Premixed charge compression ignition engine with optimal combustion control

• US 6,915,776 B2
• Filed: 10/15/2003
• Issued: 07/12/2005
• Est. Priority Date: 08/23/1996
• Status: Expired due to Fees

• Current Assignee: Cummins Incorporated
• Original Assignee: Cummins Incorporated
• Inventors: Hunter, Gary L., Moore, Greg A., Durrett, Russ P., Wagner, Julie A., Akinyemi, Omowoleoa C., Mudd, Jackie M., Muntean, George G., Flynn, Patrick F., Wright, John F., zur Loye, Axel O.
• Primary Examiner(s): KWON, JOHN
• Application Number:
  US10/684,560
• Publication Number:
  US 20040103860A1
• Time in Patent Office: 636 Days
• Field of Search: 123/299, 123/300, 123/304, 123/305, 123/431, 123/434, 123/435, 701/104
• US Class Current: 123/304
• CPC Class Codes: F02B 1/12 with compression ignition with fuel-air charge ignited by compression ignition of an additional fuel F02B7/00
• CPC Class Codes: F02B 19/14 with compression ignition
• CPC Class Codes: F02B 2075/025 two
• CPC Class Codes: F02B 2275/32 Miller cycle
• CPC Class Codes: F02B 29/0406 Layout of the intake air cooling or coolant circuit
• CPC Class Codes: F02B 3/06 with compression ignition compression ignition engines using air or gas for blowing fuel into compressed air in cylinder F02B13/02
• CPC Class Codes: F02B 37/04 Engines with exhaust drive and other drive of pumps, e.g. with exhaust-driven pump and mechanically-driven second pump
• CPC Class Codes: F02B 37/18 by bypassing exhaust from the inlet to the outlet of turbine or to the atmosphere
• CPC Class Codes: F02D 13/0203 Variable control of intake and exhaust valves
• CPC Class Codes: F02D 13/0215 changing the valve timing only
• CPC Class Codes: F02D 13/0234 changing the valve timing only
• CPC Class Codes: F02D 13/0265 Negative valve overlap for temporarily storing residual gas in the cylinder
• CPC Class Codes: F02D 13/0269 Controlling the valves to perform a Miller-Atkinson cycle
• CPC Class Codes: F02D 13/028 for two-stroke engines
• CPC Class Codes: F02D 15/04 by alteration of volume of compression space without changing piston stroke
• CPC Class Codes: F02D 19/0605 to adjust the fuel pressure or temperature
• CPC Class Codes: F02D 19/0649 Liquid fuels having different boiling temperatures, volatilities, densities, viscosities, cetane or octane numbers
• CPC Class Codes: F02D 19/0665 Tanks, e.g. multiple tanks
• CPC Class Codes: F02D 19/081 Adjusting the fuel composition or mixing ratio; Transitioning from one fuel to the other
• CPC Class Codes: F02D 2013/0292 in the start-up phase, e.g. for warming-up cold engine or catalyst
• CPC Class Codes: F02D 35/023 : by determining the cylinder pressure
• CPC Class Codes: F02D 35/028 : by determining the combustion timing or phasing
• 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 41/0087 : Selective cylinder activation, i.e. partial cylinder operation deceleration cut-off F02D41/123
• CPC Class Codes: F02D 41/3029 : further comprising a homogeneous charge spark-ignited mode
• CPC Class Codes: F02D 41/3035 : a mode being the premixed charge compression-ignition mode
• CPC Class Codes: F02D 41/3041 : with means for triggering compression ignition, e.g. spark plug
• CPC Class Codes: F02D 41/3076 : with special conditions for selecting a mode of combustion, e.g. for starting, for diagnosing
• CPC Class Codes: F02D 41/38 : of the high pressure type
• CPC Class Codes: F02M 26/01 : Internal exhaust gas recirculation, i.e. wherein the residual exhaust gases are trapped in the cylinder or pushed back from the intake or the exhaust manifold into the combustion chamber without the use of additional passages
• CPC Class Codes: F02M 26/04 : with a single turbocharger
• CPC Class Codes: F02M 26/07 : Mixed pressure loops, i.e. wherein recirculated exhaust gas is either taken out upstream of the turbine and reintroduced upstream of the compressor, or is taken out downstream of the turbine and reintroduced downstream of the compressor
• CPC Class Codes: F02M 26/08 : for engines having two or more intake charge compressors or exhaust gas turbines, e.g. a turbocharger combined with an additional compressor
• CPC Class Codes: F02M 26/23 : Layout, e.g. schematics
• CPC Class Codes: F02M 26/28 : with liquid-cooled heat exchangers
• CPC Class Codes: F02M 26/33 : controlling the temperature of the recirculated gases
• CPC Class Codes: F02M 26/43 : in which exhaust from only one cylinder or only a group of cylinders is directed to the intake of the engine
• CPC Class Codes: F02M 31/02 : for heating F02M31/005 takes precedence; for purifying liquid fuel F02M37/30
• CPC Class Codes: F02M 31/20 : for cooling F02M31/005 takes precedence; use of cold F02M17/52; cooling of charging-air or of scavenging-air F02B29/04
• CPC Class Codes: F02P 19/00 : Incandescent ignition, e.g. during starting of internal combustion engines; Combination of incandescent and spark ignition
• CPC Class Codes: Y02T 10/12 : Improving ICE efficiencies
• CPC Class Codes: Y02T 10/30 : Use of alternative fuels, e.g. biofuels
• CPC Class Codes: Y02T 10/40 : Engine management systems

Abstract

A premixed charge compression ignition engine, and a control system, is provided which effectively initiates combustion by compression ignition and maintains stable combustion while achieving extremely low nitrous oxide emissions, good overall efficiency and acceptable combustion noise and cylinder pressures. The present engine and control system effectively controls the combustion history, that is, the time at which combustion occurs, the rate of combustion, the duration of combustion and/or the completeness of combustion, by controlling the operation of certain control variables providing temperature control, pressure control, control of the mixture'"'"'s autoignition properties and equivalence ratio control. The combustion control system provides active feedback control of the combustion event and includes a sensor, e.g. pressure sensor, for detecting an engine operating condition indicative of the combustion history, e.g. the start of combustion, and generating an associated engine operating condition signal. A processor receives the signal and generates control signals based on the engine operating condition signal for controlling various engine components to control the temperature, pressure, equivalence ratio and/or autoignition properties so as to variably control the combustion history of future combustion events to achieve stable, low emission combustion in each cylinder and combustion balancing between the cylinders.

Claims

1. A method for operating a premixed charge, compression ignition engine, the engine having a cylinder and a piston moveable in the cylinder, and the method comprising the steps of:

providing in the cylinder a gaseous medium containing oxygen;

forming a combustible mixture by mixing generally homogeneously into the gaseous medium a first fuel that tends to autoignite relatively less readily and a second fuel that tends to autoignite relatively more readily; and

compressing the combustible mixture with the piston until combustion starts, wherein combustion starts at multiple ignition sites distributed throughout the combustible mixture after a delay in a timing of the start of combustion determined by a ratio of the first fuel to the second fuel.

2. The method of claim 1 wherein the first fuel is gaseous and the second fuel is a liquid having a relatively high cetane number.

3. A method for operating a premixed charge, compression ignition engine, the engine having a cylinder and a piston moveable in the cylinder, and the method comprising the steps of:

providing in the cylinder a gaseous medium containing oxygen;

forming a combustible mixture by mixing generally homogeneously into the gaseous medium a first fuel that tends to autoignite relatively less readily and a second fuel that tends to autoignite relatively more readily;

compressing the combustible mixture with the piston until combustion starts, wherein combustion starts at multiple ignition sites distributed throughout the combustible mixture after a delay in a timing of the start of combustion determined by a ratio of the first fuel to the second fuel; and

controlling the timing of the start of combustion by varying the ratio of the amount of the first fuel to the amount of the second fuel.

4. The method of claim 3 wherein the method further comprises advancing the timing of the start of combustion by decreasing the ratio of the amount of the first fuel to the amount of the second fuel.

5. The method of claim 4 wherein an operation cycle of the engine includes an intake event, a compression event, a combustion event and an expansion event;

said timing of the start of combustion being a function of engine speed; and

wherein the method further comprises the steps of;

controlling the power provided by the engine by varying the total amount of the first fuel and the second fuel provided in the combustible mixture;

determining the ratio of the first fuel to said second fuel giving a desired timing of the start of combustion; and

mixing into the combustible mixture for a cycle an amount of said second fuel giving said desired timing of the start of combustion.

6. The method of claim 5 wherein the method further comprises the step of adding a portion of exhaust gases into said gaseous medium to control the duration of the combustion event.

7. A method of operating an engine, comprising the steps of:

mixing a first fuel, a second fuel and oxygen in a cylinder when a piston is approximately between 180 degrees and 60 degrees before a top dead center position;

varying a timing of a start of combustion at least in part by providing the first fuel and the second fuel to the cylinder in a determined ratio;

initiating combustion by compression igniting the mixture when the piston is between 20 crank angle degrees before the top dead center position and 10 crank angle degrees after the top dead center position.

8. The method of claim 7 wherein said mixing step includes a step of injecting liquid fuel from a fuel injector directly into the cylinder.

9. The method of claim 7 wherein said mixing step includes a step of routing a gaseous fuel into the cylinder.

10. The method of claim 7 wherein said mixing step includes a step of providing compressed air to the cylinder.

11. The method of claim 7 wherein said varying step includes a step of retarding said timing of the start of combustion at least in part by reducing a ratio of fuel with a high cetane number relative to fuel with a low cetane number.

12. The method of claim 7 wherein said varying step includes a step of advancing said timing of the start of combustion at least in part by increasing a ratio of fuel with a high cetane number relative to fuel with a low cetane number.

13. The method of claim 7 including a step of adjusting combustion duration at least in part by recirculating exhaust gases into the cylinder.

14. An engine comprising;

an engine body with at least one cylinder;

a piston slidably positioned in each said at least one cylinder, and being movable between a bottom dead center position and a top dead center position;

a liquid fuel supply valve attached to said engine body;

a gaseous fuel supply valve attached to said engine body;

an electronic control unit in control communication with said liquid fuel supply valve and said gaseous fuel supply valve, and being operable to actuate said liquid fuel supply valve when said piston is approximately between 180 degrees and 60 degrees before the top dead center position.

15. The engine of claim 14 wherein said liquid fuel supply valve is a fuel injector positioned to inject fuel directly into said cylinder.

16. The engine of claim 14 including an exhaust gas recirculation system attached to said engine body.

17. The engine of claim 14 including a turbocharger operably coupled to said cylinder.

18. The engine of claim 14 wherein said electronic control unit functions to determine a change to the ratio of a liquid fuel to a gaseous fuel supplied to said cylinder.

19. A premixed charge compression ignition internal combustion engine, comprising:

an engine body;

a combustion chamber formed in the engine body;

an intake air system for delivering intake air, including at least one of air and a mixture of air and fuel, to said combustion chamber;

combustion control system for controlling combustion events to reduce emissions, said combustion history control system including a mixture autoignition property control system for varying an autoignition property of the mixture, said mixture autoignition property control system including a first fuel supply for supplying a first fuel to the engine and a second fuel supply connected to at least one of said intake air system and said combustion chamber for supplying a second fuel to the engine, said first fuel having a first autoignition property and said second fuel having a second autoignition property different from said first autoignition property; and

a processor adapted to control an amount of said second fuel delivered to said at least one of said intake air system and said combustion chamber.

20. A method for operating a homogeneous charge, compression ignition engine, the engine having a cylinder and a piston moveable in the cylinder, and the method comprising the steps of:

providing in the cylinder a gaseous medium containing oxygen;

forming a combustible mixture by mixing generally homogeneously into the gaseous medium a first fluid fuel that is relatively difficult to ignite and a second fluid fuel that is relatively easy to ignite; and

compressing the combustible mixture with the piston until combustion starts generally simultaneously at a plurality of locations distributed throughout the combustible mixture after an ignition delay determined by the proportion of the first fuel to the second fuel.

21. The method of claim 20 wherein the first fuel is gaseous and the second fuel is a liquid having a relatively high cetane number.

22. A method for operating a homogenous charge, compression ignition engine, the engine having a cylinder and a piston moveable in the cylinder, and the method comprising the steps of:

providing in the cylinder a gaseous medium containing oxygen;

forming a combustible mixture by mixing generally homogeneously into the gaseous medium a first fluid fuel that is relatively difficult to ignite and a second fluid fuel that is relatively easy to ignite;

compressing the combustible mixture with the piston until combustion starts generally simultaneously at a plurality of locations distributed throughout the combustible mixture after an ignition delay determined by the proportion of the first fuel to the second fuel; and

wherein the ignition delay begins when the piston is at a predetermined rotational position relative to top dead center and wherein the method further comprises the step of controlling the ignition delay by varying the ratio of the amount of the first fuel to the amount of the second fuel.

23. The method of claim 22 wherein the method further comprises shortening the ignition delay by decreasing the ratio of the amount of the first fuel to the amount of the second fuel.

24. The method of claim 23 wherein the method further comprises the step of recirculating a portion of exhaust gases into said gaseous medium to control a duration of the combustion phase.

25. A method of operating an engine, comprising the steps of:

mixing a first fuel, a second fuel and oxygen in a cylinder when a piston is closer to a bottom dead center position than to a top dead center position;

adjusting an ignition delay at least in part by providing the first fuel and the second fuel to the cylinder in a determined proportion;

compression igniting the mixture when the piston is closer to the top dead center position than the bottom dead center position.

26. The method of claim 25 wherein said mixing step includes a step of injecting liquid fuel from a fuel injector directly into the cylinder.

27. The method of claim 25 wherein said mixing step includes a step of routing a gaseous fuel into the cylinder.

28. The method of claim 25 wherein said mixing step includes a step of providing compressed air to the cylinder.

29. The method of claim 25 wherein said adjusting step includes a step of enlarging said ignition delay at least in part by reducing a proportion of fuel with a high cetane number relative to fuel with a low cetane number.

30. The method of claim 25 wherein said adjusting step includes a step of reducing said ignition delay at least in part by increasing a proportion of fuel with a high cetane number relative to fuel with a low cetane number.

31. The method of claim 25 including a step of adjusting combustion duration at least in part by recirculating exhaust gases into the cylinder.

32. An engine comprising;

an engine housing with at east one cylinder;

a piston slidably positioned in each said at least one cylinder, and being movable between a bottom dead center position and a top dead center position;

a liquid fuel supply valve attached to said engine housing;

a gaseous fuel supply valve attached to said engine housing;

a controller in control communication with said fuel injector and said gaseous fuel supply valve, and being operable to actuate said fuel injector when said piston is closer to said bottom dead center position than said top dead center position.

33. The engine of claim 32 wherein said fuel injector includes a nozzle tip located in said cylinder.

34. The engine of claim 32 including an exhaust gas recirculation system attached to said engine housing.

35. The engine of claim 32 including a turbocharger operably coupled to said cylinder.

36. The engine of claim 32 wherein said controller includes an ignition delay adjuster operable to determine an adjustment to a proportion of a liquid fuel to a gaseous fuel supplied to said cylinder.