Modelling, effect and behaviour of the EGR venturi in a heavy-duty diesel engine

The objective of this work is to make an analysis of the behaviour of the venturi in real working conditions. The modelling of the venturi, as well as the experimental and modelled results obtained, will be described. Modelled and measured techniques have been used to realize this work. A new model of the venturi was developed and using this, it is possible to find important instantaneous variables of the venturi. In order to adjust the calculated model, it was necessary to characterise the steady flow test rig of the venturi. In addition, the information obtained from the engine tests has been essential to correctly adjust the model. Therefore, a combination of the information obtained from both the venturi test and from modelled work was necessary in order to understand the behaviour of the venturi installed in an engine. Different tests have been performed on each venturi. This singular device has been tested while installed in an engine that has a real pulsating flow, while other tests of the venturi have been performed in a test flow rig. Relevant variables which have been measured, are the pressures at the inlet, at the throat of the venturi and at one point downstream of it. Additionally, a theoretical calculation has been carried out, focusing on the gas evolution through the venturi. Thus, the pressure loss parameters for different parts of the venturi, such as the converging part or the EGR junction in the venturi, have been obtained. Normally, the flow is pulsating in the engine manifolds and so the response of the venturi is of special interest when it is used to produce an EGR pulsating mass flow. This response influences the EGR production and, of course, the characteristics of the venturi, such as the pressures loss parameters, which are very important for correctly modelling the venturi. Copyright © 2001 SAE International and Messe Düsseldorf.