There is a problem of a rapid decline in production caused by the repeated heating of the near-wellbore zone during steam stimulation. Finding a suitable foam system to expand the area of the steam chamber and slow down the rapid production of hot water during the recovery process can effectively improve the effect of steam stimulation. In this paper, CGS foam was prepared with high-temperature-resistant surfactant GD, graphite particles, and clay particles. Through the study of foam properties, it was found that with the addition of particles, the strength of the foam’s liquid film, half-life time, and temperature resistance was greatly improved. The appropriate permeability of the CGS foam and the movement characteristics of it in formations with different permeabilities were studied through a plugging experiment with a sand pack. The plugging performances of the GD foam, CGS foam, and pure particles in a simulated reservoir were compared. The development of the steam cavity during t... [more]

Previously conducted studies have established the conversion relationship between incident energy, reflected energy, transmitted energy and absorbed energy of rocks under dynamic load. In this paper, the combined dynamic and static loading tests of sandstone under different prestress and different bedding angles are carried out to explore the law of the influence of prestress and bedding angles on energy evolution and damage evolution. The purpose is to provide some reference for deep mining, rock engineering design and geological hazard assessment. The energy conversion and damage characteristics of sandstone in the whole process of deformation are studied, and the internal energy conversion mechanism of sandstone under dynamic load is proposed. It is found that the increase in prestress will lead to the increase in the initial energy value of sandstone and further affect the shape of the energy evolution curve. In addition, the relationship between strain and energy transformation is... [more]

Tight-sandstone oil and gas resources are the key areas of unconventional oil and gas resources exploration and development. Because tight-sandstone reservoirs usually have the characteristics of a low porosity and ultralow permeability, large-scale hydraulic fracturing is often required to form artificial fractures with a high conductivity to achieve efficient development. The brittleness of rock is the key mechanical factor for whether fracturing can form a complex fracture network. Previous scholars have carried out a lot of research on the brittleness characteristics of conglomerate and shale reservoirs, but there are few studies on the brittleness characteristics of sandstone with different types and different coring angles in tight-sandstone reservoirs and the fracture propagation law of sandstone with different brittleness characteristics. Based on this, this paper carried out a systematic triaxial compression and hydraulic fracturing experiment on the tight sandstone of Shan 1... [more]

In view of the high impact of extreme disasters, this paper comprehensively evaluates power grid performance from a new low-carbon toughness perspective. First, considering the increase in carbon emissions and the recovery time of carbon emissions, low-carbon resilience indicators are proposed. At the same time, considering the power-regulation effect of the phase-shifter transformer, the fault and response model of a power grid under an ice disaster is established, and then, a comprehensive evaluation index system of low-carbon toughness of the power grid is constructed. The weight determination is carried out using the fuzzy analytic hierarchy process-entropy-based weight method, while the fuzzy comprehensive evaluation center of gravity method is used to evaluate the power grid comprehensively. Finally, examples are presented to verify the feasibility of the proposed method, emphasizing its potential for evaluating the comprehensive performance of low-carbon and toughness of the pow... [more]

TiO2 photoelectrode has become an attractive platform due to its excellent photoelectric performance and has been widely used in battery, photocatalysis, and other photoelectric fields. However, when the TiO2 photoelectrode is used in solar flow batteries, the small photo-charging current is a potential problem, which will extend the charging process and lower the battery utilization efficiency. To address this issue, Cu2O is introduced to the surface of the TiO2 photoelectrode, and Cu2O-TiO2 forms a heterojunction to improve battery performance in this work. The formation mechanism of Cu2O-TiO2 is revealed and utilized to deposit Cu2O on pre-treated FTO glass covered with TiO2 films using electrochemical deposition (ECD). The photoelectrochemical properties of Cu2O-TiO2 photoelectrodes are characterized using XRD, UV-vis diffuse reflectance spectroscopy, XPS, and electrochemical characterizations. The successful deposition of Cu2O on the surface of TiO2 photoelectrode is confirmed, an... [more]

The winding process is one of the essential processes in the manufacturing of lithium-ion batteries (LIBs). Current collector failure frequently occurs in the winding process, which severely increases the production cost and reduces production efficiency. In order to solve this problem, we first analyze the relationship between different process parameters and the failure of the current collector, and put forward the standard to determine the failure of the current collector. Moreover, we conducted tensile experiments to validate the differences in the mechanical performance of the current collector under different thicknesses. Finally, the circumferential stress and strain of the current collector winding were calculated using finite element analysis. The accuracy of the proposed criterion for determining current collector failure was verified through experimental measurements of stress and strain. The results demonstrate that the criterion proposed in this study can accurately calcul... [more]

Employing multi-stage fracturing technology in horizontally accessed wells is a well-known way to successfully develop shale reservoirs. The interaction between natural fractures and hydraulic fractures has a significant impact on the fracturing effect. In this study, a coupled model of rock deformation and fluid flow was established using the cohesive zone method to simulate the propagation of hydraulic fractures under the synergistic effect of natural fractures and wellbore interference. The influence of in situ stress, fracture spacing, the number of fracture clusters, and the fracturing methods on the formation of fracture networks was analyzed. Studies on the fracture morphology and connectivity of fracture networks show that when the in situ stress difference is small, multiple fractures can easily form, and when the in situ stress difference is large, they can easily gather into a single fracture. An excessive reduction in fracture spacing may impede the optimal propagation and... [more]

This paper establishes a mathematical model of the high-pressure common rail injection system used in diesel engines according to the parameters of its key components, and AMESim 2020 software was used to establish a simulation model of the common rail injection system used in diesel engines. The simulation model mainly includes a high-pressure oil pump model, a common rail pipe model, and a model of four injectors. This paper also describes an experimental analysis of the accuracy of the established simulation model. Through a simulation analysis of the system rail’s pressure fluctuation and pressure characteristics, it was concluded that the length of the common rail pipe, the diameter of the common rail pipe, and the inner diameter of the high-pressure fuel pipes are important influencing parameters for the rail pressure characteristics of the system. In this study, according to the original common rail pipe and high-pressure fuel pipe model, a response surface methodology was used... [more]

As the ‘heart’ of energy vehicles, the lithium-ion battery is in desperate need of precision improvement, green production, and cost reduction. To achieve this goal, the electro-hydraulic servo pump control system (EHSPCS) is applied to the lithium-ion battery pole rolling mill (LBPRM). However, this development can lead to limited dynamic performance and large power loss as a result of the EHSPCS unique volume direct-drive control mode. At present, how to solve this conflict has not been studied and how the EHSPCS component parameters influence the dynamic response, power loss, and economic performance is not clear. In this paper, a multi-objective optimization (MOO) model for the LBPRM-EHSPCS is proposed by comprehensively considering the dynamic, efficiency, and economic characteristics. Firstly, the evaluation model of the dynamic response, power loss, and cost is investigated. Then, the NSGA-II algorithm is introduced to address the Pareto front of the MOO model. Finally, the powe... [more]

In this study, a diesel engine was used to operate with blends of light fraction waste cooking oil (LFWCO) with diethyl ether (DEE). DEE was blended as an additive in the 5% to 20% ratio in steps of 5% each. The test indicates that LFWCO+15-DEE produced optimum results regarding performance and emission. The BSFC for LFWCO+15-DEE was found to be higher by about 28.9%, and the BTE was lower by about 7.6%, in contrast to diesel, at 100% operating load, respectively. For LFWCO+15-DEE the EGT was lower by about 11.9%, in contrast to neat diesel, at 100% operating load. The various emissions such as carbon monoxide (CO), nitrous oxide (NO), and smoke opacity for LFWCO+15-DEE were found to be lower by about 32.9%, 25%, and 29.4%, but the NO release was more than other blends and it was about 36%, in contrast to diesel at 100% operating load, respectively.

Research on the flow electrification characteristic is of paramount importance for ensuring the electrostatic safety of liquid hydrogen transportation systems. However, the discussion about electrostatic saturation in flow electrification has been lacking. To address this gap, a theoretical model governing the process of flow electrification is constructed which couples the charge conservation equation with the Navier-Stokes equations and applies the Neumann boundary conditions at the solid-liquid interface, and the application of this model is validated by existing experimental data with the simulation parameters of At and n being 9.08 × 1012 and 0.85 for liquid hydrogen. A comparison with benzene reveals that benzene almost reaches the electrostatic saturation state after flowing one meter, whereas the flow of liquid hydrogen remains in the linear growth stage. However, with an increase in pipe length, a gradual saturation trend emerges in the curves of streaming current versus flow... [more]

The development of natural fractures (NFs) in shale gas reservoirs is conducive to improving the productivity of shale gas wells. However, NF development leads to high-frequency frac hits between the infill and parent wells, which critically restricts its efficiency. To elucidate the large contribution of hydraulic fractures (HFs) and NFs in frac hits during the production and the development of NF-developed shale gas reservoirs, such reservoirs in the WY area of western China are taken as an example. A total of 197 frac hits well events in this area are systematically classified via the frac-hit discrimination method, and the effects of different factors on HF- and NF- dominated frac hits are classified and studied. Combined with the correlation analysis method and the chart method, the main controlling factors affecting the two types of frac hits are determined, and the corresponding frac-hit prevention countermeasures are proposed. The research demonstrates that (1) the distribution... [more]

The process of energy transition in Colombia has sparked an exploration into appropriate geographical areas for the utilization of solar energy. The country’s rugged terrain and significant climate variability pose challenges for implementing standardized technologies uniformly across all regions. Consequently, this study aims to develop and apply a mathematical model to characterize the performance of a solar adsorption cooling system under the environmental conditions found in six distinct Colombian cities, taking into account different thermal profiles and extreme weather periods such as the El Niño and La Niña phenomena. The selected mathematical model was simulated in these cities, considering ambient temperature and solar radiation variables over a twelve-month period during these extreme weather phenomena and an additional twelve-month period representative of a typical year with minimal influence from these phenomena. The results indicated that despite a lower coefficient of pe... [more]

This research proposes the dandelion optimizer (DO), a bioinspired stochastic optimization technique, as a solution for achieving maximum power point tracking (MPPT) in photovoltaic (PV) arrays under partial shading (PS) conditions. In such scenarios, the overall power output of the PV array is adversely affected, with shaded cells generating less power and consuming power themselves, resulting in reduced efficiency and local hotspots. While bypass diodes can be employed to mitigate these effects by redirecting current around shaded cells, they may cause multiple peaks, making MPPT challenging. Therefore, metaheuristic algorithms are suggested to effectively optimize power output and handle multiple peaks. The DO algorithm draws inspiration from the long-distance movement of a dandelion seed, which relies on the force of the wind. By utilizing this bioinspired approach, the DO algorithm can successfully capture the maximum power point (MPP) under different partial shading scenarios, wh... [more]

Emergency management synergy capability is not only a “touchstone” to measure the operation effect of the emergency system of coal mine enterprises, it is an important symbol to reflect its level. In order to improve the level of emergency management in coal mines based on the PPRR theory of crisis management cycle, in this paper a hierarchical evaluation index system is constructed based on the emergency management process. A quantitative evaluation model of emergency synergy capacity is proposes based on the entropy−weighted elemental topology method to conduct evaluation and model validation for the case of J coal mine in Henan Province. The results show that the overall evaluation of the emergency management synergy capability of J Coal Mine is at a “good” level, with the emergency prevention synergy capability, emergency preparedness synergy capability, and recovery and reconstruction synergy capability at a “good” level and the emergency response synergy capability is at a “avera... [more]

This paper focuses on a comprehensive stability study of a two-area power system with wind power integration and synthetic inertia control in each area, considering the effects of varying the interconnection link. Normally, synthetic inertia proposals are analyzed in one-area systems, in which stability is tested without considering transmission system phenomena, such as coherency. As modern power systems are progressively becoming interconnected, the possibility of forming two or more non-coherent areas is likely, which poses a challenge to synthetic inertia control techniques that use system frequency as a main feedback signal. In this context, this work addresses a crucial gap in the existing literature and provides a valuable starting point for studying more complex interconnected power systems with wind power integration. Simulations were performed in Matlab-Simulink considering a data-driven frequency dynamics model of the Chilean Electric System, and a wind power model with synt... [more]

This article proposes an innovative two-stage technology for biomass torrefaction generating high-quality biochar, more specifically biocoal, as solid fuel, and offering a promising solution to the challenges posed by the combustion of biomass. In particular, the higher quality of biochar as solid fuel reduces the build-up of unmanageable deposits on fired surfaces, as these deposits inhibit heat transfer and reduce the efficiency of biomass boilers. The proposed two-stage technology involves torrefaction in a hearth-type reactor at temperatures up to 250 °C, followed by a subsequent stage of cooling achieved through washing with water. The two-stage torrefaction technology is integrated within a vertical hearth reactor vessel composed of three superimposed trays serving for biomass input, torrefaction, and water washing combined with biomass cooling, respectively. Upon contact with torrefied biomass, cooling water turned into water vapor; hence, eliminating the requirement for subsequ... [more]

Rapid-cycle pressure swing adsorption (PSA) with small adsorbents particles is intended to improve mass transfer rate and productivity. However, the mass transfer mechanisms are changed with reduction of particle size during rapid-cycle adsorption process. A heat and mass transfer model of rapid-cycle PSA air separation process employing small LiLSX zeolite particles is developed and experimentally validated to numerically analyze the effects of mass transfer resistances on the characteristics of cyclic adsorption process. Multicomponent Langmuir model and linear driving force model are employed for characterizing the adsorption equilibrium and kinetic. The results of numerical analysis demonstrate that the dominant mass transfer resistance of small adsorbents particles is a combination of film resistance, axial dispersion effect and macropore diffusion resistance. The oxygen purity, recovery and productivity of the product are overestimated by ~2−4% when the effect of axial dispersion... [more]

Aiming at the optimal layout of a deep chamber for coal−gangue separation (DCCS) based on the weak stratum horizon, an in-depth study was carried out by combining field investigations, model tests, and numerical simulations. Firstly, the main structural characteristics of DCCS were summarized. Then, the deformation and failure law for rocks surrounding DCCS were revealed under different horizons in the weak stratum. Finally, the optimal layout methods of DCCS based on the thickness and horizon in the weak stratum were determined in different in situ stresses, using the proposed comprehensive evaluation method for surrounding-rock stability. The results show that if the thickness of the weak stratum was small, the side near the roof of DCCS should be arranged along the weak stratum when the lateral pressure coefficient was λ < 0.6 or λ > 1. The side near the floor of DCCS was arranged along the weak stratum when 0.6 ≤ λ ≤ 1 and the surrounding-rock stability was the best. If the thickne... [more]

Coal spontaneous combustion disasters are one of the most serious types of mine disasters in China at present, posing a huge threat to underground personal safety and coal production operations. In order to prevent and control coal spontaneous combustion hazards and construct an efficient early warning system, this paper presents a review of coal spontaneous combustion early warning based on the Web of Science database search of 583 papers related to coal spontaneous combustion early warning collected from 2002 to 2021, using VOSviewer visualization software. The number of publications and partnerships at the author, institution and country levels are obtained, and the research hotspots in the field of coal spontaneous combustion warning are obtained based on keyword co-occurrence and clustering. The results show that the research results of scholars with a high publication volume have significant influence in the field of coal spontaneous combustion warning and prevention and control,... [more]

The Baode Block in the Ordos Basin is currently one of the most successfully developed and largest gas field of low−medium rank coal in China. However, the production of coal fine has affected the continuous and stable drainage and efficient development of this area. The special response and mechanism of differential fluid action during the drainage process is one of the scientific issues that must be faced to solve this production problem. In view of this, the evolution laws of a reservoir’s macro−micro physical characteristics under different fluid conditions (fluid pressure, salinity) have been revealed, and the response mechanism of coal fine migration-induced reservoir damage has been elucidated through a nuclear magnetic resonance online displacement system. The results indicated that pores at different scales exhibited varying patterns with increasing displacement pressure. The proportion of the mesopore and transition pore is not affected by salinity and is positively correlate... [more]

In order to optimize the slit/slot geometry design of a bipropellant pintle injector, the impinging spray development of a pintle injector was numerically investigated. The VOF (volume of fluid) and LES (large eddy simulation) methods were employed for an analysis to capture the gas−liquid interface by means of the AMR (adaptive mesh refinement) method. In those simulation cases, different flowrates, slot numbers, pintle diameters, slot thicknesses and slot shapes were compared for an analysis. In a comparison of visualization and quantification, a high flowrate and large pintle diameter were shown to be more positive features for improving the atomization quality and mixing effect. As for the slot parameters and shape, the spray development was mainly determined by the flow proportion between the slit jet and slot jet. The simulation results indicated that dominant slot jets cause a more dispersed spatial distribution, which is more conducive to the subsequent improvement of combustio... [more]

In underground engineering, the deformation of surrounding rock caused by “three heights and one disturbance” leads to the failure of grouted rockbolt systems, which causes huge economic losses to the mining industry. The research shows that the failure process of grouted rockbolt systems is the result of energy accumulation and release, but the relationship between failure mode and energy dissipation is rarely studied. Based on this, the load transfer behavior, energy dissipation, failure mode and failure mechanism of the grouted rockbolt systems are investigated from the perspective of energy in this study using the indoor pullout test. Test results show that the load decreases rapidly, and the absorbed energy decreases due to the whole-body splitting crack. The absorbed energy of the specimen in the splitting crack mode is lower than that in the pullout failure mode. When the pullout load reaches its peak, the pullout load of the specimen with split failure mode decreases sharply. M... [more]

Weakly cemented soft rock mines in the Ordos Basin are susceptible to mining disasters, including roof collapse and substantial deformation of surrounding rocks, during coal mining operations. Researching the damage characteristics of structures composed of low-strength “soft rock−coal” combinations is crucial for effectively preventing and controlling disasters in deep soft rock mining. To investigate the fractal damage characteristics of soft rock−coal combinations with different height ratios, uniaxial compression tests were conducted on specimens containing soft rock percentages of 20%, 40%, 50%, 60%, and 80%. The results show that the uniaxial compressive strength and modulus of elasticity of the soft rock−coal combinations increased with increasing proportions of soft rock. The soft rock−coal combination was clearly segmented, and the 40%, 50%, and 60% soft rock−coal combinations had good self-similarity. The fractal dimensions were 2.374, 2.508 and 2.586, which are all within th... [more]

The low-fidelity simulation method cannot meet the requirements for predicting the performance of an adaptive cycle engine (ACE), especially when considering tip clearance variations in the compression and expansion systems. The tip clearances of the components of an ACE, such as the adaptive fan and turbine, vary drastically under different operating conditions. Though the tip clearance significantly impacts the engine’s performance, including its thrust and fuel consumption, variations in tip clearance are not considered in traditional ACE simulation models. This paper developed a new integrated model for predicting ACE performance, including multi-fidelity simulation models of the components and a newly developed, simplified model for predicting tip clearance. Specifically, the integrated model consists of a zero-dimensional (0D) engine performance simulation model, a three-dimensional (3D) adaptive fan numerical simulation model, a one-dimensional (1D) low-pressure-turbine (LPT) me... [more]