Method and system for emissions reduction

Patent metadata

Field	Value
Publication number	US-10184407-B2
Application number	US-201615263105-A
Country	US
Kind code	B2
Filing date	Sep 12, 2016
Priority date	Sep 12, 2016
Publication date	Jan 22, 2019
Grant date	Jan 22, 2019

Abstract

Methods and systems are provided for operating a branched exhaust assembly in a vehicle engine in order to increase catalyst efficiency and reduce engine emissions. In one example, a method may include, during a cold-start condition, flowing exhaust first through a three-way catalyst then through an underbody converter, then through a heat exchanger and then through a turbine, each exhaust component housed on different branches on the branched exhaust assembly. After catalyst activation, exhaust may flow first through the turbine, then through the underbody converter and then through the three-way catalyst, and during high engine load, exhaust entering the turbine may be cooled in order to reduce thermal load on the turbine.

First claim

The invention claimed is:

1. A method, comprising:
during cold-start, flowing exhaust first through a three-way catalyst, then an underbody converter, then an exhaust bypass passage with a heat exchanger and then a turbine;
transferring heat from exhaust to coolant circulating through the heat exchanger; and
heating an engine cylinder and piston with exhaust heat recovered at the heat exchanger.

2. The method of claim 1 , further comprising, after three-way catalyst light-off, flowing exhaust first through the turbine, then through the underbody converter and then through the three-way catalyst; and
during higher than threshold load operations, flowing a first portion of exhaust first through the heat exchanger, then the turbine, the underbody converter, and finally through the three-way catalyst, and simultaneously flowing a second portion of exhaust first through the turbine, then the underbody converter, and finally the three-way catalyst, bypassing the heat exchanger.

3. The method of claim 2 , wherein a ratio of the first portion to the second portion is adjusted based on driver demand and boost error, the adjusting including decreasing the first portion while correspondingly increasing the second portion as the driver demand increases, and increasing the first portion while correspondingly decreasing the second portion as the boost error increases, the boost error including a difference between an actual boost and a desired boost.

4. The method of claim 1 , wherein the turbine is housed in a first branch, the underbody converter is housed in a second branch, and the three-way catalyst is housed in a third branch of a branched exhaust assembly, the first branch, the second branch, and the third branch fluidically connected to each other via each of a first four-way valve and a second four-way valve.

5. The method of claim 4 , wherein the exhaust bypass passage is coupled to the first branch upstream of the turbine via a diverter valve, and the heat exchanger is housed in the exhaust bypass passage.

6. The method of claim 5 , wherein the first four-way valve is coupled to each of a first end of the first branch, a first end of the second branch, and a first end of the third branch, the second four-way valve is coupled to each of a second end of the first branch, a second end of the second branch and a second end of the third branch, and the diverter valve is coupled to the first branch at a junction with the exhaust bypass passage.

7. The method of claim 2 , wherein flowing exhaust during the cold-start includes flowing exhaust first through the three-way catalyst in a first direction, then flowing exhaust through the underbody converter in a second direction, and then flowing exhaust through the heat exchanger in the first direction, and the flowing exhaust through the turbine in the first direction, the second direction is opposite to the first direction;
wherein flowing exhaust after three-way catalyst light-off includes flowing exhaust first through the turbine in the first direction, then through the underbody converter in the second direction, and then through the three-way catalyst in the first direction; and
wherein flowing exhaust enduring higher than threshold load conditions include flowing a first portion of exhaust first through the heat exchanger in the first direction, then through the turbine in the first direction, then through the underbody converter in the second direction, and then through the three-way catalyst in the first direction, and simultaneously flowing a second portion of exhaust through the turbine in the first direction, then through the underbody converter in the second direction, and then through the three-way catalyst in the first direction bypassing the heat exchanger.

8. The method of claim 5 , wherein flowing exhaust during the cold-start further includes actuating the first four-way valve to a first position, the second four-way valve to a first position, and the diverter valve to an open position, wherein flowing exhaust after three-way catalyst light-off further includes actuating the first valve to a second position, the second valve to a second position, and the diverter valve to a closed position, and wherein flowing exhaust during higher than threshold load operation further includes actuating the first valve to the second position, the second valve to the second position, and the diverter valve to a partly open position.

9. An engine method, comprising:
during a first mode,
flowing exhaust first through a three-way catalyst housed in a third branch, then an underbody converter housed in a second branch, then a first exhaust passage, an exhaust channel, a second exhaust passage, and then a turbine housed in a first branch of a branched exhaust system;
transferring heat from exhaust flowing through the exhaust channel to coolant circulating via a concentric coolant channel; and
heating an engine cylinder and piston with exhaust heat recovered by the coolant.

10. The method of claim 9 , further comprising, during a second mode, flowing exhaust first through the turbine, then the underbody converter, and then the three-way catalyst; and
during a third mode, flowing exhaust first through the turbine, then the underbody converter, and then the three-way catalyst, and injecting a cooling fluid to the exhaust upstream of the turbine.

11. The method of claim 10 , wherein operating in the first mode includes shifting a position of a first four-way valve coupled to a first end of each of the first branch, the second branch, and the third branch to a first position, shifting a position of a second four-way valve coupled to a second end of each of the first branch, the second branch, and the third branch to a first position, shifting a position of a first three-way valve coupled to a junction of the first branch, and the first exhaust passage to a first position, and shifting a position of a second three-way valve coupled to a junction of the second exhaust passage, and the exhaust channel to a first position, and operating in each of the second mode, and the third mode include shifting the position of the first four-way valve to a second position, shifting the position of the second four-way valve to a second position, shifting the position of the first three-way valve to a second position, and shifting the position of the second three-way valve to a second position.

12. The method of claim 10 , further comprising, selecting the first mode when engine temperature is below a threshold temperature, selecting the second mode when engine temperature is above the threshold temperature and engine load is lower than a threshold load, the threshold based on the three-way catalyst light-off temperature, and selecting the third mode when engine load is higher than the threshold load.

13. The method of claim 10 , wherein injecting a cooling fluid includes injecting a cooling fluid into the exhaust, upstream of the turbine, via an injector, an amount of cooling fluid injected adjusted based on each of driver demand and boost error.

14. The method of claim 13 , wherein the cooling fluid is water, and wherein the adjusting includes decreasing the amount of cooling fluid injected as the driver demand increases, and increasing the amount as the boost error increases, the boost error including a difference between an actual boost and a desired boost.

15. The method of claim 10 , wherein each of the first mode, the second mode and the third mode include flowing exhaust through the first branch in a first direction, flowing exhaust through the second branch in a second direction, and flowing exhaust t

Assignees

• Ford Global Tech Llc

Inventors

• Zhang Xiaogang

Classifications

• F02N19/10

  by heating of engine coolants · CPC title

• F02G5/02

  Profiting from waste heat of exhaust gases · CPC title

• F02D41/0007

  for control of turbo-charged or super-charged engines (control of the pumps per se F02B37/12) · CPC title

• F01N3/2006

  Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating (by electrically controlling the supply of combustible mixture or its constituents only F02D41/0235) · CPC title

• F01N5/02 Primary

  the devices using heat · CPC title