Predictions of Diesel Engine's Performance by the DESP Program with the Combustion Chamber Coated with Metals or Ceramics

In the past decades, the diesel engines are considered as the major power source, not only because of their high thermal efficiency, high torque output, and easy maintenance; but also due to the improved exhaust emissions reduction technology. In order to increase the thermal efficiency, the low heat rejection ceramic coating engine is one of the possible solutions for future engine manufacturing. Due to the thermal insulating effects of the ceramic material (low thermal conductivity), the cylinder charge and engine components' temperatures are substantially increased. However, the thermal impact problem and the possible high friction characteristics of the new coating material can be deadly to the engine's lifetime. Various non-ceramic and ceramic materials are tested in this research to decide their thermal insulating effects on the engine performance and their downside on the friction and thermal impact problems.

The characteristics of the cylinder charge pressure against the crank angle is very important for analyzing the engine combustion pattern. The heat release calculated according to the pressure profile (differentiated by time) can tell us in details what actually happen within the combustion chamber. Thus, a good methodology to predict the cylinder charge pressure is essential in this study. The DESP (Diesel Engine Simulation) program is thus used in this research to study the effects of thermal insulation effects by coating the cylinder liner and piston surface with a thin non-ceramic (Nickel or Chrome) material or a thin ceramic (ZrO₂ or Al₂O₃+TiO₂) material. The comparisons between the non-ceramic and ceramic coatings on the engine performance are also conducted under various engine speeds and loads. The equivalence ratio (ϕ) is used in this study instead of engine load.