Enhanced Deposition, Acoustic Agglomeration, and Chladni Figures in Smoke Detectors

A full-scale house fire test was conducted to investigate the accuracy of two proposed methods for determining whether a smoke or carbon monoxide (CO) alarm sounded during a smoke exposure. One method involves examining the plastic case of the alarm's piezoelectric horn for locally enhanced soot deposition and agglomerated soot particles. The other method involves examining the metal disc of the piezoelectric horn for a Chladni figure. Pairs of detectors, each consisting of one detector with its battery properly inserted and the other with its battery disconnected, were placed throughout the house. Each of the properly charged detectors was monitored to determine if and when the detector sounded. It was found that the presence of locally enhanced deposition and soot agglomerates on the main central opening of the plastic horn enclosure of a smoke or CO detector was a strong indicator that the alarm sounded. It was also found that the use of Chladni figures on the piezoelectric discs as an indication of the smoke detector sounding was not an accurate predictor.     

火源高度对隧道烟气温度及质量流量影响研究

由于隧道发生火灾后实际的燃烧面要高于隧道地面,距离隧道拱顶也越近,因此对隧道的危害也越大。通过CFD数值模拟软件进行了一系列不同火源功率的全尺寸数值计算,研究了火源高度对隧道内温度分布及烟气质量流量的影响。研究发现:火源高度对拱顶温度分布有着明显的影响,火源高度越高,火源附近温度衰减越慢;在远离火源的地方,不同火源高度的拱顶温度衰减相差不大,考虑火源高度后拱顶温度衰减略慢于没有考虑火源高度。火源高度及火源功率对一维蔓延阶段的烟气质量流量有影响,考虑火源高度后烟气质量流量要明显小于火源位于隧道地面的情形,但随着火源功率增大,它们之间的区别越来越小。考虑火源高度后相同火源功率下烟气分层高度显著提高,而人体耐受温度位置变化不大。     

Effect of Ventilation System on Smoke and Fire Spread in a Public Transport Interchange

In this report, a large eddy simulation (LES) model is used to investigate the conventional types of ventilation system design in the context of a public transport interchange. Various airflow patterns based on two of the most popular ventilation designs (mixing and displacement) are simulated to determine their effect on the fire. The simulation program chosen is the fire dynamics simulator (FDS) published by National Institute of Standards and Technology (NIST). It is found that increased airflow causes the fire temperature to increase by as much as 500 K. Extraction of smoke mixture by fans (exhaust only system) significantly decreases the spread of smoke and fire. Ventilation inlets located at the ground level help to increase the smoke and fire intensity in the occupied zone. Displacement ventilation increases fire intensity and current.     

高铁站区人群集聚效应影响机制及规划策略研究 — —基于京、沪、渝、蓉四城案例

高铁快速建设促发集聚效应,站区 交通可达性提升,带动不同要素的空间流动 和人的集聚,形成发展动力。人群集聚状态 可以反馈并有效指导站区空间规划,已有研 究由于数据的限制等原因,多聚焦于站区空 间形态、经济发展等方面,对人群集聚定量 分析及影响机制的研究不足。本文采用手机 信令、高德地图POI等大数据和传统数据, 对北京、上海、重庆、成都4个城市的13个高 铁站区人群集聚分布特征和影响因素进行 分析,按照“人群特征—影响因素—影响机 制—规划应对”的逻辑主线展开研究。抽提 并分析交通服务设施、商业商务设施、公共 服务设施、车站区位等人群集聚的显著影响 因素,深度剖析高铁站区人群集聚的影响机制,探明站区发展的基础支撑力、节点综合力、场所驻留力的作用机理,提出“人—站—城”多视 角统筹空间关系、“时—空—量”多层次构筑高效交通、“圈—境—业”多维度动态规划站区等 相关规划策略。