Method and system for exhaust gas heat recovery
First Claim
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1. A method comprising:
- operating in a first mode with exhaust gas flowing through an exhaust bypass, and in a first direction through a heat exchanger coupled in the exhaust bypass, and then to an exhaust tailpipe; and
operating in a second mode with exhaust flowing through an exhaust passage, then in a second, opposite direction through the heat exchanger, and then to an engine intake;
selecting between the first and second mode based on engine temperature, wherein the selecting includes selecting the first mode when the engine temperature is below a threshold, and selecting the second mode when the engine temperature is above the threshold; and
maintaining operation in the first mode after the engine temperature is above the threshold responsive to a request for hot EGR.
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Abstract
Methods and systems are provided for exhaust gas heat recovery at an exhaust gas heat exchanger. Exhaust gas may flow in both directions through an exhaust bypass passage and the heat exchanger coupled to the bypass passage. Hot or cold EGR may be delivered from the exhaust passage to the engine intake manifold and heat from the exhaust gas may be recovered at the heat exchanger.
43 Citations
12 Claims
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1. A method comprising:
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operating in a first mode with exhaust gas flowing through an exhaust bypass, and in a first direction through a heat exchanger coupled in the exhaust bypass, and then to an exhaust tailpipe; and operating in a second mode with exhaust flowing through an exhaust passage, then in a second, opposite direction through the heat exchanger, and then to an engine intake; selecting between the first and second mode based on engine temperature, wherein the selecting includes selecting the first mode when the engine temperature is below a threshold, and selecting the second mode when the engine temperature is above the threshold; and maintaining operation in the first mode after the engine temperature is above the threshold responsive to a request for hot EGR. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An engine system, comprising:
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an engine intake manifold; an engine exhaust manifold including an exhaust catalyst and a muffler coupled to each other via each of an exhaust passage and an exhaust bypass, the bypass coupled parallel to the exhaust passage; an heat exchanger coupled in the exhaust bypass; a coolant system fluidly coupled to the heat exchanger and to a heater core; a valve system including a first valve coupled in the exhaust passage and a second valve coupled in the exhaust bypass upstream of a first end of the heat exchanger; an EGR passage coupling the first end of the heat exchanger to the intake manifold, the EGR passage including an EGR valve; and a controller with computer readable instructions stored on non-transitory memory for; closing the EGR valve and operating the valve system in a first mode with the first valve closed, and the second valve open, to flow exhaust gas from the catalyst to the muffler through the exhaust bypass in a first direction through the heat exchanger; in response to an increase in engine temperature, and a demand for heated EGR, opening the EGR valve while maintaining the valve system in the first mode; and in response to the increase in engine temperature and no demand for heated EGR, maintaining the EGR valve closed while transitioning the valve system to a second mode with the first valve open, and the second valve closed, to flow exhaust gas from the catalyst into the exhaust bypass with exhaust flowing in a second, opposite direction through the heat exchanger, and then flowing exhaust from the heat exchanger to the intake manifold. - View Dependent Claims (9, 10, 11, 12)
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Specification