WO2026008842A1

WO2026008842A1 - A centrifugal multi-stage pump for pumping liquidised fluids

Info

Publication number: WO2026008842A1
Application number: PCT/EP2025/069143
Authority: WO
Inventors: Michael Winther
Original assignee: Svanehoj Danmark AS
Current assignee: Svanehoj Danmark AS
Priority date: 2024-07-05
Filing date: 2025-07-04
Publication date: 2026-01-08
Anticipated expiration: 2027-01-05

Abstract

The present invention concerns a centrifugal multi-stage pump for pumping liquidised fluids, in particular fuel pump for pumping liquidised ammonia or liquid natural gas (LNG), hydrogen, methanol, ethane, liquefied petroleum gas (LPG) or the like, said pump comprising a pump unit, which is arranged on a frame, and comprises a pump housing with a lower pump inlet manifold and an upper pump discharge manifold, wherein the pump housing is provided as a pressure relief pipe having a lower, a middle and a top section; said pump further comprising a pump shaft; a plurality of impellers mounted on the pump shaft for centrifugally moving the liquidised fluid from the pump inlet manifold to the pump discharge manifold; and a drive shaft magnetically coupled to the pump shaft; and wherein an electric motor is arranged on the frame, said motor having a motor drive shaft which is connected via a transmission to the drive shaft for driving the pump.

Description

A CENTRIFUGAL MULTI-STAGE PUMP FOR PUMPING LIQUIDISED FLUIDS

FIELD OF THE INVENTION

The present invention relates to a centrifugal multi-stage pump for pumping liquidised fluids, in particular fuel pump for pumping liquidised ammonia or liquid natural gas (LNG), hydrogen, methanol, ethane, liquefied petroleum gas (LPG) or the like, said pump having a pump housing with a lower pump inlet manifold and an upper pump discharge manifold, wherein the pump housing is provided as a pressure relief pipe having a lower, a middle and a top section; said pump further comprising a pump shaft, and a plurality of impellers mounted on the pump shaft for centrifugally moving the liquidised fluid from the pump inlet manifold to the pump discharge manifold.

BACKGROUND OF THE INVENTION

Centrifugal pumps of the above-mentioned kind are known from e.g. W02024/047031A1 or WO2015/081314A2. However, these pumps are very large and not suitable for use as high-pressure booster ammonia fuel pumps for use in marine fuel systems, where high pressure and low flow is required. Other pump concepts can be used for this purpose like for instance Diaphragm, piston or Side channel pumps type.

In the maritime industry ammonia is emerging as a promising carbon-free fuel for ships, offering a pathway to decarbonize the shipping industry. However, this presents challenges related to toxicity and handling. In this relation, the above- mentioned types of pumps are not fit for the purpose for this specific marine installation type where high performance and a high level of safety against leakage is required. For use in the marine environment, it is desirable with a small footprint and low building height.

It is an object of the present invention to provide a pump which reduces the above identified drawbacks with the known pump types for use as high-pressure booster ammonia fuel pumps for use in marine fuel systems. SUMMARY OF THE INVENTION

This object is achieved in a first aspect of the invention by providing a centrifugal multi-stage pump for pumping liquidised fluids, in particular fuel pump for pumping liquidised ammonia or liquid natural gas (LNG), hydrogen, methanol, ethane, liquefied petroleum gas (LPG) or the like, said pump comprising a pump unit, which is arranged on a frame, and comprises a pump housing with a lower pump inlet manifold and an upper pump discharge manifold, wherein the pump housing is provided as a pressure relief pipe having a lower, a middle and a top section; said pump further comprising a pump shaft; a plurality of impellers mounted on the pump shaft for centrifugally moving the liquidised fluid from the pump inlet manifold to the pump discharge manifold; and a drive shaft magnetically coupled to the pump shaft; and wherein an electric motor is arranged on the frame, said motor having a motor drive shaft which is connected via a transmission to the drive shaft for driving the pump.

By the present invention there is provided a simple design of a high-pressure booster ammonia fuel pump for use in the marine fuel systems. The pump is advantageously based on a transmission driven multistage centrifugal pump with magnetic coupling and preferably hybrid thrust ball bearing lubricated by the pumped media. Hereby, there is achieved a hermetically sealed high-pressure NH3 pump with no mechanical shaft seals. The pump is driven by an electric motor which is co-arranged on the same frame as the pump unit and connected to the pump unit via a transmission. This allows for a compact design with a reduced build-height and a small footprint. This also allows for a lower manufacturing costs and a pump which is easy to service and easy to regulate. The simplicity of the pump also allows for an extended mean time between major overhauls making the pump economical in operation.

Furthermore, by the pump according to the invention by to the hermetically sealed high-pressure NH3 pump with no mechanical shaft seals, there can be achieved a high performance with a high level of safety against leakage. This is particularly advantageous in relation to toxic fuels, such as ammonia. The advantages of using a magnetic couplings are notable. By this coupling there is no vibration, because there is no contact between the driving part and the driven part of a magnetic coupling, so there is no rigid connection problem. Moreover, the magnetic coupling provides for an overload protection for the pump drive and is safe and easy in maintenance.

In the currently preferred embodiment of the invention, the pump is designed for a maximum differential pressure of 65-77 Barg for feeding an Ammonia (NH3) driven engine.

The pump shaft is preferably vertically oriented. Moreover, the drive shaft and the pump shaft are preferably provided on the same rotation axis and the electric motor drive shaft is preferably provided with an axis parallel to the pump shaft. Hereby, a compact design is achieved with a particular small footprint making the pump easy and appropriate for the requirements of a marine installation.

Preferably, the transmission is a belt transmission. Hereby an efficient transmission of power from the electric motor to the pump drive shaft is provided. The belt or parallel belts may be subjected to belt tensioning pulleys for automatically regulating the tension in the belt or belts.

In a preferred embodiment, the transmission is a timing belt transmission. Hereby, a synchronous rotation of the electric motor drive shaft and the pump drive shaft is ensured. By the term "timing belt" is meant any kind of toothed belt made of reinforced rubber or the like. Alternatively, it is realised by the invention that the transmission may be a chain drive, a gear transmission or the like.

In some preferred embodiments of the invention, the transmission is provided with a gearing ratio between the motor drive shaft and the pump shaft, such as a gearing ratio of between 1: 1 and 1: 10. Hereby, the pump can advantageously be designed with the electric motor and pump having different optimum driving characteristics. In an embodiment, it is found advantageous to provide a hybrid ceramic ball bearing which is media lubricated at the top of the pump shaft for taking up axial forces. This design is simple in design and easy to maintain as it is easy to change the bearing when it becomes worn.

In the preferred embodiments of the invention, the pump is designed as a fuel pump for pumping liquidised ammonia or liquid natural gas (LNG), hydrogen, methanol, ethane, liquefied petroleum gas (LPG) or the like.

In the preferred embodiments of the invention, the magnetic coupling involves a primary containment, which comprises a first magnetic holding rotor structure which is coupled to the pump shaft, and a secondary containment accommodating a second magnetic rotor structure connected to the pump drive shaft.

At least the first magnetic holding rotor structure comprises hermetically sealed magnets near its periphery. Accordingly, the primary containment structure may preferably comprise a containment shroud for hermetically sealing the magnetic rotor structure.

Furthermore, the second magnetic holding rotor structure may be provided concentrically around the primary containment. Thereby, the second magnetic holding rotor structure functions as the outer rotor whereas the first magnetic holding rotor structure functions as the inner rotor in the magnetic coupling.

In the first magnetic holding rotor structure, the containment shroud is preferably made from a ceramic material, such as magnesium-stabilized zirconium oxide ZrO2MgO for high pressure and high temperature stability.

The secondary containment preferably provides for the coupling housing and further comprises a safety valve and a static seal. Hereby, even if a leakage should occur from the primary containment, the second containment will absorb the fluid leaked.

DETAILED DESCRIPTION In the following, the invention is described in more detail with reference to the embodiments shown in the accompanying drawings, in which:

Fig. 1 is a side view of a pump according to a first embodiment of the invention; Fig. 2 is a top view of same; fig. 3 is a side view of the pump with a cross-sectional view of the centrifugal pump and the magnetic coupling and the transmission (section K-K in fig. 2); Fig. 4 is a detailed cross-sectional view of the top section of the pump;

Fig. 5 is a detailed cross-sectional view of the lowermost section of the pump; Fig. 6 is a close-up detailed view of the magnetic coupling at the lowermost section of the pump (detail A in fig. 5);

Fig. 7 is a detailed view of the magnets and the primary and secondary containments of the magnetic coupling (detail B in fig. 5);

Fig. 8 is a bottom view of the frame;

Fig. 9 is a detailed cross-sectional view of the middle section of the pressure relief pipe according to an embodiment of the invention;

Fig. 10 is a detailed sectional view of the inlet manifold section of the pump according to an embodiment of the invention;

Fig. 11 is a cross-sectional sideview of the pump according to a further embodiment of the pump; and

Fig. 12 is a bottom view of the pump of fig. 11.

With reference to the figures 1 and 2, a centrifugal multi-stage pump for pumping liquidised fluids is shown. The pump has a pump unit 1 which is arranged on a frame 3 next to an electric motor 2, which is also arranged on the frame 3. The motor and the pump unit 1 are connected by a transmission 4 accommodated in the frame 1. The pump unit 1 comprises a pressure relief pipe 10 and (see fig. 3) a lower pump inlet in an inlet manifold 11 and an upper pump outlet in a discharge manifold 12.

As shown in figures 3 to 5, inside the pressure relief pipe 10 there is accommodated a pump shaft 13 on which a plurality of impellers 14 are mounted for centrifugally moving the liquidised fluid from the pump inlet in the inlet manifold 11 to the pump outlet in the discharge manifold 12, whilst building up the pressure. In the shown embodiment, ten impellers 14 are provided. In the middle of the series of impellers 14 there is provided a pressure branch 19 so that the inside of the pressure relief pipe 10 is pressurised with the pressure that the first five impellers 14 have produced. By the invention it is realised that any number of impellers may be used, e.g. twelve impellers 14 may be provided if this number is more suitable for achieving the desired boost pressure of the pump 1. The boost pressure which may be achieved by a pump according to the invention may be up to 85 bars.

At the lower end of the pump unit 1, there is arranged a drive shaft 15, which is magnetically coupled to the pump shaft 13 by a magnetic coupling 5. As shown in fig. 1, 2 and 3 there is provided an electric motor 2 arranged on the frame 3 and this electric motor 2 has a motor drive shaft 21 which is connected via a transmission 4 to a drive shaft 15 for driving the pump unit 1 via the magnetic coupling 5.

The pump shaft 13 is mounted with a hybrid ball bearing 16 at the top of the discharge manifold 12. This bearing 16 takes up the axial forces in the pump 1. This top bearing is preferably a ceramic hybrid bearing, which is media lubricated and easy to change. At the bottom, just above the magnetic coupling 5, the pump shaft is accommodated in a carbon guide bearing 18, whereby precise alignment and positioning of the pump shaft 13 and the magnetic coupling 5 is ensured. Preferably, similar carbon guide bearings are also provided near the pressure branch 19 in the middle chamber of the pump to ensure alignment of the pump shaft 13.

The pressure relief pipe 10, the inlet manifold 11 and the discharge manifold 12 are securely mounted together by a number of long stay bolts 17, which safely constrains the pressure relief pipe between the inlet and outlet manifolds and thereby adds to the safety (against leakage) and allows for easy maintenance of the pump 1.

The magnetic coupling 5 is shown in more details in figures 5, 6 and 7. The magnetic coupling 5 includes a primary containment shroud 51 comprising a first magnetic holding rotor structure 13a, 54, which is coupled to the pump shaft 13, and a secondary containment 53 accommodating a second magnetic rotor structure 15a, 52, 55 connected to the drive shaft 15.

The first magnetic holding rotor structure 13a comprises hermetically sealed magnets 54 near its outer periphery. This rotor structure 13a is sealed within the primary containment which is made up by a containment shroud 51 and a cylindrical sealing cover 56 is provided for hermetically sealing the magnets 54 in the magnetic rotor structure. In this embodiment, the containment shroud 51 is made from magnesium-stabilized zirconium oxide ZrO2MgO for high temperature stability. This material Magnesia Stabilized Zirconia (MSZ) is an excellent corrosion-resistant ceramic material to meet the severe service needs of many industries. It exhibits superior resistance to thermal shock and erosion. It has low thermal expansion properties and excellent non-wetting characteristics. However, it is realised by the invention that other materials may be suitable for the containment shroud 51.

The outer second magnetic holding rotor structure 52 with the magnets 55 at its inner periphery is provided concentrically around the primary containment 51.

The secondary containment provides for a coupling housing 53 and further comprises a static seal cylinder 59 with a piston 57 and a static seal 58 therein and contained in the cylinder 59 by a leaf spring 61. This structure is making up a safety valve, which in the unlikely event of a breach in the ceramic containment shroud 51 will activate and contain the pumped media inside the coupling housing 53. Accordingly, the fail-safe piston 57 will be activated and contain the pumped media inside the coupling housing 53. If pressure increase (due to a breach) is sensed in the coupling housing 53, the following actions will happen:

• Motor power is switched off.

• Pressure forces the fail-safe piston 57 to displace along the drive shaft and contact the static seal 58;

• the content due to the breach is contained in the coupling housing.

• When the pressure is relieved, a leaf spring 61 returns the fail-safe piston 57 to its normal open position. The electric motor 2 which drives the pump unit 1 is preferably a flameproof motor for extra safety. In the shown embodiments in figures 1 and 8 and in figures 11 and 12, the transmission 4 is a timing belt transmission. As shown in fig. 8, the timing belt 4 is arranged over a motor drive pulley 42 and a pump drive shaft pulley 41. A belt tensioning system with a pulley 43 which is arranged on an arm 44 which is pivotally mounted and biased towards the belt transmission 4. By choosing the diameter of the two pulleys 41, 42 a gearing ratio between the motor drive shaft 21 and the drive shaft 15 may be provided. Hereby, the motor can be operated at for instance a higher speed than the pump - or vice versa - depending on the gearing ratio.

In fig. 9, the high performance DW-fuel multi-stage pump column. The high pressure can be handled by the pump of a low weight due to the shrouding of the pump column in a pressure relief pipe 10. The pump column comprises a plurality of impellers 14. The impellers 14 are preferably provided with balancing holes 14A. These balancing holes 14A are implemented to minimize the axial force acting on the ceramic hybrid ball bearing 16 (see fig. 4). Fig. 9 the middle section of the pump showing the pressure relief pipe. The pressure relief pipe lowers differential pressure across the final pump stages. This in turn means less stress on the housing and thereby allows for a reduced wall thickness, which in turn means lower weight. As shown in fig. 9, each pump stage provided with a carbon guide bearing 14B and fully cast bowl diffuser design 19A.

Fig. 10 shows an embodiment of the pump according to the invention, where the pump column contained in the pressure relief pipe 10 is fully drainable or at least substantially fully drainable. Opposite the inlet of the inlet manifold 11 there is provided an internal drain valve 11V mounted to the inlet manifold 11. By opening the specially designed internal drain valve 11V, the fluid inside the pump column can be drained very quickly. This is desirable when stopping the pump for servicing and repair, as the pump column may contain a large volume, such as up to 50 litres of liquidised fluid, and which otherwise must be drained by evaporation, which can take a very long time and cause a dangerous toxic environment in the space around the pump due to the nature of the fluid to be evaporated. According to this embodiment, special bores in each pump stage allows for all trapped liquid to flow to the bottom of the pump column. As shown in fig. 10, at the bottom of the pump column in the inlet manifold housing 11H there is provided a fluid connection 11F to the drainage valvellV so that the fluid from the pump flows into contact with the valve piston IIP. The valve 11V shown in fig. 10 may be a manually operated or automatically operated valve. In fig. 10 the valve is a pneumatically operated valve, which is shown in its open position. The valve is opened by pressurising the chamber 11C whereby the closing springs 11OS are compressed and the valve piston IIP is retracted (moved to the left as shown in figure 10) so that the fluid collection in the pump housing 10 and the fluid connection 11F can flow into a drainage bore 11A and back into the inlet manifold 11 from which it can be returned to the supply source, such as a fuel tank (not shown). The bores are machined in the manifold housing 11H at the bottom of the pump column,, which allows for direct access to the inlet manifold. During normal pumping operation the drain valve 11V is fully closed. The drain valve 11V is preferably mounted with double piston seals 11S for added safety. Any small amount of fluid (<500ml_) that may collect in the coupling containment shroud when draining the pump may be removed by other means than evaporation, such as applying vacuum. It is realised that this drainage valve system may be provided on other types of pumps than the pump disclosed in the present disclosure.

With reference to fig. 11 and 12, there is shown an embodiment of the pump as shown and described in the previous embodiments, wherein cooling of the transmission is provided as the transmission cooled by a high-capacity fan 4F. This cooling fan 11F is concentrically mounted on the pump drive shaft pulley 41 and adapted to provide an airflow 4CF from the surroundings of the pump drive shaft 15 and its bearings and into the frame 3 and thereby cooling the timing belt 4 along with the belt tensioning system and the bearings accommodating the pump drive shaft 15. This cooling system is advantageous as the pump hereby is provided with an active cooling of the drive shaft system, where heat may be generated in the drive system, such as in the shaft bearings, due to the relatively high speed with which the pump operates, such as up to 6000 rpm.

As mentioned above in relation to the fig. 8 embodiment, the timing belt 4 is arranged over a motor drive pulley 42 and a pump drive shaft pulley 41. The belt tensioning system with a pulley 43, which is arranged on an arm 44, which in turn is pivotally mounted and biased towards the belt transmission 4. In order to perform at high RPMs, the belt transmission 4 is preferably a heavy duty power transmission drive. This is advantageous also since it is easy to service. As an example, the belt transmission 4 is a timing belt, in particular a robust carbon reenforced timing belt, such as 1760mm x 62mm. The auto-tensioner 43 is a large 0100mm idle-wheel for prolonged belt life. The belt may easily be changed by loosening the auto-tensioner 43 and removing the belt 4 without having to dismantling the belt pulleys 42, 44.

The belt transmission 4 is accommodated in the base frame 3 and is easily accessible through large ports in the base frame 3. However, in order to reduce the noise level of the pump, which is mainly caused by the timing belt 4, the base frame 3 may advantageously be provided with sound absorbing material, such as a sound absorbing inner lining 31.

In general, when directional terms like "upper" and "lower" or similar directional references are used in the present disclosure, these terms are meant to be understood as relative terms e.g. where the term "upper" refers to a direction essentially opposite to the "lower", but it is realised that the planar assembly when in use can be positioned with any orientation.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous. Above, the invention is described with reference to some currently preferred embodiments. However, by the invention it is realised that other embodiments and variants may be provided without departing from the scope of the invention as defined in the accompanying claims.

Claims

1. A centrifugal multi-stage pump for pumping liquidised fluids, in particular fuel pump for pumping liquidised ammonia or liquid natural gas (LNG), hydrogen, methanol, ethane, liquefied petroleum gas (LPG) or the like, said pump comprising a pump unit, which is arranged on a frame, and comprises a pump housing with a lower pump inlet manifold and an upper pump discharge manifold, wherein the pump housing is provided as a pressure relief pipe having a lower, a middle and a top section; said pump further comprising a pump shaft; a plurality of impellers mounted on the pump shaft for centrifugally moving the liquidised fluid from the pump inlet manifold to the pump discharge manifold; and a drive shaft magnetically coupled to the pump shaft; and wherein an electric motor is arranged on the frame, said motor having a motor drive shaft which is connected via a transmission to the drive shaft for driving the pump.

2. A pump according to claim 1, wherein the pump shaft is vertically oriented.

3. A pump according to claim 1 or 2, wherein the drive shaft and the pump shaft are provided on the same axis of rotation.

4. A pump according to any of the preceding claims, wherein the motor drive shaft is provided with an axis parallel to the pump shaft.

5. A pump according to any of the preceding claims, wherein the transmission is a belt transmission.

6. A pump according to any of the preceding claims, wherein the transmission is a timing belt transmission.

7. A pump according to any of the preceding claims, wherein the transmission is a chain drive or a gear transmission.

8. A pump according to any of the preceding claims, wherein the transmission is provided with a gearing ratio between the motor drive shaft and the pump shaft, such as a gearing ratio of between 1: 1 and 1: 10.

9. A pump according to any of the preceding claims, wherein a hybrid ceramic ball bearing which is media lubricated is provided at the top of the pump shaft for taken up axial forces.

10. A pump according to any of the preceding claims, wherein the middle section of the pressure relief pipe is provided with a pressure branch for lowering differential pressure across the pump stages in the top section.

11. A pump according to any of the preceding claims, wherein a primary containment is provided comprising a first magnetic holding rotor structure which is coupled to the pump shaft, and a secondary containment accommodating a second magnetic rotor structure connected to the drive shaft.

12. A pump according to claim 11, wherein at least the first magnetic holding rotor structure comprises hermetically sealed magnets near its periphery.

13. A pump according to claim 11 or 12, wherein the second magnetic holding rotor structure is provided concentrically around the primary containment.

14. A pump according to any of claim 11 to 13, wherein the primary containment structure comprises a containment shroud for hermetically sealing the magnetic rotor structure.

15. A pump according to claim 14, wherein the containment shroud is made from a ceramic material, such as magnesium-stabilized zirconium oxide ZrO2MgO for high temperature stability.

16. A pump according to any of claims 11 to 15, wherein the secondary containment provides for a coupling housing and further comprises a safety valve and a static seal.