狭长空间强扰动排热通风量的优化研究

针对存在强扰动气流的狭长空间内热量不容易排出的问题,本文采用全面通风的手段来消除空间内持续散发的大量热量,并依据相似理论,利用Revit软件辅助设计搭建了模型实验台,对不同热射流温度及对应不同排热通风量的排热效果进行了优化研究。文中以评价全面排热通风量效果的评价指标——排热效率为参考,得到热射流温度在小于591K的范围内,最优的全面排热通风量值约为144．7万m3／h,当热射流温度位于591～709K时,最优的全面排热通风量值约为159．7万m3／h。     

全射流纵向通风在广州洲头咀珠江隧道中的应用

洲头咀隧道位于广州市珠江主航道上,总长1530m,本文结合工程的实际情况,对隧道的通风方式按全射流纵向通风方案、射流风机 洞口风道式排风型纵向通风方案、送风型半横向式通风方案进行了定量和定性比较,并综合考虑技术、投资和运营多方面因素确定采用全射流纵向通风方式。     

曲线隧道射流风机通风效率优化研究

隧道射流通风系统中的射流风机布置方式可以直接影响到隧道通风系统的通风效率,其中曲线隧道的射流流场分布规律又区别于一般直线隧道。本文以建宁西路地下互通工程为依托,采用CFD 软件针对曲线隧道中射流风机的横向间距与布置位置、风机偏转角度、纵向间距等参数进行数值模拟,分析了不同工况下的流场分布、风机升压能力。结果表明：在曲线隧道中,当射流风机横向间距为2 倍风机直径,且靠近隧道凸面朝凹面区偏转5°~10°时风机下游流场分布较为均匀,隧道通风效果良好;射流风机纵向布置间距不宜大于100 m。     

公路隧道超长距离纵向排烟试验研究

为研究5 km以上公路隧道超长距离全射流纵向排烟可行性与有效性,依托全长6 015 m的羊鹿山隧道,在不利于排烟的左线隧道（单向下坡）内开展20 MW现场火灾全射流纵向排烟试验。试验期间自然风速为1.0~1.6 m/s,与通风排烟方向相反,表现为排烟阻力。研究表明：左洞内开启6组射流风机时,洞内沿程风速约为3.5 m/s,开启12~15组风机时,下坡隧道内沿程风速约为5.5~7.0 m/s;20 MW油盘火试验从点火开始到烟气全部排出洞外的时间约为30 min。根据现场火灾排烟试验,对于羊鹿山隧道,在保证人员安全的情况下,采用全射流纵向排烟是可行的。     

不同风机轴距下某隧道内气流分布研究

以某三车道公路隧道结构参数为依据,建立数学模型。在纵向通风方式下,用CFD软件对隧道内气流分布进行模拟研究。分别对风机轴距为2 m、3.6 m、5.6 m工况进行模拟;当轴距为3.6 m时,气流纵向影响范围最长,纵向影响范围约150 m。在此条件下,分别对隧道不同纵向长度处的横断面的速度分布情况进行分析比较得:当纵向长度Z在200 m即风机后150 m处时,射流影响范围波及整个隧道横断面,风速基本不再变化,隧道内气流均匀性较好,处于完全稳定状态。     

公路隧道纵向射流通风的三维数值模拟与分析

以隧道纵向射流通风基本理论为基础,采用FLUENT软件,对隧道内空气的速度场及压力场作三维数值模拟与分析。在此基础上,将模拟后得到的风机升压力值与经典理论公式计算值比较,得到射流风机综合影响系数K,并进一步分析其影响因素及变化规律。研究工作可以为进一步优化纵向射流通风设计提供参考。     

火山特长公路隧道通风方案比选研究

通风系统是长大公路隧道的关键一环,对建设及后期运营费用影响较大。宁攀高速火山隧道全长7 192 m,根据需风量计算结果,可采用全射流纵向式通风。也可布设通风井进行分段通风,通过对不同通风方案进行比选,综合考虑土建费用和运营费用,火山隧道左线采用两区段通风,右线采用全射流纵向式通风。     

不同风机轴距下某隧道内气流分布研究

以某三车道公路隧道结构参数为依据,建立数学模型.在纵向通风方式下,用CFD软件对隧道内气流分布进行模拟研究.分别对风机轴距为2m、3.6m、5.6m工况进行模拟;当轴距为3.6m时,气流纵向影响范围最长,纵向影响范围约150 m.在此条件下,分别对隧道不同纵向长度处的横断面的速度分布情况进行分析比较得：当纵向长度Z在200 m即风机后150 m处时,射流影响范围波及整个隧道横断面,风速基本不再变化,隧道内气流均匀性较好,处于完全稳定状态.     

多工况下氢能源汽车隧道内火灾温度场研究

为了研究隧道内氢能源汽车分别沿上、下、前、后4个方向释放氢气并立即引燃后产生的温度场,使用Fluent软件对氢气释放并立即点燃后产生的温度场进行数值模拟仿真,分析了氢气泄漏方向和隧道通风速度对射流火焰最高温度以及高温区分布的影响,为隧道内通风速度的设定以及隧道内壁防火设计提供科学依据。结果表明：在氢能源汽车沿上、下、前、后4个方向释放氢气工况下,增大隧道纵向通风速度对降低射流火焰最高温度作用有限,但可显著减小高温区体积,从而减少射流火焰高温区对隧道各壁面造成的损伤。因此,在隧道设计阶段,建议适当增大隧道纵向通风速度,最佳通风速度为5.0～8.0 m/s;也可以考虑在隧道最右侧增加应急车道,以增大隧道壁面与车辆间的安全距离,进而保护隧道结构和车辆人员安全。     

海底公路隧道火灾数值模拟

利用FDS对某海底公路隧道进行研究,分析典型火灾条件下,纵向通风对热烟气逆流距离、隧道顶部温度以及隧道内横通道风流变化的影响。结果表明,在0.25 m/s的火灾初期通风条件下,热烟气逆流距离和火源附近拱顶温度超过安全临界温度的范围随火灾规模增大而增大;在3 m/s的灭火期通风条件下,两者随着纵向通风风速增加而减小;隧道内横通道风速先增大,后减小。     

纵向通风与侧壁开口竖井自然排烟协同作用下烟气运动模拟

为探究山岭隧道火灾烟气运移特性,采用数值模拟的方法,选取两种典型火源功率(20 MW及50 MW),分析不同纵向风速下火源位置对隧道顶棚下方沿程温度分布规律、烟气运移速率及竖井内烟气质量流量的影响规律.研究结果表明,纵向风速低于3m/s时,不同火源位置时,火源上游沿程温度均随纵向风速增加逐渐降低,而下游沿程温度随纵向风...     

基于FDS的公路隧道火灾可逆射流风机通风疏散研究

随着我国公路隧道从高速建设期转变为建设与管理并重期,可逆射流风机在隧道通风系统中得到广泛应用。为探究可逆射流风机在隧道火灾下通风运行方式对人员疏散的影响,依托广东山隧道,采用5,20 MW两种火源功率,研究不同射流风机运行方式下隧道中部区域烟气、温度、CO体积分数及能见度的变化特性。结果表明,自然风和射流风机的出口气流均会破坏烟气-空气分层结构。在隧道内部1 m/s纵向自然风的影响下,面对不同功率火源,射流风机运行模式与人员疏散方向应随之改变。     

海底特长隧道利用横通道控烟技术研究

摘 要：为了解决特长海底隧道发生火灾时的排烟问题,提出利用服务通道和联络横通道辅助送风的通风方案。利用火灾动力学模拟软件（FDS）,建立隧道火灾通风模型,通过研究通风排烟时服务隧道内补风量与横通道开启数量对火灾烟气的控制效果,确定通风系统的技术参数。结果表明：火灾发生时,事故隧道内纵向通风风速2 m/s,同时开启火源上游3 个横通道,并在服务隧道两端各施加1.3 m/s 纵向通风风速,既可将烟气控制在火源一侧,同时不影响人员安全疏散,其控烟效果与通风网络解算结果一致。采用横通道辅助送风的通风方案,控制特长海底隧道内火灾烟气蔓延是具有理论可行性的。     

Experimental investigation of air flow and temperature distribution in deep urban canyons for natural ventilation purposes

Detailed experiments have been carried out in a deep canyon in Athens during the summer period. The aim of the experimental campaign was first to evaluate the potential of natural ventilation in the urban environment and second to better understand the air flow and thermal phenomena in deep urban canyons.Extensive measurements of the surface and air temperature as well as the wind speed in the middle and close to the canyon façades have been measured in a continuous basis. In parallel, the undisturbed temperature, wind speed and direction above the canyon have been measured as well. Measurements of the airflow rate in single side and cross ventilation configurations have been carried out using tracer gas techniques, in a naturally ventilated building located in the canyon.It is found that the potential of natural ventilation for both single side and cross ventilation configurations in buildings located inside urban canyons, is seriously reduced. It is estimated, that in the specific canyon, the airflow rate for single side and cross ventilation configurations, is reduced by 82 and 68%, respectively compared to an undisturbed location. The mechanism of the air flow and temperature distribution inside the canyon is extensively analysed and the specific phenomena that determine the wind speed and direction inside the canyon are described in details.     

某机加工车间空调设计的优化

论文针对无锡某项目机加工车间空调系统设计的落地式射流柜机无法满足现场安装尺寸要求的情况,提出将空调由落地式射流柜机改为吊装射流机组,由外墙向厂房中间射流。同时,为保证靠外墙处人员的空调要求及制热时热风上升的问题,在吊装射流机组后端连接竖向风管并在低位设置回风口。为确定合适的吊装高度以满足人员区域温度及风速要求,利用CFD数值模拟方法分别对2种吊装高度下的设计方案进行气流组织分析。通过分析对比,得到满足设计要求的空调方案。     

自然通风建筑室内气流组织优化研究

通过fluent模拟软件对诸多因素中最为关键的风向、风速、开窗位置及面积等进行了优化模拟研究。结果表明:在西安地区,南向为最佳风向,室外风速在1.3～2.5 m/s之间,基本上都能满足自然通风要求,最佳风速为1.5 m/s;综合考虑采光和自然通风因素,窗户开在墙的中间为宜;北向面积适当减小有利于自然通风在室内形成较均匀的气流,在保证建筑节能标准的前提下,增大南向窗户面积有利于自然通风。     

Numerical studies on evaluation of smoke control system of underground metro rail transport system in India having jet injection system: A case study

The rail based urban transport system is being developed for national capital of India, New Delhi. The smoke control using ventilation in case of fire inside the tunnel, similar to Delhi Metro corridor has been investigated using computational fluid dynamics technique. A section of tunnel having dimensions 400 m long, 5.5 m wide and 6 m high is considered for simulation. The analysis has been carried out by assuming a variable fire source with a peak heat release rate (HRR) of 16 MW, located at the center of the tunnel. Ventilation ducts are located in the ceiling near the tunnel portals and are inclined at 10 degrees to the plane of the ceiling through which fans discharge air. The influence of the fire HRR curve slope on the smoke flow dynamics in a realistic tunnel model fitted with jet injection type longitudinal ventilation system has been investigated. In case of fire two cases are studied: (1) fans activated immediately after detection, (2) fans activated at delayed times to take into account the response time for the fans to achieve its maximum speed. The velocity of supply and exhaust fans necessary to remove smoke in 30 s from the upstream direction is determined. The velocities of fan required to produce desired critical velocity in the longitudinal direction for different HRR of fire is predicted.     

Air movement acceptability limits and thermal comfort in Brazil's hot humid climate zone

In hot humid climates, natural ventilation is an essential passive strategy in order to maintain thermal comfort inside buildings and it can be also used as an energy-conserving design strategy to reduce building cooling loads by removing heat stored in the buildings thermal mass. In this context, many previous studies have focused on thermal comfort and air velocity ranges. However, whether this air movement is desirable or not remains an open area. This paper aims to identify air movement acceptability levels inside naturally ventilated buildings in Brazil. Minimal air velocity values corresponding to 80% and 90% (V80 and V90) air movement acceptability inside these buildings. Field experiments were performed during hot and cool seasons when 2075 questionnaires were filled for the subjects while simultaneous microclimatic observations were made with laboratory precision. Main results indicated that the minimal air velocity required were at least 0.4 m/s for 26 °C reaching 0.9 m/s for operative temperatures up to 30 °C. Subjects are not only preferring more air speed but also demanding air velocities closer or higher than 0.8 m/s ASHRAE limit. This dispels the notion of draft in hot humid climates and reinforce the broader theory of alliesthesia and the physiological role of pleasure due to air movement increment.     

Predicting integrated thermal and acoustic performance in naturally ventilated high-rise buildings using CFD and FEM simulation

The study of ventilation windows for both natural ventilation and noise mitigation has drawn significant attention recently. This paper presents the numerical approaches to analyse the integrated thermal and acoustical performance of ventilation windows, for a residential building in tropical climate which employs double-layer noise mitigation window for natural ventilation. Given a set of outdoor wind conditions, the distributions of indoor flow and temperature fields are simulated using Computational Fluid Dynamics (CFD) model. The thermal comfort is evaluated using statistical Predicted Mean Vote (PMV) method. For the acoustic performance, noise radiation from road traffic is assumed as the noise source, and the sound insulation of building façade is simulated using Finite Element Method (FEM). From the simulation results, it is found that the thermal satisfaction response is closely related to the inlet wind temperature and speed, and the window opening size greatly affects the ventilation performance. From the case study in Singapore, during certain season, day/night time and with sufficient wind flow, the ventilation window can provide enough fresh air, maintain adequate thermal comfort and quiet acoustic environment for the occupants. The numerical approaches presented in this paper are applicable to general window design studies, and the simulation findings can be incorporated into green building planning. The advantages of using simulation approaches are highlighted and their limitations are discussed.