CN110685823B

CN110685823B - Fuel delivery device for cryogenic fuels

Info

Publication number: CN110685823B
Application number: CN201910598256.XA
Authority: CN
Inventors: D·施尼特格; F·豪伊
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2018-07-04
Filing date: 2019-07-04
Publication date: 2022-09-06
Anticipated expiration: 2039-07-04
Also published as: CN110685823A; DE102018210999A1

Abstract

The invention relates to a fuel supply device for cryogenic fuels, in particular for liquefied natural gas, comprising a high-pressure pump (1) having a pump head (2), in which a compression chamber (3) is formed, which can be filled with cryogenic fuel from a fuel tank (5) via an inlet valve (4) and can be connected to a high-pressure channel (7) formed in the pump head (2) via a high-pressure outlet valve (6). According to the invention, the high-pressure channel (7) can be connected to a return (9) via a cold start valve (8), wherein the cold start valve (8) has a valve tappet (11) that opens against the pressure in the high-pressure channel (7) and a further high-pressure outlet valve (10) is arranged in the high-pressure channel (7) downstream of the cold start valve (8).

Description

Fuel delivery device for cryogenic fuels

Technical Field

The present invention relates to a fuel delivery device for cryogenic fuels.

Background

The cryogenic fuel can be, in particular, Natural Gas (NG), which is stored on board the motor vehicle in liquid form (LNG) in a fuel tank specially designed for this purpose for operating the internal combustion engine.

In general, cryogenic fuels are stored onboard a motor vehicle in so-called cryogenic fuel tanks. The cryogenic fuel tank is a sufficiently isolated, deeply cooled reservoir to store cryogenic fuel in liquid form. The desired storage temperature for natural gas is, for example, -160 ℃. Hydrogen is stored at-253 ℃. Usually, these fuel tanks have their own cooling means.

In general, cryogenic fuel is removed from a fuel tank by means of a fuel delivery device which comprises at least one high-pressure pump for compressing the fuel. The high-pressure pump can be arranged partially in the fuel tank. For example, the pump head may be arranged in the fuel tank, while the drive of the pump may be arranged outside the fuel tank. This arrangement has the advantage of cooling the pump head, so that a separate cooling means for the pump can be eliminated. However, the arrangement of the high-pressure pump in sections in the fuel tank increases the complexity of the design, since the separating structure of the fuel tank is interrupted in the region of the through-guide. Therefore, fuel delivery systems for cryogenic fuels are also known from the prior art, in which a high-pressure pump is arranged outside the fuel tank and can be supplied with fuel by means of a prefeed pump arranged in the fuel tank. A separate cooling device may be provided for cooling the high-pressure pump.

DE 102016014928 a1, for example, discloses a fuel system with a fuel tank for storing liquid gas and a pump device for delivering the liquid gas. Furthermore, the fuel system comprises a cooling device for reducing the temperature of the liquid gas in a region of the fuel system, which region is fluidically coupled to the suction side of the pump device.

Disclosure of Invention

Starting from the prior art described above, the object of the present invention is to provide an alternative cooling device for a high-pressure pump, which cooling device can be implemented simply and inexpensively.

In order to solve this problem, the invention proposes a fuel delivery device for cryogenic fuels, in particular for liquefied natural gas, comprising a high-pressure pump having a pump head in which a compression chamber is formed, which can be filled with fuel from a fuel tank via an inlet valve and can be connected to a high-pressure channel formed in the pump head via a high-pressure outlet valve. According to the invention, the high-pressure channel can be connected to the return via a cold start valve, wherein the cold start valve has a valve tappet that opens against the pressure in the high-pressure channel, and wherein a further high-pressure outlet valve is arranged in the high-pressure channel downstream of the cold start valve.

Preferably, before the start-up operation after a relatively long standstill phase or during a "cold start", the compression space of the high-pressure pump can be flushed with low-temperature or deeply cooled fuel by means of a cold start valve, so that the pump head of the high-pressure pump is cooled. This prevents the liquid fuel that reaches the compression chamber as the high-pressure pump is put into operation from evaporating and reducing the efficiency of the high-pressure pump.

The high pressure built up at the start of the delivery of the high-pressure pump can be utilized for closing the cold start valve by the cold start valve being connected to the high-pressure region of the high-pressure pump and having a valve tappet opening against the pressure. The construction of the cold start valve can thus be simplified, for example the closing spring can be dispensed with. Furthermore, the hydraulic closing force ensures that the cold start valve remains closed in a sealing manner during the delivery operation of the high-pressure pump. The delivery volume can thus be completely supplied to the high-pressure accumulator connected to the high-pressure pump.

During a cold start of the high-pressure pump, a further high-pressure outlet valve arranged in the high-pressure channel downstream of the cold start valve prevents fuel loaded by high pressure from flowing back from the high-pressure reservoir into the high-pressure channel. Thus, high efficiency of the system is ensured.

The further high-pressure outlet valve arranged in the high-pressure channel downstream of the cold start valve is preferably designed such that it closes more slowly than the high-pressure outlet valve located upstream. During normal delivery operation of the high-pressure pump, therefore, only the upstream or first high-pressure outlet valve is closed. Due to the small number of closing processes, the second high-pressure discharge valve is less worn and thus carries less leakage. I.e. the second high-pressure discharge valve is sealingly closed and the system pressure can be maintained during long delivery stops. In this way the efficiency of the system can be increased.

Preferred embodiments according to the present invention are given below.

According to a preferred embodiment of the invention, the cold start valve comprises an actuator, preferably an electromagnetic actuator, by means of which the valve tappet can be opened against the pressure in the high-pressure channel. Thus, the cold start valve can be specifically actuated.

Since the actuator must work against the hydraulic closing force, in one development of the invention it is proposed to reduce the pressure in the high-pressure channel before opening the cold start valve for the cold start high-pressure pump, so that no or a low differential pressure exists across the cold start valve. The cold start valve can then be opened with a low force, so that the actuator can be designed to be correspondingly small. In this way, the energy requirement of the cold start valve can be reduced, so that a further increase in efficiency results. Furthermore, due to the smaller electrical power, the heat input due to the actuator can be reduced, which also has a positive effect on the efficiency of the system. Furthermore, the installation space requirement of the cold start valve is reduced.

Furthermore, the small actuator force required for opening the cold start valve enables an increase in the opening cross section of the cold start valve, in which way the cooling effect during cold start can be improved.

The pressure reduction in the high-pressure channel, which is proposed to reduce the required opening force before opening the cold start valve, can be caused in different ways.

According to a preferred embodiment of the invention, the high-pressure channel can be connected to the return, for example via a defined leak or throttle arranged parallel to the cold start valve. Then, via the leak or restriction, the pressure continues to decrease until pressure equilibrium occurs. Due to the small volume between the two high pressure discharge valves, only a small amount of fuel flows out via the leakage or restriction, so that losses are acceptable. Furthermore, the fuel which has been supplied to the high-pressure reservoir is prevented from flowing back into the high-pressure channel by means of the pressure difference at the second high-pressure outlet valve which is caused by the pressure drop in the high-pressure channel.

Furthermore, the high-pressure pump can be designed such that the high-pressure channel can be connected to the return line via two cold start valves arranged in parallel and having opening cross sections of different sizes. Then, for the pressure reduction, the cold start valve with the smaller opening cross section is first opened. A cold start valve for generating a large flow with a large opening cross section is opened only after the pressure reduction is completed. The smaller cold start valve provided for the pressure reduction may be designed as a valve that resists pressure or opens by means of pressure. Depending on the small opening cross section, only a small actuator force is required. Furthermore, the opening time can be kept short, since only a small amount of fuel has to escape from the high-pressure channel in order to cause the desired pressure reduction. The energy requirement of the actuator of the further cold start valve is therefore also small and negligible. The same applies with regard to the heating caused by the actuator.

Furthermore, the pressure reduction in the high-pressure channel can be caused by a cold start valve which is embodied as a valve which opens in a multi-stage manner, in particular in two stages. In the first stage, a smaller opening cross section is released in order to reduce the pressure. In the second stage, a large opening cross section is released, so that a large flow can be generated. For a two-stage opening, the cold start valve may have, for example, two valve tappets guided one inside the other, which release opening cross sections of different sizes. The outflow of fuel during the first stage can take place along a guide between two valve lifters. For this purpose, the inner valve tappet can have a flattened area or a longitudinal groove.

Preferably, at least one valve tappet of the cold start valve is guided by a valve body which at the same time forms a valve seat for the valve tappet. The guide and the seat are thus realized in one component, so that an optimal centering of the valve tappet relative to the valve seat is ensured.

Furthermore, the valve body of the cold start valve is preferably inserted, preferably screwed, into a bore of the pump head. The valve body thus facilitates the assembly of the cooling valve, since it can be preassembled together with the valve tappet and can be inserted or screwed into the bore of the pump head as a preassembled unit.

Furthermore, for the operative connection to the actuator, at least one valve tappet is passed through the valve body and through a valve screw, by means of which the actuator is fixed on or in the pump head. The structure of the cold start valve can be simplified. The electromagnetic actuator can in particular also be preassembled and can be fixed as a preassembled unit on or in the pump head of the high-pressure pump by means of valve screws.

The electromagnetic actuator preferably has an annular electromagnetic coil for acting on an armature which can be moved in a lifting manner and which is axially prestressed against the at least one valve tappet by means of the spring force of a spring. The spring pretensioning of the armature causes a force lock between the armature and the valve tappet and thus ensures the required functional connection between the actuator and the valve tappet.

In one development of the invention, it is proposed that the armature is guided by a magnetic sleeve. That is, the armature is received at least in sections in the magnetic sleeve. The magnetic sleeve is part of an electromagnetic circuit which, when the electromagnetic coil is energized, produces a magnetic field whose magnetic force acts on the armature in such a way that the armature lifts the valve tappet from the valve seat. The magnetic sleeve is preferably embedded in the electromagnetic coil, so that an electromagnetic actuator operating according to the plug-in armature principle is achieved, which is particularly compact in the axial direction. Alternatively or additionally, it is provided that the magnetic sleeve is connected to the valve screw via a further non-magnetic sleeve. The connection may be, for example, a welded connection, so that a seal is produced thereby, which prevents the electromagnetic coil from coming into contact with the fuel. Thus, the complex sealing of the electrical connection can be dispensed with.

Furthermore, it is proposed that the high-pressure pump is connected to the prefeed pump via an inflow line. The prefeed pump is therefore an integral part of the proposed fuel delivery device. The high-pressure pump is supplied with cryogenic fuel from a fuel tank by means of a prefeed pump. For this purpose, the prefeed pump is preferably arranged in the fuel tank.

Furthermore, the high-pressure pump is preferably connected to the fuel tank via a return line and a return line connected to the return line. Therefore, the fuel quantity used for cooling the high-pressure pump at the time of cold start is introduced back into the fuel tank so that the system does not lose this fuel quantity.

Drawings

Preferred embodiments of the present invention are explained in detail below with reference to the attached drawing figures, which show:

fig. 1 is a schematic longitudinal section of a first preferred embodiment of a fuel delivery device according to the invention, comprising a high-pressure pump and a prefeed pump arranged in a fuel tank,

figure 2 is a schematic longitudinal section of a pump head of a high-pressure pump of a second preferred embodiment of the fuel delivery device according to the invention,

figure 3 is a schematic longitudinal section of a pump head of a high-pressure pump of a third preferred embodiment of the fuel delivery device according to the invention,

figure 4 is a schematic longitudinal section of a cold start valve of a high-pressure pump of a fuel delivery device according to the invention,

fig. 5 a schematic longitudinal section of a valve unit of a cold start valve with two-stage opening, and

fig. 6 is an enlarged detail of fig. 5.

Detailed Description

The fuel delivery device according to the invention shown in fig. 1 comprises a high-pressure pump 1 and a prefeed pump 24 which is arranged in a fuel tank 5 for storing cryogenic fuel, in particular in the region of the liquid phase 27 of the fuel. The gas phase 26, which is formed in the fuel tank 5 as a result of heat input from the outside, is located above the liquid phase 27. The arrangement of the prefeed pump 24 in the liquid phase 27 ensures that the high-pressure pump 1 is supplied with liquid fuel with priority.

The high-pressure pump 1 shown has a pump head 2 in which a compression chamber 3 delimited by a pump piston 28 is formed. In the delivery mode of the high-pressure pump 1, the fuel present in the compression chamber 3 is compressed by means of the reciprocable pump piston 28 and is supplied to a high-pressure accumulator (not shown) via two high-

pressure outlet valves

6, 10 arranged one behind the other. The compression chamber 3 can be filled with fuel via the inlet valve 4. Fuel is supplied to the inlet valve 4 via an inflow line 23, which connects the high-pressure pump 1 to a prefeed pump 24.

A cold start valve 8, via which the compression chamber 3 can be connected to the return 9, is integrated into the pump head 2 of the high-pressure pump 1. The return 9 is connected to the fuel tank 5 via a return line 25, so that fuel which is discharged via the cold start valve 8 for flushing or for cooling the high-pressure pump 1 is returned to the fuel tank 5. Flushing or cooling is performed during a cold start, i.e. before the actual start of the high-pressure pump. This ensures that the liquid fuel is compressed preferentially during the delivery operation of the high-pressure pump 1.

As can be seen from fig. 1, the cold start valve 8 is connected to the high pressure channel 7 between the two high

pressure discharge valves

6, 10. The flushing quantity or cooling quantity is therefore fed back into the fuel tank 5 via the first high-pressure outlet valve 6 and the cold start valve 8. The flow rate at cold start is generated by the prefeed pump 24. In order to increase the flow rate during a cold start, the pump piston 28 of the high-pressure pump can be moved as in the normal delivery operation. In this way, the pressure difference at the intake valve 4 increases when fuel is sucked into the compression chamber 3. Likewise, when fuel is delivered from the compression chamber 3 into the high-pressure passage 7 or the return portion 9, the pressure difference at the first high-pressure discharge valve 6 increases. The first high-pressure outlet valve 6 and the cold start valve 8 are throttles which have to be overcome by a high pressure difference at as large a flow as possible.

The cold start valve 8 of the high-pressure pump 1 of fig. 1 can be implemented as shown in fig. 4. The cold start valve may have, in particular, a valve tappet 11 that opens against the pressure in the high-pressure channel 7 and interacts with a valve seat 15, which is formed by a valve body 14. The valve body 14 and the valve tappet 16 can be inserted, in particular screwed, in a simple manner as a preassembled unit into the bore 16 of the pump head 2 of the high-pressure pump 1. The valve tappet 11 can be prestressed against the valve seat 15 by means of a closing spring 29, however, the closing spring 29 is not absolutely necessary, since a hydraulic closing force acts on the valve tappet 11 during normal delivery operation of the high-pressure pump 1. The opening is effected by means of an actuator 12, which may be embodied in particular as an electromagnetic actuator 12. For example, as shown in fig. 4, the electromagnetic actuator 12 may have an annular electromagnetic coil 18, a lifting armature 19 and a magnetic sleeve 21. The armature 19 is guided by a magnetic sleeve 21. By means of a spring 20 arranged between the magnetic sleeve 21 and the armature 19, the armature 19 is prestressed against the valve tappet 11, so that a stroke of the armature 19 lifts the valve tappet 11 from the valve seat 15. The stroke of the armature 19 is limited by a valve screw 17, by means of which the actuator 12 is fixed in the pump head 2 of the high-pressure pump 1. The valve screw 17 is connected to the magnetic sleeve 21 via a non-magnetic sleeve 22. Preferably, the non-magnetic sleeve 22 is welded around both the magnetic sleeve 21 and the valve screw 17, so that a seal is thereby simultaneously achieved.

The cold start valve 8 shown in fig. 4 operates as follows:

if the electromagnetic coil 18 of the electromagnetic actuator 12 is energized, a magnetic field is formed, the magnetic force of which moves the armature 19 in the direction of the valve screw 17. In this case, the armature 19 lifts the valve tappet 11 off the valve seat 15, so that the cold start valve 8 opens. Fuel from the compression chamber 3 can therefore flow through the valve seat 15 and the radial bore 30 formed in the valve body 14 into the annular chamber 31, which is delimited by the valve body 14 in the bore 16. From the annular chamber 31, the fuel reaches the return 9 (not shown). To close cold start valve 8, the energization of solenoid 18 is terminated, so that closing spring 29, whose spring force is greater than the spring force of spring 20, pulls valve tappet 11 into valve seat 15. If the closing spring 29 is not present, closing is effected hydraulically. Since, if the high-pressure pump 1 starts normal delivery operation after a cold start, a pressure builds up in the high-pressure channel 7, which pressure causes a resultant force acting in the closing direction.

Since the cold start valve 8 has to open against the pressure in the high pressure channel 7, advantages arise when the pressure is low. This can be brought about in such a way that a targeted pressure reduction in the high-pressure channel 7 is promoted.

For this purpose, as shown in fig. 2, a leakage or throttle 13, which is arranged parallel to the cold start valve 8 and via which the high-pressure duct 7 can be connected to the return 9, may be provided, for example.

Furthermore, as shown in fig. 3, a further cold start valve 8' with a smaller opening cross section may be arranged, for example, parallel to the cold start valve 8. In order to reduce the pressure in the high-pressure channel 7, the smaller cold start valve 8' is therefore first opened. At the time of opening the original cold start valve 8, the pressure is reduced to such an extent that only a small actuator force is still required for opening. The original cold start valve 8 can therefore have a very large opening cross section in order to generate a large flow rate.

Furthermore, a cold start valve 8 which opens in multiple stages, in particular in two stages, can be used. In the first stage, a small opening cross section is relieved in order to bring about the desired pressure drop. Only in the second stage is a large opening cross section released for generating a large flow.

A possible embodiment of such a cold start valve 8 is shown, for example, in fig. 5 and 6. Here, the cold start valve 8 has two valve tappets 11, 11 'guided one inside the other, which release opening cross sections of different sizes, which are defined by valve seats 15, 15'. The valve seat 15 'for the inner valve tappet 11' is formed by the outer valve tappet 11. When the valve seat 15' is open, fuel can flow out through the guide. For this purpose, the inner valve tappet 11' has a flattened area (not shown). In the first stage, to open the inner valve tappet 11', a stroke h is achieved by means of an armature 19 (not shown) ₁ (see fig. 6), during which the inner valve tappet 11' moves relative to the outer valve tappet 11. In the second stage, i.e. during the travel h ₁ The armature 19 then bears against the outer valve tappet 11 and lifts it from its valve seat 15So that now a large opening cross section is released for the cold start of the high-pressure pump 1.

Claims

1. A fuel delivery device for cryogenic fuels, comprising a high-pressure pump (1) having a pump head (2), in which a compression chamber (3) is formed, which can be filled with cryogenic fuel from a fuel tank (5) via an inlet valve (4) and can be connected via a high-pressure outlet valve (6) to a high-pressure channel (7) formed in the pump head (2), characterized in that the high-pressure channel (7) can be connected to a return (9) via a cold start valve, wherein the cold start valve has a valve tappet that opens against the pressure in the high-pressure channel (7) and a further high-pressure outlet valve (10) is arranged in the high-pressure channel (7) downstream of the cold start valve.

2. The fuel delivery apparatus according to claim 1,

characterized in that the cold start valve comprises an actuator (12) by means of which the valve tappet can be opened against the pressure in the high-pressure duct (7).

3. The fuel delivery apparatus according to claim 2,

characterized in that the actuator (12) is an electromagnetic actuator.

4. The fuel delivery apparatus according to any one of claims 1 to 3,

characterized in that the high-pressure channel (7) is connected to the return (9) via a defined, leakage or throttle (13) arranged parallel to the cold start valve.

5. The fuel delivery device according to any one of claims 1 to 3,

characterized in that the high-pressure channel (7) can be connected to the return (9) via two cold-start valves arranged in parallel, wherein the cold-start valves have opening cross sections of different sizes.

6. The fuel delivery apparatus according to claim 3,

characterized in that the cold start valve (8) is embodied as a multi-stage opening valve.

7. The fuel delivery apparatus of claim 6,

characterized in that the valve has two valve tappets which are guided in a nested manner and release opening cross sections of different sizes.

8. The fuel delivery apparatus according to claim 7,

characterized in that at least one valve tappet of the cold start valve is guided by a valve body (14) which at the same time forms a valve seat (15) for the valve tappet.

9. The fuel delivery apparatus according to claim 8,

characterized in that the valve body (14) is inserted into a bore (16) of the pump head (2).

10. The fuel delivery device according to claim 8 or 9,

characterized in that, for the functional connection to the actuator (12), at least one valve tappet passes through the valve body (14) and through a valve screw (17), by means of which the actuator (12) is fixed on or in the pump head (2).

11. The fuel delivery apparatus of claim 10,

the electromagnetic actuator is characterized by an annular electromagnetic coil (18) for acting on a vertically movable armature (19), which is axially prestressed against at least one valve tappet by means of the spring force of a spring (20).

12. The fuel delivery apparatus according to claim 11,

characterized in that the armature (19) is guided by a magnetic sleeve (21).

13. The fuel delivery apparatus according to any one of claims 1, 2, 3, 6 to 9, 11 and 12,

characterized in that the high-pressure pump (1) is connected to a prefeed pump (24) via an inflow line (23).

14. The fuel delivery apparatus according to any one of claims 1, 2, 3, 6 to 9, 11 and 12,

characterized in that the high-pressure pump (1) is connected to the fuel tank (5) via the return (9) and a return line (25) connected thereto.

15. The fuel delivery apparatus according to claim 1,

characterized in that the cryogenic fuel is liquefied natural gas.

16. The fuel delivery apparatus of claim 6,

characterized in that the cold start valve (8) is embodied as a two-stage open valve.

17. The fuel delivery apparatus of claim 9,

characterized in that the valve body (14) is screwed into a bore (16) of the pump head (2).

18. The fuel delivery apparatus of claim 12,

characterized in that the magnetic sleeve is embedded in the electromagnetic coil (18) and/or connected to the valve screw (17) by means of a non-magnetic sleeve (22).

19. The fuel delivery apparatus of claim 13,

characterized in that the prefeed pump is arranged in the fuel tank (5).