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Technical Paper

Application of a Quasi-Dimensional Combustion Model to the Development of a High-EGR VVT SI Engine

2005-09-11
2005-24-070
The paper reports the research activity related to the development of a High Exhaust Gas Recirculation (EGR) Spark-Ignition (SI), 8 valve engine equipped with a variable valve timing (VVT) device. The latter imposes an equal phase displacement on both intake and exhaust camshafts (dual dependent cam phaser). Both experimental and theoretical analyses are carried out to characterize the performance of this engine architecture, and particularly to analyze the combustion process arising at low load and high EGR conditions. To this aim, a quasi-dimensional model for the simulation of the burning process is included as an external user-defined routine in a commercial 1D simulation code (GT-Power®). The whole model is validated at both wide open throttle (WOT) conditions and part-load, and then it is mainly utilized to find, by means of a parametric analysis, the lowest fuel consumption at low load.
Technical Paper

Experimental And Numerical Analysis Of A Small VVT S.I. Engine

2005-09-11
2005-24-079
Optimized valve timing, according to engine load, may lead to significant improvements in pumping losses and internal EGR generation. Thus, VVT technology constitutes an effective way to reduce both fuel consumption and pollutant emissions. In this paper, the behavior of a small displacement, 2 valve, Spark-ignition engine, with variable valve timing, has been numerically and experimentally analyzed. The use of VVT allows obtaining combined internal EGR and Reverse Miller Cycle effects so to achieve a significant dethrottling at part load operation. High EGR rates require high turbulence intensity in order to accelerate the combustion rate. The engine performs an accurate combustion chamber design and a tangential intake port able to generate optimized swirl motion, according to the engine speed and load, during both the exhaust gas re-aspiration and the intake stroke. Engine performances at different cam phaser positions have been calculated by means of a 3-D computer code.
Technical Paper

Application of an Electric Boosting System to a Small, Four-Cylinder S.I. Engine

2003-09-16
2003-32-0039
The consequences of global warming have forced the governments of developed economies to impose strict regulations on the emission of so called ‘green house gases’. Carbon dioxide, a by-product of fossil fuel combustion, is a major contributor to global warming. The focus of government treaties, in the face of continued globalization and third world development, has been to stabilize contributions of carbon dioxide to the atmosphere. Vehicle manufacturers and suppliers have tackled legislation and consumer pressures in a variety of ways. One of the most effective ways to reduce fuel consumption of passenger vehicles, consequently reducing their CO2 emissions, is so-called “engine downsizing”. This involves the improvement of the torque of a smaller displacement engine with respect to (w.r.t.) a given engine installed in a vehicle, and the use of longer gear ratios in the transmission.
Technical Paper

A Quasi-Dimensional Three-Zone Model for Performance and Combustion Noise Evaluation of a Twin-Spark High-EGR Engine

2004-03-08
2004-01-0619
The paper reports the research activity related to the development of a twin-spark SI engine equipped with a variable valve timing (VVT) device. Improvements on the fuel consumption at part load are expected when an high internal exhaust gas recirculation (internal EGR) level is realized with a proper phasing of the VVT device. The twin-spark solution is implemented to improve the burning speed at low load, and to increase the EGR tolerance levels. Both experimental and theoretical analyses are carried out to investigate the real advantages of the proposed engine architecture. In particular an original quasi-dimensional model for the simulation of the burning process in a twin-spark engine is presented. The model is mainly utilized to find the proper combination of VVT device position (and hence EGR level) and spark advance for different engine operating conditions. A comparison with the single-spark solution is also provided.
Technical Paper

Numerical and Experimental Analysis of Different Combustion Chambers for a Small Spark-Ignition Engine

2004-06-08
2004-01-1998
A small spark-ignition engine, in wide spread commercial usage since numerous years, is at present under study with the aim of improving its performance, in terms of a reduction of both fuel consumption and pollutant emissions. In previous papers, the influence of piston geometry [1] and intake system [2] on the combustion process has been evaluated by means of a 3-D computational model. In this paper, a more extensive analysis of the parameters affecting the combustion rate, hence thermal efficiency, pollutant formation and engine stability, has been carried out. In particular, at ELASIS Research Center, three prototypes featuring different combustion chambers have been realized and analyzed to the aim of assessing the influence of the squish area percentage on the flame front propagating in a quiescent charge. Furthermore, the AVL FIRE computer code has been utilized in order to simulate the engine behavior at full load operation.
Technical Paper

VVT+Port Deactivation Application on a Small Displacement SI 4 Cylinder 16V Engine: An Effective Way to Reduce Vehicle Fuel Consumption

2003-03-03
2003-01-0020
During recent years several VVT devices have been developed, in order to improve either peak power and low end torque, or part load fuel consumption of SI engines. This paper describes an experimental activity, concerning the integration of a continuously variable cam phaser (CVCP), together with an intake port deactivation device, on a small 4 cylinder 16V engine. The target was to achieve significantly lower fuel consumption under normal driving conditions, compared to a standard MPFI application. A single hydraulic cam phaser is used to shift both the intake and the exhaust cams to retarded positions, at constant overlap. Thus, high EGR rates in the combustion chamber and late intake valve closure (“reverse Miller cycle”) are combined, in order to reduce pumping losses at part load.
Journal Article

Cycle-by-Cycle Analysis, Knock Modeling and Spark-Advance Setting of a “Downsized” Spark-Ignition Turbocharged Engine

2009-09-13
2009-24-0020
Recently, a tendency is consolidating to produce low displacement turbocharged spark-ignition engines. This design philosophy, known as “engine downsizing”, allows to reduce mechanical and pumping losses at low load as a consequence of the higher operating Brake Mean Effective Pressure (BMEP). The presence of the turbocharger allows to restore the maximum power output of the larger displacement engine. Additional advantages are a higher low-speed torque and hence a better drivability and fun-to-drive. Of course, at high loads, the spark-advance must be carefully controlled to avoid the knock occurrence and this determines a substantial penalization of the fuel consumption. The knowledge of the knock-limited spark timing is hence a key point in order to reduce the fuel consumption drop at high loads.
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