Method for operating a pump arrangement for alternative fuels, in particular for methanol or ammonia, and pump arrangement

Abstract

The invention relates to a method for operating a pump arrangement (1) for alternative fuels, in particular for methanol or ammonia, comprising a pre-supply pump (2) and a high-pressure pump (3), wherein fuel is supplied by the pre-supply pump (2) to at least one pump element (4) of the high-pressure pump (3) via a feed path (5) of a low-pressure circuit (6), and fuel arising in the course of the leakage in the at least one pump element (4) is discharged via a return path (7) of the low-pressure circuit (6). According to the invention, fuel is branched off from the feed path (5), preferably downstream of the pre-supply pump (2) and upstream of a metering unit (8) integrated into the feed path (5), into a cooling path (9) and supplied to at least one cooling element (10) which is integrated into a suction chamber (11) and / or a leakage chamber (12) of the high-pressure pump (3). The invention also relates to a pump arrangement (1) for alternative fuels, which is suitable for carrying out the method or can be operated according to the method.

Description

[0001] Description

[0002] title

[0003] Method for operating a pump arrangement for alternative fuels, in particular for methanol or ammonia, and pump arrangement

[0004] The invention relates to a method for operating a pump assembly for alternative fuels, in particular for methanol or ammonia. A pump assembly suitable for carrying out the method comprises a prefeed pump and a high-pressure pump. The invention further relates to a pump assembly for alternative fuels that is suitable for carrying out the method according to the invention or that can be operated according to the method according to the invention.

[0005] The preferred field of application of the invention is engines, in particular large engines, which must be supplied with an alternative fuel.

[0006] State of the art

[0007] Fuel injection systems with pump arrangements comprising a pre-feed pump and a high-pressure pump are known from the field of internal combustion engines. State of the art, for example, are common rail injection systems for diesel fuels, which have a pump arrangement with a pre-feed pump and a high-pressure pump. The high-pressure pump in such a pump arrangement often has a suction throttle. This means that only the amount of fuel that is to be brought up to system pressure reaches the high-pressure pump. Any leakage from the pump elements of the high-pressure pump is discharged separately and remains liquid at the operating temperatures occurring even without cooling. The leakage can thus be easily and usually pressurelessly returned to the suction side of the high-pressure pump or to the fuel tank.One property of alternative fuels, such as methanol or ammonia, is that they change their state of matter even at comparatively low temperatures and pressures. A liquid fuel then becomes a gaseous fuel. According to the vapor curve for methanol, for example, this already occurs at a temperature of 65°C and ambient pressure. Since the ambient temperature in the area of ​​the engine supplied with the alternative fuel is often higher, this can lead to problems in the intake area of ​​the high-pressure pump or in a leakage path for discharging the leakage. Furthermore, compliance with relevant safety regulations can be jeopardized.

[0008] The present invention is concerned with the task of preventing the change in the aggregate state of alternative fuels when pumping to high pressure in order to avoid the associated disadvantages.

[0009] The object is achieved by the method having the features of claim 1 and by the pump arrangement having the features of claim 6. Advantageous developments of the invention can be found in the respective subclaims.

[0010] Disclosure of the invention

[0011] A method is proposed for operating a pump arrangement for alternative fuels, in particular for methanol or ammonia, comprising a pre-feed pump and a high-pressure pump. In the method, fuel is supplied to at least one pump element of the high-pressure pump via an inlet path of a low-pressure circuit with the aid of the pre-feed pump, and fuel accumulating through leakage in the at least one pump element is discharged via a return path of the low-pressure circuit. According to the invention, fuel is branched from the inlet path into a cooling path and supplied to at least one cooling element that is integrated into a suction chamber and / or a leakage chamber of the high-pressure pump.

[0012] The fuel in the supply path has a lower temperature than the fuel pumped to high pressure by the high-pressure pump. The proposed method takes advantage of this by diverting "cool" fuel from the supply path into a cooling path and supplying it to the at least one pump element of the high-pressure pump for cooling. The cooling prevents a temperature-related change in the state of the fuel from liquid to gaseous, thus avoiding the problems described above when drawing fuel into the at least one pump element and / or when returning fuel that has leaked out.

[0013] The fuel branched into the cooling path is fed to at least one cooling element that is integrated into a suction chamber and / or a leakage chamber of the high-pressure pump. Preferably, a cooling element is integrated in both the suction chamber and the leakage chamber, so that cooling of the high-pressure pump and the leakage quantity can be achieved. The cooling path can, for example, be routed such that the fuel first flows through a cooling element integrated into the suction chamber and then through a cooling element integrated into the leakage chamber. Cooled fuel is then sucked from the suction chamber into the at least one pump element. The cooling element integrated into the leakage chamber can cool the fuel that leaks into the at least one pump element before it is discharged via the return path. A quantity of fuel discharged from the inlet path via a zero-feed throttle can also be fed to the leakage chamber and cooled before it is returned.

[0014] The fuel intended for cooling is preferably branched from the inlet path into the cooling path downstream of the pre-feed pump and upstream of a metering unit integrated into the inlet path. The metering unit is used to meter the fuel to be delivered at high pressure. The metered fuel flows via the inlet path into the intake chamber and via the intake chamber to at least one pump element of the high-pressure pump.

[0015] In a further development of the invention, it is proposed that the fuel diverted into the cooling path is first cooled with the aid of a cooling device integrated into the inlet path. This measure optimizes the cooling effect achieved by the diverted fuel. The cooling device can, for example, be a heat exchanger integrated into a cooling circuit through which a coolant of the cooling circuit flows. Furthermore, it is proposed that the fuel diverted into the cooling path and supplied to the at least one cooling element be returned to a tank storing the fuel or upstream of the pre-feed pump into the inlet path. The fuel diverted into the cooling path is therefore not lost but remains available for high-pressure delivery.

[0016] Preferably, a predefined minimum pressure level is set in the return path and / or the cooling path using a pressure-maintaining valve. This pressure level is above ambient pressure and is intended to ensure the liquid state of the fuel at elevated temperatures. The minimum pressure level to be set is preferably selected depending on the vapor pressure curve of the respective fuel.

[0017] As a further development, it is proposed that fuel be diverted from the cooling path into a purge path and supplied to the at least one pump element for discharging the fuel accumulating through the leak. Purging the pump element promotes the removal of the leakage. Furthermore, cooling of the pump element can be achieved at the same time. The fuel intended for purging is preferably diverted from the cooling path into the purge path between two cooling elements. The amount diverted into the purge path can be adjusted using a throttle integrated into the purge path.

[0018] Furthermore, a pump arrangement for alternative fuels, in particular for methanol or ammonia, is proposed. The pump arrangement comprises a pre-feed pump and a high-pressure pump, wherein the pre-feed pump is integrated into an inlet path of a low-pressure circuit, via which fuel can be supplied to at least one pump element of the high-pressure pump, and wherein the low-pressure circuit comprises a return path for discharging fuel which accumulates by way of leakage in the at least one pump element.

[0019] According to the invention, a cooling path branches off from the inlet path, which leads via at least one cooling element that is integrated into a suction chamber and / or a leakage chamber of the high-pressure pump.

[0020] The proposed pump arrangement is particularly suitable for carrying out the method according to the invention described above or can be operated according to this method, so that the same advantages can be achieved. In particular, the high-pressure pump and / or the leakage quantity to be discharged via the return path can be cooled with fuel from the inlet path. The cooling prevents the fuel in the intake area of ​​the high-pressure pump and / or in the return line from changing its state from liquid to gaseous, depending on where the at least one cooling element is integrated into the high-pressure pump, in the suction chamber and / or in the leakage chamber. A cooling element is advantageously integrated into both the suction chamber and the leakage chamber.

[0021] The at least one cooling element can in particular be designed as a line or pipe which is guided through the suction chamber and / or the leakage chamber.

[0022] Preferably, the at least one cooling element penetrates the intake chamber and / or the leakage chamber, so that fuel flows around it on all sides. This creates a maximum heat transfer surface. To further improve heat transfer, the at least one heating element can have an outer contour that increases the surface area and / or be made of a material with high thermal conductivity.

[0023] The cooling path preferably branches off from the inlet pad downstream of the pre-feed pump and upstream of a metering unit. The pre-feed pump can thus be used to pump fuel via the cooling path, while the fuel quantity metered by the metering unit remains unaffected.

[0024] In a further development of the invention, it is proposed that a cooling device be integrated into the supply path, preferably downstream of the pre-feed pump and upstream of the branching cooling line. With the aid of the cooling device, the fuel can be cooled before it is branched into the cooling path, thus increasing the cooling effect. The cooling device can, for example, be a heat exchanger integrated into a cooling circuit through which a coolant from the cooling circuit flows.

[0025] According to a preferred embodiment of the invention, the cooling path opens downstream of the at least one cooling element into a tank storing the fuel or upstream of the pre-feed pump into the supply path. The fuel thus remains available. Furthermore, a pressure-maintaining valve is preferably integrated into the return path and / or the cooling path. With the aid of the pressure-maintaining valve, a minimum pressure can be maintained, which prevents a change in the state of the fuel from liquid to gaseous, even if the fuel temperature increases. Ideally, the fuel is only released to ambient pressure shortly before reaching the tank.

[0026] Furthermore, it is proposed that a purge path branch off from the cooling path, which is connected to the leakage chamber and / or the return path via the at least one pump element. The at least one pump element can be purged with the help of the fuel branched off into the purge path, thus promoting the removal of the leakage. The purge path can, for example, branch off from the cooling path between two cooling elements. A throttle is preferably integrated into the purge path. The purge quantity can be adjusted using the throttle.

[0027] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. These show:

[0028] Fig. 1 is a schematic representation of a first pump arrangement according to the invention and

[0029] Fig. 2 is a schematic representation of a second pump arrangement according to the invention.

[0030] Detailed description of the drawings

[0031] Figure 1 shows a pump arrangement 1 according to the invention for alternative fuels, for example, for methanol. The pump arrangement 1 comprises a pre-feed pump 2 and a high-pressure pump 3. With the help of the pre-feed pump 2, the fuel is withdrawn from a tank 14 and fed to at least one pump element 4 of the high-pressure pump 3 via an inlet path 5. The high-pressure pump 3 shown here comprises three pump elements 3, the number being chosen merely as an example. Upstream of the pre-feed pump 2, a filter 18 is integrated into the inlet path 5, which is intended to remove harmful particles from the fuel. Downstream of the pre-feed pump 2, a metering unit 8 is integrated into the inlet path 5, by means of which the fuel is metered. The individual pump elements 4 are supplied with fuel via suction valves 19 assigned to the pump elements 4.Via the suction valves 19, the pump elements 4 are connected to a suction chamber 11 of the high-pressure pump 3, into which the inlet path 5 opens. The fuel supplied to the pump elements 4 via the suction valves 19 is pumped at high pressure and discharged into a high-pressure line 21 via high-pressure valves 20. Fuel leaking during high-pressure delivery is discharged via a return path 7, which leads through a leakage chamber 12 of the high-pressure pump 3 and opens into the tank 14. The inlet path 5 and the return path 7 together form a low-pressure circuit 6. A zero-feed throttle 23 establishes a connection between the inlet path 5 and the return path 7, bypassing the pump elements 4.

[0032] A cooling path 9 branches off from the inlet path 5 downstream of the pre-feed pump 2 and upstream of the metering unit 8. This cooling path 9 is routed to cool the high-pressure pump 3 and the leakage quantity via a first cooling element 10 integrated into the suction chamber 11 and a second cooling element 10 integrated into the leakage chamber 12. To increase the cooling effect, a cooling device 13 is integrated into the inlet path 5 upstream of the branching cooling path 9. The cooling path 9 flows back into the inlet path 5 upstream of the pre-feed pump 2, so that the fuel diverted for cooling is not lost.

[0033] In this case, a pressure-maintaining valve 15 is integrated into each of the return path 7 and the cooling path 9. This valve(s) can be arranged inside or outside a housing 22 of the high-pressure pump 3. With the help of the pressure-maintaining valves 15, a minimum pressure can be maintained in the return path 7 and the cooling path 9.

[0034] Figure 2 shows a further pump arrangement 1 according to the invention with a pre-feed pump 2 and a high-pressure pump 3. It differs from that of Figure 1 only in that a flushing path 16 is additionally provided for flushing the pump elements 4. Flushing promotes the removal of leakage quantities. The flushing path 16 branches off from the cooling path 9 between the two cooling elements 10. The flushing quantity is adjusted via a throttle 17 integrated into the flushing path 16. Since the flushing path 16 branches off from the cooling path 9, further cooling can be achieved simultaneously with the help of the flushing quantity.

Claims

Claims 1 . Method for operating a pump arrangement (1) for alternative fuels, in particular for methanol or ammonia, comprising a pre-feed pump (2) and a high-pressure pump (3), wherein with the aid of the pre-feed pump (2) fuel is supplied to at least one pump element (4) of the high-pressure pump (3) via an inlet path (5) of a low-pressure circuit (6), and fuel accumulating as a result of leakage in the at least one pump element (4) is discharged via a return path (7) of the low-pressure circuit (6), characterized in that from the inlet path (5), preferably downstream of the pre-feed pump (2) and upstream of a metering unit (8) integrated into the inlet path (5), fuel is branched off into a cooling path (9) and supplied to at least one cooling element (10) which is integrated into a suction chamber (11) and / or a leakage chamber (12) of the high-pressure pump (3).

2. Method according to claim 1, characterized in that the fuel branched off into the cooling path (9) is previously cooled by means of a cooling device (13) integrated into the inlet path (5).

3. Method according to claim 1 or 2, characterized in that the fuel branched off into the cooling path (9) and supplied to the at least one cooling element (10) is returned to a tank (14) storing the fuel or upstream of the pre-feed pump (2) into the inlet path (5).

4. Method according to one of the preceding claims, characterized in that a predefined minimum pressure level is set in the return path (7) and / or in the cooling path (9) with the aid of a pressure-maintaining valve (15).

5. Method according to one of the preceding claims, characterized in that fuel is branched off from the cooling path (9), preferably between two cooling elements (10), into a purge path (16) and is fed to the at least one pump element (4) for discharging the fuel accumulating by way of leakage, wherein the quantity branched off into the purge path (16) is preferably adjusted with the aid of a throttle (17) integrated into the purge path (16).

6. Pump arrangement (1) for alternative fuels, in particular for methanol or ammonia, comprising a pre-feed pump (2) and a high-pressure pump (3), wherein the pre-feed pump (2) is integrated into an inlet path (5) of a low-pressure circuit (6), via which fuel can be supplied to at least one pump element (4) of the high-pressure pump (3), and wherein the low-pressure circuit (6) comprises a return path (7) for discharging fuel which accumulates as a result of leakage in the at least one pump element (4), characterized in that a cooling path (9) branches off from the inlet path (5), preferably downstream of the pre-feed pump (2) and upstream of a metering unit (8) integrated into the inlet path (5), which cooling path leads via at least one cooling element (10) which is integrated into a suction chamber (11) and / or into a leakage chamber (12) of the high-pressure pump (3).

7. Pump arrangement (1) according to claim 6, characterized in that a cooling device (13) is integrated into the inlet path (5), preferably downstream of the pre-feed pump (2) and upstream of the branching cooling line (9).

8. Pump arrangement (1) according to claim 6 or 7, characterized in that the cooling path (9) opens downstream of the at least one cooling element (10) into a tank (14) storing the fuel or upstream of the pre-feed pump (2) into the inlet path (5).

9. Pump arrangement (1) according to one of claims 6 to 8, characterized in that a pressure holding valve (15) is integrated into the return path (7) and / or into the cooling path (9).

10. Pump arrangement (1) according to one of claims 6 to 9, characterized in that from the cooling path (9), preferably between two Cooling elements (10), a flushing path (16) branches off, which is connected via the at least one pump element (4) to the leakage chamber (12) and / or the return path (7), wherein a throttle (17) is preferably integrated into the flushing path (16).

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