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Effects of Prechamber on Efficiency Improvement and Emissions Reduction of a SI Engine Fuelled with Gasoline

Istituto Motori CNR-Paolo Sementa, Francesco Catapano, Silvana Di Iorio, Bianca Maria Vaglieco
Published 2019-10-07 by SAE International in United States
The permanent aim of the automotive industry is the further improvement of the engine efficiency and the simultaneous pollutant emissions reduction.The aim of the study was the optimization of the gasoline combustion by means of a passive prechamber. This analysis allowed the improvement of the engine efficiency in lean-burn operation condition too. The investigation was carried out in a commercial small Spark Ignition (SI) engine fueled with gasoline and equipped with a proper designed passive prechamber.It was analyzed the effects of the prechamber on engine performance, Indicated Mean Effective Pressure, Heat Release Rate and Fuel Consumption were used. Gaseous emissions were measured as well. Particulate Mass, Number and Size Distributions were analyzed. Emissions samples were taken from the exhaust flow, just downstream of the valves. Four different engine speeds were investigated, namely 2000, 3000, 4000 and 5000 rpm. Stoichiometric and lean conditions at full load were considered in all tests. 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…
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Knock Onset Detection Methods Evaluation by In-Cylinder Direct Observation

Istituto Motori CNR-Francesco Catapano, Paolo Sementa, Bianca Maria Vaglieco
Published 2019-10-07 by SAE International in United States
Improvement of performance and emission of future internal combustion engine for passenger cars is mandatory during the transition period toward their substitution with electric propulsion systems. In middle time, direct injection spark ignition (DISI) engines could offer a good compromise between fuel economy and exhaust emissions. However, abnormal combustion and particularly knock and super-knock are some of the most important obstacles to the improvement of SI engines efficiency. Although knock has been studied for many years and its basic characteristics are clear, phenomena involved in its occurrence are very complex and are still worth of investigation. In particular, the definition of an absolute knock intensity and the precise determination of the knock onset are arduous and many indexes and methodologies has been proposed.In this work, most used methods for knock onset detection from in- cylinder pressure signal have been considered. Moreover, knock intensity has been evaluated by means of two common indexes. High speed imaging has been carried out in the combustion chamber of a high performance DISI engine provided with an optical window in…
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Emission Factors Evaluation in the RDE Context by a Multivariate Statistical Approach

Marianeve Costabile
Istituto Motori CNR-Livia Della Ragione, Giovanni Meccariello
Published 2019-09-09 by SAE International in United States
The Real Driving Emission (RDE) procedure will measure the pollutants, such as NOx, emitted by cars while driven on the road. RDE will not replace laboratory tests, such as the current WLTP but it will be added to them. RDE is complementary to the laboratory-based procedure to check the pollutant emissions level of a light-duty vehicle in real driving conditions. This means that the car will be driven on a real road according to random acceleration and deceleration patterns conditioned by traffic flow. So, the procedure will ensure that cars deliver real emissions over on-road and so the currently observed differences between emissions measured in the laboratory and those measured on road under real-world conditions, will be reduced. However, the identification of a path on the road to check the test conditions of RDE is not easy and hardly repeatable. In fact, when the car is driven by a real driver on a real road we need, firstly, to overcome some problems for identifying the best way to travel through an unknown traffic area to…
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CFD Modeling and Validation of the ECN Spray G Experiment under a Wide Range of Operating Conditions

Istituto Motori CNR-Marianna Migliaccio, Alessandro Montanaro, Luigi Allocca
Politecnico di Milano-Davide Paredi, Tommaso Lucchini, Gianluca D'Errico
Published 2019-09-09 by SAE International in United States
The increasing diffusion of gasoline direct injection (GDI) engines requires a more detailed and reliable description of the phenomena occurring during the fuel injection process.As well known the thermal and fluid-dynamic conditions present in the combustion chamber greatly influence the air-fuel mixture process deriving from GDI injectors.GDI fuel sprays typically evolve in wide range of ambient pressure and temperatures depending on the engine load. In some particular injection conditions, when in-cylinder pressure is relatively low, flash evaporation might occur significantly affecting the fuel-air mixing process. In some other particular injection conditions spray impingement on the piston wall might occur, causing high unburned hydrocarbons and soot emissions, so currently representing one of the main drawbacks of GDI engines. Within this context, a deep understanding of the spray evolution by means of accurate experimental and numerical investigations is of great importance for reduction of pollutant emissions and fuel consumption.This work is focused on the CFD simulation of the 8-hole, ECN Spray G injector under constant volume conditions. Calculations were carried out with the LibICE code, which is…
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Experimental and Numerical Analysis of a Pre-Chamber Turbulent Jet Ignition Combustion System

Istituto Motori CNR-Francesco Catapano, Paolo Sementa
Politecnico di Bari-Elia Distaso, Riccardo Amirante, Egidio Cassone, Pietro De Palma, Paolo Tamburrano
  • Technical Paper
  • 2019-24-0018
Published 2019-09-09 by SAE International in United States
Recent needs of reducing pollutant emissions of internal combustion engines have pushed the development of non-conventional ignition systems. One of the most promising techniques appears to be the so-called pre-chamber turbulent jet ignition combustion system in which a jet of hot combusting gases is employed to initiate the combustion in the main chamber. In the present study, the combustion process related to this ignition system has been experimentally investigated in an optically accessible single cylinder spark-ignition engine. The pre-chamber was composed of a gas injector and a spark-plug, embedded in a small annular chamber connected to the cylinder through a four-hole pipette. A small amount of methane is injected within the pre-chamber for initiating the combustion. The flame reaches the combustion chamber through four narrow orifices and rapidly consumes a homogeneous mixture of port injected methane and air. Wide open throttle condition at an engine speed of 2000 rpm was considered. The combustion process evolution and engine’s performance were analyzed in terms of 2D-digital imaging measurements as well as pressure and heat release rate traces.…
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1D Modeling of Alternative Fuels Spray in a Compression Ignition Engine Using Injection Rate Shaping Strategy

Istituto Motori CNR-Ezio Mancaruso, Luigi Sequino
Univ.di Napoli Parthenope, Ist.Mot.CNR-Carmela Perozziello
Published 2019-09-09 by SAE International in United States
The Injection Rate Shaping consists in a novel injection strategy to control air-fuel mixing quality via a suitable variation of injection timing that affects the injection rate profile. This strategy has already provided to be useful to increase combustion efficiency and reduce pollutant emissions in the modern compression ignition engines fed with fossil Diesel fuel. But nowadays, the ever more rigorous emission targets are enhancing a search for alternative fuels and/or new blends to replace conventional ones, leading, in turn, a change in the air-fuel mixture formation.In this work, a 1D model of spray injection aims to investigate the combined effects of both Injection Rate Shaping and alternative fuels on the air-fuel mixture formation in a compression ignition engine. In a first step, a ready-made model for conventional injection strategies has been set up for the Injection Rate Shaping. Experimental data collected in an optical single-cylinder compression ignition research engine via the 2D visible and infrared advanced diagnostic techniques have been used to validate the model. Commercial Diesel fuel has been used. Afterward, two parameters…
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Experimental Investigation of a Fueled Prechamber Combustion in an Optical Small Displacement SI Methane Engine

Istituto Motori CNR-Paolo Sementa, Francesco Catapano, SILVANA Di Iorio, Bianca Maria Vaglieco
Published 2019-09-09 by SAE International in United States
The constant aim of the automotive industry is the further improvement of engine efficiency and the simultaneous reduction of the exhaust emissions. In order to optimize the internal combustion engines it is necessary to further improve the basic knowledge of the thermo-fluid dynamic phenomena occurring during the combustion process. In this context, the application of optical diagnostic techniques permits a deep insight into the fundamental processes such as flow development, fuel injection, and combustion process. In this paper the analysis of the combustion process of gaseous fuel ignited by the plasma jets coming from a prechamber was performed. The investigation was carried out in an optically accessible small Direct Injection Spark-Ignition (DI SI) engine fueled with Methane. The ignition was obtained with a properly designed fueled prechamber prototype. It was equipped with a gas Direct Injector, used to inject the fuel into the prechamber, and a spark plug used to ignite the mixture. The combustion of the prechamber mixture generates four plasma jets that quickly ignite the mixture into the combustion chamber. The development of…
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Imaging and Vibro-Acoustic Diagnostic Techniques Comparison for a GDI Fuel Injector

Istituto Motori CNR-Luigi Allocca, Daniela Siano, Alessandro Montanaro, Maria Antonietta Panza
  • Technical Paper
  • 2019-24-0058
Published 2019-09-09 by SAE International in United States
This work presents the results of an experimental investigation on a GDI injector, in order to analyze fuel injection process and atomization phenomenon, correlating imaging and vibro-acoustic diagnostic techniques.A single-hole, axially-disposed, 0.200 mm diameter GDI injector was used to spray commercial gasoline in a test chamber at room temperature and atmospheric backpressure. The explored injection pressures were ranged from 5.0 to 20.0 MPa. Cycle-resolved acquisitions of the spray evolution were acquired by a high-speed camera.Simultaneously, the vibro-acoustic response of the injector was evaluated. More in detail, noise data acquired by a microphone sensor were analyzed for characterizing the acoustic emission of the injection, while a spherical loudspeaker was used to excite the spray injection at a proper distance detecting possible fuel spray resonance phenomena. In order to monitor vibration throughout the injection event, the injector was also equipped with an accelerometer sensor, adhesively mounted on the holder. Tests in both dry and fuel injection conditions allowed to distinguish the pure mechanical operation of the injector related to the needle opening and closing, and the effects…
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Dynamic Thermal Behavior of a GDI Spray Impacting on a Heated Thin Foil by Phase-Averaged Infrared Thermography

Istituto Motori CNR-Luigi Allocca, Alessandro Montanaro
University of Naples Federico II-Mattia Contino, Gennaro Cardone, Mirko Zaccara
  • Technical Paper
  • 2019-24-0036
Published 2019-09-09 by SAE International in United States
The regulations about pollutant emissions imposed by Community’s laws encourage the investigation on the combustion optimization in modern engines and in particular in those adopting the gasoline direct injection (GDI) or direct injection spark-ignited (DISI) configuration. It is known that the piston head and cylinder surface temperatures, coupled with the fuel injection pressure, strongly influence the interaction between droplets of injected fluid and the impinged wall. In the present study, the Infrared (IR) thermography is applied to investigate the thermal footprint of an iso-octane spray generated by a multi-hole GDI injector impinging on a heated thin foil. The experimental apparatus includes an Invar foil (50 μm in thickness) heated by Joule effect, clamped within a rigid frame, and the GDI injector located 11 mm above the surface. Thermal images of the impinging spray are acquired from the dry side of the foil at several time delays after the impact instant at two different injection pressures (10 and 20 MPa). The temperature difference distributions are employed to describe the unsteady dynamics of the impingement.
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Balancing Hydraulic Flow and Fuel Injection Parameters for Low-Emission and High-Efficiency Automotive Diesel Engines

Istituto Motori CNR-Gabriele Di Blasio, Carlo Beatrice, Roberto Ianniello
Continental-Giovanni Avolio
Published 2019-09-09 by SAE International in United States
The introduction of new light-duty vehicle emission limits to comply under real driving conditions (RDE) is pushing the diesel engine manufacturers to identify and improve the technologies and strategies for further emission reduction. The latest technology advancements on the after-treatment systems have permitted to achieve very low emission conformity factors over the RDE, and therefore, the biggest challenge of the diesel engine development is maintaining its competitiveness in the trade-off “CO2-system cost” in comparison to other propulsion systems. In this regard, diesel engines can continue to play an important role, in the short-medium term, to enable cost-effective compliance of CO2-fleet emission targets, either in conventional or hybrid propulsion systems configuration. This is especially true for large-size cars, SUVs and light commercial vehicles.In this framework, a comprehensive approach covering the whole powertrain is of primary importance in order to simultaneously meet the performance, efficiency, noise and emission targets, and therefore, further development of the combustion system design and injection system represent important levers for additional improvements. For this purpose, a dedicated 0.5 dm3 single-cylinder engine has…
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