The paper introduces a novel structure of a dual-band filtering Wilkinson power divider (WPD). Its essential component is a dual-band bandpass filter (BPF), implemented using coupling lines and two T-shaped resonators. The BPF is incorporated into the divider structure to suppress the unwanted harmonics within the circuit. The latter is achieved owing to a wide stopband of the filter. The designed dual-band WPD can suppress third unwanted harmonics in both channels with high levels of attenuation. The designed dual-band WPD operates at 2.6 GHz and 3.3 GHz with a return loss of 22.1 dB and 22.3 dB at the operating frequencies. Furthermore, the insertion loss and isolation are 0.3 dB and 20.2 dB at 2.6 GHz and 0.9 dB and 24.5 dB at 3.3 GHz. The analysis and simulation results are corroborated by the measurements of the fabricated divider prototype. The competitive performance of the proposed circuit is also demonstrated through comparisons with state-of-the-art divider circuits from the... [more]

Several techniques for cooling mass concrete structures were developed in order to increase structural integrity and reduce the influence of cement hydration, which sometimes causes cracking in concrete structures, negatively affecting their durability. This research focuses on cooling system design, initial investment, and the influence of different refrigerants on cooling system performance aims in producing higher quality massive concrete. Cooling aggregates in massive concrete structures such as desert dams can be performed by employing cooled air from an air conditioning duct system or chilled water. The experimental study illustrates the relationship between the coefficient of performance COP, the evaporator temperature, cooling capacity, and refrigerant mass flow rate as a function of the evaporator temperature, cooling capacity, and refrigerant mass flow rate. The findings of the experiments were utilized to verify a numerical model developed utilizing engineering equation solv... [more]

In order to solve the problem of uneven air inlet flow in the guide channel of autoclave, three optimization schemes for the guide plate were proposed. The flow field in the guide channels of autoclave was simulated and analyzed by the realizable k-epsilon turbulence model and dynamic boundary method. The results show that the three optimization schemes have a certain effect on solving the problem of uneven air inlet flow in each guide channel, but some of them also have some negative effects. The integration of the three optimization schemes effectively increases the total air inlet flow of the guide channels; the increase ratio reaches 4.15%, improves the flow-field characteristics at the outlet of the guide channels and greatly reduces the difference in the air inlet flow in the left and right guide channels; the difference ratio drops from 62.61% to 5.37%.

In this study, we developed the design process and optimization of structural parameters of a new low-NOx burner based on low-NO combustion technology and the flame stabilization principle. Firstly, on the basis of the two-stage swirl burner, we applied the fuel-graded combustion technology and introduced the central nozzle structure to explore the influence law of graded combustion on NO emissions. Secondly, on the previously optimized structure, the matching law between the first- and second-stage cyclone blades is analyzed to obtain the optimum structural design solution for heat exchange efficiency and flame front length. Finally, a new conical blunt structure is introduced in conjunction with the flame stabilization principle, and we discuss the effects of different half cone angles on the flame stabilization, flame front length, and heat exchange efficiency of the burner. The research in this paper provides a reliable direction for the design optimization of low-NOx burners.

In this paper, two design optimisation methods are evaluated using gradient-based optimisation for electric vehicle traction applications. A driving cycle-based approach is used to evaluate specific operational points for the design optimisation procedure. To determine the operational points, an energy centre of gravity (ECG) approach is used. Both optimisation methods are described, namely the point based method and the flux mapping method, with a focus on the flux mapping procedure. Within the flux mapping approach, an inner optimisation loop is defined in order to maintain the stability of gradient calculation for the gradient-based optimisation. An emphasis is placed on the importance of how the optimisation problem is defined, in terms of the objective function and constraints, and how it affects a gradient based optimisation. Based on a design case study conducted in the paper, it is found that the point-based strategy realised motor designs with a slightly lower overall cost (5.... [more]

Feeding IC engines with hydrogen-rich syngas as an admixture to hydrocarbon fuels can decrease pollutant emissions, particularly NOx. It offers a potential technique for low-environmental impact hydrocarbon fuel use in automotive applications. However, hydrogen-rich reformate gas (syngas) production via fuel reforming still needs more research and optimization. In this paper, we describe the effect of a plasma torch assembly design on syngas yield and composition during plasma-assisted reforming of gasoline. Additionally, erosion resistance of the cathode-emitting material under the conditions of gasoline reforming was studied, using hafnium metal and lanthanated tungsten alloy. The gasoline reforming was performed with a noncatalytic, nonthermal, low-current plasma system in the conditions of partial oxidation in an air and steam mixture. To find the most efficient plasma torch assembly configuration in terms of hydrogen production yield, four types of anode design were tested, i.e.,... [more]

In this work, sodium aluminate alkaline solution was used to capture CO2 in a continuous bubble column scrubber and aluminum tri-hydrate (ATH) precipitates were produced. As the sodium carbonate could be recycled after the filtrated solution was crystallized by evaporation, a novel CO2 capture process was developed successfully. There were five experimental operation variables, including solution flow rate (A), concentration of the solution (B), gas flow rate (C), CO2 gas concentration (D), and liquid temperature (E), with four levels to each variable. The influence of each variable on absorption efficiency (EF), absorption rate (RA), absorption factor (φ), mass transfer coefficient (KGa), and precipitation rate (RP) in a steady state was explored in this study. The Taguchi experimental design was adopted, and 16 experiments were performed; as the optimum operating conditions found in Taguchi analysis required further verification, there were a total of 21 experiments in the end. Accor... [more]

Compared with planar-type solid oxide fuel cells (SOFCs), mono-block-layer build (MOLB)-type SOFCs have additional three-phase boundaries per unit volume, and their performance is severely limited by their longer current path. To resolve this issue, a vertical rib design, which was evaluated using a numerical method, was proposed. Compared with the conventional design, the power density for the vertical rib design increased by 12.32%. This is because the vertical rib design provides another short path for current, which not only reduces the ohmic loss in the cathode, but also decreases the ohmic polarization caused by the contact resistance. However, the vertical rib design hinders the transport of oxygen in the cathode and increases the concentration loss. Therefore, the vertical rib size design is crucial. Based on the influence of the vertical rib width, the vertical rib widths on the cathode and anode sides of 0.7 and 1 mm are recommended for different contact resistances, respecti... [more]

As an important part of the navigation facilities for water conservancy and electricity in Gezhouba, the operation safety of herringbone gates is critical. Due to the minor torsional stiffness of the gate, it is easy to produce torsional deformation during operating under the water pressure, wind load, and gravity, which may lead to fatigue damage. In this study, a gate model with a combination of plate unit and the solid unit was developed, taking a ship lock herringbone gate as an example. According to the gate load under different working conditions, such as self-weight, surge, etc., in this research, we used the finite element analysis software ANSYS to analyze and calculate the stress and strain of the gate, with and without a back tie, and obtained the characteristics of the gate torsional deformation under various working conditions. The results show that the gate’s deformation degree and the direction under different working conditions vary greatly. The maximum deformation poin... [more]

The removal of acidic gases and impurities from gas mixtures is a critical operation in the oil and gas industry. Several separation techniques, e.g., cryogenic fractionation, polymeric membranes, zeolites, and metal−organic frameworks, are employed to treat gas mixtures depending upon the nature of separation and contaminants present in the gas mixtures. However, removing N2, H2, H2S, and CO2 contents from industrial gas mixtures is a challenging step due to economic factors, high energy consumption, and effective separation. Hydrate-based separation for selective gas removal is a promising and efficient separation technique over a range of temperatures, pressures, and acidic gas contents. The enclathration of CO2, H2, N2, H2S, and other natural gas constituents effectively removes acidic gases and other contaminants from process gas streams. This work presents a novel process design to remove acidic gases and other contaminants from industrial waste gases and natural gas mixtures to... [more]

Since each branch of the multiterminal DC circuit system relies on the DC circuit breaker for breaking and fault isolation, the prohibitive cost and huge volume of the Hybrid DC Circuit Breaker (HCB) limit its development and broad application in multiterminal flexible DC systems. Multiport hybrid DC circuit breaker (MP-HDCCB) based on device and branch sharing reduces the configuration cost of the circuit breaker to a certain extent. In order to further reduce the cost of MP-HDCCB, a novel MP-HDCCB topology based on hybrid switching devices is proposed, adopting full controlled switching devices to achieve rapidity of breaking fault current, and using semi-controlled switching devices in series to withstand the transient interruption voltage (TIV), so as to reduce the construction cost and technical difficulty. In this paper, the working principle and fault breaking strategy of the topology are introduced in detail, then the parameters of the major circuit are analyzed theoretically,... [more]

The bidirectional DC-DC converters are widely used in the energy storage system (ESS) and DC distribution system. The power capacity is limited when the converter is operated with smooth power transfer. In addition, the directions of the inductor current and the capacitor voltage cannot change instantaneously. In this study, a rapid energy conversion technique for smoothing and accelerating the energy transfer under the same specification of the main components in steady state is proposed. Moreover, a bidirectional DC-DC converter with a high conversion ratio is proposed to overcome the commonly low voltage input from renewable energy sources. The operating principles of the proposed converter’s step-down and step-up modes are discussed in this study. Furthermore, to achieve rapid energy conversion, digital control is a crucial component in the converter system. A digital signal processor is used as the control platform, and a control strategy is formulated to achieve rapid energy conv... [more]

Designing waterfront redevelopment generally focuses on attractiveness, leisure, and beauty, resulting in various types of building and block shapes with limited considerations on environmental aspects. However, increasing climate change impacts necessitate these buildings to be sustainable, resilient, and zero CO2 emissions. By producing five scenarios (plus existing buildings) with constant floor areas, we investigated how buildings and district forms with building integrated photovoltaics (BIPV) affect energy consumption and production, self-sufficiency, CO2 emission, and energy costs in the context of waterfront redevelopment in Tokyo. From estimated hourly electricity demands of the buildings, techno-economic analyses were conducted for rooftop PV systems for 2018 and 2030 with declining costs of rooftop PV systems. We found that environmental building designs with rooftop PV system are increasingly economical in Tokyo with CO2 emission reduction of 2−9% that depends on rooftop si... [more]

Evaporators used in organic Rankine cycles (ORC) are designed using existing flow boiling correlations that are mainly based on HVAC&R data. However, the ORC evaporators employed in the industry typically have larger diameters and operational conditions at higher reduced pressures compared to the HVAC&R applications. The present study presents the results of flow boiling heat transfer experiments in operational conditions that are representative for an industrial waste heat recovery low-temperature ORC’s evaporator tube, by being performed at high reduced pressures and in a large-diameter horizontal tube with R245fa as working fluid. The measurements are performed within a range of mass flux, saturation temperature and heat flux at 83−283 kg/m2s, 85−120 °C (8.9−19.2 bar) and 17−29 kW/m2, respectively. Test section is a round and plain horizontal carbon steel tube with 21 mm I.D., 2.5 m length. 513 local two-phase heat transfer coefficients are recorded. The experimental results are com... [more]

This research aims to enter the miniature refrigeration machine sector with the objective of designing a small scale unit while maintaining a competitive coefficient of performance (COP), comparing with a Peltier plates system. To this end, a research of the current technology was carried out in order to obtain indicative values on the scales that were being worked on and their application. After the previous research, a refrigeration cycle was designed in EES (engineering equation solver). From this design, different conclusions were obtained: (1) The correct sizing of the compressor revolutions together with its displacement is crucial for the equipment to be able to provide the desired cooling capacity. (2) In order to obtain the desired cooling capacity in the microscale refrigeration system, the heat exchangers must have fins. (3) Of the analysed refrigerants, R600a is the best choice, as it shows favourable characteristics (high COP and low compression ratio) when working in this... [more]

At present, the wheel loaders on the market have steering vibration problems, which can be summarized as follows: the front frame and the cab vibrate violently at the beginning and at the end of steering. This paper analyzed the steering vibration mechanism by collecting the pressure at different positions of the hydraulic steering system and AMESim simulation. A cushion valve was designed to solve the problem of steering vibration. Finally, the prototype test was carried out and it was concluded that the cushion valve reduced the steering pressure starting shock by 50%, the stop vibration was reduced by 75%, and the suction problem no longer occurred. Further, the analysis provides theoretical and experimental basis for research on the steering system of loaders, and also provides new ideas for the design and optimization of vehicle steering systems.

The cavity receiver’s thermal conversion performance is critical for parabolic dish and tower Concentrated Solar Power (CSP) systems. Distinct from precedent research aiming to increase the receiver’s absorption through cavity geometry optimization, the objective of this work was to investigate the thermal conversion performance of a novel, positive conical cavity receiver design, following the heat loss reduction approach with simplified pipe forming, to stress the effectiveness of this approach in cavity receiver design, and to provide data for future optimization of the proposed design. To accomplish these goals, the novel receiver and existing designs’ heat flux absorption and heat loss are compared numerically. The resulting conversion power is also experimentally validated. The concept is inspired by analysis of formulas, suggesting the novel design may realize a thermal conversion improvement of 8.6%, at 650 K, and increases with the rise in temperature. The comprehensive numeri... [more]

As a key component of a large-capacity converter, the laminated busbar can improve the reliability, integration and power density of the converter and has great advantages in reducing the parasitic inductance of the switching loop. The laminated busbar suitable for a high-capacity back-to-back converter has a complex structure, and couple with each side converter. It has been challenging to optimize the equivalent inductance by using the traditional single-converter busbar design method. In this paper, the coupling inductance model of the back-to-back converter is established, and the relationship between the voltage stress of the switch tube and the stray inductance is analyzed in detail. Based on this, the design principle of the laminated busbar is proposed, and an optimized design structure of the laminated busbar suitable for the large-capacity back-to-back converter is given. Finally, the results were effectively verified by simulation analysis and a 180 kW integrated intermediat... [more]

Geothermal energy is one of the primary sources of clean electricity generation as the world transitions away from fossil fuels. In comparison to enhanced geothermal methods based on artificial fracturing, closed-loop geothermal systems (CLGSs) avoid seismicity-induced risk, are independent of reservoir permeability, and do not require the direct interaction between the fluid and the geothermal reservoir. In recent years, the development of CLGS technologies that offer high energy efficiencies has been explored. Research on coaxial closed-loop geothermal systems (CCLGS) and U-shaped closed-loop geothermal system (UCLGS) systems were reviewed in this paper. These studies were categorized based on their design, modeling methods, and heat transfer performance. It was found that UCLGSs had superior heat transfer performances compared to CCLGS. In addition, UCLGSs that utilized CO2 as a working fluid were found to be promising technologies that could help in addressing the future challenges... [more]

Research interest on brushless doubly fed induction machines (BDFMs) is increasing, as they offer higher reliability compared to doubly fed induction generators (DFIGs) in wind turbines. At the moment, BDFMs do not have a definitive structure nor design process, as literature is rife with different approaches to designing BDFMs. In this paper, a comprehensive review of the design of BDFMs from available literature is conducted. The evolution of cascade induction machine systems to contemporary BDFMs is first illustrated. Pioneering research work in the evolution which have influences on modern BDFM designs are highlighted. Relevant research on different aspects of present day BDFM design are then discussed. BDFM design and optimization methodologies applied in available literature are also explored.

Mandatory regulations are published worldwide for the efficiency of line-operated electric motors. The small-sized single-phase induction motors (SPIMs) will not be off the hook in terms of efficiency, since new regulations are scheduled to be introduced regarding them no later than July 2023. By doing so, the efficiency of capacitor-run SPIMs will be forced to exceed the (currently) typical ratings and comply with the requirements of the IE3 (i.e., premium) efficiency class. Since this task is challenging, the already published research works investigated several design, control, and manufacturing aspects. Nevertheless, less attention has been devoted to the study of the rotor bar’s shape impact, both on the SPIMs’ efficiency and starting capability. This gap is filled in this work by examining rotor squirrel-cage configurations with eight different bar shapes for the case of a four-pole/1.0 HP capacitor-run SPIM. A sensitivity analysis, which involves the simultaneous variation of th... [more]

Microgrids are essential elements of the energy transition because they allow optimal use of renewable energy sources (photovoltaic panels, wind turbines) and storage devices (batteries, supercapacitors) by connecting them to consumption poles (e.g., buildings, charging stations of electric vehicles). Lithium-ion batteries and supercapacitors are the main electrical storage devices usually used by microgrids for energy and power transient management. In the present paper, microgrid simulations have been performed. Electrothermal and aging models of storage components are presented. Strategies and scenarios for the batteries are presented either based on the state of charge limitation or hybrid association with supercapacitors. The contribution of this study is to provide a management strategy which considers the aging of storage systems in the real-time management of the microgrid in order to extend their life, while minimizing installation costs. The first approach for a techno-econom... [more]

As a major technical route to utilize biomass energy, biomass combustion power generation (BCPG) has been shown to be of environmental and economic significance. According to the operating experience, the installed capacity has a decisive impact on the operation and economic return of BCPG projects. In China, an installed capacity of either 30 MW or 12 MW is often chosen for constructing a BCPG project. To explore which one is more suitable for China, this paper uses actual operating data to compare the operation performance and techno-economics of two representative BCPG projects with an installed capacity of 30 MW and 12 MW. The results show that the operation situation and electricity production of the 30 MW project are better than those of the 12 MW project. The 30 MW project has a lower biomass consumption than the 12 MW project to produce per unit of electricity. The Internal Rate of Return (IRR) of the 30 MW project is greater than the industry benchmark in China and is almost t... [more]

Vapour mass transfer is often underestimated when designing the bases for structures in frost susceptible soils. Intensive and long-term vapour transport may lead to excessive frost heaving and associated issues. A vapour transport model and the algorithm of its calculation is presented in this study based on the results of experimental freeze−thaw cycles of nine soil samples with varied density. The temperature field distribution, air voids volume and the energy comprising latent heat for the phase transition and heat extracted during the temperature drop are the main parameters for determining the vapour velocity and the amount of ice formed. According to the results, the average speed of vapour transport in frozen soils was about 0.4 m/h. The amount of ice built in 1 h during uniaxial freezing due to the saturated vapour pressure difference was 1.64 × 10−5−3.6 × 10−⁵ g/h in loose samples and 1.41 × 10−⁶ g/h to 5.61 × 10−⁷ g/h in dense samples of 10 cm diameter and 10 cm high section... [more]

Agropellets are presented as a suitable product to be produced in certain agro-industries which could become Integrated Biomass Logistic Centres (IBLC) by taking advantage of its current resources during those periods in which their facilities are underused. Wheat straw and maize stalk were selected to be blended with forestry wood in an agro-industry dedicated to animal feed production. The materials were characterized to assess the quality of the input material. Taking into account the former, different pellets (blends of woody and herbaceous biomass) were produced and tested in a fixed bed reactor in order to study their combustion behaviour. Additionally, several predictive indexes were also calculated to assess sintering and deposition occurrence probability. Ash sintering degree was found to be directly related to composition and highly dependent on Si content. Moreover, an increase of the wood content in the blend did not proportionally imply a higher quality of the final blend,... [more]