The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Xinyan Huang - One of the best experts on this subject based on the ideXlab platform.
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can Peat soil support a flaming wildfire
International Journal of Wildland Fire, 2019Co-Authors: Xinyan HuangAbstract:Smouldering wildfire in Peatlands is one of the largest and longest-lasting fire phenomena on Earth, but whether Peat can support a flaming fire like other surface fuels is still unclear. Our experiments demonstrate the successful piloted flaming ignition of Peat soil with moisture up to 100 wt-% under external radiation, indicating that flames may rapidly spread on Peatland before transitioning to a conventional smouldering Peat fire. Compared with smouldering ignition, flaming ignition of Peat is more difficult, requiring a higher minimum heat flux and tripling the ignition energy. The propensity for flaming increases with a drier Peat and greater external heating. We also found that the flaming ignition temperature increases from 290 to 690°C as the Peat moisture increases to 100 wt-%. Flames from Peat soil are much weaker than those of pine needles and wood, and they eventually transition to smouldering. The heat of flaming is estimated to be 13 MJ kg−1, close to the heat of smouldering. The measured CO/CO2 ratio of flaming Peat fires is less than 0.02, much smaller than 0.2 for smouldering Peat fires. This research helps understand the development of Peat fire and the interaction between flaming and smouldering wildland fires.
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upward and downward spread of smoldering Peat fire
Proceedings of the Combustion Institute, 2019Co-Authors: Xinyan Huang, Guillermo ReinAbstract:Abstract Smoldering is the dominant combustion process in Peat fire, releasing a large amount of carbon and smoke into the atmosphere. The spread of smoldering in Peatland is a multi-dimensional process, which is slow, low-temperature, persistent, and difficult to detect. In this work, we investigate the upward spread of Peat fire from the underground to the surface after forced ignition which is a relevant configuration but rarely studied. In the experiment, ignition is not possible if the igniter is deeper than 15 cm below the free surface, regardless of moisture content or density. Once ignited, the 1st-stage upward fire spread is initiated towards the free surface (opposed smoldering) with a peak temperature of 300 °C, leaving behind a char structure that does not collapse. Then, a 2nd-stage downward spread (forward smoldering) is activated with a peak temperature of 600 °C and regression of free surface. The upward spread is faster than the downward spread. The rates of both upward and downward spread decrease as the Peat density or depth is increased. These experimental observations are successfully captured by a 1D computational model of heat and mass transfer with 5-step kinetics. Modelling results further suggest that (1) the oxygen diffusion controls the entire upward-to-downward spread of Peat fire, (2) the oxidation of Peat sustains the 1st-stage upward spread, and (3) the oxidation of char sustains the 2nd-stage downward spread. This is the first study investigating the upward spread of Peat fire, which helps understand the persistence of Peat fire and guide the fire prevention and suppression strategies.
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experimental study of the formation and collapse of an overhang in the lateral spread of smouldering Peat fires
Combustion and Flame, 2016Co-Authors: Xinyan Huang, Francesco Restuccia, Michela Gramola, Guillermo ReinAbstract:Abstract Smouldering combustion is the driving phenomenon of wildfires in Peatlands, and is responsible for large amounts of carbon emissions and haze episodes world wide. Compared to flaming fires, smouldering is slow, low-temperature, flameless, and most persistent, yet it is poorly understood. Peat, as a typical organic soil, is a porous and charring natural fuel, thus prone to smouldering. The spread of smouldering Peat fire is a multidimensional phenomenon, including two main components: in-depth vertical and surface lateral spread. In this study, we investigate the lateral spread of Peat fire under various moisture and wind conditions. Visual and infrared cameras as well as a thermocouple array are used to measure the temperature profile and the spread rate. For the first time the overhang, where smouldering spreads fastest beneath the free surface, is observed in the laboratory, which helps understand the interaction between oxygen supply and heat losses. The periodic formation and collapse of overhangs is observed. The overhang thickness is found to increase with moisture and wind speed, while the spread rate decreases with moisture and increases with wind speed. A simple theoretical analysis is proposed and shows that the formation of overhang is caused by the spread rate difference between the top and lower Peat layers as well as the competition between oxygen supply and heat losses.
Guillermo Rein - One of the best experts on this subject based on the ideXlab platform.
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upward and downward spread of smoldering Peat fire
Proceedings of the Combustion Institute, 2019Co-Authors: Xinyan Huang, Guillermo ReinAbstract:Abstract Smoldering is the dominant combustion process in Peat fire, releasing a large amount of carbon and smoke into the atmosphere. The spread of smoldering in Peatland is a multi-dimensional process, which is slow, low-temperature, persistent, and difficult to detect. In this work, we investigate the upward spread of Peat fire from the underground to the surface after forced ignition which is a relevant configuration but rarely studied. In the experiment, ignition is not possible if the igniter is deeper than 15 cm below the free surface, regardless of moisture content or density. Once ignited, the 1st-stage upward fire spread is initiated towards the free surface (opposed smoldering) with a peak temperature of 300 °C, leaving behind a char structure that does not collapse. Then, a 2nd-stage downward spread (forward smoldering) is activated with a peak temperature of 600 °C and regression of free surface. The upward spread is faster than the downward spread. The rates of both upward and downward spread decrease as the Peat density or depth is increased. These experimental observations are successfully captured by a 1D computational model of heat and mass transfer with 5-step kinetics. Modelling results further suggest that (1) the oxygen diffusion controls the entire upward-to-downward spread of Peat fire, (2) the oxidation of Peat sustains the 1st-stage upward spread, and (3) the oxidation of char sustains the 2nd-stage downward spread. This is the first study investigating the upward spread of Peat fire, which helps understand the persistence of Peat fire and guide the fire prevention and suppression strategies.
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experimental study of the formation and collapse of an overhang in the lateral spread of smouldering Peat fires
Combustion and Flame, 2016Co-Authors: Xinyan Huang, Francesco Restuccia, Michela Gramola, Guillermo ReinAbstract:Abstract Smouldering combustion is the driving phenomenon of wildfires in Peatlands, and is responsible for large amounts of carbon emissions and haze episodes world wide. Compared to flaming fires, smouldering is slow, low-temperature, flameless, and most persistent, yet it is poorly understood. Peat, as a typical organic soil, is a porous and charring natural fuel, thus prone to smouldering. The spread of smouldering Peat fire is a multidimensional phenomenon, including two main components: in-depth vertical and surface lateral spread. In this study, we investigate the lateral spread of Peat fire under various moisture and wind conditions. Visual and infrared cameras as well as a thermocouple array are used to measure the temperature profile and the spread rate. For the first time the overhang, where smouldering spreads fastest beneath the free surface, is observed in the laboratory, which helps understand the interaction between oxygen supply and heat losses. The periodic formation and collapse of overhangs is observed. The overhang thickness is found to increase with moisture and wind speed, while the spread rate decreases with moisture and increases with wind speed. A simple theoretical analysis is proposed and shows that the formation of overhang is caused by the spread rate difference between the top and lower Peat layers as well as the competition between oxygen supply and heat losses.
Mangeng Lu - One of the best experts on this subject based on the ideXlab platform.
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Influence of Ionic Liquid-Based Metal–Organic Hybrid on Thermal Degradation, Flame Retardancy, and Smoke Suppression Properties of Epoxy Resin Composites
Journal of Materials Science, 2018Co-Authors: Fei Xiao, Fubin Luo, Sa Yao, Maoping Lv, Haimei Zou, Kun Wu, Mangeng LuAbstract:A new multifunctional ionic liquid-based metal–organic hybrid (PMAIL) was synthesized by anion exchange between as-synthesized phosphonate-based ionic liquid and phosphomolybdic acid and applied to epoxy resin (EP) as an efficient flame retardant. As expected, with only 1 wt% addition of PMAIL, the char yield of EP-PMAIL1 composite at 700 °C was significantly improved by 108.3% from 12.0% for neat epoxy resin to 25.0%, demonstrating the outstanding catalytic charring effect of PMAIL. Meanwhile, EP-PMAIL6 composite (6 wt% addition) can reach V-0 rating in the UL-94 vertical burning tests easily, and its peak heat release rate and total smoke production of EP-PMAIL6 were dropped by 31.0 and 15.4%, respectively, compared with neat EP. Moreover, the results from cone calorimetry tests showed that the char yield of EP-PMAIL6 was enhanced by 162% from 9.5 to 24.9% compared with neat EP, resulting in a strong intumescent char layer structure with outstanding fire retardance and mechanical properties. The thermo-oxidative stable protective layer retarded the transfer of heat and flammable volatiles during combustion and protected the epoxy matrix from further degradation. In conclusion, our results might provide a new perspective for producing composites with excellent flame retardancy and smoke suppression properties using ionic liquid-based metal–organic hybrid.
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An efficient phosphonate-based ionic liquid on flame retardancy and mechanical property of epoxy resin
Journal of Materials Science, 2017Co-Authors: Fei Xiao, Fubin Luo, Yuyue Guo, Shiheng Zhang, Qingqing Zhu, Xiangxiang Du, Kun Wu, Mangeng LuAbstract:In order to develop a highly efficient flame-retardant system, a phosphonate-based ionic liquid named 1-vinyl-3-(diethoxyphosphoryl)-propylimidazolium bromide (IL) was synthesized and introduced into epoxy resin (EP). With only 4 wt% loading, EP/IL composite passed UL-94 V-0 rating, and its limiting oxygen index value increased to 34.9% from 25.9% for neat epoxy resin. The char yield of EP/IL-2 (2 wt%) was improved by 58.3%, and its peak of heat release rate was reduced by 65% compared with that of neat EP. The reason is that the presence of IL promoted the forming of a compact and stable phosphorus-rich residual chars. Unlike traditional additive-type flame retardant, it is very interesting that the introduction of IL changed the color and transparency of EP few and enhanced mechanical property of neat EP remarkably. Owing to the excellent compatibility and steric effect between IL and EP matrix, tensile strength was increased to 108.6 MPa for EP/IL sample from 84.9 MPa for neat EP, indicating the outstanding reinforcement effect of IL on EP composites.
Donald I Siegel - One of the best experts on this subject based on the ideXlab platform.
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groundwater flow with energy transport and water ice phase change numerical simulations benchmarks and application to freezing in Peat bogs
Advances in Water Resources, 2007Co-Authors: Jeffrey M Mckenzie, Clifford I Voss, Donald I SiegelAbstract:In northern Peatlands, subsurface ice formation is an important process that can control heat transport, groundwater flow, and biological activity. Temperature was measured over one and a half years in a vertical profile in the Red Lake Bog, Minnesota. To successfully simulate the transport of heat within the Peat profile, the U.S. Geological Survey’s SUTRA computer code was modified. The modified code simulates fully saturated, coupled porewater-energy transport, with freezing and melting porewater, and includes proportional heat capacity and thermal conductivity of water and ice, decreasing matrix permeability due to ice formation, and latent heat. The model is verified by correctly simulating the Lunardini analytical solution for ice formation in a porous medium with a mixed ice–water zone. The modified SUTRA model correctly simulates the temperature and ice distributions in the Peat bog. Two possible benchmark problems for groundwater and energy transport with ice formation and melting are proposed that may be used by other researchers for code comparison. � 2006 Elsevier Ltd. All rights reserved.
Francois Quinty - One of the best experts on this subject based on the ideXlab platform.
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energy and moisture considerations on cutover Peatlands surface microtopography mulch cover and sphagnum regeneration
Ecological Engineering, 1998Co-Authors: Jonathan S Price, Line Rochefort, Francois QuintyAbstract:This study examined (i) the effect of artificially created microtopography and straw mulch on the soil moisture and (ii) energy balance and the establishment of a Sphagnum cover on a cutover Peatland. Straw mulch caused rainfall interception approaching 2 mm per event. Although interception represented 44% of the total rainfall over the measurement period, water that evaporated from the mulch used energy that would otherwise have been used to evaporate soil water. Thus, the net effect of interception by mulch was negligible. The soil heat flux below the mulch was only 13% of the bare soil value and was decoupled from the daily net radiation. Net radiation over the bare soil was 15% greater than over the mulch. However, because of the greater heat flux into the bare Peat, the energy available for sensible and latent heat fluxes was similar between the mulch covered and bare Peat. Average evaporation from mulch and bare soil was estimated to be 2.6 and 3.1 mm d 1 , respectively. Soil water tension 1 cm below the surface remained above 100 cm (mb) all season (100% of the time) when a mulch was used, compared to only 30% of the time in the bare soil. Correspondingly, the water table was sustained above the 40 cm depth, 60% of time in the mulch covered site, compared to only 40% of the time in the bare Peat site. Negative relief
