Polyvinyl chloride (PVC) is widely applied in cables as insulation materials, which are vital for operation and control of industrial processes. However, PVC cables fires frequently occur, arousing public concern. Therefore, experimental methods are used to study flammability and flame-spread characteristics of PVC cable in this paper. Influences of cable structure and number are investigated, which is scanty in previous works. As cable core number of single cable or cable number of multiple cables rises, average flame height and width increase while the increment decreases. Formulas concerning dimensionless flame height and single cable diameter (or total width of multiple cables) are obtained. The former is negatively correlated with the latter. For single cable, convective heat transfer is dominant, and flame-spread rate decreases as cable core number increases. Cable maximum temperature, which drops first and then rises as cable core number increases, is observed in the cable core area. For multiple cable, the flame-spread rate increases as cable number increases. As the cable number rises, the length of pyrolysis and combustion zone increases while the maximum temperature of cable surface decreases. This work is beneficial to fire hazard evaluation and safety design of PVC cables.

In scenarios of compartment fire, natural smoke exhaust often confronts the challenge of environmental wind. In this work, a series of numerical simulations were conducted to study the influences of ambient wind speed, location of ventilation and fire source on pressure distribution and smoke movement in both single and multiple compartment fires. The results show that the pressure differential increases parabolically with the increasing ambient wind speed under the windward-leeward condition. The pressure differential and CO₂ exhaust rate are positively correlated with the smoke outlet area, which shows an opposite trend with the air inlet area. Under the windward-leeward and windward-sideward conditions, the outlet flow velocity gets larger as the wind speed increases, but the wind pressure has minimal impact on smoke movement under leeward-sideward condition. The airflow velocity in windward-ceiling condition is higher than that in leeward-ceiling condition and both of them increase with the increasing wind speed. As the wind speed increases, the smoke stratification in the corridor is weakened and the pressure fluctuation is exacerbated in the multi-room fire, which is beneficial for smoke control. The results obtained in this work would provide a reference for the optimal design and management of building smoke control system.

In order to study the characteristics of fire smoke spread and temperature distribution of a large indoor pedestrian street under different heat release rates and smoke exhaust modes, this paper focuses on the analysis of fire smoke spread, visibility, smoke temperature distribution and variation curves in an atrium. This paper uses a numerical simulation method to conduct research. PyroSim fire simulation software is used to calculate this project, which is based on a full-scale experimental design scheme. The numerical simulation results show that under the conditions of higher heat release rate, the smoke spread rate is greater than that under the conditions of lower heat release rate. Furthermore, the average temperature of smoke in the atrium is also greater, up to about 400 °C. The conditions of a higher heat release rate also show the characteristics of faster generation, faster spread and a larger volume of smoke. When the smoke exhaust system is turned on, the thickness of the smoke layer and the smoke temperature decrease. There then comes a situation where the stabile section of the fire ends in advance. The simulation results of vertical temperature distribution in an atrium can fit the modified McCaffrey plume model in any case. Under all cases, the smoke temperature reaches the maximum directly above the fire source. The horizontal dimensionless smoke temperature rises under the atrium roof, and decreases exponentially with the dimensionless distance from the fire source. The greater the heat release rate of fire source is, the smaller the attenuation coefficient is, with a more than 50% change. When the smoke exhaust system is turned on, the smoke flow accelerates and the smoke is cooled rapidly. Thus, the attenuation coefficient increases. Additionally, the effect of mechanical smoke exhaust is better than natural smoke exhaust, because mechanical smoke exhaust makes air flow and heat exchange more intense. The variation amplitudes of the attenuation coefficient under natural smoke exhaust and mechanical smoke exhaust are 13% and 22%, respectively.