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Effect of Prechamber on Exhaust Emission and Efficiency of a SI Small Engine Fuelled with Gaseous and Liquid Fuels

Istituto Motori CNR-Paolo Sementa
  • Technical Paper
  • 2020-37-0035
To be published on 2020-06-23 by SAE International in United States
The aim of the study was the optimization of the gasoline combustion process by means of a passive/active prechamber. The improvement of the engine efficiency in lean-burn operation condition is an opportunity to give further use of Spark Ignition (SI) engine. A commercial small Spark Ignition (SI) engine was modified with a proper designed prechamber fuelled with methane. Engine performance in terms of indicated Mean effective pressure, heat release rate and fuel Consumption were evaluated as well as gaseous emissions. Particulate Mass, Number and Size Distributions were measured. Several engine operative conditions were investigated at full load varying the engine speeds for stoichiometric and lean conditions and with different prechamber types. The results were compared with those obtained with the engine equipped with the standard spark plug. The results indicated that both performance and emissions were strongly influenced by the prechamber.
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Experimental Study of Additive-Manufacturing-Enabled Innovative Diesel Combustion Bowl Features for Achieving Ultra-low Emissions and High Efficiency

Istituto Motori CNR-Roberto Ianniello, Carlo Beatrice, Gabriele Di Blasio
GM Global Propulsion Systems-Giacomo Belgiorno, Andrea Boscolo, Gennaro Dileo, Fabio Numidi, Francesco Concetto Pesce, Alberto Vassallo
  • Technical Paper
  • 2020-37-0003
To be published on 2020-06-23 by SAE International in United States
In recent years the research on Diesel thermodynamics has been increasingly shifting from performance and refinement to ultra-low emissions and efficiency. In fact, the last two attributes are key for the powertrain competitiveness in the automotive electrified future, especially in European market where 95gCO2/km fleet average and Euro6d RDE Step2 are phasing in at the same time. The present paper describes some of the most innovative research that GM and Istituto Motori Napoli are performing in the field, exploring how the steel additive manufacturing can be used to create innovative combustion bowl features that optimize the combustion process to a level that was not compatible with standard manufacturing technologies. In particular, an innovative highly-reentrant sharp-stepped profile featuring radial-lips has been studied on a 0.5l single-cylinder engine, coupled to a state of art 2500bar fast-acting fuel injection system, with the objective to demonstrate the full potential of optimized fuel stratification and spray separation enabled by the radial mixing zone concept. The results confirm that excellent reduction of engine-out emissions vs a Euro6-b design could be achieved…
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A Power Split Hybrid Propulsion System for Vehicles with Gearbox

Istituto Motori CNR-Luigi De Simio, Michele Gambino, Sabato Iannaccone
  • Technical Paper
  • 2020-37-0014
To be published on 2020-06-23 by SAE International in United States
New internal combustion engines (ICE) are characterised by increasing maximum efficiency, thanks to the adoption of strategies like Atkinson cycle, downsizing, cylinder deactivation, waste heat recovery and so on. However, the best performance is confined to a limited portion of the engine map. Moreover, electric driving in urban areas is an increasingly pressing request, but battery electric vehicles use cannot be easily widespread due to limited vehicle autonomy and recharging issues. Therefore, in order to reduce ICE vehicle fuel consumption, by decoupling the ICE running from road load, as well as permit energy recovery and electric driving, hybrid propulsion systems are under development. This paper analyses a new patent solution for power split hybrid propulsion system with gearbox. The system comprises an auxiliary power unit, adapted to store and/or release energy, and a planetary gear set which is interposed between the ICE and the gearbox. The system is characterized by a further device coupled with the ICE to modulate the resistance torque, in order to use the auxiliary power unit also for regenerative braking. The…
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Experimental and Numerical Assessment of Active Pre-chamber Ignition in Heavy Duty Natural Gas Stationary Engine

Istituto Motori CNR-Gessica Onofrio, Carlo Beatrice
Lund University-Changle Li, Pablo Garcia Valladolid, Per Tunestal
  • Technical Paper
  • 2020-01-0819
To be published on 2020-04-14 by SAE International in United States
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…
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Under-Expanded Gaseous Jets Characterization for Application in Direct Injection Engines: Experimental and Numerical Approach

Istituto Motori CNR-Luigi Allocca, Alessandro Montanaro, Giovanni Meccariello
Università degli Studi de L'Aquila-Francesco Duronio, Stefano Ranieri
  • Technical Paper
  • 2020-01-0325
To be published on 2020-04-14 by SAE International in United States
In the last years, increasing concerns about environmental pollution and fossil sources depletion led transport sectors research and development towards the study of new technologies capable to reduce vehicles emissions and fuel consumption. Direct-injection systems (DI) for internal combustion engines propose as an effective way to achieve these goals. This technology has already been adopted in Gasoline Direct Injection (GDI) engines and, lately, a great interest is growing for its use in natural gas fueling, so increasing efficiency with respect to port-fuel injection ones. Alone or in combination with other fuels, compressed natural gas (CNG) represents an attractive way to reduce exhaust emission (high H/C ratio), can be produced in renewable ways, and is more widespread and cheaper than gasoline or diesel fuels. Gas direct-injection process involves the occurrence of under-expanded jets in the combustion chamber. An accurate characterization of such phenomena is crucial for a consequent application in DI-CNG engines.In this paper an experimental and numerical analysis of methane under-expanded jets (as surrogate of CNG) has been carried out. The fuel has been injected…
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Experimental and 1D Numerical Investigations on the Exhaust Emissions of a Small Spark Ignition Engine Considering the Cylinder-by-Cylinder Variability

Istituto Motori CNR-Luca Marchitto, Luigi Teodosio, Cinzia Tornatore, Gerardo Valentino
University of Naples-Fabio Bozza
  • Technical Paper
  • 2020-01-0578
To be published on 2020-04-14 by SAE International in United States
This paper reports a numerical and experimental analysis on a twin-cylinder turbocharged Spark Ignition engine carried out to investigate the cylinder-to-cylinder variability in terms of performance, combustion evolution and exhaust emissions.The engine was tested at 3000 rpm in 20 different steady-state operating conditions, selected with the purpose of observing the influence of cylinder-by-cylinder A/F ratio variations and the EGR effects on the combustion process and exhaust emissions for low to medium/high loads. The experimental outcomes showed relevant differences in the combustion evolution (characteristic combustion angles) between cylinders and not negligible variations in the emissions of the single cylinder exhaust and the overall engine one. This misalignment resulted to be due to differences in the injected fuel amount by the port injectors in the two cylinders, mainly deriving from the specific fuel rail geometry.The experimental data were then used to validate a 1D engine model, integrated with refined sub-models of turbulence, combustion, heat transfer and emissions. The model takes into account the in-cylinder production of noxious species, and their propagation in the exhaust system, up to…
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Development of a Sectional Soot Model Based Methodology for the Prediction of Soot Engine-Out Emissions in GDI Units

Istituto Motori - CNR-Silvana Di Iorio
Istituto Motori CNR-Adrian Irimescu
  • Technical Paper
  • 2020-01-0239
To be published on 2020-04-14 by SAE International in United States
With the aim of identifying technical solutions to lower the particulate matter emissions, the engine research community made a consistent effort to investigate the root causes leading to soot formation. Nowadays, the computational power increase allows the use of advanced soot emissions models in 3D-CFD turbulent reacting flows simulations. However, the adaptation of soot models originally developed for Diesel applications to gasoline direct injection engines is still an ongoing process. A limited number of studies in literature attempted to model soot produced by gasoline direct injection engines, obtaining a qualitative agreement with the experiments. To the authors’ best knowledge, none of the previous studies provided a methodology to quantitatively match particulate matter, particulate number and particle size distribution function measured at the exhaust without a case-by-case soot model tuning. In the present study, a Sectional Method-based methodology to quantitatively predict gasoline direct injection soot formation is presented and validated against engine-out emissions measured on a single-cylinder optically accessible gasoline direct injection research engine. While adapting the model to the gasoline direct injection soot framework, attention…
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Infrared/Visible Optical Diagnostics of RCCI Combustion with Dieseline in a Compression Ignition Engine

Istituto Motori CNR-Luigi Sequino, Ezio Mancaruso
Universitat Politecnica de Valencia-Javier Monsalve-Serrano, Antonio Garcia
  • Technical Paper
  • 2020-01-0557
To be published on 2020-04-14 by SAE International in United States
Compression ignition engines are widely used for transport and energy generation due to their high efficiency and low fuel consumption. To minimize the environmental impact of this technology, the pollutant emissions levels at the exhaust are strictly regulated. To reduce the after-treatment needs, alternative strategies as the low temperature combustion (LTC) concepts are being investigated recently. The reactivity controlled compression ignition (RCCI) uses two fuels (direct- and port- injected) with different reactivity to control the in-cylinder mixture reactivity by adjusting the proportion of both fuels. In spite of the proportion of the port-injected fuel is typically higher than the direct-injected one, the characteristics of the latter play a main role on the combustion process. Use of gasoline for direct injection is attractive to retard the start of combustion and to improve the air-fuel mixing process. In this work, the influence of the direct-injected fuel properties on RCCI combustion mode is studied in an optical compression ignition engine. Gasoline fuel is injected in the intake manifold while a blend of gasoline and diesel (a.k.a. dieseline) is…
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Effects of Ultra-High Injection Pressures up to 100 MPa on Gasoline Spray Morphology

Istituto Motori CNR-Alessandro Montanaro, Luigi Allocca, Giovanni Meccariello
  • Technical Paper
  • 2020-01-0320
To be published on 2020-04-14 by SAE International in United States
Very high pressures for injecting gasoline in internal combustion (i.c.) engines are recently explored for improving the air/fuel mixing process in order to control unburned hydrocarbons (UBHC) and particulate matter emissions such as for investigating new combustion concepts. The challenge remains the improvement of the spray parameters in terms of atomization, smaller droplets and their spread in the combustion chamber in order to enhance the combustion efficiency. In this framework, the raise of the injection pressure plays a key role in GDI engines for the trade-off of CO2 vs other pollutant emissions. This study aims contributing to the knowledge of the physical phenomena and mechanisms occurring when fuel is injected at ultra-high pressures for mapping and controlling the mixture formation. Liquid and vapor phases of the fuel, injected by a GDI multi-hole device, were investigated to highlight the pressure role (up to 100 MPa) on the spray morphology under different ambient conditions. Commercial gasoline was injected in a constant volume vessel by a prototypal 5-hole, L/d: 2.6, solenoid activated GDI injector. Nitrogen gas was pressurized…
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Sub-23 nm Particle Emissions from Gasoline Direct Injection Vehicles and Engines: Sampling and Measure

Istituto Motori CNR-Silvana Di Iorio, Francesco Catapano, Paolo Sementa, Bianca Maria Vaglieco
C.R.F. S.C.p.A-Giovanna Nicol, Mauro Francesco Sgroi
  • Technical Paper
  • 2020-01-0396
To be published on 2020-04-14 by SAE International in United States
Nowadays, the regulation regards only the particles larger than 23 nm. The attention is shifting towards the sub-23 nm particles because of their large presence at the exhaust of the modern engines and their negative impact on human health. The main challenge of the regulation of these particles is the definition of a proper procedure for their measure. The nature of the sub-23 nm particles is not well understood, and their measure is strongly affected by the sampling conditions leading to not reliable measure.The aim of this paper is to provide information on the emissions of sub-23 nm particles from GDI vehicles/engines. At the same time, the presence of volatiles, which mainly contribute to the formation of sub-23 nm particles, was evaluated and the effect of sampling conditions was investigated.The analysis was performed on a 1.8L GDI powered vehicle, widely used both in North America and Europe, and a 4-cylinder GDI engine, whose features are similar to those of the vehicle. For both the facilities, vehicle and engine, the Worldwide harmonized Light vehicles Test Cycle…