Heat transfer is one of the most fundamental engineering subjects and is found in every moment of life. Heat transfer problems, such as heating and cooling, where the transfer of heat between regions is calculated, are problems that can give exact solutions with parametric equations, many of which were obtained by solving differential equations in the past. Today, the fact that heat transfer problems have a more complex structure has led to the emergence of multivariate models, and problems that are very difficult to solve with differential equations have emerged. Optimization techniques, which are also the subject of computer science, are frequently used to solve complex problems. In this study, laminar thermal boundary layers in flow over a flat plate, a sub-problem of heat transfer, is solved with recent metaheuristic algorithms. Teaching learning-based optimization (TLBO), sine cosine optimization (SCO), gray wolf optimization (GWO), whale optimization (WO), salp swarm optimization... [more]

In Poland, there is a high ratio of private transport and unfavorable patterns of daily commuting. These patterns can be changed by introducing comfortable and eco-friendly vehicles, such as e-scooters and e-bikes. At the same time, the development of the e-micromobility-based vehicle sharing services market is developing. The aim of the article is to analyze selected e-scooters available on the Polish market and to identify the most useful vehicles from two opposing perspectives, i.e., the potential customer and owner of the vehicle sharing system. The PROSA GDSS (PROMETHEE for Sustainability Assessment—Group Decision Support System) method and the graphical representation of GAIA (Geometrical Analysis for Interactive Assistance) were used to search for a compromise and balance between the needs of the indicated stakeholders. The results of the methods used were compared with the results of the PROMETHEE GDSS method, which does not take into account the balance between the stakeholder... [more]

Green energy is a crucial component in addressing expanding energy demands and combating climate change, but the possible negative repercussions of these technologies are frequently disregarded. Green energy’s deployment is tied to environmentally sustainable development goals (SDGs). It can only be achieved by scaling up the finance of investment that provides environmental benefits through new financial instruments and new policies, such as green banks, green bonds, community-based green funds, green central banking, etc. In an effort to address the issues with IPAT and ImPACT, this study employed the STIRPAT model approach, which is a proven framework for energy economics analysis. The author gathers yearly data spanning 2002−2018 for six ASEAN member countries with the aim of investigating the relationship between CO2 emissions, green finance, energy efficiency, and the green energy index (GEX). After preliminary tests, the study employed the Westerlund test and Johansen Fisher tes... [more]

This study investigates a prediction model for the cycle injection quantity in a high-pressure common rail injector under a transient thermal boundary. The results show that the transient temperature increase curve calculated by the mathematical model of the common rail injector under adiabatic flow is significantly different from the experimental data. A non-isothermal model of the injector coupled with heat transfer is established, which considers the actual heat transfer phenomenon. The excellent agreement between the new calculation results and the experimental data confirms that the fuel injection process of a common rail injector comprises the coupled phenomena of fuel heating and heat transfer. Based on the established simulation model, it is found that in the continuous injection process of the injector, owing to the thermal effect of injection, the cycle injection quantity decreases gradually with an increase in the injector working time and then stabilizes. Under the conditio... [more]

To reduce the negative impacts of stall and surge on compressor performance, a novel combined casing treatment (CCT) structure with axial skewed slots and injection groove is proposed in this paper. The aerodynamic performance, as well as the mechanisms of loss generation, of a transonic axial compressor with NASA Rotor 67 are investigated numerically. The simulation results indicate that, compared with individual casing treatment method, the CCT works effectively with regard to operation performance. The stall margin (SM) is increased by 14.7% with 1.12% decrease in the peak efficiency. The interaction of axial skewed slots and injection groove can be explained by the enhancement of exchange flow in slots and axial motion of fluid. As a result, the leakage flow near the blade tip is eliminated and the flow separation is further suppressed. What is more, an analysis of entropy generation is also conducted. The results reveal that the effect of CCT on loss reduction mainly concentrates... [more]

In recent years, the demand for medium and large secondary batteries in EV (electric vehicle) and ESS (energy storage systems) applications has been rapidly increasing worldwide, and accordingly, the market size is increasing exponentially. However, the recent fire accidents related to secondary batteries for EVs and ESS are having a negative impact on the battery market. Therefore, this paper implements an accident simulation device to perform an external short-circuit test, one of the typical safety tests for NMC-series prismatic and pouch-type batteries that are widely used among battery cells used in medium and large secondary batteries. The implemented accident simulation device for the external short-circuit test is composed of short-circuit resistance, measuring device, control device, etc., and is configured to analyze external short-circuit characteristics according to various test conditions. Based on this, an external short-circuit test according to the type, short-circuit r... [more]

Practice shows that CO2/N2-ECBM is an effective technology to enhance coalbed methane. However, there are few field tests in which the technology is applied to enhance the gas drainage in underground coal mines, and the effect is uncertain. In this study, firstly, the reasons for the decrease of gas drainage efficiency in the exhaustion period were analyzed based on the theory of fluid mechanics. Secondly, the mechanism of N2 injection to enhance coal seam gas drainage (N2-ECGD) was discussed: with the gradual decrease of gas pressure in the drainage process, coal seam gas enters a low-pressure state, the driving force of flow is insufficient, and the drainage enters the exhaustion period. The nitrogen injection technology has triple effects of “promoting flow”, “increasing permeability” and “replacing”. Thirdly, the numerical simulations of the nitrogen pressure on drainage effect were carried out based on the fully coupled model. The results show that the higher the nitrogen pressure... [more]

The operation of natural gas grids requires electric-powered devices as data acquisition and control systems, surveillance and communication appliances, etc., often located in remote, unpopulated off-the-grid areas, where there is no personnel for surveillance, and maintenance costs are prohibitive. The literature on the power generating systems for these devices is limited to specific applications without a comparison between competing technologies, making their choice a difficult task for natural gas operators. This work presents a comprehensive up-to-date survey of market available technologies for remote power generation in the range of 20−1000 W for gas grid applications: thermoelectric generators, solid acid, direct methanol and solid oxide fuel cells, Stirling engines and microturbines. The work aims at sorting the technologies by techno-energetic, economic and environmental performance while providing specific technological characteristics and limitations. The results indicate... [more]

Oil saturation is a kind of spatiotemporal sequence that changes dynamically with time, and it is affected not only by the reservoir properties, but also by the injection−production parameters. When predicting oil saturation during water and gas injection, the influence of time, space and injection−production parameters should be considered. Aiming at this issue, a prediction method based on a controllable convolutional long short-term memory network (Ctrl-CLSTM) is proposed in this paper. The Ctrl-CLSTM is an unsupervised learning model whose input is the previous spatiotemporal sequence together with the controllable factors of corresponding moments, and the output is the sequence to be predicted. In this way, future oil saturation can be generated from the historical context. Concretely, the convolution operation is embedded into each unit to describe the interaction between temporal features and spatial structures of oil saturation, thus the Ctrl-CLSTM realizes the unified modeling... [more]

This paper presents the issues of modeling the operation process of light utility vehicles operating in military transport systems. The required condition for the effective operation of the system is to maintain the means of transport at the appropriate level of technical readiness. For this purpose, it is necessary to equip the technical system with appropriate resources enabling the efficient implementation of fuel refilling, maintenance and repair processes. Each failure of the means of transport causes a significant reduction in transport capacity, which then results in the inability to perform the planned tasks. Quality control and vehicle operation process management require advanced mathematical methods and tools. Three indicators have been proposed as quantitative characteristics for assessing and optimizing the availability of military vehicles: functional readiness, technical efficiency and airworthiness. To determine their value, a stochastic exploitation model was developed... [more]

Newly constructed devices must meet a number of requirements in terms of the level of generated disturbances. To achieve an acceptable level in such devices, filters are installed—one of the cheapest ways to reduce interference in devices. One of the key elements of the filter that is responsible for the effectiveness of noise reduction are ferrites. Unfortunately, for various devices, an individual approach should be used in the selection of filters and, accordingly, ferrites. Due to the fact that ferrites from different manufacturers do not have standardized characteristics and information on their effectiveness, the selection of the right ferrite is a very time-consuming process. Therefore, this article will present the possibilities of quickly determining selected ferrite parameters in order to ensure the necessary level of noise reduction. For this purpose, assumptions from the CISPR 17 standard will be used. For selected types of ferrites, a large number of measurements were carr... [more]

Poor control of the power grid can lead to a total system collapse, causing significant economic losses and possible damage to security and social peace. Therefore, improving power system stability, particularly transient stability, has become one of the major research topics. This paper proposes a developed modeling approach that provides the optimal stabilizer parameters of the control devices, aiming at improving the electrical network stability by minimizing the angular speed deviation in the presence of a severe disturbance event using a novel hybrid algorithm called Water Cycle-Moth Flame Optimization (WCMFO). The main advantages of the proposed method are the speed of response and its efficient exploration and exploitation ability to attain the best solution quality. This is achieved by imposing a thermodynamic incident (an abrupt change in mechanical torque) on the well-known test model (SMIB), Single Machine Infinite Bus. To test the effectiveness of the proposed method, Power... [more]

The efficient development of carbonate oil deposits with excessive fissuring is a current challenge. Uneven and rapid well stream watering is considered as one of the factors that make the process of the development of carbon deposits more complicated. The purpose of the research is to diagnose and evaluate the mechanisms of well stream watering for carbon deposits and find applicable technology to prevent it. An overview of in situ water shut-off technologies was carried out. A description of the main materials used for water shut-off is presented, and selective methods are studied in more detail. A carbonate basin of an oil field is selected as the object of investigation. The geological and physical characteristics of this deposit are given. Analysis of possible causes and sources of water cut of the fluid is made according to the technique of K.S. Chan, under which the main reason for the watering of the well production is the breakthrough of formation and injection water through a... [more]

The vortex generated around the suction region of the pump sump causes problems such as damage to the pump, increased maintenance costs, and failure to supply coolant smoothly. Therefore, analyzing vortices is essential in pump sump design. However, the CFD analysis alone is insufficient in pump sumps vortex analysis since the reliability of the results is doubtful in scaled model tests. This study conducted the model test to validate a suitable CFD simulation method by identifying the Type 2 vortex among the three types of subsurface vortices. The dye test and PIV technology were used to visualize the Type 2 subsurface vortices, whereas the PIV vorticity results were then compared to the CFD results. The average vorticity of 60.2 (1/s) was identified as the reference level of Type 2 subsurface vortices formation by mapping the dye test results with the PIV vorticity results. Furthermore, the average vorticities of 84.63 (1/s) and 85.15 (1/s) were recorded in the presence of Type 2 sub... [more]

The present work aims to evaluate the performance of the constant-volume method by several sets of experiments carried out in three different closed vessels (a sphere and two cylinders) analyzing the obtained results in order to obtain accurate laminar burning velocities. Accurate laminar burning velocities can be used in the development of computational fluid dynamics models in order to design new internal combustion engines with a higher efficiency and lower fuel consumption leading to a lower degree of environmental pollution. The pressure-time histories obtained at various initial pressures from 0.4 to 1.4 bar and ambient initial temperature were analyzed and processed using two different correlations (one implying the cubic low coefficient and the other implying the burnt mass fraction). The laminar burning velocities obtained at various initial pressures are necessary for the realization of a complete kinetic study regarding the combustion reaction and testing the actual reaction... [more]

According to the requirements of a wide speed range, a variable-geometry supersonic inlet with inner surface adjustment is studied. The basic design model of the inlet is established, and the influence of profile adjustment on the resisting back pressure ability and inlet performance boundary are analyzed using a theoretical method. Based on the numerical simulation method, the flow field simulation is carried out, and the flow field parameter distribution and performance of the adjustment inlet are studied in comparison with the fixed-geometry scheme. The results show that the starting Mach number is not changed for two inlet schemes because they have the same profile during low-speed flight. The fixed-geometry inlet has insufficient compression on the incoming flow, and the resisting back pressure ability decreases significantly during high-speed flight. The compression ratio and the compression wave system can be easily changed at the same time through the adjustment of the inner pr... [more]

Windows are responsible for significant amounts of energy loss through typical building envelopes. There have been multiple studies on heat loss through the glazing unit and frame system. This study presents an experimental investigation of a window unit and focuses specifically on the conductance between the structural elements and the frame system of a conventional house in the city of Xanthi, northern Greece. It is obvious that even a perfect window system cannot reduce heat transfer between the base of the frame and the upper surface of the floor. The experimental and simulation procedure of this project includes the installation of an insulating layer in front of the window unit for a variety of frames (solid wood, aluminum, PVC, etc.) at different distances. The main objective of this paper is to determine how effective an insulating barrier can be in respect to different types of frame, glazing, and weather conditions for the control of heat loss. Through the application of this... [more]

The supply of electric vehicles (EVs), charging infrastructure, and the demand for chargers are rapidly increasing owing to global low-carbon and eco-friendly policies. As the maintenance of charging infrastructure varies depending on the manufacturer, fault detection and maintenance cannot be conducted promptly. Consequently, user inconvenience increases and becomes an obstacle to EV distribution. Recognizing charger failure after occurrence is a management method that is not economically effective in terms of follow-up. In this study, a data collection system was developed to diagnose EV fast-charger failure remotely in advance. The power module failure-prediction and management system consists of an AC sensor, DC sensor, temperature and humidity sensor, communication board, and data processing device. Furthermore, it was installed inside the fast charger. Four AC inputs, four DC outputs, and temperature and humidity data were collected for 12 months. Using the collected data, the po... [more]

This article presents the results of experiments on the effect of chlorine dioxide, applied as an additional oxidant, on swimming pool water quality. Three doses of chlorine dioxide were applied: 22, 44 and 66 mg/m3. At each research stage, prior to the actual experiment, in which the oxidant was dosed, the background was tested, i.e., water samples were taken from a conventional treatment system (without chlorine dioxide). The experiments showed that chlorine dioxide effectively removes organic compounds and their chlorine derivatives. For the highest dose of ClO2, CODMn decreased by almost 88% and chloroform concentration by 75%. Chlorine dioxide also effectively supports water disinfection. At the highest dose, the number of mesophilic bacteria decreased by 60% and the number of psychrophiles by 94%. However, after the dosing of this oxidant had been discontinued, a deterioration of the microbiological water quality and the secondary growth of microorganisms were observed. Chlorine... [more]

Lithium-ion batteries are widely used as effective energy storage and have become the main component of power supply systems. Accurate battery state prediction is key to ensuring reliability and has significant guidance for optimizing the performance of battery power systems and replacement. Due to the complex and dynamic operations of lithium-ion batteries, the state parameters change with either the working condition or the aging process. The accuracy of online state prediction is difficult to improve, which is an urgent issue that needs to be solved to ensure a reliable and safe power supply. Currently, with the emergence of artificial intelligence (AI), battery state prediction methods based on data-driven methods have high precision and robustness to improve state prediction accuracy. The demanding characteristics of test time are reduced, and this has become the research focus in the related fields. Therefore, the convolutional neural network (CNN) was improved in the data modeli... [more]

The excitation pulse current used to drive the railgun needs to present very a high magnitude (hundreds of kA) flat-top with very low ripple. At present, the main method to obtain this current is to increase the number of the capacitive pulsed power supply (PPS) modules. However, low utilization and massive volume of the railgun system would occur with this method, hampering the application of railgun. Therefore, the utilization optimization technology of PPS is researched in this paper. In order to obtain highly stable flat-top current, the control strategy of the capacitive PPS is designed, and a new charging voltage configuration is proposed, which significantly decreases the use of the capacitive modules. Besides, a miniaturization transformation scheme of capacitive PPS is proposed based on the control strategy. The result shows that the flat-top current ripple has the biggest influence on the PPS utilization, and the smaller the flat-top current ripple, the lower the utilization.... [more]

For this study, the annual frequency of atmospheric stability and the effects of topography were investigated, using ERA5 data and data from wind observation masts installed at four locations on an island for a site under development, where bidding will soon begin. As a result, we found that a variety of atmospheric stabilities appeared at the site, and that the annual average events were not neutral but, instead, unstable. Moreover, the deviation from neutral varied depending on wind direction and the wind speed varied greatly, depending on the mast position and wind direction. Additionally, it was necessary to reproduce the wind flow separation due to topography, in order to predict the wind conditions of wind turbines located close to the island. The accuracy of the airflow simulation by large eddy simulation was validated using the mast-to-mast wind speed ratio. For simulations, we used the commercial software RIAM-COMPACT, which has been widely used in Japan, as it allows the atmo... [more]

Knowing the methane adsorption dynamic is of great importance for evaluating shale gas reserves and predicting gas well production. Many experiments have been carried out to explore the influence of many aspects on the adsorption dynamic of methane on shale rock. However, the temperature effect on the adsorption dynamic as a potential enhanced shale gas recovery has not been well addressed in the publications. To explore the temperature effect on the adsorption dynamic of methane on gas shale rock, we conducted experimental measurement by using the volumetric method. We characterized the adsorption dynamic of methane on gas shale powders and found that the curves of pressure response at different pressure steps and temperatures all have the same tendency to decrease fast at first, then slowly in the middle and remain stable at last, indicating the methane molecules are mainly adsorbed in the initial stage. Methane adsorption dynamic and isotherm can be well fitted by the Bangham model... [more]

Renewable energy consumption is the call by United Nation Sustainable Development Goals, and sustainable consumption is the only solution for the future. This study found that the solution to the framed problem has a requirement to categorize the green consumer value parameters in hierarchy of importance for five specific RESs and their alignment with environment policy based on a comparison of Poland and India. The study revealed the importance of each criterion for renewable energy sources providing, a comparative table of Poland and India. The methodological approach used secondary data for selecting countries, and primary data are used for statistical analysis of Automatic Linear Modelling. The research concludes that the CRITERIA4 is one of the most important that emerged with all five RESs for Poland and three RESs for India. Both countries are aligned with the UN sustainable development goals and are switching over to all means of sustainability. Poland scores a higher value of... [more]

This research presents a finite element multi-physics design methodology that can be used to develop and optimise the inherent functions and geometry of an innovative regenerative eddy current (REC) damper for the suspension of B class vehicles. This methodology was inspired by a previous work which has been applied successfully for the development of an eddy current (EC) damper used for the same type of applications. It is based on a multifield finite element coupled model that can be used to fulfil the electromagnetic, thermal, and fluid dynamic field properties and boundary conditions of a REC damper, as well as its non-linear material properties and boundary conditions, while also analysing its damping performance. The proposed REC damper features a variable fail-safe damping force, while electric power is advantageously regenerated at high suspension frequencies. Its damping performance has been benchmarked against that of a regular hydraulic shock absorber (selected as a referenc... [more]