In some implementations, an exhaust gas recirculation cooler may include a shell defining an internal chamber; a first tube support plate defining a first wall of the internal chamber; a second tube support plate defining a second wall of the internal chamber; a plurality of cooling tubes extending through the internal chamber from the first tube support plate to the second tube support plate, the plurality of cooling tubes being flexible tubes; and at least one separator plate, extending within the internal chamber between the first tube support plate and the second tube support plate, that partitions the internal chamber such that a first set of the plurality of cooling tubes are to a first side of the at least one separator plate and a second set of the plurality of cooling tubes are to a second side of the at least one separator plate.

Various methods and systems are provided for an exhaust gas recirculation system. In one example, an exhaust gas recirculation cooler includes a first section, arranged proximate to an exhaust gas inlet of the EGR cooler and including a first plurality of tubes and a first plurality of fins coupled to the first plurality of tubes, where at least one of the first plurality of tubes and the first plurality of fins are comprised of a first material that has a first coefficient of thermal expansion (CTE); and a second section, arranged downstream of the first section and including a second plurality of tubes and a second plurality of fins coupled to the second plurality of tubes, where the second plurality of tubes and the second plurality of fins are comprised of a second material that has a second CTE, the second CTE greater than the first CTE.

Various methods and systems are provided for an exhaust gas recirculation system. In one example, an exhaust gas recirculation cooler includes a first section, arranged proximate to an exhaust gas inlet of the EGR cooler and including a first plurality of tubes and a first plurality of fins coupled to the first plurality of tubes, where at least one of the first plurality of tubes and the first plurality of fins are comprised of a first material that has a first coefficient of thermal expansion (CTE); and a second section, arranged downstream of the first section and including a second plurality of tubes and a second plurality of fins coupled to the second plurality of tubes, where the second plurality of tubes and the second plurality of fins are comprised of a second material that has a second CTE, the second CTE greater than the first CTE.

Methods and systems are provided for carrying out on-board diagnostics of a plurality of components of an exhaust heat exchange system. In one example, degradation of one or more of a heat exchanger and a coolant system fluidically coupled to the heat exchanger may be detected based on a first temperature estimated upstream of the heat exchanger, a second temperature sensor estimated downstream of the heat exchanger, a coolant temperature, and a pressure estimated upstream of the heat exchanger. Also, degradation of a diverter valve of the heat exchange system may be detected based on inputs of a position sensor coupled to the diverter valve.

Methods and systems are provided for carrying out on-board diagnostics of a plurality of components of an exhaust heat exchange system. In one example, degradation of one or more of a heat exchanger and a coolant system fluidically coupled to the heat exchanger may be detected based on a first temperature estimated upstream of the heat exchanger, a second temperature sensor estimated downstream of the heat exchanger, a coolant temperature, and a pressure estimated upstream of the heat exchanger. Also, degradation of a diverter valve of the heat exchange system may be detected based on inputs of a position sensor coupled to the diverter valve.

An exhaust heat recovery device according to one aspect of the present disclosure includes a main flow path, a secondary flow path, a plurality of heat exchangers, and a communication portion. Exhaust gas flows in the main flow path. The secondary flow path is a flow path branched from the main flow path, and at least a portion of the exhaust gas flows in the secondary flow path. The plurality of heat exchangers are arranged in the secondary flow path. The communication portion communicates with the plurality of heat exchangers and constitutes a portion of the secondary flow path. The communication portion is provided with an exhaust gas outlet which is an outlet for exhaust gas used for exhaust gas recirculation.

A fuel injection control method includes measuring EGR (exhaust gas recirculation) rate through a CO2 sensor measuring the amount of CO2 entering the intake side of the engine, setting an optimum SCR (Steam to Carbon Ratio) value based on the measured EGR rate, calculating the amount of steam supplied to the engine based on the measured EGR rate, calculating an actual SCR value by the ratio of the steam amount and the carbon component of the fuel supplied to the engine, comparing the actual SCR value with the optimum SCR value, calculating the SCR difference value by subtracting the optimum SCR value from the actual SCR value if the actual SCR value is greater than the optimum SCR value, calculating an additional fuel amount to be added based on the SCR difference value, and injecting fuel to the fuel reformer based on the calculated additional fuel amount.

A fuel injection control method includes measuring EGR (exhaust gas recirculation) rate through a CO2 sensor measuring the amount of CO2 entering the intake side of the engine, setting an optimum SCR (Steam to Carbon Ratio) value based on the measured EGR rate, calculating the amount of steam supplied to the engine based on the measured EGR rate, calculating an actual SCR value by the ratio of the steam amount and the carbon component of the fuel supplied to the engine, comparing the actual SCR value with the optimum SCR value, calculating the SCR difference value by subtracting the optimum SCR value from the actual SCR value if the actual SCR value is greater than the optimum SCR value, calculating an additional fuel amount to be added based on the SCR difference value, and injecting fuel to the fuel reformer based on the calculated additional fuel amount.

A heat exchanger includes: a stack formed by stacking a plurality of tubes through which gas flow; a tubular inner tank in which the stack is housed; and a tubular outer tank that is mounted on the outside of the inner tank so as to define an inner space between the outer tank and an outer peripheral surface of the inner tank. Each of both end portions of the tubes has a thickness greater than each of middle portions of the tubes. The both end portions of the tubes adjacent to each other in the stack are joined together so as to form a clearance between the middle portions of the adjacent tubes in the stack. Outer peripheries of both end portions of the stack are joined to an inner peripheral surface of the inner tank. An introduction hole for introducing a cooling medium is formed in the outer tank.

A heat exchanger includes: a stack formed by stacking a plurality of tubes through which gas flow; a tubular inner tank in which the stack is housed; and a tubular outer tank that is mounted on the outside of the inner tank so as to define an inner space between the outer tank and an outer peripheral surface of the inner tank. Each of both end portions of the tubes has a thickness greater than each of middle portions of the tubes. The both end portions of the tubes adjacent to each other in the stack are joined together so as to form a clearance between the middle portions of the adjacent tubes in the stack. Outer peripheries of both end portions of the stack are joined to an inner peripheral surface of the inner tank. An introduction hole for introducing a cooling medium is formed in the outer tank.