Method for leak detection of a gas internal combustion engine

Abstract

Method for leak detection in a gas internal combustion engine while the gas internal combustion engine is in operation, comprising the steps of: providing a closed line section in a gas line (3) between a gas tank (2) and an injection device (5), measuring a first pressure value of a pressure of the gas in the closed line section of the gas line (3), comparing the first pressure value with a comparison pressure value and determining that a leak in the gas line (3) in the closed line section is present if the first pressure value is less than the comparison pressure value.

Description

[0001] The present invention relates to a method for leak detection of a gas internal combustion engine while the gas internal combustion engine is in operation, as well as a device for carrying out the method.

[0002] In gas-fired internal combustion engines, leaks in the injection system can occur during operation. These are often not detectable during operation. However, the gas leak can cause gas to accumulate outside the injection system and, in the worst case, create a flammable mixture. This poses the risk of ignition of a gas mixture outside the injection system, with correspondingly uncontrollable consequences. Disclosure of the invention

[0003] The inventive method for leak detection in a gas internal combustion engine during operation of the gas internal combustion engine with the features of claim 1 has the advantage that leaks can be detected during operation of the gas internal combustion engine. This allows gas losses, which under certain circumstances can form an ignitable mixture outside a gas line system of the gas internal combustion engine, to be prevented during operation. In particular, it is possible according to the invention for countermeasures to be taken to reduce gas leakage while the gas internal combustion engine is still in operation, in particular while driving a vehicle. Such countermeasures can be, for example, an additional pressure reduction of the gas injection pressure and / or a power reduction of the gas internal combustion engine. This allows the amount of leakage to be reduced directly.This is achieved according to the invention in that the method, in a first step, provides a closed line section with an enclosed gas volume in a gas line of the gas internal combustion engine. The gas line runs between a gas tank and an injection device, in particular an injection valve. The next step involves measuring a first pressure value of the pressure of the gas in the closed line section of the gas line. The first measured pressure value is then compared with a reference pressure value. Subsequently, it is determined that a leak exists in the gas line if the first pressure value is lower than the reference pressure value. To prevent an incorrect leak determination, it is preferable to work with a tolerance band around the measured first pressure value. The tolerance band is, for example, 10%, in particular 5%, of a predetermined target value in the gas line. Hydrogen is preferably used as the gas.As an alternative to the tolerance band, a threshold value can also be used. Preferably, the first stored pressure value is continuously compared with the currently prevailing pressure value throughout the process.

[0004] The method according to the invention is preferably carried out using conventionally available components or pressure sensors, which are provided on the gas line or on components provided in the gas line, such as a pressure limiter. This eliminates the need to provide additional components and / or sensors to carry out the method according to the invention.

[0005] The subclaims show preferred developments of the invention.

[0006] The method according to the invention is preferably carried out when the closed line section is provided with a closed injection device. This prevents distortion of the results due to injection processes of the gas internal combustion engine. Furthermore, leak detection can be carried out across an entire line section, from the gas tank to the injection device.

[0007] Preferably, the closed line section is provided by closing at least one valve. This allows the method according to the invention to be carried out particularly simply and cost-effectively.

[0008] Preferably, the step of closing a valve is performed by closing a tank valve, which is arranged in particular directly on the gas tank, so that the closed line region is preferably located between the tank valve and the injection device. Particularly preferably, at least one additional line valve, in particular at least two line valves, is arranged in the gas line to close the gas line between the tank valve and the injection device. The closed line region is preferably provided by closing the line valve.

[0009] Preferably, the closed line section is located between the line valve and the injection device. Alternatively or additionally, the closed line section is located between the tank valve and the line valve. By dividing the gas line into several closed line sections, which is possible by providing at least one or more line valves, several closed line sections can be defined by individually measuring a first pressure value in each of them. This makes it possible, in particular, to easily and quickly localize a possible leak in the gas line to one of the line sections. The pressure values ​​of the closed line sections are preferably compared with each other.

[0010] Particularly preferably, the closed line section is provided during overrun operation of the gas internal combustion engine when used in a vehicle. Alternatively, the closed line section is provided during a change in the injection mode of the gas internal combustion engine. When the injection mode changes, the injection device is closed.

[0011] Preferably, a pressure value measured during a previous measurement of the pressure in the closed line section is used as the reference pressure value. Particularly preferably, the pressure value determined during the last measurement is used as the reference pressure value. Alternatively or additionally, it is also possible to use an average of a predetermined number of the most recently measured pressure values, e.g., the last ten measured pressure values. Alternatively or additionally, a stored target pressure value is used as the reference pressure value. The target pressure value can, for example, have been determined through tests or calculations. The target pressure value is preferably temperature-dependent and is adjusted according to a temperature correction factor when the temperature changes.

[0012] Preferably, the reference pressure value is determined by monitoring a pressure curve of the line pressure in the closed line section over a period of time during which the closed pressure range was maintained. Only if the pressure deviates between a pressure value at the beginning of the period and a pressure value at the end of the period is a comparison made. In the event of a deviation, a leak is concluded, preferably taking a tolerance into account.

[0013] Preferably, the comparison pressure value is an average of previously measured first pressure values.

[0014] According to a further preferred embodiment of the invention, a correction factor for the measured first pressure value and / or the comparison pressure value is used in the leakage determination, wherein the correction factor is temperature-dependent.

[0015] The gas with which the energy converter is operated is preferably hydrogen or natural gas or CNG or LPG or methane or ethanol.

[0016] Furthermore, the present invention relates to a device, in particular a gas internal combustion engine arrangement of a vehicle, designed to carry out the method according to the invention. drawing

[0017] 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 an apparatus for carrying out the method according to the invention according to a preferred embodiment of the invention. Preferred embodiments of the invention

[0018] The following is based on reference to Fig. 1 a method for leak detection in a gas internal combustion engine 1 and a device for carrying out the method are described in detail.

[0019] The Fig. The gas internal combustion engine 1 shown schematically in FIG. 1 is a gas-powered internal combustion engine. The internal combustion engine is preferably powered by hydrogen, but can also be powered by another gaseous fuel.

[0020] A gas tank 2 is provided to supply the gas-fired internal combustion engine 1. The gas tank 2 is connected to the gas-fired internal combustion engine 1 via a gas line 3. The gas line 3 opens into a rail 14, which is connected to several combustion chambers 8 to supply the combustion chambers with fuel gas.

[0021] At least one injection device 5, preferably an injection valve, is arranged on each combustion chamber 8.

[0022] A tank valve 4 is located at the outlet of the gas tank 2 to the gas line 3. The tank valve 4 can open and close a connection between the gas tank 2 and the gas line 3.

[0023] A pressure regulator 7 is also arranged in the gas line 3. The pressure regulator 7 is designed to regulate the gas pressure in the gas line to a predetermined pressure level before it reaches the gas-fired internal combustion engine 1. A first pressure sensor 11 is arranged in the gas line upstream of the pressure regulator 7, and a second pressure sensor 12 is arranged in the gas line downstream of the pressure regulator 7. The pressure regulator 7 and the pressure sensors 11, 12 are connected to a control unit 10.

[0024] A third pressure sensor 13 is arranged in the rail 14.

[0025] The pressure regulator 7 is designed to regulate a gas pressure in the gas line upstream of the injection devices 5 to a predetermined pressure level.

[0026] Furthermore, a line valve arrangement 6 with a first line valve 6.1 and a second line valve 6.2 is arranged in the gas line 3. The two line valves 6.1 and 6.2 are arranged in series in the gas line 3 between the tank valve 4 and the injection device 5.

[0027] More precisely, the two line valves 6.1 and 6.2 are arranged between the pressure regulator 7 and the injection device 5. A fourth pressure sensor 15 is arranged between the first and second line valves 6.1, 6.2.

[0028] The tank valve 4, the injection devices 5, the line valves 6.1 and 6.2, the internal combustion engine and all pressure sensors are connected to the control unit 10.

[0029] During normal operation of the gas internal combustion engine 1, the tank valve 4 and the line valves 6.1 and 6.2 are open so that gas from the gas tank 2 can reach the rail 14 via the pressure regulator 7 and can be injected into the combustion chambers 8 via the injection devices 5.

[0030] In the method according to the invention for leak detection in the gas line 3, a first step is to create a sealed line section in the gas line 3 in which a trapped gas volume is present. The sealed line section is located between the tank valve 4 and the injection devices 5.

[0031] By providing the two line valves 6.1 and 6.2, if the line valves 6.1 and 6.2 are also closed, several closed line sections can be created in the gas line 3. For leak detection, it is only necessary that at least one pressure sensor is arranged in each closed line section. If necessary, the pressure regulator 7 can also be closed, which would allow for another closed line section.

[0032] In the next step, an initial pressure value is measured in the closed pipe section. Of course, if there are multiple closed pipe sections, an initial pressure value can be measured in each closed pipe section.

[0033] The measured first pressure value is then compared with a reference pressure value. The reference pressure value is preferably a pressure value measured in a previous measurement process. Alternatively, the reference pressure value is a stored target pressure value or an average of a plurality of measured first pressure values ​​over a period of time.

[0034] Subsequently, by comparing the first pressure value with the reference pressure value, it is determined whether or not a leak exists in the sealed section of the gas line. A leak is usually present if the first pressure value is lower than the reference pressure value.

[0035] It should be noted that, as in Fig.1, where it is possible to provide several closed pipe sections, a comparison between the individual first pressure values ​​of the respective closed pipe sections is also possible and, in the event of a deviation between measured first pressure values, it can be concluded that there is a leak in one or more of the closed pipe sections.

[0036] If the method according to the invention is applied in a vehicle, this can be performed, for example, during each overrun of the gas engine. Thus, a check of the gas line 3 for any existing leaks can be carried out even while driving.

[0037] Checking while the vehicle is moving has the advantage that countermeasures can be taken to reduce a leak while the vehicle is in motion. One countermeasure, for example, is an additional pressure reduction via pressure regulator 7. Furthermore, a warning signal can be sent to a vehicle user that there is a gas leak in the gas line, allowing the user to immediately stop the vehicle and stop operating it.

[0038] Thus, according to the invention, by closing valves, one or more closed pipeline sections can be created in which leakage detection is possible. Leakage detection can preferably be carried out exclusively using pressure sensors, which are usually already present in the gas pipeline system. This minimizes the investment costs for implementing the method according to the invention.

[0039] Further preferably, a correction factor can be used when determining leakage if there is a significant difference in temperature between the measurement of the first pressure value and a measurement of the reference pressure value. This eliminates measurement errors resulting from different temperatures during the measurement.

[0040] Thus, according to the invention, even smaller losses in the gas line 3 can be detected. For leak detection, operating phases of the gas combustion engine are used in which no gas injection occurs. This can be, on the one hand, overrun mode or, on the other hand, for example, a change in the injection mode of the gas combustion engine. Thus, according to the invention, a very accurate statement regarding the tightness of the gas system can be made without additional expensive sensors. This allows even spontaneously occurring leaks to be detected immediately, and appropriate safety measures to be initiated.

[0041] Leak detection can also be carried out if there are several injection valves per cylinder and a rail is used, even if not all injection valves are used for the injection process.

[0042] Furthermore, it is possible to carry out the leak detection method according to the invention in a forced-controlled manner, for example after a predetermined period of use of the gas internal combustion engine.

Claims

[1] A method for leak detection in a gas internal combustion engine while the gas internal combustion engine is in operation, comprising the steps: - Providing a closed line section in a gas line (3) between a gas tank (2) and an injection device (5), - measuring a first pressure value of a pressure of the gas in the closed line section of the gas line (3), - Comparing the first pressure value with a reference pressure value and - Determining that there is a leak in the gas line (3) in the closed line section if the first pressure value is less than the reference pressure value. [2] Method according to claim 1, wherein the closed line region is provided in a closed injection device (5). [3] Method according to one of the preceding claims, wherein the closed line region is provided by closing at least one valve. [4] Method according to claim 3, wherein the step of closing the valve comprises the step of closing a tank valve (4) arranged on the gas tank (2) so that the closed line region lies between the tank valve (4) and the injection device (5). [5] Method according to claim 4, wherein at least one line valve (6.1, 6.2) is arranged in the gas line (3) and wherein the closed line region lies between the line valve (6.1, 6.2) and the injection device (5) and / or wherein the closed line region lies between the tank valve (4) and the line valve (6.1, 6.2). [6] Method according to one of the preceding claims, wherein the closed line region is provided during a coasting operation of a vehicle in which the gas internal combustion engine is used, or wherein the closed line region is used during a change of an injection mode, wherein the injection device (5) is closed during the change. [7] Method according to one of the preceding claims, wherein the comparison pressure value is a pressure value which was measured during a previous measurement of the pressure in the closed line region, in particular the pressure value of the last measuring process, and / or wherein the comparison pressure value is a stored target pressure value. [8] Method according to one of the preceding claims, wherein the comparison pressure value is an average value of previously measured first pressure values. [9] Method according to one of the preceding claims, wherein a temperature correction factor is used in the leakage determination if a temperature during the measurement of the first pressure value deviates from a temperature during the measurement of the comparison pressure value or the predetermined target pressure value. [10] Device arranged to carry out a method according to one of claims 1 to 9.

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