13 September 2007
Ricardo announced that it has achieved Tier 2 Bin 5 emissions without the use of NOx aftertreatment. This milestone was demonstrated with a prototype automotive diesel engine on a test bed. The research continues with the aim of demonstrating clean diesel technology capable of achieving California Super Ultra-Low Emission (SULEV) and the equivalent US EPA Tier 2 Bin 2 requirements. Such an advanced diesel would be positioned alongside gasoline hybrid and fuel cell powered vehicles as future high fuel-economy, environmentally friendly automotive product, said Ricardo.
The prototype engine, developed as part of Ricardo’s ACTION (Advanced Combustion Technology to Improve engine-Out NOx) research, incorporates such technologies as advanced air handling systems, two-stage series-sequential turbocharging, advanced exhaust gas recirculation, and closed-loop cylinder pressure-based engine controls. The aftertreatment system in the Tier 2 Bin 5 engine includes a diesel oxidation catalyst (DOC) and diesel particulate filter (DPF). Ricardo believes that Tier 2 Bin 2/Cal SULEV emissions will be achieved by adding a NOx adsorber catalyst to the system.
A major emphasis has been placed on achieving low emissions under transient conditions to maintain or improve the engine responsiveness without deteriorating emissions performance. The engine has been developed with a competitive power rating of 65 kW/l to meet US emission regulations for both sea level and altitude compliance.
Having demonstrated the performance on the test bed, the powertrain has now been installed in a test vehicle to enable calibration refinement and validation. In the coming months Ricardo intends to carry out vehicle testing to validate the achievement of SULEV/Tier 2 Bin 2.
Ultra-low engine-out NOx levels can be achieved through premixed, low-temperature combustion strategies, with high ratios of exhaust gas recirculation. These strategies become possible through advanced closed-loop combustion control. However, a number of issues still need to be resolved, including increased CO and HC emissions at very low temperatures, fuel economy, and increased noise.