 4 (a) is a diagram of the change of the fire plume in the shaft structure under different heat release rates of the fire source, Figure 4 (b) is a diagram of the change of the fire plume in the free space under different heat release rates of the fire source, from the above two diagrams, it can be obtained that the average flame height of the fire plume increases with the increase of the heat release rate of the fire source.
[0115] Please refer to Figure 5 for the relationship diagram of the average flame height of the fire plume and the heat release rate of the fire source under different opening sizes of the top of the shaft, according to the diagram, the average flame height of the fire plume first decreases and then increases with the decrease of the opening size of the top of the shaft.
[0116] Please refer to Figure 6 for the change diagram of the average flame height of the fire plume under different opening sizes of the top of the shaft when the heat release rate of the fire source is constant.
[0117] Please refer to Figure 7 for the relationship diagram of the average flame height of the fire plume and the opening size of the top of the shaft under different heat release rates of the fire source, under various open conditions, the minimum flame height is maintained at about l=0.9m.
[0118] Based on the above Figures 4-7 , it can be concluded that:
[0119] (1) When 0.9m<l (i.e. the opening size of the top of the shaft experimental model) <∞, the shaft limits the air entrainment from the side of the burner, which reduces the overall combustion efficiency, because less fresh air is entrained to the top opening of the shaft. Therefore, the actual heat release rate of the fire source is lower than the nominal heat release rate of the fire source, and the average flame height of the fire plume decreases with the decrease of the opening size of the top of the shaft.
[0120] (2) When 0.4m<l (i.e. the opening size of the top of the shaft experimental model) <0.9m, due to the chimney effect caused by the shaft, the outflow driven by buoyancy dominates in the opening area, thereby significantly reducing the inflow of air, and the unburned fuel moves upward to a place with fresh air for combustion, and the average flame height of the fire plume increases.
[0121] Then, refer to Figure 10 , Figure 10For the vertical temperature variation graph of the shaft structure under different heat release rates of the fire source, it can be seen that the central temperature in the shaft decreases with the increase of the vertical height above the fire source. At the same time, the fire power has a great influence on the vertical distribution of temperature. With the increase of the fire power, the temperature at each height position in the shaft increases.
[0122] Please also refer to Figures 11-14 For a certain heat release rate of the fire source, the vertical temperature variation graph of the shaft structure under different sizes of the shaft top opening. With the decrease of the size of the shaft top opening, the suppression effect of the shaft on the fire plume is greatly enhanced, so the temperature of the shaft may change greatly. Given a relatively large shaft top opening, especially when the size of the shaft top opening is in the range of 0.8m-1.0m, the temperature of the upper part of the shaft is very low (about 100-200K). With the decrease of the size of the shaft top opening, the overall temperature in the shaft rises sharply, which is due to three factors: first, the exchange between hot flue gas and fresh air at the opening is suppressed, especially since the opening is small, the air entrainment into the shaft is severely hindered; second, due to the chimney effect in the shaft, the flame is more likely to be sucked into the upper part of the shaft; finally, since the shaft side wall hinders the heat transfer to the surrounding environment, the cumulative effect of the shaft becomes more significant.
[0123] Step S300, determining the basic physical quantity of the influencing factor, converting the relationship between the flame characteristic parameter and the influencing factor into a dimensionless relationship.
[0124] Specifically, the basic physical quantity is the fire source characteristic length D, the environmental density p ∞ , the constant-pressure specific heat C p , the environmental temperature T ∞ , and the gravitational acceleration g.
[0125] Further, the dimensionless relationship is:
[0126]
[0127] In the formula,
[0128] Step S400, performing nonlinear fitting on the results of the scatter plot, and establishing a fire plume representation model based on the dimensionless relationship to calculate the fire plume characteristic parameter.
[0129] Specifically, through data integration, the fire plume representation model is:
[0130]
[0131] It should be noted that after nonlinear fitting on the results of the scatter plot, the formula (3) is obtained. The procedure is as follows:
[0132] Based on Considering that most thermocouples are located in the intermittent flame region, the normalized temperature rise is expressed as The relationship with the normalized vertical height Z / H is:
[0133]
[0134] According to the simulation results, the following Table 2 can be obtained:
[0135] Table 2
[0136]
[0137] In order to better express the trend of the coefficients, χχ0and λλ0are put into the correlation, where χ0and λ0are 4.3 and -2.73, respectively, which are applicable to the free condition (close to the McCaffrey model).
[0138] As Figure 24 shown, with the increase of the opening size at the top of the shaft, the coefficient χχ0first decreases and then increases, indicating that there is a significant piecewise correlation, that is:
[0139]
[0140] However, λλ0shows a monotonous increasing trend (as Figure 25 shown).
[0141]
[0142] In this way, the above plume characterization model is obtained by combining equation (4) and equation (5).
[0143] Specifically, please refer to Figure 26 for the comparison of the theoretical value and the experimental value of the temperature rise, which shows a good fitting result.
[0144] Please refer to Figure 8 for the plume average flame height fitting diagram obtained based on the above experimental working conditions according to the plume characterization model, it can be seen that the two exponential modes are consistent with the flame behavior affected by air entrainment and chimney effect, respectively. In comparison, the transition point is related to l / D=3, which is consistent with the critical opening size of 0.9m described above. At the same time, with the increase of the opening size at the top of the shaft to infinity, it reflects the free condition without the shaft, and the flame height calculated by the plume characterization model can be well fitted with the Heskestad model (as Figure 9 shown), with a maximum error of 8%.
[0145] It should be noted that the size of the fire source size D in the present application should not be less than 0.3m. That is, the fire plume characterization model provided by the present application is suitable for the case of l / D>1.3 and D>0.3m.
[0146] In the technical scheme of the present application, the fire plume characterization model is obtained by nonlinear fitting of simulation data obtained by simulation experiment through a fire plume evolution experiment device, and has high accuracy; when performing prediction calculation, the influencing factors are determined according to the actual situation of the fire, and then the average flame height of the fire plume under the shaft structure and the temperature rise in the vertical direction inside the shaft are calculated based on the fire plume characterization model, thereby providing guidance for fire rescue and improving disaster relief efficiency.
[0147] The above only describes the preferred embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation made by using the content of the present application specification and drawings, or direct / indirect application in other related technical fields is included in the patent protection scope of the present application.
Claims
1. A method for calculating a fire plume characteristic parameter, suitable for a shaft structure, characterized in that, The method for calculating the fire plume characteristic parameter comprises the following steps: Step S100, determining the influence factors of the fire plume characteristics under the shaft structure, and establishing a relationship between the fire plume characteristic parameters and the influence factors, wherein the fire plume characteristic parameters include the average fire plume height and the temperature rise in the vertical direction inside the shaft; Step S200, performing simulation experiments through a fire plume evolution experimental device to obtain simulation results under different working conditions, drawing the simulation results into a scatter plot, and determining the influence of the influence factors on the fire plume characteristic parameters; Step S300, determining the basic physical quantities of the influence factors, and converting the relationship between the fire plume characteristic parameters and the influence factors into a dimensionless relationship; Step S400, performing nonlinear fitting on the results of the scatter plot, and establishing a fire plume representation model based on the dimensionless relationship to calculate the fire plume characteristic parameters; The influencing factors include shaft height H, shaft top opening size l, fire source characteristic length D, vertical height Z of the flame to a certain position in the shaft, fire source heat release rate Q, ambient density p ∞ , constant-pressure specific heat C p , ambient temperature T ∞ , gravitational acceleration g; The fire plume representation model is: In the formulae, L f H is the average plume height of the fire under the shaft structure; ΔT z ΔT is the temperature rise at a certain height in the shaft.
2. The method of claim 1, wherein, The relationship between the fire plume characteristic parameters and the influence factors is: In the formula, T z is the temperature at a certain height position in the shaft.
3. The method of claim 2, wherein, The basic physical quantities are the fire characteristic length D, the ambient density p ∞ , the constant-pressure specific heat C p , the ambient temperature T ∞ , the gravitational acceleration g; The dimensionless relationship is:
4. A flame plume evolution experiment device suitable for the method of calculating the characteristic parameters of a flame plume according to any one of claims 1-3, characterized in that, The fire plume evolution experimental device comprises: A plurality of shaft models, each of which is arranged in the shape of a cuboid and extends in the up-down direction, each of which is enclosed by a fireproof glass and three fireproof plates in the circumferential direction, the sizes of the plurality of shaft models are different, and one of them is set as a shaft experimental model; A fire source simulation assembly comprising a burner, which is arranged in the shaft experimental model; A temperature measurement assembly arranged in the shaft experimental model, comprising a plurality of temperature detection pieces, which are distributed at intervals in the up-down direction, and each of which is used to detect the temperature at a certain height position in the shaft experimental model; A photographing component arranged outside the shaft experimental model and corresponding to the fireproof glass of the shaft experimental model, which is used to obtain flame images by photographing; and A control processing terminal electrically connected with the temperature measurement assembly and the photographing component, which is used to receive and process the information transmitted by the temperature measurement assembly and the photographing component to represent the fire plume evolution process under the shaft structure.
5. The fire plume evolution experiment apparatus of claim 4, wherein, The fire source simulation assembly further comprises a gas cylinder and a gas flow meter, which are arranged outside the shaft experimental model, the gas cylinder is connected with the burner through a gas supply pipe, and the gas flow meter is arranged in the gas supply pipe.
6. The fire plume evolution experiment apparatus of claim 4, wherein, The burner is a porous gas burner; The temperature detection piece is a thermocouple; The photographing component is a CCD camera.
7. The fire plume evolution experiment apparatus of claim 4, wherein, The fireproof glass is a high-temperature-resistant fireproof glass; The fireproof plate is a strong silicate fireproof plate.
8. A method of using a fire plume evolution experiment apparatus, suitable for use with the fire plume evolution experiment apparatus of any one of claims 4-7, the method comprising: The use method of the fire plume evolution experimental device comprises the following steps: Step S1, selecting one of the plurality of shaft models with different sizes as a shaft experimental model for experiment; Step S2, placing a burner and a temperature measurement assembly in the shaft experimental model, and arranging a photographing component outside the shaft experimental model and corresponding to the fireproof glass of the shaft experimental model, wherein the temperature measurement assembly comprises a plurality of temperature detection pieces, and the plurality of temperature detection pieces are distributed at intervals in the up-down direction; Step S3, start the burner to carry out simulation experiment, and adjust the output power of the burner for many times, measure a plurality of temperature data through the temperature measuring assembly, and obtain a plurality of flame images through the photographing assembly, and transmit to the control processing terminal for processing; Step S4, repeatedly carry out the steps S2-S3 to carry out experiments by replacing the shaft model of different sizes as the shaft experiment model, and obtain simulation results under different working conditions.