Method for operating a gas combustion engine

Abstract

The present invention relates to a method for operating a gas internal combustion engine, comprising the steps of: detecting an anomaly event during a combustion process in a cylinder of the gas internal combustion engine, counting the number of occurrences of the anomaly event in this cylinder, wherein a counting value Z is incremented by 1 each time the anomaly event occurs when the counting value Z reaches a threshold value S, starting a countdown counter (3) which begins with a predetermined first value A1 and determining a first quantity of water W1 to be injected, which is injected into this cylinder during the next combustion process. If the anomaly event occurs again during the next combustion process in this cylinder, the countdown counter (3) is incremented by a predetermined second value A2, and a second quantity of water W2 to be injected is determined based on the second value A2.and if the anomaly event does not occur during the next combustion process in this cylinder, the countdown counter (3) is reduced by 1, and a third water quantity W3 to be injected is determined, whereby a water quantity to be injected is injected during subsequent combustion processes until the countdown counter (3) is zero.

Description

State of the art

[0001] The present invention relates to a method for operating a gas internal combustion engine upon detection of an anomaly event, such as knocking or pre-ignition, and to a device for carrying out the method.

[0002] Water injection systems are known from conventional internal combustion engines, which are particularly powered by gasoline, in order to increase the performance and / or efficiency of the internal combustion engine. However, such known systems cannot be readily used in gas internal combustion engines, which are powered by hydrogen, for example. In particular, the combustion of hydrogen is much more prone to pre-ignition than, for example, gasoline. Furthermore, hydrogen is also very prone to uncontrolled combustion during the compression stroke of the gas internal combustion engine, well before the ignition point. This can cause knocking and peak combustion pressures that can be greater than twice the normal combustion pressures.Therefore, increased attention must be paid to reducing pre-ignition events in gas combustion engines and an adapted strategy must be provided to reduce such pre-ignition and knocking. Disclosure of the invention

[0003] The method according to the invention for operating a gas internal combustion engine with the features of claim 1 enables, upon detection of an anomalous event, in particular knocking or pre-ignition, reduction strategies and / or avoidance strategies specifically tailored to the gas internal combustion engine to be implemented in order to prevent the anomalous events as quickly as possible. For this purpose, a water rate is used for water injection in the gas internal combustion engine. In particular, it can prevent excessive water from being injected when an anomalous event occurs, allowing optimal use of a water quantity that is only available to a limited extent in a vehicle.Furthermore, it can be prevented in particular that excessive water ingress leads to the repelling of an oil wall film on a cylinder liner of a combustion chamber of the gas internal combustion engine or to a leakage via a piston seal during further operation of the gas internal combustion engine.

[0004] This is achieved according to the invention in that the method for operating the gas combustion engine comprises the following steps: In a first step, an anomaly event is detected during a combustion process in a cylinder of the gas internal combustion engine. If such an anomaly event is detected, the number of occurrences of the anomaly event in the cylinder is counted. A counter value Z is incremented by 1 for each occurrence of the anomaly event. When the counter value Z reaches a threshold value S, a countdown timer is started. The countdown timer begins with a predetermined first value A1. Subsequently, a determination is made of a first quantity of water W1 to be injected, which is injected during the next combustion process into the cylinder in which the anomaly event occurred. If the anomaly event occurs again in a subsequent combustion process in this cylinder, the countdown timer is incremented by a predetermined second value A2, and a second quantity of water W2 to be injected is redetermined.If the anomaly event no longer occurs during the next combustion event in this cylinder, the countdown counter is reduced by 1, and a third water quantity W3 to be injected is determined. The water quantity to be injected is determined during subsequent combustion events in this cylinder until the countdown counter reaches zero.

[0005] Thus, if an anomaly event occurs during a combustion process in a cylinder, a counter strategy can be implemented. The threshold value S can, for example, be 1, so that the counter strategy starts immediately upon the occurrence of the anomaly event. The predefined first value A1 of the countdown counter is set to a value, for example 10, to ensure that water injection occurs in the next combustion processes corresponding to the number of the first value A1 in the cylinder in which the anomaly event occurred. The water injection can be an additional water injection, i.e., an additional amount of water injected at a predefined base water rate, or, if no water injection has yet occurred, an absolute water rate to avoid the anomaly event.

[0006] Water is preferably injected directly into a combustion chamber and / or into a suction area of ​​the gas combustion engine.

[0007] The subclaims show preferred developments of the invention.

[0008] The anomalous event is typically knocking or pre-ignition. In such anomalous events, (additional) water injection is very helpful in preventing knocking and / or pre-ignition as quickly as possible.

[0009] Further preferably, the gas combustion engine has multiple cylinders, and the method is performed individually for each cylinder. This allows appropriate countermeasures to be implemented directly in the cylinders in which the anomaly occurred.

[0010] Further preferably, if the method has detected an anomaly event in one cylinder of the gas internal combustion engine, a correspondingly adjusted water injection is carried out in the other cylinders of the gas internal combustion engine in which no anomaly event has occurred. The method according to the invention can be carried out in the same way in the other cylinders not affected by the anomaly event, in the same way or in an adjusted way. Preferably, the same first amount of water is injected into the other cylinders as in the cylinder in which the anomaly event occurred.

[0011] Preferably, in the other cylinders in which no anomaly event has occurred, water injection is carried out until the countdown timer is set to zero.

[0012] If a base water injection is already being performed in the cylinder in which the anomaly event occurred, the water quantity determined by the method according to the invention is an additional water quantity. Alternatively, the determined first water quantity to be injected is the total water quantity injected into the cylinder with the anomaly event.

[0013] The first water quantity W1 to be injected is preferably determined from a characteristic curve KL dependent on the value of the countdown counter. For example, each value of the countdown counter can be assigned an individual first water quantity W1. For example, a larger additional water quantity can be injected at the beginning of the process than towards the end of the process, when the countdown counter approaches zero.

[0014] Further preferably, the first water quantity W1 from the characteristic curve dependent on the value of the countdown counter is additionally multiplied by a weighting factor GF. The weighting factor GF is preferably determined using a first characteristic map KF1. The first characteristic map KF1 can be based on a load and / or a speed and / or a target or actual torque of the gas internal combustion engine and / or an air mass and / or a fuel mass and / or a relative air charge and / or a relative fuel quantity and / or a power output of the gas internal combustion engine.

[0015] Further preferably, a minimum water flow rate is used as long as a cylinder's countdown counter is greater than zero. The minimum water flow rate is preferably determined using a separate characteristic map KF2, which depends in particular on the speed and load of the gas combustion engine.

[0016] Preferably, a comparison is made with a base water rate, which is determined by other factors of the gas engine. A comparison is then made between the base water rate and the minimum water rate, and the higher water rate is used for the next water injection. If no countdown counter of the cylinders of the gas engine is greater than zero, i.e., if no anomaly event occurs, there is no limitation of the base water rate used during operation of the gas engine. This allows the base water rate to be adapted to the given conditions of the gas engine and, for example, a water quantity to be optimized in order to conserve the gas engine's water supply.

[0017] Furthermore, the present invention relates to a device which is configured to carry out the method according to the invention. Short description of the drawings

[0018] A preferred embodiment of the invention will be described in detail below with reference to the accompanying drawings. In the drawing: Fig. 1 a schematic representation of a device for carrying out the method for operating a gas combustion engine upon detection of an anomaly event. Preferred embodiment of the invention

[0019] The following is based on reference to Fig. 1 a method according to the invention and a device according to the invention are described in detail.

[0020] During operation of a gas combustion engine, anomalous events such as pre-ignition and / or knocking can occur in a cylinder of the gas combustion engine.

[0021] To prevent damage to the gas-fired engine, water is injected in addition to the injected gaseous fuel. The gaseous fuel is preferably hydrogen. Since hydrogen combustion has a significantly greater tendency, particularly toward pre-ignition, selecting an optimal water rate W for water injection is particularly important.

[0022] The water is preferably injected into an intake port of the gas combustion engine and / or directly into a combustion chamber of a cylinder.

[0023] According to the present invention, a method is implemented, for example, in a control unit 2, in which a water injection rate W is determined, which depends on various influencing variables. The method according to the invention can be used, in particular, to counteract the occurrence of knocking and / or pre-ignition in a cylinder.

[0024] The method according to the invention is carried out when, in a first step, an anomaly event is detected during a combustion process in a cylinder 1 of the gas internal combustion engine. The gas internal combustion engine preferably has several cylinders.

[0025] After the anomaly event is detected, the number of occurrences of the anomaly event in that cylinder is counted. The anomaly event can occur in only one cylinder or in multiple cylinders. The method according to the invention is then carried out individually in each cylinder in which the anomaly event occurs.

[0026] When counting the number of occurrences of the anomaly event, a count value Z is incremented by 1 for each occurrence of the anomaly event. When the count value Z reaches a threshold value S, a countdown counter 3 is started.

[0027] The threshold value S can be any value and, for example, can take the value 1, so that the countdown timer 3 starts to start immediately after the first occurrence of the anomaly event.

[0028] Countdown counter 3 is started with a predefined first value A1. The value A1 is preferably speed-dependent and can be, for example, 10.

[0029] When the countdown timer starts, a first quantity of water W1 to be injected is also determined, which is injected during the next combustion process in the cylinder in which the anomaly event occurred.

[0030] The first water quantity W1 to be injected is determined using a characteristic curve KL, which preferably depends on the value of the countdown counter. It is possible to assign a specific water rate to each separate, different value currently displayed by the countdown counter, or alternatively, to always provide the same water rate regardless of the countdown counter value.

[0031] As in Fig. 1, the first water quantity W1 can be multiplied by a weighting factor GF. The weighting factor GF can be determined from a first characteristic map KF1. In Fig. 1, two variables X1, X2 are shown as input variables by way of example, however, any number and combination of input variables can be used. Input variables can include, for example, a load and / or a speed of the gas engine and / or a setpoint or actual torque of the gas engine and / or an air mass and / or a fuel mass and / or a relative air charge and / or a relative fuel quantity and / or a power of the gas engine.

[0032] The first water quantity W1 multiplied by the weighting factor GF is called W1'. As can be seen from Fig. 1, this weighted water quantity W1' is added to a base water quantity W0 to form a water rate W to be injected.

[0033] If an anomaly event occurs again during the next combustion cycle in the cylinder in which the anomaly event occurred, the countdown counter 3 is incremented by a predetermined second value A2. The second value A2 can be equal to the first value A1. A second water quantity W2 to be injected is then redetermined. Preferably, the second water quantity W2 to be injected is greater than the previously determined first water quantity W1 in order to reduce the tendency for the anomaly event to occur.

[0034] If the anomaly event no longer occurs during the next combustion event in the cylinder after the water quantity has been injected, the countdown counter is decremented by 1. A third water quantity W3 to be injected is then determined. The third water quantity W3 can be equal to the first water quantity W1 or slightly smaller. Preferably, different water quantities are stored for each number of the countdown counter to enable economical water use during operation.

[0035] Each time the anomaly event does not occur, the countdown timer is decremented by 1, with an amount of water still being injected for each value of the countdown timer until the countdown timer finally reaches zero.

[0036] This ensures that at least one more water injection has occurred even though no further anomaly event has occurred.

[0037] If the gas combustion engine has several cylinders and several cylinders exhibit the anomaly event, a corresponding method according to the invention is carried out individually for each cylinder.

[0038] If the anomaly event does not occur in all cylinders in several cylinders, an additional water injection or even a water injection is preferably performed in the cylinders in which the anomaly event did not occur in order to counteract the tendency for an anomaly event to occur. Preferably, the same initial water quantity W1 is then injected into all cylinders as in the cylinder in which the anomaly event occurred. Preferably, the water injection is performed for all cylinders until the last countdown counter is set to zero.

[0039] The method according to the invention is preferably carried out as a cylinder-individual correction of a water rate, which is added to a cylinder-individual base water rate.

[0040] Thus, according to the present invention, a method and apparatus can be provided that enable effective adjustment of a water rate upon the occurrence of an anomalous event in a cylinder. The water rate is preferably determined individually for each cylinder, thus enabling optimal use of the usually limited water supply, e.g., in a vehicle.

Claims

[1] Method for operating a gas internal combustion engine, comprising the steps: - Detection of an anomaly event during a combustion process in a cylinder of the gas combustion engine, - Counting the number of occurrences of the anomaly event in this cylinder, whereby a count value Z is incremented by 1 for each occurrence of the anomaly event, - when the count value Z reaches a threshold value S, starting a countdown counter (3) which begins with a predetermined first value A1 and determining a first quantity of water W1 to be injected into this cylinder during the next combustion process, - if the anomaly event occurs again during the next combustion process in this cylinder, the countdown counter (3) is increased by a predetermined second value A2, and a second water quantity W2 to be injected is determined based on the second value A2, and - if the anomaly event does not occur during the next combustion process in this cylinder, the countdown counter (3) is reduced by 1 and a third water quantity W3 to be injected is determined, - whereby a quantity of water to be injected is injected during subsequent combustion processes until the countdown counter (3) is zero. [2] The method of claim 1, wherein the anomaly event is knock or pre-ignition. [3] Method according to one of the preceding claims, wherein the gas internal combustion engine comprises a plurality of cylinders and the method is carried out individually for each cylinder. [4] The method of claim 3, wherein when the method detects an anomaly event in one cylinder, water injection occurs in the other cylinders in which no anomaly event occurs. [5] Method according to claim 4, wherein in the other cylinders in which no anomaly event occurs, the same amount of water W1 is injected as in the cylinder in which the anomaly event occurs. [6] A method according to claim 4 or 5, wherein the water injection into the other cylinders in which no anomaly event occurs is carried out until the countdown counter (3) is set to zero. [7] Method according to one of the preceding claims, wherein in the cylinder in which the anomaly event occurs, the first water quantity W1 is an additional water quantity injected in addition to a base water quantity or is a water quantity injected without a base water quantity. [8] Method according to one of the preceding claims, wherein the determination of the first water quantity W1 is determined from a water rate W of a characteristic curve KL dependent on the value of the countdown counter. [9] Method according to claim 8, wherein the first water quantity W1 is multiplied by a weighting factor GF. [10] Method according to claim 9, wherein the weighting factor GF is calculated from a first characteristic map K1 as a function of a load of the gas internal combustion engine and / or a speed of the gas internal combustion engine and / or a target or actual torque of the gas internal combustion engine and / or an air mass and / or a fuel mass and / or a relative air charge and / or a relative fuel quantity and / or a power of the gas internal combustion engine. [11] Device arranged to carry out a method according to one of the preceding claims.

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