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Lyon R.E.,U.S. Federal Aviation Administration | Safronava N.,Technology and Management International LLC | Senese J.,Technology and Management International LLC | Stoliarov S.I.,University of Maryland University College
Thermochimica Acta | Year: 2012

A thermokinetic model for the reaction rates of solids measured in constant heating rate differential thermal analysis is derived from heat transfer and chemical kinetics. An explicit result is obtained for the maximum reaction rate in a constant heating rate experiment in terms of the thermal properties of the solid, the activation energy of the thermal process, the heat of reaction, the sample mass and the heating rate in the test. The theoretical predictions compare well with numerical simulations and experimental data for polyoxymethylene and polystyrene obtained by two different thermal analysis methods using three different instruments over a wide range of sample mass and heating rate. Based on these results, an accuracy criterion for thermal analysis measurements is proposed that is consistent with recommended practices. © 2012 Elsevier B.V. All rights reserved.


Lyon R.E.,U.S. Federal Aviation Administration | Safronava N.,Technology and Management International LLC | Quintiere J.G.,University of Maryland University College | Stoliarov S.I.,University of Maryland University College | And 2 more authors.
Fire and Materials | Year: 2014

Five material properties commonly used to describe the fire behavior of solids were evaluated as sole explanatory variables for four small-scale fire tests with pass/fail outcomes by using a physically based probabilistic (phlogistic) burning model. The phlogistic model describes the likelihood of passing vertical Bunsen burner tests and a regulatory heat release rate test reasonably well over a wide range of material properties, as deduced from the correlation coefficient and mean deviation of the predicted and measured values. Of the thermal, combustion, and fire properties examined, the best predictors of the likelihood of passing the fire tests of this study were the heat of combustion of the sample, the heat release capacity, and the heat release parameter. The relative merits and drawbacks of qualitative (threshold) and quantitative (probabilistic) approaches to predicting fire test results using thermal and combustion properties are discussed. Published 2013. This article is a U.S. Government work and is in the public domain in the USA. © Published 2013. This article is a U.S. Government work and is in the public domain in the USA.


Oztekin E.,Technology and Management International LLC | Crowley S.,Faa ghes Technical Center | Lyon R.,Faa ghes Technical Center
22nd Annual Conference on Recent Advances in Flame Retardancy of Polymeric Materials 2011 | Year: 2011

The fire performance of a semi-crystalline thermoplastic, poly(aryl-ether-ether-ketone) (PEEK) was investigated using a cone calorimeter, thermal analysis and numerical modeling in an effort to explain the observed variability in fire test results with this polymer. The heat release rate, total heat release, mass loss, effective heat of combustion, and the ignition times at various heat flux settings and sample thicknesses were measured for PEEK samples that were conditioned to three levels of moisture: 0% (dry), 0.35% (ambient) and 0.73% (wet). The fire response changed drastically over this small range of moisture. For wet samples, both the ignition time and the peak heat release rate were lower, and visual inspection of the samples during the cone calorimeter tests indicated small bubbles forming on the surface of the specimen at the melting temperature of PEEK prior to ignition. For dry samples, a glossy smooth surface was formed and surface bubbles were absent prior to ignition. Numerical modeling of PEEK burning behavior, treating bubble formation as a physical process that reduced the thermal conductivity of the surface and the in-depth absorption of radiation, was able to account for the effect of moisture on fire test results. © (2011) by BCC Research All rights reserved.


Lyon R.E.,U.S. Federal Aviation Administration | Safronava N.,U.S. Federal Aviation Administration | Safronava N.,Technology and Management International LLC
Journal of Thermal Analysis and Calorimetry | Year: 2013

Pyrolysis models for burning solids in fire simulations are sensitive to the values of the activation energy, frequency factor, and reaction order that characterize the thermal decomposition of the solid to gaseous fuel, so direct measurement of these kinetic parameters is recommended, and simple methods are preferred. Three direct methods were evaluated with regard to the ability of their kinetic parameters to reproduce the thermal decomposition of five polymers measured by differential thermogravimetric analysis using the reaction order model. It was found that the two multiple heating rate methods produced identical, physically based kinetic parameters, while the peak property method produced non-physical kinetic parameters. However, all of these kinetic parameters in a single-step reaction order model gave reasonably good conversion histories for non-charring and moderately charring polymers. For a highly charring polymer, the conversion histories were poorly described without a multiple step reaction. The temperature at the maximum rate of conversion was found to be essentially independent of the reaction order, which decouples the frequency factor from the reaction order in the direct kinetic methods. Any of the direct methods are sufficiently accurate to obtain kinetic parameters for pyrolysis models because of the inherent spatial and temporal averaging of reaction rates at the burning surface of a thick solid and the uncertainty in the heat transfer mechanisms and thermo-physical parameters used in the models. © 2013 Akadémiai Kiadó, Budapest, Hungary.


Oztekin E.S.,Technology and Management International LLC | Blake D.,Fire Research Program | Lyon R.E.,Fire Research Program
50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition | Year: 2012

According to Federal Aviation Regulations, fire and smoke detector devices installed in aircraft cargo compartments are required to alarm within the first sixty seconds of fire initiation. Expensive and time consuming in-flight and ground tests are conducted to verify compliance and to grant approval for these detection systems. In an effort to minimize the number of certification tests required, Federal Aviation Administration (FAA) is evaluating computational fluid dynamics (CFD) as a tool to predict fire-induced flow behavior in aircraft cargo compartments. The objective of the present study is to evaluate the predictive abilities of available open-source CFD solvers for the transport of smoke and hot gases due to a small fire source in an enclosure. Numerical simulations are carried out using Fire Dynamics Sim- ulator (FDS)1 developed by National Institute of Standards and Technology (NIST). The simulation results are compared with an extensive set of data collected from fire tests of the forward cargo compartment of Boeing 707 for three different fire scenarios. The se- lected metrics for the comparison are the predictions of temperature, light transmission and concentrations of carbon monoxide and carbon dioxide in the first three minutes of the test initiation. Furthermore, model estimates for temperature fields are compared with correlations widely-used and relied upon in the fire research community. Copyright © 2012 American Institute of Aeronautics and Astronautics, Inc.


Walters R.N.,U.S. Federal Aviation Administration | Safronava N.,Technology and Management International LLC | Lyon R.E.,U.S. Federal Aviation Administration
Combustion and Flame | Year: 2015

A microscale combustion calorimeter (MCC) was modified to study gas phase combustion of polymers and flame-retardant plastics by adding carbon monoxide (CO) and carbon dioxide (CO2) analyzers to the standard oxygen (O2) analyzer. Experiments were conducted on 22 hydrocarbon, heteroatom and halogen-containing polymers of known composition over a wide range of combustion temperatures and oxygen concentrations. At high temperatures and excess oxygen when combustion was complete, the oxygen consumed (δO2) and CO2 produced by combustion of the pyrolysis gases were in quantitative agreement with theoretical values for all of these charring and non-charring polymers. At lower combustor temperatures, halogen-containing polymers exhibited significantly reduced fuel oxidation rates, as evidenced by a shift in maximum δO2, CO and CO2 yields to much higher temperatures. © 2014 .


Oztekin E.S.,Technology and Management International LLC | Blake D.,U.S. Federal Aviation Administration | Lyon R.E.,U.S. Federal Aviation Administration
Fire and Materials 2013 - 13th International Conference and Exhibition, Conference Proceedings | Year: 2013

The effect of ventilation on the fire-induced flow behavior is studied numerically. Simulation results are compared with an extensive set of data collected from the fire tests of below cargo compartment of a McDonnell Douglas DC-10. The average production rates of species along with the heat release and mass loss rates of the fire source employed in the full-scale tests were determined from the cone calorimetry tests. The fire source has a maximum heat release rate of 5 kW. The forced ventilation through the ceiling air inlets have a total volume flux of approximately 0.19 m3/s. In addition, there is a leakage around the compartment door as a result of the pressure differential. The selected metrics for comparison are the predictions of temperatures, light transmissions, and concentrations of carbon monoxide (CO) and carbon dioxide (CO2) in the first three minutes of the test. The overall objective of this study is to improve understanding of the transport of smoke and hot gases in enclosures, specifically applied to aircraft cargo compartments. An improved understanding will enable better decisions on the selection and utilization of fire/smoke detection systems.

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