Is Thermal Barrier Coating for Low Heat Rejection in SI Engines or Diesel Engines?

The diesel / gasoline engine rejects about two thirds of the heat energy of the fuel, one-third to the coolant, and one third to the exhaust, leaving only about one-third as useful power output. Theoretically if the heat rejected could be reduced, then the thermal efficiency would be improved, at least up to the limit set by the second law of thermodynamics. Low Heat Rejection (LHR) engines aim to do this by reducing the heat lost to the coolant. The diesel / Gasoline engine with its combustion chamber walls insulated by ceramics is referred to as LHR engine. Ceramic based thermal barrier coatings are considered as candidate materials for coating of engine components subjected to elevated temperatures in operating conditions. In this communication attempts are made to review the effect of certain ceramic coatings on low heat rejection engines. Ceramics, in contrast to metals are often more resistance to oxidation, corrosion, wear as well as being better thermal insulator. They have a higher thermal durability than metals. To control temperature distribution and heat flow in a structure low thermal conductivity ceramics can be used. . These thermal barrier coatings (TBC) provide the potential for higher thermal efficiencies of the engine, improved combustion and reduced emissions. Certain experimental results incorporating thermal barrier coatings have controversial results and hence a question is raised to see whether ceramic coating can be recommended for d.c. engines which are suitable for S.I engines. In this context the present communication analyses the pros and cons of the performance of ceramic coatings. Results are analysed and presented in this