建筑火灾烟气迁移特性研究及排烟设计

在火灾烟气迁移和机械加压补风的理论研究基础上,基于FDS火灾模拟软件的大涡模拟（LES）及Smagorinsky亚格子尺度模型对某大学宿舍楼进行实体建模。危害性气体CO在水平方向上的体积分数演变非常相近,火源处产生的危害性气体成分能够沿着水平方向传播到远距离处而自身体积分数的变化很小,CO的体积分数峰值随高度呈现明显的阶梯变化。数值模拟结果证明,火灾中大量的人员都死于远距离处的主要原因可能是吸入了大量迎面而来的（而不是身后面赶上的）烟气中危害性气体CO,由此对建筑防火结构设计中针对高层建筑火灾烟气迁移问题提出了改进意见。     

FDS场模拟计算中的网格分析

基于场模拟的火灾动力学模型（FDS）中网格的划分直接影响到计算结果的误差，甚至关系到计算结果的正确性。运用FDS对相同计算区域内的4种不同网格划分情况分别进行数值模拟，比较不同网格尺寸对计算结果的影响，从而对FDS的网格划分问题得到进一步的认识。     

Critical wind velocity for arresting upwind gas and smoke dispersion induced by near-wall fire in a road tunnel

In case of a tunnel fire, toxic gas and smoke particles released are the most fatal contaminations. It is important to supply fresh air from the upwind side to provide a clean and safe environment upstream from the fire source for people evacuation. Thus, the critical longitudinal wind velocity for arresting fire induced upwind gas and smoke dispersion is a key criteria for tunnel safety design. Former studies and thus, the models built for estimating the critical wind velocity are all arbitrarily assuming that the fire takes place at the centre of the tunnel. However, in many real cases in road tunnels, the fire originates near the sidewall. The critical velocity of a near-wall fire should be different with that of a free-standing central fire due to their different plume entrainment process. Theoretical analysis and CFD simulation were performed in this paper to estimate the critical velocity for the fire near the sidewall. Results showed that when fire originates near the sidewall, it needs larger critical velocity to arrest the upwind gas and smoke dispersion than when fire at the centre. The ratio of critical velocity of a near-wall fire to that of a central fire was ideally estimated to be 1.26 by theoretical analysis. Results by CFD modelling showed that the ratio decreased with the increase of the fire size till near to unity. The ratio by CFD modelling was about 1.18 for a 500kW small fire, being near to and a bit lower than the theoretically estimated value of 1.26. However, the former models, including those of Thomas (1958, 1968), Dangizer and Kenndey (1982), Oka and Atkinson (1995), Wu and Barker (2000) and Kunsch (1999, 2002), underestimated the critical velocity needed for a fire near the tunnel sidewall.     

Uncertainty analysis and robust control of fuel delivery systems considering nitrogen crossover phenomenon

In this paper, the fuel delivery subsystem (FDS) with hydrogen recirculation and anode bleeding is applied in proton exchange membrane fuel cell (PEMFC) system, which is utilized to supply hydrogen to the anode of stack and recirculate fuel back to the supply line. As the diffusion of nitrogen from cathode to anode is inevitable in a real PEMFC during long-term operation. To prevent system performance decline due to nitrogen accumulation. Therefore, this paper firstly develops a control-oriented nonlinear dynamic FDS model involving gas diffusion. Additionally, the FDS is very sensitive to operating environment, uncontrolled operation conditions may cause stack degradation. Specifically, a method based on Monte Carlo simulation is proposed to identify the key parameter boundaries. Then the gas distribution in FDS due to nitrogen crossover is analyzed in detail. After this, a hybrid robust methodology based on sliding mode algorithm is also proposed to maintain adequate hydrogen pressure supply, suitable hydrogen and nitrogen content in the system in presence of nitrogen crossover and renewed uncertainties. Finally, the performance of the presented controller is compared with nonlinear PID (NPID) control and nonlinear multi-input-multi-output (NMIMO) control through a hardware-in-the-loop test bench. Experimental results show that the hybrid controller is accurate and suitable for control purpose, the nitrogen content is restricted to the given range and the variation of output voltage is limited to the desired boundaries, the feasibility and effectiveness are validated.     

原木楞堆细水雾灭火过程数值模拟

采用FDS模拟对原木楞堆细水雾灭火过程.通过分析雾滴直径、喷雾速率和喷头与楞堆顶面距离不同情况下楞堆燃烧周围温度的变化规律,选定了贮木场楞堆细水雾化灭火系统的合理参数.模拟结果表明,雾滴直径在100～150 m、喷头与楞堆顶面距离约5m时,细水雾灭火系统的灭火效果最好;雾滴速率为30～70 m/s时对灭火能力的影响不走,在设计细水雾灭火系统时可不予考虑.     

火灾中人员伤亡原因及疏散行为

根据火灾调查取得的有关参数,使用FDS火灾模拟软件对火灾过程进行了模拟,取得了楼梯间内一氧化碳、二氧化碳、氧气含量及能见度等模拟数据。燃烧产物毒害性、高温烟气、烟气减光性是火灾中致人伤亡的原因。针对火灾中人员的疏散行为,分析了火灾事故教训,提出了预防伤亡的措施。     

乌鲁木齐市“7·19”自建房火灾事故数值重构

采用大涡模拟技术对"7.19"乌鲁木齐市重大火灾事故进行数值重构。根据火灾事故的调查结果报告,建立与物理模型并进行网格划分和初始边界条件设定,在Linux系统下再现火灾发展的三个阶段以及烟气蔓延过程,分析此次火灾在短时间内造成大量人员伤亡的原因。通过对可燃物质量损失的计算模拟壁面装修材料的烧损痕迹图,推断起火点位置、火势蔓延方向,帮助火灾调查人员快速确定起火部位。     

基于FDS的某地下车库防排烟系统优化

通过定量计算分析选择某地下车库最不利防烟分区和典型火灾场景,采用FDS验证排烟口数量及位置等设置方式和排烟量变化对排烟效果的影响,通过计算排烟口等效面积参数,从经济性角度优化设计防排烟系统,并强调水喷淋系统的重要性。     

Probabilistic simulation of cable performance and water based protection in cable tunnel fires

Nuclear power plants contain a significant amount of fire load in form of electrical cables. The performance of the cables is interesting both from the fire development and system failure viewpoints. In this work, cable tunnel fires are studied using numerical simulations, focusing on the fire spreading along power cables and the efficiency of the water suppression in preventing the cable failures. Probabilistic simulations are performed using Monte Carlo technique and the Fire Dynamics Simulator (FDS) as the deterministic fire model. The primary fire load, i.e. the power cables are modelled using the one-dimensional pyrolysis model, for which the material parameters are estimated from the experimental data. Two different water suppression systems are studied. The simulation results indicate that using either suppression system decreased the heat release rate in the tunnel to less than 10% of the non-suppressed case. Without water suppression, the cables of the second sub-system were damaged in almost all fires, but when either of the studied water suppression systems was used, the probability of the cable failures was decreased to less than 1%. This result indicates that in current scenario, the probability of losing both sub-systems is determined directly by the suppression system unavailability.     

油浸式电力变压器老化状态评估方法

介绍油浸式电力变压器油纸绝缘系统的介电响应模型,分析回复电压法、极化/去极化电流法、频域谱测量法3种非破坏性变压器老化状态的评估方法,为油浸式电力变压器老化状态评估工作提供参考.