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Abstract The Shenzhen–Zhongshan Bridge is a 24‐km‐long bridge and tunnel system, including a 6.8‐km‐long super cross section subsea tunnel. To solve the smoke exhaust problem of a super large cross‐section subsea tunnel, the tunnel has a new smoke exhaust system that combines a horizontal smoke exhaust cross section at the top and sidewall smoke exhaust holes. In order to evaluate the potential fire hazards of this type of tunnel, a 1:30 tunnel model was established and 140 small‐scale experiments on underwater tunnel fires were conducted. By changing the fire power, fire location, and fan operation mode, different scenarios of submarine immersed tunnel fire were simulated and the related key parameters such as fire smoke diffusion behavior and smoke temperature distribution were studied. On this basis, the optimal smoke control strategy was proposed for different fire scenarios. The research results indicate that the new smoke exhaust system can fully utilize the smoke flow characteristics, significantly improve smoke exhaust efficiency, and increase available evacuation time, thus further enhancing the fire safety of super large cross‐section subsea tunnels.

This study analyzed the unique aspects of smoke movement and control requirements in metro tunnel fires, and summarized the key scientific issues in the research of metro tunnel fires. This study reviewed the research progress and achievements of domestic and foreign scholars in various aspects including metro train fire combustion and plume behavior, smoke temperature distribution characteristics under the tunnel ceiling, smoke control characteristics, and characteristics of personnel evacuation. It highlighted the importance of integrating traditional subway section smoke control systems with new technologies such as artificial intelligence and the internet of things to enhance section fire prevention and control capabilities, which is deemed a crucial direction for future research. [ABSTRACT FROM AUTHOR]

Large occupied spaces such as the atria can have additional internal elements like balconies, stairs, or decorations. Unfortunately, detailed design rules for smoke management systems are lacking in these large contemporary spaces. A series of smoke tests and CFD simulations were conducted to address this shortfall. The project's first step was realised with full-scale hot smoke tests in Smoke Laboratory, which allowed the observation of a significant influence of the suspended balconies on smoke mass production. CFD simulations confirmed the preliminary observations and were used to evaluate this phenomenon quantitatively. This proved that the wider the balcony, the greater the mass increase. The same fire scenarios were examined with theoretical NFPA 92 correlations dedicated to axisymmetric and balcony spill plumes. They showed that using the standard axisymmetric plume correlation in a complex atrium could lead to a strong underprediction of the required smoke control system parameters. A proposed adapted balcony spill plume correlation can improve the smoke mase calculations. Practical application: This study demonstrates that existing standards like NFPA 92 NFPA 204, or BS 7346-4. Do not cover the need for smoke control systems in complex and irregular atria solutions, which often appear in modern buildings. It has been proven that the obstructions in the atrium space significantly influence the smoke mass production. As a consequence, using the original axisymmetric plume correlation in a complex atrium could lead to a strong underprediction of smoke control system requirements. The authors proposed a new correlation for the approach to smoke control systems parameters approach at the design process. [ABSTRACT FROM AUTHOR]

Railroad transportation has been widely adopted and developed in recent years. In particular, many railroads have been built on complex terrains such as plateaus and mountainous areas, and these tunnels are generally characterized by large inclination angles or very long lengths and are equipped with rescue stations. These factors lead to changes in environmental conditions, tunnel geometry, and the angle of inclination, thus presenting new challenges to ventilation as well as fire safety in railroad tunnels. This review argues that there is a lack of systematic and comprehensive analysis of smoke control in railroad tunnel fires, including horizontal tunnels, inclined tunnels, and rescue stations within long railroad tunnels. Hence, this work attempts to address the key fire safety characteristics from the existing literature covering critical velocity, back-layering length, the maximum temperature under the ceiling of the tunnel, and longitudinal smoke temperature distribution. Important factors affecting smoke movements such as fire source, tunnel geometries, and blockages are also evaluated. Moreover, this study calls attention to the impact of extended blockages and temperature distribution in blocked railroad tunnels, as well as emerging innovative solutions such as intelligent monitoring and disaster prevention technologies for smoke control in railroad tunnels. [ABSTRACT FROM AUTHOR]

[Objective] The smoke exhaust paths for metro terminal station storage tracks and reserved main lines are different from those for various auxiliary lines in middle stations, thus it is necessary to study suitable smoke exhaust schemes for these scenarios. [Method] The general requirements in current standards for vertical and horizontal smoke exhaust design in underground interval are introduced. Taking Fengyiqiao South Station, the terminal station of Beijing Subway Fangshan Line North Extension project, as example, the vertical and horizontal smoke exhaust schemes for the storage track and the reserved main line are designed and comparatively analyzed. SES software is applied to simulate and analyze the smoke exhaust paths and wind speeds at different locations on the two auxiliary lines during a fire event. The smoke exhaust design characteristics of metro terminal lines that are not explicitly mentioned in current standards are highlighted. [Result & Conclusion] Whether adopting vertical or horizontal smoke exhaust schemes, metro terminal storage tracks and reserved main lines can meet the smoke exhaust design requirements for underground intervals outlined in the standards. Terminal storage stacks and reserved main lines have conditions suitable for horizontal smoke exhaust, therefore it is recommended to g prioritize the use of horizontal smoke exhaust schemes due to lower investment and less operation-maintenance workload.

AbstractThis study determined the optimum number of water spray particles and the angle of the inner angle of the nozzle, simulated and studied the suppression effect of the water curtain system on roadway belt fires and toxic and harmful gases, and analysed the barrier effect of heat and smoke under the water curtain system using the flow field. The results show that the number of water curtain rows has a suppressive effect on the temperature and that increasing the number of rows has a better barrier effect on the hot smoke downstream of the roadway. From the velocity and temperature fields, it is clear that there is significant upward movement between the water mists of the water curtain system, which is caused by the water mists colliding with each other on the roadway floor. These jets are entrained into the water mists and merge to form an area of upward movement that acts as a 'barrier’ to prevent the fumes from spreading downstream of the water curtain. When the water curtain system is activated, it increases the concentration of component gases in the downstream space of the roadway and rapidly restores visibility to meet the requirements for safe evacuation.

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This paper aims to study the effects of altitude and the size of smoke outlet on fire smoke diffusion and discharge in semi-lateral smoke exhaust highway tunnels. At first, simulations of semi-lateral smoke exhaust highway tunnels were carried out in FDS (Fire Dynamics Simulator), then the distribution laws of temperature, CO concentration, smoke mass flow, and visibility in the tunnel under the conditions of different altitudes and smoke outlet areas were analyzed to figure out the effects of altitude and size of smoke outlet on fire smoke diffusion and discharge in the said tunnels. The results suggest that, in case of the same fire source power, the velocity of smoke diffusion increases with the altitude; for curves of different altitudes, the tunnel roof temperature features are basically the same, that is, the higher the altitude, the higher the temperature at the tunnel roof. When the fire source power is 20 MW, the smoke mass flow at the smoke outlet decreases with the increase of altitude, but the CO concentration grows with it, indicating that the smoke exhaust efficiency is higher in high-altitude areas. When the altitude reaches 4200 m and the fire source power is 20 MW, with the increase of smoke outlet area, the smoke discharge effect of the tunnel shows an upward trend, taking both the smoke discharge effect and economy into consideration; the smoke outlet should take a size of 4 x 3 m.

Longitudinal ventilation and smoke extraction by shaft are common smoke control methods in road tunnel fires. Tunnels often adopt one of these methods in practical engineering. However, it may have a better effect to adopt the method of mixing the two smoke exhaust methods together, which has not been revealed in the previous literature. Hence, the coupled effects of longitudinal ventilation and natural ventilation with shafts on the smoke control in tunnel fires were studied in this work. Numerical simulation was carried out considering different longitudinal ventilation velocities (0–4 m/s) and 4 kinds of typical shaft arrangements (shaft lengths range of 3–12 m, shaft intervals range of 27–60 m). The smoke spread length and smoke exhaust efficiency were analyzed systematically. Results show that (1) with the increase in longitudinal ventilation velocity, the total smoke spread length firstly decreases (V < 1 m/s) and then keeps almost constant (1 m/s < V < 2 m/s), finally increasing significantly (V > 2 m/s). (2) The length of the dangerous area (over 60 °C) at human height is basically 0 for all cases (except for Scenario 4 of shaft arrangement) when the longitudinal ventilation velocity is less than 2 m/s. (3) The CO smoke flow rate through the shaft is relatively high when the longitudinal ventilation velocity is within the range of 1–2 m/s for 4 kinds of shaft arrangement scenarios. Factors such as smoke spread and smoke exhausted through the shaft are comprehensively considered to judge smoke exhaust performance. The following conclusions can be drawn: when the ventilation velocity ranges from 1–2 m/s, it has a positive impact on the smoke control in tunnel fires with natural ventilation with shafts. When the ventilation velocity exceeds 2 m/s, the total smoke spread length and the length of the danger area increase, and the smoke stratification becomes worse, which brings inconvenience to rescue work. The results can provide reference for the design of fire protection in tunnels. [ABSTRACT FROM AUTHOR]

Fire accidents cause damage and injuries; hence, fire protection is imperative for building construction. Smoke control reduces smoke concentrations as well as the temperature to enable evacuation of building residents. Moreover, firefighters easily extinguish fire with low smoke concentrations and temperatures. In this study, the Fire Research Station, UK standard, was applied to calculate the flow rate of the smoke exhaust fan for a basement with dimensions of 30 m × 20 m × 4 m using a computational fluid dynamic (CFD) code in the transient mode. The model was established by Revit 2020, and the fire simulation was conducted using Autodesk CFD 2020. The fire simulation was analyzed under the total exhaust fan volume values of 20000 m3/h, 50000 m3/h and 100000 m3/h, the air change per hour (ACH) values equivalent to 8.5, 21 and 42.5, respectively. The results reveal that the total exhaust fan volume of 100000 m3/h is optimum because at 1200 s, after the fire, the temperature of the basement is less than 1.4 m is less than 65 °C, and smoke visibility is ∼10 m. Moreover, the amount of smoke escaping through the doors was the lowest. This condition is suitable for evacuation and for firefighters to put out the fire. In addition, a volume of 100000 m3/h was compatible with the formula of the standard. Therefore, Autodesk CFD is also an optimum choice for engineers to verify their design before conducting site work to save time and increase confidence.

This study has examined some important aspects of the engineered smoke control system, namely the shape of smoke reservoirs and the quantity and distribution of smoke extract points within a smoke compartment. Three different shapes of smoke reservoirs have been selected for analysis, namely square, rectangular, and T-shaped. The shape of the smoke reservoir has been varied, but the area, length and height have been kept identical. Four different configurations of extract points have been used in each shape of the reservoir: a single extract point located at the corner of the smoke reservoir, a single extract point located at the centre of the smoke reservoir, two extract points evenly distributed within the smoke reservoir and four extract points distributed within the reservoir. These configurations were implemented in three different shaped reservoirs: square, rectangular and Tshaped. The area, length and height of the reservoirs have been kept identical. In this work, the design parameters such as area and length of the reservoir, extract rate of smoke, replacement of air in the reservoir and other parameters have been stipulated from the Singapore Fire Code and Building Research Establishment Report. Fire Dynamics Simulator (FDS) model has been employed for this research, and results show that variations in the shape of smoke reservoirs or quantity and distribution of smoke extract points do have an effect on the tenability within the smoke compartment. Generally, it has been found that the untenable conditions within a square-shaped smoke reservoir increased at the slowest rate, given the fact that the smoke compartment is symmetrically shaped with equal dimensions on all four sides of the compartment. The smoke compartment with the most number of bends, i.e. the T-shaped smoke reservoir, has shown that the untenable conditions increase at the fastest rate, followed by the most elongated shaped smoke compartment (i.e. rectangular). For the other part of the research, results have shown that the provision of four extract points evenly distributed within the smoke reservoir resulted in the most favourably stable smoke layer and the untenable conditions within the smoke compartment increased at the slowest rate. However, one vent in the centre shows a better outcome than two evenly distributed points. It has been exhibited in this research that varying the shape of the smoke reservoirs, the quantity and/or the distribution of smoke extract points does affect its tenability within a smoke compartment. A sensitivity analysis has confirmed these findings. [ABSTRACT FROM AUTHOR]

Air-doors are important facilities for regulating the air flow in a mine ventilation network. It is of value to study the influence of air-doors, which are adjacent to a fire source on smoke back-layering in order to build a rational ventilation system. By regulating air-doors in a mine ventilation network test platform, two typical mine ventilation networks, with parallel branches and a diagonal branch, were constructed. During the study, into the closing degree of the air-doors adjacent to a fire source in a ventilation network with parallel branches, the back-layering length is up to 3.70 m when the ventilation velocity is 1.40 m/s. When the air-door on the return side of the adjacent branch is closed, the back-layering subsides within 1 min and the upstream temperature drops rapidly to normal. When the air-door is half closed, there is still a back-layering flow within 5 min. Smoke control, with the air-door is closed, is better than when the air-door is half closed. Based on this, tests into the influence of the closing position of air-doors, which are adjacent to a fire source, were carried out in a ventilation network with a diagonal branch. Results indicate that when the ventilation velocity is 1.70 m/s, the back-layering flow spreads to the diagonal branch, and the air flow velocity of both the adjacent branch and the diagonal branch increases. When closing the air-door on the return side of the adjacent branch, the back-layering rapidly subsided. The wind velocity on the intake side of the adjacent branch is stabilized after a rapid decrease, and the wind velocity of the diagonal branch is stabilized after a rapid increase. When closing the air-door on the intake side of the adjacent branch, the smoke from the diagonal branch spreads. Compared with closing the intake side air-door, closing the air-door on the return side of the adjacent branch is more effective in preventing back-layering. This work provides a reference for preventing back-layering and guiding the evacuation of people from the upstream of a fire source. [ABSTRACT FROM AUTHOR]

A novel real-time control method, named SF-B control method, was proposed and a comprehensive numerical simulation study was conducted for feasibility analysis. The simulation utilized a combination of Python scripts and FDS. The SF-B control method incorporates automatic detection and localization of the fire source, and the existing ventilation velocity is corrected based on the real-time state of motion of smoke fronts and the back-layering length. The control logic of the SF-B control method was described in detail, and the criterion for determining stabilization was provided. After a comparison with PID control method, scenarios involving random constant HHRs, random fire locations and variable HRR were set up for separate simulations, and the results were compared with previous experimental findings. The outcomes demonstrate that the fluctuation of the SF-B control method is only about 1/10 of that of the PID control method, and the control performance is not significantly influenced by the HRR or fire location. It shows a more powerful control ability on smoke back-layering in scenarios involving variable HRR. This method exhibits excellent compatibility with different fire conditions, showcasing high ventilation control efficiency, robust control capabilities, and delivering reliable control results. [ABSTRACT FROM AUTHOR]

The critical velocity plays a significant role in the design of the ventilation system in tunnels, from which the ventilation velocity of fresh air for preventing the smoke back-layering in tunnel fires can be determined. In this work, a full-range analytical solution to the equation for the critical velocity was derived. Specifically, we first proved that the unconstrained equation for the critical velocity has and only has one positive real solution, and then we proved that the positive real solution has a unified expression for different cases of tunnel fires. Finally, the analytical solution that satisfies the constraints was obtained, which was also compared with the iterative solution. The result shows that the analytical solution can avoid the negative and complex solutions automatically, which is more stable than the iterative solution. Furthermore, the analytical solution was compared with the simulation and experimental results, which were found to be in excellent agreements with each other. For tilted tunnels, the influence of the Froude number on the analytical solution of the critical velocity was also investigated by comparing the critical velocities obtained based on two different correlations of the Froude number.

Summary: The engine room of ships with poor ventilation has high concentrations of accumulated smoke during the fires. In some ways, the existing forced ventilation and water mist fire extinguishing can aggravate the occurrence of back‐burning and flame strengthening. In this article, a novel way to control smoke is proposed. Based on nano‐MgO particles, the adsorption mechanism of MgO at different temperatures (300–500 K) was simulated and analyzed using the Monte Carlo method. And the macroscopic adsorption effects of smoke at different angles (30°, 80°, and 110°) of nano‐MgO vertical spray were studied in a closed confined space of 1.5 × 1.5 × 1 m3, where the diesel oil was used as a fire source. The results show that the nano‐MgO have a good dissipation effect on the fire smoke through the analysis of the temperature, smoke concentration and adsorption amount in the confined space, which can effectively reduce the smoke concentration and improve the visibility in the space. The adsorption effect of nano‐MgO is the best when the spray angle is 30°, the adsorption effect of nano‐MgO is the largest when the pressure is 300 KPa and the temperature is 300 K. Besides, the adsorption of nano‐MgO and carbon smoke particles changed from single‐layer to multilayer adsorption in the process of interaction. The research results provide a theoretical basis for the application of nano‐MgO particles in smoke control of the fire in the ship engine room. [ABSTRACT FROM AUTHOR]

Industrial power plant buildings differ from all other types of buildings, mainly due to their significant heights and volumes without internal floor sections, exceptionally heat gains during daily work, and potentially high fire risk. Those buildings consist of boiler and turbine houses with multilevel stairways. This complicated architecture creates an extraordinary natural thermal stack effect, causing special ventilation and smoke control systems requirements, adapted to their specific structures and internal conditions. The paper demonstrates a proposal for optimal thermal smoke control ventilation solutions in industrial power plant buildings designated on the basis of performance-based calculations and confirmed by CFD simulations. It demonstrates the possibilities of using daily ventilation in the boiler houses in a function of smoke control systems in the event of a fire and defines fundamental rules for designing the system. Additionally, a new method of sufficient staircase (pylons) protection with a modified pressurization system is proposed. [ABSTRACT FROM AUTHOR]

Longitudinal ventilation fans in extra-long submarine tunnels are usually arranged at both ends of the tunnel limited by the tunnel cross section, which is usually hindered by insufficient power caused by extra-long ventilation distances. In this paper, the conception of a ventilation mode is proposed that services the tunnel and cross passages, to provide auxiliary air supply to the main tunnel. Two critical factors have been analyzed on the premise of evacuation safety, which combine to affect the ventilation efficiency in the case of an accident inside the tunnel, these are: air volume within the service tunnel, and cross passage open numbers. FDS simulation software is used to simulate the tunnel model; consider the number of cross passages from one to four; and simulate the service tunnel airflow velocity of 0.7 m/s, 0.75 m/s, 0.85 m/s, 1.0 m/s and 1.3 m/s. The results show that when 1.3 m/s wind speed is applied at both ends of the service tunnel, and three cross passages are operated, 20 MW of fire smoke within the accident tunnel can be effectively controlled; additionally, the wind speed in the cross passage will not hinder the evacuation. The simulation results are verified by ventilation network calculation. [ABSTRACT FROM AUTHOR]

It is common for fire engineers in the UK to consider a time-dependent series of events when using the Fire Dynamics Simulator to assess the performance of residential corridor smoke control systems. A significant proportion of this established timeline focusses on producing the necessary buildup of smoke and heat in the apartment of origin, prior to any smoke spreading to the corridor or stairs. This paper proposes an alternative approach that enables a compressed modelling timeline by using uniform initial condition parameters in the apartment of origin for the soot mass fraction, room gas temperature, wall and ceiling temperatures, and slab temperature. These conditions can be applied from the outset for separate means of escape and firefighting phases, providing greater flexibility and reducing the wall-clock times for simulations. To achieve this, simulations for a 1000 kW medium growth rate fire in a single reasonable worst-case exemplar arrangement were undertaken using an established timeline approach. This was then used to estimate the approximate initial conditions needed to inform the compressed timeline input parameters. When comparing the established and compressed timeline approaches, close agreement was demonstrated for the estimated conditions of corridor visibility and temperature. The paper also suggests prospective correlations for the initial condition parameters needed to represent a given maximum heat release rate. The paper ultimately provides engineers with a method for residential corridor smoke control modelling that reduces simulation times, as well as providing greater consistency in the demonstrated performance, by proposing initial conditions independent of the dimensions of the apartment. [ABSTRACT FROM AUTHOR]

This study was motivated by the lack of understanding of the smoke control effect on an ultra-wide tunnel fire, with different smoke exhaust patterns (sidewall and top exhaust patterns) and longitudinal air supply volume (0, 30%, 50%, 70%, and 90%). A full-scale ultra-wide tunnel model was constructed based on the FDS and the fire parameters were analyzed, such as the longitudinal spread distance of smoke, the smoke layer height and the temperature at safe height. In addition, the smoke exhaust efficiency was calculated based on the mass flux of CO2, and the smoke control effect with different smoke exhaust patterns and air supply volumes was compared. Results show that the smoke exhaust patterns and air supply ratios have a great influence on smoke spread distance and exhaust efficiency. The smoke spread distance is shortened by increasing the longitudinal air supply volume, and when the ratio of air supply volume to smoke exhaust volume is less than 50%, the top exhaust pattern can control the spread of smoke better with a smaller smoke spread distance. In addition, the height of the smoke layer is controlled above the safe height of 2 m under the top smoke exhaust, and the temperature at both ends of the tunnel (25 °C) is lower than that under the sidewall exhaust pattern (35 °C). The smoke exhaust efficiency was calculated based on the mass flow rate of CO2, and the exhaust efficiency of the top exhaust pattern (~70%) is significantly higher than that of the sidewall exhaust pattern (~55%). However, as the air supply volume increases, there is a reduced increase in the exhaust efficiency. Therefore, taking the economic cost into account, the air supply ratios of 30% and 50% are the best for top and sidewall exhaust patterns, respectively. The results of this work provide important information about smoke distribution characteristics in an ultra-wide tunnel fire and may guide its design of smoke exhaust. [ABSTRACT FROM AUTHOR]

Smoke control in a longitudinally ventilated tunnel with various blockage conditions was investigated experimentally. A total of 28 tests were conducted with a focus on single blockage with a short distance from the fire source, although continuous blockage and semicontinuous blockage were also discussed. Both gas and pool fires were used. The aim was to understand the influence of upstream blockage on critical velocity and babcklayering length. The results confirm that blockage ratio is a critical parameter when determining the critical velocity and backlayering length. The longitudinal location of the blockage in relation to the fire source also influences the values of critical velocity and backlayering length. The experiments presented are in scale 1 to 3.3, representing a medium sized tunnel. The focus was on free flow conditions and blockage ratios of regular sizes. For the various tested scenarios with single blockage, the reduction ratio of critical velocity appears to be slightly less than the blockage ratio. However, when the blockage is attached to the upstream side of the fire source, the reduction ratio of critical velocity approximately equals the blockage ratio. • Influence of upstream blockage was studied in 1:3.3 scale tunnel fire tests. • Different blockage ratios and blockage locations in relation to fire were tested. • Longitudinal distance between blockage and fire source plays a key role. • Reduction of critical velocity due to blockage is highly related to blockage ratio. • Backlayering length with blockage follows same trend as that without blockage. [ABSTRACT FROM AUTHOR]

• Smoke spread in TGS independent of temperature attenuation, incomplete chimney and entrainment. • The combustion of the polyurethane flame-retardant material is controllable by fire source distance. • Smoke diffusion analyses on the effects of the heat release rate, the air inflow velocity et.al are carried out. • A horizontal smoke plate (HSP) for temporary smoke control is proposed. In this study, field tests and numerical simulations were conducted to investigate the smoke diffusion mechanism and mitigation design for a fire accident occurring in a special hybrid structure, i.e., the tunnel-groove structure (TGS) of a large hydropower station. It is found that the characteristics of the smoke spread in the TGS include the smoke temperature attenuation, incomplete chimney effect and smoke entrainment. The combustion of the polyurethane flame-retardant material is controllable and extinguishes immediately after the fire source is removed. However, there is a fire risk in a relatively closed space under the conditions of strong winds, especially at the connection port with the external environment, due to the wind tunnel and chimney effects, which result in rapid smoke diffusions. During the fire accident, the smoke first fills in the entire tunnel (89 m long), then propagates upward along the groove, and finally reaches the dam top (115 m above the tunnel) in 10 s. The heat release rate (HRR) was determined as approximately 50 MW and the maximum velocity of the smoke spread along the dam surface could reach 10 m/s. As a result, nearly no time was available for the workers in the groove to evacuate when the fire accident occurred. Sensitivity analyses were further conducted to study the effects of different parameters, such as the HRR, the air inflow velocity and the radial gate opening, on the smoke diffusion in the TGS. A horizontal smoke plate (HSP) was proposed for the temporary smoke control to prevent life from losses due to the smoke diffusion in the TGS. The safe and dangerous zones near the dam surface were identified by analyzing the characteristics of the smoke temperature and visibility. It was finally concluded that the HSP can mitigate the smoke and heat along the groove. The results from this study may serve as a useful reference for the smoke control design in the TGS or other similar structure configurations. [ABSTRACT FROM AUTHOR]

Longitudinal ventilation and smoke extraction by shaft are common smoke control methods in road tunnel fires. Tunnels often adopt one of these methods in practical engineering. However, it may have a better effect to adopt the method of mixing the two smoke exhaust methods together, which has not been revealed in the previous literature. Hence, the coupled effects of longitudinal ventilation and natural ventilation with shafts on the smoke control in tunnel fires were studied in this work. Numerical simulation was carried out considering different longitudinal ventilation velocities (0–4 m/s) and 4 kinds of typical shaft arrangements (shaft lengths range of 3–12 m, shaft intervals range of 27–60 m). The smoke spread length and smoke exhaust efficiency were analyzed systematically. Results show that (1) with the increase in longitudinal ventilation velocity, the total smoke spread length firstly decreases (V < 1 m/s) and then keeps almost constant (1 m/s < V < 2 m/s), finally increasing significantly (V > 2 m/s). (2) The length of the dangerous area (over 60 °C) at human height is basically 0 for all cases (except for Scenario 4 of shaft arrangement) when the longitudinal ventilation velocity is less than 2 m/s. (3) The CO smoke flow rate through the shaft is relatively high when the longitudinal ventilation velocity is within the range of 1–2 m/s for 4 kinds of shaft arrangement scenarios. Factors such as smoke spread and smoke exhausted through the shaft are comprehensively considered to judge smoke exhaust performance. The following conclusions can be drawn: when the ventilation velocity ranges from 1–2 m/s, it has a positive impact on the smoke control in tunnel fires with natural ventilation with shafts. When the ventilation velocity exceeds 2 m/s, the total smoke spread length and the length of the danger area increase, and the smoke stratification becomes worse, which brings inconvenience to rescue work. The results can provide reference for the design of fire protection in tunnels.

In the base, working of ventilation system can be analyzed in regular and incidental modes of operation. This paper concerns the specification of the longitudinal ventilation necessary to prevent upstream movement of combustion products in a tunnel fire. In this work the objective of the study is to analyze the road way tunnel ventilation system using CFD software to create comfort ventilation system in the tunnel. The comfort ventilation concept refers to the situation when air quality within the tunnel is reduced due to presence of polluted air in the tunnel. This paper is focused on ventilation system in a road traffic tunnel in moment of accident situation as fire. In this investigation numerical simulation of fire was carried out and determination of a critical air velocity depending on the power of the fire was conducted. The output results of the software developed for this purpose, which is also used in the realization of practical projects, are shown. [ABSTRACT FROM AUTHOR]

The modelling of common corridor smoke control systems in residential buildings is one of the most frequently undertaken performance-based assessments by fire engineers in the UK. However, there is limited understanding of how the deterministic assumptions provided in modelling guidance are derived, and to what extent these are representative of a range of possible outcomes. To place these assumptions into context, the Monte Carlo method is applied using the zone modelling software B-RISK for an exemplar residential arrangement. Distribution functions are adopted to inform inputs for fire parameters, sprinkler performance, and occupant behavioural characteristics. An output distribution for the corridor smoke clearance time is determined and compared to the clearance time of an equivalent set of deterministic simulations applying the assumptions of modelling guidance. The probabilistic study indicates that modelling guidance assumptions typically result in a scenario severity greater than the 99th percentile of possible outcomes. The work also considers the sensitivity of individual input parameters, ranking these based on their impact. These sensitivity analyses highlight the importance of occupant behavioural assumptions around the pre-evacuation time and door open time, and the significance of fire parameters including the elevation of the fuel bed, soot yield, and fire growth rate. Sprinkler parameters are shown to have a lesser impact on the corridor clearance time. The work therefore provides practitioners with an indication of which parameters are worth considering in greater detail when assessing scenario sensitivity. [ABSTRACT FROM AUTHOR]

Long motorway tunnels equipped with two independent unidirectional galleries are usually provided with longitudinal ventilation. This ventilation scheme, when applied to smoke control, can generate significant pressure differences between both roadway galleries, which may have an impact on the use of transverse galleries (escape routes). This paper present two-case studies where the results of measurements of these pressure differences taken in Marão and Gardunha tunnels allowed the assessment of relevant flow parameters, as the pressure loss coefficient of the entrance portal, the friction factor in the tunnel and the coefficient of installation of the jet fans. The assessed parameters were used in the steady-flow energy equation for a streamtube to predict the impact of pressure differences on the protection of transverse galleries (emergency exits) in the case of fire. The results show that the predicted pressure in the fire road gallery increases upstream the location of the fire and decreases downstream that location, when taking the pressure profile of the flow without fire as a reference. The models show that predicted pressure differences between the two road galleries in case of fire may be within the interval [200 Pa; − 100 Pa] in Marão tunnel and [12 Pa; − 48 Pa] in Gardunha Tunnel, while the measurements in the no fire case show that they lay within the interval [29 Pa; − 50 Pa] in Marão tunnel and [− 13 Pa; − 35 Pa] in Gardunha Tunnel. [ABSTRACT FROM AUTHOR]

Atria within buildings present an environment which allows smoke to spread around a building in a fire situation. This could create dangerous conditions for the evacuation of people. Smoke control ventilation systems in atria work in the case of a fire, keeping evacuation routes available for people. They play a significant role in sustainable, holistic building fire strategies, and are most often designed following prescriptive requirements. However, contemporary, complex atria with additional architectural elements—such as transversal balconies—may not meet the standard approach, and require individual, performance-based research. This article proves a thesis that the atrium's architecture can impact the effectiveness of smoke control systems, and suggests how to verify them based on CFD simulations. In the presented example, the authors suggest an improvement of people's safety in a fire scenario by extending the preliminary smoke control system parameters, or by providing smoke curtains at additional levels of the atrium. [ABSTRACT FROM AUTHOR]

The following technical note demonstrates full-scale staircase test results of the pressure differential system improvement method described by Fryda et al. in 2021. It is a continuation of experimental research on the impact of the escape route's leakages on the pressure differential systems for staircases. Based on the lab experiments, it has been found that an additional throttle of the leak implemented in the pressure differential system improves its effectiveness and allows it to be more precisely adjusted to the required overpressure. The results presented in this article have confirmed this hypothesis and provided the opportunity to apply for new patent solutions of a special throttle of the leak control and pressure regulating system. The proposed new leakage-based improvements could increase the efficiency of existing systems based on proportional-integral-derivative controller and could also be installed in new buildings. [ABSTRACT FROM AUTHOR]

In order to effectively draft a smoke control design standard of the rail transit underground parking lot, this paper takes an underground two-level parking lot in a subway as the object and conducts a deep analysis on the relevant smoke control design standard. Starting from aspects of fire danger level of buildings, occupant density and safety evacuation time, and combining with industry standards launched in recent years, the paper makes a research on smoke control design plan and principles for rail transit underground parking lot. By establishing the most disadvantageous fire scene, the paper adopts theoretical analysis and three-dimensional numerical simulation methods to perform simulation analyses on smoke flow and safe evacuation environment to obtain available time for occupant evacuation. The results show that fire source distribution and smoke diffusion in the parking lot have a longitudinal characteristic, and it is suggested that the length of a train should be taken as the length of the long side for smoke control area; in the event of a fire in the parking lot, the occupant evacuation time should be short, and the required smoke exhaust rate can be calculated with reference to the empirical formula proposed by Japanese scholars. [ABSTRACT FROM AUTHOR]

In the present study, the effect of the use of false-ceiling on fire-induced smoke flow characteristics in tunnels is investigated using a 3D developed computational fluid dynamics tool. The critical velocity, the minimum required tunnel ventilation velocity to stop the smoke flow from moving toward the tunnel inlet (toward the upstream of the fire source), and the maximum gas temperature beneath the ceiling are selected to evaluate the smoke flow control in presence of the false-ceiling. The hydraulic height of the cross-sectional geometry of the tunnel is used as the characteristic length in order to dimensional analyze and compare the non-dimensional results. The results indicate that the use of the false-ceiling reduces the critical velocity and the smoke backlayering, while increases the maximum ceiling gas temperature. Reducing the critical velocity results in ventilation cost reduction (positive impact), while increasing the maximum gas temperature beneath the ceiling increases the risk of instrumental and life damages (negative impact). The detailed results and corresponding physical discussions are presented to clarify the reason for the significant differences between the results of the tunnels with and without false-ceiling.

The paper is focused on the topic of smoke control in a confined, underground cellar area of a historical building, that is undergoing conversion to a restaurant. Similar venues were host to some of the most devastating fires in history. We have investigated the performance of a novel solution, "smart smoke control (SSC)", and compared its performance with "traditional" smoke venting solution. The investigation was based on CFD simulations performed in a commercial code ANSYS Fluent, modified with user-defined functions to include for the steering algorithm of the SSC. The simulation results for a traditional system were unsatisfactory, while the SSC removing substantially more smoke (approx. 50% more) has provided tenable conditions over the whole course of the analysis. The results indicate that smoke control solutions based on the adaptive performance of the smoke exhaust fan, based on the conditions within the protected premise, can be favourable for compartments with the limited size of the smoke reservoir or limited space available for ducts. These findings are also true for existing buildings, where it may be advantageous to replace the existing smoke control solution with SSC. Future investigations should include full-scale experiments, and improvements in the simple algorithms used so far. [ABSTRACT FROM AUTHOR]

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