This paper proposes an alternative multiconductor transmission line model that combines the folded line equivalent with the modal transformation. The folded line equivalent decomposes the nodal admittance matrix of a transmission line into its open-circuit and short-circuit contributions. These contributions are fitted to rational functions, which are associated with Norton equivalent circuits based on their state space models. The proposed model uses an orthogonal matrix to transform voltages and currents from the phase domain to the folded line equivalent domain and vice versa. Because the transformation matrix is orthogonal, we represent it using ideal transformers in simulation software. First, we use a circuit representation of Clarke’s matrix to decompose a transmission line into its modes. Then, each mode is decomposed into its open-circuit and short-circuit contributions using a circuit implementation of the proposed matrix. The proposed approach can accurately represent short... [more]

Porosity and permeability alteration due to the thermo-poro-elastic stress field disturbance from the cold fluid injection is a deciding factor for longer, more economic, and safer heat extraction from an enhanced geothermal system (EGS). In the Soultz-sous-Forêts geothermal system, faulted zones are the main flow paths, and the resulting porosity−permeability development over time due to stress reorientation is more sensitive in comparison with the regions without faulted zones. Available operational and field data are combined through a validated numerical simulation model to examine the mechanical impact on the pressure and temperature evolution. Results shows that near the injection wellbore zones, permeability and porosity values are strongly affected by stress field changes, and that permeability changes will affect the overall temperature and pressure of the system, demonstrating a fully coupled phenomenon. In some regions inside the faulted zones and close to injection wellbore... [more]

The paper presents a new approach to designing the stator of a multistage centrifugal pump, which has a simple structure, satisfactory operating parameters, and is easy to manufacture. The stator is distinguished by its lack of a classic diffuser part, with the shape of its crossover being similar to a segment of a spherical surface. This solution was patented in 1989, but to date it is not well known and practically not used. The paper attempts to identify the flow phenomena in such a stator and also to examine the impact of the design features of the stator on the pump’s operating parameters. Both experimental methods and numerical modelling were used in the research.

The Magnetotelluric (MT) method is a widely used and effective method of exploring geothermal resources because it can reveal geological information at a great depth and is cost effective. In order to further improve the reliability and rationality of MT data interpretation, MT responses for a typical hydrothermal system and a hot dry rock (HDR) and partial melting system are investigated by a finite-element (FE) forward modeling approach based on unstructured tetrahedral grids that can handle with complex-shaped geothermal systems. These two geothermal models, designed by the 3ds Max software, are comprised of a clay cap, a reservoir, and a heat source, and are discretized into tetrahedral elements by TetGen software. The results show that the apparent resistivities at the broadband of frequencies are mainly affected by the shallow low-resistivity clay cap due to its strong shielding effects, and the induction arrows effectively reflect the boundary of the clay cap. The conductive hea... [more]

Identification of harmonic sources contributing to harmonic distortion, and characterization of harmonic current injected by them, are crucial tasks in harmonic analysis of modern power systems. In this paper, these tasks are addressed based on the permissible current limits recommended by IEEE 519 Standard, with a determination of whether or not injected harmonics are within these limits. If limits are violated, the extent of the violations are characterized to provide information about harmonic current levels in the power system and facilitate remedial actions if necessary. A novel feature extraction method is proposed, whereby each set of harmonic measurements in a power system are transformed into a unique RGB image. Harmonic State Estimation (HSE) is discretized as a classification problem. Classifiers based on deep learning have been developed to subsequently locate and characterize harmonic sources. The approach has been demonstrated effectively both on the IEEE 14-bus system, a... [more]

A Cascadia Subduction Zone (CSZ) earthquake will cause widespread damage to numerous lifelines and infrastructure along the northern US west coast. The goal of the presented research is to provide a bottom up estimate of the impact on and subsequent recovery of a Cascadia Subduction Zone earthquake on the US western grid to supplement and enhance the expert opinion estimates provided to date. The scope is limited to only consideration of shaking damage to utility substation equipment components of a power system model. The analysis utilizes probabilistic models of damage and recovery for substation power system assets, along with graph techniques for modeling connectivity, and Monte Carlo quasi steady state power flow solutions. The results show that a conservative estimate of the initial damage and loss of load is approximately 4000 MW, with a recovery estimate of 230 days.

A hydrodynamic wind−wave combined power generation system is a new type of energy device that uses wind and ocean current energy to generate electricity. In this paper, the hydrodynamics of a wind−wave combined power generation system was simulated in Fluent. The fluid−structure coupling simulation of the vortex vibration of the cylindrical oscillator was realized using UDF and dynamic mesh technology. The Vortex-Induced Vibration (VIV) characteristics of the cylindrical oscillator were analyzed, and the reliability of the numerical simulation method was verified by comparing the amplitude and trajectory of the eddy-excited vibration with the classic experiments of Jauvtis and Williamson. The VIV characteristics of cylindrical oscillators with different mass ratios were studied in terms of vibration response, motion trajectory, and the streamwise equilibrium position. The effect of the mass ratio on the hydrodynamics of a wind−wave combined power generation system was simulated using s... [more]

Enhancing the performance of photovoltaic (PV) systems has recently become a key concern because of the market demand for green energy. To obtain the most possible power from the solar module, it is imperative to allow the PV system to operate at its maximum power point (MPP) regardless of the climatic conditions. In this study, a comparison of distinctive Maximum Power-Point Tracking (MPPT) techniques is provided, which are Perturb and Observe (P&O) and Modified Variable Step-Size P&O, as well as Incremental Conductance (INC) and Modified Variable Step-Size INC, using a boost converter for two types of solar panels. Using MATLAB software, simulations have been performed to assess the efficiency of the solar module under several environmental conditions, standard test conditions (STCs), and sudden and ramp variations in both solar irradiance and temperature. The output power efficiency, time response, and steady-state power oscillations have all been taken into account in this study. T... [more]

Iran is one of the most energy-consuming countries, especially in the construction sector, and more than 40% of its energy consumption is in the construction sector. Therefore, considering the very high potential of Iran in the field of solar energy, the need to pay attention to providing part of the energy required by buildings by solar energy seems necessary. The study of the effect of climate on the performance of a BIPV has not been done in Iran so far. Also, the use of ranking methods using the weighting of parameters affecting the performance of BIPV has not been done so far. The purpose of this study is to investigate the power supply of BIPV connected to the grid in the eight climates of Iran. Technical−economic−environmental energy analyses were performed by HOMER 2.81 software. In order to study different types of BIPV, four angles of 0°, 30°, 60°, and 90° were considered for the installation of solar cells. The effective output parameters of HOMER software were weighted by t... [more]

The article discusses the process of designing and testing as well as their results, carried out in order to increase the efficiency of axial fans, implemented as part of the European project INESI. Modifications of existing solutions based on rapid prototyping methods were presented. Scanning, FEM and CFD numerical calculations and 3D printing were used for that purpose. Rapid prototyping involved the use of a steel blade base and 3D-printed complex aerodynamic shapes that were bonded to create completely new blades. After their installation on the new rotor, enabling the angle of attack adjusting, a number of verifying tests of the fan were carried out. The solution was successfully tested and the results are discussed in the article.

The timescale of the energy-release process of an energy storage system has put forward higher requirements with the increasing proportion of new energy power generation in the power grid. In this paper, a new type of compressed-air energy storage system with an ejector and combustor is proposed in order to realize short-timescale and long-timescale energy-release processes under the non-supplementary combustion condition and ejector supplementary combustion condition, respectively. A simulation model of the new system is established in APROS software. The results of this study show that the new system can realize continuous power output when energy storage and energy release operate simultaneously, and especially when the ejector coefficient is 0.8 and burner thermal power is 10 MW, the power-generation time is 12.45 h and the total generated power is 140,052 kW∙h, which are 15.6 and 17.5 times greater those of the short-timescale condition, respectively. In summary, the compressed-ai... [more]

A numerical procedure was developed to determine a variable-pitch law that maximized the performance of a vertical-axis wind turbine (VAWT). The methodology was based on the determination, for each blade, of the angle of attack maximizing the stationary aerodynamic efficiency at prescribed azimuthal positions. The angles of attack were determined by means of a panel method with a low computational effort, and the methodology was implemented in Matlab® software (version R2021a) allowing us to achieve in real time a variable-pitch law suitable for the turbine geometry. The variable pitch law was validated by considering its effect on the torque of a 2D model of an H-Darrieus turbine. U-RANS analyses were carried out with a K−ωSST model and a sliding-mesh technique was used to prescribe the blade motion around the shaft and pitch motion. Results showed how the variable-pitch law delayed the dynamic stall and improved the aerodynamic performance considerably.

In northern Afghanistan, the Kashkari oil field’s first production well was drilled in 1976, and by 1979, there were a total of ten wells drilled in the area. According to the results of surveys and calculations conducted by research institutions, the total amount of original oil in place (OOIP) in the Kashkari oil site was around 140 million barrels (MMbbls). Therefore, a method to increase the total amount of recoverable oil in the Kashkari oil field by low-salinity water flooding is presented in this study. First, the oil extraction method by low-salinity water injected into the underlying petroleum storage tank was examined by both a laboratory core flooding test and a numerical simulation model. Laboratory conditions (temperature, pressure, rock properties, and oil properties) were designed to mimic those of the Kashkari oil field. Additionally, different injection (Inj) and production patterns were considered to achieve the best results. Next, results obtained from the laboratory... [more]

The parallel expander ORC system is one of the solutions for providing an additional power output by improving the partial-load performance of an ORC. The parallel expander system corresponds to partial-load conditions by switching between various combinations of the expanders. During this process, the dynamic behavior occurs, which have not been characterized well in the open literature according to the best of the authors’ knowledge. In this study, we developed a dynamic modeling of an ORC system using dual expanders (DE-ORC) to study the dynamic responses during its mode changes. System components were simulated using an open-source library of ThermoCycle written in Modelica language. For each component, empirical parameters were implemented based on the experimental results. Furthermore, during the mode change that involved going from dual expander mode to singular expander mode, and to prevent the formation of the droplet in the expanders, a control strategy was proposed and simul... [more]

In this study, we first considered the influence of micro-nozzle wall roughness structure on molecular collision and reflection behavior and established a modified CLL model. The DSMC method was used to simulate and analyze the flow of the micro-nozzle in the cold gas micro-propulsion system, and the deviation of simulation results before and after the improvement of CLL model were compared. Then, the rarefied flow characteristics under a small needle valve opening (less than 1%) were focused on the research, and the particle position, molecular number density, and spatial distribution of internal energy in the micro-nozzle were calculated. The spatial distributions of the flow mechanism in the micro-nozzle under different needle valve openings were compared and analyzed. It was found that when the needle valve opening is lower than 1%, the slip flow and transition flow regions move significantly upstream of the nozzle, the free molecular flow distribution region expands significantly,... [more]

The effect of supersonic air temperature on the mixing characteristics of liquid hydrocarbon fuel injected into three different supersonic airflows elevated in three steps from 373 K to 673 K was investigated numerically. Compressible Reynolds-averaged Navier−Stokes (RANS) equations were solved together with species conservation equation using ANSYS Fluent for two-phase flow simulations including fuel droplet breakup and evaporation. The turbulence model needed to close the RANS equations used the Shear Stress Transport (SST) k-ω model. The Eulerian−Lagrangian model was employed to track fuel droplets in mainstream air, and the Kelvin−Helmholtz and Rayleigh−Taylor (KH-RT) models were used to simulate the droplet breakup process. Numerical solutions were validated using experimental data. The higher the air temperature, the stronger the streamwise vortices downstream of the pylon. When the air temperature was 373 K, the liquid fuel hardly evaporated, but as the air temperature increased... [more]

In this paper, we present a detailed analysis of the possibility of using unsupervised machine learning techniques for reservoir interpretation based on the parameters obtained from geophysical measurements that are related to the elastic properties of rocks. Four different clustering algorithms were compared, including balanced iterative reducing and clustering using hierarchies, the Gaussian mixture model, k-means, and spectral clustering. Measurements with different vertical resolutions were used. The first set of input parameters was obtained from the walkaway VSP survey. The second one was acquired in the well using a full-wave sonic tool. Apart from the study of algorithms used for clustering, two data pre-processing paths were analyzed in the context of matching the vertical resolution of both methods. The validation of the final results was carried out using a lithological identification of the medium based on an analysis of the drill core. The measurements were performed in Si... [more]

This study presents a detailed dynamic modelling and generic simulation method of an oscillating diaphragm compressor for chemisorption energy technology applications. The geometric models of the compressor were developed step by step, including the diaphragm movement, compressor dimensions, chamber areas and volumes and so on. The detailed mathematical model representing the geometry and kinematics of the diaphragm compressor was combined with the motion equation, heat transfer equation and energy balance equation to complete the compressor modelling. This combination enables the novel compressor model to simultaneously handle the simulation of momentum and energy balance of the diagram compressor. Furthermore, an experimental apparatus was set up to investigate and validate the present modelling and the simulation method. The performance of the compressor was experimentally evaluated in terms of the mass flow rate of the compressor at various compression ratios. Additionally, the eff... [more]

Ice slurry is a high energy density coolant with excellent flow, phase change, and thermophysical properties. In order to investigate the recovery of ice slurry flowing through a local large heat flux segment, a 3D Eulerian-Eulerian model based on the granular kinetic theory considering the flow and melting phase change of ice slurry is developed. Sensitivity analysis of interphase forces is carried out. A comparison of the pressure drop, solid phase velocity, and heat transfer coefficient with empirical data is carried out, respectively. The calculated results are in good agreement with the experimental results, indicating that the numerical model could accurately describe the flow and melting characteristics. Thermophysical field distributions, the axial variation of ice volume fraction (IVF), recovery curve, the average heat transfer coefficient, as well as the re-uniformization length are obtained. After passing through local large heat flux segment, due to shear stress action, the... [more]

Supercritical boilers have become a major development trend in coal-fired power plants, and the air distribution strategy is a key factor in the design and operation of making it fully combustible. In this paper, the mathematical and physical models of a 350 MW supercritical boiler is established, and the optimal air distribution mode of the boiler at different load is determined based on the furnace outlet temperature, NOx concentration, and O2 content. The air distribution control strategies were derived and the corresponding procedures were established. 160 MW and 280 MW were selected for positive pagoda and 180 MW and 230 MW for waist reduced. At 290−350 MW load, the effect of adjusting the combustion damper opening on the outlet oxygen is weak, so preferentially adjusting the SOFA damper opening can achieve better results. The results show good thermal efficiency and emission performance and are applicable to adjust the air distribution mode to achieve fuller combustion of supercr... [more]

The aim of this work was to eliminate the backflow power present in an isolated three-port DC−DC converter. Backflow power (which is an inherent property of phase-shifted DC−DC converters) is the major contributor of circulating current the converter, which in turn is known to be the leading cause of system loss. The dual phase shift (DPS) control scheme (which alters the transformer voltage waveform at the different winding terminals) was used to reduce the backflow power. Mathematical relations for the backflow power present in the three-port converter were derived. And from this equation, an operating point in which the backflow power is zero was also obtained. This condition for zero backflow power was confirmed by simulations on PSIM. Added to this were simulation results that show other operating conditions in which zero backflow power could be obtained in the converter. In addition, equations for the power processed at the different ports of the converter were also presented, an... [more]

Smart water flooding (SWF) is a promising enhanced oil recovery (EOR) technique due to its economic advantages. For this process, wettability alteration is the most accepted controlling effect that leads to increased recovery factors (RFs). The main objective of this work is to investigate how the relative permeability curves’ interpolant affects the SWF mechanisms’ assessment. Wettability alteration is described by shifting these curves in simulations. Numerical simulations of core flooding tests are applied to carbonate at 114.4 °C. A comparison of oil recovery factor (RF), pH and effluent composition is performed for different injection approaches. Mg2+ and SO42− are the interpolant ions and the salinity levels range from 30 to 1 kppm. A simulation of 24 scenarios, 12 for each type of interpolant, is presented. Results show that RF changes significantly, due to salinity and composition, for each interpolant. This has a relevant influence on the interpolant. The greater the dilution,... [more]

Low-salinity water-alternating-CO2 (CO2-LSWAG) injection has been widely studied and employed due to its capability to promote enhanced oil recovery (EOR). However, there is no consensus on the dominant mechanisms for oil recovery in carbonates due to the extreme complexity of the oil−brine−rock interactions. This work proposes a comparative investigation of the physicochemical and geochemical effects of continuous CO2 and CO2-LSWAG immiscible injections on oil recovery in a carbonate core. Simulations were carried out using oil PVT properties and relative permeability experimental data from the literature. A comparison of SO42− and Mg2+ as interpolant ions, oil, water and gas production, pressure, and rock and fluid properties along the core and in the effluent was made. The results show a high recovery factor for CO2 (62%) and CO2-LSWAG (85%), even in immiscible conditions. The mineral dissolution and porosity variations were more pronounced for CO2-LSWAG than CO2. The simulation res... [more]

This research presents a comprehensive analysis of electric vehicle (EV) proliferation factors and various monetary and non-monetary value streams emerging in the EV domain. A comprehensive mathematical model is implemented to study EV proliferation and the resulting market share applicable to any geography and jurisdictional regime. Further, a novel framework is presented to analyze the interdependency between EV proliferation factors and value streams. The proposed model and framework can be leveraged to quantifiably evaluate the timeline available for grid operators to accommodate EV growth while utilizing those as Distributed Energy Resources (DERs) to improve grid reliability, commercial value, and environmental benefits. Compared to the previous studies, the analysis indicated that if all the factors which impact EV proliferation are addressed simultaneously, EV market share can surpass the internal combustion engine vehicle (ICV) in as quickly as 15−20 years. The study also high... [more]

Although many countries prefer deregulated power markets as a means of containing power costs, a monopoly may still exist. In this study, an agent-based bidding simulation framework is proposed to detect whether there will be a monopoly in the power market. A security-constrained unit commitment (SCUC) is conducted to clear the power market. Using the characteristics that the agent can fully explore in a certain environment and the Q-learning algorithm, each power producer in the power market is modeled as an agent, and the agent selects a quotation strategy that can improve profits based on historical bidding information. The numerical results show that in a power market with monopoly potential among the power producers, the profits of the power producers will not converge, and the locational marginal price will eventually become unacceptable. Whereas, in a power market without monopoly potential, power producers will maintain competition and the market remains active and healthy.