Systems and methods for control of turbine-generator via exhaust valve timing and duration modulation in a split exhaust engine system

Patent metadata

Field	Value
Publication number	US-9624850-B2
Application number	US-201414537722-A
Country	US
Kind code	B2
Filing date	Nov 10, 2014
Priority date	Nov 10, 2014
Publication date	Apr 18, 2017
Grant date	Apr 18, 2017

Abstract

Methods and systems are provided for reducing exhaust energy delivered to a turbine of a turbine-generator coupled to a split exhaust engine system in order to reduce turbine over-speed conditions and/or to reduce a generator output. In one example, a method may include retarding a first timing of a first exhaust valve utilized to deliver a blowdown portion of exhaust energy to the turbine, and/or advancing a second timing of a second exhaust valve utilized to deliver a scavenging portion of exhaust energy to an exhaust catalyst in response to a turbine speed greater than a threshold speed.

First claim

The invention claimed is:

1. A method for operating an engine with split exhaust, the method comprising:
measuring and/or estimating a turbine speed via one or more sensors during an engine operating condition; and
in response to determining, with an engine controller, that the turbine speed is greater than a first threshold turbine speed,
retarding an opening time of a first exhaust valve of a cylinder delivering exhaust gas to a turbine of a turbine-generator, the opening time of the first exhaust valve retarded via an actuation system.

2. The method of claim 1 , further comprising advancing an opening time of a second exhaust valve of the cylinder delivering exhaust to an exhaust catalyst while bypassing the turbine, and further comprising increasing an opening duration of the second exhaust valve via the actuation system in response to determining that the turbine speed is greater than the first threshold turbine speed.

3. The method of claim 2 , further comprising increasing a degree of a wastegate valve opening in response to determining that the turbine speed is greater than the first threshold turbine speed.

4. The method of claim 1 , further comprising measuring and/or estimating a generator output via one or more sensors; and
in response to determining, with the engine controller, that the generator output is greater than a threshold, retarding the opening time of the first exhaust valve, and advancing the opening time of the second exhaust valve via the actuation system, the generator output including one or more of a generator output voltage, a generator output current, or a generator output power.

5. The method of claim 4 , further comprising, in response to determining with the engine controller that a difference between the generator output and a desired generator output is less than a first threshold difference, operating the first exhaust valve at a first normal exhaust valve opening timing and a first normal exhaust valve opening duration via the actuation system; and operating the second exhaust valve at a second normal exhaust valve opening timing and a second normal exhaust valve opening duration via the actuation system.

6. The method of claim 1 , wherein the first threshold turbine speed is based on a desired generator speed.

7. The method of claim 6 , wherein the desired generator speed is based on a battery state of charge, an electrical demand or electrical load, an engine speed, an engine load, and an amount of exhaust mass flow into the turbine via the first exhaust valve.

8. The method of claim 5 , wherein the first normal exhaust valve opening timing is advanced with respect to the second normal exhaust valve opening timing.

9. A method for operating an engine with split exhaust including a turbine in a first exhaust passage coupled to a generator and an exhaust catalyst in a second exhaust passage, the method comprising:
measuring and/or estimating a turbine speed via one or more sensors during an engine operating condition; and
responsive to determining, with an engine controller, a first condition, wherein the first condition includes the turbine speed being greater than a first threshold speed and a second threshold speed,
flowing exhaust gas to the turbine via a first exhaust valve from an engine cylinder to the first exhaust passage;
flowing exhaust gas to the catalyst via a second exhaust valve from the engine cylinder to the second exhaust passage; and
advancing an opening time of the second exhaust valve relative to a normal opening time of the second exhaust valve and increasing an opening duration of the second exhaust valve relative to a normal opening duration of the second exhaust valve, wherein the first and the second exhaust valves are controlled via an actuation system.

10. The method of claim 9 , further comprising, in response to determining the first condition via the engine controller, retarding an opening time of the first exhaust valve relative to a normal opening time of the first exhaust valve, and opening a waste gate; and
further comprising, in response to determining, with the engine controller, a second condition, wherein the second condition includes the turbine speed being less than the second threshold speed and greater than the first threshold speed, and a difference between an actual generator output and a desired generator output being greater than a second threshold difference,
retarding the opening time of the first exhaust valve relative to the normal opening time of the first exhaust valve,
advancing the opening time of the second exhaust valve relative to the normal opening time of the second exhaust valve,
increasing the opening duration of the second exhaust valve relative to the normal opening duration of the second exhaust valve, and
closing the wastegate to decrease exhaust gas flow to the turbine.

11. The method of claim 10 , further comprising, responsive to determining, with the engine controller, a third condition, wherein the third condition includes the turbine speed being less than the second threshold speed, and the difference between the actual generator output and the desired generator output being less than the second threshold difference and greater than a first threshold difference, retarding the opening time of the first exhaust valve relative to the normal opening time of the first exhaust valve, advancing the opening time of the second exhaust valve relative to the normal opening time of the second exhaust valve, increasing the opening duration of the second exhaust valve relative to the normal opening duration of the second exhaust valve, and closing the wastegate to decrease exhaust gas flow to the turbine.

12. The method of claim 11 , wherein the opening time of the first exhaust valve is retarded by a greater amount in response to the first condition than in response to the second condition.

13. The method of claim 12 , wherein the opening time of the first exhaust valve is retarded by a greater amount in response to the third condition than in response to the second condition.

14. The method of claim 12 , wherein the opening duration of the second exhaust valve is greater in response to the first condition than in response to the second condition; and wherein the opening duration of the second exhaust valve in response to the second condition is greater than in response to the third condition.

15. The method of claim 10 , wherein increasing the opening duration of the second exhaust valve relative to the normal opening duration of the second exhaust valve includes advancing the opening timing of the second exhaust valve from the normal opening timing of the second exhaust valve, and not changing a closing timing of the second exhaust valve with respect to a normal closing timing of the second exhaust valve.

16. The method of claim 15 , wherein the normal opening time of the second exhaust valve includes opening the second exhaust valve between 170 and 210 degrees after top dead center and closing the second exhaust valve between 350 and 390 degrees after top dead center.

17. The method of claim 16 , wherein a first amount of exhaust gas bypassing the turbine during the first condition is greater than a second amount of exhaust gas bypassing the turbine during the second condition; and wherein the second amount of exhaust gas during the second condition is greater than a third amount of exhaust gas during the third condition.

18. A system comprising:
an engine cylinder;
a first exhaust valve for delivering an initial portion of exhaust gas from the cylinde

Assignees

• Ford Global Tech Llc

Inventors

• Ulrey Joseph Norman
• Leone Thomas G
• Styles Daniel Joseph
• Maceroni Karen Elizabeth

Classifications

• F02D13/0246

  changing valve lift or valve lift and timing · CPC title

• F01N5/04 Primary

  the devices using kinetic energy · CPC title

• F02D41/0007 Primary

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

• F02D13/0257

  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

• F02D29/06

  peculiar to engines driving electric generators · CPC title