| SPECIAL ISSUE: PUBLIC SAFETY |
|
|
|
|
|
Experimental investigation of the burning behavior of small logs with various external radiative heat fluxes |
| HU Haowei, QI Zhenyao, SHI Jingjun, JI Jie |
| State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230026, China |
|
|
|
|
Abstract Wood is widely used in building materials, furniture and handicrafts due to its excellent thermal insulation properties, mechanical strength and ornamental value. However, wood is a combustible material that undergoes pyrolysis, ignition, charring and cracking. Most current studies on the burning characteristics of wood have used relatively homogeneous artificial boards or logs without defects. However, in practical applications, wood structures vary among different species, the wood surface grain is not uniform, and there are many structural defects in the logs, such as knots. These factors cause the wood burning characteristics to differ significantly from that of a homogeneous board. This study experimentally investigated the burning of small logs made of white pine, radiata pine and Chinese fir. The burning behaviors were compared with different external radiative fluxes with measurements of the burning phenomenon, heat release rate, and ignition characteristics. The results show that the wood species, the grains and the defects (knots) all affect the wood burning characteristics. Increasing the external heat flux reduces the ignition time and increases the peak heat release rate. In the range of operating conditions in this paper, the difference of the log ignition time at the external radiative heat flux of 15 kW/m2 in the repeated tests is about 35%, which is higher than that of the homogeneous artificial wood. This trend indicates the effect of structural heterogeneity on the combustion characteristics of logs, but this difference decreases with the increase of the external radiative heat flux. For the same tree species, the combustion characteristics of sparse and dense grain samples are different. The highest ignition time difference is more than 500 s, and the charring rate is higher in the direction parallel to the grain than in the direction perpendicular to the grain. The Chinese fir contains a large number of knots, which can reduce the ignition time and increase the peak heat release rate at the low external radiative heat flux.
|
| Keywords
wood burning
log
grain
knot
charring
|
|
Issue Date: 06 May 2022
|
|
|
[1] DINWOODIE J M. Timber:Its nature and behaviour[M]. London, UK:E & FN Spon, 2000.
[2] ROSS R L. Wood handbook:Wood as an engineering material[R]. General Technical Report FPL-GTR-190. Madison, USA:Forest Products Laboratory, USDA Forest Service, 2010.
[3] 王苏盼, 黄鑫炎, 李开源. 木质材料火灾研究:前沿与展望[J]. 工程热物理学报, 2021, 42(10):2700-2719. WANG S P, HUANG X Y, LI K Y. A review of fire research on wood materials:Research advances and prospects[J]. Journal of Engineering Thermophysics, 2021, 42(10):2700-2719. (in Chinese)
[4] DINWOODIE J M. Timber:A review of the structure- mechanical property relationship[J]. Journal of Microscopy, 1975, 104(1):3-32.
[5] REGAN J W. Heat release rate characterization of NFPA 1403 compliant training fuels[J]. Fire Technology, 2021, 57(4):1847-1867.
[6] MAAKE T, ASANTE J, MWAKIKUNGA B. Fire performance properties of commonly used South African hardwood[J]. Journal of Fire Sciences, 2020, 38(5):415-432.
[7] HARADA T. Time to ignition, heat release rate and fire endurance time of wood in cone calorimeter test[J]. Fire and Materials, 2001, 25(4):161-167.
[8] HAO H L, CHOW C L, LAU D. Effect of heat flux on combustion of different wood species[J]. Fuel, 2020, 278:118325.
[9] XU Q F, CHEN L Z, HARRIES K A, et al. Combustion and charring properties of five common constructional wood species from cone calorimeter tests[J]. Construction and Building Materials, 2015, 96:416-427.
[10] WANG S P, DING P F, LIN S R, et al. Deformation of wood slice in fire:Interactions between heterogeneous chemistry and thermomechanical stress[J]. Proceedings of the Combustion Institute, 2021, 38(3):5081-5090.
[11] ISHIKAWA T, MIZUNO K, KAJIYA T, et al. Structural decay and flame retardancy of wood as a natural polymer[J]. Combustion Science and Technology, 2005, 177(4):819-842.
[12] FERRANTELLI A, BAROUDI D, KHAKALO S, et al. Thermomechanical surface instability at the origin of surface fissure patterns on heated circular MDF samples[J]. Fire and Materials, 2019, 43(6):707-716.
[13] LI K Y, HOSTIKKA S, DAI P, et al. Charring shrinkage and cracking of fir during pyrolysis in an inert atmosphere and at different ambient pressures[J]. Proceedings of the Combustion Institute, 2017, 36(2):3185-3194.
[14] LI K Y, MOUSAVI M, HOSTIKKA S. Char cracking of medium density fibreboard due to thermal shock effect induced pyrolysis shrinkage[J]. Fire Safety Journal, 2017, 91:165-173.
[15] LYONS P R A, WEBER R O. Geometrical effects on flame spread rate for wildland fine fuels[J]. Combustion Science and Technology, 1993, 89(1-4):153-165.
[16] DAHANAYAKE K C, YANG Y Z, WAN Y, et al. Study on the fire growth in underground green corridors[J]. Building Simulation, 2020, 13(3):627-635.
[17] HASBURGH L E, CRAFT S T, VAN ZEELAND I, et al. Relative humidity versus moisture content relationship for several commercial wood species and its potential effect on flame spread[J]. Fire and Materials, 2019, 43(4):365-372.
[18] FRANGI A, FONTANA M. Charring rates and temperature profiles of wood sections[J]. Fire and Materials, 2003, 27(2):91-102.
[19] SHIELDS T J, SILCOCK G W, MURRAY J J. The effects of geometry and ignition mode on ignition times obtained using a cone calorimeter and ISO ignitability apparatus[J]. Fire and Materials, 1993, 17(1):25-32.
[20] BARTLETT A I, HADDEN R M, BISBY L A. A review of factors affecting the burning behaviour of wood for application to tall timber construction[J]. Fire Technology, 2019, 55(1):1-49.
[21] TSAI K C. Orientation effect on cone calorimeter test results to assess fire hazard of materials[J]. Journal of Hazardous Materials, 2009, 172(2-3):763-772.
[22] DRYSDALE D. An introduction to fire dynamics[M]. 3rd ed. Chichester, UK:John Wiley & Sons, 2011.
[23] QUINTIERE J G. Fundamentals of fire phenomena[M].Chichester, UK:John Wiley & Sons, 2006.
[24] SULEIMAN B M, LARFELDT J, LECKNER B, et al. Thermal conductivity and diffusivity of wood[J]. Wood Science and Technology, 1999, 33:465-473. |
|
Viewed |
|
|
|
Full text
|
|
|
|
|
Abstract
|
|
|
|
|
Cited |
|
|
|
|
| |
Shared |
|
|
|
|
| |
Discussed |
|
|
|
|
2022,
Vol. 62
