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

et al. 2020

HFF

Purpose This study aims to investigate the controlling mechanisms of ambient oxygen and pressure on piloted ignition of solid combustibles under external radiant heating. Design/methodology/approach The numerical simulation method was used to model the influence of ambient oxygen concentration on the piloted ignition of a thermally irradiated solid sample in reduced pressure atmospheres. The solid phase decomposition and gas phase kinetics were solved simultaneously. Findings It was determined that the elevated oxygen atmospheres resulted in a higher flame temperature and a thicker temperature profile over the solid surface. Also, increasing oxygen and reducing pressure had a similar effect in the decrease of the ignition delay time. The shorter ignition time in reduced pressure was mainly because of the decreasing of convective heat losses from the heated solid. As oxygen was reduced, however, ignition occurred later and with a greater mass loss rate because more volatiles of solid fuel at transient ignition were required to sustain a complete reaction under an oxygen-poor condition. Research limitations/implications The results need to be verified with experiments. Practical implications The results could be applied for design and assessment of fire-fighting and fire prevention strategies in reduced pressure atmosphere. Originality/value This paper shows the effect mechanism of ambient oxygen and pressure on piloted ignition of solid combustibles.

Section: Model Descriptionmentioning

confidence: 99%

Numerical study on the effect of oxygen concentration on the piloted ignition of PMMA in reduced pressure atmospheres

Wang

Zhou

et al. 2020

HFF

“…On the other hand, atriums were usually studied as shafts which have a similar structure. A number of numerical 11–15 and experimental 16,17 models have been developed to describe the thermal behavior of fire smoke in shafts. In shafts, stack effect 18–23 is an important factor that drives the fire smoke movement, which has been investigated extensively in studies.…”

Section: Introductionmentioning

confidence: 99%

Heat transfer and smoke flow filling progress in a super-high atrium under influence of fire source characteristics

Wang

Journal of Fire Sciences

2019

Self Cite

Heat transfer and smoke flow filling progress in a super-high atrium is studied in this article. The influences of heat release rate and fire source height were considered. It was found that the fire smoke layer could not reach the top of the atrium when the heat release rate was very low and the fire source was located at the bottom of the atrium. The temperature of smoke layer interface and Δ Tmax were linearly positively related to Q2/3, while Δ Pmax was quadratically positively related to Q2/3. At the top of the atrium, the temperature rise and fire source height were consistent with the Boltzmann model. As the fire smoke rose with a velocity, a relatively low-pressure area was generated below. The pressure variation in this area was negatively index-related to the fire source height.

“…In addition, the distribution of temperature, pressure and velocity can be observed in any desired plane. As FDS is gradually improved, its reliability and practicability have been repeatedly verified for shaft fire scenarios (Chen et al, 2015;Li et al, 2018).…”

Section: Simulation Setup 21 Introduction To Fdsmentioning

confidence: 99%

Transport phenomena of fire-induced smoke flow in a semi-open vertical shaft

De-Cheng

Zhou

Liu

et al. 2018

HFF

Purpose The purpose of this study is to investigate the transport phenomena of smoke flow in a semi-open vertical shaft. Design/methodology/approach The large eddy simulation (LES) method was used to model the movement of fire-induced thermal flow in a full-scale vertical shaft. With this model, different fire locations and heat release rates (HRRs) were considered simultaneously. Findings It was determined that the burning intensity of the fire is enhanced when the fire attaches to the sidewall, resulting in a larger continuous flame region in the compartment and higher temperatures of the spill plume in the shaft compared to a center fire. In the initial stage of the fire with a small HRR, the buoyancy-driven spill plumes incline toward the side of the shaft opposite the window. Meanwhile, the thermal plumes are also directed away from the center of the shaft by the entrained airflow, but the inclination diminishes as HRR increases. This is because a greater HRR produces higher temperatures, resulting in a stronger buoyancy to drive smoke movement evenly in the shaft. In addition, a dimensionless equation was proposed to predict the rise-time of the smoke plume front in the shaft. Research limitations/implications The results need to be verified with experiments. Practical implications The results could be applied for design and assessment of semi-open shafts. Originality/value This study shows the transport phenomena of smoke flow in a vertical shaft with one open side.