Optimized lambda and compression temperature control for compression ignition engines

• US 6,273,076 B1
• Filed: 12/16/1997
• Issued: 08/14/2001
• Est. Priority Date: 12/16/1997
• Status: Expired due to Term

• Current Assignee: Clean Air Power, Inc. (Clean Air Power Ltd.)
• Original Assignee: Servojet Products International, Inc.
• Inventors: Beck, Niel Lenannes, Wong, Hoi Ching, Gebert, Kresimir
• Primary Examiner(s): SOLIS, ERICK R
• Application Number:
  US08/991,413
• Time in Patent Office: 1,337 Days
• Field of Search: 123/679, 123/689, 123/562, 123/563, 123/565, 123/704, 605/99, 606/12
• US Class Current: 123/679
• 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 2275/32 Miller cycle
• CPC Class Codes: F02B 29/0412 Multiple heat exchangers arranged in parallel or in series
• CPC Class Codes: F02B 29/0418 the intake air cooler having a bypass or multiple flow paths within the heat exchanger to vary the effective heat transfer surface
• CPC Class Codes: F02B 29/0493 Controlling the air charge temperature
• CPC Class Codes: F02B 37/00 Engines characterised by provision of pumps driven at least for part of the time by exhaust
• 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 39/08 Non-mechanical drives, e.g. fluid drives having variable gear ratio
• 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 13/0253 Fully variable control of valve lift and timing using camless actuation systems such as hydraulic, pneumatic or electromagnetic actuators, e.g. solenoid valves
• CPC Class Codes: F02D 13/0269 Controlling the valves to perform a Miller-Atkinson cycle
• CPC Class Codes: F02D 13/06 Cutting-out cylinders
• CPC Class Codes: F02D 15/04 by alteration of volume of compression space without changing piston stroke
• CPC Class Codes: F02D 19/023 to adjust the fuel mass or volume flow
• CPC Class Codes: F02D 19/0642 at least one fuel being gaseous, the other fuels being gaseous or liquid at standard conditions
• CPC Class Codes: F02D 2041/001 for engines with variable valve actuation
• CPC Class Codes: F02D 2041/1433 using a model or simulation of the system
• CPC Class Codes: F02D 2200/0406 Intake manifold pressure
• CPC Class Codes: F02D 2200/0414 : Air temperature
• CPC Class Codes: F02D 2200/0602 : Fuel pressure
• CPC Class Codes: F02D 2250/31 : Control of the fuel pressure
• CPC Class Codes: F02D 2250/32 : Air-fuel ratio control in a diesel engine
• CPC Class Codes: F02D 41/0007 : for control of turbo-charged or super-charged engines control of the pumps per se F02B37/12
• 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 41/0027 : the fuel being gaseous non-electrical control F02D19/02
• CPC Class Codes: F02D 41/14 : Introducing closed-loop corrections
• CPC Class Codes: F02D 41/1448 : the characteristics being an exhaust gas pressure
• CPC Class Codes: F02D 41/1458 : with determination means using an estimation
• CPC Class Codes: F02D 41/3035 : a mode being the premixed charge compression-ignition mode
• CPC Class Codes: F02D 41/3827 : for diesel engines
• CPC Class Codes: F02M 26/05 : High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system 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 26/33 : controlling the temperature of the recirculated gases
• CPC Class Codes: F02M 63/0225 : Fuel-injection apparatus having a common rail feeding several injectors F02M63/0003 takes precedence; Means for varying pressure in common rails; Pumps feeding common rails
• CPC Class Codes: Y02T 10/12 : Improving ICE efficiencies
• CPC Class Codes: Y02T 10/30 : Use of alternative fuels, e.g. biofuels

Abstract

The performance of a compression ignition internal combustion engine is improved by optimizing excess air ratio (lambda) and/or intake air charge temperature (ACT) on a full time, full range basis. The basic procedure is to first determine the desired or optimum lambda and then to control ACT and intake manifold absolute pressure (MAP) to maintain them at the optimum values for the fuel quantity required at a particular operating point. This approach allows control of both temperature and pressure of the air entering the engine. Full range control requires that lambda and ACT be controlled both upward and downward to achieve optimal engine performance. Control of both lambda and ACT is further enhanced through the use of a supercharger with adjustable input power installed in series with a standard turbocharger compressor of the engine. Supercharger control may if desired be supplemented with turbo air bypass (TAB) control, turbocharger variable area nozzle or wastegate, turboexpander control, and intake and exhaust valve control including skip fire of both fuel and air. The essence of optimized lambda control is to measure the physical properties of the working fluid in the intake manifold, exhaust manifold, or both, compute the actual value of lambda, and compare that actual value with an optimum value for the prevailing engine operating conditions. This comparison yields an error signal which is then used to control the magnitude of the required adjustment in turbocharger pressure or other engine operating parameter.

Claims

1. A method of optimizing excess air ratio (lambda) in a liquid-fueled compression ignition engine, comprising:

(A) monitoring operation of said engine;

(B) determining an optimum lambda for optimizing at least one of a plurality of engine performance characteristics at prevailing engine speed and load conditions, said optimal lambda varying in response to different engine speed and load conditions and the at least one of the plurality of engine performance characteristics; and

(C) automatically adjusting at least one engine operating parameter so as to cause the actual lambda to selectively increase and decrease to approach the optimum lambda at the prevailing speed and load conditions.

2. A method as defined in claim 1, further comprising automatically repeating the steps (A) through (C) in a closed loop and on a cylinder by cylinder and cycle by cycle basis for so long as said engine is operating so as to obtain and maintain an actual lambda which at least essentially equals the optimum lambda.

3. A method as defined in claim 2, wherein

the monitoring step includes monitoring an engine operating parameter indicative of the actual lambda and then calculating the actual lambda, and

the adjusting step comprises 1) obtaining an error signal representative of the difference between the optimum lambda and the actual lambda, and 2) adjusting the engine operating parameter by a magnitude which is dependent on the magnitude of the error signal.

4. A method as defined in claim 3, wherein the adjusting step comprises adjusting inlet air pressure for a turbocharger of said engine.

5. A method as defined in claim 1, wherein the selected engine performance characteristic is one of brake specific energy consumption (BSEC) and brake specific NO_x emissions (BSNO_x).

6. A method as defined in claim 5, wherein the optimum lambda is one which strikes an optimum trade-off between BSEC and BSNO_x at prevailing engine operating conditions.

7. A method as defined in claim 1, wherein the optimum lambda is one which minimizes smoke and particulate emissions at prevailing engine operating conditions.

8. A method as defined in claim 1, further comprising adjusting compression temperature by adjusting cylinder valve operation timing.

9. A method as defined in claim 8, further comprising selectively suppressing operation of intake and exhaust valves of said engine to obtain skip fire of both air and fuel.

10. A method as defined in claim 1, further comprising adjusting fuel flow to said engine under transient engine operating conditions under which the optimum lambda cannot be obtained by control of airflow alone.

11. A method of optimizing excess air ratio (lambda) in a liquid-fueled compression ignition engine, comprising:

(A) monitoring operation of said engine;

(B) determining an optimum lambda for optimizing a selected engine performance characteristic at a prevailing engine operating condition;

(C) automatically adjusting at least one engine operating parameter so as to cause the actual lambda to approach the optimum lambda; and

(D) adjusting the operation of a supercharger which is located in series with a turbocharger thereby to adjust inlet air pressure for said turbocharger.

12. A method of optimizing excess air ratio (lambda) in a compression ignition engine, comprising:

(A) monitoring operation of said engine;

(B) determining an optimum lambda for optimizing a selected engine performance characteristic at a prevailing engine operating condition; and

(C) automatically adjusting at least one engine operating parameter so as to cause the actual lambda to selectively increase and decrease to approach the optimum lambda; and

(D) determining an optimum ACT for a selected engine performance characteristic at a prevailing engine operating condition;

(E) adjusting at least one engine operating parameter so as to cause an actual ACT to approach the optimum ACT; and

(F) repeating the ACT determining and adjusting steps in a closed loop until the actual ACT at least essentially equals the optimum ACT.

13. A method as defined in claim 12, wherein the adjusting step comprises adjusting at least one of 1) cylinder intake valve operation timing, 2) operation of an intercooler located between a turbocharger of said engine and an air intake manifold of said engine, and 3) operation of an expansion turbine located between said turbocharger and said air intake manifold of said engine.

14. A method as defined in claim 13, wherein said expansion turbine is a turbine of a turboexpander located downstream of a supercharger of said engine.

15. A method as defined in claim 13, wherein said expansion turbine is a turbine of a combined supercharger/turboexpander assembly of said engine.

16. A method as defined in claim 13, further comprising reducing ACT to below ambient temperature using said expansion device in combination with an aftercooler.

17. A method of optimizing air charge temperature (ACT) in a compression-ignition engine, comprising:

(A) monitoring operation of said engine;

(B) determining an optimum ACT for optimizing a selected engine performance characteristic at a prevailing engine operating condition; and

(C) automatically adjusting at least one engine operating parameter so as to cause the actual ACT to approach the optimum ACT.

18. A method as defined in claim 17, further comprising automatically repeating the steps (A) through (C) in a closed loop control strategy for so long as said engine is operating so as to obtain and maintain an actual ACT which at least essentially equals the optimum ACT.

19. A method as defined in claim 17, wherein the adjusting step comprises adjusting inlet air pressure for a turbocharger of said engine.

20. A method as defined in claim 19, wherein the adjusting step comprises adjusting the operation of a supercharger which is located in series with said turbocharger thereby to adjust the inlet air pressure for said turbocharger.

21. A method as defined in claim 17, wherein the adjusting step comprises adjusting at least one of 1) cylinder intake valve operation timing, 2) operation of an intercooler located between a turbocharger of said engine and an air intake manifold of said engine, and 3) operation of an expansion turbine located between said turbocharger and said air intake manifold of said engine.

22. A method as defined in claim 17, further comprising adjusting compression temperature by adjusting cylinder valve operation timing.

23. A method of optimizing performance of a compression ignition engine, comprising the steps of:

(A) monitoring engine operation to obtain an indication of prevailing engine operating conditions;

(B) determining, based upon prevailing engine operating conditions, optimum values of excess air ratio (lambda) and air charge temperature (ACT) required to optimize a selected engine performance characteristic;

(C) determining the actual lambda and the actual ACT;

(D) automatically adjusting at least one engine operating parameter to cause both the actual ACT and the actual lambda to approach the optimum ACT and the optimum lambda; and

(E) automatically repeating steps (A) through (D) in a closed loop control strategy so as to obtain and maintain essentially optimum values of ACT and lambda at prevailing engine operating conditions.

24. A method as defined in claim 23, wherein the adjusting step comprises adjusting both ACT and lambda by adjusting the operation of a supercharger located in series with a turbocharger thereby to adjust the inlet air pressure for said turbocharger.

25. A method as defined in claim 23, wherein the adjusting step comprises adjusting ACT and the resulting compression temperature by adjusting at least one of 1) cylinder intake valve operation timing, 2) operation of an intercooler located between a turbocharger of said engine and an air intake manifold of said engine, and 3) operation of an expansion turbine located between said turbocharger and said air intake manifold of said engine.

26. A method as defined in claim 23, further comprising adjusting compression temperature by adjusting cylinder valve operation timing.

27. A method as defined in claim 26, further comprising selectively suppressing operation of intake and exhaust valves of said engine to obtain skip fire of both air and fuel.

28. A method as defined in claim 23, wherein the adjusting step comprises 1) obtaining first and second error signals representative of the difference between the optimum lambda and the actual lambda and the difference between the optimum ACT and the actual ACT, respectively, and 2) adjusting at least one engine operating parameter by a magnitude which is dependent on the magnitudes of the first and second error signals.

29. A method of optimizing performance of a compression ignition engine, comprising the steps of:

(A) monitoring engine operation to obtain an indication of prevailing engine operating conditions;

(B) determining, based upon prevailing engine operating conditions, optimum values of excess air ratio (lambda) and air charge temperature (ACT) required to optimize an engine performance characteristic;

(C) determining the actual lambda and the actual ACT;

(D) comparing the actual lambda and the actual ACT to the optimal lambda and the optimal ACT and, if necessary to cause the actual lambda and the actual ACT to approach the desired lambda and the desired ACT, selectively and automatically

(1) increasing lambda by increasing the pressure of a turbocharger of said engine by adjusting the operation of a supercharger which is located in series with the turbocharger,

(2) decreasing lambda by decreasing the pressure of the turbocharger by adjusting the operation of the supercharger,

(3) increasing ACT by at least one o

(a) recirculating air from an outlet of a compressor of said turbocharger, through a supercharger, and back to an inlet of said compressor of said turbocharger prior to inducting the recirculated air into an intake manifold of said engine,

(b) decreasing a percentage of total intake airflow through an intercooler located downstream of said turbocharger, and

(c) decreasing a percentage of intake air flowing through an aftercooler and an expansion turbine located downstream of said intercooler, and,

(4) decreasing ACT by at least one of

(a) increasing the pressure of the turbocharger by adjusting the operation of the supercharger,

(b) increasing the percentage of total intake airflow through the intercooler, and

(c) increasing the percentage of intake air flowing through said aftercooler and said expansion turbine; and

for so long as said engine is operating, repeating steps (A) through (D) in a closed loop routine so as to obtain and maintain optimum values of ACT and lambda at prevailing engine operating conditions.

30. A method as defined in claim 29, further comprising adjusting compression temperature by adjusting cylinder valve operation timing.

31. A method as defined in claim 29, further comprising selectively suppressing operation of intake and exhaust valves of said engine to obtain skip fire of both air and fuel.

32. A liquid fueled compression ignition internal combustion engine comprising:

(A) a plurality of cylinders each having an intake port and exhaust port;

(B) a fuel supply system which selectively supplies a fuel to said cylinders, wherein said fuel is one which ignites by compression;

(C) an air supply system which supplies air to said intake ports of said cylinders; and

(D) electronic control means for controlling operation of at least one of said air supply system and said fuel supply system to;

(1) monitor operation of said engine;

(2) determine an optimum lambda for optimizing a selected engine performance characteristic at prevailing engine speed and load conditions, the optimal lambda varying with varying speed and load conditions; and

(3) automatically adjust at least one engine operating parameter so as to cause the actual lambda to selectively increase and decrease to approach the optimum lambda at the prevailing speed and load conditions; and

(4) repeat operations (1) through (3) on a full time, a full range basis.

33. A compression ignition internal combustion engine comprising:

(A) a plurality of cylinders each having an intake port and exhaust port;

(B) a fuel supply system which selectively supplies a fuel to said cylinders, wherein said fuel is one which ignites by compression;

(C) an air supply system which supplies air to said intake ports of said cylinders; and

(D) electronic control means for controlling operation of at least one of said air supply system and said fuel supply system to;

(1) monitor operation of said engine;

(2) determine an optimum lambda for optimizing a selected engine performance characteristic at a prevailing engine operating condition the optimal lambda varying with engine operating conditions; and

(3) automatically adjust at least one engine operating parameter so as to cause the actual lambda to selectively increase and decrease to approach the optimum lambda; and

(4) repeat operations (1) through (3) on a full time, a full range basis;

(E) electronic control means for controlling operation of at least one of said air supply system and said fuel supply system to;

(1) monitor operation of said engine;

(2) determine an optimum lambda for optimizing a selected engine performance characteristic at a prevailing engine operating condition; and

(3) automatically adjust at least one engine operating parameter so as to cause the actual lambda to selectively increase and decrease to approach the optimum lambda; and

(E) a turbocharger having an air outlet in fluid communication with the intake ports of the cylinders and having an air inlet;

(F) a supercharger having an air outlet in fluid communication with said air inlet of said turbocharger and having an air inlet; and

(G) a control device which is coupled to said electronic control means and which selectively controls operation of said supercharger.

34. An engine as defined in claim 33, wherein said air supply system further comprises a turboexpander which is located downstream of said turbocharger.

35. An engine as defined in claim 33, wherein said air supply system further comprises a turbo air bypass (TAB) valve which is coupled to said electronic control means and which is actuatable to selectively permit at least partial bypass of said supercharger and said turbocharger.

36. A compression ignition internal combustion engine comprising:

(A) a plurality of cylinders each having an intake port and exhaust port;

(B) a fuel supply system which selectively supplies a fuel to said cylinders, wherein said fuel is one which ignites by compression;

(C) an air supple system which supplies air to said intake ports of said cylinders; and

(D) electronic control means for controlling operation of at least one of said air supply system and said fuel supple system to;

(1) monitor operation of said engine;

(2) determine an optimum lambda for optimizing a selected engine performance characteristic at a prevailing engine operating condition the optimal lambda varying with engine operating conditions; and

(3) automatically adjust at least one engine operating parameter so as to cause the actual lambda to selective increase and decrease to approach the optimum lambda; and

(4) repeat operations (1) through (3) on a full time, a full range basis;

(G) a combined supercharger/turbo expander assembly having

(1) a first air inlet,

(2) a first air outlet in fluid communication with said air inlet of said turbocharger,

(3) a second air inlet in fluid communication with said air outlet of said turbocharger, and

(4) a second air outlet in fluid communication with the intake ports of the cylinders.

37. A compression ignition internal combustion engine comprising:

(A) a plurality of cylinders each having an intake port and exhaust port;

(B) a fuel supply system which selectively supplies a fuel to said cylinders, wherein said fuel is one which ignites by compression;

(C) an air supply system which supplies air to said intake ports of said cylinders; and

(D) electronic control means for controlling operation of at least one of said air supply system and said fuel supply system to

(1) monitor engine operation to obtain an indication of prevailing engine operating conditions,

(2) determine an optimum ACT for optimizing a selected engine performance characteristic at a prevailing engine operating condition, and

(3) automatically adjust at least one engine operating parameter so as to cause the actual ACT to approach the optimum ACT.

38. An engine as defined in claim 37, wherein said air supply system comprises

a turbocharger having an air outlet in fluid communication with the intake ports of the cylinders and having an air inlet, and

a supercharger having an air outlet in fluid communication with said air inlet of said turbocharger and having an air inlet, and

a control device which is coupled to said electronic control means and which selectively controls operation of said supercharger.

39. An engine as defined in claim 37, wherein said air supply system comprises 1) an intercooler located in an air supply line leading to said intake ports and 2) a valve which is coupled to said electronic control means and which is actuatable to selectively permit at least at least partial bypass of said intercooler.

40. An engine as defined in claim 37, wherein said air supply system comprises 1) an expansion turbine located in an air supply line leading to said intake ports and 2) a valve which is coupled to said electronic control means and which is actuatable to selectively permit at least at least partial bypass of said expansion turbine and said aftercooler.

41. An engine as defined in claim 40, wherein said supercharger comprises a portion of a combined supercharger/turboexpander assembly, and wherein said expansion turbine is mounted on a common shaft with a compressor and another turbine of said combined supercharger/turboexpander assembly.

42. An engine as defined in claim 37, further comprising, for each of said cylinders, at least one electronically controlled intake valve and at least one electronically controlled exhaust valve, and wherein said electronic means control is coupled to each of said intake valves and said exhaust valves and controls said intake valves and said exhaust valves so as to obtain the optimum ACT and/or compression temperature.

43. A combined supercharger/turboexpander assembly for use in an internal combustion engine, said assembly comprising:

(A) a rotatable shaft;

(B) a rotary device which is mounted on said shaft and which is configured to be driven by a power source to drive said shaft to rotate;

(C) a compressor which is mounted on said shaft, said compressor having

     1) an air inlet and

     2) an air outlet configured to be placed in fluid communication with an air inlet of a turbocharger of said engine; and

(D) an expansion turbine which is mounted on said shaft, said expansion turbine having

     1) a second air inlet configured to be placed in fluid communication with an air outlet of said turbocharger, and

     2) a second air outlet in fluid communication with intake ports of cylinders of said engine.

44. An assembly as defined in claim 43, wherein said rotary device is disposed axially between said compressor and said expansion turbine.

45. An assembly as defined in claim 43, wherein said rotary device comprises a hydraulically-driven turbine.

46. A method of optimizing excess air ratio (lambda) in a liquid-fueled compression ignition engine, comprising:

(A) monitoring operation of said engine, the monitoring step including monitoring an engine operating parameter indicative of the actual lambda and then calculating the actual lambda;

(B) determining an optimum lambda for optimizing a selected engine performance characteristic at a prevailing engine speed and load conditions, said optimal lambda varying for different engine speed and load conditions;

(C) automatically adjusting at least one engine operating parameter so as to cause the lambda to selectively increase and decrease to approach the optimum lambda at the prevailing speed and load conditions, the adjusting step comprising

     1) obtaining an error signal representative of the difference between the optimum lambda and the actual lambda, and

     2) adjusting inlet air pressure for a turbocharger of said engine by a magnitude which is dependent on the magnitude of the error signal; and

(D) automatically repeating the steps (A) through (C) in a closed loop and on a cylinder by cylinder and cycle by cycle basis for so long as said engine is operating so as to obtain and maintain an actual lambda which at least essentially equals the optimum lambda.

47. A method as defined in claim 46, wherein the adjusting step comprises adjusting the operation of a supercharger which is located in series with said turbocharger thereby to adjust the inlet air pressure for said turbocharger.