室外风对高层建筑竖井内烟气运动影响的数值模拟

采用火灾模拟专业软件FDS对不同火源位置、不同风向条件下火灾烟气的运动进行模拟,测定典型位置处温度、速度、CO及CO2体积分数变化情况。实验结果表明:在近地风场中,风向对竖井内烟气蔓延的影响大小顺序为迎风>背风>侧风,竖井开口位于迎风面时,外界风对竖井内烟气运动影响最大:火源位于中性面以上时,烟气通过竖井与前室的开口向竖井内蔓延,并向下运动;而火源位于中性面以下时,前室内烟气向外部运动,竖井内无烟气流入。     

A Comparative Study on the Influence of Ventilation on Weather- and Fire-Induced Stack Effect in the Elevator Shafts of a High-Rise Building

This work assessed the impact of ventilation on both weather- and fire-induced stack effect in an 18-story high-rise office building. Elevator shafts are considered the main route of vertical air movement. Pressure distribution induced by cold weather within the elevator shafts was calculated theoretically. Computational fluid dynamics simulations of fire in the same high-rise building under different ventilation conditions were carried out with a fire dynamics simulator. It was found that ventilation exerted a more complex impact on fire than the weather-induced stack effect. For the weather-induced stack effect, the ventilation condition of the building only affected the height of the neutral pressure plane; in fire situations, it did not only affect the height of the neutral pressure plane in a similar manner to the weather-induced stack effect, but also influenced temperature and pressure distributions in the elevator shafts. The smoke movement and the distributions of temperature and pressure in elevator shafts are also learned. The smoke movement in high rises experienced four typical stages after ignition. The ventilation condition of the fire floor influences gas flow into elevator shafts, while that of the upper floors impacts the smoke rise speed in vertical shafts. When the stack effect finally reaches steady state, the gas temperature in the shaft decreases exponentially with height. Based on this assumption, a theoretical model was presented to characterize the fire-induced stack effect in typical high rises. Results showed that the model successfully predicts the pressure distribution in high-rise buildings.     

Smoke movement in elevator shafts during a high-rise structural fire

In high-rise fires, smoke is often the leading cause of fatalities. Therefore, in the event of a fire, the ability to predict the movement of smoke throughout a tall structure is of vital importance. Smoke moves depending on a number of interacting and complex factors including weather conditions, building construction, operation of HVAC equipment, as well as the location and intensity of the fire. Smoke often travels long distances from the fire floor, and in the particular case of a high-rise fire, smoke frequently moves to upper floors via open passages such as elevator shafts and stairwells.     

A network-based smoke control program with consideration of energy transfer in ultra-high-rise buildings, CAU_ESCAP

Ultra-high-rise buildings allow for the efficient use of land, but they are vulnerable to disasters such as fires. Therefore, the development of network models for analyzing the characteristics of smoke movement in ultra-high-rise buildings is necessary for cost-effective design of smoke control systems and operation decisions. A new network-based smoke control program, CAU_ESCAP, is developed in this study, which is a program that can consider the energy transfer. CAU_ESCAP is validated with existing programs, ASCOS and COSMO, by analyzing the smoke movement. After that, fire in an ultra-high-rise building of 55 stories is applied with CAU_ESCAP for analyzing the smoke movement and the mass flow rate of the smoke control system due to the variation of heat release rate and door conditions of the fire floor. The pressure difference between the fire room and the protecting area does not vary in the closed-door case in the fire room, but vary significantly in the opened-door case. Therefore, the smoke from fire would be spread to other spaces if there is no instantaneous increase in the mass flow rate of pressurization when the door is opened by occupants for evacuation.     

耦合电梯门狭缝流动的高层竖井火灾烟气模拟

利用FDS 建立17 层高层办公楼数值模型,考虑狭缝的小开口流动,耦合了基于开口流动理论的HVAC 模型,研究高层建筑内烟气通过电梯竖井的蔓延过程,得到了高层建筑内烟囱效应诱导的火灾烟气蔓延规律。高层建筑内较低层发生的火灾会显著加热电梯竖井中的气体,形成烟囱效应,高层建筑内部会形成中性面。通过将HVAC 模型与基于标准流量系数的模型进行比较,可以发现这两种方法计算的质量流量相差约1.5 倍。这是由于采用的HVAC 模型并没有考虑狭缝处的开口流动损失。通过进一步修正,取开口损失系数K 值为3.56 能得到较好的模拟结果。     

高层建筑竖井内烟气流动特性及控制方法

竖井火灾烟气流动特性和控制是与高层建筑火灾安全紧密相关的问题。从竖井烟气流动作用因素、烟气参数分布特性与烟气上升速度3个方面论述了对于高层建筑竖井烟气流动特性的研究现状。总结了目前常用的竖井烟气控制方法及工程实践中存在的问题,提出了改善烟气控制效果的方法和思路。     

含吹拔空间的高层建筑火灾烟气流动数值模拟

研究设有吹拔空间的高层建筑烟气流动及火灾蔓延特征,分析其对防火分区和安全疏散的影响。采用性能化消防设计的方法对某设有74.65 m、55.95 m双吹拔空间的一类高层建筑建立火灾发展模型、设计火灾场景、用CFD火灾模拟软件进行数值模拟。结果表明该建筑利用吹拔空间自然排烟时各火灾场景均能满足各层人员疏散的性能指标,在吹拔空间四周环廊上设置挡烟垂壁影响烟气的顺畅排出,缩短了危险来临时间,增大了火灾的危害性。提出吹拔空间式建筑宜利用烟囱效应优先采用自然排烟方式,烟气控制宜疏堵结合,以疏导为主的设计理念。     

浅谈高层建筑的火灾特点及预防对策

分析了高层建筑发生火灾的特点及其危险性和危害性,针对高层建筑火灾的特点,必须做好高层建筑的防火工作,并就设计思想、防火分隔、防火排烟、安全疏散、室内装修、陈设、防火自救等问题进行了探讨.     

COSMO—Software for designing smoke control systems in high-rise buildings

A differential computer model specifically designed to quantify smoke movement during a fire in a high-rise structure is described. The basic conservation equations are transformed into a computer code which can be used to determine the paths that smoke will take during a fire. The program is a tool for fire protection engineers to design a smoke management plan with the ultimate goal of improving occupant safety in the event of a fire. The computer code is based on a modified and improved differential smoke control model for the conditions in the floor spaces, stairwells and elevator shafts and it considers a complete set of variables that influence the motion of smoke throughout the building. Program output suggests ways to alter the pressure distribution within the building by using air handling equipment, so that occupants will have smoke-free areas on the floors and inside of the fire escape stairwells. Results for several example cases are provided, and the results are used to illustrate how smoke movement can be managed in order to mitigate dangerous conditions within the building.     

重庆市发展长江水源热泵的水源概况分析

为了解重庆段长江水作为热泵冷热源的概况,对重庆段长江水温的横断面变化和时间变化进行了实测分析,并对江水的水质和水位变化进行了分析,得到长江水温在整个横断面基本恒定,而江水的夏季月平均温度在22~25℃,冬季月平均温度在11~16℃,水温日变化幅度不超过0.5℃。是一种具有良好品质的稳定的冷热源。而长江水作为水源热泵的冷热源,主要解决的水质问题是泥沙和悬浮物,在三峡库区形成后水位变化可达到30 m,因此取水方式可考虑采用浮船取水方式。     

Wind effects on smoke motion and temperature of ventilation-controlled fire in a two-vent compartment

High-rise building fire is often influenced by the ambient wind. Study concerning fire behavior in the compartment of high-rise buildings in wind environment is needed for exploring some effective methods used for evaluation of compartment fire smoke movement and control. In this paper, smoke flowing direction and temperature of ventilation-controlled fire in a two-vent compartment are studied when ambient wind blows to the vent at higher altitude. It is found that there is a critical wind speed, above which the direction of smoke movement is dominated by wind rather than by buoyancy. It is also found that ambient wind has a complex influence on smoke temperature in the compartment. When wind speed exceeds another critical value, only one steady state appears in the smoke temperature rising curve. Otherwise three steady states appear. Heat transfer through the compartment walls has great influence on the second critical wind speed.     

Numerical simulation of the spread of smoke in an atrium under fire scenario

The Fire Dynamics Simulator code is used to investigate the smoke movement in an atrium under fire scenario. At first, by comparing with experimental data of the atrium fire under low and high heat release rates, reasonable model constants of C_s and Pr_t and appropriate grid system are determined for simulating smoke movement in the atrium, the simulation results are in good agreement with those experimental data. Then, the performance of different smoke exhaust methods in the atrium is studied. Smoke filling processes are investigated under different natural and enhanced smoke exhaust methods. Simulated results show that natural smoke exhaust method is preferred when the smoke exhaust vents are located at the ceiling of the atrium. On the other hand, when the smoke exhaust vents are located on the walls of the atrium, the higher positions of the smoke exhaust vents are preferred. In addition, the influence of the fire source locations on the smoke spreading process is presented in this paper, three kinds of fire source locations are studied, they are central fire, side wall fire and corner fire. Results indicate that the descending process of the smoke layer is the slowest when the fire source is at the corner of the atrium.     

Dimensionless analytical solutions for steady-state fire smoke spread through high-rise shaft

Analytical solutions in terms of dimensionless numbers for the smoke spread through high-rise shafts during fires are essential to provide a fundamental understanding of smoke transport physics, which is a complex coupled heat and mass transfer problem. Existing solutions are often dimensional based on simplification of the problem such as assuming adiabatic conditions. In order to obtain the dimensionless analytical solutions, energy balance equation, mechanical energy equation and mass balance equation were established for smoke spread in high-rise buildings under both mechanical and natural venting conditions. Experiments were designed and conducted on two scaled shafts with different sizes and materials, and the measured results were compared to the dimensionless analytical solutions. It was found that the dimensionless analytical solutions could predict temperature profiles, mass flow rate and neutral plane level accurately. The effect of the adiabatic assumption on the accuracy was also discussed. For example, due to the adiabatic assumption, the error of the calculated mass flow rate required during mechanical venting to maintain a high-rise shaft smoke free was found to increase with a dimensionless number, ω, defined by the geometrical and thermal properties of the shaft.     

太原理工大学北区新教学主楼的防火设计

从高层建筑的火灾危险性入手,通过对太原理工大学北区新教学主楼防火和防烟分区的划分、对安全疏散的考虑以及室内消防给水系统和消防装置的设置等的充分分析,论述了如何成功地进行教学楼建筑的防火设计,为防火设计工作提供了依据。     

高层建筑条形走廊自然排烟效果的数值模拟与评价

采用场-区模型模拟火灾发生时高层建筑条形走廊内的自然排烟过程,考虑了室外风向、风速、起火房间位置、走廊宽度和外窗尺寸、季节以及内走廊长度等因素对自然排烟过程的影响,对模拟结果进行分析并得出相应结论,结果显示当内走廊长度超过30m时,走廊内采用自然排烟不能保证人员的安全疏散。     

Study of FDS simulations of buoyant fire-induced smoke movement in a high-rise building stairwell

Numerical simulations of fire-induced smoke movement in the stairwell of a high-rise building are conducted using FDS, version 6.0.1, with default settings. Twelve scenarios are considered. The required fineness of the grid has been determined in earlier work by considering both the fire source and the vent flow, and by assessing the velocity profile at the bottom opening and the vertical distribution of temperature in the stairwell. In the present study, the results including the airflow velocity at the bottom opening, vertical distribution of temperature, the temperature at the middle opening, pressure distribution, and neutral plane height in the stairwell, are compared to experimental data. For the average velocity through the bottom opening, a maximum deviation of 16.23% is obtained. Good agreement is achieved for the vertical temperature inside the stairwell (maximum relative deviation of 12.3%). By analyzing the temperature at the middle opening, it is found that the smoke moves faster than in the experiment. The influence of the staircase on the pressure distribution is demonstrated by comparing two cases: one with and one without staircase. The difference between the pressure inside the stairwell and the pressure outside increases with height, due to fire-induced buoyancy. However, the pressure difference evolution is non-monotonic when there are staircases inside the stairwell. The neutral plane height value, as obtained by post-processing the simulation results, is too high in the simulations, compared to experimental data and the corresponding analytical expression. Finally, the influence of the turbulence model is shown to be negligible.     

高层建筑烟气扩散与控制计算机模拟进展

描述了高层建筑火灾烟气的危害性,介绍了目前世界上高层建筑火灾烟气扩散和控制领域的计算机模拟研究方法和成就,分析了不同方法各自的不足,指出了改进方法。     

提高高层建筑消防防火排烟设计的整体效果

随着城市化进程的不断加快,高层建筑的建设数量也在不断增加。而在高层建筑工程的设计与建设中,消防防火排烟设计的合理性会对整体工程的消防防火质量起到有效的保障作用,最大限度确保用户的生命与财产安全。基于此,文章对高层建筑工程中的消防防火排烟设计进行分析,期望可以为高层建筑工程消防防火排烟设计质量的提升和整体工程的安全保障提供一定参考。     

试析高层建筑防排烟系统的常见问题

防排烟系统设施是高层建筑保障人民生命财产安全不可缺少的消防安全设施.防排烟系统共有三种类型:自然排烟系统、机械排烟系统、机械加压送风系统.由于部分设计、施工人员对防排烟设施的结构、作用、性能缺乏了解,对国家规范标准理解不够透彻,往往导致在设计、施工中出现防排烟系统设施配置被忽略或有配置而功能不全等现象.本文主要列举了高层建筑的3种防排烟系统在设计、施工和验收中的若干常见问题,以期引起设计、施工、管理和使用人员的重视.     

超高层建筑商业裙楼性能化设计

总结超高层建筑商业裙楼存在的火灾危险性,如功能复杂、火灾蔓延迅速、扑救困难、人员疏散困难等。以广州东塔商业裙楼为例,分析其消防设计难点。根据消防安全工程原理和性能化防火设计思想,如准安全区、防火单元等,从裙楼防火分隔、防排烟方案、人员疏散等方面提出其消防性能化设计方案,为类似工程的消防性能化设计提供参考。