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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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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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Functional Requirements to Exceed the 100 kW/l Milestone for High Power Density Automotive Diesel Engines

SAE International Journal of Engines

General Motors-Francesco Concetto Pesce, Alberto Vassallo
Istituto Motori CNR-Gabriele Di Blasio, Carlo Beatrice, Giacomo Belgiorno
  • Journal Article
  • 2017-24-0072
Published 2017-09-04 by SAE International in United States
The paper describes the challenges and results achieved in developing a new high-speed Diesel combustion system capable of exceeding the imaginative threshold of 100 kW/l. High-performance, state-of-art prototype components from automotive diesel technology were provided in order to set-up a single-cylinder research engine demonstrator.Key design parameters were identified in terms boost, engine speed, fuel injection pressure and injector nozzle flow rates. In this regard, an advanced piezo injection system capable of 3000 bar of maximum injection pressure was selected, coupled to a robust base engine featuring ω-shaped combustion bowl and low swirl intake ports.The matching among the above-described elements has been thoroughly examined and experimentally parameterized. The tests confirmed the benefits of the employment of very high fuel injection pressures as a way to decouple the trade-off between an excellent power rating and emissions / NVH / CO2 at part load, whose combination truly defines the leading edge of modern diesel engines for automotive application.The paper also discusses the system sensitivity to the boundary conditions, of the charging and exhaust systems, and develops a balanced…
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Estimation of DPF Soot Loading through Steady-State Engine Mapping and Simulation for Automotive Diesel Engines Running on Petroleum-Based Fuels

GM Powertrain-Alberto Vassallo
General Motors Global Propulsion Systems-Francesco Barba, Vincenzo Greco
Published 2017-09-04 by SAE International in United States
The aim of the present study is to improve the effectiveness of automotive diesel engine and aftertreatment calibration process through the critical evaluation of several methodologies to estimate the soot mass flow produced by diesel engines fueled by petroleum fuels and filtered by Diesel Particulate Filters (DPF). In particular, its focus has been the development of a reliable simulation method for the accurate prediction of the engine-out soot mass flow starting from Filter Smoke Number (FSN) measurements executed in steady state conditions, in order to predict the DPF loading considering different engine working conditions corresponding to NEDC and WLTP cycles.In order to achieve this goal, the study was split into two main parts:Correlation between ‘wet PM’ (measured by soot filter weighing) and the ‘dry soot’ (measured by the Micro Soot Sensor MSS). Test activities have been carried out taking into account different boundaries conditions such as calibration, driving cycle, sampling probes positions;Identification of a reliable and accurate method that allows estimating the ‘dry soot’ starting from the FSN measurements. Different equations available in literature have…
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An Investigation of Radiation Heat Transfer in a Light-Duty Diesel Engine

SAE International Journal of Engines

GM Powertrain-Alberto Vassallo
General Motors Global R & D-Alok Warey, Vicent Domenech
  • Journal Article
  • 2015-24-2443
Published 2015-09-06 by SAE International in United States
In the last two decades engine research has been mainly focused on reducing pollutant emissions. This fact together with growing awareness about the impacts of climate change are leading to an increase in the importance of thermal efficiency over other criteria in the design of internal combustion engines (ICE). In this framework, the heat transfer to the combustion chamber walls can be considered as one of the main sources of indicated efficiency diminution. In particular, in modern direct-injection diesel engines, the radiation emission from soot particles can constitute a significant component of the efficiency losses. Thus, the main of objective of the current research was to evaluate the amount of energy lost to soot radiation relative to the input fuel chemical energy during the combustion event under several representative engine loads and speeds. Moreover, the current research characterized the impact of different engine operating conditions on radiation heat transfer. For this purpose, a combination of theoretical and experimental tools were used. In particular, soot radiation was quantified with a sensor that uses two-color thermometry along…
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Experimental and Numerical Investigations of Close-Coupled Pilot Injections to Reduce Combustion Noise in a Small-Bore Diesel Engine

SAE International Journal of Engines

General Motors Company-Alok Warey, Francesco Pesce, Richard Peterson, Alberto Vassallo
Sandia National Laboratories-Stephen Busch, Kan Zha, Paul C. Miles
  • Journal Article
  • 2015-01-0796
Published 2015-04-14 by SAE International in United States
A pilot-main injection strategy is investigated for a part-load operating point in a single cylinder optical Diesel engine. As the energizing dwell between the pilot and main injections decreases below 200 μs, combustion noise reaches a minimum and a reduction of 3 dB is possible. This decrease in combustion noise is achieved without increased pollutant emissions. Injection schedules employed in the engine are analyzed with an injection analyzer to provide injection rates for each dwell tested. Two distinct injection events are observed even at the shortest dwell tested; rate shaping of the main injection occurs as the dwell is adjusted. High-speed elastic scattering imaging of liquid fuel is performed in the engine to examine initial liquid penetration rates. The penetration rate data provide evidence that rate shaping of the initial phase of the main injection is occurring in the engine and that this rate shaping is largely consistent with the injection rate data, but the results demonstrate that these changes are not responsible for the observed trend in combustion noise.A zero-dimensional model is created to…
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Effect of High Levels of Boost and Recirculated Exhaust Gas on Diesel Combustion Characteristics at Part Load

General Motors Co.-Venkatesh Gopalakrishnan, Alberto Vassallo, Richard C. Peterson, Joaquin De la Morena
Published 2014-04-01 by SAE International in United States
Future diesel combustion systems may operate with significantly higher levels of boost and EGR than used with present systems. The potential benefits of higher boost and EGR were studied experimentally in a single-cylinder diesel engine with capability to adjust these parameters independently. The objective was to study the intake and exhaust conditions with a more optimum combustion phasing to minimize fuel consumption while maintaining proper constraints on emissions and combustion noise. The engine was tested at four part-load operating points using a Design of Experiments (DOE) approach. Two of the operating points correspond to low-speed and low-load conditions relevant for the New European Driving Cycle (NEDC). The other two points focus on medium load conditions representative of the World-wide harmonized Light-duty Test Procedures (WLTP). For the NEDC relevant conditions, improved fuel consumption was not achievable due to combustion noise constraints and the requirement for a very high turbocharger efficiency improvement of more than 20%. For the WLTP points, the Net Specific Fuel Consumption (NSFC) was improved by 11-12% with higher boost and EGR and improved…
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