Method for predicting highest temperature and position of fire ceiling of underground inclined tunnel

Abstract

The invention discloses a method for predicting the highest temperature and the position of a ceiling of an underground inclined tunnel in a fire disaster, belongs to the technical field of tunnel fire safety, and solves the problem of large error of a method for determining the highest temperature and the position of the ceiling of the inclined tunnel in the fire disaster in the prior art, and the method comprises the following steps: S1, calculating a dimensionless induced wind speed; and S2, determining a flue gas flowing state according to the dimensionless induced wind speed, and calculating the position of the highest temperature of the ceiling and the highest temperature of the ceiling. Compared with the prior art, the method has the following advantages that the fire early warning capability is improved, the position of a fire source can be effectively recognized by accurately predicting the highest temperature and position of the ceiling when the fire occurs in the inclined tunnel, important reference is provided for rescue workers, and the timeliness and accuracy of fire emergency response are enhanced. The highest temperature of the ceiling and the position of the ceiling are predicted, protection measures can be taken in time or in advance, damage of fire to the tunnel structure is reduced, and the service life of the tunnel is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel fire safety, and in particular relates to a method for predicting the maximum temperature and position of a ceiling in an underground inclined tunnel fire. Background Art

[0002] With the rapid development of my country's national economy and the acceleration of urbanization, urban road traffic construction faces severe problems such as tight urban land use and traffic congestion on trunk roads. Ground transportation can no longer meet the needs of urban development. Therefore, urban underground tunnel transportation has developed. Due to the narrow and long structural characteristics of the tunnel, once a fire occurs, high-temperature toxic and harmful smoke will spread along the ceiling to both ends of the tunnel. If the smoke generated by the fire cannot be discharged in time, the smoke will accumulate on the tunnel ceiling, resulting in an increase in tunnel smoke concentration and smoke layer thickness, seriously affecting fire rescue and personnel escape. One of the most important standards is the maximum temperature of the ceiling. The maximum temperature can effectively predict the location of the fire and evaluate the damage of high temperature to the tunnel structure. In horizontal tunnels, the maximum temperature of the ceiling is only related to the power of the fire source and the ventilation status. In the absence of ventilation, the maximum temperature of the ceiling is directly above the fire source. In the case of longitudinal ventilation, the maximum temperature of the ceiling is downstream of the fire source, and the maximum temperature of the ceiling will drop significantly.

[0003] However, urban highway tunnels are usually shallow, small in height, short in length, and often have a certain slope. In order to achieve more effective ventilation and drainage, the "Highway Tunnel Design Code" stipulates that the longitudinal slope of ordinary highway tunnels should generally be no less than 0.3% and no more than 3%. However, due to the complex terrain and geological conditions, urban underground tunnels such as mountain tunnels and cross-river tunnels have much larger slopes than ordinary highway tunnels. When a fire occurs in an inclined tunnel, the smoke flow state in the tunnel will change significantly under the action of the chimney effect. Therefore, it is necessary to explore a method for determining the maximum ceiling temperature and its location specifically for inclined tunnel fires. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the method for predicting the maximum ceiling temperature and its position in an underground inclined tunnel fire provided by the present invention solves the problem of large errors in the prior art method for determining the maximum ceiling temperature and its position in an inclined tunnel fire.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: a method for predicting the maximum temperature and position of the ceiling of an underground inclined tunnel fire, comprising the following steps:

[0006] S1. Calculate dimensionless induced wind speed;

[0007] S2. Determine the smoke flow state based on the dimensionless induced wind speed, and calculate the location of the maximum ceiling temperature and the maximum ceiling temperature.

[0008] Further: In S1, the dimensionless induced wind speed is calculated The specific expression is:

[0009]

[0010] In the formula, H * is the dimensionless downstream height difference, and H*=L D sin(arctanα) / h,L D is the downstream length of the fire source, α is the tunnel slope, and h is the tunnel height.

[0011] Further: In S2, the expression for calculating the position d of the maximum temperature of the ceiling is specifically:

[0012]

[0013] In the formula, H ef It is the vertical distance from the fire source surface to the ceiling.

[0014] Further: In S2, the method for calculating the maximum temperature of the ceiling is specifically:

[0015] Calculate the maximum temperature rise of the ceiling. Calculate the maximum temperature of the ceiling based on the maximum temperature rise of the ceiling. Among them, calculate the maximum temperature rise of the ceiling ΔT max The specific expression is:

[0016]

[0017] In the formula, Q c is the convective heat release rate, c p is the specific heat capacity of air.

[0018] The beneficial effects of the present invention are as follows: the present invention provides a method for predicting the maximum temperature and position of the ceiling of an underground inclined tunnel fire, which has the following advantages over the prior art:

[0019] (1) Improve fire warning capabilities: By accurately predicting the maximum ceiling temperature and location when a fire occurs in an inclined tunnel, the fire source location can be effectively identified, providing important reference for rescue personnel and enhancing the timeliness and accuracy of fire emergency response.

[0020] (2) Reduce structural damage: By predicting the maximum ceiling temperature and its location, protective measures can be taken in time or in advance to reduce fire damage to the tunnel structure and extend the service life of the tunnel.

[0021] (3) Adaptability to complex terrain: This method provides a special prediction method for the maximum ceiling temperature and its location based on the special geographical and geological conditions of urban underground tunnels, so that it can be effectively used in tunnels with different slopes and different fire locations and has wide applicability.

[0022] (4) Improving safety standards: providing a scientific basis for the management and response to inclined tunnel fires, promoting the improvement of industry safety standards, and ensuring the safe operation of urban public transportation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a flow chart of the method for predicting the maximum temperature and position of the ceiling of an underground inclined tunnel during a fire.

[0024] Figure 2 Schematic diagram of the highest temperature location on the ceiling of an inclined tunnel fire. DETAILED DESCRIPTION

[0025] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0026] Embodiment 1:

[0027] like Figure 1 As shown, in one embodiment of the present invention, a method for predicting the maximum temperature and position of a fire ceiling in an underground inclined tunnel comprises the following steps:

[0028] S1. Calculate dimensionless induced wind speed;

[0029] S2. Determine the smoke flow state based on the dimensionless induced wind speed, and calculate the location of the maximum ceiling temperature and the maximum ceiling temperature.

[0030] In S1, the dimensionless induced wind speed is calculated The specific expression is:

[0031]

[0032] In the formula, H * is the dimensionless downstream height difference, and H*=L D sin(arctanα) / h,L D is the downstream length of the fire source, which is the distance between the fire source and the high-end exit of the tunnel, α is the tunnel slope, and h is the tunnel height.

[0033] In this embodiment, the dimensionless induced wind speed may also be calculated by the following formula:

[0034]

[0035] Where g is the acceleration due to gravity, v is inflow is the induced wind speed, b f0 is the radius of the fire source, T0 and ρ0 are the ambient temperature and density respectively.

[0036] In S2, the expression for calculating the position d of the maximum temperature of the ceiling is specifically:

[0037]

[0038] In the formula, H ef It is the vertical distance from the fire source surface to the ceiling.

[0039] In S2, the method for calculating the maximum temperature of the ceiling is specifically:

[0040] Calculate the maximum temperature rise of the ceiling. Calculate the maximum temperature of the ceiling based on the maximum temperature rise of the ceiling. Among them, calculate the maximum temperature rise of the ceiling ΔT max The specific expression is:

[0041]

[0042] In the formula, Q c is the convective heat release rate, c p is the specific heat capacity of air.

[0043] like Figure 2 As shown, in this embodiment, based on the method for determining the maximum ceiling temperature and position of an urban underground inclined tunnel fire, a fire scene of 150m×7.2m×4.8m, a downstream length of 67.5m, a slope of 5%, and a fire source power of 5MW is taken as an example to determine the maximum ceiling temperature and its position.

[0044] The dimensionless induced wind speed was calculated to be 0.209 using the formula of S1. Substituting it and other parameters into the formula of S2, the maximum temperature rise of the ceiling was calculated to be 228.28°C. The calculated maximum temperature position of the ceiling was 4.75m downstream of the fire source.

[0045] The beneficial effects of the present invention are as follows: the present invention provides a method for predicting the maximum temperature and position of the ceiling of an underground inclined tunnel fire, which has the following advantages over the prior art:

[0046] (1) Improve fire warning capabilities: By accurately predicting the maximum ceiling temperature and location when a fire occurs in an inclined tunnel, the fire source location can be effectively identified, providing important reference for rescue personnel and enhancing the timeliness and accuracy of fire emergency response.

[0047] (2) Reduce structural damage: By predicting the maximum ceiling temperature and its location, protective measures can be taken in time or in advance to reduce fire damage to the tunnel structure and extend the service life of the tunnel.

[0048] (3) Adaptability to complex terrain: This method provides a special prediction method for the maximum ceiling temperature and its location based on the special geographical and geological conditions of urban underground tunnels, so that it can be effectively used in tunnels with different slopes and different fire locations and has wide applicability.

[0049] (4) Improving safety standards: providing a scientific basis for the management and response to inclined tunnel fires, promoting the improvement of industry safety standards, and ensuring the safe operation of urban public transportation.

[0050] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "thickness", "upper", "lower", "horizontal", "top", "bottom", "inner", "outer", "radial", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying the relative importance or the number of implicitly specified technical features. Therefore, the features defined by "first", "second", and "third" may explicitly or implicitly include one or more of the features.

Claims

1. A method for predicting the maximum ceiling temperature and its location in underground inclined tunnel fires, characterized in that: The following steps are involved: S1. Calculate dimensionless induced wind speed; S2. Determine the smoke flow state based on the dimensionless induced wind speed, and calculate the location of the maximum ceiling temperature and the maximum ceiling temperature.

2. The method for predicting the maximum ceiling temperature and its position in an underground inclined tunnel fire according to claim 1, characterized in that: In S1, the dimensionless induced wind speed is calculated The specific expression is: In the formula, H * is the dimensionless downstream height difference, and H*=L D sin(arctanα) / h,L D is the downstream length of the fire source, α is the tunnel slope, and h is the tunnel height.

3. The method for predicting the maximum ceiling temperature and its position in an underground inclined tunnel fire according to claim 2, characterized in that: In S2, the expression for calculating the position d of the maximum temperature of the ceiling is specifically: In the formula, H ef It is the vertical distance from the fire source surface to the ceiling.

4. The method for predicting the maximum ceiling temperature and its position in an underground inclined tunnel fire according to claim 3, characterized in that: In S2, the method for calculating the maximum temperature of the ceiling is specifically: Calculate the maximum temperature rise of the ceiling. Calculate the maximum temperature of the ceiling based on the maximum temperature rise of the ceiling. Among them, calculate the maximum temperature rise of the ceiling ΔT max The specific expression is: In the formula, Q c is the convective heat release rate, c p is the specific heat capacity of air.

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