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Ricercatore t.d. art. 24 c. 3 lett. B
Dipartimento di Scienze e Metodi dell'Ingegneria

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2023 - Thermal Energy and Luminosity Characterization of an Advanced Ignition System Using a Non-Intrusive Methodology in an Optically Accessible Calorimeter [Articolo su rivista]
Martinelli, R.; Ricci, F.; Discepoli, G.; Petrucci, L.; Papi, S.; Grimaldi, C. N.

2022 - A Development of a New Image Analysis Technique for Detecting the Flame Front Evolution in Spark Ignition Engine under Lean Condition [Articolo su rivista]
Petrucci, Luca; Ricci, Federico; Mariani, Francesco; Discepoli, Gabriele

2021 - Energy characterization of an innovative non-equilibrium plasma ignition system based on the dielectric barrier discharge via pressure-rise calorimetry [Articolo su rivista]
Ricci, F.; Discepoli, G.; Cruccolini, V.; Petrucci, L.; Papi, S.; Di Giuseppe, A.; Grimaldi, C. N.

A dielectric barrier discharge igniter (BDI) ensures engine stable combustion at lean and/or diluted conditions by the generation of non-equilibrium low-temperature plasma (LTP), strong promoter of the ignition, in a wide mixture volume. Beside this, a substantial amount of thermal energy is also released in the medium to enhance the chemical reactions of fuel oxidation. Therefore, the measurement of thermal energy is crucial to characterize the igniter capability to guarantee a robust combustion onset and it can be performed only in controlled environments. In this work, a Radio-Frequency BDI was tested via pressure-based calorimetry by evaluating the thermal energy released during the discharge in a controlled environment represented by a constant volume vessel. The corresponding thermal efficiency was evaluated as well. Pure nitrogen and air were exploited at engine-relevant pressure levels by varying the discharge features as its time duration and intensity (the latter by peak electrode voltage variation), to fully characterize the igniter behavior. Both media showed similar trends of absorbed and released energy but differences up to 50% were found for the latter. This trend was found to be linear, unexpectedly in contrast to the quadratic one showed by the LTP corona streamer-type igniter (CSI). Furthermore, the thermal energy dependence from pressure showed a change up to complete independence at a specific electrode value. To provide an explanation for such different behaviors, a comparative analysis between the diverse discharges of the two igniters was carried out. Moreover, by varying voltage and duration, the device was found to be able to release up to 60 mJ in the tested point with very low dispersion, essential to guarantee stable combustion ignition at challenging operating conditions for next-generation internal combustion engines.

2021 - Luminosity and Thermal Energy Measurement and Comparison of a Dielectric Barrier Discharge in an Optical Pressure-Based Calorimeter at Engine Relevant Conditions [Abstract in Atti di Convegno]
Ricci, F.; Cruccolini, V.; Discepoli, G.; Petrucci, L.; Grimaldi, C.; Papi, S.

The amount of the thermal energy released in a gas mixture is crucial to characterize the igniter capability to start a robust ignition in internal combustion engines, especially in challenging operating conditions as high EGR dilution or very lean mixture. Nevertheless, the thermal energy measurement can be performed only in controlled environments, such as constant volume vessels, while it is not feasible in metal engines. This work proposes to find a correlation between the released thermal energy and the luminosity generated by the same discharge event in an optical vessel. This correlation implies that energy information could be indirectly obtained through feasible optical measurements in optical engines, and even in metal engines via low-cost diagnostic tools such as borescopes. The experimental campaign is carried out with a non-equilibrium plasma igniter, a dielectric-barrier discharge igniter (BDI). This choice is due to the inherent igniter features (i.e., the development of a volumetric discharge and the capability to modulate the discharge intensity) that makes it suitable for the purpose of the proposed campaign. Pure nitrogen, at engine-relevant pressure, is used as medium inside the vessel. The electrode voltage is varied from inception to the highest value allowed; a sweep of discharge duration is performed as well.

2021 - Streamers Variability Investigation of a Radio-Frequency Corona Discharge in an Optical Access Engine at Different Speeds and Loads [Relazione in Atti di Convegno]
Ricci, F.; Martinelli, R.; Petrucci, L.; Discepoli, G.; Grimaldi, C. N.; Papi, S.

2020 - An optical method to characterize streamer variability and streamer-to-flame transition for radio-frequency corona discharges [Articolo su rivista]
Cruccolini, V.; Grimaldi, C. N.; Discepoli, G.; Ricci, F.; Petrucci, L.; Papi, S.

In recent years, radio-frequency corona ignition gained increasing interest from the engine research community because of its capability to extend the engine stable operating range in terms of lean and EGR dilution. The corona discharge generates streamers coming from a star-shaped electrode, generally consisting of four or five tips. The temporal and spatial variability of such streamers in length, orientation, and branching can be factors that affect the combustion onset and, therefore, engine cycle-to-cycle variability. Generally, the latter is reduced with respect to a conventional spark igniter at the same air-fuel ratio, but still present. In this work, analysis on the corona discharge and on the subsequent combustion onset was carried out in an optically accessible engine by means of the detection, via high-speed camera, of the natural luminosity of streamers and flames. A method to characterize spatial and temporal variability in motored conditions is firstly presented. A statistical analysis of the streamer behavior was performed, by separately analyzing the streamers generated by each tip of the star-shaped electrode. Finally, an original method aimed at determining the moment of the first flame appearance, caused by the combustion onset, is presented. The outcome of this work can be used to improve the knowledge on corona discharge, in particular on the stochastic behavior that characterizes the streamers. The presented optical analysis can also be adapted to other volumetric, single-or multi-point ignition systems.

2020 - Comparative Analysis between a Barrier Discharge Igniter and a Streamer-Type Radio-Frequency Corona Igniter in an Optically Accessible Engine in Lean Operating Conditions [Relazione in Atti di Convegno]
Cruccolini, V.; Discepoli, G.; Ricci, F.; Petrucci, L.; Grimaldi, C.; Papi, S.; Dal Re, M.

Among plasma-assisted ignition technologies, the Radio-Frequency (RF) corona family represents an interesting solution for the ability to extend the engine operating range. These systems generate transient, non-thermal plasma, which is able to enhance the combustion onset by means of thermal, kinetic and transport effects. Streamer-type RF corona discharge, at about 1 MHz, ignites the air-fuel mixture in multiple filaments, resulting in many different flame kernels. The main issue of this system is that at high electrode voltage and low combustion chamber pressure a transition between streamer and arc easily occurs: In this case transient plasma benefits are lost. A barrier discharge igniter (BDI), supplied with the same RF energy input, instead, is more breakdown-resistant, so that voltage can be raised to higher levels. In this work, a streamer-type RF corona igniter and a BDI were tested in a single-cylinder optical engine fueled with gasoline. Combustion behavior was characterized at stable, near-stable and unstable conditions (depending on IMEP coefficient of variation), increasing the air-fuel ratio starting from a near-stoichiometric mixture. For each test point the maximum allowable electrode voltage for both the igniters was used: In the streamer-type corona case it had to be limited because of the arc transition. Both indicating and imaging analysis were carried out, the latter by means of a high-speed camera that records the natural luminosity of early flames. Raw exhaust gas analysis was carried out as well. Results in terms of cycle-to-cycle variability, combustion duration, pollutant emissions, flame radii evolution and flame growth speed, as well as flame probability presence, are presented. The outcomes of this research can improve the knowledge on streamer-type corona and BDI and can be used to assess the operating range for the control parameters of these igniters.

2020 - Economics of innovative high capacity-to-power energy storage technologies pointing at 100% renewable micro-grids [Articolo su rivista]
Baldinelli, A.; Barelli, L.; Bidini, G.; Discepoli, G.

Intermittency and unpredictability of variable renewable energy sources, as well as the mismatch between generation and users’ demand, are the major hurdles to overcome looking at 100% renewable grids. Energy storage (ES) technologies are the answer to this question, yet high market costs are still compared to market parity. For the possibility to decouple capacity and power, hence tailoring the energy storage features according to the main functions required, the solutions investigated are based on Vanadium Redox Flow Batteries (VRFBs) and Reversible Solid Oxide Cells (rSOC). In low interconnected micro-grids, the decoupled sizing of capacity and power is an essential feature to attain higher cost-effectiveness. Current metrics for the economics of renewable energy storage fail to a large extent in assessing the value of stored energy, especially when the power source is scarcely predictable. This paper presents improved techno-economic metrics to compare high capacity-to-power ES technologies for renewable-based micro-grids. The new metrics synthetically translates energy efficiency and quality of system integration into monetary terms, going beyond the classic definition of Levelized Cost of Electricity (LCOE). Then, they provide a tool to understand where the main causes of payback deferral stand. For the case-study analysed, different storage assets (VRFB, rSOC and hybrid rSOC) for installations in households featuring 25 kWh bulk capacity and 1.5 kW discharging power are evaluated. The LCOE is equal to 0.438€‧kWh−1, 0.739€‧kWh−1 and 0.769€‧kWh−1 for VRFB, rSOC and hybrid rSOC respectively. Yet, considering the unit of stored energy, the hybrid rSOC storage system is more convenient than the basic rSOC (2.05€‧kWh−1 versus 2.61€‧kWh−1), but far less cheap than VRFBs (0.560€‧kWh−1).

2020 - Experimental characterisation of the thermal energy released by a Radio-Frequency Corona Igniter in nitrogen and air [Articolo su rivista]
Discepoli, G.; Cruccolini, V.; Ricci, F.; Di Giuseppe, A.; Papi, S.; Grimaldi, C. N.

The Radio-Frequency Corona Ignition System is characterised by a wide initial combustion volume and precursors production, via radical insemination by the streamers, in addition to high released thermal energy. These features lead to faster combustion, a higher tolerance for lean mixtures and EGR dilutions and, in general, more adaptability. The thermal energy released by the igniter to the surrounding medium can help to understand the performance, the behaviour and the application range. This paper proposes a systematic experimental analysis of the thermal energy released by the igniter at room temperature, via pressure-based calorimetry. This analysis, carried out at different pressures (up to 10 bar) and medium type (air or nitrogen), is extended to the whole range of the corona igniter control parameters, namely streamer duration and driving voltage. The latter is proportional to the maximum electrode voltage, as shown in the model here presented, and as confirmed by experiments. The results show, for all the vessel pressures, the high energetic efficiency of the ignition system and the high amount of the released energy. The latter is found to increase linearly with the corona streamers duration and quickly with the driving voltage up to the streamer-to-arc transition threshold. The efficiency tends to reach a defined upper limit. For each tested point, the energy released to pure nitrogen is higher than to air, which evidences the impact of the oxygen presence under streamer exposure.

2020 - Optical and Energetic Investigation of an Advanced Corona Ignition System in a Pressure-Based Calorimeter [Abstract in Atti di Convegno]
Cruccolini, V.; Discepoli, G.; Ricci, F.; Grimaldi, C. N.; Di Giuseppe, A.

In recent years, radio-frequency corona igniters have been extensively studied for their capability to ensure an effective ignition also in lean or diluted mixtures. Corona ignition is volumetric, with streamers coming from a star-shaped electrode. During the discharge, many radicals and excited species, able to speed up the combustion onset, are generated. At the same time, corona igniters are able to release a considerable amount of thermal energy inside the combustion chamber. The correct determination of such energy is crucial to evaluate the effectiveness of the ignition. In this work, corona discharge is experimentally evaluated inside an optical vessel. In this apparatus, the released thermal energy is measured by means of pressure-based calorimetry, and at the same time the natural luminosity of the streamers is recorded with a high-speed camera. The goal is to find a relationship between thermal energy release and streamers luminosity. Tests are performed using nitrogen as medium, at different pressure levels inside the vessel. The peak electrode voltage is varied to characterize the igniter behaviour in different operating conditions. The results of this work can be used to quantify the corona ignition capabilities to involve a wide amount of medium while releasing a high amount of thermal energy. A repeatability evaluation of streamer evolution is investigated as well.

2019 - Experimental and Numerical Investigations of the Early Flame Development Produced by a Corona Igniter [Relazione in Atti di Convegno]
Ricci, F.; Zembi, J.; Battistoni, M.; Grimaldi, C.; Discepoli, G.; Petrucci, L.

In order to reduce engine emissions and fuel consumption, extensive research efforts are being devoted to develop innovative ignition devices, able to extend the stable engine operating range towards increasing lean conditions. Among these, radio frequency corona ignition systems, which produce a strong electric field at a frequency of about 1 MHz, can create discharges characterized by simultaneous thermal and kinetic effects. These devices can considerably increase the early flame growth speed, initiating the combustion process in a wide region, as opposed to the local ignition generated by traditional sparks. To explore the corona ignition behavior, experimental campaigns were carried out to investigate different operating conditions, in a constant volume calorimeter designed to measure the deposited thermal energy. The present work compares the combustion development generated by a traditional spark and the corona igniter through computational fluid dynamics simulations. First, simulations are carried out to reproduce the experimental results in the calorimeter, comparing the measured and predicted pressure traces in an inert environment. The validated approach is then applied in a second step to the engine simulations to predict the combustion behavior, using a RANS turbulence model. Computational results are able to reproduce the faster burn rate generated by the corona system in the initial stage of the combustion.

2019 - Lean combustion analysis using a corona discharge igniter in an optical engine fueled with methane and a hydrogen-methane blend [Articolo su rivista]
Cruccolini, Valentino; Discepoli, Gabriele; Cimarello, Alessandro; Battistoni, Michele; Mariani, Francesco; Nazareno Grimaldi, Carlo; Dal Re, Massimo

The robustness of combustion initiation is one of the main issues of actual spark-ignition engines, especially for highly-diluted or lean mixtures. In this work, the effects on combustion stabilization obtained by the usage of a radio-frequency corona igniter were evaluated on a single-cylinder optical engine. The comparison with a conventional spark igniter was carried out using pure methane fuel and a blend of hydrogen and methane. For each combination of fuel and igniter, the combustion stability was explored at different air–fuel ratios, from stoichiometric conditions to the lean stable limit (up to λ=2.0 with the corona igniter and the hydrogenmethane mixture). The combustion analysis was carried out by using the synchronized indicating and imaging data. The latter is essential to estimate the contribution of the corona igniter, which was found to be considerable only before the 5% of mass fraction burned. The corona effect igniter, with respect to a conventional spark igniter, was able to extend the lean stable limit of about 0.15 λ units with methane fuel, and about 0.10 λ units with the hydrogen-methane blend in the tested engine point. Early flame analysis confirmed the capability of corona igniter to improve combustion onset speed and to obtain a more stable and repeatable flame kernel. The findings of this study can help for a better implementation of corona ignition with gaseous low-carbon fuels, and in particular to achieve a higher lean limit extension without the drawback of a performance decay given by a substantial hydrogen enrichment.

2019 - Performance analysis of artificial neural networks for control in internal combustion engines [Relazione in Atti di Convegno]
Petrucci, L.; Ricci, F.; Mariani, F.; Grimaldi, C. N.; Discepoli, G.; Violi, M.; Matteazzi, N.

In the last years the Electronic Control Units (ECUs) technology has evolved both in terms of hardware and firmware. The tasks requested to ECUs are, as a matter of fact, ever more challenging, due to the growing complexity of the internal combustion engines control, causing increasing needs in terms of computational speed, as well as memory amount. In order to limit look up tables and white box models in ECUs, also Artificial Neural Networks (ANNs) were proposed for the use in different types of tasks, as On-Board Diagnosis, virtual sensors and ECU look up table replacement. ANNs showed a good performance in all these cases. In this paper, the application of ANNs as virtual sensors is further analyzed, in particular in order to verify their performance when used to set-up multiple sensors by using a single ANN module. In this work ANNs were used to evaluate pressure and flowrate in different points of a lubrication circuit of bench and connecting rod bearings.

2018 - Combustion Behavior of an RF Corona Ignition System with Different Control Strategies [Relazione in Atti di Convegno]
Cimarello, A.; Valentino, Cruccolini; Discepoli, G.; Battistoni, M.; Mariani, F.; Grimaldi, Carlo; Dal Re, Massimo

It has been proved that Radio Frequency Corona, among other innovative ignition systems, is able to stabilize combustion and to extend the engine operating range in lean conditions, with respect to conventional spark igniters. This paper reports on a sensitivity analysis on the combustion behavior for different values of Corona electric control parameters (supply voltage and discharge duration). Combustion analysis has been carried out on a single cylinder PFI gasoline-fueled optical engine, by means of both indicating measurements and imaging. A high-speed camera has been used to record the natural luminosity of premixed flames and the obtained images have been synchronized with corresponding indicating acquisition data. Imaging tools allowed to observe and measure the early flame development, providing information which are not obtainable by a pressure-based indicating system. At different air-fuel ratio values, ranging from stoichiometric to lean limit, combustion stability has been evaluated for each combination of supply voltage and corona duration. Varying these parameters, it has been possible to assess the operating range of the corona igniter. In some limiting instances (far from normal operating range) not all the Corona igniter electrode tips were able to generate a discharge, worsening combustion onset: a statistical analysis of this phenomenon has been carried out. Cycle-resolved equivalent flame radii development and flame probability at fixed equivalent radius have been investigated for each condition. Finally, a suitable dataset of supply voltage and corona duration values, which guarantee a fast combustion onset and stable conditions, has been determined.

2018 - Experimental Assessment of a Pressure Wave Charger for Motorcycle Engines [Relazione in Atti di Convegno]
Cruccolini, V.; Discepoli, G.; Zembi, J.; Battistoni, M.; Mariani, F.; Grimaldi, C. N.

2018 - Experimental assessment of spark and corona igniters energy release [Relazione in Atti di Convegno]
Discepoli, G.; Cruccolini, V.; Re, M. Dal; Zembi, J.; Battistoni, M.; Mariani, F.; Grimaldi, C. N.

2017 - Assessment of Port Water Injection Strategies to Control Knock in a GDI Engine through Multi-Cycle CFD Simulations [Relazione in Atti di Convegno]
Battistoni, Michele; Grimaldi, Carlo N.; Cruccolini, Valentino; Discepoli, Gabriele; De Cesare, Matteo

Water injection in highly boosted gasoline direct injection (GDI) engines has become an attractive area over the last few years as a way of increasing efficiency, enhancing performance and reducing emissions. The technology and its effects are not new, but current gasoline engine trends for passenger vehicles have several motivations for adopting this technology today. Water injection enables higher compression ratios, optimal spark timing and elimination of fuel enrichment at high load, and possibly replacement of EGR. Physically, water reduces charge temperature by evaporation, dilutes combustion, and varies the specific heat ratio of the working fluid, with complex effects. Several of these mutually intertwined aspects are investigated in this paper through computational fluid dynamics (CFD) simulations, focusing on a turbo-charged GDI engine with port water injection (PWI). Different strategies for water injection timing, pressure and spray targeting are investigated. Two combustion modeling approaches are used and compared, the perfectly stirred reactor model with reduced chemical kinetics for a TPRF surrogate, and the G-equation turbulent combustion model. Combustion rate results are validated against available experimental engine data, in regular and knocking conditions. Multi-cycle simulations are required because of the wall film dynamics, and therefore have been performed to assess the effect of water injection strategies. The results of the study are an assessment of the optimal injection parameters, in terms of injector location, injection timing and primary atomization quality, for achieving the maximum effectiveness of water injection. Knock occurrences are in very good agreement with the experimental data and its suppression is demonstrated through the injection of water at a ratio of 30% to the fuel mass.

2017 - Molten Carbonate Fuel Cell performance analysis varying cathode operating conditions for carbon capture applications [Articolo su rivista]
Audasso, E.; Barelli, Linda; Bidini, Gianni; Bosio, B.; Discepoli, Gabriele

The results of a systematic experimental campaign to verify the impact of real operating conditions on the performance of a complete Molten Carbonate Fuel Cell (MCFC) are presented. In particular, the effects of ageing and of different contents of water, oxygen and carbon dioxide in the cathodic feeding stream are studied through the analysis of current-voltage curves and Electrochemical Impedance Spectroscopy (EIS). Based on a proposed equivalent electrical circuit model and a fitting procedure, a correlation is found among specific operating parameters and single EIS coefficients. The obtained results suggest a new performance monitoring approach to be applied to MCFC for diagnostic purpose. Particular attention is devoted to operating conditions characteristic of MCFC application as CO2 concentrators, which, by feeding the cathode with exhaust gases, is a promising route for efficient and cheap carbon capture.

2017 - Redox flow battery instead of rSOC for resilient energy systems in off-grid remote areas or in non- or low interconnected islands: why not? [Relazione in Atti di Convegno]
Barelli, L.; Bidini, G.; Casciola, M.; Discepoli, G.; Donnadio, A.; Gallorini, F.; Troni, E.

Penetration of renewable energy plants is strongly slowed by the characteristic intermittency and fluctuating production trend, which significantly mismatches with typical users' load profiles, with negative impacts on grid stability and safety. The widespread of energy storage could mitigate these issues; rSOC and VRFB application is compared for off-grid remote areas or in non- or low interconnected ones.

2016 - Co-electrolysis of water and CO2 in a solid oxide electrolyzer (SOE) stack [Articolo su rivista]
Cinti, Giovanni; Discepoli, Gabriele; Bidini, Gianni; Lanzini, A.; Santarelli, M.

2016 - Erratum to “Kinetic modelling of molten carbonate fuel cells: Effects of cathode water and electrode materials” (Journal of Power Sources (2016) 330 (18–27)(S0378775316311430) (10.1016/j.jpowsour.2016.08.123)) [Articolo su rivista]
Arato, E.; Audasso, E.; Barelli, L.; Bosio, B.; Discepoli, G.

The publisher regrets that caption text has been incorrectly placed for Figures 5 and 8. The corrections are as follows: • Part of the caption for Figure 5 appears on p. 23 “c) H2O molar fraction of 30% … the water presence at the cathode side (dashed line)”. This should be deleted.• Part of the caption for Figure 8 appears on p. 24 “(b) map of the anode CO2 molar fraction values … with no water vapour in the cathode feed”. This should be appended to the end of the current caption for Figure 8 with the lettering amended. The full caption of Figure 8 should be: “Fig. 8. (a) Map of the current density values over the surface of the cell working in the reference conditions (b) map of the anode CO2 molar fraction values over the surface of the cell working in reference conditions; maps of the cathode polarization resistance values over the surfaces of the cell: (c) shows the map of the resistance of a cell fed with 30% of water vapour, while (d) shows the map of resistance of a cell with no water vapour in the cathode feed.”The publisher would like to apologise for any inconvenience caused.

2016 - Experimental investigation of SO2 poisoning in a Molten Carbonate Fuel Cell operating in CCS configuration [Articolo su rivista]
DELLA PIETRA, Massimiliano; Discepoli, Gabriele; Bosio, Barbara; Mcphail, Stephen J.; Barelli, Linda; Bidini, Gianni; Ribes Greus, Amparo

One of the most interesting innovations in the CCS (Carbon Capture and Storage) field is the use of MCFCs as carbon dioxide concentrators, feeding their cathode side (or air side) with the exhaust gas of a traditional power plant. The feasibility of this kind of application depends on the resistance of the MCFC to air-side contaminants, with particular attention to SO2. The aim of this work is to investigate the effects of poisoning when sulphur dioxide is added to the cathodic stream in various concentrations and in different operating conditions. This study was carried out operating single cells (80 cm2) with a cathodic feeding composition simulating typical flue gas conditions, i.e. N2, H2O, O2 and CO2 in 73:9:12:6 mol ratio as reference mixture. On the anodic side a base composition was chosen with H2, CO2 and H2O in 64:16:20 mol ratio. Starting from these reference mixtures, the effect of single species on cell poisoning was experimentally investigated considering, as main parameters chosen for the sensitivity analysis, SO2 (0–24 ppm) and CO2 (4–12%) content in the cathodic feeding mixture, H2 (40–64%) content in the anodic stream as well as the operating temperature (620–680 °C). Results showed that degradation caused by SO2 poisoning is strongly affected by the operating conditions. Data gathered during this experimental campaign will be used in a future work to model the poisoning mechanisms through the definition of MCFC electrochemical kinetics which take into account the SO2 effects.

2016 - Kinetic modelling of molten carbonate fuel cells: Effects of cathode water and electrode materials [Articolo su rivista]
Arato, E.; Audasso, E.; Barelli, Linda; Bosio, B.; Discepoli, Gabriele

Through previous campaigns the authors developed a semi-empirical kinetic model to describe MCFC performance for industrial and laboratory simulation. Although effective in a wide range of operating conditions, the model was validated for specific electrode materials and dry feeding cathode compositions. The new aim is to prove that with appropriate improvements it is possible to apply the model to MCFC provided by different suppliers and to new sets of reactant gases. Specifically, this paper describes the procedures to modify the model to switch among different materials and identify a new parameter taking into account the effects of cathode water vapour. The new equation is integrated as the kinetic core within the SIMFC (SIMulation of Fuel Cells) code, an MCFC 3D model set up by the PERT group of the University of Genova, for reliability test. Validation is performed using data collected through tests carried out at the University of Perugia using single cells. The results are discussed giving examples of the simulated performance with varying operating conditions. The final formulation average percentage error obtained for all the simulated cases with respect to experimental results is maintained around 1%, despite the difference between the basic and the new conditions and facilities.

2016 - Off-design operation of coal power plant integrated with natural gas fueled molten carbonate fuel cell as CO2 reducer [Articolo su rivista]
Discepoli, Gabriele; Milewski, Jarosław; Desideri, Umberto

2016 - Performance assessment of natural gas and biogas fueled molten carbonate fuel cells in carbon capture configuration [Articolo su rivista]
Barelli, Linda; Bidini, Gianni; Campanari, Stefano; Discepoli, Gabriele; Spinelli, Maurizio

The ability of MCFCs as carbon dioxide concentrator is an alternative solution among the carbon capture and storage (CCS) technologies to reduce the CO2 emission of an existing plant, providing energy instead of implying penalties.Moreover, the fuel flexibilityexhibited byMCFCs increases the interest on such a solution. This paper provides the performance characterization of MCFCs operated in CCS configuration and fed with either natural gas or biogas. Experimental results are referred to a base CCS unit constituted by a MCFC stack fed from a reformer and integrated with an oxycombustor. A comparative analysis is carried out to evaluate the effect of fuel composition on energy efficiency and CO2 capture performance. A higher CO2 removal ability is revealed for the natural feeding case, bringing to a significant reduction in MCFC total area (11.5%) and to an increase in produced net power (þ13%). Moreover, the separated CO2 results in 89% (natural gas) and 86.5% (biogas) of the CO2 globally delivered by the CCS base unit. Further investigation will be carried out to provide a comprehensive assessment of the different solutions eco-efficiency considering also the biogas source and availability.

2016 - SOFC operating with ammonia: Stack test and system analysis [Articolo su rivista]
Cinti, Giovanni; Discepoli, Gabriele; Sisani, Elena; Desideri, Umberto

2015 - Design and preliminary operation of a gasification plant for micro-CHP with internal combustion engine and SOFC [Relazione in Atti di Convegno]
Moriconi, Nicola; Laranci, Paolo; D'Amico, Michele; Bartocci, Pietro; D'Alessandro, Bruno; Cinti, Giovanni; Baldinelli, Arianna; Discepoli, Gabriele; Bidini, Gianni; Desideri, Umberto; Cotana, Franco; Fantozzi, Francesco

A gasification plant was designed and built to test syngas production from biomass for electricity generation on microscale. The plant is mainly composed by a downdraft reactor, a gas cleaning section with a cyclone and a wet scrubber, a blower for syngas extraction and an ICE (Internal Combustion Engine, Lombardini LGA 340), equipped with an alternator. A small quantity of producer was also eventually sent to a button cell SOFC (Solid Oxide Fuel Cell) for preliminary characterization. The plant was tested in a preliminary experimental campaign to evaluate mass and energy balances and process efficiency. Woody biomass was used and the producer gas firstly passed through impingers bottles, to condense and measure tar concentration (according to CEN/TS 15439), and then the remaining uncondensed gas was analyzed with a micro-GC (Gas Chromatograph). The paper presents and discusses the results of the preliminary tests carried out.

2015 - Dimethyl sulfide adsorption from natural gas for solid oxide fuel cell applications [Articolo su rivista]
Barelli, Linda; Bidini, Gianni; Desideri, Umberto; Discepoli, Gabriele; Sisani, Elena

The use of solid oxide fuel cell (SOFC) systems in micro-CHP applications is of great interest because of high efficiency, low emissions and absence of noise. However, SOFCs are sensitive to degradation caused by organic sulfur compounds present in natural gas or added as odorants. Among them, dimethyl sulfide (DMS) is one of the sulfur species most resistant to purification treatments and, relative to DMS removal, a lack in literature is highlighted for the investigated application. Regarding adsorption technology, the present work deals with an organic sensitivity performance analysis of different commercial sorbents. Virgin and impregnated activated carbons and a natural zeolite were tested, varying gas hourly space velocity, reactor geometry and filter assembly. Because of differences in activity towards DMS exhibited by the investigatedmaterials, to exploit their selectivity, also layered sorbentswere realized and tested. Starting from resulting data, for the yearly operation of 1 kWel SOFC-based micro-CHP system, an optimization of filter assembly (also considering multi-layered configurations) and operative conditions was performed, leading to a strong reduction in filter volume (up to five times) and cost (more than three times), with overall pressure drops compatible with pipeline gas distribution pressure.

2014 - Adsorptive removal of H2S in biogas conditions for high temperature fuel cell systems [Articolo su rivista]
Sisani, Elena; Cinti, Giovanni; Discepoli, Gabriele; Penchini, Daniele; Desideri, Umberto; Marmottini, Fabio

Desulfurization represents a crucial step in fuel processing for high temperature fuel cells, because of catalysts stringent requirements. Moreover, when fuel cell stacks are used in micro-CHP applications, it is necessary to build an efficient and compact system. The use of biogas from anaerobic digestion could have a significant impact in terms of fossil fuels saving and environmental conservation. Biogas contains different impurities, among which H2S represents one of the most harmful components. Adsorption tests for H2S removal were carried out in biogas conditions, using commercial adsorbents, defining the materials characterized by the best performance and resulting in a predominance of impregnated activated carbons. The influence on adsorption capacity of operating parameters, such as gas hourly space velocity, gas matrix composition (N2, CH4 and CO2), humidity, temperature (30–150 °C), H2S concentration (50–1000 ppmv) and filter geometry, was investigated. The aim of the study was the functional parameters optimization to obtain a compact filter with high removal activity.

2014 - Experimental Analysis of SOFC Fuelled by Ammonia [Articolo su rivista]
Cinti, Giovanni; Desideri, Umberto; Penchini, Daniele; Discepoli, Gabriele

In this study, ammonia is presented as a feasible fuel for solid oxide fuel cells (SOFCs). Ammonia has several interesting features as fuel due to low-production cost, high-energy density and, focusing on fuel cells and hydrogen application, ammonia is an excellent H2 carrier thanks to high value of volumetric and gravimetric densities. The paper reports experimental test performed to evaluate the feasibility of NH3 directly fed to a 50 cm2 single cell SOFC. A test plan was developed to compare pure ammonia with an equivalent mix of ammonia, nitrogen, and hydrogen and the study of temperature and voltage values strongly indicates that a two stage oxidation of ammonia can be predicted and a previous cracking reaction occurs in the cell due to the nickel catalytic contribution. The study of temperatures and of heat flows show how the cell is cooled down to lower temperature because of heat adsorbed by the reaction and by flow mix entering the anode. The study shows also how for operative temperatures below 800 °C the cracking reaction takes place in the cell active area. Efficiency test demonstrates that the cell can operate at 300 mW cm–2 and 30% efficiency based on ammonia LHV.

2014 - Modeling the performance of MCFC for various fuel and oxidant compositions [Articolo su rivista]
Jarosław, Milewski; Discepoli, Gabriele; Desideri, Umberto

100 cm2 molten carbonate fuel cells (MCFC) was used for testing the fuel and oxidant composition influence on MCFC performance as a temperature function. The fuel composition varies over the cell surface, and throughout the stack, because inlet fuel is rich in H2 (and CO2), while the exhaust stream is depleted. The cell performance is usually not uniform over the entire surface. It is thus necessary to examine the cell performance as a function of fuel utilization. In a laboratory-sized cell, this is usually difficult to do. An alternative approach is to investigate performance as a fuel composition function. Based on the obtained experimental data for different compositions, the MCFC mathematical model was calibrated. The new approach for modeling the voltage was used. Electrochemical, thermal, electrical and flow parameters are collected in the 0-D mathematical model. A validation process for various experimental data was made and adequate results are shown.

2014 - Theoretical study and performance evaluation of hydrogen production by 200 W solid oxide electrolyzer stack [Articolo su rivista]
Daniele, Penchini; Cinti, Giovanni; Discepoli, Gabriele; Desideri, Umberto

High temperature steam electrolyzers, taking advantage of high temperature heat, can produce more hydrogen by using less electrical energy than low temperature electrolyzers. This paper presents an experimental study on hydrogen production by using a 200 W solid oxide stack working in reverse mode. A thermodynamic study of the process was performed by measuring the heat and mass balance of stack at different operating conditions. Different definitions of efficiency were used to highlight the limit and potential of the process. The I–V curve, the flow rate measurements and the GC analysis on outlet flows were used to calculate the hydrogen and oxygen productions. In addition, the influence of steam dilution, water utilization and operating temperature on conversion efficiency and stack's thermal balance was evaluated. With this aim, the tests were performed at three operating temperature (700 °C, 750 °C and 800 °C) over a range of steam inlet concentration from 50% to 90% and water utilization up to 70%. The hydrogen and oxygen flows produced by electrolysis, at different loads, were directly measured after water condensation: net flows up to 2.4 ml/(min cm2) of hydrogen and 1.2 ml/(min cm2) of oxygen were measured and compared to the theoretical ones, showing a good agreement.

2013 - Adsorptive removal of H2S in biogas conditions for high temperature fuel cell systems [Relazione in Atti di Convegno]
Sisani, Elena; Castelli, Alessia; Cinti, Giovanni; Discepoli, Gabriele; Penchini, Daniele; Desideri, Umberto

2013 - Characterization of a 100 W SOFC stack fed by carbon monoxide rich fuels [Articolo su rivista]
Penchini, Daniele; Cinti, Giovanni; Discepoli, Gabriele; Sisani, Elena; Desideri, Umberto

This paper presents the evaluation of the performance of a 100 W Solid Oxide Fuel Cell (SOFC) stack with CO rich fuels as anode gas. The study aims at measuring the Open Circuit Voltage (OCV) and the Area Specific Resistance (ASR) when the amount of CO in the anode flow varies from 0 to 40% in volume. At the same time, the FCTestQA procedures were applied and evaluated as methodology for Solid Oxide Fuel Cell testing. The theoretical OCV was measured considering both H2 and CO oxidation and the water gas shift reaction. The OCV values, as a function of CO concentration, resulted closely related to theoretical ones and the ASR value, calculated for different mixtures of fuel, did not change with anode gas composition and it seemed to be a function of the temperature and the degradation of the materials only.

2012 - Carbon capture with molten carbonate fuel cells: Experimental tests and fuel cell performance assessment [Articolo su rivista]
Discepoli, Gabriele; Cinti, Giovanni; Desideri, Umberto; Penchini, Daniele; Proietti, Stefania

Molten carbonate fuel cells (MCFCs) may operate as CO2 separators and concentrators while generating electric power, being thus a very interesting candidate to be used as carbon capture systems in fossil fired power plants.The main aim of this work is to understand the MCFC performance, its potential and efficiency to separate CO2 from the exhaust gas of fossil fired power plants and the effect of critical parameters such as the cathodic carbon dioxide concentration (XCO2) and utilization (UCO2), as well as the partial pressure ratio between oxygen and carbon dioxide (PO2/PCO2) and other parameters such as the oxygen concentration (XO2), utilization (UO2) and the total cathodic flow rate (Qcat). This was achieved by studying the experimental behaviour of a single MCFC when it is fed with a mixture simulating the composition of the exhaust gases of a combined heat and power plant, in order to point out potential limitations in the fuel cell operating conditions.In particular, the carbon dioxide concentration in the cathodic section was shown to be a critical factor at low values, that can both induce quick voltage drops and make the cell sensitive to the other parameters, which are otherwise not so important.

2012 - SOFC micro-CHP integration in residential buildings [Relazione in Atti di Convegno]
Desideri, Umberto; Cinti, Giovanni; Discepoli, Gabriele; Sisani, Elena; Penchini, Daniele

2011 - Carbon dioxide separation for CHP power plants [Poster]
Cinti, G; Curbis, F; Penchini, D; Discepoli, G; Sisani, E; Desideri, U

2011 - Characterization of 100w SOFC stack fed by carbon monoxide rich fuels [Relazione in Atti di Convegno]
Penchini, D; Cinti, G; Discepoli, G; Sisani, E; Desideri, U

The rapid growth in terms of efficiency and performance of the solid oxide fuel cell (SOFC) technology in recent years has led SOFC to be one of the possible solutions for the exploitation of different types of fuels obtained from fossil or renewable sources. A lot of processes, such as waste incineration or anaerobic digestion, during operation produce exhaust gases that can be efficiently exploited in SOFC systems. SOFCs, thanks to their operating condition, run with standard fuels such hydrogen and methane as well as fuel waste gas, like biogas or landfill gas, or gas plant, like pyrogas. The aim of this work is to compare the performance of an 100W stack SOFC when it is fed by different fuel compositions.

2011 - Experimental Comparison and Performance Evaluation of Planar Solid Oxide Single Cell [Relazione in Atti di Convegno]
Cinti, Giovanni; Desideri, Umberto; Discepoli, Gabriele; Sisani, Elena; Penchini, Daniele

Nowadays, in a world characterized by the need to reduce the production of pollutants, by global climate changes, by the progressive lack of availability of cheap fossil fuels, one of the most important goals of scientific research is to design systems that can provide energy with low environmental impact. Planar Solid Oxide Fuel Cells (SOFC) are considered to be power generators with high efficiency independent on size and low emissions. Fuel cell laboratory (FCLab) of University of Perugia has focused his studies on SOFC operating at high temperature (800–1000°C), characterized by greater flexibility in the choice of fuel. This study focuses on definition and realization of experimental test able to define the quality of a SOFC single cell and on the effect of test condition parameter. The performance of the cell is evaluated via polarization curves realized in different external conditions. Area Specific Resistance (ASR) is used as main test output. Results analysis confirm that ASR gives important information on fuel cell performance and can be used to compare an qualify SOFC single cell.

2011 - Experimental analysis of SOFC fuelled by ammonia [Relazione in Atti di Convegno]
Cinti, G; Discepoli, G; Penchini, D; Sisani, E; Desideri, U

2011 - Experimental test of carbon capture from cogeneration plant with MCFC coupled [Relazione in Atti di Convegno]
Discepoli, Gabriele; Cinti, Giovanni; Penchini, Daniele; Sisani, Elena; Desideri, Umberto

Molten carbonate fuel cells are natural CO2 separators and concentrators. In this work we analyze a single MCFC behavior feeds with a mixture simulating a cogeneration power plant exhaust gas, so to replicate the coupling with a real plant. The main aim of this work is to understand the MCFC performances, its capability and efficiency to separate CO2, its dependence from critical parameters such as the cathodic carbon dioxide concentration (XCO2) and utilization (UCO2), as well as the partial pressure ratio between oxygen and carbon dioxide (PO2/PCO2) in addition to other derived parameters as the oxygen concentration (XO2), utilization (UO2) and the total cathodic flow rate (Qcat). In particular, in the cathodic section, the carbon dioxide concentration is critical at low values and can both induce quick voltage drop and make the cell sensitive to the other parameters otherwise not so decisive.

2011 - Impact of operating conditions on H2S adsorption for fuel cell systems [Poster]
Sisani, E; Cinti, G; Discepoli, G; Penchini, D; Desideri, U

2011 - SOFC material and stack characterization tests for micro-CHP application [Relazione in Atti di Convegno]
McPhail, S J; Padella, F; Bellusci, M; Cinti, G; Discepoli, G

2011 - SOFC material and stackcharacterizationtests for micro-CHP application [Poster]
McPhail Stephen, J; Padella, F; Bellusci, M; Cinti, G; Discepoli, G

2011 - Sulphur compounds removal from natural gas using porous materials for high temperature fuel cell applications [Poster]
Sisani, E; Penchini, D; Cinti, G; Discepoli, G; Desideri, U

2009 - Analysis of performance decay of MCFC single cell under H2S poisoning [Relazione in Atti di Convegno]
Discepoli, Gabriele; Desideri, Umberto; Cinti, Giovanni; Massa, Roberta; Cruciani, David

2009 - Desulphurization Finalized to Fuel Cells Technology [Relazione in Atti di Convegno]
Sisani, E; Cinti, G; Discepoli, G; Desideri, U

2009 - H2S Poisoning Contamination Effect On Solide Oxide Fuel Cell [Poster]
Cinti, G; Desideri, U; Discepoli, G

Molten Carbonate Fuel Cells (MCFC) features lead to their use in combined plant for distributed power and heat generation. Natural gas, biogas, syngas and landfill gas can be exploited as energy and heating sources, because rich of CH4, CO and/or H2. Nevertheless all of them contain variable quantities of H2S, a poisoning gas, responsible of fuel cell component damages. In this work we investigated MCFC single cell performance decay under stress conditions due to use of H2S in the inlet anodic gas. Besides the main parameters (voltage, power, efficiency) it is important to investigate the influence of various work conditions, as fuel mix and the relative pressure of fuel and poison.

2007 - 1D, 2D, 3D wavelet methods for gamma‐ray source analysis [Relazione in Atti di Convegno]
Ciprini, S; Tosti, G; Marcucci, F; Cecchi, C; Discepoli, G; Bonamente, E; Germani, S; Impiombato, D; Lubrano, P; Pepe, M

An example of wavelet transforms applied to data from EGRET and data of the GLAST pre-launch simulations is reported. ID wavelet transform can be an useful tool in the analysis of gamma-ray source variability, while 2D/3D wavelet transform is a potential partner tool of the standard Likelihood analysis, in the frame of gamma-ray source detection.