夏季湿热环境下温度-风速适宜值实验研究

一定温度环境下增大风速可以提高人体热舒适并降低能耗,但较高温度环境下增大风速对人体热舒适的改善作用降低。为了探究夏季湿热环境下风速对温度的补偿作用,提出适宜的风速值,本文系统地研究了高湿环境(80%相对湿度)下从偏热到高温范围内风速的积极改善作用和改善效率。通过在人工气候室营造4种温度水平(28、30、32、34℃),采用落地扇正面吹风,控制风速为0.8～1.4 m/s,共完成8个工况、168人次受试者热舒适实验,获取了受试者的主观感受及生理反应。建立了整体热感觉与温度和风速之间的预测评估模型,得到热中性状态下不同温度对应的舒适风速;在32、34℃环境下,提高风速不能使受试者达到热舒适状态,但对热感觉及皮肤温度仍具有改善作用,进而提出利用平均皮肤温度变化率评价不同风速下的吹风效率,得到对应温度下的有效风速值。将舒适风速与有效风速相结合,得到了夏季湿热环境下不同温度的适宜风速推荐值。     

基于风速风向联合分布理论的梁桥风荷载分析

由于桥梁结构通常作为一种大型结构,顺桥向与横桥向尺寸、刚度以及动力特性都存在较大的差异,所以风荷载从桥梁的不同方向作用于结构上,荷载效应会产生较大的差异。本文以风速风向联合分布法为理论基础,基于近10年来新疆木垒地区风速风向数据资料,得到采用三种不同的概率分布模型计算得到的木垒地区不同风向不同重现期内的基本风速。通过从风速风向联合分布概型进行拟合分析,通过拟合分析,在考虑风向影响下,分析了钢板组合梁风荷载的基本特点,通过分析得出不同时期下的基本风速值以及最大风速和最小风速的关系。     

低气压环境下空气流速对人体热感觉影响的研究

通过问卷调查的形式,研究了20名处于不同大气压力环境中受试者的热感觉和风速期望随空气流速变化的情况,进而分析了不同大气压力环境中,空气流速对用风速期望进行评价的吹风感和人体平均热感觉(MTS)的影响.研究表明:低气压环境下人体对空气流速变化的感觉不如常压下敏感,人体在较高温度下对风速变化的感觉不如较低温度下敏感.在20～22 ℃时,低气压环境下微风速(<0.2 m/s)范围内的风速变化对身着厚重衣物的受试者的热感觉影响十分微小.     

隧道风速测试方法研究

基于多通道热线风速仪,研制了用于隧道防排烟系统检测的隧道横断面多点风速测量系统,提出了基于该系统的测量方法,可实现不同形状隧道、不同位置测点布置的多点风速测量,同时具备数据自动采集和处理功能;利用该装置,按等面积法在几种不同测点布置方案下开展了风速测量试验,在不同风速情况下多次试验,结果表明该试验装置满足大断面隧道风速测量要求。     

背景风速对上游有阻挡建筑的街谷环境的影响

通过数值模拟针对街谷上游存在阻挡建筑时,研究了不同背景风速下,街谷内速度场和污染物浓度场的变化特征。结果表明,街谷内风速和湍流强度的增加幅度小于背景风速的增大幅度,但背景风速的变化对街谷内的气流流态和分布规律几乎没有影响。在风速和湍流强度的双重影响下,污染物浓度的减小幅度大于风速增加的幅度。因此对于目前的城市街谷来说,可以根据风速的不同对城市交通管理做出相应的调整。     

对数律和指数律风剖面的差异分析及其对桥梁抗风性能评价的影响

现有的公路桥梁抗风设计采用指数律风速剖面来计算各个基准高度的平均风速,然而气象学实践和一些国家规范中早已采用对数律风速剖面,两种风速剖面在不同高度处的平均风速差异及其对桥梁抗风的影响应当值得关注。对比了不同地表粗糙类型下对数律模型和指数律模型在不同高度处的风速差异,并采用ANSYS有限元软件计算了实桥在风荷载下的位移和桥塔弯矩差异。结果表明,在地表粗糙度较大和离地高度较大时,对数律和指数律模型的风速差异较为明显,风荷载的差异对桥梁内力和位移造成的影响不可忽略。有必要进一步研究这两种风速剖面模型在高空处的准确性,以更好地指导桥梁的抗风设计。     

一种可变径微风速标定装置及标定方法的研究

通过理论分析,研制了一种可变径负压式微风速标定装置,通过确定标准点风速,实现风速的高精度标定与校正,并根据不同大小的标定风速通过变管径的方式进一步提高标定准确度,并且实现微风速(0.2~2.0m/s)的标定与校正。通过对其在不同风机频率、不同标准风道管径下进行了6种工况的标定试验,试验结果表明:该标定装置中,测试段管径为99.7mm的标准风道用于标定2m/s以上的风速,测试段管径为196.7mm的标准风道用于对0.2~2.0m/s的微风速进行标定。两种管径下的标定误差均在5%以内。     

CLT型静电旋风除尘器性能的实验研究

研究了用 CLT 型旋风子制作的静电旋风除尘器的性能,即在不同入口风速及不同电场电压下除尘效率与阻力。得出了静电旋风除尘器的除尘效率,在一定风速范围内及特定电压下的“峰值”规律.     

夏季办公建筑风速对人体热舒适影响的实验研究

将主观问卷调查与生理指标测试相结合进行了实验研究,分析了不同风速条件下生理指标和主观评价指标的变化特征,分别建立了风速与生理指标及生理指标与主观评价指标的预测模型,以实现对生理指标和主观评价指标的预测。研究结果显示:在不同风速条件下,仅有皮肤温度与皮肤导热热流量存在显著性关联,且均随风速的增大呈降低趋势,心率与心率变异性的变化并不明显;在设定的热环境条件下,受试者能够接受的风速范围为0.15~0.35m/s,感觉中性的风速为0.3m/s。     

太阳房集热墙风口平均风速测定方法研究

本文对被动式太阳房集热墙风口平均风速的测定进行了研究。通过实验室模拟风口实验,测量分析风口截面上不同风量下风口的平均风速,找出测点风速等于平均风速的分布区域,将一个风速传感器探头放在该区域测出的风速即可代表风口的平均风速。将实验结果在青藏铁路线上被动式太阳房现场进行了校核,从而实现了对被动式太阳房集热墙风口平均风速的自动监测。     

Indoor Air Flow and Pollutant Removal in a Room with Task Ventilation

We studied the performance of a task ventilation system that permits occupants to control the flow rate and direction of air supplied to their work space through four floor-mounted supply grill. Air exited the room through a ceding-mounted return grill. To study air-flow patterns, we measured the age of air at multiple locations using a tracer gas stepup. To study the intra-room transport of tobacco smoke particles, cigarettes were smoked mechanically in one workstation and particle concentrations were measured at multiple locations. Our major findings were as follows: (1) deviations from uniform age of air, and uniform particle concentration, were generally less than 30 percent; (2)some supply air short-circuits to the return grill when directed toward the return with high velocity; (3) low supply velocities resulted in a floor-to-ceiling displacement flow; (4) directing the supply air toward the occupant, of partially toward the occupant, typically yielded an age of air at the occupant's breathing level that was 15 to 25 percent lower than the age at other breathing-level locations; (5) with low supply velocities und air directed toward the occupants, tobacco smoke particle concentrations in a ventilated non-smoking workstation were 50 percent of the chamber-average concentration.     

Experimental Investigation of Effect of External Side Wind on Fire Behaviors in a Corridor Connected to a Shaft

High-rise buildings are usually in a windy environment. The motion of fire-induced smoke and fire behaviors may be strongly affected by the external wind forces except by the stack effect. It turns out that wind with different directions and velocities can cause disparity in fire dynamics. Since most previous researches only focused on the cross wind conditions, this work investigated the effect of external side wind from 0 m/s to 1.21 m/s on the air flow behaviors, combustion characteristics of methanol pools and smoke temperature in a 1/6 scaled corridor connected to a 6-floor shaft. A remarkable observation is that the external side wind (parallel to top window, shown in Fig. 1) leads to pressure attenuation inside building and induces air to flow inside through bottom door. Therefore, the smoke spreads faster under the synergic effects of side wind and stack effect. At the steady stage, the supplement air flow velocity increases with wind velocity but remains proportional to 1/3 power of HRR. An equation incorporating the wind effect is proposed to predict the air flow velocity. Results also show that compared to cross wind conditions, the mass loss rates of methanol pools increase at high wind velocities. The wind effect on smoke temperature is obvious in cases with small pools. Here, the temperature first increases to a peak value and then decreases with increased wind velocity. However, the temperature remains the same in cases with large pools within our wind velocity range. The temperature in the shaft is also correlated with mass loss rate and wind velocity. This work shows that external side wind would increase the fire hazard of buildings by contributing to the combustion and spreading of smoke. Thus engineers should consider the effect of side wind carefully when designing smoke control system.

     

空气幕对列车车厢火灾烟气的影响规律研究

为研究防烟空气幕对列车车厢火灾烟气的影响规律,建立了CRH2A 动车组一节车厢的内部模型,利用FDS 模拟软件对列车车厢火灾时期的烟气流动规律进行数值模拟。依据给定火灾场景下烟气水平运动速度设置空气幕水平切向速度,通过改变空气幕安装角度,研究车厢内部火灾时,在空气幕作用下车厢空间各区域烟气层高度的变化,温度及CO 浓度的分布情况。结果表明：火源功率为3 MW 时,空气幕安装角度θ=45̊ ,水平与垂直方向速度均为4 m/s 时,防烟效果较好。     

空气幕-顶部排烟系统控烟排烟有效性的研究

在火源两侧设置两道空气幕能有效阻隔火灾蔓延和烟气扩散。为了探明低射流风速下空气幕在点式集中排烟隧道内对火灾特征参数的影响,通过FDS研究了不同排烟量、射流速度和射流角度下隧道内烟气蔓延、温度分布和排烟效率的变化。结果表明:当HRR为30 MW时,射流速度至少应不小于2.5 m/s才能保证空气幕的隔烟作用;当射流速度在2.5 m/s以下时,射流角度越大空气幕的隔烟效果越差,这明显不同于射流速度较大的情形;空气幕能很容易地将空气幕外的温度控制在40 ℃以下,射流角度对逃生区域的温度分布影响不大,主要影响火羽流的分布;相同射流角度下排烟量越大排烟效率先升高后减小,而相同排烟量下随着射流角度的增大排烟效率逐渐减小;对于30 MW的火灾规模,推荐的控烟方案为:射流速度为2.5 m/s,排烟量为120 m³/s。     

对优化防烟方案"论据链"的分析与探讨

针对现行防火规范第8章第8.3.2条规定的四种加压送风防烟方案,根据气流流动特性分为两类,对表8.3.2-1,8.3.2-3以及表8.3.2-4三种防烟方案,选择了有代表性的范例,应用当量流通面积流量分配法对10种不同的工况进行讨论,针对每个工况的4个子项分别建立数学模型,并进行数值计算;对表8.3.2-2,8.3.2-4防烟方案中的风量,按流体网络方法进行校验性计算,获得大量数据;通过以上分析计算,得到类似矩阵的数据集,形成了一个完整的优化防烟方案论据链。     

高海拔双向行车公路隧道火灾控烟风速研究

雀儿山隧道为高海拔双向行车公路隧道,发生火灾后需要兼顾火灾点两侧人员的疏散,烟气控制较单向行车隧道复杂。采用FDS软件对雀儿山隧道进行火灾三维数值模拟,研究了高海拔双向行车公路隧道火灾时的烟气流动规律和能见度分布规律。研究结果表明:高海拔隧道火灾烟气流动比低海拔隧道速度快;纵坡隧道发生火灾时,若不采取任何控烟措施,烟流在火风压效应的作用下会从高洞口排出,而烟流沿下坡方向的蔓延距离仅在10 m左右,火灾烟气沿火灾点两侧蔓延极不对称;当隧道高洞口控制风速过大或横通道内控制风速过小时,易出现烟气蔓延对称性不佳或烟气窜入横通道,故二者应合理取值;当隧道高洞口施加0.5 m/s的风速、横通道施加1.0 m/s的风速时,烟气在火灾点两侧基本呈对称蔓延,且火灾两侧的能见度也基本对称;建议类似于依托工程的单洞双向行车公路隧道火灾疏散救援阶段,隧道高洞口风速控制在0.5 m/s左右、横通道内风速控制在1.0 m/s左右,以利于人员逃生。     

Using FDS to Simulate Smoke Layer Interface Height in a Simple Atrium

This study examines the possible effects of various make-up air supply arrangements and velocities in an atrium smoke management system. Variations include velocities ranging from 0.5 to 3.0 m/s. The arrangement of make-up air supply injection points include symmetrically located vents placed low in the spaced, an array of vents distributed from the floor to the ceiling, and asymmetrically located vents. Fire Dynamic Simulator version 4.06 is applied to simulate ten scenarios in a 30.5 m cubical domain with a fire source simulating a stack of pallets with an approximate peak heat release rate of 5 MW. Results show that make-up air supply velocities should be diffused such that little to no velocity effects reach the fire. Make-up air should be supplied to the fire symmetrically for the best chance of not disturbing the fire plume. Disturbing the fire and smoke plume results in a significant increase in the smoke production rate, as evidenced by a deeper smoke layer.     

移动式排烟机安放位置的讨论

以实体试验研究单个移动式排烟机在不同安放距离、不同俯仰角下对封堵面积和排烟量的影响.得出排烟口和送风口的风速分布图,确定排烟机的最佳安放位置,不同安放位置下的实际排烟量.单个排烟机的最大封堵直径为1.4m;排烟机的最佳俯仰角度约为18.,安放距离为1..～1.5m.排烟机放置在建筑内进行排烟时应注意防止烟气倒灌.     

高层建筑火灾中气雾混流风幕阻烟性能模拟研究

采用Fire Dynamic Simulation(FDS)模拟软件模拟了高层建筑条形走廊内四种不同工况下的烟气蔓延扩散特征,对比分析烟气传播规律,通过比较关键位置处的温度和一氧化碳体积分数,评估气雾混流风幕的防烟效果。研究结果表明,气雾混流风幕能够有效地阻隔高温有毒烟气蔓延,延长人员疏散时间且不影响人员的自由出入,从而保证人员安全疏散。     

Studies on buoyancy driven two-directional smoke flow layering length with combination of point extraction and longitudinal ventilation in tunnel fires

This paper investigates the buoyancy-driven smoke flow layering length (both upstream and downstream) beneath the ceiling with combination of point extraction and longitudinal ventilation in tunnel fires. A theoretical model is developed based on previous back-laying model with only longitudinal ventilation, with modified actual heat release rate, as well as modified upstream and downstream opposing longitudinal air flow velocities by the induced flow velocity due to point extraction. Experiments are carried out in a reduced scale model tunnel with dimensionless of 72 m×1.5 m×1.3 m. A LPG porous gas burner is used as fire source. The smoke flow layering length both upstream and downstream are identified based on temperature profiles measured along the ceiling, for different experiment conditions. CFD simulations with FDS are also performed for the same scenarios. Results show that with combination of point extraction and longitudinal ventilation, the smoke flow layering length is not symmetric where it is longer downstream than that upstream. The upstream smoke layering length decreases, while the downstream layering length increases with increase in longitudinal ventilation velocity; and they both decrease with increase in point extraction velocity. The predictions by the proposed theoretical model agree well with the measurements and simulation results.