This study investigates a two-step inorganic mineralization treatment designed to improve the fire performance, mechanical properties, and leaching resistance of poplar wood. White poplar (Populus alba L.) was impregnated under vacuum–pressure conditions using sodium silicate, followed by boric acid and calcium chloride. The treatment resulted in a weight percent gain of approximately 51%, indicating substantial retention of treatment-derived inorganic material within the wood structure. Surface hardness increased significantly, by approximately 60%, whereas the increases in the modulus of rupture (18.6%) and modulus of elasticity (17.5%) were not statistically significant. Thermal analysis revealed increased residual mass after treatment under both inert and oxidative atmospheres. Fire performance was substantially enhanced, with the maximum heat release rate decreasing from 239 to 126 kW/m2 and the time to ignition increasing from 14 to 26 s. The limiting oxygen index increased from 18% for untreated wood to 44% after treatment and remained higher than that of untreated wood after leaching (23%). The treatment retained 64.2 ± 2.4% of the treatment-derived mass after leaching; however, increased equilibrium moisture content and partial loss of water-soluble components were observed. Overall, the results indicate that two-step silicate–borate–calcium mineralization is a promising approach for simultaneously improving the fire and selected mechanical properties of poplar wood, although further optimization is required to enhance moisture behaviour and long-term treatment durability.
This study investigates the combustion of natural gas in a simple 2 kW co-flow laboratory burner with the primary objective of identifying the most effective combination of interchangeable mixing-chamber nozzle and oxidizer swirler for achieving stable combustion, comparatively low CO emissions, and favorable NOx trends over a wide range of oxygen concentrations in the oxidizer (21%, 30%, 50%, and 75% O2). Interchangeable mixing-chamber nozzles were designed based on theoretical calculations to maintain flame stability under different oxygen concentrations, while five types of oxidizer swirlers (OZ-1 to OZ-5), selected on the basis of a literature review, were developed to intensify fuel–oxidizer mixing by disrupting the natural gas jet and inducing swirl within the mixing chamber. For comparison, experiments were also performed without a swirler (OZ-0). Experimental measurements were conducted in cylindrical combustion chambers, allowing simultaneous monitoring of the temperature distribution along the vertical axis, visual flame assessment, and flue gas analysis. The effects of oxygen concentration and swirler geometry on combustion characteristics were evaluated using thermocouple temperature measurements, CO and NOx emission analysis, thermal imaging, and qualitative CFD simulations of the cold flow field through the swirlers, performed for illustrative/screening purposes only and without quantitative influence on the experimental design or conclusions. The results demonstrated that swirler OZ-4, combined with the corresponding mixing-chamber nozzle, exhibited favorable overall combustion performance under the tested laboratory conditions, producing a stable flame with comparatively low CO emissions and favorable NOx trends throughout the investigated range of oxygen concentrations. The originality of this work lies in the development of a compact, structurally simple burner concept that enables stable combustion with comparatively low CO emissions under varying levels of oxygen enrichment while maintaining good flame stability, under the tested laboratory conditions. This work is presented as an introductory, screening-level study, intended to identify promising nozzle–swirler combinations and to establish a methodological and experimental basis for more detailed follow-up research, rather than as a definitive, fully validated characterization of burner performance.
The International Maritime Organization (IMO) circular MSC.1/Circ.1647 requires a ship’s fuel cell space to be bounded by “A-60” divisions and permits equivalent-safety alternatives without defining equivalence. This study proposes a framework that reads boundary rating, fire exposure and shutdown response as interacting protection layers. A full-bore rupture of an in-service vessel’s 10 mm, 0.8 MPa line gives a 4.75 MW source term. The boundary is loaded with prescribed fluxes of 50–250 kW/m2, not a predicted fire field. A one-dimensional wall model, calibrated on one test series and checked against seven independent tests, was run over 60 cases of grade, shutdown time and exposure. At 250 kW/m2, the modelled A-60 column exceeds the 140 and 180 °C rise limits after about 24 and 40 min. Resolved spatially, the local limit is still exceeded. Shutdown speed sets what the boundary contributes: A-30 and A-15 stay within an insulation-only A-60 benchmark if isolation occurs within 102–103 s, against 1.8–5.1 s from component data. This is one building block of an equivalence case, not A-60 or system-level equivalence: integrity, reliability and explosion are not assessed. MSC.1/Circ.1701 calls for detectors suitable for hydrogen fires. Hydrogen-capable detectors exist, but the cited route through the Fire Safety Systems (FSS) Code to EN 54-10 supplies no harmonized hydrogen test fire.
Lightweight structural materials in aerospace are often vulnerable to degradation when exposed to thermal loads; this can lead to catastrophic loss of structural integrity. Existing passive fire protection methods add weight or fail to maintain strength under simultaneous thermal and mechanical loads. This study investigates and expands on the previous understanding of polymer–metal laminates (PMLs) for the enhancement of fire structural survivability for lightweight load-bearing structures. Novel PML designs, featuring stainless steel 304, aluminium and copper foil combinations, were manufactured onto aluminium substrates and later subjected to a combined thermo-mechanical load. The results demonstrated that integrating stainless steel 304 front layers into 10-ply laminate configurations enhanced the substrate’s fire structural survivability. Compared to front-facing aluminium laminate layers, the stainless steel 304 front layers improved the substrate’s thermal flux exposure time under a tensile force by 122%. Even after accounting for the increased weight, it was determined that two front-facing stainless steel 304 layers provided a normalised performance gain of 64%. These findings demonstrate the potential for fire structural survivability enhancements within aerospace environments using multi-metAl–PML configurations.
Explosive spalling is the most serious fire-induced deterioration mechanism of high-strength concrete (HSC), yet the influence of the two principal variables—compressive strength and internal moisture content—has not been quantified experimentally over a wide strength range. In this study, 144 cylindrical specimens (ø100 × 200 mm) were produced from four concrete strength grades (21, 50, 80 and 100 MPa) and three curing conditions (air, sealed and high-temperature water curing) together with an oven-drying treatment so as to obtain a controlled variation of moisture content, and were heated for 15 and 30 min following the KS F 2257-1 (ISO 834-1) standard fire curve. The spalling appearance, cracking characteristics, residual compressive strength and pore structure were measured. Normal-strength concrete (NSC) of 21 MPa did not spall under any combination of heating time, curing method and moisture content, whereas every 100 MPa-grade specimen spalled severely, and they were in some cases completely destroyed. For 50–80 MPa HSC, the occurrence of spalling showed no consistent correlation with strength or with moisture content, which indicates that initial imperfections of the material dominate the onset of spalling. The spalling of HSC occurred mainly within the first 15 min of heating and its severity increased with compressive strength and heating time, while the influence of moisture content was threshold-like rather than monotonic. Threshold moisture contents for spalling-free behaviour were estimated as about 3% for 50–80 MPa and about 1% for 100 MPa and above, although these provisional thresholds require confirmation by tests at intermediate moisture contents. The residual compressive strength ratio after 15 min of heating averaged about 88% for the 21 MPa NSC and about 87% and 80% for the 50 and 80 MPa HSC, respectively, but after 30 min it decreased to about 64% for 21 MPa, 53% for 50 MPa, 43% for 80 MPa and 39% for 100 MPa.
