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Is the “K Value” of an Engine Truly Fuel Independent?
Technical Paper
2020-01-0615
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
The octane appetite of an engine is frequently characterised by the so-called K value. It is usually assumed that K is dependent only on the thermodynamic conditions in the engine when knock occurs. In this work we test this hypothesis: further analysis was conducted on experimental results from SAE 2019-01-0035 in which a matrix of fuels was tested in a single cylinder engine. The fuels consisted of a relatively small number of components, thereby simplifying the analysis of the chemical kinetic proprieties.
Through dividing the original fuel matrix into subsets, it was possible to explore the variation of K value with fuel properties. It was found that K value tends to increase slightly with RON. The explanation for this finding is that higher RON leads to advanced ignition timing (i.e. closer to MBT conditions) and advanced ignition timing results in faster combustion because of the higher pressures and temperatures reached in the thermodynamic trajectory. The Livengood-Wu integral can be employed to show that for higher octane fuels, knock onset occurs at a higher temperature and pressure. Thus, the fuel octane quality can impact the thermodynamic trajectory in the engine.
Authors
- Andrea Festa - University of Bath
- Masahiko Shibuya - Shell Lubricants Japan K. K.
- Sandro Gail - Shell Global Solutions (Deutschland) GmbH
- Roger Cracknell - Shell Global Solutions (UK)
- Masaharu Kassai - Nissan Motor Co., Ltd.
- Taisuke Shiraishi - Nissan Motor Co., Ltd.
- Allen Aradi - Shell Global Solutions (US)
Citation
Cracknell, R., Kassai, M., Shiraishi, T., Festa, A. et al., "Is the “K Value” of an Engine Truly Fuel Independent?," SAE Technical Paper 2020-01-0615, 2020, https://doi.org/10.4271/2020-01-0615.Data Sets - Support Documents
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