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Abstract |
Cylinder Pressure and Ionization Current Modeling for Spark Ignited Engines
Engine management systems (EMS) need feedback on combustion performance to
optimally control internal combustion engines. Ion sensing is one of
the cheapest and most simple methods for monitoring the combustion
event in a spark ignited engine, but still the physical processes
behind the formation of the ionization current are not fully understood. The goal here is to investigate models for ionization currents and
make a connection to combustion pressure and temperature. A model for
the thermal part of an ionization signal is presented that connects
the ionization current to cylinder pressure and temperature. One
strength of the model is that it after calibration has only two free
parameters, burn angle and initial kernel temperature. By fitting the
model to a measured ionization signal it is possible to estimate both
cylinder pressure and temperature, where the pressure is estimated
with good accuracy. The parameterized ionization current model is
composed by four parts; a thermal ionization model, a model for
formation of nitric oxide, a combustion temperature model and a
cylinder pressure function. The pressure function is an empirical
function design where the parameters have physical meaning and the
function has the main properties of a solution to the cylinder
pressure differential equations. The sensitivity of the ionization
current model to combustion temperature and content of nitric oxide is
investigated to understand the need of sub-model complexity. Two main results are that the pressure model itself well captures the
behavior of the cylinder pressure, and that the parameterized
ionization current model can be used with an ionization current as
input and work as a virtual cylinder pressure sensor and a combustion
analysis tool. This ionization current model not only describes the
connection between the ionization current and the combustion process,
it also offers new possibilities for EMS to control the internal
combustion engine.
Ingemar Andersson
2002
Informationsansvarig: webmaster
Senast uppdaterad: 2021-11-10
