Application of the hottest wire type optical fiber

Application of linear optical fiber temperature detectors in roof buildings

Abstract: through practical tests, the combustion characteristics of buildings with plant materials on the roof are analyzed, and it is proved that linear optical fiber temperature detectors can effectively detect this kind of building fire in the early stage

key words: linear optical fiber temperature detector; Plant materials; Fire judgment algorithm

most of the historical ancient buildings and ancient sites with wooden structure, and the roofs are mostly made of thatch, bark, thin wood and other plant materials. In hot summer, such buildings are more likely to catch fire from the roof surface. In case of a fire in a building, the flame develops rapidly, which may not only cause the ancient buildings and ancient sites to burn down, but also spread to adjacent buildings. The traditional fire detector is mainly used to detect the fire inside the building at an early stage, but the effect of early detection of the fire from the roof surface is not very obvious

in this paper, the detection performance of the linear optical fiber temperature detector using the fire judgment algorithm is actually verified through the combustion test of various materials by setting up a building model with a plant material roof outdoors and setting a linear optical fiber temperature detector on the roof surface to collect data. The test shows that by setting a linear optical fiber temperature detector on the roof surface, It can effectively realize the early detection of ancient buildings with plant material roofs and enhance the strength of core basic industries

1 fire judgment algorithm

the flow chart of fire judgment algorithm is shown in Figure 1. Linear optical fiber temperature detectors are set on the outer and inner surfaces of the roof, and output analog values as the ambient temperature changes. The analog value is converted into the detection temperature value TN after data processing. TN is compared with the preset constant temperature value TSL in the constant temperature comparison part. When it is greater than TSL, a fire alarm signal is sent

Figure 1 flow chart of fire judgment algorithm

the detected temperature value TN is simultaneously input into the temperature difference detection part. Compared with the reference temperature setting value TC, the temperature difference value is Δ t。 The reference temperature value TC is the corrected temperature value calculated every time in the reference temperature correction part according to the following formula

tc = tc'+0.16 (TN TC)

tn: the detection temperature value of this time

tc: the reference temperature value of this time

tc': the next reference temperature value

the temperature difference value that will be calculated in the temperature difference detection part Δ T input to the fire judgment section, when Δ When t is greater than the preset temperature value ts in the fire determination part, a fire alarm signal is sent

Figure 2 shows the reference temperature value TC and temperature difference value when the detection temperature value TN of linear optical fiber temperature detector rises linearly Δ T curve over time. As shown in Figure 2, when the detection temperature value TN represented by the solid line rises in a straight line according to a certain trend, the reference temperature value TC calculated according to the formula is shown as the dotted line, and the change over time also rises according to the same trend. Therefore, the temperature difference value Δ T tends to a fixed value after a period of time

Fig. 2 detection temperature value TN and reference temperature value TC

Fig. 3 takes the temperature rise rate of detection temperature TN as the parameter, detection temperature TN and reference temperature if the machine is in standby state: the temperature difference value of degree TC Δ Time variation curve of T. It can be seen from the figure that the larger the temperature rise rate of the detected temperature, the temperature difference finally tends to a higher value; The smaller the temperature rise rate of the detection temperature, the temperature difference finally tends to a lower value

Figure 3 temperature difference time change with the temperature rise rate of the detected temperature as the parameter

2 data acquisition test

the temperature of the thatch roof is high in summer. Therefore, the temperature data of the thatch roof surface are collected through the test, and the causes and characteristics of false alarm are analyzed to effectively distinguish the real fire

as shown in Figure 4, the roof material of the building model is thatch. The roof is 240cm long, 130em wide, 35 cm thick, with an inclination of 45 degrees, and placed from east to west. The thatch part is 220cm long and 110cm wide

Figure 4 building model during the Spring Festival

as shown in Figure 5, linear optical fiber temperature detectors are set along two vertical lines on the roof surface, with an interval of 50 cm. Thermocouples and illuminance meters are set on the roof surface at the same time. The time interval of data collection is 16S

Fig. 5 optical fiber setting diagram

the test results are shown in Fig. 6. The detection temperature of the linear optical fiber temperature detector increases with the rise of the sun, and decreases when the weather changes from sunny to cloudy. The experimental data show that the detection temperature of the linear optical fiber temperature detector is closely related to the illumination of sunlight

3 combustion test

linear optical fiber temperature detectors, point infrared flame detectors and point ultraviolet flame detectors are respectively set on the outer surface of the roof of the model, and linear optical fiber temperature detectors and point smoke fire detectors are respectively set on the inner surface of the roof. The detection temperature value of the linear optical fiber temperature detector is TN, the constant temperature judgment value TSL is set to 60 C, and the temperature difference judgment value TS is set to 7 C. the roof materials are used for the combustion test with thatch, cypress bark, and veneer respectively

3.1 thatch roof combustion test

the test condition is set as that the roof surface is on fire and the wind blows over the roof. The test results are shown in Figure 7. The linear optical fiber temperature detector sends out fire alarm signals almost at the same time as the flame. Point type ultraviolet and infrared flame detectors also alarm faster for open fires on thatched roofs. The point type smoke detector set on the inner surface of the roof has a late alarm time, mainly because the wind blows over the roof, and it is difficult for smoke to enter the building

Figure 7 thatch roof combustion test

3.2 cypress bark roof combustion test

the test conditions are set as the roof surface is on fire, and the wind blows directly to the roof, making HPM develop a wide range of flame retardant products, smoke easy to enter the room. The test results are shown in Figure 8. The linear optical fiber temperature detector sends a fire alarm signal in the smoldering stage. When the cypress bark is burning, the smoldering fire characteristics are relatively obvious. When the indoor smoke reaches a certain concentration, the point type smoke detector sends out a fire alarm signal; The point type ultraviolet and infrared flame detector has a late alarm time because its detection principle is mainly to detect the flame

figure 8 cypress bark roof combustion test

3.3 thin wood roof combustion test

the test conditions are the same as cypress bark roof combustion test. The test results are shown in Figure 9. The linear optical fiber temperature detector sends a fire alarm signal in the smoldering stage. When the veneer burns, the flame is extremely small and almost smoldering. Therefore, similar to the cypress bark roof combustion test, the alarm time of the point type smoke detector is faster, and the alarm time of the point type ultraviolet and infrared flame detector is later

Fig. 9 thin wood roof combustion test

the test results show that the linear optical fiber temperature detector using the fire judgment algorithm can effectively prevent false alarms, and has significant effectiveness in fire detection compared with the alarm time of point type infrared and ultraviolet flame detectors set on the outer surface of the roof and point type smoke fire detectors set on the inner surface of the roof

4 conclusion

through the combustion test of the building model with plant-based material roof outdoor, it is proved that the linear optical fiber temperature detector using the fire judgment algorithm in this paper can effectively realize the early detection of fire disaster in ancient buildings and ancient sites with plant-based material roof, and has strong practicality and effectiveness

References:

[1] Yamashita Bangbo, et al. Application of optical fiber detectors in ancient buildings. Technical papers of Nippon Keiji Co., Ltd., 1998, total No. 14. (end)