US Patent 7571608 Turbocharged engine system and method of operation

A system is provided. The system includes an internal combustion engine having an intake manifold and an exhaust manifold. The system also includes a high pressure turbocharger having a variable geometry high pressure turbine drivingly coupled to a high pressure compressor, wherein the variable geometry high pressure turbine is driven by a first portion of exhaust gases from the exhaust manifold, wherein the high pressure compressor is configured to compress an intake air and to provide the compressed intake air to the intake manifold. The system also includes a low pressure turbocharger having a variable geometry low pressure turbine drivingly coupled to a low pressure compressor, wherein the variable geometry low pressure turbine is driven by a second portion of the exhaust gases from the exhaust manifold, wherein the low pressure compressor is configured to compress a third portion of the exhaust gases from the exhaust manifold and to provide the compressed third portion to the intake manifold, wherein the first and second portions of the exhaust gases are different from one another.