Measurement and Modeling of Compressor Surge on Engine Test Bench for Different Intake Line Configurations

Surge occurrence in automotive engine turbochargers is known to be dependent on the installation conditions. It is proven that the flow pattern produced by the inlet ducting at the compressor inducer modifies surge margin. But also the engine intake line acoustics, both compressor upstream and downstream, affects turbocharger surge. In the paper the effect of different parameters in the intake line geometry on compressor surge is investigated. Modifications in the air filter volume, compressor inlet geometry and compressor outlet length have been considered. Surge limit obtained on a steady gas-stand is compared to those measured on the engine test bench using two different methodologies. Testing results show significant differences in term of surge line shift and the corresponding engine low end torque.

A 1D model of the engine has been built using a non-steady compressor model able to predict surge occurrence. This model is based on the Greitzer's lumped model and uses the steady flow map extended to the surge and negative flow zones. In the paper some results of the model are presented showing the difficulty of predicting surge limit in engine steady conditions.