吸气式火灾探测系统采样管网优化设计

对吸气式火灾探测报警系统中采样管网进行优化设计是提高其探测性能的重要手段。基于流体动力学原理,建立管网内气体运动数学模型,给出各状态参数之间的关系式。分析常见管网布置方式的优缺点,提出吸气式采样管网的优化设计方案:视每个采样孔为1个点型感烟探测器,采样孔间距基本一致,调整孔径使各采样孔进气量相同,孔数较多时,可增设末端孔,以缩短气体样本传输时间。从理论上分析管网参数对探测性能的影响,并利用Fluent 6.3进行相应的数值模拟。结果表明,样本传输时间与管长、管径、开孔数成正比,与总流量和末端孔孔径成反比。

Optimized design of pipe network for aspiration fire-alarming system

This paper aims to present our optimized design version of pipe network for aspirating fire detective alarming system in hoping to enhance the fire alarming behavior.In our paper,we have established a physical and mathematical model of gas sucking-up in sampling pipe network based on the fluid dynamic principle and investigated the relation of the state parameters of gas-sampling,such as the gas pressure,velocity,the local loss and frictional loss from the theoretical point of view.In so doing,we have fully described the two most favorable methods of pipe design at present,and analyzed their advantages and disadvantages of the said system.Furthermore,we have worked out a new project by adjusting the diameters of sampling holes to ensure their air-input rate equally and making it as a spot-type detector by increasing the sensitivity of each sampling port of aspirating smoke detector.While keeping the distance of all the sampling ports equal,we have managed to change their positions in accordance with the specific conditions of the area.The hole in the end cap has been particularly laid out so as to reduce the gas-transferring time.In our optimized design version of the pipe network,we have taken particular measures to keep the balance of the gas-flowing rate of sampling holes so as to maximize the gas sampling transferring time from the farthest sampling point to the detector within 120 seconds.If such demands cannot be satisfied,it would be necessary to adjust the diameter of the sampling port,or change the structure of network,such as the length of the sampling pipes or the number of the sampling holes.And,finally,the paper has also made a discussion of the effects of various parameters on the gas transferring time by taking the advantages of the original mathematical model.At the same time,we have also adopted some commercial CFD software(e.g.Fluent 6.3) to simulate the working conditions of the smoke detector,and recorded the transferring time of the gas sample in the different parts of pipe network.The theoretical and simulation results show that the gas-transferring time can be expected to increase with the number of sampling holes,length and diameter of pipe, whereas decreasing with the total flow and the hole diameter in the end cap.