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Author Hernandez, N.; Fuentes, A.; Reszka, P.; Fernandez-Pello, A.C.
Title Piloted ignition delay times on optically thin PMMA cylinders Type
Year 2019 Publication Proceedings Of The Combustion Institute Abbreviated Journal Proc. Combust. Inst.
Volume 37 Issue 3 Pages 3993-4000
Keywords Integral heat equation; P-1 radiation model; Analytical model; Critical heat flux; Optically thin solids
Abstract The theory to predict ignition of solid fuels exposed to incident radiant heat fluxes has permitted to obtain simple correlations of the ignition delay time with the incident heat flux which are useful in practical engineering applications. However, the theory was developed under the assumption that radiation does not penetrate into the solid phase. In the case of semi-transparent solids, where the penetration of radiation plays an important role in the heating and subsequent ignition of the fuel, the predictions of the classical ignition theory are not applicable. A new theory for the piloted ignition of optically thin cylindrical fuels has been developed. The theory uses an integral method and an approximation of the radiative transfer equation within the solid to predict the heating of an inert solid. An exact and an approximate analytical solution are obtained. The predictions are compared with piloted ignition experiments of clear PMMA cylinders. The results indicate that for opticallythin media, the heating and ignition are not sensible to the thermal conductivity of the solid, they are highly dependent on the in-depth absorption coefficient. Using the approximate solution, the correlation 1/t(ig) proportional to (q)over dot(inc)'' was established. This correlation is adequate for engineering applications, and allows the estimation of effective properties of the solid fuel. The form of the correlation that was obtained is due to the integral method used in the solution of the heat equation, and does not imply that the semi-transparent solid behaves like a thermally thin material. The approximate solution presented in this article constitutes a useful tool for pencil-and-paper calculations and is an advancement in the understanding of solid-phase ignition processes. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
Address [Hernandez, N.; Fuentes, A.] Univ Tecn Feder Santa Maria, Dept Ind, Valparaiso, Chile, Email: pedro.reszka@uai.cl
Corporate Author Thesis
Publisher Elsevier Science Inc Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1540-7489 ISBN Medium
Area Expedition Conference
Notes WOS:000456628600154 Approved
Call Number UAI @ eduardo.moreno @ Serial 973
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Author Rivera, J.; Hernandez, N.; Consalvi, JL.; Reszka, P.; Contreras, J.; Fuentes, A.
Title Ignition of wildland fuels by idealized firebrands Type
Year 2021 Publication Fire Safety Journal Abbreviated Journal Fire Saf. J.
Volume 120 Issue Pages 103036
Keywords PILOTED IGNITION; PINE NEEDLES; CONE CALORIMETER; MOISTURE; TIME; BEDS
Abstract Experiments were carried out in the Idealized-Firebrand Ignition Test (I-FIT), a bench scale apparatus specifically designed to test the ignition of forest fuel layers from a representative firebrand. A cylindrical heater was used to model the firebrand, which allowed to control the incident radiative heat flux on the specimen, from the critical heat flux up to 25 kW/m2, for five different porosities of the fuel layer. Experimental ignition delay times were interpreted based on a theoretical model of the radiative heating of the fuel layer. Radiative heat transfer within the fuel layer was modeled by using the P1 approximation. In the limit of small ignition delay times an analytical expression was derived to correlate the inverse of the ignition time to the incident heat flux. This analytical expression is used to obtain the ignition temperature and effective properties for the forest fuel layers, namely the product of the fuel volume fraction by solid fuel density and solid heat capacity. Analytical solutions were found to be consistent with experimental data and a correlation relating the inverse of the non-dimensional time-toignition to the non-dimensional heat flux is provided.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0379-7112 ISBN Medium
Area Expedition Conference
Notes WOS:000639876600016 Approved
Call Number UAI @ alexi.delcanto @ Serial 1388
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