The efficient utilization of energy in rich fuel detonation processes and the effective control method of soot are important topics in combustion research. In this paper, we numerically study the detonation wave behavior of acetylene−air systems in rich fuel condition by using a reduced reaction mechanism. The non-stiff terms of the governing equations are solved explicitly using the gas kinetic scheme, and the stiff terms are solved implicitly. Our results show that the acetylene pyrolysis is the dominant reaction process. The oxidation reaction is exploited to initiate the reaction induction process, providing the required energy to overcome the potential energy barrier. The secondary detonation structure is due to the stable interaction of the transverse waves and the combined action of the vinyl reaction system, thus effectively improve the energy release rate and providing a powerful solution for the fuel-rich high-energy release of advanced heat engines. The area of the unreacted... [more]

User behaviour can significantly affect indoor thermal comfort conditions, as well as energy consumption, especially in existing buildings with high thermal masses where natural cross ventilation is the main strategy to reduce cooling loads. The aims of this paper were: (i) to compare how behavioural changes evaluated by means of rule-based and stochastic models lead to changes in indoor thermal comfort levels, and (ii) to define the patterns of indoor thermal comfort in historic residential buildings in future scenarios. To this end, a historic building located in Molfetta (Southern Italy) was analysed using a dynamic energy simulation engine in five weather scenarios (Typical Meteorological Year, current extreme weather file 2018, predicted weather files for 2020, 2050, and 2080 generated by morphing method), and stochastic and rule-based models for window openings were adopted and compared. The results showed that the stochastic model was more accurate than the rule-based one, resul... [more]

The increasing energy demand has led to more explorations in the oil and gas industry. To achieve this, marine risers and pipelines are used to convey fluid and other resources to meet the increasing demand. In recent years, hybrid flexible composite risers have become more adaptable. Flexible risers have already proven to be a popular riser solution for various floating production systems in shallow to deepwater in many parts of the world due to their good dynamic behaviour and dependability. The hybrid flexible composite riser is made up of numerous layers of plastics, flexible pipes, composites, and steel. Some innovative monitoring methods, such as Fiber Optics Bragg Gratings (FBG), are based on a clamped composite structure with embedded optical fibre. This study presents characteristics of the monitoring techniques of composite flexible riser technology. The advantages of the monitoring techniques include aiding composite riser measurements, recording data from riser deformation,... [more]

The imbalance market is very volatile and often exhibits extreme price spikes. This makes it very hard to model; however, if predicted correctly, one could make significant gains by participating on the right side of the market. In this manuscript, we conduct a very short-term probabilistic forecasting of imbalance prices, contributing to the scarce literature in this novel subject. The forecasting is performed 30 min before the delivery, so that the trader might still choose the trading place. The distribution of the imbalance prices is modelled and forecasted using methods well-known in the electricity price forecasting literature: lasso with bootstrap, gamlss, and probabilistic neural networks. The methods are compared with a naive benchmark in a meaningful rolling window study. The results provide evidence of the efficiency between the intraday and balancing markets as the sophisticated methods do not substantially overperform the intraday continuous price index. On the other hand,... [more]

Domestic coal and waste resources, which are valuable sources of carbon, can support efforts to transform a linear economy into a circular carbon economy. Their use, as an alternative to conventional, imported fossil resources (crude oil, natural gas) for chemical production, provides an opportunity for Poland to solve problems related to competitiveness, security of supply, and sustainable development in various industries. This is important for Poland because it can provide it with a long-term perspective of economic growth and development, taking into account global trends (e.g., the Paris Agreement) and EU legislation. The article presents a concept to support the transformation from linear toward a circular carbon economy under Polish conditions. The carried-out analyses showed that coal, RDF, and plastic waste fuels can be a valuable source of raw material for the development of the chemical industry in Poland. Due to the assumed availability of plastic waste and the loss of carb... [more]

In this study, a highly conductive composite bipolar plate with an embedded conductive carbon nanofiber network was prepared by chemical vapor deposition, and a conductive network was constructed inside the composite bipolar plate. The latter network was then compared with a conductive network formed by directly adding carbon nanotubes more evenly distributed. The optimum preparation methods of vapor-grown carbon fibers and the fiber content were analyzed, and the specific surface area and porosity of the bipolar plates were measured and analyzed using a BET test. The results show that the carbon nanofibers prepared under the conditions of 700 °C and a content of 2% exhibited the best effect on improving the performance of the bipolar plates. The conductivity of the prepared bipolar plates could reach 255.2 S/cm, which is 22.1% higher than treatment with multi-walled carbon nanotubes. The bending strength of the prepared bipolar plates was 47.92 MPa, and the interface contact resistanc... [more]

In recent years, anaerobic membrane bioreactors (AnMBRs) technology, a combination of a biological reactor and a selective membrane process, has received increasing attention from both industrialists and researchers. Undoubtedly, this is due to the fact that AnMBRs demonstrate several unique advantages. Firstly, this paper addresses fundamentals of the AnMBRs technology and subsequently provides an overview of the current state-of-the art in the municipal and domestic wastewaters treatment by AnMBRs. Since the operating conditions play a key role in further AnMBRs development, the impact of temperature and hydraulic retention time (HRT) on the AnMBRs performance in terms of organic matters removal is presented in detail. Although membrane technologies for wastewaters treatment are known as costly in operation, it was clearly demonstrated that the energy demand of AnMBRs may be lower than that of typical wastewater treatment plants (WWTPs). Moreover, it was indicated that AnMBRs have th... [more]

The coordination of optimal overcurrent relays (OCRs) for modern power networks is nowadays one of the critical concerns due to the increase in the use of renewable energy sources. Modern grids connected to inverter-based distributed generations (IDGs) and synchronous distributed generations (SDGs) have a direct impact on fault currents and locations and then on the protection system. In this paper, a new optimal OCR coordination scheme has been developed based on the nonstandard time−current characteristics (NSTCC) approach. The proposed scheme can effectively minimize the impact of distributed generations (DGs) on OCR coordination by using two optimization techniques: genetic algorithm (GA) and hybrid gravitational search algorithm−sequential quadratic programming (GSA−SQP) algorithm. In addition, the proposed optimal OCR coordination scheme has successfully employed a new constraint reduction method for eliminating the considerable number of constraints in the coordination and tripp... [more]

The development of decarbonised systems is being fostered by the increasing demand for technological solutions for the energy transition. Solid Oxide Cells are high-efficiency energy conversion systems that are foreseen for commercial development. They exhibit potential power generation and power-to-gas applications, including a reversible operation mode. Long-lasting high performance is essential for guaranteeing the success of the technology; therefore, it is fundamental to provide diagnosis tools at this early stage of development. In this context, operando analysis techniques help detect and identify incipient degradation phenomena to either counteract damage at its origin or correct operando protocols. Frequent switches from the fuel cell to the electrolyser mode add more challenges with respect to durable performance, and deep knowledge of reverse-operation-induced damage is lacking in the scientific and technical literature. Following on from preliminary experience with button c... [more]

The Huaibei coalfield is an important coal base and one of the hot spots of coalbed methane development in China. Therefore, a detailed understanding of gas occurrence in the Huaibei coalfield is of great significance. This paper analyzes the gas occurrence from the perspective of multiple-level tectonic control, i.e., the regional tectonic level, the coalfield tectonic level, the mining area tectonic level, and the coal mine tectonic level. This study deduces that gas occurrence in the Huaibei coalfield is characterized by multiple-level tectonic control. At the regional level, the Huaibei coalfield is located in the southeast margin of the North China plate, affected by the tectonic evolution of the North China plate and by the evolution of the Dabie−Tanlu−Sulu orogenic belt. Therefore, the regional geological tectonic is complex, leading to the high gas content and serious gas hazard. At the coalfield level, gas occurrence in the Huaibei coalfield is controlled by east−west faults,... [more]

The heat pump system has been widely used in residential and commercial applications due to its attractive advantages of high energy efficiency, reliability, and environmental impact. The massive exergy loss during the isenthalpic process in the expansion valve is a major drawback of the heat pump system. Therefore, the Tesla turbine exergy analysis in terms of transiting exergy efficiency is investigated and integrated with the transcritical heat pump system. The aim is to investigate the factors that reduce exergy losses and increase the coefficient of performance and exergy efficiency. The contribution of this paper is twofold. First, a three-dimensional numerical analysis of the supercritical CO2 flow simulation in the Tesla turbine in three different geometries is carried out. Second, the effect of the Tesla turbine on the coefficient of performance and exergy efficiency of the heat pump system is investigated. The effect of the rotor speed and disk spacing on the Tesla turbine po... [more]

Hydrogen fuel cell vehicles can complement other electric vehicle technologies as a zero-emission technology and contribute to global efforts to achieve the emission reduction targets. This article spotlights the current deployment status of fuel cells in road transport. For this purpose, data collection was performed by the Advanced Fuel Cells Technology Collaboration Programme. Moreover, the available incentives for purchasing a fuel cell vehicle in different countries were reviewed and future perspectives summarized. Based on the collected information, the development trends in the last five years were analyzed and possible further trends that could see the realization of the defined goals derived. The number of registered vehicles was estimated to be 51,437 units, with South Korea leading the market, with 90% of the vehicles being concentrated in four countries. A total of 729 hydrogen refueling stations were in operation, with Japan having the highest number of these. The analysis... [more]

This paper establishes a multidisciplinary method combining conjugate heat transfer (CHT) and thermal stress for a high-temperature Ni-based superalloy turbine rotor blade with integrated cooling structures. A conjugate calculation is performed to investigate the coolant flow characteristics, heat transfer, and thermal stress of the rotor blade under rotating and stationary conditions to understand the effects of rotation on the multidisciplinary design of the blade. Furthermore, the maximum resolved shear stress among the 30-slip systems and the corresponding dominant slip system are obtained to predict the deformation tendency of the blade by employing the crystal plasticity finite element method (CPFEM) and considering the specified anisotropic blade material (GTD-111). The results show that the forces of rotation, including centrifugal and Coriolis forces, and their induced buoyancy force, alter the coolant flow field and thus affect the rotor blade’s heat transfer distribution com... [more]

Sustainable transportation has a significant impact on factors related to urban development and economic development. Therefore, much research is being undertaken to select the best strategies to manage sustainable transportation. Transportation requires a carefully designed method to manage the development of mobility modes in terms of the pollution they produce or the use of renewable energy sources. However, due to numerous preferences of decision-makers and data uncertainty problems, it is challenging to select the optimal strategy. In this paper, we focus on creating a framework for determining the best strategy for sustainable transportation management. For this purpose, T-spherical fuzzy graphs will be used, which, together with the combination of Laplacian Energy, can accurately represent decision-makers’ preferences in an uncertain environment. Due to the lack of limitations of T-spherical fuzzy graphs and its numerous membership functions, decision-makers can decide which fac... [more]

The existing experimental technology cannot accurately and quantitatively measure the flow field structure and the wall boundary layer displacement effect in the axial flow pump. Based on SST k-ω turbulence model, a three-dimensional unsteady numerical simulation of the whole flow field of an axial flow pump was presented at the designed operating point to overcome the weakness of traditional measurement methods in measuring the flow field of the axial flow pump. The flow field structure of the axial flow pump inlet was studied quantitatively and the result was compared with the theoretical design value. It was found that there is an obvious impeller rotation effect and end-wall effect in the flow field of the axial flow pump inlet. The distribution law of the impeller inlet flow field and the crowding coefficient caused by the wall boundary layer were obtained. The pump inlet measurement point in the experiment and calculation domain inlet in the simulation should be kept at a distanc... [more]

Pre-chamber turbulent jet ignition represents one of the most promising techniques to improve spark ignition engines efficiency and reduce pollutant emissions. This technique consists of igniting the air-fuel mixture in the main combustion chamber by means of several hot turbulent flame jets exiting a pre-chamber. In the present study, the combustion process of a 4-stroke, gasoline SI, PFI engine equipped with a passive pre-chamber has been investigated through three-dimensional CFD (Computational Fluid Dynamics) analysis. A detailed chemistry solver with a reduced reaction mechanism was employed to investigate ignition and flame propagation phenomena. Firstly, the combustion model was validated against experimental data for the baseline engine configuration (i.e., without pre-chamber). Eventually, the validated numerical model allowed for predictive simulations of the pre-chamber-equipped engine. By varying the shape of the pre-chamber body and the size of pre-chamber orifices, differ... [more]

The article is seeking to analyse the coal transition in three Polish lignite regions as part of the scientific discussion on a just transition, which is a big challenge, especially in the regions and countries dependent on their own coal deposits as the main source of energy. Polish lignite mines are now entering the phase-out of coal, which results from implementing the assumptions of the Green Deal and the Paris climate agreement. The article answers the following question: what is the socio-economic resilience of coal regions in the context of the projected closure of mines in the coming years? The empirical analyses are based on secondary statistical data. The analysis and comparison of basic statistical data, i.e., the level of employment and lignite extraction in three lignite regions in the period from the end of the Second World War to 2017, allowed the authors to determine the phases of the adaptive cycle in which the individual regions are. In the second part of the study, t... [more]

With the development of pipeline networks, many safety accidents were caused by pipeline stress concentration; it is of great significance to accurately monitor the pipeline stress state for maintaining pipeline safety. In this paper, based on alternating current stress measurement (ACSM) methods, a 3D simulation model of a pipeline electromagnetic field was established by ANSYS software. The distribution law of the pipeline magnetic field and eddy current field were analyzed, and the influence of size and structure parameters of the coil inside the probe were studied. The internal stress detection system of the pipeline was designed, and the static tensile stress measurement experiment was carried out. Simulation and test results showed that the excitation coil with a larger diameter-to-height ratio had a higher measurement sensitivity. The sensitivity of the probe decreased monotonically with the increase of the difference between inner diameter and outer diameter of the detection co... [more]

Magnetic gears (MGs) have gained increasing attention due to their sound performance in high torque density and low friction loss. Aiming to maximize the torque density, topology design has been a popular issue in recent years. However, studies on the optimization comparisons of a general MG topology pattern are very limited. This paper proposes a Taguchi-method-based optimization method for a general MG topology pattern, which can cover most of the common types of radially magnetized concentric-surface-mounted MGs (RMCSM-MGs). The Taguchi method is introduced to evaluate the influence of each parameter in MGs. Moreover, the parameter value range is re-examined based on the sensitivity analysis results. The genetic algorithm (GA) method is adopted to optimize the topology pattern in the study.

Depleting fossil fuel resources and anthropogenic climate changes are the reasons for the intensive development of new, sustainable technologies based on renewable energy sources. One of the most promising strategies is the utilization of hydrogen as an energy vector. However, the limiting issue for large-scale commercialization of hydrogen technologies is a safe, efficient, and economical method of gas storage. In industrial practice, hydrogen compression and liquefaction are currently applied; however, due to the required high pressure (30−70 MPa) and low temperature (−253 °C), both these methods are intensively energy consuming. Chemical hydrogen storage is a promising alternative as it offers safe storage of hydrogen-rich compounds under ambient conditions. Although many compounds serving as hydrogen carriers are considered, some of them do not have realistic perspectives for large-scale commercialization. In this review, the three most technologically advanced hydrogen carriers—di... [more]

Nowadays, Wireless Power Transfer (WPT) technology is receiving more attention in the automotive sector, introducing a safe, flexible and promising alternative to the standard battery chargers. Considering these advantages, charging electric vehicle (EV) batteries using the WPT method can be an important alternative to plug-in charging systems. This paper focuses on the Inductive Power Transfer (IPT) method, which is based on the magnetic coupling of coils exchanging power from a stationary primary unit to a secondary system onboard the EV. A comprehensive review has been performed on the history of the evolution, working principles and phenomena, design considerations, control methods and health issues of IPT systems, especially those based on EV charging. In particular, the coil design, operating frequency selection, efficiency values and the preferred compensation topologies in the literature have been discussed. The published guidelines and reports that have studied the effects of... [more]

As the natural gas pipeline network becomes larger and more complicated, a stricter requirement of computation efficiency for the large and complicated network transient simulation should be proposed. The adaptive time step method has been widely used in the transient simulation of natural gas pipeline networks as a significant way to improve computation efficiency. However, the trial calculation process, which is the most time-consuming process in time step adjustment, was used to adjust the time step in these methods, reducing the efficiency of time step adjustment. In order to reduce the number of trial calculations, and improve the calculation efficiency, an improved adaptive time step method is proposed, which proposes the concept of energy number and judges the energy number of the boundary conditions after judging whether the variation of the pipeline state is tolerable. A comparison between the adaptive time step method and the improved adaptive time step method in the restart... [more]

In this study, the operating conditions of the tri-generation model in actual field situations for terminal complex buildings were investigated. The operational characteristics of the installed tri-generation system (TGS), and performance in terms of relative primary energy savings (RPES), were evaluated to confirm its market competitiveness against separate heat and power (SHP). As a result of the analysis, the technological superiority of the TGS model compared to the SHP method was much lower than theoretical expectation, which was 17.9% in the best case and close to 0 in the worst case. The importance of the TGS’s operational strategy to achieve annual operational economics was emphasized based on the analysis of the TGS’s actual daily operational data. The sustainability of the TGS model in the era of climate change was also evaluated through RPES sensitivity analysis according to the level of renewable power generation in the power sector, which is rapidly increasing in response... [more]

Battery storage is emerging as a key component of intelligent green electricitiy systems. The battery is monetized through market participation, which usually involves bidding. Bidding is a multi-objective optimization problem, involving targets such as maximizing market compensation and minimizing penalties for failing to provide the service and costs for battery aging. In this article, battery participation is investigated on primary frequency reserve markets. Reinforcement learning is applied for the optimization. In previous research, only simplified formulations of battery aging have been used in the reinforcement learning formulation, so it is unclear how the optimizer would perform with a real battery. In this article, a physics-based battery aging model is used to assess the aging. The contribution of this article is a methodology involving a realistic battery simulation to assess the performance of the trained RL agent with respect to battery aging in order to inform the selec... [more]

This article presents a methodology for predicting the absolute methane emission rate for longwall caving extraction based on the determination of destressing zones generated by longwall mining operations, by means of numerical modelling. This methodology was applied for the conditions of the K-2 longwall panel in the KWK Pniówek mine. The finite difference method code FLAC2D was employed as an element of the methodology to determine the destressing zones. All results including the numerical modelling results, empirical results and the measured (in situ) results were gathered in the comparative analysis. As the final results, the accuracy and reliability of the proposed methodology were evaluated.