Methods and systems for EGR control

Patent metadata

Field	Value
Publication number	US-9309837-B2
Application number	US-201313966006-A
Country	US
Kind code	B2
Filing date	Aug 13, 2013
Priority date	Aug 13, 2013
Publication date	Apr 12, 2016
Grant date	Apr 12, 2016

Abstract

Methods and systems are provided for using compressor recirculation flow via a venturi to enhance low pressure EGR flow. The opening of a compressor recirculation valve can be adjusted based on EGR flow demand to recirculate cooled compressed air through a venturi while generating vacuum for drawing EGR. The approach allows for concurrent EGR control and surge control.

First claim

The invention claimed is:

1. A method for an engine, comprising:
recirculating an amount of compressed air from downstream of a charge air cooler to a compressor inlet through a first compressor recirculation passage via a venturi based on EGR flow demand while recirculating another amount to the compressor inlet through a second compressor recirculation passage not including a venturi based on a surge margin; and
using vacuum generated at the venturi to draw EGR into the compressor inlet.

2. The method of claim 1 , wherein the EGR is low pressure EGR drawn into the compressor inlet from downstream of an exhaust turbine, through an EGR passage including an EGR valve.

3. The method of claim 2 , wherein recirculating the amount of compressed air includes adjusting an opening of a first compressor recirculation valve coupled in the first compressor recirculation passage upstream of the venturi to recirculate an amount of cooled compressed air based on the EGR flow demand, and further based on a water content of the EGR.

4. The method of claim 3 , further comprising mixing the drawn EGR with compressor recirculation flow at the venturi, the EGR passage coupled to only the first compressor recirculation passage at the venturi, the EGR valve positioned in the EGR passage upstream of an inlet of the venturi.

5. The method of claim 3 , wherein recirculating the another amount of compressed air recirculated through the second compressor recirculation passage includes adjusting an opening of a second compressor recirculation valve coupled in the second compressor recirculation passage, the opening of the second valve increased as the surge margin decreases.

6. The method of claim 5 , wherein the EGR valve is an on/off valve and wherein the EGR valve is shifted to an on position in response to the EGR flow demand.

7. The method of claim 6 , wherein each of the first and second compressor recirculation valves and are continuously variable valves, and wherein each of the first compressor recirculation valve and the EGR valve are coupled upstream of an inlet of the venturi.

8. The method of claim 6 , wherein the EGR flow demand is based on engine operating conditions including exhaust emissions, and wherein the opening of the first compressor recirculation valve is further adjusted based on an exhaust pressure to provide sufficient venturi vacuum to provide the EGR flow demand.

9. The method of claim 8 , further comprising, in response to an indication of surge, fully opening the second compressor recirculation valve while maintaining the opening of the first compressor recirculation valve and while maintaining the EGR valve in the on position.

10. A method for an engine, comprising,
adjusting an opening of a first valve based on a surge limit and a water content of low-pressure exhaust gas recirculation (EGR) to draw compressor recirculation flow from downstream of a charge air cooler to a compressor inlet via a venturi; and
adjusting an opening of a second valve based on vacuum drawn at the venturi to draw the EGR into the compressor inlet via an EGR passage coupled to the compressor recirculation passage at the venturi.

11. The method of claim 10 , wherein each of the first and second valves are continuously variable valves, the first valve coupled upstream of an inlet of the venturi in a compressor recirculation passage, the second valve coupled upstream of the inlet of the venturi in the EGR passage.

12. The method of claim 11 , further comprising drawing a vacuum at the venturi via the compressor recirculation flow, wherein an amount of vacuum drawn at the venturi is based on the opening of the first valve.

13. The method of claim 12 , wherein adjusting an opening of the second valve includes adjusting the opening of the second valve based on a vacuum demand to draw EGR into the compressor inlet at a flow rate determined based on engine operating conditions.

14. The method of claim 13 , wherein the opening of the second valve is further adjusted based on exhaust pressure.

15. The method of claim 14 , wherein adjusting the opening of the first valve includes increasing the opening of the first valve as a margin to the surge limit decreases.

16. The method of claim 15 , wherein adjusting the opening of the second valve includes decreasing an opening of the EGR valve as the amount of vacuum drawn at the venturi increases to draw EGR into the compressor inlet at the determined flow rate.

17. The method of claim 16 , further comprising mixing the compressor recirculation flow with the drawn EGR at the venturi before delivering the mixture to the compressor inlet.

18. An engine system, comprising:
an engine including an intake and an exhaust;
a turbocharger including an exhaust turbine driven by an intake compressor;
a charge air cooler coupled downstream of the compressor;
a first compressor recirculation passage including a first valve and a venturi, the first passage coupling an outlet of the charge air cooler to an inlet of the compressor, the venturi positioned downstream of the first valve in the first passage;
a second compressor recirculation passage including a second valve, the second passage parallel to the first passage and coupling the outlet of the charge air cooler to the inlet of the compressor;
an EGR passage including an EGR valve for recirculating exhaust residuals to the first compressor recirculation passage, downstream of the venturi; and
a controller with computer readable instructions for,
adjusting an opening of the first valve based on an exhaust pressure upstream of an inlet of the EGR passage to generate venturi vacuum to provide a desired EGR flow; and

adjusting an opening of the second valve based on a margin to compressor surge with the first valve open.

19. The system of claim 18 , wherein each of the first and second valves are continuously variable valves, and wherein the EGR valve is an on/off valve that is shifted to an on position by the controller when EGR flow is desired.

20. The system of claim 19 , wherein the adjusting includes increasing an opening of the second valve as the margin to compressor surge increases and increasing an opening of the first valve as an amount of the venturi vacuum required to draw in the desired EGR flow from the EGR passage towards the compressor inlet increases, the EGR flow mixed with the compressor recirculation flow through the first passage upstream of the compressor inlet.

Assignees

• Ford Global Tech Llc

Inventors

• Ulrey Joseph Norman
• Mcconville Gregory Patrick
• Styles Daniel Joseph
• Pursifull Ross Dykstra
• Shelby Michael Howard

Classifications

• F02M25/07 Primary

  Mechanical Engineering · mapped topic

• F02D41/0065

  Specific aspects of external EGR control (constructional details of EGR system F02M26/00) · CPC title

• F02D41/0007

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

• F02M25/0709

  Mechanical Engineering · mapped topic

• F02M25/0727

  Mechanical Engineering · mapped topic