Turbocharger Centrifugal Compressor Casing Treatment for Improved BPF Noise Using Computational Fluid Dynamics
The conventional ported shroud recirculation casing treatment elevates narrowband noise at blade pass frequency. A new ported shroud recirculating casing treatment implemented, in Ford’s 3.5L turbo gas engine, as NVH (Noise Vibration and Harshness) counter measure to reduce whoosh (broadband flow noise) noise without elevating narrowband noise at blade pass frequency. The new ported shroud recirculating casing treatment, with holes between the main and secondary recirculating passage, and a slight cross-sectional area reduction just upstream of the impeller, designed to reduce whoosh noise without elevating sub-synchronous (first order) and synchronous (sixth order) tonal noise at blade pass frequency. The new ported shroud casing treatment design decreased narrowband tonal noise sound pressure level by 3-6 dB in the low to mid flow region compared to the baseline design. Computational Fluid Dynamics (CFD) tools was used to develop this casing treatment design.