Search Results (482)

Variable-thrust liquid rocket engines are essential for precision landing in deep-space exploration, reusable launch vehicle recovery, high-accuracy orbital maneuvers, and emergency obstacle evasions of space drones. However, with the increasingly complex space missions, challenges remain with the development of different technical schemes. In view of these issues, this paper systematically reviews the technology’s evolution through mechanical throttling, electromechanical precision regulation, and commercial space-driven deep throttling. Then, the development of key variable thrust technologies for liquid rocket engines is summarized from the perspective of thrust regulation and control strategy. For instance, thrust regulation requires synergistic flow control devices and adjustable pintle injectors to dynamically match flow rates with injection pressure drops, ensuring combustion stability across wide thrust ranges—particularly under extreme conditions during space drones’ high-maneuver orbital adjustments—though pintle injector optimization for such scenarios remains challenging. System control must address strong multivariable coupling, response delays, and high-disturbance environments, as well as bottlenecks in sensor reliability and nonlinear modeling. Furthermore, prospects are made in response to the research progress, and breakthroughs are required in cryogenic wide-range flow regulation for liquid oxygen-methane propellants, combustion stability during deep throttling, and AI-based intelligent control to support space drones’ autonomous orbital transfer, rapid reusability, and on-demand trajectory correction in complex deep-space missions. Full article

Efficient plastic waste end-of-life management is a serious worldwide environmental issue motivated by growing waste production and negative effects of wrongful disposal. This study presents a comparative overview of plastic waste management regimes within the European Union (EU), the United States of America (USA), and Romania, ranked with circular economy goals. By using the United States Environmental Protection Agency (US EPA) Waste Reduction Model (WARM), version 16, the study provides a quantified score to greenhouse gas (GHG) emissions within three large options of management: recycling, energy recovery through combustion, and landfilling. The model setup utilizes region-specific information on legislation, base technology, and recycling efficiency. The outcomes show that recycling always entails net GHG emissions reductions, i.e., −4.49 kg CO_2e/capita/year for EU plastic waste and −20 kg CO_2e/capita/year for USA plastic waste. Combustion and landfilling have positive net emissions from 1.76 to 14.24 kg CO_2e/capita/year. Economic indicators derived from the model also show significant variation: salaries for PET management amounted to USD 2.87 billion in the EU and USD 377 million in the USA, and tax collection was USD 506 million and USD 2.01 billion, respectively. The conclusions highlight the wider environmental and socioeconomic benefits of recycling and reinforce its status as a cornerstone of circular-economy sustainable plastic waste management and a strategic element of national development agendas, with special reference to Romania’s national agenda. Full article

Cattle manure accounts for approximately one-third of the total livestock manure produced in the Republic of Korea and is typically composted. To elucidate its feasibility as a renewable resource, this study evaluated the conversion of cattle manure into a solid biofuel and the nutrient recovery potential of its combustion residues. Solid fuel was prepared from cattle manure collected in Gyeongsangbuk-do, Korea, and its fuel characteristics and ash composition were analyzed after combustion. Combustion tests conducted using a dedicated solid fuel boiler showed that an average lower heating value of 13.27 MJ/kg was achieved, meeting legal standards. Under optimized combustion, CO and NO_x emissions (129.9 and 41.5 ppm) were below regulatory limits (200 and 90 ppm); PM was also within the 25 mg/Sm³ standard. The bottom ash contained high concentrations of P₂O₅ and K, and its heavy metal content was below the regulatory threshold, suggesting its potential reuse as a fertilizer material. Although the Zn concentration in the fly ash exceeded the standard, its quantity was negligible. Therefore, the solid fuel conversion of cattle manure can become a viable and environmentally sustainable solution for both bioenergy production and nutrient recycling, contributing to improved waste management in livestock operations. Full article

Petroleum oily sludge (OLS), a hazardous by-product of the petroleum industry, and high-alkali lignite (HAL), an underutilized low-rank coal, pose significant challenges to sustainable waste management and resource efficiency. This study systematically investigated the combustion behavior, reaction pathways, and gaseous-pollutant-release mechanisms across varying blend ratios, utilizing integrated thermogravimetric-mass spectrometry analysis (TG-MS), interaction analysis, and kinetic modeling. The key findings reveal that co-combustion significantly enhances the combustion performance compared to individual fuels. This is evidenced by reduced ignition and burnout temperatures, as well as an improved comprehensive combustion index. Notably, an interaction analysis revealed coexisting synergistic and antagonistic effects, with the synergistic effect peaking at a blending ratio of 50% OLS due to the complementary properties of the fuels. The activation energy was found to be at its minimum value of 32.5 kJ/mol at this ratio, indicating lower reaction barriers. Regarding gas emissions, co-combustion at a 50% OLS blending ratio reduces incomplete combustion products while increasing CO₂, indicating a more complete reaction. Crucially, sulfur-containing pollutants (SO₂, H₂S) are suppressed, whereas nitrogen-containing emissions (NH₃, NO₂) increase but remain controllable. This study provides novel insights into the synergistic mechanisms between OLS and HAL during co-combustion, offering foundational insights for the optimization of OLS-HAL combustion systems toward efficient energy recovery and sustainable industrial waste management. Full article

This study examines the influence of particle size on the flotation kinetics parameters of both raw and waste fine coal originating from the anthracite mine “Vrška Čuka”, Serbia. Flotation kinetics modeling was performed using MATLAB for nonlinear regression analysis, based on coal flotation test data. The correlation between total combustible recovery and flotation time was determined using the following models: Classical, Klimpel, Kelsall, Modified Kelsall, and Fully Mixed. The coefficients of determination range from 0.9724 (the Klimpel model) to 1 (the modified Kelsall model) for raw coal and from 0.8609 (the Klimpel model) to 0.9981 (the modified Kelsall model) for waste coal. Although both the Classical and Modified Kelsall models demonstrated a good correlation with the experimental data, the Modified Kelsall model provided a slightly better fit. The maximum values of the flotation rate constant (k) for both coals were obtained for the particle size-class (−0.1 + 0.053) mm for the Classical model and (−0.2 + 0.1) mm for the modified Kelsall model. The relation between flotation kinetics constant (k) and average particle size value (d_sr) was estimated for the Classical model and the modified Kelsall model. It was observed that the flotation kinetics constant (k) for coal particle size could be predicted satisfactorily. Full article

Data scarcity hampers the implementation of circular economy (CE) in rural historical small towns (HSTs) where traditional agricultural practices persist outside formal monitoring systems. In this regard, this study proposes and tests an estimation framework to quantify agricultural waste flows and energy recovery potential. The methodology combines waste generation coefficients from peer-reviewed literature with administrative data to generate actionable CE assessments. Application to four Sicilian HSTs within the Local Action Group (LAG) “Terre dell’Etna e dell’Alcantara” exhibits substantial waste generation potential despite their small size. The agricultural enterprises generate an estimated 6930–7130 tons of annual agricultural waste under moderate production scenarios, comprising grape pomace (3250 tons), pruning residues (3030 tons), and mixed processing wastes (650–850 tons). The energy recovery potential ranges from 20–30 TJ through direct combustion to 4.9–8.1 TJ via anaerobic digestion. Sensitivity analysis indicates balanced contributions from all three key parameters (enterprise density, yields, and waste coefficients), each accounting for 31–35% of output variance. The framework provides resource-constrained municipalities with a cost-effective tool for preliminary CE assessment, enabling identification of priority interventions without expensive primary data collection. From a managerial perspective, local administrators can leverage this tool to transform routine administrative data into actionable CE strategies. Full article

Electric passenger vehicles are set to dominate the European car market, driven by EU climate policies and the 2035 ban on internal combustion engine production. This study assesses the sustainability of this transition, focusing on global warming potential and Critical Raw Material (CRM) extraction throughout its life cycle. The intensive use of CRMs raises environmental, economic, social, and geopolitical concerns. These materials are scarce and are concentrated in a few politically sensitive regions, leaving the EU highly dependent on external suppliers. The extraction, transport, and refining of CRMs and battery production are high-emission processes that contribute to climate change and pose risks to ecosystems and human health. A Life Cycle Assessment (LCA) was conducted, using OpenLCA software and the Ecoinvent 3.10 database, comparing a Peugeot 308 in its diesel and electric versions. This study adopts a cradle-to-grave approach, analyzing three phases: production, utilization, and end-of-life treatment. Key indicators included Global Warming Potential (GWP100) and Abiotic Resource Depletion Potential (ADP) to assess CO₂ emissions and mineral resource consumption. Technological advancements could mitigate mineral depletion concerns. Li-ion battery recycling is still underdeveloped, but has high recovery potential, with the sector expected to expand significantly. Moreover, repurposing used Li-ion batteries for stationary energy storage in renewable energy systems can extend their lifespan by over a decade, decreasing the demand for new batteries. Such innovations underscore the potential for a more sustainable electric vehicle industry. Full article

When there are several different types of heat-storage ceramic bricks (checkers) that can be arranged in a regenerative combustion system, one must find an optimal arrangement (with the highest long-term Waste Heat Recovery Ratio) of these checkers, possibly of different types, in this regenerative combustion system. However, the number of possible arrangements of checkers in a heat regenerator could be huge. For example, when 5 different types of checkers are available for each of 14 positions in a heat regenerator, the total number of possible arrangements of checkers is 6,103,515,625. It is impractical to completely evaluate the efficiency of each of the 6,103,515,625 arrangements of checkers by 3D CFD simulations on Ansys Fluent. Here, we propose an optimization algorithm by tree search to tackle this optimization problem. This tree search method is motivated by the recent applications of Artificial Intelligence, based on combination of Deep Learning with Monte-Carlo Tree Search, to the incredibly complicated board game Go. Empirical evidence shows that this simple tree search algorithm leads to fast convergence of an optimization search and successfully suggests the optimal arrangement of checkers. This simple tree search method/algorithm may effectively enhance the thermal efficiency of a regenerative combustion system. Full article

Hybrid-energy vessels offer significant advantages in reducing carbon emissions and air pollutants by integrating traditional internal combustion engines, electric motors, and new energy technologies. However, during operation, the high reliance of hybrid-energy ships on networks and communication systems poses serious data security risks. Meanwhile, the complexity of energy scheduling presents challenges in obtaining feasible solutions. To address these issues, this paper proposes an innovative two-stage security optimization scheduling framework aimed at simultaneously improving the security and economy of the system. Firstly, the framework employs a CNN-LSTM hybrid model (WOA-CNN-LSTM) optimized using the whale optimization algorithm to achieve real-time detection of false data injection attacks (FDIAs) and post-attack data recovery. By deeply mining the spatiotemporal characteristics of the measured data, the framework effectively identifies anomalies and repairs tampered data. Subsequently, based on the improved multi-objective whale optimization algorithm (IMOWOA), rapid optimization scheduling is conducted to ensure that the system can maintain an optimal operational state following an attack. Simulation results demonstrate that the proposed framework achieves a detection accuracy of 0.9864 and a recovery efficiency of 0.969 for anomaly data. Additionally, it reduces the ship’s operating cost, power loss, and carbon emissions by at least 1.96%, 5.67%, and 1.65%, respectively. Full article

This study explores innovative strategies for decarbonizing sludge thermal treatments used in electrical power generation, with a focus on integrating sensor technologies and artificial intelligence. Sludge, a carbon-intensive byproduct of wastewater treatment, presents both environmental challenges and opportunities for energy recovery. The paper provides a comprehensive analysis of thermal processes such as pyrolysis, gasification, co-combustion, and emerging methods, including hydrothermal carbonization and supercritical water gasification. It evaluates their carbon mitigation potential, energy efficiency, and economic feasibility, emphasizing the importance of catalyst selection, carbon dioxide capture techniques, and reactor optimization. The role of real-time monitoring via sensors and predictive modeling through artificial intelligence (AI) is highlighted as critical for enhancing process control and sustainability. Case studies and recent advances are discussed to outline future pathways for integrating thermal treatment with circular economy principles. This work contributes to sustainable waste-to-energy practices, supporting global decarbonization efforts and advancing the energy transition. Full article

This paper deals with combustion air humidification for application with a biomass boiler and a spray flue gas condenser. The use of a combustion air humidifier increases the dew point temperature of the flue gas, thereby increasing the potential for heat recovery in the flue gas condenser and increasing the amount of heat supplied to the thermal system. The air humidification process in a counter current spray humidifier was experimentally analysed under conditions corresponding to the use before a biomass boiler with a flue gas condenser. For air heating and humidification, temperature factor values of up to 0.90 can be obtained; this value is mainly influenced by the ratio of the spray water and humidified air flow rates. The volumetric heat transfer coefficient is significantly affected by the humidified air velocity, although this velocity is negligible compared to the counter current spray water velocity. The volumetric heat transfer coefficient reaches higher values at higher spray water temperatures and therefore higher air heating. The whole process is also affected by the saturation of the incoming air, where the dew point temperature of the air drawn in from the surroundings is lower than its temperature. These results can be used as basic information for the design of combustion air humidifiers, for the selection of their operating parameters, and for a basic balancing of the energy contribution of the combustion air humidifier before a more detailed design of the whole system. Full article

Prolonged conflicts in Iraq over the past four decades have profoundly disrupted environmental systems, not only through immediate post-conflict emissions—such as residues from munitions and explosives—but also via long-term infrastructural collapse, population displacement, and unsustainable resource practices. Despite growing concern over air quality in conflict-affected regions, comprehensive assessments integrating long-term data and localized measurements remain scarce. This study addresses this gap by analyzing the environmental consequences of sustained instability in Mosul, focusing on air pollution trends using both remote sensing data (1983–2023) and in situ monitoring of key pollutants—including PM_2.5, PM₁₀, TVOCs, NO₂, SO₂, and formaldehyde—at six urban sites during 2022–2023. The results indicate marked seasonal variations, with winter peaks in combustion-related pollutants (NO₂, SO₂) and elevated particulate concentrations in summer driven by sandstorm activity. Annual average concentrations of all six pollutants increased by 14–51%, frequently exceeding WHO air quality guidelines. These patterns coincide with worsening meteorological conditions, including higher temperatures, reduced rainfall, and more frequent storms, suggesting synergistic effects between climate stress and pollution. The findings highlight severe public health risks and emphasize the urgent need for integrated urban recovery strategies that promote sustainable infrastructure, environmental restoration, and resilience to climate change. Full article

The Combined Cycle Combined Heat and Power (CCCHP) systems are an effective way to improve energy efficiency and reduce emissions. This paper examines the energy and environmental impact of CCCHP combustion using waste biomass like the biomass of spent wash (SW), waste crankcase oil (WCO), and bagasse (BA) using an advanced Ebsilon Professional 16 software simulation model. The simulations were designed to achieve 150 MW total power output and 25 MW heating energy. Simulation results indicate that the minimum fuel feed requirement of a 10.762 kg/s flow rate was recorded at the highest calorific value (CV) fuel briquette of 1:8 ratio BA–WCO. The BA–WCO system demonstrates a significantly higher heat recovery capacity in the heat recovery steam generator (HRSG) compared to the BA–SW system. At a 1:8 ratio, it recovers 1463 kJ/kg versus 583 kJ/kg, and 1391 kJ/kg versus 498 kJ/kg at a 1:3 ratio. The CCCHP efficiency was much higher for BA–WCO than those developed from spent wash–bagasse, yielding up to 41.1% compared to a maximum of 26.71%. Furthermore, the BA–WCO system showed a better result than the BA–SW CCCHP system by emitting a low amount of flue gas with low temperature. Full article

Oil shale, an unconventional oil and gas resource, can generate the required hydrocarbons through high-temperature pyrolysis. In situ conversion extraction technology utilizes downhole heaters to directly inject high-temperature heat into the oil shale layer to achieve the effect of oil and gas recovery. For the metal material components of the combustion heaters, the uneven temperature fields experienced during the start of operations, processing, and end of operations can lead to fatigue conditions, such as high-temperature creep, micro-damage, and micro-deformation due to thermal effects. To prevent the occurrence of the aforementioned issues, it is necessary to conduct fatigue life analysis of downhole combustion heaters. By combining actual combustion heater operation experiments with finite element simulation, this paper analyzes the impact of temperature, structure, and stress amplitude on the fatigue life of heaters. The results indicate that the fatigue life of the heaters is most significantly influenced by the metal gaskets, and the higher the exhaust gas temperature, the lower the fatigue life of the heater. Heating operations significantly reduce the fatigue life of the heater, while cooling operations have almost no effect on the fatigue life. Circular-pore metal gaskets have a higher fatigue life than those with a square hole shape. Considering only the thickness of the metal gaskets, the thicker the gasket, the higher the fatigue life. Stress amplitude has the most significant impact on the fatigue life of the heater; when the stress amplitude is doubled, the metal gaskets quickly undergo fatigue damage. Full article

A new type of hydrogen, produced in situ in petroleum reservoirs, is proposed. This technology is based on ex situ catalytic gasification of biomass, combining two thermal enhanced oil recovery techniques currently used in industrial fields: cyclic steam stimulation and in situ combustion. This hydrogen, named “light-blue hydrogen”, is produced in reservoirs, like naturally occurring white hydrogen, and from fossil fuels, like blue hydrogen. The color light blue results from the blending of white and blue. This approach is particularly suitable for mature petroleum reservoirs, which are in the final stages of production or no longer producing oil. This manuscript describes the method for producing light-blue hydrogen in situ, its commercial application prospects, and the challenges for developing and scaling up this technology. Full article