Herwig Ofner

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

Potential of Dimethylether as an alternative Diesel fuel for a CO 2 sustainable powertrain solution

Worldwide, combustion engines will remain as major power unit for vehicle propulsion in long-term. Consequently, immediate measures are claimed to reduce the current CO2 production from combustion engines which are accomplished by three approaches: (1) an increase of the thermal efficiency, (2) the application of fuels with low carbon content and (3) the production of fuels from renewable feedstocks. The first aspect clearly emphasizes compression ignition (CI) engines, the second aspect draws the attention to hydrogen and single C-bonded fuels and the third aspect has initiated sensitive discussions about renewable resources which lead to the commitments of first/ second/ third generation biofuels. In this context, the use of Ethers as neat or blended fuels for combustion engines has been discussed for more than 20 years. Among these, the simplest compound, Dimethylether CH3-O-CH3 (DME), has an exceptional position as a neat fuel for compression ignition (CI) engines due to its excellent ignition and combustion properties which have been well investigated published by many authors.

Neue Technologien für Verbrennung – Ladungswechsel – Mechanik – Einspritzung

The development of commercial vehicle on-road applications, such as long haul trucks or busses, is driven by the optimization of the total cost of ownership (TCO) which relates the initial product cost with operating cost. Long haul truck applications have high annual mileage at high engine loads. Thus the operating costs dominate the total cost of ownership. Consequently lowest possible fuel consumption is one of the major drivers for long haul truck applications all over the world.