Numerical Simulation of the Evacuation Process in a Tunnel during Contraflow Traffic Operations

The purpose of this numerical research is to assess the evacuation process in a tunnel under the contraflow condition. Numerical simulations utilizing FDS+Evac codes associated with a fire dynamic simulator (FDS) model simulating a fire scenario are used to simulate evacuation and to predict the impact of a 100 MW fire scenario on the occupants inside the tunnel. Traffic and passenger conditions are based on real data from a tunnel in the UK. Two fire loads, 100 MW and 5 MW, are studied to represent an HGV and a passenger car fire. The 100 MW fire source, caused by an unexpected heavy good vehicle (HGV) catching fire, is located in the middle of the tunnel and at 20% of tunnel length to study the effect of fire source location on the usage of emergency exits and tenability thresholds. The dimensions and the inclination angle of the existing roadway tunnel are 1836 m (L) × 7.3 m (W) × 5 m (H) and 4%, respectively. It should be noted that the 4% inclination of the tunnel causes asymmetry propagation of smokes thus the visibility of the downstream and upstream from the fire behave differently. The maximum needed time to evacuate using all egress, the amount of fractional effective dose and visibility at the human’s height are analyzed. Simulation results indicate that when a realistic worst-case fire scenario is modeled, all evacuees can survive before the combustion gases and heat influence their survivability.

Managing Safety and Ensuring Asset Integrity Through Judicious PFP Application

Passive fire protection (PFP) is applied to steel structures in process plants to delay temperature rise and maintain structural integrity until active firefighting methods are deployed and fire is contained. Our largest gas plant was developed in several phases spanning over 25years with fireproofing designed and applied as per existing philosophy during respective execution phases. During recent Risk Management Survey, potential gaps in fireproofing were observed and survey recommended a campaign to review and identify similar gaps across entire Plant. This paper highlights the approach for gap identification, assessment and optimal recommendations which ensure safety and asset integrity while avoiding high OPEX. Fire hazard evaluation is carried out based on risk assessment of fire and hydrocarbon leakage scenarios in process plant, and recommendations for fire prevention, protection and firefighting measures are provided. Requirement of fire protection is dependent on fire source and resulting fire influence zone (fireproofing zone drawings, FPZ). Structures which are located within the FPZ are then evaluated as per identified criteria in a sequential approach (e.g. whether sudden collapse will cause significant damage, structure supports equipment containing toxic material etc.). Further detailed assessment of structural members and their impact on overall structural stability and integrity is carried out for identified structures to determine fireproofing needs. Based on the outcome, fireproofing is applied for identified members. The scope involved assessment of structural steel fireproofing in the entire complex comprising of over 40 numbers process units and 12 numbers utility units. Several teams conducted physical site survey to identify the actual fireproofing based on zone drawings across the entire plant. Desktop assessment and identification of gaps were carried out primarily based on Project fireproofing specifications, fireproofing zone drawings, fireproofing location drawings, fireproofing schedule, structural design calculations and 3-D models wherever available for respective areas. Study revealed that actual fireproofing at site in each phase of plant is consistent within all process units installed as part of that particular project, however inconsistencies were observed when compared across the different phases, probably due to different interpretation of requirements. To ensure consistency a common criteria was established considering fire source, equipment supported by structure, criticality of member and industry standards. Optimized solutions was recommended to avoid high OPEX while ensuring asset integrity and safety. Fireproofing criteria are general guidelines susceptible to various interpretations by respective users. Establishment of common criteria and elimination of ambiguities in specifications enables consistent application of fireproofing, resulting in optimization while ensuring asset safety and integrity. The approach adopted by ADNOC Gas Processing can be shared with other group companies to enable each organization be prepared to justify the actions in case of any external / internal audits.

Examination of Spreading-Induced Changes in Fire Properties in Upper Layer of Compartment

In this study, a large compartment was used and opening shapes were changed to set fire-source conditions and then combustion tests were conducted to quantitatively measure temperature and heat flux near a façade wall. In addition, q was inferred from the relationship between z and q for the top of the opening under different fire-source conditions and for various opening shapes so that q could be used as a reference index.

Experimental study on the effect of canyon cross wind on temperature distribution of buoyancy-induced smoke layer in tunnel fires

Experiments were conducted in a 1:20 arced tunnel model to investigate the effect of canyon cross wind on buoyancy-induced smoke flow characteristics of pool fires, involving smoke movement behaviour and longitudinal temperature distribution of smoke layer. The canyon wind speed, longitudinal fire location and fire size were varied. Results show that there are two special smoke behaviours with the fire source positioned at different flow field zones. When the fire source is positioned at the negative pressure zone, with increasing canyon wind speed, the smoke always exists upstream mainly due to the vortex, and the smoke temperature near the fire source increases first and then decreases. However, when the fire source is located in the transition zone and the unidirectional flow zone, there is no smoke appearing upstream with a certain canyon wind speed. Meanwhile, the smoke temperature near the fire sources are decreases with increasing canyon wind speed. The dimensionless temperature rise of the smoke layer ΔTs* along the longitudinal direction of the tunnel follows a good exponential decay. As the canyon wind speed increases, the longitudinal decay rate of ΔTs* decreases. The longitudinal decay rate of ΔTs* downstream of the fire is related to the fire location and canyon wind speed, and independent of the fire size. The empirical correlations for predicting the longitudinal decay of ΔTs* downstream of the fire are established. For a relatively large-scale fire, the longitudinal decay rate of ΔTs* upstream of the fire increases as the distance between the fire source and the upstream portal increases, especially for larger canyon wind speeds.

Study on the Effect of Jet Direction of Compound Air Curtain on Smoke Control

High temperature smoke caused by fire is a major cause of casualties. In order to ensure the safety of personnel, it is very important to control the spread of smoke and enable personnel to quickly withdraw from the fire scene. While traditional hard isolation, such as fire doors, may hinder the safe evacuation of people, the use of an air curtain as a flexible isolation has received more and more attention from researchers. In this paper, the influence of jet direction of compound air curtain on the smoke control effect was studied, and six working conditions were designed. The temperature and smoke isolation of the compound air curtain were numerically simulated by using ANSYS FLUENT software. The parameters such as temperature, velocity pressure and velocity streamline were analyzed, and the smoke control effects of six different jet directions were discussed. The simulation results were verified by Pyrosim fire simulation software simulation software. The results show that the direction of jet flow has a significant influence on the smoke control effect, and the fire smoke control effect under working conditions 4 and 5 is better. The working condition 5 (both air curtain A and air curtain B have outward jet direction) has the best smoke prevention effect, which is suitable for a situation that is close to the fire source. Working condition 4 (outward direction of air curtain A and inward direction of air curtain B) has the second-best effect of smoke prevention, which is suitable for situations far from the fire source.

Experimental Study on the Fire Resistance Performance of Partition Board under the Condition of Small Fire Source

Fire safety of ancient wooden buildings is one of the most important issues in the world. In this paper, partition boards with different thicknesses from 15 to 25 mm were heated by a 15-cm-diameter pool fire and a methane Bunsen burner. The temperatures and the carbonization rate of partition boards were measured and analyzed. The results show that when a pool fire was used to heat the wood sample at a distance of 30 cm, two flames appear on the sample surface. When a Bunsen burner heats the sample, the sample is burned until the center point is burned through. The thickness of the sample is increased by 5 mm, and the acceleration time of the temperature rise rate at the center is doubled. Under the condition of a pool fire, the thickness of the sample is increased by 5 mm, and the average carbonization rate at the center point is reduced by 40%. Under the condition of Bunsen burner, the average carbonization rate of the center point decreases exponentially when the thickness of the sample increases by 5 mm. In the case of the same fire source, the carbonization rate of the samples with different thicknesses has the same change trend in the horizontal and vertical directions. Compared with the pool fire, the burn-through time of the center point of the sample is reduced in the case of the Bunsen burner for a sample of the same thickness, and the average carbonization rate of each measuring point increases.