Estimation of the EGR rate in a GDI engine working in stratified mode using the ionization current
The goal of this thesis is to get a feedback from the cylinder of
the amount of Exhaust Gas Recirculation (EGR) being used. To get
the feedback the in-cylinder measurement technique of measuring
the ionization current is used. The ion current signal is analyzed
to extract the information about the amount of exhaust gas in the
cylinder.
Two basically different methods are used for estimating the EGR
rate. The first method is based only on general knowledge of how
the EGR rate affects the ion current signal. The second method is
based upon the physics of the combustion process.
In the first method two different filters are tested, a static
Kalman filter and a dynamic Kalman filter. The first filter
produces the best results. With this filter an accurate estimation
of the EGR rate is reached within 40 cycles. The dynamic filter is developed
in an attempt to get a faster estimation. But using this filter no acceptable
results are reached. The faster estimation makes it so that the output never
stabilizes on one value.
For the physically based approach the speed of the flame and the
speed with which the flame kernel expands through the cylinder are
studied. It is shown that the laminar burning speed of the flame
would prove to be a good way of estimating the EGR rate if a
physical connection between the ionization signal and the laminar
burning speed of the flame speed could be found. No such
connection is found in this thesis and thus no estimation of the
EGR rate can be made using this method.
Mattias Bruce
2000
Informationsansvarig: webmaster
Senast uppdaterad: 2021-11-10
LiU Homepage
