Abstract
The gas exchange influences to a large extent power, emissions and fuel consumption of internal combustion engines.
The analysis and optimization of the gas exchange is of
primary importance and will become more so with the new
homogeneous combustion utilizing high degrees of exhaust
gas recirculation (EGR).
Low pressure measurement using piezoresistive absolute
pressure sensors has become an important tool for the design
and optimization of the gas exchange, for the analysis of
process variables and for simulation validation. The advantages of an absolute pressure measurement are the high
precision (including dynamics) and the ability to resolve the
pressure differences between cylinders and single cycles.
Capturing both the dynamic behaviour and an exact pressure
level are critical for low pressure calculations, with new miniaturized piezoresistive pressure sensors installation is possible
directly into the cylinder head to enable this. A sensor position near the valve is most suitable as the effort for modelling
the system is reduced. In the exhaust manifold however, a
cooling adapter will be necessary unless the sensor is installed
directly in the cylinder head.
The utilization of a cooled switching adapter allows a precise
zero point correction of the piezoresistive pressure sensor,
therefore a reference precision (±1 mbar) can be achieved in
any operating condition.
Low pressure indication using a piezoelectric sensor and
pneumatic pressure measurement (remote sensing system)
is not recommended to evaluate the absolute pressure in the
exhaust.