Switchable dual-port casing treatment scheme for an enhanced turbocharger compressor operating range

For both diesel and gasoline internal-combustion engines, stringent emissions regulations and fuel economy requirements have significantly intensified the demand on the turbocharger compressor operating flow range with high efficiency levels. To address these needs, the ongoing research and development effort has been focused on advanced turbocharger technologies for a high efficiency and a wide operating range. In this paper, a research effort is reported to enhance further the classic ported shroud or recirculating casing treatment with the addition of two switchable ports along the impeller shroud, which allows an augmented high-speed choke flow range without sacrificing the surge margin and efficiency. Impeller aerodynamic blade design considerations for exploiting this new dual-port casing treatment concept are discussed. Flow bench test results demonstrate that the underlying concepts of the new dual-port casing treatment implemented with a recently developed advanced centrifugal compressor impeller lead to 12% extra flow capacity at the rated speed over the same compressor with a conventional single-port recirculating casing treatment.