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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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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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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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Effects of the Ambient Conditions on the Spray Structure and Evaporation of the ECN Spray G

Istituto Motori CNR-Luigi Allocca, Alessandro Montanaro, Giovanni Meccariello
Published 2019-04-02 by SAE International in United States
The use of Gasoline Direct Injection (GDI) continuously increases due to the growing demand of efficiency and power output for i.c. engines. The optimization of the fuel injection process is essential to prepare an air-fuel mixture capable to promote efficient combustion, reduced fuel consumption and pollutant emissions. Good spray atomization facilitates fuel evaporation in i.c. engines thus contributing to the fuel economy and lowering the emissions. One of the key features of a multi-hole injector is to provide an optimal spray pattern in the combustion chamber and a good mixture homogenization considering the engine-specific characteristics such fuel mass-flow rate, cylinder geometry, injector position, and charge motion.This work aims to investigate the injection processes of an eight-hole direct-injection gasoline injector from the Engine Combustion Network (ECN) effort on gasoline sprays (Spray G, serial #19).The main objective is to evaluate both liquid and vapor phase envelope to extend the dataset for the Spray G covering a broader operating range. The tests were conducted fluxing iso-octane in a heated constant-volume pressurized vessel. A hybrid optical setup, Z-type schlieren…
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Statistical Determination of Local Driving Cycles Based on Experimental Campaign as WLTC Real Approach

Istituto Motori CNR-Giovanni Meccariello, Livia Della Ragione
Published 2017-09-04 by SAE International in United States
In the context of a transport sustainability, some solutions could be proposed from the integration of many disciplines, architects, environmentalists, policy makers, and consequently it may be addressed with different approaches. These solutions would be applied at different geographical levels, i.e. national, regional or urban scale. Moreover, the assessment of cars emissions in real use plays a fundamental role for their reductions. This is also the direction of the new harmonized test procedures (WLTP). Furthermore, it is fundamental to keep in mind that the new WLTC cycle will reproduce a situation closer to the reality comparing to the EUDC/NEDC driving cycle. In this paper, we will be focused on vehicle kinematic evaluation aimed at valuation of traffic situation and emissions. For this purpose, driving data and emissions were acquired during an experimental campaign through six instrumented vehicles by PEMS for the simultaneous acquisition of emissions, kinematic variables and GPS localization data. Moreover, the analyzed vehicles have different type approval classes and different displacements. At this time, we present a different statistical approach to classify the…
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Vapor and Liquid Phases of the ECN Spray G Impacting on a Flat Wall at Engine-Like Conditions

Istituto Motori CNR-Alessandro Montanaro, Luigi Allocca, Maurizio Lazzaro, Giovanni Meccariello
Published 2016-10-17 by SAE International in United States
Mixture formation is fundamental for the development of the combustion process in internal combustion engines, for the energy release, the consumption, and the pollutant formation. Concerning the spark ignition engines, the direct injection technology is being considered as an effective mean to achieve the optimal air-to-fuel ratio distribution at each operating condition, either through charge stratification around the spark plug and stoichiometric mixture under the high power requirements. Due to the highest injection pressures, the impact of a spray on the piston or on the cylinder walls causes the formation of liquid film (wall-film) and secondary atomization of the droplets. The wall-film could have no negligible size, especially where the mixture formation is realized under a wall-guided mode.The present work aims to report the effects of the ambient pressure and wall temperature on the macroscopic parameters of the spray impact on a wall. The spray-wall interaction was realized inside an optically-accessible quiescent vessel and its development was analyzed by a z-shaped combined schlieren / Mie scattering set-up, using a high-speed C-Mos camera for the image…
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Impinging Jets of Fuel on a Heated Surface: Effects of Wall Temperature and Injection Conditions

Istituto Motori CNR-Alessandro Montanaro, Luigi Allocca, Maurizio Lazzaro, Giovanni Meccariello
Published 2016-04-05 by SAE International in United States
In spark ignition engines, the nozzle design, fuel pressure, injection timing, and interaction with the cylinder/piston walls govern the evolution of the fuel spray inside the cylinder before the start of combustion. The fuel droplets, hitting the surface, may rebound or stick forming a film on the wall, or evaporate under the heat exchange effect. The face wetting results in a strong impact on the mixture formation and emission, in particular, on particulate and unburned hydrocarbons. This paper aims to report the effects of the injection pressure and wall temperature on the macroscopic behavior, atomization, and vaporization of impinging sprays on the metal surface.A mono-component fuel, iso-octane, was adopted in the spray-wall studies inside an optically-accessible quiescent vessel by imaging procedures using a Z-shaped schlieren-Mie scattering set-up in combination with a high-speed C-Mos camera. The arrangement was capable to acquire alternatively schlieren and Mie-scattering images in a quasi-simultaneous fashion using the same optical path. This methodology allowed complementing the liquid phases of the impact, obtained by the Mie scattering, with the liquid/vapor ones collected by…
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Schlieren and Mie Scattering Imaging System to Evaluate Liquid and Vapor Contours of a Gasoline Spray Impacting on a Heated Wall

Istituto Motori CNR-Alessandro Montanaro, Luigi Allocca, Giovanni Meccariello, Maurizio Lazzaro
Published 2015-09-06 by SAE International in United States
In internal combustion engines, the direct injection at high pressures produces a strong impact of the fuel on the combustion chamber wall, especially in small-bore sizes used for passenger cars. This effect is relevant for the combustion process resulting in an increase of the pollutant emissions and in a reduction of the engine performances. This paper aims to report the effects of the injection pressure and wall temperature on the macroscopic behavior and atomization of the impinging sprays on the wall.The gasoline spray-wall interaction was characterized inside an optically accessible quiescent chamber using a novel make ready Z-shaped schlieren-Mie scattering set-up using a high-speed C-Mos camera as imaging system. The arrangement was capable to acquire alternatively the schlieren and Mie-scattering images in a quasi-simultaneous fashion using the same line-of-sight. This methodology allowed complementing the Mie scattering images, adapting to the liquid phase, with the schlieren ones for the determination both of the liquid and vaporing phase during the single cycle. A single-hole axially disposed injector was used, 0.200 mm in diameter L/d=1.0, while the injection…
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Real Driving Emissions of a Light-Duty Vehicle in Naples. Influence of Road Grade

Istituto Motori CNR-Maria Vittoria Prati, Giovanni Meccariello, Livia Della Ragione, Maria Antonietta Costagliola
Published 2015-09-06 by SAE International in United States
The aim of this study is to investigate the parameters influencing the real driving emission monitoring with particular attention towards the influence of road gradient. For this purpose, an experimental activity was carried out with a Euro 5 Diesel light-duty vehicle, driven along two tracks of Naples characterized by a different road gradient: the first pattern is quite flat, the second includes positive (+2.9%) and negative (−3.6%) road gradient.Exhaust emissions of CO, THC, NOx, CO2 were acquired on road by using a portable emission measuring system (PEMS) connected also to the Engine Control Unit for saving the main engine parameters and to the GPS for the geographical coordinates and altitude. The acquired speed profiles were repeated on the chassis-dynamometer without simulating the road gradient. In such way, comparison between on road and laboratory results over the flat pattern allowed to identify the main differences among the two testing procedures for pollutant emission measurements. Moreover, the influence of slope variability was statistically evaluated by comparing laboratory and on-board results of the pattern in altitude.Results highlight a…
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Real Time Emissive Behaviour of a Bi-Fuel Euro 4 SI Car in Naples Urban Area

SAE International Journal of Fuels and Lubricants

Istituto Motori CNR-Giovanni Meccariello, Livia Della Ragione, Maria Vittoria Prati, Maria Antonietta Costagliola, Valerio Saccoccia
  • Journal Article
  • 2013-24-0173
Published 2013-09-08 by SAE International in United States
An experimental campaign was carried out to evaluate the influence of CNG and gasoline on the exhaust emissions and fuel consumption of a bi-fuel passenger car over on-road tests performed in the city of Naples. The chosen route is very traffic congested during the daytime of experimental measurements. An on-board analyzer was used to measure CO, CO2, NOx tailpipe concentrations and the exhaust flow rate. Throughout a carbon balance on the exhaust pollutants, the fuel consumption was estimated. The exact spatial position was acquired by a GPS which allowed to calculate vehicle speed and the traffic condition was monitored by a video camera. Whole trip realized by the vehicle was subdivided in succession of kinematic sequences and the vehicle emissions and fuel consumption were analyzed and presented as value on each kinematic sequence. Moreover, throughout a multivariate statistical analysis of sequences, the driving cycles characterizing the use of vehicle were identified.Finally, comparison between regulated emissions of CNG and gasoline configurations was performed qualitatively by the analysis of speed and emission profiles belonging to the same…
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