Browsing by Author "Pagliaro, John Leonard"
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Item Experimental and Computational Analysis of the Fire Suppression Effectiveness of Halon 1301 Replacements(2012) Pagliaro, John Leonard; Sunderland, Peter B; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Experimental and computational work was performed to help understand why sub-inerting concentrations of HFC-125 (C2HF5) produced overpressures in the FAA aerosol can explosion test. The fire suppression performance of HCFC-123 (C2HCl2F3) was also investigated to determine whether it may perform better than HFC-125. Thermodynamic analysis shows that both agents increase the overall heat release for lean mixtures containing the aerosol can contents. HFC-125 also increases the overall reaction rate when added to lean mixtures. The overall reaction rate of mixtures containing HCFC-123 is generally lowered when sub-inerting concentrations are added. Experimental results showed that HCFC-123 has a lower minimum inerting concentration (8.9%) than HFC-125 (13.5%). Mixtures containing HCFC-123 were found to produce peak pressures in the 2 L chamber that were estimated to cause overpressures in the FAA chamber. Nitrogen dilution resulting in 20% oxygen in air was successful at eliminating the overpressure of mixtures containing HCFC-123.Item Inhibition of Laminar Premixed Flames by Halon 1301 Alternatives(2015) Pagliaro, John Leonard; Sunderland, Peter B.; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Halon 1301 (CF3Br) has been banned (by the Montreal Protocol) because of its ozone depleting potential. Even though a critical-use exemption of CF3Br has been granted for commercial aircraft cargo bay applications, the European Union is requiring replacement in new aircraft by 2018 and in existing aircraft by 2040. As a result of the expected phase-out, the FAA tested three alternatives (C2HF5, C3H2F3Br, and C6F12O) in a cargo bay simulator, and under certain conditions, apparent combustion enhancement was observed (even though the agents showed promise in standard tests). To understand the enhancement, experiments and numerical analysis are performed to: 1) test the concepts developed via previous numerical simulations and analysis of the FAA tests, 2) reproduce the phenomena observed in the complex full-scale FAA experiments in laboratory-scale experiments which might serve as a screening tool, 3) provide preliminary validation of recently developed kinetic mechanisms (which are used to understand the phenomena), and 4) examine the performance of potential replacements that were not tested by the FAA. Two spherically expanding flame experiments were built to measure laminar burning velocity, peak pressure rise, and flame response to stretch. For each experiment, developments included designing the chamber, creating the operating procedure, setting up the necessary data acquisition and operation controls, and developing data reduction and post-processing routines. Numerical modeling with detailed kinetics was performed to interpret experimental results and to validate kinetic mechanisms. The most significant findings of this study include the enhancement of lean CH4-air flames by the proposed alternative agents, the potential of HCFC-123 as a halon replacement, and excellent agreement between burning velocity predictions (with detailed chemical mechanisms) and measurements for hydrocarbon-air flames inhibited by CF3Br, C2HF5, C3H2F3Br, C6F12O, and C2HF3Cl2.