【作者】 李振华；

【导师】 汪箭；

【作者基本信息】 中国科学技术大学 ， 安全技术及工程， 2009， 博士

【摘要】 随着经济高速发展的趋势向内地的移动,青藏高原上的发展建设,尤其是建筑业的发展,正逐步加快。由于地理地域的特点,对现有的消防技术手段是否适用没有进行过专门的研究。由于海拔高度的增加造成的高原特殊低压低氧环境,首先会影响可燃物燃烧速率,随着海拔的升高和大气压强的降低可燃物燃烧速率将会降低,相同条件下燃烧时间会增加。燃烧速率的降低将影响燃烧产物(如气体浓度、烟雾粒子的浓度和光学属性)和烟气羽流运动,同时燃烧速率的降低将造成热释放速率降低,并影响温升、火焰面积和火焰辐射等参量。西藏地区特殊的高原低压低氧环境,使西藏地区火灾的发生发展都和内地有其不同的特点和规律,这也决定了西藏高原火灾的防治和探测规律与内地的有所不同,尤其是高原燃烧的烟气特性对于高原地区的火灾防治和探测有很大的影响。高原环境变化给火灾防治带来了新课题,迫切需要我们对西藏高原低压低氧环境下的燃烧特性和烟气特性进行研究,研究高原环境下的燃烧特性和烟气特性可为西藏高原的火灾防治和早期探测提供科学依据。为了研究西藏高原特殊低压低氧条件下的燃烧特性和烟气特性,本文首先在拉萨和合肥相同的实验条件下开展木垛和正庚烷对比燃烧实验。实验通过热电偶测量燃烧的温度、电子天平测量失重、热辐射通量计测量热辐射通量、高速摄像仪测量火焰形状、运用光学密度法测量烟气组分浓度。通过两地实验结果的对比分析,揭示了西藏高原低压低氧条件下的燃烧特性,讨论了导致西藏高原燃烧特性的影响因素,为下一步的研究提供指导和参考。通过两地对比燃烧实验,归纳出了拉萨的燃烧特性,由于西藏的海拔高度变化范围很大,为了更进一步研究西藏高原其它海拔高度下的可燃物燃烧特性和烟气特性,设计了车载可移动燃烧小室,在西藏不同海拔高度进行燃烧实验,以研究高原特殊环境下可燃物燃烧特性和烟气特性岁海拔高度升高的变化规律。前两部分实验研究我们分析得到高原地区的主要燃烧特性是火焰辐射系数明显低于常压地区,其机理是由于火焰中的碳颗粒体积分数高于常压下的,为了验证这一推断,最后一部分实验研究的重点是火焰中碳颗粒的体积分数。以现有的实验手段,火焰中的碳颗粒很难收集,所以研究重点在于测量烟气中烟颗粒的浓度。通过乙炔气体火和正庚烷油盘火对比燃烧实验,测量得到西藏高原特殊环境下的烟气浓度并与内地实验结果进行对比分析,得出了西藏高原烟气浓度低于合肥的结论,验证了前面对高原燃烧特性影响机理的推断。该部分实验还测量了烟气的温度、CO浓度等烟气特性参数。给出了高原环境下气体火和油盘火的燃烧特性和烟气特性。更多还原

【Abstract】 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.更多还原