bluuebunny/crossref_metadata_2025 huggingface dataset:
The Spectroscopic Classification of Astronomical Transients (SCAT) Survey: Overview, Pipeline Description, Initial Results, and Future Plans
Authors: Tucker M. A. , Shappee B. J. , Huber M. E. , Payne A. V. , Do A. , Hinkle J. T. , de Jaeger T. , Ashall C. , Desai D. D. , Hoogendam W. B. , Aldering G. , Auchettl K. , Baranec C. , Bulger J. , Chambers K. , Chun M. , Hodapp K. W. , Lowe T. B. , McKay L. , Rampy R. , Rubin D. , Tonry J. L.
Published: December 2022

We present the Spectroscopic Classification of Astronomical Transients (SCAT) survey, which is dedicated to spectrophotometric observations of transient objects such as supernovae and tidal disruption events. SCAT uses the SuperNova Integral-Field Spectrograph (SNIFS) on the University of Hawai’i 2.2 m (UH2.2m) telescope. SNIFS was designed specifically for accurate transient spectrophotometry, including absolute flux calibration and host-galaxy removal. We describe the data reduction and calibration pipeline including spectral extraction, telluric correction, atmospheric characterization, nightly photometricity, and spectrophotometric precision. We achieve ≲5% spectrophotometry across the full optical wavelength range (3500–9000 Å) under photometric conditions. The inclusion of photometry from the SNIFS multi-filter mosaic imager allows for decent spectrophotometric calibration (10%–20%) even under unfavorable weather/atmospheric conditions. SCAT obtained ≈640 spectra of transients over the first 3 yr of operations, including supernovae of all types, active galactic nuclei, cataclysmic variables, and rare transients such as superluminous supernovae and tidal disruption events. These observations will provide the community with benchmark spectrophotometry to constrain the next generation of hydrodynamic and radiative transfer models.
Effectively enhancing silicon-vacancy emission in a hybrid diamond-in-pit microstructure
Authors: Romshin Alexey M , Gritsienko Alexander V , Lega Peter V , Orlov Andrey P , Ilin Alexey S , Martyanov Artem K , Sedov Vadim S , Vlasov Igor I , Vitukhnovsky Alexei G
Published: December 2022

Solid-state photon emitters at room temperature appear to be promising candidates for a variety of nanophotonic applications. In this regard, coupling photon emitters with various optical cavities providing pronounced directivity, high photoexcitation and emission rates is extremely desirable. Here, we introduce the novel concept of deterministically coupling color centers in nanodiamonds (NDs) with gold nanopits. We show that in this case, emission of silicon-vacancy (SiV−) centers at the zero-phonon line can exceed that of a ND on a gold surface by a factor of 62. The obtained results reveal an effective pumping of the SiV-centers in NDs along with the active switching of the SiV-centers from the dark to the bright state by plasmon mode that opens the way to design controllable resonance systems with diamond-based photonic emitters.
Method of simulating hybrid STT-MTJ/CMOS circuits based on MATLAB/Simulink
Authors: Ji Min-Hui , Zhang Xin-Miao , Pan Meng-Chun , Du Qing-Fa , Hu Yue-Guo , Hu Jia-Fei , Qiu Wei-Cheng , Peng Jun-Ping , Lin Zhu , Li Pei-Sen
Published: December 2022

The spin-transfer-torque (STT) magnetic tunneling junction (MTJ) device is one of the prominent candidates for spintronic logic circuit and neuromorphic computing. Therefore, building a simulation framework of hybrid STT-MTJ/CMOS (complementary metal–oxide–semiconductor) circuits is of great value for designing a new kind of computing paradigm based on the spintronic devices. In this work, we develop a simulation framework of hybrid STT-MTJ/CMOS circuits based on MATLAB/Simulink, which is mainly composed of a physics-based STT-MTJ model, a controlled resistor, and a current sensor. In the proposed framework, the STT-MTJ model, based on the Landau–Lifshitz–Gilbert–Slonczewsk (LLGS) equation, is implemented using the MATLAB script. The proposed simulation framework is modularized design, with the advantage of simple-to-use and easy-to-expand. To prove the effectiveness of the proposed framework, the STT-MTJ model is benchmarked with experimental results. Furthermore, the pre-charge sense amplifier (PCSA) circuit consisting of two STT-MTJ devices is validated and the electrical coupling of two spin-torque oscillators is simulated. The results demonstrate the effectiveness of our simulation framework.
All-optical switches based on three-soliton inelastic interaction and its application in optical communication systems
Authors: Wang Shubin , Zhang Xin , Ma Guoli , Zhu Daiyin
Published: December 2022

In high-speed optical communication systems, in order to improve the communication rate, the distance between pulses must be compressed, which will cause the problem of the interaction between optical pulses in optical communication systems, which has been widely concerned by researches. In this paper, the bilinear method will be used to analyze the coupled high-order nonlinear Schrödinger equations and obtain their three-soliton solutions. Then, the influence of the relevant parameters in the three-soliton solution on the soliton inelastic interaction is studied. In addition, the constraint conditions of each parameter in the three-soliton solution are analyzed, the inelastic interaction properties of optical solitons under different parameter conditions are obtained, and the relevant laws of the inelastic interaction of solitons are studied. The results will have potential applications in the soliton control, all-optical switching and optical computing.
Single-frequency linearly polarized Q-switched fiber laser based on Nb2GeTe4 saturable absorber
Authors: Chen Si-Yu , Deng Hai-Qin , Zhang Wan-Ru , Dai Yong-Ping , Wang Tao , Yu Qiang , Li Can , Jiang Man , Su Rong-Tao , Wu Jian , Zhou Pu
Published: December 2022

We report a single-frequency linearly polarized Q-switched fiber laser based on an Nb2GeTe4 saturable absorber (SA). The Nb2GeTe4 SA triggers passive Q-switching of the laser, and an un-pumped Yb-doped fiber together with a 0.08-nm-bandwidth polarization-maintaining fiber Bragg grating (FBG) acts as an ultra-narrow bandwidth filter to realize single-longitudinal-mode (SLM) oscillation. The devices used in the laser are all kept polarized, so as to ensure linearly polarized laser output. Stable SLM linearly polarized Q-switching operation at 1064.6 nm is successfully achieved, producing a laser with a shortest pulse width of 1.36 μs, a linewidth of 28.4 MHz, a repetition rate of 28.3 kHz–95.9 kHz, and a polarization extinction ratio of about 30 dB. It is believed that the single-frequency linearly polarized pulsed fiber laser studied in this paper has great application value in gravitational wave detection, beam combining, nonlinear frequency conversion, and other fields.
Asymmetric magnetoimpedance effect and dipolar interactions of FINEMET/SiO2/FePd composite ribbons
Authors: Guo Yong-Bin , Wang Dao , Wang Zhong-Min , Ma Lei , Zhao Zhen-Jie
Published: December 2022

The dipolar interactions are investigated through the asymmetric magneto-impedance in FINEMET/SiO2/FePd composite ribbons. The interface between the hard (FePd layer) phase and soft (FINEMET ribbon) phase is coherent by SiO2 layer in FINEMET/SiO2/FePd composite ribbons, which effectively induces dipolar interactions. The contribution of dipolar interaction to the bias field (H
b) by asymmetrical giant magneto-impedance and magnetic properties is analyzed. The results show that H
b response decreases with the increase of the SiO2 layer thickness, indicating that the linear region near-zero field can be tuned by the thickness of SiO2 layer. These results allow the GMI ratio (58%) and characteristic frequency (500 kHz) to be optimized. The transverse and longitudinal magnetic domain structures of FINEMET ribbon and FePd film are confirmed, respectively. The composite ribbons with high GMI ratio and low frequency can be applied to linear magnetic sensors.
The identification of interacting brain networks during robot-assisted training with multimodal stimulation
Authors: Wang Duojin , Huang Yanping , Liang Sailan , Meng Qingyun , Yu Hongliu
Published: December 2022

Objective. Robot-assisted rehabilitation training is an effective way to assist rehabilitation therapy. So far, various robotic devices have been developed for automatic training of central nervous system following injury. Multimodal stimulation such as visual and auditory stimulus and even virtual reality technology were usually introduced in these robotic devices to improve the effect of rehabilitation training. This may need to be explained from a neurological perspective, but there are few relevant studies. Approach. In this study, ten participants performed right arm rehabilitation training tasks using an upper limb rehabilitation robotic device. The tasks were completed under four different feedback conditions including multiple combinations of visual and auditory components: auditory feedback; visual feedback; visual and auditory feedback (VAF); non-feedback. The functional near-infrared spectroscopy devices record blood oxygen signals in bilateral motor, visual and auditory areas. Using hemoglobin concentration as an indicator of cortical activation, the effective connectivity of these regions was then calculated through Granger causality. Main results. We found that overall stronger activation and effective connectivity between related brain regions were associated with VAF. When participants completed the training task without VAF, the trends in activation and connectivity were diminished. Significance. This study revealed cerebral cortex activation and interacting networks of brain regions in robot-assisted rehabilitation training with multimodal stimulation, which is expected to provide indicators for further evaluation of the effect of rehabilitation training, and promote further exploration of the interaction network in the brain during a variety of external stimuli, and to explore the best sensory combination.
Effects of bootstrap current on magnetic configuration in Chinese first quasi-axisymmetric stellarator
Authors: Liu Haifeng , Zhang Jian , Xu Yuhong , Shimizu Akihiro , Cooper Wilfred Anthony , Okamura Shoichi , Isobe Mitsutaka , Wang Xianqu , Huang Jie , Cheng Jun , Liu Hai , Zhang Xin , Tang Changjian
Published: December 2022

Neoclassical properties in quasi-axisymmetric (QA) stellarators are analogous to these in tokamaks. Consequently, a substantial bootstrap current could significantly modify the MHD equilibrium properties of a QA stellarator, which is an important characteristic in this type of stellarator. This paper is dedicated to systemically investigate the effects of bootstrap current on the magnetic configuration in Chinese first quasi-axisymmetric stellarator (CFQS). For the first time, self-consistent bootstrap currents in free-boundary equilibria are calculated with an accurate Fokker–Planck neoclassical numerical mode in CFQS. Several important results are achieved: (a) as the bootstrap current grows with increasing volume-averaged normalized pressure

β

, magnetic shear develops in the bulk plasma and meanwhile, a deep magnetic well is robustly sustained, which leads to improved stabilization of interchange modes up to

β
∼
2.0

%

. (b) In the analysis of global ideal MHD instability, as the bootstrap current rises to 39 kA (

β
∼
1.3

%

), external kink modes become destabilized and the unstable mode with m/n = 2/1 is dominant. (c) From

β
=
0

to 1.5%, the bootstrap current hardly changes the QA property and a low neoclassical transport is maintained. However, as

β

is enhanced beyond 2.0%, the substantial bootstrap current gives rise to an increase of non-QA magnetic field components, which weakens the neoclassical transport properties. (d) An increase of the negative magnetic shear at the core region by the bootstrap currents has a favorable effect on the properties of J (second adiabatic invariant). The maximum-J region can be extended by raising bootstrap currents.
Global gyrokinetic simulation of edge coherent mode in EAST
Authors: Xie Baoyi , Ye Lei , Chen Yang , Zhao Pengfei , Ye Yang , Lin Xin , Lan Heng , Guo Wenfeng , Xiang Nong
Published: December 2022

Linear and nonlinear simulations are carried out for the edge coherent mode (ECM) using the global gyrokinetic code GEM based on the EAST experimental parameters. The linear simulation results show that ECM is an electrostatic mode with dominant toroidal mode number n = 18 and frequency about 48 kHz, and propagates along the direction of electron diamagnetic drift, which are consistent with the experimental results. In addition, the density and electron temperature gradients destabilize the mode, while the collision stabilizes the mode. The nonlinear simulation results show that the saturated particle and heat fluxes induced by ECM are mainly due to the perturbed electrostatic ExB drift, and the fluxes of electrons and ions are almost equal. The ECM drives significant outward particle and heat fluxes, thus greatly promoting the maintenance of the long pulse H-mode. The Fourier decomposition of fluxes and potentials demonstrate that the intermediate-n modes of n = 14, 18 grow fastest in the linear phase, while in the nonlinear saturation phase, the low-n modes such as n = 4, 6 dominate and the fluxes are mainly contributed by the mode of n = 10. It is found that zonal flow is not the dominant saturation mechanism of the turbulence. The inverse spectral cascade of turbulence is inevitably observed in the nonlinear saturation process, indicating that it is a more universal turbulence saturation mechanism. It is also found that radial electric field can greatly reduce the turbulence intensity and transport level. From the analyses of frequency and transport channels, it can be concluded that ECM appears to be the collisionless trapped electron mode.
Research on crowd dynamic risk management based on the psychological stress perception function
Authors: Ma Jun , Wang Meiling , Li Linze
Published: December 2022

Number of people, density and so on are often used as a risk indicator in crowd dynamic risk management, but crowd size cannot truly reflect the change process of psychological stress perception that leads to crowd behavior disorder. Therefore, this research calculates risk index thresholds from the perspective of psychological stress perception to help managers assess crowd-gathering risks. On the one hand, the behavior model and psychological stress perception model are constructed based on corresponding experiments at the micro layer. On the other hand, risk decision models, including the average density and phubbers ratio, are built at the macro level. Finally, a long subway transfer channel was used as a simulation scenario, and the critical value of the decision quantity was determined by taking the psychological stress perception of the crowd as the objective function. The simulation shows that the perceived pressure of the crowd changes nonlinearly with time. The simulation result of the critical threshold can be divided into four zones, namely, the safety area, warning area, disposal area and dangerous area, so that managers can take targeted measures. The results are validated by applying psychological stress perception to practical population risk management.
Dynamic Modelling of a Heat Exchanger Network for a Dairy Plant
Authors: Casadei Riccardo , Lorenzini Marco , Fattini Daniele , Valdiserri Paolo
Published: December 2022

In co-and trigeneration plants with internal combustion engines, waste heat from their cooling system can be fed to a heat exchanger network for office heating, hot water production, or used in industrial processes. At the same time, care must be exerted not to cool the return fluid below a threshold, in order to avoid piston seizure. In this work, the heat exchanger network is that of a gas-engine trigeneration system for a large dairy plant in Rome. Since its daily and weekly production schedule is subject to several changes, temperature control must be both precise and efficient. A thermal-hydraulic, dynamic (i.e. time-dependent) model of the heat exchanger network was developed in Matlab/Simulink, to obtain the instantaneous pressure, mass flowrate and temperature of the fluids along the network. The approach is mixed, a lumped-parameter description of the hydraulic and thermal networ, and finite volumes for the heat exchangers. The model has been verified and validated with experimental, steady-state data from the dairy plant and the results found satisfactory.
A Methodology to identify appropriate refurbishment strategies towards zero energy buildings in a hot and humid climate
Authors: Austin Miguel Chen , Carpino Cristina , Mora Dafni , Arcuri Natale
Published: December 2022

Significant actions on the building stock are required to reduce energy consumption and emissions from buildings and achieve carbon neutrality by 2050. Consistently, the renovation approach of existing buildings could aim to obtain nearly Zero Energy Buildings or Net Zero Energy Buildings (NZEB). In particular, the solutions to obtain zero-energy buildings vary according to the reference climatic conditions and the technical-constructive characteristics of the buildings undergoing renovation. As part of a research project involving the Technological University of Panama (UTP) and the University of Calabria (UNICAL), this work presents a preliminary investigation aimed at identifying the most appropriate technological solutions to convert existing buildings in Panama into zero-energy buildings. In particular, the study seeks to characterize the energy demand of buildings in the research area, consisting of Panama City, and to identify a set of possible energy efficiency measures applicable in hot and humid climates through dynamic simulations. The preliminary results from the sensitivity and optimization analyses highlight the capacity of local regulations and buildings’ capacity towards achieving zero-energy buildings by enhancing the efficiency of appliances, lighting, and air conditioner system, but also by implementing passive strategies such as the bioclimatic strategies.
Design and partial-load operation of a reversible Solid Oxide Cell system with molten salts thermal storage
Authors: Ficili Marco , Colbertaldo Paolo , Guandalini Giulio , Campanari Stefano
Published: December 2022

The increasing penetration of renewable energy sources in the electricity mix requires efficient storage solutions on the seasonal scale. Reversible Solid Oxide Cell (rSOC) systems are receiving increased attention as viable options to fulfil this requirement. In this work, a MW-scale rSOC system capable of working over a large operating window is studied via modelling on Aspen Plus®. To ease the thermal integration, a molten salt thermal storage is coupled to the system, enabling heat recovery in fuel cell mode, which is then exploited for water evaporation in electrolysis mode. The rSOC stack is designed to operate exothermically in the electrolysis mode at nominal load. In both modalities, the air mass flow rate is regulated to control the stack temperature, while limiting the in-out gradients within 100°C. At nominal load, the system achieves an electrical efficiency of 52% in fuel cell mode and of 87% in electrolysis mode. The operation at low partial loads, due to the decrease of the air flow rate, requires an additional high-temperature heat source to guarantee the heat integration. In this regard, the adoption of an electrical resistance in electrolysis mode and a hydrogen-fed combustor in fuel cell mode are selected as viable solutions to amplify the operating range of the system. As a results, the system can be operated down to the 30% of the stack nominal power in both modalities, where the system achieves an electric efficiency of 44% and 80% in fuel cell and electrolysis mode, respectively.
Thermo-physical properties of paraffin wax with iron oxide nanoparticles as phase change material for heat storage applications
Authors: Jebali Meriem , Colangelo Gianpiero , Haurie Laia , Bekri-Abbes Imene , Lacasta Ana Maria
Published: December 2022

Phase change materials (PCMs) are growing in importance in many thermal applications as heat storage or to smooth the energy peak demand in many technological fields in industrial as well as in civil applications. Conductive nanoparticles can be added to phase change material to improve their thermo-physical properties. In this work, Iron oxide nanoparticles (IOx-NPs) were synthesized using a simple and green synthesis method, free of toxic and harmful solvents, using the extract of a plant as a reducer and stabilizer at two different temperatures of calcination 500°C and 750°C. The metallic oxide was used as an additive with 2% wt. compositions to paraffin wax to prepare a nanocomposite. The variation in thermal properties of paraffin wax in the composite was experimentally investigated. The biosynthesized IOx-NPs were characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) and Thermal Gravimetric Analysis (TGA) techniques. The thermal properties of the synthesized nanocomposites were characterized by a thermal conductivity analyzer and differential scanning calorimetry (DSC). The FTIR spectra showed a bond at 535 cm-1, which confirms the Fe-O vibration. The XRD powder analysis revealed the formation of the cubic phase of Fe3O4 with an average particle size of 11 nm at 500°C and the presence of the phase α-Fe2O3 with Fe3O4 at 750°C. Scanning Electron Microscopy (SEM) showed that the obtained oxide was made up of particles of nanoscale size. Experimental measurements showed that the presence of nanoparticles can improve the latent heat capacity by a maximum of 16.16 % and the thermal conductivity of the nanocomposites by a maximum of 16.99%.
Downsizing the electric machines of energy-efficient electro-hydraulic drives for mobile hydraulics
Authors: Padovani D , Fresia P , Rundo M , Altare G
Published: December 2022

The poor energy efficiency of state-of-the-art mobile hydraulics affects the carbon dioxide released into the atmosphere and the operating costs. These crucial factors require urgent improvements that can be addressed by the electrification of fluid power. This approach has already generated electro-hydraulic drives that remove flow throttling and enable energy recovery. However, the entire power managed by the actuators of conventional systems must pass through the electric machines. This characteristic is unfeasible for medium-to-high power applications since they need electric motors and electronics with high power ratings and large onboard generation of electricity. Thus, this paper applies to a hydraulic excavator’s boom the idea of splitting the power being transferred to/from the actuator between the hydraulic and electric domains (i.e., a centralized hydraulic power supply is involved). The objective is downsizing the power rating of the boom’s electric components while maintaining the high-power output of the hydraulic actuator. The results show the expected behavior of the hybrid excavator in terms of motion control, but only 57% of the boom’s peak power is now exchanged electrically. The resulting electric machine with 61% downsizing favors the system’s cost and compactness supporting the electrification process that is aligned with the low-carbon economy.
Life Cycle Analysis of a Hydrogen Valley with multiple end-users
Authors: Concas Giulia , Cocco Daniele , Lecis Lorenzo , Petrollese Mario
Published: December 2022

This paper aims to evaluate the environmental impact along the overall life cycle of the various components of a Hydrogen Valley with multiple end-users fed by green hydrogen. As case study, a hydrogen valley including a MW-scale electrolyser powered by different percentages of energy supplied by a wind farm and/or a photovoltaic plant, and an H2 storage section is considered. The H2 produced is used to feed a fleet of fuel cell electric vehicles and a stationary fuel cell, while the residue H2 is injected in a natural gas pipeline considering a maximum safety limit of 5%vol. When the safety limit is reached, the H2 overproduction can be used to produce biomethane through a biological hydrogen methanation process. With the aim of analysing the actual contribution of these hydrogen-based ecosystems towards more sustainable energy systems, a Life Cycle Analysis of the hydrogen valley is carried out. The results show that the final use of hydrogen for fuel cell electric vehicles produces the most valuable environmental benefits. Moreover, Hydrogen Valley solutions integrated with photovoltaic plants allows to maximize the use of H2 in fuel cell electric vehicles and therefore are the most valuable choice from an environmental point of view.
Process Design and Techno-Economic Assessment of biogenic CO2 Hydrogenation-to-Methanol with innovative catalyst
Authors: Lombardelli G , Consonni S , Conversano A , Mureddu M , Pettinau A , Gatti M
Published: December 2022

A small-scale 10 ton per day methanol (MeOH) synthesis plant, from CO2 and hydrogen, is designed and simulated with Aspen Plus and a techno-economic analysis is conducted. The e-fuel (MeOH) is produced in a conventional fixed bed reactor featuring an innovative Cu/Zn/Al/Zr catalyst, converting biogenic CO2 from a biogas upgrading plant with H2 produced by a grid powered PEM electrolyzer. The process is thermally autonomous as a result of heat integration and combustion of purged unconverted reactants. A sensitivity analysis is carried out in order to evaluate and compare the impact of the different technical (purge fraction, Gas Hourly Space Velocity and Pressure of the methanol synthesis) and economic parameters (Capital Charge Factor, electricity and H2 cost) on the Levelized Cost Of Methanol (LCOM). Results show that, although the energy efficiency is greater (47.4 % electricity to methanol conversion) in the scenario with “self-sufficiency” in which all the net heat required by the process is provided by off-gas streams, the case with the highest profitability is the one with maximum methanol yield and, therefore, minimum purge and non-zero thermal energy import (provided by a biogas boiler). The best case scenario features a LCOM equal to 1,361 €/tonMeOH, with a GHSV of 7,500 h−1 and synthesis reactor operating at 70 bar, 250 °C. H2 production cost is the key variable and shall be reduced from the base case value of 5.8 €/kgH2 to 1.6 €/kgH2 in order to make the CO2 to methanol plant competitive with a MeOH market price of 550 €/tonMeOH; synthesis reactor operating conditions have more limited impact from a cost perspective, except for the purge fraction that shall be optimized to maximize the amount of MeOH produced.
Design and experimental set-up of hydrogen based microgrid: characterization of components and control system development
Authors: Cava Carmine , Cosentini Carlotta , Gagliardi Gabriele Guglielmo , Cedola Luca , Caputi Michele Vincenzo Migliarese , Aresti Marco , Borello Domenico
Published: December 2022

In this study, the implementation of a hydrogen microgrid is investigated, considering the integration of H
2 production, storage, and energy conversion to feed a typical end-user. A remote control system has been realized through LabVIEW software, allowing to monitor real-time all the devices and analyze their performances. The integrated system is composed of a PEM electrolyzer (325 W), a storage system based on metal hydrides (two tanks, 54 g of hydrogen each, 1.08 wt%) and an energy converter (PEM Fuel Cell stack, 200 W). A programmable electronic load was used to set a power demand throughout the year, simulating an end-user. Data collected from each component of the micro-grid were used to characterize the energetic performance of the devices, focusing on the H
2 production via electrolyzer, charging cycles of the H
2 storage system, and energy conversion efficiency of the FC stack. Finally, the global efficiency of the microgrid is computed. Even though the system is realized in laboratory scale, this circumstance will not invalidate the significance of the configuration due to modularity of all the technologies that can be easily scaled up to realistic scales.
Thermodynamic Analysis of a Small-scale Biomethane Liquefaction Process
Authors: Tamburrano P , Salvatori M , Fedele M , Meschia M , Distaso E , De Palma P , Amirante R
Published: December 2022

Liquid biomethane, obtained from anaerobic digestion of organic biomass, upgrading and liquefaction processes, is regarded as one of the most effective renewable biofuels to be extensively employed in the transport and power generation sectors for mitigation of greenhouse gas emissions. In this paper, a novel biomethane liquefaction process for small-scale plants is presented and thermodynamically assessed by means of a detailed thermodynamic model that employs the libraries of Fluid Prop, being very accurate for thermodynamic calculations of complex fluids. The thermodynamic model allows the heat exchanger geometry to be accurately determined and crucial parameters to be adjusted, such us the composition of the refrigerant and the operating conditions of both the biomethane and the refrigerant. The proposed model has general validity and can also be used to study the most promising biomethane liquefaction technologies for small-scale plants.
Advances in 1D thermo-fluid dynamic simulation of SI hydrogen-fueled engine
Authors: Ballerini Alberto , Cerri Tarcisio , Marinoni Andrea Massimo , Onorati Angelo
Published: December 2022

This work has the objective to describe the improvement introduced in the 1D thermo-fluid dynamic simulation code developed to simulate hydrogen-fueled Internal Combustion Engines. Two main topics have been analyzed. The first regarding the simulation of unsteady flows in the whole intake and exhaust system and the injection process of the fuel, considering a mixture of ideal gases as working fluid with specific heats depending on both gas temperature and composition. The second one focused on the combustion process, where the correlation-based approach used to compute the laminar flame speed for the homogeneous air-hydrogen mixture has been substituted by a Tabulated Kinetic approach. New correction factors that account for surface instabilities have been also added to obtain a more accurate prediction of the combustion process. The modifications introduced have been validated against experimental values comparing in-cylinder pressure trends, intake and exhaust instantaneous pressure pulses taken at different locations. Finally, the results obtained from the simulations of a novel hydrogen-fueled heavy-duty engine are presented.
A dynamic model of a Hybrid Electric Propulsive System for degradation assessment
Authors: Donateo T , Spada Chiodo L , Ficarella A
Published: December 2022

The present study proposes a model for the simulation of the steady-state and transient behaviors of a Hybrid Electric Propulsive System (HEPS), in presence of several forms and degrees of performance degradation. The power system, which is made of a turboshaft engine coupled with an electric power source is intended for urban air mobility applications. The proposed model encompasses the capability of modeling battery aging effects, and, consequently, updating the performance of the system with battery life. Moreover, the versatility of the proposed model makes it suitable for the analysis of the dynamic behavior of the system, for example in presence of small perturbations around predefined operational settings or following a known mission profile. In this investigation the model is applied to the test of the HEPS under different operating conditions with different degradation criteria, affecting both the thermal and the electric drive with different levels of severity. The application of the model allowed the generation of relevant information concerning the propulsive system state of health which will be processed with the employment of machine learning algorithms in an accompanying paper.
A methodology to initialize tumble flow fields for fast 3D-CFD simulations of pent-roof SI engines
Authors: Ramognino F , Sforza L , Lucchini T , D’Errico G , Onorati A
Published: December 2022

The demand of powertrain technologies able to efficiently employ several non-fossil fuels types, as bio or synthetic ones, compels to develop simplified strategies to accelerate the engines industrial optimization. High-tumble ultra-lean SI engines are currently an attractive option, thanks to their fuel flexibility and the potential of extending the lean combustion limit with novel ignition strategies. This work presents a methodology to initialize tumble flow fields at closed-valves inside pent-roof SI engines, without the need of simulating the gas exchange process. First, assuming an elliptical-shaped vortex, a velocity field is initialized into the cylinder according to the target tumble ratio at inlet valve closing (IVC). Then, the flow field is evolved at fixed piston position for a time duration proportional to the integral time scale of turbulence. This process is essential to adapt the vortex morphology to the surrounding geometrical details, despite some kinetic energy is lost due to frictions. To compensate this last effect, the velocity field is re-scaled at the end of the process to match the initial tumble ratio. Finally, the parameters affecting the tumble initialization are calibrated by comparing the development of the flow-field during the compression stroke with the results from a full-cycle simulation in a pent-roof SI engine. The methodology is validated on the Darmstadt optical engine. First, the numerical velocity fields are compared against PIV measurements at different crank-angles. Then, the combustion prediction is also evaluated, to assess the quality of the initialized tumble flow field. The achieved results are satisfactory, demonstrating the industrial applicability of the presented methodology.
Numerical Investigation on the Effects of the Setting of the Load Control System of a Formula SAE Single-Cylinder Turbocharged Engine on Fuel Efficiency and Performance
Authors: Raspanti S , Ciampolini M , Bigalli S , Fabiani A , Romani L , Ferrara G
Published: December 2022

The target of motorsport has always been maximising the performance. Increasingly stringent rules on fuel usage, however, have moved the research on engine design and control rules toward efficiency enhancement. Turbocharging is a typical solution to match both targets; however, it suffers from the turbo-lag phenomenon, especially when the maximum power is limited by an air restrictor. In the present paper, an investigation on a combined solution aimed at contemporarily improving transient response and efficiency in FSAE events, both leading to a higher score, is carried out. In detail, the adoption of an anti-lag valve and an efficiency-based control schedule, markedly exploiting the wastegate actuator, is proposed in place of the classic combination blow-off valve and performance-based strategy. The analyses were carried out on the 520 cm3 single-cylinder 4-stroke turbocharged engine of the Firenze Race Team. In order to predict the potential of the proposed load control solution, a predictive combustion engine model (which design process is exhaustively described in the paper), adopting the K-k-ε turbulence model, was developed in the GT-Suite software and calibrated by means of test-bench data and 3-D CFD analyses. A vehicle model, calibrated by means of telemetry data, was finally developed to compare the proposed solution to the baseline load control system in typical race conditions, showing benefits in terms of performance, drivability, and efficiency.
1D/3D simulation procedure to investigate the potential of a lean burn hydrogen fuelled engine
Authors: Teodosio Luigi , Berni Fabio , Lanotte Alfredo , Malfi Enrica
Published: December 2022

In recent years hydrogen, especially the one generated by renewable energy, is gaining increasing attention as a clean fuel to support the future mobility towards efficient and low emission solutions for propulsion systems. In this scenario, the present work deals with the virtual conversion of a single-cylinder Diesel engine, conceived for marine applications, into a hydrogen Spark Ignition (SI) unit. A simulation methodology is adopted, combining 1D and 3D Computational Fluid Dynamics (CFD) methods. First, experiments are realized on the original Diesel engine mounted on a test bench, collecting main performance indicators and emissions. A complete 1D engine model (GT-Power™) is developed and validated against measurements. Then, a 3D model of the cylinder (STAR-CD) is set-up and the related combustion outcomes are compared both with 1D and experimental results, showing an overall good agreement. In the second stage, the Diesel unit is converted into a port-injected hydrogen SI engine; the 3D model is re-arranged and utilized to reproduce pre-mixed hydrogen combustions under ultra-lean air/fuel (A/F) mixtures. Also, the 1D model is partly modified and coupled to an advanced combustion sub-model integrated with fast tabulated chemical kinetics to predict the knock. In particular, 1D combustion evolution is calibrated against the results of 3D CFD hydrogen combustion simulation. Finally, the calibrated 1D model is applied to investigate the advantages of ultra-lean hydrogen combustion in terms of efficiency, NO, and unburned H2 formation at medium/high loads.
New Experimental Vapor-Liquid Equilibria Data and Thermodynamic Modelling for R1234yf/propane/R32 as low-GWP Mixtures in Heat Pump Applications
Authors: Panzeri A , Bona D Di , Signorini S , Molinaroli L , Gatti M
Published: December 2022

This paper presents new experimental results for the Vapor – Liquid Equilibria of binary mixtures of R1234yf and propane at 277 and 313 K. The newly collected data are then used, in combination with other existing data retrieved from the literature, to calibrate the Peng-Robinson Equation of State with suitable accuracy for domestic vapour compression heat pump cycles simulations. After calibration, the Equation of State is applied to numerical simulations, in Aspen Plus, aimed at finding the optimal refrigerant composition, among ternary mixtures containing R1234yf, propane and R32. Results identify a Pareto curve where the optimal mixtures (with flammability lower or equal to A2L and GWP < 500) are represented in terms of two contrasting objectives: COP and the volumetric heating effect. Ternary mixtures containing propane and R1234yf respectively in the range 0÷12%mass and 18÷30%mass are Pareto optimal: the mixture with the best COP (2.7% lower than R410A one) is the binary pair R32 = 70% + R1234yf = 30%, a composition very close to the one of the commercial refrigerant R454B. On the other hand, the mixture with the largest volumetric effect (6.5% higher than R410A one) is the ternary blend R32 = 70% + R1234yf = 18% + propane = 12%. This study confirms that is quite challenging to find R410A replacements featuring at the same time reasonable heating capacity and a COP not lower than R410A one.
Butane-based heat pump for advanced GTCC applications: static and dynamic model validation
Authors: Anfosso Chiara , Gini Lorenzo , Mantelli Luca , Ferrando Marco , Reboli Tommaso , Traverso Alberto
Published: December 2022

The Thermochemical Power Group (TPG) of the University of Genoa is investigating innovative solutions to increase the flexibility of gas turbine combined cycles (GTCC) and extend their operative range by integrating large size high performance heat pumps. Achieving this goal would make GTCCs more competitive in the future energy market, which will be characterized by a heavy presence of non-dispatchable renewable energy sources.

Within this framework, the authors designed and built a new experimental facility to emulate advanced GTCCs at laboratory scale, integrating a 100 kWel micro gas turbine (MGT), a 10 kWel heat pump (HP) and a 180 kWh cold thermal energy storage (TES), with scale-up equations and dynamic models, capable of hardware-in-the-loop tests.

The focus of this article is on the HP, which uses n-butane (R600) as working fluid and can be used both to heat and cool down the MGT compressor intake. The HP features one superheater and a 6-cylinder reciprocating compressor, which rotational speed can be continuously varied from 900rpm to 1800rpm.

A dynamic model of the HP was developed in TRANSEO, with dedicated Matlab-Simulink® models. This model includes all the components of the HP closed loop, making it possible to simulate its performance and monitor all the main process parameters, such as compressor operation and condensing pressure. This model can be used to simulate the HP in various conditions, including part-load and transient operations, and to aid the design of the advanced GTCC control system. The evaporator and condenser models solve a system of non-linear equations to compute pressure, temperature, and distribution of the different phases of the working fluid along the heat exchangers. Such phase distribution is computed following a moving boundary approach.

An experimental campaign was carried out to collect data regarding the stationary performance of the HP. Values of COP and thermal power were analysed as a function of compressor speed and pressure at the condenser, keeping the conditions at the evaporator constant. Then, its transient behaviour was characterized, observing its response to step changes of both evaporator and condenser thermal loads. The model was then successfully calibrated and validated on both stationary and transient data, showing good accuracy.

Based on these results, it will be possible to integrate the HP model within larger system simulation tools. Having an accurate digital twin of the whole GTCC integrating HPs and TES will make possible to develop and verify complex control logics on many different scenarios, relying on a safe model-in-the-loop setup, before actual implementation in the field.
Using Life Cycle Assessment in tenders to enhance the sustainable procurement of External Thermal Insulation Composite Systems
Authors: Cardarelli A , Baffo I , Ubertini S , Barbanera M
Published: December 2022

Green Public Procurement (GPP) is a policy instrument to decrease the environmental impact of products and services and create environmental value for society. A new method for assessing environmental award criteria in GPP processes was developed to integrate environmental and economic criteria into public tenders for External Thermal Insulation Composite Systems (ETICS). The main objective of this study was to identify the effect that the inclusion of environmental impacts can have on decision-making in public procurement. At this scope, an environmental benchmark for the main phases of the supply chain (production, installation and disposal) of ETICS that use different insulating materials, including EPS and mineral wool, was defined for different Life Cycle Assessment (LCA) impact categories after a detailed literature review. Then the monetisation method of the externalities was applied to combine the environmental impacts and the direct costs associated with the manufacture of the ETICS system by obtaining a single score for the selection of the best bid from the environmental and economic point of view. This methodology was implemented in a spreadsheet and a case study was analysed as a practical application of the tool developed for the determination of the global index. The case study simulated a tender in which three contractors provided their bid for an ETICS system. The overall investigation of the results obtained in the case study showed that the environmental externalities have a rather limited incidence compared to direct costs (between 0.8 and 10%). However, even if the lower direct costs were provided by contractor 1 (87.72 €/m2) in comparison to contractor 2 (87.80 €/m2) and contractor 3 (92.74 €/m2), the slightly higher environmental impacts caused the costs to rise. The most environmentally and economically advantageous bid was then provided by contractor 2, for which the global index was the lowest for each monetisation method applied. For all the impact categories considered, the production stage (A1-A3) represents the most significant contribution. The thermal insulation material and the finishing coat provide the greatest contribution to the environmental impact. The tool was designed to improve the knowledge of the economic and environmental performances of ETICS systems, which might be also used by public administrations to define minimum environmental requirements and maximum specific costs when preparing tenders for the energy requalification of buildings.
Thermodynamic Analysis of a Parabolic Trough Collector (PTC) operating with gas-phase nanofluids
Authors: Settino Jessica , Ferraro Vittorio , Carpino Cristina , Marinelli Valerio
Published: December 2022

Parabolic Trough Collectors (PTC) are the most developed and established technology among the concentrated solar power systems. However, the majority of the PTC power plants currently in operation uses synthetic oils or molten salts as heat transfer fluids (HTF), with a limited operating temperature range. To operate at higher temperatures, the use of pressurized gases as working fluid has been recently proposed in several studies. However, in this case a large pumping power is required. In this work, the use of gas-solid suspensions in a commercial PTC has been analyzed. A thermodynamic analysis has been performed to investigate the effect of three different gas-solid suspensions: Argon-Al2O3, Carbon Dioxide-Al2O3 and Air-Al2O3. The performance of these gas-phase nanofluids has been compared to the use of pure gases. Power output, pumping power, outlet fluid temperature and global efficiency of the parabolic trough system have been determined. The analysis shows a substantial decrease of the pumping power. Thanks to this advantage, the use of gas-phase nanofluids in parabolic trough collectors could represent an interesting possibility.
How to Increase Savonius Power Coefficient: Ducted Rotor Performance with Different Overlap Ratios
Authors: Brusca S , Galvagno A , Lanzafame R , Mauro S , Messina M
Published: December 2022

The use of ducted configuration to increase the efficiency of wind turbine rotors is gaining wide attention in the scientific community. Specifically for mini and micro rotors in urban environment applications this solution demonstrated to be very attractive. The possibility to overcome the Betz limit for power coefficient was widely demonstrated in ducted horizontal axis wind turbines. However, very few studies have dealt with ducted Savonius rotor despite these rotors represented an efficient solution for urban environment thanks to their simplicity, their cheapness and the low cut in velocity in highly turbulent conditions as well. Furthermore, the ducted Savonius concept, might be applicable to oscillating water column wave energy devices, thanks to its self-rectifying capability and simplicity. For these reasons, the authors carried out an experimental campaign to verify the impact of ducting the Savonius rotor, thus leading the way for a possible exploitation of this configuration in many practical applications. Specifically, The present paper deals with a study of ducted Savonius type air turbine performance. In particular, turbine performance was studied as a function of turbine overlap ratio. Four overlap ratios were tested: 0, 1/6, 1/3 and 1/2. A specific experimental setup was built to test ducted turbine, while bare turbine performance was measured using a wind tunnel. All tests were performed at fixed air velocity: 5 m/s. On the basis of the results, it is possible to state that ducted turbine performance is higher than bare turbine performance, at all tip speed ratios and for all overlap ratios. The optimal turbine overlap ratio is equal of 1/3.