Research On The Fuel Combustion Characteristics And The Flue Gas Characteristics Under The Tibetan Plateau Environment Of Hyperpiesia And Hypoxia

With rapid economic development shifting to inland,the development and construction of Qinghai-Tibet Plateau,particularly the development of the construction industry,is gradually speeding up.Due to the geographic characteristics, there has been no special study on whether the existing fire safety techniques are applicable.The special plateau environment of hyperpiesia'and hypoxia caused by the increase in altitude,first of all,will affect the burning rate of fuel which lowers with elevated altitude and reduced atmospheric pressure,resulting in an increased burning time under the same conditions.The decrease in burning rate will affect the combustion products(such as the gas concentrations,the concentrations and optical characteristics of smoke particles) and the smoke plume movement.Meanwhile,it will cause a lower heat release rate and impact the parameters such as the temperature rise,the flame area and the flame radiation etc..The plateau environment of hyperpiesia and hypoxia in Tibet makes the occurrence and development of fires different with inland in characteristics and laws,which determines a different prevention and detection for fires between the Tibetan Plateau and the inland. Especially,the fuel gas characteristics for plateau burning will have a great impact on the prevention and detection for fires at high altitude.The environment change of plateau has brought about a new topic on the fire prevention and control,which urgently needs us to study the combustion characteristics and gas properties under the plateau environment of hyperpiesia and hypoxia in Tibet and provide a scientific basis for the prevention and early detection for fires in Tibetan Plateau.In order for the combustion characteristics and gas properties under the plateau environment of hyperpiesia and hypoxia in Tibet,this paper has firstly carried out comparative combustion experiments with wood crib and n-heptane under the same conditions in both Lhasa and Hefei.In the course of these experiments,the combustions temperatures,the weight loss,the thermal radiation flux,the flame shape and the concentration of flue gas components were measured with the thermocouples, the electronic balance,the flux of thermal radiation,the high-speed camera and the optical density,respectively.Through the comparative analysis of experimental results in both two places,the combustion characteristics under the plateau environment of hyperpiesia and hypoxia in Tibet were studied and the influencing factors for these combustion characteristics were also discussed,which provided a guidance and reference for the next phase of research.Through the comparative combustion experiments,this paper has summed up the combustion characteristics in Lhasa.Due to a large change scope of altitude in Tibet and in order for a further study on the combustion characteristics and gas properties under the other altitudes in Tibet,a car mobile combustion chamber was designed.And combustion experiments under different altitudes in Tibet were conducted to study the changes of fuel combustion characteristics and gas properties with elevated altitudes under the special plateau environment.Based on the above two experimental studies,we inferred the main combustion characteristic at high altitude which was that the flame radiation coefficient was obviously lower than that in atmospheric region and the mechanism which was due to higher volume fraction of carbon particles than that under atmospheric pressure.To validate this infer,the focus of last experimental study was on the volume fraction of carbon particles in the flame.For the existing experimental means,it is very difficult to collect the carbon particles in the flame,thus the focus has been changed to measure the concentration of smoke particles in the smoke. Through the comparative experiments performed on the acetylene gas fires and the n-heptane oil pan fires,the flue gas concentrations under the special plateau environment in Tibet were measured and compared with the experimental results in the inland,which showed that the flue gas concentration in Tibetan Plateau was lower than that in Hefei and verified the previous infer for the impact mechanism of combustion characteristics in plateau.In this part of experiments,the flue gas parameters of flue gas temperatures and CO concentrations etc.were also measured. Moreover,the combustion characteristics and flue gas characteristics of the gas fires and the oil pan fires under plateau environment were further given.