Alois Danninger

Limits for NOx Reduction by EGR in a Heavy Duty Diesel Engine at Stationary and Transient Conditions

Exhaust gas recirculation (EGR) is an effective engine internal measure to reduce NOx emissions. This is e.g. constituted by the fact that the NOx limit of the current European on-road emission regulation EURO V can be met exclusively by the application of EGR (an overview on emissions regulations is e.g. given in [1]). However, the proposed NOx limits for the upcoming regulations have been lowered significantly which implicates much higher EGR rates compared to the EURO V applications if this strategy is further pursued. This is valid for both the future on-road regulation (EURO VI) and the off-road regulation (Stage IV). In this paper main focus is laid on off-road applications.One of the main challenges of this task refers to transient engine operation which also requires EGR. Thus, great demands are made to the design and calibration of the charging system in order to guarantee acceptable load response characteristics during the acceleration phases.An experimental study was carried out with a modified EURO V heavy duty engine which was operated in an engine test cell under stationary and transient conditions with various engine settings. These primarily referred to the EGR rate and smoke limitations during transient operation. In this way the NOx, soot and load response characteristics were systematically investigated. With the used test engine the NOx emissions could not be lowered below a level of approximately 0.6 g/kWh in the Non-Road Transient Test Cycle (NRTC) [1] without a significant deterioration in load response (for comparison — the proposed Stage IV NOx limit is 0.4 g/kWh in the NRTC).Copyright

Online calculation of diesel engine torque dynamics

In current vehicles the actual value of engine torque is provided as interface signal to powertrain control units. For transient operation the dynamic behaviour of the combustion engine has to be estimated e.g. in the transmission control unit in order to coordinate the powertrain components. Due to the lack of provided data on the dynamic behaviour it needs to be modelled separately in each control unit, mainly map-based with high calibration effort. The engine control unit (ECU) has access to the relevant sensor and reference values for online calculation of diesel engine dynamics. Within this publication a model-based online torque calculation is proposed taking into account information that is already available in standard ECUs. Additionally the current torque reserve is computed. The calculation of characteristic parameters defining the dynamic behaviour for torque requests is outlined. Based on these signals prediction of engine dynamics is simplified and can significantly reduce the calibration effort e.g. in transmission control unit. The presented paper describes the calculation method and compares simulation results to engine test bed measurements for validation.