bluuebunny/crossref_metadata_2025 huggingface dataset:
Machine learning seizure prediction: one problematic but accepted practice
Authors: West Joseph , Dasht Bozorgi Zahra , Herron Jeffrey , Chizeck Howard J , Chambers Jordan D , Li Lyra
Published: December 2022

Objective. Epilepsy is one of the most common neurological disorders and can have a devastating effect on a person’s quality of life. As such, the search for markers which indicate an upcoming seizure is a critically important area of research which would allow either on-demand treatment or early warning for people suffering with these disorders. There is a growing body of work which uses machine learning methods to detect pre-seizure biomarkers from electroencephalography (EEG), however the high prediction rates published do not translate into the clinical setting. Our objective is to investigate a potential reason for this. Approach. We conduct an empirical study of a commonly used data labelling method for EEG seizure prediction which relies on labelling small windows of EEG data in temporal groups then selecting randomly from those windows to validate results. We investigate a confound for this approach for seizure prediction and demonstrate the ease at which it can be inadvertently learned by a machine learning system. Main results. We find that non-seizure signals can create decision surfaces for machine learning approaches which can result in false high prediction accuracy on validation datasets. We prove this by training an artificial neural network to learn fake seizures (fully decoupled from biology) in real EEG. Significance. The significance of our findings is that many existing works may be reporting results based on this confound and that future work should adhere to stricter requirements in mitigating this confound. The problematic, but commonly accepted approach in the literature for seizure prediction labelling is potentially preventing real advances in developing solutions for these sufferers. By adhering to the guidelines in this paper future work in machine learning seizure prediction is more likely to be clinically relevant.
Stereo-EEG recordings extend known distributions of canonical movement-related oscillations
Authors: Rockhill Alexander P , Mantovani Alessandra , Stedelin Brittany , Nerison Caleb S , Raslan Ahmed M , Swann Nicole C
Published: December 2022

Objective. Previous electrophysiological research has characterized canonical oscillatory patterns associated with movement mostly from recordings of primary sensorimotor cortex. Less work has attempted to decode movement based on electrophysiological recordings from a broader array of brain areas such as those sampled by stereoelectroencephalography (sEEG), especially in humans. We aimed to identify and characterize different movement-related oscillations across a relatively broad sampling of brain areas in humans and if they extended beyond brain areas previously associated with movement. Approach. We used a linear support vector machine to decode time-frequency spectrograms time-locked to movement, and we validated our results with cluster permutation testing and common spatial pattern decoding. Main results. We were able to accurately classify sEEG spectrograms during a keypress movement task versus the inter-trial interval. Specifically, we found these previously-described patterns: beta (13–30 Hz) desynchronization, beta synchronization (rebound), pre-movement alpha (8–15 Hz) modulation, a post-movement broadband gamma (60–90 Hz) increase and an event-related potential. These oscillatory patterns were newly observed in a wide range of brain areas accessible with sEEG that are not accessible with other electrophysiology recording methods. For example, the presence of beta desynchronization in the frontal lobe was more widespread than previously described, extending outside primary and secondary motor cortices. Significance. Our classification revealed prominent time-frequency patterns which were also observed in previous studies that used non-invasive electroencephalography and electrocorticography, but here we identified these patterns in brain regions that had not yet been associated with movement. This provides new evidence for the anatomical extent of the system of putative motor networks that exhibit each of these oscillatory patterns.
Towards a mesoscale physical modeling framework for stereotactic-EEG recordings
Authors: Mercadal Borja , Lopez-Sola Edmundo , Galan-Gadea Adrià , Al Harrach Mariam , Sanchez-Todo Roser , Salvador Ricardo , Bartolomei Fabrice , Wendling Fabrice , Ruffini Giulio
Published: December 2022

Objective. Stereotactic-electroencephalography (SEEG) and scalp EEG recordings can be modeled using mesoscale neural mass population models (NMMs). However, the relationship between those mathematical models and the physics of the measurements is unclear. In addition, it is challenging to represent SEEG data by combining NMMs and volume conductor models due to the intermediate spatial scale represented by these measurements. Approach. We provide a framework combining the multi-compartmental modeling formalism and a detailed geometrical model to simulate the transmembrane currents that appear in layer 3, 5 and 6 pyramidal cells due to a synaptic input. With this approach, it is possible to realistically simulate the current source density (CSD) depth profile inside a cortical patch due to inputs localized into a single cortical layer and the induced voltage measured by two SEEG contacts using a volume conductor model. Based on this approach, we built a framework to connect the activity of a NMM with a volume conductor model and we simulated an example of SEEG signal as a proof of concept. Main results. CSD depends strongly on the distribution of the synaptic inputs onto the different cortical layers and the equivalent current dipole strengths display substantial differences (of up to a factor of four in magnitude in our example). Thus, the inputs coming from different neural populations do not contribute equally to the electrophysiological recordings. A direct consequence of this is that the raw output of NMMs is not a good proxy for electrical recordings. We also show that the simplest CSD model that can accurately reproduce SEEG measurements can be constructed from discrete monopolar sources (one per cortical layer). Significance. Our results highlight the importance of including a physical model in NMMs to represent measurements. We provide a framework connecting microscale neuron models with the neural mass formalism and with physical models of the measurement process that can improve the accuracy of predicted electrophysiological recordings.
Modeling transcranial magnetic stimulation coil with magnetic cores
Authors: Makaroff Sergey N , Nguyen Hieu , Meng Qinglei , Lu Hanbing , Nummenmaa Aapo R , Deng Zhi-De
Published: December 2022

Objective. Accurate modeling of transcranial magnetic stimulation (TMS) coils with the magnetic core is largely an open problem since commercial (quasi) magnetostatic solvers do not output specific field characteristics (e.g. induced electric field) and have difficulties when incorporating realistic head models. Many open-source TMS softwares do not include magnetic cores into consideration. This present study reports an algorithm for modeling TMS coils with a (nonlinear) magnetic core and validates the algorithm through comparison with finite-element method simulations and experiments. Approach. The algorithm uses the boundary element fast multipole method applied to all facets of a tetrahedral core mesh for a single-state solution and the successive substitution method for nonlinear convergence of the subsequent core states. The algorithm also outputs coil inductances, with or without magnetic cores. The coil–core combination is solved only once i.e. before incorporating the head model. The resulting primary TMS electric field is proportional to the total vector potential in the quasistatic approximation; it therefore also employs the precomputed core magnetization. Main results. The solver demonstrates excellent convergence for typical TMS field strengths and for analytical B–H approximations of experimental magnetization curves such as Froelich’s equation or an arctangent equation. Typical execution times are 1–3 min on a common multicore workstation. For a simple test case of a cylindrical core within a one-turn coil, our solver computed the small-signal inductance nearly identical to that from ANSYS Maxwell. For a multiturn rodent TMS coil with a core, the modeled inductance matched the experimental measured value to within 5%. Significance. Incorporating magnetic core in TMS coil design has advantages of field shaping and energy efficiency. Our software package can facilitate model-informed design of more efficiency TMS systems and guide selection of core material. These models can also inform dosing with existing clinical TMS systems that use magnetic cores.
Effect of pre-irradiation defects on helium trapping and diffusion in RAFM steel
Authors: Duan Xiuxuan , Jin Shuoxue , Song Yamin , Wang Yanli , Xiong Yi , Zhang Weiping , Li Shilei , Cao Xingzhong
Published: December 2022

In order to analyze the effect of pre-irradiation defects on helium trapping and diffusion behaviors in detail by slow positron beam, Si ion with high energies (300 keV and 6 MeV) and 100 eV helium plasma were sequentially introduced into reduced activation ferritic/martensitic steel. Massive microscopic defects were observed in Si ion irradiated specimens. Low energy helium (∼100 eV) atoms could diffuse into much deeper region in metals without displacement damage. In the diffusion process of helium atoms, they would be trapped by the Si-ion pre-irradiation defects. The formation of He-vacancy complexes would affect the annihilation of positrons with the electrons in pre-irradiation defects and decrease the S parameters. The shallow region defects induced by 300 keV irradiation have more obvious advantage of hindering the diffusion of helium over the deep defects than that in 6 MeV irradiation. Thus, the pre-introduced defects can trap effectively helium atoms and hinder their diffusion.
Energy Performance of Annual Operation of Heat Pump Coupled with Ground Ice Storage and Photovoltaic/Thermal modules
Authors: Noro Marco , Mancin Simone , Zilio Claudio
Published: December 2022

The use of heat pumps for annual climatization is a suitable mean of achieving the 2030 European decarbonization target (-55% with respect to 1990 CO2 emissions). The use of seasonal energy storages allows to store one of the two contemporaneous effects (thermal and cooling energy) produced by the heat pump to be used successively when it is necessary. This paper focuses on a dynamic simulation to size the heating and cooling plant and define a suitable control logic for a refurbished building located in northern Italy. The plant is set up by an electric heat pump in annual operation, coupled with a ground ice storage. Ice produced during heating operation is used in summer to face cooling loads (free cooling). PhotoVoltaic/Thermal modules allow to increase the grid independency and to reduce primary energy consumption of the plant as they can be suitably cooled in any season, by recovering heat for domestic hot water or the ground. A dynamic simulation of the system allows for a full description of the behaviour of the ice tank during the charging and discharging processes. In addition, a primary energy performance analysis of the whole plant is reported, also in comparison to a dual source heat pump configuration for the same building.
Use of sustainable Phase Change Material (PCM) in mortars for building energy efficiency
Authors: Sarcinella Antonella , de Aguiar Josè Luis Barroso , Frigione Mariaenrica
Published: December 2022

Academic and industrial research are moving towards the development of innovative solutions and materials able to limit energy consumption for the thermoregulation of a building. One solution is the use of phase change materials (PCMs) that can absorb, store, and release energy according to their physical state that changes when the ambient temperatures changes. In this work, new sustainable PCMs were developed through the “form-stable” method according to the principles of Circular Economy. The new PCM materials consisted, in fact, of an inert matrix (obtained as byproduct of stone processing) impregnated by low toxic, low flammable polymer, namely polyethylene glycol (PEG). The PEG/stone composite materials were used to replace the fine aggregates in mortars based on different binders providing the mortars with thermoregulation performance. A comprehensive characterization was performed on the new PCMs by evaluating their thermal stability and thermal efficiency. The main properties (in fresh and hardened states) of the mortars with or without PCMs were analyzed. The mortars containing PCMs were also subjected to further investigations to evaluate their thermal behavior in response to external climatic conditions. Encouraging results were obtained, confirming the effectiveness of the mortars containing the new PCMs in the thermoregulation of indoor environments.
Energy audit of 1900s buildings for sustainable renovation
Authors: Cardinale Nicola , Negro Elisabetta , Selicati Valeria
Published: December 2022

This project focuses on the dynamic modelling of two buildings: a school and a public building, both located in the Basilicata and Puglia regions. In order to define the passive energy requirement of the building and propose some energy efficiency solutions, an energy diagnosis was conducted in dynamic settings on these structures. The EnergyPlus™ calculation code is the method utilized for energy diagnosis in the dynamic regime. The dynamic technique enables simulation of real-world building circumstances and plant design based on real-world requirements and building management.

Both buildings have significant historical significance, therefore improving their energy efficiency must take this into account.

In the design of energy efficiency solutions, the enclosure’s properties are critical. It is the primary source of heat loss and sunlight gain, and it has an impact on indoor comfort.

It is vital to consider often contradicting features of the building’s casing, such as heating, cooling, and natural and artificial lighting, when designing the building’s casing. For example, large levels of natural light must be allowed without excessive solar gains during the summer while still ensuring an acceptable quantity of solar earnings during the winter to reduce heating loads. As a result, the efficient configuration can’t just look at one element at a time; it has to look at all of them at the same time, taking into account all of the interactions between the many sources of energy usage. Thermo-hygrometric comfort is another factor to consider when it comes to protecting the human condition.

The goal of integrated design for a long-term major redevelopment is to establish the best balance between energy efficiency and environmental burdens, not just during the operational period, but throughout the life cycle. During the redesign process, resources such as life cycle analysis (LCA - Life Cycle Assessment) can be used to objectively quantify the possible environmental implications of new materials, systems, and energy flows (from their supply up to future disposal scenarios at the end of life). Furthermore, by comparing several project options, it is possible to identify which, with the same energy efficiency, causes the least environmental damage. Economic and social sustainability analyses can also be combined.

Modern building relief techniques (geometric, material, and thermal) were applied in this study for energy diagnosis and LCA analysis to determine the optimal design options for environmental impacts. The thermal power plants that the solution proposes are completely integrated within the buildings in which they will be put and manage to ensure a perfect mix of energy savings, economic savings, and environmental sustainability.
Effect of nanofluid on a Low-enthalpy geothermal plant
Authors: Buonomo B , Ciccarelli V , Manca O , Nardini S , Plomitallo R E
Published: December 2022

In Italy 40% of total energy consumption is destined for buildings. To reduce energy consumption and consequently achieve a reduction in carbon dioxide emissions, it is necessary to design well and build better. The technologies that make it possible to increase the energy saving of buildings for civil use are linked to three main aspects: envelope, insulation, and air conditioning; high efficiency systems, integrated building-plant design, use of appliances and lighting with low energy consumption, use of energy from renewable sources; building automation. In this work, the energy demand of a building located in Campania is supplied by a low-enthalpy geothermal plant where the working fluid is a nanofluid. Building thermal loads and performance of the geothermal plant are evaluated by means of TRNSYS®. Borehole heat exchangers design is carried out by means of the ASHRAE procedure. The geothermal system is designed considering the geological characteristics of the site, the characteristics of the geothermal plant and energy conversion system. The performance of the system is evaluated for different nanofluid as working fluid, water-Al2O3, water-CuO and water-SiO2, for several nanoparticle concentrations.
Energy Storage System based on Biomimetic Strategies: Concept Design and Performance Assessment in Buildings
Authors: Dodón Alisson , Quintero Vanessa , Austin Miguel Chen
Published: December 2022

Due to the constant growth in energy demand worldwide, renewable systems require more maintenance and electrical energy generation, which also involves an increase in storage capacity. Solar energy is one of the renewable sources with the greatest opportunity to cover this increasing demand as it promises in areas of power generation for residential, commercial, and industrial applications. Currently, there are several conventional electricity energy storage systems whose contributions have been presented at a building scale; batteries being the last the most used in the market for their ability to react instantly to changes in energy demand, but they are not totally eco-friendly. Nowadays, alternatives are being searched to reduce the ecological footprint that continues affecting the environment. To decrease carbon emissions and propose a “green” storage system, this research implements biomimetic strategies following the steps of the problem-based approach with the operating principle of lithium-ion batteries as a basis. As a result, a preliminary design of an equivalent circuit is presented that simulates the behavior of a natural cell based on the energy admission and storage processes of an oriental hornet, as well as the discharge mechanism of an electric eel.
Performance Assessment of Hydraulic Micro Relief Valve
Authors: Chiavola O , Frattini E , Palmieri F
Published: December 2022

Directly operated relief valves often exhibit abnormal or unstable behavior resulting in noise, premature wear, degraded performance, and failure. In this work, an investigation is carried out to assess the role of the hydraulic damper on the poppet element. The article reports the details of the investigation approach, integrating specific experimental tests with lumped-parameter modelling.Starting from a reference layout, the hydraulic behavior of different damper configurations is characterized (ranging from undamped to strongly damped poppets), for pressure and flow-rate conditions typically encountered in micro-hydraulic power packs. Depending on the damper design, the poppet operation ranges from unacceptability (due to noise) to fine-tuned response. The investigation give the chance to highlight how the damper layout impacts on the valve behaviour, in terms of pressure overshoot and settling time and provides the necessary information for relief valve design, modelling and analysis.
Detailed simulations of an aircraft fuel system by means of Simulink
Authors: Sciatti F , Tamburrano P , De Palma P , Distaso E , Amirante R
Published: December 2022

The fuel system is one of the most important and complex parts of aircraft, being tasked with suppling the correct quantity of fuel to the aircraft engine during all operative conditions, from flight to ground operation. It must operate efficiently in any condition to guarantee safety and reliability. A fuel system for kerosene-based fuels (i.e., jet fuels) is a combination of hydraulic components, namely, tanks, pumps, bypass valves, safety valves, servovalves. The aim of this paper is to provide an accurate simulation model of an entire fuel system for gas turbine (turboprop and turbofan) engines, which can be used by manufacturers and researchers to evaluate the performance of the fuel system under different operating conditions for given components or to select the geometries of the components to obtain specific performance levels. The numerical code is developed in the Simulink environment, which is a software package widely used in industry. A detailed description of the model is provided in this paper, and results under specific operating conditions are shown and discussed. The power consumption of the system is assessed as well, with indication of the main sources of losses, which will be useful for current EU projects aimed at reducing the power consumption of aircraft.
A lumped parameter and CFD combined approach for the lubrication analysis of a helical gear transmission
Authors: Muzzioli G , Paini G , Denti F , Paltrinieri F , Montorsi L , Milani M
Published: December 2022

This paper proposes a combined 1D-3D approach for the lubrication analysis of a standard transmission including two helical gears. A lumped parameter model of the entire lubrication system is developed to predict the flow distribution within the circuit and the localized pressure drops along the lines. This model considers the geometrical features of the real system, and it combines the experimental characteristic curves of the main hydraulic components. The steady-state condition is investigated, and the corresponding lubrication flow is provided as a boundary condition for a three-dimensional CFD model. The overset mesh method is employed to address the instantaneous position of the gears in the contact region and the Volume of Fluid (VOF) model assesses the multi-phase phenomenon. The turbulent behavior of the flow is described by the two-equation realizable k-ε model, and the incompressible assumption is made for both oil and air. The effect of different nozzles configurations on the lubrication efficiency is analyzed and the internal system fluid-dynamics is investigated to point out the oil path. The numerical results are discussed in terms of the volume fraction of oil on the gears teeth, the passive torques at the shafts and the associated power losses under specific operating conditions.
Accuracy Assessment of the Eulerian Two-phase Model for the CFD Simulation of Gas Bubbles Dynamics in Alkaline Electrolyzers
Authors: Dreoni M , Balduzzi F , Ferrara G , Bianchini A
Published: December 2022

To date, the most industrially developed technology to produce green hydrogen is represented by alkaline water electrolysis (AWE). To improve on design and efficiency of these devices, however, multiphysics simulations based on Computational Fluid Dynamics (CFD) are needed, able to account for electrophysical phenomena and multiphase flows. Focusing on internal flow optimization, the requirements for CFD simulations are anyhow extremely challenging, since solving the gas bubbles’ motion implies the solution of a two-phase flow characterized by very low Reynolds numbers and a high fraction of dispersed gas. Despite some interesting studies have been presented in the literature so far, validation of CFD results with detailed experimental measurements is quite rare and, therefore, the reliability of the adopted modelling approaches is not assessed yet. This study presents the results of a multivariate CFD analysis of an electrochemical cell and its validation through a literature test case. Bubbles generation is introduced as a source term, thus overlooking for the moment the electrochemistry to focus on fluid-dynamics. In particular, attention is given to the Eulerian multiphase modelling, investigating the influence of both the inter-phase interaction sub-models’ settings (e.g., lift and drag forces, virtual-mass force) and the general settings of the simulation. The mean velocity field of the PIV-measured bubbles is considered to assess the accuracy of numerical predictions, while the available high-definition flow pictures allow a qualitative assessment of the bubbles size and location. CFD results are shown to be in decent agreement with experimental data and able to reproduce the key flow features such as the spreading of the bubble curtains and the gas shifting towards the inner part of the cell. The effect of the bubbles’ diameter and of source layer thickness is also discussed.
Alternative fuels for hard-to-abate sectors: a carbon intensity assessment
Authors: Prussi M , Chiaramonti D
Published: December 2022

Heavy duty is a hard-to-abate segment of transport. Heavy duty freight sector includes road, maritime and the fast-growing aviation segments. Due to the need of energy dense vector, specifically for freight sector, the liquid alternative fuels are considered as the most effective short-to-medium term option to allow decarbonisation. The possibility to uptake these fuels in heavy-duty road and maritime is investigated in this paper, with the goal of highlighting the potentials and the existing bottlenecks. The eLNG and bio-LNG are considered as alternative fuel for road Heavy Duty, while hydrogen, ammonia and eDiesel have been selected for maritime. The potential GreenHouse Gases (GHG) saving for such alternative fuels are estimated on the basis of Well-to-Tank approach, and compared with the relative fossil benchmark. The results show the benefit of using LNG from residues for road sector, and potentially the maritime. Regarding the e-fuels, the GHG savings are potentially relevant, but using low carbon electricity for their production is crucial.
Techno-economic assessment of enhanced Biogas&Power-to-SNG processes with high-temperature electrolysis integration
Authors: Colbertaldo P , Guandalini G
Published: December 2022

Biogenic energy sources are essential elements of the decarbonization pathways, but are strongly constrained by the limited availability. In this context, Biogas&Power-to-X technologies are strongly supported as a promising solution to foster renewable power generation and drive sector coupling opportunities. This work investigates enhanced Synthetic Natural Gas (SNG) production processes for the repurposing of biogas plants. As an alternative to combined heat and power applications via internal combustion engines, the Italian legislation is supporting biogas-to-biomethane upgrading, focusing on the transport market. The proposed integrated plant scheme is a flexible solution based on Power-to-Hydrogen and methanation, able to exploit both electric and gas grid connections, enhancing biomethane production. Advanced process schemes are studied combining solid oxide electrolysers that exploit the methanation waste heat as input thermal energy and flexible PEM electrolysers that improve the part-load operation. The calculated efficiency at max load is about 55% for the Power-to-Methane block and nearly 75% for the overall integrated plant. Results show limited sensitivity of efficiency to input power variations, making the system suitable for the recovery of surplus renewable power generation.
Numerical characterization of hydrogen under-expanded jets: influence of the nozzle cross-section shape
Authors: Anaclerio Giuseppe , Capurso Tommaso , Torresi Marco , Camporeale Sergio Mario
Published: December 2022

This historical moment is characterized by a great awareness regarding the need to reduce the Greenhouse Gas emissions (GHG), which are responsible for the climate change and its detrimental consequences. Green hydrogen produced by means of Power-to-Gas technologies from renewables is gaining momentum as a possible clean fuel for the future mobility. In such a context, traditional injectors for hydrocarbon fuels are currently being tailored to be used with hydrogen. The short time available for the injection process leads to the employment of a high inlet pressure, resulting in the formation of an under-expanded jet. In this work, the main characteristics of these jets are analyzed by means of Computational Fluid Dynamics (CFD) for a Nozzle Pressure Ratio (NPR) equal to 10. Then, to provide insights regarding the dependence of the air-hydrogen mixing on section shape of the nozzle, comparisons have been performed by changing the nozzle cross-section (circular, rectangular, and elliptical), keeping constant the mass flow rate to highlight the different levels of axial penetration and radial spread observed when varying the aspect ratio (1.5, 5.0, 8.0).
CFD simulations of under-expanded hydrogen jets under high-pressure injection conditions
Authors: Rahantamialisoa F.N.Z , Zembi J. , Miliozzi A. , Sahranavardfard N. , Battistoni M.
Published: December 2022

Large-eddy simulations (LES) of hydrogen jets under highly under-expanded conditions are carried out. Computational fluid dynamics (CFD) analysis appears extremely useful to fully understand and optimize the hydrogen injection process, like in internal combustion engines. This work aims to analyze hydrogen high-pressure injection in the near-nozzle region, investigating the formation process and the structure of the Mach disks and the transition to turbulent jets, for nozzle pressure ratios (NPR) of 5.8 and 30. A real fluid model is utilized and compared against the simpler ideal gas model, for injections into an ambient pressure environment. Furthermore, hydrogen-air mixing evolution is investigated in the far-field region. Average quantities obtained from statistical analysis on LES simulations are compared with available data. The near nozzle region, except for the initial transient part, is better captured by accurate spatial discretization methods, while properly predicting far-field effects, like turbulence and acoustic effects, seems to be mostly related to time discretization schemes.
Hybrid Hydrogen production: Application of CO2 heat pump for the high-temperature water electrolysis process
Authors: Mojtahed Ali , De Santoli Livio
Published: December 2022

Hydrogen is considered an energy vector which ensures a pivotal role in the energy market in near future. As a subsequent, the need to provoke novel technologies and investigate the potential layouts rising from hybridization remains on the shoulder of research literature., The current work investigates the potential role of the supercritical CO2 heat pump to contribute to hydrogen production inside a hybrid energy system. The case study is a generic biogas power plant characterized by the combination of diverse hydrogen production technologies such as water electrolysis and the reforming process. Water electrolysis takes place through high (SOEC) and low-temperature(AEC) The role of the heat pump unit is defined to operate between these two technologies to recover heat losses and transfer them to high-temperature electrolysis. The performance of the CO2 cycle in the presented hybrid energy system is simulated via MATLAB SIMULINK and the effective indicators to improve its performance have been carried out.In the end, the result of the simulation shows a production rate of 19.27 kgH2/h. Furthermore, thanks to heat recovery the total thermal efficiency increases by 80%. It also reveals that the heat pump unit operates with COP in the range of 4.5 – 3.3 based on pressure ratios providing temperature in the range of 151-184 °C by fixing the cold sink input temperature and pressure at 70 °C, 75 bar respectively.
1D-3D coupled approach for the evaluation of the in-cylinder conditions for Gasoline Compression Ignition Combustion
Authors: Viscione Davide , Bianchi Gian Marco , Ravaglioli Vittorio , Falfari Stefania , Cazzoli Giulio , Silvagni Giacomo , Mariani Valerio , Corsi Marzia
Published: December 2022

Nowadays, progressive improvements of engine performance must be performed to reduce fuel consumption, which directly affects the amount of CO2 released in the atmosphere. For this purpose, considering modern technologies in the automotive scenario, Gasoline Compression Ignition (GCI) combustion might represent one promising solution, since it experiences high thermal efficiency of Compression Ignited (CI) engines and pollutant emission mitigation. This paper shows the first step of a project aimed at reproducing the combustion behavior of a Diesel engine running with GCI combustion by means of CFD simulations. In particular, this work presents a methodology used to reconstruct the mixing process inside the cylinder before the combustion event, since those engines are dramatically sensitive to the global and local mixture quality. Firstly, a reverse-engineering procedure aimed at generating the CAD model of the engine was performed. Afterwards, the discharge coefficients of the intake and exhaust valves through specifically designed 3D CFD simulations were determined, which was necessary due to the customized intake/exhaust line. Eventually, to reasonably reconstruct the in-cylinder state, the Rate of Heat Release (RoHR) curve, calculated from the analysis of the in-cylinder pressure signal running the engine in GCI mode, was imposed in GT-Power by means of a combination of Wiebe functions with the purpose of generating representative trends of pressure, temperature, and mass flow to properly define the domains of the CFD model.
CFD investigation of the radiative heat transfer effects on the adoption of an electrical heated catalyst to increase the abatement efficiency
Authors: Barillari Loris , Torre Augusto Della , Montenegro Gianluca , Onorati Angelo
Published: December 2022

The thermal transient of the after-treatment system (ATS) during the cold start and the typical urban drive low load engine operations is a crucial point for the conversion efficiency. In this context, the adoption of electrical heating is regarded as an effective solution to promote the catalytic activity and the pollutants abatement. This paper focuses on the evaluation of the radiative heat transfer affecting the operation of an electrical heated catalyst employed to increase the abatement efficiency of a standard catalyst. The modeling methodology relies on a CFD framework based on a Conjugate Heat Transfer (CHT) approach in OpenFOAM, so that a detailed characterization of the thermal transient of the different components of the exhaust line can be achieved. The electrical heating device under investigation is based on a metallic support and it is heated by the Joule effect. The distribution of the heat and its subsequent interaction with the gas flow significantly influence the catalyst operations. In this context, the CFD modeling framework has been further developed so that it is possible to accurately evaluate the radiative heat transfer in correspondence of the porous regions. The description of such features is mandatory for an accurate prediction of the maximum electrical heating device temperatures, resulting in a reliable estimation of the gas flow temperature and its subsequent interaction with the catalyst. The simulation methodology has been applied at first excluding the radiative heat transfer. Then, the developed radiation modeling is applied, so that its influence on the ATS performance can be fully evaluated.
Batteries Thermal Management for Hybrid plug-in Powertrains
Authors: Perrone D. , Falbo L. , Castiglione T. , Ficarella A. , Bova S.
Published: December 2022

Lithium-ion batteries have become the primary battery technology used for electric and hybrid vehicles powertrains. Battery temperature, however, is a critical factor for these devices, as it influences battery performance life-time and safety and must be preferably kept in the 15-35 °C range. A dynamic electro-thermal model of a lithium iron phosphate battery was developed. The model predicts battery voltage and temperature evolution in different operating conditions. A battery equivalent circuit model (ECM) with an open circuit voltage source, an ohmic resistance and a capacitor-resistor pair in series is adopted. The state-of-charge is determined by the Coulomb counting approach and the battery temperature is computed by carrying out an energy balance for the cell. The balance takes into account the difference between the heat generated within the cell and the heat loss to the environment. Finally a controller, which cools or heats the battery in order to keep its temperature in the desired range, was developed. The case of the battery pack of a hybrid plug-in powertrain during a WLTP cycle is simulated and the result of different environmental conditions are presented.
Effect of coil charge duration on combustion variability and flame morphology in a GDI engine working in lean burn conditions
Authors: Cecere G , Merola S S , Irimescu A , Millo F , Rolando L
Published: December 2022

Spark ignition (SI) and subsequent flame front development exert a significant influence on cyclic variability of internal combustion engines (ICEs). The increasing exploitation of lean air-fuel mixtures in SI engines to lower fuel consumption and CO2 emissions is driving the scientific community towards the search for innovative combustion strategies. Moreover, although lean combustion has been widely investigated and an important number of studies is already present in literature, the high cyclic variability typical of this combustion process still represents a major hinder to its exploitation. This study aims to investigate the effects of increasing ignition energy on combustion characteristics of lean mixtures. Tests were performed on an optically accessible gasoline direct injection (GDI) engine that allowed to investigate the correlation between the thermodynamic results and spark arc-flame morphology. Engine speed was fixed at 2000 rpm, a relative air fuel ratio (AFRrel) of about 1.3 was selected and ignition timing was set at 12 crank angle degrees (CAD) bTDC. Coil charge duration was swept from 10 to 40 CAD. Two intake pressure levels were investigated, the first corresponding to wide open throttle under naturally aspirated operating mode, the second with an intake pressure of 1.2 bar, thus corresponding to a boosted operating condition. Two dedicated scripts built using NI Vision were employed for image processing, allowing the evaluation of temporal and spatial evolution of the early stages of combustion. Arc elongation and flame front contour were used as correlation parameters that characterize flame kernel inception and development. The results confirm that, as expected, the increase of the coil charge duration tends to reduce cyclic variability in terms of engine output. The optical investigations revealed that for both examined cases the standard deviation related to the wrinkling effect on flame edge at CA5 decreased as the coil charge duration increased.
On Iso-octane Combustion with Ozone Addition under HCCI Engine-Like Conditions
Authors: D’Amato Marco , Magi Vinicio , Viggiano Annarita
Published: December 2022

Numerical simulations were carried out to study the influence of ozone on the Ignition Delay Time (IDT) of iso-octane/air mixtures under typical operating conditions of HCCI engines. 0-D and 2-D CFD simulations were carried out to compute IDT and to characterize compression, combustion, and expansion in an HCCI engine, respectively. A kinetic model was developed by merging a mechanism for iso-octane, a sub-mechanism for nitrogen oxides, and a sub-mechanism for ozone. The model was used to investigate iso-octane/air/ozone mixtures under typical operating conditions of HCCI engines running with very lean mixtures (equivalence ratio equal to 0.3). Parametric analyses were carried out considering different values of temperature (500 to 1200 K), pressure (15 to 40 bar) and ozone concentration (0 to 50 ppm). The results show that as ozone concentration increases IDT decreases, with a greater impact at low temperatures, and the NTC (Negative Temperature Coefficient) effect decreases. However, the reduction of IDT with ozone addition is less as ozone concentration increases, especially at low temperatures. An increased pressure, on the other hand, generally promotes faster ozone decomposition and enhances ozone effect on IDT reduction for all temperatures except in the range 760-840 K, where the opposite effect occurs due to NTC phenomenon. Finally, when temperature is very high, i.e. 1200 K, both ozone and pressure have little influence on the percentage reduction of IDT.
The state of the electrical sector in Western Balkan countries. Case study: Republic of Kosovo
Authors: Mexhuani A , Bylykbashi K , Jupaj B , Shala A , Rubini L
Published: December 2022

The electricity sector around the world is considered one of the most important sectors, which has a direct impact on the economic development of a country. Based on the increase in energy consumption, the crisis with the emission of high levels of harmful gases - the greenhouse effect and the expansion at the economic level of countries, electricity, namely the increase of energy capacity will remain key issues for future discussion at the global level. Electricity is the engine of the rapid economic development of a country; necessarily the well-being of citizens to access to energy sources and energy stability is a key requirement of every consumer, producer or economic operator. How much capacity do countries in the world have to respond to the increase in energy consumption in the future and what sources will be oriented so that the consequences are minimal for the environment, is a question that needs continuous detailed study and concrete approaches from relevant institutions and professionals in this field. Security in electricity supply is essential for our society and necessary for the 24/7 principle for the digital economy. The recent difficulties caused by the Covid-19 pandemic remind us of the great importance of electricity in all aspects of our lives, from the availability of medical equipment and IT systems - for work from home as a growing trend of systemizing jobs during 2020. Ensuring a secure and reliable electricity supply is of paramount importance to all countries in the world. Considering the Western Balkans as one of the regions which since the 90s most of it has been an area which has emerged from devastating wars and which have affected every sphere, including the energy sector. So, the development of the energy sector is one of the most critical issues in the Western Balkans region. Based on the considerable potential of electricity production from renewable sources, it is considered that the production of electricity from RES will create a stable and functional system of energy production by contributing to the principle of diversification of electricity production and decentralization of the power system. So, renewable energy is considered a promising method for building sustainable and resilient energy systems that provide affordable energy to boost a region economic development, reducing import dependence. The purpose of this scientific research is to discuss the development and current state of electricity production from renewable sources in the Western Balkans, with special emphasis on the Republic of Kosovo. Considering that all Western Balkan countries have set targets or targets for RES in their energy policies but not always these pre-defined targets are easily achievable in practice due to thevarious challenges facing the energy sector in this region.
Re-Powering Italian Wind Farms: a Feasibility Study from Theory to Practice
Authors: Sensi L , Melani PF , Venturi A , Giusti M , Mungo G , Tomassetti V , Bianchini A
Published: December 2022

The installation of new renewable power plants in Italy is currently hindered by various concurrent factors, the length of the authorization process above all. The average time to authorize a wind farm is about five and a half years, mainly due to the binding judgment of the EIA (Environmental Impact Assessment). Italy however is now in a phase where many of the first-installed wind farms are close to their end of life. In this perspective, a promising solution is given by the re-powering of existing wind farms, since they can access a simplified authorization procedure under the Legislative Decree 08/11/2021, n. 199 et seq., which reduces by one third the bureaucratic burden and it lets non-binding the evaluation of the landscape authorities. Moving from this background, the study provides a feasibility study on the re-powering of Italian wind farms. Starting from the database available at GSE (Gestore dei Servizi Energetici), a new re-powering scenario has been defined, accounting for the constraints on the site area, number and dimension of the turbines imposed by the art. 32 of Law 29/07/2021, n. 108. The effectiveness of the re-powering intervention has been evaluated in terms of energetic yield, considering the increased capacity factor of the new turbines, economic revenue and environmental footprint. To verify its feasibility on a real application, a wind farm owned by AGSM-AIM S.p.A., for which wind, terrain, and production data were available, has been selected. Different plant layouts have been analyzed in the WindPro software, and compared in terms of power, producibility and capacity factor. The feasibility of the different layouts has also been verified by on-field inspections.
Definition of the induction time for CO2 and CH4 hydrate via evaluation of the heat released during the process and the gas consumption rate.
Authors: Gambelli A M , Filipponi M , Rossi F
Published: December 2022

The induction period is defined as the time required to obtain a detectable quantity of hydrates during their natural or artificial production. This period includes the initial nucleation phase and part of the following massive growth phase. Several methods were thought to measure its length: the most adopted are the visual observation of the process and the direct measure of the temperature increase. However, these techniques are not always feasible and their accuracy is often low. This work deals with the definition of the induction time by considering the heat produced during the process, which is proportional to the temperature but significantly less affected by the stochastic nature of the process. In order to prove the feasibility of the process, the results were then compared with what obtained by considering the gas consumption rate to measure the induction time. The proposed method was validated for methane hydrates. The same confirmation was not possible for carbon dioxide hydrates, due to the high solubility in water of this species and the consequent overestimation of the gas consumption during the process.