Method and system for exhaust aftertreatment

Patent metadata

Field	Value
Publication number	US-10473020-B2
Application number	US-201615218639-A
Country	US
Kind code	B2
Filing date	Jul 25, 2016
Priority date	Jul 25, 2016
Publication date	Nov 12, 2019
Grant date	Nov 12, 2019

Abstract

Methods and systems are provided for reducing engine emissions using a branched exhaust system. In one example, a branched exhaust system may include a plurality of sub-branches each housing a distinct exhaust component, and an order of exhaust flow through each of the exhaust components may be adjusted based on engine operating conditions and temperature demand of the distinct components.

First claim

The invention claimed is:

1. A method for an engine comprising:
adjusting a plurality of valves coupled to each of a first, second, third, and fourth sub-branch of a branched exhaust system, each sub-branch arranged parallel to a main exhaust passage and housing a distinct exhaust component; and
varying an order of exhaust flow through the distinct exhaust components based on a temperature, wherein each of the plurality of valves is adjustable to one of a first position, a second position, and a third position intermediate to the first and second positions.

2. The method of claim 1 , wherein the first and second sub-branches are arranged on one side of the main exhaust passage while the third and fourth sub-branches are arranged on another side of the main exhaust passage, opposite the one side, and wherein varying the order of exhaust flow includes diverting all exhaust flow initially towards the first and second sub-branches during a first condition when the temperature is lower than a threshold temperature and/or an engine speed is higher than a threshold speed, and diverting all exhaust flow initially towards the third and fourth sub-branches during a second condition when the temperature is higher than the threshold temperature and/or the engine speed is lower than the threshold speed.

3. The method of claim 2 , wherein the varying further includes:
routing all exhaust flow through the first sub-branch and then through the second sub-branch when the temperature is higher than the threshold temperature;
routing all exhaust flow through the second sub-branch and then through a second branch, bypassing the first sub-branch when the temperature is lower than the threshold temperature;
routing all exhaust flow through the fourth sub-branch and then through the third sub-branch when NOx loading at a selective catalytic reduction (SCR) catalyst is higher than a threshold loading; and
routing all exhaust flow through the third sub-branch and then through the fourth sub-branch when soot loading at a diesel particulate filter (DPF) is higher than a threshold soot load.

4. The method of claim 2 , wherein the first and second sub-branches are separated by a fifth sub-branch arranged parallel to both the first and second sub-branches such that exhaust flow between the first sub-branch and the second sub-branch is via the fifth sub-branch, and wherein the third and fourth sub-branches are separated by a sixth sub-branch arranged parallel to both such that exhaust flow between the third sub-branch and the fourth sub-branch is via the sixth sub-branch.

5. The method of claim 3 , wherein the first sub-branch houses a turbine, the second sub-branch houses a diesel oxidation catalyst (DOC), the third sub-branch houses the DPF, and the fourth sub-branch houses the SCR catalyst.

6. The method of claim 5 , wherein varying the order of exhaust flow based on the temperature includes adjusting based on a relative temperature demand of each distinct exhaust component.

7. The method of claim 6 , wherein the varying includes:
responsive to a vehicle acceleration, based on a higher temperature demand at the turbine, routing exhaust first through the turbine before routing exhaust through each of the DOC, the DPF, and the SCR catalyst;
responsive to an engine cold-start, based on a higher temperature demand at the DOC, routing exhaust first through the DOC before routing exhaust through each of the DPF and the SCR catalyst;
responsive to DPF regeneration conditions being met, based on a higher temperature demand at the DPF, routing exhaust first through the DPF and then through each of the SCR catalyst, the turbine, and the DOC; and
responsive to SCR purge conditions being met, based on a higher temperature demand at the SCR, routing exhaust first through the SCR and then through each of the DPF, the DOC, and the turbine.

8. The method of claim 6 , wherein the varying includes:
during a first DPF regeneration condition when an engine temperature is below a threshold temperature, flowing exhaust first through the DOC, then through the DPF, and finally through the SCR catalyst, bypassing the turbine;
during a second DPF regeneration condition when the engine temperature is above the threshold temperature, and an engine load is in a mid-load region, flowing exhaust first through the DOC, then through the turbine, then through the DPF, and finally through the SCR catalyst;
during a third DPF regeneration condition when a vehicle is accelerating, flowing exhaust first through the turbine, then through the DOC, then through the DPF, and finally through the SCR catalyst; and
during a fourth DPF regeneration condition when the engine temperature is above the threshold temperature and the engine load is higher than a threshold load, flowing a first part of exhaust first through the turbine, bypassing the DOC, and a second part of exhaust first through the DOC, bypassing the turbine, then flowing a combined first and second parts of exhaust through the DPF, and finally through the SCR catalyst.

9. The method of claim 8 , wherein the varying further includes:
during a first SCR catalyst purge condition when the engine temperature is below the threshold temperature, flowing exhaust first through the DOC, then through the SCR catalyst, and finally through the DPF, bypassing the turbine;
during a second SCR catalyst purge condition when the engine temperature is above the threshold temperature and the engine load is in the mid-load region, flowing exhaust first through the DOC, then through the turbine, then through the SCR catalyst, and finally through the DPF;
during a third SCR catalyst purge condition when the vehicle is accelerating, flowing exhaust first through the turbine, then through the DOC, then through the SCR catalyst, and finally through the DPF; and
during a fourth SCR catalyst purge condition when the engine temperature is above the threshold temperature and the engine load is higher than the threshold load, flowing a first part of exhaust first through the turbine, bypassing the DOC, and a second part of exhaust first through the DOC, bypassing the turbine, then flowing a combined first and second parts of exhaust through the SCR catalyst, and finally through the DPF.

10. The method of claim 9 , wherein the varying further includes:
during a fifth DPF regeneration condition when the engine temperature is above the threshold temperature and the engine load is below an idle load threshold, flowing exhaust first through the DPF, then through the SCR catalyst, then through the turbine, and finally through the DOC; and
during a fifth SCR catalyst purge condition when the engine temperature is above the threshold temperature and the engine load is below the idle load threshold, flowing exhaust first through the SCR catalyst, then through the DPF, then through the turbine, and finally through the DOC.

11. The method of claim 10 , further comprising, during each of the first, second, third, and fourth SCR purge conditions, flowing exhaust through the DPF in a first direction and, during the fifth SCR purge condition, flowing exhaust through the DPF in a second direction, the first direction opposite to the second direction, wherein, during exhaust flow through the DPF in the first direction, ash is removed from a first set of cells of the DPF and, during exhaust flow through the DPF in the second direction, ash is removed from a second remaining set of cells of the DPF.

12. The method of claim 8 , wherein a ratio of the first part of exhaust to the second part of exhaust is based on a driver demand and a boost error, the second part of exhaust decreased while the first part of exhaust is cor

Assignees

• Ford Global Tech Llc

Inventors

• Zhang Xiaogang

Classifications

• F01N3/023

  using means for regenerating the filters, e.g. by burning trapped particles · CPC title

• F01N2900/1614

  NOx amount trapped in catalyst · CPC title

• F01N3/2066

  Selective catalytic reduction [SCR] · CPC title

• F01N2900/1606

  Particle filter loading or soot amount · CPC title

• F01N3/103

  Oxidation catalysts for HC and CO only · CPC title