A scaled-down fire test platform for dispersed exhaust tunnels and a smoke exhaust efficiency calculation method

Abstract

This invention belongs to the research field of tunnel fire smoke control and proposes a decentralized exhaust tunnel scaled-down fire test platform and a smoke exhaust efficiency calculation method. The test platform's shaft height is adjustable, the shaft length can be continuously varied, the shaft smoke exhaust efficiency can be measured in real time, and the optimal shaft size and longitudinal wind speed can be determined. Through testing, the smoke exhaust efficiency and smoke spread distance under different shaft sizes and longitudinal wind speeds can be measured and analyzed, and the shaft size and longitudinal wind speed for optimal smoke exhaust performance can be determined. This invention can provide guidance for the ventilation and smoke exhaust design of tunnels with natural shaft smoke exhaust and tunnels that combine shaft and longitudinal ventilation for smoke exhaust.

Description

Technical Field

[0001] The present invention belongs to the research field of tunnel fire smoke control and relates to a decentralized emission tunnel scaled-down fire test platform and a smoke exhaust efficiency calculation method. Background Art

[0002] With my country's rapid economic and social development, the scale of tunnel construction has exploded. Currently, China has become the country with the largest and fastest-growing tunnel infrastructure in the world. Statistics show that by the end of 2022, my country's total tunnel mileage reached 48,762 kilometers, of which highway and railway tunnels accounted for 54.93% and 45.07%, respectively.

[0003] The increase in the number and total mileage of tunnels has further increased the probability of tunnel fire accidents. Because tunnels are narrow, long, and relatively enclosed, smoke from fires spreads rapidly and fills the tunnel space, posing a significant threat to trapped personnel and rescuers. According to statistics, approximately 85% of deaths are caused by asphyxiation from inhaling toxic and hazardous smoke. Therefore, tunnel fires are prone to causing mass casualties, significant economic losses, and severe social impacts.

[0004] In order to control the spread of smoke from tunnel fires and exhaust smoke in a timely and rapid manner, a series of ventilation and smoke exhaust measures are taken in actual projects. For urban tunnels and extra-long highway tunnels, vertical shaft smoke exhaust or a combination of vertical shaft and longitudinal ventilation is generally used to control smoke. Therefore, the smoke exhaust effect under different shaft sizes (length-to-width ratio, width-to-height ratio) and longitudinal wind speeds has received widespread attention. However, it is worth noting that, on the one hand, most of the current research on the smoke exhaust effect of shafts is based on numerical simulations. The simulation results are affected by the grid size and various assumptions, and it is difficult to reflect the actual fire scene. The reliability of the research results needs to be further verified by experimental means. On the other hand, in limited related experimental studies, there is a problem that the size of the shaft group (length and height) is difficult to continuously change and adjust, and it is difficult to accurately and quickly obtain the optimal shaft size corresponding to the optimal smoke exhaust effect.

[0005] In the study of the analysis of the smoke exhaust effect of the shaft based on numerical simulation, the width, length, height and longitudinal wind speed of the shaft can be continuously changed. The variation law of the smoke exhaust efficiency of the shaft with the longitudinal wind speed, shaft width, height and length is explored. The smoke flow behavior in the shaft and the smoke spread length of the tunnel ceiling are observed by setting velocity slices and temperature slices to evaluate the smoke exhaust effect. The accuracy of the velocity slice and temperature slice data is greatly affected by the computing resources and grid size. In effective experimental studies, the length and width of the shaft are mainly changed by adding fixed-size partitions. The adjustable range is limited, and almost no scholars have changed the height of the shaft. Among them, the widely used smoke exhaust efficiency calculation formula is as follows:

[0006]

[0007] Where m e is the CO mass flow rate (kg / s) discharged from the shaft; m represents the total CO generated (kg / s). This method uses CO concentration to characterize the flue gas mass flow rate. When the fuel in a fire is a clean fuel, such as a fire caused by a methanol or ethanol tanker leaking and igniting in a tunnel, the flue gas produced by the combustion is obviously primarily CO2. Therefore, using CO concentration to quantify the flue gas mass flow rate is not reasonable in this scenario.

[0008] In summary, the shortcomings of existing methods include:

[0009] First, numerical simulation methods cannot overcome the errors caused by factors such as grid size and computing resources on the simulation results, and the reliability of the simulation results needs to be verified through experimental means. Second, the range of adjustment for the length and height of the shaft in existing relevant scaled-down experimental platforms is relatively limited, which affects the accurate determination of the optimal shaft size. Third, the existing widely used smoke exhaust efficiency calculation is characterized by CO concentration, which is no longer applicable when the fire source is clean fuel. Therefore, in order to study the smoke exhaust efficiency of the shaft under real fire scenarios and determine the optimal shaft size, it is urgent to build a test platform that can continuously and dynamically adjust the shaft length and width, propose a calculation method for the shaft smoke exhaust efficiency applicable to different fuels, and find the optimal shaft size and the optimal longitudinal wind speed for smoke exhaust. Summary of the Invention

[0010] To address the aforementioned issues, the present invention proposes a scaled-down fire test platform for decentralized exhaust tunnels and a smoke exhaust efficiency calculation method. The test platform's shaft height is adjustable, the shaft length can be continuously varied, the shaft smoke exhaust efficiency can be measured in real time, and the optimal shaft size and longitudinal wind speed can be determined. Through testing, the smoke exhaust efficiency and smoke spread distance under different shaft sizes and longitudinal wind speeds can be measured and analyzed, and the shaft size and longitudinal wind speed for optimal smoke exhaust performance can be determined. This invention can provide guidance for the design of ventilation and smoke exhaust tunnels with natural shaft exhaust and tunnels that combine shaft and longitudinal ventilation for smoke exhaust.

[0011] The technical solutions of the present invention are as follows:

[0012] A decentralized discharge tunnel scaled-down fire test platform, comprising:

[0013] The tunnel body constitutes the basic structure of the test platform, including the bottom surface, ceiling and two side walls, one of which is made of transparent fireproof glass panels to facilitate observation of the spread of smoke in the tunnel and the smoke flow pattern in the shaft. The ceiling is provided with a number of openings;

[0014] Several shaft size variable devices, each of which is provided at each opening of the tunnel main body ceiling, and includes two long plates, a short plate, two slide rails, and an L-shaped plate. The short plate is provided between the two long plates, with both ends fixedly connected to the two long plates. The two long plates are provided with slide rails on their upper surfaces, and the L-shaped plate is slidably connected to the long plates via the slide rails to achieve dynamic adjustment of the shaft length;

[0015] The air velocity measurement system is arranged in the main body of the tunnel and includes multiple air velocity measurement points arranged along the height direction of the tunnel. It is used to measure the air velocity at different heights in the tunnel to ensure the stability and uniformity of the wind speed;

[0016] The flue gas temperature collection system includes multiple thermocouples arranged below the center of the shaft and inside the shaft to measure the temperature of the flue gas and evaluate the smoke spread and exhaust efficiency;

[0017] The flue gas velocity collection system includes multiple hot wire anemometers arranged below the center of the shaft and inside the shaft to measure the flue gas velocity and further analyze the flow characteristics of the flue gas;

[0018] The fire source simulation device is located at the bottom of the tunnel body and is used to simulate the fire source.

[0019] Furthermore, a fire source device operating window that can be opened and closed is provided on the other side wall of the tunnel body, which is used to adjust the fire source position and ignite the fire source.

[0020] Furthermore, the test platform also includes an axial flow fan located at one end of the tunnel body, which is used to generate longitudinal airflow and adjust the wind speed through a connected inverter to simulate smoke diffusion under different wind speed conditions.

[0021] Furthermore, the test platform also includes a rectifying section, which is composed of a curtain yarn, a metal mesh, a honeycomb panel and a curtain yarn in sequence, and is located after the axial flow fan to make the wind speed stable and uniform, thereby providing stable airflow conditions for the simulation experiment.

[0022] Furthermore, the air flow rate measurement system includes at least three air flow rate measurement points, which respectively measure the air flow rates near the tunnel ceiling, near the ground and in the center of the tunnel.

[0023] Furthermore, the test platform also includes a flow field visualization device, including several light sources and high-speed cameras, for observing and recording the spread of smoke in the tunnel, the thickness of the smoke layer and the flow pattern of smoke in the shaft.

[0024] Furthermore, the fire source simulation device includes a gas burner, a gas cylinder, a flow meter and a gas hose. The gas cylinder, flow meter and gas burner are connected in sequence through the gas hose, and the gas flow is adjusted by the flow meter to change the fire source power.

[0025] Furthermore, the long board, short board and L-shaped board are all made of transparent acrylic boards.

[0026] Furthermore, slots are provided at the upper edges of the long plates, short plates and L-shaped plates, which are used to change the height of the shaft by adding acrylic plates.

[0027] A method for calculating the smoke exhaust efficiency of a vertical shaft is provided. By using the above-mentioned decentralized exhaust tunnel scaled-down fire test platform to measure the smoke flow velocity and temperature data during the stable combustion phase, the smoke exhaust efficiency of the vertical shaft under different vertical shaft lengths, heights, and longitudinal wind speeds is calculated using the following formula:

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034] Wherein, η is the smoke exhaust efficiency; is the mass flow rate of flue gas discharged from the shaft (kg / s); is the gas mass flow rate discharged from the shaft (kg / s); is the mass flow rate of air discharged from the shaft (kg / s); ρ s,shaft is the density of the flue gas discharged through the shaft (kg / m 3 );v s,shaft is the flow rate of flue gas discharged through the shaft (m / s); A s,shaft is the area of ​​smoke discharged through the shaft (m 2 );ρ s,tunnel is the smoke density in the tunnel below the shaft (kg / m 3 );v s,tunnel is the flue gas velocity in the tunnel in front of the corresponding shaft (m / s); W tunnel is the tunnel width (m); h s,tunnel is the thickness of the smoke layer in the tunnel in front of the corresponding shaft (m); is the fire source power (kW); H tunnel is the tunnel height (m); T amb is the ambient temperature (K); ρ amb is the ambient density (kg / m 3 );T s,tunnel is the temperature of the smoke layer in the tunnel in front of the shaft (K).

[0035] Furthermore, by varying the shaft size and longitudinal wind speed, and calculating the smoke exhaust efficiency based on the aforementioned parameter data obtained from the test platform, and analyzing the smoke recirculation length and downstream spread distance, the smoke exhaust efficiency and smoke exhaust effect under different shaft sizes and longitudinal wind speeds can be obtained. By comparing the smoke exhaust efficiency and smoke exhaust effect, the higher the smoke exhaust efficiency, the shorter the smoke recirculation length, and the shorter the smoke spread distance, the better the smoke exhaust efficiency and smoke exhaust effect, and the corresponding shaft size and longitudinal wind speed are achieved.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] In response to existing research on the smoke exhaust effect of dispersed emission tunnel fires, the present invention overcomes the defect of using numerical simulation methods, which causes the reliability of research results to be affected by grid size and computing resources. Through a scaled-down test platform with corresponding scale, it can reflect the actual tunnel fire scene and obtain the most realistic smoke temperature and flow rate data to calculate the smoke exhaust efficiency, thereby realizing the reliability analysis of the vertical shaft smoke exhaust effect.

[0038] At the same time, this invention overcomes the challenges of existing decentralized tunnel fire reduction test platforms, such as the non-continuous adjustment of shaft length and height, the limited adjustment range, and the difficulty in observing the flow field within the shaft. By adding two slide rails and an L-shaped slide plate to the shaft, the shaft length can be continuously and dynamically adjusted. Furthermore, slots are added to the upper edge of the transparent acrylic sheet that forms the shaft, enabling adjustment of the shaft height. The use of transparent acrylic sheeting to form the shaft facilitates observation of the smoke flow pattern within the shaft using a sheet light source and a high-speed camera.

[0039] To address the shortcomings of existing shaft smoke exhaust efficiency calculations, which use CO concentration as a metric and are unsuitable for clean fuel fires, this paper proposes a shaft smoke exhaust efficiency calculation method applicable to various fire scenarios, with a wider range of applications. By using thermocouples and hot-wire anemometers to obtain data such as tunnel smoke temperature, smoke spread velocity, smoke layer thickness, smoke temperature and flow velocity at the exit of the shaft, and the area occupied by the smoke, the shaft smoke exhaust efficiency can be calculated.

[0040] In order to solve the problem that it is difficult to accurately define the optimal shaft size and the optimal longitudinal wind speed, the present invention can obtain the shaft smoke exhaust efficiency and smoke spread distance under different shaft sizes and longitudinal wind speeds through dynamic calculation, and continuously and dynamically adjust the shaft size and longitudinal wind speed by comparing the smoke exhaust effects. Finally, the optimal shaft size and optimal longitudinal wind speed corresponding to the best smoke exhaust effect can be obtained, providing guidance for the design of smoke exhaust parameters for dispersed emission tunnel fires. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1Schematic diagram of a scaled-down fire test platform for a dispersed emission tunnel according to an embodiment of the present invention.

[0042] Figure 2 Schematic diagram of a device for adjusting shaft size in an embodiment of the present invention.

[0043] Figure 3 Schematic diagram of the arrangement of thermocouples and wind speed measuring points below the shaft in an embodiment of the present invention.

[0044] Figure 4 This is a flow chart of measuring shaft smoke exhaust efficiency in an embodiment of the present invention.

[0045] In the figure: 1. Axial flow fan with inverter, 2. Rectifier section, 3. Air velocity measurement system, 4. Tunnel main structure, 5. Fire source device operation window, 6. Gas burner, 7. Gas cylinder, 8. Glass rotor flowmeter, 9. Gas hose, 10. Vertical shaft, 11. Thermocouple, 12. Hot wire anemometer, 13. Vertical ruler, 14. High-speed camera, 15. Light source sheet, 16. Long board, 17. Short board, 18. L-shaped board, 19. Slide rail, 20. Pulley, 21. Temperature collector, 22. Card slot. DETAILED DESCRIPTION

[0046] The principles and features of the present invention are described below with reference to the accompanying drawings and specific embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0047] Example 1

[0048] like Figures 1 to 3 As shown, a decentralized emission tunnel reduced-size fire test platform includes: a tunnel body 4, several shaft size variable devices 10, an air flow rate measurement system 3, a smoke temperature collection system 3, a smoke flow rate collection system, a fire source simulation device, an axial flow fan 1, a rectifying section 2 and a flow field visualization device.

[0049] The tunnel body 4, forming the basic structure of the test platform, includes a floor, ceiling, and two side walls. One side wall is constructed from transparent fireproof glass to facilitate observation of smoke spread within the tunnel and smoke flow patterns within the shaft. The other side wall, floor, and ceiling are constructed from fireproof materials, preferably stainless steel. The upper ceiling is provided with several openings, and a layer of calcium silicate fiberboard is laid underneath to maximize the simulation of the heat exchange conditions of an actual tunnel ceiling (made of concrete). A retractable fire source operating window is provided on the other side wall of the tunnel body. The length and width of the window are both larger than the fire source itself and are used to adjust the fire source's position and ignite it.

[0050] Several shaft size variable devices, each shaft size variable device is provided at each opening of the tunnel main body ceiling, including two long plates 16, a short plate 17, two slide rails 19 and an L-shaped plate 18, the long plate, short plate and L-shaped plate are all made of transparent acrylic plates, the short plate is provided between the two long plates, and the two long plates 16 are fixedly connected at both ends; the two slide rails 19 are fixedly connected to the two long plates 16 respectively, and the length of the slide rail 19 is the sum of the lengths of the long plates 16 and the L-shaped plates 18; four pulleys 20 are provided on the bottom surface of the L-shaped plate 18, and the L-shaped plate 18 is slidably connected to the long plates 16 through the pulleys 20 and the slide rails 19, so as to facilitate the continuous dynamic adjustment of the shaft length; the long plates, short plates and L-shaped plates are also provided with slots at their upper edges for changing the shaft height by adding acrylic plates ( Figure 2 ).

[0051] The air velocity measurement system 3, located at the center of the tunnel body 4, includes multiple air velocity measurement points arranged along the tunnel's height. Each measurement point is equipped with a hot-wire anemometer, positioned horizontally with the probe facing the incoming airflow. This system measures air velocity at different heights within the tunnel to ensure stable and uniform wind speed. At least three air velocity measurement points are provided, measuring air velocity near the tunnel ceiling, near the ground, and at the tunnel center. The velocity variance corresponding to these measurement points is calculated to assess the stability and uniformity of the longitudinal wind speed.

[0052] The flue gas temperature collection system includes multiple thermocouples 11 arranged below the center of the shaft and inside the shaft. These are used to measure the flue gas temperature and assess the spread and exhaust efficiency of the smoke. Specifically, a series of thermocouples are arranged at a position 0.01H below the tunnel ceiling (H is the tunnel height) to measure the maximum ceiling temperature and calculate the distance of smoke spread. A thermocouple tree is also arranged below the center of the shaft to measure the temperature and thickness of the smoke layer. Thermocouples are also arranged inside the shaft to measure the temperature of the smoke discharged through the shaft.

[0053] The flue gas velocity collection system includes a plurality of hot wire anemometers 12 arranged below the center of the shaft and inside the shaft, and is used to measure the velocity of the smoke layer in the tunnel and the velocity of the smoke discharged through the shaft.

[0054] The fire source simulation device includes a gas burner 6, a gas cylinder 7, a gas hose 9, and a flowmeter 8 located at the bottom of the tunnel body. The gas cylinder 7, flowmeter 8, and gas burner 6 are connected in sequence via the gas hose 9. The gas burner 6 is a square basin made of steel plate, the gas cylinder 7 is a liquefied petroleum gas cylinder, and the flowmeter 8 is a glass rotor flowmeter. Fine sand is laid inside the gas burner, and the sand surface is smooth. Fireproof cotton is placed under the fine sand. Liquefied petroleum gas is supplied through the gas hose 9. The gas flow rate can be adjusted by the flowmeter 8, thereby changing the fire source power. The fire source power is calculated by the gas supply rate. The advantage of gas fire is that the fire source power can be kept stable as the burning time changes, thus achieving a stable fire source power.

[0055] The axial flow fan 1 is located at one end of the tunnel body and is used to generate longitudinal airflow. The wind speed is adjusted by the connected frequency converter to simulate smoke diffusion under different wind speed conditions.

[0056] The rectifying section 2 is composed of four parts in sequence: tent yarn, metal mesh, honeycomb panel and tent yarn. It is located after the axial flow fan 1 and is used to make the wind speed stable and uniform, providing stable airflow conditions for the simulation experiment, and then analyzing the influence of different longitudinal wind speeds on the smoke exhaust efficiency of the shaft.

[0057] The flow field visualization device includes several light sheets 15 and a high-speed camera 14, used to visually observe the smoke flow patterns within the shaft, determine the smoke spread distance, and visually determine the smoke layer thickness. Specifically, in this example, two light sheets are provided: one is positioned from downstream toward upstream of the fire source, and the other is positioned from the tunnel floor toward the tunnel ceiling. The high-speed camera is placed on the side wall of the transparent fireproof glass panel, and a vertical ruler 13 is placed below the shaft. Combined with the smoke spread images captured by the high-speed camera, the vertical ruler is used to determine the smoke layer interface and thickness.

[0058] The tunnel body, axial flow fan, rectifier section and shaft group are connected by flanges, bolts and nuts. The joints of each component are sealed with tin foil to ensure that smoke does not leak during the test.

[0059] The test data can be used to calculate the smoke exhaust efficiency of the shaft under different shaft sizes and longitudinal wind speeds. By comparing the smoke exhaust efficiency and the smoke spread range, the shaft size and longitudinal wind speed can be continuously adjusted to determine the optimal shaft size and optimal longitudinal wind speed.

[0060] Example 2

[0061] A method for calculating shaft smoke exhaust efficiency utilizes data from the aforementioned decentralized exhaust tunnel scaled-down fire test platform. Prior to the test, the shaft dimensions to be analyzed are determined, including shaft width, length, and height, as well as the fire source power and longitudinal wind speed range. The shaft's L-shaped slide is then moved to the end closest to the shortest slide, closing the shaft. A temperature collector and hot-wire anemometer are then activated to collect temperature and velocity data. A light source and high-speed camera are then activated to record the smoke flow patterns within the shaft and tunnel.

[0062] For comparative analysis, we first analyzed the smoke flow behavior in tunnels without shaft-based natural smoke exhaust. First, by turning the gas cylinder valve and adjusting the flow meter, combustible gas was delivered to the gas burner through a hose. After igniting the fire, relevant test data was collected.

[0063] The vertical wind speed is then adjusted by the frequency converter to reach the wind speed value to be analyzed. The shafts are then opened one by one, and the shaft sizes are adjusted from the minimum size to the maximum. During this period, the smoke exhaust efficiency and smoke spread range obtained under different shaft sizes and longitudinal wind speeds are analyzed, and the smoke exhaust effects are compared. Based on the calculation results, the shaft size range is narrowed, and the shaft size is further adjusted. The smoke exhaust efficiency and smoke exhaust results under different shaft sizes are measured in real time. When the smoke exhaust efficiency is maximized and the smoke reflow length and spread distance are shortest, it is considered that the corresponding shaft size and longitudinal wind speed have reached the optimal level. If it is necessary to determine the optimal shaft size and longitudinal wind speed under different fire source powers, it is only necessary to adjust the flow meter to achieve the desired fire source power for analysis.

[0064] The flue gas velocity and temperature data during the stable combustion phase were measured, and the shaft exhaust efficiency was calculated under different shaft lengths, heights, and longitudinal wind speeds. The formula is as follows:

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071] Wherein, η is the smoke exhaust efficiency; is the mass flow rate of flue gas discharged from the shaft (kg / s); is the gas mass flow rate discharged from the shaft (kg / s); is the mass flow rate of air discharged from the shaft (kg / s); ρs,shaft is the density of the flue gas discharged through the shaft (kg / m 3 );v s,shaft is the flow rate of flue gas discharged through the shaft (m / s); A s,shaft is the area of ​​smoke discharged through the shaft (m 2 );ρ s,tunnel is the smoke density in the tunnel below the shaft (kg / m 3 );v s,tunnel is the flue gas velocity in the tunnel in front of the corresponding shaft (m / s); W tunnel is the tunnel width (m); h s,tunnel is the thickness of the smoke layer in the tunnel in front of the corresponding shaft (m); is the fire source power (kW); H tunnel is the tunnel height (m); T amb is the ambient temperature (K); ρ amb is the ambient density (kg / m 3 );T s,tunnel is the temperature of the smoke layer in the tunnel in front of the shaft (K).

[0072] like Figure 4 As shown, the specific steps for conducting the test based on the decentralized exhaust tunnel scaled-down fire test platform and smoke exhaust efficiency calculation method of the present invention are as follows:

[0073] First, measure and determine the tunnel width W tunnel 、Tunnel height H tunnel , ambient temperature T amb and environmental density ρ amb After the fire source power remains stable, obtain the key characteristic parameter data of the flue gas. The fire source power calculation formula is:

[0074]

[0075] η is the combustion efficiency, which is generally determined by the fuel type, ΔH is the combustion heat of the fuel (kJ / kg), is the mass burning rate (kg / s), for gas fire, It is the product of fuel density and output gas flow rate.

[0076] The smoke spreading image in the tunnel is obtained by using a light sheet and a camera, and the height of the smoke layer interface is determined by combining a vertical ruler. From this, the thickness of the smoke layer in the tunnel below the shaft can be determined. s,tunnel , and average the temperature data measured by the thermocouple measuring points above the smoke layer interface, and average the flue gas velocity data measured by the wind speed measuring points above the smoke layer interface, thereby obtaining the smoke layer temperature T in the tunnel in front of the shaft. s,tunnel , Smoke flow velocity v in the tunnel in front of the shaft s,tunnel .

[0077] At the same time, the smoke exhaust image at the shaft mouth is obtained by the light source and the camera above the shaft. According to the image analysis, the smoke exhaust area A at the smoke exhaust port is obtained. s,shaft Based on thermocouple and wind speed measurement points at the shaft entrance, the average temperature and average exhaust flue gas velocity within the exhaust area are obtained. By entering these parameters into the exhaust efficiency calculation formula, the exhaust efficiency for a specific shaft size and longitudinal wind speed can be calculated, enabling real-time measurement of exhaust efficiency.

[0078] At the same time, based on the temperature data of thermocouples arranged 0.01H below the ceiling along the longitudinal centerline of the tunnel, the location where the temperature suddenly increases at the measuring point is determined as the smoke front position, so that the smoke backflow length and downstream spread distance can be obtained, and the smoke exhaust effect can be analyzed.

[0079] In summary, the smoke exhaust efficiency and smoke exhaust effect under a specific shaft size can be obtained. Furthermore, by increasing the shaft size, the smoke exhaust efficiency and smoke exhaust effect under different shaft sizes and longitudinal wind speeds can be obtained. The higher the smoke exhaust efficiency, the shorter the smoke reflow length, and the shorter the smoke spread distance, the better the smoke exhaust efficiency and smoke exhaust effect. By comparing the two groups of smoke exhaust efficiency and smoke exhaust effect, and further narrowing the range of shaft sizes, the recommended shaft size is given by the dichotomy method, and the shaft smoke exhaust efficiency is given in turn based on the real-time measurement system. When the shaft smoke exhaust efficiency is the largest, the smoke reflow length and the smoke spread distance are the shortest, it is considered that the corresponding shaft size and longitudinal wind speed are optimal.

[0080] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for calculating the smoke exhaust efficiency of a shaft, characterized in that: The smoke flow rate and temperature data at the stable combustion stage were measured using a dispersed exhaust tunnel scaled fire test platform. The smoke exhaust efficiency of the shaft under different shaft lengths, heights, and longitudinal wind speeds was calculated using the following formula: ， in, For smoke exhaust efficiency; is the mass flow rate of flue gas discharged from the shaft; is the gas mass flow rate discharged from the shaft; is the mass flow rate of air exhausted from the shaft; is the density of flue gas discharged through the shaft; is the flow rate of flue gas discharged through the shaft; is the area of ​​flue gas discharged through the shaft; is the smoke density in the tunnel below the corresponding shaft; is the flue gas velocity in the tunnel in front of the corresponding shaft; is the tunnel width; is the thickness of the smoke layer in the tunnel in front of the corresponding shaft; is the fire source power; is the tunnel height; is the ambient temperature; is the environmental density; is the temperature of the smoke layer in the tunnel in front of the shaft; The decentralized discharge tunnel scaled-down fire test platform comprises: The tunnel body (4) constitutes the basic structure of the test platform, including a bottom surface, a ceiling and two side walls, wherein one side wall is formed by a transparent fireproof glass plate, and the ceiling is provided with a plurality of openings; A plurality of shaft size-variable devices (10), each of which is provided at each opening of the ceiling of the tunnel body (4), and comprises two long plates (16), a short plate (17), two slide rails (19) and an L-shaped plate (18); the short plate (17) is provided between the two long plates (16), with both ends fixedly connected to the two long plates (16); the two long plates (16) are provided with slide rails (19); and the L-shaped plate (18) is slidably connected to the long plate (16) via the slide rails (19); An air velocity measurement system (3) is arranged in the tunnel body (4), comprising a plurality of air velocity measurement points arranged along the height direction of the tunnel, for measuring the air velocity at different heights in the tunnel; a flue gas temperature collection system comprising a plurality of thermocouples (11) arranged below the tunnel ceiling, below the center of the shaft, and inside the shaft for measuring the temperature of the flue gas; A flue gas velocity collection system includes a plurality of hot wire anemometers (12) arranged below the center of the shaft and inside the shaft for measuring the flue gas velocity; The fire source simulation device is located at the bottom of the tunnel body (4) and is used to simulate the fire source.

2. The method for calculating the smoke exhaust efficiency of a shaft according to claim 1, characterized in that: A fire source device operating window (5) that can be opened and closed is provided on the other side wall of the tunnel body (4) and is used to adjust the position of the fire source and ignite the fire source.

3. The method for calculating the smoke exhaust efficiency of a shaft according to claim 1, characterized in that: The test platform also includes an axial flow fan (1) located at one end of the tunnel body (4) for generating longitudinal airflow and adjusting the wind speed via a connected frequency converter to simulate smoke diffusion under different wind speed conditions.

4. The method for calculating the vertical shaft smoke exhaust efficiency according to claim 1, characterized in that: The test platform also includes a rectifying section (2), which is composed of four parts in sequence: a curtain yarn, a metal mesh, a honeycomb panel and the curtain yarn, and is located after the axial flow fan to ensure a stable and uniform wind speed.

5. The method for calculating the vertical shaft smoke exhaust efficiency according to claim 1, characterized in that: The air velocity measurement system includes at least three air velocity measurement points, which respectively measure the air velocity near the tunnel ceiling, near the ground and in the center of the tunnel.

6. The method for calculating the smoke exhaust efficiency of a shaft according to claim 1, characterized in that: The test platform also includes a flow field visualization device, including a plurality of light sources (14) and a high-speed camera (15), for observing and recording the spread of smoke in the tunnel, the thickness of the smoke layer and the flow pattern of smoke in the shaft.

7. The method for calculating shaft smoke exhaust efficiency according to claim 1, characterized in that: The fire source simulation device comprises a gas burner (6), a gas cylinder (7), a flow meter (8) and a gas hose (9); the gas cylinder (7), the flow meter (8) and the gas burner (6) are connected in sequence via the gas hose (9); the gas flow rate is adjusted via the flow meter (8) to change the fire source power.

8. The method for calculating shaft smoke exhaust efficiency according to claim 1, characterized in that: The long plate (16), the short plate (17) and the L-shaped plate (18) are all made of transparent acrylic plates.

9. The method for calculating the smoke exhaust efficiency of a vertical shaft according to claim 1, characterized in that: The long plate (16), the short plate (17) and the L-shaped plate (18) are provided with slots at their upper edges for changing the height of the shaft by adding acrylic plates.

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