Search Results (4)

In the global shift toward sustainable energy, enhancing the efficiency of renewable energy systems plays a pivotal role in advancing the Sustainable Development Goals. This study focuses on optimizing the design of a corrugated-flange diffuser integrated with a wind turbine to enhance its performance, particularly in low-wind conditions. While most previous research has examined wind farm performance at high wind speeds, the challenge of effective power extraction at low wind speeds remains largely unresolved. The potential of diffusers to enhance wind turbine efficiency under low-wind conditions has received limited investigation, with most prior studies focusing solely on empty diffuser configurations without turbine integration. In addition, the influence of flange geometry on diffuser performance remains largely unexplored. In this study, parametric analyses were conducted to identify the optimal diffuser design, followed by comparative performance evaluations of configurations with and without turbine integration, using computational fluid dynamics (CFD) simulations. The results show that integrating a turbine with the optimized corrugated-flange diffuser increased flow velocity by 67.85%, achieving an average of approximately 14 m/s around the blade region. In comparison, the optimized corrugated-flange diffuser alone increased flow velocity by 44%, from 4.5 m/s to 8.036 m/s. These findings highlight the potential of optimized diffuser designs to enhance small-scale wind turbine performance in low-wind conditions. Full article

The core challenges to automatic full-horizon tracking are how to establish a potential local connection relationship between the horizon points, conduct accurate global diffusion in a three-dimensional space, and finally, how to form a complex horizon surface. The existing attribute-based horizon-tracking methods based on waveform similarity, dip guidance, and RGT (relative geological time) can not solve the problems of local connection and global diffusion at the same time. In view of this challenge, this paper proposes an automatic 3D seismic horizon-tracking method based on global corrugated diffusion, which can completely integrate local connection and global diffusion so that all horizons in the whole data volume can be interpreted simultaneously. For the problem of local horizon-point connection, this paper uses the correlation between seismic trace pairs based on DTW (dynamic time warping) correlation to mine the connection mode between horizon points. For the global diffusion problem, this paper proposes the realization of global modeling based on the relationship between seismic samples, constructing a complex 3D horizon through a central ripple-diffusion process. The example shows that the horizon tracked by this method well reflects the original stratum occurrence and stratum-contact relationship, retains the structural details, accurately reflects the structural shape, and realizes automatic tracking across faults. Full article

Hexavalent chromium (Cr(VI)) is a heavy metal that is highly soluble and exhibits toxic effects on biological systems. Nevertheless, it is used in many industrial applications. The adsorption process of Cr(VI), using activated carbon (AC), is under investigation globally. On the other hand, around six million tons of spent coffee is sent to landfill annually. In the spirit of cyclic economy, this research investigated the production of AC from spent coffee for the removal of Cr(VI) from wastewater. The AC was produced via pyrolysis process under a nitrogen atmosphere. Chemical activation using potassium hydroxide (KOH) occurred simultaneously with the pyrolysis process. The produced AC was tested as an absorber of Cr(VI). The best fitted kinetic model was the diffusion–chemisorption model. A 24-h adsorption experiment was carried out using a solution with a pH of 3 and an initial Cr(VI) concentration of 54.14 ppm. This resulted in an experimental maximum capacity of 109 mg/g, while the theoretical prediction was 137 mg/g. It also resulted in an initial adsorption rate (r_i) of 110 (mg/(g h)). The Brunauer–Emmett–Teller surface area (S_gBET) was 1372 m²/g, the Langmuir surface area (S_gLang.) was 1875 m²/g, and the corrugated pore structure model surface area (S_gCPSM) was 1869 m²/g. The micropore volume was 84.6%, exhibiting micropores at D_micro1 = 1.28 and D_micro2 = 1.6 nm. The tortuosity factor (τ) was 4.65. Full article

A compressible single step chemistry Direct Numerical Simulation (DNS) database of freely propagating premixed flames has been used to analyze different entropy generation mechanisms. The entropy generation due to viscous dissipation within the flames remains negligible in comparison to the other mechanisms of entropy generation. It has been found that the entropy generation increases significantly due to turbulence and the relative magnitudes of the augmentation of entropy generation and burning rates under turbulent conditions ultimately determine the value of turbulent second law efficiency in comparison to the corresponding laminar values. It has been found that the entropy generation mechanisms due to chemical reaction, thermal conduction and mass diffusion in turbulent flames strengthen with decreasing global Lewis number in comparison to the corresponding values in laminar flames. The ratio of second law efficiency under turbulent conditions to its corresponding laminar value has been found to decrease with increasing global Lewis number. An increase in heat release parameter significantly augments the entropy generation due to thermal conduction, whereas other mechanisms of entropy generation are marginally affected. However, the effects of augmented entropy generation due to thermal conduction at high values of heat release parameter are eclipsed by the increased change in availability due to chemical reaction, which leads to an increase in the second law efficiency with increasing heat release parameter for identical flow conditions. The combustion regime does not have any major influence on the augmentation of entropy generation due to chemical reaction, thermal conduction and mass diffusion in turbulent flames in comparison to corresponding laminar flames, whereas the extent of augmentation of entropy generation due to viscous dissipation in turbulent conditions in comparison to corresponding laminar flames, is more significant in the thin reaction zones regime than in the corrugated flamelets regime. However, the ratio of second law efficiency under turbulent conditions to its corresponding laminar value does not get significantly affected by the regime of combustion, as viscous dissipation plays a marginal role in the overall entropy generation in premixed flames. Full article