线型红外光束感烟探测器的响应性能研究

利用CFD场模拟软件FDS,对线型红外光束感烟探测器的响应性能进行预测,研究火源类型、火源功率、探测器设置高度、水平安装位置等因素对报警时间的影响.结果表明,相同高度处火灾探测器的响应时间随火源与探测器水平距离的增大而增大;火源功率对探测器的影响随距离增大而减小;火源类型不同,探测器响应数量差异很大.     

格栅式吊顶场所火灾探测器安装设计的研究

采用16只光电感烟探测器分别置于格栅吊顶上下方,以木材热解阴燃火为燃烧物研究格栅吊顶不同镂空比对探测器响应的影响.改变火源为棉绳热解阴燃火比较探测器的响应.以FDS模拟对实体实验进行补充,研究格栅安装高度、格栅厚度对探测器响应的影响.结论:镂空比小于15%时格栅吊顶下方的探测器先报警;镂空比为15%～30%是格栅吊顶上下方探测器出现交叉报警;镂空比大于30%时格栅上方探测器先报警.不同燃烧物对探测器响应随镂空比变化的规律无影响;格栅安装高度和格栅厚度不影响格栅吊顶上下方探测器响应顺序随镂空比的变化规律.     

A first approximation method for smoke detector placement based on design fire size,critical velocity,and detector aerosol entry lag time

An analog light-scattering-type smoke detector was tested in a wind tunnel at various low velocities. The air flow in the wind tunnel contained an aerosol concentration that resulted in a high ambient optical density, simulating smoke well above threshold optical detector density. The objective of this research was to determine the lag time to alarm, t, associated with difficulty of smoke entry into a detector. A critical velocity was identified for the smoke detector, below which the lag time increased exponentially with decreasing velocity. Increased lag time results in the detector responding unacceptably late—or not at all—even when ambient obscuration is well above limits defined in UL standard tests.A preliminary method for placing smoke detectors has been developed, based on a user-defined design fire size and the detector aerosol-entry lag time. The preliminary method applies only to flaming fires producing smoke, with the detector far from a wall and mounted on smooth ceilings. The critical velocity value used in the examples in this paper applies only to the smoke detector configuration tested in this work, at the evaluated sensitivity setting, with the optical densities reached using the generated artificial smoke. Any variation in detector housing, design, operation principle, or application with different aerosols requires specific tests to determine a different critical velocity.This paper provides the basis for further development of a smoke detector placement method based on a design fire size and the proposed detector critical velocity concept. It does not presume to report a unique critical velocity for all smoke detectors, but suggests that such a value may indeed exist, but with differing values among different smoke detectors.     

点型光电广谱感烟火灾探测器的研制

开发了红外光对典型烟雾颗粒0°～180°可变散射角感烟实验装置,以确定峰值波长为(900±100)nm红外光适宜和最佳的前向、后向散射感烟角.研制了一种实用新型光电感烟火灾探测器.通过试验研究4种试验火典型烟雾对此传感器的响应规律,确立了甄别黑烟或白烟的火灾探测报警算法处理技术.试验证明探测器对于可燃物阴燃或明火产生的不同粒径、不同颜色、不同温度的广谱烟雾达到了良好的均衡灵敏响应性能.     

客船火灾烟气蔓延及火灾探测器响应试验研究

基于对某豪华客船的实地调研,搭建了客船客舱区域火灾烟气蔓延模拟试验平台,通过典型火源燃烧试验研究了客船客舱区域的烟气蔓延特性,得到起火客舱及人员疏散走道典型截面不同高度的温度分布规律,以及不同类型船用火灾探测器的探测响应时间。基于试验结论,提出客船火灾探测器选型及烟气控制建议,也可为客船人员安全疏散研究提供一定的借鉴。     

Flame and smoke detection method for early real-time detection of a tunnel fire

This paper presents an image-processing technique for automatic real-time flame and smoke detection in a tunnel environment. To avoid the large-scale damage caused by fire occurring in different environments, there are many studies about discovering and minimizing an incident as fast as possible. However, we need an original algorithm specialized for a tunnel fire, because this environment is quite different and it is difficult to apply existing fire detection algorithms to a tunnel environment. Therefore, this paper proposes an original algorithm that applies to a tunnel environment. Color and motion information are used to minimize false detections in tunnels, and this information enables us to detect the exact position of an event at an early stage, by detection, test, and verification procedures. The experimental results show the validity and efficiency of the proposed algorithms by a comparison of the characteristics of each algorithm.     

Experimental measurements,integral modeling and smoke detection of early fire in thermally stratified environments

Building fires go through a series of stages. They start with a fire plume period during which buoyant fire smoke rises to the ceiling. A second stage is the following enclosure smoke-filling period. In this paper, the first stage is the subject, especially for the fire plume behavior in thermally stratified environments in large volume spaces. In NFPA 92B, Morton's integral equation was introduced for calculating the maximum plume rise, and beam smoke detectors were recommended for smoke detection design. In this work, experiments and CFD simulations were conducted in a small-scale enclosure and a large space to investigate early fire movements in temperature-stratified ambients. The results show that in a thermally stratified environment, the axial temperature and velocity of a fire plume decrease more quickly along the vertical axis than in uniform environment, and in some cases the fire plume ceases to rise. The previous integral equation was shown to underestimate the actual maximum height of a fire smoke plume, and also was unable to explain the differences of the maximum heights of low-density and high-density smoke plumes with the same stratification and outlet conditions. The integral equation was improved by introducing two correction factors, and extended for non-linear temperature stratified environments. A light section smoke detection method with three space-protected area was suggested and discussed.     

气溶胶特性引起的感烟探测器灵敏性的数值预测

本研究结合时滞动力学灵敏度算法，描述了感烟探测器的反应时间，与时滞动力学灵敏度算法同时，大涡模拟火灾模型预测了与探测器相接近的烟浓度值，并描述了烟进入传感小室的输送情景。基于初始粒子的大小和分布，计算传感小室内的烟粒子浓度。由标准试验方法得出了实验数据。比较预测值和实验值，得出了合理一致的结果。     

A study of an optimal smoke control strategy for an Urban Traffic Link Tunnel fire

An Urban Traffic Link Tunnel (UTLT) is a novel type of underground transportation system consisting of a main tunnel in a loop shape and several linked tunnels. It has a higher level of fire risk compared to other common road tunnels. In this study, numerical study was conducted to investigate the smoke control strategies for a designed fire scenario in the Beijing Center Business District (CBD) UTLT. An optimal smoke control strategy was developed and evaluated using three criteria: critical velocity, minimal smoke spreading area and available safe evacuation time. In developing the optimal smoke control strategy, six different smoke control strategies for the UTLT were evaluated initially by the criterion of critical velocity, and one of those control strategies was chosen as the primary strategy by steady simulation. This strategy was then modified according to the dynamic simulated results of smoke movements to satisfy the other two criteria. Consequently, the optimal smoke control strategy for the UTLT based on the primary strategy was obtained. The transient distributions of the smoke spread, smoke temperature and CO₂ concentration, were analyzed.     

电缆燃烧典型火源模拟方法综述

针对电缆火灾问题,综述了国内外电缆火灾模拟试验及电缆燃烧测试中使用的火源模拟方法,并对比探讨了多种火源模拟方法的点火时间、火源温度、火源面积、火源功率、可扩展性、可移动性以及可持续使用性等方面的差异:燃气喷灯法和辐射加热法(锥形量热计)所需点火时间短;电加热法火源温度高,操作简便易移动;燃油点火法的点火面积大,可扩展性...     

A Probabilistic Model for Fire Detection with Applications

A probabilistic model for estimating the activation time of ceiling-mounted fire detection devices is described. The probabilistic model builds on the deterministic model, DETACT, by introducing probability distribution functions in place of point estimates for the parameters governing fire detector response, including the fire heat release rate history, the detector activation temperature, response time index and conductance parameter and the location of the device. The probabilistic model incorporates only parameter uncertainty. Model uncertainties associated with the deterministic model for estimating the activation time of ceiling mounted fire detectors have not been addressed. An example application of the probabilistic model is discussed. The probabilistic results provide valuable insights about the relevant parameters involved in a time to detection analysis.     

A probabilistic occupant response model for fire emergencies

The present paper describes a probabilistic occupant response model for fire emergencies, which is integrated into a fire risk analysis model called CUrisk. Based on the PIA process, i.e., Perception, Interpretation and Action, the occupant response model predicts the probabilities of occupants perceiving fire signals due to direct perception, receiving fire alarms due to the activation of local alarms, sprinklers, the central alarm and the voice alarm, being warned by the other occupants and fire department, and taking actions including pulling the fire alarm, warning other occupants, calling the fire department, and commencing evacuation. The occupant response model is applied to predict the probabilities of evacuation initiation for a number of scenarios that consider combinations of fire detection and alarm systems for a mid-rise building. The results of the model show that asleep occupants need much longer response time to start evacuating and have lower probabilities of starting evacuation than awake occupants, which are consistent with what is observed in reality. Additionally, fire protection systems with only local alarms and only sprinklers connected to the central alarm can be improved significantly with systems with smoke detectors alone or combined with sprinklers connected to a central alarm, which result in higher probabilities of evacuation initiation with shorter delay times.     

倾斜入射地震波作用下成层场地动力反应的界面子波算法

为提高成层半空间自由波场的一维化时域方法的计算效率和精度,分析了SH波在层状介质中的传播方式、旅行时间和反射系数等问题,基于惠更斯–菲涅耳波动观点,将波阻抗界面看作次级子波源(简称为界面子波),提出了倾斜入射地震波作用下成层场地动力反应的界面子波算法,并通过模型试算验证了此方法的正确性。与常规数值法相比,此方法无需划分网络单元,也无需处理人工边界条件,从而极大地减少了计算工作量和节点之间的传递误差,具有速度快、精度高、稳定性好等特点,是一种计算成层场地动力反应的实用方法。     

A fast flow control algorithm for real-time emergency evacuation in large indoor areas

Evacuation in an emergency is always an important issue for shopping malls, subway stations and other populous indoor places. The purpose of evacuation is to evacuate people from the danger zone through exits within the shortest possible time. To help evacuation missions to be carried out efficiently and effectively by rescuers, a fast evacuation approach is needed.     

A temporal hybrid dynamic integration algorithm strategy for inelastic time history analysis of high‐rise reinforced concrete structures under strong earthquakes

A complete earthquake time history analysis (THA) requires a stable, accurate, and efficient dynamic integration algorithm. It is not rare to encounter numerical divergence when some implicit algorithms are used to deal with severe materially or geometrically nonlinearities. For explicit algorithms, computational efficiency is always a major concern. A temporal hybrid dynamic algorithm (THDA) strategy, which is specialized in the inelastic THAs of high‐rise reinforced concrete (RC) structures experiencing severe plasticity development, is developed herein. A preliminary evaluation is carried out on three low‐rise structural models, that is, two frame structures and one wall‐frame structure, for each group of collected implicit algorithms and explicit algorithms. From the evaluation, four alternatives are generated for the subsequent detailed assessment. A general framework for the THDA is proposed and implemented on a finite element analytical platform. The four alternatives are assessed based on their performance on a high‐rise frame core‐tube RC structure. The assessment indicates that the proposed THDA strategy can give rise to a more compatible dynamic integration algorithm for the complete THAs of high‐rise building structures when they are experiencing severe damage. The concerns about the computational stability, accuracy, and efficiency of the dynamic algorithms can be well balanced by the THDA.