Yanqiu Chen

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 ...

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 con...

Gas characteristics and effectiveness of smoke control systems in elevator lobbies during elevator evacuation in a high-rise building fire

ABSTRACT Elevator evacuation has attracted increasing attention as an efficient transport method in high-rise buildings, which is one of the most complex and interesting areas of modern fire research. Through a 3D numerical model built from ANSYS Fluent, this paper studied the influence of elevator motion on the gas characteristics as well as the effectiveness of the smoke control system in the lobby during elevator evacuation in a high-rise building fire. Pressure distribution, temperature distribution and CO concentration distribution in the elevator lobby were analyzed. It was found that the elevator motion decreased the pressure in the elevator lobby while increased the temperature and CO concentration, which indicated that more fire smoke had spread into the lobby when the elevators moved and the effectiveness of the smoke control systems had been weaken. When the elevator velocity was increased from 0 m/s to 2 m/s, the lowest pressure in the lobby was decreased by 566.7%; the temperature line was mostly above the line representing the still elevator; the CO concentration experienced the most change at the height of 2 m: the highest CO concentration was, respectively, increased by 30.4% and 26.7% when the air supply volume (qs) was 0 m3/h and 20000 m3/h. As the air supply volume in the lobby increased, the pressure was increased while the temperature and the CO concentration was decreased. Changes of temperature lines and CO concentration lines under various air supply volumes were very similar. When qs was increased from 0 m3/h to 20000 m3/h, the pressure in the lobby was increased from 0 Pa to around 8 Pa, the highest temperature and CO concentration were decreased by 23.8% and 87.5%, respectively.