This study develops and validates a methodology for quantifying the inerting performance of aerosol fire suppressants. Standard inerting tests (e.g., ASTM E681, ASTM E2079, BS EN 1839) assume a quiescent mixture; however, this condition cannot be maintained for aerosols due to gravitational settling, resulting in challenges in both repeatability and concentration measurement.A cup burner apparatus was modified using propane as fuel and adding spark ignition and photodiode-based flame detection. The methodology establishes controlled air and fuel flows, introduces the suppressant above the inerting threshold, and then incrementally reduces the suppressant concentration while applying periodic ignition attempts. With each ignition attempt, the duration of luminosity is recorded. Performance benchmarks were established using Halon 1301 (CF3Br) and HFC-125 (C2F5H) at their baseline inerting concentrations (6.1% and 15.7% by volume, respectively). A sodium bicarbonate aerosol demonstrated equivalent performance at a concentration of 98 ± 14.2 g/m3.The proposed methodology provides a practical, reproducible means of quantifying the inerting performance of aerosol suppressants relative to gaseous reference agents within a single test apparatus. It establishes internally calibrated benchmarks that complement existing test methods and provides a practical framework for evaluating and qualifying future aerosol-based technologies for aerospace fire protection and related applications.
Compartment fires with external flaming have been studied extensively through experimental and theoretical work. The current study adds to this through detailed flow analysis, using CFD results obtained with FDS (version 6.9.1). A range of facing wind conditions and opening configurations are considered. CFD results are validated in terms of temperatures, heat fluxes and flame heights, through comparison to experimental data. A detailed analysis of the flow fields inside and outside the compartment with facade flame is discussed, allowing for a more complete discussion of the entrainment phenomena, as caused by the buoyancy and the facing wind. Qualitative changes in flow fields are explained. Stagnation points are found and their locations vary with wind speeds and distances between openings. Flame merging, or not, is visualized and explained by these stagnation points. Qualitatively reliable CFD results for the flow field complement the experimental data, thus providing a detailed understanding of the mechanisms governing entrainment and external flaming in wind-affected compartment fires.
Heat release is a fundamental metric in combustion and fire research, and oxygen consumption calorimetry (OCC) is widely used to characterize heat release from diverse materials under various burning conditions. Paramagnetic O2 analyzers are widely used in OCC to measure the O2 volume fraction before and after combustion, with the measurement generally based on O2 being the dominant strongly paramagnetic species in the sampled gas. This work shows that the assumption could fail for nitrogen-containing materials. NO and NO2 are also paramagnetic and can enhance the paramagnetic signal, bias the inferred O2 volume fraction, and result in a systematic underestimation of OCC-derived heat release. We quantify the relationship between NOx-induced bias in the apparent O2 volume fraction and the resulting bias in heat release measurement, using paramagnetic oxygen analysis and the Thornton–Huggett theory of OCC. We also introduce a dimensionless factor Rbias to quantify the proportion of NOx-induced bias to apparent heat release. Literature has shown that NOx formation is widespread but varies significantly in the combustion of different polymers, suggesting material-dependent NOx-induced bias. Comparative cone-calorimeter tests on polyurethane, polyamide 6, and polyamide 10 further confirm that NOx interference can introduce systematic bias into measured heat-release parameters, with NOx removal producing consistent increases in measured peak heat release rate (PHRR) and potentially altering the relative heat-release ranking between materials. Analysis of 15,969 records of oxygen consumption in cone-calorimeter tests indicates that Rbias is typically below 10% under common conditions, with a theoretical upper bound of ∼18%. These results identify a non-negligible source of bias in OCC using paramagnetic oxygen analysis for nitrogen-containing materials and provide a basis for more reliable heat-release evaluation.
The purpose of this note is to determine the plume parameter, Γi, for a canonical fire configuration, namely a pool fire. The evaluation of this parameter, which characterizes the plume nature (forced or lazy), requires knowledge of the vertical velocity and temperature of the gases in the near-field region above the fire source. Order-of-magnitude estimates of these two quantities are obtained by combining two formulations of the convective heat release rate. A numerical application presented for a heptane pool fire indicates a plume parameter greater than unity, which thus suggests a lazy plume behavior. This is a result that is likely to be of interest to researchers who use surrogate buoyant plumes in their laboratory experiments for smoke propagation and control issues.
To address the safety issues associated with lithium-ion batteries, the thermal runaway behavior of Li(NixCoyMnz)O2 (NCM) ternary lithium-ion batteries under overcharging, overheating, and thermo-electric coupling conditions was studied. Battery surface temperature, voltage, mass loss, and behavioral characteristics were monitored. The results showed that the time to trigger thermal runaway was significantly reduced under coupled thermo-electric abuse conditions. Under overheating conditions, the maximum temperature of the battery reached 748.4 °C, with an average temperature rise rate of 1.76 °C/s. As the heating power increased from 40 W to 70 W, the thermal runaway trigger time shortened by 352 s. Under overcharging conditions, as the overcharge rate increased from 0.5C to 2C, the maximum temperature of the battery reached 149.8 °C, with an average temperature rise rate of 0.19 °C/s. Under coupled thermo-electric conditions, the maximum temperature of the battery reached 712.8 °C, with an average temperature rise rate of 1.85 °C/s. Compared with individual overheating conditions, the thermal runaway trigger times were shortened by 146 s, 23 s, 12 s, and 11 s, respectively. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses of the batteries revealed that under thermo-electric coupling conditions, the internal structural damage of the battery was more severe. These findings provide valuable data and insights for the safer design of lithium-ion batteries.
