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In order to study the fire detection method of cable tunnel. We carried out physical experiments in the cable tunnel test section, using the heater pyrolyze PVC so that its pyrolysis as the ignition source obtained a total of 17 fire source location points in the horizontal and vertical directions of seven different fire detectors, and only processed the response time data of the alarm detector obtained the response time and the analysis results were drawn. With the increase of the distance from the fire source, the response time of each type of detector increases in different forms. It is found that the detection distance of the grating fiber temperature sensor is shorter, and the response time near the fire source is more stable. The detection performance of the point pyrolytic particle detector is more affected by the detection distance, which is advantageous for the detection point to have better response performance. The intelligent active suction detector is also affected by the detection distance, which is less affected than the point detector, the response time curve is more stable, and the detection performance is better at each test point. Clc number: X Document Identification Code; A.

In this study, a numerical model of the cable cabin of a comprehensive pipe gallery was established to study the smoke flow diffusion behaviour of a comprehensive pipe gallery fire under a rectangular cross-section. The effects of fire source power (Q = 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 MW) and fire source location (D = 10, 20, 40, 50, 60, 80, 100 m) on the smoke flow characteristics—such as smoke layer height and thickness, longitudinal airflow velocity, and ceiling temperature distribution—were analysed, and the corresponding prediction model was fitted. The results show the following: (1) The height of the smoke layer decreases with increasing fire power, and the predictive model of the smoke layer thickness obtained from the fitting is proportional to the smoke mass flow rate and inversely proportional to the aspect ratio of the pipe gallery. (2) Longitudinal air velocity prediction models of D < 50 m and D ≥ 50 m are fitted, and the average error between them and the numerical simulation values is 9.611%. (3) The temperature decay gradient of the smoke decreases gradually with increasing distance from the fire source, while there is a significant temperature difference between the two sides of the fire source. The average relative errors of the dimensionless temperature rise models fitted upstream and downstream of the fire source in the form of Δ T T 0 = A e B D − X H + C exponentials with respect to the numerical simulations were 11.688% and 7.296%, respectively. The results of the study can provide a reference for smoke flow and fire prevention and control in comprehensive pipe galleries. [ABSTRACT FROM AUTHOR]

Smoke mass flow rate (SMFR) is an important factor for smoke control in tunnel fire. The presence of bifurcation structure can lead to the flow redistribution and distinctive characteristics. In the current study, a relational expression for the SMFR in branched tunnel was theoretically derived. A series of numerical simulations with Fire Dynamics Simulator(FDS) were conducted to investigate the effects of multiple factors on the smoke mass flow and validate the predictions. The results indicated that for a T-shaped tunnel, the amount of smoke flowing into the branch is mainly depends on the thickness and temperature of the incoming smoke flow from mainline, affecting by heat release rate(HRR) and tunnel section size, while the influence of the bifurcation angle and longitudinal position of fire source is unremarkable. Fairly good agreement was achieved between the predictions and simulation results. This research can be instrumental in estimating the SMFR in T-shaped tunnel fire scenarios and offer valuable insights for smoke management strategies.

In order to study the influence of different fire source positions on fire smoke spread and fire parameters under normal ventilation, the distribution of smoke flow, temperature, and CO concentration in the tunnel under three conditions of single fire source at the roof, single fire source at the floor, and double fire sources at the roof and floor was simulated and analyzed. The results concluded that in terms of smoke thickness, the downstream settling of smoke was significant for fire at the floor and fire at both roof and floor, but no upward plume was observed for fire at the roof, and the smoke flow is more concentrated in the top. In terms of the backflow distance, the fire source in the floor is the shortest, followed by the fire source in the roof, and the fire source in the roof and the floor is the largest; the main influencing factor is the maximum smoke flow temperature difference in the roof. In terms of temperature distribution, the roof smoke flow temperature decreases with the increase of the distance from the fire source, and the fire source is located at the roof and floor at the same time. For the upper roof smoke flow temperature, the roof and floor fire is the largest and the floor fire is the smallest, while the downstream is completely opposite. In addition, the smoke flow temperature of the roof fire at 2 m height is lower than that of the other two conditions. For the CO volume fraction at the height of 2 m, the peak concentration of roof fire and floor fire appears at the front of the fire smoke, while the floor fire appears near the fire source, and the CO volume fraction upstream of the fire source is significantly higher than the latter under the former two working conditions.

In this study, a numerical model of the cable cabin of a comprehensive pipe gallery was established to study the smoke flow diffusion behaviour of a comprehensive pipe gallery fire under a rectangular cross-section. The effects of fire source power (Q = 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 MW) and fire source location (D = 10, 20, 40, 50, 60, 80, 100 m) on the smoke flow characteristics—such as smoke layer height and thickness, longitudinal airflow velocity, and ceiling temperature distribution—were analysed, and the corresponding prediction model was fitted. The results show the following: (1) The height of the smoke layer decreases with increasing fire power, and the predictive model of the smoke layer thickness obtained from the fitting is proportional to the smoke mass flow rate and inversely proportional to the aspect ratio of the pipe gallery. (2) Longitudinal air velocity prediction models of D < 50 m and D ≥ 50 m are fitted, and the average error between them and the numerical simulation values is 9.611%. (3) The temperature decay gradient of the smoke decreases gradually with increasing distance from the fire source, while there is a significant temperature difference between the two sides of the fire source. The average relative errors of the dimensionless temperature rise models fitted upstream and downstream of the fire source in the form of ΔTT0=AeBD−XH+C exponentials with respect to the numerical simulations were 11.688% and 7.296%, respectively. The results of the study can provide a reference for smoke flow and fire prevention and control in comprehensive pipe galleries.

Aiming at the shortcomings of isotope radon detection method, which has large workload, long period, and is easily restricted by climate and environmental factors this paper proposes the use of radon generated during the process of migration to the surface to accurately reflects the solid-state length of the cumulative value of parent radon over a period of time. Long-lived radon daughter 210Po fire detection method based on radiochemical analysis method to measure 210Po activity concentration to detect hidden mine fire areas. In order to explore the effect and accuracy of the radon progeny 210Po fire detection method in on-site detection, this paper carried out on-site experimental research in Liuwan Coal Mine where the fire source location is known. The radon gas concentration at the measuring point and the activity concentration of its solid long-lived daughter 210Po are measured. By comparing the correlation between radon gas concentration and 210Po activity concentration detection results and its influencing factors, the technology of using radon daughter 210Po to detect the location of coal spontaneous combustion in goaf is demonstrated. The results show that the radon concentration in the near-surface soil layer in the fire area has a strong correlation with the 210Po activity concentration in the overall distribution, but the 210Po activity concentration is less disturbed by external factors, and its distribution can more accurately reflect the underground coal spontaneous combustion fire area. Compared with the isotope radon detection method, the radon progeny 210Po fire detection method has higher detection accuracy, wider application range and higher application value.

This work presents an experimental investigation on ceiling-vented compartment fire behavior and thermal characteristics with different fire source locations under the effect of wind associated by CFD simulations. Experiments were carried out under the ambient wind condition, and the fire source was respectively set at windward side, center and leeward side. Results show that: (1) In no-wind cases, a critical heat release rate is found at which the inside temperature decreases with the increasing of fire heat release rate indicating flame flows outside. The critical HRR for fire source attached to sidewall is slightly larger than that when the fire source is located at compartment center, and it increases as vent dimension increases. (2) In ambient wind condition, there is a travelling process that the flame transfers from windward side to leeward side with the increasing of fire HRR. The critical HRR for the transition increases as vent size increases, and decreases as wind speed increases, and is basically independent of fire source location, which is proved to be related to air inflow rate. A Froude number is proposed to characterize the wind effect based on air inflow analysis, and the critical HRR for transition is represented well by the Froude number. • Ceiling-vented fire with different fire source locations under wind was studied. • Temperature profile and flame transition behavior were characterized. • Effects of wind and vent dimension on air inflow and flow field were analyzed. • Prediction model for flame transition based on the air inflow rate was proposed. [ABSTRACT FROM AUTHOR]

The aspirating smoke detector (ASD) is one of the most critical pieces of equipment for detecting smoke in a protected area when a fire occurs. It has more advantages than a conventional smoke detector because it can be used in extreme conditions, such as cold storage facilities or hot aisle containment areas. ASD uses a fan to draw air from the protected area into the pipe network system via pipe holes. The sucked air is transported into the sensing chamber to detect smoke. If the obscuration in the sensing chamber is greater than the setpoint, the ASD will sound an alarm so that people realize there is a fire. For this reason, investigating the effect of the pipe hole network on obscuration in the ASD is critical. In this study, a Pipe Hole Network Program was developed to consider the pipe flow parameter. A numerical study based on the program and an experimental study was performed. The results showed that the numerical results had the same trend as the experimental study. The further the location of the fire source was, the lower the obscuration was. In addition, the correlation between the obscuration parameter and the fire source distance was also derived. It could be used to predict the fire source location in the aspirating smoke detection system. [ABSTRACT FROM AUTHOR]

Based on analysis of principle and characteristics of mine fire monitoring methods such as temperature monitoring method, gas monitoring method, smoke monitoring method, visible light image monitoring method and infrared image monitoring method, a mine fire monitoring and trend prediction method based on multi-parameter fusion was proposed. Conclusions were got as following:① Thermocouple temperature measurement method and semiconductor temperature measurement method have advantages of high accuracy, strong real-time performance and early detection of early fire, but there are disadvantages such as large sensor consumption and large maintenance workload; Infrared temperature measurement method has advantages of wide monitoring range and easy sensor arrangement, but shielding and coal dust between sensor and measured object will affect monitoring result; Fiber distributed temperature measurement method has advantages of multi-point temperature monitoring and small amount of cable consumption, but there are disadvantages such as easy damage, complicated installation and difficult maintenance of optical fiber. ② Gas monitoring method and smoke monitoring method have advantages of wide monitoring range, convenient use and maintenance, but there are disadvantages such as cannot monitor early fire with low concentration of index gas and less smoke. ③ Visible light image monitoring method has advantages of wide monitoring range, convenient use and maintenance, low cost, but interference sources such as roadway light, miner's lamp, vehicle lamp and red clothes and smoke will affect monitoring effect, and the method cannot monitor early fire with no flame and less smoke.④ Infrared image monitoring method has advantages of wide monitoring range, convenient use and maintenance, but cost is high, and shielding and coal dust between infrared camera and measured object will affect monitoring effect. ⑤ Mine fire monitoring and trend prediction method based on multi-parameter fusion of temperature, smoke, gas concentration, odor, wind direction, wind speed, air volume, visible light image and infrared image can not only detect fire in time, but also locate fire source and predict fire development trend.

The effect of different fire source locations on the environment of a subway station was investigated in this paper. Visibility, temperature and carbon monoxide at the evacuation stairs in the subway station were computed by Fire Dynamics Simulator (FDS). Different fire source locations have different evacuation features. Fire source 2and 3 have the most negative effect on evacuation. Therefore, relevant departments should take some measures to avoid fires breaking out in these places. [ABSTRACT FROM AUTHOR]

Since there exists few effective fire detection technologies for underground pipe gallery application, a temperature data-driven bio-inspired artificial intelligence algorithm is developed to detect fire source in 3D space of the underground pipe gallery, in which a simple physical model is used. In the developed algorithm, Ant colony optimization (ACO) is the first time to be used to determine tunnel fire source, and the new and special pheromone evaporation method and heuristic factor are developed for fitting the concerned problem here. Three fire experiments are used to support the ability of the algorithm. Satisfactory results can always be obtained, which shows that the developed algorithm can be used to estimate the tunnel fire source as well as temperature prediction. In addition, since only temperature data at several sensors is necessary in the developed algorithm, it has a very wide popularization and engineering application prospects due to its advantages of the global optimal ability and computational efficiency as well as the low economic cost. [ABSTRACT FROM AUTHOR]