Variable Inlet Bypass for Efficient Wide Flow Range Turbocharger Compressor

Increased use of Exhaust Gas Recirculation (EGR) combined with engine downsizing has pushed automotive turbocharger compressor operation towards and often beyond its efficient and stable operating boundaries. Much of the drive cycle is spent operating the compressor at low flow rates and low pressure ratios, near the compressor surge line, in an area which is usually of low efficiency. Our preliminary assessment, based on a critical review of previously proposed solutions guided by skillful deployment of advanced compressor aerodynamics, along with considerations for proper matching of turbine and compressor operation in the turbocharger, has led us to conceive of a single -shaft and single-stage Variable Bypass Centrifugal Compressor (VBCC) with the potential to efficiently widen the stable operating range of a turbocharger without the complexities of a dual sequential turbocharging scheme. Our VBCC consists of a separate axial inducer aerodynamically matched to a centrifugal impeller with vaneless diffuser/volute housing. The singular innovation herein is the variable bypass feature implemented with a partial-height VIGV and meridionally split axial inducer. As the compressor is throttled at part-load, the VIGV can be set such that the pumping characteristics of the outer fractional part of the flow path can be regulated in such a way that more of the bulk flow is bypassed towards the healthier inner part of the flow path. We are proposing an R & amp;D project whose overall objective is to advance and demonstrate efficient wide operating range VBCC technology to the level where, when integrated analytically within an advanced automotive turbocharger application, a potential for 3% reduction in fuel consumption for the FTP cycle shall be provided, with associated transient response and cost benefits. The advanced developments required for the solution proposed herein are expected to have far -reaching applications for numerous turbocharged engine applications, including both Diesel and gasoline engines, where fuel efficiency, transient response, and affordability are important. Benefiting from the availability of advanced computational tools, component test capabilities, and the unsurpassed turbomachinery technology expertise of Concepts NREC (CN), the three-phase effort envisioned herein provides a balanced research and development approach to a successful efficient and operationally flexible high-boost pressure turbocharger.