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.
A glove requires a balance between thermal protection and hand dexterity, limiting the thickness of insulating layers and increasing the risk of hand burns. Phase change material (PCM) can absorb large amounts of latent heat while maintaining a constant melting temperature, which makes it a potential high-performance thermal insulation material. This study is the first experimental investigation using a three-dimensional (3D) gloved-hand model to identify the optimum design of PCM-integrated structural firefighting gloves for enhanced thermal protection. The gloves were exposed to radiant heat sources in a furnace to simulate flashover and other hazardous fireground conditions. Our findings indicated that the PCM layer could extend glove thermal protection times by 30%-107% under heat exposures. Thicker PCM provided greater thermal protection. However, PCM released latent heat as it solidified during the post-exposure period, reducing the heat dissipation rate at the skin surface. Thicker PCM layers resulted in a lower cooling rate during the post-exposure period. Therefore, an optimal PCM thickness of 0.5 mm was identified for firefighter gloves when both heat-exposure and post-exposure conditions were considered. Additionally, several distinct moisture content levels in the PCM-integrated glove were studied to explore how the moisture content affected the glove thermal performance.
As critical components of modern transportation infrastructure, tunnels exhibit highly complex and dynamic fire environments due to their enclosed and elongated structures. To improve the prediction accuracy of tunnel fire source locations and ceiling temperature distributions under complex fire conditions, this study proposes a multi-start mutation particle swarm optimization (MSM-PSO) algorithm based on the traditional particle swarm optimization (PSO) method. The proposed algorithm dynamically adjusts the inertia weight and learning factors while integrating a multi-start search strategy and mutation operations. During the iterative search process, random perturbations are applied to the position or velocity of selected particles with a specified probability, effectively enhancing the global search capability and preventing premature convergence to local optima. The full-scale experiments were conducted to validate the effectiveness of the proposed method. The results demonstrated that the prediction performance for both fire source location and ceiling temperature distribution was substantially enhanced. Compared to both the standard PSO and adaptive PSO algorithms, the proposed method demonstrates superior prediction accuracy and stability, particularly in three-parameter fire source localization and ceiling temperature estimation. The proposed method provides a reliable technical reference for intelligent fire suppression system design and emergency decision-making in tunnel fire rescue.
Bio-based thermal insulation must resist fire without losing its insulating function. Corn pith and alginate panels were engineered with a phytate-derived phosphorus compound (PA-THAM) and disodium octaborate tetrahydrate (DOT), and retained low thermal conductivity (approximately 0.035Wm-1K-1) and low density (59kgm-3). Thermogravimetric analysis showed the peak mass-loss rate falling by approximately 65% and the maximum degradation temperature rising from 280°C to 310°C. Smouldering was strongly suppressed: 8 wt% PA-THAM alone reduced the propagation speed by nearly an order of magnitude and induced self-extinction at an onset temperature of 310°C, while the combined PA-THAM/DOT system raised the smouldering ignition threshold by 70°C and 90°C depending on loading, with no propagation to burn-out. Under flaming conditions the same formulations behaved very differently: cone calorimetry gave a moderate reduction in peak heat release rate, of up to 20%, and a longer flaming period, but no resolvable change in total heat release, effective heat of combustion or smoke production. This identifies a predominantly condensed-phase barrier, formed by phosphorus-induced dehydration and carbonisation and possibly reinforced by boron-mediated crosslinking, and shows that smouldering performance cannot be inferred from bench-scale flaming tests.
