Design Of Smoke Control Systems Research Articles

A study of the critical velocity and the confinement velocity of fire accident in a longitudinally ventilated underground train with different door opening scenarios

The critical velocity, confinement velocity and smoke back-layering length are significant factors for smoke control in a tunnel fire. This research aims to analysis the correlation of these 3 key smoke control parameters in the different door opening scenarios during a fire in the metro train carriage that stopped in the tunnel. Scaled model experiment measurement and numerical simulations were carried out for the propagation and control of smoke. Five fire locations in the train and two side doors opening scenarios of the train were considered. Results show that smoke back-layering length in the train can be barely influenced by the activation time of the longitudinal ventilation system. However, the opening of side doors could result in a shorter smoke back-layering length in the train. Furthermore, we present a dimensionless correlation for the critical velocity and confinement velocity of underground train fires caused by fires in the double-length narrow space of an underground tunnel. This study provides a predictive model for the design of smoke control systems for fire of train stopped in underground tunnels.

Numerical and experimental study on the effects of a ceiling beam on the critical velocity of a tunnel fire based on virtual fire source

Ceiling beams, such as smoke screens, supporting beams, and ceiling pipelines, exist in several types of tunnels. The ceiling structure of a tunnel has a significant influence on smoke propagation. This study determines the critical velocity required to control fire smoke in a tunnel with a ceiling beam. We conducted model experiments and numerical simulations to analyze the effects of a ceiling beam on air flow structure and smoke propagation. An air re-circulation length model was fitted to determine whether a fire source lies within the vortex swirling zone. Using a virtual fire source, we obtained the critical velocity prediction model for a tunnel with a ceiling beam. The results indicate that the re-circulation length of the vortex swirling zone is determined by the beam height and tunnel height, but is independent of the longitudinal airflow speed. The form of the critical velocity model for a tunnel with a ceiling beam is consistent with that of conventional models, wherein the dimensionless critical velocity is proportional to the dimensionless heat release rate raised to the power of one-third. This implies that a virtual fire source can be used to determine the critical velocity. The proposed prediction model of the critical velocity for a tunnel with a ceiling beam is an improvement on previous models and can be used in the design of smoke control systems in tunnels with beams.

Computational fluid dynamics-assisted smoke control system design for solving fire uncertainty in buildings

For every fire prevention design, ensuring safe evacuation and preventing the fire from spreading are primary considerations. However, actual fire scenarios inevitably involve many uncertainties, such as the fire source location, the heat release rate, the fire growth coefficient and so on, which make it difficult for the traditional fire prevention system to achieve these primary considerations. In this paper, an optimum and intelligent system design was developed using the feedback of real-time fire characteristics based on precise control logic using computational fluid dynamics. The new system can make an intelligent adjustment to adapt the real-time fire and to obtain the best smoke exhaust condition by coupling the smoke control system and a physical boundary. The fire uncertainties were used to validate the system design, based on a conventional composite building containing room, corridor and atrium. The results show that the intelligent system is capable of providing different and reasonable reactions for various fire scenarios and of ensuring the safe evacuation of the building. Some limitations of the system have been improved by incorporating a constraint factor into activation procedures for solving extra-large and ultra-fast fires. In general, this intelligent design proved useful as a smoke control system which could be implemented in many similar buildings.

Review and Validation of the Current Smoke Plume Entrainment Models for Large-Volume Buildings

The design of smoke management systems in large-volume enclosures is of utter importance for life safety, property protection, and business continuity in case of fire. Despite the recent international trend in smoke control design towards the use of advanced fire models, simple plume entrainment correlations are the basis of the discipline and are still a common practice since they are often incorporated in technical documents for the design of smoke control systems. Different plume entrainment correlations have been developed over the years and are cited in different national codes and design guides. These correlations have been widely investigated for fires in small enclosures, but their applicability and accuracy in large enclosures is not clear. The present work studies the suitability and applicability of these approaches to properly predict the fire induced conditions within large volumes. The results obtained from the plume entrainment correlations have been compared with full scale experimental data in an 8.000 m3 enclosure. Based on the results obtained by this analysis performed in a large-volume enclosure, the current methods available of modelling fire and determining the smoke produced by the fire might not be suitable. It was observed that for the steady state, the McCaffrey correlation gave results closest to the experiments, and for the transient evolution of the smoke layer, the Zukoski correlation. On the contrary, the popular Thomas method underpredicted smoke production and entrainment, giving the highest smoke layer interface heights and leading to estimations that are not conservative (with errors between 36.5% and 101%). The authors analyze the reasons for the discrepancies and give some practical recommendations for the design of smoke control in large volume buildings, such as that the use of such models to predict the smoke production of a given fire shall be only a first approximation and not a design tool, especially when using those models that have not shown a good match to the experimental data.

Numerical analysis of combined buoyancy-induced and pressure-driven smoke flow in complex vertical shafts during building fires

Purpose – The purpose of this paper is to study the behavior of smoke flow in building fires and optimize the design of smoke control systems. Design/methodology/approach – A total of 435 3-D fire simulations were conducted through NIST fire dynamics simulator to analyze thermal behavior of combined buoyancy-induced and pressure-driven smoke flow in complex vertical shafts, under consideration of influence of heat release rate (HRR) and locations of heat sources. This influence was evaluated through neutral pressure plane (NPP), which is a critical plane depicting the flow velocity distributions. Hot smoke flows out of shafts beyond the NPP and cold air flows into shafts below the NPP. Findings – Numerical simulation results show that HRR of heat source has little influence on NPP, while location of heat source can make a significant difference to NPP, particularly in cases of multi-heat source. Identifying the location of NPP helps to develop a more effective way to control the smoke with less energy consumption. Through putting an emphasis on smoke exhausting beyond the NPP and air supplying below the NPP, the smoke control systems can make the best use of energy. Research limitations/implications – Because of the chosen research approach, the research results may need to be tested by further experiments. Practical implications – The paper includes implications for the optimization of smoke control systems design in buildings. Originality/value – This paper fulfills an identified need to research the behavior of hot smoke in building fires and optimize the design of smoke control systems.

대공간의 기계배연 시스템에 대한 설계 및 수치해석적 분석

대공간은 높은 층고로 인해서 화재시 연기 발생량이 수십만 CMH에 달할 수 있으며, 연기의 국한화가 일반 건물에 비해 어렵기 때문에 대공간에 효과적인 연기제어 시스템의 설계와 운영이 요구된다. 본 연구에서는 실제 대공간 규모의 해석모델에 대해서 현재 제시되어 있는 설계기준을 근거로 대공간의 기계배연 시스템에 대한 설계를 수행하고, 3차원 수치해석 기법을 활용하여 설계안에 대한 수치적 분석을 수행하였다. 그리고 설계안의 배연량을 변경해 가며 수치해석을 수행하고 결과를 분석하였다. 연기층 두께, 발열량, 플럼의 질량유량, 공급공기의 속도, 배기구 1개당 최대유량 및 배기구간 최소거리 등의 주요 설계인자를 반영하여 설계를 수행한 결과 대공간의 건물높이가 25 m이고 정상성상의 발열량이 5,275 kW인 경우 전체 배연량은 527,459 CMH로 계산된다. 그리고 기계배연 시스템에서 배연량이 감소하면 연기층 높이가 낮아지고 연기층의 온도가 상승한다. Because of extended floor height in large space, smoke generated in fire would possibly reach to hundreds of thousands CMH and more difficulty in limiting the smoke than normal building requires effective smoke control system design and operation for a large space. In this study, design of mechanical smoke control for a large space was carried out based on existing design standard with regard to large space model and numerical analysis was also carried out using 3D numerical analysis method. Numerical analysis was carried out while changing flow rate of mechanical exhaust, which was followed by analysis of the result. As a result of implementing the design by incorporating major design factors including thickness of smoke layer, heat release rate, mass flow rate of plume, air supply velocity, maximum flow rate per exhaust outlet and minimum distance between exhaust outlets, total exhaust flow rate was calculated as 527,459 CMH when building height was 25 m and heat release rate of steady state was 5,275 kW. And the less the exhaust flow rate, the lower the smoke layer height and higher the smoke layer temperature.

Turbulent smoke flow in evacuation staircases during a high-rise residential building fire

Purpose – The purpose of this paper is to study the behavior of smoke flow in a typical high-rise residential building fire in six common smoke control systems. Design/methodology/approach – The pressure, temperature and CO2 concentration were used to trace the motion of turbulent smoke flow through CFD. Findings – It is found that the hot smoke could rise up and spread into the indoor space on the upper floors through the staircase. When the pressure in the evacuation staircase is higher, it would be more difficult for the smoke to enter the staircase and transport vertically. On the other hand, the smoke would soon transport to the indoor space on the upper floors horizontally. During this process, the smoke shows a more disorder horizontal transport under the sole effect of thermal buoyancy than the co-existence of thermal buoyancy and the air inlet. Research limitations/implications – Because of the chosen research approach, the research results may need to be tested by further experiments. Practical implications – The paper includes implications for the design of smoke control systems and evacuation in a building fire. Originality/value – This paper fulfils an identified need to study the behavior of smoke in a fire and optimize the design of smoke control systems.

Numerical Studies on Smoke Spread in Urban Underground Tunnel with Horizontal Junctions

Urban underground tunnels usually have lager traffic volumes and complex structures comparing with other kinds of tunnel. This can give higher fire risk and also make smoke control to become more difficult once the fire occurs. The effect of the fire size and intersection angle on the smoke spread and smoke mass flow distribution in underground urban tunnel with horizontal junctions are studied by the numerical simulation in this paper. The results show that the power size can affect the smoke spread heavily, but it has little effect on the smoke mass flow distributions between the downstream main tunnel and the branch tunnels. Variation of the intersection angle almost have an effect on the smoke spread in upstream main tunnel, but its effect on the smoke spread and smoke mass flow distributions in branch tunnel cannot be neglect. The results are expected to be useful for the smoke control system design in these kinds of tunnels.

Influence of atrium roof geometries on the numerical predictions of fire tests under natural ventilation conditions

The use of computational fluid dynamics (CFD) as a tool for the design of smoke control systems and fire protection in large spaces has become more frequent as accuracy and computational speeds increase. In the present work Fire Dynamic Simulator (FDSv5) has been used to study two full-scale experiments conducted in Murcia (Spain) of 1.36MW and 2.34MW pool fires burning inside a 20m cubic atrium under natural ventilation conditions. Different cartesian-grid approximations to the real geometry of the pyramidal roof have been investigated in order to assess the effect of stair stepping on the smoke layer and the temperature field. In general terms, good agreement between experiments and numerical simulations is found for all model roof geometries, especially far away from the fire source and the centreline. For example, at a height of 15m, the temperature differences between all geometry approximations are lower than 10%. This shows that the cartesian-grid simplifications proposed here are a good choice and allow for saving some computational resources. In order to extend the results to different designs, the model has then been applied to study a range of 16 different atrium geometries, varying the area-to-height-squared ratio from 0.4 to 3.8. In addition, a comparison with simulation with a previous version of the code, FDSv4, shows that it predicts higher temperatures and slower ascends of the smoke layer than FDSv5, the difference being lower than 12% and 100s respectively.

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.

The Study on Influence Factors of the Mechanical Smoke Evacuation System in Atrium Buildings

Abstract This paper starts from the structure features and fire characteristics of an atrium building, and clarifies the importance of the mechanical smoke extraction system. The disadvantages of China's code about the smoke control system design in an atrium are analyzed. The influencing factors of the smoke removal efficiency is studied in this paper including smoke evacuation quantity, atrium shape coefficient, smoke exhaust fan start-up time and heat release rate.The future research direction is put forward according to the conclusion.

Application of Computer Simulation Technique in Smoke Control System Design

The fire simulation technology is widely used with the rapid development of computer technology. Taking a 12-story building for calculation, numerical simulation method is used to analyze the wind speed distribution characteristics of opening stairwell door and lobby door under different air supply volume. Then the appropriate pressurized air supply mode and back pressure coefficient value under natural smoke venting have been recommended. The researches show that computer simulation can be used in smoke control system design to help determine pressurized air supply mode and design parameters, so as to solve difficult problems in engineering design.

Engineering Simulation of Smoke Extraction Design in Atrium Fires of Student Union

Atrium of student union is a typical crowded place, it is difficult to achieve within the fire and smoke-protect separation. Once smoke entered, the security evacuation of personnel was threatened by rapidly spread smoke. In this paper, the atrium smoke exhaust design was researched, first introduces the method of smoke control in atrium buildings, research Smoke control system design theory with engineering examples, using FDS for atrium smoke control the numerical simulation, calculate a variety of exhaust design simulation results was calculated, enhanced the scientific and economy of smoke design through comparing.

Robust Optimal Design of Smoke Control System by CFD and Genetic Algorithms

Robust Optimal Design of Smoke Control System by CFD and Genetic Algorithms

A critical study on fire-induced aerodynamics of balcony spill plumes

Balcony spill plume is one of the main plume forms in an atrium fire, its thermal behavior which is important to the designers for the smoke control system design is still not well understood now. The fire-induced aerodynamics of balcony spill plume would be studied by the numerical method in this paper. Some uncertainties relating to the available calculation methods for the smoke production rate would be reexamined. Numerical results indicated that using an entrainment coefficient 0.11 would be better than 0.16 in describing the entrainment behavior, end effect should not be ignored for the plume being not two-dimensional (2-D). Suitable empirical spill plume equations would be recommended for the smoke management system design.

Relation between horizontal ventilation velocity and backlayering distance in large closed car parks

Due to the ceiling jet phenomenon, smoke above a fire source has a natural tendency to spread under the ceiling in all directions, until a barrier is reached. The present study focuses on smoke control, rather than smoke clearance, in large closed car parks. A particular situation is that the ceiling height is much lower than the horizontal car park dimensions. Also, flame heights can be in the same order of magnitude as the ceiling height, so that flames can penetrate into the smoke layer under the ceiling near the fire source. Smoke control in case of fire in large car parks can be established by horizontal mechanical ventilation. A ‘critical ventilation velocity’ exists, for which no smoke backlayering occurs, i.e. the car park is maintained smoke-free at one side of the fire source. In many cases, however, backlayering can be allowed to a certain distance. We analyse the results from a large series of CFD-simulations, used as numerical experiments, and illustrate that there is a relation between the horizontal ventilation velocity and the backlayering distance. The backlayering distance varies linearly with the difference between the critical ventilation velocity and the actual ventilation velocity of the incoming fresh air. We perform a parameter study with variation of heat release rate per unit area, fire source area, car park width and car park height. We show that the coefficient in the mentioned linear relationship is independent of the fire source area, the car park height and the car park width, but increases with decreasing heat release rate per unit area. We compare the results for the critical ventilation velocity in car parks to results obtained in tunnel fires. We confirm the observations that the critical ventilation velocity increases with fire source area and heat release rate per unit area, as well as a small influence of the car park width. We observe an increase of the critical ventilation velocity with increasing car park height. Finally, we point out that care must be taken when a smoke control system design is based on volume flow rates, calculated from cold inlet flow velocities, as differences between extraction velocities and incoming air velocities can be substantial.

CFDと遺伝的アルゴリズム（GA）の連成解析による煙制御システムの最適化

CFDと遺伝的アルゴリズム（GA）の連成解析による煙制御システムの最適化

Benefits Of Field Modelling For Smoke Control Assessment In Large Volume

The aim of this paper is to present a comparison of results obtained with several fire models on an application of smoke control system design for a large volume within the new French regulation framework. Three fire models are used: a simple hot layer model, a 2-zone model (FISBA) and a field model (FDS). The large volume used as a sample is 5000 m2 of floor area and 19 m high. Three different exhaust configurations are studied for one single 5 MW fire scenario. Results show a good agreement between models for no or low exhaust flow rate while discrepancy increases for high exhaust flow rate. Discrepancy, which affects smoke control system design and fire safety analysis, is mainly explained by the strong fluid movements that are predicted with field modelling. Further research is need in order to determine which model is better adapted to a specific situation with regards to building volume dimensions, fire heat release rate and exhaust rate.

Stack effects on smoke propagation in subway stations

In fires of subway stations, the most immediate threat to passengers' life is not the direct exposure to fire, but the smoke inhalation because it contains hot air and toxic gases. To understand the mechanisms driving the motion of smoke is therefore an important issue of fire safety, and the stack effect is found to be an important mechanism having significant influence. In this paper, we compute the three-dimensional smoke flow fields under various fires happened in a representative subway station of Taipei Rapid Transit System. To clarify the mechanisms corresponding to the stack effect, a simplified three-dimensional configuration is also considered. Results indicate that, without mechanical smoke control, the stack effect plays a decisive role and is virtually the sole factor influencing the smoke movement. Because of the stack effect, most or sometimes all of the smoke will choose a vertical shaft (usually a stairwell) to evacuate, and the cross sectional area of the shaft and the location of fire determine which shaft is chosen. Present computational results show the evidences of the importance of the stack effect and provide both valuable information to the design of the passenger evacuation routes in fires as well as criteria to the design of smoke control systems of subway stations.

Extraction Modes in Performance-Based Design of Smoke Control System in Shopping Malls

Extraction Modes in Performance-Based Design of Smoke Control System in Shopping Malls