Gaseous fuel engine system and method of operating same

Abstract

Operating a gaseous hydrogen fuel engine (10) includes controlling injection timing of gaseous hydrogen fuel injected into a flow of pressurized intake air so as to produce a pre-cooling flow of pressurized intake air into a cylinder (14) in the engine, a post-purge flow through an intake duct (24), and an intermediate flow of both pressurized intake air and gaseous hydrogen fuel into the cylinder. Undesired combustion, such as pre-ignition and / or tempering, may be limited. Related devices and control logic are also disclosed.

Description

[0001] Government Interest Statement

[0002] This invention was made with Government support under Contract DE-EE0009422 awarded by the DOE. The Government has certain rights in this invention. Technical Field

[0003] The present disclosure relates generally to operating a gaseous fuel engine using gaseous hydrogen fuel, and more particularly to controlling the injection timing of the gaseous hydrogen fuel to limit undesirable combustion. Background Art

[0004] Internal combustion engines are well known and widely used throughout the world for a variety of purposes, ranging from vehicle propulsion to pump and compressor operation and the generation of electrical power. Fuel is admitted into one or more cylinders of the engine and ignited to produce a controlled combustion reaction that drives pistons coupled to a crankshaft. For over a century, a wide variety of fuel types and operating strategies have been used.

[0005] In recent decades, regulatory and commercial concerns about reducing certain emissions from conventional internal combustion engines have increased. Liquid fuel engines that rely on petroleum distillate fuels are still widely used and are likely to remain so for the foreseeable future. However, petroleum distillate fuels can produce undesirable amounts of nitrogen oxides, particulate matter, and so-called greenhouse gases. Gaseous fuel engines utilizing, for example, natural gas can address some of these issues, particularly with respect to particulate emissions, but may still produce NOx, carbon dioxide, and carbon monoxide.

[0006] To further improve and manipulate the emissions characteristics of internal combustion engines, the use of gaseous hydrogen fuel, either as a primary fuel or as a supplement to other gaseous fuels, has been the subject of significant engineering effort in recent years. Gaseous hydrogen fuel offers the promise of minimizing undesirable emissions. However, hydrogen has relatively low flammability limits and a relatively fast in-situ flame speed. For this reason, manufacturers have encountered numerous technical obstacles in successfully implementing gaseous hydrogen fuel, particularly in reciprocating piston engines. International Patent Application No. WO2014053167A1 discloses an example of a gaseous fuel engine capable of at least some hydrogen operation. Summary of the Invention

[0007] In one aspect, a method of operating an engine includes moving an intake valve in the engine from a closed position to an open position to fluidly connect a cylinder in the engine to an intake conduit feeding pressurized intake air, and injecting gaseous hydrogen fuel into the flow of pressurized intake air when the intake valve is open. The method also includes controlling the timing of injection of the gaseous hydrogen fuel relative to the position of the intake valve, and generating a forward cooling flow of the pressurized intake air into the cylinder, a post-purge flow of the pressurized intake air through the intake conduit, and an intermediate flow of both the pressurized intake air and the gaseous hydrogen fuel into the cylinder based on controlling the timing of injection of the gaseous hydrogen fuel. The method also includes moving the intake valve from an open position to a closed position and igniting a combustion charge of the gaseous hydrogen fuel and the pressurized intake air in the cylinder.

[0008] In another aspect, a method for operating a gaseous hydrogen fueled engine system includes cooling the cylinder via a flow of pressurized intake air into the cylinder of the gaseous hydrogen fueled engine through an intake valve, and initiating injection of gaseous hydrogen fuel into the pressurized intake air flow. The method also includes forming a combustion charge of gaseous hydrogen fuel and pressurized intake air in the cylinder, and terminating the injection of the gaseous hydrogen fuel when the intake valve is open. The method also includes purging an intake port of the gaseous hydrogen fuel with pressurized intake air delivered to the cylinder via the intake valve after terminating the injection of the gaseous hydrogen fuel. The method further includes igniting the combustion charge in the cylinder, and limiting undesired combustion of the gaseous hydrogen fuel and pressurized intake air in at least one of the cylinder or the intake port based on cooling the cylinder and purging the intake port, respectively.

[0009] In another aspect, a gaseous fuel engine system includes an engine having an engine housing, an exhaust port, an exhaust valve, an intake port, and an intake valve, the engine housing having a cylinder formed therein, the intake valve being movable from a closed position to an open position to fluidly connect the cylinder to the intake port. The engine system also includes an intake conduit having an intake runner that, together with the intake port, forms a flow path for delivering a pressurized intake air flow to the cylinder. The engine system also includes a fuel system having a gaseous hydrogen fuel supply and a fuel inlet valve coupled to the intake runner or the intake port at an injection position, and an igniter positioned in the cylinder to ignite a combustion charge of gaseous hydrogen fuel and pressurized intake air. The engine system further includes an engine timing sensor configured to generate an engine timing signal indicative of a position of the intake valve, and an injection control unit coupled to the engine timing sensor and in control communication with the fuel inlet valve. The injection control unit is configured to command opening of the fuel inlet valve to commence injection of gaseous hydrogen fuel into the pressurized intake air flow before the intake valve reaches an open position, and to command closing of the fuel inlet valve to terminate injection of the gaseous hydrogen fuel before the intake valve returns from the open position to the closed position. The injection control unit is further configured to control timing of the commanded opening and commanded closing of the fuel inlet valve to generate a forward cooling flow of the pressurized intake air into the cylinder, a post-purge flow of the pressurized intake air through the intake duct, and an intermediate flow of both the pressurized intake air and the gaseous hydrogen fuel into the cylinder. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic diagram of a gaseous fuel engine system according to one embodiment;

[0011] Figure 2 is a schematic, partially cutaway side view of a portion of a gaseous fuel engine system according to one embodiment;

[0012] Figure 3 is a schematic diagram of an engine cylinder head assembly according to one embodiment;

[0013] Figure 4 is a top view of an engine cylinder head assembly according to one embodiment;

[0014] Figure 5 is a top view of an engine cylinder head assembly according to one embodiment;

[0015] Figure 6 is a top view of an engine cylinder head assembly according to one embodiment;

[0016] Figure 7 is a conceptual diagram of intake air mass flow between intake valve opening timing and intake valve closing timing according to one embodiment; and

[0017] Figure 8 is a flowchart illustrating an exemplary method and logic flow according to one embodiment. DETAILED DESCRIPTION

[0018] refer to Figure 1 , shows a gaseous fuel engine system 8 according to one embodiment. The engine system 8 includes a gaseous fuel engine 10 having an engine housing 12 with a plurality of combustion cylinders 14 formed therein. The engine 10 may include any number of cylinders (including a total of one cylinder) in any suitable arrangement (such as in-line, V-type, or other arrangements). The engine 10 also includes a plurality of exhaust ports 16 within the engine housing 12, a plurality of intake ports 20 within the engine housing 12, and exhaust and intake valves as described in conjunction with subsequent figures.

[0019] Engine system 10 also includes an intake duct 24 comprising a plurality of intake runners 26. Each intake runner 26, together with a corresponding one of the intake ports 20, forms a flow path that delivers pressurized intake air to cylinders 14. Intake duct 24 receives the intake air from a fresh air inlet 28, where it is compressed in a compressor 30 of a turbocharger 32. Turbocharger 32 includes a turbine 34. An aftercooler 36 cools the pressurized intake air fed through intake duct 24. An intake manifold 38 receives the pressurized intake air and distributes it to intake runners 26. Each intake runner, in turn, feeds the pressurized intake air to one of the intake ports 20 and, thereafter, to one of the cylinders 14. A plurality of exhaust runners 40 extend from cylinders 14 to an exhaust manifold 42. The exhaust passes through turbine 34 to rotate compressor 30 and, thereafter, reaches an exhaust outlet 44. In some embodiments, aftertreatment devices may be positioned to mitigate emissions in the exhaust gas flow passing through outlet 44. In other cases, no aftertreatment of the exhaust gas from engine 10 may be employed at all.

[0020] The engine system 8 also includes a fuel system 48. The fuel system 48 includes a gaseous hydrogen fuel supply source 50. The gaseous hydrogen fuel supply source 50 may contain gaseous molecular hydrogen in a pressurized state. In some cases, the gaseous hydrogen fuel may be fed to the fuel system 48 from a supply conduit connected to a reformer or another supply source of gaseous hydrogen fuel. The gaseous hydrogen fuel contemplated within the scope of the present disclosure may include gaseous molecular hydrogen as described above, as well as various blends including gaseous hydrogen as a primary component. In many cases, the gaseous fuel engine system 8 may operate on substantially pure gaseous molecular hydrogen, natural gas, methane, ethane, biogas, and various blends thereof. The fuel system 48 may also include at least one pump 54 that delivers the gaseous hydrogen fuel and typically increases the pressure of the gaseous hydrogen fuel to the desired injection pressure. The fuel system 48 also includes a plurality of fuel inlet valves 52. Each fuel inlet valve 52 will typically be coupled to one of the intake runners in the intake runner 26 or one of the intake ports 20 at the injection location. However, embodiments are contemplated in which gaseous hydrogen fuel is injected into the intake manifold 38 or elsewhere in the engine system 8 , including via fumigation or direct injection.

[0021] The engine 10 can be spark-ignited and includes a plurality of igniters 56, each positioned in one of the cylinders 14 to ignite the combustion charge of gaseous hydrogen fuel and pressurized intake air therein. The igniters 56 may include a pre-chamber spark plug, a pre-chamber ignition device with a separate and dedicated fuel supply (such as gaseous hydrogen fuel or another fuel), or another other electrically operated ignition mechanism. Each of the fuel inlet valves 52 can be electrically actuated, such as by an electrical control current that energizes the solenoid-operated valve to begin injection of the gaseous hydrogen fuel and de-energizes it to end injection of the gaseous hydrogen fuel. As described above, certain challenges have been observed in controlling the combustion of gaseous hydrogen fuel. As will be further apparent from the following description, the engine system 10 is uniquely configured and operated to limit undesirable combustion of the gaseous hydrogen fuel, such as pre-ignition occurring in the cylinder 14, flashback caused by ignition in the intake port 26, or other forms of undesirable combustion (including, in some cases, undesirable combustion phasing).

[0022] The engine system 8 also includes an engine timing sensor 62 configured to generate an engine timing signal indicating the position of the intake valve associated with the cylinder 14, and an injection control unit 64 in the control system 60. The injection control unit 64 can be coupled to the engine timing sensor 62 and in control communication with each of the fuel inlet valves 52. The injection control unit 64 can include any suitable computerized control unit having a central processing unit (CPU), such as a microprocessor, a microcontroller, or another central processing unit. The injection control unit 64 can be provided with a suitable computer-readable memory, such as RAM, ROM, SDRAM, FLASH, etc., storing program control instructions that, when executed by a computer processor, cause the engine system 8 to operate in the manner disclosed herein.

[0023] The engine system 8 can be used in a variety of applications, including operating a drive train in a mobile land vehicle or watercraft, operating a pump or compressor (such as for the delivery of gas or liquid), and for generating electricity. In the illustrated embodiment, the engine system 8 is coupled to a load 46, which includes a generator that operates an electric motor. In power applications, the engine system 8 can also be used to provide power to a local or regional power grid, or to charge an energy storage device, to name a few examples.

[0024] Now also refer to Figure 2 , shows additional exemplary features of the engine system 8 including the engine cylinder head 66 of the engine housing 12. As described above, each fuel admission valve 52, sometimes referred to below in the singular, can be coupled to the intake runner 26 or intake port 20 at an injection position. Figure 2 In the embodiment shown in FIG, the injection location is defined by a fuel inlet opening 68 formed in the intake runner 26. The intake runner 26 is attached to the engine cylinder head 66 to feed pressurized intake air into the intake port 20. The fuel inlet valve 52 is operable to inject gaseous hydrogen fuel into the intake runner 26 such that the injected gaseous hydrogen fuel is delivered to an associated one of the cylinders 14 along with the pressurized intake air flow. Figure 2 Also shown are a plurality of exhaust valves 18 and a plurality of intake valves 22, each associated with a corresponding one of the cylinders 14. The intake valve 22, sometimes referred to hereinafter in the singular, is movable from a closed position to an open position to fluidly connect the corresponding cylinder 14 to the intake port 20. As discussed further herein, by selectively timing the start of fuel injection and the end of fuel injection, different flow combinations of pressurized intake air and gaseous hydrogen fuel can be supplied to the corresponding cylinder 14 to have a desired effect with respect to limiting undesirable combustion.

[0025] To this end, the injection control unit 64 may be configured to command the opening of the fuel admission valve 52 before the intake valve 22 reaches the open position to begin injecting the gaseous hydrogen fuel into the pressurized intake air flow fed through the intake runner 26 and the intake port 20. The injection control unit 64 may also be configured to command the closing of the fuel admission valve 52 before the intake valve 22 returns from the open position to the closed position to end the injection of the gaseous hydrogen fuel. The injection control unit 64 may also be configured to control the timing of commanding the opening and closing of the fuel admission valve 52 to generate a front cooling flow of the pressurized intake air entering the cylinder 14, a post purge flow of the pressurized intake air through the intake duct 24 and the intake runner 26 and the intake port 20, and an intermediate flow of both the pressurized intake air and the gaseous hydrogen fuel entering the cylinder.

[0026] Therefore, it can be appreciated that, based on controlling the timing of gaseous hydrogen fuel injection, a front cooling flow of pressurized intake air entering cylinder 14, a rear purge flow of pressurized intake air through intake conduit 24, and an intermediate flow of both pressurized intake air and gaseous hydrogen fuel can be generated. The front cooling flow may essentially consist solely of pressurized intake air that cools the inner surface of cylinder 14. However, in some embodiments, the front cooling flow may include some gaseous hydrogen fuel. The rear purge flow may essentially consist solely of pressurized intake air, and the intermediate flow may include both pressurized intake air and gaseous hydrogen fuel. In a refinement, controlling the timing of gaseous hydrogen fuel injection may include commencing gaseous hydrogen fuel injection before intake valve 22 reaches an open position and terminating gaseous hydrogen fuel injection before intake valve 22 reaches a closed position. In another refinement, controlling the timing of gaseous hydrogen fuel injection may include commencing gaseous hydrogen fuel injection after initiating movement of intake valve 22 from a closed position toward an open position.

[0027] Thus, the concepts contemplated herein can be understood as providing an initial flow to cool the cylinder 14, an intermediate flow containing some or all of the gaseous hydrogen fuel that will form the combustion charge, and a post-flow that is substantially free of gaseous hydrogen fuel to purge the intake port 20. Thus, pre-ignition in the cylinder 14 can be limited or eliminated at lower temperatures than would otherwise be possible. The risk of flashback based on residual gaseous hydrogen fuel in the intake port 20 can also be reduced. After generating the front cooling flow, post-purge flow, and intermediate flow, the intake valve 22 can be moved back to the closed position, and the igniter 56 energized to ignite the combustion charge of gaseous hydrogen fuel and pressurized intake air in the cylinder 14.

[0028] exist Figure 2 It will be recalled from the illustration of FIG that the injection location of the intake duct 24 upstream of the engine housing 66 is defined by the fuel inlet opening 68 in the intake runner 26. Referring now to FIG. Figure 3, shows an engine cylinder head 66 according to another embodiment, and this engine cylinder head can be used in engine applications similar to engine system 8, but with respect to the injection location of the gaseous hydrogen fuel. Engine cylinder head 166 includes intake port 120 and fuel inlet opening 168 formed therein. Fuel inlet opening 168 is formed in engine cylinder head 166, and thus directly into the engine housing. Engine cylinder head 166 includes an upper surface 170 and a lower surface 172. Thus, injection of the gaseous hydrogen fuel can occur downward through upper surface 170 and directly into intake port 120.

[0029] Go to Figure 4 , an engine cylinder head 266 according to yet another embodiment is shown. The engine cylinder head 266 includes an intake port 220 coupled to an intake runner 226, and an exhaust port 216. The intake opening 221 will be understood to fluidly connect the intake port 220 to the cylinder. The exhaust opening 217 formed in the engine cylinder head 266 will similarly be understood to fluidly connect the cylinder to the exhaust port 216. The igniter hole 257 is centrally located between the intake opening 221 and the exhaust opening 217. An igniter, such as a spark plug, is shown at 256 and is supported in the igniter hole 257. In Figure 4 In FIG, a fuel inlet opening 268 extends horizontally through the engine cylinder head 266 to fluidly connect to the intake port 220. The fuel inlet valve 252 is shown coupled to the fuel inlet opening 268. Figure 4 In the embodiment of FIG. 5 , a horizontally extending fuel intake opening 268 is shown fluidly connected to the intake port 220 generally between the two intake openings 221 in a right to left direction.

[0030] Now go to Figure 5 , shows an engine cylinder head 366 according to yet another embodiment, which includes an intake port 320, an intake opening 321 and a fuel inlet opening 368. Figure 3 and Figure 4 In the embodiment of Figure 5 In the embodiment of FIG, a fuel inlet opening 368 extends through the engine cylinder head 366 to connect directly to the intake port 320. Compared to those previous embodiments, an inlet flow of gaseous hydrogen fuel 387 can be injected generally aligned with the inlet flow direction 385 of the pressurized intake air. The fuel inlet valve is shown at 352.

[0031] Go to Figure 6 , shows an engine cylinder head 466 according to yet another embodiment and including an intake port 420. The fuel inlet valve 452 is shown coupled to the fuel inlet opening 468. Figure 6 In the embodiment of FIG. 4 , the direction of entry of the injected gaseous hydrogen fuel 487 is opposite to the direction of entry of the pressurized intake air 485. Figure 6 In the embodiment, relative to Figure 3-5 Embodiments of the invention provide for enhanced mixing of hydrogen fuels; however, each different embodiment may have different inherent advantages and applications.

[0032] Industrial Applicability

[0033] With reference generally to the accompanying drawings, and now also with reference to Figure 7 , shows a conceptual diagram 500 illustrating intake mass flow through the intake valve between intake valve opening 510 and intake valve closing 520. It will be recalled that controlling the injection timing of gaseous hydrogen fuel according to the present disclosure can create a pre-cooling flow of pressurized intake air into the cylinder. Figure 7 , a front cooling flow 530 may be generated after the intake valve opens 510, as the intake valve begins to open but before the injection of gaseous hydrogen fuel begins at 560. An intermediate flow of both pressurized intake air and gaseous hydrogen fuel occurs after the start of injection 560 and is shown at 540. The end of injection is shown at 570. A post purge flow of pressurized intake air is shown at 550, occurring before the intake valve closes 520.

[0034] It will be recalled that the injection control unit 64 receives an engine timing signal, such as a crank angle timing signal, from the engine timing sensor 62. Thus, the engine timing signal can indicate the position of each of the intake valves in the engine 10. Therefore, the injection control unit 64 can be understood to control the start and end of injection of the gaseous hydrogen fuel based on the position of the intake valves. It will be recalled that gaseous hydrogen can have a relatively low flammability limit, which generally means that ignition of the gaseous hydrogen fuel can be achieved at a relatively low concentration. Given the lower flammability limit of the gaseous hydrogen fuel, the injection control unit 64 can meter the injection of the gaseous hydrogen fuel to provide as much gaseous hydrogen fuel as possible without reaching or exceeding the lower flammability limit. Figure 7 A generally gradual delivery of gaseous hydrogen fuel at an injection timing that is substantially in phase with the valve timing of the intake valves is shown.

[0035] In an improved solution, the front cooling flow does not have to be completely free of gaseous hydrogen fuel, but may contain some gaseous hydrogen fuel. Therefore, the injection of metered gaseous hydrogen fuel may include metered injection so that the front cooling flow contains a first amount of gaseous hydrogen fuel, and the intermediate flow 540 contains a second amount of gaseous hydrogen fuel that is generally greater than the first amount. The injection of metered gaseous hydrogen fuel may also include distributing the total amount of gaseous hydrogen fuel injected between the first amount and the second amount based on at least one of the engine speed or the engine load. It has been observed that at higher engine speeds and higher engine loads, the gaseous hydrogen fuel can be ignited more easily even in the absence of an ignition source such as a spark. Therefore, by providing some initial gaseous hydrogen fuel in the front cooling flow and providing more gaseous hydrogen fuel in the intermediate flow, the total amount of gaseous hydrogen fuel can be maximized without reaching or exceeding the lower flammability limit.

[0036] Now go to Figure 8 , a flowchart 600 illustrating an exemplary method and logic flow according to one embodiment is shown. At box 610, the compressor is operated to provide a pressurized intake air feed through the intake conduit. From box 610, the flowchart 600 proceeds to box 620 to move the intake valve from a closed position toward an open position. From box 620, the flowchart 600 proceeds to box 630 to begin injecting gaseous hydrogen fuel into the pressurized intake air flow. From box 630, the flowchart 600 proceeds to box 640 to move the intake valve from an open position toward a closed position. From box 640, the flowchart 600 proceeds to box 650 to end the injection of the gaseous hydrogen fuel. From box 650, the flowchart 600 proceeds to box 660 to ignite the combustion charge of gaseous hydrogen fuel and pressurized intake air in the cylinder.

[0037] This description is for illustrative purposes only and should not be interpreted as narrowing the scope of the present disclosure in any way. Therefore, it will be understood by those skilled in the art that, without departing from the complete and reasonable scope and spirit of the present disclosure, various modifications can be made to the embodiments disclosed herein. By viewing the drawings and the appended claims, other aspects, features and advantages will become apparent. As used herein, the articles "a" and "an" are intended to include one or more items and can be used interchangeably with "one or more". When intended to represent only one item, the term "one" or similar language is used. In addition, as used herein, the term "has, have, having" or the like is intended to be an open term. In addition, the phrase "based on" is intended to mean "based at least in part on", unless otherwise expressly stated.

Claims

1. A method of operating an engine (10), comprising: moving an intake valve (22) in an engine from a closed position to an open position to fluidly connect a cylinder (14) in the engine to an intake conduit (24) feeding pressurized intake air; injecting gaseous hydrogen fuel into the pressurized intake air stream when the intake valve is open; controlling the injection timing of the gaseous hydrogen fuel relative to the position of the intake valve; generating a front cooling flow of pressurized intake air into the cylinder, a post purge flow of pressurized intake air through the intake conduit, and an intermediate flow of both pressurized intake air and the gaseous hydrogen fuel into the cylinder based on controlling the injection timing of the gaseous hydrogen fuel; moving the intake valve from the open position to the closed position; and The combustion charge of gaseous hydrogen fuel and pressurized intake air in the cylinder is ignited.

2. The method of claim 1 , wherein injecting the gaseous hydrogen fuel comprises allowing injection of the gaseous hydrogen fuel at an injection location in the intake conduit upstream of an engine housing (12) of the engine; The injection location is defined by a fuel inlet opening (68) in an intake runner (26) of the intake duct.

3. The method of claim 1 , wherein injecting the gaseous hydrogen fuel comprises injecting the gaseous hydrogen fuel into an intake port (120, 220, 320, 420) through a fuel inlet opening (168, 268, 368, 468) formed in the engine housing.

4. The method according to any one of claims 1 to 3, wherein controlling the injection timing of the gaseous hydrogen fuel comprises starting the injection of the gaseous hydrogen fuel before the intake valve reaches the open position, and ending the injection of the gaseous hydrogen fuel before the intake valve reaches the closed position. 5 . The method of claim 4 , wherein controlling the timing of injection of the gaseous hydrogen fuel further comprises initiating injection of the gaseous hydrogen fuel after initiating movement of the intake valve from the closed position. 6 . The method of claim 1 , wherein controlling the injection timing of the gaseous hydrogen fuel comprises injecting the gaseous hydrogen fuel at an injection timing that is substantially in phase with a valve timing of the intake valve.

7. The method of any one of claims 1-6, wherein injecting gaseous hydrogen fuel further comprises metering injection of the gaseous hydrogen fuel such that the front cooling stream contains a first amount of the gaseous hydrogen fuel and the intermediate stream contains a second amount of the gaseous hydrogen fuel greater than the first amount; and Wherein metering the injection of the gaseous hydrogen fuel includes apportioning a total amount of injected gaseous hydrogen fuel between the first amount and the second amount based on at least one of engine speed or engine load.

8. The method of any one of claims 1-7, further comprising limiting the amount of the gaseous hydrogen fuel in the cylinder to below a lower flammability limit based on metering the injection of the gaseous hydrogen fuel.

9. A method of operating a gaseous hydrogen fuel engine system (8), comprising: cooling a cylinder (14) in a gaseous hydrogen fueled engine (10) via a flow of pressurized intake air into the cylinder through an intake valve (22); commencing injection of gaseous hydrogen fuel into the pressurized intake air stream; forming a combustion charge of said gaseous hydrogen fuel and pressurized intake air in said cylinder; ending the injection of the gaseous hydrogen fuel when the intake valve is open; After the injection of the gaseous hydrogen fuel is completed, purging the intake port (20, 120, 220, 320, 420) of the gaseous hydrogen fuel with pressurized intake air delivered into the cylinder via the intake valve; igniting the combustion charge in the cylinder; as well as Undesirable combustion of the gaseous hydrogen fuel and pressurized intake air in at least one of the cylinder or the intake port is limited based on cooling of the cylinder and purging of the intake port, respectively. 10 . The method of claim 9 , further comprising injecting the gaseous hydrogen fuel according to an injection timing that is substantially in phase with a valve timing of the intake valve.

11. The method of claim 9 or 10, further comprising metering the injection of the gaseous hydrogen fuel so that a forward flow that cools the cylinder includes some gaseous hydrogen fuel and a backward flow that purges the intake port is substantially free of the gaseous hydrogen fuel; wherein metering the injection of the gaseous hydrogen fuel includes distributing a total amount of the gaseous hydrogen fuel between the front flow containing a smaller amount of the gaseous hydrogen fuel and an intermediate flow containing a larger amount of the gaseous hydrogen fuel to maintain the amount of the gaseous hydrogen fuel in the cylinder below a lower flammability limit; Metering further includes varying the metering of the gaseous hydrogen fuel on a cycle-by-cycle basis based on at least one of engine speed or engine load; and The gaseous hydrogen fuel enters an intake duct at a location upstream of an engine housing (12) of the engine.

12. A gaseous fuel engine system (8), comprising: An engine (10) comprising an engine housing (12) having a cylinder (14) formed therein, an exhaust port (16), an exhaust valve (18), an intake port (20), and an intake valve (22), the intake valve being movable from a closed position to an open position to fluidly connect the cylinder to the intake port; an intake conduit (24) comprising an intake runner (26, 226) that, together with the intake port, forms a flow path for delivering a pressurized intake air flow to the cylinder; a fuel system (48) comprising a gaseous hydrogen fuel supply (50) and a fuel admission valve (52, 252, 352, 452) coupled to the intake runner or the intake port at an injection location; an igniter (56, 256) positioned in the cylinder to ignite the combustion charge of gaseous hydrogen fuel and pressurized intake air; an engine timing sensor (62) configured to generate an engine timing signal indicative of a position of the intake valve; as well as an injection control unit (64) coupled to the engine timing sensor and in control communication with the fuel admission valve, the injection control unit being configured to: commanding opening of the fuel admission valve to initiate injection of the gaseous hydrogen fuel into the pressurized intake air flow before the intake valve reaches the open position; commanding closure of the fuel admission valve to terminate injection of the gaseous hydrogen fuel before the intake valve returns from the open position to the closed position; as well as The timing of the commanded opening and commanded closing of the fuel admission valve is controlled to produce a front cooling flow of the pressurized intake air into the cylinder, a post purge flow of the pressurized intake air through the intake conduit, and an intermediate flow of both the pressurized intake air and the gaseous hydrogen fuel into the cylinder.

13. The engine system of claim 12 , wherein the injection control unit is further configured to meter the injection of the gaseous fuel based on at least one of engine speed or engine load so as to maintain the total amount of the gaseous hydrogen fuel in the cylinder below a lower flammability limit based on at least one of engine speed or engine load.

14. The engine system of claim 12 or 13, wherein the injection location is defined by a fuel inlet opening (168, 268, 368, 468) formed in the engine housing.

15. The engine system of claim 12 or 13, wherein the injection location is defined by a fuel inlet opening (68) formed in the intake runner.

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