To investigate the charring rate of timber beams exposed to three-side fire, a total of fifteen new and used Douglas-Fir timber beams in four groups exposed to three-side fire were experimentally studied, together wit...To investigate the charring rate of timber beams exposed to three-side fire, a total of fifteen new and used Douglas-Fir timber beams in four groups exposed to three-side fire were experimentally studied, together with the finite element analyses of the temperature distribution in the beam section. The durations of fire exposure were 0 (on a test piece), 10, 15, 20 and 30 min, according to the ISO 834 standard fire curve. The charring depth of each timber beam was calculated by averaging the values at one-third and two-thirds along each cross section to give the charring rate of timber beams. It was found that the timber beam's charring rate reduces as the duration of fire exposure increases and the vertical charring rate is slightly higher than the horizontal one. The areas of beam sections reduce due to charring and the strength and stiffness of the pyrolysis layer near the charring edge decrease owing to the high-temperature. The average horizontal and vertical charring rates are 0.98 and 1.08 mm/min, respectively. To take into account the difference between the test furnace temperature curve and the ISO 834 stand- ard fire curve, some corrections were made for these data to yield the solution for charring rate. With the help of the finite element software ANSYS, the temperature distribution of the wood's cross-section was analyzed. The longer the exposure time is, the greater the effect of density will impose on the distribution of temperature, but the moisture content has no effect.展开更多
Some ablation experiments of Ethylene-Propylene-Diene Monomer(EPDM)insulator were carried out in quasi-static low temperature gas environment,gas-phase environment,two-phase environment with Al2O3 grain and high conce...Some ablation experiments of Ethylene-Propylene-Diene Monomer(EPDM)insulator were carried out in quasi-static low temperature gas environment,gas-phase environment,two-phase environment with Al2O3 grain and high concentration Al2O3 grain gas environments.Their charring ablation rate,thickness,surface morphology and main ingredient of the charring layer were analyzed.The experiment results show that the main influent factors for the charring ablation rate are the gas temperature,grain concentration and state of grain impact;the main influent factors for the charring layer thickness are the gas velocity and environment pressure;and the process of SiO2 migrating in the charring layer occur commonly in different gas environments.They provide a foundation for the ablation mechanism research and modeling of EPDM insulator.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 51178115)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘To investigate the charring rate of timber beams exposed to three-side fire, a total of fifteen new and used Douglas-Fir timber beams in four groups exposed to three-side fire were experimentally studied, together with the finite element analyses of the temperature distribution in the beam section. The durations of fire exposure were 0 (on a test piece), 10, 15, 20 and 30 min, according to the ISO 834 standard fire curve. The charring depth of each timber beam was calculated by averaging the values at one-third and two-thirds along each cross section to give the charring rate of timber beams. It was found that the timber beam's charring rate reduces as the duration of fire exposure increases and the vertical charring rate is slightly higher than the horizontal one. The areas of beam sections reduce due to charring and the strength and stiffness of the pyrolysis layer near the charring edge decrease owing to the high-temperature. The average horizontal and vertical charring rates are 0.98 and 1.08 mm/min, respectively. To take into account the difference between the test furnace temperature curve and the ISO 834 stand- ard fire curve, some corrections were made for these data to yield the solution for charring rate. With the help of the finite element software ANSYS, the temperature distribution of the wood's cross-section was analyzed. The longer the exposure time is, the greater the effect of density will impose on the distribution of temperature, but the moisture content has no effect.
基金Sponsored by the National Nature Science Foundation of China(50876091)
文摘Some ablation experiments of Ethylene-Propylene-Diene Monomer(EPDM)insulator were carried out in quasi-static low temperature gas environment,gas-phase environment,two-phase environment with Al2O3 grain and high concentration Al2O3 grain gas environments.Their charring ablation rate,thickness,surface morphology and main ingredient of the charring layer were analyzed.The experiment results show that the main influent factors for the charring ablation rate are the gas temperature,grain concentration and state of grain impact;the main influent factors for the charring layer thickness are the gas velocity and environment pressure;and the process of SiO2 migrating in the charring layer occur commonly in different gas environments.They provide a foundation for the ablation mechanism research and modeling of EPDM insulator.
