Systems and methods for increasing engine power output under globally stoichiometric operation

Patent metadata

Field	Value
Publication number	US-11248554-B2
Application number	US-201916559448-A
Country	US
Kind code	B2
Filing date	Sep 3, 2019
Priority date	Sep 3, 2019
Publication date	Feb 15, 2022
Grant date	Feb 15, 2022

Abstract

Methods and systems are provided for increasing engine power via partial engine enrichment and exhaust gas recirculation. In one example, a method may include enriching a first set of engine cylinders and enleaning a second, remaining set of the engine cylinders, exhaust gas from the first set and the second set producing a stoichiometric mixture at a downstream emission control device, and providing exhaust gas recirculation (EGR) to an intake passage of the engine from the first set of cylinders and not from the second set. In this way, cooling effects from the partial enrichment and the EGR enable engine air flow, and thus engine power, to be increased while an efficiency of the emission control device is maintained, thereby decreasing vehicle emissions.

First claim

The invention claimed is:

1. A method, comprising:
while operating an engine with a positive engine torque demand increasing to greater than a threshold torque and a rate of exhaust gas recirculation (EGR) reaching a threshold rate, enriching a first set of cylinders and enleaning a second, remaining set of cylinders, exhaust gas from the first set of cylinders and the second set of cylinders producing a stoichiometric mixture at a downstream emission control device, and providing the EGR to an intake passage of the engine from the first set of cylinders and not from the second set of cylinders, wherein an amount of enriching of the first set of cylinders and enleaning of the second set of cylinders is increased responsive to the engine torque demand being greater than the threshold torque and further responsive to the rate of the EGR reaching the threshold rate; and
gradually decreasing the rate of the EGR responsive to the engine torque demand being greater than the threshold torque and further responsive to the rate of the EGR reaching the threshold rate.

2. The method of claim 1 , wherein the first set of cylinders includes a first half of a total number of cylinders in the engine and the second set of cylinders includes a second half of the total number of cylinders in the engine.

3. The method of claim 2 , wherein the first set of cylinders includes cylinders of a first engine bank and the second set of cylinders includes cylinders of a second engine bank.

4. The method of claim 1 , wherein the first set of cylinders flow exhaust gas to a first exhaust manifold and the second set of cylinders flow exhaust gas to a second exhaust manifold, and wherein the first exhaust manifold and the second exhaust manifold are not directly coupled.

5. The method of claim 4 , wherein an EGR passage couples the first exhaust manifold to the intake passage of the engine, the EGR passage including an EGR valve and an EGR cooler disposed therein, and wherein providing the EGR to the intake passage of the engine from the first set of cylinders and not from the second set of cylinders includes at least partially opening the EGR valve.

6. The method of claim 5 , wherein the EGR passage is coupled to the first exhaust manifold upstream of a turbine of a turbocharger and is coupled to the intake passage downstream of a compressor of the turbocharger.

7. The method of claim 6 , wherein exhaust gas from both the first exhaust manifold and the second exhaust manifold flows through the emission control device, the emission control device coupled in an exhaust passage downstream of the turbine.

8. The method of claim 6 , wherein the turbine is a dual scroll turbine, the second exhaust manifold coupled to a first, hotter scroll of the dual scroll turbine and the first exhaust manifold coupled to a second, cooler scroll of the dual scroll turbine.

9. The method of claim 1 , further comprising advancing spark timing in both the first set of cylinders and the second set of cylinders, the advancing individually adjusted for each cylinder.

10. A method, comprising:
operating an engine in a stoichiometric mode, a power exhaust gas recirculation (EGR) mode, and a split lambda mode;
selecting between operating the engine in the stoichiometric mode, the power exhaust gas recirculation (EGR) mode, and the split lambda mode based on an engine torque demand;
the stoichiometric mode including operating all engine cylinders at a stoichiometric air-fuel ratio (AFR), the power EGR mode including operating all engine cylinders at the stoichiometric AFR while increasing an EGR rate, and
the split lambda mode including operating a first half of the engine cylinders rich and a second half of the engine cylinders lean while providing EGR from the first half of the engine cylinders only.

11. The method of claim 10 , further comprising operating with the engine torque demand being less than a first, lower threshold, operating with the engine torque demand being greater than the first threshold and less than a second, higher threshold, and operating with the engine torque demand being greater than the second threshold;
wherein the first half of the engine cylinders are coupled to a first exhaust manifold and the second half of the engine cylinders are coupled to a second exhaust manifold, the first exhaust manifold and the second exhaust manifold isolated from one another upstream of an exhaust passage, and wherein selecting between operating the engine in the stoichiometric mode, the power EGR mode, and the split lambda mode based on the engine torque demand includes:
selecting the stoichiometric mode responsive to the engine torque demand being less than a first, lower threshold;
selecting the power EGR mode responsive to the engine torque demand being greater than the first threshold and less than a second, higher threshold; and
selecting the split lambda mode responsive to the engine torque demand being greater than the second threshold.

12. The method of claim 11 , wherein a degree of enrichment of the first half of the engine cylinders is increased and the EGR rate is decreased as the engine torque demand further increases above the second threshold.

13. The method of claim 10 , wherein operating the first half of the engine cylinders rich and the second half of the engine cylinders lean produces a stoichiometric mixture at a downstream emission control device having a brick and positioned to receive exhaust gas from both the first half of the engine cylinders and the second half of the engine cylinders.

14. The method of claim 10 , wherein operating the engine in the stoichiometric mode includes increasing engine torque by increasing an amount of boost provided by a turbocharger, operating the engine in the power EGR mode includes increasing engine torque by increasing the EGR rate until a threshold rate is reached while further increasing the amount of boost provided by the turbocharger, and operating in the split lambda mode includes increasing engine torque by increasing a degree of enrichment of the first half of the engine cylinders while decreasing the EGR rate and still further increasing the amount of boost provided by the turbocharger.

15. A system, comprising:
an engine, including a plurality of cylinders;
a first exhaust manifold coupled to a first set of the plurality of cylinders and a second exhaust manifold coupled to a second, remaining set of the plurality of cylinders, the first exhaust manifold separate from the second exhaust manifold; and
a controller with computer readable instructions stored on non-transitory memory that, when executed during engine operation, cause the controller to:
operate the first set of the plurality of cylinders at a rich air-fuel ratio and operate the second set of the plurality of cylinders at a lean air-fuel ratio responsive to an engine demand increasing above an upper threshold demand and a rate of an exhaust gas recirculation (EGR) reaching a threshold rate, and then decreasing the rate of the EGR; and
operate the first set of the plurality of cylinders and the second set of the plurality of cylinders at a same air-fuel ratio responsive to the engine demand remaining below the upper threshold demand.

16. The system of claim 15 , further comprising an EGR passage coupled between the first exhaust manifold and an intake passage of the engine, the EGR passage including an EGR valve and an EGR cooler disposed therein, and wherein the controller includes further computer readable instructions stored in non-transitory memory that, when executed during engine operation, cause the controll

Assignees

• Ford Global Tech Llc

Inventors

• Puntambekar Aakash

Classifications

• F02D41/0085

  Balancing of cylinder outputs, e.g. speed, torque or air-fuel ratio · CPC title

• F02D21/04

  with circulation of exhaust gases in closed or semi-closed circuits · CPC title

• F02D41/005 Primary

  according to engine operating conditions · CPC title

• F02D41/26 Primary

  using computer, e.g. microprocessor · CPC title

• F02D41/1475

  Regulating the air fuel ratio at a value other than stoichiometry · CPC title