Design method for natural ventilation of highway tunnel vertical shaft based on unpowered hood

Abstract

The invention belongs to the technical field of tunnel natural ventilation and smoke exhaust, and relates to a highway tunnel vertical shaft natural ventilation design method based on an unpowered hood. The method comprises the following steps that the tunnel height, the fire source heat release rate, the environment air density, the air constant pressure specific heat capacity, the environment air temperature, the pressure intensity in a tunnel, the pressure intensity outside the tunnel, the smoke temperature in the fire disaster and the occupied area of a single unpowered hood on the top of a vertical shaft are collected; determining the width and height of the vertical shaft; determining the effective exhaust volume flow rate of a single unpowered hood; determining the total smoke discharge volume flow to be borne by the vertical shaft in the tunnel fire; the number of the needed unpowered air caps is determined according to the total smoke exhaust volume flow needing to be borne by the vertical shaft in the tunnel fire disaster, the effective exhaust volume flow of the single unpowered air cap, the occupied area of the single unpowered air cap on the top of the vertical shaft and the width and height of the vertical shaft. The ventilation hood can be combined with an unpowered hood to achieve the optimal ventilation effect, and the ventilation and smoke exhaust effect of the vertical shaft is further improved.

Description

Technical Field

[0001] This invention belongs to the field of tunnel natural ventilation and smoke extraction technology, and relates to a design method for natural ventilation of highway tunnel shafts based on non-powered wind caps. Background Technology

[0002] With the booming development of the transportation industry, the passenger and freight turnover of transportation systems is constantly increasing, inevitably raising the probability of traffic accidents in tunnels and further leading to fires. Due to the narrow and elongated structure of tunnels, once a tunnel fire occurs, it is likely to cause serious consequences such as traffic disruption, structural damage, and mass casualties. Therefore, an effective tunnel smoke extraction system is of great significance for ensuring the safety of personnel and the integrity of the tunnel structure during a fire. Tunnel smoke extraction often uses vertical shaft natural ventilation methods. However, research has found that in the early stages of a fire, backdrafts can occur in the shafts, and the higher the ambient wind speed, the more unfavorable it is for smoke extraction. Furthermore, because the shafts connect to the ground, sunlight and rain / snow can directly enter the tunnel, easily affecting the driver's visibility and causing slippery roads, thus increasing the probability of accidents in the tunnel to some extent.

[0003] Currently, the natural ventilation method for highway tunnel shafts based on non-powered ventilators can not only prevent backflow of air, but also prevent sunlight and rain / snow from intruding and causing driver visibility problems and road slipperiness, thus reducing the probability of accidents in the tunnel. However, there is still a lack of perfect design solutions on how to combine non-powered ventilators with the best ventilation effect, which affects the improvement of the ventilation and smoke extraction effect of the shaft. Summary of the Invention

[0004] The purpose of this invention is to provide a design method for natural ventilation of highway tunnel shafts based on non-powered ventilators, which can be combined with non-powered ventilators to achieve the best ventilation effect and further improve the ventilation and smoke extraction effect of the shaft.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows: A design method for natural ventilation of highway tunnel shafts based on non-powered ventilation caps includes the following steps: The data collected included tunnel height, heat release rate from the fire source, ambient air density, specific heat capacity of air at constant pressure, ambient air temperature, pressure inside the tunnel, pressure outside the tunnel, smoke temperature during a fire, and the floor space occupied by a single non-powered ventilation cap at the top of the shaft. The width and height of the shaft are determined based on the tunnel height, the heat release rate of the ignition source, the ambient air density, the specific heat capacity of air at constant pressure, and the ambient air temperature. The pressure difference between the inside and outside of the tunnel is determined based on the pressure inside and outside the tunnel, and the effective exhaust volume flow rate of a single non-powered ventilator is determined based on the pressure difference between the inside and outside of the tunnel. The total smoke exhaust volume flow rate that the vertical shaft needs to handle during a tunnel fire is determined based on the heat release rate of the fire source, ambient air density, specific heat capacity of air at constant pressure, ambient air temperature and smoke temperature during the fire. The required number of non-powered ventilation caps is determined based on the total smoke exhaust volume flow rate that the shaft needs to handle during a tunnel fire, the effective exhaust volume flow rate of a single non-powered ventilation cap, the floor space occupied by a single non-powered ventilation cap at the top of the shaft, and the width and height of the shaft.

[0006] The invention is further characterized by: When determining the width and height of the shaft based on the tunnel height, the heat release rate of the fire source, the ambient air density, the specific heat capacity of air at constant pressure, and the ambient air temperature, the width of the shaft is first determined based on these factors, and then the height of the shaft is determined based on the ratio of its width to its height.

[0007] When determining the width of the shaft based on the tunnel height, the heat release rate of the ignition source, the ambient air density, the specific heat capacity of air at constant pressure, and the ambient air temperature, the following formula is used for calculation: , In the formula, Q The rate of heat release from the ignition source. Q * is a dimensionless quantity representing the rate of heat release from the ignition source. ρ 0 represents ambient air density. c p The specific heat capacity of air at constant pressure. T 0 represents the ambient air temperature. g It is the acceleration due to gravity. H The height of the tunnel. w s The width of the shaft. w * represents the dimensionless quantity of the shaft width.

[0008] The height of the shaft is determined based on the ratio of its width to its height, and is calculated using the following formula: , In the formula, h The height of the shaft. w s This refers to the width of the shaft.

[0009] When determining the effective exhaust volume flow rate of a single non-powered ventilation cap based on the pressure difference inside and outside the tunnel, the following formula is used for calculation: , In the formula, ∆ P The pressure difference between the inside and outside of the tunnel, V The effective exhaust volume flow rate of a single unpowered wind cap. a0 represents the baseline differential pressure constant at zero flow rate, with a value of 197 Pa. a 1 represents the linear term pressure difference coefficient, with a value of -26622 Pa·s / m. 3 , a 2 represents the quadratic pressure differential coefficient, with a value of 1094045 Pa·s. 2 / m 6 , a 3 represents the cubic differential pressure coefficient, with a value of -13,798,300 Pa·s. 3 / m 9 .

[0010] When determining the total smoke exhaust volume flow rate that the vertical shaft needs to handle during a tunnel fire based on the heat release rate of the fire source, ambient air density, specific heat capacity of air at constant pressure, ambient air temperature, and smoke temperature during the fire, the following formula is used for calculation: , In the formula, Q 需求 This refers to the total smoke exhaust volume flow rate that the shaft must handle during a tunnel fire. η For safety margin, a value of 1.2 to 1.5 is used. Q The rate of heat release from the ignition source. ρ 0 represents ambient air density. c p ∆ is the specific heat capacity of air at constant pressure. T ∆ represents the temperature difference between the flue gas and the ambient air. T=T 1 -T 0, T 1 represents the smoke temperature during a fire, with a value ranging from 200℃ to 300℃. T 0 represents the ambient air temperature. k 0 represents the vertical shaft smoke exhaust efficiency, with a value ranging from 0.6 to 0.8.

[0011] When determining the required number of non-powered ventilation caps based on the total smoke exhaust volume flow rate that the shaft needs to handle during a tunnel fire, the effective exhaust volume flow rate of a single non-powered ventilation cap, the floor space occupied by a single non-powered ventilation cap at the top of the shaft, and the width and height of the shaft, the following formula is used: , In the formula, N The number of non-powered windproof caps required. Q 需求 This refers to the total smoke exhaust volume flow rate that the shaft must handle during a tunnel fire. V The effective exhaust volume flow rate of a single unpowered wind cap. η For safety margin, a value of 1.2 to 1.5 is used. A 风帽 The floor space occupied by a single non-powered wind cap at the top of the shaft. ws The width of the shaft. h The height of the shaft. k The effective utilization coefficient of the top area of ​​the shaft is 0.7 to 0.9.

[0012] After determining the required number of non-powered ventilation caps, the shaft is constructed at the top of the tunnel according to the width and height of the shaft, and then the corresponding number of non-powered ventilation caps are evenly installed at the top of the shaft.

[0013] When the corresponding number of non-powered vent caps are evenly installed at the top of the shaft, each non-powered vent cap is connected to the top of the shaft through a reducing adapter.

[0014] The design method for natural ventilation of highway tunnel shafts based on non-powered wind caps of the present invention has the following advantages: This invention collects data on tunnel height, heat release rate of the fire source, ambient air density, specific heat capacity of air at constant pressure, ambient air temperature, internal tunnel pressure, external tunnel pressure, smoke temperature during a fire, and the area occupied by a single non-powered ventilation cap at the top of the shaft. Then, based on the tunnel height, heat release rate of the fire source, ambient air density, specific heat capacity of air at constant pressure, and ambient air temperature, it determines the width and height of the shaft. Next, it determines the pressure difference between the inside and outside of the tunnel based on the internal and external tunnel pressures, and then determines the effective exhaust volume flow rate of a single non-powered ventilation cap based on this pressure difference. Finally, it determines the total smoke exhaust volume flow rate that the shaft needs to handle during a tunnel fire based on the heat release rate of the fire source, ambient air density, specific heat capacity of air at constant pressure, ambient air temperature, and smoke temperature during a fire. Finally, it determines the required number of non-powered ventilation caps based on the total smoke exhaust volume flow rate that the shaft needs to handle during a tunnel fire, the effective exhaust volume flow rate of a single non-powered ventilation cap, the area occupied by a single non-powered ventilation cap at the top of the shaft, and the width and height of the shaft. This allows for optimal ventilation by combining the ventilation caps with the ventilation caps, further improving the ventilation and smoke exhaust effect of the shaft. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall process of the present invention.

[0016] Figure 2 This is a schematic diagram of the overall structure of the present invention.

[0017] Figure 3 This is a curve showing the relationship between the volumetric flow rate and pressure difference of a single non-powered ventilator according to the present invention.

[0018] Figure label: 1. Tunnel, 2. Shaft, 3. Adapter, 4. Non-powered wind cap. Detailed Implementation

[0019] The technical solutions of the present invention will now be described clearly and in detail with reference to the accompanying drawings. In the description of the embodiments of the present invention, unless otherwise stated, " / " indicates "or," for example, A / B can mean A or B. "And / or" in the text is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. Furthermore, in the description of the embodiments of the present invention, "multiple" refers to two or more. The terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0020] like Figure 1 , Figure 2 As shown, this invention provides a design method for natural ventilation of highway tunnel shafts based on non-powered ventilation caps, comprising the following steps: The data collected included the height of tunnel 1, the heat release rate of the fire source, the density of ambient air, the specific heat capacity of air at constant pressure, the ambient air temperature, the internal pressure of tunnel 1, the external pressure of tunnel 1, the smoke temperature during the fire, and the area occupied by a single non-powered wind cap 4 at the top of shaft 2. The width and height of shaft 2 are determined based on the height of tunnel 1, the heat release rate of the fire source, the density of ambient air, the specific heat capacity of air at constant pressure, and the ambient air temperature. The pressure difference between the inside and outside of tunnel 1 is determined based on the pressure inside and outside of tunnel 1, and the effective exhaust volume flow rate of a single non-powered vent cap 4 is determined based on the pressure difference between the inside and outside of tunnel 1. The total smoke exhaust volume flow rate that shaft 2 needs to bear during a fire in tunnel 1 is determined based on the heat release rate of the fire source, ambient air density, specific heat capacity of air at constant pressure, ambient air temperature and smoke temperature during the fire. The required number of non-powered ventilation caps 4 is determined based on the total smoke exhaust volume flow rate that shaft 2 needs to handle during a fire in tunnel 1, the effective exhaust volume flow rate of a single non-powered ventilation cap 4, the floor area occupied by a single non-powered ventilation cap 4 at the top of shaft 2, and the width and height of shaft 2.

[0021] In summary, this invention collects data on the height of tunnel 1, the heat release rate of the fire source, the ambient air density, the specific heat capacity of air at constant pressure, the ambient air temperature, the internal pressure of tunnel 1, the external pressure of tunnel 1, the smoke temperature during a fire, and the floor area occupied by a single non-powered ventilation cap 4 at the top of shaft 2. Then, based on the height of tunnel 1, the heat release rate of the fire source, the ambient air density, the specific heat capacity of air at constant pressure, and the ambient air temperature, the width and height of shaft 2 are determined. Furthermore, based on the internal and external pressures of tunnel 1, the pressure difference between the inside and outside of tunnel 1 is determined, and based on this pressure difference, the effective exhaust volume of a single non-powered ventilation cap 4 is determined. The flow rate is then determined based on the heat release rate of the fire source, ambient air density, specific heat capacity of air at constant pressure, ambient air temperature, and smoke temperature during the fire. Finally, the required number of non-powered ventilators 4 is determined based on the total smoke exhaust volume flow rate required by shaft 2 during a fire in tunnel 1, the effective exhaust volume flow rate of a single non-powered ventilator 4, the floor area of ​​a single non-powered ventilator 4 at the top of shaft 2, and the width and height of shaft 2. This allows for the optimal ventilation effect when combined with the non-powered ventilators, further improving the ventilation and smoke exhaust effect of the shaft.

[0022] When determining the width and height of shaft 2 based on the height of tunnel 1, the heat release rate of the fire source, the density of ambient air, the specific heat capacity of air at constant pressure, and the ambient air temperature, the width of shaft 2 is first determined based on the tunnel height, the heat release rate of the fire source, the density of ambient air, the specific heat capacity of air at constant pressure, and the ambient air temperature, and then the height of shaft 2 is determined based on the ratio of the width to the height of shaft 2.

[0023] When determining the width of shaft 2 based on the height of tunnel 1, the heat release rate of the ignition source, the ambient air density, the specific heat capacity of air at constant pressure, and the ambient air temperature, the following formula is used for calculation: .

[0024] In the formula, Q The rate of heat release from the ignition source. Q * is a dimensionless quantity representing the rate of heat release from the ignition source. ρ 0 represents ambient air density. c p The specific heat capacity of air at constant pressure. T 0 represents the ambient air temperature. g It is the acceleration due to gravity. H The height of Tunnel 1 w s For the width of shaft 2, w * represents the dimensionless quantity of the width of shaft 2.

[0025] The height of the shaft is determined based on the width-to-height ratio of shaft 2, using the following formula: .

[0026] In the formula, h The height of shaft 2 w s The width of shaft 2.

[0027] like Figure 3 As shown, when determining the effective exhaust volume flow rate of a single non-powered ventilator 4 based on the pressure difference inside and outside tunnel 1, the following formula is used for calculation: .

[0028] In the formula, ∆ P The pressure difference between the inside and outside of tunnel 1 is expressed in Pa. V The effective exhaust volume flow rate of a single unpowered wind cap 4, in m³ / s. 3 / s, a 0 represents the baseline differential pressure constant at zero flow rate, with a value of 197 Pa. a 1 represents the linear term pressure difference coefficient, with a value of -26622 Pa·s / m. 3 , a 2 represents the quadratic pressure differential coefficient, with a value of 1094045 Pa·s. 2 / m 6 , a 3 represents the cubic differential pressure coefficient, with a value of -13,798,300 Pa·s. 3 / m 9 .

[0029] Among them, a single non-powered windproof cap has 4 units, with a diameter of 25cm, such as... Figure 3 As shown, as the pressure difference increases, the ventilation volume of the non-powered hood 4 increases. However, when the pressure difference is greater than 15Pa, vortices will form inside the shaft 2 and the non-powered hood 4. The dissipation of turbulent kinetic energy will cause the pressure difference of the wind ball to decrease. The additional aerodynamic resistance is not conducive to ventilation and smoke exhaust. Based on this curve, the non-powered hood 4 at the top of the shaft 2 should be arranged reasonably.

[0030] When determining the total smoke exhaust volume flow rate that shaft 2 needs to handle during a fire in tunnel 1, based on the heat release rate of the fire source, ambient air density, specific heat capacity of air at constant pressure, ambient air temperature, and smoke temperature during the fire, the following formula is used for calculation: .

[0031] In the formula, Q 需求 This represents the total smoke exhaust volume flow rate that shaft 2 needs to handle during a fire in tunnel 1. η For safety margin, a value of 1.2 to 1.5 is used. Q The rate of heat release from the ignition source. ρ 0 represents ambient air density. c p ∆ is the specific heat capacity of air at constant pressure. T ∆ represents the temperature difference between the flue gas and the ambient air. T=T 1 -T 0, T 1 represents the smoke temperature during a fire, with a value ranging from 200℃ to 300℃. T 0 represents the ambient air temperature. k 0 represents the smoke exhaust efficiency of shaft 2, with a value ranging from 0.6 to 0.8.

[0032] When determining the required number of non-powered ventilation caps 4 based on the total smoke exhaust volume flow rate that shaft 2 needs to handle during a fire in tunnel 1, the effective exhaust volume flow rate of a single non-powered ventilation cap 4, the floor area occupied by a single non-powered ventilation cap 4 at the top of shaft 2, and the width and height of shaft 2, the following formula is used for calculation: .

[0033] In the formula, N The number of non-powered windproof caps (4) required. Q 需求 This represents the total smoke exhaust volume flow rate that shaft 2 needs to handle during a fire in tunnel 1. V The effective exhaust volume flow rate of a single unpowered wind cap 4 η For safety margin, a value of 1.2 to 1.5 is used. A 风帽 The area occupied by a single non-powered wind cap 4 at the top of shaft 2. w s For the width of shaft 2, h The height of shaft 2 k is the effective utilization coefficient of the top area of ​​shaft 2, with a value of 0.7~0.9. ⌈⌉ indicates rounding up, and ⌊⌋ indicates rounding down.

[0034] After determining the required number of non-powered ventilation caps 4, the shaft 2 is constructed at the top of the tunnel 1 according to the width and height of the shaft 2, and then the corresponding number of non-powered ventilation caps 4 are evenly installed at the top of the shaft 2.

[0035] When the corresponding number of non-powered wind caps 4 are evenly installed on the top of the vertical shaft 2, each non-powered wind cap 4 is connected to the top of the vertical shaft 2 through a reducing adapter 3.

[0036] The design method for natural ventilation of highway tunnel shafts based on non-powered wind caps of the present invention has the following other advantages: First, this invention utilizes a non-powered wind cap to ventilate the interior of the tunnel, eliminating the need for additional electricity or mechanical equipment, thus achieving effective utilization of wind energy and significantly reducing energy consumption and maintenance costs.

[0037] Secondly, by making reasonable use of the combination of the non-powered wind cap with shaft parameters such as width and height, the present invention can significantly improve the smoke extraction effect of the shaft during a fire and reduce the length of smoke backflow.

[0038] Third, compared to the original vertical shaft ventilation method, and especially considering the low efficiency of the original vertical shaft ventilation in the absence of a fire, which makes it difficult to effectively expel polluted gases from inside the tunnel, the ventilation method based on the non-powered wind cap of this invention can achieve smooth operation when the wind speed is not less than 0.2m / s or the temperature difference between the inside and outside of the tunnel is greater than 0.5℃, expelling pollutants from inside the tunnel and overcoming the problem of backflow, while avoiding the negative effects of ambient wind on vertical shaft smoke exhaust.

[0039] Fourth, the design scheme of the present invention can flexibly adjust the shaft design parameters and the number of non-powered ventilation caps according to the specific environment of the tunnel (such as tunnel length, location, temperature changes, etc.). Different tunnel layouts and functional requirements can achieve the optimal ventilation effect through simple adjustment of shaft size and configuration of the number of non-powered ventilation caps. This technology can be applied in both new tunnels and renovation of old tunnels, greatly improving its applicability and flexibility.

[0040] It is understood that this invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this invention. Furthermore, under the teachings of this invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this invention are within the protection scope of this invention.

Claims

1. A design method for natural ventilation of a highway tunnel shaft based on a passive cowling, characterized in that, The method comprises the following steps: collecting the tunnel height, the heat release rate of the fire source, the environmental air density, the air constant-pressure specific heat capacity, the environmental air temperature, the tunnel internal pressure, the tunnel external pressure, the smoke temperature during the fire, and the area occupied by a single unpowered hood on the top of the shaft; determining the width and height of the shaft according to the tunnel height, the heat release rate of the fire source, the environmental air density, the air constant-pressure specific heat capacity, and the environmental air temperature; determining the effective exhaust volume flow rate of a single unpowered hood according to the tunnel internal pressure and the tunnel external pressure, and determining the effective exhaust volume flow rate of the single unpowered hood according to the tunnel internal pressure and the tunnel external pressure difference; determining the total exhaust volume flow rate of the shaft during the tunnel fire according to the heat release rate of the fire source, the environmental air density, the air constant-pressure specific heat capacity, the environmental air temperature, and the smoke temperature during the fire; determining the number of required unpowered hoods according to the total exhaust volume flow rate of the shaft during the tunnel fire, the effective exhaust volume flow rate of a single unpowered hood, the area occupied by the single unpowered hood on the top of the shaft, the width and height of the shaft.

2. A design method of natural ventilation of a highway tunnel shaft based on a non-powered hood according to claim 1, characterized in that, When determining the width and height of the shaft according to the tunnel height, the heat release rate of the fire source, the environmental air density, the air constant-pressure specific heat capacity, and the environmental air temperature, the width of the shaft is determined according to the tunnel height, the heat release rate of the fire source, the environmental air density, the air constant-pressure specific heat capacity, and the environmental air temperature, and the height of the shaft is determined according to the width and height ratio of the shaft.

3. A design method of natural ventilation of a highway tunnel shaft based on a non-powered hood according to claim 2, characterized in that, When determining the width of the shaft according to the tunnel height, the heat release rate of the fire source, the environmental air density, the air constant-pressure specific heat capacity, and the environmental air temperature, the following formula is used for calculation: ， where Q HRR is the heat release rate of the fire, Q * is a dimensionless quantity of the heat release rate of the fire, When determining the height of the shaft according to the width and height ratio of the shaft, the following formula is used for calculation: 0 is the ambient air density, c p Cp is the air constant pressure specific heat capacity, T 0 is the ambient air temperature, When determining the effective exhaust volume flow rate of a single unpowered hood according to the tunnel internal pressure and the tunnel external pressure difference, the following formula is used for calculation: g is the acceleration due to gravity, H H is the height of the tunnel, w s W is the width of the shaft, w * is a dimensionless quantity of the width of the shaft.

4. A design method of a highway tunnel shaft natural ventilation based on a non-powered cowling according to claim 2, characterized in that, When determining the total exhaust volume flow rate of the shaft during the tunnel fire according to the heat release rate of the fire source, the environmental air density, the air constant-pressure specific heat capacity, the environmental air temperature, and the smoke temperature during the fire, the following formula is used for calculation: ， wherein h is the shaft height, w s is the shaft width.

5. A design method of natural ventilation of a highway tunnel shaft based on a non-powered hood according to claim 1, characterized in that, When determining the number of required unpowered hoods according to the total exhaust volume flow rate of the shaft during the tunnel fire, the effective exhaust volume flow rate of a single unpowered hood, the area occupied by the single unpowered hood on the top of the shaft, the width and height of the shaft, the following formula is used for calculation: ， where ΔP is the pressure difference across the tunnel, P is the pressure difference between the inside and outside of the tunnel, V is the effective exhaust volume flow rate of a single unpowered hood, a 0 is the reference pressure difference constant at zero flow rate, and has a value of 197 Pa, a 1 is the linear term pressure difference coefficient, and has a value of -26622 Pa·s / m 3 , a 2 is the quadratic term pressure difference coefficient, and has a value of 1094045 Pa·s 2 / m 6 , a 3 is the cubic term pressure difference coefficient, and has a value of -13798300 Pa·s 3 / m 9 .

6. A design method of natural ventilation of a highway tunnel shaft based on a non-powered hood according to claim 1, characterized in that, After the number of required unpowered hoods is determined, the shaft is constructed on the top of the tunnel according to the width and height of the shaft, and the corresponding number of unpowered hoods are uniformly installed on the top end of the shaft. ， wherein, Q 需求 Q is the total exhaust volume flow of smoke that the shaft needs to bear when a tunnel fire occurs, When the corresponding number of unpowered hoods are uniformly installed on the top end of the shaft, each unpowered hood is connected with the top end of the shaft through a variable-diameter adapter. K is a safety factor, and is taken as 1.2-1.5, Q Q is the heat release rate of the fire source, ​ 0 is the ambient air density, c p Cp is the air constant-pressure specific heat capacity, and T is the temperature difference between the smoke and the ambient air, ​ 1 -T 0, T 1 is the smoke temperature when a fire occurs, and is taken as 200-300°C, T 0 is the ambient air temperature, k 0 is the shaft smoke exhaust efficiency, and is taken as 0.6-0.

8.

7. The method of designing a passive cowl based natural ventilation for a highway tunnel shaft according to claim 1, wherein, ​ ， wherein, N N is the number of required unpowered hoods, Q 需求 Q is the total exhaust volume flow rate required to be borne by the shaft during a tunnel fire, V Q is the effective exhaust volume flow rate of a single unpowered hood, ​ F is a safety factor, and is 1.2-1.5, A 风帽 A is the floor area occupied by a single unpowered hood at the top of the shaft, w s W is the width of the shaft, h H is the height of the shaft, k K is an effective utilization coefficient of the area at the top of the shaft, and is 0.7-0.

9.

8. A design method of a highway tunnel shaft natural ventilation based on unpowered cowls according to claim 1, characterized in that, ​ 9. A design method of a highway tunnel shaft natural ventilation based on unpowered cowls according to claim 1, characterized in that, ​

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