Case study: An experimental noise reduction study of an extended flow range automotive turbocharger centrifugal compressor

A new turbocharger compressor was designed to reduce noise at the compressor inlet, while allowing peak engine torque and power to be increased by 28% and 29%, respectively, relative to the previous generation (baseline) production engine with identical displacement. Experimental compressor performance and acoustic results were presented for three incremental changes, in order to isolate the impact of individual design features. The new larger impeller with reworked aerodynamics increased the SPL of mid flow range whoosh noise, relative to the baseline compressor. Adding a ported shroud to the new impeller reduced the maximum whoosh noise level below that of the baseline design, but significantly elevated narrowband noise at the blade-pass frequency. The final new compressor design featured the larger impeller with reworked aerodynamics, a ported shroud recirculating casing treatment, holes between the main and secondary recirculation passage, and a slight cross-sectional area reduction just upstream of the impeller. This final configuration decreased overall SPL by 3â–“6 dB(A) in the low to mid flow region, where it was elevated for the baseline compressor. The maximum flow rate of the new compressor increased significantly, and the flow rate at the deep surge boundary increased slightly. Relative to the baseline design, the efficiency of the new compressor was up to 8 percentage points lower at the low flow boundary and up to 18 percentage points higher at elevated flow rates.