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Balancing Hydraulic Flow and Fuel Injection Parameters for Low-Emission and High-Efficiency Automotive Diesel Engines

Continental-Giovanni Avolio
General Motors-Francesco Concetto Pesce, Alberto Vassallo, Giacomo Belgiorno
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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PIV and DBI Experimental Characterization of Air Flow-Spray Interaction and Soot Formation in a Single Cylinder Optical Diesel Engine Using a Real Bowl Geometry Piston

GM Global Propulsion Systems-Alberto Vassallo
General Motors Italia S.r.l.-Francesco Concetto Pesce
Published 2019-09-09 by SAE International in United States
With demanding emissions legislations and the need for higher efficiency, new technologies for compression ignition engines are in development. One of them relies on reducing the heat losses of the engine during the combustion process as well as to devise injection strategies that reduce soot formation. Therefore, it is necessary a better comprehension about the turbulent kinetic energy (TKE) distribution inside the cylinder and how it is affected by the interaction between air flow motion and fuel spray. Furthermore, new diesel engines are characterized by massive decrease of NOx emissions. Therefore, considering the well-known NOx-soot trade-off, it is necessary a better comprehension and overall quantification of soot formation and how the different injection strategies can impact it. The present study aims to define a methodology to analyze the velocity field and consequently TKE distribution as well as to characterize soot formation inside of a real bowl geometry considering different operating conditions. For that purpose, two different optical techniques were simultaneously applied in this study. On the one hand, in-cylinder velocity fields were measured by using…
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Key Fuel Injection System Features for Efficiency Improvement in Future Diesel Passenger Cars

SAE International Journal of Advances and Current Practices in Mobility

Continental Corp-Giovanni Avolio
GM Global Propulsion Systems-Alberto Vassallo
  • Journal Article
  • 2019-01-0547
Published 2019-04-02 by SAE International in United States
Diesel will continue to be an indispensable energy carrier for the car fleet CO2 emission targets in the short-term. This is particularly relevant for heavy-duty vehicles as for mid-size cars and SUVs. Looking at the latest technology achievements on the after-treatment systems, it can be stated that the concerning about the NOx emission gap between homologation test and real road use is basically solved, while the future challenge for diesel survival is to keep its competitiveness in the CO2 vs cost equation in comparison to other propulsion systems.The development of the combustion system design still represents an important leverage for further efficiency and emissions improvements while keeping the current excellent performance in terms of power density and low-end torque.The paper describes the results achieved in developing a new diesel combustion system for car application that, leveraging on the high flexibility of the latest fuel injection technology, combines outstanding power and fuel efficiency with low pollutant emissions in ultralight engine designed for lower maximum peak cylinder pressure. The study has been carried out on a 0.5l…
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A Dynamic Test Bench for the Assessment of Common Rail Fuel Injection Systems Impact on CO2 Emissions over the WLTP Cycle

General Motors GPS - Torino-Francesco Concetto Pesce
Università degli Studi di Perugia-Andrea Cavicchi, Lucio Postrioti
Published 2019-04-02 by SAE International in United States
The internal combustion engine technological development is today driven by the pollutants and carbon dioxide (CO2) emission reduction targets imposed by law. The request of lowering CO2 emission reflected in a push towards the improvement of engine efficiency, without sacrificing performances and drivability.The latest generations of Diesel engines for passenger cars are characterized by increasing injection pressure levels (250 MPa for the current production). Enhancing the injection pressure has the drawback of increasing the energy needed to pressurize the fuel and thus the high-pressure fuel pump energy request. A small but not negligible quantity of fuel has to be burned in order to provide this energy, generating a contribution in CO2 emission. In this frame, the injector back-flow represents a significant energy loss for the fuel injection system and for the whole engine.The energetic analysis of the overall fuel injection system of a modern passenger car is therefore interesting.In this research an experimental test bench was developed in order to energetically assess the behavior of a common-rail fuel injection system over the Worldwide harmonized Light…
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The Key Role of Advanced, Flexible Fuel Injection Systems to Match the Future CO2 Targets in an Ultra-Light Mid-Size Diesel Engine

SAE International Journal of Engines

Continental GmbH, Germany-Giovanni Avolio
General Motors Global Propulsion Systems, Italy-Alberto Vassallo, Francesco Concetto Pesce
  • Journal Article
  • 03-12-02-0010
Published 2019-01-23 by SAE International in United States
The article describes the results achieved in developing a new diesel combustion system for passenger car application that, while capable of high power density, delivers excellent fuel economy through a combination of mechanical and thermodynamic efficiencies improvement. The project stemmed from the idea that, by leveraging the high fuel injection pressure of last generation common rail systems, it is possible to reduce the engine peak firing pressure (pfp) with great benefits on reciprocating and rotating components’ light-weighting and friction for high-speed light-duty engines, while keeping the power density at competitive levels. To this aim, an advanced injection system concept capable of injection pressure greater than 2500 bar was coupled to a prototype engine featuring newly developed combustion system. Then, the matching among these features has been thoroughly experimentally examined. The results confirmed the benefits of the employment of high fuel injection pressures as a way to reduce the pfp, combining competitive performance and excellent fuel efficiency with emissions and noise, vibration, and harshness (NVH) requirements of last generation diesel engines for passenger car applications. In…
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The Key Role of Advanced, Flexible Fuel Injection Systems to Match the Future CO2 Targets in an Ultra-Light Mid-Size Diesel Engine

Continental Corp-Giovanni Avolio
GM Global Propulsion Systems-Alberto Vassallo, Francesco Concetto Pesce
Published 2018-05-30 by SAE International in United States
The paper describes the results achieved in developing a new diesel combustion system for passenger car application that, while capable of high power density, delivers excellent fuel economy through a combination of mechanical and thermodynamic efficiencies improvement.The project stemmed from the idea that, by leveraging the high fuel injection pressure of last generation common rail systems, it is possible to reduce the engine peak firing pressure (pfp) with great benefits on reciprocating and rotating components light-weighting and friction for high-speed light-duty engines, while keeping the power density at competitive levels. To this aim, an advanced injection system concept capable of injection pressure greater than 2500 bar was coupled to a prototype engine featuring newly developed combustion system. Then, the matching among these features have been thoroughly experimentally examined.The results confirmed the benefits of the employment of high fuel injection pressures as a way to reduce the pfp, combining competitive performance and excellent fuel efficiency with emissions and Noise Vibration Harshness (NVH) requirements of last generation diesel engines for passenger car applications. In particular, the paper…
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Experimental Analysis of Fuel and Injector Body Temperature Effect on the Hydraulic Behavior of Latest Generation Common Rail Injection Systems

GM Global Propulsion Systems-Francesco Concetto Pesce, Umberto Ferrara
Universita degli Studi di Perugia-Andrea Cavicchi, Lucio Postrioti
Published 2018-04-03 by SAE International in United States
The present paper describes the effect of thermal conditions on the hydraulic behavior of Diesel common rail injectors, with a particular focus on low temperatures for fuel and injector body. The actual injection system thermal state can significantly influence both the injected quantity and the injection shape, requiring proper amendments to the base engine calibration in order to preserve the combustion efficiency and pollutant emissions levels. In particular, the introduction of the RDE (Real Driving Emission) test cycle widens the effective ambient temperature range for the homologation cycle, this way stressing the importance of the thermal effects analysis. An experimental test bench was developed in order to characterize the injector in an engine-like configuration, i.e. fuel pump, piping, common rail, pressure control system and injectors. One of the injectors is used for the measurement of injection rate time profile by means of a Zeuch method-based injection analyzer, mean injected volume per shot and dynamic pressure time-history at pump outlet and injector inlet. The fuel temperature, measured at the fuel pump inlet, and the injector body…
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Open Access

Multi-Objective Optimization of Fuel Injection Pattern for a Light-Duty Diesel Engine through Numerical Simulation

SAE International Journal of Engines

General Motors Global Propulsion Systems-Francesco Concetto Pesce
Politecnico di Torino-Andrea Piano, Federico Millo, Francesco Sapio
  • Journal Article
  • 2018-01-1124
Published 2018-04-03 by SAE International in United States
Development trends in modern common rail fuel injection systems (FIS) show dramatically increasing capabilities in terms of optimization of the fuel injection strategy through a constantly increasing number of injection events per engine cycle as well as through the modulation and shaping of the injection rate. In order to fully exploit the potential of the abovementioned fuel injection strategy optimization, numerical simulation can play a fundamental role by allowing the creation of a kind of a virtual test rig, where the input is the fuel injection rate and the optimization targets are the combustion outputs, such as the burn rate, the pollutant emissions, and the combustion noise (CN). Starting from a previously developed 1D-CFD (Computational Fluid Dynamics) virtual test rig, obtained coupling a 1.6L, 4-cylinder turbocharged diesel engine model with a 1D-CFD injector model, this article presents a methodology for optimizing the fuel injection strategy aiming to minimize brake-specific fuel consumption (BSFC) and CN without exceeding the brake-specific NOx (BSNOx) baseline value. The Non-dominated Sorting Genetic Algorithm (NSGA-III) was used in GT-SUITE environment for Pareto…
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Digital Shaping and Optimization of Fuel Injection Pattern for a Common Rail Automotive Diesel Engine through Numerical Simulation

General Motors Global Propulsion Systems-Francesco Concetto Pesce
Politecnico di Torino-Francesco Sapio, Andrea Piano, Federico Millo
Published 2017-09-04 by SAE International in United States
Development trends in modern Common Rail Fuel Injection System (FIS) show dramatically increasing capabilities in terms of optimization of the fuel injection pattern through a constantly increasing number of injection events per engine cycle along with a modulation and shaping of the injection rate. In order to fully exploit the potential of the abovementioned fuel injection pattern optimization, numerical simulation can play a fundamental role by allowing the creation of a kind of a virtual injection rate generator for the assessment of the corresponding engine outputs in terms of combustion characteristics such as burn rate, emission formation and combustion noise (CN). This paper is focused on the analysis of the effects of digitalization of pilot events in the injection pattern on Brake Specific Fuel Consumption (BSFC), CN and emissions for a EURO 6 passenger car 4-cylinder diesel engine. The numerical evaluation was performed considering steady-state conditions for 3 key points representative of typical operating conditions in the low-medium load range. The optimization process was carried out through numerical simulation, by means of a suitable target…
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Numerical Investigation on the Effects of Different Thermal Insulation Strategies for a Passenger Car Diesel Engine

SAE International Journal of Engines

General Motors Global Propulsion Systems-Giancarlo Cifali, Francesco Concetto Pesce
Politecnico di Torino-Sabino Caputo, Federico Millo
  • Journal Article
  • 2017-24-0021
Published 2017-09-04 by SAE International in United States
One of the key technologies for the improvement of the diesel engine thermal efficiency is the reduction of the engine heat transfer through the thermal insulation of the combustion chamber. This paper presents a numerical investigation on the effects of the combustion chamber insulation on the heat transfer, thermal efficiency and exhaust temperatures of a 1.6 l passenger car, turbo-charged diesel engine. First, the complete insulation of the engine components, like pistons, liner, firedeck and valves, has been simulated. This analysis has showed that the piston is the component with the greatest potential for the in-cylinder heat transfer reduction and for Brake Specific Fuel Consumption (BSFC) reduction, followed by firedeck, liner and valves. Afterwards, the study has been focused on the impact of different piston Thermal Barrier Coatings (TBCs) on heat transfer, performance and wall temperatures. This analysis has been performed using a 1-D engine simulation code coupled with a lumped mass thermal model, representing the engine structure. A time-periodic wall conduction model has been used to calculate the wall temperature swings along the combustion…
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