Exhaust gas recirculation system for a turbocharged internal combustion engine

摘要

An exhaust gas recirculation (EGR) enhancement system for a turbocharged internal combustion engine includes a throttle valve arranged in the exhaust duct of the engine, downstream of the EGR system. The throttle valve is controlled in response to engine load and engine speed to selectively provide back pressure upstream of the throttle valve to selectively drive an EGR exhaust flow through an EGR duct to the intake manifold. An embodiment of the EGR system includes a cooler that lowers the temperature of the EGR exhaust flow to provide better reductions in nitric oxide emissions. The exhaust turbine of the turbocharger may be of the fixed geometry type or the variable geometry type to provide a turbine with a fixed or variable swallowing capacity. The fixed geometry turbine is preferably equipped to allow excess pressure to be released through a wastegate duct arranged in fluid parallel with the exhaust turbine, thereby allowing for higher power and higher speeds.