Studies On Smoke Movement And Smoke Management In Atrium Fire

The emergence of atrium in modern buildings has challenged the fire safety protection technology, that is the concept of floor-to-floor compartmentation, adopted in tradition buildings. Studies on smoke movement and smoke management in an atrium become the focus of fire research fieldsThis thesis surveys the current situation of research on smoke movement and smoke management at broad and home. The methods of smoke management system design are provided. NFPA 92B, that is the guide for smoke management systems in malls atria and large areas published by National Fire Protection Association, and regulations of atrium design in current national code (Code for Fire Protection Design of Tall Buildings GB50045-95) are discussed, and thus areas of this project are specified. This thesis presents the results obtained from experiments in a scaled-model and numerical predictions.A survey of the geometrical shapes of the atrium spaces in China mainland was carried out. From results, the types of atria can be classified according to their shape ratios. Non-dimension analysis and similarity theory were used to discuss the simulation principle and criteria for simulating smoke movement in atrium fire. Physical meanings of criteria are fully analyzed; the practical feasibility and the limitation of scale modeling study are discussed. An experimental reduced-scale compartment, which is a 1/8-scale modeling of the PolyU/USTC Atrium, is established. The experiments of smoke filling and mechanical exhaust during atrium fires are conducted. The data obtained from scaled model experiment were compared with those obtained in the full-scale prototype experiments through the preservation of the Froude number. The good results were achieved between the model and prototype for natural smoke filling. It showed that the Froude number was reasonable, and the approach to use reduced-scale model technique for studying the natural smoke filling with pre-flash fire is practicable.The results indicate that the stratification effect between upper layer and lower layer can be discerned in the smoke natural filling process, but its interface is obscure. It also can be found that the time required to fill an atrium with smoke is very short. Smoke is the major cause of hazard during atrium fire. The method of smoke extraction through the mechanical exhaust system is an effective approach to maintain the smoke layer at asteady clear height. The ventilation rates and the fire loads are the important factors affecting the stability of the smoke layer. Based on experimental data, an equation for predicting the position of the smoke layer interface for high atrium with steady fire during smoke filling, and an equation for predicting plume mass flow rate, which shows the characteristic of confined plume, are obtained.The field models for smoke flow in atrium, takings into account strong buoyancy, turbulence, radiation exchange and wall heat losses are developed, A six-flux radiation model was included in a general mathematical model for fires, which the fire is taken as a volumetric heat source. A computer program, the prediction software of atrium fire is developed from the general-purpose compute program. The numerical results calculated by the program are compared with the experiments; the agreement between the prediction and experiment is good. It makes validation of the software. By using prediction software, the effect of fire location, fire size and atrium shape on the smoke layer development is studied. The natural ventilation system and mechanical smoke exhaust system are simulated. The effect of various parameters including the heat release rate, natural vent areas, and atrium type on the natural system effectiveness is studied. It also investigates the impact of various parameters including fire size, volumetric flow rate for the smoke exhaust system, volumetric flow rate for the air supply, atrium type and the number of the exhaust inlets on the effectiveness of a smoke management system. It is helpful for the atrium smo...