An accelerated T-A formulation based on a like-quasi-isotropic conductor, composed of a quasi-isotropic conductor and helical tapes, is developed and presented. This formulation reduces the degree of freedom of soluti...
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An accelerated T-A formulation based on a like-quasi-isotropic conductor, composed of a quasi-isotropic conductor and helical tapes, is developed and presented. This formulation reduces the degree of freedom of solution and is suitable for calculating of magnetization losses of large magnets. We use simulation and experiment methods to study the composition of the magnetization losses of a like-quasi-isotropic conductor and find a way to reduce the AC losses.
The ultra-supercritical double-reheat boiler has attracted more attention because of high parameters (steam with high temperature and pressure), low pollution and large capacity. However, there are some difficulties i...
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The ultra-supercritical double-reheat boiler has attracted more attention because of high parameters (steam with high temperature and pressure), low pollution and large capacity. However, there are some difficulties in the development of this technology, such as adjusting the reheat steam temperature. In this study, computational fluid dynamics simulation is used to analyze a 660 MW double-reheat tower-type pulverized coal-fired boiler. The influence of flue gas recirculation (FGR) on heat transfer characteristics and combustion process in the furnace (including heating surfaces in the upper parts of the furnace) are evaluated. The user-defined function approach predicates the CO reduction effect on NOx. The results show that the flow at the horizontal section through the centerline of recirculating flus gas nozzles is rotating. The velocity distribution changes into an elliptical rotating flow when FGR ratio is 20%. At higher FGR ratios, the high-temperature area (1565-1700 K) shrinks and both the NOx concentration at the low-temperature superheater outlet and the O-2 concentration in the burner zone descend. The O-2 concentration at the low-temperature superheater outlet first increases and then decreases. In the main combustion zone, the heat flux peak of water-cooled wall is about 330 kW m(- 2). As FGR ratio increases from 0% to 20%, the rate of heat absorption of water-cooled wall to that of total boiler decreases by 3.50%. These rates for reheater and superheater increase by 2.53% and 2.13%, respectively.
The application of high temperature vulcanized (HTV) silicone rubber materials in transmission lines insulators has been extensive. However, with the accumulation of pollution and moisture on the surface of HTV silico...
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The application of high temperature vulcanized (HTV) silicone rubber materials in transmission lines insulators has been extensive. However, with the accumulation of pollution and moisture on the surface of HTV silicone rubber, the insulation reliability gradually decreases, which may even lead to flashover. In this paper, hyperspectral imaging technology is utilized as a rapid and effective tool for the visual characterization of pollution and moisture parameters of the polluted HTV silicone rubber. Based on the analysis of reflection spectra, it has been determined that the pollution degree has a positive effect and the moisture content has a negative effect on the reflection characteristics of HTV silicone rubber, respectively. Further quantitative analysis of reflectance values at various moisture conditions reveals that exponential relationships can be observed between reflectance values and moisture contents at a certain wavelength. At the same time, linear correlations between reflectance values and pollution degrees (quantified as equivalent salt deposit density (ESDD)) at a certain wavelength are also proposed. By integrating the exponential and linear relationships, a double-exponential model is formulated to concurrently characterize the ESDD and moisture content (MC). Furtherly, from the perspective of engineering application, to enhance the model's robustness, a set of equations combining spectral indexes and spectral shape feature parameters is initially formulated for the calculating of ESDD and MC. Given the synchronous inversion and visualization capabilities of pollution and moisture parameters of the polluted HTV silicone rubber surface, the visual characterization model serves as a valuable tool for protecting against pollution flashover failures and designing power equipment insulation.
Theoretical and experimental studies suggest that both Hermitian and non-Hermitian quasicrystals show localization due to the fractal spectrum and to the transition to diffusive bands via exceptional points, respectiv...
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Theoretical and experimental studies suggest that both Hermitian and non-Hermitian quasicrystals show localization due to the fractal spectrum and to the transition to diffusive bands via exceptional points, respectively. Here, we present an experimental study of a dodecagonal photonic quasicrystal based on electromagnetically induced transparency in a Rb vapor cell. First, we observe the suppression of the wave packet expansion in the Hermitian case. We then discover a new regime, where increasing the non-Hermiticity leads to delocalization, demonstrating that the behavior in non-Hermitian quasicrystals is richer than previously thought.
Conducting hydrogels have attracted much attention for the emerging field of hydrogel bioelectronics, especially poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) based hydrogels, because of their ...
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Conducting hydrogels have attracted much attention for the emerging field of hydrogel bioelectronics, especially poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) based hydrogels, because of their great biocompatibility and stability. However, the electrical conductivities of hydrogels are often lower than 1 S cm(-1 )which are not suitable for digital circuits or applications in bioelec txonics. Introducing conductive inorganic fillers into the hydrogels can improve their electrical conductivities. However, it may lead to compromises in compliance, biocompatibility, deformability, biodegradability, etc. Herein, a series of highly conductive ionic liquid (IL) doped PEDOT:PSS hydrogels without any conductive fillers is reported. These hydrogels exhibit high conductivities up to approximate to 305 S cm(-1), which is approximate to 8 times higher than the record of polymeric hydrogels without conductive fillers in literature. The high electrical conductivity results in enhanced areal thermoelectric output power for hydrogel-based thermoelectric devices, and high specific electromagnetic interference (EMI) shielding efficiency which is about an order in magnitude higher than that of state-of-the-art conductive hydrogels in literature. Furthermore, these stretchable (strain >30%) hydrogels exhibit fast self-healing, and shape/size-tunable properties, which are desirable for hydrogel bioelectronics and wearable organic devices. The results indicate that these highly conductive hydrogels are promising in applications such as sensing, thermoelectrics, EMI shielding, etc.
For proton exchange membrane fuel cells (PEMFCs) powered vehicles using on-board H2 production by methanol steam reforming (SRM), how to enhance the anti-oxidation and anti-sintering abilities of SRM catalysts are two...
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For proton exchange membrane fuel cells (PEMFCs) powered vehicles using on-board H2 production by methanol steam reforming (SRM), how to enhance the anti-oxidation and anti-sintering abilities of SRM catalysts are two challenges. Herein, to address the two challenges, a PdZn@ZnO catalyst has been synthesized by in-situ transformation of Pd@ZnO core-shell structure under thermal treatment and H2 reduction, which is a facile and green method. The PdZn@ZnO catalyst exhibited an excellent anti-oxidation ability without obvious change in catalytic activity before and after oxidation treatment. Density functional theory calculations revealed that the abundant PdZn/ZnO interface sites of PdZn@ZnO catalyst could suppress O2 dissociation and subsequent oxidation of the PdZn catalyst. In addition, ZnO shell of PdZn@ZnO prevented the encapsulated PdZn alloys from sintering, resulting in its superior stability to those of the reported catalysts. The PdZn@ZnO catalyst showed great potential for the on-board production of hydrogen for PEMFC-powered vehicles.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Considering the supply and pressure limit of the cooling air, an efficient cooling technique with lower pressure loss is greatly required for the gas turbine blade. Various advanced wall-attached secondary ribs using ...
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Considering the supply and pressure limit of the cooling air, an efficient cooling technique with lower pressure loss is greatly required for the gas turbine blade. Various advanced wall-attached secondary ribs using a uniform arrangement scheme can remarkably offer convection heat transfer augmentation but are followed by an increased pressure loss penalty. In this context, a hierarchical arrangement scheme with flexibly varying rib height is proposed and numerically assessed in serpentine cooling channels considering a wide Reynolds number range. Considering twelve novel hierarchical schemes and the conventional uniform scheme, a comparative investigation is elaborately carried out for turbulent flow and heat transfer. Compared with the uniform scheme, all hierarchical schemes can achieve a substantial reduction in pressure loss but suffer from heat transfer attenuation to different extents. Especially, in a U-shaped cooling channel, the optimal scheme followed by a linearly decreasing rib size achieves a 44.18 %similar to 44.82 % reduction in pressure loss, with only a 7.61 %similar to 10.43 % attenuation in heat transfer. The main reason is owing to the mutual interaction between rib- and bend-induced secondary vortices. The combination of small ribs and the triggered mainstream lowering significantly suppress the rib-induced streamwise recirculation vortices and spanwise recirculation vortices accompanied by bend-induced secondary flows, consequently the substantial drag reduction. The marginal heat transfer deterioration is due to the lowering effect which provides a supplementary enhancement for the weak flow impingement behind small ribs. Considering the S-shaped cooling channel, the optimal hierarchical scheme still provides a substantial drag reduction and consequently improves the overall performance by up to 161.48 % in (Nu/Nu(0))/(f/f(0)) and 31.99 % in (Nu/Nu(0))/(f/f(0))(1/3). Generally, this work significantly highlights that the hierarchical design
Non-Newtonian fluids play a vital role in industrial production. It is of great significance to study the mixing and chaotic characteristics of flow field in static mixers for the energy utilization. An improved struc...
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Non-Newtonian fluids play a vital role in industrial production. It is of great significance to study the mixing and chaotic characteristics of flow field in static mixers for the energy utilization. An improved structure of S-Type static mixer is proposed. In order to deeply investigate the flow characteristics of non-Newtonian fluids in S-Type static mixers, experimental and numerical studies are conducted on the mixing efficiency and chaotic behaviors under different flow rates. The PLIF method is adopted to visually study the distribution of CMC solutions with different mass concentrations. It is found that the average deviation of coefficient of variation (CoV) between experiment and Second-order simulation scheme is 4.15%. The simulation results show that the M number in SType-b mixer is 10.13-18.29 %, 10.82-22.26 %, and 20.39-27.35 % higher than that of the Kenics, Komax, and S-Type static mixers, respectively. Additionally, the S-Type-b static mixer exhibits a higher average Lyapunov exponent (LEave) and lower variance of the Lyapunov exponent (LEvar) under different flow rates, which indicates that the S-Type-b static mixer has better flow stability. The structural parameters of S-Type-b mixer are optimized using Response Surface Methodology (RSM) and Non-dominated Sorting Genetic Algorithm II (NSGA-II). The optimal design parameters ensure that the M number of the S-Type-b static mixer is 0.2926 and LEave reaches 5.3246, which significantly improves the mixing efficiency and system stability.
Addressing the escalating challenge of CO2 emissions necessitates the exploration of innovative reduction strategies well beyond the reach of conventional methods. Within this ambit, the integration of nonthermal plas...
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Addressing the escalating challenge of CO2 emissions necessitates the exploration of innovative reduction strategies well beyond the reach of conventional methods. Within this ambit, the integration of nonthermal plasma with advanced catalytic materials emerges as a cutting-edge approach for the effective decomposition of CO2. This investigation focuses on the decomposition of CO2 facilitated by dielectric barrier discharge plasma in conjunction with different metal-supported catalysts (Ni-CuO, Co-CuO and NiCo-CuO), offering a comparative analysis with the plasma-alone system. Notably, the synergistic interaction between plasma and a NiCo-CuO catalyst markedly enhances the CO2 conversion efficiency, achieving an optimal conversion rate of 30.5% and an optimal energy efficiency of 6.16%. Further characterizations using optical emission spectroscopy (OES) and intensified charge-coupled device imaging demonstrate that the incorporation of NiCo-CuO not only improves the uniformity of the plasma discharge but also alters the plasma energy distribution within the discharge zone, favoring the generation of excited species and their subsequent catalytic reactions on the Ni-Co-Cu surface. The findings from this study offer crucial insights into the mechanisms underlying plasma-catalyzed CO2 dissociation processes, and may offer a promising avenue toward sustainable carbon management.
Renewable energy sources, such as wind and solar photovoltaic, have been widely deployed in power systems due to the decarbonization transition target and technological advances. The large-share integration of renewab...
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Renewable energy sources, such as wind and solar photovoltaic, have been widely deployed in power systems due to the decarbonization transition target and technological advances. The large-share integration of renewable generation contributes to the construction of a low-carbon power system and imposes significant flexibility requirements for the power system. The reliability and security in power system operation and RES generation accommodation are deeply involved with the configuration mixes and the portfolio of flexible resources. Therefore, this paper proposes a coordinated capacity expansion planning model with a variety of flexibility technologies, including thermal power flexibility retrofitting, energy storage systems, demandside responses, as well as concentrating solar power plants. A scenario-based approach is adopted to capture uncertainties from electric load and renewable generation. The proposed planning model is constructed as a two-stage stochastic planning framework, where the first stage optimizes investment strategies of flexible technologies while the second stage determines the optimal power dispatch for all generation assets under different operation conditions. The hourly operation simulation model is also embedded in the proposed planning model with detailed operation constraints. The effectivity of the proposed coordinated planning model is verified by a modified reliability and operation test system. Numerical results show that different combinations of flexibility technologies have distinct impacts on the power system's economic and environmental performances, which implies the significance of finding an optimal portfolio of flexibility resources in the power system with large-scale renewable energy sources. (c) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under theCCBY-NC-ND license (http://***/licenses/by-nc-nd/4.0/).
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