Operational ranges of compressors are limited when running at low mass flow. In particular, large pressure fluctuations occur when reaching surge that can cause rapid deterioration of the bearing system and considerably increase the level of noise. In order to extent the operability of their turbochargers, Honeywell equipped its compressor housings with ported shrouds located at the inlet. The ported shroud has been demonstrated to allow a larger range of operability with minor negative impact on the compressor efficiency.
In a collaborative work between Honeywell and the University of Cincinnati, a turbocharger bench facility was designed and tested. The size of the compressor was typical for a turbocharger used on diesel engines. The goal of the experimental study was to develop better understanding of the flow dynamic in the compressor housing that affects stall and surge for different operating conditions. This was possible performing dynamic pressure measurements at the inlet and outlet of the compressor. Several operational points were studied permitting to identify three different phenomena. At normal working, both 2D and stereoscopic Particle Imaging Velocimetry (PIV) measurements of the instantaneous and mean velocity field were performed. At incipient and full surge, phase-locked PIV measurements were added.
In this paper, satisfactory characterization of the compressor instabilities was achieved. Specific behavior of the surge was studied at different pressure ratios. Early detection of surge was demonstrated combining both the frequency domain and the statistical temporal analysis. PIV measurements allowed the characterization of complex flow interactions at the entrance of the compressor in surge and the validation of computational fluid dynamics results at stable regime, for this specific model of turbocharger.