METHOD OF INJECTING AMMONIA FUEL INTO A RECIPROCATING ENGINE

Abstract

A method of injection of liquid or gaseous ammonia fuel into a reciprocating engine that includes at least two cylinders, each cylinder including a piston that moves reciprocally within that cylinder, each cylinder having a head location at one end located opposite to a compression end of the piston and defining a combustion chamber therebetween, the cylinder including at least one inlet valve through which combustion gases are fed into the combustion chamber and at least one exhaust valve through which spent combustion gases egress the combustion chamber, the piston moving the cylinder in a cycle between top dead center where the piston is located closest to the head location and bottom dead center where the piston is located furthest from the head location, and including at least one fuel injector located at or in the head location, and wherein the method comprises: injecting the ammonia fuel into the combustion chamber of each cylinder as at least one fuel jet with a timing of: after the at least one exhaust valve of the respective cylinder is substantially closed; and before the respective piston moves to at most 35 degrees, preferably at most 45 degrees, prior to top dead centre.

Claims

1.-39. (canceled)

40. A method of injection of liquid or gaseous ammonia fuel into a reciprocating engine that includes at least two cylinders, each cylinder including a piston that moves reciprocally within that cylinder, each cylinder having a head location at one end located opposite to a compression end of the piston and defining a combustion chamber therebetween, the cylinder including at least one inlet valve through which combustion gases are fed into the combustion chamber and at least one exhaust valve through which spent combustion gases egress the combustion chamber, the piston moving the cylinder in a cycle between top dead center where the piston is located closest to the head location and bottom dead center where the piston is located furthest from the head location, and including at least one fuel injector located at or in the head location, and wherein the method comprises: injecting the ammonia fuel into the combustion chamber of each cylinder as at least one fuel jet with a timing of: after the at least one exhaust valve of the respective cylinder is substantially closed; and before the respective piston moves to at most 35 degrees, preferably at most 45 degrees, prior to top dead centre.

41. The method of claim 40, wherein the ammonia fuel is injected into the combustion chamber of each cylinder during compression stroke of the engine cycle.

42. The method of claim 40, wherein the ammonia fuel is injected into the combustion chamber of each cylinder with a timing of at least one of: (A) after the at least one exhaust valve is substantially closed; and before the piston moves to 35 degrees prior to top dead centre; (B) after the at least one exhaust valve is substantially closed; and before the piston moves to 45 degrees prior to top dead centre; or (C) after the at least one exhaust valve is substantially closed; after the at least one inlet valve is closed; and before the piston moves to 35 degrees before top dead centre.

43. The method of claim 40, wherein the ammonia fuel is injected into the combustion chamber of each cylinder such that one of the following occurs: (A) the fuel jets enter the cylinder having a jet centreline that is at an angle of between −90° and −35° relative to a base line which is perpendicular to the centreline of the respective cylinder; (B) the fuel jets enter the cylinder having a jet centreline that is at an angle of between −90° and −50°, preferably between −90° and −65° relative to a base line which is perpendicular to the centreline of the respective cylinder; (C) the fuel jets enter the cylinder having a jet centreline that is at an angle of between −90° and −30° relative to a base line which is perpendicular to the centreline of the respective cylinder; (D) the fuel jets enter the cylinder having a jet centreline that is at an angle of between −90° and −65° relative to a base line which is perpendicular to the centreline of the respective cylinder, and wherein injection is timed to occur after the at least one exhaust valve closes and before the piston moves to 35 degrees of top dead centre; or (E) that the fuel jets enter the cylinder having a jet centreline that is at an angle of between −90° and −50° relative to a base line which is perpendicular to the centreline of the respective cylinder, and wherein injection is timed to occur after the at least one exhaust valve closes and before the piston moves to 45 degrees of top dead centre.

44. The method of claim 40, wherein the ammonia fuel is: at least one of a gaseous ammonia fuel, or a liquid ammonia fuel; or a blend of liquid ammonia with at least one or water, or another fuel, preferably selected from at least one of: iron picrate solution, hydrazine, or ammonium nitrate.

45. The method of claim 40, wherein the at least one fuel injector is located in a cylinder head at the head location and comprises at least one of: a single fuel injector located in the center of the cylinder head; or at least two fuel injectors spaced apart across the diameter of the cylinder head.

46. The method of claim 40, wherein the at least one fuel injector comprises one of: at least one semi-axial nozzle fuel injector located near the centre of the cylinder with near fuel jets directed downwards; or at least one semi-axial discharge nozzle liquid ammonia injector(s) located near the cylinder wall with near semi-axial fuel jets directed downwards towards the piston.

47. The method of claim 40, wherein the reciprocating engine comprises at least one of: a compression ignition engine; or a spark, plasma or laser ignition engine; a two-stroke engine, or a four-stroke engine; or crosshead or trunk uniflow engine.

48. The method of claim 40, wherein the head location comprises a cylinder head of the cylinder.

49. The method of claim 40, wherein each cylinder including two pistons that move reciprocally within that cylinder in opposite directions, forming a compression end at the head location and combustion chamber therebetween, at least one inlet valve through which combustion gases are fed into the combustion chamber and at least one exhaust valve through which spent combustion gases egress the combustion chamber, the pistons moving the cylinder in a cycle between top dead center where the piston is located closest to the opposite piston and bottom dead center where the piston is located furthest from the opposite piston, and including at least one fuel injector located in the cylinder wall.

50. A method of injection of liquid or gaseous ammonia fuel into a reciprocating engine that includes at least two cylinders, each cylinder including a piston that moves reciprocally within that cylinder, each cylinder having a head location at one end located opposite to a compression end of the piston and defining a combustion chamber therebetween, the cylinder including at least one inlet valve through which combustion gases are fed into the combustion chamber and at least one exhaust valve through which spent combustion gases egress the combustion chamber, the piston moving the cylinder in a cycle between top dead center where the piston is located closest to the head location and bottom dead center where the piston is located furthest from the head location, and including at least one fuel injector located in the wall of the cylinder spaced away from the head location, the injector being positioned to inject fuel into the combustion chamber, and wherein the method comprises: injecting the ammonia fuel into the combustion chamber of each cylinder as at least one fuel jet such that the fuel jets enters the combustion chamber having a jet centreline that is at an angle of between −80° and 80° relative to a base line which is perpendicular to the centreline of the respective cylinder, and wherein injection is timed to occur: after the at least one exhaust valve of the respective cylinder is substantially closed; and before the at least one fuel injector is covered by the respective piston when moving from bottom dead center to top dead center in each respective cylinder.

51. The method of claim 50, wherein the injectors are located in the cylinder sidewall in the lower half of the cylinder relative to movement of the piston between top deal center and bottom dead center.

52. The method of claim 50, wherein the ammonia fuel is injected into the combustion chamber of each cylinder during compression stroke of the engine cycle, and preferably after the at least one inlet valve is closed.

53. The method of claim 50, wherein the at least one fuel jet is injected into combustion chamber having one of: a jet centreline that is at an angle of −80° and 40° relative to a base line which is perpendicular to the centreline of the respective cylinder; a jet centreline that is at an angle of −80° and 0° relative to a base line which is perpendicular to the centreline of the respective cylinder; or a jet centreline that is at an angle of −80° and −40° relative to a base line which is perpendicular to the centreline of the respective cylinder.

54. The method of claim 50, wherein the ammonia fuel is: at least one of a gaseous ammonia fuel, or a liquid ammonia fuel; or a blend of liquid ammonia with at least one or water, or another fuel, preferably selected from at least one of: iron picrate solution, hydrazine, or ammonium nitrate.

55. The method of claim 50, wherein the at least one fuel injector comprises at least one of: a single fuel injector; at least two fuel injectors circumferentially spaced apart around the circumference of the cylinder wall. at least one semi-axial nozzle fuel injector located near the centre of the combustion chamber when the piston is bottom dead center with near fuel jets directed downwards; or at least one liquid ammonia injector placed low in the cylinder wall, preferably closer to the compression end of the piston than the cylinder head when the piston is bottom dead center.

56. The method of claim 50, wherein the reciprocating engine comprises at least one of: a compression ignition engine; or a spark, plasma or laser ignition engine; a two-stroke engine, or a four-stroke engine; or a crosshead or a trunk uniflow engine

57. The method of claim 50, wherein the head location comprises a cylinder head of the cylinder.

58. The method of claim 50, wherein each cylinder including two pistons that move reciprocally within that cylinder in opposite directions, forming a compression end at the head location and combustion chamber therebetween, at least one inlet valve through which combustion gases are fed into the combustion chamber and at least one exhaust valve through which spent combustion gases egress the combustion chamber, the pistons moving the cylinder in a cycle between top dead center where the piston is located closest to the opposite piston and bottom dead center where the piston is located furthest from the opposite piston, and including at least one fuel injector located in the cylinder wall.

59. The method of claim 50, further comprising: injecting a pilot fuel, preferably diesel, into the combustion chamber subsequent to injection of the ammonia fuel into the combustion chamber of each cylinder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0084] The present invention will now be described with reference to the figures of the accompanying drawings, which illustrate particular preferred embodiments of the present invention, wherein:

[0085] FIG. 1 illustrates the methodology used in the present specification for determining jet angles of fuel injected into a cylinder of an engine through an injector.

[0086] FIG. 2 illustrates a system used for specifying fuel jet angles relative to the cylinder centre line of a cylinder of an engine.

[0087] FIG. 1 is a schematic cross-sectional view of one cylinder of a conventional (prior art) trunk uniflow 2-stroke engine showing a radial nozzle fuel injector located near the centre of the cylinder with fuel jets directed outwards.

[0088] FIG. 2 is (A) a schematic cross-sectional view of one cylinder of a conventional (prior art) crosshead uniflow 2-stroke engine showing a side-discharge fuel injector of the cylinder located near the cylinder wall with fuel jets directed radially inwards; and (B) a close-up of the fuel jet and fuel jet angle A measured relative to the injector and baseline X shown in (A).

[0089] FIG. 3 is a schematic cross-sectional view of one cylinder of a trunk uniflow 2-stroke engine with an injector configuration according to one embodiment of the present invention showing a semi-axial nozzle fuel injector located near the centre of the cylinder with near fuel jets directed downwards. Pilot injectors/ignition devices are not shown for clarity.

[0090] FIG. 4 is a schematic cross-sectional view of one cylinder of a crosshead uniflow 2-stroke engine of one cylinder with an injector configuration according to an embodiment of the present invention having a semi-axial discharge nozzle liquid ammonia injector(s) located near the cylinder wall with near semi-axial fuel jets directed downwards towards the piston. Pilot injectors/ignition devices are not shown for clarity.

[0091] FIG. 5 is a schematic cross-sectional view of one cylinder of a trunk uniflow 2-stroke engine with an injector configuration according to an embodiment of the present invention showing a semi-axial nozzle fuel injector located near the centre of the cylinder with near fuel jets directed downwards.

[0092] FIG. 6 is a schematic cross-sectional view of one cylinder a crosshead uniflow 2-stroke engine with an injector configuration according to an embodiment of the present invention comprising liquid ammonia injectors placed low in the cylinder wall with various jet alignment options. Pilot injectors/ignition devices are not shown for clarity.

DETAILED DESCRIPTION

[0093] The method of the present invention provides a method injecting a gaseous or liquid ammonia fuel that improves ammonia ignition and combustion in an internal combustion engine using that liquid or gaseous ammonia fuel. The present invention can also improve ammonia vaporisation after injection into the cylinder, reducing compression work of the engine and also reducing NOx, nitrogen-based particulate emissions for uniflow 2-stroke engines.

Jet Fuel Injection Angles

[0094] FIGS. 1 and 2 illustrate the system and methodology used in the present specification to measure and specify the angle A of a fuel jet injected into the combustion chamber of a cylinder engine (not illustrated for ease of reference of the schematic) from a fuel jet injector.

[0095] Firstly, as shown in FIG. 1 a fuel jet 115 injected from an injector 110 will undergo a degree of spread as the fuel jet 115 emanates out from the nozzle 118 of the fuel injector 110. All angles A referenced with respect to a fuel jet hereinafter are with reference to the centreline Y of the jet spray of the respective fuel jet 115 starting from the injection point M at the nozzle 118.

[0096] Secondly, all angles of the fuel jet 115 sprayed within the cylinder are measured relative to a baseline X. Baseline X is a line which is perpendicular to the centreline CL of the respective cylinder. For ease of reference, the baseline X can be positioned to intersect through point of intersection I with the centreline Y of the fuel jet 115 to show angle A therebetween. However, it should be appreciated that this baseline can be used as a reference for angle A at any suitable position relative to the centreline Y of the fuel jet 115.

[0097] Using the centreline CL of the respective cylinder, baseline X and fuel jet centreline Y, the angle A references the angle the fuel jet 115 is sprayed out from the nozzle 118 of injector 110 into the combustion chamber of the cylinder.

[0098] FIG. 2 illustrates six examples of this measurement using this system. B All angles A are measured between the fuel jet centreline Y of each fuel jet and baseline Y which is perpendicular to the centreline CL of the respective cylinder. As measured in FIG. 1, the illustrative angles are set out in Table 1:

TABLE-US-00001 TABLE 1 Measured fuel-jet examples Angle A Injector No. Fuel Jet (degrees) 210 215 −20 220 225 −20 230 235 0 240 245 20 250 255 −70 2160 265 −20

[0099] Using this nomenclature, the angle A of a variety of fuel jets can be described.

[0100] It should be noted that while the fuel jet angles A will be described in terms of their inclination in a single plane, compound jet angles could also advantageously be used with ammonia fuel jets directed either with or against the swirl flow pattern in the combustion air as usually induced by the scavenge belt ports to improve cylinder emptying of exhaust gases. The fuel jet angle(s) A are measured as true angles with respect to the cylinder centre line (CL) and a plane normal to the cylinder centre line (CL).

Conventional Fuel Injection

[0101] The present invention more effectively uses ammonia as a combustion fuel in an internal combustion engine by using different method of ammonia injection, particularly for uniflow 2-stroke engines. As a point of comparison, FIGS. 3 and 4 provide a schematic showing the method of fuel injection of fuel in a conventional (prior art) trunk uniflow 2-stroke engine (FIG. 3) and a conventional (prior art) crosshead uniflow 2-stroke engine (FIG. 4).

[0102] Firstly, referring to FIG. 3, which illustrates a cross-sectional view of one cylinder 300 and piston 305 combination for a conventionally fuelled trunk piston uniflow 2-stroke engine. The cylinder 300 includes a cylinder head 308 having a radial nozzle fuel injector 310 located near the centre of the cylinder 300 and cylinder head 308 which directs fuel jets 315 outwardly therefrom towards the cylinder walls 312. The cylinder head 308 includes exhaust outlet valves 330. As illustrated, the piston 305 includes a connecting rod 322 which is connected at the other end to a crankshaft (not shown). The cylinder 300 also includes a scavenger belt 360 which include inlet ports 335 that are uncovered by the piston 305 towards the bottom of the piston stroke (when the piston 305 is close to bottom dead center). In this schematic, the fuel is injected through injector 310 such that the centreline Y of fuel jets 315 form an angle A of −30° and +5° relative to baseline X. The injectors 310 would typically include 4 to 16 orifices in the nozzle. The fuel injection events are time to start between 35° and 10° of crankshaft rotation before the piston reaches the top of the compression stroke i.e. before top dead centre (BTDC).

[0103] FIG. 4 illustrates a cross-sectional view of one cylinder 400 and piston 405 combination of a conventionally fuelled crosshead uniflow 2-stroke engine. The illustrated cylinder 400 includes a cylinder head 408 having at least two side-discharge fuel injectors 410 located near the cylinder wall 412 with fuel jets 415 directed inwards (i.e. away from the cylinder walls 412). The cylinder head 408 includes a central exhaust outlet valve 430. As illustrated, the piston 405 includes a piston rod 422 which is interconnected at the other end to a crosshead then connecting rod to a crankshaft (not shown). The cylinder 400 also includes a surrounding scavenge box 455 which encloses a scavenge belt 460 in the cylinder wall 412 which include inlet ports 435 that are uncovered by the piston 405 towards the bottom of the piston stroke (when the piston 405 is close to bottom dead center). Piston rod 422 intersects and is inserted through scavenger box 453 via stuffing box 465. As shown, the fuel is injected through injectors 410 as fuel jets 415 which form an angle A of between −25° and +5° relative to baseline X. The injectors 410 would typically include 4 to 8 orifices in the nozzle. The fuel injection events are time to start between 15° of crankshaft rotation BTDC through to several degrees after top dead centre (ATDC) depending on engine size and fuel ignition properties.

Fuel Injection of the Present Invention

[0104] The present invention comprises different injection arrangements based on newly discovered requirements for fuelling engines with either liquid or gaseous ammonia fuels. The inventor has found that more effective combustion can be achieved when ammonia fuel is injected much earlier in the compression cycle of each cylinder of an engine than for that normally taught for compression ignition engines, for example the two prior art engine configuration discussed above in relation to FIGS. 3 and 4. Fuel injection for the injection regime of the present invention occurs just after the exhaust valve(s)/ports are closed and deeper into the cylinder volume (i.e. steeper fuel jet injection angle) to ensure sufficient time for vaporisation and mixing, reduce compression work and to allow more complete combustion.

[0105] FIG. 5 shows a cross-sectional view of one cylinder 500 and piston 505 combination for a trunk piston uniflow 2-stroke engine using the ammonia fuel injection method of the present invention. The cylinder and piston configuration are the same as described in relation to FIG. 3. Accordingly, like features have been provided the same reference numeral plus 200. In this schematic, the ammonia fuel is injected through injector 510 such that the centreline Y of fuel jets 515 enter the cylinder at an angle A of −90° and −35°. The injector 510 would typically include 1 to 4 orifices in the nozzle. Ammonia injection is timed to occur after the exhaust valve(s) 530 close and before 45 crank degrees of top dead centre. The exhaust valves 530 are closed during ammonia injection so to limit/control ammonia slip to the exhaust.

[0106] FIG. 6 which illustrates a cross-sectional view of one cylinder 600 and piston 605 combination of a fuelled crosshead uniflow 2-stroke engine 400. using the ammonia fuel injection method of the present invention. The cylinder and piston configuration are the same as described in relation to FIG. 4. Accordingly, like features have been provided the same reference numeral plus 200. In this schematic, the ammonia fuel is injected through injector 610 such that the centreline Y of fuel jets 615 enter the cylinder at angle A of between −90° and −30°. The injector 610 would typically include 1 to 4 orifices in the nozzle. Ammonia injection is timed to occur after the exhaust valve(s) 630 close and before 35 crank degrees of top dead centre. The exhaust valves 630 are closed so to limit/control ammonia slip to the exhaust.

[0107] An alternative form of invention applied to trunk piston uniflow 2-stroke engines where the ammonia fuel is injected using the fuel injection method of the present invention is shown in FIG. 5. A cross-sectional view of one cylinder 700 and piston 705 is illustrated. The cylinder and piston configuration are the same as described in relation to FIG. 3. Accordingly, like features have been provided the same reference numeral plus 400. This embodiment is a side injector configuration, having semi-axial nozzle ammonia fuel injector 710 located in the cylinder wall 712 with near fuel jets 715 directed towards the centre of the cylinder. This injector 710 would typically include 1 to 4 orifices in the nozzle. For large cylinders several such injectors may be used to improve mixing and reduce the chilling effect on the cylinder wall—a suitable arrangement is using one injector for each 300-400 mm increment of cylinder circumference. In this schematic, the fuel injector 710 is located in the lower half 770 of the cylinder 700 relative to piston travel between top dead center and bottom dead center (piston-top travel) and the one or more fuel jets 712 are injected into combustion chamber 750 of the cylinder 700 in an angle A of −80° to 80° relative to baseline X. As shown in this schematic, fuel jets 715 may travel upwardly or downwardly relative to the injector 710. Ammonia injection is timed to occur after the exhaust valve(s) 730 close and before the piston covers the injection port(s). The exhaust valve(s) 730 are closed so to limit/control ammonia slip to the exhaust. This arrangement is advantageous for smaller bore trunk engines as it frees the cylinder head/cover for the location of the pilot injector(s) (for example 711 described in more detail below) or other ignition devices. In all cases injection timing would be after the exhaust valve(s) are closed and before the piston covers the injection port(s) 735 on the up-stroke or compression stroke. The location of the fuel jet 715 and the jet angle A used can be further optimised to provide the required mixing of the air-fuel in the cylinder 700.

[0108] An alternative form of invention as applied to crosshead uniflow 2-stroke engines the fuel is injected using the ammonia fuel injection method of the present invention is shown in FIG. 6. A cross-sectional view of one cylinder 800 and piston 805 is illustrated. The cylinder and piston configuration are the same as described in relation to FIG. 4. Accordingly, like features have been provided the same reference numeral plus 400. This embodiment is a side injector configuration, having ammonia injectors 810 placed low in the cylinder wall 812 with various jet alignment options. The injector 810 typically has 1 to 4 orifices in the nozzle. For large cylinders several such injectors may be used to improve mixing and reduce the chilling effect on the cylinder wall—a suitable arrangement is using one injector for each 300-400 mm increment of cylinder circumference. In this schematic, the fuel injector 810 is located in the lower half 870 of the cylinder 800 relative to piston travel between top dead center and bottom dead center (piston-top travel) and one or more fuel jets 812 are injected into the combustion chamber 850 at an angle A of −80° to 80°. As shown in this schematic, fuel jets 815 may travel upwardly or downwardly relative to the injector 810. Ammonia injection is timed to occur after the exhaust valve(s) 830 close and before the piston covers the injection port(s). The exhaust valves 830 are closed so to limit/control ammonia slip to the exhaust. This arrangement is advantageous for smaller bore engines as it frees the cylinder head/cover for the location of the pilot injector(s) or other ignition devices.

[0109] While the invention as shown in FIG. 3 to FIG. 6 relates mostly to injection of liquid ammonia, these arrangements could also use gaseous ammonia injection, with the vaporisation produced external to the cylinder and advantageously using waste heat such as engine coolant. Advantages of the gaseous version of the invention include efficient utilisation of low-grade waste heat such as from hot engine coolant, better fuel-air mixing, higher compression temperature which is of particular advantage to assist combustion for faster engines. In addition, subject to avoiding excessive ammonia slip to the exhaust the injection of gaseous ammonia before the piston closing the scavenge ports would displace some combustion air in the cylinder effectively reducing compression loss for a given expansion work and give a higher fuel:air ratio for a given boost/scavenge air pressure. A further advantage of this embodiment of the invention is that relatively ammonia vaporiser temperatures of 60 to 100° C. would produce vapour at sufficiently high pressure to allow direct cylinder injection without the use of a gas compressor.

[0110] Whilst the invention has been described with reference to liquid ammonia fuel, other blends of liquid ammonia with various amounts of water can be used.

[0111] Whilst the invention has been described with reference to liquid ammonia fuel, other blends of liquid ammonia with various amounts of other soluble, miscible, emulsion or slurried fuels can be used, these include, but are not restricted to, iron picrate solution, hydrazine, ammonium nitrate, various oxygenated liquids added to enhance ignition, combustion, lubrication or reduce NOx or particulate emissions.

[0112] Whilst the invention has been described with reference to fuel injectors for injection of ammonia fuel only, in further embodiments the injectors could serve both to inject the liquid ammonia and then inject a pilot fuel such as diesel. One embodiment that could include a pilot injector 711 is shown in FIG. 7, where the pilot injector 711 is included in the cylinder head 708. It is envisaged that such injectors would have separate nozzles for the ammonia and pilot fuel wherein the liquid ammonia is injected according to the present invention and the pilot fuel is injected just before the required onset of combustion as in conventional diesel engines. In this embodiment, the amount of pilot injection could also advantageously be used to start and warm the engine before using liquid ammonia and/or be used for low load operation although in normal operation only 2 to 5% of the fuel energy would be necessary for ignition.

[0113] Whilst the invention has been described concerning compression ignition and pilot injection being used for ignition control in further embodiments of the present invention other methods of ignition could advantageously be used including spark, plasma and laser ignition.

[0114] Whilst the invention has been described with reference to 2-stroke engines, the invention can also be applied to the compression stroke of 4-stroke engines.

[0115] Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is understood that the invention includes all such variations and modifications which fall within the spirit and scope of the present invention.

[0116] Where the terms “comprise”, “comprises”, “comprised” or “comprising” are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other feature, integer, step, component or group thereof.