Low thermal inertia thermal barrier coatings for spark ignition engines: An experimental study

Abstract

Application of thermal barrier coatings in spark ignition engines have historically been avoided due to the knock penalty associated with higher surface temperatures induced by the ceramic layer. However, advances in low thermal inertia coatings (i.e. temperature swing coatings) that combine low thermal conductivity with low volumetric heat capacity can prevent excessively high surface temperatures during the intake stroke and reduce or avoid knock while improving performance and efficiency. In this study, a novel coating material was tested in a low compression ratio spark ignition engine to evaluate the performance of an advanced low thermal inertia coating during steady and cold-start conditions. A total of four pistons with this novel material was tested, with an additional piston coated with gadolinium zirconate. Spark timing sweeps demonstrated a maximum 0.8% relative thermal efficiency gain with a thin coating of the novel material. The novel material coated above 200-microns showed a deterioration in performance and efficiency due to charge heating increasing knock propensity. Cold-start tests demonstrated that charge heating is beneficial for reducing unburned hydrocarbons and particle matter emissions.

Coating roughness impact on the combustion chambers life of the turbo engines

“…Plasma flame spraying is generally used to apply the ceramic and base coat layers because it has proved to provide durable and reproducible coatings. The studies on the coating material and on its application are still being performed, [14][15][16][17][18][19][20] but besides the thermo-mechanical properties of the TBC, its surface roughness may also affect the performance of the coating, especially the life of the liner and so the combustion chamber of the turbo engine. Predicting component life is an essential part of reliability and service warranties and several efforts have been made in this area.…”