The Effect of Selective Insulation on the Performance, Combustion, and NO Emissions of a DI Diesel Engine

The performance, combustion and NO emission characteristics of a naturally aspirated, DI diesel engine having selected parts of the combustion chamber insulated were investigated experimentally and analytically. In this study two insulation schemes, namely insulation of the piston crown and insulation of the cylinder head, using thin ceramic thermal barrier coatings, are compared with the baseline engine (no coatings). Experiments under different operating conditions of load, speed and injection timing for the baseline engine and the two insulation schemes were conducted. The experimental results showed that insulation of the piston crown is more effective than insulation of the cylinder head in improving the brake specific fuel consumption (BFSC) and NO emission of the engine Compared to the baseline engine, coating the piston crown lowered the NO emission under all operating conditions and consistently improved BSFC at the highest load and highest speed test conditions.

A modified KIVA II code was used to model the engine with and without the selective insulation schemes. The KIVA results were in support of the experimental results and lend insight into the combustion phenomena that produce the observed effects.