Claims:1. A method comprising:
feeding air (31) and at least one fuel (44, 46) into a plurality of cylinders (26) of an engine (12);
combusting the at least one fuel (44, 46) using the air (31) in the plurality of cylinders (26); and
injecting a predefined quantity of a gaseous medium (47) into each cylinder of the plurality of cylinders (26) during a predefined piston stroke in each cylinder (26) to enhance mixing of the air (31) with the at least one fuel (44, 46) and propelling of combustion products towards a piston squish region (68) in each cylinder (26).

2. The method of claim 1, wherein the at least one fuel (44, 46) comprises natural gas and diesel.

3. The method of claim 2, wherein feeding the air (31) and the at least one fuel (44, 46) comprises feeding a mixture of the air (31) and the natural gas into the plurality of cylinders (26).

4. The method of claim 3, wherein feeding the air (31) and the at least one fuel (44, 46) comprises injecting a predefined pilot quantity of the diesel to the mixture of the air (31) and the natural gas into the plurality of cylinders (26).

5. The method of claim 4, wherein feeding the air (31) and the at least one fuel (44, 46) comprises injecting the predefined pilot quantity of the diesel and the gaseous medium (47) through a plurality of injection holes (78, 80) of each injector of a plurality of injectors (42, 43) to a corresponding cylinder of the plurality of cylinders (26).

6. The method of claim 4, wherein feeding the air (31) and the at least one fuel (44, 46) comprises:
injecting the predefined pilot quantity of the diesel through a plurality of first fuel injectors (40) to the plurality of cylinders (26);
injecting the natural gas through a second fuel injector (42) to an inlet manifold (16) of the engine (12); and
injecting the gaseous medium (47) through a plurality of gaseous medium injectors (43) to the plurality of cylinders (26).

7. The method of claim 2, wherein the predefined piston stroke is a compression stroke.

8. The method of claim 1, wherein the predefined piston stroke is an expansion stroke.

9. The method of claim 1, wherein the gaseous medium (47) comprises air.

10. The method of claim 1, wherein the gaseous medium (47) comprises an inert gas.

11. The method of claim 1, wherein the predefined quantity is less than or equal to 5 percent of a quantity of the air (31) fed to each cylinder of the plurality of cylinders (26).

12. The method of claim 1, wherein injecting the predefined quantity of the gaseous medium (47) comprises injecting the predefined quantity of the gaseous medium (47) at a pressure greater than an in-cylinder pressure into each cylinder of the plurality of cylinders (26).

13. The method of claim 1, wherein injecting the predefined quantity of the gaseous medium (47) comprises injecting the predefined quantity of the gaseous medium (47) at a temperature equal to a temperature of the air (31) at an outlet of an after cooler (30) of the engine (12), into each cylinder of the plurality of cylinders (26).

14. The method of claim 1, wherein injecting the predefined quantity of a gaseous medium (47) into each cylinder of the plurality of cylinders (26) during the predefined piston stroke in each cylinder (26) comprises reducing generation of nitrogen oxide emissions during the combustion of the at least one fuel (44, 46).

15. An engine (12) comprising:
a plurality of cylinders (26);
an inlet manifold (16) coupled to the plurality of cylinders (26), for feeding air (31) to the plurality of cylinders (26);
a plurality of first fuel injectors (40) provided to the plurality of cylinders (26) respectively, for injecting a first fuel (44) to the plurality of cylinders (26);
an exhaust manifold (18) coupled to the plurality of cylinders (26), for directing flow of an exhaust gas (27) from the plurality of cylinders (26); and
a plurality of gaseous medium injectors (43) provided to the plurality of cylinders (26) respectively, wherein the plurality of gaseous medium injectors (43) is configured to inject a predefined quantity of a gaseous medium (47) into the plurality of cylinders (26) respectively during a predefined piston stroke in each cylinder (26) to enhance mixing of the air (31) with the first fuel (44) and propelling of combustion products towards a piston squish region (68) in each cylinder (26).

16. The engine (12) of claim 15, further comprising a second fuel injector (42) coupled to the inlet manifold (16), for injecting a second fuel to the inlet manifold (16), wherein the inlet manifold (16) is used to feed a mixture of the air (31) and the second fuel (46) to the plurality of cylinders (26).

17. The engine (12) of claim 16, further comprising a control unit (32) coupled to the plurality of first fuel injectors (40), the second fuel injector (42), and the plurality of gaseous medium injectors (43).

18. The engine (12) of claim 15, wherein each gaseous medium injector of the plurality of gaseous medium injectors (43) is disposed proximate to a respective first fuel injector of the plurality of first fuel injectors (40).

19. The engine (12) of claim 18, wherein each gaseous medium injector (43) is integrated to the respective first fuel injector of the plurality of first fuel injectors (40).

20. The engine (12) of claim 18, wherein each gaseous medium injector (43) is coupled to a corresponding cylinder head of each cylinder of the plurality of cylinders (26).

21. The engine (12) of claim 18, wherein each gaseous medium injector of the plurality of gaseous medium injectors (43) is configured to inject the predefined quantity of the gaseous medium (47) used for cooling the respective first fuel injector of the plurality of first fuel injectors (40).

22. The engine (12) of claim 15, wherein each first fuel injector of the plurality of first fuel injectors (40) comprises a plurality of first injection holes (78) and each gaseous medium injector of the plurality of gaseous medium injectors (43) comprises a plurality of second injection holes (80), wherein a number of the plurality of first injection holes (78) is less than or equal to a number of the plurality of second injection holes (80).

23. The engine (12) of claim 15, further comprising a common rail (51) coupled to the gaseous medium injectors (43), wherein the common rail (51) is used to store and feed the gaseous medium (47) to the plurality of gaseous medium injectors (47).

24. The engine (12) of claim 15, wherein each injector among the plurality of first fuel injectors (40) comprises a plurality of injection holes (78), wherein each gaseous medium injector among the plurality of gaseous medium injectors (43) is coupled to a corresponding first fuel injector among the plurality of first fuel injectors (40), and wherein the plurality of injection holes (78) is used to inject the first fuel (40) and the gaseous medium (47) to a corresponding cylinder among the plurality of cylinders (26).
, Description:BACKGROUND
[0001] The invention relates generally to an engine and a method of operating the same.
[0002] Typically, in internal combustion engines, air enters through an inlet manifold and mixes with a fuel to form an air-and-fuel mixture. The air and fuel mixture is combusted within a plurality of cylinders to drive pistons which rotatably turn a corresponding crankshaft to generate drive torque. For a dual fuel engine, for example, diesel and natural gas may be utilized as fuels. In such a dual fuel engine, natural gas is injected upstream of intake valves of the cylinders and a mixture of air and the natural gas is fed into the cylinders. For certain engines, natural gas is introduced upstream of a turbocharger compressor. Diesel is injected into the cylinders and combustion is initiated by auto-ignition. Specifically, combustion of premixed air and natural gas mixture in the cylinders is initiated by the auto-ignition of a pilot quantity of the diesel.
[0003] Lower pilot quantity of diesel is desired since the combustion potentially leads to lower exhaust emissions and higher engine efficiency in particular for low emission engines. However, it is observed that due to injection of lower pilot quantity of diesel, combustion in the cylinders propagates slowly. As a result, the extent to which the air-fuel mixture can be made leaner is limited particularly for high speed reciprocating engines. Therefore, the thermal efficiency and reduction in nitrogen oxide emissions are limited.
[0004] Additionally, lower pilot quantity of diesel leads to smaller penetration of diesel vapor. The pilot diesel ignites at a location proximate to a center of the cylinder. The combustion flame has to propagate up to a piston squish region. The piston starts moving downwards during the expansion stroke before the combustion flame reaches the piston squish region. The downward movement of the piston results in deceleration of the propagation of the combustion flame into the squish region leading to lower combustion efficiency.
[0005] There is need for an enhanced engine and a method for operating the same.
BRIEF DESCRIPTION
[0006] In accordance with one embodiment of the present invention, a method is disclosed. The method includes feeding air and at least one fuel into a plurality of cylinders of an engine. The method also includes combusting the at least one fuel using the air in the plurality of cylinders. The method further includes injecting a predefined quantity of a gaseous medium into each cylinder of the plurality of cylinders during a predefined piston stroke in each cylinder to enhance mixing of the air and the at least one fuel and propelling of combustion products towards a piston squish region in each cylinder.
[0007] In accordance with another embodiment of the present invention, an engine is disclosed. The engine includes a plurality of cylinders and an inlet manifold coupled to the plurality of cylinders, for feeding air to the plurality of cylinders. The method also includes a plurality of first fuel injectors provided to the plurality of cylinders respectively, for injecting a first fuel to the plurality of cylinders. The method further includes an exhaust manifold coupled to the plurality of cylinders, for directing flow of an exhaust gas from the plurality of cylinders. a plurality of gaseous medium injectors provided to the plurality of cylinders respectively, wherein the plurality of gaseous medium injectors is configured to inject a predefined quantity of a gaseous medium into the plurality of cylinders respectively during a predefined piston stroke in each cylinder to enhance mixing of the air and the first fuel and propelling of combustion products towards a piston squish region in each cylinder.
DRAWINGS
[0008] These and other features, aspects, and advantages of the present technology will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
[0009] FIG. 1 is a schematic diagrammatical representation of a vehicle having a control system in accordance with an embodiment of the present invention;
[0010] FIG. 2 is a schematic diagrammatical representation of a dual fuel engine having fuel and gaseous medium injection control features in accordance with certain embodiments of the present invention;
[0011] FIG. 3 is a sectional view of one cylinder provided with a corresponding first fuel injector and a gaseous medium injector in accordance with the embodiment of FIG. 2;
[0012] FIG. 4 is a sectional view of the first fuel injector and the gaseous medium injector in accordance with the embodiment of FIG. 3;
[0013] FIG. 5 is a sectional view of a first fuel injector and a gaseous medium injector in accordance with another embodiment of the present invention;
[0014] FIG. 6 is a graphical representation of variation in nitrogen oxide emission with reference to variation in base specific fuel consumption of a dual fuel engine in accordance with certain embodiments of the present invention;
[0015] FIG. 7 is a graphical representation representative of variation in nitrogen oxide emission with reference to variation in engine efficiency of a dual fuel engine in accordance with certain embodiments of the present invention; and
[0016] FIG. 8 is a graphical representation representative of variation in heat release rate with reference to variation in crank angle of a single fuel engine in accordance with certain embodiments of the present invention.
DETAILED DESCRIPTION
[0017] In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings.
[0018] As used herein, the term "non-transitory computer-readable media" is intended to be representative of any tangible computer-based device implemented in any method or technology for short-term and long-term storage of information, such as computer-readable instructions, data structures, program modules and sub-modules, or other data in any device. Therefore, the methods described herein may be encoded as executable instructions embodied in a tangible, non-transitory, computer readable medium, including, without limitation, a storage device and/or a memory device. Such instructions, when executed by a processor, cause the processor to perform at least a portion of the methods described herein. Moreover, as used herein, the term "non-transitory computer-readable media" includes all tangible, computer-readable media, including, without limitation, non-transitory computer storage devices, including, without limitation, volatile and nonvolatile media, and removable and non-removable media such as a firmware, physical and virtual storage, CD-ROMs, DVDs, and any other digital source such as a network or the internet, as well as yet to be developed digital means, with the sole exception being a transitory, propagating signal.
[0019] As used herein, the terms "software" and "firmware" are interchangeable, and may include any computer program stored in memory for execution by devices that include, without limitation, mobile devices, clusters, personal computers, workstations, clients, and servers.
[0020] As used herein, the term "computer" and related terms, e.g., "computing device", are not limited to integrated circuits referred to in the art as a computer, but broadly refers to at least one microcontroller, microcomputer, programmable logic controller (PLC), application specific integrated circuit, and other programmable circuits, and these terms are used interchangeably herein.
[0021] Referring to FIG. 1, a schematic diagrammatical representation of a vehicle 10 moving from a first operating point to a second operating point along a predefined path is shown. In the illustrated embodiment, the vehicle 10 is a locomotive. Suitable vehicles include passenger and non-passenger vehicles, hybrid vehicles, off-highway vehicles, on-road vehicles (such as tractor trailers), tracked vehicles, rail vehicles, marine propulsion system, and marine on-board power generation system, and the like. The vehicle 10 includes a dual fuel engine 12 and an exemplary control system 14 coupled to the dual fuel engine 12.
[0022] In the illustrated embodiment, the vehicle 10 is driven by the engine 12 utilizing a plurality of fuels. In the exemplary engine 12, a reduction in nitrogen oxide (NOx) and particulate matter (PM) emissions is enabled by combusting a relatively larger fraction of the premixed fuel. However, relative costs and availability of different fuels are constantly in flux. For example, in some embodiments, diesel and natural gas may be utilized to drive the engine 12. If the cost of diesel increases relative to the cost of the natural gas, more natural gas may be used resulting in reduced cost and emissions. If the cost of natural gas is increased relative to the cost of the diesel, then more diesel may be used to drive the engine 12. It should be noted herein that in certain embodiments, the vehicle 10 may also utilize other fuels instead of diesel, natural gas. The number of fuels may vary depending upon the application.
[0023] The exemplary control system 14 is used to control a plurality of fuel injectors and gaseous medium injectors (not shown in FIG. 1) of the engine 12. The fuel injectors are controlled to inject a predefined quantity of one or more fuels into each cylinder of a plurality of cylinders (not shown in FIG. 1) of the engine 12. Further, specifically, the gaseous medium injectors are controlled to inject a predefined quantity of a gaseous medium into each cylinder of a plurality of cylinders of the engine 12 during a predefined piston stroke in each cylinder. The injection of the gaseous medium provides additional momentum and thereby increase penetration of ignition sources in the plurality of cylinders. The injection of the gaseous medium enhances turbulence and mixing of air and fuel(s), faster propelling of combustion products to a piston squish region, and dispersion of high temperature combustion zones within each cylinder. It should be noted herein that the term “combustion products” may refer to complete combustion products (water vapor, carbon dioxide, and the like), intermediate products (such as certain radicals), and combustion flame. As a result, generation of nitrogen oxide emissions is reduced and engine efficiency is enhanced.
[0024] Although a multi fuel engine is discussed herein, the exemplary control unit 14 and an associated control method may also be applicable to other types of engines, for example, a single fuel engine. Similarly, although a vehicle is discussed herein, the exemplary control system 14 and an associated method may also be applicable for other mobile applications. In certain other embodiments, the exemplary control system 14 and an associated method may also be applicable for stationary applications. Such applications can be, for example, a power generation application or a mechanical drive application. The dual fuel engine 12 and the control system 14 are explained in greater detail with reference to subsequent figures.
[0025] Referring to FIG. 2, a schematic diagrammatical representation of the dual fuel engine 12 having fuel and gaseous medium injection control features is illustrated in accordance with certain embodiments of the present invention.
[0026] The illustrated engine 12 includes an inlet manifold 16 and an exhaust manifold 18. The engine 12 is provided with a turbocharger 20 having a compressor 22 and a turbine 24. The compressor 22 is operated to supply compressed air 31 to the inlet manifold 16 for combustion within a plurality of cylinders 26. The turbine 24 is coupled to the exhaust manifold 18, such that combustion exhaust gases 27 from the cylinders 26, expand through the turbine 24, putting work onto and rotating a turbocharger shaft 28 coupled to the compressor 22. The compressor 22 draws ambient air 29 through a filter (not shown) and provides the compressed air 31 to a heat exchanger (after cooler) 30. The temperature of the ambient air 29 is increased due to compression through the compressor 22. The compressed air 31 flows through the heat exchanger 30 such that the temperature of the compressed air 31 is reduced prior to delivery into the inlet manifold 16 of the engine 12. In one embodiment, the heat exchanger 30 is an air-to-water heat exchanger, which utilizes a liquid coolant to facilitate removal of heat from the compressed air 31. In another embodiment, the heat exchanger 30 is an air-to-air heat exchanger, which utilizes the ambient air 29 to facilitate removal of heat from the compressed air 31. In another embodiment, the heat exchanger 30 is a combination of an air-to-air heat exchanger and an air-to-water heat exchanger, which utilizes both the ambient air 29 and liquid coolant to facilitate removal of heat from the compressed air 31. The exhaust manifold 18 is used to direct the flow of the exhaust gases 27 from the plurality of cylinders 26.
[0027] In the illustrated embodiment, the control system 14 includes a control unit 32. In one embodiment, the control unit 32 is an electronic logic controller that is programmable by a user. In the illustrated embodiment, at least one sensor 34 is coupled to the engine 12 and configured to detect a position of a piston 36 in each of the plurality of cylinders 26. The control unit 32 is configured to receive output signals 38 representative of piston positions from the at least one sensor 34.
[0028] A plurality of first fuel injectors 40 and a second fuel injector 42 are used for introduction of a first fuel 44 and a second fuel 46 respectively (for example, diesel and natural gas) into the plurality of cylinders 26 of the engine 12. In one embodiment, specifically, the first fuel injectors 40 are used to inject the first fuel 44 into the plurality of cylinders 26 of the engine 12. The second fuel injector 42 is used to inject the second fuel 46 into the inlet manifold 16 of the engine 12. In such an embodiment, the inlet manifold 16 is used to feed a mixture of the second fuel 46 and the compressed air 31 to the plurality of cylinders 26. Further, a plurality of gaseous medium injectors 43 are used to inject a gaseous medium 47 into the plurality of cylinders 26 of the engine 12. The piston 36 is slidably disposed in each cylinder 26 and reciprocates between a top dead center position and a bottom dead center position of each cylinder 26. In the illustrated embodiment, the plurality of first fuel injectors 40 is coupled to a common rail 49 which is coupled to a pressure pump (not shown). The common rail 49 is used to store and feed the first fuel 44 to the plurality of first fuel injectors 40. Similarly, the plurality of gaseous medium injectors 43 is coupled to another common rail 51 which is coupled to another pressure pump (not shown). The common rail 51 is used to store and feed the gaseous medium 47 to the plurality of gaseous medium injectors 43. The pressure pumps can be controlled to control the pressure of the first fuel 44 and the gaseous medium 47 fed via the respective common rails 49, 51 to the injectors 40, 43.
[0029] The control unit 32 is operable to receive output signals 38 from the at least one sensor 34 and produce control signals 48, 50, 52 to control the first fuel injectors 40, the second fuel injector 42, and the gaseous medium injectors 43 respectively. The steps involved in controlling the first fuel injectors 40, the second fuel injector 42 and the gaseous medium injectors 43 are explained in greater detail below. The number of first fuel injectors 40, the second fuel injector 42, and the gaseous medium injectors 43 may vary depending on the application.
[0030] A signal acquisition system 54 receives the plurality of output signals 38 from the at least one sensor 34 and transmits the plurality of output signals 38 to the control unit 32. The control unit 32 includes a database 56, an injector control module 58, a processor 60, and a memory 64.
[0031] The database 56 may be configured to store predefined information about the engine 12. For example, the database 56 may store information relating to type of fuels, type of gaseous medium, quantity of fuel injection, quantity of gaseous medium injection, piston position, fuel injection pressure, gaseous medium injection pressure, ambient temperature, exhaust emissions, injection duration, and the like. Furthermore, the database 56 may be configured to store actual sensed/detected information from the at least one sensor 34. The algorithm facilitates the processing of the output signals 38 from the above-mentioned at least one sensors 34.
[0032] In one embodiment, the database 56 may be stored in a single memory module at one location. In other embodiments, the database 56 may be stored in a plurality of memory modules in a distributed manner. The database 56 may be at least one of a SQL database, an Oracle database, and a MySQL database. In alternate embodiments, other types of databases including relationship database systems (RDBS) may be used to store the plurality of rules. It may be noted herein that in one embodiment, the database 56 is a customized database. In other embodiments, the database 56 may be an off-the-shelf database.
[0033] The injector control module 58 is communicatively coupled to the database 56. The injector control module 58 may be stored in the memory 64 and executable by the processor 60. In an alternate embodiment, the injector control module 58 may also be a specialized hardware such as a Field Programmable Gate Array (FPGA).
[0034] The injector control module 58 includes codes and routines configured to control the first fuel injectors 40, the second fuel injector 42, and the gaseous medium injectors 43 for controlling injection of the first and second fuels 44, 46 and the gaseous medium 47 respectively into the cylinders 26. In one embodiment, the first fuel injectors 40, the second fuel injectors 42, and the gaseous medium injectors 43 are controlled to control a quantity of injection of the first and second fuels 44, 46 and the gaseous medium 47 respectively into the cylinders 26. In another embodiment, injection timing of the first fuel injectors 40, the second fuel injector 42, and the gaseous medium injectors 43 are controlled. In yet another embodiment, the first fuel injectors 40, the second fuel injector 42, and the gaseous medium injectors 43 are controlled to control injection duration of the first and second fuels 44, 46 and the gaseous medium 47 respectively into the cylinders 26. In yet another embodiment, the first and second fuel injectors 40, 42 and the gaseous medium injectors 43 are controlled to control injection pressure of the first and second fuels 44, 46 and the gaseous medium 47 respectively into the cylinders 26. In one embodiment, the injector control module 58 includes a set of instructions executable by the processor 60. In another embodiment, the injector control module 58 is stored in the memory 64 and is accessible and executable by the processor 60. In either embodiment, the injector control module 58 is adapted for communication and cooperation with the processor 60 and other modules of the control unit 32.
[0035] The processor 60 is communicatively coupled to the database 56 and other modules of the control unit 32. The processor 60 may include at least one arithmetic logic unit, microprocessor, general purpose controller or other processor arrays to perform the desired computations. In one embodiment, the processor 60 is a custom hardware configured to perform functions of the control unit 32 and the signal acquisition system 54. In another embodiment, the processor 60 is a digital signal processor or a microcontroller. The processor 60 may also be configured to manage the contents of the database 56. In some embodiments, other type of processors, operating systems, and physical configurations are envisioned.
[0036] The memory 64 is coupled to the processor 60 and may also be optionally coupled to the other modules of the control unit 32. The memory 64 is configured to store instructions performed by the processor 60 and contents of the database 56. The memory 64 may be a non-transitory storage medium. For example, the memory 64 may be a dynamic random access memory (DRAM) device, a static random access memory (SRAM) device, flash memory, or other memory devices. In one embodiment, the memory 64 may include a non-volatile memory or similar permanent storage device, and media such as a hard disk drive, a floppy disk drive, a compact disc read only memory (CD-ROM) device, a digital versatile disc read only memory (DVD-ROM) device, a digital versatile disc random access memory (DVD-RAM) device, a digital versatile disc rewritable (DVD-RW) device, a flash memory device, or other non-volatile storage devices. In one embodiment, the memory 64 may be communicatively coupled to the processor 60. In an alternative embodiment, the memory 64 is an on-board memory of the processor 60.
[0037] In an exemplary embodiment, the non-transitory computer readable medium encoded with a program, instructs the processor 60 to perform functions associated with the control unit 32 for controlling the plurality of first fuel injectors 40, the second fuel injector 42, and the gaseous medium injectors 43. The program instructions include one or more functions of the database 56, the injector control module 58, and the signal acquisition system 54.
[0038] During operation, a mixture of the compressed air 31 and the second fuel 46 is fed via the inlet manifold 16 to the plurality of cylinders 26 during an intake piston stroke. In one embodiment, the second fuel 46 is natural gas. Further, a predefined pilot quantity of the first fuel 44 is injected to the mixture of the compressed air 31 and the second fuel 46. In one embodiment, the first fuel 44 is diesel. In one specific embodiment, the predefined pilot quantity of the first fuel 44 is about 1 percent to 2 percent of the total quantity of fuel energy introduced into the cylinders 26. The first fuel 44 and the second fuel 46 are combusted using the compressed air 31 within the plurality of cylinders 26.
[0039] Further, a predefined quantity of the gaseous medium 47 is injected into the plurality of cylinders 26 during a predefined piston stroke in each cylinder 26. Specifically, the injection of the gaseous medium 47 is initiated after combustion of the second fuel 46 is initiated by the injection of the first fuel 44. In one embodiment, the predefined quantity of the gaseous medium 47 is injected during a compression stroke of the piston 36 in each cylinder 26. For example, the predefined quantity of the gaseous medium 47 is injected when a position of the piston 36 is approximately between 20 degrees before top dead center up to the to dead center during the compression stroke. In such an embodiment, the predefined quantity of the gaseous medium 47 may be less than or equal to 5 percent of a quantity of the compressed air 31 fed to each cylinder 26. Further, the gaseous medium 47 may be injected at a pressure greater than an in-cylinder pressure in each cylinder 26. For example, the gaseous medium 47 may be injected at a pressure which is 10 bars more than the in-cylinder pressure. Additionally, the gaseous medium 47 may be injected at a same temperature as the compressed air 31 at an outlet 45 of the after cooler 30. In one embodiment, the gaseous medium 47 may be injected at a temperature slightly greater than the ambient temperature. In one specific embodiment, the gaseous medium 47 includes air. In another specific embodiment, the gaseous medium includes an inert gas such as nitrogen. In certain other embodiments, for a single fuel engine, if only the first fuel 44 (for example, diesel) is used, then the gaseous medium 47 may be injected during an expansion stroke of the piston 36. For example, the predefined quantity of the gaseous medium 47 is injected when a position of the piston 36 is approximately between top dead center up to the to approximately 20 degrees after top dead center during the expansion stroke. In such embodiments, the injection of the gaseous medium 47 facilitates to enhance mixing of the compressed air 31 and the at least one fuel and propelling of combustion products towards a piston squish region (not shown in FIG. 2) in each cylinder 26.
[0040] FIG. 3 is a sectional view of one cylinder 26 provided with the corresponding first fuel injector 42 and the gaseous medium injector 43 in accordance with the embodiment of FIG. 2. It should be noted herein that for the ease of illustration, only one cylinder 26 is shown.
[0041] The corresponding piston 36 is disposed within the cylinder 26 and configured to reciprocate between a top dead center position (TDC) and a bottom dead center position (BDC). The cylinder 26 is closed at one end by a cylinder head 62 and open at other end to permit free oscillation of a connecting rod (not shown) which is coupled to a crankshaft (not shown). In the illustrated embodiment, the corresponding first fuel injector 42 and the gaseous medium injector 43 are coupled to the cylinder head 62.
[0042] In the illustrated embodiment, the first fuel injector 40 is used to inject the first fuel 44 into the cylinder 26 of the engine 12. As noted earlier, the second fuel injector 42 is used to inject the second fuel 46 into the inlet manifold 16 of the engine 12. The gaseous medium injector 43 is used to inject the gaseous medium 47 into the cylinder 26 of the engine 12. In the illustrated embodiment, the gaseous medium injector 43 is disposed proximate to the first fuel injector 40. The gaseous medium injector 43 is used to inject a predefined quantity of the gaseous medium 47 into the cylinder 26 during a predefined piston stroke to enhance mixing of the compressed air 31, the first fuel 44, and the second fuel 46 and propelling of combustion products including a generated flame 66 towards a piston squish region 68 in the cylinder 26.
[0043] In one embodiment, the engine 12 is a four-stroke engine. In another embodiment, the engine 12 is a two-stroke engine. In one specific embodiment, if the engine 12 is a dual fuel engine, the gaseous medium injector 43 is used to inject a predefined quantity of the gaseous medium 47 into the cylinder 26 during a compression stroke of the piston 36. In another specific embodiment, if the engine 12 is a single fuel engine, the gaseous medium injector 43 is used to inject a predefined quantity of the gaseous medium 47 into the cylinder 26 during an expansion stroke of the piston 36. The injection of the predefined quantity of the gaseous medium 47 facilitates to accelerate combustion within the cylinder 26 and thereby increase the thermal efficiency by (a) pushing the combustion flame 66 deeper towards the piston squish region 68 (b) enhancing the in-cylinder turbulence and (c) dispersing the local high temperature combustion regions within the cylinder 26 resulting in reduction of nitrogen oxide emissions.
[0044] FIG. 4 is a sectional view of first fuel injector 42 and the gaseous medium injector 43 in accordance with the embodiment of FIG. 3. A high-pressure pump (not shown) is used to feed the first fuel at a high pressure to the common rail. The common rail is a pressure accumulator where the first fuel is stored at the high pressure. The common rail is used to supply the first fuel at high pressure to the first fuel injectors 42. For ease of illustration, in the illustrated embodiment, only one first fuel injector 42 is shown. The first fuel injectors 42 are typically controlled by an electronic controlled unit.
[0045] When In the illustrated embodiment, when the first fuel injector 42 is electrically activated, the valve needle 74 is biased mechanically or hydraulically upwards to an open position. As a result, the first fuel 44 is injected from a port (not shown) formed in a valve needle guide through a plurality of first injection holes 78 into the cylinder 26. When the first fuel injector is deactivated, the biasing force is removed and the valve needle 74 is moved downwards to a closed position. As a result, the port formed in the valve needle guide is closed and the injection of the first fuel 44 through the plurality of first injection holes 78 is cut-off.
[0046] In the illustrated embodiment, the gaseous medium injector 43 is disposed proximate to the first fuel injector 42. Specifically, the gaseous medium injector 43 is integrated to the first fuel injector 42. More specifically, the gaseous medium injector 43 is disposed surrounding the spring-loaded valve needle 74 of the first fuel injector 42. The gaseous medium injector 43 is used to inject the gaseous medium 47 into the cylinder 26 of the engine 12. The injection of the gaseous medium 47 facilitates to cool a tip of the first fuel injector 42 since the gaseous medium injector 43 is disposed proximate to the first fuel injector 42. The gaseous medium injector 43 may have a similar configuration as the first fuel injector 42.
[0047] In the illustrated embodiment, the gaseous medium 47 is injected through a plurality of second injection holes 80 of the gaseous medium injector 43 into the cylinder 26. A number of the first injection holes 78 is less than or equal to a number of the second injection holes 80.
[0048] FIG. 5 is a sectional view of the first fuel injector 42 and a gaseous medium injector 82 in accordance with another embodiment of the present invention. In the illustrated embodiment, the first fuel injector 42 includes the valve needle 74 disposed inside the housing 76. The valve needle 74 is positioned to reciprocate between an open position and a closed position.
[0049] As discussed earlier, when the valve needle 74 is biased upwards to an open position, the first fuel 44 is injected from the port (not shown) formed in the valve needle guide through the plurality of first injection holes 78 into the cylinder 26. When the valve needle 74 is biased downwards to a closed position, the port formed in the valve needle guide is closed and the injection of the first fuel 44 through the plurality of first injection holes 78 is cut-off.
[0050] In the illustrated embodiment, the gaseous medium injector 43 is disposed proximate to the first fuel injector 42. Specifically, the gaseous medium injector 43 is disposed separate from the first fuel injector 42. More specifically, the gaseous medium injector 43 is disposed in the cylinder head 62. The gaseous medium injector 43 is used to inject the gaseous medium 47 into the cylinder 26 of the engine 12. The gaseous medium injector 43 may have a similar configuration as the first fuel injector 42. The gaseous medium 47 is injected through the plurality of second injection holes 80 of the gaseous medium injector 43 into the cylinder 26.
[0051] FIG. 6 is a graphical representation 88 of variation in nitrogen oxide emission with reference to variation in base specific fuel consumption of a dual fuel engine in accordance with certain embodiments of the present invention. The base specific fuel consumption is represented by x-axis and nitrogen oxide emission is represented by y-axis. A curve 90 is representative of decrease in nitrogen oxide emission with reference to increase in base specific fuel consumption without injection of the gaseous medium. In accordance with the embodiment of the present invention, a predefined quantity of a gaseous medium is injected into each cylinder of the plurality of cylinders during a predefined piston stroke in each cylinder to enhance mixing of the air and the at least one fuel and propelling of combustion products towards a piston squish region in each cylinder. The curve 92 is representative of decrease in nitrogen oxide emissions with reference to decrease in base specific fuel consumption due to injection of the gaseous medium.
[0052] FIG. 7 is a graphical representation 94 of variation in nitrogen oxide emission with reference to variation in engine efficiency of a dual fuel engine in accordance with certain embodiments of the present invention. The engine efficiency is represented by x-axis and nitrogen oxide emission is represented by y-axis. A curve 96 is representative of decrease in nitrogen oxide emission with reference to decrease in engine efficiency without injection of the gaseous medium. In accordance with the embodiment of the present invention, a predefined quantity of a gaseous medium is injected into each cylinder of the plurality of cylinders during a predefined piston stroke in each cylinder to enhance mixing of the air and the at least one fuel and propelling of combustion products towards a piston squish region in each cylinder. The curve 98 is representative of decrease in nitrogen oxide emissions with reference to increase in engine efficiency due to injection of the gaseous medium. In one embodiment, for a multi fuel engine, the injection of the gaseous medium results in a gain of 1.8 percent indicated engine efficiency while reducing the nitrogen oxide emissions by 30 percent. The gain in indicated engine efficiency and reduction in nitrogen oxide emissions can be further enhanced by optimizing the amount of gaseous medium injected, gaseous medium injection pressure, injection timing of the gaseous medium, and temperature of the injected gaseous medium. In another embodiment, for a single fuel engine, the injection of the gaseous medium results in a gain of 2.5 percent indicated engine efficiency while reducing the particulate matter emissions by 75 percent.
[0053] FIG. 8 is a graphical representation 100 representative of variation in heat release rate with reference to variation in crank angle of a single fuel engine in accordance with certain embodiments of the present invention. Crank angle is represented by x-axis and heat release rate is represented by y-axis. Heat release rate is the rate at which chemical energy of fuel is released by the combustion process. A curve 102 is representative of variation in heat release rate with reference to variation in crank angle without injection of the gaseous medium. In accordance with the embodiment of the present invention, a predefined quantity of a gaseous medium is injected into each cylinder of the plurality of cylinders during a predefined piston stroke in each cylinder to enhance mixing of the air and the at least one fuel and propelling of combustion products towards a piston squish region in each cylinder. The curve 102 is representative of variation in heat release rate with reference to variation in crank angle due to injection of the gaseous medium. It can be noted herein that the variation in heat release rate with reference to variation in crank angle is substantially same with or without injection of the gaseous medium. In one embodiment, when the gaseous medium is injected, base specific fuel consumption and emission of particulate matter are reduced and engine efficiency is increased. In one specific embodiment, emission of particulate matter is reduced by 72 percent and the engine efficiency is increased by 2.5 percent.
[0054] Furthermore, the skilled artisan will recognize the interchangeability of various features from different examples. Similarly, the various methods and features described, as well as other known equivalents for each such method and feature, can be mixed and matched by one of ordinary skill in this art to construct additional systems and techniques in accordance with principles of this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages described above may be achieved in accordance with any particular example. Thus, for example, those skilled in the art will recognize that the systems and techniques described herein may be embodied or carried out in a manner that achieves or improves one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
[0055] While only certain features of the technology have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the claimed inventions.