Balance shafts are often used to improve the engine vibration characteristics of three-cylinder engines. The balance damping gear with a damping ring is an important part connecting the crankshaft and the balance shaft transmission. The stiffness characteristics of the damping ring and the unbalance of the gear have an important influence on its vibration suppression performance, but the coupled influence of the stiffness characteristics of the damping ring and the unbalanced characteristics of the vibration damping gear is unknown. In this paper, a multi-body dynamic bending−torsional coupling model of the transmission system of a three-cylinder engine with a balance damping gear is constructed considering the equivalent stiffness of the balance shaft support. Based on the fourth-order Runge−Kutta method, the influence laws of different rotational speeds, load torques, gear unbalance, radial stiffness and torsional stiffness of the damping ring on the vibration characteristics of the... [more]

In this paper, through a similar simulation experiment, the roof rock breaking situation of horizontal sublevel caving method in extremely thick and steep inclined coal seam is studied, and the response characteristics of coal and rock mass under different dynamic load strength are analyzed. The mechanical response mechanisms of different mining positions under the influence of dynamic load and the law characteristics of the surrounding rock from elastic deformation to impact failure are revealed. The study shows that with the increase in the horizontal sublevel mining depth, the roof is gradually broken from the suspended state, and the broken block fills the goaf. The thin rock strata form a granular structure, and the thick rock strata form a block splicing and occlusion structure. On the same side of the coal seam floor, the concentrated stress gradually increases, and the closer the distance from the goaf is, the more obvious the stress change in the coal body below is. With the i... [more]

This study shows the results of a simulation tool using the TRNSyS 2017 simulator, validated with experimental data from a greenhouse in an arid zone in northwestern Mexico. Additionally, experimental data on the performance of geothermal heat pumps are shown during the year 2020 in heating and cooling mode. With this information, an average deviation of the simulator for the outlet fluid temperature of the geothermal heat exchanger (GHE) of 2.77% and an average deviation of the coefficient of performance in cooling mode (EER) of the geothermal heat pump (GHP) of 3.7% was obtained. In the experimental study, it was observed that in the last 2 weeks of July and the first 2 weeks of August, the subsoil is saturated, which causes a decrease in the thermal inertia of the GHE. During the experimental study, it was possible to determine that the flow indicated in the GHE to obtain the highest performance of the GHP system in greenhouses in arid zones corresponds to 1 GPM, obtaining an EER of... [more]

In the complex fracturing process of shale gas wells, casing is subjected to serious deformation, which can easily to the failure of wellbore integrity and the reduction of well construction productivity. It is particularly important to clarify the casing deformation mechanism and carry out effective control. Based on the logging data of casing deformation from well and full-scale indoor tests, the casing deformation mechanism is mainly considered to be shear and non-uniform extrusion deformation caused by formation slip and displacement control, i.e., the ultimate working conditions. The slip displacement boundary (<40 mm) under complex fracturing conditions is quantified to provide the design and optimization basis. Then, the influence laws of steel grade and wall thickness on the shear and non-uniform extrusion bearing characteristics are studied, using unconventional oil and gas well casing simulation test systems for 110 ksi (φ139.7 × 10.54 mm) and 125 ksi (φ139.7 × 12.7 mm) ca... [more]

Lithium-ion batteries are state of the art and, still, their performance is constantly improving. To increase the energy density and electric conductivity, electrodes are usually calendered. Hereby, a higher degree of compaction, while reducing structural damage, can be reached by heating the calendering rolls. For industrially relevant line speeds, it is however questionable whether the contact time between electrode and roll is sufficient to reach the full positive effect of the increased temperature. This study shows a numerical approach based on the discrete element method to simulate the heating behavior of electrodes before and during calendering using a typical NMC-622-cathode as a model structure. To improve the results of existing, more simplified discrete element method simulations, which neglect the heat transfer through the carbon black−binder matrix, an extension with heat transfer through the carbon black−binder matrix has been implemented. Considering process parameters,... [more]

Research aimed at finding alternative fuels to replace petroleum diesel (petrodiesel) used in controlled combustion engines (CCEs) has identified biodiesel as one of the main candidates, due to its sustainability and potential for use in energy matrices. In this study, the gas emissions from a diesel CCE were investigated, with a focus on total hydrocarbons (THC) and carbon monoxide (CO). Biodiesel (B100) samples derived from the transesterification of frying oil, produced applying conventional chemical catalysis (CC) or non-thermal plasma (NTP) technology, were tested as alternative fuels. Three engine rotation speeds were investigated (900, 1500, and 2500 rpm) and biodiesel samples obtained from the residual frying oil were compared with conventional road diesel (S-500) without biodiesel added, acquired from a gas station. Blends were also prepared with S-500 and B100 obtained applying NTP for 15 or 30 min, in mixes containing 2, 12, 20, and 50% of biodiesel. These blends showed redu... [more]

The non-oxygenated oil product of the pyrolysis of polypropylene cannot be used directly as an engine fuel due to its high content of alkenes. However, high pressure of hydrogen gas is commonly employed in the hydrotreatment of alkenes to produce alkanes. A semi-batch hydrogenation reaction using a hydrogen gas self-inducing impeller to internally recirculate the hydrogen gas has been implemented in the present work to provide small hydrogen gas bubbles so that the gas dispersion in the liquid phase is intensified. This technique is expected to improve the contact of hydrogen, oil, and the Ni/Al2O3 catalyst, which in turn alleviates high pressures of hydrogen gas. The hydrogenation reaction was performed at 185 °C with an impeller speed of 400 rpm. The pressure was varied from 2 to 8 bar. At the pressure of 2 bar, the main reactions are the hydrogenation of alkenes and cyclization of alkenes leading to cycloalkane formation, while at the pressures of 4, 6, and 8 bar, the main reactions... [more]

Countries have started to aggressively undertake energy structure transformation strategies in order to reach the objective of carbon neutrality. Both clean and efficient coal energy use and clean energy use will be crucial to the process of changing the energy structure since the two cannot be totally replaced within a short period of time. In this study, we quantify emotions as an irrational factor, combine them with an evolutionary game using RDEU theory, and build an evolutionary game model between government regulators and energy consumers. We then analyze how low-carbon emotions of decision-makers affect their choice of strategy and the transformation of the energy structure. The findings support that by affecting the relative importance of each strategic choice, emotions have a profound impact on the evolutionary steady state of the system. Appropriate stress and anxiety can increase decision-makers’ feelings of responsibility, while pleasant emotions frequently support strategi... [more]

Hydraulic fracture networks, especially fracture geometry, height growth, and proppant transport within the networks, present a critical influence on productivity evaluation and optimization of fracturing parameters. However, information about hydraulic fracture networks in post-fractured formations is seldom available. In this study, the characteristics (density and orientation) of hydraulic fractures were obtained from field observations of cores taken from conglomerate hydraulic fracturing test site (CHFTS). A large number of fractures were observed in the cores, and systematic fracture description was carried out. The fracture analysis data obtained includes fracture density, fracture depth, fracture orientation, morphology, fracture surface features, apertures, fill, fracture mechanical origin (type), etc. Our results show that 228 hydraulic fractures were intersected in a span of 293.71 m of slant core and composed of irregularly spaced single fractures and fracture swarms. One o... [more]

Biopharmaceutical and pharmaceutical manufacturing are strongly influenced by the process analytical technology initiative (PAT) and quality by design (QbD) methodologies, which are designed to enhance the understanding of more integrated processes [...]

Pumped-storage hydropower (PSH) stations are an efficient emission-free technology to balance renewable energy generation instabilities. The pump-turbine is a core component of PSH stations requiring frequent start-up, shutdown, and working conditions for regulation tasks, making it prone to instabilities. Based on entropy production theory and vortex dynamics, we analyzed the energy loss characteristics for three working conditions of the pump, pump brake, and turbine when shutting down the pump-turbine. The results showed that the entropy production and vorticity of the spiral casing and draft tube remain almost constant, while the entropy production and vorticity of the runner region substantially change from the late pump braking to the late turbine condition. The entropy production and vorticity are derived from the guide vane transitioning to the runner flow channel through the vaneless space. The change law of energy loss through entropy production agrees with the change law of... [more]

In June 2021, the United States (US) Department of Energy (DOE) hosted the first-ever Hydrogen Shot Summit, which lasted for two days. More than 3000 stockholders around the world were convened at the summit to discuss how low-cost clean hydrogen production would be a huge step towards solving climate change. Hydrogen is a dynamic fuel that can be used across all industrial sectors to lower the carbon intensity. By 2030, the summit hopes to have developed a means to reduce the current cost of clean hydrogen by 80%; i.e., to USD 1 per kilogram. Because of the importance of clean hydrogen towards carbon neutrality, the overall DOE budget for Fiscal Year 2021 is USD 35.4 billion and the total budget for DOE hydrogen activities in Fiscal Year 2021 is USD 285 million, representing 0.81% of the total DOE budget for 2021. The DOE hydrogen budget of 2021 is estimated to increase to USD 400 million in Fiscal Year 2022. The global hydrogen market is growing, and the US is playing an active role... [more]

Natural gas hydrates (NGHs) have been recognized as a potential substitute for traditional fossil fuels. Mining NGH reservoirs can decrease the strength of the reservoirs, especially while improving production, and the double-well mining of NGHs also significantly reduces the strength of reservoirs. This study develops a thermofluid-solid multifield coupling model for mining NGHs through depressurization while considering the NGH decomposition kinetics and physical properties of NGH reservoirs. The influence of the formation responses and burial conditions on the slope stability in the depressurization process of NGHs is analyzed by combining it with the finite-element strength-reduction method. Results show that the decomposition zones of NGHs are nonuniformly distributed in space and have an irregular prismatic shape. The pore pressure propagates from the wellbores to the surrounding areas, forming cylindrical high-pressure-drop zones. Plastic zones first appear in the decomposition... [more]

Test suite code coverage is often used as an indicator for test suite capability in detecting faults. However, earlier studies that have explored the correlation between code coverage and test suite effectiveness have not addressed this correlation evolutionally. Moreover, some of these works have only addressed small sized systems, or systems from the same domain, which makes the result generalization process unclear for other domain systems. Software refactoring promotes a positive consequence in terms of software maintainability and understandability. It aims to enhance the software quality by modifying the internal structure of systems without affecting their external behavior. However, identifying the refactoring needs and which level should be executed is still a big challenge to software developers. In this paper, the authors explore the effectiveness of employing a support vector machine along with two optimization algorithms to predict software refactoring at the class level.... [more]

Rotating cavitation (RC) in inducers mainly degrades performance with unstable radial force. In this paper, the influence of step casings on cavitation performance and the instabilities of inducers were numerically investigated. Firstly, a numerical scheme was validated by means of a comparison with experimental measurements taken for an original inducer (Model O). We then performed simulations with five different step casing models (Models A−E), in which the starting locations and enlargement sizes of the step casings were altered. The interaction between tip leakage flow and main flow in the inter-blade passages was found to highly affected by cavity structure and blade loading. Considering both cavitation performance and radial force, our results suggest that Model E is an alternative improvement. In short, this study provides a standard workflow for the effective suppression of rotating cavitation in inducers by the simple adoption of the step casing configuration presented here in... [more]

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]