Exploiting SI engine efficiency through lean burn operation in combination with stroke extension, miller timings and high compression ratios Technische Universität Braunschweig

Format:

Book

Conference/Event

Author/Creator:

Wenz, Erich, author.

Contributor:

Eilts, Peter

Pauls, Alexander

Thielen, Marvin

Todt, Arne

Conference Name:

15th International Conference on Engines & Vehicles (2021-09-12 : Capri, Italy)

Language:

English

Physical Description:

1 online resource cm

Place of Publication:

Warrendale, PA SAE International 2021

Summary:

Individual transport plays a considerable role in global greenhouse gas emissions. Hence, the worldwide legislation increases the demands on the automotive industry with regard to emissions. The European Union currently limits the fleet emissions of CO2 to 95 g/km. Further reduction by 37.5% until 2030 is certain. Because internal combustion engines will likely play an important role in the future transport, particularly in hybrid propulsion systems, further improvement of the combustion system is necessary. Therefore, the potential of lean burn combustion in combination with other technologies is investigated. The primary focus is on the improvement of SI engine efficiency. For the investigations conducted, an extremely downsized SI single cylinder research engine is upgraded with different engine technologies. The stroke-to-bore ratio is increased to 1.5, leading to higher piston speeds. The resulting increase in tumble and hence turbulent flame speed supports sufficient combustion performance of highly diluted mixtures. In order to further increase the thermodynamic efficiency, miller timings are realised in form of late intake valve closing. Additionally, the compression ratio is increased to ε = 15. The investigations reveal that relative air/fuel ratios of up to λ = 1.6 are possible while maintaining reasonable combustion stability. The use of late intake valve closing limits the maximum possible enleanment, but allows similar efficiencies compared to reference timings with higher dilution. Increasing the compression ratio allows further increase in efficiency, especially when combined with the miller timings. Lean operation allows to increase engine efficiency at low load as well as high load operation. Best values are achieved in mid loads, where an indicated efficiency of ηi = 44.1% is possible

Notes:

Vendor supplied data

Publisher Number:

2021-24-0034

Access Restriction:

Restricted for use by site license