Quantifying Benefits of Dual Cam Phasers, Lean Mixture and EGR on the Operating Range and Fuel Economy of a PFI NVO CAI Engine IFP

Format:

Conference/Event

Author/Creator:

Duffour, Duffour, author.

Contributor:

Knop, Vincent

Leone, Thomas

Pascal, Vincent

Vangraefschepe, Franck

Conference Name:

SAE 2010 World Congress & Exhibition (2010-04-13 : Detroit, Michigan, United States)

Language:

English

Physical Description:

1 online resource

Place of Publication:

Warrendale, PA SAE International 2010

Summary:

Among the existing concepts that help to improve the efficiencyof spark-ignition engines at part load, Controlled Auto-Ignition(CAI) is an effective way to lower both fuel consumption andpollutant emissions. This combustion concept is based on theauto-ignition of an air-fuel-mixture highly diluted with hot burntgases to achieve high indicated efficiency and low pollutantemissions through low temperature combustion. To minimize the costsof conversion of a standard spark-ignition engine into a CAIengine, the present study is restricted to a Port Fuel Injectionengine with a cam-profile switching system and a cam phaser on bothintake and exhaust sides.In a 4-stroke engine, a large amount of burnt gases can betrapped in the cylinder via early closure of the exhaust valves.This so-called Negative Valve Overlap (NVO) strategy has a keyparameter to control the amount of trapped burnt gases andconsequently the combustion: the exhaust valve-lift profile. Thepresent study shows that intake valve-lift profile, air-fuel ratioand EGR are also relevant parameters to control CAI combustionmode.First, a reference CAI operating area with constant valve-lifttimings and stoichiometric mixture is presented. Specific intakeand exhaust valve-lift profiles with reduced maximum valve-lift andopening duration are implemented. The gains associated with dualcam phasers and lean burn mixture on both the CAI operating areaand fuel consumption are then detailed. Lastly, the positive impactof EGR on the extension of the CAI operating area towards higherloads and on the improvement of efficiency is quantified.To complete the test bench data, the operating points areanalyzed with system simulation to investigate the mean in-cylinderconditions (species and temperature) just before auto-ignition andto understand the consequences of the different strategies. Anenergy balance on a standard spark-ignition operating point and onvarious CAI operating points is also presented to point out theorigins of the fuel economy

Notes:

Vendor supplied data

Publisher Number:

2010-01-0844

Access Restriction:

Restricted for use by site license