Influence of Fuel Composition and Combustion Process on Thermodynamic Parameters of SI Engines Daimler AG

Format:

Conference/Event

Author/Creator:

Ritzinger, Ritzinger, author.

Contributor:

Boulouchos, Konstantinos

Koch, Thomas

Lehmann, Jürgen

Conference Name:

SAE 2012 International Powertrains, Fuels & Lubricants Meeting (2012-09-18 : Malmo, Sweden)

Language:

English

Physical Description:

1 online resource

Place of Publication:

Warrendale, PA SAE International 2012

Summary:

In the field of heavy-duty applications almost all engines applythe compression ignition principle, spark ignition is used only inthe niche of CNG engines. The main reason for this is the highefficiency advantage of diesel engines over SI engines. Beside thisdrawback SI engines have some favorable properties like lowerweight, simple exhaust gas aftertreatment in case of stoichiometricoperation, high robustness, simple packaging and lower costs. Themain objective of this fundamental research was to evaluate thelimits of a SI engine for heavy-duty applications.Considering heavy-duty SI engines fuel consumption under fullload conditions has a high impact on CO₂ emissions. Therefore,downsizing is not a promising approach to improve fuel consumptionand consequently the focus of this work lies on the enhancement ofthermal efficiency in the complete engine map, intensivelyconsidering knocking issues.Using a single-cylinder research engine, basic mechanisms toreduce knocking tendency have been evaluated. Subject of this partof the investigations was the influence of valve timing and cooledEGR on the knocking behavior of a stoichiometric SI engine.Generally cooled EGR and early or late inlet valve closing arereducing knocking tendency, due to benefits during gas exchangelate intake valve closing has a greater potential to improveefficiency. A combination of both mechanisms is possible, leadingto a reduction of specific fuel consumption of up to 18% in theinvestigated operation point, using RON95.Another promising way to improve the CO₂ balance of the engineis the usage of ethanol as fuel, as it is possible to produceethanol from regenerative sources. In most cases ethanol is blendedwith gasoline to reduce the fossil energy demand. This work focuseson four different blends E0, E25, E85 and E97. As a first step,investigations of the influence of the different ethanol blends onemissions, fuel consumption and general thermodynamic behavior havebeen accomplished. As a second step, the knocking behavior of thedifferent blends has been analyzed more deeply. In order todetermine the knock limited compression ratio of the differentblends, the compression ratio was increased stepwise. For pureRON95 the knock limited compression ratio is in the region of 11,for E25 it is 13 and with E85 and E97 a compression ratio of 14.5is realizable. With this compression ratio a break efficiency ofover 41% could be demonstrated

Notes:

Vendor supplied data

Publisher Number:

2012-01-1633

Access Restriction:

Restricted for use by site license