Method and system for exhaust gas heat recovery

Patent metadata

Field	Value
Publication number	US-10858983-B2
Application number	US-201916267782-A
Country	US
Kind code	B2
Filing date	Feb 5, 2019
Priority date	May 10, 2016
Publication date	Dec 8, 2020
Grant date	Dec 8, 2020

Abstract

Methods and systems are provided for controlling exhaust flow and recovering heat from exhaust gas under different operating conditions. In one example, motive flow of fresh air via an ejector coupled to an exhaust bypass assembly may be utilized to divert exhaust through a heat exchanger during cold-start conditions and heat extracted from the exhaust gas may be utilized for passenger cabin heating and other vehicle heating demands. The exhaust bypass assembly may also be used for EGR delivery wherein the exhaust heat exchanger may be used as an EGR cooler.

First claim

The invention claimed is:

1. A method for a turbocharged engine comprises: responsive to a demand for compressor bypass flow, recirculating a portion of boosted air from downstream of a compressor to upstream of the compressor via an ejector; and drawing exhaust flow from downstream of an exhaust catalyst into a heat exchanger coupled in an exhaust bypass via ejector generated vacuum.

2. The method of claim 1 , wherein the demand for compressor bypass flow is in response to one or more of an operator tip-out event, and an indication of compressor surge.

3. The method of claim 1 , wherein recirculating the portion of boosted air from downstream of the compressor to upstream of the compressor via an ejector includes opening a first valve housed in a first passage coupling an engine intake passage, downstream of the compressor, to a motive inlet of the ejector, the ejector coupled in the exhaust bypass, and further opening a second valve housed in a low-pressure EGR passage, the low-pressure EGR passage coupling the exhaust bypass to the intake passage, upstream of the compressor.

4. The method of claim 3 , wherein the portion of boosted air flowing through an intake passage enters the first passage from downstream of the compressor, and then after flowing through the heat exchanger returns to the intake passage, upstream of the compressor, through the low-pressure EGR passage.

5. The method of claim 3 , further comprising, a degree of opening of the first valve and the portion of boosted air recirculated to upstream of the compressor is based on each of a margin to compressor surge and engine heating demand, the degree of opening of the first valve increased with one or more of a decrease in the margin to compressor surge and an increase in engine heating demand.

6. The method of claim 1 , further comprising, transferring heat from the drawn exhaust to a coolant flowing through the heat exchanger and flowing the coolant with the transferred heat through an engine block and/or an engine head for engine heating.

7. The method of claim 6 , further comprising, flowing the coolant with the transferred heat through and heating a vehicle cabin by drawing air through a heater core.

8. The method of claim 1 , further comprising, mixing the drawn exhaust flow with the portion of boosted air before recirculating the drawn exhaust flow mixed with the portion of exhaust air to upstream of the compressor.

9. The method of claim 1 , wherein the ejector is coupled upstream of the heat exchanger in the exhaust bypass.

10. An system for an engine comprises: an ejector coupled in an exhaust bypass, upstream of a heat exchanger; a first intake passage coupling an engine intake manifold from downstream of a compressor to a motive inlet of the ejector; a first EGR delivery passage coupling the exhaust bypass from downstream of the heat exchanger to the engine intake manifold, downstream of the compressor; and a second EGR delivery passage coupling the exhaust bypass from downstream of the heat exchanger to the engine intake manifold, upstream of the compressor.

11. The system of claim 10 , the system further comprises, a first valve coupled to the first intake passage, a second valve coupled to the first EGR delivery passage, a third valve coupled to the second EGR delivery passage, and a controller with computer readable instructions stored on non-transitory memory for: operating the engine system in at least one of a first mode, a second mode, a third mode, and a fourth mode via adjustments to one or more of the first valve, the second valve, and the third valve.

12. The system of claim 11 , wherein operation in the first mode comprises: closing an exhaust wastegate valve coupled to a turbine driving the compressor, opening the first valve and closing each of the second and the third valve to flow intake air to an exhaust tailpipe through the ejector via the first intake passage, using ejector vacuum to draw exhaust gas from an exhaust passage, downstream of an exhaust catalyst, into the heat exchanger in the exhaust bypass, and transferring exhaust heat to coolant circulating through the heat exchanger, operation in the first mode carried out during one or more of an engine temperature being lower than a threshold temperature, a charge air cooler condensate level being higher than a threshold level, and an operator cabin heating demand being higher than a threshold demand.

13. The system of claim 12 , wherein operation in the second mode comprises: opening each of the first valve, the second valve, and the third valve to recirculate exhaust to the intake manifold through the heat exchanger via each of the first EGR delivery passage and the second EGR delivery passage, and transferring exhaust heat to coolant circulating through the heat exchanger, operation in the second mode carried out during one or more of the engine temperature being higher than the threshold temperature, the charge air cooler condensate level being lower than the threshold level, and the operator cabin heating demand being lower than the threshold demand.

14. The method of claim 12 , wherein operation in the third mode comprises: opening each of the first valve and the second valve, closing the third valve to flow cooler intake air from downstream of the compressor and upstream of a charge air cooler through each of the ejector and the heat exchanger, transferring heat from the circulating coolant to the cooler intake air at the heat exchanger, and then recirculating heated intake air to the intake manifold, downstream of the charge air cooler via the first EGR passage, operation in the third mode carried out during a higher than threshold demand for charge air heating.

15. The method of claim 12 , wherein operation in the fourth mode comprises: opening each of the first valve and the third valve, and closing the second valve to recirculate intake air from downstream of the compressor to upstream of the compressor via the ejector, the heat exchanger, and the second EGR delivery passage, operation in the fourth mode carried out when a margin to compressor surge is lower than a threshold.

16. The system of claim 11 , wherein the controller includes instructions for transitioning between the modes responsive to a change in engine operating conditions, including at least one of a change in boost demand, change in engine temperature, change in cabin heating demand, and change in compressor inlet pressure.

17. A method for a turbocharged engine comprising: during an engine cold-start, routing exhaust gas from downstream of an exhaust catalyst to a tailpipe via an exhaust heat exchanger coupled to an exhaust bypass passage, and transferring heat from the exhaust gas to a coolant circulating through the heat exchanger; and after a catalyst light-off, recirculating exhaust gas from downstream of the exhaust catalyst to an intake passage via the exhaust heat exchanger, and transferring heat from the exhaust gas to the coolant circulating through the heat exchanger.

18. The method of claim 17 , wherein the coolant with the transferred heat is routed through one or more components including a heater core, an engine block, and an engine head to transfer heat from the coolant to the one or more components.

19. The method of claim 17 , wherein during the engine cold-start, a wastegate valve coupled across an exhaust turbine is closed and a first valve in a first intake passage coupling an engine intake manifold to a motive inlet of an ejector housed in the exhaust bypass passage is opened to flow air boosted by an intake compress

Assignees

• Ford Global Tech Llc

Inventors

• Uhrich Michael James
• Ulrey Joseph Norman
• Pursifull Ross Dykstra

Classifications

• F02B37/183 Primary

  Arrangements of bypass valves or actuators therefor · CPC title

• B60H1/18

  the air being heated from the plant exhaust gases {(B60H1/025 takes precedence)} · CPC title

• F01P3/20 Primary

  Cooling circuits not specific to a single part of engine or machine (F01P3/22 takes precedence) · CPC title

• F02M31/087

  Heat-exchange arrangements between the air intake and exhaust gas passages, e.g. by means of contact between the passages · CPC title

• Y02T10/12

  Improving ICE efficiencies · CPC title