Method and system for an exhaust heat exchanger

Patent metadata

Field	Value
Publication number	US-10316801-B2
Application number	US-201715407154-A
Country	US
Kind code	B2
Filing date	Jan 16, 2017
Priority date	Jan 16, 2017
Publication date	Jun 11, 2019
Grant date	Jun 11, 2019

Abstract

Methods and systems are provided for exhaust gas heat recovery and exhaust gas recirculation (EGR) cooling using a single split heat exchanger. Exhaust heat from each of a first portion of exhaust routed to the intake manifold as EGR and a second portion of exhaust diverted via a bypass passage for exhaust heat recovery may be transferred to a coolant flowing through the heat exchanger. The direction of coolant flow via the heat exchanger may be adjusted based on the coolant temperature.

First claim

The invention claimed is:

1. A method, comprising:
transferring heat from a first portion of exhaust from an engine flowing through an exhaust gas recirculation (EGR) passage to coolant in a first branch of a heat exchanger;
transferring heat from a second portion of exhaust flowing through an exhaust bypass to coolant in a second branch of the heat exchanger;
flowing a third portion of exhaust from downstream of an exhaust catalyst to a tailpipe, directly, without flowing through the EGR passage or the exhaust bypass; and
selecting, via a controller, a direction of coolant flow through the first and the second branch based on a sensed coolant temperature.

2. The method of claim 1 , wherein the first portion of exhaust flowing through the EGR passage includes exhaust drawn from a main exhaust passage based on engine load and delivered to an engine intake, upstream of a compressor, the first portion of exhaust drawn from upstream of a turbine when the engine load is lower than a threshold, and drawn from downstream of the turbine when the engine load is higher than the threshold, the turbine positioned in the main exhaust passage and coupled to the compressor which provides compressed air to the engine intake.

3. The method of claim 2 , wherein the second portion of exhaust flowing through the exhaust bypass includes the second portion of exhaust flowing from the main exhaust passage, downstream of each of the turbine and the exhaust catalyst positioned in the main exhaust passage downstream of the turbine, into the exhaust bypass, and from the exhaust bypass into the tailpipe via a diverter valve, the diverter valve coupled at a junction of an outlet of the exhaust bypass and the main exhaust passage.

4. The method of claim 3 , wherein a ratio of the second portion of exhaust to the third portion of exhaust is based on an engine heating demand, the second portion increased relative to the third portion as the engine heating demand increases, and wherein an opening of the diverter valve is adjusted based on the second portion relative to the third portion, the opening increased with an increase in the second portion relative to the third portion.

5. The method of claim 4 , wherein coolant flows sequentially through the first branch and the second branch of the heat exchanger, and wherein selecting the direction of coolant flow includes:
flowing coolant through the first branch and then through the second branch when an EGR cooling demand is higher than the engine heating demand; and
flowing coolant through the second branch and then through the first branch when the EGR cooling demand is lower than the engine heating demand, the EGR cooling demand based on an engine dilution demand.

6. The method of claim 3 , further comprising, for a threshold duration following an engine cold-start, containing exhaust within each of an exhaust manifold coupled to the engine, a first exhaust bypass passage, and a first portion of the EGR passage by closing a first valve coupling the EGR passage to the main exhaust passage downstream of the turbine, and after the threshold duration has elapsed, opening the first valve to flow exhaust from upstream of the turbine to upstream of the exhaust catalyst via the first exhaust bypass passage, while bypassing the turbine, and then flowing exhaust from downstream of the exhaust catalyst to the tailpipe via the exhaust bypass.

7. The method of claim 6 , further comprising, transferring heat from exhaust flowing from downstream of the exhaust catalyst to the tailpipe via the exhaust bypass to coolant flowing through the second branch of the heat exchanger, and then transferring heat from the coolant to an engine block based on engine heating demand.

8. The method of claim 1 , wherein selecting the direction of coolant flow includes:
flowing coolant simultaneously through each of the first branch and the second branch in a first direction while exhaust flows through the EGR passage and the bypass passage in a second direction when the coolant temperature is lower than a threshold temperature; and
flowing coolant simultaneously through each of the first branch and the second branch in the second direction while exhaust flows through the EGR passage and the exhaust bypass in the second direction when the coolant temperature is higher than the threshold temperature, the first direction opposite to the second direction.

9. The method of claim 8 , further comprising, flowing coolant simultaneously through each of the first branch and the second branch in the first direction until the coolant temperature reaches the threshold temperature, and then flowing coolant through each of the first branch and the second branch in the second direction.

10. The method of claim 1 , wherein coolant enters each of the first branch and the second branch of the heat exchanger via a common coolant inlet and flows simultaneously through each of the first branch and the second branch, before combining at a common coolant outlet and exiting the heat exchanger, and wherein the direction of coolant flow via the first branch is same as the direction of coolant flow via the second branch.

11. The method of claim 10 , further comprising flowing heated coolant exiting the common coolant outlet through one or more of an engine block, a heater core, and a radiator based on engine heating demand relative to cabin heating demand.

12. An engine method comprising:
diverting a first portion of exhaust from an exhaust passage of an engine into an exhaust gas recirculation (EGR) passage;
diverting a second portion of exhaust from the exhaust passage into an exhaust bypass;
transferring heat from the first portion of exhaust to coolant flowing through a first section of a branched heat exchanger;
transferring heat from the second portion of exhaust to coolant flowing through a second section of the heat exchanger; and
varying coolant flow through the first and second sections based on the first portion relative to the second portion, via a switching valve,
wherein the heat exchanger is configured as a loop, coolant flows through the first and second sections sequentially, and a direction of coolant flow through the first section is opposite to the direction of coolant flow through the second section.

13. The method of claim 12 , wherein the first portion of exhaust is based on engine dilution demand, and wherein diverting the first portion includes, during a higher than threshold engine load, adjusting opening of a first valve coupled to the exhaust passage, downstream of a turbine positioned in the exhaust passage, to flow exhaust from downstream of the turbine to an engine intake, and during a lower than threshold engine load, adjusting opening of a second valve coupled to the exhaust passage, upstream of the turbine, to flow exhaust from upstream of the turbine to the engine intake, an opening of the first valve or the second valve increasing as the engine dilution demand increases.

14. The method of claim 12 , wherein the second portion of exhaust is based on at least one of an engine temperature and a vehicle cabin heating demand, the second portion decreased as one of the engine temperature increases and the vehicle cabin heating demand decreases, and wherein diverting the second portion includes increasing an opening of a diverter valve at a junction of the exhaust passage and the exhaust bypass as the engine temperature decreases, the opening of the diverter valve increased with an increase in the second portion.

15. The method of claim 12 , wherein the varying coolant flow includes varying an order of sequential coolant flow thro

Assignees

• Ford Global Tech Llc

Inventors

• Zhang Xiaogang

Classifications

• F02M26/04 Primary

  with a single turbocharger · CPC title

• F02M26/16

  with EGR valves located at or near the connection to the exhaust system · CPC title

• F02M26/28 Primary

  with liquid-cooled heat exchangers · CPC title

• F02M26/24

  with two or more coolers · CPC title

• F02M26/05

  High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor · CPC title