Piston pump

Abstract

The present disclosure relates to a piston pump for pumping liquefied fluid, in particular a cryogenic fuel pump for pumping liquefied fuel, such as liquefied natural gas (LNG), hydrogen, methanol, ammonia and the like, the pump comprising: a pump housing (1) having a piston chamber (4) formed inside and in which an inlet flow valve (8) and a discharge check valve (6) are provided; a piston having a piston head (2) and a piston rod (3), said piston being arranged to reciprocate in a piston chamber along a longitudinal axis to compress the fluid in the chamber to an elevated pressure; first sealing means (21) provided on the piston head between the inner circumferential surface of the chamber and the piston head; and a second sealing arrangement arranged between the piston rod and the bore (10) of the pump housing, where the second sealing arrangement comprises a pressurized sealing device arranged in the bore of the housing between the at least two sealing rings (33, 34) and a source of pressurized fluid, and where the pressurized sealing device is arranged in the bore of the housing between the at least two sealing rings (33, 34). The pressurized sealing apparatus comprises an inlet (31) and an outlet (36) for pressurized lubricating fluid, a source of pressurized fluid for providing pressurized fluid in a fluid stream to the inlet.

Description

Technical Field

[0001] The present invention relates to a piston pump for pumping liquefied fluids, in particular a cryogenic fuel pump for pumping liquefied fuels (such as liquefied natural gas (LNG), hydrogen, methanol, ammonia, etc.), the pump comprising a pump housing having a piston chamber formed therein, and an inlet flow valve and a discharge check valve arranged in the pump housing; a piston having a piston head and a piston rod, the piston being arranged to reciprocate along a longitudinal axis in the piston chamber to compress the fluid in the chamber to an elevated pressure, and a first sealing device being arranged on the piston head and located between the inner circumferential surface of the chamber and the piston head. Background Art

[0002] Typically, a piston pump consists of a high-pressure end, where a piston head reciprocates in a piston chamber and pressurizes incoming liquid before discharging it at an elevated pressure. The other end of the piston pump is the low-pressure end. The piston is driven by a piston rod, which is sealed to a bore in the pump housing through which it reciprocates.

[0003] US2019 / 0293067A1 discloses a piston pump of the type initially mentioned, in which a supply chamber is closed by a cover on the side opposite the piston, the cover including a first flow channel allowing the supply of cryogenic liquid from the supply chamber and a second flow channel allowing the pumped liquid to be discharged. The piston head is sealed to the piston bore to ensure that the liquid does not escape the supply chamber when pressurized by the piston head. The piston is driven in a reciprocating motion in the bore. A plurality of bore seals are provided in the bore, which receives the piston passing through the pump body.

[0004] Purpose of the Invention

[0005] The seal between the piston rod and the bore may be susceptible to wear, and in order to achieve an acceptable service life of the pump, the number of sealing rings is increased. However, the object of the present invention is to provide an alternative or at least a supplementary solution to multiple sealing rings so that the number of sealing rings can be reduced. Summary of the Invention

[0006] In the present invention, several embodiments of a cryogenic piston pump are described. Thus, the present invention relates to a piston pump for pumping liquefied fluids, in particular a cryogenic fuel pump for pumping liquefied fuels such as liquefied natural gas (LNG), hydrogen, methanol, etc., comprising a pump housing having a piston chamber formed therein and an inlet flow valve and a discharge check valve disposed therein; a piston having a piston head and a piston rod, the piston being configured to reciprocate along a longitudinal axis in the piston chamber to compress the fluid in the chamber to an elevated pressure; a first sealing device disposed on the piston head between an inner circumferential surface of the chamber and the piston head; and a second sealing device disposed between the piston rod and a bore in the pump housing, wherein the second sealing device comprises a pressurized sealing device and a pressurized fluid source, the pressurized sealing device being disposed in the bore of the housing between at least two sealing rings, and wherein the pressurized sealing device comprises an inlet and an outlet for pressurized lubricating fluid, the pressurized fluid source providing pressurized fluid in a fluid stream to the inlet.

[0007] By providing a pressurized sealing device around the piston rod, an active seal is provided to prevent liquid from escaping from the space behind the piston head into the bore.This solution is advantageous because additional lubrication of the piston rod is provided.

[0008] In an embodiment of the invention, the pressurized sealing device comprises an annular groove in the bore. This allows a reservoir for the lubricating fluid to be formed annularly around the piston rod.

[0009] In some embodiments, the pressurized lubricating fluid can be the pump's liquefied fuel, i.e., the pump's primary cargo fluid. In other currently preferred embodiments, the pressurized seal includes an inlet and an outlet for a pressurized lubricating fluid, such as a lubricating oil, that provides a barrier and lubrication between the bore behind the piston head and the piston rod. Providing the pressurized fluid for sealing ensures that no external fluid (gas or liquid) will pass through the annular seal area between the bore and the piston rod.

[0010] Preferably, a return fluid flow is provided between the outlet and the pressurized fluid source to form a closed-loop fluid system. Thus, a closed-loop sealed fluid system can be provided. Advantageously, a filter is provided in the return fluid flow. Thus, any contaminants in the fluid can be removed, thereby protecting the sealing device.

[0011] Preferably, the source of pressurized fluid comprises a pressure intensifier. Thus, the pressurized fluid is advantageously supplied to the inlet of the pressurized sealing device at an elevated pressure (such as 1 bar above the pressure of the cryogenic fluid). Thus, the elevated pressure is ensured, thereby maintaining the seal.

[0012] In an embodiment of the high-pressure piston pump according to the invention, the pump housing comprises a sealing housing, and at least the second sealing device of the pressurized sealing arrangement is arranged in the sealing housing. This allows the pump housing to be designed in a modular manner, which is more efficient in production and easier to maintain.

[0013] In a preferred embodiment, the seal housing includes a heating system for providing the seal material with a temperature higher than that of the cryogenic fluid. The higher temperature may be in the range of between 0°C and 45°C, and in a preferred embodiment is approximately 20°C. This allows for a better seal due to the higher viscosity of the seal fluid and is made possible by the provision of thermal insulation within the seal housing so that the seal does not affect the temperature of the main cargo being pumped by the piston pump at temperatures higher than the cryogenic temperature range for which the pump is designed to operate.

[0014] In a currently preferred embodiment, the second sealing device comprises at least two pressurized sealing devices mounted between at least two sealing rings.Thereby, excess sealing fluid can be retained in the annular sealing area between the bore and the piston rod.

[0015] As mentioned above, the second sealing device may also provide lubrication of the piston rod.

[0016] From the above description of some preferred embodiments, it is noteworthy that the first sealing device includes a plurality of piston rings that seal the gap between the inner circumferential surface of the chamber and the piston head. DETAILED DESCRIPTION

[0017] The present invention is described below with reference to the accompanying drawings, in which:

[0018] Figure 1 is a side sectional view of a low-temperature and high-pressure piston pump according to an embodiment of the present invention;

[0019] Figure 2 is a schematic detailed side cross-sectional view of a low-pressure end of a piston pump having a second sealing arrangement;

[0020] Figure 3 is a detailed side cross-sectional view of the piston chamber end of a piston pump having an inlet valve; and

[0021] Figures 4 to 6 Detailed cross-sectional view of the inlet, filling, and discharge of fluid in the piston chamber of a piston pump.

[0022] exist Figure 1, an embodiment of a cryogenic piston pump for pumping liquefied fluids is shown. The pump is a cryogenic fuel pump for pumping liquefied fuels (such as liquefied natural gas (LNG), hydrogen, methanol, etc.). The pump comprises a pump housing 1 having a piston chamber 4 formed therein, and an inlet flow valve 5 and a discharge check valve 6 mounted in the piston chamber 4. Inside the housing 1, a piston consisting of a piston head 2 and a piston rod 3 is provided. In the housing 1, a housing volume 7 is also formed behind the piston head 2, i.e., a housing volume 7 on the side of the piston head 2 opposite to the piston chamber 4. The piston head 2 is arranged to reciprocate along a longitudinal axis in the piston chamber 4 to compress the fluid in the chamber 4 to an elevated pressure.

[0023] When the piston 2 is retracted in the piston chamber, liquefied fluid is drawn from the fluid chamber 9 into the piston chamber 4 through the inlet fluid channel 5 and the inlet valve 8, and then when the piston head 2 advances, the liquid in the piston chamber 4 is pressurized, and the pressurized liquid is then discharged through the discharge valve 6. In order to ensure that the liquid does not escape from the piston chamber 4 into the housing volume 7 when pressure builds up in the piston chamber 4 (and thereby increase the pressure difference between the piston chamber 4 and the housing volume 7), a first sealing device 21 is provided on the piston head 2 between the inner circumferential surface of the piston chamber 4 and said piston head 2. These first sealing devices 21 may be piston rings arranged annularly around the piston head 2.

[0024] At the low-pressure end of the pump, in the housing 1 opposite the piston chamber 4, a second sealing device 30 is provided between the piston rod 3 and the bore 10 of the pump housing 1. The second sealing device 30 comprises a pressurized sealing device 31 which is provided in the bore 10 of the housing 1 between at least two sealing rings 33, 34.

[0025] exist Figure 2 , a more detailed view of the low pressure end of the second sealing device according to an embodiment of the present invention is shown. Figure 2 As shown, the housing is provided with two pressurized sealing devices 30, each of which includes an annular groove 35 in the bore 10. Each pressurized sealing device 30 further includes an inlet 31 and an outlet 32 ​​for a pressurized fluid (such as oil), and a pressurized fluid source 36 for supplying the pressurized fluid in the fluid flow to the inlet 31 via a fluid line 38. Starting from the outlet 32, a return fluid flow line 39 is provided between the outlet 32 ​​and the pressurized fluid source 36 to form a closed-loop fluid system. The return fluid line 39 is connected and a filter 37 is provided in the return fluid flow to remove any contaminants from the fluid. The pressurized fluid source includes a booster 36, whereby the pressurized fluid is pressurized at an elevated pressure (such as 1 bar (P) above the supply pressure of the cryogenic fluid). gas+1 bar)) is supplied to the inlet 31 of the pressurized sealing device 30. The pressure intensifier 36 is also connected to the housing volume 7 via a fluid line 40, and thereby the fluid is at the pressure P of the cryogenic fluid. gas Next is supplied.

[0026] The portion of the pump housing 1 that houses the second sealing device 30 is configured as a sealed housing 1A. The sealed housing 1A may be provided with a heating system 12 for providing the sealed fluid with a temperature higher than that of the cryogenic fluid. The heating system may be any suitable heating system, such as a heating chamber through which the fluid flows, or other types of heating systems.

[0027] exist Figure 1 and Figure 2 In the illustrated embodiment, the second sealing device includes at least two pressurized sealing devices 30 installed between a plurality of sealing rings 33 and 34 on both sides of the pressurized sealing device 30 .

[0028] By means of the second sealing device, an additional pressurized fluid conduit 35 may be provided, which is used not only for sealing but also for lubrication of the piston rod 3, which reciprocates in the bore 10 of the housing 1. The fluid conduit 35 is annularly arranged in the bore 10 of the sealing housing 1A. Each conduit 35 is provided with a fluid inlet 31 and a fluid outlet 32. On each side of the pressurized seal 30, a plurality of sealing rings 33 and 34 are provided to confine the oil in the sealing device 30. The fluid inlet 31 is supplied with pressurized fluid, such as oil, through a one-way valve 31A in the inlet 31. The outlet 32 ​​is preferably positioned opposite the inlet 31 and is also provided with a one-way valve 32A. Thereby, the fluid flow is regulated. In Figure 1 and Figure 2 In the embodiment shown, two sealing devices 30 are provided and two inlets 31 receive pressurized fluid from a pressure intensifier 36 via fluid lines 38. The pressure is increased to ensure that an oil seal is maintained between the piston rod 3 and the bore 10.

[0029] exist Figure 3 In the Figure 1 Detailed view of the high-pressure end of the piston pump, in which the piston chamber 4, the inlet flow valve 8 and the discharge valve 6 are provided. The pump housing 1 is provided with a fluid chamber 9 arranged annularly around the piston chamber 4. The inlet flow valve 8 and the discharge check valve 6 are provided in the housing 1 for supplying fluid from the fluid chamber 9 to the piston chamber 4 through the inlet valve 8 and discharging the fluid from the piston chamber 4 at an increased pressure through the discharge check valve 6. Figure 1 As explained, the piston has a piston head 2 and a piston rod 3, and the piston head 2 is arranged to reciprocate along a longitudinal axis in a piston chamber 4 to compress fluid in the chamber 4 to an elevated pressure.

[0030] The fluid in the annular fluid chamber 9 is under pressure and flows through the evenly angularly spaced inlet flow channels 5 towards openings in these channels 5. The inlet flow valve device 8 comprises an annular inflow space 51 which is concentric with the fluid chamber 9 and has a common wall 52 with the fluid chamber 9, and in which the fluid channels 5 are arranged such that fluid communication between the fluid chamber 9 and the annular inflow space 51 can be established via a plurality of fluid openings provided by the fluid channels 5 in the common wall 52 between the fluid chamber 9 and the inflow space 51. A valve plate 81 is arranged in the inflow space 51 and is spring-loaded such that the valve plate 81 is biased by the spring force towards the common wall 52 and thereby blocks the flow in the fluid channels 5 by blocking the fluid openings on the inflow space side of the common wall 52.

[0031] The valve plate 81 is annular. The common wall 52 is also annular and is arranged concentrically with the longitudinal axis. The spring loading of the valve plate 81 is provided by a plurality of springs 82 (see Figure 3 ) provided, these springs provide a spring force in the axial direction against the flow direction in the fluid channel 51, such as Figure 3 In some preferred embodiments, the spring 82 is a coil spring. In the housing 1 , the annular inflow space 51 is formed integrally with the piston chamber 4 , and the fluid flow in the inflow space 51 will flow radially inwardly into the piston chamber 4 .

[0032] This spring force biases the valve plate 81 toward closing the fluid flow through the fluid channel 5, but when the piston head 2 retracts in the piston chamber 4 and the pressure thereby drops in the chamber 4, the pressure from the fluid in the fluid chamber 9 forces the valve plate 81 backwards and loads the spring 82, thereby opening the inlet valve device 8.

[0033] When the piston head 2 advances again in the piston chamber, the pressure in the chamber 4 increases and the valve plate 81 is immediately forced back to the closed position, thereby preventing any fluid from flowing back into the fluid chamber 9. Instead, the discharge check valve 6 opens. The discharge valve 6 is coaxially arranged on the longitudinal axis of the pistons 2, 3.

[0034] The discharge check valve 6 includes a valve head 61 that is biased toward a valve seat 62 formed in the housing 1. The valve head 61 is subjected to a spring force in the axial direction toward the piston chamber 4. When the pressure in the piston chamber 4 exceeds a certain threshold, the spring force urging the valve head 61 toward the valve seat 62 is overcome, and the valve head 61 moves backward from the closed position to the open position, whereby the fluid from the piston chamber 4 is discharged through the discharge check valve 6 at an elevated pressure relative to the pressure in the fluid chamber 9.

[0035] The steps in the piston pump cycle are Figures 4 to 6 Shown step by step.

[0036] exist Figure 4 In FIG. 4 , the step of drawing the fluid into the piston chamber 4 is shown. The inlet valve 8 is opened when the valve plate 81 is forced forward and the fluid flows into the piston chamber 4, as shown by arrow F. i shown.

[0037] This is because the piston head 2 travels backwards and creates a lower pressure in the piston chamber 4. This lower pressure causes the inlet valve plate 81 to open and move against the spring 82, and liquid will flow into the piston chamber 4 until the piston head 2 reaches the bottom position, i.e. the most retracted position.

[0038] exist Figure 5 In FIG, this position is shown, wherein the piston head 2 is in the bottom position and fluid has entered the piston chamber 4. As the piston chamber 4 is now filled, the piston 2 will now begin to move forward again. This causes the inlet valve plate 81 to close, and high pressure will build up in the piston chamber during the piston travel.

[0039] exist Figure 6 In FIG. 4 , the discharge step is shown. The piston 2 moves forward and creates high pressure in the cylinder 4. This causes the outlet valve 6 to open and move against the spring 63. The fluid will flow out of the piston chamber 4 until the piston 2 reaches the top position. This discharge flow is indicated by arrow F. o As soon as the piston head 2 starts to retract again, the outlet valve 6 will close again.

[0040] In this disclosure, the term "discharge check valve" is used for a check valve, ie a one-way valve that generally allows fluid to flow through it in one direction only.

[0041] Although the present invention has been described in conjunction with specific embodiments, it should not be interpreted as being limited in any way to the examples presented. The scope of the invention is defined by the appended claims. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Moreover, references to "a" or "an" and the like should not be interpreted as excluding a plurality. The use of reference numerals in the claims relative to the elements shown in the drawings should not be interpreted as limiting the scope of the invention. In addition, individual features mentioned in different claims may be advantageously combined, and the mention of these features in different claims does not exclude that a combination of features is impossible and advantageous.

[0042] Above, the invention has been described with reference to some presently preferred embodiments. However, it will be appreciated that other embodiments and variations may be provided without departing from the scope of the invention as defined in the appended claims.

Claims

1. A piston pump for pumping a liquefied fluid, in particular a cryogenic fuel pump for pumping a liquefied fuel, such as liquefied natural gas (LNG), hydrogen, methanol, ammonia, etc., the pump comprising: a pump housing having a piston chamber formed inside the pump housing and having an inlet flow valve and a discharge check valve disposed therein; a piston having a piston head and a piston rod, the piston being arranged to reciprocate along a longitudinal axis in the piston chamber to compress a fluid in the chamber to an elevated pressure, a first sealing device disposed on the piston head between the inner circumferential surface of the chamber and the piston head; and A second sealing device, the second sealing device is arranged between the piston rod and the hole of the pump housing, wherein the second sealing device includes a pressurized sealing device and a pressurized fluid source, the pressurized sealing device is arranged in the hole of the housing and is located between at least two sealing rings, and wherein the pressurized sealing device includes an inlet and an outlet for pressurized lubricating fluid, and the pressurized fluid source is used to provide pressurized fluid in the fluid flow to the inlet.

2. The pump according to claim 1, wherein The pressurized seal device includes an annular groove located in the bore.

3. The pump according to claim 1 or 2, wherein: The pressurized lubricating fluid is lubricating oil, which provides a barrier and lubrication between the bore behind the piston head and the piston rod.

4. A pump according to any one of the preceding claims, wherein A return fluid flow is provided between the outlet and the pressurized fluid source to form a closed-loop fluid system.

5. The pump according to claim 4, wherein A filter is disposed in the return fluid stream.

6. A pump according to any one of the preceding claims, wherein The source of pressurized fluid includes a pressure intensifier.

7. A pump according to any one of the preceding claims, wherein The pressurized fluid is supplied to the inlet of the pressurized sealing device at an elevated pressure, such as 1 bar above the supply pressure of the cryogenic fluid.

8. A pump according to any one of the preceding claims, wherein The pump housing comprises a sealing housing, and wherein at least the pressurized sealing device in the second sealing arrangement is arranged in the sealing housing.

9. The pump according to claim 8, wherein The sealed housing includes a heating system for providing a sealing material with a temperature higher than that of the cryogenic fluid.

10. A pump according to any one of the preceding claims, wherein The second sealing device comprises at least two pressurized sealing devices mounted between at least two sealing rings.

11. A pump according to any one of the preceding claims, wherein The second sealing device provides lubrication of the piston rod.

12. A pump according to any one of the preceding claims, wherein The first sealing device includes a plurality of piston rings that seal a gap between an inner circumferential surface of the chamber and the piston head.

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