FUEL BLEND SENSING SYSTEM

• US 20110208409A1
• Filed: 08/03/2009
• Published: 08/25/2011
• Est. Priority Date: 08/01/2008
• Status: Abandoned Application

• Current Assignee: Purdue Research Foundation (Purdue University)
• Original Assignee: Purdue Research Foundation (Purdue University)
• Inventors: Snyder, David Benjamin, Shaver, Gregory Matthew
• Application Number:
  US13/056,732
• Publication Number:
  US 20110208409A1
• Time in Patent Office: Days
• US Class Current: 701/109
• CPC Class Codes: F02D 19/084 Blends of gasoline and alcohols, e.g. E85
• CPC Class Codes: F02D 19/088 by estimation, i.e. without using direct measurements of a corresponding sensor
• CPC Class Codes: F02D 2200/0418 Air humidity
• 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 41/0052 Feedback control of engine parameters, e.g. for control of air/fuel ratio or intake air amount
• 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
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

While the materials compatibility challenges have largely been met in “flex-fuel” vehicles, the engine and aftertreatment operation has not been optimized as function of fuel type (i.e. ethanol, biodiesel, etc.). The full-scale introduction of alternative fuels is most likely going to occur as blends with conventional fuels. This is seen to some extend with the limited introduction of E85 (85% ethanol, 15% gasoline) and B20 (20% biodiesel, 80% conventional diesel.). This further exacerbates the challenge of accommodating variable fuel properties, as there will be differences in combustion properties due to both the type of alternative fuel (i.e. pure biodiesel vs. pure diesel) and blend ratio (i.e. B20 vs. B80). Real-time estimation of the fuel blend is key to the optimized use of two-component fuels (e.g. diesel-biodiesel, gasoline-ethanol, etc.). The approach outlined here uses knowledge of the exhaust composition, fuel and air delivery rates to the engine to estimate the fuel blend. The strategy is illustrated with a production wideband O₂ in the engine'"'"'s exhaust stream, coupled with the knowledge of the air-fuel ratio, to estimate the percentage of biodiesel in fuel being delivered to a 2007 Cummins turbo-diesel engine.

Claims

1. An apparatus comprising:

an internal combustion engine including an air intake to provide an airflow;

a fuel source to provide a fuel flow to the engine to mix with the airflow for combustion by the engine, the engine producing an exhaust flow from the combustion;

a wide-band oxygen sensor disposed in the exhaust flow for providing a signal representative of free oxygen content; and

a controller responsive to the signal, an amount of the fuel flow, and an amount of the airflow to determine oxygen content of fuel in the fuel flow.

2. The apparatus of claim 1, wherein said controller includes operating logic defining an estimator to determine the oxygen content of the fuel as a function of the signal, the amount of the fuel flow, and the amount of the airflow.

3. The apparatus of claim 1, wherein said controller includes memory and the operating logic is at least partially in the form of programming instructions executable by the controller, the programming instructions being stored in the memory.

4. The apparatus of claim 1, wherein said controller includes means for selectively providing exhaust gas recirculation in response to the oxygen content of the fuel.

5. The apparatus of claim 1, wherein said controller includes means for selectively adjusting an aftertreatment subsystem in response to the oxygen content of the fuel.

6. The apparatus of claim 1 wherein the fuel comprises a mixture of a first composition which includes oxygen and a second composition which substantially does not include oxygen.

7. The apparatus of claim 6 wherein the first composition is one of biodiesel or ethanol and the second composition is one of diesel fuel or gasoline.

8. The apparatus of claim 6 wherein the first composition is one of ethanol, methanol, dimethyl ether or biodiesel fuel.

9. The apparatus of claim 1 wherein said controller operates said engine with an air to fuel ratio that includes less than a stoichiometric amount of fuel.

10. A method of operating an internal combustion engine, comprising:

providing an internal combustion engine, and a mixed fuel including a first fuel which includes oxygen and a second fuel which substantially does not include oxygen;

operating the engine with the mixed fuel;

calculating the flow rate of fuel into the engine during said operating;

calculating the flow rate of air into the engine during said operating;

measuring the free oxygen content of the exhaust gas from the engine; and

interpreting the ratio of the first fuel to the second fuel from the fuel flow rate, air flow rate, and oxygen content.

11. The method of claim 10 which further comprises using the ratio to control the engine.

12. The method of claim 10, which further comprises modifying an engine operating parameter in response to the oxygen content of the fuel flow.

13. The method of claim 12, wherein said modifying comprises at least one of:

modifying an exhaust gas recirculation flow rate;

modifying an exhaust gas recirculation fraction target;

modifying a fuel injection pressure;

modifying a fuel injection timing;

modifying a torque rating of the engine;

or

modifying an emissions operating mode of the engine.

14. The method of claim 10, which further comprises determining the oxygen content of the first fuel.

15. The method of claim 10, which further comprises determining an oxygen mole fraction of the exhaust flow in response to the oxygen content of the exhaust flow, and determining the composition of the fuel flow according to the equation:

16. The method of claim 10 wherein the internal combustion engine is a compression ignition engine, and the second fuel is diesel fuel.

17. The method of claim 10 wherein the internal combustion engine is a spark ignition engine, and the second fuel is gasoline.

18. The method of claim 10 wherein the first composition is one of ethanol, methanol, dimethyl ether or biodiesel.

19. The method of claim 10 wherein said operating is with an air to fuel ratio that includes less than a stoichiometric amount of fuel.

48. The method of claim 10 which further comprises measuring the humidity of the air entering the engine and wherein said interpreting the ratio of the first fuel to the second fuel includes the humidity of the entering air.

20. A method of operating an internal combustion engine, comprising:

providing an internal combustion engine,

providing a first mixed fuel having a first predetermined mixture ratio of a first hydrocarbon fuel having a first molar quantity of oxygen mixed with a second hydrocarbon fuel having a second molar quantity of oxygen,

providing a second mixed fuel having a second predetermined mixture ratio of the first hydrocarbon fuel mixed with the second hydrocarbon fuel, the first mixture ratio being different than the second mixture ratio, and

providing a general relationship of fuel mixture ratio to the free oxygen content of the engine exhaust gas and also to at least one of the engine airflow rate or the engine fuel flow rate,

operating the engine with the first mixed fuel and measuring first data during said first operating including the free oxygen of the exhaust gas and the one of airflow rate or fuel flow rate;

operating the engine with the second mixed fuel and measuring second data during said second operating including the free oxygen of the exhaust gas and one of airflow rate or fuel flow rate; and

modifying the general relationship with the first data and the second data to a specific relationship.

21. The method of claim 20 wherein the engine is a first specific engine chosen from a family of similar engines, and which further comprises controlling a plurality of engines chosen from the family with an algorithm using the specific relationship.

22. The method of claim 20 wherein said providing includes a plurality of programmable electronic control modules each capable of controlling an internal combustion engine, and which further comprises programming the modules with software coding corresponding to the specific relationship.

23. The method of claim 20 wherein said providing includes an electronic control module having software, and which further comprises controlling the engine by the electronic control module with software coding corresponding to the specific relationship.

24. The method of claim 20 wherein said modifying includes preparing a tabular relationship of fuel mixture ratio to the free oxygen content.

25. The method of claim 20 wherein said modifying includes preparing a functional relationship of fuel mixture ratio to the free oxygen content.

26. The method of claim 20 wherein the general relationship includes a proportionality constant relating the fuel mixture ratio, the free oxygen content, and the one of airflow rate or fuel flow rate.

27. The method of claim 26 wherein said modifying includes assigning a number to the proportionality constant.

28. The method of claim 20 wherein the general relationship includes a mathematical combustion model having a term corresponding to free oxygen in the combustion products.

29. The method of claim 28 wherein said modifying includes changing the term.

30. The method of claim 20 wherein the general relationship includes a mathematical combustion model having terms corresponding to each of the free oxygen in the combustion products, the airflow rate, and the fuel flow rate.

31. The method of claim 20 wherein the general relationship includes at least 3 coefficients and said modifying includes assigning a value to each of the coefficients.

32. The method of claim 20 wherein one of the first or second molar quantities of oxygen is about zero.

33. The method of claim 20 wherein the engine is a compression ignition engine.

34. The method of claim 33 wherein one of the first hydrocarbon fuel or the second hydrocarbon fuel is diesel fuel.

35. The method of claim 34 wherein the other of the first hydrocarbon fuel or the second hydrocarbon fuel is a biodiesel fuel.

36. The method of claim 20 wherein the engine is a spark ignition engine.

37. The method of claim 36 wherein one of the first hydrocarbon fuel or the second hydrocarbon fuel is gasoline.

38. The method of claim 37 wherein the other of the first hydrocarbon fuel or the second hydrocarbon fuel is an alcohol.

42. The method of claim 20 wherein the fuel mixture ratio can be expressed as the volumetric fuel blend fraction, and the general relationship is of the type:

43. The method of claim 42 wherein said modifying includes using the first data and the second data to determine at least one of C1, C2, or C3.

44. The method of claim 20 wherein the fuel mixture ratio can be expressed as the volumetric fuel blend fraction, and the general relationship is of the type:

45. The method of claim 44 wherein said modifying includes using the first data and the second data to determine at least one of C₁, C₂, C₅, or C₄.

46. The method of claim 28 wherein the term is:

47. The method of claim 28 wherein the term is one of the following:

39. A method of analyzing fuel combusted in an engine, comprising:

providing an internal combustion engine, a first mixed fuel having a first mixture ratio of a first hydrocarbon fuel with a first molar quantity of oxygen mixed with a second hydrocarbon fuel with a second molar quantity of oxygen, a second mixed fuel having a second mixture ratio of the first hydrocarbon fuel mixed with the second hydrocarbon fuel, the first ratio being different than the second ratio, and an equation that relates the fuel mixture ratio to the free oxygen content of the engine exhaust gas and to the engine airflow rate and engine fuel flow rate, the equation having a plurality of coefficients;

operating the engine with the first mixed fuel at a speed and torque and measuring the free oxygen of the exhaust gas, engine airflow rate, and engine fuel flow rate;

operating the engine with the second mixed fuel at a plurality of speeds and torques and measuring the free oxygen of the exhaust gas, engine airflow rate, and engine fuel flow rate at each speed and torque; and

using the measured data from said operating with the first mixed fuel and from said operating with the second mixed fuel to establish each of the coefficients.

40. The Method of claim 39 wherein the equation includes a first term interrelating the oxygen content, airflow rate, and fuel flow rate, a second term interrelating the airflow rate and the fuel flow rate, and a third term that is constant, and the first term is multiplied by a first coefficient, the second term is multiplied by a second coefficient, and the third coefficient is the constant, and the sum of the first term, second term, and third term corresponds to the mixture ratio.

41. The Method of claim 40 wherein the equation includes a fourth term comprising a fourth coefficient multiplying the oxygen content, and the fourth term is added to the first term, second term, and third term.