CN116663104A - Design method for critical large-spacing range of key smoke outlets of tunnel - Google Patents

Design method for critical large-spacing range of key smoke outlets of tunnel Download PDF

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CN116663104A
CN116663104A CN202310548289.XA CN202310548289A CN116663104A CN 116663104 A CN116663104 A CN 116663104A CN 202310548289 A CN202310548289 A CN 202310548289A CN 116663104 A CN116663104 A CN 116663104A
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tunnel
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姜学鹏
张子迪
刘琪
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Wuhan University of Science and Engineering WUSE
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Abstract

The application discloses a method for designing critical large-spacing range of key smoke outlets of tunnels, which comprises the following steps: step 1, determining the safety thickness of a smoke layer, step 2, when no smoke discharging effect exists in a tunnel, enabling fire smoke to be free to travel and delay, and knowing the thickness h of the smoke layer L Deducing and calculating to obtain the distance L from the fire source; step 3, when the tunnel has key smoke discharging effect, the fire smoke is delayed by smoke discharging suction force, and the thickness h of the smoke layer is known L* Deriving and calculating to obtain the distance L from the fire source * The method comprises the steps of carrying out a first treatment on the surface of the Step 4, determining the minimum critical large distance D of key smoke outlets 1 Maximum critical large distance D 2 And obtaining the critical large-spacing range of the key smoke outlets of the tunnel. The application calculates the prescriptionThe method is simple, can quickly obtain critical large-distance range of key smoke outlets according to different tunnel sizes, has better practical applicability, and provides theoretical support for smoke control of key smoke outlets of tunnels and personnel evacuation safety.

Description

Design method for critical large-spacing range of key smoke outlets of tunnel
Technical Field
The application relates to the technical field of tunnel fire smoke control, in particular to a method for designing critical large-spacing range of key smoke outlets of tunnels.
Background
Due to the long and narrow and closed nature of tunnels, tunnels have unique spatial structures and fire properties compared to other buildings. The tunnel fire seriously threatens the life safety of drivers, passengers and fire-fighting rescue workers in the tunnel, and meanwhile, the tunnel fire also can damage the tunnel structure to cause secondary accidents, so that larger life and property losses are caused. The key smoke discharging mode is widely applied to highway tunnels, but the current key smoke discharging mode has small smoke outlet spacing, a plurality of smoke discharging quantity and large air leakage quantity, so that the construction and operation costs are high. Therefore, on the premise of ensuring the safety of the personnel evacuation environment, the reduction of the tunnel construction and operation cost is extremely important.
The key smoke discharging mode is to accurately control a smoke discharging valve of a smoke discharging air pipe, and smoke discharging is organized by utilizing a smoke outlet nearest to a fire accident point of a traffic tunnel, so that the smoke discharging efficiency of a smoke discharging system is greatly improved. The large spacing is the key smoke outlet spacing breaks through the limit of the conventional spacing 60m, and fire smoke is discharged timely and effectively under the condition that the safety of personnel evacuation environment is ensured.
In the current stage of standardization and actual tunnel engineering, a conventional key smoke discharging control mode with the smoke outlet spacing not exceeding 60m is mostly adopted, and the defects of small spacing, high cost, serious air leakage due to a plurality of smoke outlets and the like exist. In order to reduce the tunnel construction and operation cost, the limit of 60m smoke outlet spacing is broken through on the premise of ensuring the personnel evacuation environment safety, the large spacing range of the critical smoke outlets is theoretically analyzed and researched, and theoretical support is provided for the key smoke discharge fire smoke control of the tunnel and the personnel evacuation safety.
Disclosure of Invention
In order to solve the problems existing in the background technology, the application aims to provide a design method for a critical large-spacing range of key smoke outlets of tunnels, which can be used for designing and calculating a smoke outlet system by adopting the calculation method for the critical large-spacing range provided by the application for a plurality of tunnels with longer length and larger construction cost.
In order to achieve the above purpose, the present application provides the following technical solutions: a design method for critical large-spacing range of key smoke outlets of tunnels comprises the following steps:
step 1, determining the allowable height of smoke in a tunnel under the condition of ensuring the safety of a personnel evacuation environment, and obtaining the allowable thickness h of a smoke layer according to the design size of the tunnel L ＝h L* ；
Step 2, calculating that no smoke discharging effect exists in the tunnel according to the relation between the thickness of the smoke layer and the distance between the fire sources and the tunnel size, wherein the thickness of the smoke layer is h under the condition that fire smoke freely spreads L The distance L from the fire source is 2L as the minimum critical large distance D of the key smoke outlet 1 ；
Step 3, calculating the thickness h of the smoke layer under the condition that the smoke of the fire is spread by the smoke suction force under the key smoke discharging effect in the tunnel according to the relation between the thickness of the smoke layer and the distance between the fire source and the tunnel size and the power of the fire source L* Distance L from the fire source * Will be 2L * As the maximum critical large spacing D of key smoke outlet 2 ；
Step 4, obtaining critical large-spacing range D, D of key smoke outlet of tunnel 1 ≤D≤D 2 。
In the method for designing the critical large-distance range of the key smoke outlets of the tunnel, in the step 1, the conditions for ensuring the safety of the personnel evacuation environment are as follows:
the visibility of the smoke in the tunnel at the allowable height should meet V z More than or equal to 10m, and the temperature should satisfy T z The temperature is less than or equal to 60 ℃, and the allowable height of flue gas in the tunnel is 2m.
In the method for designing the critical large-distance range of the key smoke outlet of the tunnel, in the step 2, the relation between the thickness of the smoke layer and the distance of the fire source is as follows:
in the smoke layer thickness h L ＝(H-2)，D 1 Represents the minimum critical large distance of key smoke outlets, L represents the free-propagation time-delay fire sourceDistance, W, represents tunnel width and H represents tunnel height.
Optionally, in the step 2, when the free propagation of the fire smoke is delayed, the distance L from the fire source is:
wherein L represents the distance from the fire source of free propagation time, B represents the temperature attenuation coefficient of free propagation time, h L The thickness of the smoke layer during free propagation is shown in FIG. 1, W represents the tunnel width, ρ a Represents the air density at ambient temperature, T a Represents the ambient temperature, T L The smoke temperature at the distance L from the fire source of free propagation time is represented, g represents the acceleration of gravity, beta represents the entrainment coefficient of smoke, and h 0 The smoke layer thickness near the fire source is represented, gamma represents the mass flow rate attenuation coefficient, and H represents the tunnel height.
In the step 3, the relation between the thickness of the smoke layer and the distance of the fire source is as follows:
in the smoke layer thickness h L ＝(H-2)，D 2 Represents the maximum critical large distance of key smoke outlets, L * The distance from the fire source when the key smoke discharging effect is achieved is represented, W represents the tunnel width, H represents the tunnel height, and Q represents the fire source power.
Optionally, in the step 3, when the smoke is discharged with emphasis, the distance from the fire source is L * The method comprises the following steps:
wherein L is * B' represents the temperature attenuation coefficient and h when the key smoke discharging function is provided L* The thickness of the smoke layer when the key smoke discharging effect is shown in FIG. 2, W represents the tunnel width and ρ a Represents the air density at ambient temperature, T a Represents the ambient temperature, T L* Indicating the distance L from the fire source when the key smoke discharging function is provided * The temperature of the flue gas, g represents the acceleration of gravity, beta represents the entrainment coefficient of the flue gas, h 0 Represents the thickness of the smoke layer near the fire source, gamma represents the attenuation coefficient of the mass flow rate, H represents the tunnel height, Q represents the power of the fire source, T e Indicating the temperature of the exhaust port, V e Indicating the amount of exhaust smoke.
Compared with the prior art, the application has the beneficial effects that: the method is simple, the verification comparison mode is reasonable, the critical large-spacing range of the key smoke outlet can be obtained rapidly according to different tunnel sizes, the method for calculating the critical large-spacing range can be adopted for designing and calculating the smoke discharging system, and the method is suitable for tunnels with different sizes in the key smoke discharging mode. According to the method, the critical large-spacing range of the key smoke outlet of the tunnel is obtained through theoretical analysis, then the critical large-spacing range is compared with a numerical simulation calculation result, the accuracy of a theoretical calculation formula is verified, the actual applicability of the critical large-spacing range calculation method of the key smoke outlet of the tunnel is highlighted, the calculated result has innovation and actual engineering significance, and theoretical support is provided for key smoke discharge fire smoke control and personnel evacuation safety of the tunnel.
Description of the drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute an undue limitation. In the accompanying table:
FIG. 1 is a schematic diagram of the development of free-spread smoke in a tunnel according to the present application;
FIG. 2 is a schematic diagram of smoke development under the effect of focused smoke evacuation in a tunnel according to the application;
FIG. 3 is a schematic diagram of a tunnel model constructed in accordance with the present application;
table 1 is a table of operating conditions under different tunnel parameters according to the present application;
table 2 shows the critical large spacing range of the smoke outlet under different parameters of the application;
Detailed Description
The principles and features of the present application are described below with reference to the drawings and specific embodiments, the examples being provided for illustration only and not for the purpose of limiting the application.
The calculation method of the critical large-distance range of the key smoke outlet of the tunnel, referring to fig. 1 and 2, comprises the following steps:
step 1, when no smoke exhausting effect exists in the tunnel, free propagation of fire smoke is delayed, and the thickness h of a smoke layer is known L Deducing and calculating to obtain the distance L from the fire source; the method comprises the following steps:
the flue gas development in the tunnel can be divided into four stages (fig. 1):
1: plume freely rises and hits ceiling
2: radial spread
3: overgrowth from radial to longitudinal
4: one-dimensional horizontal spreading;
as shown in fig. 1, the thickness of the smoke layer at a distance x=l from the fire source is h L The mass flow rate of the flue gas is m L . Compared with the actual tunnel length, the length of the flue gas development stages 1-3 is shorter, the total mass flow rate of the flue gas development stages 1-3 can be regarded as a whole, and the longitudinal length is negligible.
m 1 For symmetrical plume entrainment, the mass flow rate of the flue gas in stage 1 can be estimated from the formula in article Entrainment in fire plumes by Zukoski et al:
m 1 ＝0.063Q 1/3 H 5/3 (1)
where H represents the tunnel height and Q represents the fire source power.
In the flue gas development stages 1 and 2, the flue gas can be mixed with surrounding cold air after striking the ceiling, so that the mass flow rate of the flue gas is increased, the flue gas layer is thickened, and therefore, the initial mass flow rate m of the flue gas entering the flue gas development stage 4 t Can be represented by the following formula (γ=1.90):
m t ＝γm 1 (gamma is the coefficient) (2)
Further, according to the symmetry of the free spreading smoke development, after the smoke collides with the wall, the mass flow rate of the smoke spreads leftwards or rightwards:
m 2 ＝1/2γm 1 (3)
the mass flow rate of flue gas at a distance x=l from the fire source can be expressed as:
m e ＝ρ a βWu (5)
wherein: m is m β The mass entrainment rate of the smoke development stage 4 is represented, beta represents entrainment coefficient, beta=0.005 is taken, W represents tunnel width, u represents longitudinal average spreading speed of the smoke layer, ρ a Representing the air density at ambient temperature.
At the 4, x position of the flue gas development stage, the longitudinal average propagation velocity u x Can be calculated by the following formula:
wherein u is x Represents the longitudinal average spreading speed of the smoke at the x position, T a Indicating ambient temperature, deltaT x Represents dimensionless temperature rise at the x position, g represents gravitational acceleration and h x The thickness of the smoke layer at the x position is shown.
In combination with the above, the mass flow rate of the flue gas at the position x=l from the fire source can be changed to:
furthermore, m L The mass flow rate can also be expressed according to a basic calculation formula:
simultaneously the formulas (1), (7) and%8) In combination with ideal gas state equationCan obtain the distance L from the fire source and the thickness h of the flue gas layer L Is defined by the relation:
T L the smoke temperature, ρ, at the distance L from the fire source of the free tendril L The air density at the distance L from the fire source is represented by the free propagation time;
further, for the convenience of calculation, the left side of the relation is simplified, and the relation can be calculatedAverage smoke layer thickness reduced to the range of 0-Lm +.>Wherein h is 0 The thickness of the flue gas layer near the fire source is approximate (h is shown according to the research on the transport rule of tunnel fire flue gas under the longitudinal ventilation in Zhao Sheng) 0 Take 0.3 m). Formula (9) may be modified by:
further, according to the study of Hu Longhua et al, decay of buoyant smoke layer temperature along the longitudinal direction in tunnel fires, it is shown that the dimensionless temperature rise and longitudinal distance at x under the ceiling can be represented by the following formula:
ΔT x ＝ΔT max e -Bx (11)
in the formula DeltaT x Represents the dimensionless temperature rise at the x position, deltaT max The highest temperature rise of the flue gas is represented, B represents a free-propagation time-delay temperature attenuation coefficient, B=0.025 is taken, Q represents the power of a fire source, and H represents the height of a tunnel.
And (3) obtaining the distance L from the fire source and the thickness h of the flue gas layer by combining the formulas (10) - (12) L Is defined by the relation:
wherein L represents the distance from the free propagation time to the fire source, B represents the free propagation time temperature attenuation coefficient, and B=0.025, h is taken L Represents the thickness of the smoke layer during free propagation, W represents the tunnel width and ρ a Representing air density at ambient temperature, taking ρ a ＝1.2kg/m 3 ，T a Indicating the ambient temperature, taking T a ＝293K，T L The temperature of the flue gas at the distance L from the fire source is expressed by the free tendril time delay, and T is taken L =313 k, g represents gravitational acceleration, taking g=9.8 m/s 2 Beta represents the smoke entrainment coefficient, taking beta=0.005, h 0 Indicating the thickness of the smoke layer near the fire source, taking h 0 =0.3m, γ represents the mass flow rate decay coefficient, γ=1.90, and h represents the tunnel height.
Step 2, when the tunnel has key smoke discharging effect, the fire smoke is delayed by smoke discharging suction force, and the thickness h of the smoke layer is known L* Deriving and calculating to obtain the distance L from the fire source * The method comprises the steps of carrying out a first treatment on the surface of the The method comprises the following steps:
assuming that the smoke outlet is not "suck-through", the smoke layer can still keep a relatively stable state as the free spreading at this time, and the smoke below the smoke outlet can be considered to be still in a one-dimensional horizontal spreading stage (figure 2).
The smoke generation amount under the tunnel section height H is taken as the key smoke discharge amount, and can be calculated by referring to the technical standard of a building smoke prevention and discharge System (GB 51251-2017):
in the middle of：V e Represents the key smoke discharge amount T a Represents the ambient temperature, Q represents the fire source power, H represents the tunnel height, c p Represents the constant pressure specific heat, ρ of air a Indicating the gas density at ambient temperature.
Further, when the smoke spreads to the smoke outlet, part of the smoke is discharged, so that the smoke mass flow rate m L* Flue gas mass flow rate m being free propagation time L Subtracting the m being discharged e . Obtain the distance fire source x=l * The mass flow rate of flue gas at the flue gas outlet can be expressed as:
m β ＝ρ a βWu (5)
m e ＝ρ e V e (16)
wherein: m is m β Represents the mass entrainment rate of the smoke development stage 4, beta represents entrainment coefficient, W represents tunnel width, u represents the longitudinal average spreading speed of the smoke layer, V e Smoke discharge amount ρ of smoke discharge system a Representing the gas density at ambient temperature ρ e Indicating the density of the smoke at the smoke outlet.
Since the smoke below the smoke outlet is still in the one-dimensional horizontal spreading stage, then at the x position, the longitudinal average spreading speed can still be calculated by the following formula:
wherein u is x Represents the longitudinal average spreading speed of the smoke at the x position, T a Indicating ambient temperature, deltaT x Represents dimensionless temperature rise at the x position, g represents gravitational acceleration and h x The thickness of the smoke layer at the x position is shown.
Simultaneously with the above formulas (1) to (3), (5) to (6) and (15) to (16), the distance from the fire source x=l is obtained * Smoke quality at locationFlow rate m L* The method can be changed into that:
furthermore, m L* The mass flow rate can also be expressed according to a basic calculation formula:
by combining the formulas (17) - (18), the distance L from the smoke outlet to the fire source can be obtained * With the thickness h of the flue gas layer L* Is defined by the relation:
further, for the convenience of calculation, the left side of the relation is simplified, and the relation can be calculatedReduced to 0-L * Average smoke layer thickness in the m range +.>Wherein h is 0 Approximately the thickness of the flue gas layer near the fire source, h 0 Take 0.3m. Formula (19) may be modified by:
further, since the smoke below the smoke outlet is still in a one-dimensional horizontal spreading stage, according to the research of Hu Longhua and the like, decay of buoyant smoke layer temperature along the longitudinal direction in tunnel fires, and the research of the tunnel fire smoke transportation law under the longitudinal ventilation in Zhao Sheng, it is shown that the dimensionless temperature rise under the ceiling at the smoke outlet x can be represented by the following formula:
ΔT x ＝ΔT max e -B′x (21)
in the formula DeltaT x Represents the dimensionless temperature rise at the x position, delta T max The highest temperature rise of the flue gas is represented, B' represents the temperature attenuation coefficient with key smoke discharging effect, Q represents the power of a fire source, and H represents the height of a tunnel.
The above formulas are combined to obtain the distance L from the fire source * With the thickness h of the flue gas layer L* Is defined by the relation:
wherein L is * The distance from the fire source when the key smoke discharging effect is shown, B 'is the temperature attenuation coefficient when the key smoke discharging effect is shown, and B' =0.015 and h are taken L* The thickness of the smoke layer when the key smoke discharging effect is shown, W is the tunnel width, ρ a Representing air density at ambient temperature, taking ρ a ＝1.2kg/m 3 ，T a Indicating the ambient temperature, taking T a ＝293K，T L* Indicating the distance L from the fire source when the key smoke discharging function is provided * Temperature of flue gas is taken as T L* =313 k, g represents gravitational acceleration, taking g=9.8 m/s 2 Beta represents the smoke entrainment coefficient, taking beta=0.005, h 0 Indicating the thickness of the smoke layer near the fire source, taking h 0 =0.3m, γ represents the mass flow rate attenuation coefficient, γ=1.90, h represents the tunnel height, Q represents the fire source power, T e Indicating the temperature of the smoke outlet, taking T e ＝313K，V e Indicating the amount of exhaust smoke.
Step 3, determining a minimum critical large distance D of key smoke outlets under the condition of ensuring the safety of personnel evacuation environment 1 Maximum critical large distance D 2 When no smoke exhausting effect exists in the tunnel, free propagation of fire smoke is delayed, the thickness of the smoke layer is fast, so that the thickness of the smoke layer is 2m close to the fire source, and 2L is taken asIs the minimum critical large distance D 1 When the tunnel has key smoke discharging effect, the fire smoke is delayed by smoke discharging suction force, the thickness of the smoke layer is slow, so that the thickness of the smoke layer is 2m far away from the fire source, and 2L is taken as the minimum critical large distance D 2 Obtaining a critical large-spacing range of a key smoke outlet of a tunnel; the method comprises the following steps:
according to volume 3 of "fire plan, public fire facilities, building fire design" of "Fire Engineering Guidelines" and "Chinese fire Manual", it is known that: in order to ensure the safety of people evacuation environment, the visibility at the position with the clear height of 2m should meet the requirement of V z More than or equal to 10m, and the temperature should satisfy T z The temperature is less than or equal to 60 ℃. Therefore, the safety of the personnel evacuation environment can be ensured only by ensuring no smoke at the position with the clear height of 2m.
Further, when no smoke exhausting effect exists in the tunnel, the free propagation of fire smoke is delayed, and the height of the smoke layer at the position far away from the fire source is 2m (namely the thickness h of the smoke layer L = (H-2) m), if the key smoke outlet is set for smoke evacuation, the safety of people evacuation environment can be ensured, then the minimum critical large distance D of the key smoke outlet of the tunnel is obtained according to formula (13) and substitutes the related parameter data, as shown in fig. 1 1 ＝2L；
Wherein D is 1 The minimum critical large distance of key smoke outlets is represented, L represents the distance from a fire source due to free propagation, W represents the width of a tunnel, and H represents the height of the tunnel.
Further, when the tunnel has key smoke exhausting function, the fire smoke is delayed by the smoke exhausting suction force, the height of the smoke layer at the position far from the fire source is 2m (namely the thickness h of the smoke layer L* = (H-2) m), the security of the personnel evacuation environment can be ensured, and then the maximum critical distance D of the key smoke outlet of the tunnel is obtained according to the formula (23) and substituting the related parameter data as shown in fig. 2 2 ＝2L*。
Wherein D is 2 Represents the maximum critical large distance of key smoke outlets, L * The distance from the fire source when the key smoke discharging effect is achieved is represented, W represents the tunnel width, H represents the tunnel height, and Q represents the fire source power.
Further, under the condition of ensuring the safety of personnel evacuation environment, the critical large-distance range of the key smoke outlets of the tunnel is:
D 1 ≤D≤D 2 (26)
wherein D is 1 Represents the minimum critical large distance of key smoke outlets, D 2 The maximum critical large distance of the key smoke outlets is shown, and D is the distance of the key smoke outlets.
By the calculation method, critical large-distance range of key smoke outlets can be rapidly obtained according to different tunnel sizes.
Furthermore, the application also comprises the verification of the calculation method, which is specifically as follows:
(1) Substituting parameters such as the size of the physical tunnel and the power of the fire source into the critical large-spacing range of the key smoke outlet of the tunnel in the step 3 (table 1), and calculating to obtain a theoretical critical large-spacing range calculated value through a theoretical formula (table 2);
TABLE 1
Numbering device Fire source power/MW Tunnel dimension (height x width)/m
A1-A5 20 5×9/5×10/6×11/6×12/7×13
B1-B5 30 5×9/5×10/6×11/6×12/7×13
C1-C5 40 5×9/5×10/6×11/6×12/7×13
D1-D5 50 5×9/5×10/6×11/6×12/7×13
TABLE 2
(2) FDS numerical simulation part:
fire dynamics simulation software (FDS) is prior art.
Tunnel models of 1000m length and different widths and heights were constructed using FDS software, as shown in fig. 3. The fume exhaust port is positioned on the top plate of the tunnel, and the fume exhaust port has a transverse length of 2.5m and a longitudinal length of 6m. The size of a fire source of a fire disaster is 8m times the width of the fire source, 3m times the height of the fire source of the fire disaster is 0m, layer measuring points are arranged at intervals of 0.5m in the longitudinal center of a model tunnel, and the height of a flue gas layer can be directly obtained through the layer measuring points. The tunnel ambient temperature and pressure were 20℃and 101kPa, respectively, with a simulated calculation time of 600s. By setting different fire source powers and different tunnel size working conditions as shown in table 1, through 'layer' measuring points (see fig. 3) in FDS software, the flue gas layer height at each measuring point can be directly obtained, and then the distance between the flue gas layer and the fire source at the position with the height of 2m can be directly obtained, so that a simulated critical large distance range (see table 2) can be obtained, and the simulated critical large distance range is analyzed and compared with the theoretical calculation value in the step (1):
the theoretical critical large-pitch range and the simulated critical large-pitch range are compared to obtain the simulated large-pitch range which is slightly smaller than the theoretical value, and the theoretical calculated value is slightly larger because the theoretical calculated value does not consider the influence of other influence factors, but the error result of each working condition is smaller than 10% through error calculation, so that the calculation formula of the theoretical critical large-pitch range is accurate and the applicability of the actual tunnel engineering can be met.
The foregoing description of the preferred embodiments of the application is not intended to limit the application to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the application are intended to be included within the scope of the application.

Claims (4)

1. The design method of the critical large-spacing range of the key smoke outlet of the tunnel is characterized by comprising the following steps of:
step 1, determining the allowable height of smoke in a tunnel under the condition of ensuring the safety of a personnel evacuation environment, and obtaining the allowable thickness h of a smoke layer according to the design size of the tunnel L ＝h L* ；
Step 2, calculating that no smoke discharging effect exists in the tunnel according to the relation between the thickness of the smoke layer and the distance between the fire sources and the tunnel size, wherein the thickness of the smoke layer is h under the condition that fire smoke freely spreads L The distance L from the fire source is 2L as the minimum critical large distance D of the key smoke outlet 1 ；
Step 3, calculating the thickness h of the smoke layer under the condition that the smoke of the fire is spread by the smoke suction force under the key smoke discharging effect in the tunnel according to the relation between the thickness of the smoke layer and the distance between the fire source and the tunnel size and the power of the fire source L* Distance L from the fire source * Will be 2L * As the maximum critical large spacing D of key smoke outlet 2 ；
Step 4, obtaining critical large-spacing range D, D of key smoke outlet of tunnel 1 ≤D≤D 2 。
2. The method for designing critical large-pitch range of key smoke outlets of tunnels according to claim 1, wherein in the step 1, the conditions for ensuring the safety of people evacuation environment are as follows:
the visibility of the smoke in the tunnel at the allowable height should meet V z More than or equal to 10m, and the temperature should satisfy T z The temperature is less than or equal to 60 ℃, and the allowable height of flue gas in the tunnel is 2m.
3. The method for designing a critical large-pitch range of a key smoke outlet of a tunnel according to claim 1, wherein in the step 2, a relation between a smoke layer thickness and a fire source distance is:
in the smoke layer thickness h L ＝(H-2)，D 1 The minimum critical large distance of key smoke outlets is represented, L represents the distance from a fire source due to free propagation, W represents the width of a tunnel, and H represents the height of the tunnel.
4. The method for designing a critical large-pitch range of a key smoke outlet of a tunnel according to claim 1, wherein in the step 3, a relation between a smoke layer thickness and a fire source distance is:
in the smoke layer thickness h L ＝(H-2)，D 2 Represents the maximum critical large distance of key smoke outlets, L * The distance from the fire source when the key smoke discharging effect is achieved is represented, W represents the tunnel width, H represents the tunnel height, and Q represents the fire source power.
CN202310548289.XA 2023-05-16 2023-05-16 Design method for critical large-spacing range of key smoke outlets of tunnel Pending CN116663104A (en)

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