As emission regulations are becoming increasingly stringent worldwide, multiple exhaust aftertreatment devices are considered in order to minimize diesel engine tailpipe emissions. For the typical diesel applications in developing markets like India, the fuel consumption is a very decisive selling argument for customers. The total cost of ownership needs to be as low as possible. To meet these competing requirements, the aftertreatment and engines must be optimized at the same time as the performance of the one system affects the other.
In state-of-the-art calibration processes, the aftertreatment systems are considered separately from the calibration of the thermodynamics. This conventional approach makes it more challenging to achieve a simultaneous optimization of the fuel consumption and tailpipe emissions under transient operating conditions. In addition, the final operation is significantly affected by the gear shifting profile, defined by diverse rules in the case of manual transmission vehicles; while defined by a calibrated shifting strategy in the case of automatic ones.
To meet this goal, a longitudinal simulation approach is developed by FEV GmbH, which enables a simultaneous optimization of the multiple subsystems considering engine thermodynamic, controls, transmission system, gear shifting strategy and exhaust aftertreatment.
With this approach, the optimization parameters can be chosen freely e.g. air and fuel path controls for different engine modes, gear shifting strategy, vehicle inertia class, aftertreatment system design such as size, the PGM loading and the catalyst formulation.
The results indicate that BS V emission norms could be met with the application of a DPF, however for BS VI the use of deNOx aftertreatment systems will probably be mandatory for standard diesel vehicles. Lean NOx Trap (LNT) systems would enable to meet the limits, while SCR coated DPF (SDPF) approach would allow to increase the engineering margin while still improving the fuel economy. The total fuel consumption reduction will depend on the introduction of further new technologies such as split cooling, or even Low Pressure EGR (LPEGR).