عنوان مقاله [English]
When the fire in the room reaches a critical state, the leaving hot gases can create hazards for the upper floors. In this paper, different fire cases with more and less natural ventilation than the critical state are discussed, and the temperature, velocity, and toxic species are discussed. A two-floor building is simulated using a large eddy simulation and PIMPLE algorithm at different fuel flow rates and how the fire spreads upstairs is examined. Fuel flow rates are considered at three heat release rates of 500, 1000 and 5000 kW. In order to accurately analyze toxic species, the FGM combustion model is used and the results are compared with the experimental results. The relative error are less than 15%. With increasing fuel heat release rates, the upper floor is more exposed to fire hazards such that if the heat release rates is 500 kW, the temperature in the second floor reaches 390 Kelvin and the carbon monoxide species reaches 25 ppm. But if the heat release rates is below 1000 kW, the upper floor will not be at particular risk. Generally, the level of diffusion of carbon monoxide into the second floor is lower than the toxicity level for humans (25-50 ppm) and the second floor is not particularly endangered for carbon monoxide gases.