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Published in:
2018 | OriginalPaper | Chapter
Chemical Analysis of Potential Initiating Fluid for Low-Speed Pre-ignition
Authors : Terence F. Alger, Thomas E. Briggs Jr.
Published in: Knocking in Gasoline Engines
Publisher: Springer International Publishing
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Abstract
Low-Speed Pre-Ignition (LSPI) has become a major challenge for the light duty automotive industry. The movement to downsize engines and add turbocharging has improved performance and fuel economy, but the in-cylinder conditions created have led to this stochastic and destructive knocking behavior. Many researchers studying the LSPI phenomenon have hypothesized that it is caused, at least in part, by fluid which is ejected from the piston crevice region.
If this hypothesis is true, it is critical to understand the nature of this fluid. It is well understood that there will be lubricating oil present in the crevice from the action of the rings upon the oil film on the liner. And, at the high load conditions where LSPI occurs, it may be assumed that some fuel will be present as well. However, neither of these fluids will auto-ignite in the manner seen during LSPI events. The hypothesis requires that some characteristics of the crevice fluid are altered from the original fluids.
To investigate this aspect of LSPI, a rapid-acting sampling valve was developed to permit sampling of the fluid in the piston crevice while avoiding sampling of cylinder contents when the piston crevice was not at the sampling location. The samples were analyzed with a two-dimensional gas chromatograph-mass spectrometer which allowed detailed speciation of the samples.
Sampling was performed with the engine running on fuels and lubricants which either increased or reduced LSPI occurrence. There were clear differences in the chemical content of the samples between these cases which indicate that some chemical reactions must take place in the crevice that impact the LSPI behavior of the engine.