Browse Publications Technical Papers 1999-01-3579
1999-10-25

In-cylinder Liquid Fuel Layers, Cause of Unburned Hydrocarbon and Deposit Formation in SI Engines? 1999-01-3579

In-cylinder reaction processes in a production port-fuel-injection (PFI) spark-ignition engine having optical access were visualized using a high speed four-spectra IR Imaging system. Over one thousand sets of digital movies were accumulated for this study. To conduct a close analysis of this vast amount of results, a new data analysis and presentation method was developed, which permits the simultaneous display of as many as twenty-eight (28) digital movies over a single PC screen in a controlled manner, which is called the Rutgers Animation Program (RAP for short).
The results of this parametric study of the in-cylinder processes (including the period before and after the presence of luminous flame fronts) suggest that, even after the engine was well warmed, liquid fuel layers (LFL) are formed over and in the vicinity of the intake valve to which the PFI was mated. The sluggish consumption of those LFL, which continued even until the exhaust valve opens, is expected to be one of the main emission sources of unburned hydrocarbon.
Inspection of deposit formation on over twenty-four (24) cylinders (of the engines provided by the manufacturer after some lengthy operation) revealed a predictable pattern. Deposits were found to occur only in areas where the reacting LFL were observed.
The mutually consistent findings from this parametric study are reported. Some of the results from the study will be presented by using the RAP at the meeting.

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