The Simulation Study On Sediment Combustion Model In Air Duct

The ventilation and air conditioning system of building supplies comfortable environment for work and life, but there are a lot of sediment accumulating in the air duct because of the activity of the work and living. The sediment will lead the invalidation of the fire proofing valve, fire detector and other fire proofing establishment, and will make some effect on the fire happen and propagation. At present, the influencing factors of fire and it's jeopardize are regarded importantly by correlative research organization in some countries, however, the influence of sediment in ventilation and air conditioning system on building fire is referred rarely.In the introduction, it is considered that the air duct system is the most important way to spread the fire by analyzing the fire examples which caused by air duct system in home and abroad. By analyzing the present researches in home and abroad, the article advances to simulate and analyze the combustion phenomenon of the sediment in the air duct by FDS.The article introduces the mathemetics principle of FDS, including fundamental conservation equations, combustion model, thermal radiation model and thermal boundary conditions. And introduce each function of FDS and Smokeview, using procedure, methods of dealing with the output data and methods of designating the fire power.It analyzes the combustion reaction mechanism in the air duct in detail. Using a simple mathematical model of the combustion in air duct to analyze the gas phase equations of combustion zone, excess fuel zone and preheating zone. We can get the distribution curve of gas temperature at different time by analyzing the gas phase equation. The rate of fire spread expression can be derived from the solid phase equation. Combining gas solid phase equations, the expressions of gas temperature and fuel distribution which both are the functions of time and position are derived.It introduces the experimental apparatus of the combustion in the air duct, builds reconstruction of the combustion model by FDS, and uses the experimental data to validate the simulate result, in order to validate the feasibility and rationality of the simulation software applying to the reconstruction of the fire. And analyze the error between the results of experiment and simulation. We can observe the development of the fire in the air duct clearly by Smokeview which can get the three-dimensional animation. And analyze the distributions of airflow and temperature in the air duct.It uses FDS to simulate and analyze the combustion situation, by changing ventilation conditions in air duct, heat source conditions and the thermophysical properties to analyze these factors how to influence the combustion situation in air duct.