Spot fire increase the difficulty of fire-fighting and threaten public safety,and therefore it is important to study ignition probabilities of fuel bed by different firebrands,in order to understand ignition mechanism...Spot fire increase the difficulty of fire-fighting and threaten public safety,and therefore it is important to study ignition probabilities of fuel bed by different firebrands,in order to understand ignition mechanisms and analyze the formation of spot fires.This will provide an important basis for further study to improve the fire-fighting efficiency and reduce casualties.In this study,the ignition probabilities of larch(Larix gmelinii)fuel beds with different moisture levels and packing ratios by diffreent firebrands,including cones and twigs of different sizes,was investigated.Ignition experiments were conducted at different wind speeds generated by fans.The results show that,regardless of moisture content and packing ratio,ignition probability is zero when there is no wind.Both moisture content and wind speed significantly infuence ignition probability,while packing ratio has almost no effect.The maximum moisture content at which firebrand ignition occurred was 50%,and ignition probability increased with wind speed and decreased with moisture content.Cones have the highest ignition probability,followed by large twigs and by small twigs.Ignition probability is also affected by firebrand shapes and sizes that determine their potential heat and contact area to the fuel bed.Two empirical models were established to link ignition probability with fuel properties and wind speed.This study will help clarify the mechanism of spot ignition and reduce corresponding losses.展开更多
This paper presents an extensive experimental investigation campaign concerning the thermal fire reaction of firebrands,as they accumulate on the exterior walls of dwellings,a common occurrence in southern Europe.Thre...This paper presents an extensive experimental investigation campaign concerning the thermal fire reaction of firebrands,as they accumulate on the exterior walls of dwellings,a common occurrence in southern Europe.Three types of wall core layers were studied:bricks,designed according to the Exterior Thermal Insulation Composite Systems(ETICS)methodology,cross-laminated timber(CLT)and normal wood(NW),both utilizing the sandwich methodology.The wall specimens are made of a combination of materials such as three types of mortar(Tria,Sika,and Weber),and various thermal insulation materials,such as agglomerates of composite cork,impermeable membranes,rigid rock wool,fireproof paint,and extruded polystyrene rigid foam(XPS),which are recommended for their good performance against fire and high temperatures.Firebrands are then deposited on the localized surfaces of the wall specimens,and the temperature is recorded in each layer.This study aims to precisely verify the firebrand reaction to fire,including the type of ignition,smoke and droplet production.The insulation capabilities of each insulation and wall system will also be analyzed.展开更多
基金funded by the Sub topic of 13th Five-Year-Plan National Key Research and Development Project(2017YFD0600106-2)National Natural Science Foundation Project(31,400,551,31,870,644)。
文摘Spot fire increase the difficulty of fire-fighting and threaten public safety,and therefore it is important to study ignition probabilities of fuel bed by different firebrands,in order to understand ignition mechanisms and analyze the formation of spot fires.This will provide an important basis for further study to improve the fire-fighting efficiency and reduce casualties.In this study,the ignition probabilities of larch(Larix gmelinii)fuel beds with different moisture levels and packing ratios by diffreent firebrands,including cones and twigs of different sizes,was investigated.Ignition experiments were conducted at different wind speeds generated by fans.The results show that,regardless of moisture content and packing ratio,ignition probability is zero when there is no wind.Both moisture content and wind speed significantly infuence ignition probability,while packing ratio has almost no effect.The maximum moisture content at which firebrand ignition occurred was 50%,and ignition probability increased with wind speed and decreased with moisture content.Cones have the highest ignition probability,followed by large twigs and by small twigs.Ignition probability is also affected by firebrand shapes and sizes that determine their potential heat and contact area to the fuel bed.Two empirical models were established to link ignition probability with fuel properties and wind speed.This study will help clarify the mechanism of spot ignition and reduce corresponding losses.
基金the Foundation for Science and Technology(FCT),Portugal,for the Project“New Fireproof Dwellings for Wildfire PTDC/ECI-CON/2240/2020”(DOI:10.54499/PTDC/ECI-CON/2240/2020)the Foundation for Science and Technology's support through funding UIDB/04625/2020 from the research unit CERIS(DOI:10.54499/UIDB/04625/2020)+1 种基金the financing of the doctoral grants SFRH/BD/03935/2023(DOI:10.54499/2023.03935.BD)SFRH/BD/04011/2023(DOI:10.54499/2023.04011.BD).
文摘This paper presents an extensive experimental investigation campaign concerning the thermal fire reaction of firebrands,as they accumulate on the exterior walls of dwellings,a common occurrence in southern Europe.Three types of wall core layers were studied:bricks,designed according to the Exterior Thermal Insulation Composite Systems(ETICS)methodology,cross-laminated timber(CLT)and normal wood(NW),both utilizing the sandwich methodology.The wall specimens are made of a combination of materials such as three types of mortar(Tria,Sika,and Weber),and various thermal insulation materials,such as agglomerates of composite cork,impermeable membranes,rigid rock wool,fireproof paint,and extruded polystyrene rigid foam(XPS),which are recommended for their good performance against fire and high temperatures.Firebrands are then deposited on the localized surfaces of the wall specimens,and the temperature is recorded in each layer.This study aims to precisely verify the firebrand reaction to fire,including the type of ignition,smoke and droplet production.The insulation capabilities of each insulation and wall system will also be analyzed.
