Exhaust gas recirculation system

An exhaust gas recirculation system configured to be provided in an internal combustion engine including a cylinder, an intake passage through which air introduced into the cylinder flows, an exhaust passage through which exhaust gas discharged from the cylinder flows, and a forced-induction device that compresses the air flowing through the intake passage, wherein

• the forced-induction device includes a turbine provided in the exhaust passage and a compressor provided in the intake passage and operates in synchronization with the turbine,
• the exhaust gas recirculation system comprises:
• a high-pressure EGR device that recirculates exhaust gas flowing through the exhaust passage to the intake passage as high-pressure EGR gas;
• a low-pressure EGR device that recirculates exhaust gas flowing through the exhaust passage to the intake passage as low-pressure EGR gas;
• and
• a controller configured to control the high-pressure EGR device and the low-pressure EGR device so as to adjust a recirculation amount of the high-pressure EGR gas and a recirculation amount of the low-pressure EGR gas,
• the high-pressure EGR device includes a high-pressure EGR passage,
• a first end of the high-pressure EGR passage is connected to a section of the exhaust passage upstream of the turbine,
• a second end of the high-pressure EGR passage is connected to a section of the intake passage downstream of the compressor,
• the low-pressure EGR device includes a low-pressure EGR passage and a cooling device,
• a first end of the low-pressure EGR passage is connected to a section of the exhaust passage downstream of the turbine,
• a second end of the low-pressure EGR passage is connected to a section of the intake passage upstream of the compressor,
• the cooling device cools the low-pressure EGR gas flowing through the low-pressure EGR passage, and
• the controller is configured to
• identify an operating region of the internal combustion engine based on an output torque and an engine rotation speed of the internal combustion engine;
• calculate a residual amount that is an estimated value of an amount of condensed water remaining in the low-pressure EGR passage;
• and
• when the residual amount is greater than a determination value corresponding to the operating region, operate the low-pressure EGR device so as to reduce the recirculation amount of the low-pressure EGR gas.