Method and apparatus for operating an internal combustion engine employing first and second EGR flowpaths

An internal combustion engine system, comprising:

• an internal combustion engine including an air intake system and an exhaust manifold;
• an exhaust purifying device fluidly coupled to the exhaust manifold;
• a first EGR valve disposed to control flow of exhaust gas between the exhaust manifold and the air intake system, wherein a first EGR flow path is defined between the exhaust manifold, the first EGR valve and the air intake system;
• a second EGR valve disposed to control flow of exhaust gas between an inlet that is disposed downstream of the exhaust purifying device and the air intake system, wherein a second EGR flow path is defined between the inlet disposed downstream of the exhaust purifying device, the second EGR valve and the air intake system;
• a temperature sensor disposed in the exhaust gas feedstream upstream of the exhaust purifying device;
• and
• a controller, in communication with the internal combustion engine and the temperature sensor and operatively connected to the first and second EGR valves, the controller including an instruction set, the instruction set executable to:
• monitor, via the temperature sensor, the temperature of the exhaust gas feedstream upstream of the exhaust purifying device, and
• control the first EGR valve to control flow of exhaust gas to the air intake system via the first EGR flow path and control the second EGR valve to control flow of exhaust gas to the air intake system via the second EGR flow path based upon the temperature of the exhaust gas feedstream upstream of the exhaust purifying device, including the internal combustion engine being operated in an EGR split mode when the temperature of the exhaust gas feedstream is greater than a low temperature threshold, including:
• an initial split selected between the first and second EGR flow paths based upon engine speed and engine load parameters, and
• the initial split adjusted based upon the temperature of the exhaust gas feedstream and the engine load parameter;
• wherein the initial split is adjusted based upon the temperature of the exhaust gas feedstream only when the engine load parameter is less than a maximum load threshold.

An internal combustion engine system, comprising:

• an internal combustion engine including an air intake system and an exhaust manifold;
• an exhaust purifying device fluidly coupled to the exhaust manifold;
• a first EGR valve disposed to control flow of exhaust gas between the exhaust manifold and the air intake system, wherein a first EGR flow path is defined between the exhaust manifold, the first EGR valve and the air intake system;
• a second EGR valve disposed to control flow of exhaust gas between an inlet that is disposed downstream of the exhaust purifying device and the air intake system, wherein a second EGR flow path is defined between the inlet disposed downstream of the exhaust purifying device, the second EGR valve and the air intake system;
• a temperature sensor disposed in the exhaust gas feedstream upstream of the exhaust purifying device;
• and
• a controller, in communication with the internal combustion engine and the temperature sensor and operatively connected to the first and second EGR valves, the controller including an instruction set, the instruction set executable to:
• monitor, via the temperature sensor, the temperature of the exhaust gas feedstream upstream of the exhaust purifying device, and
• control the first EGR valve to control flow of exhaust gas to the air intake system via the first EGR flow path based upon the temperature of the exhaust gas feedstream upstream of the exhaust purifying device, including the internal combustion engine being operated in an EGR split mode when the temperature of the exhaust gas feedstream is greater than a low temperature threshold, including:
• an initial split selected between the first and second EGR flow paths based upon engine speed and engine load parameters, and
• the initial split adjusted based upon the temperature of the exhaust gas feedstream and the engine load parameter;
• wherein the initial split is adjusted based upon the temperature of the exhaust gas feedstream only when the engine load parameter is less than a maximum load threshold.