The variety of increasingly complex powertrains including Plug-In
Hybrid Electric Vehicles (PHEVs) is associated with a number of
challenges to measure exhaust gas emissions: Although the
conventional constant volume sampling (CVS) and exhaust gas
measurement systems remain a high precision emission
measurement concept new questions occur that need to be
answered, such as mass transport, catalyst cooling during ICE-off
and emission measurement accuracy.
Mass transport of exhaust emissions from the transfer tube into the
dilution tunnel during engine-off complicates phase assignment. This
includes the investigation of the physical processes that are diffusion
on basis of concentration differences, extraction due to the CVS
underpressure and convection because of density diversities.
Catalyst cooling will be investigated using a temperature sensor
positioned at the oxy catalyst of a Diesel-PHEV. This involves
analyzing the catalyst temperature change during engine-off phases
and evaluating the emission of pollutants after the engine restarts
during a driving cycle.
Emission measurement accuracy is influenced since PHEV are
partially operated with the electric motor during a driving cycle, or
switched off while idling. Therefore concentrations of gaseous
components in the diluted exhaust batches are decreasing, which
causes an increase in analysis error. In order to reduce measurement
errors an alternative measurement procedure “During Test Top Off”
(DTTO) has been developed: with this procedure the batches are only
filled when the combustion engine is operated - or near the end of a
driving cycle to sample enough batch volume for an accurate
analyzer reading. The results will show if this alternative procedure
can improve measurement errors and thus complies with the error
limits of the European emission regulations.
«
The variety of increasingly complex powertrains including Plug-In
Hybrid Electric Vehicles (PHEVs) is associated with a number of
challenges to measure exhaust gas emissions: Although the
conventional constant volume sampling (CVS) and exhaust gas
measurement systems remain a high precision emission
measurement concept new questions occur that need to be
answered, such as mass transport, catalyst cooling during ICE-off
and emission measurement accuracy.
Mass transport of exhaust emission...
»