CN113312771B - Calculation method and application of limited wind speed of side key smoke exhaust of tunnel - Google Patents

Calculation method and application of limited wind speed of side key smoke exhaust of tunnel Download PDF

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CN113312771B
CN113312771B CN202110598123.XA CN202110598123A CN113312771B CN 113312771 B CN113312771 B CN 113312771B CN 202110598123 A CN202110598123 A CN 202110598123A CN 113312771 B CN113312771 B CN 113312771B
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姜学鹏
刘婵
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Wuhan University of Science and Engineering WUSE
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Abstract

The invention relates to a method for calculating limited wind speed of side key smoke exhaust of a tunnel and application thereof, comprising the following specific steps of: determining a limited wind speed ucDefining, determining influencing factors, establishing a limited wind speed ucA relationship to an influencing factor; determining basic dimension, and establishing limited wind speed ucA dimensional relation with the influencing factor; determining basic physical quantity, obtaining dimensionless items of influence factors according to the pi theorem, and deducing to obtain the limited wind speed ucThe dimensionless calculation formula of (1); obtaining the numerical value of the smoke backflow length L of the fire under different working conditions through numerical simulation, obtaining the limited wind speed through the smoke backflow length, drawing the simulation result into a scatter diagram, and determining the influence factors on the limited wind speed ucThe influence of (c); performing data fitting on the result to obtain the value of each unknown coefficient in the dimensionless relational expression, and further establishing the dimensionless limited wind speed ucThe calculation formula of (2). The method has the advantages of being simple, suitable for different tunnels, greatly influencing the efficient utilization of the smoke exhaust capacity of the tunnels and providing guidance for fire smoke control and fire rescue of the side key smoke exhaust tunnels.

Description

Calculation method and application of limited wind speed of side key smoke exhaust of tunnel
Technical Field
The invention relates to the technical field of tunnel fire smoke control, in particular to a calculation method and application of a limited wind speed of side key smoke exhaust of a tunnel.
Background
Fire is one of the greatest risks for tunnel operation. The tunnel has a long, narrow and closed characteristic, so that the tunnel has a unique space structure and fire characteristics compared with a common ground building. Once a fire disaster occurs in the tunnel, smoke cannot be discharged in time, people are very easy to suffocate or be poisoned, vehicles in the tunnel cannot drive away in time to form secondary damage, and serious disastrous accidents of group death and group injury are caused. The limited wind speed is controlled, so that the smoke exhaust capacity of the tunnel can be efficiently utilized, and the smoke is controlled within a certain range, so that people can be evacuated and rescued.
Limited wind speed u in tunnel fire scenecDefinition of (1): when the flue gas countercurrent length is insensitive to the flow velocity of the changed smoke outlet, the corresponding minimum longitudinal induced wind speed is called as the limited wind speed ucThe flue gas countercurrent length refers to the distance between the fire source and the smoke outlet in the tunnel traveling direction, as shown in FIG. 2, and the limited wind speed ucEnsure the flue gasThe proper wind speed of the longitudinal induced wind, which is not increased by the reduction of the flow speed of the smoke outlet, of the countercurrent length is a control index for controlling the non-diffusion and non-spreading of the smoke. The current research mainly explores a method for calculating the critical wind speed, the critical wind speed is the longitudinal wind speed which just enables the flue gas countercurrent length to be zero, the upstream of a fire source can be ensured to have no flue gas, but the critical wind speed is adopted to control the flue gas to spread, on one hand, the critical wind speed is theoretically larger than the limited wind speed, so the flue gas cannot be discharged to the nearest upstream smoke outlet; on the other hand, the prediction model of the critical wind speed of the fire in the side point type smoke discharging mode is related to the lateral dimensionless smoke discharging amount, the dimensionless fire source heat release rate and the distance between the dimensionless smoke discharging port and the fire source, so that the countercurrent of the smoke is controlled by the longitudinal wind speed predicted by the critical wind speed model and still influenced by the change of the smoke discharging amount.
At present, most of existing limited wind speed calculation methods are used for determining limited wind speed according to the ratio of the smoke backflow length to the tunnel height under the condition that a smoke exhaust port is located at the top of a tunnel, the smoke exhaust port in the tunnel in a side key smoke exhaust mode is located on the side wall of the tunnel, and compared with top smoke exhaust, the stress state and the motion state of smoke are changed at the moment, and a calculation method for limited wind speed of fire disasters of the tunnel in the side key smoke exhaust mode is not available at home and abroad.
Disclosure of Invention
The invention aims to solve the technical problem of providing a calculation method and application of limited wind speed of key smoke discharge fire on the side part of a tunnel, and aims to solve the technical problem.
The technical scheme for solving the technical problems is as follows:
a method for calculating limited wind speed of side key smoke discharge fire of a tunnel comprises the following specific steps:
s1: determining limited wind speed u in tunnel fire scenecEstablishing said limited wind speed ucThe relationship to the influencing factor: f (u)c,Q,ρ0,CP,T0,g,HD)＝0；
The influencing factors comprise the heat release rate Q and the air density rho of the fire source0Constant pressure specific heat of air CpAir temperature T0Acceleration of gravity g, tunnel height HDThe number n of physical parameters is 7 and the heat release rate Q of the fire source is in kg.m2/s3Air density ρ0Unit of (b) is kg/m3Constant pressure specific heat of air CpHas the unit of m2/s2K, air temperature T0Has the unit of K and the unit of the gravity acceleration g is m/s2Height H of tunnelDThe unit of (a) is m;
s2: determining basic dimension according to the unit of the influence factor, representing the influence factor by the basic dimension, and establishing the limited wind speed ucA dimensional relationship to the influencing factor;
s3: determining basic dimension according to the unit of the influence factor, representing the influence factor by the basic dimension, and establishing the limited wind speed ucA dimensional relationship to the influencing factor;
in the step S3, the basic dimensions include mass M, time T, length L, and temperature T, and the basic dimension number η is 4;
in the step S3, the limited wind speed ucThe relationship with the influencing factor is as follows:
f(Lt-1,ML2t-3,ML-3,L2t-2T-1,T,Lt-2,L)＝0；
s4: determining the basic physical quantity of the influence factors, obtaining the number of dimensionless parameters of the influence factors as n-eta-3 according to the pi theorem, and selecting the variable H directly related to the length L according to the selection principle of the circulation quantity in the pi theoremDSelecting a variable T directly related to the temperature T0Selecting a variable g directly related to the time t, and selecting a variable ρ directly related to the mass M0Using the 4 circulation quantities and all other parameters in other n-eta physical parameters to form dimensionless parameter pi1、Π2、Π3Converting the relational expression in the step S3 into a dimensionless relational expression, and then obtaining the limited wind speed ucThe dimensionless calculation formula of (1);
in the step S4, non-dimensional parameter Π of the influencing factor1、Π2、Π3Comprises the following steps:
Figure GDA0003574147540000031
the limited wind speed ucThe dimensionless formula of calculation is:
Figure GDA0003574147540000032
namely, it is
Figure GDA0003574147540000033
uc *Is dimensionless wind speed, Q**Is a dimensionless power;
s5: FDS numerical simulation part: establishing a scaled geometric model of the tunnel, setting a virtual fire source as propane combustion, simulating different fire source heat release rates, setting the smoke outlet flow velocity v to gradually increase from small to large to obtain different smoke countercurrent lengths L fitted by FDS software, and when the trend that the smoke countercurrent length L decreases along with the increase of the smoke outlet flow velocity v becomes slow, the induced wind speed generated by the smoke outlet flow velocity v in the tunnel at the moment is the actual limited wind speed u under the fire conditioncAnd measuring and recording the limited wind speed ucThe method comprises the following steps of (1) providing two smoke outlets along the longitudinal direction on one side wall in a tunnel, arranging a fire source between the two smoke outlets, enabling the fire source to be located on the central line of a middle lane of a unidirectional three-lane, adopting steady fire or t square fire, uniformly arranging a plurality of temperature measuring points in the reduced-scale geometric model along the longitudinal direction of the top wall at intervals, and extracting the limited wind speed u fitted by FDS softwarecThe cross section of the reduced scale geometric model is provided with a plurality of flow velocity measuring points, and the limited wind speed u fitted by FDS software is extractedc；
S6: and (3) solid simulation: establishing a scaled geometric model of the tunnel, and setting different fire conditions in the scaled geometric model, including using fuelThe burner is used as a fire source, different fire source heat release rates are simulated, different smoke outlet flow velocities v are set and used for controlling different smoke backflow lengths L, the longitudinal wind speed is changed under the condition of the fire, the time when the smoke backflow length is not influenced by the smoke outlet flow velocity is observed, and the actual limited wind speed u at the time is measuredcAnd measuring and recording the limited wind speed ucThe tunnel is internally provided with two smoke outlets along the longitudinal direction, a fire source is arranged between the two smoke outlets and is positioned on the central line of a middle lane of the unidirectional three lanes, a plurality of temperature sensors are uniformly arranged in the reduced scale geometric model along the longitudinal direction of the top wall at intervals, and the limited wind speed u is measuredcThe wind speed meter is arranged on one section of the reduced scale geometric model to measure the limited wind speed uc；
S7: the limited wind speed u under different fire conditions is obtained according to the steps S5 and S6cAnd the numerical values of the influencing factors, respectively drawing the simulation results into scatter diagrams, and if the fitted line graphs are similar, selecting the scatter diagram obtained in the step 5 to fit data;
s8: performing data fitting on the resulting scattergrams of the scattergram obtained in step S5 to obtain unknown coefficients k in the dimensionless calculation formula in step S42Taking the value of (a), and taking the obtained uc *＝k1Q**Drawing a scatter diagram and performing data fitting to obtain the unknown coefficient k in the dimensionless calculation formula in the step S41To establish said limited wind speed u in a dimensionless mannercThe calculation formula of (2):
Figure GDA0003574147540000041
on the basis of the technical scheme, the invention can be further improved as follows.
Further, the application of the method for calculating the limited wind speed of the side key smoke exhaust of the tunnel comprises the following steps:
step 1, according to a calculation formula L of the reverse flow length of the smoke of the tunnel side-direction key smoke discharge fire*＝76(v*)-1.67(Q*)0.56(l*)-0.23And the acquired fire information: q, rho0、Cp、T0、g、HD、L、l、WDCalculating the smoke countercurrent length L, L of the tunnel in which the fire occurs*＝L/HD，l*＝l/HD，Q*＝Q/(HD 3/2g1/2WDT0Cpρ0)，v*Is a dimensionless smoke evacuation rate, wherein WDThe tunnel width, v the smoke outlet flow speed and l the distance from the smoke outlet to the fire source;
step 2, if L is larger than L, calculating the limited wind speed u of the side key smoke discharge of the tunnelcAnd the fans of the station halls at the two ends of the tunnel accident section simultaneously exhaust air to the accident section to form longitudinal air, and the flow velocity of the longitudinal air is greater than ucUntil the temperature sensor or CO alarm in the tunnel detects that the flue gas counter-flow length L is equal to L, then the flow speed of the longitudinal wind is reduced to uc；
And 3, if the L of the wind discharged by the fans of the station halls at the two ends of the accident section of the tunnel is less than L, reducing the flow velocity of longitudinal wind to be less than ucUntil the fume counterflow length L equals to L, then the flow speed of longitudinal wind is raised to uc。
Compared with the prior art, the invention has the beneficial effects that:
the method is simple, parameters can be set according to the actual conditions of the tunnel, and the method is suitable for different tunnels adopting side key smoke exhaust modes. The method is scientific and effective, applies pi theorem and dimension analysis, and has more theoretical basis. There is no calculation method for the limited wind speed in the side key smoke exhaust mode. The method considers the main influence factors of the heat release rate of the fire source in the process of dimension relation derivation, and the obtained result has innovation and practical engineering significance. The limited wind speed of the tunnel fire has great influence on the efficient utilization of the tunnel smoke discharge capacity, and guidance can be provided for the fire rescue of the tunnel fire under the condition of side key smoke discharge through predicting and calculating the limited wind speed of the tunnel fire.
Drawings
FIG. 1 is a flowchart of a method for calculating a limited wind speed of side-focused smoke evacuation of a tunnel according to the present invention;
FIG. 2 is a schematic view of a limited wind speed in a side-focused smoke evacuation mode according to the present invention;
FIG. 3 is a schematic view of a reduced-size model tunnel built in the present invention;
FIG. 4 is a graph of the limited wind speed versus the heat release rate of the fire source in the present invention;
FIG. 5 is a diagram of the result of a numerical simulation of a limited wind speed according to the present invention;
FIG. 6 is a cross-sectional view of the FDS software at the Velocity measurement point to directly measure induced wind Velocity.
In the drawings, the components represented by the respective reference numerals are listed below:
1. the tunnel comprises a one-way three-lane tunnel, 2, a smoke exhaust port, 3, a temperature measuring point, 4 and a flow velocity measuring point.
Detailed Description
The principles and features of this invention are described in connection with the drawings and the detailed description of the invention, which are set forth below as examples to illustrate the invention and not to limit the scope of the invention.
As shown in fig. 1 to 5, the invention provides a method for calculating limited wind speed of side-focused smoke discharge fire of a tunnel, which comprises the following specific steps:
s1: determining limited wind speed u in tunnel fire scenecDefinition of (1): when the flue gas countercurrent length is insensitive to the flow velocity of the changed smoke outlet, the corresponding minimum longitudinal induced wind speed is called as the limited wind speed ucThe flue gas countercurrent length refers to the distance between the fire source and the smoke outlet in the tunnel advancing direction.
S2: determining limited wind speed u in tunnel fire scenecEstablishing said limited wind speed ucThe relationship to the influencing factor: f (u)c,Q,ρ0,CP,T0,g,HD)＝0；
The influencing factors comprise the heat release rate Q of the fire source and the air density rho0Constant pressure specific heat of air CpAir temperature T0Acceleration of gravity g, tunnel height HDThe number n of physical parameters is 7 and the heat release rate Q of the fire source is in kg.m2/s3Air sealDegree rho0In units of kg/m3Constant pressure specific heat of air CpHas the unit of m2/s2K, air temperature T0Has the unit of K and the unit of the gravity acceleration g is m/s2Height H of tunnelDThe unit of (d) is m.
S3: determining basic dimension according to the unit of the influence factor, representing the influence factor by the basic dimension, and establishing the limited wind speed ucA dimensional relationship to the influencing factor;
in the step S3, the basic dimensions include mass M, time T, length L, and temperature T, and the basic dimension number η is 4;
in the step S3, the limited wind speed ucThe relationship with the influencing factor is as follows:
f(Lt-1,ML2t-3,ML-3,L2t-2T-1,T,Lt-2,L)＝0；
s4: determining the basic physical quantity of the influence factors, obtaining the number of dimensionless parameters of the influence factors as n-eta-3 according to the pi theorem, and selecting the variable H directly related to the length L according to the selection principle of the circulation quantity in the pi theoremDSelecting a variable T directly related to the temperature T0Selecting the variable g directly related to the time t, and selecting the variable ρ directly related to the mass M0Using the 4 circulation quantities and all other parameters in other n-eta physical parameters to form dimensionless parameter pi as circulation quantity1、Π2、Π3Converting the relational expression in the step S3 into a dimensionless relational expression, and then obtaining the limited wind speed ucThe dimensionless calculation formula of (1);
in the step S4, non-dimensional parameter Π of the influencing factor1、Π2、Π3Comprises the following steps:
Figure GDA0003574147540000071
the limited wind speed ucDimensionless computing equation ofThe formula is as follows:
Figure GDA0003574147540000072
namely, it is
Figure GDA0003574147540000081
uc *Is dimensionless wind speed, Q**Is a dimensionless power;
s5: FDS numerical simulation part: and establishing a scaled geometric model of the tunnel, setting a virtual fire source for propane combustion, and simulating different heat release rates of the fire source. The size of the smoke outlet is 0.3m multiplied by 0.1m, the flow velocity v of the smoke outlet is gradually increased from small to large to obtain different smoke countercurrent lengths L fitted by FDS software, and when the trend that the smoke countercurrent length L is reduced along with the increasing of the flow velocity v of the smoke outlet becomes slow, the induced wind speed generated by the flow velocity v of the smoke outlet in the tunnel at the moment is the actual limited wind speed u under the fire conditioncAnd measuring and recording the limited wind speed ucThe scaled geometric model of the tunnel is as follows, 1:10 reduced size, length x width x height 50m x 1.1m x 0.45 m; two smoke outlets 2 are arranged on one side wall in the unidirectional three-lane tunnel 1 along the longitudinal direction, a fire source is arranged between the two smoke outlets, the fire source is positioned on the central line of a middle lane of the unidirectional three lanes, steady fire or t square fire is adopted, and the size is 0.6m multiplied by 0.2 m; the power of the fire source is 9.5-94.9 kW, the corresponding full-size fire source heat release rate is 3-30 MW, a plurality of temperature measuring points are uniformly arranged in the reduced scale geometric model at intervals along the longitudinal direction of the top wall, and the limited wind speed u fitted by FDS software is extractedcThe cross section of the reduced scale geometric model is provided with a plurality of flow velocity measuring points, and the limited wind speed u fitted by FDS software is extractedc；
S5: entity experiment part: the method comprises the steps of establishing a reduced scale geometric model of the tunnel, setting different fire conditions in the reduced scale geometric model, and simulating different heat release rates of the fire source by using a burner as the fire source. The size of the smoke outlet is 0.3m multiplied by 0.1m, and different flow velocities v of the smoke outlet are set and used for controlling different smoke outletsThe smoke gas countercurrent length L is changed under the fire condition, the longitudinal wind speed is changed, the time when the smoke gas countercurrent length is not influenced by the flow speed of the smoke outlet is observed, and the actual limited wind speed u at the time is measuredcAnd measuring and recording the limited wind speed ucThe scaled geometric model of the tunnel is as follows: 10 reduced size, length x width x height 10m x 1.1m x 0.45 m; two smoke outlets 2 are arranged on one side wall in the unidirectional three-lane tunnel 1 along the longitudinal direction, a fire source is arranged between the two smoke outlets, the fire source is positioned on the central line of a middle lane of the unidirectional three lanes, and the length, the width and the size of the fire source are multiplied by 15cm and 15 cm; the power of the fire source is 9.5-94.9 kW, and the corresponding full-size heat release rate of the fire source is 3-30 MW. A plurality of temperature sensors are uniformly installed at intervals in the length-wise direction of the top wall in the reduced scale geometric model to measure the limited wind speed ucThe wind speed meter is arranged on one section of the reduced scale geometric model to measure the limited wind speed uc；
S6: the limited wind speed u under different fire conditions is obtained according to the step S5cAnd the numerical values of the influencing factors, and drawing the simulation result into a scatter diagram;
s7: performing non-linear fitting on the resulting scattergrams of all scattergrams to obtain each unknown coefficient k in the dimensionless calculation formula in the step S41、k2To establish said limited wind speed u in a dimensionless mannercThe calculation formula of (2):
Figure GDA0003574147540000091
the above fire dynamics simulation software (FDS) is prior art.
In step S5, the FDS numerical simulation section, the unidirectional three-lane tunnel 1 is 1:10 reduced in size length × width × height 50m × 1.1m × 0.45 m; two smoke outlets 2 are arranged on one side wall in the unidirectional three-lane tunnel 1, a plurality of temperature measuring points 3 are uniformly arranged on the inner top wall of the unidirectional three-lane tunnel at intervals, and a plurality of flow velocity measuring points 4 are arranged on the section of a certain position of the tunnel.
In step S5, in the physical experiment part, the unidirectional three-lane tunnel 1 is 1:10 reduced in size, length × width × height, 10m × 1.1m × 0.45 m; two smoke outlets 2 are arranged on one side wall in a unidirectional three-lane tunnel 1, a plurality of temperature measuring points 3 are uniformly arranged on the inner top wall of the unidirectional three-lane tunnel at intervals, a section of a certain position of the tunnel is provided with a plurality of flow velocity measuring points 4, each temperature measuring point 3 is provided with a k-type thermocouple with the diameter of 1mm and the probe of 0.1m in a manner that can be thought by a person skilled in the art, each thermocouple sensor is connected with a 32-channel paperless recorder through a circuit, the temperature sensor detects the temperature of the corresponding temperature measuring point 3 and sends a corresponding temperature signal to a controller, and the controller receives and stores the corresponding temperature signal. Each flow velocity measuring point 4 is provided with a flow velocity measuring point in a manner that can be thought by those skilled in the art, a hot wire anemometer with the model number (Anemomaster KA23) is adopted to detect the wind velocity at the corresponding flow velocity measuring point 4, and a corresponding wind velocity signal is sent to the controller, and the controller receives and stores the corresponding flow velocity signal. The controller, the temperature sensor and the wind speed sensor all adopt the prior art, and control circuits among the temperature sensors, the wind speed sensors and the controller are also in the prior art. On the basis of the above conditions, values of the heat release rate of the fire source and the flow rate of the smoke outlet are sequentially changed to form different smoke backflow lengths, under the fire condition of each heat release rate of the fire source, the flow rate of the smoke outlet and the smoke backflow length, the longitudinal wind speed is changed to observe and measure to obtain the limited wind speed values under different fire conditions, and the specific simulation result is shown in table 1:
table 1 FDS numerical simulation results:
Figure GDA0003574147540000101
the simulation procedure is exemplified by the first group: when the first group Q is 9.5kW, the changed flow speed of the smoke outlet is 3m/s to 11m/s, and finally the smoke countercurrent length is reduced from 5.95m to 0.75m, and the reduction process finds that when the smoke countercurrent length reaches 1.05m/s, the flow speed of the smoke outlet is increased, and the smoke countercurrent length L is reduced slowly, so that the smoke countercurrent length L becomes insensitive. The flow Velocity of the smoke outlet corresponding to the 1.05m is 8m/s, induced wind speeds are generated at two ends of the accident tunnel due to the fact that the flow Velocity of the smoke outlet is 8m/s, the value of the induced wind speed is the limited wind speed corresponding to Q being 9.5kW, the induced wind speed value of 0.51m/s is directly measured through a Velocity measuring point of the FDS, and the measuring point is shown in figure 6. The simulation process for the remaining groups is similar.
Table 2 results of the physical experiments:
Figure GDA0003574147540000111
because the experiment condition is limited, the actual tunnel is not long enough, only a plurality of groups of experiments with small heat release rate of the fire source can be carried out, and the maximum fan power of the experiment can only lead the flow velocity of the smoke outlet to reach 11 m/s. So the whole experimental data is less. And in winter, the difference between the numerical simulation and the environmental temperature of a laboratory is large, and the final experiment result has errors with the FDS simulation result. The error of the first group of experimental simulation is small, and the experimental trend of the other groups is the same. This experiment verifies the correctness of the results of the FDS simulation. Drawing a scatter diagram according to the numerical simulation results of the tables 1 and 2 to obtain the limited wind speed ucWith respect to the variation relationship of each influencing factor, specifically as shown in fig. 4, the FDS simulation result and the entity experiment result have the same trend, and thus the obtained functions are similar:
FIG. 4 shows a limited wind speed ucThe relation graph of the heat release rate Q of the fire source can be obtained from the graph of FIG. 4cThe heat release rate Q of the fire source is increased and then tends to be stable;
data fitting of FIG. 4 with 0rigin software yields uc *And Q**Has the function relationship of
Figure GDA0003574147540000112
I.e. 0 < Q**When k is less than or equal to 0.52, k21 is ═ 1; when Q is**When > 0.52, k2＝0；
To determine the coefficient k in the above formula1And k1Value of "" A, B, D, Ec *＝k1Q**The calculated values of (A) are plotted in FIG. 5. it can be seen from FIG. 5 that the numerical simulation results all fluctuate around a straight line, k1Is 0.34, and the correlation coefficient is 0.99，k1' is 0.4. Shows the dimensionless limited wind speed uc *The numerical calculation formula of (a) and the numerical simulation result of (b) are consistent. Will k1Substituting 0.34 into the above formula can obtain the dimensionless limited wind speed uc *The calculation formula of (2) is as follows:
Figure GDA0003574147540000121
in the formula: u. ofc *: dimensionless restricted wind speed, Q**: dimensionless fire source heat release rate.
By the method, the numerical value of the limited wind speed under different fire source heat release rates can be quickly obtained.
The invention has the beneficial effects that: parameters can be set according to the actual conditions of the tunnel, and the tunnel smoke exhausting device is suitable for different tunnels adopting side key smoke exhausting modes. The method is scientific and effective, applies theorems and dimension analysis and has a theoretical basis. Dimensionless limited wind speed u for fire without tunnelc *The method takes the most important influence factors into consideration in the process of dimension relation derivation, and the obtained result has innovation and practical engineering significance. The limited wind speed of the tunnel fire has great influence on the efficient utilization of the tunnel smoke discharge capacity, and guidance can be provided for the fire rescue of the tunnel fire under the condition of side key smoke discharge through predicting and calculating the limited wind speed of the tunnel fire.
An application of a calculation method of a limited wind speed of side key smoke exhaust of a tunnel,
step 1, according to a calculation formula L of the tunnel side key smoke discharge fire smoke countercurrent length of patent CN111027176A*＝76(v*)-1.67(Q*)0.56(l*)-0.23And the acquired fire information: q, rho0、Cp、T0、g、HD、L、l、WDCalculating the smoke countercurrent length L, L of the tunnel in which the fire occurs*＝L/HD，l*＝l/HD，Q*＝Q/(HD 3/2g1/2WDT0Cpρ0)，v*Is dimensionless smoke discharge rate, v*＝v/(HD 1/2g1/2) Wherein W isDThe tunnel width, v the smoke outlet flow speed and l the distance from the smoke outlet to the fire source;
step 2, if L is larger than L, calculating the limited wind speed u of the side key smoke discharge of the tunnelcAnd the fans of the station halls at the two ends of the accident section of the tunnel simultaneously exhaust air to the accident section to form longitudinal wind, and the flow velocity of the longitudinal wind is greater than ucUntil the temperature sensor or CO alarm in the tunnel detects that the length L of the flue gas counter flow is equal to L, then the flow speed of the longitudinal wind is reduced to uc；
And 3, if the L of the wind discharged by the fans of the station halls at the two ends of the accident section of the tunnel is less than L, reducing the flow velocity of longitudinal wind to be less than ucUntil the fume counterflow length L equals to L, then the flow speed of longitudinal wind is raised to uc。
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (2)

1. A method for calculating limited wind speed of side key smoke discharge fire of a tunnel comprises the following specific steps:
s1: determining limited wind speed u in tunnel fire scenecEstablishing said limited wind speed ucThe relationship to the influencing factor: f (u)c,Q,ρ0,CP,T0,g,HD)＝0；
The influencing factors comprise the heat release rate Q and the air density rho of the fire source0Constant pressure specific heat of air CpAir temperature T0Acceleration of gravity g, tunnel height HDThe number n of physical parameters is 7 and the heat release rate Q of the fire source is in kg.m2/s3Air density ρ0Unit of (b) is kg/m3Constant pressure specific heat of air CpHas the unit of m2/s2K, air temperature T0Has the unit of K and weightThe unit of the acceleration g of the force is m/s2Height H of tunnelDThe unit of (a) is m;
s2: determining basic dimension according to the unit of the influence factor, representing the influence factor by the basic dimension, and establishing the limited wind speed ucA dimensional relationship to the influencing factor;
s3: the basic dimension comprises mass M, time T, length L and temperature T, and the basic dimension number eta is 4;
in the step S2, the limited wind speed ucThe relationship with the influencing factor is as follows:
f(Lt-1,ML2t-3,ML-3,L2t-2T-1,T,Lt-2,L)＝0；
s4: determining the basic physical quantity of the influence factors, obtaining the number of dimensionless parameters of the influence factors as n-eta-3 according to the pi theorem, and selecting the variable H directly related to the length L according to the selection principle of the circulation quantity in the pi theoremDSelecting a variable T directly related to the temperature T0Selecting a variable g directly related to the time t, and selecting a variable ρ directly related to the mass M0Using the 4 circulation quantities and all other parameters in other n-eta physical parameters to form dimensionless parameter pi1、Π2、Π3Converting the relational expression in the step S3 into a dimensionless relational expression, and then obtaining the limited wind speed ucThe dimensionless calculation formula of (1);
in the step S4, non-dimensional parameter Π of the influencing factor1、Π2、Π3Comprises the following steps:
Figure FDA0003574147530000021
the limited wind speed ucThe dimensionless formula of calculation is:
Figure FDA0003574147530000022
namely, it is
Figure FDA0003574147530000023
uc *Is dimensionless wind speed, Q**Is a dimensionless power;
s5: FDS numerical simulation part: establishing a scaled geometric model of the tunnel, setting a virtual fire source as propane combustion, simulating different fire source heat release rates, setting the smoke outlet flow velocity v to gradually increase from small to large to obtain different smoke countercurrent lengths L fitted by FDS software, and when the trend that the smoke countercurrent length L decreases along with the increase of the smoke outlet flow velocity v becomes slow, the induced wind speed generated by the smoke outlet flow velocity v in the tunnel at the moment is the actual limited wind speed u under the fire conditioncAnd measuring and recording the limited wind speed ucThe method comprises the following steps of (1) providing two smoke outlets along the longitudinal direction on one side wall in a tunnel, arranging a fire source between the two smoke outlets, enabling the fire source to be located on the central line of a middle lane of a unidirectional three-lane, adopting steady fire or t square fire, uniformly arranging a plurality of temperature measuring points in the reduced-scale geometric model along the longitudinal direction of the top wall at intervals, and extracting the limited wind speed u fitted by FDS softwarecThe cross section of the reduced scale geometric model is provided with a plurality of flow velocity measuring points, and the limited wind speed u fitted by FDS software is extractedc；
S6: and (3) solid simulation: establishing a tunnel reduced scale geometric model, setting different fire conditions in the reduced scale geometric model, including using a burner as a fire source, simulating different fire source heat release rates, setting different exhaust port flow velocities v, controlling different flue gas countercurrent lengths L, changing the longitudinal wind speed under the fire condition, observing the time when the flue gas countercurrent length is not influenced by the exhaust port flow velocity, and measuring the actual limited wind speed u at the timecAnd measuring and recording the limited wind speed ucThe tunnel is internally provided with two smoke outlets along the longitudinal direction on one side wall, a fire source is arranged between the two smoke outlets and is positioned on the central line of the middle lane of the unidirectional three lanes, and the scale is geometrically reducedA plurality of temperature sensors are uniformly arranged in the model at intervals along the lengthwise direction of the top wall, and the limited wind speed u is measuredcThe wind speed meter is arranged on one section of the reduced scale geometric model to measure the limited wind speed uc；
S7: the limited wind speed u under different fire conditions is obtained according to the steps S5 and S6cAnd the numerical values of the influencing factors, respectively drawing the simulation results into scatter diagrams, and if the fitted line graphs are similar, selecting the scatter diagram obtained in the step 5 to fit data;
s8: performing data fitting on the result scatter points of all the scatter diagrams obtained in the step (5) to obtain an unknown coefficient k in the dimensionless calculation formula in the step (S4)2Is selected from the group consisting of
Figure FDA0003574147530000031
Drawing a scatter diagram and performing data fitting to obtain the unknown coefficient k in the dimensionless calculation formula in the step S41To establish said limited wind speed u in a dimensionless mannercThe calculation formula of (c):
Figure FDA0003574147530000032
2. the application of the method for calculating the limited wind speed of side-focused smoke exhaust of the tunnel according to claim 1 comprises the following steps:
step 1, according to a calculation formula L of the reverse flow length of the smoke of the tunnel side-direction key smoke discharge fire*＝76(v*)-1.67(Q*)0.56(l*)-0.23And the acquired fire information: q, rho0、Cp、T0、g、HD、L、l、WDCalculating the smoke countercurrent length L, L of the tunnel in which the fire occurs*＝L/HD，l*＝l/HD，Q*＝Q/(HD 3/2g1/2WDT0Cpρ0)，v*Is a dimensionless smoke evacuation rate, wherein WDThe tunnel width, v the smoke outlet flow speed and l the distance from the smoke outlet to the fire source;
step 2, if L is larger than L, calculating the limited wind speed u of the side key smoke exhaust of the tunnelcAnd the fans of the station halls at the two ends of the accident section of the tunnel simultaneously exhaust air to the accident section to form longitudinal wind, and the flow velocity of the longitudinal wind is greater than ucUntil the temperature sensor or CO alarm in the tunnel detects that the length L of the flue gas counter flow is equal to L, then the flow speed of the longitudinal wind is reduced to uc；
And 3, if the L of the wind discharged by the fans of the station halls at the two ends of the accident section of the tunnel is less than L, reducing the flow velocity of longitudinal wind to be less than ucUntil the fume counterflow length L equals to L, then the flow speed of longitudinal wind is raised to uc。
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