Numerical investigation of thermal barrier coating on performance and emissions of HPDI dual-fuel engine

Thermal barrier coatings (TBC) represent a promising technology for enhancing the thermal efficiency of internal combustion engines. This study investigates the impact of TBC on in-cylinder combustion processes of a dual-fuel HPDI engine to achieve higher energy conservation with low heat transfer loss. In the present study, a one-dimensional conjugate heat transfer (1D CHT) model is constructed that incorporates TBC material features. By coupling the 1D CHT model with the three-dimensional combustion model of dual-fuel HPDI engines in CONVERGE software, the influences of TBC to the combustion process and temperature distribution within the engine cylinder is illustrated in details. Meanwhile, the adiabatic combustion characteristics of HPDI engines are investigated based on various adiabatic components or porosity. The results demonstrate that the reduction in heat transfer under P_TBC (TBC on top boundary of piston) conditions leads to an increase in the volume proportions of the high-temperature intervals within the cylinder, thus enhancing both mixture activity and heat release rate. The combination of these two factors lead to a 0.4% increase in indicated thermal efficiency under P_TBC conditions compared to the baseline. Under the current injection strategy, P_TBC conditions could effectively eliminate the heat flow area in the piston bowl and step area, thereby significantly reducing heat transfer loss. Since heat transfer loss is basically influenced by both temperature difference between fluid and wall as well as thermal conductivity of TBC, increasing porosity therefore is able to enhance thermal resistance by reducing thermal conductivity of TBC. However, when there is an increased temperature difference between fluid and wall, increasing porosity does not continually lead to a further reduction of heat transfer loss. Finally, it is observed that the utilization of P_TBC with a porosity of 0.1 resulted in an increase of 0.7% in the indicated thermal efficiency compared to the baseline, while marginally reducing CH4 and CO emissions.