System and method for controlling an engine air-fuel ratio

Patent metadata

Field	Value
Publication number	US-9863342-B2
Application number	US-201514864984-A
Country	US
Kind code	B2
Filing date	Sep 25, 2015
Priority date	Sep 25, 2015
Publication date	Jan 9, 2018
Grant date	Jan 9, 2018

Abstract

Various methods and systems are provided for adjusting an air-fuel ratio for combustion in an engine. In one embodiment, a method for an engine (e.g., a method for controlling an engine system) comprises responding to a sensed change in a load on the engine, or indications of engine knock or misfire, by one or more of: altering a speed of the engine, adjusting a fueling flow rate into at least one cylinder of the engine, and adjusting a position of a valve in a bypass passage configured to direct compressed intake air away from cylinders of the engine to obtain a determined air-fuel ratio; and thereby maintaining an air-fuel ratio in a determined range.

First claim

The invention claimed is:

1. A method for an engine, comprising:
responding to a sensed change in a load on the engine, or indications of engine knock or misfire, by:
operating in a first mode and, in the first mode, altering a speed of the engine to obtain a determined air-fuel ratio within a determined range; and
operating in a second mode and, in the second mode, adjusting a position of a valve in a bypass passage configured to direct compressed intake air away from cylinders of the engine to obtain the determined air-fuel ratio within the determined range.

2. The method of claim 1 , wherein the determined air-fuel ratio is based on the sensed change in load or indications of engine knock or misfire and additional engine operating conditions including one or more of a measured oxygen or other gaseous emission level in an exhaust passage of the engine, a substitution ratio of natural gas to diesel fuel injected into the engine, an intake manifold pressure, a calculated or measured cylinder pressure, an exhaust temperature, or the speed of the engine.

3. The method of claim 1 , wherein altering the speed of the engine includes:
increasing the speed of the engine to increase airflow to at least one cylinder of the engine in response to the determined air-fuel ratio being greater than a current air-fuel ratio during the sensed change in load or indications of engine knock or misfire; and
decreasing the speed of the engine to decrease airflow to the at least one cylinder in response to the determined air-fuel ratio being less than the current air-fuel ratio.

4. The method of claim 1 , further comprising operating in a third mode and, in the third mode, adjusting a fueling flow rate into at least one cylinder of the engine, wherein adjusting the fueling flow rate includes:
increasing a flow of one or more fuels to the at least one cylinder in response to the determined air-fuel ratio being less than a current air-fuel ratio during the sensed change in load or indications of engine knock or misfire; and
decreasing the flow of the one or more fuels to the at least one cylinder in response to the determined air-fuel ratio being greater than the current air-fuel ratio.

5. The method of claim 4 , wherein the engine is a dual fuel engine combusting natural gas and diesel fuel and wherein adjusting the fueling flow rate includes increasing or decreasing the flow of the natural gas and increasing or decreasing the flow of the diesel fuel while maintaining a substitution ratio of the natural gas to diesel fuel.

6. The method of claim 1 , wherein the bypass passage is coupled to an intake passage of the engine upstream of engine cylinders and downstream of a turbocharger compressor and wherein adjusting the position of the valve includes:
opening the valve to dump compressor intake air prior to it entering the engine cylinders in response to the determined air-fuel ratio being less than a current air-fuel ratio during the sensed change in load or indications of engine knock or misfire; and
closing the valve to direct intake air to the engine cylinders in response to the determined air-fuel ratio being greater than the current air-fuel ratio.

7. The method of claim 1 , further comprising, in response to a wheel slip condition indicated by a wheel spin detector of a vehicle in which the engine is installed, operating in a fourth mode and in the fourth mode, adjusting a fueling flow rate into at least one cylinder of the engine, adjusting the position of the valve, adjusting injection timing of one or more fuels injected into the at least one cylinder, and transferring the load on the engine to one or more resistive grids of the vehicle or to an energy storage device.

8. The method of claim 1 , wherein the indications of engine knock or misfire are determined based on one or more of an output of a knock sensor, an output of a misfire sensor, or an inferred or expected knock or misfire event based on engine operating conditions and wherein the sensed change in the load on the engine is a change in notch level.

9. A method for an engine, comprising:
responsive to a change in a desired air-fuel ratio, adjusting an air-fuel ratio of the engine, where the engine is a dual fuel engine combusting diesel fuel and natural gas, to a determined level by:
during a first condition, adjusting a speed of the engine;
during a second condition, adjusting fuel flow of one or more of the diesel fuel and the natural gas to engine cylinders of the engine; and
during a third condition, adjusting an engine bypass valve adapted to divert intake air away from the engine cylinders to a location external to the engine.

10. The method of claim 9 , wherein the first condition includes one or more of an indication of knock or misfire, decreased combustion efficiency or increased emissions, or a change in an engine operating condition that results in the change in the desired air-fuel ratio while a power level of the engine is maintained.

11. The method of claim 9 , wherein the second condition includes one or more of a wheel slip condition or a change in a demanded power output of the engine that results in the change in the desired air-fuel ratio being above a threshold amount of change.

12. The method of claim 9 , wherein the third condition includes one or more of a wheel slip condition or a change in a demanded power output of the engine that results in the change in the desired air-fuel ratio being below a threshold amount of change.

13. The method of claim 9 , further comprising:
during a fourth condition when the change in the desired air-fuel ratio is greater than a threshold or when knock or misfire are occurring, adjusting each of the fuel flow to the engine cylinders and the engine bypass valve to adjust the air-fuel ratio to the determined level in response to the change in the desired air-fuel ratio;
during a fifth condition when the change in the desired air-fuel ratio is greater than the threshold and the engine bypass valve cannot be adjusted due to the engine bypass valve already being in a desired position for obtaining the desired air-fuel ratio, adjusting each of the fuel flow to the engine cylinders and the speed of the engine to adjust the air-fuel ratio to the determined level in response to the change in the desired air-fuel ratio; and
during a sixth condition when the change in the desired air-fuel ratio is less than the threshold, adjusting each of the speed of the engine and the engine bypass valve to adjust the air-fuel ratio to the determined level in response to the change in the desired air-fuel ratio.

14. The method of claim 9 , further comprising, during a seventh condition when the change in the desired air-fuel ratio is greater than a threshold and knock or misfire are expected based on the change in the desired air-fuel ratio, adjusting each of the fuel flow to the engine cylinders, the speed of the engine, and the engine bypass valve to adjust the air-fuel ratio to the determined level in response to the change in the desired air-fuel ratio.

15. The method of claim 9 , wherein the engine bypass valve is positioned in a bypass passage, the bypass passage coupled to an intake passage of the engine upstream of the engine cylinders and downstream of a turbocharger compressor of the engine.

16. A system for an engine, comprising:
a first intake air duct coupled to a first engine cylinder bank;
a turbocharger including a compressor at least partially driven by a turbine, where the first intake air duct is coupled to an outlet of the compressor;
a bypass passage coupled to the first intake air duct,

Assignees

• Gen Electric

Inventors

• Tulapurkar Chetan Sharadchandra
• Gokhale Manoj
• Primus Roy James
• Trask Leslie Orin
• Mischler James Robert
• Klingbeil Adam Edgar
• Lavertu Thomas Michael

Classifications

• F02D41/1475

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

• F02D19/081

  Adjusting the fuel composition or mixing ratio; Transitioning from one fuel to the other · CPC title

• F02B37/16

  by bypassing charging air · CPC title

• F02D41/021

  Introducing corrections for particular conditions exterior to the engine (conjoint control of vehicle sub-units for propelling the vehicle B60W30/18) · CPC title

• F02D41/1456

  with sensor output signal being linear or quasi-linear with the concentration of oxygen · CPC title