Systems and methods for a split exhaust engine system

Patent metadata

Field	Value
Publication number	US-10107220-B2
Application number	US-201615382556-A
Country	US
Kind code	B2
Filing date	Dec 16, 2016
Priority date	Dec 16, 2016
Publication date	Oct 23, 2018
Grant date	Oct 23, 2018

Abstract

Methods and systems are provided for operating a split exhaust engine system that provides blowthrough air and exhaust gas recirculation to an intake passage via a first exhaust manifold and exhaust gas to an exhaust passage via a second exhaust manifold. In one example, an amount of opening overlap between a plurality of intake valves and a first set of exhaust valves coupled to the first exhaust manifold may be adjusted responsive to a transition from an estimated combustion air-fuel content to a leaner air-fuel content of the blowthrough air on a cylinder to cylinder basis. As one example, the transition may be determined from an output of an oxygen sensor positioned within the first exhaust manifold or an exhaust runner of each of the first set of exhaust valves.

First claim

The invention claimed is:

1. A method, comprising:
flowing boosted blowthrough air from a plurality of intake valves to a first exhaust manifold coupled to an intake passage via a first set of exhaust valves; and
adjusting an amount of opening overlap between the plurality of intake valves and the first set of exhaust valves responsive to a transition from an estimated combustion air-fuel content to a leaner air-fuel content of the blowthrough air on a cylinder to cylinder basis.

2. The method of claim 1 , wherein each cylinder includes one exhaust valve of the first set of exhaust valves and one intake valve of the plurality of intake valves and wherein each exhaust valve of the first set of exhaust valves opens at a different time in an engine cycle.

3. The method of claim 2 , further comprising determining the transition from the estimated combustion air-fuel content to the leaner air-fuel content of the blowthrough air for each cylinder based on an output of an oxygen sensor positioned in the first exhaust manifold while the one exhaust valve of the first set of exhaust valves for a corresponding cylinder is open.

4. The method of claim 2 , further comprising determining the transition from the estimated combustion air-fuel content to the leaner air-fuel content of the blowthrough air for each cylinder based on an output of an oxygen sensor positioned in a runner of each exhaust valve of the first set of exhaust valves.

5. The method of claim 1 , wherein the transition from the estimated combustion air-fuel content to the leaner air-fuel content of the blowthrough air includes an increase in an oxygen level determined from an output of a first oxygen sensor disposed in one of the first exhaust manifold and a runner of each exhaust valve of the first set of exhaust valves from a lower, first level of oxygen to a higher, second level of oxygen following opening of each exhaust valve of the first set of exhaust valves.

6. The method of claim 5 , wherein the blowthrough air is intake air that does not undergo combustion and further comprising estimating a total amount of the blowthrough air flowing to the intake passage from the first exhaust manifold during a single engine cycle based on the second level of oxygen for each exhaust valve of the first set of exhaust valves.

7. The method of claim 5 , further comprising adjusting one or more of airflow and fueling to engine cylinders to maintain exhaust gas flowing through an exhaust passage at stoichiometry in response to an output of a second oxygen sensor disposed in the exhaust passage, wherein the exhaust passage is coupled to a second exhaust manifold coupled to a second plurality of exhaust valves.

8. The method of claim 1 , wherein adjusting the amount of opening overlap between the plurality of intake valves and the first set of exhaust valves includes increasing the amount of opening overlap in response to the estimated total amount of the blowthrough air being less than a desired blowthrough air amount for current engine operating conditions.

9. The method of claim 8 , wherein increasing the amount of opening overlap includes one or more of advancing an opening timing of the plurality of intake valve and retarding a closing timing of the first set of exhaust valves.

10. The method of claim 1 , wherein adjusting the amount of opening overlap between the plurality of intake valves and the first set of exhaust valves includes adjusting the amount of opening overlap between opening of each intake valve of the plurality of intake valves and closing of a corresponding exhaust valve of the first set of exhaust valves, for each cylinder.

11. A method, comprising:
flowing exhaust gases and non-combusted blowthrough air to an intake passage via a first exhaust manifold coupled to a first set of exhaust valves;
flowing only exhaust gases to an exhaust passage via a second exhaust manifold coupled to a second set of exhaust valves;
measuring a transition between a combustion air-fuel content and a leaner air-fuel content of gases expelled from each exhaust valve of the first set of exhaust valves, for each cylinder; and
adjusting engine operation based on the measured transition.

12. The method of claim 11 , wherein adjusting engine operation includes adjusting one or more of an amount of opening overlap between a plurality of intake valves and the first set of exhaust valves, a position of an EGR valve positioned in an EGR passage coupled between the first exhaust manifold and the intake passage, and a position of a bypass valve positioned in a bypass passage coupled between the first exhaust manifold and the exhaust passage.

13. The method of claim 11 , wherein measuring the transition is performed via a first oxygen sensor disposed in the first exhaust manifold.

14. The method of claim 13 , further comprising adjusting one or more of airflow and fueling to each cylinder in response to an output of a second oxygen sensor disposed in the exhaust passage.

15. The method of claim 11 , wherein measuring the transition for each cylinder is performed via a plurality of oxygen sensors, each oxygen sensor of the plurality of oxygen sensors positioned in a runner of a different one of the first set of exhaust valves.

16. The method of claim 11 , further comprising operating the first set of exhaust valves and the second set of exhaust valves at different timings.

17. A method, comprising:
estimating an amount of blowthrough air, that hasn't been combusted, flowing from a first set of cylinder exhaust valves to an intake passage via a first exhaust manifold based on a measured oxygen content in the first exhaust manifold, where the first set of cylinder exhaust valves are operated at a different timing than a second set of cylinder exhaust valves coupled to an exhaust passage via a second exhaust manifold; and
adjusting an engine operating parameter based on the estimated amount of blowthrough air.

18. The method of claim 17 , wherein the measured oxygen content in the first exhaust manifold is determined based on an output of an oxygen sensor positioned in the first exhaust manifold.

19. The method of claim 17 , wherein the first exhaust manifold is coupled to the intake passage via an exhaust gas recirculation (EGR) passage and wherein an EGR valve is disposed in the EGR passage.

20. The method of claim 19 , wherein adjusting the engine operating parameter based on the estimated amount of blowthrough air includes adjusting one or more of a timing of the first set of cylinder exhaust valves, a timing of a set of cylinder intake valves, and a position of the EGR valve to deliver a desired amount of blowthrough air to the intake passage via the first exhaust manifold and EGR passage.

21. The method of claim 17 , wherein adjusting engine operation based on the estimated amount of blowthrough air includes adjusting a position of a bypass valve positioned in a bypass passage coupled between the first exhaust manifold and the exhaust passage based on a desired amount of blowthrough air.

22. A method, comprising:
for each cylinder of a plurality of engine cylinders:
while an intake valve and an exhaust valve of a same engine cylinder are open at a same time, flowing blowthrough air through the same engine cylinder and to an intake passage via an exhaust gas recirculation (EGR) passage fluidly coupled with the exhaust valve; and
adjusting an amount of valve opening overlap between the intake valve and exhaust valve responsive to a transition from a c

Assignees

• Ford Global Tech Llc

Inventors

• Ulrey Joseph Norman
• Surnilla Gopichandra

Classifications

• F02D13/0257 Primary

  Independent control of two or more intake or exhaust valves respectively, i.e. one of two intake valves remains closed or is opened partially while the other is fully opened · CPC title

• F02D41/064

  at cold start (F02D41/067 takes precedence) · CPC title

• F02M26/20

  Feeding recirculated exhaust gases directly into the combustion chambers or into the intake runners · CPC title

• F01N13/107

  More than one exhaust manifold or exhaust collector · CPC title

• F02B25/145

  with intake and exhaust valves exclusively in the cylinder head · CPC title