CN116050107A - FDS numerical simulation method under different fire scenes - Google Patents

Abstract

The application discloses an FDS numerical simulation method under different fire scenes, which is characterized by comprising the following steps: creating a structural model of the L-shaped subway transfer station; the structural model of the L-shaped subway transfer station is imported into an FDS for numerical simulation; setting different fire scenes to obtain a method for restricting fire in different fire scenes. According to the method, a 'model-simulation' research mode is adopted, a structural model of an 'L' -shaped subway transfer station is established and is led into an FDS (fully drawn vehicle) for numerical simulation, different fire scenes are designed, the distribution rules of environmental parameters such as a temperature field, a visibility field and the like in the station when different fan switches are adopted to be matched under each fire scene are discussed, and an optimal fan matching mode under different fire scenes is provided so as to achieve the purpose of limiting the development of a fire by using ventilation means.

Description

FDS numerical simulation method under different fire scenes

Technical Field

The invention relates to the field of fire prevention and control, in particular to an FDS numerical simulation method under different fire scenes.

Background

In fire, smoke is usually the main cause of death, a proper forced ventilation smoke control system is arranged in a subway station, and reasonable regulation and control measures are applied to enable fans to be matched with each other, so that the escape time of people can be effectively prolonged, and convenience is brought to disaster relief work of firefighters. In fact, a large number of studies have shown that: the important fire-fighting measures in subway fires are to control the smoke diffusion through effective ventilation and smoke discharge, thereby increasing the personnel evacuation safety time, enhancing the fire-fighting rescue and reducing the casualties. Therefore, research on subway fire accidents is very necessary. At present, research on subway fires at home and abroad has formed a research mode, namely, a station body structure model is established under the support of field investigation and engineering drawings, and then a laboratory scale reduction model is established to carry out laboratory scale reduction mechanical smoke discharge experiments or fire experiments on site, and on the other hand, fire simulation software (FDS) is utilized to simulate the change of in-station environmental parameters during fires and compare the change with experimental results. The research on subway fires is not complete, and the research is focused on cross transfer or multi-line transfer of two-line transfer, and research blank exists for L-type transfer of two-line transfer.

In fact, the "L" type conversion of two-line transfer is a practically usual transfer form and has its unique fire hazard: the subway station is characterized in that a building main body is underground, and the dependence degree of the station on ventilation and illumination facilities is high; compared with the common station, the transfer station has the advantages that the number of electrical equipment and the flow of people are at a large level, and the fire hazard of the transfer station is increased: the L-shaped subway transfer station has the advantages that due to the unique long and narrow structure, the evacuation distance of people is long, and the evacuation time is long; the spreading direction of the fire smoke is consistent with the evacuation direction of the personnel, so that the possibility of the personnel being injured by the smoke is increased.

Disclosure of Invention

The method aims at establishing a structural model of an L-shaped subway transfer station by adopting a model-simulation research mode, importing the structural model into an FDS (fully drawn vehicle) for numerical simulation, designing different fire scenes, discussing the distribution rule of environmental parameters such as a temperature field, a visibility field and the like in the station when different fan switches are adopted to be matched under each fire scene, and providing an optimal fan matching mode under different fire scenes so as to achieve the purpose of limiting the development of fire by using ventilation means. To achieve the above object, the present application provides the following solutions:

the FDS numerical simulation method under different fire scenes comprises the following steps:

s1, creating a structural model of an L-shaped subway transfer station;

s2, importing a structural model of the L-shaped subway transfer station into an FDS (finite description space) for numerical simulation;

s3, setting different fire scenes to obtain a method for limiting fire in the different fire scenes.

Preferably, the structural model of the 'L' -shaped subway transfer station specifically comprises:

a station body structure model and an in-station ventilation model;

the station body structure model comprises an L-shaped station main body; an exit, a hall floor and a platform floor; the ventilation model comprises a piston air pavilion and a common ventilation air pavilion.

Preferably, the piston wind booth specifically comprises:

the piston wind pavilion is used for connecting tunnels in the section and reducing piston wind generated when vehicles enter the station.

Preferably, the common ventilation air pavilion is arranged in the L-shaped station and is used for taking charge of all mechanical ventilation.

Preferably, the numerical simulation is performed by introducing into the FDS:

a plurality of grid lap joints are adopted for the structural model of the L-shaped subway transfer station, and a model grid lap joint diagram is obtained;

setting combustion in the FDS as unsteady combustion by using a heat release rate model to obtain a relationship between a heat release rate and time:

Q＝αt ²

wherein Q is the rate of heat release; alpha is a growth coefficient; t is time;

and carrying out numerical simulation according to the model grid overlap graph and the relation between the heat release rate and time.

Preferably, during the growth phase of the fire, α determines the heat release rate of the fire, and is divided into four models, the present application takes the form of ultrafast, i.e. α= 0.1878.

Preferably, the different fire scenes specifically include:

fire scene 1: the cigarette end ignites the burner to cause a fire;

fire scene 2: a circuit failure causes a fire;

fire scene 3: the gate circuit failure causes a fire.

Preferably, the method for limiting fire disaster in different fire disaster scenes specifically comprises the following steps:

longitudinally comparing different fan matching schemes; the parameter of 'distance from the trend of the fire source' is introduced as an abscissa parameter for longitudinal comparison of the temperature and the concentration of carbon monoxide, and the parameter of 'area occupation ratio of a visibility region below 10 m' is introduced as an ordinate parameter for longitudinal comparison of the visibility.

The beneficial effects of this application are:

according to the method, a 'model-simulation' research mode is adopted, a structural model of an 'L' -shaped subway transfer station is established and is led into an FDS (fully drawn vehicle) for numerical simulation, different fire scenes are designed, the distribution rules of environmental parameters such as a temperature field, a visibility field and the like in the station when different fan switches are adopted to be matched under each fire scene are discussed, and an optimal fan matching mode under different fire scenes is provided so as to achieve the purpose of limiting the development of a fire by using ventilation means.

Drawings

For a clearer description of the technical solutions of the present application, the drawings that are required to be used in the embodiments are briefly described below, it being evident that the drawings in the following description are only some embodiments of the present application, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a flow chart of a method of restricting fires in different fire scenarios in accordance with an embodiment of the present application;

FIG. 2 is a diagram of an L-shaped subway transfer station design structure model of a method for limiting fire in different fire scenes according to an embodiment of the application;

FIG. 3 is a diagram of mechanical ventilation lines of A, B, C wind kiosks in L-shaped subway stations and a relative position relationship diagram thereof according to the method for limiting fire in different fire scenes in the embodiment of the application;

FIG. 4 is a network overlap diagram of an L-shaped subway transfer station model of a method for limiting fire in different fire scenarios according to an embodiment of the present application;

FIG. 5 is a station fume propagation state diagram of an L-shaped subway transfer station based on a first fire scene, which is a method for limiting fire in different fire scenes according to the embodiment of the application;

FIG. 6 is a temperature distribution diagram of an L-shaped subway transfer station based on a first fire scene, which is a method for limiting fire in different fire scenes according to the embodiment of the application;

FIG. 7 is a visibility distribution diagram of an L-shaped subway transfer station based on fire scene one of a method for limiting fire in different fire scenes according to an embodiment of the present application;

FIG. 8 is a graph showing the concentration of CO at a station of an L-shaped subway transfer station based on fire scene one, which is a method for limiting fire in different fire scenes according to the embodiment of the application;

FIG. 9 is a longitudinal comparison chart of environmental parameters in an L-shaped subway transfer station based on different fan cooperation modes of a first fire scene in a fire disaster limiting method of different fire scenes according to the embodiment of the application;

fig. 10 is a station smoke spread state diagram of an L-shaped subway transfer station based on a second fire scene, which is a method for restricting fire in different fire scenes according to an embodiment of the present application;

FIG. 11 is a temperature distribution diagram of an L-shaped subway transfer station based on a second fire scene, which is a method for limiting fire in different fire scenes according to the embodiment of the application;

FIG. 12 is a visibility distribution diagram of an "L" subway transfer station based on a second fire scene, which is a method for restricting fire in different fire scenes according to an embodiment of the present application;

FIG. 13 is a graph showing the concentration of CO at a station of an L-shaped subway transfer station based on a second fire scene, which is a method for limiting fire in different fire scenes according to the embodiment of the application;

fig. 14 is a longitudinal comparison chart of environmental parameters in an L-shaped subway transfer station based on different fan matching modes of a second fire scene in the method for limiting fire in different fire scenes according to the embodiment of the application;

FIG. 15 is a station fume propagation state diagram of an L-shaped subway transfer station based on a fire scene III, which is a method for limiting fire in different fire scenes according to the embodiment of the application;

FIG. 16 is a temperature distribution diagram of an "L" subway transfer station based on fire scenario three for a method of restricting fire in different fire scenarios in an embodiment of the present application;

FIG. 17 is a visibility distribution diagram of an "L" subway transfer station based on fire scene three, which is a method for restricting fire in different fire scenes according to an embodiment of the present application;

FIG. 18 is a plot of station CO concentration for an "L" subway transfer station based on fire scenario three, an embodiment of a method for restricting fire from different fire scenarios;

fig. 19 is a longitudinal comparison diagram of environmental parameters in an L-shaped subway transfer station based on different fan cooperation modes of a third fire scene in the method for limiting fire in different fire scenes according to the embodiment of the application.

Detailed Description

The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.

In order that the above-recited objects, features and advantages of the present application will become more readily apparent, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings.

In this embodiment, as shown in fig. 1-19, a method for restricting fire in different fire scenarios includes the following steps:

creating a structural model of the L-shaped subway transfer station;

and establishing a subway station structure model by adopting CAD 3D. Through earlier field investigation and partial drawing reference, a design structure model diagram of a large L-shaped subway transfer station is shown in fig. 2.

The station is in an L-shaped transfer form, the station main body is in an L-shape, and 6 outlets are arranged in the station. The station main body is L-shaped and is divided into three layers in the vertical direction, namely a station hall layer, a No. 2 wire platform layer and a No. 1 wire platform layer from top to bottom. The underground layer is a subway station hall layer, the effective length of the No. 1 wire station hall in the east-west direction is 160m, the effective length of the No. 2 wire station hall in the north-south direction is 56m, the effective length of the No. 2 wire station hall in the east-west direction is 23m, and the effective length of the No. 180m in the north-south direction. The hall layer part has 6 entrances and exits with the connection ground, the hall layer 1 is provided with 3 escalators and a straight cylinder type barrier-free elevator which are connected with the hall layer 1 of the underground three layers, and the hall layer 2 is provided with 3 escalators and a straight cylinder type barrier-free elevator which are connected with the hall layer 2 of the underground two layers. The underground two layers are No. 2 line island type platforms, the east-west effective width of the platforms is 14m, and the north-south effective length of the platforms is 160m. The effective length of the No. 2 wire tunnel is 120m, and the effective width is 3m. The lower space of the three escalators is respectively provided with 3 cables and equipment rooms, two sides of the escalator are provided with closed shielding doors with the size of 6000mm multiplied by 3000mm, 20 doors are arranged on each side, the south side of the No. 2 line platform layer is provided with a transfer space communicated with the No. 1 line platform layer, and passengers with the No. 2 lines and the No. 1 lines realize transfer through the space. The underground three layers are No. 1 line island type platforms, the east-west trend effective length of the platform layer is 141m, the north-south effective width is 18m, 3 cables and equipment rooms are respectively arranged in the lower space of the three escalators, shielding doors with the size of 6000mm multiplied by 3000mm are arranged on two sides of each of the three escalators, 20 shielding doors are respectively arranged on each side, and a transfer space is arranged on the east side of the No. 1 line platform layer and is communicated with the No. 2 line platform layer.

The station is provided with 4 piston wind kiosks in total and is used for connecting tunnels in an interval to reduce piston wind generated when vehicles enter the station, and mechanical ventilation is not arranged in the piston wind kiosks. As shown in fig. 3. In addition, the station is provided with 3 common ventilation air pavilions in total for mechanical ventilation in the station, and the stations are named as A, B, C air pavilions respectively. A. B, C the mechanical ventilation pipeline diagram of the wind pavilion and the relative position relationship are shown in fig. 4.

The A wind pavilion is positioned near the 13 # outlet and positioned on the western side of the station, is connected with two sets of east-west moving ventilation pipelines and is responsible for mechanical ventilation of the 1 # line platform and the 1 # line area of the station hall layer. The A wind pavilion No. 1 line platform ventilation pipeline is located on the ceiling of the No. 1 line platform layer, two sides of the platform are respectively provided with a ventilation pipeline, each ventilation pipeline is provided with 4 ventilation openings, 8 ventilation openings are all responsible for ventilation of the No. 1 line platform layer. A wind pavilion layer ventilation pipeline is located in the No. 1 line area of the ceiling of the hall layer, and the south side and the north side of the ventilation pipeline are respectively provided with 4 ventilation openings, 8 ventilation openings are all arranged on each ventilation pipeline, and the ventilation of the No. 1 line area of the hall layer is ensured. And the B wind pavilion is positioned near the No. 5 outlet and positioned on the south side of the station, is connected with two sets of ventilation pipelines running in the south-north direction and is responsible for mechanical ventilation of the No. 2 line platform and the south side of the No. 2 line area of the station hall layer. Wherein the ventilation pipeline of the station platform with the No. 2 wire of the B wind pavilion is positioned on the ceiling of the station platform with the No. 2 wire, the two sides of the station platform are respectively provided with a ventilation pipeline, each pipeline is provided with 5 ventilation openings, 10 ventilation openings are all responsible for ventilation of the station platform with the No. 2 wire. And the ventilation pipeline of the station hall layer of the B wind pavilion is positioned on the south ceiling of the No. 2 line part of the station hall layer, the pipeline is in the north-south trend, one ventilation pipeline is arranged on each of the two sides of the station platform, and each pipeline is provided with 6 ventilation openings in total, which are responsible for the ventilation of the south side of the No. 2 line area of the station hall layer. And the C wind pavilion is positioned near the No. 9 outlet and positioned at the north side of the station, is connected with a set of ventilation pipelines running in the north-south direction and is responsible for mechanical ventilation at the north side of the No. 2 line area of the hall. The C air pavilion pipeline is located on the north ceiling of the No. 2 line part of the hall, one ventilation pipeline is arranged on each of the two sides of the hall, 3 ventilation openings are formed in each pipeline, 6 ventilation openings are formed in total, and the ventilation of the north ceiling of the No. 2 line part of the hall is responsible.

The structural model of the L-shaped subway transfer station is imported into an FDS for numerical simulation;

this simulation will take the heat release rate model, which in order to more scientifically reflect the changes in the environmental parameters in the station during a fire, sets the combustion in the FDS as non-steady state combustion, the heat release rate versus time is as follows:

Q＝αt ² ；

wherein:

q-heat release rate, kw;

alpha-growth coefficient, kw.s-2;

t-time, s;

in the growth stage of fire, the heat release rate of the fire is determined by alpha, and the fire is divided into four models respectively: slow type (α= 0.002931), medium type (α= 0.01127), fast type (α= 0.04689), ultra-fast type (α= 0.1878), the study adopted ultra-fast type. According to SFPE fire protection engineering manual, energy output of fire is set to be in the range of 100 KW-50 MW, medium-sized fire is selected, and fire power is set to be 5MW. Therefore, a cube with the size of 1m multiplied by 1m is arranged, the fire source surface with the maximum heat release power of 1000kw per square meter is respectively arranged on five other surfaces of the cube except the surface contacted with the ground, so that the total fire source power of the whole fire source cube reaches 5MW, the condition of smoke flow is considered to be observed, the reactant is selected from polyurethane with larger smoke generation amount, and the numerical value of 'CO yield' in a polyurethane combustion product is determined to be 0.2 by searching SFPE fire protection engineering manual.

The ultra-fast type ventilation system not only can save simulation time, but also can adopt the highest heat release rate, the corresponding fire scene is more severe in simulation, the reliability of the finally obtained ventilation scheme is higher, and on the other hand, the safety threshold of the ventilation scheme is increased from the angle of fire scene parameter setting.

Since the structure of the "L" type subway transfer station belongs to an irregular shape, the form of multiple grid lap joints is adopted herein on the grid drawing of pyrosim. The mesh size was 1m×1m, and 4000896 total meshes were overlapped with the model mesh as shown in fig. 4.

The influence of the smoke blocking vertical wall and the glass fence at the position of the escalator mouth on the smoke flow is considered during the establishment of the model. And neglecting the influence of real-time personnel flow and evacuation in the subway station on the smoke flow. Wherein the load-bearing column body and the equipment are made of default concrete materials, and do not participate in combustion.

In order to more macroscopically observe the environmental parameter changes, the sensors are arranged in 2D slices, and are divided into a temperature sensor (thermocouple), a CO volumetric flow sensor and a smoke flow visibility sensor. The CO volume flow sensor, the thermocouple and the visibility sensor are arranged on a z-axis slice with the vertical height of 1.7m from the ground between the hall layer and the station layer of the No. 1 line and the No. 2 line.

Mechanical smoke discharge establishment: the study adopts an ' exhaust ' surface to establish mechanical smoke discharge, pulls a ' vent ' surface at a vent reserved position of a vent pipeline in a model, creates a new ' surface ', sets the property of the ' surface as the ' exhaust ' surface, and selects the constant flow of the vent ' ex haust ' as 8m according to the number of vents of each layer in the model ³ /s。

According to the analysis of the major fire cases of the foreign subways, the result shows that among the fire causes of the subways, the electrical fire, smoking and mechanical faults respectively occupy 26%, 13% and 11% of the total fire causes. The subway fire caused by these three causes accounts for 50% of the total number of subway fires. Therefore, in order to conveniently observe the smoke spreading condition and environmental parameters when the different subway station layer structures are on fire, the subway fire cause is respectively arranged in each layer of the subway station layer structures, and the fire sources are a gate, a circuit device and a non-extinguished cigarette end respectively.

Fire scene: the ambient temperature in the subway station is 20 ℃, the external ambient pressure is selected to be 101.325Kpa, after a train enters the station, a shielding door is opened, and three fire source position scenes are respectively arranged: the entrance gate of the hall layer is located in the center stairway under equipment room 1 and the stairway under equipment room 2.

Fire scene one: the cigarette end ignites a large garbage bin beside the equipment room below the No. 1 line central stair. (i.e., no. 1 line platform west fire)

Fire scene two: the circuit fault in the equipment room below the No. 2 line stairs fires. (i.e., north fire hazard at station No. 2)

Fire scene three: the gate circuit malfunctions and fires. (i.e., fire at entrance of hall layer 1)

And determining the matching modes of opening and closing of fans in the corresponding fire scene according to the fire scene and the fire source position characteristics, wherein the matching modes of the fire scene design and the corresponding fans in the station are shown in the table 1.

TABLE 1

Under the condition of first fire scene, we simulate the spreading characteristics, temperature, CO concentration and visibility of the station smoke of the No. 1 station in 360s under the matching conditions of different fans. The spreading state of the station smoke at 360s is shown in fig. 5, the temperature distribution of the station at 360s is shown in fig. 6, the visibility of the station at 360s is shown in fig. 7, and the concentration distribution of the station CO at 360s is shown in fig. 8.

In order to better compare the influence degree of each fan matching scheme which is positioned in the station and is responsible for mechanical ventilation in the station on the environmental parameters in the station, different fan matching schemes are longitudinally compared. The parameter of 'distance from the trend of the fire source' is introduced as the abscissa parameter of longitudinal comparison of temperature and CO concentration, and the parameter of 'area occupation ratio of the visibility region below 10 m' is introduced as the ordinate parameter of longitudinal comparison of visibility. The fire scene is a different fan cooperation mode station internal environment parameter longitudinal pair such as that shown in fig. 9.

Aiming at a first fire scene (Western fire of a No. 1 wire platform), the highest temperature in the station can reach 95 ℃ under the condition of not starting mechanical smoke discharge, after ventilation of the No. 1 wire platform is started, the temperature is reduced to about 85 ℃, and other fans on the basis are started in a superimposed manner, so that the upper limit of the temperature in the station is not further reduced. Whether or not the mechanical smoke is opened, the high temperature area in the platform will first appear near the two ends of the platform and near the smoke blocking vertical wall under the stairwell. After the ventilation of the A wind pavilion of the station hall layer A and the station hall layer B is started, the superposition ventilation of the B wind pavilion ensures that the high-temperature smoke flow in the station platform is accelerated to diffuse to form a relative local high-temperature area with the same time, and the superposition of the C wind pavilion can not obviously influence the temperature distribution. For the fire disaster in the middle area of the No. 1 wire, under the condition that mechanical smoke discharge is not started, smoke can spread to all spaces except the north part of the No. 2 wire of the hall layer, and ventilation of the stations of the No. 1 wire and the No. 2 wire can be achieved by only starting ventilation of the stations of the No. 1 wire and the No. 2 wire, so that the smoke can be controlled to be in the station layer of the No. 1 wire 120s before the fire disaster occurs, but once the time exceeds 120s, the scheme is not advantageous. When the lines 1 and 2 and the hall layer A air pavilion are opened, the smoke can be controlled to be within the minimum diffusion range of the smoke within 6 minutes, and when the hall layer B, C air pavilions are sequentially overlapped and opened, the influence range of the smoke can be enlarged. Aiming at the fire disaster in the middle area of the No. 1 line, the visibility is obviously reduced near the trend end point of the platform, and after the No. 1 line, the No. 2 line and the station hall layer A air pavilion are opened for ventilation, the superposition ventilation of the B, C air pavilion can not obviously influence the visibility level. On the basis of opening the ventilation of the lines 1 and 2, the ventilation of the station hall layer fans is opened without obvious influence on the concentration distribution of CO, but the upper limit of the concentration of CO in the station can be effectively reduced after the ventilation of the station hall layer fans is opened, so that the upper limit of the concentration of CO in the station is smaller than a safety critical value of 250 ppm.

In the aspect of temperature control, the four-temperature control is matched, so that the effect is relatively good. In the aspect of visibility control, the area ratio of the visibility region below 10m of the combination of the four and the combination of the five is at the relative lowest level, and the intersecting other combination modes are greatly improved. In the aspect of CO concentration control, the three, four and five coordination methods have similar effect trend and relatively optimal control effect in the range 60m away from the fire source point, and the control effect of the three coordination method in the area outside 60m is better than that of the four coordination method and the five coordination method.

Fire scene two

Under the condition of the first fire scene, the spreading state of the station smoke at 360s is shown in fig. 10, the temperature distribution of the station at 360s is shown in fig. 11, the visibility of the station at 360s is shown in fig. 12, and the concentration distribution of the station CO at 360s is shown in fig. 13. The longitudinal pairs of environmental parameters in the station of the two different fan cooperation modes of the fire scene are shown in fig. 14. Aiming at a fire scene II (No. 2 line station north fire), the highest temperature in the station can reach 95 ℃ under the condition that mechanical smoke discharge is not started, the upper limit of the temperature of the station cannot be reduced when the mechanical smoke discharge is started, but the temperature distribution in the station is obviously changed from relatively uniform distribution to cross distribution in different temperature areas after the mechanical smoke discharge is started. The high temperature region first occurs near the station strike end point. When only the station layer of the No. 2 wire is opened for discharging smoke, the smoke can be controlled to reach 6 minutes at the station layer of the No. 2 wire, but the concentration of the smoke in the station is extremely high, compared with the situation that after the station layer of the No. 2 wire is opened for ventilation, the station layer B, C wind pavilion is opened for ventilation or the whole station is opened for ventilation, and the smoke diffusion range of the station layer of the No. 2 wire part or the station layer of the No. 2 wire can be controlled respectively. The ventilation of the station platform and the ventilation of the station hall C are started for 360 seconds after the fire disaster occurs, the visibility level of more than 28.5m can be still maintained at the north side of the station platform, and the superimposed ventilation of the B, A air pavilion has no influence on the visibility. The upper limit concentration of the station CO can be obviously reduced by opening the mechanical smoke exhaust, and the superposition ventilation of the A air pavilion can not obviously influence the concentration of the station CO after the station ventilation of the No. 2 wire and the ventilation of the B, C air pavilion are opened. In the aspect of temperature control, the effect of the four matching modes is not great, and the temperature control performance of matching three in the area 100m away from the fire source point is relatively good. On the visibility parameter, the visibility area with the visibility area of less than 10m of the third matching is the least, but the visibility control effect of the third matching and the fourth matching is good, and the visibility control effect is almost lower than 50% compared with the third matching. In the aspect of CO concentration control, in the range of 40m from a fire source point, the CO concentration control effects of the four matching modes are not very different, and in the area of 40m from the fire source point, the control effects of the matching three and the matching four are obviously better. Therefore, the influence of the influence range of the smoke is important to consider when selecting the fan matching mode. The range of spreading of smoke in the ventilation of the No. 2 wire platform is larger in the matching of the third smoke, the range of the smoke in the hall layer is smaller, the smoke in the matching of the fourth smoke is opposite, the middle part and the south of the area of the No. 2 wire platform are not influenced by the spreading of smoke in the matching of the fourth smoke, and the spreading range of the smoke in the hall layer is obviously larger.

Fire scene three:

under the condition of the first fire scene, the spreading state of the station smoke at 360s is shown in fig. 15, the temperature distribution of the station at 360s is shown in fig. 16, the visibility of the station at 360s is shown in fig. 17, and the concentration distribution of the station CO at 360s is shown in fig. 18. The longitudinal pairs of environmental parameters in the station of the three different fan cooperation modes of the fire scene are shown in fig. 19.

For fire scene three (fire at entrance of station hall layer 1 wire part), when opening A wind pavilion ventilation, can control the range of spreading flue gas in station hall layer 1 wire part to junction corner, the flue gas can hardly spread to station hall 2 wire part in 6 minutes, and B, C wind pavilion's stack ventilation can enlarge the diffusion area of smoke flow. When the A wind pavilion is opened for ventilation and the B, C wind pavilion is overlapped for ventilation, the local high-temperature area in the station is obviously enlarged, and the temperature of the south area of the connecting corner and the No. 2 line part of the hall layer at the same time is obviously increased. The visibility and the CO concentration show the same law as the temperature. The superposition of ventilation of the visible wind pavilion does not improve the environment of the station hall for the fire scene three, but rather worsens the environmental parameters.

Through longitudinal comparison, the mode of only opening the ventilation of the A wind pavilion has a remarkable effect on the improvement of visibility, the area occupation ratio of the visibility region below 10m is far smaller than that of other fan matching modes, the CO concentration can be controlled at a relatively low level by using the two modes of only the ventilation of the A wind pavilion and the ventilation of the A, B at the same time on the basis of CO concentration comparison, and the temperature can be controlled relatively well in the region which is at a relatively lowest temperature, especially 40m away from a fire source, on the basis of the longitudinal comparison of the temperature.

According to the simulation result, the conventional fan matching scheme cannot control the smoke to the maximum extent to improve the environment in the station. Therefore, by comprehensively considering the longitudinal comparison result of the parameters in the station and the smoke spreading condition, a proposed fan matching mode and a fan superposition ventilation dual function different from the conventional fire fan matching scheme are given for the first, second and third fire scenes:

(1) For fire scene one (fire on the western side of the station platform with the wire number 1), a matching mode of opening the station layer A, B wind pavilion with the wires number 1 and 2 for ventilation (matching four) is recommended. Aiming at a fire scene II (a fire on the north side of a No. 2 line platform), the consideration of the factors of the spreading range of the smoke is enhanced, so that the proposal mode is divided into two cases, namely when people on the No. 2 line platform are seriously evacuated, the proposal is made that all air pavilions on the No. 2 line platform layer and the hall layer are ventilated (matched with the fourth mode). And when the evacuation emphasis is on the hall layer, the ventilation of the hall layer B, C wind pavilion and the No. 2 line are recommended (matched with the third wind pavilion), so that the spreading range of the smoke spreading to the hall layer can be effectively reduced. And (3) aiming at a fire scene III (fire at the entrance of a station hall layer No. 1 line), the station hall layer A wind pavilion is ventilated in a ventilation matching mode.

(2) For the L-shaped subway transfer station, all fans cannot be started to ventilate when a fire disaster occurs, and on one hand, the superposition ventilation of the fans can control the diffusion of smoke, reduce the upper temperature limit and the regional temperature, improve the local visibility level and reduce the local CO concentration. On the other hand, the superposition ventilation of fans can cause the turbulence of wind flow in a station, and the phenomena of accelerating the diffusion of high-temperature smoke flow to form a local high-temperature area, accelerating the diffusion of local smoke flow to reduce the visibility of the local area and increasing the concentration of local CO can occur. Therefore, corresponding fan matching modes are adopted for different fire scenes.

The above embodiments are merely illustrative of the preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, but various modifications and improvements made by those skilled in the art to which the present invention pertains are made without departing from the spirit of the present invention, and all modifications and improvements fall within the scope of the present invention as defined in the appended claims.

Claims (8)

1. The FDS numerical simulation method under different fire scenes is characterized by comprising the following steps of:

s1, creating a structural model of an L-shaped subway transfer station;

s2, importing a structural model of the L-shaped subway transfer station into an FDS (finite description space) for numerical simulation;

s3, setting different fire scenes to obtain a method for limiting fire in the different fire scenes.

2. The method for simulating FDS numerical values in different fire scenes according to claim 1, wherein the structural model of the L-shaped subway transfer station specifically comprises:

a station body structure model and an in-station ventilation model;

the station body structure model comprises an L-shaped station main body; an exit, a hall floor and a platform floor; the ventilation model comprises a piston air pavilion and a common ventilation air pavilion.

3. The method for simulating FDS values in different fire scenes according to claim 2, wherein the piston wind booth has the following functions:

the piston wind pavilion is used for connecting tunnels in the section and reducing piston wind generated when vehicles enter the station.

4. A method of numerical simulation of FDS in different fire scenarios according to claim 3, characterized in that said common ventilation air booth is provided in said "L" station for taking care of all mechanical ventilation.

5. The method for numerical simulation of FDS in different fire scenarios according to claim 1, wherein the numerical simulation is performed by introducing the FDS:

a plurality of grid lap joints are adopted for the structural model of the L-shaped subway transfer station, and a model grid lap joint diagram is obtained;

setting combustion in the FDS as unsteady combustion by using a heat release rate model to obtain a relationship between a heat release rate and time:

Q＝αt ²

wherein Q is the rate of heat release; alpha is a growth coefficient; t is time;

and carrying out numerical simulation according to the model grid overlap graph and the relation between the heat release rate and time.

6. The method according to claim 5, wherein α determines the heat release rate of the fire during the growth phase of the fire, and is divided into four models, wherein the present application adopts an ultrafast type, i.e., α= 0.1878.

7. The method for FDS numerical simulation under different fire scenarios according to claim 1, wherein the different fire scenarios specifically include:

fire scene 1: the cigarette end ignites the burner to cause a fire;

fire scene 2: a circuit failure causes a fire;

fire scene 3: the gate circuit failure causes a fire.

8. The method for simulating FDS numerical values under different fire scenes according to claim 7, wherein the method for limiting fire under different fire scenes specifically comprises:

longitudinally comparing different fan matching schemes; the parameter of 'distance from the trend of the fire source' is introduced as an abscissa parameter for longitudinal comparison of the temperature and the concentration of carbon monoxide, and the parameter of 'area occupation ratio of a visibility region below 10 m' is introduced as an ordinate parameter for longitudinal comparison of the visibility.

Images