The use of electric vehicles (EVs) has recently increased in a smart city environment. With this, the optimal location of the charging station is a great challenge and, hence, the energy efficiency performance (EEP) of an electrical system is important. Ideally, the EEP is realized through passive energy boosters (PEBs) and active energy boosters (AEBs). PEBs require no external resources, and EEP is achieved through altering the network topology and loading patterns, whereas, in AEBs, integrating external energy resources is a must. The EEP has also become dynamic with the integration of an energy storage system (ESS) in a deregulated environment. Customer energy requirement varies daily, weekly, and seasonally. In this scenario, the frequent change in network topology requires modifying the size and location of AEBs. It alters the customers’ voltage profile, loadability margin, and supply reliability when the EV works differently as a load or source. Therefore, a comprehensive EEP an... [more]

The capacity fading and thermal safety issues caused by the volume effect of Si-based anodes and unstable solid electrolyte interphase (SEI) films during long-term cycling limit its large-scale application. In this study, silane polymer compound (2-cyanoethyl) triethoxysilane (TCN) was selected as an electrolyte additive to improve the reversibility and thermal safety of Si-based anode lithium-ion batteries (LIBs). TCN prevented the thermal interaction between the vitiated anode and electrolyte, and the onset temperature of the thermal reaction increased from 122.22 to 127.07 °C, as demonstrated by the results of thermogravimetric analysis and differential scanning calorimetry. The thermal stability of lithiated anodes containing various electrolytes was then assessed using a range of thermo-kinetic models. The results revealed that the activation energy of Si-based lithiated anodes increased from 68.46 to 91.32 kJ/mol, while the thermal hazard greatly decreased. Additionally, the elec... [more]

Numerical modeling is a widely used method in geotechnical engineering to understand the interactive responses of infrastructures with soils or/and rocks in both civil and mining engineering [...]

As the mining depth increases, in underground tunnels, caverns or pillar goaf, a rock burst is one of the important accidents that threaten mine safety. Drilling pressure relief becomes one of the main means of preventing rock bursts, which affect the mechanical properties and stability of the coal and rock in underground excavations. However, the surrounding rock of the roadway or the coal body is usually broken, and the pressure relief of the large-diameter borehole will affect its support. A segmented hole-reaming technology is proposed and applied in a coal mine in China. A pressure-relief mechanic model of segmented hole reaming was built. The coal sample had an elastic modulus of 0.35 GPa, the UCS and UTS were 17.4 MPa and 1.41 MPa, the Poisson ratio was 0.27, the cohesive force was 2.81 MPa, and the friction was 23.7°. The pressure relief range of the boreholes with different diameters, horizontal in situ stress coefficients, cohesive forces, and friction angles were analyzed. W... [more]

The aim of this paper was to study the suppression influence of water mist on oil pool fires, taking diesel fires and n-heptane fires as experimental objects. The effects of spray pressure and temperature on water mist suppression were examined, and an experimental platform for the suppression of water mist in a small space was set up. Their fire prevention performance and fire extinguishing mechanisms were analyzed by comparing the flame temperature and extinguishing time of diesel and n-heptane pool fire. Three types of spray pressure were set. Water mist was designed at different temperatures and design experiments were carried out for this purpose. The change process of smoke concentration, thermocouple temperature, and flame combustion under different working conditions were analyzed, and the factors affecting the fire extinguishing effect of water mist on oil pool fire were discussed. The results show that 20 °C water mist is more effective at medium and high pressure than at low... [more]

The reduction of metal oxides by biochar is an important reaction for many biomass utilization technologies. This work investigated the temperature−programmed reduction (TPR) of NiO/Al2O3 by in situ generated biochar from citric acid pyrolysis. Firstly, NiO/Al2O3 was loaded with citric acid by impregnation and then heated from ambient temperature to 900 °C in a N2 flow. The process was on−line analyzed by the TGA−FTIR technique. Secondly, a series of intermediates was obtained and characterized by XRD, CHNO elemental analysis, and temperature programmed oxidation (TPO). Lastly, a control experiment of unsupported NiO was conducted to show the influence of Al2O3 support on the NiO reduction. Results showed that the whole heating process could be resolved into two parts that is citric acid pyrolysis and NiO reduction at a heating rate of 5 °C/min. The NiO reduction occurred above 400 °C with the biochar from citric acid pyrolysis as reductant. In the temperature−programmed reduction proc... [more]

The application of hydrogen fuel in ORP engines makes the engine power density much higher than that of a reciprocating engine. This paper investigated the impacts of combustion characteristics, energy loss, and NOx emissions of a hydrogen-fuelled ORP engine by ignition timing over various equivalence ratios using a simulation approach based on FLUENT code without considering experiments. The simulations were conducted under the equivalence ratio of 0.5~0.9 and ignition timing of −20.8~8.3° CA before top dead centre (TDC). The engine was operated under 1000 RPM and wide-open throttle condition which was around the maximum engine torque. The results indicated that significant early ignition of the ORP engine restrained the flame development in combustion chambers due to the special relative positions of ignition systems to combustion chambers. In-cylinder pressure evolutions were insensitive to early ignition. The start of combustion was the earliest over the ignition timing of −17.3° C... [more]

Based on the acoustic wave finite element (AWFE) method, one can establish an AWFE method and study the influence of mechanical parameters on the shale reservoir acoustic wave propagation characteristics. The different crack characteristics and different crack multi-physical coupling phenomena are studied by using the AWFE method on shale gas reservoir cracks. To calculate the shape and position along the crack near a side borehole, the model parameters are compared with the simulation results. The reflection waveform characteristics of adjacent cracks are studied by using the AWFE method. By considering the borehole axis of symmetry, for an acoustic impedance discontinuous interface on one side of the two-dimensional axisymmetric AWFE, one can establish a borehole cross-crack and an arc cross-crack reflection interface model with the AWFE method. By processing the waveform data received by different receiving points under the same source distance, the parameters, such as the reflectio... [more]

A thermal behavior study of lipid-extracted Nannochloropsis gaditana (LEA) was performed in a thermogravimetric analyzer. The study was performed by heating the sample under different heating rates (5, 10, and 15 °C/min) from room temperature to 1000 °C using N2 gas as the medium. This is crucial for thermal stability studies in a kinetic control regime. The following three stages of chemical decompositions were found: (1) moisture removal (2) devolatilization (3) fixed carbon decomposition; maximum decomposition was observed at the second stage. Activation energies of the LEA were studied using the Flynn−Wall−Ozawa model and Kissinger−Akahira−Sunose model. Main sample decomposition was observed from 100−700 °C during volatile matter evaporation. The thermal behavior study findings were used for the gasification of the sample with air to study the effect of varying reaction parameters on the compositions of the synthesis gas yield. Maximum H2 yield was found at 700 °C and 0.7 g, which... [more]

This study implements a multifunctional charger based on a dual-switching, bidirectional flyback converter (DSBFC). The proposed charger adopts seven charging methods, including the incremental-current charging, constant-voltage (CV) charging, constant-current (CC) charging, pulse-current (PC) charging, triangular-current (TC) charging, sinusoidal-current (SC) charging, and positive/negative pulse-current (Reflex) charging methods. The charging process of a lithium-ion battery is divided into three stages: an initial term, a mid-term, and a final term. In the initial term, the incremental-current charging method is used in the initial term of charging for a soft start and to inhibit an increase in temperature. In the mid-term, five charging methods, including CC, PC, TC, SC, and Reflex-current charging, are used for charging. The CV charging method prevents overcharging the lithium-ion battery in the final term. Based on our experimental results, this study compares the four charging m... [more]

Underground salt cavern gas storage is the best choice for the production peak adjustment and storage of natural gas, and is a basic means to ensure the safe supply of natural gas. However, in the process of these caverns dissolving due to water injection, argillaceous insoluble sediments in the salt layer will fall to the bottom of the cavity and expand, occupying a large amount of the storage capacity and resulting in the reduction of the actual gas storage space. Effectively reducing the volume of sediments at the bottom of the cavity is a potential way to expand the storage capacity of the cavity. In this study, a method to reduce the volume of argillaceous insoluble sediments with particle sizes ranging from 10 mesh to 140 mesh, via a chemical shrinkage agent, has been proposed. Firstly, the inorganic polymer shrinkage agent PAC30 was synthesized, and then a set of dynamic shrinkage evaluation methods was established to evaluate the influence of temperature, particle size, concent... [more]

Biodiesel, which possesses the dominant advantages of low emissions and environmental friendliness, is a competitive alternative fuel to petroleum-derived diesel. The cetane number, which indicates ignition delay characteristics, is considered the most significant fuel property of biodiesel. Determining the cetane number for biodiesel by general testing equipment is time-consuming and costly; hence, a simple and convenient predictive formula for the cetane number of biodiesel is a significant task to be carried out. A reliable and convenient predictive method for determining the cetane number is proposed in this study. The key parameters for the cetane number of biodiesel were first screened out. The analysis of multiple linear regressions using the available software SPSS for statistical analysis was carried out to obtain the regression coefficients of those key parameters and intercepts to establish the predictive model. Other available experimental data verified the validity of the... [more]

In order to study the influence of the change of the guide vane airfoil on the flow characteristics in the draft tube of a reversible hydraulic turbine, a reversible hydraulic turbine was used as the object of study, and the effect of the change on the flow pattern, energy loss, and pressure pulsation in the draft tube area was studied based on the SST k-ω turbulence model. The results show that under low flow conditions, the modified movable guide vane directly affects the direction and speed of water entering the draft tube, reduces the density of vortex in the draft tube area, reduces the impact on the near wall of the draft tube during the rotation of the vortex belt, and improves the stability of the unit operation. The turbulent energy comparison graph shows that the energy loss in the bent elbow section and the diffusion section of the draft tube is reduced, and the energy return coefficient of the draft tube is improved by calculating that the energy recovery level of the draft... [more]

Two different strategies are provided to generate solutions to the three-dimensional heat diffusion equation. The first strategy is inspired by the well-known one-dimensional heat polynomial, which consists of an infinite set of polynomials, which are solutions to the one-dimensional heat diffusion equation. The second strategy is based on an exponential type function. None of the solutions presented here can be obtained by the method of separation of variables. The mathematical developments proving that, indeed, the particular solutions generated with both strategies satisfy the three-dimensional heat diffusion equation are presented. The analytical solutions are validated by generating the corresponding numerical solutions with the method of finite differences. When comparing both analytical and numerical solutions, it is found that they are identical. In addition, as part of the results, it is found that there are exponential solutions that reproduce the behavior of polynomial solut... [more]

The constant emission of greenhouse gases into the atmosphere, due to the continuous burning of fossil fuels, has been driving researchers to develop an environmentally friendly alternative fuel solution. An experimental investigation was conducted on a laboratory scale, to evaluate the physicochemical qualities, performance, emissions, and combustion characteristics of sea mango oil biodiesel blends and pure diesel fuel on a single-cylinder, variable compression ratio (VCR) engine. Tests were conducted at 1500 rpm, 210 bar, and 23° bTDC, under varying loading circumstances of 0, 3, 6, 9, and 12 kgs, and compression ratios 16:1, 17:1, and 18:1, respectively. The findings revealed that higher compression ratios (CRs) improve the performance, emission, and combustion characteristics of an engine. At CR 18:1, BTHE, SFC, and EGT improved by 8.78%, 11.18%, and 2.52% more than the standard compression ratio (17:1). The CO, HC, and smoke emissions also lowered by 14.65%, 18.56%, and 11.56%, r... [more]

Shale oil reservoirs are characterized by having various types of vertical sublayers, a large contrast in rock mechanical properties, well-developed bedding, and high clay content, which are likely to cause rock elastic−plastic deformation. In numerical simulations of hydraulic fracture (HF) propagation in the shale oil reservoirs, the effects of rock elastic−plastic deformation and complex bedding structure on the layer-crossing behavior of HF are not considered. To understand the mechanism of HF height growth in shale oil reservoirs, we used the cohesive zone method to establish an elastic−plastic finite element model of HF propagation by considering the effects of shell limestone interlayers, the Mohr−Coulomb yield criterion for shear−plastic failure, the cross-mechanical interaction between bedding and shale oil reservoir, and the complex situations such as the HF height across high-electrical resistivity bedding and high-conductivity fractures. The effects of internal friction ang... [more]

The incursion of disruptive technologies, such as the Internet of Things, information technologies, cloud computing, digitalization and artificial intelligence, into current production processes has led to a new global industrial revolution called Industry 4.0 or Manufacturing 4.0. This new revolution proposes digitization from one end of the value chain to the other by integrating physical assets into systems and networks linked to a series of technologies to create value. Industry 4.0 has far-reaching implications for production systems and engineering education, especially in the training of mechatronic engineers. In order to face the new challenges of the transition from manufacturing 3.0 to Industry 4.0 and 5.0, it is necessary to implement innovative educational models that allow the systematic training of engineers. The competency-based education model has ideal characteristics to help mechatronic engineers, especially in the development of specific competencies. This article pr... [more]

Hydraulic fracture morphology and propagation mode are difficult to predict in layers of the various lithological strata, which seriously affects exploitation efficiency. This paper studies the fundamental mechanical and microscopic properties of the two main interfaces in inter-salt shale reservoirs. On this basis, cement-salt combination samples with composite interfaces are prepared, and hydraulic fracturing tests are carried out under different fluid velocities, viscosity, and stress conditions. The result shows that the shale bedding and salt-shale interface are the main geological interfaces of the inter-salt shale reservoir. The former is filled with salt, and the average tensile strength is 0.42 MPa, c = 1.473 MPa, and φ = 19.00°. The latter is well cemented, and the interface strength is greater than that of shale bedding, with c = 2.373MPa and φ = 26.15°. There are three basic fracture modes for the samples with compound interfaces. Low-viscosity fracturing fluid and high-vis... [more]

Conservation of energy usage is essential in chemical process plants due to the expanded energy users and demands alongside the carry-on hike of energy prices. This study analyzed the performance of energy savings in a heat exchanger network (HEN). It is based on decreasing utility usage while increasing process-to-process heat exchange in HEN using a path combination approach at different heat recovery approach temperatures (HRATs). The approach generates different combined path options for heat shifting from utilities to exchangers in a HEN. In terms of cost targeting, the optimal HRAT in a HEN is determined for each path’s combination option. The study focused on the HEN of crude oil preheat trains. Shifting heat load between utilities implies adding and subtracting loads to and from exchangers in a HEN. Therefore, a minor retrofit to compensate for the heat transfer area is required for some HEN exchangers. The optimum HRAT corresponding to the lowest total cost was determined for... [more]

The equilibrium potentials of iron in a LiF-BeF2-FeF2 melt were measured using the EMF method and were dependent upon the temperature and iron fluoride concentrations. The empirical equations for the isotherms and equilibrium polytherms of the iron fluoride concentration were obtained. The cathode polarization of iron fluoride in the molten mixture of lithium and beryllium fluoride was measured using the current switch off method from the stationary state. It was found that in the studied temperature and concentration ranges of iron fluoride in the LiF-BeF2 electrolyte, the valence state of iron in the melt is mainly +2. According to the experimental values of the equilibrium potentials of the iron electrode in the LiF-BeF2-FeF2 melt, the conditional standard potentials of iron were calculated relative to the fluoride reference electrode in the molten mixture of lithium and beryllium fluoride. The conditional standard values of the Gibbs energy change were calculated at the formation o... [more]

In recent years, the technology of storing and transporting natural gas in the form of hydrate has received a lot of attention. At present, the research on the synthesis of natural gas hydrate for the purpose of storage and transportation is still in the laboratory stage, and its synthesis process is in the design and conception stage. The influencing factors of natural gas hydrate synthesis under pilot-scale conditions are more complex. Moreover, pilot experiments are oriented to actual production, and its economic feasibility and operational convenience have higher requirements. This paper aimed to study the influencing factors of gas hydrate synthesis by spray method under pilot-scale conditions. Under specific conditions of surfactant and pressure, we carried out research on the effects of reaction temperature, different forms of atomizers, high-pressure pump flow, experimental water, and other factors. Experiments show that the optimal synthesis conditions were a temperature of −5... [more]

The preparation and application of ultra-clean coal is one of the important aspects of clean energy technology. However, the preparation of ultra-clean coal is mainly chemical methods, which are low in efficiency, high in energy consumption and expensive. It is urgent to find an effective method to prepare ultra-clean coal. In this paper, the combined method of grinding and the collector gasification flotation method was used to obtain ultra-clean coal. The effects of grinding time on the particle size composition, mineral dissociation, surface properties and flotation results of coal samples were studied. The grinding test results show that with the increase in grinding time, the particle size and the pore diameter of coal samples decreased gradually, while the specific surface area and pore volume of coal samples gradually increased. When the grinding time was 20 min, the D90 and D[4,3] of grinding products were 5.20 um and 4.23 um, respectively. The ash content of −1.3 g/cm3 was les... [more]

Aiming at the problem where the current engineering wake model does not describe the wind speed distribution of the wake in the complex terrain wind farm completely, based on the three-dimensional full wake model (3DJGF wake model), this paper proposed a wake model that can predict the three-dimensional wind speed distribution of the entire wake region in the complex wind farm, taking into account the Coanda effect, wind shear effect, and wake subsidence under the Gaussian terrain. Two types of Doppler lidar were used to conduct wind field experiments, and the inflow wind profile and three-dimensional expansion of the wake downstream of the wind turbine on the Gaussian terrain were measured. The experimental results showed that the wake centerline and terrain curve showed similar variation characteristics, and the near wake profile was similar to a super-Gaussian shape (asymmetric super-Gaussian shape) under low-wind-speed conditions, while the near wake profile presented a bimodal sha... [more]

Nitrous oxide is widely used as oxidizer or nitriding agent in numerous industrial activities such as production of adipic acid and caprolactam and even for production of some semiconductors. Further, it is used as an additive in order to increase the power output of engines, and as an oxidizer in propulsion systems of rockets, because it has a large heat of formation (+81.6 kJ mol−1). N2O is highly exothermic, and during its decomposition a supplementary heat amount is released, so it needs special handling conditions. The combustion of fuels in nitrous oxide atmosphere can lead to high unstable and turbulent deflagrations that speedily self-accelerate and therefore a deflagration can change to a detonation. The peak explosion pressure and the maximum rate of pressure rise of explosions in confined spaces are key safety parameters to evaluate the hazard of processes running in closed vessels and for design of enclosures able to withstand explosions or of their vents used as relief dev... [more]

In this paper, a novel high-efficiency bidirectional isolated DC−DC converter that can be applied to an energy storage system for battery charging and discharging is proposed. By integrating a coupled inductor and switched-capacitor voltage doubler, the proposed converter can achieve isolation and bidirectional power flow. The proposed topology comprises five switches and a common core coupled inductor that uses only a set of complementary pulse-width-modulated signals to control and achieve high voltage gain without requiring high turn ratios or excessive duty cycles. Moreover, the proposed topology can recover the leakage inductance energy to improve the conversion efficiency. The main switches exhibit zero-voltage switching, which reduces the switching losses. A 500-W bidirectional converter is used to verify the feasibility of the proposed bidirectional converter through theoretical analysis and experiments. The experimental results indicate that the highest efficiency of the propo... [more]