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Showing records 346 to 370 of 668. [First] Page: 1 11 12 13 14 15 16 17 18 19 Last
Design and Optimization of the Slide Guide System of Hydraulic Press Based on Energy Loss Analysis
Mengdi Gao, Haihong Huang, Zhifeng Liu, Xinyu Li, John W. Sutherland
November 28, 2018 (v1)
Keywords: design optimization, eccentric loads, energy loss, hydraulic press, stiffness
The clearances in the slide guide system of a hydraulic press are one of the significant factors affecting its accuracy. These clearances also affect the energy consumption of the press. An energy loss model that considers the oil leaks and friction associated with these clearances was proposed, and the size of clearances was optimized based on the model. The maximum allowable eccentric load and the energy loss on the wedge clearance condition were calculated to ensure the slide and guide pillars function properly. The stiffness of pillars and wear of guide rails were checked under an eccentric load condition. A case for rapid sheet metal forming with a 20 MN hydraulic press was examined. For this case, the optimum fit clearances were found to be approximately 0.4 mm. The energy loss under an eccentric load condition was increased by approximately 83% compared to a non-eccentric load condition. The pillars were optimized by reducing excessive stiffness, which served to decrease the pi... [more]
Hydrothermal Conversion of Neutral Sulfite Semi-Chemical Red Liquor into Hydrochar
Ramy Gamgoum, Animesh Dutta, Rafael M. Santos, Yi Wai Chiang
November 28, 2018 (v1)
Keywords: ash content, higher heating value, hydrochar, hydrothermal conversion, red liquor, thermogravimetric analysis
Hydrochar was produced from neutral sulfite semi-chemical (NSSC) red liquor as a possible bio-based solid fuel for use in power generation facilities. Hydrothermal conversion (HTC) experiments were conducted using a fixed liquor-to-water volume ratio of 1:8 and reaction time of 3 h. Solutions were processed using different chemical additives, pH and temperature conditions to determine the optimum conditions required for producing a high energy content solid fuel. The hydrochar samples produced were analyzed by ultimate, thermogravimetric (TGA) and Fourier transform infrared spectroscopy (FTIR) analyses to determine physicochemical properties that are important for utilization as a fuel. The residual process liquids were also analyzed to better understand the effect of HTC process conditions on their properties. It was determined that the optimum conditions for producing a solid fuel was at a reaction temperature of 250 °C, in the presence of acetic acid at pH 3. The maximum energy cont... [more]
Controlled Al3+ Incorporation in the ZnO Lattice at 188 °C by Soft Reactive Co-Sputtering for Transparent Conductive Oxides
Salvatore Sanzaro, Antonino La Magna, Emanuele Smecca, Giovanni Mannino, Giovanna Pellegrino, Enza Fazio, Fortunato Neri, Alessandra Alberti
November 28, 2018 (v1)
Subject: Materials
Keywords: Al doped ZnO (AZO), co-sputtering, doping, dye-sensitized solar cells (DSCs), low temperature, transparent conductive oxide (TCO)
Transparent conductive oxide (TCO) layers, to be implemented in photo-anodes for dye-sensitized solar cells (DSCs), were prepared by co-deposition of ZnO and Al using pulsed-direct current (DC)-magnetron reactive sputtering processes. The films were deposited at low deposition temperatures (RT-188 °C) and at fixed working pressure (1.4 Pa) using soft power loading conditions to avoid intrinsic extra-heating. To compensate the layer stoichiometry, O₂ was selectively injected close to the sample in a small percentage (Ar:O₂ = 69 sccm:2 sccm). We expressly applied the deposition temperature as a controlling parameter to tune the incorporation of the Al3+ species in the targeted position inside the ZnO lattice. With this method, Aluminum-doped Zinc Oxide films (ZnO:Al) were grown following the typical wurtzite structure, as demonstrated by X-ray Diffraction analyses. A combination of micro-Raman, X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry (SE) analyses has shown... [more]
Performance Evaluation of a Helical Coil Heat Exchanger Working under Supercritical Conditions in a Solar Organic Rankine Cycle Installation
Marija Lazova, Henk Huisseune, Alihan Kaya, Steven Lecompte, George Kosmadakis, Michel De Paepe
November 28, 2018 (v1)
Keywords: concentrated PV collectors, heat exchanger design, helical coil heat exchanger, organic Rankine cycle (ORC), supercritical heat transfer
Worldwide interest in low grade heat valorization using organic Rankine cycle (ORC) technologies has increased significantly. A new small-scale ORC with a net capacity of 3 kW was efficiently integrated with a concentrated solar power technology for electricity generation. The excess heat source from Photovoltaic (PV) collectors with a maximum temperature of 100 °C was utilized through a supercritical heat exchanger that uses R-404A as working medium. By ensuring supercritical heat transfer leads to a better thermal match in the heat exchanger and improved overall cycle efficiency. A helical coil heat exchanger was designed by using heat transfer correlations from the literature. These heat transfer correlations were derived for different conditions than ORCs and their estimated uncertainty is ~20%. In order to account for the heat transfer correlation uncertainties this component was oversized by 20%. Next, a prototype was built and installed in an integrated concentrated photovoltaic... [more]
Thermo-Structural Response Caused by Structure Gap and Gap Design for Solid Rocket Motor Nozzles
Lin Sun, Futing Bao, Ning Zhang, Weihua Hui, Shaozeng Wang, Nan Zhang, Heng Deng
November 28, 2018 (v1)
Keywords: frictional interfaces, gap design, structure gap, thermo-structural
The thermo-structural response of solid rocket motor nozzles is widely investigated in the design of modern rockets, and many factors related to the material properties have been considered. However, little work has been done to evaluate the effects of structure gaps on the generation of flame leaks. In this paper, a numerical simulation was performed by the finite element method to study the thermo-structural response of a typical nozzle with consideration of the structure gap. Initial boundary conditions for thermo-structural simulation were defined by a quasi-1D model, and then coupled simulations of different gap size matching modes were conducted. It was found that frictional interface treatment could efficiently reduce the stress level. Based on the defined flame leak criteria, gap size optimization was carried out, and the best gap matching mode was determined for designing the nozzle. Testing experiment indicated that the simulation results from the proposed method agreed well... [more]
Dynamic Stall Control on the Wind Turbine Airfoil via a Co-Flow Jet
He-Yong Xu, Chen-Liang Qiao, Zheng-Yin Ye
November 28, 2018 (v1)
Keywords: co-flow jet, dynamic stall, flow control, numerical simulation, wind turbine
Dynamic stall control of a S809 airfoil is numerically investigated by implementing a co-flow jet (CFJ). The numerical methods of the solver are validated by comparing results with the baseline experiment as well as a NACA 6415-based CFJ experiment, showing good agreement in both static and dynamic characteristics. The CFJ airfoil with inactive jet is simulated to study the impact that the jet channel imposes upon the dynamic characteristics. It is shown that the presence of a long jet channel could cause a negative effect of decreasing lift and increasing drag, leading to fluctuating extreme loads in terms of drag and moment. The main focus of the present research is the investigation of the dynamic characteristics of the CFJ airfoil with three different jet momentum coefficients, which are compared with the baseline, giving encouraging results. Dynamic stall can be greatly suppressed, showing a very good control performance of significantly increased lift and reduced drag and moment.... [more]
A Criterion for Rating the Usability and Accuracy of the One-Diode Models for Photovoltaic Modules
Aldo Orioli, Alessandra Di Gangi
November 28, 2018 (v1)
Keywords: five-parameter model, I-V characteristics, one-diode equivalent circuit, photovoltaic modules, solar energy
In selecting a mathematical model for simulating physical behaviours, it is important to reach an acceptable compromise between analytical complexity and achievable precision. With the aim of helping researchers and designers working in the area of photovoltaic systems to make a choice among the numerous diode-based models, a criterion for rating both the usability and accuracy of one-diode models is proposed in this paper. A three-level rating scale, which considers the ease of finding the data used by the analytical procedure, the simplicity of the mathematical tools needed to perform calculations and the accuracy achieved in calculating the current and power, is used. The proposed criterion is tested on some one-diode equivalent circuits whose analytical procedures, hypotheses and equations are minutely reviewed along with the operative steps to calculate the model parameters. To assess the achievable accuracy, the current-voltage (I-V) curves at constant solar irradiance and/or cel... [more]
Distribution of Clay Minerals in Light Coal Fractions and the Thermal Reaction Products of These Clay Minerals during Combustion in a Drop Tube Furnace
Sida Tian, Yuqun Zhuo, Zhonghua Zhan, Xinqian Shu, Zhizhong Kang
November 28, 2018 (v1)
Keywords: aluminosilicate components, ash formation, coal slagging characteristics, density separation, mineral matter distribution
To estimate the contribution of clay minerals in light coal fractions to ash deposition in furnaces, we investigated their distribution and thermal reaction products. The light fractions of two Chinese coals were prepared using a 1.5 g·cm−3 ZnCl₂ solution as a density separation medium and were burned in a drop-tube furnace (DTF). The mineral matter in each of the light coal fractions was compared to that of the relevant raw coal. The DTF ash from light coal fractions was analysed using hydrochloric acid separation. The acid-soluble aluminium fractions of DTF ash samples were used to determine changes in the amorphous aluminosilicate products with increasing combustion temperature. The results show that the clay mineral contents in the mineral matter of both light coal fractions were higher than those in the respective raw coals. For the coal with a high ash melting point, clay minerals in the light coal fraction thermally transformed more dehydroxylation products compared with those i... [more]
A Multi-Point Method Considering the Maximum Power Point Tracking Dynamic Process for Aerodynamic Optimization of Variable-Speed Wind Turbine Blades
Zhiqiang Yang, Minghui Yin, Yan Xu, Zhengyang Zhang, Yun Zou, Zhao Yang Dong
November 28, 2018 (v1)
Subject: Optimization
Keywords: aerodynamic optimization, closed-loop system, maximum power point tracking (MPPT) control, multi-point method, variable-speed wind turbine (VSWT)
Due to the dynamic process of maximum power point tracking (MPPT) caused by turbulence and large rotor inertia, variable-speed wind turbines (VSWTs) cannot maintain the optimal tip speed ratio (TSR) from cut-in wind speed up to the rated speed. Therefore, in order to increase the total captured wind energy, the existing aerodynamic design for VSWT blades, which only focuses on performance improvement at a single TSR, needs to be improved to a multi-point design. In this paper, based on a closed-loop system of VSWTs, including turbulent wind, rotor, drive train and MPPT controller, the distribution of operational TSR and its description based on inflow wind energy are investigated. Moreover, a multi-point method considering the MPPT dynamic process for the aerodynamic optimization of VSWT blades is proposed. In the proposed method, the distribution of operational TSR is obtained through a dynamic simulation of the closed-loop system under a specific turbulent wind, and accordingly the m... [more]
Hybridization of Chaotic Quantum Particle Swarm Optimization with SVR in Electric Demand Forecasting
Min-Liang Huang
November 28, 2018 (v1)
Keywords: chaotic quantum particle swarm optimization (CQPSO), electric load forecasting, quantum behavior, support vector regression (SVR)
In existing forecasting research papers support vector regression with chaotic mapping function and evolutionary algorithms have shown their advantages in terms of forecasting accuracy improvement. However, for classical particle swarm optimization (PSO) algorithms, trapping in local optima results in an earlier standstill of the particles and lost activities, thus, its core drawback is that eventually it produces low forecasting accuracy. To continue exploring possible improvements of the PSO algorithm, such as expanding the search space, this paper applies quantum mechanics to empower each particle to possess quantum behavior, to enlarge its search space, then, to improve the forecasting accuracy. This investigation presents a support vector regression (SVR)-based load forecasting model which hybridizes the chaotic mapping function and quantum particle swarm optimization algorithm with a support vector regression model, namely the SVRCQPSO (support vector regression with chaotic quan... [more]
Working Fluid Stability in Large-Scale Organic Rankine Cycle-Units Using Siloxanes—Long-Term Experiences and Fluid Recycling
Tobias G. Erhart, Jürgen Gölz, Ursula Eicker, Martijn van den Broek
November 28, 2018 (v1)
Keywords: fluid recycling, fluid stability, operational experience, organic rankine cycle (ORC), siloxane, working fluid
The results in this work show the influence of long-term operation on the decomposition of working fluids in eight different organic rankine cycle (ORC) power plants (both heat-led and electricity-led) in a range of 900 kW el to 2 MW el . All case study plants are using octamethyltrisiloxane (MDM) as a working fluid; the facilities are between six to 12 years old. Detailed analyses, including the fluid distribution throughout the cycle, are conducted on one system. All presented fluid samples are analyzed via head space gas chromatography mass spectrometry (HS-GC-MS). Besides the siloxane composition, the influence of contaminants, such as mineral oil-based lubricants (and their components), is examined. In most cases, the original working fluid degrades to fractions of siloxanes with a lower boiling point (low boilers) and fractions with a higher boiling point (high boilers). As a consequence of the analyses, a new fluid recycling and management system was designed and... [more]
Development of Near Optimal Rule-Based Control for Plug-In Hybrid Electric Vehicles Taking into Account Drivetrain Component Losses
Hanho Son, Hyunsoo Kim
November 28, 2018 (v1)
Keywords: drivetrain component losses, dynamic programming (DP), mode control strategy, plug-in hybrid electric vehicle (PHEV)
A near-optimal rule-based mode control (RBC) strategy was proposed for a target plug-in hybrid electric vehicle (PHEV) taking into account the drivetrain losses. Individual loss models were developed for drivetrain components including the gears, planetary gear (PG), bearings, and oil pump, based on experimental data and mathematical governing equations. Also, a loss model for the power electronic system was constructed, including loss from the motor-generator while rotating in the unloaded state. To evaluate the effect of the drivetrain losses on the operating mode control strategy, backward simulations were performed using dynamic programming (DP). DP selects the operating mode, which provides the highest efficiency for given driving conditions. It was found that the operating mode selection changes when drivetrain losses are included, depending on driving conditions. An operating mode schedule was developed with respect to the wheel power and vehicle speed, and based on the operatin... [more]
Mitigation Emission Strategy Based on Resonances from a Power Inverter System in Electric Vehicles
Li Zhai, Xinyu Zhang, Natalia Bondarenko, David Loken, Thomas P. Van Doren, Daryl G. Beetner
November 28, 2018 (v1)
Keywords: electric vehicles (EVs), electromagnetic interference (EMI), mitigation emission, power inverter, resonance
Large dv/dt and di/dt outputs of power devices in the DC-fed motor power inverter can generate conducted and/or radiated emissions through parasitics that interfere with low voltage electric systems in electric vehicles (EVs) and nearby vehicles. The electromagnetic interference (EMI) filters, ferrite chokes, and shielding added in the product process based on the “black box” approach can reduce the emission levels in a specific frequency range. However, these countermeasures may also introduce an unexpected increase in EMI noises in other frequency ranges due to added capacitances and inductances in filters resonating with elements of the power inverter, and even increase the weight and dimension of the power inverter system in EVs with limited space. In order to predict the interaction between the mitigation techniques and power inverter geometry, an accurate model of the system is needed. A power inverter system was modeled based on series of two-port network measurements to study t... [more]
Assessing Steady-State, Multivariate Experimental Data Using Gaussian Processes: The GPExp Open-Source Library
Sylvain Quoilin, Jessica Schrouff
November 28, 2018 (v1)
Keywords: experimental data, feature selection, Gaussian processes, kriging, outlier, regression, surface response
Experimental data are subject to different sources of disturbance and errors, whose importance should be assessed. The level of noise, the presence of outliers or a measure of the “explainability” of the key variables with respect to the externally-imposed operating condition are important indicators, but are not straightforward to obtain, especially if the data are sparse and multivariate. This paper proposes a methodology and a suite of tools implementing Gaussian processes for quality assessment of steady-state experimental data. The aim of the proposed tool is to: (1) provide a smooth (de-noised) multivariate operating map of the measured variable with respect to the inputs; (2) determine which inputs are relevant to predict a selected output; (3) provide a sensitivity analysis of the measured variables with respect to the inputs; (4) provide a measure of the accuracy (confidence intervals) for the prediction of the data; (5) detect the observations that are likely to be outliers.... [more]
Three-Dimensional Finite-Element Analysis of the Short-Time and Peak Withstand Current Tests in Substation Connectors
Francesca Capelli, Jordi-Roger Riba, Joan Pérez
November 28, 2018 (v1)
Keywords: connector, finite element method, peak withstand current test, short-time withstand current test, Simulation, substation
Power devices intended for high-voltage systems must be tested according to international standards, which includes the short-time withstand current test and peak withstand current test. However, these tests require very special facilities which consume huge amounts of electrical power. Therefore, mathematical tools to simulate such tests are highly appealing since they allow reproducing the electromagnetic and thermal behavior of the test object in a fast and economical manner. In this paper, a three-dimensional finite element method (3D-FEM) approach to simulate the transient thermal behavior of substation connectors is presented and validated against experimental data. To this end, a multiphysics 3D-FEM method is proposed, which considers both the connector and the reference power conductors. The transient and steady-state temperature profiles of both the conductors and connector provided by the 3D-FEM method prove its suitability and accuracy as compared to experimental data provid... [more]
A Multi-Component Additive to Improve the Thermal Stability of Li(Ni1/3Co1/3Mn1/3)O₂-Based Lithium Ion Batteries
Qingsong Wang, Lihua Feng, Jinhua Sun
November 28, 2018 (v1)
Subject: Materials
Keywords: electrolyte, lithium ion battery (LIB) safety, multi-component (MC) additive, thermal stability
To improve the safety of lithium ion batteries, a multi-component (MC) additive (consisting of vinylene carbonate (VC), 1,3-propylene sulfite (PS) and dimethylacetamide (DMAC)) is used in the baseline electrolyte (1.0 M LiPF₆/ethylene carbonate (EC) + diethyl carbonate (DEC)). The electrolyte with the MC additive is named safety electrolyte. The thermal stabilities of fully charged Li(Ni1/3Co1/3Mn1/3)O₂ (NCM) mixed with the baseline electrolyte and safety electrolyte, respectively, are investigated using a C80 micro-calorimeter. The electrochemical performances of the NCM/baseline electrolyte/Li and NCM/safety electrolyte/Li half cells are evaluated using galvanostatic charge/discharge, cyclic voltammetry and alternating current (AC) impedance. The experimental results demonstrate that the fully charged NCM-safety electrolyte system releases less heat and reduces the main sharp exothermic peak value to a great extent, with a reduction of 40.6%. Moreover, the electrochemical performance... [more]
The Influence of Slight Protuberances in a Micro-Tube Reactor on Methane/Moist Air Catalytic Combustion
Ruirui Wang, Jingyu Ran, Xuesen Du, Juntian Niu, Wenjie Qi
November 28, 2018 (v1)
Keywords: catalytic combustion, methane/moist air, micro-tube reactor, slight protuberances
The combustion characteristics of methane/moist air in micro-tube reactors with different numbers and shapes of inner wall protuberances are investigated in this paper. The micro-reactor with one rectangular protuberance (six different sizes) was studied firstly, and it is shown that reactions near the protuberance are mainly controlled by diffusion, which has little effect on the outlet temperature and methane conversion rate. The formation of cavities and recirculation zones in the vicinity of protuberances leads to a significant increase of the Arrhenius reaction rate of CH₄ and gas velocity. Next, among the six different simulated conditions (0⁻5 rectangular protuberances), the micro-tube reactor with five rectangular protuberances shows the highest methane conversion rate. Finally, the effect of protuberance shape on methane/moist air catalytic combustion is confirmed, and it is found that the protuberance shape has a greater influence on methane conversion rate than the number of... [more]
Development of a PEM Fuel Cell City Bus with a Hierarchical Control System
Siliang Cheng, Liangfei Xu, Jianqiu Li, Chuan Fang, Junming Hu, Minggao Ouyang
November 28, 2018 (v1)
Keywords: city bus, hierarchical control, performance analysis, the polymer electrolyte membrane (PEM) fuel cell
The polymer electrolyte membrane (PEM) fuel cell system is considered to be an ideal alternative for the internal combustion engine, especially when used on a city bus. Hybrid buses with fuel cell systems and energy storage systems are now undergoing transit service demonstrations worldwide. A hybrid PEM fuel cell city bus with a hierarchical control system is studied in this paper. Firstly, the powertrain and hierarchical control structure is introduced. Secondly, the vehicle control strategy including start-stop strategy, energy management strategy, and fuel cell control strategy, including the hydrogen system and air system control strategies, are described in detail. Finally, the performance of the fuel cell was analyzed based on road test data. Results showed that the different subsystems were well-coordinated. Each component functioned in concert in order to ensure that both safety and speed requirements were satisfied. The output current of the fuel cell system changed slowly an... [more]
CFD Analysis on the Thermal Hydraulic Performance of an SAH Duct with Multi V-Shape Roughened Ribs
Anil Kumar, Man-Hoe Kim
November 28, 2018 (v1)
Keywords: heat transfer enhancement, SAH, solar energy, thermal hydraulic performance
This study presents the heat transfer and fluid flow characteristics in a rib-roughened SAH (solar air heater) channel. The artificial roughness of the rectangular channel was in the form of a thin circular wire in discrete multi V-pattern rib geometries. The effect of this geometry on heat transfer, fluid flow, and performance augmentation was investigated using the CFD (computational fluid dynamics). The roughness parameters were a relative discrete distance of 0.69, a relative rib height of 0.043, a relative rib pitch of 10, a relative rib width of 6.0, and a flow-attack-angle of 60°. The discrete width ratios and Reynolds numbers ranged from 0.5 to 2.0 and from 2000 to 20,000, respectively. The CFD results using the renormalization k-epsilon model were in good agreement with the empirical relationship. This model was used to investigate the heat transfer and fluid flow characteristics in the multi V-pattern rib roughened SAH channel. The thermo-hydraulic performance was found to be... [more]
A Design Alternative to Improve the Interconnection Capability of New Distributed-Generation Installations into Existing Griddle
José Agüero-Rubio, Javier López-Martínez, José Ignacio Rojas-Sola, Ángel Jesús Callejón-Ferre
November 28, 2018 (v1)
Keywords: distributed generation, distribution grids, grid-connected, installation efficiency, low voltage feeders, sustainable cities
Most distributed-generation facilities are performed on pre-built distribution grids. The design conditions of these existing grids may limit the ability of new users to get a connection due to technical and/or cost constraints. This work proposes a simple solution, adjusted to the relevant regulations and embodied in a radial distribution grid of Spanish low voltage, to improve the interconnection of distributed generation, usually grid connected photovoltaic systems. The proposed solution, based on increasing the section of the neutral line, achieves a capacity of increasing the length of the supply grid by more than 20%.
Fundamental Active Current Adaptive Linear Neural Networks for Photovoltaic Shunt Active Power Filters
Muhammad Ammirrul Atiqi Mohd Zainuri, Mohd Amran Mohd Radzi, Azura Che Soh, Norman Mariun, Nasrudin Abd Rahim, Shahrooz Hajighorbani
November 28, 2018 (v1)
Keywords: artificial neural network (ANN), current harmonic, digital signal processor (DSP), photovoltaic (PV), shunt active power filter (SAPF), Simulink/MATLAB, total harmonic distortion (THD)
This paper presents improvement of a harmonics extraction algorithm, known as the fundamental active current (FAC) adaptive linear element (ADALINE) neural network with the integration of photovoltaic (PV) to shunt active power filters (SAPFs) as active current source. Active PV injection in SAPFs should reduce dependency on grid supply current to supply the system. In addition, with a better and faster harmonics extraction algorithm, the SAPF should perform well, especially under dynamic PV and load conditions. The role of the actual injection current from SAPF after connecting PVs will be evaluated, and the better effect of using FAC ADALINE will be confirmed. The proposed SAPF was simulated and evaluated in MATLAB/Simulink first. Then, an experimental laboratory prototype was also developed to be tested with a PV simulator (CHROMA 62100H-600S), and the algorithm was implemented using a TMS320F28335 Digital Signal Processor (DSP). From simulation and experimental results, significant... [more]
Life Cycle Assessment of a HYSOL Concentrated Solar Power Plant: Analyzing the Effect of Geographic Location
Blanca Corona, Diego Ruiz, Guillermo San Miguel
November 28, 2018 (v1)
Subject: Energy Policy
Keywords: biomethane, Chile, environment, Kingdom of Saudi Arabia, Life Cycle Assessment (LCA), Mexico, Natural Gas, solar energy, South Africa, Spain
Concentrating Solar Power (CSP) technology is developing in order to achieve higher energy efficiency, reduced economic costs, and improved firmness and dispatchability in the generation of power on demand. To this purpose, a research project titled HYSOL has developed a new power plant, consisting of a combined cycle configuration with a 100 MWe steam turbine and an 80 MWe gas-fed turbine with biomethane. Technological developments must be supported by the identification, quantification, and evaluation of the environmental impacts produced. The aim of this paper is to evaluate the environmental performance of a CSP plant based on HYSOL technology using a Life Cycle Assessment (LCA) methodology while considering different locations. The scenarios investigated include different geographic locations (Spain, Chile, Kingdom of Saudi Arabia, Mexico, and South Africa), an alternative modelling procedure for biomethane, and the use of natural gas as an alternative fuel. Results indicate that... [more]
Numerical Modeling of Variable Fluid Injection-Rate Modes on Fracturing Network Evolution in Naturally Fractured Formations
Yu Wang, Xiao Li, Bo Zhang
November 28, 2018 (v1)
Keywords: hydraulic fracturing, hydraulic fracturing effectiveness, numerical simulation, variable injection-rate technology
In this study, variable injection-rate technology was numerically investigated in a pre-existing discrete fracture network (DFN) formation, the Tarim Basin in China. A flow-stress-damage (FSD) coupling model has been used in an initial attempt towards how reservoir response to variable injection-rates at different hydraulic fracturing stages. The established numerical model simultaneously considered the macroscopic and microscopic heterogeneity characteristics. Eight numerical cases were studied. Four cases were used to study the variable injection-rate technology, and the other four cases were applied for a constant injection-rate in order to compare with the variable injection-rate technology. The simulation results show that the variable injection-rate technology is a potentially good method to a form complex fracturing networks. The hydraulic fracturing effectiveness when increasing the injection-rate at each stage is the best, also, the total injected fluid is at a minimum. At the... [more]
A New Predictive Model Based on the ABC Optimized Multivariate Adaptive Regression Splines Approach for Predicting the Remaining Useful Life in Aircraft Engines
Paulino José García Nieto, Esperanza García-Gonzalo, Antonio Bernardo Sánchez, Marta Menéndez Fernández
November 28, 2018 (v1)
Keywords: aircraft engine, artificial bee colony (ABC), multivariate adaptive regression splines (MARS), prognostics, reliability, remaining useful life (RUL)
Remaining useful life (RUL) estimation is considered as one of the most central points in the prognostics and health management (PHM). The present paper describes a nonlinear hybrid ABC⁻MARS-based model for the prediction of the remaining useful life of aircraft engines. Indeed, it is well-known that an accurate RUL estimation allows failure prevention in a more controllable way so that the effective maintenance can be carried out in appropriate time to correct impending faults. The proposed hybrid model combines multivariate adaptive regression splines (MARS), which have been successfully adopted for regression problems, with the artificial bee colony (ABC) technique. This optimization technique involves parameter setting in the MARS training procedure, which significantly influences the regression accuracy. However, its use in reliability applications has not yet been widely explored. Bearing this in mind, remaining useful life values have been predicted here by using the hybrid ABC⁻... [more]
Simultaneous Optimization of Topology and Component Sizes for Double Planetary Gear Hybrid Powertrains
Weichao Zhuang, Xiaowu Zhang, Huei Peng, Liangmo Wang
November 28, 2018 (v1)
Subject: Optimization
Keywords: energy management, hybrid electric vehicles (HEVs), optimal design methodology, topology optimization
Hybrid powertrain technologies are successful in the passenger car market and have been actively developed in recent years. Optimal topology selection, component sizing, and controls are required for competitive hybrid vehicles, as multiple goals must be considered simultaneously: fuel efficiency, emissions, performance, and cost. Most of the previous studies explored these three design dimensions separately. In this paper, two novel frameworks combining these three design dimensions together are presented and compared. One approach is nested optimization which searches through the whole design space exhaustively. The second approach is called enhanced iterative optimization, which executes the topology optimization and component sizing alternately. A case study shows that the later method can converge to the global optimal design generated from the nested optimization, and is much more computationally efficient. In addition, we also address a known issue of optimal designs: their sens... [more]
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