Search Results (42)

The activity of the present work is part of a research project aimed at proposing a solution for off-grid charging stations relying on the adoption of a reciprocating engine fuelled with alternative renewable fuels. This technology has as its main advantage the zero-carbon emissions impact of biofuels with small modifications to current ICE technology and refuelling infrastructure. This research is founded on preliminary experimental tests carried out on a six-cylinder spark-ignition engine adapted to pure ethanol fuelling with a single-point injection system. The experimental results obtained at different engine loads have been useful to build and validate a CFD model by testing several kinetic mechanisms and for the proper calibration of a flame speed model. Nevertheless, due to the chemical and physical properties of alcohols such as ethanol, this type of fuelling system leads to a significant non-uniformity of the mixture among the cylinders, and in some cases, to rich air-to-fuel ratio; numerical simulations are performed to address such an issue, and to evaluate performance and exhaust emissions, in terms of CO, CO₂, and NO_x. Finally, a study on spark timing variation is presented as well, to study its effect on performance and pollutants. Full article

Fire is a destructive hazard impacting residential, industrial, and forested environments. Once ignited, fire becomes difficult to control, and recovery efforts are often extensive. Therefore, early detection is critical for effective firefighting. This study presents a mobile robotic system designed for early fire detection, integrating a Raspberry Pi, RGB (red, green and blue), and night vision-NIR (near infrared reflectance) cameras. A four-stage hybrid-cascade machine learning model was developed by combining state-of-the-art (SotA) models separately trained on RGB and NIR images. The system accounts for both daytime and nighttime conditions, achieving F1 scores of 96.7% and 95.9%, respectively, on labeled fire/non-fire datasets. Unlike previous single-stage or two-stage vision pipelines, our work delivers a lightweight four-stage hybrid cascade that jointly fuses RGB and NIR imagery, integrates temporal consistency via ConvLSTM, and projects a robot-centric “safe-approach distance” in real time, establishing a novel edge-level solution for mobile robotic fire detection. Based on real-life test results, the robotic system with this new hybrid-cascade model could detect the fire source from a safe distance of 500 mm and with notably higher accuracy compared to structures with other models. Full article

Air-supported membrane structures (ASMS) are widely applied in warehouses and large-span venues due to their lightweight and cost-effective nature. However, as a storage building with a lot of combustible material and significant fire hazards, it imposes stringent demands on structural stability and safety. This paper investigates the impact of fire-induced effects on stability using Fire Dynamics Simulator (FDS) software, with a case study focusing on an ASMS coal storage bin. The study comprises two key components: (1) internal pressure stability and (2) thermal stability. Results show that ambient temperature, leakage area and air supply govern non-fire pressure stability, with a 10 K increase reducing pressure by 9.4 Pa. During fires, HRR, location and growth type effect the stability of ASMS buildings. Thermal stability analysis reveals 6 m horizontal spacing can prevent coal ignition (<12.5 kW/m², <100 °C), while 10 m vertical spacing can avoid PVC membrane pyrolysis. These findings provide critical design guidelines for ASMS fire protection, highlighting the necessity of asymmetric safety margins due to vertical–horizontal radiation anisotropy. Full article

5-aminotetrazole (5AT)-based gas generators, particularly the 5AT/NaIO₄ system, have garnered interest for their high gas production and energy potential. This study investigates the impact of various metal oxides (MnO₂, Al₂O₃, TiO₂, CuO, Fe₂O₃, MgO, ZnO, and MoO₃) on the thermal decomposition and combustion performance of 5AT/NaIO₄. The REAL calculation program was used to infer reaction products, which indicated that the gas products are almost all harmless, with negligibly low percentages of NO and CO. Thermogravimetric analysis revealed that metal oxides, especially MoO₃, significantly advance the decomposition process above 400 °C, reducing the activation energy by 130 kJ/mol and lowering critical ignition and thermal explosion temperatures. Combustion performance tests and closed bomb tests confirmed MoO₃’s positive effect, accelerating reaction rates and enhancing decomposition efficiency. The system’s high Gibbs free energy indicates non-spontaneous reactions. These findings provide valuable insights for designing environmentally friendly gas generators, highlighting MoO₃’s potential as an effective catalyst. Full article

Hybrid Rocket Engines (HREs) combine the advantages of solid and liquid propellants, offering thrust control, simplicity, safety, and cost efficiency. Part of the research on this rocket architecture focuses on optimising combustion chamber design to enhance performance, a process traditionally reliant on time-consuming experimental adjustments to chamber lengths. In this study, two configurations of HREs were designed and tested. The tests aimed to study the impact of post-chamber lengths on rocket engine performance by experimental firings on a laid-back test engine. This study focused on designing, manufacturing, and testing a laid-back hybrid engine with two chamber configurations. The engine features a small combustion chamber, an L-shaped mount, a spark ignition, and nitrogen purging. Data acquisition includes thermocouples, pressure transducers, and a load cell for thrust measurement. Our experimental findings provide insights into thrust, temperature gradients, pressure, and plume characteristics. A non-linear regression model derived from the experimental data established an empirical relationship between performance and chamber lengths, offering a foundation for further combustion flow studies. The post-chamber length positively impacted the engine thrust performance by 2.7%. Conversely, the pre-chamber length negatively impacted the performance by 1.3%. Further data collection could assist in refining the empirical relation and identifying key threshold values. Full article

Solar photovoltaic (PV) systems in buildings must comply with both electrotechnical standards for module safety and local building codes, which typically do not address their electrical nature. This regulatory gap creates challenges in assessing the fire performance of PV systems. This paper presents a procedure to adapt a common test method used in some building codes to assess external fire conditions for roofs, while maintaining operative PV modules. Two configurations were tested: an organic PV thin film on a metallic sandwich panel and a glass–glass-encapsulated organic PV module. The tests were conducted under high voltage and current conditions to simulate the systems’ behavior within a larger PV array. Significant electric arcs were observed during testing of the metallic sandwich panel configuration without glass protection when subjected to high voltages or currents. In these cases, total heat release increased by at least 30% compared to non-electrically loaded scenarios or glass-insulated PV modules, likely due to a greater damaged surface area. Electric arcs created new ignition sources, damaging whole PV modules, whereas in the case with no electrical load, propagation flames advanced toward both the upper edge and the corners of the sample, ultimately damaging the entire triangular area above the fire source. The results indicate that the electrical characteristics of PV systems can significantly impact external fire spread behavior. The study identifies challenges in maintaining system activity during testing and simulating real scenarios and proposes for future research directions. Full article

The RED II Directive requires European Union member states to increase the share of renewable energy in the transport sector to at least 14% by 2030. In January 2024, Poland replaced E5 gasoline (95 octane) with E10, which contains up to 10% bioethanol derived from second-generation sources such as agricultural residues. The transition to E10 raises concerns about the ability of engine management systems to adapt to its different air–fuel ratio (AFR) requirements. The AFR for E10 (13.82) is 1.98% lower than for E5 (14.25) and 3.88% lower than for pure gasoline (14.7). Research conducted on a spark-ignition engine (with AFR regulation) using an exhaust gas analyzer demonstrated that during the combustion of E5 and E10 fuels with correctly adjusted AFR and operation at λ = 1, the use of E10 potentially increases CO₂ and NO_x emissions despite reductions in CO and HC. However, when calibrated for E5 and operated with E10 fuel, an increase in CO₂ and HC concentrations in the exhaust gases is observed, along with a reduction in CO and NO_x. This phenomenon is attributed to operation with lean mixtures, at λ = 1.02. This study investigates both the theoretical and experimental impact of this fuel transition. Fuel systems typically adjust engine operation based on exhaust gas analysis but cannot recognize fuel type, leading to incorrect λ values when the AFR differs from the ECU’s programming. Effective adaptation would require additional fuel composition sensors and editable ECU mappings. For older vehicles or small non-road engines, manual adjustments to injection or carburetor systems may be necessary. Full article

In the current investigation, a novel methodology was employed to assess iron powder as a recyclable and sustainable energy carrier. Concurrently, an examination of the modeling of iron powder ignition and the ensuing heat output from the burner was undertaken. The flame temperature was determined by examining the light intensity emitted by the particles as they melted, which is directly related to the particle’s cross-sectional area. An account of the characterization of the experimental procedure, validation, and calibration is presented. Through measurements, distinct one-to-one correlations have been established between the scales of flame combustion and the temperatures of particles of varying sizes of iron. Additionally, a theoretical model for the combustion of expanding particles, particularly iron, within the diffusion-limited regime has been rigorously developed. This model delves into the spectra acquired from particle flames within the burner, utilizing Partial Least Squares Regression (PLSR) and Principal Component Analysis (PCA). This study investigates the use of optical fiber spectroscopy to predict flame temperature and assess iron powder size. The aim was to investigate how different sizes of iron powder affect flame temperature and to create calibration models for non-destructive prediction. The study shows that smaller particles had an average temperature of 1381 °C while larger particles reach up to 1842 °C, demonstrating the significant impact of particle size on combustion efficiency. The results were confirmed using advanced statistical methods, including PLSR and PCA, with PCA effectively differentiating between particle sizes and PLSR achieving an R² value of 0.90 for the 30 µm particles. Full article

The smoldering of pine needle fuel beds (PNBs) has been a common subject of research because of its importance in initiating the rekindling of forest floor fires. Experimental studies of the coupling effects of the bulk density and external heat supply on smoldering in PNBs have been scarce up to now. In this study, laboratory smoldering experiments were conducted to study the coupling effects of bulk density (30–55 kg m⁻³) and heat supply (ignition-off temperature T_off = 190 °C and 230 °C). Different ignition modes were observed under the same conditions, including non- ignition (NI), flaming ignition (FI), and the smoldering-to-flaming (StF) transition. The results in this study showed that the bulk density had distinct effects on different ignition modes: the increase in the bulk density facilitated the StF transition but impeded the FI. The coupling effects between the bulk density and heat supply became more intricate, especially at lower bulk densities and at a reduced heat supply. Additionally, a simple energy balance equation was established to explain the coupling effects of bulk density and heat supply on ignition behavior. The critical mass loss rate (MLR) for the StF transition ranged from 0.01 g s⁻¹ to 0.03 g s⁻¹, while the critical MLR for FI was 0.035 g s⁻¹. The modified combustion efficiency (MCE) index for the StF transition decreased from approximately 79.6% to 70.1% as the density increased from 30 kg m⁻³ to 55 kg m⁻³. In contrast, the MCE for FI was approximately 90% across all the bulk densities. The StF transition delay time increased from 50 s at 30 kg m⁻³ to 1296 s at 55 kg m⁻³ when T_off = 230 °C. Further reduction in heat supply led to an increase in the delay time for the StF transition by diminishing the intensity of smoldering combustion. This work advances the fundamental understanding of how heat supply and bulk density impact smoldering ignition modes, ultimately aiding in the development of wildfire prevention strategies. Full article

Nowadays, emissions from internal combustion engines are a relevant topic of investigation, taking into account the continuous reduction of emission limits imposed by environmental regulatory agencies around the world, obviously as the result of earnest studies that have pointed out the impact on the human health of high levels of contaminants released into the environment. Over recent years, the use of biofuels has contributed to attenuating this environmental issue; however, new problems have been raised, such as NOx emissions tend to increase as the biofuel percentage in the fuel used in engines increases. In this research, the emissions of a compression ignition internal combustion engine modeled as a variable volume reactor with homogeneous combustion were numerically investigated. To analyze the combustion process, a detailed kinetics model tailored specifically for this purpose was used. The kinetics model comprised 30,975 chemical reactions involving 691 chemical species. Mixtures of fuel surrogates were then created to represent the fuel used in the Brazilian fuel marketplace, involving (i) fossil diesel—“diesel A”, (ii) soybean diesel—“biodiesel”, and (iii) hydrotreated vegetable oil— “HVO”. Surrogate species were then selected for each of the aforementioned fuels, and blends of those surrogates were then proposed as mixture M1 (diesel A:biodiesel:HVO—90:10:0), mixture M2 (diesel A:biodiesel:HVO—85:15:0), and mixture M3 (diesel A:biodiesel:HVO—80:15:5). The species allowed in the kinetics model included all the fuel surrogates used in this research as well as the target emission species of this study: total hydrocarbons, non-methane hydrocarbons, carbon monoxide, methane, nitrogen oxides, carbon dioxide, soot, and soot precursors. When compared to experimental trends of emissions available in the literature, it was observed that, for all the proposed fuel surrogates blends, the numerical approach performed in this research was able to capture qualitative trends for engine power and the target emissions in the whole ranges of engine speeds and engine loads, despite the CO and NOx emissions at specific engine speeds and loads. Full article

The Preboreal (11.75–10.70 ka BP) is still the least paleogeographically studied time interval in the central part of the East European Plain. High-resolution multi-proxy studies of lacustrine sediments at the Seltso site located in the Desna River floodplain (Dnieper River basin) were conducted. Radiocarbon dating, loss-on-ignition determination, sedimentological and palynological studies and identification of Non-Pollen Palynomorphs in lacustrine sediments allow us to reconstruct changes in vegetation caused by rapid warming at the Younger Dryas–Holocene boundary, short-term climatic fluctuations within the Preboreal and subsequent resumption of warming. Initial Preboreal warming reached its maximum at about 11.5 ka BP when a relatively dry continental climate existed. Between 11.4 and 11.2 ka BP, a short-term cooling corresponding to the Preboreal Oscillation in Greenland occurred, as indicated by a significant reduction of woody vegetation and expansion of open plant communities. In the Late Preboreal, approximately 11.2–10.7 ka BP, warming resumed, which was accompanied by a decrease in the climate continentality. Comparison with high-resolution lithological and palynological data from eight reliably dated sections of the central East European Plain indicates that in northwestern and central Europe, the impact of the Preboreal Oscillation cooling on the vegetation and the lake ecosystems’ development was probably somewhat stronger. Full article

Polymers are essential in several sectors, yet some applications necessitate surface modification. One practical and eco-friendly option is non-thermal plasma exposure. The present research endeavors to examine the impacts of dielectric barrier discharge atmospheric pressure plasma on the chemical composition and wettability properties of acrylonitrile butadiene styrene surfaces subject to the action of additive manufacturing. The plasma source was produced by igniting either helium or argon and then adjusted to maximize the operational conditions for exposing polymers. The drop in contact angle and the improvement in wettability after plasma exposure can be due to the increased oxygen-containing groups onto the surface, together with a reduction in carbon content. The research findings indicated that plasma treatment significantly improved the wettability of the polymer surface, with an increase of up to 60% for both working gases, while the polar index increased from 0.01 up to 0.99 after plasma treatment. XPS measurements showed an increase of up to 10% in oxygen groups at the surface of He–plasma-treated samples and up to 13% after Ar–plasma treatment. Significant modifications were observed in the structure that led to a reduction of its roughness by 50% and also caused a leveling effect after plasma treatment. A slight decrease in the glass and melting temperature after plasma treatment was pointed out by differential scanning calorimetry and broadband dielectric spectroscopy. Up to a 15% crystallinity index was determined after plasma treatment, and the 3D printing process was measured through X-ray diffraction. The empirical findings encourage the implementation of atmospheric pressure plasma-based techniques for the environmentally sustainable manipulation of polymers for applications necessitating higher levels of adhesion and specific prerequisites. Full article

Fires resulting from antecedent fires, known as exposure fires, can manifest across diverse environments, including suburban, urban, and rural areas. Notably, exposure fires represented by structure-destroying fires within the wildland–urban interface (WUI) can extend into non-WUI suburban and urban regions, presenting significant challenges. Leveraging data from the United States National Fire Incident Reporting System (NFIRS) spanning 2002 to 2020, this study investigates 131,739 exposure fire incidents impacting 348,089 features (incidents). We analyze reported economic costs, affected feature types, and property utilization patterns for these exposure fires. We also compare these exposure fires to information documented in other databases. Finally, we examine structure separation distance at residential dwellings and describe ignition pathways for selected fires. Reported property losses for some fire incidents amounted to USD 5,647,121,172, with content losses totaling USD 1,777,345,793. Prominent fire incident categories include buildings, vehicles, and natural vegetation fires, predominantly occurring in residential, outdoor, and storage areas. While the NFIRS lacked information on most major structure-destroying WUI fires, highlighting this analysis’s lack of statistical representation, it did provide insights into less extensive exposure fires, both WUI and non-WUI, unrecorded elsewhere. Our study reveals significant distinctions in the distribution of separation distances between damaged-to-damaged structures (average separation of 6.5 m) and damaged-to-not-damaged structures (average separation of 18.1 m). Notably, 84% of the incidents in exposure fires involved fire suppression defensive actions. These defensive actions contributed to the differences in structure separation distance distributions, highlighting the often-neglected role of these measures in assessing structure responses during WUI fires. We examined ignition pathways at select exposure fires, highlighting some common features involved in fire spread and challenges in documenting these pathways. Finally, we propose a set of idealized attributes for documenting exposure fires, accentuating the inherent difficulties in collecting such data across expansive geographical areas, particularly when striving for statistical representation. Our findings yield valuable insights into the multifaceted nature of exposure fires, informing future research and database development to aid in mitigating their impact on vulnerable communities. Full article

This study investigates the impact of different biofuels, such as pure hydrogenated vegetable oil, hydrogenated vegetable oil, and biobutanol, as well as their blends, on the non-energetic operational characteristics of a compression ignition internal combustion engine. The research investigations were conducted using a turbocharged direct injection compression ignition engine that was put within a Skoda Octavia 1.9 TDI automobile. Throughout the investigation, the primary emphasis was placed on analyzing energy characteristics such as power, brake-specific fuel consumption (BSFC), brake thermal efficiency (BTE), and other related factors. The analysis involved the utilization of multiple combinations of bio-based fuels, namely four mixes of HVO with biobutanol (HVO100, HVOB5, HVOB10, and HVOB20), which were subsequently compared to fossil diesel (D100). The findings of the study indicate that the utilization of HVO100 fuel results in notable reductions in power output and mass fraction when compared to D100 gasoline. HVO100 fuel demonstrates superior performance to D100 gasoline, exhibiting a range of 1.7% to 28% improvement in brake-specific fuel consumption. Additionally, at an engine speed of 4500 rpm, the use of HVO100 fuel leads to a decrease in brake thermal efficiency of 4.4%. Full article

In the unfortunate event of a fire, within the context of the evolution of façade fires, with a specific focus on the utilization of polystyrene thermal insulation (external thermal insulation composite system façades—ETICS façades), this study delves into the investigation of fires ignited by containers containing plastic bottles. Through an examination of the fluctuating temperatures within the affected room and its adjacent areas, as well as an assessment of the fire’s impact on polystyrene thermal insulation, this paper underscores the significance of incorporating non-combustible barriers into the building’s thermal insulation system. The tests conducted revealed that the temperature inside the room reached a maximum of 1100 °C, subsequently decreasing to 800 °C at a height of 2.5 m and approximately 400 °C at a height of 5 m. For this research, two 1100-L containers of household waste were employed, each weighing 45.5 kg and possessing a gross calorific value of 46.97 MJ/kg, with 10.7 kg of PET bottles inside, characterized by a higher calorific value of 23.90 MJ/kg as the source of the fire. Heat release rate highest values were obtained between 11 and 17 min, with a maximum value of 4919 kW. Thus, even in the absence of specific legislation, this study emphasizes the imperative need to establish safety distances for the storage of household waste away from the building’s façade to mitigate the risk of fire propagation, particularly in relation to materials such as polystyrene thermal insulation. Furthermore, in certain situations, extensive fire experiments on a grand scale, like the one undertaken in this research, hold a crucial position in confirming numerical findings for global researchers. This process assures the reliability and real-world usefulness of fire safety studies through the experimental outcomes presented in this investigation. Full article