Method for operating a hydrogen combustion engine

Abstract

The present invention relates to a method for operating a hydrogen combustion engine when pre-ignitions occur in a cylinder at a first operating point (P1) of the hydrogen combustion engine, comprising the steps of: detecting a pre-ignition in a cylinder, summing the number of pre-ignitions in the cylinder up to a predefined first sum value (A1), injecting a predetermined first quantity of water (W1) into the cylinder when the sum of the number of pre-ignitions in the cylinder reaches the first sum value (A1), checking whether the pre-ignition occurs in the cylinder again after the injection of the first quantity of water (W1), continuing the injection of the first quantity of water (W1), which has been increased by a second quantity of water (W2), if the check has indicated that the pre-ignition has occurred again in the cylinder, and ending the water injection and storing the first operating point (P1) with the associated first sum value (A1) of the occurrence of the number of pre-ignitions and with the associated injected quantity of water (W1+W2) if the check of the pre-ignition in the cylinder has indicated that pre-ignition no longer occurs.

Description

[0001] Description

[0002] title

[0003] Method for operating a hydrogen combustion engine

[0004] State of the art

[0005] The present invention relates to a method for operating a hydrogen internal combustion engine when pre-ignition occurs in a cylinder at an operating point of the hydrogen internal combustion engine, and to a control unit configured for carrying out the method according to the invention.

[0006] One problem with hydrogen combustion engines is the potential for pre-ignition. This involves premature and uncontrolled combustion before the actual ignition, which can pose a significant risk of damage to the engine. Water injection can be used to reduce or eliminate pre-ignition. Ideally, the optimal amount of water should always be injected to prevent pre-ignition.

[0007] Disclosure of the invention

[0008] The inventive method for operating a hydrogen internal combustion engine with the features of claim 1 when pre-ignition occurs in a cylinder has the advantage that an optimal amount of water for suppressing pre-ignition can be determined and injected. The injection can take place directly into a combustion chamber and / or a pre-combustion chamber area. A learning system can be provided which can also adapt to changing external conditions, such as wear of the internal combustion engine over time. This is achieved according to the invention by the method detecting pre-ignition in a cylinder of the hydrogen internal combustion engine in a first step. In a next step, the pre-ignition events that have occurred are summed up to a first, predetermined total value A1. The total value A1 is an integer and can also be one.In the next step, a first predetermined quantity of water W1 is injected to counteract the occurrence of pre-ignition. The system then checks whether pre-ignition occurs again on the cylinder of the hydrogen combustion engine within a monitoring window. If pre-ignition occurs again within the monitoring window, the injection of the first quantity of water W1 is continued and, preferably incrementally, increased by a second quantity of water W2 until either no further pre-ignitions occur within the monitoring window or a maximum permissible quantity of water is reached. Subsequently, an operating point P1 is recorded, along with the associated first total value A1 of the occurrence of pre-ignition and the corresponding total quantity of water W1 + W2 at which no further pre-ignition occurs.Thus, according to the invention, the frequency of pre-ignition and the associated total injected amount of water W1 + W2, at which pre-ignition no longer occurs, are stored at an operating point P1.

[0009] The dependent claims describe preferred embodiments of the invention.

[0010] If pre-ignition occurs in a cylinder at several different operating points, the corresponding values ​​for the sum value A1 and the total amount of water W1 + W2 are preferably stored separately for each operating point. Preferably, a corresponding characteristic map with a large number of operating points is created.

[0011] If pre-ignition occurs again at the first operating point P1, the corresponding stored amount of water per injection process is used for this first operating point P1 in order to suppress any pre-ignitions that have occurred as quickly as possible.

[0012] If pre-ignition occurs again at the same initial operating point P1, i.e., for the second time, the corresponding injected water quantity is preferably increased by a further amount of water. If this suppresses pre-ignition in a subsequent cycle of the hydrogen combustion engine, the additional water quantity and, if applicable, a second corresponding total value A2 (if different from the first total value A1) are stored for the initial operating point P1.

[0013] To prevent the second water quantity W2 from being set too high, a value for the second water quantity W2 is preferably adjusted to prevent pre-ignition at the first operating point P1 in this cylinder. This adjustment can be made by subtracting a predetermined reduction value R from the second water quantity W2 for the first operating point P1, or by storing the previous value for the water quantity W2. This process can be repeated until, in particular, the base water quantity is reached again and a critical number of pre-ignitions on the corresponding cylinder has not been exceeded. If pre-ignition occurs again, the modified stored water quantity would then be used.

[0014] Preferably, the amount of water to be injected when pre-ignition occurs is an additional amount of water injected in addition to a base amount of water already injected, or the amount of water to be injected is the total amount of water to be injected. This means that the method according to the invention can be carried out if a base amount of water has already been injected and pre-ignition still occurs; in that case, the additional amount of water is injected, or no water is injected, and when pre-ignition occurs, the first amount of water W1 is used to suppress the pre-ignition.

[0015] Preferably, when the amount of water to be injected reaches a predetermined threshold, it is further specified according to the invention that this threshold value of water quantity is maintained and no further increase of the water quantity is carried out. This serves to protect the hydrogen combustion engine.

[0016] If pre-ignition still occurs after reaching the threshold, particularly if it exceeds a predetermined number of pre-ignitions per cylinder, the operating point of the hydrogen combustion engine is preferably adjusted to reduce its power output and thus achieve an operating point where pre-ignition no longer occurs. This is particularly important for protecting the components of the hydrogen combustion engine if it is no longer possible to inject an additional amount of water to suppress pre-ignition.

[0017] If no further pre-ignition occurs at this operating point after a certain period of time, the water quantity can be reduced in steps until either pre-ignition occurs again or the base water quantity is reached. These reduced values ​​are also stored accordingly in the characteristic map area.

[0018] The method according to the invention is preferably carried out cylinder-specifically for each cylinder individually.

[0019] Preferably, the frequency of pre-ignition in a cylinder is recorded, and if a predetermined frequency is exceeded, it is determined that this operating point is exempt from water reduction. Thus, operating ranges with a very high tendency towards pre-ignition can be exempted from a reduction in the amount of water injected.

[0020] It is further preferred that several operating points in which pre-ignition occurs are combined into a single operating map area. If pre-ignition then occurs in one of the operating points within the combined operating map area, an average value for the amount of water to be injected, based on the multitude of operating points in this operating map area, can preferably be used to try to suppress the pre-ignition.

[0021] Furthermore, the present invention relates to a control unit designed to carry out the method according to the invention.

[0022] The hydrogen combustion engine is preferably used in a vehicle. Drawing

[0023] A preferred embodiment of the invention is described in detail below with reference to the accompanying drawing. The drawing shows:

[0024] Figure 1 is a schematic flowchart illustrating the method according to the invention.

[0025] Preferred embodiments of the invention

[0026] The following describes, with reference to Figure 1, a method for operating a hydrogen internal combustion engine when pre-ignition occurs in a cylinder at a first operating point of the hydrogen internal combustion engine according to the invention.

[0027] The process is carried out individually for each cylinder of the hydrogen combustion engine and can be performed on both single-cylinder and multi-cylinder hydrogen combustion engines.

[0028] Pre-ignitions in a cylinder can be detected using known sensors, such as knock sensors.

[0029] According to the inventive method, in a first step S1 is detected whether pre-ignition occurs in a cylinder.

[0030] In a second step S2, the frequency of pre-ignition in the cylinder is counted. The number of pre-ignitions in a cylinder is summed, and in a third step S3, it is checked whether a first predefined sum value A1 of the number of pre-ignitions in a cylinder has been reached (Y) or not (N).

[0031] If the first predetermined total value A1 has not yet been reached, the process returns to step S1 and continues to check whether pre-ignition occurs. It should be noted that in the second step S2, if pre-ignition does not occur, the counter can be reset to zero, or the total value A1 can be set to zero only after a predetermined number of cycles without pre-ignition, for example, 10 cycles.

[0032] If the first total value A1 is reached, the procedure proceeds to the fourth step S4. In the fourth step S4, an initial quantity of water W1 to be injected is determined, which is intended for injection to suppress pre-ignition in the monitored cylinder. This initial quantity of water W1 is then injected.

[0033] In a fifth step, S5, it is checked again whether pre-ignition occurs after the initial water injection with the first quantity of water, W1. If pre-ignition persists (Y in step S5), water is injected again, increasing the initial quantity of water, W1, by a second quantity, W2, and the process returns to step S4. The water quantity can be increased until pre-ignition no longer occurs. If pre-ignition no longer occurs (N), the process proceeds to the sixth step, S6. In the sixth step, S6, the water injection is either stopped or the process returns to a baseline water injection.

[0034] The process then proceeds to a seventh step S7, in which a first operating point P1, at which pre-ignition has occurred, is stored with the associated first sum value A1 of the occurrence of the number of pre-ignitions and the associated final amount of water (W1 +W2) to suppress pre-ignitions at this operating point.

[0035] The stored values ​​can then be directly output as a preventive measure to suppress pre-ignition as soon as pre-ignition occurs again at this operating point P1.

[0036] If no further pre-ignition occurs at operating point P1 after a certain period, the amount of water can be reduced in steps until either pre-ignition occurs again or a predetermined base water quantity is reached. These reduced values ​​are also stored accordingly in the characteristic map. This procedure can be executed if, on the one hand, a base water injection has already taken place and pre-ignition still occurs in the cylinder, or if no water injection takes place and pre-ignition occurs.

[0037] The first sum value A1 can also be adjusted and, for example, take the value one.

[0038] The data is preferably stored in a characteristic map that spans load and speed. It is also possible to group several operating points where pre-ignition occurred into a specific characteristic map range.

[0039] It is also preferably possible that the amount of water injected is adjusted incrementally depending on the number of pre-ignitions in a cylinder. This adjustment can be based on a time period within the operating point or map range where no pre-ignition occurred, or alternatively, where the vehicle has been refueled with water. It is also preferably possible that

[0040] Areas of the operating map that show a very high tendency for pre-ignition are exempt from a reduction in the amount of water to be injected.

[0041] Thus, according to the invention, a learning system can be provided which, in the event of pre-ignition, injects an adapted, optimal amount of additional water or base water to suppress the pre-ignition.

Claims

Claims 1. Method for operating a hydrogen internal combustion engine when pre-ignition occurs in a cylinder at a first operating point (P1) of the hydrogen internal combustion engine, comprising the steps: - Detecting a pre-ignition in a cylinder, - Summing up the number of pre-ignitions in the cylinder up to a predetermined first total value (A1), - Injecting a predetermined first quantity of water (W1) into the cylinder when the sum of the number of pre-ignitions in the cylinder reaches the first total value (A1), - Check if pre-ignition occurs again in the cylinder after the injection of the first amount of water (W1), - if the check reveals a recurrence of pre-ignition in the cylinder, continue the injection of the first quantity of water (W1), which has been increased by a second quantity of water (W2), and if the check of pre-ignition in the cylinder reveals that no further pre-ignition occurs, stop the water injection and - Saving the first operating point (P1) with the associated first total value (A1) of the occurrence of the number of pre-ignitions and the associated amount of water injected (W1 +W2).

2. Method according to claim 1, wherein if pre-ignition occurs again at a later time in the first operating point (P1), the associated amount of water (W1 + W2) stored for this first operating point (P1) is used for water injection.

3. Method according to claim 2, wherein if pre-ignition occurs again in the cylinder at the first operating point (P1), the associated injected quantity of water (W1 +W2) is increased to a further quantity of water and this quantity of water is stored for the first operating point (P1).

4. Method according to claim 2, wherein, if pre-ignition no longer occurs in the cylinder at the first operating point (P1), a third quantity of water (W3) is stored, which lies between the second quantity of water (W2) and the first quantity of water (W1).

5. Method according to one of the preceding claims, wherein the amount of water to be injected is an additional amount of water in addition to a base amount of water already to be injected when pre-ignition occurs, or wherein the amount of water to be injected is a total amount of water to be injected if no water injection has taken place when pre-ignition occurs.

6. Method according to one of the preceding claims, wherein when the amount of water to be injected reaches a predetermined threshold, the amount of water to be injected is maintained without further increase even if further pre-ignitions occur, in order to protect the internal combustion engine from excessive water ingress.

7. Method according to claim 6, wherein if a number of pre-ignitions exceeds a predetermined value, the operating point of the hydrogen combustion engine is changed, in particular to a power-reduced operating point.

8. Method according to one of the preceding claims, wherein the method is carried out cylinder-specifically for each cylinder individually.

9. Method according to one of the preceding claims, wherein the frequency of occurrence of pre-ignitions at an operating point of the hydrogen combustion engine is recorded and, if a certain frequency is exceeded, this operating point is excluded from a reduction in the amount of water.

10. Control unit, configured to carry out a method according to any of the preceding claims.

Images