Search Results (187)

Fire refers to a disaster caused by combustion that is uncontrolled in the temporal and spatial dimensions, occurring in diverse complex scenarios where timely and effective detection is crucial. However, existing fire detection methods are often challenged by the deformation of smoke and flames, resulting in missed detections. It is difficult to accurately extract fire features in complex backgrounds, and there are also significant difficulties in detecting small targets, such as small flames. To address this, this paper proposes a YOLO-Multi-scenario Fire Detector (YOLO-MFD) for multi-scenario fire detection. Firstly, to resolve missed detection caused by deformation of smoke and flames, a Scale Adaptive Perception Module (SAPM) is proposed. Secondly, aiming at the suppression of significant fire features by complex backgrounds, a Feature Adaptive Weighting Module (FAWM) is introduced to enhance the feature representation of fire. Finally, considering the difficulty in detecting small flames, a fine-grained Small Object Feature Extraction Module (SOFEM) is developed. Additionally, given the scarcity of multi-scenario fire datasets, this paper constructs a Multi-scenario Fire Dataset (MFDB). Experimental results on MFDB demonstrate that the proposed YOLO-MFD achieves a good balance between effectiveness and efficiency, achieving good effective fire detection performance across various scenarios. Full article

The combustion of fossil fuels is a major source of greenhouse gas emissions, drives climate change, and has intensified the search for cleaner energy alternatives such as biomass. Biomass derived from renewable organic materials, is considered a sustainable and carbon-neutral energy source. While biomass represents a renewable and clean energy source, its combustion, especially in pellet form, can produce various pollutants such as CO₂, SO₂, NO₂, CO, and PM. This study focuses on analyzing the combustion of six different pellet brands and the emissions they produce. A dedicated experimental procedure was designed and implemented to evaluate the combustion performance. The temperature shows a gradual increase in ambient temperature around 2.5 °C across all tests, with a similar behavior, the temperature of flue gas shows a similar behavior between tests with temperatures peaking around 300 °C and 340 °C. In the tests conducted, all pellets complied with the legal emission limits defined by legislation. The efficiency calculated using the direct method was lower by around 55%, primarily due to the use of an older boiler (manufactured in 2004) and short duration of the test. The indirect method shows better efficiency, around 70%, influenced by lower moisture content of the pellets. The results indicate that B pellets had a superior performance compared to the others evaluated. Full article

This paper explores cleaner and techno-economically viable solutions to provide electricity, heat, and cooling using green hydrogen (H₂) and green ammonia (NH₃) across the entire decarbonized value chain. We propose integrating a 100% hydrogen-fueled internal combustion engine (e.g., Jenbacher JMS 420) as a stationary backup solution and comparing its performance with other backup technologies. While electrochemical storage systems, or battery energy storage systems (BESSs), offer fast and reliable short-term energy buffering, they lack flexibility in relocation and typically involve higher costs for extended backup durations. Through five case studies, we highlight that renewable-based energy supply requires additional capacity to bridge longer periods of undersupply. Our results indicate that, for cost reasons, battery–electric solutions alone are not economically feasible for long-term backup. Instead, a more effective system combines both battery and hydrogen storage, where batteries address daily fluctuations and hydrogen engines handle seasonal surpluses. Despite lower overall efficiency, gas engines offer favorable investment and operating costs in backup applications with low annual operating hours. Furthermore, the inherent fuel flexibility of combustion engines eventually will allow green ammonia-based backup systems, particularly as advancements in small-scale thermal cracking become commercially available. Future studies will address CO₂ credit recognition, carbon taxes, and regulatory constraints in developing more effective dispatch and master-planning solutions. Full article

Antioxidant gel foams are promising materials for coal mine fire prevention due to their unique physicochemical properties. To address the limitations of conventional suppression methods under high-temperature conditions, this study investigates a newly developed antioxidant gel foam and its mechanism in inhibiting coal spontaneous combustion. A novel antioxidant gel foam was formulated by incorporating TBHQ and modified montmorillonite into a sodium alginate-based gel system. This formulation enhances the thermal stability, water retention, and free radical scavenging capacity of the gel. This study uniquely combines multi-scale experimental methods to evaluate the performance of this material in coal fire suppression. Multi-scale experiments, including FTIR, leakage air testing, programmed temperature rise, and small-scale fire extinction, were conducted to evaluate its performance. Experimental results indicate that the antioxidant gel foam exhibits excellent thermal stability in the temperature range of 200–500 °C. Its relatively high decomposition temperature enables it to effectively resist structural damage in high-temperature environments. During thermal decomposition, the gel releases only a small amount of gas, while maintaining the integrity of its internal micro-porous structure. This characteristic significantly delays the kinetics of coal oxidation reactions. Further research revealed that the spontaneous combustion ignition temperature of coal samples treated with the gel was significantly higher, and the oxygen consumption rate during spontaneous combustion was significantly reduced, indicating that the gel not only effectively suppressed the acceleration of the combustion reaction but also significantly reduced the release of harmful gases such as HCl. Scanning electron microscope analysis confirmed that the gel maintained a good physical structure under high temperatures, forming an effective oxygen barrier, which further enhanced the suppression of coal spontaneous combustion. These findings provide important theoretical and practical guidance for the application of antioxidant gel foams in coal mine fire prevention and control, confirming that this material has great potential in coal mine fire safety, offering a new technological approach to improve coal mine safety. Full article

This experimental study examines the particle-level combustion behavior of high-volatile bituminous coal and walnut shell particles in oxyfuel environments, with a particular focus on the gas-phase ignition characteristics and the structural development of volatile flames. Particles with similar size and shape distributions (a median diameter of about 126 µm and an aspect ratio of around 1.5) are combusted in hot flows generated using lean, flat flames, where the oxygen mole fraction is systematically varied in both CO₂/O₂ and N₂/O₂ atmospheres while maintaining comparable gas temperatures and particle heating rates. The investigation employs a high-speed multi-camera diagnostic system combining laser-induced fluorescence of OH, diffuse backlight-illumination, and Mie scattering to simultaneously measure the particle size, shape, and velocity; the ignition delay time; and the volatile flame dynamics during early-stage volatile combustion. Advanced detection algorithms enable the extraction of these multiple parameters from spatiotemporally synchronized measurements. The results reveal that the ignition delay time decreases with an increasing oxygen mole fraction up to 30 vol%, beyond which point further oxygen enrichment no longer accelerates the ignition, as the process becomes limited by the volatile release rate. In contrast, the reactivity of volatile flames shows continuous enhancement with an increasing oxygen mole fraction, indicating non-premixed flame behavior governed by the diffusion of oxygen toward the particles. The analysis of the flame stand-off distance demonstrates that volatile flames burn closer to the particles at higher oxygen mole fractions, consistent with the expected scaling of O₂ diffusion with its partial pressure. Notably, walnut shell and coal particles exhibit remarkably similar ignition delay times, volatile flame sizes, and OH-LIF intensities. The substitution of N₂ with CO₂ produces minimal differences, suggesting that for 126 µm particles under high-heating-rate conditions, the relatively small variations in the heat capacity and O₂ diffusivity between these diluents have negligible effects on the homogeneous combustion phenomena observed. Full article

A series of fire experiments were conducted in a 0.5 m × 0.5 m × 0.5 m room, and a single door-like opening was adopted. The height of the openings was 20 cm, and the width of the openings varied from 10 cm to 30 cm, with ventilation factors ranging from 0.0089 m^5/2 to 0.0268 m^5/2. The ventilation constant and combustion efficiency were studied and compared with those of other researchers. It was found that the so-called ventilation constant can hardly be a constant, and it varied greatly, around 0.357–0.436, at different ventilation conditions. The overall combustion efficiency varied greatly at different opening sizes and flow rates, and it was as low as 0.5, even when the flame was ejected. Full article

Particulate matter (PM) emissions from combustion-based heating systems have been identified as a major contributor to environmental issues and human health risks. Particularly, small-scale residential combustion was responsible for 58% of the total PM_2.5 emissions in Europe in 2020, with domestic heating using wood-based fuels accounting for around 56% of soot emissions. Reducing PM_2.5 emissions has become a major goal of European environmental policies, which have included it among the key targets of the Zero Pollution Action Plan. In this framework, this study presents a performance analysis of a newly developed PM abatement system consisting of a passive cyclone abatement system (PCAS) specifically designed for small residential pellet stoves. The system was tested under steady-state and non-steady-state operating conditions. The experimental results showed that the PCAS abatement system effectively captured PM at a rate of 10.64 mg/MJ, with great efficiency in capturing particles ≥ 10 µm. The heavy metal content in the captured material was below the limit values for agricultural application-destined soil. A Life Cycle Assessment showed that the PCAS could achieve net-zero PM emissions in 1 year and 8 months. Finally, the economic analysis revealed that the PCAS is significantly more cost-effective: over a 10-year period, it could save up to €4000 in installation, maintenance, and energy costs compared to conventional active systems. These findings highlight the effectiveness of this design of PCAS as in reducing PM emissions from residential heating systems and provide valuable insights for the development of future abatement systems. Full article

In this paper, developed in the context of the Clean Sky 2 project SIENA (Scalability Investigation of hybrid-Electric concepts for Next-generation Aircraft), an extensive analysis is carried out to identify and accelerate the development of innovative propulsion technologies and architectures that can be scaled across five aircraft categories, from small General Aviation airplanes to long-range airliners. The assessed propulsive architectures consider various components such as batteries and fuel cells to provide electricity as well as electric motors and jet engines to provide thrust, combined to find feasible aircraft architectures that satisfy certification constraints and deliver the required performance. The results provide a comprehensive analysis of the impact of key technology performance indicators on aircraft performance. They also highlight technology switching points as well as the potential for scaling up technologies from smaller to larger aircraft based on different hypotheses and assumptions concerning the upcoming technological advancements of components crucial for the decarbonization of aviation. Given the considered scenarios, the common denominator of the obtained results is hydrogen as the main energy source. The presented work shows that for the underlying models and technology assumptions, hydrogen can be efficiently used by fuel cells for propulsive and system power for smaller aircraft (General Aviation, commuter and regional), typically driven by propellers. For short- to long-range jet aircraft, direct combustion of hydrogen combined with a fuel cell to power the on-board subsystems appears favorable. The results are obtained for two different temporal scenarios, 2030 and 2050, and are assessed using Payload-Range Energy Efficiency as the key performance indicator. Naturally, introducing such innovative architectures will face a lack of applicable regulation, which could hamper a smooth entry into service. These regulatory gaps are assessed, detailing the level of maturity in current regulations for the different technologies and aircraft categories. Full article

Compression via pressure waves is an effective but specific way of compressing gases. This paper presents a broad overview of work related to the use of unsteady processes in the construction of micro-engines. The main advantages of wave rotors, such as a low rotor speed, self-cooling channels, high compression in a single stage, and the possibility of operating at a very small geometric scale, are addressed, and their disadvantages, such as the requirement of the precise synchronization of wave processes and poor torque-generation properties, are also outlined. This review highlights the possibility of operating at a geometric scale, which conventional solutions have failed to achieve. In the thermodynamic cycle of a micro-engine, a compression process carried out in an unsteady manner is superior in efficiency to stationary solutions. On the contrary, in the expansion process, fluid inertia is an obstacle to the full utilization of the thermal energy transferred to the fluid in the combustion chamber. The best solution is, therefore, a favorable combination of both features, leading to unsteady compression and steady-state expansion in the heat engine cycle. This article presents an overview of the existing technical solutions and published research results devoted to the construction of pressure wave compression micro-engines: patents, scientific publications describing various research methods, numerical calculations, and the experimental results of unusual technical solutions. Characteristic solutions and problems arising in the development of these methods, which range from superchargers to autonomous engines, are presented and discussed. Directions for further research are suggested. Full article

Eco-driving is a key strategy for reducing energy consumption and emissions in electric vehicles (EVs) and internal combustion engine (ICE) vehicles. However, research gaps remain regarding its effectiveness across different driving environments, vehicle types, transmission systems, and contexts. This research evaluates eco-driving efficiency in urban and interurban settings, comparing small (Caceres) and large (Madrid) cities and assessing EVs ICE with direct, manual, and automatic transmissions. The authors conducted a large-scale driving experiment in Spain, with over 500 test runs across different road types. Results in the large city show that eco-driving reduces energy consumption by 30.4% in EVs on urban roads, benefiting from regenerative braking, compared to 10.75% in manual ICE vehicles. Automatic ICE vehicles also performed well, with 29.55% savings in local streets. In interurban settings, manual ICE vehicles achieved the highest savings (20.31%), while EVs showed more minor improvements (11.79%) due to already optimized efficiency at steady speeds. The small city showed higher savings due to smoother traffic flow, while single-speed transmissions in EVs enhanced efficiency across conditions. These findings provide valuable insights for optimizing eco-driving strategies and vehicle design. Future research should explore AI-driven eco-driving applications and real-time optimization to improve sustainable mobility. Full article

In this study, the potential use of corn-based crude bioethanol was investigated as an alternative energy source for marine fuel oil under increasingly stringent maritime emissions regulations. A small-scale combustion chamber with a capacity of approximately 1 ton was developed, and comparative combustion tests were conducted with various fuel types, including MGO, diesel, kerosene, and BE100. In addition, component analysis was performed and compared using the ISO-8217 method. Complete combustion of the fuel was performed under the same experimental conditions of stable atmospheric pressure and temperature. BE100 exhibited an 8.3% increase in the oxygen concentration and a 5.9% reduction in the carbon dioxide emissions compared to MGO. Despite the low nitrogen oxide (NOx) emissions of MGO at approximately 34.4 ppm, BE100 demonstrated superior reduction potential, with a reading of 1.9 ppm. Sulfur oxides (SOx) were not detected in any of the fuels tested, underscoring the high quality of the currently available low-sulfur MGO. The exhaust gas temperatures were reduced by approximately 44.6% when using BE100, from 367.1 °C for MGO to 203.2 °C for BE100. However, the combustion efficiency of BE100 was 8.3% lower than that of MGO. While crude bioethanol shows promise in reducing exhaust gas emissions, its limited thermal output poses a challenge for direct substitution. Future studies should investigate the development of blended fuels combining bioethanol and conventional marine fuels to improve the performance and sustainability. Full article

Solid recovered fuel (SRF) is highly suited for thermal treatment, but its low bulk density and other physical properties limit the number of compatible energy systems that can effectively process it. This study presents the findings on SRF energy utilisation, focusing on mechanical treatment and a novel approach to its small-scale co-combustion with certified softwood (SW) pellets and catalytic flue gas control. In this study, the processes of certified SRF feedstock characterisation and mechanical treatment were thoroughly examined. Unique SRF pellets of proper mechanical properties were experimentally prepared for real-scale experiments. Mechanical and chemical properties, such as mechanical resilience, toughness, moisture and heating value, were examined and compared with standard SW A1 class pellets. The prepared SRF pellets possessed an energy density of 30.5 MJ∙kg⁻¹, meeting the strict requirements from multiple perspectives. The influence of pelletisation temperature on pellet quality was investigated. It was found that increased resilience and a water content of 1.59% were achieved at a process temperature equal to 75 °C. Moreover, the moisture resilience was found to be significantly better (0.5 vs. 14.23%) compared with commercial SW pellets, while the hardness and durability values were reasonably similar: 40.7 vs. 45.2 kg and 98.74 vs. 98.99%, respectively. This study demonstrates that SRF pellets, with their improved mechanical and energy properties, are a viable alternative fuel, from a technical standpoint, which can be fully utilised in existing combustion units. Full article

Cooking with firewood in inefficient stoves primarily affects the rural population in poor and developing countries, usually lacking access to clean and modern energy sources. La Guajira, Colombia, is especially affected, with 40% to 60% of the departmental households relying on firewood, which increases to 80% in rural areas. In the department, only 40.4% of the population have access to natural gas, which drops to 6% in the indigenous reservations, while 68.4% have access to electricity, which reduces to 22% in indigenous reservations. Rural areas with agricultural production in the department can benefit from biomass wastes to address firewood consumption. This study quantified the agricultural biomass waste inventory in La Guajira to assess their availability for energy valorization as cooking fuel or, when possible, for electricity generation. The geolocalization of biomass wastes and rural communities was developed to overlap biomass production with the demand for firewood. Moreover, briquetting, anaerobic digestion, and direct combustion were considered small- and medium-scale options for the energy valorization of biomass wastes. Results highlighted the department’s yearly production of 292,760 to 522,696 t of agricultural biomass wastes between 2010 and 2023. These wastes could yield an estimated 381 to 521 TJ/year of electricity using direct combustion, coinciding with some 21% to 28% of the electricity demand in 2022 in La Guajira. Furthermore, this electricity potential could replace 57% to 78% of the demand for firewood in the department using electric stoves. Moreover, anaerobic digestion could produce from 8.6 to 10 million m³/year, enough to replace between 16% and 18% of the demand for firewood using biogas stoves. Finally, briquettes could replace between 28% and 49% of the firewood demand, considering the adoption of improved biomass stoves. Considering that direct combustion and anaerobic digestion technologies would be efficient on the medium scale, briquettes surfaced as the most viable approach at the small scale to take advantage of agricultural wastes to replace firewood in households in rural areas. Full article

Timber-clad facades, traditionally prevalent in North America and Scandinavia, are gaining popularity in central Europe and the UK for applications beyond low-rise buildings. Timber differs from typical cladding materials, such as masonry, due to its non-uniformity, combustibility, and moisture sensitivity, requiring unique design considerations to manage these characteristics. This paper investigates the fire hazards associated with timber cladding, particularly focusing on thermally modified timber, motivated by the 2019 Samuel Garside House fire in the UK. The study aims to address five key research questions: (1) the impact of thermal modification on external fire spread hazards, (2) the fire risk associated with slatted timber configurations, (3) the effectiveness of fire-retardant treatments, (4) the correlation between small-scale standard tests and large-scale behaviours, and (5) the adequacy of current fire safety guidance in addressing these hazards. The experimental campaign involved four timber sample variants: (i) virgin timber, (ii) new thermally modified timber, (iii) aged thermally modified timber, and (iv) fire-retardant-treated thermally modified timber. These samples were tested across four different methods, including the single-flame source test, mass loss cone test, single burning item (SBI) test, and an intermediate-scale test. Results indicated that thermal modification slightly increased the peak heat release rate (HRR) compared to virgin timber. The configuration of timber slats significantly impacted HRR, with vertically oriented slats demonstrating higher HRR than horizontally oriented flat cedar cladding. Fire-retardant treatments substantially reduced HRR, achieving Euroclass B in vertical slatted configurations. However, the long-term efficacy of these treatments under ageing and weathering conditions remains unexplored. This research underscores the need for clarifications in the guidance in timber cladding design, considering the observed fire hazards in different slat configurations and the efficacy of fire-retardant treatments. Full article

This study investigates the performance of DC corona discharge electrostatic precipitators (ESPs) for NO conversion to increase DeNO_x technologies’ efficiency for small-scale biomass combustion systems. Experiments were conducted using a 5 kW automatic wood pellet domestic heat source with combustion gas treated in a specially designed ESP operated in both positive and negative corona modes, resulting in a reduction in NO concentrations from 130 mg/m³ to 27/29 mg/m³ for positive/negative polarities (at 0 °C and 101.3 kPa). NO conversion efficiency was evaluated across a range of specific input energies (SIEs) from 0 to 50 J/L. The results demonstrate that DC corona ESPs can achieve up to 78% NO reduction, with positive corona demonstrating a greater energy efficiency, requiring a lower SIE (35 J/L) compared to the negative corona mode (48 J/L). A detailed analysis of reaction pathways revealed distinct conversion mechanisms between the two modes. In positive corona, dispersed active species distribution led to more uniform NO conversion, while negative corona exhibited concentrated reaction zones with about 20% higher ozone production. The reactions involving O and OH radicals were more important in positive corona, whereas ozone-mediated oxidation dominated in negative corona. The research results demonstrate that ESP technology with DC corona offers a promising, energy-efficient solution for NO_x control in small-scale combustion systems. Full article