Catalytic Combustion in Internal Combustion Engines: A Possible Explanation for the Woschni Effect in Thermally-Insulated Diesel Engines.
NAVAL RESEARCH LAB WASHINGTON DC SURFACE CHEMISTRY BRANCH
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This report describes research undertaken to determine if catalytic combustion effects occur with the use of zirconia ZrOsub2 thermal barrier coatings TBCs, or other coatings, in diesel engines, and if so, whether these effects have significant impact upon engine combustion, fuel economy, or pollutant emissions. A simple furnace system was used to identify catalytic combustion effects in the ignition and combustion of propaneair mixtures over catalyst-doped m-ZrOsub2 spheres. Three classes of catalysts were examined zirconia-stabilizing oxides CeOsub2, Ysub2Osub3, MgO, transition metal oxides Cosub3Osub4, Crsub2Osub3, Fesub2O3, and noble metals Pt. Each class exhibited characteristic combustion effects, with the ignition temperature increasing, e.g., from approximately 2000 deg C for Pt to 5500 deg C for the stabilizing oxides. The results suggest that the Woschni effect, a controversial phenomenon wherein thermal-insulating measures are postulated to actually increase heat transfer from the diesel combustion chamber, may be only a manifestation of catalytic combustion. Previous research on catalytic combustion in internal combustion engines is briefly reviewed and discussed. An earlier version of this report is to be published in J. Surface and Coatings Technology as Catalytic Combustion Effects on m-ZrOsub2 Doped with Various Metal Nitrates.
- Combustion and Ignition
- Reciprocating and Rotating Engines