Air entrainment and thermal radiation from heptane pool fires

An experimental study was made to explore the air entrainment into heptane pool fires and the smoke blocking effect on thermal radiation from fire. Heptane was burned in five different sized tanks 0.3 m, 0.6 m, 1 m, 2 m, and 6 m in diameter, and its burning rate, flame temperature, vertical hot gas velocity, and thermal radiation were measured. It was found that the total amount of air entrainment is about 5 times the stoichiometric air requirement. A smoke block effect appeared at tank diameter of 2 m or more.     

滑坡冲击铲刮效应物理模型试验及机制探讨

 滑坡–碎屑流在高速运动过程中对基底物质存在明显的冲击铲刮作用,从而造成滑坡体积不断增大,扩大其致灾影响范围。通过开展物理模型试验研究滑坡物质的颗粒粒径和体积以及基底物质的粒径和堆积厚度对铲刮效应的影响,同时采用MotionPro-Y3–S1高速摄像机观察冲击铲刮过程。试验结果表明：滑坡物质在运动过程中强烈地冲击铲刮基底物质,使其高速飞溅及剪切运动;铲刮距离随滑坡物质体积、粒径以及基底物质颗粒粒径的增大和可侵蚀基底厚度的减小而增大。结合试验现象以及前人的研究成果对滑坡冲击铲刮机制进行探讨：滑坡–碎屑流的冲击铲刮作用在前缘主要表现为冲切破坏,它以撞击力的形式使基底物质发生破坏而铲刮,而在中后部主要表现为运动剪切作用,以剪切力的形式使基底物质发生剪切破坏而被铲刮。     

Experimental studies on air entrainment and oxygen content downstream of sharp-crested weirs

The concentration of dissolved oxygen (DO) is an important indicator of water quality because aquatic life survives on the DO in water. A free overfall jet from a weir plunging into downstream water causes entrainment of air bubbles if the free overfall jet velocity exceeds a certain critical value and hence aeration occurs. This paper investigates the free overfall jets from sharp‐crested weirs and their effect on air entrainment and aeration efficiency. The results indicate that the air entrainment and aeration efficiency of triangular sharp‐crested weirs are significantly better than those for the other sharp‐crested weir types. Therefore, the triangular sharp‐crested weirs can be used as highly effective aerators in streams, rivers, constructed channels, fish hatcheries, water treatment plants, etc. Regression equations were obtained for the triangular sharp‐crested weirs relating air entrainment rate and aeration efficiency to drop height, discharge and angle in the triangular sharp‐crested weir. There was good agreement between the measured values and the values computed from the predictive equations.     

Air water flows in building drainage systems

This paper investigates the mechanisms of two-phase flows that occur in commercial and industrial roof drainage systems. Both traditional gravity-fed and siphonic roof drainage systems are examined.

Air entrainment plays a fundamental role in the performance of siphonic roof drainage systems. In particular, air entrainment has a significant effect on:

• maximum system flowrate capacity;

• pipe friction losses;

• operational system pressures;

• operational gutter water depths; and

• ability of the system to prime.

However, experimental results presented here demonstrate that the reduction in system capacity is not directly proportional to the increase in air content. One possible explanation for this is that water and air will be affected differently by sub-atmospheric pressures. The effect air entrainment has on roof drainage performance is investigated. The ways in which air is introduced into the system are identified and the effects of different air/water ratios are quantified. Finally methods for reducing air entrainment are described.     

引气作用及其对混凝土性能的影响

引气作用可以改善混凝土抗冻性 ,但是在土木工程建设中 ,很多人还不了解如何运用和实施引气作用 ,文章对引气作用相关问题的介绍可能是有所裨益的     

Modelling concentration fluctuations and individual exposure in complex urban environments

One of the key problems in coping with deliberate or accidental atmospheric releases, which in many cases are short or/and result in high concentrations, is the ability to reliably predict the individual exposure during the event. Furthermore, for consequence assessment and countermeasures application, it is more realistic to rely on the maximum expected dosage rather than on the actual dosage. Recently, Bartzis et al. (2008) have introduced an approach relating maximum dosage to parameters such as concentration variance and turbulence integral time scale. The need for an estimation of these parameters poses new challenges to CFD models. In the CFD RANS model ADREA, new approaches have been implemented recently, where the parameterization of the dispersion of a pollutant emitted from a point source depends not only on the parameters of turbulence, but also on the pollutant travel times. In this study the new methodology is tested against MUST and FLADIS field experimental data, which consist of high resolution concentration time series enabling the production of short term dosage data. The present comparisons further strengthen the evidence that the applied methodology is capable of dealing properly with complex transient dispersion phenomena.     

V2F模型在室内空气流动数值模拟中与其他湍流模型的比较研究

介绍了V2F模型的表达式。对Annex20算例进行了模拟计算,将V2F模型、雷诺应力模型、标准K-ε模型、低雷诺数K-ε模型、RNGK-ε模型的模拟结果与其他研究者的实验结果进行了比较。结果表明,V2F模型在模拟室内空气流动中优于其他湍流模型。     

城镇高氨氮污水的吹脱除氮试验研究

针对高浓度氨氮废水进入城镇市政管网所造成的污水厂脱氮效果较差的情况,提出了采用吹脱除氮法作为污水厂的二级生物处理或一级强化处理的预处理,并进行了试验研究,考察了污水pH、吹脱气水比、进水氨氮浓度、水力负荷等因素对吹脱效果的影响。结果表明,污水最佳pH值为10.511,增加水力停留时间可提高对氨氮的去除率,水温为15℃时气水比应控制在3 360∶1以上,水力负荷可选择在2.04~3.57 m3/(m2.h)。试验表明吹脱法除氮处理工艺可作为脱氮除磷二级生物处理或一级强化处理的预处理。     

裂缝性页岩储层多级水力裂缝扩展规律研究

水力裂缝监测技术显示页岩储层中水力裂缝形态复杂,与传统的砂岩储层有本质区别,传统的裂缝扩展模型难以描述和解释页岩地层裂缝扩展的复杂性。基于线弹性断裂力学理论,针对页岩地层裂缝发育的特征,采用位移不连续法建立了一种多裂缝扩展二维数值模型,模拟了页岩地层中水力裂缝在随机分布的天然裂缝干扰下扩展的复杂形态。数值模拟显示,当相对净压力较大、天然裂缝与初始水力裂缝最优扩展方向夹角较大时,更倾向于形成复杂形态裂缝;水平应力差较大时,水力裂缝分叉的几率越小,通过对页岩露头的真三轴水力压裂物理模拟试验研究进一步验证了数值模拟方法的合理性,龙马溪组页岩地层的微地震监测解释结果与本数值模拟结果吻合良好。     

中餐厅新风量以及机械排风量的确定方法

中餐厅的通风是保证其室内空气品质的主要手段。中餐厅的新风量与机械排风量相互关联。本文分析了中餐厅的新风量以及机械排风量的确定原则。指出中餐厅的新风量按满足卫生要求确定即可；而机械排风量不仅与新风量有关，还受中餐厅内人员密度的大小以及正压值影响；中餐厅内的机械排风量与新风量的比值并非一个定值：     

现有建筑物空调新风系统存在问题及其思考

现有建筑物中央空调通风系统的新风供应情况，直接关系到人们的生活工作环境。本文通过对现有建筑物空调新风系统的调查，从设计、设备供给、施工安装、系统调试和运行管理等环节进行分析，对空调新风口设置、空调新风短路、新风量不足、送风与排风不匹配、新风分配不合理、空调系统的过滤和加湿及空调系统的运行管理等七个方面的问题进行了探讨和思考，以便正确地认识和评估目前我国空调新风系统的现状。     

汽车内空气污染及净化

汽车在使用过程中会在车厢内产生不同程度的有害气体污染。本文通过分析汽车内空气品质的特点和污染的主要来源,提出净化车内空气首先应该加强汽车空调系统通风和净化功能,其次可以在汽车内单独放置净化器,另外应从源头上减少各方面进入车内的污染。     

一次泵空调冷水系统的水力特性与节能分析

以一次泵空调冷水系统为研究对象,针对其水力特性与节能方式进行了理论分析。结果表明:末端为空调机的一次泵水系统易出现大温差小流量的情况,而末端为空调机与风机盘管组合形式的系统易出现小温差大流量情况。在冷负荷减少时,为更好的确保一次泵空调冷水系统节能运行,采用定水量系统调节冷水机组出口水温时应减少水系统的旁通水量;采用水泵变频调节且水泵所占空调水系统能耗比大于0.3,当系统的水力特性越接近末端为空调机形式的水力特性时,采用水泵变频调节效果越好(节能率大于10%)。在采用调节冷水机出水温度和变频调节冷水量匹配冷负荷时,冷水过量情况仍然存在,需旁通水量,水泵定频和变频时,可分别根据单台冷水机水流量的1.2~1.8、0.2~1倍来选择旁通管径。     

北京市住宅空气质量及相关能耗调查及分析

近年来,我国北方地区空气污染问题日益严重,频频发生的雾霾现象使得人们越来越重视室内空气质量。调查了北京市部分家庭对雾霾的认知以及所采取的改善室内空气质量的措施。发现未来2~3年内将会有72.8%的家庭采用空气净化器来改善室内空气质量,并由此推算出全年北京市住宅用于空气净化的建筑能耗量。     

膜除湿技术在压缩空气干燥及空调领域的应用

阐述膜除湿原理,介绍膜材料类型、形态。对膜除湿技术在压缩空气干燥领域、空调领域(全热回收、空气除湿)的应用进行了综述。     

工程机械液压系统的安装调试方法

介绍了工程机械液压管和液压元件的安装，调试过程，阐述了液压系统的清选方法，以达到指标维修保养的目的，指出液压元件属高精密件，必须做好液压系统的安装和调试。     

我国液压传动的现状及发展

通过对世界流体传动及控制技术发展趋势的分析 ,介绍了我国液压行业面临的危机和现状以及和世界水平的差距 ,并提出我国液压行业的发展方向和对策。     

流量喷嘴及其在实验室风量测量中的应用

根据国内外文献并结合作者数年来的实践经验,详细地叙述了当今广泛应用于实验室风量测量的多喷嘴风量测量装置的设计、风量计算和风量调节等问题。给出了该装置的设计实例。     

三峡电厂发电机层夏季分层空调气流组织设计与分析

围绕三峡电站主厂房发电机层夏季分层空调的气流组织设计问题,首先逐一分析其系统划分、气流组织形式、空调送风状态与送风量等相关条件,依据国内较为成熟的研究成果,确立其分层空调气流组织计算模型并进行其应用方法的探讨。在此基础上,笔者使用ＦＯＲＴＲＡＮ７７语言编制了名为ＡＦＤＣ／ＬＡＣＳ的计算机应用程序,以标准机组段下游侧空调系统为代表,就不同空调设计工况条件进行其分层空调气流组织计算。通过对众多符合检验