WO2012125151A1

WO2012125151A1 - Method and system of controlling combustion in a cylinder of an engine

Info

Publication number: WO2012125151A1
Application number: PCT/US2011/028419
Authority: WO
Inventors: Mahmoud S. El-Beshbeeshy; Grzegorz Siuchta
Original assignee: International Engine Intellectual Property Company, Llc
Priority date: 2011-03-15
Filing date: 2011-03-15
Publication date: 2012-09-20

Abstract

A diesel engine and a method of operating the same is provided. The method provides a quantity of air and recirculated exhaust gas is provided into a combustion chamber of a cylinder. The recirculated exhaust gas makes up at least 30 % of the total volume of air and recirculated exhaust gas provided into the combustion chamber. A quantity of fuel is injected into the combustion chamber of the cylinder after a piston within the cylinder has passed top dead center. The quantity of fuel within the combustion chamber combusts.

Description

METHOD AND SYSTEM OF CONTROLLING COMBUSTION IN A CYLINDER OF

AN ENGINE

DESCRIPTION

TECHNICAL FIELD

[0001] The present disclosure relates to a system and method of controlling combustion within an internal combustion engine by controlling exhaust gas recirculation ("EGR") and fuel injection into the engine. The fuel injection is controlled such that combustion of the fuel produces emission levels compliant with the emission requirements without the need for post combustion after-treatment devices and processes.

BACKGROUND

[0002] Many modern diesel engines have an exhaust system that features an exhaust gas recirculation ("EGR") system that routes a portion of engine exhaust gas into an air intake system, such that a mixture of fresh air and engine exhaust is supplied to a combustion chamber during engine operation. In order to reduce certain pollutants found in exhaust gas of an internal combustion engine, such as NOx and particulate matter, several approaches have been tried, including using an after-treatment chemical in conjunction with a catalytic converter, a system often referred to as a selective catalyst reduction system or an "SCR system." An SCR system adds complexity to an engine, and requires a catalyst that must be periodically replenished, which increases operating costs. If the catalyst is not replenished, the engine exhaust typically will not meet emission standards, and the engine may be required to cease operations.

[0003] Compression ignition in an internal combustion engine, such as combustion in a diesel engine, may occur in two general modes, pre-mix combustion and diffuse combustion. During pre-mix combustion, also known as pre-mix charge compression ignition ("PCCI"), fuel is typically injected into the cylinder well before the piston reaches top dead center ("TDC") such that the fuel and air entering the cylinder have time to mix well prior to the start of ignition of the fuel-air mixture. PCCI has not been widely utilized in commercial engines, and typically has only been used in situations where low power output has been required from the engine. PCCI additionally offers less control over the timing of combustion, as the combustion is driven solely by the combustion properties of the fuel-air mixture, as fuel injection has stopped prior to ignition of the fuel-air mixture. PCCI has been found to offer improved emissions from the combustion of fuel. [0004] Conversely, diffuse combustion is typically used in most commercial diesel engines, and involves injection of at least a portion of the fuel from a particular fuel injection into a flame that has formed from the combustion of the fuel-air mixture within the cylinder. Diffuse combustion allows control over the timing of combustion, particularly the end of combustion, as fuel is being injected into the cylinder after the start of ignition of the fuel-air mixture. Diffuse combustion is used in situations where power output from the engine is higher than in PCCI, and diffuse combustion typically produces additional particulate emissions and NOx emissions than PCCI. Diffuse combustion will involve a small amount of PCCI, as some fuel is injected prior to ignition of the fuel-air mixture, but typically only around one percent (1 %) of the fuel combusted during a particular fuel injection is combusted in PCCI.

[0005] Therefore, a need exists for an engine capable of meeting emission standards without the use of an after-treatment system to control parameters useful in reducing emissions of the engine.

SUMMARY

[0006] According to one process, a method of operating a diesel engine is provided. A quantity of air and recirculated exhaust gas is provided into a combustion chamber of a cylinder. The recirculated exhaust gas makes up at least 30% of the total volume of air and recirculated exhaust gas provided into the combustion chamber. A quantity of fuel is injected into the combustion chamber of the cylinder after a piston within the cylinder has passed top dead center. The quantity of fuel within the combustion chamber combusts.

[0007] According to another process, a method of injecting fuel into a combustion chamber for an internal combustion diesel engine is provided. A fuel injector is disposed in fluid communication with a combustion chamber of a cylinder. A quantity of fuel is injected at a pressure of at least 2500 bar into the combustion chamber of the cylinder after a piston within the cylinder has passed top dead center. The injection of fuel has a first stage and a second stage. A peak rate of fuel injection of the first stage is higher than a peak rate of fuel injection of the second stage.

[0008] According to a further process, a method of operating a diesel engine is provided. A quantity of air and recirculated exhaust gas is provided into a combustion chamber of a cylinder. The recirculated exhaust gas makes up at least 30% of the total volume of air and recirculated exhaust gas that is provided. A quantity of fuel is injected into the combustion chamber of the cylinder at a pressure of at least 3000 bar. The injection occurs after a piston within the cylinder has passed top dead center. The injection has a first stage and a second stage. The quantity of fuel combusts within the combustion chamber. The first stage has a higher rate of injection than the second stage. The first stage and the second stage form a single continuous injection of fuel.

[0009] According to one embodiment, a diesel engine system comprises a plurality of cylinders, a plurality of reciprocating pistons, a plurality of fuel injectors, an air intake system, an exhaust gas recirculation system, and an electronic control module. Each of the plurality of cylinders has a combustion chamber. One piston is disposed within each of the plurality of cylinders. Each of the reciprocating pistons has a piston bowl with a central hemispherical structure that reduces the volume of the combustion chamber. One fuel injector is disposed in fluid communication with each of the plurality of cylinders. The fuel injectors deliver fuel into the combustion chambers at a pressure above 3000 bar during both a first stage and second stage of injection. A peak injection rate during the first stage is higher than a peak injection rate during the second stage. The air intake system is disposed in fluid communication with the combustion chambers to deliver an oxygen containing mixture to each combustion chamber. The exhaust gas recirculation system controls an amount of exhaust gas recirculated into air intake system. The exhaust gas recirculation system provides at least 30% of the total volume of air and recirculated exhaust gas within the air intake system. The electronic control module is programmed to control the delivery of fuel by the fuel injector such that the delivery of fuel into the combustion chamber begins after the piston has passed top dead center.

[0010] According to another embodiment, a diesel engine system comprises a plurality of cylinders, a plurality of reciprocating pistons, a plurality of fuel injectors, an air intake system, an exhaust gas recirculation system, and an electronic control module. Each of the plurality of cylinders forms a combustion chamber. One piston is disposed within each of the plurality of cylinders. The reciprocating piston has a piston bowl. The piston generates a compression ratio within the combustion chamber of 16 or less. One fuel injector is disposed in fluid communication with each of the plurality of cylinders to provide an injection angle of at least 155°. The fuel injector delivers fuel into the combustion chamber at a pressure above 3000 bar. The fuel injector delivers fuel in a first stage and a second stage. The peak injection rate declines from the first stage to the second stage. The air intake system is disposed in fluid communication with the combustion chamber to deliver an oxygen containing mixture to the combustion chamber. The exhaust gas recirculation system controls an amount of exhaust gas recirculated into the air intake system. The exhaust gas recirculation system provides at least 35% of the total volume of air and recirculated exhaust gas within the air intake system. The electronic control module is programmed to control the delivery of fuel by the fuel injector such that the delivery of fuel into the combustion chamber begins after the piston has passed top dead center.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a schematic diagram showing an engine;

[0012] FIG. 2a is a sectional view of an engine showing a cylinder having a piston with a volume reducing structure;

[0013] FIG. 2b is a section view of the piston of claim 2;

[0014] FIG. 3 is a graphical depiction of a fuel injection according to one process; and

[0015] FIG. 4 is a graphical depiction of a fuel injection according to another

embodiment.

DETAILED DESCRIPTION

[0016] FIG. 1 shows an engine 10 having an exhaust system 12. The exhaust system 12 has an exhaust gas recirculation ("EGR") portion 13. The EGR portion 13 has an EGR cooler 14 and an EGR valve 16. The EGR cooler 14 reduces the temperature of exhaust gas within the EGR portion 13. The exhaust system 12 additionally is shown as having a first turbocharger turbine 18 and a second turbocharger turbine 20. The EGR valve 16 controls the flow of exhaust gas within the EGR portion 13.

[0017] The engine 10 additionally has an air intake system 22. The air intake system 22 has a first turbocharger compressor 24 and a second turbocharger compressor 26. A charge air cooler 28 is additionally provided to cool intake air within the air intake system 22. A first throttle valve 30 and a second throttle valve 32 are also disposed within the air intake system 22. The first turbocharger turbine 18 and the first turbocharger compressor 24 form a first turbocharger and the second turbocharger turbine 20 and the second turbocharger compressor 26 form a second turbocharger. It is contemplated that the first turbocharger and the second turbocharger may be variable geometry turbochargers. The engine 10 additionally has a electronic control module ("ECM") programmed to control electronic aspects of engine operation, such as fuel injection timing, EGR valve positions, variable geometry turbocharger settings and the like.

[0018] Turning now to FIG. 2a, a cross section of a cylinder 34 of the engine 10 is shown. The cylinder 34 has a piston 36 that moves reciprocally within the cylinder 34. A cylinder head 38 is disposed above the cylinder 34, such that the movement of the piston 36 within the cylinder 34 increases a pressure within the cylinder 34. An in-cylinder pressure sensor 40 is additionally provided. The in-cylinder pressure sensor 40 is disposed within the cylinder head 38 and a portion of the in-cylinder pressure sensor 40 is exposed within the cylinder 34. The in-cylinder pressure sensor 40 monitors the pressure within the cylinder 34.

[0019] As best observed in FIG. 2b, the piston 36 forms a combustion bowl 42 at a top end of the piston 36. The combustion bowl 42 has a volume reducing structure 44 that reduces the volume of the combustion bowl 42. The volume reducing structure 44 is generally hemispherical as shown in FIG. 2b, and reduces the volume of the combustion bowl 42 near the center of the combustion bowl 42. The combustion bowl 42 has a diameter D and a height H. The ratio of the diameter D to the height H forms an aspect ratio D/H for the piston 36. The aspect ratio D/H for the piston 36 is higher than 4, and it is contemplated that the aspect ratio D/H may be as high as 6. Thus, compared to its diameter D, the height, or depth, of the combustion bowl 42 of the piston 36 is small, resulting in a shallow combustion bowl 42.

[0020] The piston 36 additionally has stepped regions 46 located on each side of the combustion bowl 42. The stepped regions 46 deflect fuel entering the combustion bowl 42 towards either a top surface 50 of the piston 36, or towards a bottom surface 48 of the combustion bowl 42 of the piston 36. The deflection of fuel entering the combustion bowl 42 enhances mixing of the fuel with air in the combustion bowl 42 such that more complete combustion of fuel may be obtained.

[0021] The volume reducing structure 44 enhances air flow within the combustion bowl 42. The volume reducing structure 44 creates a flow of air towards a center of the combustion bowl 42 as the piston 36 moves downward in the cylinder 34. This air flow opposes fuel F entering the combustion bowl from 42 from a fuel injector 52. The fuel F flows from the fuel injector 52 at a fuel injection angle a. The air flow towards the center of the combustion bowl 42 from the volume reducing structure 44 enhances mixing of fuel and air within the combustion bowl 42, encouraging more complete combustion of the fuel F. In addition to enhancing the mixing of fuel and air, the flow of air towards the center of the combustion bowl 42 additionally allows the utilization of a larger percentage of air within the combustion bowl 42, as the air flow generated by the volume reducing structure 44 causes air located in regions that otherwise would not be available to interact with fuel during combustion. [0022] As shown in FIG. 2b, the fuel F is injected at an angle a that may vary from about 150° to about 170°. This injection angle a is a wider injection angle than previously utilized in many prior applications. One reason for this wider injection angle a is that the fuel injector 52 injects fuel at a very high injection pressure of at least 3000 bar. Utilizing a high injection pressure better atomizes fuel F during injection, enhancing the mixing of fuel F with air.

[0023] Turning now to FIG. 3, a graph 54 showing rate of fuel injection versus crank angle is shown. The graph 54 has an injector opening portion 56 during which the fuel injection rate increases quickly and peaks at a maximum injection rate 58. After the maximum injection rate 58, the fuel injection rate decays during a PCCI portion 60 and a diffuse combustion portion 62. The graph 54 has an injector closing portion 64 during which the fuel injection rate decreases quickly as the injector closes. The PCCI portion 60 transitions to a diffuse combustion portion at a start of ignition crank angle 66. The period of time from the start of fuel injection until the start of ignition crank angle 66 is referred to as the ignition delay period.

[0024] The rate of fuel injection during the PCCI portion 60 is higher than the rate of fuel injection during the diffuse combustion portion 62. The higher rate of injection during the PCCI portion 60 allows from about 10% to about 30% of the fuel to be injected during the PCCI portion. Injected fuel during the PCCI portion produces lower levels of particulate matter emission levels and NOx emission levels during the combustion of fuel than injection of fuel during the diffuse combustion portion 62. The injection of fuel during the PCCI portion allows better mixing of fuel with air in the cylinder 34, such that areas within the cylinder having high concentrations of fuel are avoided, as it has been found that areas with high concentrations of fuel within the cylinder 34 produce localized high temperature regions within the cylinder 34 during combustion, and the high temperature regions within the cylinder 34 during combustion produce higher levels of NOx. Injected fuel during the diffuse combustion portion 62 allows the control of the end of combustion of fuel during a combustion cycle.

[0025] As shown in FIG. 3, the start of fuel injection occurs after the piston has passed top dead center ("TDC") 68. Having the start of fuel injection occur after the piston has passed TDC 68 results in fuel being injected into a cooler cylinder 34, as temperature within the cylinder from compression begins to fall once the piston has passed TDC. Injecting fuel into a cooler cylinder 34 allows for a longer ignition delay, improving mixing of fuel and air, further helping to avoid high temperature regions within the cylinder 34 that produce higher levels of NOx during combustion.

[0026] As shown in FIG. 3, the graph 54 showing the rate of fuel injection versus crank angle reaches the maximum rate of injection 58 and gradually decays during both the PCCI portion 60 and the diffuse combustion portion 62. The shape of the graph 54 is consistent with the use of a intensified injection system, such as a unit- injector type fuel system, where the fuel injector does not have electronically controlled injector nozzle openings, but instead relies on the pressure of the fuel being injected to open the injector nozzle openings. A damping rate may be selected for the injector nozzles, such that the closing of the injector nozzles is gradual, to create a larger number of crank angle degrees with a high rate of fuel injection, such as the generally trapezoidal shape of the graph 54 of the rate of fuel injection versus crank angle.

[0027] The high fuel rate of injection and the high injection pressure allows the total degrees of crank angle during which fuel is being injected into the cylinder to be reduced. For example, a conventional fuel injection may last up to about 30° of crank angle, while the high rate of injection of the present disclosure allows fuel injection to take place over a range of about 10° to about 15°.

[0028] In order to determine the start of ignition crank angle, the in-cylinder pressure sensor 40 is utilized. The pressure monitored within the cylinder 34 begins to rise rapidly when combustion is initiated. Therefore, it is possible to utilize the in-cylinder pressure sensor 40 for a control system that adjusts the timing of the fuel injection to ensure that the rate of fuel injection decreases once the start of ignition crank angle 66 has been reached .

[0029] FIG. 4 depicts a graph 70 showing a rate of fuel injection versus crank angle for a particular fuel injection. The graph 70 has an injector opening portion 74 during which the fuel injection rate increases quickly and peaks at a maximum injection rate 75. After the maximum injection rate 75, the fuel injection rate remains generally constant during a PCCI portion 76 of the fuel injection. The rate of injection transitions rapidly to a lower rate of injection during a diffuse combustion portion 78 of the fuel injection. The graph 70 additionally has an injector closing portion 80 during which the fuel injection rate decreases quickly as the injector closes. The PCCI portion 76 transitions to a diffuse combustion portion at a start of ignition crank angle 82.

[0030] The rate of fuel injection during the PCCI portion 76 is higher than the rate of fuel injection during the diffuse combustion portion 78. The higher rate of injection during the PCCI portion 76 allows from about 10% to about 30% of the fuel to be injected during the PCCI portion. Injected fuel during the PCCI portion 76 produces lower levels of particulate matter emission levels and Ox emission levels during the combustion of fuel, than injection of fuel during the diffuse combustion portion 78. The injection of fuel during the PCCI portion 76 allows better mixing of fuel with air in the cylinder 34, such that areas within the cylinder 34 having high concentrations of fuel are avoided, as it has been found that areas with high concentrations of fuel within the cylinder 34 produce localized high temperature regions within the cylinder 34 during combustion, and the high temperature regions within the cylinder 34 during combustion produce higher levels of NOx. Injected fuel during the diffuse combustion portion 78 allows the control of the end of combustion of fuel during a combustion cycle.

[0031] As shown in FIG. 4, the start of fuel injection occurs after the piston has passed TDC 68. Having the start of fuel injection occur after the piston has passed TDC 68 results in fuel being injected into a cooler cylinder 34, as temperature within the cylinder 34 from compression begins to fall once the piston has passed TDC 68. Injecting fuel into a cooler cylinder 34 allows for a longer ignition delay, improving mixing of fuel and air, further helping to avoid high temperature regions within the cylinder 34 that produce higher levels of NOx during combustion.

[0032] As shown in FIG. 4, the graph 70 showing the rate of fuel injection versus crank angle reaches a maximum rate of injection 75 and generally maintains that rate of injection during the PCCI portion 76. As the ignition delay period ends, and the diffuse combustion portion 78 begins, the rate of fuel injection is rapidly decreased from the maximum rate of injection 75. The shape of the graph 70 is consistent with the use of a high-pressure common rail fuel injection system, where the fuel injector has electronically controlled injector nozzle openings, such as an electrically controlled valve to open and close the injector nozzle openings. As the opening and closing of the injector nozzle openings may be precisely controlled, the graph 70 generally resembles two rectangles; a first rectangle for the PCCI portion 76, and a second rectangle for the diffuse combustion portion 78.

[0033] The high fuel rate of injection and the high injection pressure allows the total degrees of crank angle during which fuel is being injected into the cylinder to be reduced. For example, a conventional fuel injection may last up to about 30° of crank angle, while the high rate of injection of the present disclosure allows fuel injection to take place over a range of about 10° to about 15°. Lessening the number of crank angle degrees required for the fuel injection allows better control of the overall combustion process. [0034] In order to determine the start of ignition crank angle, the in-cylinder pressure sensor 40 is utilized. The pressure monitored within the cylinder 34 begins to rise rapidly when combustion is initiated. Therefore, it is possible to utilize the in-cylinder pressure sensor 40 for a control system that adjusts the timing of the fuel injection to ensure that the rate of fuel injection decreases once the start of ignition crank angle 82 has been reached.

[0035] It is contemplated that the graphs showing the rate of fuel injection versus crank angle 54, 70 will be utilized in similar in-cylinder conditions. It is contemplated that the engine 10 will have an EGR rate of between about 30% and about 55%, that fuel injection pressure will be between about 2000 bar to about 4000 bar, that the start of fuel injection will occur at a crank angle from about 5° after TDC to about 10° after TDC, and that an intake manifold temperature is less than about 145° F.

[0036] The use of higher EGR rates, for example, above 30%, reduces the amount of oxygen within the cylinder 34 that may be used for combustion of fuel. Therefore, proper mixing of fuel and air within the cylinder is needed to properly combust the fuel. The use of higher EGR rates additionally results in an air/fuel ratio of from about 15 to about 19 when the engine 10 is operating at rated load. Additionally, it is contemplated that a compression ratio of less than about 16 will be found within the engine 10.

Claims

CLAIMS What is claimed is:

1. A method of operating a diesel engine comprising:

providing a quantity of air and recirculated exhaust gas into a combustion chamber of a cylinder, the recirculated exhaust gas making up at least 30 % of the total volume of air and recirculated exhaust gas provided into the combustion chamber;

injecting a quantity of fuel into the combustion chamber of the cylinder after a piston within the cylinder has passed top dead center; and

combusting the quantity of fuel within the combustion chamber.

2. The method of claim 1 , wherein the injecting a quantity of fuel begins when the piston is between approximately five and ten degrees (5° - 10 °) after top dead center.

3. The method of claim 1, wherein the recirculated exhaust gas makes up between approximately 30% and 55% of the total volume of air and recirculated exhaust gas provided.

4. The method of claim 1, wherein the recirculated exhaust gas makes up between approximately 35% and 40% of the total volume of air and recirculated exhaust gas provided.

5. The method of claim 1 , wherein the injecting a quantity of fuel is performed at a fuel injection pressure of at least 2500 bar.

6. The method of claim 1 , wherein the injecting a quantity of fuel begins at an initial rate of injection and the rate declines over the remaining period of injection.

7. The method of claim 1 , wherein the injecting a quantity of fuel has a first stage and a second stage, wherein the rate of injection is higher during the first stage than during the second stage.

8. The method of claim 7, wherein the first stage of fuel injection is before start of ignition of the fuel in the combustion chamber, and the second stage of fuel injection commences after the start of ignition of the fuel.

9. The method of claim 8, wherein between approximately 10% and 30% of the total quantity of fuel injected is injected into the combustion chamber during the first stage of injection.

10. The method of claim 8, wherein between approximately 15% and 20% of the total quantity of fuel injected is injected into the combustion chamber during the first stage of injection.

11. The method of claim 8, wherein the injecting a quantity of fuel begins when the piston is between five and ten degrees (5° - 10 °) after top dead center.

12. A method of injecting fuel into a combustion chamber for an internal combustion diesel engine comprising:

providing a fuel injector disposed in fluid communication with a combustion chamber of a cylinder; and

injecting a quantity of fuel at a pressure of at least 2500 bar into the combustion chamber of the cylinder after a piston within the cylinder has passed top dead center;

wherein, the injecting a quantity of fuel has a first stage and a second stage, a peak rate of fuel injection of the first stage being higher than a peak rate of fuel injection of the second stage.

13. The method of claim 12, wherein the first stage and the second stage form a continuous injection.

14. The method of claim 12, wherein the rate of fuel injection gradually declines between the first stage and the second stage.

15. The method of claim 12, wherein the rate of fuel injection sharply declines between the first stage and the second stage.

16. The method of claim 12, wherein the injecting a quantity of fuel begins when the piston is between five and ten degrees (5° - 10 °) after top dead center.

17. The method of claim 12, wherein the first stage of fuel injection is before start of ignition of the fuel in the combustion chamber, and the second stage of fuel injection commences after the start of ignition of the fuel.

18. A method of operating a diesel engine comprising:

providing a quantity of air and recirculated exhaust gas into a combustion chamber of a cylinder, the recirculated exhaust gas making up at least 30% of the total volume of air and recirculated exhaust gas provided;

injecting a quantity of fuel into the combustion chamber of the cylinder at a pressure of at least 3000 bar, the injecting occurring after a piston within the cylinder has passed top dead center, the injecting having a first stage and a second stage; and

combusting the quantity of fuel within the combustion chamber;

wherein the first stage has a higher rate of injection than the second stage, and the first stage and the second stage form a single continuous injection of fuel.

19. The method of claim 18, wherein the rate of injection is higher during the first stage than during the second stage.

20. The method of claim 18, wherein the first stage of fuel injection occurs before combusting fuel in the combustion chamber, and the second stage of fuel injection commences after the start of combusting fuel within the combustion chamber.

21. The method of claim 18, wherein the recirculated exhaust gas makes up between approximately 35% and 40% of the total volume of air and recirculated exhaust gas provided.

22. The method of claim 18, wherein the injecting a quantity of fuel begins when the piston is between five and ten degrees (5° - 10 °) after top dead center.

23. The method of claim 18, wherein the injecting a quantity of fuel is at an injection angle of from approximately 150° to about 170°.

24. The method of claim 18, wherein the rate of fuel injection gradually declines between the first stage and the second stage.

25. The method of claim 18 wherein the rate of fuel injection sharply declines between the first stage and the second stage.

26. A diesel engine system comprising:

a plurality of cylinders, each of the plurality of cylinders having a combustion chamber;

a plurality of reciprocating pistons, one piston being disposed within each of the plurality of cylinders, the reciprocating piston having a piston bowl with a central hemispherical structure that reduces the volume of the combustion chamber;

a plurality of fuel injectors, one fuel injector being disposed in fluid communication with each of the plurality of cylinders, the fuel injector delivering fuel into the combustion chamber at a pressure above 3000 bar during both a first stage and second stage of injection, wherein a peak injection rate during the first stage is higher than a peak injection rate during the second stage;

an air intake system disposed in fluid communication with the combustion chambers to deliver an oxygen containing mixture to each combustion chamber;

an exhaust gas recirculation system that controls an amount of exhaust gas recirculated into the air intake system, the exhaust gas recirculation system providing at least 30% of the total volume of air and recirculated exhaust gas within the air intake system; and

an electronic control module programmed to control the delivering of fuel by the fuel injector such that the delivering of fuel into the combustion chamber begins after the piston has passed top dead center.

27. The diesel engine system of claim 26, wherein the rate of fuel injection gradually declines between the first stage and the second stage.

28. The diesel engine system of claim 26, wherein the rate of fuel injection sharply declines between the first stage and the second stage.

29. The diesel engine system of claim 26, wherein the fuel injectors being adapted to inject between approximately 10% and 30% of the fuel injection occurs during the first stage.

30. The diesel engine system of claim 26, wherein the electronic control module is programmed to control the delivering of fuel by the fuel injector into the combustion chamber when the piston is between approximately five and ten degrees (5° - 10°) after top dead center.

31. The diesel engine system of claim 26, wherein the fuel injectors have an injection angle between approximately 150° to about 170°.

32. The diesel engine system of claim 26, wherein the fuel injectors are adapted to deliver fuel into the combustion chamber at a pressure above 3500 bar.

33. The diesel engine system of claim 26, wherein the exhaust gas recirculation system providing between approximately at least 35% and about 45% of the total volume of air and recirculated exhaust gas within the air intake system.

34. A diesel engine system comprising:

a plurality of cylinders, each of the plurality of cylinders forming a combustion chamber;

a plurality of reciprocating pistons, one piston being disposed within each of the plurality of cylinders, the reciprocating piston having a piston bowl, the piston generating a compression ratio within the combustion chamber of 16 or less;

a plurality of fuel injectors, one fuel injector being disposed in fluid communication with each of the plurality of cylinders to provide an injection angle of at least 155°, the fuel injector delivering fuel into the combustion chamber at a pressure above 3000 bar, the fuel injector delivering fuel in a first stage and second stage, wherein peak injection rate declines from the first stage to the second stage;

an air intake system disposed in fluid communication with the combustion chamber to deliver an oxygen containing mixture to the combustion chamber;

an exhaust gas recirculation system that controls an amount of exhaust gas recirculated into the air intake system, the exhaust gas recirculation system providing at least 35% of the total volume of air and recirculated exhaust gas within the air intake system; and an electronic control module programmed to control the delivery of fuel by the fuel injector such that the delivery of fuel into the combustion chamber begins after the piston has passed top dead center.

35. The diesel engine system of claim 34, wherein the rate of fuel injection gradually declines between the first stage and the second stage.

36. The diesel engine system of claim 34, wherein the rate of fuel injection sharply declines between the first stage and the second stage.

37. The diesel engine system of claim 34, wherein the fuel injectors being adapted to inject between approximately 10% and 30% of the fuel injection occurs during the first stage.

38. The diesel engine system of claim 34, wherein the fuel injectors are adapted to deliver fuel into the combustion chamber at a pressure from about 3200 bar to about 3500 bar.

39. The diesel engine system of claim 34, wherein the exhaust gas recirculation system providing between approximately 40% and about 45% of the total volume of air and recirculated exhaust gas within the air intake system.

40. The diesel engine of claim 34, wherein the piston has a central hemispherical structure that reduces the volume of the piston bowl.

41. The diesel engine of claim 40, wherein the piston has a step portion on a sidewall of the piston bowl.