Combustion technology to achieve engine thermal efficiency of 40% for HVs engine

Enhancing engine thermal efficiency is an important means of improving the vehicle fuel economy. Hybrid Vehicles (HVs) engine uses higher brake mean effective pressure (BMEP) area and higher engine thermal efficiency area compared to conventional engines. Therefore improving the maximum engine thermal efficiency leads to better fuel economy of the hybrid vehicles. Over the course of engine development for Prius, the maximum engine thermal efficiency has been raised to 38.5% by adopting Atkinson cycle, cooled exhaust gas recirculation (EGR), an electrical water pump, and low friction technologies. It will be required that the engine thermal efficiency exceeds 40% to meet the social demand in the near future. To enhance the engine thermal efficiency, it is essential to improve the anti-knock quality and to reduce cooling heat loss. Therefore the cooled EGR technology which leads to reduce cooling heat loss and improve the anti-knock quality is focused on and has been widely spread throughout the world. Toyota has been launching new engies with ESTEC (Economy with Superior Thermal Efficient Combustion) since 2014.
This paper describes the combusiton technologies to achive engine thermal efficincy of 40% such as high tumble that are able to expand the EGR limit.