Two simplified models for predicting minimum extinguishing concentration(MEC) of ultrafine water mist(UFM)(<10 m) were developed based on limiting oxygen concentration(LOC) and combustion limit temperature(CLT),res...Two simplified models for predicting minimum extinguishing concentration(MEC) of ultrafine water mist(UFM)(<10 m) were developed based on limiting oxygen concentration(LOC) and combustion limit temperature(CLT),respectively.Experiment was conducted using a modified cup burner which can reduce the surface adsorption of UFM.Two typical liquid fuels,n-heptane and ethanol,were used in the experiment.Tests using the same scenario were repeated 20 times or 10 times according to the variance of extinguishing time.The average and the standard deviations of extinguishing time were used to evaluate the fire extinguishing performance of UFM.Experimental results agree well with the model based on LOC,and disagree with the model based on CLT.The disagreements were explained by analyzing flow behavior of UFM.It was concluded that the primary mechanism of fire extinguishment with UFM was oxygen dilution.展开更多
The mechanisms of suppressing a laminar methane-air co-flow diffusion flame formed on a cup burner with water vapor have been studied experimentally and numerically. The methane burned in a steel cup surrounded by a g...The mechanisms of suppressing a laminar methane-air co-flow diffusion flame formed on a cup burner with water vapor have been studied experimentally and numerically. The methane burned in a steel cup surrounded by a glass chimney. A mist generator produced fine droplets delivered though the glass chimney with air. These droplets were heated into water vapor when they went though the diffuser. The extinguishing limit was obtained by gradually increasing the amount of water vapor to replace the air in the coflowing oxidizer stream. Results showed that the agent concentration required for extinguishment was constant over a wide range of the oxidizer velocity, i.e., a so-called "plateau region". The measured extinguishing mass fractions of the agents were: (16.7 ± 0.6)% for H2O, (15.9 ± 0.6)% for CO2, and (31.9 ± 0.6)% for N2. The computation used the Fire Dynamics Simulator (FDS) de- veloped by the NIST. The numerical simulations showed that the predicted water vapor extinguishing limits and the flickering frequency were in good agreements with the experimental observations and, more importantly, revealed that the sup- pression of cup-burner flames occurred via a partial extinction mechanism (in which the flame base drifts downstream and then blows off) rather than the global extinction mechanism of typical counter-flow diffusion flames. And the flame-base oscillation just before the blow-off was the key step for the non-premixed flame extinction in the cup burner.展开更多
为系统分析杯式燃烧器的发展动态,基于Web of Science核心合集采集到的322篇杯式燃烧器相关文献,采用VOSviewer对文献进行计量及科学知识图谱网络分析。结果表明:杯式燃烧器及其相关领域在世界范围内的关注度正在上升;中国是该领域文献...为系统分析杯式燃烧器的发展动态,基于Web of Science核心合集采集到的322篇杯式燃烧器相关文献,采用VOSviewer对文献进行计量及科学知识图谱网络分析。结果表明:杯式燃烧器及其相关领域在世界范围内的关注度正在上升;中国是该领域文献数量最多的国家,发文量占总数的40%,并持续关注该领域;LIAO Guangxuan是发文数量最多的作者,以其为中心形成了较大的合作网络;通过研究热点分析,发现对杯式燃烧器中扩散火焰微观层次的研究可能会成为一个趋势,灭火剂形态将向复合型发展,因此有必要对杯式燃烧器作出改进,使其能够适应不断发展变化的灭火剂形态。展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 51028401)Jiangsu Province-Supporting Science and Technology Program (Project No. BE2010677)the Research Grant Council of the Hong Kong Administrative Region,China (Project No.CityU118909)
文摘Two simplified models for predicting minimum extinguishing concentration(MEC) of ultrafine water mist(UFM)(<10 m) were developed based on limiting oxygen concentration(LOC) and combustion limit temperature(CLT),respectively.Experiment was conducted using a modified cup burner which can reduce the surface adsorption of UFM.Two typical liquid fuels,n-heptane and ethanol,were used in the experiment.Tests using the same scenario were repeated 20 times or 10 times according to the variance of extinguishing time.The average and the standard deviations of extinguishing time were used to evaluate the fire extinguishing performance of UFM.Experimental results agree well with the model based on LOC,and disagree with the model based on CLT.The disagreements were explained by analyzing flow behavior of UFM.It was concluded that the primary mechanism of fire extinguishment with UFM was oxygen dilution.
基金Supported by the China NKBRSF project (Grant No. 2001CB409600)
文摘The mechanisms of suppressing a laminar methane-air co-flow diffusion flame formed on a cup burner with water vapor have been studied experimentally and numerically. The methane burned in a steel cup surrounded by a glass chimney. A mist generator produced fine droplets delivered though the glass chimney with air. These droplets were heated into water vapor when they went though the diffuser. The extinguishing limit was obtained by gradually increasing the amount of water vapor to replace the air in the coflowing oxidizer stream. Results showed that the agent concentration required for extinguishment was constant over a wide range of the oxidizer velocity, i.e., a so-called "plateau region". The measured extinguishing mass fractions of the agents were: (16.7 ± 0.6)% for H2O, (15.9 ± 0.6)% for CO2, and (31.9 ± 0.6)% for N2. The computation used the Fire Dynamics Simulator (FDS) de- veloped by the NIST. The numerical simulations showed that the predicted water vapor extinguishing limits and the flickering frequency were in good agreements with the experimental observations and, more importantly, revealed that the sup- pression of cup-burner flames occurred via a partial extinction mechanism (in which the flame base drifts downstream and then blows off) rather than the global extinction mechanism of typical counter-flow diffusion flames. And the flame-base oscillation just before the blow-off was the key step for the non-premixed flame extinction in the cup burner.
文摘为系统分析杯式燃烧器的发展动态,基于Web of Science核心合集采集到的322篇杯式燃烧器相关文献,采用VOSviewer对文献进行计量及科学知识图谱网络分析。结果表明:杯式燃烧器及其相关领域在世界范围内的关注度正在上升;中国是该领域文献数量最多的国家,发文量占总数的40%,并持续关注该领域;LIAO Guangxuan是发文数量最多的作者,以其为中心形成了较大的合作网络;通过研究热点分析,发现对杯式燃烧器中扩散火焰微观层次的研究可能会成为一个趋势,灭火剂形态将向复合型发展,因此有必要对杯式燃烧器作出改进,使其能够适应不断发展变化的灭火剂形态。
