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- ArtykułOtwarty dostępRecent advances in low-gradient combustion modelling of hydrogen fuel blends(2022) Buczyński, Rafał; Uryga-Bugajska, Ilona; Tokarski, MieszkoLow-gradient combustion (LGC) proved to be an effective alternative technology to reduce pollutant emissions and carbon footprint, specifically when combined with hydrogen as a fuel or blend component. This novel technology offers several advantages over conventional combustion regimes, including a more effective control of emissions and providing greater flexibility in fuel application. The impact of hydrogen on this regime is still not well-known, especially when it comes to the combustion of pure hydrogen and fuels with a high hydrogen content. In the last two decades, numerical simulations have become a powerful tool that facilitates the research and design of LGC, particularly in terms of stability of the process and the emission of pollutants. This article provides an up-to-date review of recent trends and theoretical knowledge in low-gradient combustion. This includes the guidelines and recommendations applied to LGC modelling. Comparisons have been made between the recently published modelling approaches presented by the authors, including a detailed assessment of the discrepancies in the temperature predictions. The challenges and limitations associated with the LGC combustion modelling of conventional fuels (i.e., natural gas, methane, syngas) blended with hydrogen are also discussed. The review demonstrated that the Eddy Dissipation Concept (EDC) is the most common turbulent chemical interaction model employed in LGC combustion simulations. The performance of the EDC can be significantly improved by variable constants $C_{𝛾}$ and $C_{𝜏}$ based on local turbulent Reynolds and Damköhler numbers. However, the most recent publications indicate that the flamelet-based approach can be considered as a promising (and more cost-effective) alternative to the EDC. Furthermore, the chemical kinetic studies considered in this review confirm that there is no detailed reaction mechanism capable of accurately predicting the temperature profile along with the emissions of the main species of interest, i.e., NOx, CO, CO2, and OH. Although GRI-Mech 2.11 is the most widely used mechanism in LGC simulations, providing satisfactory overall accuracy.
- ArtykułOtwarty dostępSteering triboelectric and mechanical properties of polymer fibers with carbon black(2023) Szewczyk, Piotr K.; Taşlı, Ali Emre; Knapczyk-Korczak, Joanna; Stachewicz, UrszulaWydział Inżynierii Metali i Informatyki PrzemysłowejThe development of wearable electronics has spurred an increased interest in self-powered systems and triboelectric nanogenerators (TENGs). To enhance the output performance of TENGs, researchers have dedicated significant efforts toward finding effective ways to increase triboelectric and mechanical performance. This study examined how conductive carbon black (CB) affects the mechanical and triboelectric properties of electrospun fibers made of polyurethane (PU), polystyrene (PS), and polycarbonate (PC). The addition of CB affected their mechanical properties, including increased tensile strength and decreased elongation at break. Importantly, triboelectric testing revealed that incorporating CB decreased the triboelectric output of PU and PS by over 90%, while it increased the output of PC by 260%. These findings indicate that CB's effects on triboelectric properties depend on the material and its content, underscoring the importance of selecting CB content carefully for optimal mechanical and triboelectric performance in electrospun fibers and composites. This research validates the development of advanced composite materials for electrostatic discharge protection and energy harvesting applications.
- ArtykułOtwarty dostępOil-infused polymer fiber membranes as porous patches for long-term skin hydration and moisturization(2023) Szewczyk, Piotr K.; Kopacz, Michał; Krysiak, Zuzanna; Stachewicz, UrszulaSkin allergies and diseases, including atopic dermatitis (AD), affect millions worldwide. Current treatments for AD are often expensive, leading to a need for cost-effective solutions. Here, using fiber-based patches to maintain and increase skin hydration is explored, which helps treat eczema and AD. Nanofiber membranes are manufactured via electrospinning of eight different polymers: nylon 6 (PA6), polyimide (PI), poly(3-hydroxybuty-rate-co-3-hydroxyvalerate (PHBV), poly(l-lactide) (PLLA), polycaprolactone (PCL), and polystyrene (PS), and two molecular weights poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (PVB). Further, their morphology is examined through scanning electron microscopy (SEM), fibers, and pores diameter, wettability, and membrane thickness. Additionally, water vapor transmission rates (WVTR) are measured, and notably, skin hydration tests are conducted before and after using evening primrose oil-infused patches. The comparison and findings highlight the flexibility of electrospun patches, demonstrating their potential in maintaining skin hydration for 6 h and enhancing skin moisture, which are necessary in AD treatment. These insights, which focus on selecting the most effective performance patches, help improve skin moisture, leading to tailored treatments for AD, which can significantly impact the efforts to reduce healthcare costs and simplify skincare steps.
- ArtykułOtwarty dostępWear-resistant smart textiles using nylon-11 triboelectric yarns(2023) Szewczyk, Piotr K.; Busolo, Tommaso; Kar-Narayan, Sohini; Stachewicz, UrszulaWydział Inżynierii Metali i Informatyki PrzemysłowejThe ever-increasing demand for self-powered systems such as glucose biosensors and mixed reality devices has sparked significant interest in triboelectric generators, which hold large potential as renewable energy solutions. Our study explores new methods for integrating energy-harvesting capabilities into smart textiles by developing strong and efficient yarns that can convert mechanical energy into electrical energy through a triboelectric effect. Specifically, we focused on Nylon-11 (PA11), a material known for its crystalline structure well-suited for generating a powerful triboelectric response. To achieve this, we created triboelectric yarns by electrospinning PA11 fibers onto conductive carbon yarns, enabling energy-harvesting applications. Extensive testing demonstrated that these yarns possess exceptional durability, surpassing real-life usage requirements while experiencing minimal degradation. Additionally, we developed a prototype haptic device by interweaving tribopositive PA11 and tribonegative poly(vinylidene fluoride) (PVDF) triboelectric yarns. Our research has successfully yielded durable and efficient yarns with strong energy-harvesting capabilities, opening up possibilities for integrating smart textiles into practical scenarios. These technologies are promising steps to achieve greener and more reliable self-powered systems.
- ArtykułOtwarty dostępDirect electrospinning of short polymer fibers: factors affecting size and quality(2024) Ura, Daniel Paweł; Stachewicz, UrszulaWydział Inżynierii Metali i Informatyki PrzemysłowejThe growing demand for lightweight and robust materials drives the development of polymer-based and fiber-reinforced composites. Here, using short fibers offers several advantages; however, currently employed methods for producing short fibers, such as homogenization, result in a wide dispersion of dimensions in the produced fibers, which is an undesirable effect in composite materials. In this study, electrospinning is used to produce polymer short fibers directly. This research highlights, for the first time, the differences in the electrospinning process dynamics between short and continuous fibers. By adjusting parameters: voltage and distance, we control dimensions of short fibers below 1 µm in diameter and around 4 µm in length to a few microns in diameter and approximately 14 µm in length. Direct electrospinning of short fibers offers significant advantages, including a narrow size distribution and reproducibility compared to chopped continuous fibers with homogenization.