Time-domain modelling of turbo-compressors in direct injection diesel engines

Abstract

In this paper, the development and validation of a new turbo-compressor model for one-dimensional flow modelling in intake systems of turbocharged internal-combustion engines are presented. The proposed model is based, as usual, on data contained in the turbo-compressor operating chart. However, whereas in the usual models the turbo-compressor is simply considered as a quasi-steady boundary condition to a pipe, here it is regarded as consisting of two cavities, simulating the rotor and the stator, with the compressor chart imposed as a boundary condition between them. This simple solution gives the possibility of computing the flow upstream of the turbo-compressor, which is not straightforward with the usual models. The proposed model has been validated against experimental tests performed on an engine test bench. Two different turbo-compressors were considered, for automotive and truck application respectively. Instead of the direct comparison between calculated and measured instantaneous pressures shown in most of the literature on one-dimensional flow modelling, here the validation methodology is based on the consideration of pressure components (forward and backward waves), as usual in the acoustic literature. These components may be obtained from multiple sensor measurements and their use for model validation is equivalent to the consideration of flow velocity additionally to pressure.