LiU Homepage
Abstract |
Spark Advance Modeling and Control
One possible measurement is the in-cylinder pressure, which gives the torque,
but also contains important information about the combustion. The cylinder
pressure can accurately be modeled using well known single-zone thermodynamic
models which include the loss mechanisms of heat transfer and crevice flows. A
systematic procedure for identifying heat-release model parameters is presented.
Three well-known combustion descriptors have been presented in the literature
that relate the phasing of the pressure signal to the optimal ignition timing. A
parametric study was performed showing how changes in model parameters influence
the combustion descriptors at optimum ignition timing.
Another possible measurement is the ionization current that uses the spark
plug as a sensor, when it is not used for ignition. This is a direct in-cylinder
measurement which is rich in information about the combustion. A novel approach
to spark-advance control is presented, which uses the ionization current as a
sensed variable. The feedback control scheme is closely related to schemes based
on in-cylinder pressure measurements, that earlier have reported good results. A
key idea in this approach is to fit a model to the measured ionization current
signal, and extract information about the peak pressure position from the model
parameters.
The control strategy is validated on an SI production engine, demonstrating
that the spark-advance controller based on ionization current interpretation can
control the peak pressure position to desired positions. A new method to
increase engine efficiency is presented, by using the closed-loop spark-advance
control strategy in combination with active water injection. However, the major
result is that the controller maintains an optimal spark advance under various
conditions and in the presence of environmental disturbances such as air
humidity.
Lars Eriksson
1999
Informationsansvarig: webmaster
Senast uppdaterad: 2021-11-10
