四川凉山州林区腐殖质阴燃传播特性的试验研究

Experimental study on smouldering propagation characteristics of humus in Liangshan Prefecture,Sichuan Province

腐殖质层是分布在北美、欧洲和亚洲的森林和沼泽中的生物燃料,容易发生阴燃,即一种缓慢、低温、无焰和最持久的燃烧现象。腐殖质阴燃消耗大量的有机生物质燃料,导致温室气体释放到大气中,引起雾霾事件。采用四川凉山彝族自治州(26.401194°N,102.705102°E)森林腐殖质为试验材料,研究燃料床长度、含水率和粒径对腐殖质阴燃传播特性(阴燃传播速率、阴燃温度)的影响。结果表明,在不同燃料床长度的试验中,阴燃极值温度在600~900℃,腐殖质阴燃极值温度随着燃料深度和燃料床长度的增加而增加。同时,腐殖质阴燃传播速度随着含水率的增加(0~30%)而降低。在不同粒径的试验中,随着粒径的减小,阴燃时间延长,最高温度升高,阴燃高温持续时间也变长,其中上层传播速度受粒径的影响波动最为明显。研究可为四川凉山州林区地表腐殖质火灾预防提供一定的参考。

Duff layers serve as biofuel in forests and swamps spanning North America,Europe,and Asia.These regions are susceptible to smouldering combustion,characterized by slow,low-temperature,flameless burning-the most enduring form of combustion phenomena.Smouldering duff fires consume large quantities of organic biomass fuels,leading to the emission of greenhouse gases into the atmosphere.Additionally,they contribute to a notable degradation in air quality,precipitating major regional crises commonly referred to as haze events.In this study,forest duff sourced from the well-distributed forests of Liangshan Autonomous Prefecture,Sichuan,China(26.401194°N,102.705102°E)was utilized as the experimental fuel.The research focused on investigating the impact of fuel bed length,moisture content,and particle size on smouldering propagation characteristics,such as smouldering spread rate and temperature,of forest duff.The findings indicated a direct correlation between the peak smouldering temperature of forest duff and both fuel depth and bed length,with temperatures ranging from 600℃to 900℃across all scenarios.Conversely,the smouldering spread rate of forest duff exhibited a decline as moisture content increased(030%),attributable to the high specific heat capacity of water.In conclusion,the peak smouldering temperature and duration of smouldering both increased as particle size decreased,owing to the elevated ash content in smaller particles.As the particle size decreased,the period of sustained high smouldering temperature extended.This phenomenon can be attributed to the accumulation of ash in small particles,leading to the formation of a thicker ash layer above the smouldering front.This layer acts as a barrier,impeding the diffusion of oxygen and subsequently prolonging the duration of smouldering.During the experiments,the impact of particle size on the spread of the upper duff layer exhibited the most pronounced fluctuations.The smouldering front expanded more rapidly in the upper and lower duff layers compared to the middle duff layer.These research findings offer valuable insights that can aid in the mitigation and management of underground smouldering fires involving forest duff in the Liangshan Autonomous Prefecture,Sichuan,China.