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Viggiano, Annarita
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How to Improve SI Engine Performances by Means of Supercritical Water Injection

University of Basilicata – Potenza 85100-Antonio Cantiani, Annarita Viggiano, Vinicio Magi
Published 2019-10-07 by SAE International in United States
The efficiency of ICEs is strongly affected by exhaust gases and engine cooling system heat losses, which account for about 50% of the heat released by combustion. A promising approach is to transfer this exhaust heat to a fluid, like water, and inject it into the combustion chamber under supercritical conditions. In such a way, the recovered energy is partially converted into mechanical work, improving both engine efficiency and performance.A quasi-dimensional model has been implemented to simulate an SI engine with supercritical water injection. Specifically, a spark ignition ICE, four-stroke with Port Fuel Injection (PFI) has been considered. The model accounts for gas species properties, includes valves opening/closing, wall heat transfer, a water injection model and a combustion model. The influence of some injection parameters, i.e. Water/Fuel ratio (W/F), Start Of water Injection (SOI) and Water Injection Duration (WID), on engine performances and efficiency is discussed in details.The results show that an increase of W/F ratio has the strongest impact on the performances with respect to SOI and WID, i.e. higher W/F ratio, SOI closer…
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Optimization of Multi Stage Direct Injection-PSCCI Engines

Università degli Studi della Basilicata-Annarita Viggiano, Vinicio Magi
  • Technical Paper
  • 2019-24-0029
Published 2019-09-09 by SAE International in United States
The more and more stringent regulations on emissions lead the automotive companies to develop innovative solutions for new powertrain concepts, including the employment of advanced combustion strategies and mixture of fuels with different thermochemical properties. HCCI combustion coupled with the partial direct injection of the charge is a promising technique, in order to control the performance and emissions and to extend the operating range.In this work an in-house developed multi-dimensional CFD software package has been used to analyze the behavior of a multi stage direct injection - partially stratified charge compression ignition engine fueled with PRF97. A combustion model based on the partially stirred reactor concept to include the influence of turbulence on chemistry has been employed. Specifically, a skeletal kinetic reaction mechanism for PRF oxidation, with a dynamic adaptive chemistry technique to reduce the computational cost of the simulations has been used. Most of the fuel is injected during the intake stroke, in order to get a homogeneous mixture of fuel and air, whereas the remaining part is injected at the end of the…
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An Investigation on the Performance of Partially Stratified Charge CI Ethanol Engines

University of Basilicata-Annarita Viggiano, Vinicio Magi
Published 2011-04-12 by SAE International in United States
The partial fuel stratification, by means of direct fuel injection, is one of the most suitable combustion strategies in order to overcome the limits of ignition control and operating range of HCCI engines. In this work, a multidimensional model, coupled with a detailed kinetic mechanism for ethanol oxidation, is used to investigate the performance of a partially stratified charge CI engine fueled by ethanol. The model, which accounts for turbulence effects on combustion, has been validated in a previous work, against experimental results in terms of both HCCI engine performance and emissions.In this work, computations have been carried out by varying the fraction of the fuel stratified charge and the injection timing and by considering different flow structures within the cylinder. By increasing the amount of stratified fuel, the rate of the pressure rise and the heat release rate reduce, while the peak of the heat release rate delays, since the zones of the chamber, where the liquid fuel is located, are relatively cold and rich to ignite, thus the combustion process slows down. However,…
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Multidimensional Simulation of Ethanol HCCI Engines

Department of Environmental Physics and Engineering – University of Basilicata-Annarita Viggiano, Vinicio Magi
Published 2009-09-13 by Consiglio Nazionale delle Ricerche in Italy
This work explores the coupling of advanced combustion strategies for engines with bio-based fuels. The characteristics of ethanol combustion in HCCI mode are investigated by using a multidimensional CFD model coupled with an accurate combustion model. In such a model, the chemical source terms are computed by a detailed kinetic mechanism and are corrected in order to take into account the influence of turbulence. The predictive capability of the model is proven by comparing the results with experimental measurements. The sensitivity analysis to initial and boundary conditions gives suggestions in order to increase engine efficiency and reduce pollutant emissions.
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