Research On Several Influence Factors In The Road Tunnel Application Of Distributed Optical Fiber Temperature Fire Detection System Fire Detection System

Distributed Optical Fiber Temperature Fire Detection Systems (DTS) has been widely used in the road tunnel to monitor fire hazards, for it is able to sound an alarm at the early stage of tunnel fires, which has a significant effect on the disaster emergency measures carried out timely, the control of fire scale and decreases in personnel casualties&property losses. However, the experimental research on application of DTS in road tunnel is less. What’s more, China has not ever issued professional national standard on installation parameters (the distance between the DTS and tunnel top, laying spacing) and the applicable tunnel height of DTS, and norms regarding these parameters in foreign countries and Chinese provinces are different with each other. Therefore, it’s very important for practical application and promotion of the DTS to conduct research on related influence factors in its road tunnel application.In this thesis, firstly, based on extensive investigations on tunnel fire detection technology home and abroad&application status of DTS, the fiber overview, thermometry principle and structure design of DTS was introduced. Then, the fundamental properties of DTS chosen for experimet have been proved to meet the requirements, through test on temperature accuracy, positioning accuracy and response time of the system and so on, so the following real fire experiment can be continued.Secondly, we built the30m×7.6m×7.8m full size platform for the real tunnel fire experiment, through the contrastive analysis on the temperature distribution and DTS alarm response, the following conclusions can be made:(1) When the tunnel ventilation is longitudinal, the DTS alarm position deviates from the actual fire source, and with the increase in wind speed, alarm time becomes longer. So the deviation effects of ventilation on DTS detection positions need to be considered in the practical tunnel-fire detection.(2) The power and position of fire which affect the temperature distribution in the tunnel both indicate positive correlation with the DTS response time. The initial temperature of miniwatt fire source and the fire in the vehicle bottom and ground cannot reach the valve of normal fixed-temperature fire alarm, thus the fire alarm cannot work, and instead the differential temperature alarm should be installed to detect the fire.(3) The temperature-rise speed and alarm response time are faster when the distance between the optical fiber and the tunnel roof is100m than when that distance is300m. Based on comparison of different places’ standards, and to be more advantageous for fire detection, the optimal installation position of DTS should be50-100m away from the highway tunnel roof.Thirdly, through comparative analysis to FDS model depicting the development process of fire with different tunnel heights(5m、6m、7m、8m、9m、10m、11m.12m), it can be found that with the increase in tunnel height, the DTS alarm-position deviation and the alarm response time become larger, and the fixed-temperature detection warning begins to lose efficacy when the height becomes12m.Finally, by combining real fire experiment with CFD numerical simulation, we concluded that the space of fiber optic laying should be reduced with the increasing of tunnel height to ensure effects of the DTS detection, and the recommended values of the DTS laying space in different height of tunnel were given.