Research On The Pool Fire Flame And Plume Characteristics Under Plateau Enviroment

Tibet plateau as the Tibetan Buddhism Holy Land, has many old historic buildings, these historic buildings are of superior special significance in history, religion, culture and national politics. The plateau historic building fire as a result of the plateau environment climate, the historic building itself unique construction shape's influence, has unique fire characteristic in the plateau environment. Therefore, do some research on the combustion characteristic of combustible substance in plateau environment, have important significance for understanding plateau fire characteristic, the prevention of the occurrence plateau historic building fire, the effective conduct of fire suppression.Comparing with the plain standard condition, the plateau low oxygen low pressure environment will have different influence on the fuel combustion characteristic. Firstly, the absolute oxygen concentration in the environment will reduce the combustion rate of the fuel, and will have the adverse effect to the combustion sufficiency, which will affect the fuel production product. Secondly, the lower fuel burning rate will further affect the fire energy release rate, reduce the energy transportation to the fire plume, in addition, the low pressure condition will affect the combustion shape of the inflammable steam. Then it will affect the plume's ascending velocity and the temperature drop scope in the plume rise process. In view of the different combustion characteristic change and rule in plateau environment, it is necessary to conduct special research on the influence form of the combustion characteristic as well as the concrete influence mechanism under the plateau low oxygen and low pressure condition. This thesis mainly research to address the above problem, the specific e work mainly includes:Choose some typical flammable liquids as fuel in Lhasa, study the oil pool fire burning rate difference between plateau and plain environment and determine the pressure and oxygen concentration influence on the combustion rate and the corresponding relationship between them, theoretically analyzes the impact mechanism of pressure and oxygen concentration in the combustion rate, contrasts the CO concentration in two places to analyze the oxygen and pressure effects as well as the effects reason, comparing the flame images difference in the combustion stability stages in two places and get the impact reason of differences, analyze the difference of temperature rise in the plume center and the impact reason of differences.Discovered from the research that regarding the same type and the size fuel, the burning rate speed in plateau is lower than in the plain and the combustion time is longer, The fuel combustion rate and the pressure are proportionalβ, valueβis different along with different fuel type.Based on the flame light points analysis, carries on the programming through MATLAB to centralized processing the flame image, the study found the oil pan the same size, Lhasa flame area are larger and the flame width are narrower than Hefei. Lhasa flame oscillation frequency are quicker than Hefei. Under each kind of size Lhasa flame height are larger than Hefei, that the average flame difference vary greatly, the continual flame height difference also vary greatly, but the gross flame height difference vary small. By fitting curve obtained suitable formula for the average flame height and the oscillation frequency in the plateau environment.The temperature of the same height of the continuous flame in the plateau is lower than in the plain by comparison, as the height increases, the plume core temperature decrease in the plateau is relatively smaller than in the plain, not all plume temperature of the same height in plateau is higher than in the plain. The classic temperature formula developed in standard atmospheric conditions does not apply to calculate the plateau temperature, then the temperature formula which obtained by fitting the experimental data is used to calculate the high altitude plume.The paper also analyze detailed the impact reason of different pressure and oxygen concentration affect the burning rate and combustion product concentration. Analysis both of the different combustion rate and combustion efficiency causes different heat release rate in two places, which will affect the flame shape in certain aspects, analyze the specific impact factors. Analyze the flame height differences which will inevitably lead to the difference of three plume regions division (continuous flame area, intermittent flame, buoyant plume) based on flame height, which will also affect the plume centerline temperature,then analyze the specific impact factors.