Methods and system for controlling surge in a two-stage turbocharger

Patent metadata

Field	Value
Publication number	US-9822694-B2
Application number	US-201213570462-A
Country	US
Kind code	B2
Filing date	Aug 9, 2012
Priority date	Aug 9, 2012
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

Various methods and systems are provided for controlling air flow in a two-stage turbocharger. In one example, an engine method comprises adjusting one or more exhaust gas recirculation valves to maintain a first turbocharger within a first air flow range, and adjusting a turbocharger bypass valve to maintain a second turbocharger within a second air flow range.

First claim

The invention claimed is:

1. A method, comprising:
adjusting a turbocharger bypass valve to maintain a second turbocharger within a second air flow range;
adjusting a first exhaust gas recirculation valve and a second exhaust gas recirculation valve based on a designated intake oxygen amount, both exhaust gas recirculation valves further selectively adjusted based on the adjustment of the turbocharger bypass valve to decrease exhaust gas recirculation flow to an intake of an engine in order to maintain a first turbocharger within a first air flow range, different than the second air flow range; and
compensating for the decreased exhaust gas recirculation flow by adjusting one or more engine operating parameters.

2. The method of claim 1 , wherein compensating for the decreased exhaust gas recirculation flow by adjusting one or more engine operating parameters comprises adjusting engine speed without increasing vehicle speed to maintain the first and second turbochargers within the first air flow range and the second air flow range, respectively, and wherein the first and second turbochargers are arranged in series.

3. The method of claim 1 , further comprising adjusting the turbocharger bypass valve to maintain cylinder pressure below a peak combustion pressure.

4. The method of claim 1 , wherein the turbocharger bypass valve comprises a turbine bypass valve of the second turbocharger, the turbine bypass valve coupled in a bypass line, the bypass line including an inlet coupled to an exhaust passage upstream of an inlet of a turbine of the second turbocharger and an outlet coupled to the exhaust passage downstream of an outlet of the turbine of the second turbocharger.

5. The method of claim 1 , wherein the turbocharger bypass valve comprises a compressor bypass valve of the second turbocharger.

6. The method of claim 4 , further comprising directing exhaust gas from the engine to the turbine of the second turbocharger, directing exhaust gas from the turbine of the second turbocharger to a turbine of the first turbocharger, and when the first exhaust gas recirculation valve is open, directing a portion of exhaust gas from upstream of the turbine of the second turbocharger back to the intake of the engine, where the outlet of the bypass line is coupled to the exhaust passage upstream of an inlet of the turbine of the first turbocharger.

7. The method of claim 1 , wherein adjusting the first exhaust gas recirculation valve and the second exhaust gas recirculation valve based on a desired intake oxygen amount comprises:
adjusting the first and second exhaust gas recirculation valves to respective base exhaust gas recirculation positions that provide the designated intake oxygen amount; and
wherein both exhaust gas recirculation valves being further selectively adjusted based on the adjustment of the turbocharger bypass valve comprises, responsive to air flow through the first turbocharger being at or below a surge level, adjusting the first and second exhaust gas recirculation valves away from the respective base exhaust gas recirculation positions to maintain the first turbocharger within the first air flow range.

8. The method of claim 1 , wherein the first air flow range comprises a first mass air flow above a surge level and below a choke level for the first turbocharger, and wherein the second air flow range comprises a second mass air flow above a surge level and below a choke level for the second turbocharger.

9. The method of claim 1 , wherein the first and second turbochargers have relative to each other at least one difference selected from: air output pressure, rotational speed, air mass throughput, surge threshold value, and stall state threshold value; and, the adjusting of the first and second exhaust gas recirculation valves is based at least in part on the air output pressure, rotational speed, air mass throughput, surge threshold value, or stall state threshold value of the first turbocharger, the second turbocharger, or a combination of both the first and second turbochargers.

10. An engine method, comprising:
adjusting an exhaust gas recirculation amount provided to an intake of an engine responsive to an actual exhaust gas recirculation amount deviating from a desired exhaust gas recirculation amount, the desired exhaust gas recirculation amount a function of a designated intake oxygen fraction;
adjusting mass air flow through a high-pressure stage of a two-stage turbocharger to maintain the high-pressure stage below a maximum mass air flow; and
responsive to operation at or below a surge level, instead of adjusting the exhaust gas recirculation amount responsive to the actual exhaust gas recirculation amount deviating from the desired exhaust gas recirculation amount, reducing the exhaust gas recirculation amount provided to the intake of the engine to prevent a surge event of a low-pressure stage of the two-stage turbocharger.

11. The method of claim 10 , wherein adjusting the mass air flow through the high-pressure stage further comprises adjusting the mass air flow to maintain a designated peak combustion pressure.

12. The method of claim 10 , wherein adjusting the mass air flow through the high-pressure stage further comprises adjusting a turbine bypass valve of the high-pressure stage.

13. The method of claim 10 , wherein the exhaust gas recirculation amount is reduced to prevent the surge event responsive to a decrease in engine load.

14. The method of claim 13 , wherein the high-pressure stage includes a different transient response to the decrease in engine load than a low-pressure stage transient response to the decrease in engine load, and further comprising, during the decrease in engine load, reducing the exhaust gas recirculation amount in order to compensate for the different transient responses.

15. The method of claim 10 , wherein the exhaust gas recirculation amount is reduced to prevent the surge event responsive to the adjusting of the mass air flow through the high-pressure stage, the adjusting of the mass air flow through the high-pressure stage including moving a turbine bypass valve of the high-pressure stage into an open position.

16. The method of claim 10 , wherein the exhaust gas recirculation amount is decreased based on a trajectory of exhaust gas recirculation amounts that track a surge level of the low-pressure stage, the trajectory including a path through a compressor map of the low-pressure stage defining a series of pressure ratio and mass flow points, the path parallel to the surge level.

17. The method of claim 10 , further comprising, responsive to reducing the exhaust gas recirculation amount, retarding fuel injection timing by an amount proportional to the reduction of the exhaust gas recirculation amount.

18. The method of claim 10 , further comprising, responsive to reducing the exhaust gas recirculation amount, increasing engine speed to generate excess torque beyond a traction demand and dissipating excess energy from the excess torque to a self-load system.

19. An engine system, comprising:
an engine;
a two-stage turbocharger system coupled to the engine and including a high-pressure stage and a low-pressure stage, airflow through the high-pressure stage controlled by a turbine bypass valve;
an exhaust gas recirculation (EGR) system including an EGR metering valve and an EGR bypass valve, the EGR system configured to selectively route exhaust from a first subset of cylinders of the engine to an intake of the engine via the EGR metering valve or to atmosphere via the EGR bypass val

Assignees

• Mischler James Robert
• Loringer Daniel Edward
• Blythe Neil Xavier
• Henry Luke
• Malone Matthew John
• Polkus Greg Thomas
• Gen Electric

Inventors

• Mischler James Robert
• Loringer Daniel Edward
• Blythe Neil Xavier
• Henry Luke
• Malone Matthew John
• Polkus Greg Thomas

Classifications

• Y02T10/47

  Cross-Sectional Technologies · mapped topic

• F02B29/0412

  Multiple heat exchangers arranged in parallel or in series · CPC title

• F02M26/43

  in which exhaust from only one cylinder or only a group of cylinders is directed to the intake of the engine · CPC title

• F02B37/013 Primary

  with exhaust-driven pumps arranged in series · CPC title

• F02B37/127

  Mechanical Engineering · mapped topic