Modeling of a Diesel Engine with Intake Throttle, VGT, and EGR
A mean value model of a diesel engine with intake throttle, VGT, and EGR is
developed, parameterized, and validated. The intended model applications are
system analysis, simulation, and development of model-based control systems.
The goal is to construct a model that describes the gas flow dynamics
includ- ing the dynamics in the intercooler pressure, manifold pressures,
turbocharger, EGR, and actuators with few states in order to have short
simulation times. An investigation of model complexity and descriptive
capabilities is performed, resulting in a model that has only eleven
states. To tune and validate the model, stationary and dynamic measurements
have been performed in an engine labo- ratory at Scania CV AB. All the model
parameters are estimated automatically using weighted least squares
optimization of both the sub-models and the com- plete model.
Dynamic measurements and simulations show that the proposed model cap- tures
the essential system properties, i.e. non-minimum phase behaviors, over-
shoots, and sign reversals. Validations of the entire model show that the
mean value of all absolute relative errors for all measured outputs are
equal to 7.4%.
A system analysis of the proposed model is performed in order to obtain
insight into a VGT and EGR control problem where the goal is to control the
performance variables oxygen fuel ratio lambdaO and EGR-fraction xegr. Step
responses over the entire operating region show that the channels VGT to
lambdaO, EGR to lambdaO, and VGT to xegr have sign reversals.
Johan Wahlström and Lars Eriksson
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Last updated: 2021-11-10