Time division multiplexing early-stage smoke and fire detection system for multi-building-group complex underground structure

Abstract

The invention discloses a time division multiplexing early-stage smoke and fire detection system for a multi-building-group complex underground structure. The system comprises a general control unit which comprises a signal processing system and a laser emission system; the laser emission system comprises a pulse fiber laser with the central wavelength of 1572 nm, and pulse light is alternately emitted through an internal optical switch and used for detecting the CO2 concentration and the smoke concentration; the laser emission system is connected with the N arranged probes through the N-channel optical fiber optical switch; according to the invention, high real-time performance is achieved, cooperative detection of multiple building groups can be realized, and sensitive early-stage smoke and fire detection capability is realized.

Description

Technical Field

[0001] The present invention relates to the field of laser radar technology, and in particular to a time-division multiplexed early smoke and fire detection system for complex underground structures of multiple buildings. Background Art

[0002] Currently, smoke and fire detection systems for traditional underground complexes (such as subway tunnels, utility corridors, and underground shopping malls) typically utilize a sensor network approach: point-type smoke / heat detectors or linear beam detectors, deployed regionally and directly connected to a control host. Detector signals are processed by a centralized controller via wired or wireless transmission, then uploaded to a monitoring platform, triggering an alarm.

[0003] However, the above-mentioned traditional sensor network solutions have problems such as insufficient real-time and reliability, weak collaborative detection capabilities for multiple building clusters, and low sensitivity for early fire and smoke detection. In terms of real-time and reliability, fire and smoke signal transmission delays are high, and multi-channel signals are prone to conflict or loss (especially wireless solutions). In addition, the underground environment's strong attenuation characteristics for electromagnetic waves limit the reliability of wireless solutions. In terms of collaborative detection capabilities for multiple building clusters, each building cluster is independently networked, and data needs to be transferred multiple times, resulting in delays and superposition. This makes it difficult to uniformly process fire and smoke signals across building clusters, and the existence of information islands. In terms of early fire and smoke detection sensitivity, traditional detectors respond slowly to tiny fireworks or local high temperatures and are prone to missed reports. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a time-division multiplexed early smoke and fire detection system for complex underground structures of multiple building complexes, which can achieve high real-time performance, can be used for collaborative detection of multiple building complexes, and has sensitive early smoke and fire detection capabilities, so as to solve the problems existing in the background technology.

[0005] Technical solution: The present invention discloses a time-division multiplexing multi-building complex underground structure early smoke and fire detection system, comprising: a master control unit including a signal processing system and a laser emission system; the laser emission system includes a pulsed fiber laser with a central wavelength of 1572nm, which emits a wavelength of λ alternately through an internal optical switch. on =1572.335nm, λ off =1572.454nm pulse light is used to detect CO2 concentration and smoke concentration; the laser emission system is connected to multiple deployed probes through an N-channel fiber optic switch.

[0006] Furthermore, multiple probes are arranged according to the structural characteristics of the underground layers of each building and activated in sequence through a time-division multiplexing strategy.

[0007] Furthermore, the probe layout needs to completely cover the underground space.

[0008] Furthermore, the time interval between each channel in the optical switch is T, that is, the detection time of each probe is T; the probes are classified according to the building and all the probes of building 1 to building X are activated in sequence.

[0009] Furthermore, the signal processing system uses the echo signal Q on and Q off Inverse calculation of CO2 concentration and smoke concentration.

[0010] Furthermore, according to Q on and Q off Calculation of CO2 concentration includes the following steps:

[0011] Step 1, calculate the distance R j The differential optical depth ΔDOD at , as shown in formula (1):

[0012]

[0013] Step 2, calculate the actual CO2 concentration X (ppm) according to formula (2):

[0014]

[0015] Where R = 8.314 Pa·m 3 / (mol·K) is the gas constant, T is the measurement temperature, and ΔR is the j The distance resolution at NA is 6.022×10 23 is Avogadro's constant, and P is the total gas pressure. on and σ off is λ on and λ off The corresponding laser absorption cross section is related to temperature and pressure and can be found through the HITRAN database.

[0016] Furthermore, according to Q off Calculate smoke density:

[0017] (1) According to the detected Q off (R j ), according to formula (3) the laser radar equation:

[0018]

[0019] Get λ off The transmittance of laser atmospheric transmission Where E is the energy of the emitted single pulse, η0 is the optical efficiency of the transmitted signal, and η q is the quantum efficiency, h is the Planck constant, A t is the area of ​​the telescope, R jis the distance, j indicates the distance guide, v is the emission frequency, O(R j ) is the geometric overlap factor, β is the Mie scattering backscattering coefficient;

[0020] (2) According to Calculate the aerosol extinction coefficient α a , that is, formula (4):

[0021]

[0022] Among them, α a is the extinction coefficient caused by aerosol scattering and absorption, α m is the extinction coefficient of the molecule.

[0023] (3) Calculate the smoke concentration N. The aerosol extinction coefficient is proportional to the smoke concentration, as shown in formula (5):

[0024]

[0025] Where k is the mass extinction coefficient, unit is m 2 / g, determined by the physical and chemical properties of the smoke, which can be obtained by looking up the table.

[0026] Furthermore, thresholds are set for CO2 concentration and smoke concentration to provide graded warnings for fire.

[0027] Furthermore, the graded warning is as follows: first, determine whether the smoke concentration exceeds the threshold. If so, issue a preliminary warning; then determine whether the CO2 concentration exceeds the threshold. If so, trigger the alarm mechanism and link the fire protection system.

[0028] Beneficial effects: Compared with the existing technology, the present invention has the following significant advantages: (1) Traditional point sensors / temperature sensors rely on physical contact and require smoke to diffuse to the vicinity of the sensor. The system proposed by this technology uses laser remote sensing detection technology to monitor changes in trace smoke concentrations and trace CO2 concentrations in the air, and achieve non-contact early detection in the early stages of a fire. (2) Traditional sensor networks are subject to electromagnetic interference from the underground environment, while the optical fiber of this system is resistant to electromagnetic interference, and the system is more stable. (3) Traditional sensor networks require relay amplifiers, and the signal attenuation is severe. The optical fiber of this system has low loss characteristics, does not require relays, and can achieve unified management of cross-regional data. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the present invention;

[0030] Figure 2 It is a schematic diagram of the probe arrangement structure of the present invention;

[0031] Figure 3 It is a schematic diagram of the time division multiplexing opening probe of the present invention;

[0032] Figure 4 It is a hierarchical warning flow chart of the present invention. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0034] like Figure 1 As shown, the embodiment of the present invention provides a time-division multiplexing multi-building complex underground structure early smoke and fire detection system, comprising: a master control unit including a signal processing system and a laser emission system; the laser emission system includes a pulsed fiber laser with a central wavelength of 1572nm, which emits a wavelength λ alternately through an internal optical switch on =1572.335nm, λ off =1572.454nm pulse light is used to detect CO2 concentration and smoke concentration; the laser emission system is connected to multiple probes through an N-channel fiber optic switch. Figure 2 As shown in Figure 1, multiple probes are deployed based on the structural characteristics of each building's underground layer and activated sequentially using a time-division multiplexing strategy. The probes must be deployed to completely cover the underground space, and the fiber optic transmission path must be resistant to electromagnetic interference. The time interval between each channel in the optical switch is T, that is, the detection time of each probe is T; Figure 3 As shown, the probes are classified according to the building. First, each probe in building 1 is opened in turn. After all probes in building 1 complete the detection, the probes under the next building are opened in turn until building X.

[0035] Among them, the signal processing system uses the echo signal Q on and Q off Inverse calculation of CO2 concentration and smoke concentration. on and Q off Calculation of CO2 concentration includes the following steps:

[0036] Step 1, calculate the distance R j The differential optical depth ΔDOD at , as shown in formula (1):

[0037]

[0038] Step 2, calculate the actual CO2 concentration x (ppm) according to formula (2):

[0039]

[0040] Where R = 8.314 Pa·m 3 / (mol·K) is the gas constant, T is the measurement temperature, and ΔR is the jThe distance resolution at NA is 6.022×10 23 is Avogadro's constant, and P is the total gas pressure. on and σ off is λ on and λ off The corresponding laser absorption cross section is related to temperature and pressure and can be found through the HITRAN database.

[0041] Among them, according to Q off Calculate smoke density:

[0042] (1) According to the detected Q off (R j ), according to formula (3) the laser radar equation:

[0043]

[0044] Get λ off The transmittance of laser atmospheric transmission Where E is the energy of the emitted single pulse, η0 is the optical efficiency of the transmitted signal, and η q is the quantum efficiency, h is the Planck constant, A t is the area of ​​the telescope, R j is the distance, j indicates the distance guide, v is the emission frequency, O(R j ) is the geometric overlap factor, β is the Mie scattering backscattering coefficient;

[0045] (2) According to Calculate the aerosol extinction coefficient α a , that is, formula (4):

[0046]

[0047] Among them, α a is the extinction coefficient caused by aerosol scattering and absorption, α m is the extinction coefficient of the molecule.

[0048] (3) Calculate the smoke concentration N. The aerosol extinction coefficient is proportional to the smoke concentration, as shown in formula (5):

[0049]

[0050] Where k is the mass extinction coefficient, unit is m 2 / g, determined by the physical and chemical properties of the smoke, which can be obtained by looking up the table.

[0051] like Figure 4As shown, thresholds are set for CO2 and smoke concentrations to provide graded early warnings for fire severity. During the combustion process, incomplete combustion at the beginning produces a large amount of smoke. Once the fire reaches a certain intensity, it combines with oxygen in the air to fully combust and produce CO2. During graded early warnings, the smoke concentration is first determined to be above the threshold. If so, an initial early warning is issued. The CO2 concentration is then determined to be above the threshold. If so, an alarm mechanism is triggered and the fire protection system (such as sprinkler / ventilation) is activated.

Claims

1. A time-division multiplexing system for early smoke and fire detection in complex underground structures of multiple buildings, characterized by: include: The main control unit includes a signal processing system and a laser emission system; the laser emission system includes a pulsed fiber laser with a central wavelength of 1572nm, which emits wavelengths λ alternately through an internal optical switch on =1572.335nm, λ off =1572.454nm pulse light is used to detect CO2 concentration and smoke concentration; the laser emission system is connected to the N probes through an N-channel fiber optic switch.

2. The time-division multiplexing multi-building complex underground structure early smoke and fire detection system according to claim 1 is characterized in that: Multiple probes are arranged according to the structural characteristics of the underground layers of each building and activated in sequence through a time-division multiplexing strategy.

3. The time-division multiplexing multi-building complex underground structure early smoke and fire detection system according to claim 2 is characterized in that: The probe layout must completely cover the underground space.

4. The time-division multiplexing multi-building complex underground structure early smoke and fire detection system according to claim 1 is characterized in that: The time interval between each channel in the optical switch is T, that is, the detection time of each probe is T; the probes are classified according to the building and all probes from building 1 to building X are activated in sequence.

5. The time-division multiplexing multi-building complex underground structure early smoke and fire detection system according to claim 1 is characterized in that: The signal processing system uses the echo signal Q on and Q off Inverse calculation of CO2 concentration and smoke concentration.

6. The time-division multiplexing multi-building complex underground structure early smoke and fire detection system according to claim 5 is characterized in that: According to Q on and Q off Calculation of CO2 concentration includes the following steps: Step 1, calculate the distance R j The differential optical depth ΔDOD at , as shown in formula (1): Step 2, calculate the actual CO2 concentration x (ppm) according to formula (2): Where R = 8.314 Pa·m 3 / (mol·K) is the gas constant, T is the measurement temperature, and ΔR is the j The distance resolution at NA is 6.022×10 23 is Avogadro's constant, and P is the total gas pressure. on and σ off is λ on and λ off The corresponding laser absorption cross section is related to temperature and pressure and can be found through the HITRAN database.

7. The time-division multiplexing multi-building complex underground structure early smoke and fire detection system according to claim 5, characterized in that: According to Q off Calculate smoke density: (1) According to the detected Q off (Rj), from the laser radar equation (3): Get λ off The transmittance of laser atmospheric transmission Where E is the energy of the emitted single pulse, η0 is the optical efficiency of the transmitted signal, and η q is the quantum efficiency, h is the Planck constant, A t is the area of ​​the telescope, R j is the distance, j indicates the distance guide, v is the emission frequency, O(R j ) is the geometric overlap factor, β is the Mie scattering backscattering coefficient; (2) According to Calculate the aerosol extinction coefficient α a , that is, formula (4): Among them, α a is the extinction coefficient caused by aerosol scattering and absorption, α m is the extinction coefficient of the molecule. (3) Calculate the smoke concentration N. The aerosol extinction coefficient is proportional to the smoke concentration, as shown in formula (5): Where k is the mass extinction coefficient, unit is m 2 / g, determined by the physical and chemical properties of the smoke, which can be obtained by looking up the table.

8. The time-division multiplexing multi-building complex underground structure early smoke and fire detection system according to claim 4 is characterized in that: Thresholds are set for CO2 concentration and smoke concentration to provide graded early warnings for fires.

9. The time-division multiplexing multi-building complex underground structure early smoke and fire detection system according to claim 8, characterized in that: The specific graded warning is as follows: first determine whether the smoke concentration exceeds the threshold. If so, a preliminary warning is issued; then determine whether the CO2 concentration exceeds the threshold. If so, the alarm mechanism is triggered and the fire protection system is linked.

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