Method for operating an internal combustion engine with hydrogen and pre-chamber spark plug for igniting an air-hydrogen mixture in a combustion chamber

Abstract

A method for operating an internal combustion engine (10) with hydrogen as fuel is proposed, in which hydrogen is directly injected into the combustion chamber (13) of the internal combustion engine and the ignition of the air-hydrogen mixture in the combustion chamber (13) is effected by means of a prechamber spark plug (1). An operating state of the internal combustion engine (10) is identified in which there is a tendency towards pre-ignition. In the identified operating range, the internal combustion engine is operated with a time overlap of the opening of the air intake valve (2) and the exhaust gas exhaust valve (3) of the combustion chamber (13). Furthermore, a prechamber spark plug (1) with a prechamber cover (4) for igniting an air-hydrogen mixture introduced into the combustion chamber (13) of an internal combustion engine (10) is proposed, wherein the prechamber cover (4) has a flushing opening (6). The flushing opening (6) is configured to form an air flow in the prechamber cover (4) with the air intake valve (2) and the exhaust gas exhaust valve (3) of the combustion chamber being open at the same time.

Description

Technical Field

[0001] The present invention relates to a method for operating an internal combustion engine with hydrogen according to the preamble of the independent claim, and a pre-combustion chamber spark plug for igniting an air-hydrogen mixture introduced into the combustion chamber of the internal combustion engine. Background Technology

[0002] A method for operating an internal combustion engine with hydrogen is known from DE 10 2021 210 398 A1, wherein a so-called scavenging process is performed when the turbocharger speed is insufficient in order to increase the turbocharger speed and thus also increase the filling degree of the internal combustion engine with air. Summary of the Invention

[0003] The advantages of this invention, and the advantages of the method according to this invention, are that it avoids irregular operating states of the internal combustion engine, such as pre-ignition or detonation. Therefore, reliable operation of the internal combustion engine using hydrogen as fuel is achieved. The pre-combustion chamber spark plug according to this invention enables such improved operation of the internal combustion engine using hydrogen because it ensures reliable flushing of residual gas from the pre-combustion chamber cap of the pre-combustion chamber spark plug. This prevents hot gas from remaining in the combustion chamber of the internal combustion engine, which could form the starting point for pre-ignition or detonation. Thus, the operational safety of the internal combustion engine using hydrogen as fuel with a pre-combustion chamber spark plug is improved.

[0004] Further advantages and improvements are obtained through the features of the dependent claims. The method according to the invention is improved by the sufficient overlap of the opening of the air intake valve and the exhaust valve over a crankshaft angle range exceeding 10°, particularly exceeding 20°. Operating ranges with a tendency relative to pre-ignition can be identified particularly easily by considering a family of characteristic curves of motor speed and motor load, or motor torque, which have been previously determined for applications of the type of internal combustion engine. In particular, ranges with low motor speed and high motor load, or high motor torque, are therefore particularly readily used in the method according to the invention.

[0005] The pre-combustion chamber spark plug according to the invention is meaningfully designed with flushing openings oriented towards the air intake valve and towards the exhaust valve. Therefore, the airflow between the air intake valve and the exhaust valve can be used particularly effectively to flush the volume within the pre-combustion chamber cover. Flushing of the pre-combustion chamber cover is particularly effective when the flushing openings are oriented at an angle of 15° to 45° relative to the flat area in the combustion chamber where the pre-combustion chamber spark plug is arranged. Here, two to eight flushing openings have proven advantageous. The flushing openings can be constructed particularly easily as cylindrical openings within the pre-combustion chamber cover. To improve flow, the flushing openings can also be constructed in a conical shape. Advantageously, the flushing openings oriented towards the air intake valve are constructed to taper gradually from the outside inwards, and the flushing openings oriented towards the exhaust valve are constructed to taper gradually from the inside outwards. This significantly improves the supply of fresh air into the volume of the pre-combustion chamber cover and the outflow of air from the inner cavity of the pre-combustion chamber cover. Overall, the measures mentioned significantly reduce the tendency of hydrogen-fueled internal combustion engines to engage in pre-ignition or detonation. This improves the operational safety of hydrogen-fueled internal combustion engines. Attached Figure Description

[0006] Embodiments of the invention are illustrated in the accompanying drawings and will be explained in more detail in the following description.

[0007] Figure 1 The cross-section shows the combustion chamber of the internal combustion engine along with the air intake valve, pre-combustion chamber spark plug, and exhaust valve. Figure 2 The first arrangement of the air intake valve, exhaust valve, and flushing opening in the pre-combustion chamber spark plug is shown. Figure 3 A second arrangement of the air intake valve, exhaust valve, and flushing opening in the pre-combustion chamber spark plug is shown. Figure 4 A third arrangement of the air intake valve, exhaust valve, and flushing opening in the pre-combustion chamber spark plug is shown. Figure 5 The diagram shows the cylindrical flushing opening in the pre-combustion chamber spark plug along with the pre-combustion chamber cover. Figure 6 The conical flushing opening in the pre-combustion chamber spark plug, along with the pre-combustion chamber cover, is shown. Figure 7 The conical flushing opening in the pre-combustion chamber spark plug, along with the pre-combustion chamber cover, is shown. Figure 8 A family of characteristic curves of an internal combustion engine for use with the method according to the invention is shown. Detailed Implementation

[0008] exist Figure 1 The diagram schematically illustrates an internal combustion engine 10, which has a cylinder 11 and a piston 12 disposed therein. The remaining volume of the cylinder 11 forms a combustion chamber 13 via the piston 12, into which a combustible mixture of fuel and air is introduced and burned. The pressure within the combustion chamber 13 is increased by burning the fuel-air mixture, and this pressure is converted into mechanical work by the movement of the piston 12. This relates to conventional internal combustion engines, and more particularly to Otto-type internal combustion engines.

[0009] In order to ignite the fuel and air mixture in the combustion chamber 13, a so-called pre-combustion chamber spark plug 1 is arranged in the combustion chamber 13. Figure 1 The pre-combustion chamber spark plug is schematically shown. The pre-combustion chamber spark plug 1 has an ignition electrode 5 surrounded by a pre-combustion chamber cover 4. The pre-combustion chamber cover has different openings 6, 7, and 8, which respectively connect the inner cavity of the pre-combustion chamber cover 4 to the combustion chamber 13. A flushing opening 6 allows a combustible mixture of fuel and air to enter the ignition electrode 5. This flushing opening is typically, more precisely, constructed parallel to the upper side of the combustion chamber 13 and advantageously oriented towards the air intake valve 2 or the exhaust valve 3. To ignite the fuel and air mixture, an ignition spark is achieved at the ignition electrode 5, thereby igniting the combustible mixture in the immediate surrounding environment, i.e., combustion. The combustion is transmitted to the remaining combustion chamber 13 through the ignition beam opening 8 of the pre-combustion chamber cover 4, which is oriented towards the center of the combustion chamber 13, and ignites the combustible mixture of fuel and air within the combustion chamber 13. Because combustion in the pre-combustion chamber cover 4 increases the pressure inside the cover, the high-pressure combustion gases are forced through the ignition beam opening 8 to the center of the combustion chamber 13, and are responsible for reliably igniting the fuel-air mixture in the combustion chamber 13 over a large area. The combustion gases leaking from the ignition beam opening 8 are therefore also referred to as the ignition beam. The other openings 7 of the pre-combustion chamber cover 4 are oriented between the flushing opening 6 and the ignition beam opening 8, and point towards the combustion chamber 13 at an angle of approximately 45°. These openings 7 function as both the flushing opening 6 and the ignition beam opening 8, but with less efficiency than either the flushing opening 6 or the ignition beam opening 8. This type of method for igniting the mixture in the combustion chamber 13 is particularly suitable for igniting mixtures with a significant excess of air relative to the amount of fuel introduced, i.e., lean-burn mixtures. This type of combustion method is particularly applicable when an internal combustion engine is running on combustible gases, especially hydrogen, as fuel. Advantageously, hydrogen can be reliably ignited over a wide range of air-to-hydrogen mixture ratios.

[0010] It is also significant that the flushing opening 6 and the ignition beam opening 8 differ in cross-sectional size. For the flushing opening 6, a smaller cross-section than the ignition beam opening 8 has proven advantageous; the cross-section of the flushing opening 6 typically falls within 25% to 100% of the cross-section of the ignition beam opening. Correspondingly, the cross-section of the 45° opening 7 can also be accommodated. The cross-sections of openings 6, 7, and 8 must be empirically adapted to the corresponding motor type.

[0011] A blow-in valve 15 is provided to introduce fuel, i.e., hydrogen, into the combustion chamber 13. Hydrogen is directly blown into the combustion chamber 13 through the blow-in valve 15. An air intake valve 2 is provided to introduce air, and an exhaust valve 3 is provided to remove combustion exhaust gases. When the air intake valve 2 is open, air is introduced into the combustion chamber 13 through an intake pipe (not shown). When the exhaust valve 3 is open, the combustion exhaust gases contained in the combustion chamber 13 are discharged from the combustion chamber 13 and exited to the surrounding environment through an exhaust pipe (not shown).

[0012] The problem with this type of internal combustion engine is that the hot residual gases from combustion remain in the combustion chamber before a fresh mixture of hydrogen and air is introduced. Due to these hot residual gases, undesirable pre-reaction of the hydrogen-air mixture may occur, or in the worst case, premature ignition of the hydrogen-air mixture in combustion chamber 13, known as pre-ignition. This type of premature ignition is highly detrimental because subsequent combustion does not occur at the optimal time point, which allows for the optimal conversion of released energy into mechanical work. Furthermore, these hot residual gases can also lead to detonation, i.e., uncontrolled combustion, in which high pressure peaks occur. The cavity inside the pre-combustion chamber spark plug 1 is particularly problematic here because residual hot combustion gases preferentially remain there due to geometric conditions.

[0013] According to the present invention, operating ranges of the internal combustion engine 10 that are problematic in terms of pre-ignition are identified, and improved flushing of the cavity of the pre-combustion chamber cover 4 is ensured within these operating ranges. To this end, in the identified operating ranges exhibiting a tendency relative to pre-ignition, the air intake valve 2 and exhaust valve 3 are operated such that the opening times of the two valves overlap. This method is also known as scavenging. Scavenging is conventionally used to supply a higher quantity of gas to the turbocharger of the internal combustion engine in a range of low engine speeds and low loads, in order to rapidly increase the turbocharger's power. These operating ranges typically do not correspond to operating ranges exhibiting a tendency relative to pre-ignition.

[0014] exist Figure 1In the diagram, two valves, air intake valve 2 and exhaust valve 3, are schematically shown in the open state, thus creating a direct airflow from air intake valve 2 to exhaust valve 3. The pre-combustion chamber spark plug 1 is typically arranged in the middle region of the combustion chamber and is therefore directly within this airflow. The pre-combustion chamber cover 4 of the pre-combustion chamber spark plug 1 has multiple flushing openings 6 through which the airflow passes through the inner cavity of the pre-combustion chamber cover 4, thus ensuring effective removal of hot residual gases. Hot residual gases are reliably removed from the inner cavity of the pre-combustion chamber cover 4.

[0015] exist Figure 2 The diagram shows an advantageous arrangement of the pre-combustion chamber spark plug 1, or flushing opening 6, relative to the air intake valve 2 or the exhaust valve 3. It shows the arrangement from below to... Figure 1 The view is of the upper side of the combustion chamber. However, the view of the pre-combustion chamber spark plug 1 is shown as a cross-section of the pre-combustion chamber cover 4 and the flushing opening 6, thus revealing the arrangement of the flushing opening 6 relative to the air intake valve 2 and the exhaust valve 3. Two air intake valves 2 on the left side of the pre-combustion chamber spark plug 1 and two exhaust valves 3 on the right side of the pre-combustion chamber spark plug 1 are shown respectively. Multiple valves are advantageous in order to improve the area for the inflow and outflow of air and exhaust gases. Figure 2 As can be identified, the four flushing openings are arranged such that one flushing opening faces the air intake valve 2 and one flushing opening faces the exhaust valve. This allows for effective airflow through the flushing openings 6, or the inner cavity of the pre-combustion chamber cover 4.

[0016] exist Figure 3 The text shows the relationship with... Figure 2 The same view as in the diagram, however, with an alternative arrangement of flushing opening 6 with pre-combustion chamber cover 4. Figure 3 Each valve has only one flushing opening 6 facing the two air intake valves 2 and one flushing opening 6 facing the two exhaust valves 3. This orientation of the flushing openings 6 allows for a common flow from the two air intake valves 2 towards the two exhaust valves 3.

[0017] exist Figure 4 As shown in Figure 2 Or a view like 3, which combines Figure 2 and 3The two diagrams show flushing openings 6. Therefore, there are flushing openings 6 oriented directly towards the single air intake valve 2 or the single exhaust valve 3, and also one flushing opening oriented towards the middle between the two air intake valves 2 or the middle between the two exhaust valves 3. Thus, all possible flow conditions between the different air intake valves 2 and the different exhaust valves 3 are used to flush the inner cavity of the pre-combustion chamber cover 4.

[0018] exist Figure 5 The image shows a detailed cross-sectional view of the pre-combustion chamber spark plug 1. The ignition electrode 5 is positioned at the center of the pre-combustion chamber cover 4. Figure 5 In the diagram, the ignition electrode is constructed in the classic spark plug type with hook-shaped and needle-shaped electrodes. However, other arrangements of the ignition electrode 5 are also feasible. Figure 5 In the diagram, the pre-combustion chamber cover 4 has four flushing openings 6 and ignition beam openings 8 arranged differently. The pre-combustion chamber spark plug 1 is arranged on the flat area 14 on the upper side of the combustion chamber 13. Figure 5 The flushing openings 6 are each constructed as cylindrical openings, meaning that the cross-section of the flushing openings 6 remains unchanged within the pre-combustion chamber cover 4. The four flushing openings 6 have angles α ranging from 15 to 45° with respect to the flat region 14. Here, angle α is defined relative to the flat region 14 from the central axis of each flushing opening 6. Due to this angular orientation, the flushing openings are particularly well-suited to: enable airflow from the air intake valve 2 to the interior of the pre-combustion chamber cover 4, or to enable the flow of exhaust gas or residual gas from the interior of the pre-combustion chamber cover 4 towards the exhaust valve 3. (As already relative to...) Figure 1 As explained, the flushing opening 6 with a 45° orientation also functions as an ignition beam opening, but this is not discussed further here. For Figure 5 The description will not continue. Figure 1 The distinction is made between openings 6 and 7 because... Figure 1 The opening 7 also functions as a flushing opening. The additional opening in the pre-combustion chamber cover 4, oriented perpendicular to the flat region 14 as an ignition beam opening 8, is of lesser importance for flushing residual gases from the interior of the pre-combustion chamber cover 4. The ignition beam opening 8 guides the combustion gases deep into the combustion chamber 13 from the interior of the pre-combustion chamber cover 4, which is advantageous for igniting the mixture in the combustion chamber 13.

[0019] exist Figure 6 The image also shows a detailed view of the pre-combustion chamber spark plug 1, the ignition electrode 5 along with the pre-combustion chamber cover 4, and the four flushing openings 6. The angular orientation of the central axis of the flushing openings 6 corresponds to... Figure 5 The same angle α relative to the flat region 14. However, unlike... Figure 5 Each flushing opening 6 is tapered, with its cross-section gradually decreasing from the outside to the inside, meaning the cross-section of the flushing opening decreases towards the inner cavity of the pre-combustion chamber cover. This results in an acceleration of the flow of fresh gas into the inner cavity of the pre-combustion chamber cover 4. The taper of the flushing opening 6 is chosen such that the sidewall of the flushing opening 6 has an angle β on the order of 5° to 20° relative to its central axis. The ignition beam opening 8 is as follows... Figure 5 The opening is constructed in a cylindrical shape, as in the example.

[0020] exist Figure 7 The image also shows a detailed view of the pre-combustion chamber spark plug 1 together with the ignition electrode 5 of the pre-combustion chamber cover 4 and the four flushing openings 6. The angular orientation of the flushing openings 6 corresponds to... Figure 5 The same angle α relative to the flat region 14 is present. Furthermore, the flushing opening 6 is also tapered, with the taper differing depending on whether it is oriented towards the air intake valve 2 or the exhaust valve 3. Figure 7 The flushing opening on the left side is oriented towards the air intake valve, and the cross-section of the flushing opening 6 gradually decreases from the outside to the inside, meaning that the cross-section on the outer side of the pre-combustion chamber cover 4 is larger than the cross-section on the inner side of the pre-combustion chamber cover 4. Figure 7 The flushing opening 6 on the right side is oriented towards the exhaust valve 3, and the cross-section of the flushing opening 6 gradually decreases from the inside to the outside, meaning that the cross-section on the inner side of the pre-combustion chamber cover 4 is larger than the cross-section on the outer side of the pre-combustion chamber cover 4. This achieves acceleration of the gas flowing into and out of the pre-combustion chamber cover 4. This arrangement further improves the flushing of residual gas from the pre-combustion chamber cover 4. The ignition beam opening 8 is as follows... Figure 5 The opening is constructed in a cylindrical shape, as in the example. Figure 8The text elucidates the identification of the operating range of the internal combustion engine 10 relative to its pre-ignition tendency. A family of characteristic curves of motor speed n versus motor torque M, or motor load, is plotted. Here, curve 80 shows the feasible operating range of the internal combustion engine, where operation is only possible below curve 80. Curve 80 thus shows the maximum torque achievable by the internal combustion engine 10 at the corresponding speed. Operation below or above a specific speed is not possible. Furthermore, range 81 is shown, characterized by low speeds and high motor torque M. In range 81, the internal combustion engine has a particularly high pre-ignition tendency, especially with fuels with very strong ignition capabilities, such as hydrogen, which can burn in a very wide mixture ratio of air and hydrogen. Therefore, within this operating range, the internal combustion engine is operated according to the invention with a temporal overlap in the opening of the air intake valve 2 and the exhaust valve 3, so as to correspondingly reduce or eliminate the tendency relative to pre-ignition through improved flushing of residual gases from the combustion chamber 13 or from the pre-combustion chamber cover 4. The temporal overlap means that both valves are opened at the same time.

[0021] Of course, the transition region between range 81 and the nearby operating conditions of the internal combustion engine is not defined as a clear line, because pre-ignition is a statistical process, and therefore a pre-ignition tendency means that pre-ignition occurs more statistically. Therefore, range 81 is defined such that the probability of pre-ignition exceeds a pre-given threshold. When the threshold is exceeded, scavenging is activated to reduce the pre-ignition tendency, that is, the statistical probability of pre-ignition. Alternatively, multiple ranges can be set that differ in their pre-ignition tendency and accordingly tailor the overlap of the opening of the air intake valve 2 and the exhaust valve 3. Thus, for example, a range with a 30° crankshaft angle for overlap can be set in a range with a very high pre-ignition tendency, and a range with a 15° crankshaft angle for overlap can be set in a range with a slightly reduced pre-ignition tendency.

[0022] right Figure 8 The determination of the family of characteristic curves shown is carried out during the application phase of the internal combustion engine, in which the engine operates across all operating ranges and its tendency relative to pre-ignition is determined. Then, the respective adaptations to the operating conditions of the internal combustion engine and... Figure 8 As shown, these are recorded in a family of characteristic curves and used for the operation of internal combustion engines.

Claims

1. A method for operating an internal combustion engine (10) using hydrogen as fuel, wherein the hydrogen is directly blown into the combustion chamber (13) of the internal combustion engine, wherein, Ignition of the air-hydrogen mixture in the combustion chamber (13) is achieved by a pre-combustion chamber spark plug (1), characterized in that the presence of the internal combustion engine (10) in an operating state relative to the tendency of pre-ignition is identified, and the internal combustion engine is operated in the identified operating range with the overlap of the opening times of the air intake valve (2) and the exhaust valve (3) of the combustion chamber (13).

2. The method according to claim 1, characterized in that, The overlap in the opening time of the air intake valve (2) and the exhaust valve (3) covers a crankshaft angle range of the internal combustion engine (10) exceeding 10°, and especially exceeding 20°.

3. The method according to claim 1 or 2, characterized in that, Operating states with a tendency relative to pre-ignition are identified by means of a family of characteristic curves, which correspond the operating parameters of the internal combustion engine (10) to the tendency relative to pre-ignition.

4. The method according to claim 3, characterized in that, The operating range (81) of the internal combustion engine, which has low speed (n) and high torque (M), corresponds to a high tendency relative to pre-ignition.

5. A pre-combustion chamber spark plug (1) for igniting an air-hydrogen mixture introduced into a combustion chamber (13) of an internal combustion engine (10), the pre-combustion chamber spark plug having a pre-combustion chamber cap (4) surrounding an ignition electrode (5) of the pre-combustion chamber spark plug (1), characterized in that, The pre-combustion chamber cover (4) has a flushing opening (6) configured to form an airflow in the pre-combustion chamber cover (4) when the air intake valve (2) and exhaust valve (3) of the combustion chamber are opened simultaneously.

6. The pre-combustion chamber spark plug (1) according to claim 5, characterized in that, When installed in the combustion chamber (13), a flushing opening (6) is provided in the direction of the air intake valve (2) of the combustion chamber and a flushing opening is provided in the direction of the exhaust valve (3).

7. The pre-combustion chamber spark plug (1) according to claim 5 or 6, characterized in that, The pre-combustion chamber spark plug (1) is configured to be arranged in a flat area (15) at the top of the combustion chamber of the combustion chamber (13), and the flushing opening (6) has an angle of 15° to 45° relative to the flat area (15) of the combustion chamber.

8. The pre-combustion chamber spark plug (1) according to claims 5 to 7, characterized in that, It is equipped with 2 to 8 flushing openings (6).

9. The pre-combustion chamber spark plug (1) according to claims 5 to 8, characterized in that, The flushing opening (6) is constructed as a columnar opening in the pre-combustion chamber cover (4).

10. The pre-combustion chamber spark plug (1) according to claims 5 to 9, characterized in that, The flushing opening is constructed as a conical opening in the pre-combustion chamber cover.

11. The pre-combustion chamber spark plug (1) according to claim 10, characterized in that, The flushing opening (6) oriented toward the air intake valve (2) is constructed in a cone shape that gradually narrows from the outside to the inside, and the flushing opening (6) oriented toward the exhaust valve (3) is constructed in a cone shape that gradually narrows from the inside to the outside.

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