Intelligent ventilation and smoke prevention method based on three-dimensional interconnected underground space

Abstract

The present application belongs to the technical field of underground tunnel ventilation and smoke control and fire emergency response, and in particular to an intelligent ventilation and smoke control method based on three-dimensional interconnected underground space. The method comprises the following steps: S1: constructing a system hardware framework; S2: constructing a fire simulation working condition library; S3: temperature data validity and fire determination; S4: real-time positioning of a fire source based on a weighted centroid; S5: dynamic working condition matching and feedforward pressure prediction; S6: variable frequency speed regulation and establishment of a positive pressure barrier; and S7: closed-loop feedback and normal reset. The present application effectively compensates for the response lag of physical barrier facilities, significantly improves the positioning accuracy of linear fire sources, realizes dynamic variable air volume control based on the whole process of a fire, greatly shortens the emergency decision response time, and innovatively adopts a prefabricated working condition library + real-time lookup table technology path, replacing time-consuming real-time CFD simulation calculation. The system only needs to perform feature retrieval to output a control instruction, which can improve the decision response speed and meet the rapid disposal needs of sudden fires.

Description

Technical Field

[0001] This invention relates to the field of ventilation, smoke control, and fire emergency response technology for underground tunnels, specifically an intelligent ventilation and smoke control method based on a three-dimensional interconnected underground space. Background Technology

[0002] Typical scenarios include large-scale pumped storage power stations, urban underground utility tunnels, cross-regional tunnel complexes, and underground transportation network hubs. A significant characteristic of these projects is the large number of interconnected nodes between different functional zones and main traffic arteries. In order to meet the actual needs of transporting large equipment and facilitating high-density personnel passage, it is often difficult to install normally closed physical fire doors or physical fire compartments at the interconnected sections, resulting in the space being physically open or semi-open.

[0003] These interconnected underground spaces typically serve as core hubs for energy transmission and information exchange, often containing high-density power and control cables. Cables, as one of the primary fire load sources in underground engineering, exhibit significant propagation characteristics along their path. Unlike traditional point-source fires, once a cable fire occurs, the flames rapidly advance along the cable trays or supports, causing the fire source location to dynamically shift over time. The amount of smoke and thermal pressure generated also exhibit complex time-varying characteristics as the burning length increases.

[0004] In the event of an internal fire, open passageways can easily become rapid pathways for smoke to spread. Due to the combined effects of linear combustion characteristics and the unique chimney effect of underground spaces, high-temperature toxic smoke can quickly overcome resistance along the path and spread across areas under pressure differentials. Once smoke intrudes into core areas such as refuge buffer zones, it will not only seriously threaten the safe operation of valuable equipment inside, but also directly deteriorate the evacuation environment and cause critical rescue routes to fail.

[0005] Currently, smoke control designs for such large, interconnected three-dimensional spaces still primarily rely on traditional constant-volume ventilation, utilizing fixed-frequency fans to deliver air at constant positive pressure. However, this static defense approach has significant limitations when dealing with long-distance fires. On one hand, due to the large depth and randomness of the fire source location in underground spaces, the pressure attenuation of smoke reaching the connecting sections varies greatly, making it difficult for a fixed air volume to match the pressure demands arising from spatial heterogeneity. On the other hand, fire development exhibits typical time-varying characteristics, with the thermal pressure generated by the smoke fluctuating dramatically with the fire's intensity, rendering static airflow ineffective in precisely counteracting the dynamic pressure.

[0006] In this "one-size-fits-all" ventilation model, engineering practice often faces the dilemma of smoke control failure and evacuation difficulties. If the designed air supply intensity is too high, in the early stages of a fire or in distant fire conditions, it will lead to an excessive positive pressure gradient at the connection section, making the evacuation door unable to open due to the pressure difference on both sides exceeding the standard limit, seriously hindering personnel escape. Conversely, if the air supply intensity is insufficient, in the intense stage of a fire or in close-range fire conditions, the constant airflow will be unable to withstand the peak impact of smoke pressure, leading to the intrusion of toxic smoke. Therefore, developing an intelligent ventilation and smoke control system that can combine fire source location detection and fire evolution prediction to achieve dynamic and precise adjustment of air volume is of extremely important engineering significance for ensuring the overall safety of large and complex underground projects. Summary of the Invention

[0007] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0008] To address the aforementioned technical problems, according to one aspect of the present invention, the present invention provides the following technical solution:

[0009] S1: Constructing the system hardware framework: including the sensing unit, decision-making unit, and execution unit;

[0010] S2: Construct a fire simulation case library: Use fluid dynamics software to establish a 1:1 numerical model of the connecting channel and the core functional area, and set the fire source location and the heat release rate of cable fire.

[0011] S3: Temperature data validity and fire determination: The validity of the temperature data collected by the sensing unit is verified, and a fire is determined to have occurred when a continuous over-temperature zone that meets the preset length, temperature threshold and duration requirements appears in the connection channel.

[0012] S4: Real-time fire source location based on weighted centroid: The thermal control position of the fire source is calculated based on the relative temperature rise weight of each sampling point in the overheat zone, and the fire spread rate is calculated from the change of the fire front position in the continuous sampling period.

[0013] S5: Dynamic operating condition matching and feedforward pressure prediction: Input the fire source thermal control location, fire spread speed and current fire development stage into the fire simulation operating condition library, obtain the pressure evolution curve of the connection section by looking up the table or interpolation, and read the predicted intrusion pressure at future time. Superimpose the safety margin to obtain the target defense positive pressure.

[0014] S6: Variable frequency speed regulation and positive pressure barrier establishment: Calculate the target total pressure required by the air supply unit based on the target defense positive pressure and the friction resistance and local resistance of the air supply path, and convert the target operating frequency of the air supply unit according to the fan similarity law.

[0015] S7: Closed-loop feedback and normal reset: The operating frequency of the air supply unit is adjusted in a closed loop according to the actual pressure of the connection section, and the emergency mode is exited after the fire is extinguished, and the normal ventilation frequency is restored.

[0016] As a preferred embodiment of the intelligent ventilation and smoke prevention method based on three-dimensional interconnected underground space described in this invention, in step S1, the sensing unit adopts a DTS distributed fiber optic temperature measurement host laid along the top of the connecting channel to collect and transmit temperature distribution data along the path in real time. The DTS distributed fiber optic temperature measurement host is connected to the decision unit through an RS485 communication interface and transmits temperature and location data in real time using the Modbus-RTU protocol. The decision unit is based on a PLC controller and integrates a pre-made fire simulation condition library and intelligent calculation module. The PLC controller receives DTS data at its input end and is connected to a frequency converter through a 4-20mA analog interface at its output end. The execution unit is a blower unit configured at the top of the core functional area. Its motor is connected to the frequency converter. The frequency converter receives frequency commands from the PLC through the analog interface to adjust the speed of the blower unit, thereby forming airflow defense at the connection between the connecting channel without physical separation and the core functional area.

[0017] As a preferred embodiment of the intelligent ventilation and smoke prevention method based on three-dimensional interconnected underground space described in this invention, the specific method of S2 is as follows: Based on the fire characteristics of cables, multiple preset fire source locations, multiple fire spread rates, and a ramp function is used to control the heat release rate of the cables. The fire growth period is 0-420s, the stable period is 420-600s, and the decay period is 600-1200s. Pressure evolution curves when smoke spreads to the connection section under different combined operating conditions are calculated. The preset fire source locations, fire spread rate levels, heat release rate stages, and pressure evolution curves are mapped and stored in the decision unit.

[0018] As a preferred embodiment of the intelligent ventilation and smoke prevention method based on three-dimensional interconnected underground space described in this invention, in step S3, the temperature validity verification includes determining at least one of the following: communication interruption of distributed fiber optic temperature measurement data, spatial breakpoint, single-point abnormal jump, continuous sampling inconsistency, and temperature change exceeding the physical change limit. If there is a communication interruption, spatial breakpoint, single-point abnormal jump, continuous sampling inconsistency, or temperature change exceeding the physical change limit, the temperature data is determined to be invalid, triggering a sensor fault alarm and maintaining or switching to a preset safe ventilation mode. If the temperature data is valid, it is further determined whether a continuous over-temperature zone with a length of not less than 2m appears in the connecting channel, and the temperature in the continuous over-temperature zone is not lower than 60℃ and lasts for not less than 3s, then a fire is determined to have occurred and the emergency control logic is entered.

[0019] In a preferred embodiment of the intelligent ventilation and smoke prevention method based on three-dimensional interconnected underground space described in this invention, in step S4, to address the problem that the longitudinal wind speed of the connecting passage may cause the hot airflow to drift and result in inaccurate positioning of the traditional highest temperature point, a weighted centroid algorithm is adopted to select the start and end coordinates of the overheated area, perform integral weighting calculation on the temperature data in the area, calculate the thermal control position of the fire source, and simultaneously calculate the fire spread rate by the change in the fire front position within a continuous sampling period.

[0020] As a preferred embodiment of the intelligent ventilation and smoke control method based on three-dimensional interconnected underground space described in this invention, the specific method of S5 is as follows: when the thermal control position of the fire source and the fire spread speed are between adjacent preset indices in the fire simulation condition library, the system first performs linear interpolation along the direction of the fire source position, and then performs linear interpolation along the direction of the fire spread speed to obtain the pressure evolution curve of the connection section corresponding to the current fire state; the system extracts the expected smoke pressure value after the preset time window based on the current moment, and adds a safety margin on this basis to calculate the target defense positive pressure value required for the core functional area.

[0021] As a preferred embodiment of the intelligent ventilation and smoke prevention method based on three-dimensional interconnected underground space described in this invention, the specific method of S6 is as follows: the decision unit calculates the target total pressure required by the air supply unit based on the friction resistance and local resistance along the air supply path superimposed on the target defense positive pressure, and calculates the target operating frequency of the air supply unit according to the fan similarity law.

[0022] As a preferred embodiment of the intelligent ventilation and smoke prevention method based on three-dimensional interconnected underground space described in this invention, the specific method of S7 is as follows: A safety limiting logic is introduced, that is, it is determined whether the calculated target operating frequency exceeds the rated upper limit frequency of the air supply unit. If it exceeds the limit, the rated frequency is forcibly corrected to prevent equipment overload damage. Based on the decision result, the PLC controller sends an adjustment command to the frequency converter to control the air supply unit to accelerate operation in advance. The system synchronously triggers the audible and visual alarm at the connection section to warn on-site personnel and uploads key data such as fire location, pressure value, and equipment status to the SCADA central control system in real time to achieve remote monitoring and linkage.

[0023] As a preferred embodiment of the intelligent ventilation and smoke prevention method based on three-dimensional interconnected underground space described in this invention, the decision unit executes a fire source location and pressure prediction algorithm. The DTS distributed temperature sensing fiber optic system collects temperature distribution data T(x) within the connected channel in real time. When a continuous area is detected, i.e., a length greater than 2m and a temperature exceeding 60°C, a fire is determined to have occurred. The decision unit uses a weighted centroid algorithm to calculate the thermal control location of the fire source, and the calculation formula is as follows:

[0024]

[0025] In the formula, L c Let x1 and x2 be the start and end coordinates of the overheated zone, x be the spatial coordinates of any sampling point within the overheated zone, and T(x) be the real-time temperature data collected by the DTS distributed fiber optic temperature measurement host at the top of the connecting channel. Subsequently, the system searches the database for adjacent simulation conditions based on the calculated thermal control position of the fire source. If the fire source location is between preset points La and Lb, a linear interpolation method is used to generate the pressure evolution curve corresponding to the thermal control position of the fire source. The calculation formula is as follows:

[0026]

[0027] In the formula P c (t) represents the pressure evolution curve of the entire process corresponding to the thermal control location of the fire source, L a L b As a preset point, P a (t),P b (t) is the curve of cross-sectional pressure at a preset point as a function of time;

[0028] The system sets a feedforward response time window, based on the current moment, in the synthesized pressure evolution curve P c The timeline is read forward on (t) to obtain the expected intrusion pressure value at future moments. The calculation formula is as follows:

[0029]

[0030] In the formula P pred (t) represents the expected pressure intrusion value at a future time. t is the preset time window, t now The current moment;

[0031] The system performs dynamic positive pressure control, calculating the target defense positive pressure required for the core functional area. The calculation formula is as follows:

[0032]

[0033]

[0034] In the formula P target For the purpose of protecting against positive pressure, P pred (t) represents the expected pressure intrusion value at a future time, P safe For safety margin, P req ΔP is the target total pressure required by the blower unit. l For local resistance loss, ΔP f This refers to the friction loss along the air supply path;

[0035] The target operating frequency of the blower unit is calculated based on the similarity law of fans. After receiving the command, the frequency converter adjusts the speed of the blower unit to establish a positive pressure barrier at the connection section that matches the fire development. The calculation formula is as follows:

[0036]

[0037] In the formula, f target For the target operating frequency, f rate For the rated frequency of the air supply unit, P rate The rated total pressure of the air supply unit;

[0038] The frequency converter instructs the blower unit to adjust its speed and establish a dynamic positive pressure barrier at the connection section, forcing the flue gas flow direction to remain on one side of the connection channel.

[0039] Compared with the prior art, the beneficial effects of this invention are:

[0040] Effectively compensates for the response lag of physical barriers. Addressing the issues of delayed action and malfunction risks associated with the closing of normally open fireproof roller shutters, this invention establishes a stable positive pressure gradient. Before the physical barrier takes effect, the air pressure difference effectively overcomes the thermal buoyancy of smoke, preventing smoke from flowing back into the core functional area.

[0041] Significantly improves the positioning accuracy of linear fire sources. A weighted centroid algorithm is used to process DTS monitoring data, effectively filtering out local data jumps caused by wind speed in connecting channels and sensor noise, achieving precise positioning of the thermal control location of linear fire sources and ensuring accurate matching of operating conditions.

[0042] This system enables dynamic variable air volume control throughout the entire fire process. Based on the time-varying heat release rate characteristics of cable fires and the similarity law of fans, the air supply frequency is dynamically adjusted at each stage of fire growth, stabilization, and decay. This ensures the pressure margin required for smoke control while avoiding energy waste caused by excessive air supply.

[0043] This significantly shortens emergency decision-making and response time. It innovatively adopts a pre-built operational condition library combined with real-time table lookup technology, replacing time-consuming real-time CFD simulation calculations. The system only needs to perform feature retrieval to output control commands, improving decision-making response speed and meeting the rapid response needs of sudden fires. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and detailed embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0045] Figure 1 This is a system hardware architecture diagram of an intelligent ventilation and smoke prevention method based on a three-dimensional interconnected underground space according to the present invention.

[0046] Figure 2 This is a flowchart of an intelligent ventilation and smoke prevention method based on a three-dimensional interconnected underground space according to the present invention;

[0047] Figure 3 This is a cross-sectional pressure evolution curve of a near-field fire condition in Embodiment 1 of the present invention, which is a smart ventilation and smoke prevention method based on a three-dimensional interconnected underground space.

[0048] Figure 4 This is a cross-sectional pressure evolution curve for a mid-distance fire condition in Embodiment 2 of the present invention, which describes an intelligent ventilation and smoke prevention method based on a three-dimensional interconnected underground space.

[0049] Figure 5 This is a cross-sectional pressure evolution curve for a long-distance fire condition in Embodiment 3 of the present invention, which describes an intelligent ventilation and smoke prevention method based on a three-dimensional interconnected underground space.

[0050] In the diagram: 1. Natural smoke exhaust outlet; 2. Fire source; 3. DTS distributed temperature sensing fiber optic cable; 4. Direction of fire smoke spread; 5. Connection channel; 6. Direction of positive pressure protection for the fan; 7. DTS distributed fiber optic temperature measurement host; 8. Audible and visual alarm; 9. Connection section; 10. Differential pressure sensor; 11. Core functional area; 12. Air supply unit; 13. PLC controller; 14. Frequency converter; 15. Signal transmission cable; 16. SCADA central control system. Detailed Implementation

[0051] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0052] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0053] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0054] This invention utilizes a pre-built dynamic fire evolution database in FDS, combined with a distributed fiber optic temperature measurement system to monitor the fire source status in real time, and intelligently controls the speed of variable frequency fans to adjust the positive pressure value at the connection section, thereby achieving dynamic isolation of smoke generated by fire and providing a new method for fire ventilation in interconnected underground spaces.

[0055] Please see Figure 1 A smart ventilation and smoke control method based on three-dimensional interconnected underground space includes the following steps:

[0056] S1: System Hardware Configuration and Closed-Loop Link. The hardware architecture of this system mainly includes a sensing unit, a decision-making unit, and an execution unit. In terms of electrical connections, the sensing unit uses a DTS distributed fiber optic temperature measurement host 7 (model DTS-3000), which collects temperature signals along the path via a DTS distributed temperature-sensing fiber optic cable 3 (multimode 62.5 / 125μm) laid at the top of the connection channel 5. The sampling interval is set to 1m, and the temperature measurement accuracy is ±1°C. The DTS distributed fiber optic temperature measurement host 7 is connected to the decision-making unit via an RS485 communication interface, using the Modbus-RTU protocol to transmit temperature and location data in real time.

[0057] The decision-making unit uses PLC controller 13 (Siemens S7-1500 series PLC) as the core controller. Its input terminal receives DTS data, and its output terminal is connected to frequency converter 14 (ABB ACS880 series) through a 4-20mA analog interface.

[0058] The execution unit consists of two variable frequency air supply units 12 suspended from the top of the core functional area, each with a rated air volume of 120,000 m³ / h. 3 / h, rated full pressure 600Pa, the motor is connected to the frequency converter 14 through the signal transmission cable 15, the frequency converter 14 adjusts the speed according to the frequency command sent by the PLC controller 13 and feeds back the operating status.

[0059] S2: Constructing a Fire Simulation Condition Library. To address the technical challenge of excessively long real-time CFD fluid calculations during fires, which cannot meet the requirements for emergency response speed, this invention adopts an "offline prefabrication, online table lookup" strategy. Before system operation, a 1:1 numerical model of the connecting channel 5 (1000m long, 8m×8m cross-section) and the core functional area 11 is established using FDS fluid dynamics software. The mesh size is set to 0.2m×0.2m×0.2m to ensure calculation accuracy, the ambient temperature is set to 20°C, and the cable fire spread rate and heat release rate are set. For the fire characteristics of cables, a segmented heat release rate model is constructed using the ramp function. The fire growth period is 0-420s, the stable period is 420-600s, and the decay period is 600-1200s. By pre-setting several characteristic fire source 2 locations (such as 50m, 100m, 200m, 500m, etc. from the connection section) in the connection channel 5, the smoke spread process after ignition at each location is simulated, and dynamic data of the critical intrusion total pressure value when the smoke front reaches the connection section is extracted as a function of time. Finally, the correspondence between these characteristic locations, fire spread rate and pressure evolution curves is generated into a multi-dimensional database and stored in the PLC controller 13.

[0060] S3: Temperature Data Validity and Fire Detection. During online operation, the DTS distributed fiber optic temperature measurement host 7 collects the temperature distribution along the connection channel 5 according to a preset sampling period, and the differential pressure sensor 10 collects the actual pressure difference at the connection section 9. The PLC controller 13 first verifies the validity of the temperature data. The validity verification includes communication status verification, spatial continuity verification, single-point abnormal jump verification, and continuous sampling consistency verification. When there are breaks in the temperature data, communication loss, local jumps without physical meaning, or continuous sampling inconsistencies, the system triggers a sensor fault alarm and can enter a preset safe ventilation mode. If the temperature data passes the validity verification, it further determines whether there is a continuous over-temperature zone with a length of not less than 2m in the connection channel, and the temperature in the continuous over-temperature zone is not lower than 60℃ and lasts for not less than 3s. If so, a fire is determined and the emergency control logic is entered.

[0061] S4: Real-time Fire Source Location Based on Weighted Centroid. To address the issue of thermal airflow drift caused by longitudinal wind speed in the connecting channel, resulting in inaccurate positioning of the traditional highest temperature point, this solution employs a weighted centroid algorithm for fire source location correction. Instead of directly locking onto the highest temperature point, the decision unit selects the start and end coordinates of the overheated area and performs integral weighting calculations on the temperature data within that area to calculate the thermal control position of fire source 2. Simultaneously, the fire spread rate is calculated by the change in the fire front position within a continuous sampling period. This processing method effectively filters out positioning errors caused by sensor noise and airflow drag, ensuring that the fire source thermal control position parameters input to the control system are accurate and continuously stable.

[0062] S5: Dynamic Operating Condition Matching and Feedforward Pressure Prediction. Based on the calculated real-time thermal control position of the fire source, the system executes feedforward predictive control logic to overcome the response lag of the actuator. The DTS distributed fiber optic temperature measurement host 7 receives the fiber optic signal and transmits it to the PLC controller 13. The PLC controller 13 searches the operating condition database according to the thermal control position of the fire source 2. When the thermal control position of the fire source and the fire spread speed are between adjacent preset indices in the fire simulation operating condition database, the system first performs linear interpolation along the direction of the fire source position, and then performs linear interpolation along the direction of the fire spread speed to obtain the pressure evolution curve of the connection section corresponding to the current fire state. Based on the current moment, the system extracts the expected smoke pressure value after a preset time window in the future, and adds a safety margin to calculate the target defense positive pressure value required for the core functional area 11. This step achieves the active defense effect of "pressure rises before smoke arrives".

[0063] S6: Variable Frequency Speed ​​Regulation and Positive Pressure Barrier Establishment. Based on the similarity law of fans, the decision-making unit converts the calculated target positive pressure for defense into the target operating frequency of the air supply unit 12. On this basis, the system introduces safety limiting logic, that is, it judges whether the calculated target operating frequency exceeds the rated upper limit frequency of the air supply unit 12. If it exceeds the limit, the rated frequency is forcibly corrected to prevent equipment overload damage. According to the decision result, the PLC controller 13 sends an adjustment command to the frequency converter 14 to control the air supply unit 12 to accelerate in advance. The system synchronously triggers the audible and visual alarm 8 at the connection section to warn on-site personnel and uploads key data such as fire location, pressure value, and equipment status to the SCADA central control system 16 in real time, realizing remote monitoring and linkage. Through the above process, the system can establish a positive pressure air barrier matching the fire development on one side of the core functional area 11 before the smoke spreads to the connection section, effectively blocking the backflow of smoke by utilizing aerodynamic pressure difference, thereby ensuring the safety of the core functional area 11 in the absence of normally closed fire doors.

[0064] S7: Closed-loop feedback and normal reset. While executing control, the system continuously monitors temperature changes within connection channel 5 and pressure status in core functional area 11. When the actual pressure value collected in real-time by differential pressure sensor 10 is lower than the target positive pressure value calculated by the system for the air supply unit 12, PLC controller 13 instructs frequency converter 14 to increase the output frequency to accelerate the operation of air supply unit 12 and increase the air volume, forming a real-time closed-loop feedback. If a temperature drop is detected and the fire is determined to be extinguished, the system will automatically exit emergency mode, instruct air supply unit 12 to resume its normal ventilation frequency, and complete the system reset.

[0065] The specific algorithm of this invention is as follows: When the system is running online, the decision unit executes the fire source location and pressure prediction algorithm. The DTS distributed temperature sensing fiber optic cable 3 collects temperature distribution data T(x) within the connecting channel 5 in real time. When a continuous area is detected, i.e., a length greater than 2m and a temperature exceeding 60°C, a fire is determined to have occurred. To eliminate the location error caused by the ventilation speed of the connecting channel 5 and the sensor noise floor, the decision unit uses a weighted centroid algorithm to calculate the thermal control position of the fire source. The calculation formula is as follows:

[0066]

[0067] In the formula, L c Here, x1 and x2 represent the start and end coordinates of the overheated area, x represents the spatial coordinates of any sampling point within the overheated area, and T(x) represents the real-time temperature data collected by the DTS distributed fiber optic temperature measurement host 7 at the top of the connecting channel. This algorithm achieves high-precision positioning by integrating the high-temperature area. Subsequently, the system retrieves adjacent simulation conditions from the database based on the calculated thermal control position of the fire source. If the fire source location is between preset points La and Lb, a linear interpolation method is used to generate the pressure evolution curve corresponding to the thermal control position of the fire source. The calculation formula is as follows:

[0068]

[0069] In the formula P c (t) represents the pressure evolution curve of the entire process corresponding to the thermal control location of the fire source, L a L b As a preset point, P a (t),P b (t) is the curve of cross-sectional pressure at a preset point changing with time.

[0070] The system sets a feedforward response time window, based on the current moment, in the synthesized pressure evolution curve P c The timeline is read forward on (t) to obtain the expected intrusion pressure value at future moments. The calculation formula is as follows:

[0071]

[0072] In the formula P pred (t) represents the expected pressure intrusion value at a future time. t is the preset time window, t now This refers to the current moment.

[0073] The system performs dynamic positive pressure control, calculating the target defense positive pressure required for the core functional area. The calculation formula is as follows:

[0074]

[0075]

[0076] In the formula P target For the purpose of protecting against positive pressure, P pred (t) represents the expected pressure intrusion value at a future time, P safe For safety margin, P req ΔP is the target total pressure required by the blower unit. l For local resistance loss, ΔP f This refers to the resistance loss along the air supply path.

[0077] Based on the similarity law of fans, the target operating frequency of the blower unit 12 is calculated. After receiving the command, the frequency converter 14 adjusts the speed of the blower unit 12 to establish a positive pressure barrier at the connection section that matches the fire development. The calculation formula is as follows:

[0078]

[0079] In the formula, f target For the target operating frequency, f rate For the rated frequency of the blower unit 12, P rate The rated full pressure of the air supply unit 12.

[0080] According to this instruction, the frequency converter 14 adjusts the speed of the blower unit 12 to establish a dynamic positive pressure barrier at the connection section, forcing the flue gas flow direction to remain on one side of the connection channel.

[0081] To verify the wide applicability and beneficial effects of the present invention under different fire scenarios, this embodiment conducted experimental verification under three specific working conditions (near, medium and far) and provides detailed parameter settings and result data.

[0082] Example 1: Close-range high-pressure impact condition. The fire source is set at 100m from the core functional area, a high-risk condition. 30 seconds after the fire starts, the DTS monitors an abnormal temperature in the 98m-102m section. The PLC, using a weighted centroid algorithm, calculates the thermal control position of the fire source to be approximately 100.1m, and the fire spread velocity is obtained as 0.24m / s from the change in the fire front position. The system directly matches the condition "100m + 0.24m / s" in the database. Due to the close distance, the system predicts that the smoke will reach the connection section at 420 seconds, with an expected peak pressure of 42Pa. The PLC calculates the positive pressure at the target section to be 48Pa. Considering that the airflow needs to pass through the space of the core functional area to reach the connection section, and needs to overcome the local resistance and pressure attenuation along the flow path caused by the air supply shaft, the silencer plenum box, and the equipment in the plant, the similarity law formula is applied, and the frequency converter is instructed to output 45.6Hz. The measured results show that a positive pressure of 48 Pa was established in the core functional area within 390 seconds. When the flue gas leading edge arrived at 420 seconds, the wind speed at the connecting section was 1.2 m / s, successfully blocking the high-pressure flue gas outside the core functional area (the pressure evolution curve of the section is shown in Figure 1). Figure 3 (As shown).

[0083] Example 2: Mid-range interpolation matching condition. The fire source was set 280m away from the core functional area to test the interpolation accuracy of the algorithm. 60 seconds after the fire started, the algorithm calculated the thermal control position L of the fire source. c =280.5m, between the preset points of 200m and 300m. The system automatically retrieves two sets of data and performs linear interpolation to predict the critical flue gas pressure at 240 seconds as 14Pa. The system sets the target positive pressure to 19Pa and calculates the target frequency to be approximately 42Hz. The 19Pa positive pressure established at the connection section effectively blocks the flue gas and avoids excessive noise and unnecessary energy consumption in the core functional area due to excessive airflow. A reverse airflow of 0.8m / s is always maintained at the connection section (the pressure evolution curve of the section is shown in Figure 1). Figure 4 (As shown).

[0084] Example 3: Long-Distance Attenuation Energy-Saving Condition. The fire source was set at 500m and in the fire attenuation stage. The DTS (Digital Sensing System) detected a decrease in the temperature rise rate, precisely at a preset characteristic point. The database showed that the flue gas pressure at 900s had decreased from a peak of 12Pa to 4Pa. Based on the real-time pressure curve, the decision unit automatically lowered the target positive pressure to 9Pa, and the fan frequency automatically and smoothly decreased from the initial 35Hz to 28Hz. During this stage, the system power consumption was only 17% of the rated power, achieving significant energy-saving operation, while preventing difficulties in opening evacuation doors in core functional areas due to excessive air supply (cross-sectional pressure evolution curve as shown in the figure). Figure 5 (As shown).

[0085] Although the present invention has been described above with reference to embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, as long as there is no structural conflict, the features in the disclosed embodiments can be combined with each other in any manner. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A smart ventilation and smoke control method based on a three-dimensional interconnected underground space, characterized in that, Includes the following steps: S1: Constructing the system hardware framework: including the sensing unit, decision-making unit, and execution unit; The sensing unit employs a DTS distributed fiber optic temperature measurement host installed along the entire connecting channel to collect and transmit temperature distribution data along the path in real time. The DTS distributed fiber optic temperature measurement host is connected to the decision unit via an RS485 communication interface and uses the Modbus-RTU protocol to transmit temperature and location data in real time. The decision unit is based on a PLC controller and integrates a pre-built fire simulation condition library and intelligent calculation module. The PLC controller receives DTS data at its input end and connects to the frequency converter at its output end via a 4-20mA analog interface. The execution unit is a blower unit configured at the top of the core functional area. Its motor is connected to the frequency converter, which receives frequency commands from the PLC via an analog interface to adjust the speed of the blower unit, thereby forming an airflow defense at the connection between the connecting channel and the core functional area where there is no physical barrier. S2: Construct a fire simulation case library: Use fluid dynamics software to establish a 1:1 numerical model of the connecting channel and the core functional area, and set the fire source location and the heat release rate of cable fire. Based on the fire characteristics of cables, multiple preset fire source locations, multiple fire spread rates, and the heat release rate of the cable are set using a ramp function. The fire growth period is 0-420s, the stable period is 420-600s, and the decay period is 600-1200s. The pressure evolution curves of smoke spreading to the connection section under different combinations of working conditions are calculated. The preset fire source locations, fire spread rate levels, heat release rate stages, and pressure evolution curves are mapped and stored in the decision unit. The decision unit executes a fire source location and pressure prediction algorithm. The DTS distributed temperature sensing fiber optic system collects real-time temperature distribution data T(x) within the connection channel. When a continuous area is detected, i.e., a length greater than 2m and a temperature exceeding 60°C, a fire is determined to have occurred. The decision unit uses a weighted centroid algorithm to calculate the thermal control location of the fire source. The calculation formula is as follows: In the formula, L c Let x1 and x2 be the start and end coordinates of the overheated zone, x be the spatial coordinates of any sampling point within the overheated zone, and T(x) be the real-time temperature data collected by the DTS distributed fiber optic temperature measurement host at the top of the connecting channel. Subsequently, the system searches the database for adjacent simulation conditions based on the calculated thermal control position of the fire source. If the thermal control position of the fire source is between preset points La and Lb, a linear interpolation method is used to generate the pressure evolution curve corresponding to the thermal control position of the fire source. The calculation formula is as follows: In the formula P c (t) represents the pressure evolution curve of the entire process corresponding to the thermal control location of the fire source, L a L b As a preset point, P a (t),P b (t) is the curve of cross-sectional pressure at a preset point as a function of time; The system sets a feedforward response time window, based on the current moment, in the synthesized pressure evolution curve P c The timeline is read forward on (t) to obtain the expected intrusion pressure value at future moments. The calculation formula is as follows: In the formula P pred (t) represents the expected pressure intrusion value at a future time. t is the preset time window, t now The current moment; The system performs dynamic positive pressure control, calculating the target defense positive pressure required for the core functional area. The calculation formula is as follows: In the formula P target To protect the target section from positive pressure, P pred (t) represents the expected pressure intrusion value at a future time, P safe For safety margin, P req ΔP is the target total pressure required by the air supply unit. l For local resistance loss, ΔP f This refers to the friction loss along the air supply path; The target operating frequency of the blower unit is calculated based on the similarity law of fans. After receiving the command, the frequency converter adjusts the speed of the blower unit to establish a positive pressure barrier at the connection section that matches the fire development. The calculation formula is as follows: In the formula, f target For the target operating frequency, f rate For the rated frequency of the air supply unit, P rate The rated total pressure of the air supply unit; The frequency converter instructs the blower unit to adjust its speed and establish a dynamic positive pressure barrier at the connection section, forcing the flue gas flow direction to remain on one side of the connection channel. S3: Temperature data validity and fire determination: The validity of the temperature data collected by the sensing unit is verified, and a fire is determined to have occurred when a continuous over-temperature zone that meets the preset length, temperature threshold and duration requirements appears in the connection channel. S4: Real-time fire source location based on weighted centroid: The thermal control position of the fire source is calculated based on the relative temperature rise weight of each sampling point in the overheat zone, and the fire spread rate is calculated from the change of the fire front position in the continuous sampling period. S5: Dynamic operating condition matching and feedforward pressure prediction: Input the fire source thermal control location, fire spread speed and current fire development stage into the fire simulation operating condition library, obtain the pressure evolution curve of the connection section by looking up the table or interpolation, and read the predicted intrusion pressure at future time. Superimpose the safety margin to obtain the target defense positive pressure. S6: Variable frequency speed regulation and positive pressure barrier establishment: Calculate the target total pressure required by the air supply unit based on the target defense positive pressure and the friction resistance and local resistance of the air supply path, and convert the target operating frequency of the air supply unit according to the fan similarity law. S7: Closed-loop feedback and normal reset: The operating frequency of the air supply unit is adjusted in a closed loop according to the actual pressure of the connection section, and the emergency mode is exited after the fire is extinguished, and the normal ventilation frequency is restored.

2. The intelligent ventilation and smoke control method based on a three-dimensional interconnected underground space according to claim 1, characterized in that, In step S3, the temperature validity verification includes determining at least one of the following: communication interruption, spatial breakpoint, single-point abnormal jump, continuous sampling inconsistency, and temperature change exceeding the physical change limit of the distributed fiber optic temperature measurement data. If any of these conditions exist, the temperature data is determined to be invalid, triggering a sensor fault alarm and maintaining or switching to a preset safe ventilation mode. If the temperature data is valid, it is further determined whether a continuous over-temperature zone with a length of not less than 2 m appears in the connection channel, and the temperature in the continuous over-temperature zone is not lower than 60°C and lasts for not less than 3 seconds. In this case, a fire is determined to have occurred and the emergency control logic is entered.

3. The intelligent ventilation and smoke control method based on a three-dimensional interconnected underground space according to claim 1, characterized in that, In S4, to address the issue that longitudinal wind speed in the connecting channel may cause hot airflow to drift and lead to inaccurate positioning of the traditional highest temperature point, a weighted centroid algorithm is adopted. The start and end coordinates of the overheated area are selected, and the temperature data in the area is integrated and weighted to calculate the thermal control position of the fire source. At the same time, the fire spread rate is calculated by the change in the fire front position within a continuous sampling period.

4. The intelligent ventilation and smoke control method based on a three-dimensional interconnected underground space according to claim 1, characterized in that, The specific method of S5 is as follows: when the thermal control position of the fire source and the fire spread speed are between adjacent preset indices in the fire simulation condition library, the system first performs linear interpolation along the direction of the fire source position, and then performs linear interpolation along the direction of the fire spread speed to obtain the pressure evolution curve of the connection section corresponding to the current fire state; the system extracts the expected smoke pressure value after the preset time window based on the current moment, and adds a safety margin on this basis to calculate the target defense positive pressure value required by the core functional area.

5. The intelligent ventilation and smoke control method based on a three-dimensional interconnected underground space according to claim 1, characterized in that, The specific method of S6 is to calculate the target total pressure required by the air supply unit based on the calculated target defense positive pressure superimposed with the friction resistance and local resistance of the air supply path, and to convert the target operating frequency of the air supply unit according to the fan similarity law.

6. The intelligent ventilation and smoke prevention method based on a three-dimensional interconnected underground space according to claim 1, characterized in that, The specific method of S7 is to introduce safety limiting logic, that is, to determine whether the calculated target operating frequency exceeds the rated upper limit frequency of the air supply unit. If it exceeds the limit, the rated frequency is forcibly corrected to prevent equipment overload damage. According to the decision result, the PLC controller sends an adjustment command to the frequency converter to control the air supply unit to accelerate in advance. The system synchronously triggers the audible and visual alarm at the connection section to warn on-site personnel, and uploads key data such as fire location, pressure value and equipment status to the SCADA central control system in real time to realize remote monitoring and linkage.

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