发泡网层数对水成膜泡沫灭火剂性能影响实验研究

基于自主研发的气液两相式泡沫枪,测试发泡网层数对水成膜泡沫灭火剂的发泡倍数和25%析液时间的影响,分析泡沫析液过程、发泡倍数对泡沫携液能力的影响,同时通过调节发泡网层数变动发泡倍数扑救航空燃油池火。结果表明,随发泡网层数的增加,发泡倍数和25%析液时间先增大后趋于稳定;泡沫携液能力随发泡倍数的增加而减小;发泡倍数越高,灭火效果越好,17倍时比5倍时的灭火时间缩短近70s。     

泡沫枪管径对泡沫发泡性能影响的试验研究

基于国家标准的传统自吸式泡沫枪,设计了不同尺寸的泡沫枪喷嘴,并从泡沫枪喷嘴直径尺寸、泡沫的接收距离等角度分析水成膜泡沫灭火剂的发泡倍数以及25%析液时间的变化规律。实验结果表明,在一定范围内,随着泡沫枪管径的增加,发泡倍数和25%析液时间均呈现出先增加后趋于稳定的规律;在一定距离范围内接收泡沫时,随着接收距离的增加,发泡倍数与25%析液时间呈现变大的趋势,但变化幅度不是很大。     

泥石流软基消能排导槽流速与消能特性试验研究

排导槽内泥石流流速是排导槽设计时需要考虑的重要参数之一。使用泥石流原样进行室内模型实验,探究了不同泥石流重度、肋槛间距、排导槽坡度下泥石流在排导槽内流速的变化规律和排导槽肋槛对泥石流的消能规律。研究得到如下结论:试验条件下,泥石流排导槽对泥石流流速的降低率随泥石流重度变化不大;泥石流在排导槽内平均流动速度随泥石流重度的增加而减少,随泥石流排导槽坡度的增大而增大,随肋槛间距的增加而增加;泥石流在排导槽内消能率呈现如下规律:单个肋槛平均消能率随泥石流重度的增大而增大,随排导槽坡度的增大而增大。不同肋槛间距下,泥石流在排导槽内整体消能率随肋槛间距的增大而降低,单个肋槛平均消能率随肋槛间距的增大而增大。根据本文研究相关成果,在进行泥石流排导槽设计时,通过合理设计排导槽横断面、坡度、肋槛等参数,能有效控制泥石流流速,达到降低泥石流冲击破坏的目的。     

软土地基土工带加筋碎石垫层试验研究

加筋垫层能够提高地基承载力,增加地基稳定性。对某土质条件的加筋垫层进行现场试验,研究加筋垫层的作用和影响加筋效果的主要因素。分析了加筋层数、筋带间距、加筋线密度等参数对加筋地基强度和变形的影响。试验结果表明,垫层加筋后地基承载力显著增加,而且双层加筋效果更好。对于双层加筋,随着荷载的增加,靠近基底的筋带才先发挥作用。影响加筋效果的主要因素有加筋层数和加筋带的间距等。     

交错布局轻型双坡房屋群表面风压特性

为了研究交错布局轻型双坡房屋群表面风压特征及周围风环境,基于流体动力学基本原理和大气边界层理论,采用流体动力学分析软件FLUENT,结合风洞试验数据研究计算域大小、网格数量及湍流模型等关键技术与参数,建立了双坡房屋群的数值风洞模型。以横向疏密系数、纵向疏密系数及风向角为参数,运用数值风洞对轻型双坡房屋群进行60种工况的风压分布特性研究,得到风致干扰效应下房屋群表面风压分布规律;引入干扰因子将目标房屋相对单体的受扰程度量化,得到房屋群的风荷载体型系数;计算了90°风向角下房屋间监测点的风速,借助风速比指标对室外风环境进行评估。结果表明:90°风向角下,交错布局群体房屋的纵向无干扰间距为4L（L为房屋长度）,横向无干扰间距为5B（B为房屋宽度）;房屋群横向间距为0.5B、纵向间距为2L~4L时室外风环境较好。     

风速对木垛火燃烧速率的影响

正木垛火作为标准火,既可以用于房间火试验,也可用于林野火燃烧速率试验。林野火的主要特点是普遍受风速影响。美国农业部林业局选取不同尺寸的燃烧木垛在0~0.7m/s风速下开展试验,研究风速对林野火燃烧速率的影响。结果表明,风速对燃烧速率的影响取决于燃料层厚度,较大尺寸的燃料因孔隙率大其燃烧速率增加明显,     

机械泵入式压缩气体泡沫系统性能研究

针对环氧丙烷储罐火灾难以扑灭的难题,研发了一种机械泵入式压缩气体泡沫灭火系统。开展性能试验,分别测试加入6%AFFF和6%PO泡沫液时的压力降、混合比、发泡倍数、泡沫混合液流量、举高喷射等参数。试验表明:该泡沫系统的压力降不超过0.15 MPa,泡沫混合液喷射流量大于210 m~3/h,发泡倍数为7.0～7.5,各项指标均达到灭火设计要求,可完全扑灭环氧丙烷储罐全面积火灾。     

纵向通风下隧道内重石脑油燃烧温度分布与火焰倾角研究

搭建了1:10的缩尺寸隧道模型,考虑不同火源功率和纵向风速开展了纵向通风下隧道内重石脑油燃烧的试验研究,测量了隧道内顶棚下方纵向温度分布,并量化了火焰的倾斜角度。结果表明：随着纵向通风风速的增加,隧道内温度整体呈降低趋势,顶棚下方最高温度逐渐减小,进而提出了纵向通风下隧道内重石脑油燃烧时顶棚下方最高温度的估算模型。火焰倾斜角度随纵向风速的增加而呈增加趋势。当纵向风速较低（小于1 m/s）时,随着纵向风速的增加火焰倾斜角度明显增大;当纵向风速较大（大于1 m/s）时,纵向风速对火焰倾斜角度的影响不明显。     

缠绕螺旋线斜拉索气动性能的试验研究

为研究缠绕螺旋线对斜拉索气动性能的影响,进行光拉索和缠绕螺旋线拉索的测力和测压风洞试验。首先,考虑强迫振动装置的尺寸要求,制作光拉索和缠绕螺旋线拉索模型,并在拉索轴向布置7圈风压测点,其中,螺旋线直径包括2mm、3mm、4mm三种、螺旋线间距包括200mm、300mm、600mm三种;然后,在HD-2风洞实验室的强迫振动装置上进行50种工况的拉索测力和测压风洞试验;最后,在试验数据的基础上,详细研究螺旋线对拉索气动力、旋涡脱落和风压轴向相关性等的影响。研究结果表明,缠绕螺旋线能减弱斜拉索旋涡脱落的强度,使得斜拉索的风压轴向相关性显著降低;在5～20m/s的风速范围内,缠绕螺旋线拉索的平均阻力系数甚至小于光拉索的值,并随着风速的增加,风压轴向相关性降低。     

纵向通风下公路隧道双火源火灾烟气扩散研究

采用试验与数值模拟研究隧道双火源火灾临界风速变化,重点研究双火源功率和火源间距对临界风速的影响。结果表明：随着火源间距增加,临界风速逐渐降低,当两火源间距达到极限距离时,临界风速不再变化;当进风口侧火源功率确定时,在极限间距内出风口侧火源功率增大时,临界风速增大,说明出风口侧的火源对进风口侧的烟气回流有促进作用;在极限间距内,临界风速随火源间距增加呈二次方递减到一个稳定值;两火源总功率越大,临界风速随着间距增加降低的幅度越明显。并得到了临界风速的预测公式。     

负离子空气净化器去除氨气的试验研究

针对负离子空气净化器去除氨气的有效性开展了试验研究.利用风道式空气净化性能实验台研究了负离子去除氨气的效率与迎面风速、外施电压、初始氨气浓度的关系.在环境试验舱里测试了负离子净化器样机去除氨气性能的有效性.结果 表明:负离子样机能较有效地去除氨气;在其他条件不变时,该负离子装置对氨气的去除效率随风速的增大而逐渐降低;随...     

圆盘通风制曲设备气流组织均匀性优化

针对南方某酱油制造厂圆盘通风制曲设备内气流组织不均匀问题,采取测试、数值模拟方法对气流组织优化措施进行探讨。改造前测试结果:下风室的最大风速与最小风速相差较大,不均匀系数接近甚至超过1,说明下风室的气流组织明显不均匀。上风室的最大风速与最小风速相差较小,不均匀系数也比较小,仍存在一定的不均匀性。改造前模拟结果:下风室内气流组织明显不均匀。在0.9 m测试截面上,空气在进风口后形成了明显的高速区,并延伸至风室壁面,导致风室内壁面的风速比较高。在2.5 m测试截面上,受进风影响,进风口后高速区上部出现了最大流速,远离进风口一侧的风室内壁面风速比较高。改造措施:措施1:加宽排风口。措施2:加大下风室中心柱直径。措施3:进风口增加导流板。措施4:在进风口增加导流板的基础上,加大下风室中心柱直径。措施5:进风口增设多孔板罩。与改造前相比,措施1~3对改善气流组织均匀性的作用并不明显,进风口后仍存在明显高速区,并延伸至风室壁面,导致风室内壁面附近的风速比较高。虽然措施4的进风口后仍存在明显高速流,但延伸长度缩短,风室内壁面附近的高速区也得到有效缓解。与改造前及措施1~4相比,采取措施5后,进风口后未出现明显的高速区,测试截面的气流组织均匀性得到明显改善。在5种措施中,措施5对2.5 m测试截面气流组织的改善效果最明显。措施5对圆盘通风制曲设备气流组织的改善效果最优。在研究的孔板开孔率中(55%、35%、18%),最佳开孔率为35%。改造后测试结果:与改造前相比,各测试截面上的风速分布更加均匀。各测试截面的不均匀系数均出现了下降,说明措施5对改善圆盘通风制曲设备内气流组织不均匀问题有效。     

风管出口位置对隧道施工通风效果影响的研究

为研究风管出口位置对公路隧道施工通风效果的影响,利用流体力学软件Fluent,建立隧道三维模型并进行了数值模拟。通过分别对风管管口与工作面5种布设距离及4种布设形式下流场特性的对比,分析了管口与工作面距离及风管附壁程度对流速变化和有效射程的影响。并进一步探讨了风管出口不同位置对局部风阻压力的影响。模拟结果表明:在相同的入口速度条件下,风管附壁程度越高、距离工作面越近,射流速度变化梯度越大,通风效果越明显;风管管口离工作面越近引起的局部压力损失越大。     

地铁站台火灾轨顶风道及专用排烟管协同排烟方案比较研究

通过实测及模拟的方法,对地铁站台火灾时,轨顶排热风道和端部专用排烟风管2种协同排烟方案进行了比较研究。研究结果表明：轨顶风道协同排烟方案有效可行,在8A编组车站的研究中侧排烟量占总排烟量的50%以上,屏蔽门漏风量接近20 m3/s,该方案能提供更大的楼梯处向下风速。而专用排烟管协同排烟方案因未开启隧道风机,在楼梯开口面积较大的不利情况下,楼梯处风速存在无法达标的风险,故推荐在车站条件较差时优先采用轨顶风道协同排烟方案。     

Comparison and further development of parametric tropical cyclone models for storm surge modelling

Cyclone forced storm surges cause severe damage to coastal structures and loss of human lives and properties. In cyclone protection and warning it is important to be able to calculate the cyclone air pressure and wind field on the basis of rather limited information, such as cyclone position, pressure drop, maximum wind speed and radius to maximum wind speed. In the present work, parametric cyclone models based on such limited information are investigated and compared. Analytical expressions of the tangential and radial velocity distributions are derived from the governing momentum equations. It is found that the analytical models provide very similar air pressure and tangential wind speed distributions. Instead of using a simple formulation of the deflection angle, the derived analytical expression of the radial velocity distribution is used and compared to earlier numerical solutions. A procedure is formulated for estimation of the shape of the cyclone on the basis of maximum wind speed versus pressure drop relations. Finally, examples of comparisons of measured and calculated air pressures and wind speeds and directions are presented.     

Experimental and numerical investigation on the distribution characteristics of wind pressure coefficient of airflow around enclosed and open-window buildings

In the present paper, the distribution characteristics of the wind pressure coefficient of the air flow around enclosed and open-window buildings were studied by using wind tunnel model tests and numerical analyses. A typical high-rise building model was designed and wind tunnel tests were performed for the airflow around the building for an enclosed and an open-window condition. The experimental findings were complemented by the numerical analysis. This study shows that the opening windows of a building has little influence on the wind pressure coefficients in the area around the window of adjacent area from window edge; the wind pressure coefficient increases slightly after opening the windows of the buildings. Opening the windows in the rooms adjacent to this window decreases the ventilation efficiency of the room although the influence is small. The time-average value of the wind pressure coefficient can effectively represent the magnitude of the instantaneous wind pressure coefficient. The wind pressure coefficient is independent of the wind velocity of inflow. Furthermore, this study also proposed the distribution characteristics of wind pressure coefficients with different incident angles of wind.     

Single-sided natural ventilation driven by wind pressure and temperature difference

Even though opening a window for ventilation of a room seems very simple, the flow that occurs in this situation is rather complicated. The amount of air going through the window opening will depend on the wind speed near the building, the temperatures inside and outside the room, the wind direction, the turbulence characteristics in the wind and the pressure variations caused by e.g. wind gusts. Finally, it also depends on the size, type and location of the opening. Many of these parameters are unsteady which makes the calculation of air-change rates even more complicated. In this work, full-scale wind tunnel experiments have been made with the aim of making a new expression for calculation of the airflow rate in single-sided natural ventilation. During the wind tunnel experiments it was found that the dominating driving force differs between wind speed and temperature difference depending on the ratio between the forces and the wind direction. This change is also found in the velocity profiles measured in the opening, which might change from wind dominated to temperature dominated under the same wind direction but with increasing temperature difference.     

地铁轨顶排热系统协同站台火灾排烟方案研究

以武汉某地铁车站为例,通过数值模拟和实验测试,对地铁车站站台发生火灾时轨顶排热系统协同站台火灾排烟方案和站台端部专用排烟风管方案进行研究。研究表明,轨顶排热系统协同站台火灾排烟方案可行,各楼梯、扶梯口处均能形成向下不小于1.5 m/s 阻止烟气向上蔓延的气流;当轨顶侧排烟口均匀布置时,站台火灾联动设备最少,协同排烟效果最好。站台端部专用排烟风管协同站台火灾排烟方案,在车站楼梯、扶梯口数量较多时,楼梯、扶梯口部阻挡气流风速存在低于1.5 m/s 的风险,应慎重选用。     

基于空气幕和挡烟垂壁的地铁站烟气控制

通过研究空气幕和挡烟垂壁阻挡烟气蔓延的性能,结合地铁站模型,利用FDS对控烟措施进行研究分析.考虑挡烟垂壁的高度以及空气幕的风速大小对烟气蔓延控制效果的影响.结果表明,挡烟垂壁高度越大越能有效控制烟气蔓延至站厅层;空气幕的风速适当增大能有效地把烟气控制在站台层.二者的有效结合、合理设置能抑制烟气蔓延至站厅层.     

Effect of inclined roof on the airflow associated with a wind driven turbine ventilator

Rotating wind driven turbine ventilator has been used as cost-effective environmental friendly natural ventilation device. Rotating wind driven turbine ventilator type of device is usually installed on the rooftop to extract air extract air flow from a building to improve air quality and comfort. Performance investigations carried thus far on turbine ventilator have ignored the effect of the inclination on rooftop. An experimental program was, therefore, formulated at the aerodynamic laboratory of the University of New South Wales to study such effect on a simulated rooftop. The results obtained from the measured forces and rotational speeds on different configurations indicate that the effect is minimal in extracting air from a building at low wind speed. The static pressure and skin friction distributions on the simulated roof further supports this finding. Two important conclusions can be drawn from the present investigation: firstly, the presence of the inclined roof may extend the safety margin in the operation of a turbine ventilator at high wind speed by reducing the magnitude of the total force that acts on the ventilator; secondly the dependency of the total fore on low Reynolds number suggests that the efficiency and reliability of operation of such ventilator should be boosted through the provision of other power source such as solar power at low wind speed.