Internal combustion engine

Abstract

To provide an internal combustion engine that has high cost effectiveness and can easily detect leakage in a valve of a fuel supply system to avoid damage in a wide range and a risk of potential safety.SOLUTION: An internal combustion engine for vessel propulsion includes at least one cylinder and a fuel supply system. The fuel supply system includes: a first cylinder fuel supply passage including a first main valve and a first auxiliary valve disposed upstream of the first main valve; and a second cylinder fuel supply passage including a second main valve and a second auxiliary valve disposed upstream of the second main valve. A first pressure sensor providing a first pressure signal is disposed between the first main valve and the first auxiliary valve, and a second pressure sensor providing a second pressure signal is disposed between the second main valve and the second auxiliary valve. The internal combustion engine further includes a comparison unit that compares the first pressure signal with the second pressure signal in order to detect non-correspondence between the first and second pressure signals. This invention also relates to a leakage detection method for detecting leakage in a valve of the fuel supply system and a computer program product.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an internal combustion engine for the propulsion of a ship, having at least one cylinder.The present invention also relates to a leak detection method and a computer program product for detecting leaks in valves in a fuel supply system. [Background technology]

[0002] When designing ships such as container ships or tankers, the primary focus is to operate in a cost-effective manner while preventing safety and environmental damage on board. To operate in a safe and cost-effective manner, it is important to detect failures in engine components before they fail to the point that they require replacement, and before the failure affects other engine components.

[0003] Small leaks in fluid passages, valves, etc. are difficult to detect but significant because the leak is small and the damage is so minimal that it only requires a minor repair or replacement, such as of the leaking valve, and not the associated parts. However, if the leak is not detected while it is small, the repairs can be much more extensive and expensive, and the vessel may even be prevented from operating while the repairs are made. Summary of the Invention [Problem to be solved by the invention]

[0004] It is an object of the present invention to overcome, in whole or in part, the above-mentioned disadvantages and drawbacks of the prior art, and more specifically to provide an improved internal combustion engine that can detect valve leaks in the fuel delivery system in a simple manner to avoid extensive damage and potential safety hazards, while still being cost-effective. [Means for solving the problem]

[0005] The above objects, together with numerous other objects, advantages, and features which will become apparent from the following description, are achieved by an internal combustion engine for propulsion of a marine vessel, the internal combustion engine having at least one cylinder, - a fuel supply system, a first cylinder fuel supply passage including a first main valve and a first secondary valve disposed upstream of the first main valve; a second cylinder fuel supply passage including a second main valve and a second auxiliary valve disposed upstream of the second main valve; a fuel supply system comprising: a first pressure sensor providing a first pressure signal is disposed between the first main valve and the first sub-valve, and a second pressure sensor providing a second pressure signal is disposed between the second main valve and the second sub-valve; This is achieved by the solution according to the invention with an internal combustion engine further comprising a comparison unit for comparing the first pressure signal with the second pressure signal in order to detect a discrepancy between the first pressure signal and the second pressure signal.

[0006] Additionally, the at least one cylinder may be a first cylinder, and the internal combustion engine may further include a second cylinder.

[0007] Additionally, a first cylinder fuel supply passage supplies fuel to one of the first and second cylinders, and a second cylinder fuel supply passage supplies fuel to one of the first and second cylinders.

[0008] In another internal combustion engine for propulsion of a marine vessel, the internal combustion engine may have at least a first cylinder and a second cylinder; - a fuel supply system, a first cylinder fuel supply passage for supplying fuel to one of the first and second cylinders, the first cylinder fuel supply passage including a first main valve and a first secondary valve disposed upstream of the first main valve; a second cylinder fuel supply passage for supplying fuel to one of the first and second cylinders, the second cylinder fuel supply passage including a second main valve and a second auxiliary valve disposed upstream of the second main valve; a fuel supply system comprising: a first pressure sensor providing a first pressure signal is disposed between the first main valve and the first sub-valve, and a second pressure sensor providing a second pressure signal is disposed between the second main valve and the second sub-valve; The internal combustion engine further comprises a comparison unit that compares the first pressure signal with the second pressure signal to detect a discrepancy between the first pressure signal and the second pressure signal.

[0009] When an internal combustion engine operates at low load and / or low pressure, the pressure in the fuel supply system does not increase to the same extent, such as 300 bar, when the valve is closed as when the engine operates at high load or pressure. Therefore, more conventional methods of leak detection do not work effectively. However, by measuring and comparing the pressure, or a representation thereof, between the main and secondary valves in both the first and second cylinder fuel supply passages, small leaks or malfunctions can be detected because environmental factors, such as low pressure and low load, affect the pressure in each of the first and second cylinder fuel supply passages equally, and therefore the pressure increase does not need to be as high to detect even small leaks.

[0010] By measuring and comparing the pressure, or a representation thereof, between the main and sub-valves in both the first and second cylinder fuel supply passages, the pressure signals can be compared so that even if the pressure signals change, even if the supply pressure changes, or other factors around the fuel supply system change, the correlation between the pressure signals will be fairly stable, allowing leaks or malfunctions, albeit still very small, to be detected.

[0011] The method results in an improved internal combustion engine in which leaking or faulty valves in the fuel supply system can be detected in a simple manner, and such detection can prevent widespread damage and safety risks, which means that the internal combustion engine is more cost-effective because repairs or replacement of leaking or faulty valves can be carried out before major damage occurs.

[0012] In known internal combustion engines, leak detection of valves in fuel supply passages that supply fuel to cylinders is performed using several tests, such as a volumetric test, a drop test, a curve fit test, a fluctuation test, and a maximum pressure test, so that leaks or malfunctions can be detected at an early stage. In particular, the curve fit test has been found to be inappropriate for engines operating at low pressures and low loads. The present invention requires only one test.

[0013] Additionally, the first cylinder fuel supply passage can be in fluid communication with the first cylinder, and the second cylinder fuel supply passage can be in fluid communication with either the first cylinder or the second cylinder.

[0014] Additionally, the first cylinder fuel supply passage can be fluidly connected to the first cylinder for injection of fuel into the first cylinder, and the second cylinder fuel supply passage can be fluidly connected to the first cylinder for injection of fuel into the first cylinder, or the second cylinder fuel supply passage can be fluidly connected to the second cylinder for injection of fuel into the second cylinder.

[0015] Additionally, the fuel delivery system may include a main supply passage fluidly connected with the first cylinder fuel delivery passage and the second cylinder fuel delivery passage.

[0016] Additionally, the main supply passage is disposed upstream of the first cylinder fuel supply passage and the second cylinder fuel supply passage.

[0017] Additionally, the fuel supply system may include a pump, and the main supply passage may be fluidly connected to the pump for pumping fuel to both the first cylinder fuel supply passage and the second cylinder fuel supply passage.

[0018] Additionally, the fuel supply system may include a pressure control valve, and the main supply passage may be fluidly connected to the pressure control valve to control fuel to both the first cylinder fuel supply passage and the second cylinder fuel supply passage.

[0019] Additionally, the first pressure sensor may measure a real-time and / or continuous first pressure signal, and the second pressure sensor may measure a real-time and / or continuous second pressure signal.

[0020] Additionally, the fuel can be propane, butane, methanol, methane, ethanol, ethene, ethane, ammonia, propylene, butylene, isobutane, n-butane, hydrogen, kerosene, nitromethane, liquefied petroleum gas, bioethanol, or biodiesel.

[0021] Additionally, the fuel may be the only fuel supplied to at least one cylinder.

[0022] Additionally, the fuel may be a secondary fuel, and the primary fuel may be diesel, gasoline, or petroleum.

[0023] Additionally, the primary fuel may have a sulfur content of at least 0.05%.

[0024] Furthermore, the fuel may be liquid or gaseous.

[0025] Additionally, the main valve may have an open time period that is shorter than the open time period of the secondary valve.

[0026] Additionally, the secondary valve may open before the main valve opens.

[0027] Book inventionBy using the measurement and comparison of the pressure, leaks or malfunctions, especially in secondary valves, can be monitored and detected, which is very difficult in known systems where curve-fit testing is performed. When using curve-fit testing, the measured pressure is usually compared to a reference curve, but external factors such as operation at low load or low pressure will affect the results, so the interval by which the measured pressure differs from the reference curve needs to be very wide to accommodate engine operation at low load and low pressure. When the interval needs to be wide to prevent the engine from being unintentionally shut down, small leaks will not be detected. Leaks in secondary valves, also known as window valves, can be a potential safety hazard, so it is important to detect such leaks at an early stage.

[0028] Additionally, the secondary valve may be open while the main valve is closed.

[0029] Additionally, the secondary valve may be closed while the main valve is closed.

[0030] Additionally, the main valve may be open and / or closed while the secondary valve is open.

[0031] Moreover, the first pressure signal may form a first pattern, and the second pressure signal may form a second pattern, and the comparison unit may compare the first pattern with the second pattern to detect a correlation and verify whether the correlation is within a predetermined interval.

[0032] "Correlation" means any statistical relationship, such as the statistical variance between two sets of pressure signal data, i.e., any type of association that refers to the degree to which pairs of variables are linearly related.

[0033] Furthermore, the comparison unit may be a central processing unit (CPU), a control unit, an integrated circuit such as a microchip or chip, a comparator unit, or a hardware or software based comparator.

[0034] The comparison unit may also include pattern recognition software.

[0035] Additionally, the internal combustion engine may also include a third and fourth cylinder fed by two fuel supply passages, each having a pressure sensor, a secondary valve, and a main valve.

[0036] Additionally, the internal combustion engine may also have at least six cylinders.

[0037] Additionally, the first pressure signal may have a predetermined number of data points in a predetermined time period.

[0038] Additionally, the second pressure signal may have a predetermined number of data points in a predetermined time period.

[0039] Additionally, the predetermined time period may be from one operating position of one of the valves to the same operating position being performed again.

[0040] The predetermined time period may also be from the closing of the secondary valve to the next closing of the secondary valve.

[0041] Moreover, the combustion engine system may further comprise a turbocharger disposed downstream of the internal combustion engine.

[0042] Additionally, the turbocharger may include a turbine and a compressor.

[0043] Additionally, the present invention provides a leak or malfunction detection method for detecting a leak or malfunction in a valve in a fuel supply system for supplying fuel to at least one cylinder of an internal combustion engine, comprising: - measuring a first pressure signal over a first time period with a first pressure sensor in a first cylinder fuel supply passage of the fuel supply system between a first main valve and a first auxiliary valve; - measuring a second pressure signal by a second pressure sensor in a second cylinder fuel supply passage of the fuel supply system between the second main valve and the second auxiliary valve during the first time period or the second time period; - comparing the first pressure signal with the second pressure signal to detect a leak in one of the valves or a malfunction of one of the valves; The present invention relates to a method for detecting a leak or defect, including:

[0044] Furthermore, the invention relates to a computer program product comprising a computer readable medium carrying computer program code means which, when loaded, cause a computer to carry out the method for detecting leaks or malfunctions.

[0045] Furthermore, the internal combustion engine may be a large two-stroke internal combustion engine.

[0046] Additionally, the internal combustion engine may be a large turbocharged two-stroke internal combustion engine of the crosshead type.

[0047] Furthermore, the internal combustion engine may be a two-stroke or a four-stroke internal combustion engine.

[0048] The invention and its advantages will be explained in more detail below with reference to the accompanying schematic drawings which show, for illustrative purposes, some non-limiting embodiments. [Brief explanation of the drawings]

[0049] [Figure 1] 1 is a schematic diagram of a fuel supply system for an internal combustion engine; [Figure 2] 2 is a schematic diagram of another fuel supply system for an internal combustion engine. [Figure 3] 1 is a schematic diagram of yet another fuel delivery system for an internal combustion engine. [Figure 4] FIG. 4 is a schematic diagram of a first pressure signal and a second pressure signal. DETAILED DESCRIPTION OF THE INVENTION

[0050] All figures are schematic, not necessarily to scale, and show only those parts that are necessary to clarify the invention, other parts being omitted or only suggested.

[0051] FIG. 1 is a schematic diagram of a fuel supply system 4 of an internal combustion engine 1 for propulsion of a vessel, such as a container ship or a tanker. The internal combustion engine 1 may be a stationary engine. Thus, the internal combustion engine 1 may be a two-stroke or four-stroke internal combustion engine 1. The internal combustion engine 1 comprises a first cylinder 2 and a fuel supply system 4. The fuel supply system 4 comprises a first cylinder fuel supply passage 5, 5a for supplying fuel to the first cylinder 2 and a second cylinder fuel supply passage 5, 5b for supplying fuel to the first cylinder 2. Thus, the first cylinder fuel supply passage 5, 5a is in fluid communication with the first cylinder 2 for injection of fuel into the first cylinder 2, and the second cylinder fuel supply passage 5, 5b is in fluid communication with the same first cylinder 2 for injection of fuel into the first cylinder 2 at different positions along the circumference of the first cylinder 2. The first cylinder fuel supply passage 5, 5a includes a first main valve 6, 6a and a first sub-valve 7, 7a located upstream of the first main valve 6, 6a. The second cylinder fuel supply passage 5, 5b includes a second main valve 6, 6b and a second sub-valve 7, 7b located upstream of the second main valve 6, 6b. The fuel supply system 4 further includes a first pressure sensor 8, 8a providing a first pressure signal 9, 9a, the first pressure sensor 8, 8a being arranged to measure the pressure between the first main valve 6, 6a and the first sub-valve 7, 7a. The fuel supply system 4 also includes a second pressure sensor 8, 8b providing a second pressure signal 9, 9b, the second pressure sensor being arranged to measure the pressure between the second main valve 6, 6b and the second sub-valve 7, 7b. The internal combustion engine 1 further comprises a comparison unit 10 that compares the first pressure signal 9, 9a with the second pressure signal 9, 9b to detect a discrepancy between the first pressure signal 9, 9a and the second pressure signal 9, 9b, which discrepancy indicates a leak in one of the valves 6, 6a, 6b, 7, 7a, 7b. The comparison unit 10 receives the first pressure signal 9, 9a from the first pressure sensor 8, 8a and the second pressure signal 9, 9b from the second pressure sensor 8, 8b, as indicated by the dotted lines in Figure 1.

[0052] Small leaks in, or failures of, the main valves 6, 6a, 6b or secondary valves 7, 7a, 7b are difficult to detect but significant because the leaks are small and the damage is so minimal that it only requires minor repairs or replacement of the leaking valve. Furthermore, leaks in, or failures of, secondary valves 7, 7a, 7b can pose a potential safety hazard. However, if the leak or failure is not detected while it is small, repairs can be much more extensive and costly, and the vessel may even be prevented from operating while repairs are made.

[0053] When the internal combustion engine 1 operates at low load and / or pressure, the pressure in the fuel supply system 4 does not increase to the same extent, such as 300 bar, when the valves 6, 7 are closed as when the engine operates at high load or pressure. Therefore, more conventional methods of leak detection do not work effectively enough.

[0054] In known internal combustion engines, leak detection of valves in fuel supply passages that supply fuel to cylinders is performed using several tests, such as volumetric tests, drop tests, curve fit tests, fluctuation tests, and maximum pressure tests, so that leaks or malfunctions can be detected at an early stage. In particular, the curve fit test has been found to be inappropriate for engines operating at low pressures and low loads.

[0055] However, by measuring and comparing the pressure or a representation thereof between the main valve 6 and the secondary valve 7 in both the first cylinder fuel supply passage 5, 5a and the second cylinder fuel supply passage 5, 5b, small leaks or malfunctions can be detected because ambient factors such as low load and low pressure affect the pressure in each of the first cylinder fuel supply passage 5, 5a and the second cylinder fuel supply passage 5, 5b equally and therefore the increase in pressure does not need to be as high to detect even small leaks or any malfunctions.

[0056] By measuring the pressure, or a representation thereof, between the main valve 6, 6a, 6b and the sub-valve 7, 7a, 7b in both the first cylinder fuel supply passage 5, 5a and the second cylinder fuel supply passage 5, 5b, the pressure signals can be compared, so that even if the pressure signals 9a, 9b change, even if the supply pressure changes or other factors around the fuel supply system 4 change, the correlation between the pressure signals will be fairly stable, allowing even very small leaks or malfunctions to be detected. In this way, an improved internal combustion engine 1 is obtained in which leaks or malfunctions of valves 6, 7 in the fuel supply system 4 can be detected in a simple manner, which can prevent widespread damage and safety risks. This means that the internal combustion engine 1 is more cost-effective, as repairs or replacements of leaking or malfunctioning valves 6, 7 can be carried out before major damage occurs. Furthermore, the present invention requires only one test.

[0057] The main valves 6, 6a, and 6b have an open time period shorter than the open time period of the sub-valves 7, 7a, and 7b. The sub-valves 7, 7a, and 7b open before the main valves 6, 6a, and 6b open, and therefore also provide a window for fluid communication to the main valves 6, 6a, and 6b, and are therefore referred to as window valves. Thus, the sub-valves 7, 7a, and 7b open while the main valves 6, 6a, and 6b are closed, and the sub-valves 7, 7a, and 7b close while the main valves 6, 6a, and 6b are closed. The main valves 6, 6a, and 6b open and / or close while the sub-valves 7, 7a, and 7b are open.

[0058] The first pressure sensor 8, 8a measures a real-time and / or continuous first pressure signal 9, 9a, and the second pressure sensor 8, 8b measures a real-time and / or continuous second pressure signal 9, 9b. In this way, a leak or fault can be detected, although still very small, at any time during the sequence, because the pressure signals 9, 9a, 9b can be compared at any given time during the sequence of opening and closing of the valves 6, 6a, 6b, 7, 7a, 7b.

[0059] In FIG. 2 , an internal combustion engine 1 includes a first cylinder 2 and a second cylinder 3. A fuel supply system 4 includes a first cylinder fuel supply passage 5, 5a for supplying fuel to the first cylinder 2 and a second cylinder fuel supply passage 5, 5b for supplying fuel to the second cylinder 3. The first cylinder fuel supply passage 5, 5a includes a first main valve 6, 6a, a first pressure sensor 8, 8a, and a first auxiliary valve 7, 7a, and the second cylinder fuel supply passage 5, 5b includes a second main valve 6, 6b, a second pressure sensor 8, 8b, and a second auxiliary valve 7, 7b. The first cylinder fuel supply passage 5, 5a is in fluid communication with the first cylinder 2 for injection of fuel into the first cylinder 2, and the second cylinder fuel supply passage 5, 5b is in fluid communication with the second cylinder 3 for injection of fuel into the second cylinder 3. 2, a comparison unit 10 compares a first pressure signal 9, 9a from a first pressure sensor 8, 8a with a second pressure signal 9, 9b from a second pressure sensor 8, 8b to detect discrepancies between the first pressure signal 9, 9a and the second pressure signal 9, 9b. The first pressure signal 9, 9a corresponds to the pressure measured in a first cylinder fuel supply passage 5, 5a that provides fuel to a first cylinder 2, and the second pressure signal 9, 9b corresponds to the pressure measured in a second cylinder fuel supply passage 5, 5b that provides fuel to a second cylinder 3. Because fuel is injected into the first cylinder 2 before being injected into the second cylinder 3, the peaks of the first pressure signal 9, 9a are shifted in time with respect to the peaks of the second pressure signal 9, 9b.

[0060] 1-3, fuel delivery system 4 further includes a main supply passage 12 fluidly connected with first cylinder fuel supply passage 5, 5a and second cylinder fuel supply passage 5, 5b for supplying fuel from pump 11. Thus, main supply passage 12 is located upstream of first cylinder fuel supply passage 5, 5a and second cylinder fuel supply passage 5, 5b. Although the pressure of fuel entering first cylinder fuel supply passage 5, 5a may vary slightly from the pressure of fuel entering second cylinder fuel supply passage 5, 5b, the correlation between first pressure signal 9, 9a and second pressure signal 9, 9b will be the same when the difference in pressure is substantially the same. Comparing the first pressure signal 9, 9a with the second pressure signal 9, 9b still provides an early warning of a leak in one of the valves 6, 6a, 6b, 7, 7a, 7b or a malfunction of one of the valves 6, 6a, 6b, 7, 7a, 7b, and therefore detection of a leak or malfunction is independent of such pressure changes in the main supply passage 12.

[0061] The internal combustion engine 1 of Figure 3 has four cylinders: a first cylinder 2, a second cylinder 3, a third cylinder 14, and a fourth cylinder 15. Both the third cylinder 14 and the fourth cylinder 15 are fed with fuel from two fuel supply passages 5, 5a, and 5b via a first portion 12a and a second portion 12b of a main supply passage 12. Each of the two fuel supply passages 5, 5a, and 5b has a pressure sensor 8, a secondary valve 7, and a main valve 6. The fuel supply system 4 includes a pump 11 that supplies fuel to all four cylinders 2, 3, 14, and 15 through the fuel supply passages 5, 5a, and 5b.

[0062] 4, the first pressure signals 9, 9a form a first pattern P1, and the second pressure signals 9, 9b form a second pattern P2. Comparing the first pattern P1 with the second pattern P2 results in a correlation. A comparison unit 10 compares the first pattern P1 with the second pattern P2 to detect the correlation. If the correlation is within a predetermined interval, the valves 6, 6a, 6b, 7, 7a, 7b operate as planned, but if the correlation is outside the predetermined interval, there may be a leak in one of the valves 6, 6a, 6b, 7, 7a, 7b or there may be a malfunction in one of the valves 6, 6a, 6b, 7, 7a, 7b. In Figure 4, the correlation is smaller for the second pressure signals 9, 9b than for the first pressure signals 9, 9a. When the first pressure signals 9, 9a and the second pressure signals 9, 9b are continuously measured and compared, the patterns P1, P2 remain the same, and the correlation remains the same as long as the valves 6, 6a, 6b, 7, 7a, 7b are operating as planned without any leaks or malfunctions, as shown in Figure 4. If one of the first main valves 6, 6a or the first sub-valves 7, 7a is not operating according to plan, the first pressure signals 9, 9a will change the first pattern P1, and the correlation will fall outside the predetermined interval. Since the first pattern P1 may change due to pressure fluctuations somewhere in the fuel supply system 4, such fluctuations will also affect the second pattern P2, and when comparing the first pressure signal 9, 9a with the second pressure signal 9, 9b, if the change is due to other changes somewhere in the fuel supply system 4 and not due to a malfunction in one of the main valves 6, 6a, 6b or the secondary valves 7, 7a, 7b, the correlation will be the same and within a predetermined interval. Therefore, when comparing the continuously measured first and second pressures, i.e., when comparing the first pressure signal 9, 9a and the second pressure signal 9, 9b, other system changes are smoothed out, so that the predetermined interval of correlation can be set very narrowly, and by comparing the first pressure signal 9, 9a and the second pressure signal 9, 9b, small changes resulting from leaks in the main valves 6, 6a, 6b or the sub-valves 7, 7a, 7b or malfunctions of the main valves 6, 6a, 6b or the sub-valves 7, 7a, 7b can be detected early.If the first pressure signal 9, 9a type is compared with other pressure signals, system changes may affect only one of the pressure signals, and so the correlation interval would need to be set fairly wide as operation would be stopped too frequently, so small leaks or malfunctions would not be detected as early as when the first pressure signal 9, 9a is compared with the second pressure signal 9, 9b.

[0063] In Fig. 4, the first pressure signal 9, 9a has a predetermined number of data points in a predetermined time period when measured continuously in real time. The second pressure signal 9, 9b is illustrated by a dotted line, but the second pressure signal 9, 9b also has a predetermined number of data points in a predetermined time period when measured continuously in real time. The predetermined time period can be from the closing of the sub-valve 7, 7a, 7b (indicated by arrow C2 in Fig. 4) to the next closing of the sub-valve 7, 7a, 7b, as shown in Fig. 4, or any other period from one operating position to the reoccurrence of the same operating position. That is, it can be a series including one or all of the operating positions of the valves 6, 6a, 6b, 7, 7a, 7b, meaning and counting all operating positions of the main valves 6, 6a, 6b both open and closed and all operating positions of the sub-valves 7, 7a, 7b both open and closed. Closing of the main valves 6, 6a, 6b is illustrated by arrow C1, opening of the main valves 6, 6a, 6b is illustrated by arrow O1, opening of the secondary valves 7, 7a, 7b is illustrated by arrow O2, and closing of the secondary valves 7, 7a, 7b is illustrated by arrow C2. The predetermined time period may be a period shorter than a sequence including one or all of the operating positions of the valves 6, 6a, 6b, 7, 7a, 7b, for example, from the closing of the main valves 6, 6a, 6b as illustrated by arrow C1 to the closing of the secondary valves 7, 7a, 7b as illustrated by arrow C2.

[0064] Two similar valves 6, 6a, 6b, 7, 7a, 7b never function in exactly the same way and changes will occur from one fuel supply passage 5, 5a, 5b to another fuel supply passage 5, 5a, 5b when setting up the fuel supply system 4 and cylinders 2, 3, 14, 15 etc. By measuring and comparing the pressure in two equivalent passages 5, 5a, 5b, leaks in either the main valves 6, 6a, 6b or the sub-valves 7, 7a, 7b or malfunctions of either the main valves 6, 6a, 6b or the sub-valves 7, 7a, 7b can be detected at an early stage. The changes in the pressure signals 9, 9a, 9b may be pressure changes due to the settings of the internal combustion engine 1 or the valves 6, 6a, 6b, 7, 7a, 7b themselves, but when the internal combustion engine 1 or valves 6, 6a, 6b, 7, 7a, 7b are installed and operating as intended, the pressure signal 9, 9a, 9b for one fuel supply passage 5, 5a, 5b with both a main valve 6, 6a, 6b and a secondary valve 7, 7a, 7b will change in the same way as the other fuel supply passage 5, 5a, 5b with both a main valve 6, 6a, 6b and a secondary valve 7, 7a, 7b.

[0065] As noted above, fuel is injected into the first cylinder 2 before being injected into the second cylinder 3, so that the peaks of the first pressure signal 9, 9a are offset in time relative to the peaks of the second pressure signal 9, 9b. Thus, by measuring and comparing the pressure in two equivalent passages 5, 5a, 5b, if one supply passage 5, 5a, 5b supplies fuel to the first cylinder 2 and the other supply passage 5, 5a, 5b supplies fuel to the second cylinder 3, the first pressure signal 9, 9a will be offset in time from the second pressure signal 9, 9b. When comparing these pressure signals 9, 9a, 9b, the first pressure signal 9, 9a will be offset in time to match the pattern / sequence of the second pressure signal 9, 9b so that the opening and closing of the valves 6, 6a, 6b, 7, 7a, 7b are aligned.

[0066] The comparison unit 10 can be a central processing unit (CPU), a control unit, a comparator unit, or a hardware or software based comparator. The comparison unit 10 can use pattern recognition software.

[0067] The fuel supplied through the main supply passage 12 can be propane, ethene, ethane, butane, methanol, methane, ethanol, ammonia, propylene, butylene, isobutane, n-butane, hydrogen, kerosene, nitromethane, liquefied petroleum gas, bioethanol, or biodiesel. Thus, the fuel can be the only fuel supplied to the cylinders 2, 3, 14, 15, or it can be a secondary fuel, with the primary fuel being diesel, gasoline, or petroleum. The fuel can be liquid or gaseous. Thus, the primary fuel can have a sulfur content of at least 0.05%.

[0068] The present invention also relates to a leak detection method for detecting leaks in valves 6, 6a, 6b, 7, 7a, 7b in a fuel supply system 4 for at least a first cylinder 2 and a second cylinder 3 of an internal combustion engine 1, in which a first pressure signal 9, 9a is measured in a first cylinder fuel supply passage 5, 5a of the fuel supply system 4 by a first pressure sensor 8, 8a between a first main valve 6, 6a and a first auxiliary valve 7, 7a during a first time period, and a second pressure signal 9, 9b is measured in a second cylinder fuel supply passage 5, 5b of the fuel supply system 4 by a second pressure sensor 8, 8b between a second main valve 6, 6b and a second auxiliary valve 7, 7b during the first time period or a second time period, and the first pressure signal 9, 9a is compared with the second pressure signal 9, 9b to detect a leak in one of the valves 6, 6a, 6b, 7, 7a, 7b.

[0069] The invention also relates to a computer program product comprising a computer readable medium carrying computer program code means, said computer program product being adapted to cause a computer to carry out a leak detection method when loaded.

[0070] While the present invention has been described above in connection with preferred embodiments thereof, it will be apparent to those skilled in the art that several modifications are possible without departing from the invention as defined by the following claims. [Explanation of symbols]

[0071] 1. Internal combustion engine 2. First cylinder 3 Second Cylinder 4 Fuel supply system 5, 5a First cylinder fuel supply passage 5, 5b Second cylinder fuel supply passage 6, 6a First main valve 6, 6b Second main valve 7, 7a First sub-valve 7, 7b Second sub-valve 8, 8a First pressure sensor 8, 8b Second pressure sensor 9, 9a First pressure signal 9, 9b Second pressure signal 10 Comparison Units 11 Pump 12 Main supply passage 12a First Section 12b Second Part 14 Third Cylinder 15 Fourth Cylinder C1 Close main valves 6, 6a, and 6b C2 Close sub-valves 7, 7a, and 7b O1 Open main valves 6, 6a, and 6b Open O2 sub-valves 7, 7a, and 7b P1 First pattern P2 Second pattern

Claims

1. An internal combustion engine (1) for propulsion of a vessel, said internal combustion engine (1) having at least one cylinder (2), A fuel supply system (4), a first cylinder fuel supply passage (5, 5a) including a first main valve (6, 6a) and a first sub-valve (7, 7a) arranged upstream of the first main valve (6, 6a); a second cylinder fuel supply passage (5, 5b) including a second main valve (6, 6b) and a second sub-valve (7, 7b) disposed upstream of the second main valve (6, 6b); a fuel supply system (4) comprising: a first pressure sensor (8, 8a) for providing a first pressure signal (9, 9a) is arranged between the first main valve (6, 6a) and the first sub-valve (7, 7a), and a second pressure sensor (8, 8b) for providing a second pressure signal (9, 9b) is arranged between the second main valve (6, 6b) and the second sub-valve (7, 7b); The internal combustion engine (1) further comprises a comparison unit (10) for comparing the first pressure signal (9, 9a) with the second pressure signal (9, 9b) to detect a discrepancy between the first pressure signal (9, 9a) and the second pressure signal (9, 9b).

2. 2. The internal combustion engine (1) of claim 1, wherein the at least one cylinder is a first cylinder (2), and the internal combustion engine (1) further comprises a second cylinder (3), the second cylinder (3) being connected to the fuel supply system (4).

3. 3. An internal combustion engine (1) according to claim 1 or 2, wherein the fuel supply system (4) comprises a main supply passage (12) fluidly connected to the first cylinder fuel supply passage (5, 5a) and the second cylinder fuel supply passage (5, 5b).

4. 2. The internal combustion engine (1) according to claim 1, wherein the first pressure sensor (8, 8a) measures a real-time and / or continuous first pressure signal (9, 9a) and the second pressure sensor (8, 8b) measures a real-time and / or continuous second pressure signal (9, 9b).

5. 2. The internal combustion engine (1) of claim 1, wherein the fuel is propane, butane, methanol, methane, ethanol, ethane, ethene, ammonia, propylene, butylene, isobutane, n-butane, hydrogen, kerosene, nitromethane, liquefied petroleum gas, bioethanol, or biodiesel.

6. 2. An internal combustion engine (1) according to claim 1, wherein the main valve (6, 6a, 6b) has an opening time period that is shorter than the opening time period of the sub-valves (7, 7a, 7b).

7. 2. The internal combustion engine (1) according to claim 1, wherein the sub-valves (7, 7a, 7b) open before the main valves (6, 6a, 6b) open.

8. 2. An internal combustion engine (1) according to claim 1, wherein the first pressure signals (9, 9a) form a first pattern (P1) and the second pressure signals (9, 9b) form a second pattern (P2), and the comparison unit (10) compares the first pattern (P1) with the second pattern (P2) to detect a correlation and verify whether the correlation is within a predetermined interval.

9. 2. A leak detection method for detecting a leak in a valve (6, 6a, 6b, 7, 7a, 7b) in a fuel supply system (4) for supplying fuel to at least one cylinder (2) of an internal combustion engine (1) according to claim 1, comprising: measuring the first pressure signal (9, 9a) by the first pressure sensor (8, 8a) between the first main valve (6, 6a) and the first sub-valve (7, 7a) in the first cylinder fuel supply passage (5, 5a) of the fuel supply system (4) for a first time period; measuring the second pressure signal (9, 9b) by the second pressure sensor (8, 8b) between the second main valve (6, 6b) and the second sub-valve (7, 7b) in the second cylinder fuel supply passage (5, 5b) of the fuel supply system (4) during the first time period or the second time period; comparing said first pressure signal (9, 9a) with said second pressure signal (9, 9b) to detect a leak in one of said valves (6, 6a, 6b, 7, 7a, 7b); A leak detection method comprising:

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