Direct injection hydrogen-diesel dual fuel system for internal combustion engines

Abstract

The present invention provides a direct injection hydrogen-diesel dual fuel system for an internal combustion engine that allows for retrofitting of existing diesel engines, the system comprising a cylinder head of the engine having a first injection hole and a second injection hole, a diesel pilot injector disposed in the first injection hole, and a hydrogen injector disposed in the second injection hole, the hydrogen injector comprising a gasoline direct injector having an outer shank and a distal output end, and a nozzle cap welded to the outer shank and covering the distal output end.

Description

[Technical field]

[0001] The present invention relates generally to a system for direct injection of hydrogen into a combustion chamber, and more particularly, but not exclusively, to a system for converting a conventional diesel engine into a dual fuel engine. [Background technology]

[0002] As reported in the International Journal of Hydrogen Energy, "Hydrogen-fueled internal combustion engines (H2ICE) are an attractive energy conversion technology with a wide range of advantages, including high thermodynamic efficiency and ease of retrofitting existing oil- and gas-fueled engines and existing engineering and manufacturing infrastructure. Successful development of H2ICE will have a significant impact on propulsion and stationary applications, thereby accelerating the market penetration of hydrogen as the energy carrier of the future." International Journal of Hydrogen Energy 46 (2021) pg. 1303.

[0003] Hydrogen dual fuel engines, which inject hydrogen fuel and a small amount of diesel pilot fuel simultaneously into the engine combustion chamber, appear to be a very promising design. However, a significant technical challenge to further research and commercialization of the dual fuel concept is the lack of a commercially available hydrogen fuel injection system that is effective in a dual fuel engine environment.

[0004] In particular, prior art hydrogen fuel injection systems were susceptible to hydrogen leakage from the injectors, and such prior art systems were unable to successfully manage the relatively high hydrogen gas pressures required for direct hydrogen injection into the cylinders in an effective dual fuel engine.

[0005] Therefore, there is a need for improved direct injection hydrogen-diesel dual fuel systems for internal combustion engines. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to overcome and / or alleviate one or more of the disadvantages of the prior art, or to provide consumers with a useful or commercial choice. [Means for solving the problem]

[0007] In a first aspect, although not necessarily its only or broadest aspect, the present invention relates to a direct injection hydrogen-diesel dual fuel system for an internal combustion engine, the system comprising: a cylinder head of the engine having a first injection hole and a second injection hole; a diesel pilot injector disposed within the first injection hole; a hydrogen injection device disposed in the second injection hole, The hydrogen injection device is a gasoline direct injector having an outer shank and a distal output end; a nozzle cap covering the distal output end, the nozzle cap being welded to the outer shank.

[0008] Preferably, the distal end of the nozzle cap is provided with a Teflon seal.

[0009] Preferably, the nozzle cap includes an O-ring seal.

[0010] Preferably, access is provided to the rear end of the gasoline direct injector by means of a lubricant supply adaptor for receiving lubricant.

[0011] Preferably, the diesel pilot injector is mounted centrally in the cylinder head and the longitudinal axis of the hydrogen injector extends towards the centre of the cylinder.

[0012] Preferably, the system further includes an engine controller programmed to inject diesel fuel via the diesel pilot injector into the hydrogen charge injected from the hydrogen injector.

[0013] Preferably, the system further includes an engine controller programmed to inject diesel fuel via the diesel pilot injector before or after injecting a hydrogen charge from the hydrogen injector, whereby the hydrogen charge is injected into a diesel flame to create a hydrogen diffusion flame or the diesel flame is generated within a partially premixed hydrogen charge.

[0014] Preferably, the controller is programmable to adjust the injection timing and dwell time of both the diesel pilot injector and the hydrogen injector.

[0015] Preferably the gasoline direct injector is a multi-hole spray guide injector.

[0016] Preferably, the nozzle cap defines annular flow regions which merge into a single output aperture.

[0017] Preferably, the nozzle cap has a single output hole with a diameter of about 1 mm.

[0018] Preferably, the system further comprises a hydrogen boost pump supplying hydrogen to the hydrogen injection device at a pressure of at least 20 MPa.

[0019] Preferably, the hydrogen injectors are lubricated with oil or diesel fuel.

[0020] Preferably, the nozzle cap comprises stainless steel. [Brief description of the drawings]

[0021] In order that the invention may be more easily understood and that those skilled in the art may be able to carry it out in practice, preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0022] [Figure 1]1 is a schematic diagram of a hydrogen injection device according to an embodiment of the present invention;

[0023] [Diagram 2] FIG. 1 is a schematic diagram of a direct injection hydrogen-diesel dual fuel test rig system for an internal combustion engine in accordance with an embodiment of the present invention.

[0024] [Diagram 3] 3 is a cross-sectional side view of a portion of the engine cylinder head shown in FIG. 2 according to one embodiment of the present invention.

[0025] [Figure 4] FIG. 3 is a bottom view of a portion of the engine cylinder head of FIG. 2 covering an illustrated active cylinder, according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The present invention relates to a hydrogen direct injection system for an internal combustion engine. Elements of the invention are shown in simplified schematic form in the drawings so as to show only the specific details necessary to understand the embodiments of the invention and not to obscure the disclosure with undue detail that will be apparent to those skilled in the art in light of the specification.

[0027] In this patent specification, adjectives such as first and second, left and right, top and bottom, top and bottom, upper and lower, ascending and descending, above and below, etc., are used only to distinguish one element or method step from another element or method step without necessarily requiring a particular relative position or order described by the adjective. Words such as "comprising" or "including" are not used to specify an exclusive set of elements or method steps. Rather, such words merely specify a minimum set of elements or method steps that are included in a particular embodiment of the invention.

[0028] According to one aspect, the present invention is defined as a hydrogen direct injection system for an internal combustion engine, the system comprising: a cylinder head of the engine having a first injection hole and a second injection hole; a diesel pilot injector disposed within the first injection hole; a hydrogen injection device disposed in the second injection hole, The hydrogen injection device is a gasoline direct injector having an outer shank and a distal output end; and a nozzle cap covering the distal output end, the nozzle cap being welded to the outer shank.

[0029] Advantages of some embodiments of the present invention include providing a system that can be easily retrofitted to existing diesel engines. An improved nozzle cap allows for leak-free coupling to commercially available gasoline direct injectors. Additionally, the engine control unit can be programmed to independently adjust the injection timing and dwell time of both the diesel pilot injector and the hydrogen injector. This allows for easy experimental tuning of engine efficiency and emissions levels, among other things, resulting in significant reductions in CO2 emissions.

[0030] Furthermore, in some embodiments of the invention, hydrogen can reach up to 90% energy fraction as the primary fuel, with diesel pilot injected up to 10% as the ignition source. This represents a significant improvement over conventional port-injected hydrogen-diesel dual fuel engines, where the hydrogen energy fraction is limited to a maximum of about 40%. Embodiments of the invention may also outperform conventional hydrogen spark ignition engines operating at lower compression ratios, as higher engine efficiency is achieved than the diesel engine baseline. Additionally, some embodiments of the invention may achieve CO2 reductions of 70% or more, including retrofit applications for many existing diesel engines.

[0031] Those skilled in the art will appreciate that not all of the above advantages are included in all embodiments of the present invention.

[0032] Figure 1 is a schematic diagram of a hydrogen injection device 100 according to one embodiment of the present invention. The hydrogen injection device 100 includes a gasoline direct injector 105 having an external shank 110 and a distal output end 115. Box A' shows a close-up cross-sectional view of elements of Box A shown in dashed lines in Figure 1.

[0033] A nozzle cap 120 covers the distal output end 115. The nozzle cap 120 is generally cylindrical and fits over the outer shank 110 of the gasoline direct injector 105. An annular weld 125 locks the nozzle cap 120 to the shank 110 and also ensures a seal between the nozzle cap 120 and the shank 110.

[0034] The nozzle cap 120 may be made from a variety of stainless steel or other alloys.

[0035] The distal end 130 of the nozzle cap 120 includes an annular Teflon seal 135. Additionally, an O-ring 140 is fitted around the middle of the nozzle cap 120. When assembled to the cylinder head of an internal combustion engine, the Teflon seal 135 and the O-ring 140 enable the nozzle cap 120 to fit snugly and seal against the through-hole of the engine cylinder head with the gasoline direct injector 105 installed.

[0036] The gasoline direct injector 105 may be, for example, a commercially available multi-hole spray-guided gasoline direct injector such as that manufactured by Robert Bosch GmbH under part number GDI0261500533. In this embodiment, the original six 0.16 mm output holes are combined into a single 1.0 mm output hole 145 in the hydrogen injector 100.

[0037] When operating as a component of the hydrogen injection system 100, the gasoline direct injector 105 typically requires lubrication to prevent the internal needle of the injector 105 from failing. When the injector 105 is used in a gasoline combustion engine, the injector 105 can be used without additional lubrication, since gasoline fuel acts as an excellent lubricant. However, in the hydrogen injection system 100 of the present invention, the gaseous hydrogen flowing through the injector 105 may not provide sufficient lubrication. Therefore, in the injector 100, access is provided to the rear end of the gasoline direct injector 105 using a lubricant supply adapter 150 to receive the lubricant. According to some embodiments, it is sufficient to supply one drop of engine oil into the adapter 150 every day. Alternatively, in other embodiments, the adapter 150 may be automated to periodically inject the injector 105 with a lubricant, such as diesel fuel.

[0038] 2 is a schematic diagram of a direct injection hydrogen-diesel dual fuel test rig system 200 for an internal combustion engine, according to one embodiment of the present invention. The system 200 is arranged as a test rig for a single cylinder common rail diesel engine 205, and uses a modified commercial in-line four cylinder diesel engine. The system 200 includes an engine cylinder head 210, in which the hydrogen injector 100, as previously described, is disposed to supply hydrogen fuel to an active cylinder 215 of the engine 205. A diesel pilot injector 220 is also disposed in the cylinder head 210.

[0039] A diesel tank 225 supplies diesel fuel to a conventional high pressure common rail pump 230 which delivers injection pressures of more than 100 MPa to a common rail 235 connected to the diesel pilot injectors 220 .

[0040] The low pressure hydrogen tank 240 supplies hydrogen gas to the hydrogen boost pump 245, which in turn supplies an injection pressure of 20 MPa to the hydrogen injection device 100. The boost pump controller 250 allows for effective and efficient control of the operating parameters of the hydrogen boost pump 245. Furthermore, in the test rig system 200, the hydrogen boost pump 245 is essentially an accumulator (e.g., a volume of 1000 cm 3 ) allows hydrogen to be supplied from a low pressure hydrogen tank 240 (e.g., a 13.7 MPa G size bottle).

[0041] The relatively high pressure operation of the hydrogen boost pump 245 at 20 MPa is important for effective hydrogen direct injection by the hydrogen injection apparatus 100. Those skilled in the art will appreciate that the "choked flow" theory suggests that the injection pressure must be at least two times higher than a given backpressure to avoid the adverse effects that the backpressure in the active cylinder 215 has on the hydrogen gas flow rate. Typically, the compression pressure at top dead center (TDC) of a diesel engine does not exceed 10 MPa, so the hydrogen injection apparatus 100 described herein meets the requirements of the choked flow theory.

[0042] A dynamometer 255 is connected to the crankshaft of the engine 205 and is used to control engine speed and load conditions. An engine controller 260 controls the general engine operating conditions and is connected to a data acquisition system 265. A pressure transducer 267 is connected to the active cylinder 215 and provides in-cylinder pressure data to the data acquisition system 265 which can be used to calculate the apparent heat release rate (aHRR) and an indicated engine efficiency. A rotary encoder 270 measures the position and movement of the engine crankshaft and this information is provided to the engine controller 260.

[0043] An intake surge tank 275 is connected to the intake manifold of the engine 205 and an exhaust surge tank 280 is connected to the exhaust manifold of the engine 205. NOx (NO and NO2) emissions from the engine are measured by a Non-Dispersive Infrared (NDIR) analyzer 285 and Carbon Dioxide (CO2) emissions are measured by a separate NDIR gas analyzer 290.

[0044] 3 is a cross-sectional side view of a portion of an engine cylinder head 210 according to one embodiment of the present invention. To minimize modification of the off-the-shelf cylinder head, the hydrogen injector 100 is shown positioned within the original glow plug hole of the cylinder head 210, with the longitudinal axis of the hydrogen injector extending toward the center of the cylinder as shown, effectively directing the hydrogen charge away from the wall. A diesel pilot injector 220 is also positioned in the cylinder head 210, centrally mounted as in most off-the-shelf diesel engines.

[0045] 4 is a bottom view of the portion of the engine cylinder head 210 overlying the active cylinder 215, according to one embodiment of the invention, showing the relative positions of the intake valves, exhaust valves, water jacket, hydrogen injector 100, diesel pilot injector 220, and pressure converter 267.

[0046] Those skilled in the art will appreciate that the present invention may be implemented in various types of diesel engines and may provide immediate and substantial benefits to testing equipment for direct injection hydrogen-diesel dual fuel systems for internal combustion engines.

[0047] The above description of various embodiments of the present invention is intended to be illustrative to one of ordinary skill in the relevant art. This description is not intended to be exhaustive, nor is it intended to limit the present invention to the single embodiment disclosed. Many alternatives and modifications of the present invention will be apparent to those of ordinary skill in the art having the above teachings. Thus, while several alternative embodiments have been specifically described, other embodiments will be apparent to, or relatively easily developed by, those of ordinary skill in the art. Therefore, this patent specification is intended to cover all alternatives, modifications and variations of the present invention described herein, as well as other embodiments that fall within the spirit and scope of the invention as described above.

Claims

1. 1. A direct injection hydrogen-diesel dual fuel system for an internal combustion engine, comprising: a cylinder head of the engine having a first injection hole and a second injection hole; a diesel pilot injector disposed within the first injection hole; a hydrogen injection device disposed in the second injection hole, The hydrogen injection device is a gasoline direct injector having an outer shank and a distal output end; a nozzle cap covering the distal output end, the nozzle cap being welded to the outer shank.

2. The system of claim 1 , wherein the distal end of the nozzle cap comprises a Teflon seal.

3. The system of claim 1 , wherein the nozzle cap comprises an O-ring seal.

4. 10. The system of claim 1, wherein access to a rear end of the gasoline direct injector is provided using a lubricant supply adapter for receiving lubricant.

5. 2. The system of claim 1, wherein the diesel pilot injector is centrally mounted in the cylinder head and the longitudinal axis of the hydrogen injector extends toward the center of the cylinder.

6. 10. The system of claim 1, further comprising an engine controller programmed to inject diesel fuel via said diesel pilot injector into the hydrogen charge injected from said hydrogen injector.

7. 10. The system of claim 1, further comprising an engine controller programmed to inject diesel fuel through said diesel pilot injector before or after injecting a hydrogen charge from said hydrogen injector, whereby said hydrogen charge is injected into a diesel flame to produce a hydrogen diffusion flame or said diesel flame is generated within a partially premixed hydrogen charge.

8. 8. A system as claimed in claim 6 or 7, wherein the controller is programmable to adjust injection timing and dwell time of both the diesel pilot injector and the hydrogen injector.

9. 10. The system of claim 1, wherein the gasoline direct injector is a multi-hole spray guide injector.

10. The system of claim 9 , wherein the nozzle cap defines an annular flow area converging with a single output hole.

11. 10. The system of claim 1, wherein the nozzle cap comprises a single output hole having a diameter of about 1 mm.

12. 10. The system of claim 1, further comprising a hydrogen boost pump supplying hydrogen to the hydrogen injection device at a pressure of at least 20 MPa.

13. The system of claim 1 , wherein the hydrogen injectors are lubricated with oil or diesel fuel.

14. The system of claim 1 , wherein the nozzle cap comprises stainless steel.

Images