Innovative Concept in Diesel Low Load Emission Compliance for EU7 and Beyond

Authors

Dr. M. Elicker, Dr. M. Scheidt, Schaeffler Technologies AG & Co. KG, Herzogenaurach;
Dr. M. Brauer, R. Pohlke, Dr. K. Hielscher, IAV GmbH, Berlin;
J. Geddes, J. Kiyanni, Jaguar Land Rover Ltd., Coventry

Year

2020

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 813

Summary

This paper describes the potential of an innovative valve lift strategy for exhaust gas temperature management on Jaguar Land Rover’s AJ200D EU6d compliant an in-line four-cylinder diesel engine.
In contrast to the frequently investigated variability for internal exhaust gas recirculation, the innovative valve lift strategy is mainly based on an intake-side variability for throttle-free reduction of the cylinder charge. The variable valve control was realised by the eRocker system with switchable
roller finger followers from Schaeffler Technologies AG und Co KG.
In the first step, the valve lift strategies were designed with the aid of 1D simulation. The variability on the intake side was realised by an early intake valve closing, also known as "Miller cycle". The use of the exhaust valve's secondary lift enables internal exhaust gas recirculation. Under the given boundary conditions, the combination of two different secondary exhaust valve lifts with 1.5 mm and
0.9 mm secondary lift height and an intake valve lift with 90 °CA opening duration turned out to be suitable. The simulation shows a considerable potential for raising the exhaust gas temperature and thereby significantly reducing fuel consumption compared to conventional heating measures.
In the second step, the eRocker system was integrated into an AJ200D diesel engine. The potential for exhaust gas temperature management was experimentally investigated on the engine test bench within a temperature range of -7 °C to 90 °C.
• At an engine coolant and oil temperature of 90 °C ("engine temperature"), the early intake valve closing allowed a reduction in fuel consumption to a certain extent below the level of the reference point without heating measures, while significantly increasing the exhaust gas temperature at the same time. Compared to conventional heating measures, a benefit in fuel consumption up to 8 % was achieved with acceptable HC and CO emissions.
• At an engine temperature of 20 °C the strategy with early intake valve closure, used in addition to internal exhaust gas recirculation, did not lead to any further benefit in fuel consumption. It rather caused unstable combustion with a low fuel conversion factor, which led to high HC and CO emissions. In contrast, the strategy with internal exhaust gas recirculation without an early intake valve closure showed a benefit in fuel consumption of up to 11 % compared with the conventional heating strategy, whilst keeping HC and CO emissions unchanged.
• An operation at -7 °C engine temperature (by forced cooling of the oil and coolant) generally leads to poor ignition conditions in the combustion chamber. For this reason an operation with early intake valve closing was not possible. The use of internal exhaust gas recirculation increased combustion stability with reduced CO and HC emissions and achieved a benefit in fuel consumption of up to 9 % compared to conventional heating strategies.
The results of the engine test bench measurements confirmed the findings originally found in the simulation phase of the project. The valve lift configuration designed in the simulation proved to be effective in real world engine operation, whereby high exhaust gas temperatures and significant advantages in fuel consumption were achieved. Additionally potentials to reduce raw engine-out
emissions were also confirmed.