Experimental and scale up study of the flame spread over the PMMA sheets
TL;DR: In this article, the downward flame spread over polymethylmethacrylate sheets with thickness from 1.75 to 5.75 mm has been examined in the quiescent environment, and the dependence of the flame spread rate on the thickness of sheets is obtained by one-dimensional heat transfer model.
Abstract: To explore the flame spread mechanisms over the solid fuel sheets, downward flame spread over vertical polymethylmethacrylate sheets with thicknesses from 1.75 to 5.75 mm have been examined in the quiescent environment. The dependence of the flame spread rate on the thickness of sheets is obtained by one-dimensional heat transfer model. An equation for the flame spread rate based on the thermal properties and the thickness of the sheet by scale up method is derived from this model. During combustion, temperature within the gas and solid phases is measured by a fine thermocouple. The pyrolysis temperature, the length of the pyrolysis zone, the length of the preheating zone, and the flame temperature are determined from the experimental data. Mathematical analysis has yielded realistic results. This model provides a useful formula to predict the rate of flame spread over any thin solid fuel.
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TL;DR: In this article, the orientation effects during inclined downward flame spread processes were thoroughly investigated by experimental and theoretical methods, and the mechanism of orientation effect during the flame spread process was qualitatively analyzed in detail, and simplified expressions of flame spread rate of the two insulation materials with different orientations were deduced.
83 citations
TL;DR: In this paper, the authors reveal flame spread characteristics of the insulation material, expanded polystyrene (EPS) with different thicknesses under different environmental conditions (pressure and oxygen concentration).
Abstract: The objective of this study was to reveal flame spread characteristics of the insulation material, expanded polystyrene (EPS) with different thicknesses under different environmental conditions (pressure and oxygen concentration). Experiments were carried out in small-scale flame spread experimental benches in the Tibetan plateau and Hefei, respectively, with EPS sample sheets inclined horizontally. Changes in the flame spread speed, average length of the pool fire, average maximum flame height, and maximum flame temperature in the surface flame zone were used to determine the effect of the plateau and plain environments on flame spread characteristics. The results showed that with the increase in sample thickness, the values of these parameters increased both in Lhasa and Hefei. The values of flame spread speed, average length of the pool fire, and average maximum flame height in Hefei were all larger than those in Lhasa, while the maximum flame temperature in the surface flame zone in Hefei was less tha...
31 citations
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...acquisition system, (3) heat flow meter, (4) heat flux acquisition device, (5) PC, and (6)...
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TL;DR: In this paper, a single-wall corrugated board is selected to evaluate the influence on the flame spread with different board width, heat release rate of fire source and the board located angle.
14 citations
TL;DR: In this paper, the fire behavior of a vinyl-based lining material with and without anti-corrosion painting has been evaluated through 35 and 50 kW/m 2 cone calorimeter tests.
Abstract: Fire behaviour of a vinyl based lining material with and without anti-corrosion painting has been evaluated through 35 and 50 kW/m 2 cone calorimeter tests. The minimum heat flux requited for surface ignition was estimated. The data were compared by those provided by a revised Kokkala-Thomas’s classification index prediction model, the Ostman-Tsantaridis empirical linear regression model, and the Hansen-Hovde multiple discriminant function analysis. All results collected allowed to predict the material flashover time and to classify the lining material. The results illustrate some differences in the classification of the material due to different approaches of the models used.
7 citations
Cites background from "Experimental and scale up study of ..."
...Because of that bench scale cone tests a frequently used to evaluate the fire behaviors of materials with small samples [1-4]....
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04 Jul 2018
TL;DR: RBCs can produce a considerable amount of heat, due to the light energy from the curing lights and exothermic reaction of polymerization, which affects their clinical longevity and ease of use.
Abstract: One of the main objectives in research and development of resin based cements (RBCs) is to enhance their clinical longevity and ease of use. In spite of the undeniable technological advances introduced in the last few decades, the polymerization shrinkage i.e. strain that accompanies the chain-growth polymerization of dimethacrylate monomers remains one of the major concerns for the clinical performance of composite restorations. Also, RBCs can produce a considerable amount of heat, due to the light energy from the curing lights and exothermic reaction of polymerization.
6 citations
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TL;DR: In this paper, heat transfer and gas phase chemical kinetic aspects of the flame spread process are addressed separately for the spread of flames in oxidizing flows that oppose or concur with the direction of propagation.
Abstract: Recent advances in the experimental study of the mechanisms controlling the spread of flames over the surface of combustible solids are summarized in this work. The heat transfer and gas phase chemical kinetic aspects of the flame spread process are addressed separately for the spread of flames in oxidizing flows that oppose or concur with the direction of propagation. The realization that, in most practical situations, the spread of fire in opposed gas flows occurs at near extinction or non-propagating conditions is particularly significant. Under these circumstances, gas phase chemical kinetics plays a critical role and it must be considered if realistic descriptions of the flame spread process are attempted. In the concurrent mode of flame spread, heat transfer from the flame to the unburnt fuel appears to be the primary controlling mechanism. Although gas phase chemcial kinetics is unimportant in the flame spreading process, it is important in the establishment and extension of the diffusion ...
266 citations
TL;DR: In this article, the transient, one-dimensional, thermally thick, noncharring solid material version of a numerical thermal degradation model is used to analyze the thermal degradation process of poly(methyl methacrylate) when subjected to a radiation source from a graphite plate.
Abstract: The transient, one-dimensional, thermally thick, noncharring solid material version of a numerical thermal degradation model is used to analyze the thermal degradation process of poly(methyl methacrylate) when subjected to a radiation source from a graphite plate. A theory is developed to account for oxygen-sensitive thermal degradation, which is based on differences in polymer degradation behavior in inert and non-inert environments. The model includes condensed phase heat transfer, in-depth thermal and oxidative decomposition, advective mass transfer, and in-depth absorption of radiation. It is found that an increase in gas-phase oxygen concentration decreases the surface temperature and increases the gasification rate substantially. The predictions yield physically realistic results when compared with published experimental data for an external radiation source with flux of 17 k W.m - 2 .
30 citations
TL;DR: A simplified analysis and data acquired in the 4.5 s drop tower in MGLAB, Japan in a quiescent oxygen/nitrogen environment are presented in this article for the prediction of the flammability limit.
26 citations
TL;DR: In this article, the authors established bounds on the surgface temperature of polymethylmethacrylate slabs burnings steadily in oxygen-nitrogen mixtures and showed that the dependence of regression rate on surface temperature agrees with a theoretical deduction that employs kinetic data for bulk degredation in an asymptotic analyste for large activation energy.
15 citations
TL;DR: In this paper, the authors addressed the numerical study of the transient laminar opposed-flow flame spread over a solid fuel in a quiescent ambient, where the transient governing equations - full Navier-Stokes, energy, and species (oxygen and volatiles) for the gas phase, and continuity and energy equations for the solid phase (fuel) with primitive variables are discretized in a staggered grid by a control volume approach.
Abstract: The present work is addressed to the numerical study of the transient laminar opposed-flow flame spread over a solid fuel in a quiescent ambient. The transient governing equations - full Navier-Stokes, energy, and species (oxygen and volatiles) for the gas phase, and continuity and energy equations for the solid phase (fuel) with primitive variables are discretized in a staggered grid by a control volume approach. The second-order Arrhenius kinetics law is used to determine the rate of consumption of volatiles due to combustion, and the zero-order Arrhenius kinetics law is used to determine the rate of degradation of solid fuel. The equations for the fluid and solid phases are solved simultaneously using a segregated technique. The physical and thermo-physical properties of the fluid (air) such as density, thermal conductivity, and viscosity vary with temperature. The surface regression of the solid fuel is modeled numerically using a discrete formulation, and the effect upon the results is analyzed. The surface regression of the solid fuel as shown affects on the fuel surface and gas temperature, mass flux and velocity of volatiles on the top surface of fuel, total energy transferred to the solid phase, etc. It seems the results to be realistic. .
12 citations