Fire plume characteristic parameter calculation method, evolution experiment device and use method

Abstract

The invention discloses a fire plume characteristic parameter calculation method, an evolution experiment device and a use method, and the fire plume characteristic parameter calculation method comprises the steps: determining influence factors of flame characteristics under a vertical shaft structure, and building a relational expression between the flame characteristic parameters and the influence factors, the flame characteristic parameters comprise the average flame height of the plume and the temperature rise in the vertical shaft in the vertical direction; performing a simulation experiment through a fire plume evolution experiment device to obtain simulation results under different working conditions, drawing a scatter diagram, and determining the influence of influence factors on flame characteristic parameters; determining basic physical quantities of the influence factors, and converting a relational expression between the flame characteristic parameters and the influence factors into a dimensionless relational expression; performing nonlinear fitting on the result of the scatter diagram, and establishing a fire plume characterization model based on a dimensionless relational expression; thus, the average flame height of the lower fire plume of the vertical shaft structure and the vertical temperature rise in the vertical shaft are obtained through calculation, effective guidance can be provided for fire rescue, and the disaster relief efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of fire safety technology, and in particular to a fire plume characteristic parameter calculation method, an evolution experimental device and a use method. Background Art

[0002] There are many accidents in high-rise building fires that cause casualties due to fires in cable wells, pipe wells, elevator wells and other parts of the building. "Vertical shafts" are channel-type vertical structures that often appear in high-rise buildings. They are usually used for exhaust, smoke exhaust, laying water pipes and cables or lighting, including vertical structures such as cable wells, pipe wells, and ventilation wells. Building shafts are the main channels for the development and spread of fires in high-rise buildings. Their dangers are mainly manifested in two aspects: First, the use of combustible materials and combustible components in building shafts has fire hazards. For example, the inspection doors of the shafts use ordinary wooden doors and other combustibles, which reduces the fire resistance level of the building shafts and increases the fire hazard of the building shafts; second, the building shafts are the main channels for smoke diffusion. Once a fire occurs, it often causes serious harm to personnel. Experiments have shown that in a 30-story building with a height of about 100 meters, it only takes 30 seconds for smoke to spread from the first floor to the top floor without obstruction. In other words, the vertical shaft of the entire building is a "chimney" that draws air. Once a fire occurs at the bottom of the floor, it will be accompanied by a large amount of thick smoke. The thick smoke in the chimney will form strong convection with the air on the roof, thereby intensifying the fire. This phenomenon is called the "chimney effect."

[0003] Due to the "chimney effect", stairwells, elevators and various pipe shafts in high-rise buildings often become the main channels for fire spread and expansion when a fire occurs. When a fire occurs on the ground floor and lower floors of a high-rise building, smoke can spread to dozens of floors through various shafts within tens of seconds, causing the fire to spread. This not only makes firefighting more difficult, but also endangers the lives of people escaping to the rooftop. Therefore, under the current circumstances, more effective technology is urgently needed to characterize the evolution of the fire plume under the shaft structure, so as to calculate the flame characteristic parameters (such as the average flame height of the fire plume, the vertical temperature rise inside the shaft, etc.), which can be used in fire rescue to improve disaster relief efficiency. Summary of the invention

[0004] The main purpose of the present invention is to propose a fire plume characteristic parameter calculation method, an evolution experimental device and a use method, aiming to solve the above problems.

[0005] To achieve the above object, the present invention proposes a method for calculating characteristic parameters of a fire plume, which is applicable to a vertical shaft structure and includes the following steps:

[0006] Step S100, determining the influencing factors of flame characteristics under the shaft structure, and establishing a relationship between flame characteristic parameters and the influencing factors, wherein the flame characteristic parameters include the average flame height of the fire plume and the vertical temperature rise inside the shaft;

[0007] Step S200, performing a simulation experiment through a fire plume evolution experimental device to obtain simulation results under different working conditions, and plotting the simulation results into a scatter plot to clarify the influence of the influencing factors on the flame characteristic parameters;

[0008] Step S300, determining the basic physical quantity of the influencing factor, and converting the relationship between the flame characteristic parameter and the influencing factor into a dimensionless relationship;

[0009] Step S400: performing nonlinear fitting on the result of the scatter plot, and establishing a fire plume characterization model based on the dimensionless relationship to calculate fire plume characteristic parameters.

[0010] Furthermore, the influencing factors include the shaft height H, the size of the shaft top opening l, the characteristic length of the fire source D, the vertical height Z from the flame to a certain position in the shaft, the heat release rate Q of the fire source, and the environmental density ρ ∞ , constant pressure specific heat C p 、Ambient temperature T ∞ , gravitational acceleration g.

[0011] Furthermore, the relationship between the flame characteristic parameter and the influencing factor is:

[0012]

[0013] Where, L f is the average flame height of the fire plume under the shaft structure;

[0014] ΔT z is the temperature rise at a certain height in the shaft;

[0015] T z It is the temperature at a certain height in the shaft.

[0016] Furthermore, the basic physical quantities are the characteristic length D of the fire source, the environmental density ρ ∞ , constant pressure specific heat C p 、Ambient temperature T ∞ , gravitational acceleration g;

[0017] The dimensionless relationship is:

[0018]

[0019] In the formula,

[0020] Furthermore, the fire plume characterization model is:

[0021]

[0022] The present invention also provides a fire plume evolution experimental device, which is applicable to the fire plume characteristic parameter calculation method, and the fire plume evolution experimental device comprises:

[0023] A plurality of vertical shaft models, each of which is arranged in a rectangular parallelepiped and extends in the up-down direction, each of which is formed by a fireproof glass and three fireproof panels enclosed in sequence along its circumference, the plurality of vertical shaft models have different sizes, and one of them is set as a vertical shaft test model;

[0024] A fire source simulation component, including a burner, wherein the burner is arranged in the shaft test model;

[0025] A temperature measuring component is arranged in the vertical shaft test model, comprising a plurality of temperature detection components, the plurality of temperature detection components are spaced apart in the vertical direction, and each of the temperature detection components is used to detect the temperature at a certain height position in the vertical shaft test model;

[0026] A photographing element is arranged outside the shaft test model and corresponds to the fireproof glass of the shaft test model, and is used to photograph and obtain a flame image; and

[0027] The control processing terminal is electrically connected to the temperature measurement component and the camera, and is used to receive and process the information transmitted by the temperature measurement component and the camera 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, and the gas cylinder and the gas flow meter are arranged outside the shaft test model. The gas cylinder is connected to the burner through a gas supply pipe, and the gas flow meter is arranged on the gas supply pipe.

[0029] Further, the burner is a porous gas burner;

[0030] The temperature detection element is a thermocouple;

[0031] The shooting component 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 device, which is applicable to the fire plume evolution experimental device. The method for using the fire plume evolution experimental device comprises the following steps:

[0035] Step S1, selecting one of a plurality of shaft models of different sizes as a shaft experimental model for experiment;

[0036] Step S2, placing a burner and a temperature measuring component in the shaft test model, and setting a shooting component outside the shaft test model corresponding to the fireproof glass of the shaft test model, wherein the temperature measuring component includes a plurality of temperature detecting components, and the plurality of temperature detecting components are spaced apart and distributed in the up-down direction;

[0037] Step S3, starting the burner to perform a simulation experiment, and adjusting the output power of the burner for multiple times, obtaining multiple groups of temperature data by measuring with the temperature measurement component, and obtaining multiple groups of flame images by photographing with the photographing component, and transmitting them to the control processing terminal for processing;

[0038] Step S4, replacing the shaft models of different sizes as the shaft test models for multiple times and repeating the steps S2-S3 to conduct experiments to obtain simulation results under different working conditions.

[0039] In the technical solution of the present invention, the fire plume characterization model is obtained by nonlinear fitting of simulation data obtained by simulation experiments using a fire plume evolution experimental device, and has high accuracy. When performing predictive calculations, the influencing factors are determined based on the actual fire situation, and then the average flame height of the fire plume under the shaft structure and the vertical temperature rise inside the shaft are calculated based on the fire plume characterization model, which can provide guidance for firefighting and rescue and improve disaster relief efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention 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 invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0041] Figure 1 A flow chart of a method for calculating characteristic parameters of a fire plume provided by the present invention;

[0042] Figure 2 A schematic structural diagram of an embodiment of a fire plume evolution experimental device provided by the present invention;

[0043] Figure 3 A flow chart of a method for using the fire plume evolution experimental device provided by the present invention;

[0044] Figure 4 The diagrams of the fire plume changes in the shaft structure and free space under different fire source heat release rates;

[0045] Figure 5 It is the relationship between the average flame height of the fire plume and the heat release rate of the fire source under different shaft top opening sizes;

[0046] Figure 6 The graph of the average flame height change of the fire plume under different shaft top opening sizes when the heat release rate of the fire source is constant;

[0047] Figure 7 This is the relationship between the average flame height of the fire plume and the size of the top opening of the shaft under different fire source heat release rates;

[0048] Figure 8 Models for fire plume characterization;

[0049] Fig. 9 It is a fitting diagram of the average flame height of the fire plume calculated based on the fire plume characterization model and a fitting diagram of the average flame height of the fire plume calculated based on other models;

[0050] Fig.10 This is a graph showing the change in vertical temperature in the shaft under different fire source heat release rates;

[0051] Fig.11 It is a relationship diagram between the temperature at a certain height position in the shaft and the vertical height from the flame to the height position under different shaft top opening sizes when the heat release rate of the fire source is constant;

[0052] Fig.12 It is a relationship diagram between the temperature at a certain height position in the shaft and the vertical height from the flame to the height position under different shaft top opening sizes when the heat release rate of the fire source is constant;

[0053] Fig.13 It is a relationship diagram between the temperature at a certain height position in the shaft and the vertical height from the flame to the height position under different shaft top opening sizes when the heat release rate of the fire source is constant;

[0054] Fig.14 It is a relationship diagram between the temperature at a certain height position in the shaft and the vertical height from the flame to the height position under different shaft top opening sizes when the heat release rate of the fire source is constant;

[0055] Fig.15 is the dimensionless temperature rise ΔT at a certain shaft top opening size z / T ∞ Relationship diagram with Z / H;

[0056] Fig.16 is the dimensionless temperature rise ΔT at a certain shaft top opening size z / T ∞ Relationship diagram with Z / H;

[0057] Fig.17 is the dimensionless temperature rise ΔT at a certain shaft top opening size z / T ∞ Relationship diagram with Z / H;

[0058] Fig.18 is the dimensionless temperature rise ΔT at a certain shaft top opening size z / T ∞ Relationship diagram with Z / H;

[0059] Fig.19 is the dimensionless temperature rise ΔT at a certain shaft top opening size z / T ∞ Relationship diagram with Z / H;

[0060] Fig. 20 is the dimensionless temperature rise ΔT at a certain shaft top opening size z / T ∞ Relationship diagram with Z / H;

[0061] Fig.21 is the dimensionless temperature rise ΔT at a certain shaft top opening size z / T ∞ Relationship diagram with Z / H;

[0062] Fig. 22 is the dimensionless temperature rise ΔT at a certain shaft top opening size z / T ∞ Relationship diagram with Z / H;

[0063] Fig.23 is the dimensionless temperature rise ΔT at a certain shaft top opening size z / T ∞ Relationship diagram with Z / H;

[0064] Fig.24 It is the fitting diagram of the relationship between χ / χ0 and l / D;

[0065] Fig.25 It is the fitting diagram of the relationship between λ / λ0 and l / D;

[0066] Fig.26 This is a comparison chart between the temperature rise simulation experimental value and the calculated theoretical value.

[0067] Description of Figure Numbers:

[0068] Label name Label name 100 Fire plume evolution experimental device 22 Gas cylinder 1 Shaft Model 23 Gas flow meter 11 Fireproof glass 24 Gas supply pipe 12 Fireproof board 3 Temperature measurement components 2 Fire source simulation components 31 Temperature detection parts 21 Burner 4 Photographing

[0069] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0070] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0071] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0072] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0073] Due to the "chimney effect", stairwells, elevators and various pipe shafts in high-rise buildings often become the main channels for fire spread and expansion when a fire occurs. When a fire occurs on the ground floor and lower floors of a high-rise building, smoke can spread to dozens of floors through various shafts within tens of seconds, causing the fire to spread. This not only makes firefighting more difficult, but also endangers the lives of people escaping to the rooftop. Therefore, under the current circumstances, more effective technology is urgently needed to characterize the evolution of the fire plume under the shaft structure, so as to calculate the flame characteristic parameters (such as the average flame height of the fire plume, the vertical temperature rise inside the shaft, etc.), which can be used in fire rescue to improve disaster relief efficiency.

[0074] In view of this, the present invention provides a method for calculating characteristic parameters of a fire plume. Figure 1 The present invention provides a flow chart of a method for calculating characteristic parameters of a fire plume.

[0075] See also Figure 1 , the fire plume characteristic parameter calculation method comprises the following steps:

[0076] Step S100, determining the influencing factors of flame characteristics in the vertical shaft structure, and establishing a relationship between flame characteristic parameters and the influencing factors, wherein the flame characteristic parameters include an average flame height of the fire plume and a vertical temperature rise inside the vertical shaft.

[0077] Specifically, the influencing factors include the shaft height H, the size of the shaft top opening l, the characteristic length of the fire source D, the vertical height Z from the flame to a certain position in the shaft, the heat release rate Q of the fire source, and the environmental density ρ ∞ , constant pressure specific heat C p 、Ambient temperature T ∞ , gravitational acceleration g.

[0078] The relationship between the flame characteristic parameters and the influencing factors is:

[0079]

[0080] In formula (1), L f is the average flame height of the fire plume under the shaft structure;

[0081] ΔT z is the temperature rise at a certain height in the shaft;

[0082] T z It is the temperature at a certain height in the shaft.

[0083] It should be noted that ΔT in formula (1) z =T z -T ∞ =fcn(Q, Z, l, D, ρ ∞ , C p , T ∞ , g, H) are obtained according to the McCaffrey model and the Heskestad model.

[0084] Step S200: Conduct simulation experiments using a fire plume evolution experimental device to obtain simulation results under different working conditions, plot the simulation results into a scatter plot, and clarify the influence of the influencing factors on the flame characteristic parameters.

[0085] For further information, see Figure 2 , Figure 2 An embodiment of a fire plume evolution experimental device 100 provided by the present invention is applicable to the above-mentioned fire plume characteristic parameter calculation method.

[0086] The fire plume evolution experimental device 100 includes a plurality of shaft models 1, a fire source simulation component 2, a temperature measurement component 3, a camera 4, and a control and processing terminal. Each of the shaft models 1 is arranged in a rectangular parallelepiped and extends in the up and down directions. Each of the shaft models 1 is formed by a fireproof glass 11 and three fireproof panels 12 that are enclosed in sequence along the circumference thereof. The plurality of shaft models 1 have different sizes, and one of them is set as a shaft experimental model. The fire source simulation component 2 includes a burner 21, and the burner 21 is arranged in the shaft experimental model. The temperature measurement component 3 is arranged in the shaft The experimental model includes a plurality of temperature detection components 31, which are spaced apart in the up-down direction, and each of the temperature detection components is used to detect the temperature at a certain height position in the shaft experimental model; the shooting component 4 is arranged outside the shaft experimental model and corresponds to the fireproof glass 11 of the shaft experimental model, and is used to capture the flame image; the control processing terminal is electrically connected to the temperature measurement component 3 and the shooting component 4, and is used to receive and process the information transmitted by the temperature measurement component 3 and the shooting component 4, so as to characterize the evolution process of the fire plume under the shaft structure.

[0087] In this way, the vertical shaft model 1 is used to conduct experiments. During the experiment, the temperature detection component 31 is used to measure the real-time temperatures at multiple height positions in the shaft, and then the shooting component 4 is used to capture the flame image. The temperature information and image information are processed by the control processing terminal to obtain the fire plume behavior characteristics. Then, the vertical shaft model 1 of different sizes is selected as the vertical shaft experimental model for multiple times to conduct experiments, and the output power of the burner 21 is adjusted, that is, by adjusting the parameters such as the opening size of the top of the vertical shaft and the fire source power, multiple groups of temperature information and image information are obtained, that is, 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 influencing factors on the flame characteristic parameters is clarified through a scatter plot drawn according to the simulation results.

[0088] It should be noted that, in one embodiment of the present invention, the flame image captured by the camera 4 is processed using the OTSU method.

[0089] It should also be noted that, in the present invention, the characteristic length D of the fire source is determined according to the selection of the burner 21. Specifically, in one embodiment of the present invention, the burner 21 is a 0.3m×0.3m porous gas burner, and therefore, the characteristic length D of the fire source=0.3m.

[0090] For further information, see Figure 2The fire source simulation component 2 further includes a gas bottle 22 and a gas flow meter 23. The gas bottle 22 and the gas flow meter 23 are arranged outside the shaft test model. The gas bottle 22 is connected to the burner 21 through a gas supply pipe 24. 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 can be provided, and then the relationship between the flame height and the fire source heat release rate can be obtained.

[0091] Specifically, in one embodiment of the present invention, the temperature measurement component 3 is arranged on the center line of the vertical shaft test model.

[0092] Specifically, in one embodiment of the present invention, the distance between the temperature detection member 31 located at the bottom among the plurality of temperature detection members 31 and the bottom of the shaft test model is 30 cm.

[0093] Specifically, in one embodiment of the present invention, the distance between any two adjacent temperature detection elements 31 among the plurality of temperature detection elements 31 is 10 cm.

[0094] Specifically, in an embodiment of the present invention, the sampling time interval between any two adjacent temperature detection elements 31 among the plurality of temperature detection elements 31 is 1s.

[0095] Specifically, in one embodiment of the present invention, the temperature detection element 31 is a thermocouple.

[0096] Specifically, in one embodiment of the present invention, the photographing element 4 is a CCD camera.

[0097] Specifically, in one embodiment of the present invention, 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 one embodiment of the present invention, the fireproof board 12 is a strong silicate fireproof board 12. Further, the thickness of the fireproof board 12 is 12 mm.

[0099] Specifically, in one embodiment of the present invention, the burner 21 is disposed on the center line of the vertical shaft test model.

[0100] For further information, see Figure 3 The present invention also provides a method for using a fire plume evolution experimental device, which is applicable to the fire plume evolution experimental device described above, and comprises the following steps:

[0101] Step S1: Select one of multiple shaft models of different sizes as a shaft test model for experiment.

[0102] Step S2, placing a burner and a temperature measuring component in the shaft test model, and setting a shooting component outside the shaft test model corresponding to the fireproof glass of the shaft test model, wherein the temperature measuring component includes a plurality of temperature detection components, and the plurality of temperature detection components are spaced apart in the up-and-down direction.

[0103] Specifically, in one embodiment of the present invention, the burner is a 0.3m×0.3m porous gas burner, which is arranged at the bottom center of the vertical shaft test model, the temperature detection element is a thermocouple, and a plurality of the thermocouples are arranged on the center line of the vertical shaft test model, and the shooting element is a CCD camera.

[0104] Step S3, start the burner to perform a simulation experiment, and adjust the output power of the burner multiple times, obtain multiple groups of temperature data by measuring with the temperature measurement component, and obtain multiple groups of flame images by photographing with the camera, and transmit them to the control processing terminal for processing.

[0105] In this step, the fuel supply rate is monitored and controlled by a gas flow meter, that is, the output power of the burner is adjusted to provide different fire source heat release rates to achieve the adjustment of the fire source power.

[0106] Step S4, replacing the shaft models of different sizes as the shaft test models for multiple times and repeating the steps S2-S3 to conduct experiments to obtain simulation results under different working conditions.

[0107] It should be noted that during the entire experimental process, there will be a special shaft model, that is, a shaft model with an opening size l= at the top of the shaft. The experiment is conducted using this shaft model, that is, the experiment is conducted in free space, that is, the experiment is conducted without setting up a shaft model.

[0108] Specifically, multiple experiments were conducted by adjusting the shaft model size, i.e., the shaft top opening size, and the burner output power. The specific experimental working conditions are shown in Table 1 below:

[0109] Table 1

[0110]

[0111] Step S5, processing the temperature data and the flame image by the control processing terminal to obtain the fire plume evolution process under the shaft structure, and fitting the fire plume characterization model in combination with the size of the shaft model and the output power of the burner.

[0112] In this step, the flame image captured by the camera is processed using the OTSU method.

[0113] Specifically, experiments were conducted based on the above experimental conditions (see Table 1). By processing temperature data and flame images, and combining the dimensions of the shaft model and the output power of the burner, multiple scatter plots were drawn (such as Figure 4-Figure 7 and Figure 10-Figure 14 shown), to clarify the influence of the influencing factors on the flame characteristic parameters.

[0114] First, please refer to Figure 4 , Figure 4 (a) is the variation diagram of the fire plume in the shaft structure under different heat release rates of the fire source, Figure 4 (b) is the variation diagram of the fire plume in free space under different heat release rates of the fire source. It can be obtained from the above two figures that the average flame height of the fire plume increases with the increase of the heat release rate of the fire source.

[0115] Then, please refer to Figure 5 , which is the relationship diagram between the average flame height of the fire plume and the heat release rate of the fire source under different shaft top opening sizes. According to this figure, it can be obtained that the average flame height of the fire plume first decreases and then increases with the decrease of the shaft top opening size.

[0116] Then, please refer to Figure 6 , which is the variation diagram of the average flame height of the fire plume under different shaft top opening sizes when the heat release rate of the fire source is constant.

[0117] Then, please refer to Figure 7 , which is the relationship diagram between the average flame height of the fire plume and the shaft top opening size under different heat release rates of the fire source. Under various open conditions, the minimum flame height remains at about l = 0.9m.

[0118] Combining the above Figure 4-Figure 7 , it can be concluded that:

[0119] (1) When 0.9m < l (i.e., the top opening size of the shaft experimental model) < ∞, the shaft restricts the air entrainment from the side of the burner, which reduces the overall combustion efficiency because less fresh air is entrained into 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 shaft top opening size.

[0120] (2) When 0.4m < l (i.e., the top opening size of the shaft experimental model) < 0.9m, due to the chimney effect caused by the shaft, the buoyancy-driven outflow dominates in the opening area, which significantly reduces the air inflow. The unburned fuel moves upward to the place with fresh air for combustion, and the height of the average flame height of the fire plume increases.

[0121] Then, please refer to Fig.10 , Fig.10This is a diagram of the change of vertical temperature in the shaft structure under different fire source heat release rates. 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 source power also has a great influence on the vertical distribution of temperature. With the increase of the fire source power, the temperature at each height position in the shaft increases accordingly.

[0122] Please see again Figure 11-Figure 14 , is a graph showing the change of vertical temperature in the shaft structure under different shaft top opening sizes under a certain fire source heat release rate. As the shaft top opening size decreases, the suppression effect of the shaft on the fire plume is greatly enhanced, and therefore, the temperature of the shaft may vary greatly. Given a relatively large shaft top opening, especially when the shaft top opening size ranges from 0.8m to 1.0m, the temperature in the upper part of the shaft is extremely low (about 100–200K). As the shaft top opening size decreases, the overall temperature in the shaft rises sharply, which is attributed to three factors: first, the exchange between hot smoke and cold fresh air at the opening is suppressed, especially because the air entrainment into the shaft is severely hindered due to the small opening; 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, the cumulative effect caused by the shaft becomes more significant because the shaft side walls hinder the heat transfer to the surrounding environment.

[0123] Step S300: determining the basic physical quantity of the influencing factor, and converting the relationship between the flame characteristic parameter and the influencing factor into a dimensionless relationship.

[0124] Specifically, the basic physical quantities are the characteristic length D of the fire source, the environmental density ρ ∞ , constant pressure specific heat C p 、Ambient temperature T ∞ , gravitational acceleration g.

[0125] Furthermore, the dimensionless relationship is:

[0126]

[0127] In the formula,

[0128] Step S400: performing nonlinear fitting on the result of the scatter plot, and establishing a fire plume characterization model based on the dimensionless relationship to calculate fire plume characteristic parameters.

[0129] Specifically, through data integration, the fire plume characterization model is:

[0130]

[0131] It should be noted that after performing nonlinear fitting on the results of the scatter plot, the formula (3) is obtained: The process is:

[0132] based on Considering that most of the thermocouples are located in the intermittent flame region, the normalized temperature rise is expressed as Relationship with normalized vertical height Z / H:

[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, χχ0 and λλ0 are put into the correlation, where χ0 and λ0 are 4.3 and -2.73 respectively, which is suitable for free conditions (close to the McCaffrey model).

[0138] like Fig.24 As shown in the figure, with the increase of the opening size at the top of the shaft, the coefficient χχ0 first decreases and then increases, indicating that there is a significant segmental correlation, namely:

[0139]

[0140] However, λλ0 shows a monotonically increasing trend (e.g. Fig.25 shown).

[0141]

[0142] In this way, the fire plume characterization model mentioned above is obtained by combining equations (4) and (5).

[0143] For details, please refer to Fig.26 , which is a comparison between the theoretical and experimental values ​​of the temperature rise, shows a good fitting result.

[0144] Please see again Figure 8 , is a fitting diagram of the average flame height of the fire plume obtained according to the fire plume characterization model based on the above experimental conditions. It can be seen that the two exponential modes are consistent with the flame behavior affected by air entrainment and chimney effect, respectively. In contrast, the transition point is related to l / D=3, which is consistent with the critical opening size of 0.9m mentioned above. At the same time, as the opening size at the top of the shaft increases to infinity, reflecting the free condition without the shaft, the flame height calculated by the fire plume characterization model can fit the Heskestad model well (such as Fig. 9 The maximum error is 8%.

[0145] It should be noted that the size of the fire source D in the present invention should not be less than 0.3 m. In other words, the fire plume characterization model provided by the present invention is applicable to the case where l / D>1.3 and D>0.3 m.

[0146] In the technical solution of the present invention, the fire plume characterization model is obtained by nonlinear fitting of simulation data obtained through simulation experiments using a fire plume evolution experimental device, and has high accuracy. When performing predictive calculations, the influencing factors are determined based on the actual fire situation, and then the average flame height of the fire plume under the shaft structure and the vertical temperature rise inside the shaft are calculated based on the fire plume characterization model, thereby providing guidance for firefighting and rescue and improving disaster relief efficiency.

[0147] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for calculating characteristic parameters of fire plume, applicable to vertical shaft structure, characterized in that: The fire plume characteristic parameter calculation method comprises the following steps: Step S100, determining the influencing factors of flame characteristics under the shaft structure, and establishing a relationship between flame characteristic parameters and the influencing factors, wherein the flame characteristic parameters include the average flame height of the fire plume and the vertical temperature rise inside the shaft; Step S200, performing a simulation experiment through a fire plume evolution experimental device to obtain simulation results under different working conditions, and plotting the simulation results into a scatter plot to clarify the influence of the influencing factors on the flame characteristic parameters; Step S300, determining the basic physical quantity of the influencing factor, and converting the relationship between the flame characteristic parameter and the influencing factor into a dimensionless relationship; Step S400: performing nonlinear fitting on the result of the scatter plot, and establishing a fire plume characterization model based on the dimensionless relationship to calculate fire plume characteristic parameters.

2. The method for calculating characteristic parameters of a fire plume according to claim 1, characterized in that: The influencing factors include the shaft height H, the size of the shaft top opening l, the characteristic length of the fire source D, the vertical height Z from the flame to a certain position in the shaft, the heat release rate Q of the fire source, and the environmental density ρ ∞ , constant pressure specific heat C p 、Ambient temperature T ∞ , gravitational acceleration g.

3. The method for calculating characteristic parameters of a fire plume according to claim 2, characterized in that: The relationship between the flame characteristic parameters and the influencing factors is: Where, L f is the average flame height of the fire plume under the shaft structure; ΔT z is the temperature rise at a certain height in the shaft; T z It is the temperature at a certain height in the shaft.

4. The method for calculating characteristic parameters of a fire plume according to claim 3, characterized in that: The basic physical quantities are the characteristic length of the fire source D, the environmental density ρ ∞ , constant pressure specific heat C p 、Ambient temperature T ∞ , gravitational acceleration g; The dimensionless relationship is: In the formula, 5. The method for calculating characteristic parameters of a fire plume according to claim 4, characterized in that: The fire plume characterization model is:

6. A fire plume evolution experimental device, applicable to the fire plume characteristic parameter calculation method according to any one of claims 1 to 5, characterized in that: The fire plume evolution experimental device comprises: A plurality of vertical shaft models, each of which is arranged in a rectangular parallelepiped and extends in the up-down direction, each of which is formed by a fireproof glass and three fireproof panels enclosed in sequence along its circumference, the plurality of vertical shaft models have different sizes, and one of them is set as a vertical shaft test model; A fire source simulation component, including a burner, wherein the burner is arranged in the shaft test model; A temperature measuring component is arranged in the vertical shaft test model, comprising a plurality of temperature detection components, the plurality of temperature detection components are spaced apart in the vertical direction, and each of the temperature detection components is used to detect the temperature at a certain height position in the vertical shaft test model; A photographing element is arranged outside the shaft test model and corresponds to the fireproof glass of the shaft test model, and is used to photograph and obtain a flame image; and The control processing terminal is electrically connected to the temperature measurement component and the camera, and is used to receive and process the information transmitted by the temperature measurement component and the camera to characterize the evolution process of the fire plume under the shaft structure.

7. The fire plume evolution experimental device according to claim 6, characterized in that: The fire source simulation component also includes a gas cylinder and a gas flow meter, which are arranged outside the shaft test model. The gas cylinder is connected to the burner through a gas supply pipe, and the gas flow meter is arranged on the gas supply pipe.

8. The fire plume evolution experimental device according to claim 6, characterized in that: The burner is a porous gas burner; The temperature detection element is a thermocouple; The shooting component is a CCD camera.

9. The fire plume evolution experimental device according to claim 6, characterized in that: The fireproof glass is high temperature resistant fireproof glass; The fireproof board is a strong silicate fireproof board.

10. A method for using a fire plume evolution experimental device, applicable to the fire plume evolution experimental device according to any one of claims 6 to 9, characterized in that: The method for using the fire plume evolution experimental device comprises the following steps: Step S1, selecting one of a plurality of shaft models of different sizes as a shaft experimental model for experiment; Step S2, placing a burner and a temperature measuring component in the shaft test model, and setting a shooting component outside the shaft test model corresponding to the fireproof glass of the shaft test model, wherein the temperature measuring component includes a plurality of temperature detecting components, and the plurality of temperature detecting components are spaced apart and distributed in the up-down direction; Step S3, starting the burner to perform a simulation experiment, and adjusting the output power of the burner for multiple times, obtaining multiple groups of temperature data by measuring with the temperature measuring component, and obtaining multiple groups of flame images by photographing with the photographing component, and transmitting them to the control processing terminal for processing; Step S4, replacing the shaft models of different sizes as the shaft test models for multiple times and repeating the steps S2-S3 to conduct experiments to obtain simulation results under different working conditions.

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