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The forthcoming introduction of the EURO VII regulation requires urgent strategies and solutions for the reduction of sub-23 nm particle emissions. Although they have been historically considered as particulate matter-free, the high interest for Natural Gas (NG) Heavy-Duty engines in the transport sector, demands their compliance with the new proposed regulations.In order to obtain high conversion of gas pollutants and a strong abatement of the emitted particles, the use of Particle Filters in NG aftertreatment (CPF) in conjunction with the Three-Way Catalyst (TWC) may represent an attractive and feasible solution.Performances of a cordierite filter were explored through an extensive experimental campaign both in Steady-State conditions and during transient engine maneuvers that involved a whole analysis of the emitted particles in terms of number and mass.This investigation assessed different emitted particle reduction efficiency, highlighting distinct levels between no-load (low idle phases) and load operating conditions.The analysis was supported by the development of a specific 1D filtration model to evaluate the particles abatement. This model was also validated during a World Harmonized Transient Cycle (WHTC), proving to be a valuable tool for understanding filtration phenomena during critical phases of the cycle.The tested filter technology showed high filtration efficiency with global levels approaching 90% over the whole cycle, without significant increase in backpressures and fuel consumption.The performed analysis lays the foundation for the use of innovative and simplified filtration models to support the optimization process of this device in view of the next stringent regulations.

Increasingly stringent pollutant and CO2 emission standards require the car manufacturers to investigate innovative solutions to further improve the fuel economy and environmental impact of their fleets. Nowadays, NOx emissions standards are stringent for spark-ignition (SI) internal combustion engines (ICEs) and many techniques are investigated to limit these emissions. Among these, an extremely lean combustion has a large potential to simultaneously reduce the NOx raw emissions and the fuel consumption of SI ICEs. Engines with pre-chamber ignition system are promising solutions for realizing a high air-fuel ratio which is both ignitable and with an adequate combustion speed.In this work, the combustion characteristics of an active pre-chamber system are experimentally investigated using a single-cylinder research engine. The engine under exam is a large bore heavy-duty unit with an active pre-chamber fuelled with compressed natural gas.In first stage, an experimental campaign was carried out for four different conditions of load and air/fuel ratio, at the same engine speed, then a 3D CFD analysis was realised to evaluate the in-cylinder turbulence and pre-chamber pressure traces. Global engine operating parameters as well as cylinder pressure traces, inside main combustion chamber and pre-chamber, were recorded and analysed. Based on the available 3D and experimental data, a phenomenological model of this unconventional combustion system is developed and validated.The model is implemented in a commercial 1D code. The proposed numerical approach shows the ability to simulate the experimental data with good accuracy, with no case-dependent tuning. The model demonstrates to correctly describe the behaviour of a pre-chamber combustion system under the four operating conditions and to capture the physics behind such an innovative combustion system concept.

Hydrogen Internal Combustion Engines (H2-ICEs) are subject to increased attention thanks to their extremely low criteria pollutant emission and near-zero CO2 tailpipe emissions. However, to further minimize exhaust emissions and increase the efficiency of a H2-ICE, it is important to carefully control the relative air-fuel ratio of operation, i.e. Lambda (λ), which will lead in turn to an optimal combustion process. The precise λ control mainly relies upon the methodology to calculate λ on board of the engine, where the availability of reliable sensors specifically-developed for hydrogen combustion is currently limited. In this article, a comparative analysis of different methodologies for the calculation of λ is performed, comparing four methodologies: exhaust gas analysis through a Spindt-Brettschneider approach (λEMI), raw Universal Exhaust Gas Oxygen (λR-UEGO), processed Universal Exhaust Gas Oxygen (λP-UEGO) and speed-density (λSD) outputs. The experimental data used to compare the four methodologies were acquired through detailed and systematic experimentation on a fully-instrumented single-cylinder H2-ICE. Results show that the λP-UEGO is the closest one to the reference Spindt-Brettschneider analysis λEMI and the most robust to ample variations in the nominal λ values. The sensor’s raw UEGO output λR-UEGO is instead affected by the sensor calibration which is usually performed across a range of carbon-based fuels, a procedure that introduces a bias. The results can be used for the selection of the correct methodology to calculate λ in a H2-ICE and to choose optimal sensors for mobile applications.

Studies consider the influence of biofuels on the decarbonization of the transport system not negligible. The employment of fossil fuels with an even higher degree of renewable biofuel content, produced with a mature technology process, such as the Hydrotreated Vegetable Oils (HVO), are expected to increase. The research community expects valuable research results to exploit the HVO characteristics in ultra-low emission vehicles equipped with internal combustion engines. In this context, new findings in setting combustion control parameters through proper experimental design are carried out on a modern internal combustion engine architecture. An advanced injection system capable of precise close-coupled multiple injections per cycle was utilized. Steady-state engine operating conditions were selected for this experimental study. Combustion, efficiency, and engine-out emissions indicators with HVO fuel are compared with standard diesel. For assessing the difference in combustion stages, a second derivative method data analysis was performed. It is found that in comparison to diesel fuel, HVO significantly reduces regulated engine-out emissions at the same efficiency and EU 6c NOx emissions targets. To this aim, a specific set of engine control parameters were adopted. The PM decreased up to 10 %, corresponding to 0.18 g/kWh, while the CO2 reduced by about 7–8% in the range of 0.2–0.5 g/kWh. The decrease of the total PN ranges between 10 and 55%, depending on the control strategy and test point, and the particle distribution shifts towards smaller particle sizes. Outstanding improvements of the NOx-soot trade-off are verified, which in turn demonstrates the capability to operate the engine at post-EU6 NOx conditions without performance and comfort penalties. Engine-out CO and HC emission reductions are confirmed.

The increasing concern of global warming due to the ever-increasing amount of greenhouse gases (GHG) such as carbon dioxide (CO2) and pollutant emissions induces regulatory authorities to stricter emission legislation in the transportation sector. In this context, renewable fuels, such as methanol and ethanol, are considered a promising solution to mitigate the carbon footprint and reduce engine-out emissions. Based on the several studies published in the specific literature, this work aims to summarise and normalize the main outcomes, highlighting the pro and cons of exerting alcohol fuels in compression ignition engines through a critical literature review for helping the researchers, who start to work on these applications. Both dual-fuel and direct-injection fuelling concepts of diesel and alcohol (ethanol and methanol) in compression ignition engines are discussed. Analyses on the combustion, emissions and performance and CO2 are carried out. Depending on the fuel supply method and the engine type, the use of alcohol fuels performs differently in terms of emissions and engine performance. Dual Fuel combustion mode, port fuel injected alcohol, and direct-injected diesel emits higher HC and CO, while diesel-alcohol blends perform as diesel. Generally, the blends characterized by lower alcohol concentration than dual-fuel perform higher indicated thermal efficiencies. Significant benefits on NOx-soot trade-offs are observed, independently on the fuelling mode, NOx concentration, and engine type by using alcohols. The soot reduction reaches values up to 70%, and the lower carbon content of alcohols fuel reduces the CO2 up to 15%.

Increasing demands on higher performance and lower fuel consumption and emissions have led the path for internal combustion engine development; this race is nowadays directly related to CO2 emissions reduction. To drive engine development and reduce the time-to-market, the employment of numerical analysis is mandatory. This requires a continuous improvement of the simulation models toward real predictive analyses able to reduce the experimental R&D efforts. In this framework, 1D numerical codes are fundamental tools for system design, energy management optimization, and calibration. The present work is focused on the improvement of the phenomenological turbulence model, originally conceived to describe turbulence evolution in tumble-promoting engines. The turbulence model is developed with reference to a SI heavy-duty CNG engine derived from a diesel engine. In this architecture, due to the flat cylinder head, turbulence is also generated by swirl and squish flow motions, in addition to tumble motion. The presented turbulence model is validated against 3D CFD results, demonstrating to properly predict turbulence and swirl/tumble evolution under two different operating conditions, without the need for any case-dependent tuning. The developed turbulence model is coupled to a phenomenological combustion model based on the fractal geometry theory applied to the flame front surface, where the turbulence is assumed to support flame propagation through an enhancement of the flame front area with respect to the laminar counterpart. The combustion model is validated against an extensive experimental dataset, composed of 25 operating points at different engine rotational speeds and loads. The numerical/experimental comparisons of global performance parameters are satisfactory, leading to maximum errors around ±2% for the BSFC, ±2° for the main combustion events, and ±1 bar for the in-cylinder peak pressure. Burn rate profiles are very well captured by the combustion model at changing operating conditions, not requiring any case-dependent tuning. The presented results demonstrate that the turbulence/combustion models could constitute a reliable virtual test facility, contributing to supporting and driving experimental activities.

Il presente documento fa riferimento alle attività di consulenza svolte dall'Istituto Motori del Consiglio Nazionale delle Ricerche, per la Costruzioni Motori Diesel S.p.A. - CMD nell'ambito dell'OR 6 - "Integrazione, caratterizzazione sperimentale dei componenti ed analisi delle prestazioni al banco prova del propulsore ibrido" facente parte del progetto iMare. Nella prima parte sono riportate le attività indirizzate all'allestimento della sala prova motore presso la sede della CMD ad Atella (Pz), dove verrà poi alloggiato il sistema ibrido messo a punto per le successive prove al banco. In tale sezione sarà riportata una descrizione della sala prova nonché degli elementi costituenti la catena di acquisizione/controllo dei principali parametri meccanici ed elettrici. La seconda parte del report verte sulla discussione delle strategie di gestione del sistema di propulsione ibrido. In particolare l'attività è rivolta allo sviluppo ed alla simulazione numerica di differenti strategie di controllo al fine di valutarne pregi e difetti una volta fissate opportune condizioni operative replicabili poi sul sistema in scala reale come previsto dagli altri OR relativi al progetto iMare. Nella terza parte del report, sono invece riportati i risultati sperimentali ottenuti al banco prova sul sistema di propulsione prototipale. In particolare, la prima parte delle prove è stata dedicata all'allestimento del sistema di comunicazione CANBUS ed alla verifica del suo corretto funzionamento in diverse condizioni operative. Le prove successive sono state rivolte all'esecuzione dei test al banco per il sistema di propulsione ibrido, in condizioni operative rappresentative del suo funzionamento a bordo.

The transportation sector is one of the main contributors to global CO2 emissions and is expected to further increase due to the growth of population and life quality standards. Therefore, reduction CO2 emissions is the top priority to prevent the negative impacts of climate change. For these reasons, the automotive sector is facing new challenges, advanced internal combustion engines, electrification of the drive train, replacing fossil fuels can help to meet greenhouse gas emission standards and simultaneously reduce pollutants. In this study, two ethanol fueling modes, dual fuel and blend, are applied in a compression ignition engine to evaluate the effect of different engine calibration parameters on the thermodynamic and emissions. A parametric analysis is conducted for the variables, fuel substitution ratio, injection pattern, fuel injection pressure, and exhaust gas recirculation. The results demonstrate ethanol being a promising alternative to fossil fuels for the globally lower emissions in compliance with the actual advanced engine technologies. Ethanol blend improves the gross-indicated efficiency compared to the dual-fuel and diesel combustion. However, the dual-fuel emitted higher THC and CO emissions than in diesel and blend cases that have comparable levels. Ethanol blends combustion with a high level of ethanol, and EGR employing a multi-injection strategy shows a positive impact on emission reduction while maintaining high efficiency compared to the dual-fuel and diesel combustion. The dual-fuel combustion employing high ethanol, rail pressure, and EGR levels leads to important benefits, minimizing the emissions and noise and maximizing the efficiency.

In data 27/05/2021 STEMS-CNR ha firmato un contratto con ENI (n° 3500053530) per una attività di supporto tecnico-scientifico a test su strada con un autobus per trasporto extra-urbano di passeggeri, alimentato con miscele contenenti gasolio ed HVO. STEMS-CNR ha seguito l'attività sperimentale ed elaborato i dati acquisiti. Tutte le tipologie di prova previste nella fase di progettazione della sperimentazione sono state effettuate e la sperimentazione è stata condotta e si è conclusa con successo. Nel report è descritta l'attività condotta, l'analisi dei dati ed i principali risultati.

Il presente documento fa riferimento alle attività di consulenza svolte dall'Istituto di Scienze e Tecnologie per l'Energia e la Mobilità Sostenibili del Consiglio Nazionale delle Ricerche (CNR[1]STEMS) per la Costruzioni Motori Diesel S.p.A. - CMD nell'ambito dell'OR 8 - "Messa a punto del sistema ibrido di propulsione installato su un dimostratore tipo di imbarcazione fino a 10 m" del progetto iMare. Tali attività sono state concordate tra le parti, come riportato nel contratto di consulenza stipulato in data 07/05/2019 con protocollo IM-CNR 1339 del 28/05/2019. Il documento è suddiviso in due sezioni, seguendo gli obiettivi realizzativi previsti dall'OR 8 del progetto iMare. Nella prima parte del report si riportano le attività svolte presso il cantiere nautico Salpa, sito in Vitulazio (CE). Tali attività, svolte a valle dell'installazione on-board, sono state utili alla configurazione e testing del sistema di propulsione ibrido prototipale e dei relativi sistemi ausiliari. A valle della fase di testing della componentistica prevista sono inoltre riportate le attività svolte in vasca, indispensabili per il varo finale e le successive prove in mare. La seconda parte del report riporta i risultati delle prove a mare, svolte presso la banchina del Porto di Pozzuoli, con l'obiettivo di verificare le prestazioni dell'imbarcazione nelle principali condizioni di funzionamento previste da progetto.

The growing diffusion of Heavy-Duty engines powered by Natural Gas (NG) has made it necessary to investigate specific Three-Way Catalysts (TWC), with the consequent development of reliable numerical models. This reactor allows a high conversion efficiency exclusively in a limited range of Air-to-Fuel Ratio (AFR) around the stoichiometric. In highly dynamic conditions, its behavior can differ from Steady-State ones due to numerous phenomena of Oxygen Storage and oxide formation on palladium surface, not fully detected from Engine Test Bench (ETB) data. Goal of the present research activity was to develop a 1D chemical reaction model of a Pd/Rh TWC for NG application with the use of a Synthetic Gas Bench (SGB) through an extensive and innovative experimental characterization. Specific Steady-State experiments have shown a dynamics in the methane conversion, not only to ? variation but also at fixed ? and temperature conditions, linked to the reversible Pd ? PdO transformation. Through dedicated temperature-programmed oxidation and reduction (TPO / TPR) tests, hysteresis phenomena in the methane oxidation rate were highlighted. Furthermore, with fast Rich-Lean ? transitions tests, it has been also demonstrated that the presence of NO reduces the methane oxidation reaction rate. A dedicated experimental protocol has shown the high impact of Steam Reforming reaction on methane conversion, partly responsible of a particular decrease in CO conversion efficiency at high temperatures in rich and stoichiometric conditions. In addition, given the high reliability of the experimental data and the possibility of managing the chemical composition of the gas entering the catalyst, important aspects related to the NH3 formation and decomposition were analyzed. The proposed reactions kinetic scheme describes in an acceptable way the behavior of a TWC for NG application.

A wider use of biofuels in internal combustion engines could reduce the emissions of pollutants and greenhouse gases from the transport sector. In particular, due to stringent emission regulatory programs, compression ignition engine requires interventions aimed at reducing their polluting emissions. Ethanol, a low carbon fuel generally produced from biomass, is a promising alternative fuel applicable in compression ignition engines to reduce CO2 and soot emissions. In this paper, the application of a dual fuel diesel-ethanol configuration in a light-duty compression ignition engine has been numerically investigated. Ethanol is injected into the intake port, while diesel fuel is directly injected into the combustion chamber of the analyzed engine. CFD simulations have been carried out by means of the AVL Fire 3-D code. The operation at given engine load and speed has been simulated considering different diesel injection timings. Numerical results of both the diesel spray development and the dual fuel combustion process have been validated against available experimental data. 3-D analysis allowed to deeply investigate the evolution of the combustion process, particularly the transition between premixed and diffusive phase. The influence of diesel fuel direct injection timing, combustion chamber geometry, and EGR on the combustion process development, hence on engine performance and emission levels, have been highlighted. One of the main results of the use of dual fuel, diesel-ethanol configuration, is a significant reduction of soot and carbon dioxide emissions with respect to diesel-only operation.

Natural gas as an internal combustion engine fuel is taking a predominant role as a mid-term solution to pollution due to combustion driven human activities both in the energy and transport sectors. Engine researchers and manufacturers are in the process of investigating and improving strategies that decrease emissions and fuel consumption, without compromising engine performance and efficiency; active pre-chamber configurations are to be accounted for as one of these. A relatively small amount of fuel (up to 10 % of the total fuel-energy requirement) is introduced in the confined volume of the pre-chamber and forms a close-to-stoichiometric mixture with fresh charge that is introduced from the main combustion chamber during the compression stroke. After spark-ignition the products of this early stage of combustion can ignite ultra-lean mixtures (with ? up to 2) through the Turbulent Jet Ignition mechanism, hence reducing fuel consumption as well as noxious emissions such as NOx. Mixture formation in the pre-chamber has an important role in driving the combustion process that takes place therein. Prediction and control of mixture composition and distribution become necessary in view of an optimal operation, therefore precise control of the timings and procedures of fuel introduction in the pre-chamber is necessary. In this work 0D and 1D modelling in Matlab-Simulink environment was coupled and integrated with computer-aided design in order to establish geometry and fluid-dynamic parameters of the injection system components as well as characterizing flow along the route to the prechamber. This preliminary study was aimed at the layout design of the injection system. The resulting model is the starting point for the design of a Real-Time control system to employ during engine operation, in view of realistic on-road heavyduty applications.

Compression ignition (CI) engines are widely used in modern society, but they are also recognized as a significative source of harmful and human hazard emissions such as particulate matter (PM) and nitrogen oxides (NOx). Moreover, the combustion of fossil fuels is related to the growing amount of greenhouse gas (GHG) emissions, such as carbon dioxide (CO2). Stringent emission regulatory programs, the transition to cleaner and more advanced powertrains and the use of lower carbon fuels are driving forces for the improvement of diesel engines in terms of overall efficiency and engine-out emissions. Ethanol, a light alcohol and lower carbon fuel, is a promising alternative fuel applicable in the dual-fuel (DF) combustion mode to mitigate CO2 and also engine-out PM emissions. In this context, this work aims to assess the maximum fuel substitution ratio (FSR) and the impact on CO2 and PM emissions of different nozzle holes number injectors, 7 and 9, in the DF operating mode. The analysis was conducted within engine working constraints and considered the influence on maximum FSR of calibration parameters, such as combustion phasing, rail pressure, injection pattern and exhaust gas recirculation (EGR). The experimental tests were carried out on a single-cylinder light-duty CI engine with ethanol introduced via port fuel injection (PFI) and direct injection of diesel in two operating points, 1500 and 2000 rpm and at 5 and 8 bar of brake mean effective pressure (BMEP), respectively. Noise and the coefficient of variation in indicated mean effective pressure (COVIMEP) limits have been chosen as practical constraints. In particular, the experimental analysis assesses for each parameter or their combination the highest ethanol fraction that can be injected. To discriminate the effect on ethanol fraction and the combustion process of each parameter, a one-at-a-time-factor approach was used. The results show that, in both operating points, the EGR reduces the maximum ethanol fraction injectable, nevertheless, the ethanol addition leads to outstanding improvement in terms of engine-out PM. The adoption of a 9 hole diesel injector, for lower load, allows reaching a higher fraction of ethanol in all test conditions with an improvement in combustion noise, on average 3 dBA, while near-zero PM emissions and a reduction can be noticed, on the average of 1 g/kWh, and CO2 compared with the fewer nozzle holes case. Increasing the load insensitivity to different holes number was observed.

Technological and economic concerns correlated to fulfilling future emissions and CO2 standards require great research efforts to define an alternative solution for low emissions and highly efficient propulsion systems. Alternative fuel formulation could contribute to this aim. Liquefied petroleum gas (LPG) with lower carbon content than other fossil fuels and which is easily vaporized at ambient conditions has the advantage of lowering CO2 emissions and optimizing the combustion process. Liquefied petroleum gas characteristics and availability makes the fuel a promising alternative for internal combustion engines. The possible combination of using it in high-efficiency compression ignition engines makes it worth analyzing the innovative method of using LPG as a blend component in diesel. Few relevant studies are detectable in literature in this regard. In this study, two blends containing diesel and LPG, in volume ratios 20/80 and 35/65, respectively, were formulated and utilized. Their effects on combustion and emissions performance were assessed by performing proper experimental tests on a modern light-duty single-cylinder engine test rig. Reference operating points at conventional engine calibration settings were examined. A specific exhaust gas recirculation (EGR) parametrization was performed evaluating the LPG blends&rsquo, potential in reducing the smoke emissions at standard engine-out NOx levels. The results confirm excellent NOx-smoke trade-off improvements with smoke reductions up to 95% at similar NOx and efficiency. Unburnt emissions slightly increase, and to acceptable levels. Improvements, in terms of indicated specific fuel consumption (ISFC), are detected in the range of 1&ndash, 3%, as well as the CO2 decrease proportionally to the mixing ratio.

Gas engines (fuelled with CNG, LNG or Biogas) for generation of power and heat are, to this date, taking up larger shares of the market with respect to diesel engines. In order to meet the limit imposed by the TA-Luft regulations on stationary engines, lean combustion represents a viable solution for achieving lower emissions as well as efficiency levels comparable with diesel engines. Leaner mixtures however affect the combustion stability as the flame propagation velocity and consequently heat release rate are slowed down. As a strategy to deliver higher ignition energy, an active pre-chamber may be used. This work focuses on assessing the performance of a pre-chamber combustion configuration in a stationary heavy-duty engine for power generation, operating at different loads, air-to-fuel ratios and spark timings. The engine was originally a 6-cylinder compression ignition engine which is here employed as a single cylinder engine and then suitably modified to host the pre-chamber (with its natural gas injection system and spark plug) with a new bowl piston to decrease compression ratio. A 0D model is built to make a thermodynamic analysis to characterize the local conditions in the pre-chamber before spark timing (temperature, pressure and composition), based on a compressible nozzle equation for the mass transfer between the chambers and a simplified Woschni model for the pre-chamber's heat transfer. A mathematical expression was found to describe the relationship between the local conditions and the early stage of the combustion. Experimental results showed the beneficial effect of spark delay and mixture leaning for the reduction of NOx emissions, while CO, unburned hydrocarbons and engine performance see improvement with lower air-to-fuel ratios and spark advance.

Vehicles’ powertrain electrification is one of the key measures adopted by manufacturers in order to develop low emissions vehicles and reduce the CO2 emissions from passenger cars. High complexity of electrified powertrains increases the demand of cost-effective tools that can be used during the design of such powertrain architectures. Objective of the study is the proposal of a series of real-world velocity profiles that can be used during virtual design. To that aim, using three state of the art plug-in hybrid vehicles, a combined experimental, and simulation approach is followed to derive generic real-world cycles that can be used for the evaluation of the overall energy efficiency of electrified powertrains. The vehicles were tested under standard real driving emissions routes, real-world routes with reversed order (compared to a standard real driving emissions route) of urban, rural, motorway, and routes with high slope variation. To enhance the experimental activities, additional virtual mission profiles simulated using vehicle simulation models. Outcome of the study consists of specific driving cycles, designed based on standard real-world route, and a methodology for real-world data analysis and evaluation, along with the results from the assessment of the impact of different operational parameters on the total electrified powertrain.

Test di emissioni e consumi di veicoli compattatori RSU della HERA SpA alimentati con ENI diesel+. I risultati sono stati comparati con quelli ottenuti utilizzando un gasolio rappresentativo della rete di distribuzione italiana. La presente relazione descrive la strumentazione impiegata, la metodologia ed i risultati delle prove.

Il presente documento riporta si riporta una descrizione delle attività del CNR-Istituto Motori con rispettivo riferimento all'OR1.1 - Analisi e definizione dell'imbarcazione e del profilo di utilizzo: definizione della potenza termica ed elettrica da impegnare, in funzione dell'autonomia modalità elettrica e termica di navigazione ed all'OR1.2 - Analisi e definizione delle strategie di gestione dei flussi energetici del sistema di propulsione ibrido per le fasi di navigazione. le attività sono state rivolte a contestualizzare l'impiego di architetture di propulsione ibride di tipo navale, nell'ambito dell'attuale scenario normativo Europeo, incentrato sulla riduzione dell'impatto ambientale e sul miglioramento dell'efficienza della mobilità marittima. Parallelamente è stata svolta un'analisi delle principali strategie di gestione dei flussi energetici, tra sistema di accumulo e motorizzazioni termico/elettriche, per l'ottimizzazione di architetture di propulsione ibride, di impiego in ambito navale

Nell'ambito del contratto ENI-CNR n° 3500049202 è stata definita e realizzata un'attività di sperimentazione di motori FPT, installati su mezzi Trenitalia, alimentati con ENI Diesel+. Le prove sono state eseguite presso le sale prova motori dell'Officina Grandi Riparazioni (OMC) Trenitalia di Rimini nei mesi di Giugno 2019 ed Ottobre 2020. Le emissioni ed i consumi di due motori alimentati con ENI Diesel+ sono state comparate con quelle ottenute utilizzando un gasolio rappresentativo della rete di distribuzione italiana. La presente relazione descrive la strumentazione impiegata, la metodologia ed i risultati delle prove

The dual-fuel (DF) diesel-natural gas (NG) combustion concept for automotive engine applications has received increased attention in the recent years. The reasons of such interest lie in the need to identify energy sources alternative to fossil oil fuels, valid and competitive from an environmental point of view. Gaseous fuels, such as NG and methane, are very promising and highly attractive to this aim because of their easy availability, widespread distribution infrastructure, low cost, and clean-burning qualities. With respect to conventional diesel fuel, in fact, NG and methane permit a significant reduction of CO2 and are less prone to soot formation. Notwithstanding that the significant soot reduction offered by the DF engine combustion mode is a consolidated result, the compliance with future stringent regulations on engine particulate emissions will still require the adoption of after-treatment devices, such as the diesel particulate filter (DPF). Therefore, a complete characterization of the particle emissions in DF configuration appears of great interest for the design of a future DPF equipping DF engines. To this aim, an experimental research activity was performed on a multi-cylinder automotive engine operated in DF mode, with a fixed methane substitution ratio value. The tests were carried out in transient conditions, typical of the engine homologation cycles, comparing the engine performance and emissions in conventional diesel and DF combustion modes. The present paper is mainly focused on the results of the engine-out soot particle analysis, performed by means of online and offline measurement techniques. The diagnostic systems led to the characterization of emitted particles, in terms of the soot mass concentration, particle number (PN), particle size distribution function, and chemical/physical features. The use of methane in the DF engine showed relevant impact in terms of soot mass and PN reductions but not on the particle average size. On the other side, the combustion mode proved to be not influential on the collected soot reactivity as well as to show a negligible impact on the soot chemicophysical features.

The present paper describes the results of a research activity aimed to assess the potential of hydrocracked fossil oil (HCK) and Hydrotreated Vegetable Oil (HVO) blends, as future premium diesel fuels, on fuel consumption (FC) reduction of the modern automotive diesel engines. Three fuels have been formulated and tested in a light duty four-cylinder diesel engine, Euro 5 version, equipped with closed loop control of the combustion. The set of fuels comprised three experimental fuels formulated ad hoc by blending HVO and HCK streams, and an EN590-compliant commercial diesel fuel representative of the current market fuel quality. A specific test procedure based on a sequence of New European Driving Cycle (NEDC) and ARTEMIS cycles on an engine dyno test bed was applied in order to carry out accurate fuel consumption measurements versus fuel quality, so reproducing the fuel effects on FC for long mileage use of the vehicle. Results of the experimental activity proved that HCK-HVO blends give a benefit on both FC and CO 2 saving. Taking into account the strong similarity in terms of combustion system design between Euro 5 and Euro 6 engines, the estimated trends can be considered valid also for Euro 6 vehicles equipped with the same class of engines. In a next step, it is planned to validate these results by carrying out also WLTP and RDE emission tests.

An approach to reduce CO2 emissions while simultaneously keeping the soot emissions down from compression ignition (CI) engines is to blend in short chained oxygenates into the fuel. In this work, two oxygenated fuel blends consisting of diesel, gasoline and ethanol (EtOH) in the ratio of 68:17:15 and 58:14:30 have been utilized and studied in a single cylinder light duty (LD) CI engine in terms of efficiency and emissions. The reasons of utilizing gasoline in the fuel blend is due to the emulsifying properties it has while increasing the total octane rating of the fuel to be able to run the engine with a higher fraction of premixed flame. When performing the experiments, the control parameters were set as close as possible to the original equipment manufacturer (OEM) EU5 calibration of the multi-cylinder engine to study the possibility of using such blends in close to stock LD CI engines. With the oxygenates, in particular the fuel with the higher concentration of EtOH achieved an indicated net efficiency of ∼ 51% inf comparison to ∼ 47% for diesel at 8 bar BMEP. The NOX emissions increased slightly for the double injection strategy at 13 bar BMEP from ∼ 13.5 g/kW h to ∼ 14.5 g/kW h when going from diesel fuel to the higher ethanol blend. However utilizing single injection strategy at lower loads reduces the NOX. Highest soot mass measured for diesel was ∼ 0.46 g/kW h in contrast to ∼ 0.1 g/kW h for the oxygenates. Also, soot production when running the engine on the ethanol containing fuels was not significantly affected by EGR utilization as in the case of diesel. Considering particle size distribution, the particles are reduced both in terms of mean diameter and quantity. At 1500 rpm and 2 bar BMEP an increase of over ∼ 300% in THC and CO was measured, however, increasing the speed and load to above 2000 rpm and 8 bar BMEP respectively, made the difference negligible due to high in-cylinder temperatures contributing to better fuel oxidation. Despite having lower cetane numbers, higher combustion stability was observed for the oxygenates fuels.