Methods and systems are provided for an Exhaust Gas Recirculation (EGR) system for an internal combustion engine. In one example, the EGR system comprises an inlet air duct configured to provide the internal combustion engine with inlet air, an EGR diffuser configured to provide recirculated exhaust gases from the internal combustion engine to the inlet air duct through an outlet, and a resilient element, the EGR diffuser and resilient element adapted to provide homogenous mixing of EGR gases and inlet air at a specific operating condition of the vehicle.

A method of controlling exhaust gas recirculation (EGR) in a turbocharged compression-ignition engine system including an engine, an induction subsystem in upstream communication with the engine, an exhaust subsystem in downstream communication with the engine, a high pressure EGR path between the exhaust and induction subsystems upstream of a turbocharger turbine and downstream of a turbocharger compressor, and a low pressure EGR path between the exhaust and induction subsystems downstream of the turbocharger turbine and upstream of the turbocharger compressor. A target total EGR fraction for compliance with exhaust emissions criteria is determined, then a target HP/LP EGR ratio is determined to optimize other engine system criteria within the constraints of the determined target total EGR fraction.

Systems, apparatus, and methods are disclosed that include a divided exhaust engine configured to control an EGR fraction in the charge flow to the cylinders in response to an EGR fraction overshoot condition, an exhaust pressure change in the EGR loop, and/or a transient operating condition.

Systems, apparatus, and methods are disclosed that include a divided exhaust engine configured to control an EGR fraction in the charge flow to the cylinders in response to an EGR fraction overshoot condition, an exhaust pressure change in the EGR loop, and/or a transient operating condition.

Advanced combustion modes, such as PCCI, operate near the system stability limits. In PCCI, the combustion event begins without a direct combustion trigger in contrast to traditional spark-ignited gasoline engines and direct-injected diesel engines. The lack of a direct combustion trigger encourages the usage of model-based controls to provide robust control of the combustion phasing. The nonlinear relationships between the control inputs and the combustion system response often limit the effectiveness of traditional, non-model-based controllers. Accurate knowledge of the system states and inputs is helpful for implementation of an effective nonlinear controller. A nonlinear controller is developed and implemented to control the engine combustion timing during diesel PCCI operation by targeting desired values of the in-cylinder oxygen concentration, pressure, and temperature during early fuel injection.

A method of operating an internal combustion engine is provided. The method includes combusting a mixture of fresh air and fuel within multiple cylinders. The method also includes directing a first portion of exhaust gases into a first-stage turbine and a second-stage turbine of a turbocharger for expanding the exhaust gases, directing a second portion of exhaust gases from the exhaust manifold via an exhaust channel bypassing the first-stage turbine and recirculating a third portion of exhaust gases into an intake manifold after mixing with fresh air. The method includes controlling at least one of: reducing a normal engine speed at each engine power setting while maintaining constant engine power level by increasing a fuel injection per cycle; concurrently increasing a flow rate of the third portion of exhaust gas during recirculation; and advancing a fuel injection timing for reducing emission levels that meets Tier 4 requirements.

A method of operating an internal combustion engine is provided. The method includes combusting a mixture of fresh air and fuel within multiple cylinders. The method also includes directing a first portion of exhaust gases into a first-stage turbine and a second-stage turbine of a turbocharger for expanding the exhaust gases, directing a second portion of exhaust gases from the exhaust manifold via an exhaust channel bypassing the first-stage turbine and recirculating a third portion of exhaust gases into an intake manifold after mixing with fresh air. The method includes controlling at least one of: reducing a normal engine speed at each engine power setting while maintaining constant engine power level by increasing a fuel injection per cycle; concurrently increasing a flow rate of the third portion of exhaust gas during recirculation; and advancing a fuel injection timing for reducing emission levels that meets Tier 4 requirements.

A vehicle includes an internal combustion engine, and an exhaust gas recirculation system that recirculates a portion of exhaust gas into at least one cylinder. A throttle body assembly includes a throttle valve movable according to a plurality of angles between an open position and a closed position. The angle of the throttle valve adjusts a pressure differential across the exhaust gas circulation system to modify an amount of recirculated exhaust gas recirculated back to the engine. The vehicle further includes an engine controller configured to determine a target NOx flow rate corresponding to a given driving condition of the vehicle. The engine controller actively adjusts the position of a throttle valve and/or an EGR valve based on a comparison between the measured NOx flow rate and the target NOx flow rate to reduce emissions of NOx exhausted by the vehicle.

A gas flow control system is provided for at least one cylinder of an internal combustion of a motor vehicle. The gas flow control system includes a supply passage configured to supply gas to the cylinder and an exhaust gas passage configured to remove gas from the cylinder. A bypass passage is configured to connect the supply passage and exhaust gas passage, and a fluid control switch is selectively operable to supply gas out of the exhaust gas passage through the bypass passage into the supply passage in an exhaust gas return operating mode, and to supply gas out of the supply passage through the bypass passage into the exhaust gas passage in a post-air operating mode.

A gas flow control system is provided for at least one cylinder of an internal combustion of a motor vehicle. The gas flow control system includes a supply passage configured to supply gas to the cylinder and an exhaust gas passage configured to remove gas from the cylinder. A bypass passage is configured to connect the supply passage and exhaust gas passage, and a fluid control switch is selectively operable to supply gas out of the exhaust gas passage through the bypass passage into the supply passage in an exhaust gas return operating mode, and to supply gas out of the supply passage through the bypass passage into the exhaust gas passage in a post-air operating mode.