Hydrogen internal combustion engine
The hydrogen combustion engine achieves stable ignition and improved mixture formation by optimizing the distance and positioning of the ignition source and hydrogen injector, ensuring consistent ignition and performance across varying conditions.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ROBERT BOSCH GMBH
- Filing Date
- 2025-09-23
- Publication Date
- 2026-06-11
AI Technical Summary
Existing hydrogen internal combustion engines face challenges in achieving robust ignition of the hydrogen-oxygen mixture, particularly under varying external conditions.
The hydrogen combustion engine design includes a specific distance and positioning of the ignition source and hydrogen injector within the combustion chamber, ensuring an ignitable mixture is present near the ignition source across all operating conditions, with a cap to protect the injector and control hydrogen injection.
Enables stable ignition and improved mixture formation, enhancing ignition robustness and performance across the engine's operating range, independent of engine speed and air movement.
Smart Images
Figure EP2025077126_11062026_PF_FP_ABST
Abstract
Description
[0001] R.416271
[0002] - 1 -
[0003] Description
[0004] title
[0005] Hydrogen combustion engine
[0006] State of the art
[0007] The present invention relates to a hydrogen internal combustion engine with an improved system layout for improving mixture formation between hydrogen and oxygen in a combustion chamber during direct injection of hydrogen into the combustion chamber, in particular to ensure robust ignition of the hydrogen in the combustion chamber in all operating situations.
[0008] There are currently increased efforts in the art to use hydrogen as a fuel for internal combustion engines. In particular, direct injection of hydrogen into the combustion chamber of the internal combustion engine is a promising concept. A problem here is achieving robust ignition of a hydrogen-oxygen mixture, especially under varying external conditions.
[0009] Disclosure of the invention
[0010] In contrast, the hydrogen combustion engine according to the invention, with the features of claim 1, has the advantage that stable ignition is possible in all operating situations of the hydrogen combustion engine when hydrogen is directly injected into a combustion chamber of the hydrogen combustion engine. Furthermore, the hydrogen combustion engine has a surprisingly simple and cost-effective design. R.416271
[0011] - 2 -
[0012] According to the invention, this is achieved by the hydrogen internal combustion engine comprising a cylinder with a central axis XX and a cylinder head, which define a combustion chamber of the hydrogen internal combustion engine. Furthermore, the hydrogen internal combustion engine comprises a piston which is movable back and forth in the combustion chamber between a bottom dead center and a top dead center. The movement of the piston over a complete piston stroke S1 defines a working area in the combustion chamber. A free area is also defined between the working area and the cylinder head. The free area is a region in the combustion chamber which remains open during operation without the piston passing over it; that is, the piston does not pass over the free area in the combustion chamber. The hydrogen internal combustion engine further comprises an ignition source, in particular a spark plug, and a hydrogen injector for injecting gaseous hydrogen.The ignition source and the hydrogen injector are located on the cylinder head. The distance A between the ignition source and the hydrogen injector is within the range of 0.05 x D < A < 0.50 x D, where D is the diameter of the cylinder. Adhering to this specified distance between the ignition source and the hydrogen injector ensures that, when hydrogen is injected into the combustion chamber, an ignitable mixture is present in the vicinity of the ignition source under all operating conditions, thus enabling robust ignition of the hydrogen-oxygen mixture.
[0013] The distance A between the ignition source and the hydrogen injector is determined from a central axis YY of the hydrogen injector to a central axis ZZ of the ignition source on an inner wall area of the cylinder head.
[0014] The dependent claims describe preferred embodiments of the invention.
[0015] Preferably, the distance A is in a range of 0.10 x D < A < 0.35 x D, and particularly in a range of 0.20 x D < A < 0.30 x D.
[0016] Particularly reliable and stable ignition is possible when the distance of the hydrogen injector to the cylinder's central axis XX is equal to the distance of the ignition source to the cylinder's central axis XX. That is, the distance of the ignition source and the hydrogen injector to the central axis is the same. R.416271
[0017] - 3 -
[0018] Preferably, the combustion chamber of the hydrogen internal combustion engine is divided into a first region with increased charge motion and a second region with reduced charge motion, the second region completely encompassing the free zone, i.e., the region in which no piston movement takes place. The first region with increased charge motion is significantly larger than the second region with reduced charge motion.
[0019] Preferably, the second region with reduced charge motion is designed such that it encompasses part of the combustion chamber's working area. The second region is defined by a maximum distance S2 between a piston stroke position and the cylinder head and lies within a range of 0.05 x S1 < S2 < 0.2 x S1, and particularly within a range of 0.10 x S1 < S2 < 0.15 x S1, where S1 is the maximum piston stroke.
[0020] A further preferred feature is an exit angle a of hydrogen from the hydrogen injector to a central axis YY of the hydrogen injector in an angular range of 25° < a < 70°, in particular in a range of 25° < a < 50°, further in particular in a range of 25° < a < 40°, and in particular in a range of 25° < a < 35°, and is further in particular 30°.
[0021] The hydrogen injector preferably has a cap. The use of caps provides a degree of protection for the hydrogen injector from the hot combustion gases in the combustion chamber, and also allows for targeted hydrogen injection.
[0022] The cap is preferably a single-hole cap, which has only a single through-hole in the cap. The single-hole cap preferably has a coaxial region parallel to the central axis YY of the hydrogen injector and an inclined region. The inclined region is arranged at an acute angle to the coaxial region.
[0023] Preferably, the hydrogen injector extends into the second region with reduced charge motion to a first depth T1. The first depth T1 is preferably in a range of 1.5 mm < T1 < 6 mm, particularly in a range of 2 mm < T1 < 5 mm, and further, particularly in a range of 3 mm < T1 < 4 mm. R.416271
[0024] - 4 -
[0025] Preferably, the ignition source is positioned with a second depth T2 in the second region with relative charge movement, wherein T2 protrudes in a region of 0 mm < T2 < 3 mm, or the ignition source is retracted in a shaft in a region with a third depth T3, wherein -3 mm < T3 < 0 mm
[0026] The second depth T2 and the third depth T3 are each the distance of the ignition zone of the ignition source to the inner wall area of the cylinder head. If the ignition source is a spark plug, the ignition zone lies between the center electrode and the ground electrode.
[0027] Furthermore, a counterclockwise swirl is preferably formed in the working area of the combustion chamber.
[0028] Brief description of the drawings
[0029] Preferred embodiments of the invention are described in detail below with reference to the accompanying drawings. The drawing shows:
[0030] Figure 1 is a schematic sectional view of a hydrogen
[0031] Internal combustion engine according to a first preferred embodiment of the invention, wherein a piston is located at bottom dead center,
[0032] Figure 2 is a schematic sectional view corresponding to Figure 1, with the piston at top dead center.
[0033] Figure 3 shows an enlarged partial sectional view of a cylinder head.
[0034] Hydrogen combustion engine of Figure 1, and
[0035] Figure 4 shows an enlarged partial sectional view of a cylinder head of a
[0036] Hydrogen combustion engine according to a second embodiment of the invention.
[0037] Embodiments of the invention R.416271
[0038] - 5 -
[0039] Several embodiments of the invention are described in detail below, wherein identical or functionally identical parts are designated with the same reference numerals.
[0040] Figures 1 to 3 show in detail a hydrogen combustion engine 1 according to a first preferred embodiment of the invention.
[0041] Figure 1 shows the state of a piston 2 in a cylinder 3 of the hydrogen combustion engine at bottom dead center 11. Figure 2 shows the piston 2 at top dead center 12.
[0042] The hydrogen internal combustion engine 1 comprises the cylinder 3 with a central axis XX and a cylinder head 4 arranged on the cylinder 3. The cylinder 3 and the cylinder head 4 define a combustion chamber 5 of the hydrogen internal combustion engine.
[0043] Furthermore, the hydrogen combustion engine 1 includes the piston 2, which is movable back and forth in the combustion chamber 5 between bottom dead center 11 and top dead center 12 (double arrow H). Figures 1 and 2 schematically depict a complete piston stroke S1 of the piston 2 in the combustion chamber 5. The complete piston stroke S1 defines a working range 51 in the combustion chamber 5.
[0044] Furthermore, a free area 52 is defined in the combustion chamber 5, which extends between the working area 51 and the cylinder head 4. The free area is thus the area of the combustion chamber 5 that is not swept over by the piston 2 during the power stroke. In the first embodiment, the free area 52 is trapezoidal.
[0045] Figure 1 further includes an ignition source 6, in this embodiment a spark plug, and a hydrogen injector 7. The hydrogen injector 7 is configured to inject gaseous hydrogen into the combustion chamber 5. The ignition source 6 is configured to ignite a mixture of injected hydrogen and oxygen in the combustion chamber 5.
[0046] As can be seen from Figures 1 and 2, the ignition source 6 and the hydrogen injector 7 are arranged on the cylinder head 4. Thus, the hydrogen internal combustion engine is a so-called direct-injection internal combustion engine. R.416271
[0047] - 6 -
[0048] As can be seen from Figures 1 to 3, a distance A between the ignition source 6 and the hydrogen injector 7 is chosen such that the distance A lies within the range of 0.05 x D < A < 0.50 x D, where D is the diameter of the cylinder 3. In this embodiment, the distance A is 0.25 x D. The diameter D of the cylinder 3 is, in absolute terms, between
[0049] 50 mm and 250 mm, with the smaller cylinder diameters being assigned to PC (Passenger Car) applications, while the larger specifications are intended to apply to cylinder diameters D via LCV (Light Commercial Vehicle), CV (Commercial Vehicle), off-road applications up to LE (Large Engine).
[0050] The hydrogen injector 7 and the ignition source 6 are arranged such that half the distance A lies on the central axis XX of the cylinder 3. That is, the ignition source 6 and the hydrogen injector 7 are equidistant from a plane encompassing the central axis XX, which is perpendicular to the distance A.
[0051] In the first embodiment, a straight line, which denotes the distance A between ignition source 6 and hydrogen injector 7, intersects the central axis X-X; however, it should be noted that it is also possible that the ignition source 6 and the hydrogen injector 7 are arranged such that a straight line defining the distance A is offset from the central axis XX of the cylinder 3 and does not intersect the central axis.
[0052] As further shown schematically in Figure 1, the combustion chamber 5 has a first region 53 with increased charge motion and a second region 54 with reduced charge motion. The second region 54 with reduced charge motion completely encompasses the free area 52 and also an upper section of the working area 51 (see Figure 1). The region with reduced charge motion 54 is designated S2 in Figure 2. S2 defines the length of the second region 54 in the direction of the central axis XX of the cylinder 3. S2 preferably lies within a range of 0.05 x S1 < S2 < 0.20 x
[0053] 51 and in this embodiment amounts to 0.12 x S1, i.e., 12% of the piston stroke S1. R.416271
[0054] - 7 -
[0055] Furthermore, the hydrogen injector 7 includes a cap 70, which is designed as a single-hole cap, i.e., the cap 70 has exactly one outlet opening 71.
[0056] As can be seen from Figure 1, the outlet opening 71 is divided into two areas, namely a coaxial area 72, which is parallel to a central axis YY of the hydrogen injector 7 and an inclined area 73, which is inclined at an angle a to the central axis YY of the hydrogen injector 7. The angle a is preferably in a range of 25° to 70° and is 35° in the illustrated embodiment.
[0057] As can be seen further in Figure 3, the hydrogen injector 7 is arranged on the cylinder head 4 with a first depth T1 such that the hydrogen injector 7 protrudes into the combustion chamber 5 with a first depth T1. Similarly, the ignition source 6 is also arranged on the cylinder head 4 such that the ignition source 6 protrudes into the combustion chamber 5 with a second depth T2. The first depth T1 is preferably in the range of 1.5 mm < T1 < 6 mm. The second depth T2 is preferably in the range of 0 mm < T2 < 3 mm. The first and second depths T1 and T2 are each determined by an outermost point of the ignition source 6 and the hydrogen injector 7, respectively.
[0058] Figure 1 schematically illustrates the charge movements 50 in the combustion chamber 5 with circular arrows. In this embodiment, the charge movements 50 proceed counterclockwise and are thus formed as a so-called swirl motion. Alternatively, a tumble motion can also be provided.
[0059] The design of the internal combustion engine 1 in the first embodiment thus makes it possible to achieve robust ignition across the entire engine operating range, independent of engine speed and / or the degree of air movement of the mixture at the ignition source 6. In Figures 1 and 2, the jet guidance through the hydrogen injector 7 is indicated by arrow B. Arrow B is directed towards a target area 9 located in the vicinity of the ignition source 6. This ensures that a sufficient quantity of the hydrogen-oxygen mixture is supplied locally at the ignition source 6. Simultaneously, the existing charge motion 50 during the injection process is converted into an R.416271
[0060] - 8 - improved mixture formation in the remaining combustion chamber 5 is utilized. The orientation of the outlet area of the hydrogen injector 7 is therefore directed in the direction below the ignition source 6.
[0061] This allows for improved ignition and increased robustness against engine roughness. Simultaneously, the arrangement of the invention offers additional potential for performance enhancement. By injecting hydrogen into the second area 54 with reduced charge movement, the hydrogen is injected into an area with significantly lower gas movement. The charge movement 50 can further support mixture formation at the ignition source 6. The single-hole cap facilitates the targeted delivery of hydrogen to the target area 9 for mixture formation at the ignition source 6.
[0062] Furthermore, the angle a ensures that no Coanda effect of the hydrogen occurs and thus prevents hydrogen from flowing along the inner wall 40 of the cylinder head 4, which approximates a convex shape.
[0063] Figure 4 schematically shows a partial sectional view of a cylinder head 4 of an internal combustion engine 1 for hydrogen injection according to a second embodiment of the invention. As can be seen from Figure 4, the ignition source 6 is not arranged projecting into the combustion chamber 5, but is recessed in a shaft 8. The ignition source 6 is recessed by a third depth T3 from the inner wall 40 of the cylinder head 4. The depth T3 is the minimum distance of a component of the ignition source 6 from the inner wall 40 of the cylinder head 4; in this embodiment, it is the outer point of a ground electrode 60, since the ignition source 6 is designed as a spark plug.
Claims
R.416271 - 9 - Claims 1. Hydrogen internal combustion engine comprising: a cylinder (3) with a central axis XX and a cylinder head (4) defining a combustion chamber (5), a piston (2) which is reciprocally movable in the combustion chamber (5) between a bottom dead center (11) and a top dead center (12), wherein the movement of the piston (2) over a complete piston stroke S1 defines a working area (51) in the combustion chamber (5), a clearance area (52) between the working area (51) and the cylinder head (4), an ignition source (6), in particular a spark plug, and a hydrogen injector (7) for injecting hydrogen, wherein the ignition source (6) and the hydrogen injector (7) are arranged on the cylinder head (4), and wherein a distance A between the ignition source (6) and the hydrogen injector (7) is in a range of 0.05 x D < A < 0.50 x D, where D is the diameter of the cylinder (3).
2. Hydrogen combustion engine according to claim 1, wherein the distance A is in the range of 0.10 x D < A < 0.35 x D, in particular in a range of 0.20 x D < A < 0.30 x D.
3. Hydrogen internal combustion engine according to one of the preceding claims, wherein the distance of the hydrogen injector (7) to the central axis XX of the cylinder (3) is equal to the distance of the ignition source (6) to the central axis XX.
4. Hydrogen internal combustion engine according to one of the preceding claims, wherein the combustion chamber (5) is divided into a first area (53) with increased charge motion and a second area (54) with reduced charge motion, wherein the second area (54) completely encompasses the free area (52). R.416271 - 10 - 5. Hydrogen internal combustion engine according to claim 4, wherein the second region (54) comprises a part of the working region (51) of the combustion chamber (5) such that the second region (54) is defined by a maximum distance S2 in a piston position between a piston crown of the piston (2) and the cylinder head (4) in a range of 0.05 x S1 < S2 < 0.2 x S1, in particular in a range of 0.10 x S1 < S2 < 0.15 x S1, wherein S1 is a maximum piston stroke of the piston (2).
6. Hydrogen combustion engine according to one of the preceding claims, wherein an exit angle α of hydrogen from the hydrogen injector (7) to a central axis YY of the hydrogen injector (7) is in a range of 25° < α < 70°, in particular in a range of 25° < α < 50°, further in particular in a range of 25° < α < 40°, further preferably in a range of 25° < α < 35°, and in particular is 30°.
7. Hydrogen internal combustion engine according to one of the preceding claims, wherein the hydrogen injector (7) has a cap (70).
8. Hydrogen combustion engine according to claim 7, wherein the cap (70) is a single-hole cap.
9. Hydrogen combustion engine according to claim 8, wherein the single-hole cap has a coaxial region (72) parallel to the central axis YY of the hydrogen injector and an inclined region (73).
10. Hydrogen combustion engine according to one of the preceding claims, wherein the hydrogen injector (7) projects with a first depth T1 into the second region (54) of the combustion chamber (5) with reduced charge motion.
11. Hydrogen combustion engine according to claim 10, wherein the first depth T1 is in a range of 1.5 mm < T1 < 6 mm, in particular in a range of 2 mm < T1 < 5 mm and further in particular in a range of 3 mm < T1 < 4 mm. R.416271 - 11 - 12. Hydrogen internal combustion engine according to one of the preceding claims, wherein the ignition source (6) projects into the second region (54) of the internal combustion engine with reduced charge motion in a range of 0 mm < T2 < 3 mm with a second depth T2, or wherein the ignition source (6) is retracted into the cylinder head in a shaft (8) with a third depth T3, wherein the third depth T3 is in a range of -3 mm < T3 < 0 mm 13. Hydrogen internal combustion engine according to one of the preceding claims, wherein a swirl (15) in the direction counterclockwise is formed in the working area (51) of the combustion chamber (5).