Current Issue : April-June Volume : 2026 Issue Number : 2 Articles : 5 Articles
The reactivity of methane fuel was numerically studied to compare the effects of CO2 and H2O dilution of hot oxidizer atmospheres on combustion modes and flame characteristics. A nonpremixed small scale burner at 8.6kW thermal load forming central fuel jet flame in coflow oxidizer atmosphere was employed. The inlet temperature and oxidizer level were assumed to be constant to scrutinize the pure effects of the varying molar fraction of the diluents on flame parameters. The results show that the maximum flame temperature is around the same level of 1665 K for 20%H2O and 20%CO2 cases with flamelet model. H2O dilution of the hot oxidizer enhances the combustion stability, while keeping mild behavior, whereas CO2 dilution maintains an interesting locally varying combustion mode by consuming methane fuel in a longer axial distance and forming temperature jump. The calculated temperature variations show that the varying combustion parameters emerge mainly from the physical effects. It is revealed that the physical effects occurring from CO2 dilution reduce the calculated Damköhler number (Da). However, H2O dilution maintains a more uniform KðrÞ: value distribution, which is defined to quantify the degree of reduction in methane fuel reactivity, by eliminating temperature jump and maintaining combustion stability....
In 2024, synthetic fuels regained attention as potential low-emission alternatives for internal combustion engines (ICEs), particularly in sectors where electrification remains challenging. This paper compares the estimated CO2 emission factors of fossil-based fuels and synthetic fuels blended with 20% bioethanol under standardized usage conditions. A key finding is that the emission factor of synthetic fuels is highly dependent on the carbon intensity of the electricity used to produce green hydrogen via electrolysis. Using the projected EU electricity mix for 2030, synthetic fuels show no clear advantage over fossil fuels. However, with a cleaner electricity mix expected by 2050, their emission factor becomes significantly lower. From an economic standpoint, the viability of synthetic fuel production largely depends on reducing green hydrogen costs of €1.50–2.00 per kg through technological advancements and large-scale deployment. This analysis offers a realistic perspective on when and how synthetic fuels could contribute to climate objectives and outlines the technical and economic conditions necessary for their environmental and market viability....
Mercury adsorption/oxidation plays a crucial role in mercury transformation during coal combustion. To gain an intuitive understanding of the adsorption/oxidation mechanisms between mercury and fly ash, changes in mercury speciation of fly ash before and after Hg adsorption were investigated using temperature-programmed decomposition–atomic fluorescence spectroscopy (TPD-AFS). The results directly reveal that the primary adsorption/ oxidation mechanism between mercury and fly ash is the heterogeneous oxidation reaction of Hg0 to HgCl2. The mercury adsorption capacity exhibits a strong positive correlation with both the unburned carbon (UBC) content and the specific surface area (SSA) of the fly ash, whereas the presence of metal oxides has a negligible effect on mercury adsorption. Higher inlet concentrations of Hg0 enhance mercury adsorption, while flue gas components such as N2, O2, and CO2 have minimal influence on mercury adsorption....
The depletion of fossil fuel supplies and the harmful environmental effects of combustion have emerged as significant issues. One viable approach to address these challenges is optimizing fuel injection timing to improve diesel engine performance. This work studies the effects of ignition timing (IT) and premixed ratio (PR) on the performance of a diesel engine at various combustion durations (CDs) and engine loads using the Multiple Vibe 2-Zone model of the AVL BOOST program. The predictive models of optimal ITs according to CD, PR, and engine load were established based on the engine's maximum power and minimum brake-specific fuel consumption. The findings show that optimal IT and CD correlations are linear at every PR and engine load. The optimal IT rises with increasing CD and reducing PR and engine load. CD has the most significant effect on optimal IT, followed by PR, and engine load has the least influence. The largest differences in optimal IT for the maximum torque and power are 1.0, 2.3, and 11.1 crank angle degrees when changing the engine load, PR, and CD, respectively. Meanwhile, for the optimum IT to achieve minimum brake-specific fuel consumption, those corresponding values are 1.0, 2.0, and 11.0 crank angle degrees. This study aids in lowering the resources, time, and cost needed to conduct experiments to determine the ideal injection timing of the engine....
The development of advanced catalytic technologies for the combustion of low‐concentration methane is crucial for minimizing unburned CH4 emissions, consequently improving the eco‐efficiency of natural gas vehicles and power plants. The integration of effective catalysts into existing systems with minimal modifications is of paramount importance. Porous ceramic composites offer a promising alternative to traditional powder catalysts due to their high surface area, excellent thermal stability, adjustable porosity, and prolonged catalytic durability. This study introduces a trace Pd–incorporated SnO2 porous ceramic catalyst (Pd/ SnO2) fabricated using the spark plasma sintering (SPS) technique. The synthesis process uses a NaCl salt template to create a porous structure and graphite to improve Pd loading and dispersion on the SnO2 surface. An optimized 10 wt.% graphitedecorated Pd/SnO2 porous ceramic catalyst, containing a trace Pd loading of 0.17 wt.%, achieved a low T90 of 427°C during methane reforming tests and maintained stable catalytic performance after multiple temperature cycling and over 900 min of continuous operation. Enhanced activity stems from two synergies: first, graphite‐mediated uniform PdO dispersion boosting active site accessibility and second, PdO–SnO2 interfacial charge transfer generating oxygen‐deficient sites, accelerating CH4 dissociation and stabilizing Pd2+ against deactivation. These findings highlight the potential of this approach for use in the development of durable and efficient ceramic composite–based catalysts for environmental applications....
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