Robust estimation of biodiesel blend ratio for alternative fuel combustion

• US 8,594,907 B2
• Filed: 05/23/2011
• Issued: 11/26/2013
• Est. Priority Date: 05/23/2011
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Wang, Yue-Yun, Haskara, Ibrahim
• Primary Examiner(s): Cronin, Stephen K
• Assistant Examiner(s): DALLO, JOSEPH J
• Application Number:
  US13/113,177
• Publication Number:
  US 20120303245A1
• Time in Patent Office: 918 Days
• Field of Search: 123575-578, 123/299, 123/300, 123/304, 123/27.GE, 123/1.A, 123/435, 123/672, 123/674, 123/675, 123/703, 123/704, 701102-104, 701/109
• US Class Current: 701/104
• CPC Class Codes: F02D 19/0615 being initiated by automatic means, e.g. based on engine or vehicle operating conditions
• CPC Class Codes: F02D 19/082 Premixed fuels, i.e. emulsions or blends
• CPC Class Codes: F02D 2041/1417 Kalman filter
• CPC Class Codes: F02D 41/0025 Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
• CPC Class Codes: F02D 41/1454 the characteristics being an oxygen content or concentration or the air-fuel ratio
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels

Abstract

A method to control an internal combustion engine includes operating the engine with a fuel blend of a first fuel and a second fuel, monitoring a value of a first combustion parameter during engine operation, monitoring a first value for a second combustion parameter during engine operation, determining a second value for the second combustion parameter in accordance with a predetermined correspondence among the first combustion parameter, the second combustion parameter, and a predetermined fuel blend of the first fuel and the second fuel, determining the fuel blend based upon a difference between the first and second values for the second combustion parameter, and controlling the engine based upon the fuel blend.

Claims

1. Method to control an internal combustion engine fueled by a variable fuel blend of a first fuel and a second fuel, the method comprising:

operating the engine with a variable fuel blend of a first fuel and a second fuel, said variable fuel blend comprising an unknown ratio of a first portion of the first fuel and a second remaining portion of the second fuel;

monitoring a value of a first combustion parameter during engine operation;

monitoring a first value for a second combustion parameter during engine operation, wherein the first combustion parameter comprises one of an air fuel ratio and an exhaust oxygen fraction and the second combustion parameter comprises the other one of the air fuel ratio and the exhaust oxygen fraction;

determining a second value for the second combustion parameter in accordance with a predetermined correspondence among said first combustion parameter, said second combustion parameter, and a predetermined fuel blend of the first fuel and the second fuel;

only when the monitored air fuel ratio is within a predetermined range, determining the ratio of the variable fuel blend based upon a difference between the first and second values for the second combustion parameter; and

controlling the engine based upon the fuel blend.

2. The method of claim 1, wherein said first combustion parameter comprises the exhaust oxygen fraction and said second combustion parameter comprises the air fuel ratio.

3. The method of claim 1, wherein said first combustion parameter comprises the air fuel ratio and said second combustion parameter comprises the exhaust oxygen fraction.

4. The method of claim 1, wherein said predetermined fuel blend comprises 100 percent of said first fuel and 0% of said second fuel.

5. The method of claim 1, wherein said predetermined fuel blend comprises 100 percent of said second fuel and 0% of said first fuel.

6. The method of claim 1, wherein determining said second value for the second combustion parameter comprises referencing said second value from a predetermined look-up table correlating values of said first combustion parameter and said second combustion parameter at said predetermined fuel blend.

7. The method of claim 1, wherein determining said second value for the second combustion parameter comprises solving a predetermined equation representing the correspondence between said first combustion parameter and said second combustion parameter.

8. Method to control an internal combustion engine fueled by a variable fuel blend of a diesel fuel and a biodiesel fuel, the method comprising:

operating the engine with a variable fuel blend of a diesel fuel and a biodiesel fuel, said variable fuel blend comprising an unknown ratio of a first portion of the diesel fuel and a second remaining portion of the biodiesel fuel;

monitoring a value of a first combustion parameter during engine operation;

monitoring a first value for a second combustion parameter during engine operation;

wherein the first combustion parameter comprises one of an air fuel ratio and an exhaust oxygen fraction and the second combustion parameter comprises the other one of the air fuel ratio and the exhaust oxygen fraction;

determining a second value for the second combustion parameter in accordance with a predetermined correspondence among said first combustion parameter, said second combustion parameter, and a predetermined fuel blend of the diesel fuel and the biodiesel fuel;

only when the monitored air fuel ratio is within a predetermined range, determining the ratio of the variable fuel blend based upon the first and second values for the second combustion parameter; and

controlling the engine based upon the fuel blend.

9. The method of claim 8, wherein said first combustion parameter comprises the exhaust oxygen fraction and said second combustion parameter comprises the air fuel ratio.

10. The method of claim 9, wherein said predetermined fuel blend comprises 100 percent diesel fuel and 0% biodiesel fuel, and wherein determining the ratio of the variable fuel blend comprises determining a percentage of biodiesel fuel of the fuel blend in accordance with the following equation:

11. The method of claim 9, wherein determining the ratio of the variable fuel blend comprises utilizing a state space model and a Kalman filter to determine the fuel blend.

12. The method of claim 11, wherein the state space model comprises a gamma ratio utilizing the following equation:

13. The method of claim 8, wherein said first combustion parameter comprises the air fuel ratio and said second combustion parameter comprises the exhaust oxygen fraction.

14. The method of claim 13, wherein said predetermined fuel blend comprises 100 percent diesel fuel and 0% biodiesel fuel, and wherein determining the fuel blend comprises determining a percentage of biodiesel fuel of the fuel blend in accordance with the following equation:

15. The method of claim 13, wherein determining the ratio of the variable fuel blend comprises utilizing a state space model and a Kalman filter to determine the fuel blend.

16. The method of claim 15, wherein the state space model comprises a gamma ratio utilizing the following equation:

17. The method of claim 8, wherein the method is performed subsequent to fuel fill event wherein a fuel level within a fuel tank increases.

18. The method of claim 17, further comprising:

correcting a MAF sensor error subsequent to a delay after the fuel fill event sufficient for the fuel blend to reach a steady state composition.

19. The method of claim 17, further comprising:

correcting a fuel injection pulse width subsequent to a delay after the fuel fill event sufficient for the variable fuel blend to reach a steady state composition.

20. Method to control an internal combustion engine fueled by a variable fuel blend of a diesel fuel and a biodiesel fuel, the method comprising:

operating the engine with a variable fuel blend of a diesel fuel and a biodiesel fuel, said variable fuel blend comprising an unknown first portion of the first fuel and a second remaining portion of the second fuel;

monitoring a value of exhaust oxygen fraction during engine operation;

monitoring a first value for air fuel ratio during engine operation;

referencing a second value for air fuel ratio from a predetermined look-up table correlating values of exhaust oxygen fraction and air fuel ratio at a fuel blend of 100 percent diesel fuel and 0% biodiesel fuel;

only when the monitored air fuel ratio is within a predetermined range, determining the variable fuel blend based upon the first and second values for air fuel ratio; and

controlling the engine based upon the fuel blend.