Control-Oriented Compressor Model with Adiabatic Efficiency Extrapolation
Downsizing and turbocharging with single or multiple stages
has been one of the main solutions to decrease fuel consumption
and harmful exhaust emissions, while keeping a sufficient
power output. An accurate and reliable control-oriented compressor
model can be very helpful during the development phase,
as well as for engine calibration, control design, diagnostic purposes
or observer design. A complete compressor model consisting
of mass flow and efficiency models is developed and
motivated. The proposed model is not only able to represent
accurately the normal region measured in a compressor map
but also it is capable to extrapolate to low compressor speeds.
Moreover, the efficiency extrapolation is studied by analyzing
the known problem with heat transfer from the hot turbine side,
which introduces errors in the measurements done in standard
gas stands. Since the parameterization of the model is an important
and necessary step in the modeling, a tailored parameterization
approach is presented based on Total Least Squares.
A standard compressor map is the only data required to parameterize
the model. The parameterization is tested with a
database of more than 230 compressor maps showing that it can
deal well with different compressor sizes and characteristics.
Also, general initialization values for the model parameters are
provided using the complete database parameterization results.
The results show that the model accuracy is good and in general
achieves relative errors below one percent. A comparison of
the model accuracy for compressor maps with and without heat
transfer influence is carried out, showing a similar model accuracy
for both cases but better when no heat transfer is present.
Furthermore, it is shown that the model is capable to predict the
efficiency characteristics at low speed of two compressor maps,
measured with near adiabatic conditions.
Xavier Llamas and Lars Eriksson
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Last updated: 2019-08-05