Summary report of Japan Clean Air Program diesel and diesel fuel activities

Diesel emissions are significant issue worldwide, and emissions requirements have become so tough that. the application of after-treatment systems is now indispensable in many countries To meet even more stringent future emissions requirements, it has become apparent that the improvement of market fuel quality is essential as well as the development in engine and exhaust after-treatment technology. Japan Clean Air Program II (JCAP II) is being conducted to assess the direction of future technologies through the evaluation of current automobile and fuel technologies and consequently to realize near zero emissions and carbon dioxide (CO₂) emission reduction. In this program, effects of fuel properties on the performance of diesel engines and a vehicle equipped with two types of diesel NOx emission after-treatment devices, a Urea-SCR system and a NOx storage reduction (NSR) catalyst system, were examined. These engines and a vehicle were equipped with DPF, sophisticated electronic control for fuel injection, turbo-charging and cooled EGR system. Fuel properties include sulfur level, distillation characteristics, and aromatic content. For an NSR catalyst system, the effect of fuel properties on both emissions and fuel economy during around 50,000 km driving was examined. The results show that sulfur is what most influences the performance of NSR device. The mechanism of catalyst deterioration caused by sulfur is analyzed using NOx storage capacity measurement and the results indicate the deterioration is closely related to thermal aging during desulfation process. Both engine-out and tail-pipe emissions are measured and compared for the engines. The results indicate that other fuel properties influence both combustion and the conversion performance of after-treatment devices.