This thesis focuses on surge phenomenon in centrifugal compressor turbocharger, designed to boost automotive internal combustion engine. A study has been made of the current state of the art in engine supercharging. So determined, among others reasons, was that surge phenomenon is relevant today because of the trend of engine downsizing, therefore increasing the demand for higher boost pressures.
Test methods have been developed to study surge phenomenon in engine boost systems. One proposal is a technique to cause controlled surge in an engine test bench, which involves the injection of air into the engine intake manifold. This allows taking into consideration the actual conditions of operation of the intake air management group. A method of spectral analysis of the measured parameters has also been proposed in order to precisely identify and determine the onset of surge phenomenon. The engine transient tests have also been a relevant part, showing good agreement with the air injection method.
Aside from the experimental study, computer simulation has been used. One-dimensional simulation using a pressure wave action model, allowed the representation of surge phenomenon with good experimental agreement. Furthermore, three-dimensional Computational Fluid-Dynamics simulation [CFD/URANS (Unsteady Reynolds Average Navier-Stokes)], was used to study the flow patterns developed in a centrifugal compressor, which has assisted understanding of the aerodynamic factors involved.
Based on the experimental and modeling tools developed, an extensive campaign was performed to study surge phenomenon. A synthesis is present of experimental and modeling work for evaluating the performance of different supercharger circuit configurations. Of particular interest were proposed compressor inlet component geometries, which help in improving surge phenomenon margin. The effect of pulsating flow generated by the engine on the surge limit has also been studied.