Experimental study on smouldering propagation characteristics of humus in Liangshan Prefecture,Sichuan Province
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(26.401 194°N,102.705 102° 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(0-30％),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.
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