Experimental investigations of variable valve trains in combination with a second opening of an exhaust valve in partial load operation of a passenger car single-cylinder diesel engine

A manipulation of the charge exchange allows controlling the amount of residual gas during
engine warm-up. The residual gas during the warm-up phase leads to an increase of the exhaust gas
temperature and supports to reach the exhaust aftertreatment system operating temperature faster. In
addition, the warm residual gas increases the combustion chamber temperature, which reduces the
HC and CO emissions. However, fuel consumption increases. For that reason, such heating measures
should be the best compromise of both, exhaust gas temperature increase and engine efficiency in
order to provide efficient heating strategies for passenger car diesel engines.
With the aim to determine efficient heating measures for passenger car diesel engines by a valve train
manipulation, simulative and experimental investigations are carried out as part of a research project
at the Institute of Internal Combustion Engines of the Karlsruhe Institute of Technology to establish a
reliable cam design methodology.
For the experimental investigations a modern research single-cylinder diesel engine was set up on a
test bench. Additionally, a 1-D simulation model of the experimental setup was created in order to
... mehr
simulate characteristics of valve lift curves and to investigate their effects on the exhaust gas tempera-
ture and the exhaust gas enthalpy. These simulations were based on statistical experimental design
(DoE), so that all characteristics can be used sustainably for modeling and explaining their influences
on the engine operation. This methodology allows to numerically investigate promising configurations
which may also include a second opening of an exhaust or intake valve (2nd event). Subsequently,
suitable configurations were transferred to cam contours which were manufactured and experimentally
tested. To assess the potential of these individual configurations, the results obtained were compared
with each other as well as with the series configuration.
Results show that the combination of DoE and 1-D simulation for the design of camshaft contours is
well suited which was also validated with experimental results. Furthermore, the potential of residual
gas retention by favourable configurations with a 2nd event already revealed in various publications
could be confirmed with respect to exhaust gas temperature increase and engine efficiency.