bluuebunny/crossref_metadata_2025 huggingface dataset:
ACAES systems to enhance the self-consumption rate of renewable electricity in sustainable energy communities
Authors: Cocco Daniele , Licheri Fabio , Micheletto Davide , Tola Vittorio
Published: December 2022

This paper aims to evaluate the optimal configuration of an Adiabatic Compressed Air Energy Storage (ACAES) system designed to achieve the best matching between power production from non-programmable Renewable Energy Sources (RES) power plants and power demand from final users. The electrical energy demand of a small town, with a maximum power load of about 10 MW, has been considered as case study. The electrical energy can be supplied by both a photovoltaic (PV) power plant and the grid. For the ACAES system, different sizes for compressor, turbine, thermal energy storage (TES) system and air storage reservoir have been evaluated by varying the air mass flow rate of turbomachines and the charging and discharging duration times, to enhance the share of the PV energy supplied to the end user. The best performance is achieved with a PV power plant rated at about 35 MW and an ACAES section characterized by a compressor/turbine rated power of about 25-35% of the maximum power load of the end user, with a charging time of about 10 hours and a discharging time of about 20 hours. The average round-trip efficiency of the ACAES system is around 70%. On the overall, the integrated PV-ACAES system allows to cover 66% of the yearly electrical energy demand.
An Alternative Solution for Microfluidic Chip Fabrication
Authors: Ongaro C , Betti A , Zardin B , Siciliani V , Orazi L , Bertacchini J , Borghi M
Published: December 2022

This paper focuses on microfluidic devices, widely used in bioengineering. Their fabrication for research is almost entirely made of PDMS (a silicone), using photolithography and replica molding technologies, which involve many processing steps, sealed with a glass layer by plasma bonding. Our solution fabricates devices in just two steps, laser ablation of a glass layer, technology already extensively tested, and sealing with a commercial silicone layer by plasma bonding, drastically reducing skilled human operations and lead time. The paper describes the technologies with PDMS and with our solution, the design of a microfluidic test chip, the laser ablation and assessment by a confocal microscope of the microfluidic circuit in the glass layer of the chip, the plasma bonding of glass layers with PDMS and two other commercial silicones utilizing a grid of different plasma parameters, the qualitative assessment of the plasma bonding and choosing of a silicone as PDMS substitute, the extensive test on the bonding quality by two different pressure circuits on a batch of microfluidic chips realized with our proposed technology.
Design procedures for hybrid hydromechanical transmissions
Authors: Andretta N , Rossetti A , Macor A
Published: December 2022

Hybrid hydromechanical transmissions are particularly suitable for heavy vehicle and have the potential to provide better efficiencies than other hybrid architectures. However, their study must be carried out with care, since there are many possible transmission configurations and there is not one superior to the others for all applications. The particular complexity of these transmissions requires that design be treated as an optimization problem.

In this paper, the optimization procedures of the “non-optimal” type are compared with the “optimal” ones, which are more precise than the former, but much heavier in terms of calculation time. The former consist of two sections. The first one is dedicated to the simultaneous optimization of the layout and components of the non-hybrid hydromechanical transmission; the second one is dedicated to the accumulator only, which can be optimized by means of simple physical laws or by means of a “Design of Experiments “procedure.

The “optimal” procedures, on the other hand, proceed with the sizing of the entire hybrid transmission through a mathematical programming problem that can be single or multi-objective. It will be demonstrated that the DOE “non-optimal” procedure provides results very close to those derived from the “optimal” procedures, with considerable savings in calculation times.
Ammonia as a fuel for internal combustion engines: latest advances and future challenges
Authors: Langella G , de Joannon M , Sabia P , Iodice P , Amoresano A
Published: December 2022

The use of ammonia as a fuel still poses a series of challenges to be overcome, both in terms of optimization and energy efficiency of the production process, and with regard to its combustion in internal combustion engines. The two main obstacles along this way are undoubtedly the high ignition temperature and the low propagation speed of the flame front due to the slow chemical kinetics of ammonia combustion process. All these issues lead to the need to use this fuel in blended mode with other more “easy burning” fuels. This need is even more felt in cases of non-stationary combustion, such as for alternative internal combustion engines but, on the other hand, it can determine an increase in engine efficiency. In this work, these ammonia technological constraints are exposed and discussed, outlining the most recent technological solutions and those under development, which will allow an increasingly widespread use of this energy carrier as a fuel in internal combustion engines. Finally, the environmental aspects related to the greater potential emission of NOx and the techniques to limit their occurrence are analyzed.
Fluid dynamic analysis of a cryogenic piston pump
Authors: Cioni Stefano , Balduzzi Francesco , Romani Luca , Bianchini Alessandro , Ferrara Giovanni
Published: December 2022

Cryogenic piston pumps are commonly found in cryogenic systems to pressurize low-temperature liquefied fuels, such as liquified natural gas (LNG) or hydrogen, which are then gasified and stored in high-pressure vessels. The main challenges to be tackled in the design of these machines concern the low operating temperatures, high discharge pressures, and especially the need to avoid liquid evaporation, as this can lead to a reduction of volumetric efficiency or even to the shutdown of the pump. Two effects can cause the formation of vapor bubbles: cavitation, i.e., when the static pressure falls below the saturation value during the suction phase, and evaporation due to a temperature increase of the cryogenic liquid.

In this study, a numerical analysis of a cryogenic single-piston pump is carried out. In the first part of the activity, the suction phase is studied through three-dimensional, steady-state CFD simulations. The performance of the pump in terms of pressure losses is evaluated and possible improvements to the suction geometry are identified.

Then, two-phase steady-state Eulerian-Eulerian simulations are performed. The Rayleigh-Plesset model is used in order to evaluate the onset of cavitation. The minimum inlet pressure conditions that avoid cavitation are identified for two different geometries underlining the positive effect of the introduced modifications. Results show that the methodology applied in this work can lead to improvements in cryogenic pump design, reducing the static pressure losses and hence limiting the risk of cavitation.
Optimized size and schedule of the power-to-hydrogen system connected to a hydrogen refuelling station for waste transportation vehicles in Valle Camonica
Authors: Vincenti Ferdinando , Cominini Paride , Furlanetto Dario , Sorlini Antonio , Valenti Gianluca
Published: December 2022

The aim of this work is the implementation of an optimization model for a hydrogen production facility connected to a refuelling station for heavy-duty vehicles, operating in the field of waste management and transportation. The model is composed by two subsequent mixed integer linear programming problems. The first problem addresses the problem of vehicle refuelling schedule and the second deals with the plant design and operation. The outputs of the model are the design and operation parameters of the plant and the vehicle refuelling schedule, allowing for the minimum levelized cost of hydrogen. Different possibilities for the electricity supply are investigated: grid electricity, solar photovoltaic and hydroelectric. The most profitable option is the installation of a 10 MW solar photovoltaic field, with a connected 3.3 MW Electrolyzer and 3700 kg storage. The resulting levelized cost of hydrogen is 10.24 €/kg. If no revenues from the sold electricity are considered, buying electricity from the grid becomes the most cost-effective option. The electrolyzer and storage size for this case are 760 kW and 405 kg, with a levelized cost of hydrogen of 13.75 €/kg. A sensitivity analysis, performed on the latter case, shows that the most sensible input parameters are the electrolyzer specific consumption and the cost of the electricity. A statistical analysis is also performed, considering a randomized failure distribution, obtaining the optimal values for the electrolyzer capacity of 700-800 kW and a hydrogen storage size of 1300-1400 kg. The costs, considering current electricity prices and no subsidies, are still high for hydrogen penetration in the energy market.
Electrochemical Impedance Spectroscopy study on ammonia-fed Solid Oxide Fuel Cells
Authors: Cinti G. , Baldinelli A. , Bidini G. , Barelli L.
Published: December 2022

The use of ammonia as a fuel is one of the promising pathways to decarbonize the energy sector. When ammonia is converted into power in the so-called “Ammonia-to-Power”, the most interesting technology is the Solid Oxide Fuel Cell (SOFC) that can operate directly with ammonia and reach high performance in terms of efficiency. SOFCs are a high-efficiency and, potentially, low-cost technology, but still suffer from degradation issues related to internal losses. An innovative experimental technique to evaluate losses evolution caused by degradation is electrical impedance spectroscopy (EIS), followed by measurement data post-processing through the Distribution of Relaxation Times (DRT) analysis. In this study, a single SOFC is studied with a combined EIS and DRT methodology, when operating with a gas mixture of hydrogen, nitrogen and ammonia. The results identify the contribution to DRT of fuel dilution and the internal ammonia decomposition reaction.
Techno-economic study on green hydrogen production and use in hard-to-abate industrial sectors
Authors: Superchi F , Mati A , Pasqui M , Carcasci C , Bianchini A
Published: December 2022

Replacing the bulk of grey hydrogen needed by industrial processes with a green one is one of the challenges of energy transition. In this study, the problem is analyzed from the perspective of a pre-determined amount of hydrogen to be delivered to hard-to-abate industries (steel mills and chemical industries) and produced by a wind farm converted or specifically installed for the scope. A hybrid configuration of the resulting energy system is figured out, considering a wind farm of twelve utility-scale turbines (2.3 MW each, for a total of 28 MW) to be coupled with alkaline-type electrolyzers, Li-Ion batteries and a hydrogen storage system. Moreover, it is assumed that the plant can also get energy grid in specific conditions, thus not producing a 100% green hydrogen in transitory periods. Specific point of strengths of the analysis are represented by the availability of several-year wind power production data, industrial performance data for the electrolyzers, whose model also accounts for performance degradation due to temperature, realistic operational constraints and variable efficiency. A battery aging model is also considered. A techno-economic analysis for different plant configurations is carried out with the aim of assessing how the systems performs form an economic and environmental point of view. Results show that is feasible to feed the plant with a constant hydrogen flow rate at a levelized cost of hydrogen (LCOH) of 4.95 €/kg with a green index (GI) around 64%, while a configuration that may reach higher GI (70%) presents a higher LCOH (5.26 €/kg).
Numerical investigation on a thermoelectric generator in an exhaust automotive line with convergent metal foam
Authors: Buonomo B. , Cascetta F. , di Pasqua A. , Fiorito C. , Manca O.
Published: December 2022

In the present paper, a 2-D steady state convective heat transfer problem in a convergent channel partially filled with aluminum foam with an external thermoelectric generator (TEG) component is numerically solved. The channel is characterized by a length equal to 272 mm and by a height of 60 mm. The TEG has the dimensions equal to 65 mm and 8.5 mm. The investigation is executed considering the Darcy-Forchheimer-Brinkman assumption and the local thermal equilibrium (LTE) hypothesis for modelling the metal foam. The exhaust gas is considered to have the same properties of the air in corresponding to the assigned temperature of the upper surface of the thermoelectric generator. The thermophysical properties are temperature independent and the thermoelectric generator is studied as a solid with an internal energy generation. The governing equations for gas, porous media and thermoelectric generator are solved by finite volume method using the Ansys-Fluent code. Different configurations of convergent metal foam are analyzed. The aluminum foams are characterized by 5 PPI and porosity equal to 0.905, 0.946 and 0.971. Results are presented in terms of temperature distributions, thermoelectric efficiency, power density, and the Energy Performance Ratio (EPR) for different gas flow rates and aluminum foam configurations. Furthermore, a comparison with the use of the same foam samples characterized by a constant section is showed for the same system. From the comparison, it is possible to deduce how the configuration with convergent channel has a more uniform temperature profile than the geometry with constant section.
Improvements to the hybrid method applied to the design of plate-finned tube evaporators
Authors: Starace G , Macchitella S , Colangelo G
Published: December 2022

The advantage of designing plate-finned tube evaporators applying the hybrid method is to combine low computational costs with the accurate results guaranteed by the use of predictive functions based on results of either numerical, or analytical, or experimental analysis. The high flexibility of the method makes it suitable for use as an effective design tool for evaporators in a wide range of operating conditions. This paper tells about improvements and refinements to the hybrid method algorithm performed to make it even more flexible and consistent with real heat exchangers performance prediction, depending on configuration changes. Part of the algorithm code has been changed in order to extend the application range of the model and several tests have been performed by varying the operating conditions such as the temperature difference between refrigerant and air at the inlet as well as the air relative humidity. The results show how the model is sensitive to the working conditions variations.
Predictive model of cooling system for railway electric propulsion: validation of design choices and last mile analysis
Authors: De Rosa R , Belli L , Frosina E , Venanzio P , Romagnuolo L , Senatore A
Published: December 2022

For many years the most advanced railway propulsion systems have been based on the use of electric motors. Compared to the other available solutions, these are characterized by greater operating economy and less environmental pollution. In order to operate as efficiently as possible and to guarantee the high standards of electromechanical reliability, these propulsion technologies need adequate cooling systems to operate in controlled temperature conditions. Considering this, the implementation of increasingly accurate and performing simulation models can represent a significant advantage and provide great support in the optimization phase of cooling systems, in terms of reduction of dimensions and weight, rapid and low-cost experimentation, prediction of critical scenarios and choice of the best solution strategies to be taken. In this regard, in the context of the collaboration between the University of Naples Federico II, University of Sannio and the company Hitachi Rail STS S.p.A., several lumped parameter models of power converter cooling systems for railway electric propulsion were developed in the Simcenter AMESim environment. These models allowed to validate specific design choices from thermal and hydraulic perspectives, aimed at higher energy efficiency of the system, and to perform the so-called Last Mile predictive analysis, in order to evaluate the possibility of removing a vehicle from the railway line as consequence of a fault of specific components.
Application of a one-dimensional fuel-oil dilution model coupled with an empirical droplet-to-film formation strategy for predicting in-cylinder oil effects in a direct injection engine
Authors: Renzis E D , Mariani V , Bianchi G M , Falfari S , Cazzoli G
Published: December 2022

Nowadays climate change due to the unnatural increment of green-house effect is one of the most critical environmental issues. In this context, internal combustion engines are still a short - term valuable solution. This is made possible by the study and the development of synthetic or alternative fuels, such e - gasolines and hydrogen. In this context, direct injection is still the most adopted strategy to improve internal combustion engine efficiency. The installation of the injector on the cylinder head may lead to the impact of the fuel on the wall of the cylinder liner. This phenomenon causes lubricant oil dilution, possibly increasing particulate matter emission at low load and abnormal combustions, known as low - speed pre-ignitions, at high load. The present paper aims to evaluate the influence of a set of established key parameters anticipating the effects of lubricant oil - fuel diffusion through a one - dimensional model implemented in Python. The model accounts for the runtime deposition of the fuel film by means of the results of a three - dimensional Computational Fluid Dynamics spray simulation. The model accounts also for the heat and mass transfer between species and the liquid fuel phase change for a representative setup of nowadays injectors. The dilution of a multigrade lubricant oil caused by synthetic fuels under an engine cold start operative condition is evaluated in this work.
Numerical analysis of energy recovery system for turbocharged internal combustion engines via a parallel compounding turbine
Authors: Frigo Stefano , Francesconi Marco , Sani Luca , Antonelli Marco
Published: December 2022

Increasing energy efficiency requirements mandatory ask for optimizing energy utilization in many devices, which include internal combustion engines. One of the most investigated subjects is the energy recovery from the exhaust, such as turbo-compound systems, which usually consist in a secondary turbine located afterward the turbocharger. Here an alternative arrangement is proposed and analysed via a numerical model. The recovery turbine works in parallel to the main turbine and uses the gasses which would be otherwise wasted through the waste-gate valve, once the set-point boost pressure is reached. The reference case analysed is a 12.4L turbocharged diesel engine, commonly used in marine, road and light railroad applications, with a nominal power of 380kW. The results showed that an overall 8% of power can be gained, without nor increasing the fuel mass flow rate, neither requiring significant modifications to the baseline engine. Moreover, in the case of the recovery system failure, the operation of the engine is not affected, thus resulting in no engine availability reduction. This work also shows a feasible way to convert the mechanical energy delivered by the recovery turbine into electrical energy, by making use of a high-speed electrical generator.
Conceptual design and sizing optimization based on minimum energy consumption of lift-cruise type eVTOL aircraft powered by battery and fuel cell for urban air mobility
Authors: Donateo Teresa , Çinar Hasan
Published: December 2022

In conceptual studies and prototypes of aerial vehicles for Urban Air Mobility, batteries are generally adopted as only energy sources. However, batteries have a long charging time that is not suitable for consecutive flights, and a low energy density that limits the range and flight time of the aircraft. For this reason, the hybrid propulsion solution consisting of a battery and a fuel cell has attracted attention in aviation in recent years. This study proposes the conceptual design of a VTOL (Vertical Take-Off and Landing) aircraft for passenger transportation in metropolitan areas by the synergic optimization of the aircraft configuration and the sizing of the propulsion system aimed at minimizing the power request in cruise. In the proposed conceptual design method, VTOL type aircraft is powered by either the battery or the fuel cell according to the flight phase. A multivariate nonlinear optimization problem using as goal the minimization of the fuel cell size is solved. The optimal values of battery size, wing loading, aspect ratio, endurance speed, aircraft weight, maximum lift coefficient, disk loading, rotor solidity, and zero-lift drag coefficient are determined from the solution of the optimization problem.
Model-based optimization of Sliding Rotary Vane Pump for internal combustion engine cooling of heavy-duty vehicles
Authors: Fatigati F , Di Bartolomeo M , Pallante F , Lo Biundo G , Cipollone R
Published: December 2022

The reduction of CO2 and pollutant emissions of internal combustion engines (ICEs) keeping their performance close to the expectations is the main driver of the research in the transportation sector. To counteract the global warming issues international governments set strict emission limitations foreseeing severe penalties for exceeding them. The vehicle electrification surely helps to match these stringent requirements, but a net CO2 reduction can be achieved only if the electricity from the grid has low carbon content. This is not the case of most part of the Countries where the fossil fuels are still the main sources of electric energy production. Thus, considering also the still higher cost of the electric vehicles, the technological improvement of ICEs assumes a strategic importance in this transition period. Among the possible interventions ensuring to achieve this aim, the efficiency enhancement of ICE cooling pump is one of the most effective. As matter of fact, it is proven that the replacement of conventional centrifugal pump with Sliding Rotary Vane Pumps (SVRPs) lead to an interesting decrease of fuel consumption and CO2 emissions. Nevertheless, the design of this machines is not straightforward due to the complex thermo-fluid-dynamic phenomena taking place inside their chambers. This aspect is even more critical for wide operating range as in the case of heavy-duty vehicles. Here, high pump revolution speeds could be provided to satisfy the flow rate requirements thus involving efficiency deterioration due to friction losses enhancement. Therefore, to reduce the revolution speed needed by the pump to elaborate the required flow rate, a novel design strategy based on the enhancement of volumetric capability is presented. The pump resulting by this design approach was called Low Speed LS pump which was prototyped and experimentally characterized over a wide set of operating conditions. The indicated cycle was also measured to better assess the fluid-dynamic behaviour of the machine. The experimental results show a maximum efficiency close to 60% in accordance with the best literature results.
Highlighting the Role of Lubricant Oil in the Development of Hydrogen Internal Combustion Engines by means of a Kinetic Reaction Model
Authors: Distaso E. , Calò G. , Amirante R. , De Palma P. , Mehl M. , Pelucchi M. , Stagni A. , Tamburrano P.
Published: December 2022

The urgent need to reduce the dependence on fossil fuels has re-ignited the interest toward Hydrogen Internal Combustion Engines (HICEs). Nevertheless, there are still criticalities that need to be assessed for accelerating the development of this technology. The undesired but unavoidable participation of lubricant oil to the combustion process can be the cause of many of these. Due to an extremely low autoignition resistance at low temperatures, lubricant oil is considered the main responsible for the onset of abnormal combustion modes, which need to be understood for delivering reliable and ready to market HICEs. By employing a kinetic reaction mode, this work analyses the autoignition tendency of hydrogen contaminated with n-C16H34(n-hexadecane), the latter being selected as a surrogate species representative of lubricant oil chemical characteristics. Starting from the detailed CRECK model (Version 2003), a reduced mechanism with very small size (169 species and 2796 reactions) was developed, which makes it suitable for the use in practical CFD engine simulations. Zero-dimensional numerical simulations were performed employing the reduced mechanism to quantify the variation of hydrogen ignition delay time due to the presence of different amounts of lubricant oil. Operating conditions typical of engine chambers were considered in the analysis. The results show that lubricant oil can have a significant impact on the charge reactivity, especially in the low-temperature range, with consequences that can potentially hamper the development of HICEs.
Hydrogen Fuel Cell Hybrid Electric Vehicles: the Impact of Commercial Vehicle Fleets on the Penetration of Renewable Energy Sources
Authors: Bartolucci Lorenzo , Cennamo Edoardo , Cordiner Stefano , Mulone Vincenzo , Pasqualini Ferdinando , Tatangelo Camilla
Published: December 2022

The transport sector is one of the most significant contributors to greenhouse gas (GHG) emissions, with the road segment accounting for large part of the emissions and requiring immediate action to address the increasing issues of climate change. To this aim, the international community is promoting technological alternatives to fossil fuel-based powertrains, thus favoring the increase in electric vehicle (EVs) penetration. However, to be sustainable the electrification of mobility requires a large share of energy produced by renewable sources to support the decarbonization process. The simultaneous increase in volatility for both the energy demand (due to EVs diffusion) and production (due to the Renewable Energy Sources RES growth), has a significant impact on the reliability of the electricity grid infrastructure. The growth of RES penetration brings an energy production increase that may not synchronized with the demand evolution, possibly leading to a grid imbalance. To this aim, the storing potential of green hydrogen, produced from RES during energy surplus periods, could allow better exploitation of the rising installed RES capacity. The proposed study aims to analyze the benefits that can arise from introducing Fuel Cell Hybrid Electric Vehicles (FCHEVs) in a commercial electric fleet in terms of environmental and grid resilience perspectives. FCHEVs are electric vehicles propelled by a hybrid powertrain, coupling electric battery packs and a fuel cell stack as energy sources; here, hydrogen is used as an energy vector stored in high-pressurized tanks. Starting from a reference scenario of a fleet composed of 10 EVs, the number of FCHEVs is progressively increased to assess their impact on the fleet performance. A set of mission scenarios for the commercial vehicles is obtained through the Markov Chain method, starting from accurate GPS data. These different scenarios are used in a numerical model to optimally plan the fleet scheduling and their configuration in terms of vehicles associated with specific missions. Results show a reduction of up to 57 % in grid fluctuations (estimated through its standard deviation) and a decrease from 77 % to 82 % in CO2 emissions concerning traditional vehicles increasing the FCHEV penetration considering the current Italian energy scenario.
3D CFD analysis of Mixture Formation in Direct-Injection Hydrogen-fueled Internal Combustion Engines
Authors: Potenza Magda Elvira Cassone , Gaballo Maria Rosaria , Arvizzigno Antonio , Anaclerio Giuseppe , Torresi Marco , Camporeale Sergio Mario
Published: December 2022

The European Green Deal for halving greenhouse gases emissions by 2030, compared to those of 1990s, and the resulting conversion in road transport from 2035 imply the need for the automotive field. Hydrogen-fueled internal combustion engines show a good potential to satisfy the transition towards the carbon neutrality. In particular, direct injection of hydrogen in spark-ignited internal combustion engines have great efficiency potentialities, nonetheless the design optimization of the injection systems needs extensive analysis for the evaluation of the hydrogen-air mixing processes under different engine operating conditions. Transient simulations of the gas-exchange process and fuel injection and mixing are fully described within this paper for two different commercial CFD codes namely, AVL-Fire and Ansys-Fluent. Both codes use the finite-volume approach to discretize the governing equations. Numerical results from the two commercial codes have been compared against the experimental data provided by the Argonne National Laboratories in terms of contours of fuel mole-fractions and velocity-field vectors, resulting from applying laser-based techniques on an optically accessible, single-cylinder engine.
Real Time Estimation of Combustion Indicators on a 4-Cylinder CI Turbocharged Engine Based on Instantaneous Engine Speed Measurement with Rapid Prototyping Implementation
Authors: Bosi L , Catalani I , Baroni A , Romani L , Vichi G , Bellissima A , Asai G , Minamino R , Ferrara G
Published: December 2022

In the field of Internal Combustion Engines (ICEs), increasingly stricter regulations on pollutant emissions have made necessary to continuously monitor engine operation. Indeed, in order to tackle fault-induced variations in engine performance, continuous, real-time data related to the engine’s thermodynamic cycle is needed: specifically, obtaining detailed information on the engine combustion phase is paramount. Combustion indicators are calculated through in-cylinder pressure, for which both direct and indirect measurement techniques can be employed. The former are accurate, but suffer from limited durability, while the latter are less accurate, but durable and less expensive, therefore more attractive for mass production applications. A technique for reconstructing the pressure cycle of each cylinder, through the combination of instantaneous crankshaft speed signal and a 0D thermodynamic model, was developed by the authors in MATLAB-Simulink environment and validated against experimental data. The objective of the present study is to implement this model on a four-cylinders CI turbocharged engine. Specifically, since focus was put on assessing the model real-time capability, efforts were made to execute the model inside a real-time controller. The paper presents the results of the experimental campaign that was carried out to validate the developed model. The signals from the pickup wheel and the camshaft phase sensor represent the main inputs, as they allow for the calculation of the engine speed and the detection of each cylinder Firing Top Dead Center (FTDC), respectively. Pressure sensors were mounted in all the cylinders for direct pressure acquisition. Tests were carried out under different operating conditions, specifically by varying speed, load and by reproducing the effects of injector malfunction in one cylinder. The developed model proved to be sensitive to operating conditions variations, correctly calculating combustion indicators such as the Indicating Mean Effective Pressure with real-time capability.
Modeling and design optimization of a hybrid power generator for full-electric naval propulsion
Authors: Saponaro Gianmarco , Stefanizzi Michele , D’Amato Davide , Franchini Emanuele , Fornarelli Francesco , Torresi Marco , Camporeale Sergio Mario
Published: December 2022

The purpose of this work is to build a model of diesel engine useful for studying new hybrid solutions for power generation. This kind of study is of significant interest particularly for the marine sector, due to recent limitations on fuel consumption and constraints imposed on the minimum powertrain efficiency. In this paper a variable-speed diesel generator model is presented. The model simulates both the dynamic behavior of the engine and the fuel consumption during the operating cycle. This model was developed using experimental results of bench tests conducted on the VL1716C2-MLL engine by Isotta Fraschini Motori (IFM) SpA. Diesel engine dynamics is based on the formulation found in the technical literature on mean value models and then adjusted through experimental data. Special attention was paid to developing the procedure to find the minimum specific fuel consumption for a given load. Initially, the presented resutls concern the correct response of the model under different load conditions. Then, the improvement in specific fuel consumption (obtained by adjusting the engine speed according to the load), in comparison with fixed speed operation, is shown.
A preliminary computational analysis towards the use of Electrically Heated Mixing Catalyst for innovative SCR after-treatment systems
Authors: Nappi A. , Vespertini A. , Torre A. Della , Montenegro G. , Onorati A.
Published: December 2022

This work aims at investigating the possible advantages of substituting the mixer in traditional SCR systems with an Electrically Heated Catalytic structure (EHC). First of all, EHC technology is being widely investigated in literature because it offers a concrete solution for catalyst thermal activation and film formation reduction in engine cold start conditions; however, its adoption as a mixer can also guarantee other important improvements in reducing pollutant emissions. In this work, a low-pressure injection of Ad-Blue impacts an electrically heated structure and a complete analysis of liquid droplets and film evaporation is carried out. A hybrid Eulerian-Lagrangian model has been adopted on a multi-region configuration, accounting for fluid-solid conjugate heat transfer (CHT), which plays a key role in the conversion strategy: it has been demonstrated that the heated structure can be exploited to significantly increase the exhaust gas enthalpy in the cold start, which represents an important improvement for pollutant conversion. Different heating strategies are analysed, with the objective of maximising the spray evaporation and the uniformity of the ammonia distribution downstream of the mixer. The objectives of this work are emphasizing the improvements that an electrically heated mixing catalyst can bring to the traditional SCR configuration, laying the foundation for other following studies.
Assessment of a desiccant cooling system in a traditional and innovative nanofluid HVAC system
Authors: Colangelo Gianpiero , Raho Brenda , Milanese Marco , Cannoletta Donato , de Risi Arturo
Published: December 2022

The topic of energy saving is a constant in everyday life, and it is widespread all over the world. Space heating using solar panels is the most used renewable source of energy, but the application of solar energy for cooling the fluids used for refrigeration is growing very fast. Among the techniques used for refrigeration, this work focused on Desiccant Cooling. In particular, with the use of dynamic simulation software, it was possible to study the heat supplied and the energy consumption of a Heating Ventilation Air Conditioning (HVAC) system of a university building and to compare consumption with those of a Desiccant Cooling system applied to the same building. Four different cases were simulated: two related to the HVAC system, one of which operates with water and glycol and the other one with nanofluid, and the other ones to the Desiccant Cooling system with both types of fluids mentioned above. Keeping the same energy demand of the building in all the simulations, it was found that in summer the Desiccant Cooling system had higher performance than the traditional HVAC system and that the use of the nanofluid in both types of conditioning systems further increased the performance of 21%. Simulations were carried out using TRNSYS software.
The comparative analysis of the R290 heat pump system working with standard expansion valve and two-phase ejector
Authors: Fingas R , Haida M , Smolka J , Besagni G , Palacz M , Bodys J , Nowak A J
Published: December 2022

The heat pump systems play a significant role in the global energy transition process of household heating sources towards zero-emission. One of the key technologies to improve the efficiency of heat pump systems utilizing natural working fluids is application of the two-phase ejector, which is able to recover part of the expansion losses. The comparative experimental analysis of a novel ejector-based air-source R290 heat pump was performed. The two two-phase bypass ejectors were installed in a R290 heat pump unit and a number of modifications were introduced to the baseline system. The adaptions included implementation of the internal heat exchanger, increasing the superheat at the compressor suction port, and a liquid separator for handling the two-phase flow at the ejector outlet. The performance evaluation of the system was based on COP and system heating capacity. The comparative analysis with the R290 heat pump utilizing standard expansion valve and two-phase ejector was carried out for typical operating conditions for its domestic application during heating seasons. The system working with an ejector as a throttling device allowed for up to 33% of COP improvement over the system utilizing an expansion valve. Additionally, the ejector implementation resulted in decreased pressure ratio of the compressor, which increased the system heating capacity by up to 90%.
Influence of the ventilation strategy on the respiratory droplets dispersion inside a coach bus: CFD approach
Authors: Scungio Mauro , Parlani Giulia , Falcucci Giacomo
Published: December 2022

The airborne transmission of the COVID-19 virus was considered the main cause of infection. The increasing concern about the virus spread in confined spaces, characterized by high crowding indexes and an often-inadequate air exchange system, pushes the scientific community to the design of many studies aimed at improving indoor air quality. The risk of transmission depends on several factors such as droplet properties, virus characteristics, and indoor airflow patterns. The main transmission route of the SARS-CoV-2 virus to humans is the respiratory route through small (<100 μm) and large droplets. In an indoor environment, the air exchange plays a fundamental role on the dispersion of the droplets. In this study, an integrated approach was developed to evaluate the influence of the ventilation strategy on the dispersion of respiratory droplets emitted inside a coach bus. There are no specific guidelines and standards on the air exchange rate (AER) values to be respected in indoor environments such as coach buses. The aim of this work is to analyse the influence of ventilation strategy on the respiratory droplet concentration and distribution emitted in a coach bus. Ansys FLUENT was used to numerically solve the well-known transient Navier-Stokes equations (URANS equations), the energy equation and using the Lagrangian Discrete Phase Model (DPM) approach to construct the droplet trajectories. The geometry is representative of an intercity bus, a vehicle constructed exclusively for the carriage of seated passengers. The 3D CAD model represented a coach bus with an HVAC system, within which an infected subject was present. The positions of exhaust vents and air-conditioning vents were chosen to ensure complete air circulation throughout the bus. The infected subject emitted droplets with a well-defined size distribution and mass through the mouth. The air exchange is provided in two different ways: general ventilation (from air intakes positioned along the bus windows and top side of central corridor) and personal ventilation (with air intakes for each passenger). For the general ventilation a single AER value was set (0.3 m3 s−1). The first results obtained showed a slight particle dispersion in the computational domain due to the airflow rate entered through the HVAC system, but a still elevated level of particle concentration tended to accumulate on the area near to infected subject. Additional analysis was executed to evaluate the beneficial effects linked to further addition of airflow through personal air-conditioning vents placed above every passenger’s head. The results show the importance of the use of the ventilation system inside a coach bus, highlighting how the contribution linked to of the personal air exchange rate can lead to a significant reduction of droplet concentration exposure and consequently a reduction of the risk of infection from airborne diseases.
Optimal Hybrid Ventilation Strategy to Assure Adequate Indoor Thermal Comfort and Air Quality in Educational Spaces under a Tropical Climate
Authors: Quijada María Cedeño , Solano Thasnee , Austin Miguel Chen
Published: December 2022

Air quality, specifically in indoor environments, has become a growing concern. In general, people tend to spend most of their lives indoors due to the growing urbanization. Indoor air quality is associated with ventilation rates, academic performance, and occupant’s health due to the presence of indoor pollutants. Exposure to these contaminants is a risk factor for people to develop the sick building syndrome. The objective of this study was to determine an optimal hybrid ventilation strategy in a tropical climate, favoring natural ventilation with different proposed strategies, varying the opening of doors and windows, the opening time, and the occupancy, among other aspects and strategies using dynamic simulation. The results were compared with in-situ measurements and surveys conducted on students in the case study. Of the proposed strategies, it was decided as optimal hybrid strategy to increase the fresh air intake from 5 L/s*person to 10 L/s*person with the use of mechanical ventilation and reduction of occupancy, this way, in addition to improving indoor air quality, the thermal comfort of the students was ensured.
Using neural networks to predict hourly energy consumptions in office and industrial buildings as a function of weather data
Authors: Martellotta Francesco , Ayr Ubaldo , Cannavale Alessandro , Liuzzi Stefania , Rubino Chiara
Published: December 2022

Office and industrial premises are among the most energy consuming type of buildings. Compared to residential buildings, they are characterized by more regular occupation patterns and stricter control of building systems. Under these conditions, it is expected that energy consumptions may be more easily predictable and may be significantly influenced by outdoor conditions more than by individual preferences. This may result in availability of straightforward predictions of energy use (at daily or hourly basis) which may contribute to trade energy at lower costs, make a better use of renewable energies, while balancing energy saving and occupants’ comfort. An essential contribution to the ability to easily and accurately predict energy consumptions, is given by the ever-increasing number of smart and IoT-based devices that collect data inside and outside buildings and consequently make them available for processing. Taking advantage of such data, it is worth investigating if advanced artificial intelligence methods (like neural networks and machine learning) are capable of yielding predictions of energy consumptions and, ideally, indoor conditions. For the purpose of the present paper, the dataset (including both input and output parameters) was obtained through simulation (using the popular EnergyPlus tool), including one office and one industrial reference building, and using three different climatic datasets. Finally, artificial neural networks were trained assuming daily and hourly energy consumptions (subdivided by category) as the target variable, showing that in most of the cases very accurate predictions could be obtained.
Data-driven modelling for gas consumption prediction at City Gate Stations
Authors: Cheli L , Meazzini M , Busi L , Carcasci C
Published: December 2022

City Gate Stations (CGS) are critical elements of Natural Gas (NG) distribution systems, as they connect national high-pressure transmission networks with local low-pressure networks. One of their main tasks is to pre-heat the gas to avoid dangerous sub-cooling due to the Joule-Thompson effect after the pressure reduction stage. For this process, significant amounts of thermal energy are required, usually obtained by burning part of the gas flow rate. This work aims to develop a data-driven model that will serve as a tool to predict and monitor the thermal consumption of the CGS. The plant chosen as a case study for this activity is in a region of central Italy. A Multiple Linear Regression (MLR) model is developed and trained, and its predictive performance is evaluated. The model results achieved an accuracy of over 95% for the coefficient of determination. The method makes it possible to create a baseline consumption model and evaluate the performance of the CGS over time using the CUSUM technique to find variations between actual and modelled gas consumption, being an essential tool for monitoring the effectiveness of the NG preheating system.
Tuning the Discrete Wavelet Transform for Power Smoothing of Wind Turbines
Authors: Bianchini Alessandro , Mannelli Andrea , Papi Francesco , Pechlivanoglou George
Published: December 2022

In the study, an extended sensitivity analysis is presented, which was aimed at properly tuning the parameters of an algorithm based on the Discrete Wavelet Transform (DWT) for use in power smoothing of utility-scale wind turbines coupled with batteries. More specifically, a twofold implementation is proposed, so that the proposed algorithm can operate efficiently both in real time as a control system and using historical data for the preliminary sizing of the storage system. In particular, this study addresses the correct setting of the main parameters of DTW, i. e. the level of decomposition and the mother wavelet family that generates the multi-resolution analysis (MRA). Based on real wind data of an onshore site, the following wavelet families have been analyzed: Daubechies, Coiflet, Symmlet, Biorthogonal and Reverse Biorthogonal. It is shown that, as the severe wind fluctuations that need to be smoothed are a quite sudden phenomena, in which usually the wind speed increases and then decreases quickly, all the wavelet families having a centered peak show good performance. On the other hand, it is highlighted that, once the correct choice of the mother wavelet is made, neither increasing the decomposition level nor making it adjustable in time, brings significant benefits. Finally, the discussed hypothesis has been assessed in combination with the proposed technique to extend the wavelet for online control using data mirroring, corroborating the suitability of the method for use in wind energy applications.