Modelling of a Variable Venturi in a Heavy Duty Diesel Engine
The objectives in this thesis are to present a model of a variable venturi in an exhaust gas
recirculation (EGR) system located in a heavy duty diesel engine. A new legislation called
EURO~4 will come into force in 2005 which affects truck development and it will require an
On-Board Diagnostic system in the truck. If model based diagnostic systems are to be used,
one of the advantages is that the system performance will increase if a model of a variable
venturi is used.
Three models with different complexity are compared in ten different experiments. The
experiments are performed in a steady flow rig at different percentage of EGR gases and
venturi areas. The model predicts the mass flow through the venturi. The results show that the
first model with fewer simplifications performs better and has fewer errors than the other two
models. The simplifications that differ between the models are initial velocity before the
venturi and the assumption of incompressible flow.
The model that shows the best result is not proposed by known literature in this area of
knowledge and technology. This thesis shows that further studies and work on this model, the
model with fewer simplifications, can be advantageous.
Carl-Adam Torbjörnsson
2002
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