The Study Of Combustion Characteristic And Heat Transfer Mechanism Of Alcohol Pool Fire Under Oblique Air Flow

Fire research under ventilated condition is an important aspect in fire science. It is very complicated for the real condition, just as the air flow could be classified as laminar flow and turbulence flow. And the wind direction could changed but not keep horizontal. The various direction of air flow can influences the fire characteristic and also the fire development.The pool fire is a typical one in the industrial fire. Based on the liquid evaporation, boiling, air entrainment, air convection, combustion and thermal radiation, the combustion characteristic of pool fire is different under various condition. And it is the major concern on fire research.Liquid pool fire was selected as the main object considering the representational and good repeatability. According to the theory of fire dynamic and combustion, pool fire burning behavior such as burning rate, temperature, radiation heat flux, flame height, flame puffing frequency was investigated by theoretical explanation. According to the theory of fire dynamic and combustion, pool fire burning behavior such as burning rate, temperature, radiation heat flux, flame height, flame puffing frequency depending on air pressure was investigated by theoretical explanation. The main way to get the heat is thermal conduction and thermal convection for the fuel in the small size pool. It will be the same under a quiescent condition or ventilated condition. It takes less attention by now on the combustion characteristic of pool fire under an oblique air flow, which my work focus on, and also the heat transfer mechanism of it.The aim of my research is as follows:Firstly, to explore the dynamic changing regularity of the mass loss rate, flame length of pool fire with different pool size, air flow speed, wind direction and lip height; Secondly, to develop the dimensionless model of mass loss rate vs the temperature, while both of the two parameters influenced by the air flow direction; Thirdly, to study the mass loss rate and flame length of pool fire with different shape, and to develop the physical model of heat transfer; Finally, to study the combustion characteristic of pool fire with different lip height under a quiescent condition. In order to find the main factor influencing combustion characteristic of pool fire under different air flow condition, we have finished the experiments as follows:The tunnel inclination angle, or the slope angle,θ, between the axial direction of the tunnel and the horizontal plane can be altered from0°o30°, while the fuel pan is kept horizontal inside the tunnel; The airflow speed range of the tunnel is from0to3.0ms-1; A connected vessels has been set up between pool and fuel feeder, which could hold the lip height steady.The heat transfer mechanism is analysed, and a model of combustion rate is developed under oblique air flow. It is found that there is a relationship between the mass loss rate of pool fire and the temperature of rims. It is also found that the correlationindex is inversely proportional to the pool size. We also found that the mass loss rate increases with increasing the slope angle, which strengthens the wind pressure on the fuel surface. The physical model is also built for the wind pressure and the mass loss rate.The model of the flame length of pool fire is developed, a relationship has been found between flame length and Richardson number. We find that the increased rate of flame length of various fuel is different under the same value of Richardson number. The experiments found that the maximum value of flame length decreases with increasing the slope angle.We also study the combustion characteristic under different lip height, it is found that the mass loss rate and flame height of pool fire will increase firstly, and decreases with increasing the lip height. The frequency would not change with increasing the lip height but with the pool size.At last, we study the combustion characteristic under different wind direction with different lip height. It is found that the mass loss rate increases with the lip height and also the slope angle.