Analysis of Thermal Coating on Engine Performance Parameters & Fuel Economy of a Small Size NA Spark Ignition Engine

With strict upcoming regulation norms, it becomes a challenging task for automotive industry to develop highly efficient engine that meets all the regulation requirements. The focus of automakers is to utilize fuel energy in most efficient way and to reduce the energy loss from the engine to improve thermal efficiency. Heat loss to the cooling medium is one of the prime losses inside the combustion chamber. Thermal barrier coating is used to reduce heat losses across combustion chamber surfaces (Piston, head, valves and cylinder liner) as it provides good insulation because of the prominent properties of coating materials like low thermal conductivity, low heat capacity, high melting point etc.

This paper presents application and impact of thermal swing coating on thermal efficiency. Thermal swing coating material follows gas temperature quickly throughout the cycle which reduces the temperature difference between gas and coating surface and thus reduces the heat loss. The benefit of reduction in heat loss across the combustion chamber surfaces leads to increase in thermal efficiency without deteriorating volumetric efficiency since the temperature of coating material falls quickly and prevents heating of intake air. An initially developed physics based engine simulation model for three cylinder naturally aspirated SI engine in GT POWER was used to examine the impact of coating on cylinder heat transfer and thermal efficiency. A Sensitivity analysis was done to choose the best feasible thermal swing coating material and then thermal swing coating was applied on piston’s top surface and head. Initially analysis was done for single representative point (2000 RPM and 4 BMEP) with coating and without coating. The study was extended for complete WLTP cycle and performance of uncoated and coated model were compared. From the energy balance analysis, it was found that engine thermal efficiency and fuel efficiency was improved as in-cylinder heat transfer was reduced when coating was applied.