The Effects of Thermal Barrier Coatings on Diesel Engine Emissions

Abstract

This study has characterized the influence of thermal barrier coatings (TBCs) applied to combustion chamber surfaces on the emissions from an indirect injection (IDI) diesel engine. The TBCs were applied to the piston crown, the cylinder head (fire deck) and the valves of a single cylinder Yanmar TS-180 IDI diesel utility engine. The gaseous and particulate emissions from the baseline (uncoated) and ceramic-coated engine were analyzed to assess the changes in the combustion process caused by the coatings. The results of these analyses show two clear trends during operation of the baseline and ceramic-coated engine. First, comparison of the emissions from the four modes of operation for the baseline (uncoated) engine shows that particulate matter emissions (on a g/kWh basis) are highest at low load-low speed (mode 4) conditions. At low load-low speed conditions (modes 3 and 4), particulate matter decreases substantially with the TBCs present. Second, these observations combined with thermal and morphological analyses of the particulate matter show that the TBCs reduce particulate mass by reducing the volatile organic content of the particulate.