Soot and NO(x) Emissions and Combustion Characteristics of Low Heat Rejection Direct Injection Diesel Engines

Abstract : Performance and emissions data were gathered on a normally aspirated single cylinder DI engine with various combinations of ceramic coatings installed. Thin ceramic thermal barrier coatings were applied to the piston crown and bowl, the head and valves, and the cylinder liner. The coated piston and head were run singly and in combination with the cylinder liner to investigate the effects of these different coated surfaces on emissions and performance. Coating the piston crown alone results in generally lower cylinder pressure, lower brake specific fuel consumption and lower NO(x) emission compared to the baseline engine. Soot emission is typically increased below 2000 RPM and decreased above 2000 RPM. Coating the head alone reduces cylinder pressure, but generally increases specific fuel consumption and NO(x) and soot emission. The KIVA-II code was used to model the Hydra engine with the thermal coatings. The computer modeling has led to an understanding of the effect of coating the piston on NO production. The hotter piston crown warms the intake air, shortening ignition delay and decreasing the ratio of premixed to diffusion combustion, ultimately resulting III lower peak cylinder temperature and reduced NO. The KIVA-II results agree reasonably well with the experimental data for cylinder pressure and NO and soot emission. Diesel combustion, Low heat rejection engines, NO(x) Emission, Soot emission, Thermal barrier coatings.