Basic Configurations Research Articles

Improvement of combustion performance with novel vortex generators in the powder-fueled ramjets

Combustion performance of powder-fueled ramjets depends mainly on the combustor configurations. In this study, three combustors with various vortex generators are put forward firstly in powder-fueled ramjets. The comparison between three novel and the basic configurations is conducted and analyzed by transient numerical simulation. It can be proved that three configurations with various vortex generators have positive effects on the gas-particle phases flow field, mass fractions of products and combustion efficiency. The scheme of tapped vortex generator has best gas-particle flow temperature distribution and most mass fraction of products, meaning more transfer and consumption of powdered fuel. The oxygen content in the scheme of tapped vortex generator, being only 60% of that in basic scheme, also proves the conclusion. Moreover, this configuration also has most mass flow rate of Aluminum gas, products and most particles resided in the combustor, which is 2.25 times than the basic combustor.

Investigating the effect of anode materials on the performance and microbial community in an integrated chamber-free microbial fuel cell

Conventionally, there are two basic configurations for microbial fuel cell (MFC), one with anode and cathode chambers, as known as dual-chamber MFC, one with only anode chamber and a air–cathode, called single-chamber MFC. However, electrode materials' complex configuration and high resistance limit their practical applications in power generation and wastewater purification. To this end, we constructed three MFCs using carbon felt, Ni/Ti, and Ag-Ni/Ti as anodes based on our previously constructed integrated chamber-free MFC (iMFC). After 21 days of operation, the Ag-Ni/Ti-MFC performed best in bioelectricity output and removal of target pollutants. The bioelectricity output parameters were an open-circuit voltage of 0.773 V, a maximum current density of 552.1429 mA/m2, and a power density of 426.8064 mW/m2. Furthermore, the MFC achieved removals of 67.90% for the chemical oxygen demand (COD), 55.20% for total nitrogen (TN), and 61.83% for ammonia nitrogen (NH3-N). Introducing silver nanoparticles to the transmembrane and outer membrane boosted the charge extraction efficiency in the MFCs. Moreover, 16S rDNA analysis indicated that typical electricity-producing bacteria, including Comamonas, Paraclostridium, and Asaccharospora, had a higher relative abundance in the Ag-Ni/Ti-MFC anode than in other anodes. Overall, the surface structure of different anode materials plays a critical role in bioelectricity generation and wastewater purification using iMFC by affecting the mass transfer of substrates and metabolites.

Feasibility of the set-up for the different approaches in robotic head and neck surgery with the Versius Surgical System.

The Versius Surgical System is a next generation soft-tissue robot with instrument and endoscope arms split into individual modules. Despite its similarities with previous systems, the basic changes in the design raise concerns relating to the feasibility of the set-up for the different approaches in robotic head and neck surgery procedures. We used a complete unit with a surgeon's console and four modules on a training mannequin to depict the different configurations in the operating room. We tested transoral robotic surgery and the four basic configurations for the remote access to the neck: transoral/transvestibular, retroauricular, axillary and bilateral axillo-breast approaches. We obtained a high quality simulation for transoral robotic surgery, as well as for the usual remote access approaches, except for the axillary approach. We were able to obtain an optimal distribution of the modules around the surgical table and an adequate configuration of the joints allowing the instruments to reach their targets. The Versius Surgical System might be an alternative device for robotic procedures in head and neck surgery, although this needs to be proved in a clinical setting.

Wind Tunnel Study of a Grid Fin Stabilized Guided Projectile

There is a need for methods/techniques to analyze the aerodynamics of grid fins at high angle of attack. The existing methods to predict or compute the aerodynamic parameters for grid fins are inadequate at high angles of attack. The present study attempts to extend the understanding of the complex aerodynamics associated with grid fins. The analysis draws its conclusion from wind tunnel test results of five basic grid fin configurations. A vortex lattice solution was used to model the aerodynamics of the chosen grid fins. Next the analytical and empirical relations as discussed in open literature were applied to model grid fin aerodynamics at high angle of attack. The aerodynamic coefficients were computed. These coefficients were then compared with the experimental results obtained using the five grid fin configurations. To improve the matching at high angle of attack a proposed approach using Kirchoff’s theory along with vortex lattice method was applied. The results show that this approach can be a starting tool to model lattice/grid fin aerodynamics.

Comparison and Analysis of Electromagnetic Characteristics of Basic Structure of Wireless Power Coil for Permanent Magnet Motors in Electric Vehicles

The purpose of this paper is to compare and analyze the electromagnetic characteristics of the basic structure of the coil in the electromagnetic coupling mechanism for the wireless power supply of permanent magnet motors in electric vehicles. The electromagnetic coupling mechanism is one of the key technologies for wireless power transmission and the coil structure plays a key role in the transmission performance of the coupling mechanism, and different structures can achieve different performances. The central objective of coil structure studies is to investigate how the coupling coefficient can be increased to achieve greater transmitted power and higher efficiency. In this paper, we investigate two basic coil configurations, circular and square, by studying their flux density variations when used as transmitting coils and their electromagnetic coupling characteristics when used as receiving coils. Three couplers consisting of circular and square coils are also analyzed in simulations and experiments are carried out on couplings containing circular and square coils of the same area. The results of the study show that the qualitative analysis, simulation analysis and experimental results are in high agreement. The results of this paper are an important reference for the design and optimization of wireless power coils for permanent magnet motors in electric vehicles.

Magnets, Gradients, and RF Coils of MR Scanners

The topic of this paper is the parts of modern MR devices, which contain magnet coils. MR scanner magnets are made of four types of electromagnetic coils: 1) Main magnet, made of superconducting material. The main magnet of an MR (Magnetic Resonance Imaging) scanner creates a strong and uniform magnetic field around the patient being scanned. This magnetic field is typically in the range of 0.5 to 3 Tesla and is used to align the magnetic moments of the hydrogen atoms in the patient's body. The superconductors, which create the main magnetic field, should be cooled with liquid helium and liquid nitrogen. The main magnets made of superconductors should use a cryostat, with cooling vessels with liquid helium and liquid nitrogen, thermal insulation, and other protective elements of the magnet system. 2) The gradient magnetic field is made of three types of coils: x-coils, y-coils, and z-coils. The X coil, made of resistive material, creates a variable magnetic field, horizontally, from left to right, across the scanning tube; 3) The Y coil creates a variable magnetic field, vertically, from bottom to top; 4) The Z coil creates a variable magnetic field, longitudinally, from head to toe, inside the scanning tube. RF coils are used to generate RF pulses to excite the hydrogen protons (spins) in the patient's body and detect the signals emitted by the protons when they return to their equilibrium state after the RF excitation is turned off. The resulting interaction between the magnetic field and the aligned hydrogen atoms produces a signal that is used to generate the images seen in an MRI scan. The main magnetic field is what allows MR imaging to produce detailed anatomical and functional information non-invasively. The structure of the MR scanner magnet is complex. The resonant frequency changes at each point of the field in a controlled manner. Inside the copper core are embedded the windings of the main magnet made of superconducting material in the form of microfibers. A non-linear gradient field is created by coils of conductive material. It adds to the main magnetic field. Thus the resulting magnetic field is obtained. The types of magnets that exist in the basic configurations of MR scanners are analyzed. Scanners in the form of a closed cylindrical cavity generate their magnetic fields by passing current through a solenoid, which is maintained at the temperature of a superconductor. Exclusively used superconductors are niobium-titanium (NbTi), niobium-tin (Nb3Sn), vanadium-gallium (V3Ga), and magnesium-diboride (MgB2). Only magnesium diboride is a high-temperature superconductor, with a critical temperature Tc = 390K. The three remaining superconductors are low temperatures. New high-temperature superconductors have been discovered, as well as superconductors at room temperature. Newly discovered superconducting materials are not used in MR scanners.

Conceptual review and optimization of liquid air energy storage system configurations for large scale energy storage

Among energy storage systems, Liquid Air Energy Storage (LAES) is attractive because of high energy density, ease of being scaled up, absence of geographical constraints, mature technology and use of safe materials/working fluids. This work presents a critical review of LAES system configurations in the literature to identify the criteria behind their conceptual development. The goal is achieved following the HEATSEP methodology, which allowed identifying a common thread in the evolution of all LAES configurations in the literature based on very few layouts, named “basic configurations”. The optimization of these few layouts, taking into account all possible internal heat transfers, provides a unique and comprehensive overview of existing configurations in spite of their seemingly great complexity. This picture clearly indicates the link between topology and performance improvement and provides insight into the limits of the maximum possible performance gain over the existing literature. The optimal results show that the margin for improvement is quite narrow. In the case of a complete thermal integration between charge and discharge phases with the addition of Organic Rankine Cycle system a gain from 61.9 % to 64.3 % is obtained over the best performing configuration in the literature.

The spatio-temporal architecture of everyday manual behavior

In everyday activities, humans move alike to manipulate objects. Prior works suggest that hand movements are built by a limited set of basic building blocks consisting of a set of common postures. However, how the low dimensionality of hand movements supports the adaptability and flexibility of natural behavior is unknown. Through a sensorized glove, we collected kinematics data from thirty-six participants preparing and having breakfast in naturalistic conditions. By means of an unbiased analysis, we identified a repertoire of hand states. Then, we tracked their transitions over time. We found that manual behavior can be described in space through a complex organization of basic configurations. These, even in an unconstrained experiment, recurred across subjects. A specific temporal structure, highly consistent within the sample, seems to integrate such identified hand shapes to realize skilled movements. These findings suggest that the simplification of the motor commands unravels in the temporal dimension more than in the spatial one.

Basic Technological Parameters of the Activation Process for Two Bioreactor Configurations

Abstract Technological parameters of the activation process in wastewater treatment plant activation systems are analyzed for basic bioreactor configurations, for the chemostat and for the plug flow, both with the recirculation of concentrated activated sludge. The first type of bioreactors represents conventional aerated tanks, but also loop bioreactors. The second type of bioreactors includes, for example, oxidation ditches. The paper presents an evaluation of the basic technological parameters of the activation process for the two mentioned configurations of bioreactor systems with recirculation of concentrated activated sludge. In addition, a new relation for sludge age evaluation is proposed for an activation system with a plug flow bioreactor. The article also provides examples of connections between the values of the technological parameters of the activation process for the two analyzed types of bioreactor systems.

A comparative performance analysis, working fluid selection, and machine learning optimization of ORC systems driven by geothermal energy

Geothermal-energy-based desalination plants that utilize reverse osmosis (RO) are evaluated in detail with the aim of converting the thermal energy of geothermal flow into electricity based on three configurations of the organic Rankine cycle (ORC). These systems include basic ORC, parallel ORCs, and series ORCs. The performance of the proposed systems is evaluated by developing thermodynamic and economic models. A parametric study is conducted to assess the impact of main design parameters on the performance. Moreover, a multi-objective optimization procedure is implemented, by coupling the genetic algorithm (GA) with an artificial neural network (ANN), to identify optimal cycle configuration and working fluid(s) under three different heat source temperatures. For a specific geothermal temperature (135 °C), the highest exergy efficiency in the basic scheme is obtained by R1233zd (E), while ammonia yields maximum power generation. For parallel configuration, irrespective of the heat source temperature, the combination of R1233zd (E)-Ethane always leads to the highest exergy efficiency, while comparison results at 135 °C indicate that the combination favored by power generation is R1234ze (Z)-Ethane. For the series configuration, optimization results under the heat source temperature of 135 °C indicate that the ammonia-R1234ze (Z) combination is a suitable candidate under the economic objective, while ammonia-ammonia is recommended as the preferred choice thermodynamically. In addition, comparing the optimization results of the parallel configuration with the basic design reveal considerable improvements of about 150% and 60% in power generation and water production, respectively. The same comparison between series and basic configurations revealed an improvement of about 30% in power generation.

Optical pulling force on dielectric particles via metallic slab surface plasmon excitation: a comparison between transmission and reflection schemes.

In this Letter, a simple structure formed by a metallic thin layer covering a high-index substrate is used to design an optical tweezer. Owing to the interaction between the field scattered by the particle with an incident plane wave and the proposed structure, a pulling or attractive component of the optical force emerges. This component results in enhancement thanks to the surface plasmons (SPs) excitation arising from the elliptical polarization of the induced dipole moment on the particle. To further exploit the versatility of the proposed approach, we analyze two basic configurations: the reflection scheme, for which the plane wave impinges from the side where the particle is placed; and the transmission scheme, for which the incidence is made from the substrate side. Our results show that the intensity of the pulling force in the reflection scheme and for finite thickness metal layer reaches values exceeding more than twice those provided by a single metallic interface. We also demonstrate that the transmission scheme is more favorable than the reflection scheme for enhancing pulling force intensities. Our contribution can be valuable for realizing simple plasmonic schemes for improving the pulling force via interactions between the nano-particle and SP fields.

3D printing and modelling of continuous carbon fibre reinforced composite grids with enhanced shear modulus

Within this research, continuous carbon fibre (CCF) reinforced polyamide (PA) composite grids were topologically-tailored and 3D printed to show enhanced shear modulus. Based on the 3D printing trajectories, a new numerical scheme to predict the elastic responses and behaviours of the 3D printed CCF/PA composite grids was developed. To verify the design and the numerical model, specifically created shearing tests were performed. By comparison, the modelled data agrees well with the experiments. Reinforced by CCFs, the effective shear modulus of 3D printed PA specimens was found to increase by 641.3%, 437.6% and 723% for basic structural configurations with material volume fractions of 20 vol-%, 40 vol-% and 60 vol-%, respectively. Even more, an index for evaluating the CCF reinforcement efficiency, independent of the design of the reinforced structure, was proposed and applied, indicating that the effective shear modulus can be maximally enhanced by 40.5 MP once the CCF volume content is increased by 1%. This study innovatively provides a systematic approach by integrating topological design, modelling and experimental methods for creating engineering grid structures with enhanced shear modulus, and thus proving the efficiency of using continuous fibres as structural reinforcements in 3D printing for engineering applications.

Optimization design of dual microjets for the shock wave/boundary layer interaction control in the supersonic flow

The shock wave/boundary layer interaction phenomenon is harmful to the performance improvement of the hypersonic vehicle, and the microjet flow control scheme was introduced to minimize the total volume of the separation bubble and maximize the total pressure recovery coefficient simultaneously. In this paper, the dual microjets for the shock wave/boundary layer interaction control are optimized by the range analysis approach, and their flow field structures are explored and compared comprehensively. The obtained results show that the range analysis approach is a method for the optimization of the dual microjets, and the optimized models show better performances when compared with the basic configurations. In the range considered in this study, Case 5a obtained by taking the minimum total volume of the separation bubble as the target has a large total pressure loss, and its total volume of the separation bubble is 960.65 mm2, with its total pressure loss being 15.38%.

Advances in Multicore Fiber Interferometric Sensors.

In this paper, a review of multicore fiber interferometric sensors is given. Due to the specificity of fiber structure, i.e., multiple cores integrated into only one fiber cladding, multicore fiber (MCF) interferometric sensors exhibit many desirable characteristics compared with traditional fiber interferometric sensors based on single-core fibers, such as structural and functional diversity, high integration, space-division multiplexing capacity, etc. Thanks to the unique advantages, e.g., simple fabrication, compact size, and good robustness, MCF interferometric sensors have been developed to measure various physical and chemical parameters such as temperature, strain, curvature, refractive index, vibration, flow, torsion, etc., among which the extraordinary vector-bending sensing has also been extensively studied by making use of the differential responses between different cores of MCFs. In this paper, different types of MCF interferometric sensors and recent developments are comprehensively reviewed. The basic configurations and operating principles are introduced for each interferometric structure, and, eventually, the performances of various MCF interferometric sensors for different applications are compared, including curvature sensing, vibration sensing, temperature sensing, and refractive index sensing.

Mechanical Properties and Tensile Failure Mechanism of Friction Stir Welded 2219-T6 and 5A06-H112 Joints

Friction stir welding was employed to weld dissimilar 2219/5A06 Al alloys in this work. The influences of alloy positioning on the mechanical properties and fracture behavior of the joints were studied via fracture morphology observation and microstructural analysis. The results show that the difference in the plastic flow and thermal field in the welding process is caused by different basic material configurations, which results in the formation of a free strengthening phase zone and microstructural heterogeneity in the joint. The low-hardness texture component caused by the free strengthening phase zone and microstructural heterogeneity becomes crack initiation, and a crack tends to propagate along the grain boundaries. Finally, when the stronger 2219-T6 alloy was placed on the advancing side, the joints had better tensile properties. The average tensile strengths of the 2A5R and 5A2R joints can reach 79.8% (343 MPa) and 78.4% (337 MPa) of the 2219 base material, respectively.

Decentral Production of Green Hydrogen for Energy Systems: An Economically and Environmentally Viable Solution for Surplus Self-Generated Energy in Manufacturing Companies?

Power-to-X processes where renewable energy is converted into storable liquids or gases are considered to be one of the key approaches for decarbonizing energy systems and compensating for the volatility involved in generating electricity from renewable sources. In this context, the production of “green” hydrogen and hydrogen-based derivatives is being discussed and tested as a possible solution for the energy-intensive industry sector in particular. Given the sharp, ongoing increases in electricity and gas prices and the need for sustainable energy supplies in production systems, non-energy-intensive companies should also be taken into account when considering possible utilization paths for hydrogen. This work focuses on the following three utilization paths: “hydrogen as an energy storage system that can be reconverted into electricity”, “hydrogen mobility” for company vehicles and “direct hydrogen use”. These three paths are developed, modeled, simulated, and subsequently evaluated in terms of economic and environmental viability. Different photovoltaic system configurations are set up for the tests with nominal power ratings ranging from 300 kWp to 1000 kWp. Each system is assigned an electrolyzer with a power output ranging between 200 kW and 700 kW and a fuel cell with a power output ranging between 5 kW and 75 kW. There are also additional variations in relation to the battery storage systems within these basic configurations. Furthermore, a reference variant without battery storage and hydrogen technologies is simulated for each photovoltaic system size. This means that there are ultimately 16 variants to be simulated for each utilization path. The results show that these utilization paths already constitute a reasonable alternative to fossil fuels in terms of costs in variants with a suitable energy system design. For the “hydrogen as an energy storage system” path, electricity production costs of between 43 and 79 ct/kWh can be achieved with the 750 kWp photovoltaic system. The “hydrogen mobility” is associated with costs of 12 to 15 ct/km, while the “direct hydrogen use” path resulted in costs of 8.2 €/kg. Environmental benefits are achieved in all three paths by replacing the German electricity mix with renewable energy sources produced on site or by substituting hydrogen for fossil fuels. The results confirm that using hydrogen as a storage medium in manufacturing companies could be economically and environmentally viable. These results also form the basis for further studies, e.g., on detailed operating strategies for hydrogen technologies in scenarios involving a combination of multiple utilization paths. The work also presents the simulation-based method developed in this project, which can be transferred to comparable applications in further studies.

Small-signal oscillatory stability of a grid-connected PV power generation farm affected by the increasing number of inverters in daisy-chain connection

The daisy-chain connection of inverters is one of the basic configurations of the power collecting network in a grid-connected photovoltaic (PV) power generation farm. In this study, the total impact of a cluster of M similar inverters in daisy-chain connection in the PV farm is examined in the following two aspects: 1) aggregated representation of the cluster of inverters is derived for stability study based on the dynamic equivalence. The derivation confirms the rationality of representing the cluster of inverters by an aggregated inverter connected to the external system via an equivalent reactance, which is the maximum eigenvalue of the matrix of daisy-chain connection defined in the article. 2) Analysis is conducted to indicate that the risk of oscillatory instability may be collectively induced by all the inverters in the daisy-chain connection in the cluster. This explains why the increasing number of inverters may imply the possible instability risk of a PV farm. An example of a power system with a grid-connected PV power generation farm is presented in the article to demonstrate and evaluate the analytical conclusion obtained.

Design and Optimization of High-Power and Low-Frequency Broadband Transducer with Giant Magnetostrictive Material.

The applications of sensors in the aerospace industry are mostly concentrated in the middle and high frequencies, and low-frequency sensors often face the problems of low power and short working bandwidth. A lightweight, thin, high-power, low-frequency broadband transducer based on giant magnetostrictive material is designed. The design and optimization processes of the core components are introduced and analyzed emphatically. The finite element simulation results are validated by the PSV-100 laser vibration meter. Three basic configurations of the work panel are proposed, and the optimal configuration is determined by modal, acoustic, and vibration coupling analyses. Compared with the original configuration, it is found that the lowest resonant frequency of the optimal configuration is reduced by 24.6% and the highest resonant frequency within 2000 Hz is 1744.9 Hz, which is 54.2% higher than that of the original configuration. This greatly improves the vibration power and operating frequency range of the transducer. Then, the honeycomb structure is innovatively applied to the work panel, and it is verified that the honeycomb structure has a great effect on the vibration performance of the work panel. By optimizing the size of the honeycomb structure, it is determined that the honeycomb structure can improve the vibration power of the work panel to its maximum value when the distance between the half-opposite sides of the hexagon is H = 3.5 mm. It can reduce the resonant frequency of the work panel; the lowest resonant frequency is reduced by 12.8%. At the same time, the application of a honeycomb panel structure can reduce the weight of the transducer.

A review on system and materials for aqueous flexible metal–air batteries

AbstractThe exploration of aqueous flexible metal–air batteries with high energy density and durability has attracted many research efforts with the demand for portable and wearable electronic devices. Aqueous flexible metal–air batteries feature Earth‐abundant materials, environmental friendliness, and operational safety. Each part of one metal–air battery can significantly affect the overall performance. This review starts with the fundamental working principles and the basic battery configurations and then highlights on the common issues and the recent advances in designing high‐performance metal electrodes, solid‐state electrolytes, and air electrodes. Bifunctional oxygen electrocatalysts with high activity and long‐term stability for constructing efficient air electrodes in flexible metal–air batteries are summarized including metal‐free carbon‐based materials and nonprecious Co/Fe‐based materials (alloys, metal oxides, metal sulfites, metal phosphates, metal nitrates, single‐site metal–nitrogen–carbon materials, and composites). Finally, a perspective is provided on the existing challenges and possible future research directions in optimizing the performance and lifetime of the flexible aqueous solid‐state metal–air batteries.

Bismuth‐Activated Persistent Phosphors

AbstractBismuth cations (e.g., Bi3+, Bi2+) are very promising non‐rare‐earth activators in persistent luminescence (PersL) materials. Recently, much work has been devoted to modulating the host structures and defects to obtain high‐intensity luminescence and/or tunable excitation and emission bands of Bi‐activated persistent phosphors. A timely review on Bi‐based PersL phosphors would be highly attractive for future materials’ design and applications. The present review discusses the recent advances in Bi‐activated PersL phosphors with focus on the structure–defect–property relationships. Firstly, the basic ionic configurations of Bi cations as an activator are discussed in detail, followed by the classification as well as elaboration of Bi‐activated PersL phosphors according to emission wavelength. Then, the modulation strategies of PersL through adjusting the local structures are highlighted, which include defect engineering and theoretical prediction. These strategies allow for the effective regulation of PersL in Bi‐activated phosphors that have extensively been explored in information storage, X‐ray imaging, stress sensing, anti‐counterfeiting, etc. Finally, future challenges and perspectives toward Bi‐activated PersL phosphors are proposed. This review provides solid guidelines of designing diverse PersL materials with tunable properties for various optical applications in the future.