Adaptive feedforward control of exhaust recirculation in large diesel engines
Environmental concern has led the International Maritime Organization to
restrict NOx emissions from marine diesel engines. Exhaust gas recirculation
(EGR) systems have been introduced in order to comply to the new
standards. Traditional fixed-gain feedback methods are not able to control
the EGR system adequately in engine loading transients so alternative
methods are needed. This paper presents the design, convergence proofs and
experimental validation of an adaptive feedforward controller that
significantly improves the performance in loading transients. First the
control concept is generalized to a class of first order Hammerstein systems
with sensor delay and exponentially converging bounds of the control error
are proven analytically. It is then shown how to apply the method to the EGR
system of a two-stroke crosshead diesel engine. The controller is validated
by closed loop simulation with a mean-value engine model, on an engine test
bed and on a vessel operating at sea. A significant reduction of smoke
formation during loading transients is observed both visually and with an
opacity sensor.
Kr\aen Nielsen, Mogens Blanke, Lars Eriksson and Morten Vejlgaard-Laursen
Control Engineering Practice,
2017
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