System for thermal management of engine exhaust

A method for controlling a temperature of exhaust gases entering a Selective Catalytic Reduction (SCR) system for an engine, comprising:

• delivering pressurized air into the exhaust gases upstream of the SCR system, the pressurized air cooled by an air cooler;
• and
• adjusting a degree of pressurization by adjusting operation of a turbocharger pressurizing the pressurized air, wherein delivering the pressurized air into the exhaust gases further comprises injecting the pressurized air into the exhaust gases in response to the temperature of the exhaust gases increasing above a peak efficiency threshold temperature, the method further comprising controlling the injecting of the pressurized air into the exhaust gases via an exhaust gas dilution valve disposed on an exhaust line downstream of the air cooler, wherein the turbocharger is a primary turbocharger of the engine, and the pressurized air is pressurized by an engine air intake compressor of the primary turbocharger, the engine air intake compressor routing the pressurized air through a primary charge air cooler to both of an intake manifold of the engine and the SCR system, wherein the air cooler is a secondary charge air cooler different from the primary charge air cooler, and the method further comprising pressurizing the pressurized air injected into the exhaust gases via a dilution compressor of a secondary exhaust gas dilution turbocharger, the dilution compressor coupled to a dilution turbine of the exhaust gas dilution turbocharger, the dilution turbine positioned downstream of a primary exhaust turbine of the primary turbocharger, the primary exhaust turbine driving the engine air intake compressor and the dilution turbine driving the dilution compressor.

An engine system, comprising:

• an exhaust gas dilution turbocharger disposed on an exhaust passage of an engine of the engine system, the exhaust gas dilution turbocharger comprising a dilution compressor and a dilution turbine coupled to the dilution compressor;
• and
• a controller including a processor and instructions stored in a memory of the controller that when executed cause the controller to:
• prior to routing exhaust gases of the engine into a Selective Catalytic Reduction (SCR) system disposed at an outlet of the exhaust passage:
• responsive to a temperature of the exhaust gases increasing above a peak efficiency threshold temperature, dilute the exhaust gases with air pressurized by the dilution compressor, the dilution compressor driven by routing a portion of the exhaust gases through the dilution turbine, and
• responsive to the temperature of the exhaust gases being less than the peak efficiency threshold temperature, route the exhaust gases into a dilution turbine bypass line bypassing the dilution turbine.