EP4636247A1

EP4636247A1 - A reciprocating pump

Info

Publication number: EP4636247A1
Application number: EP24315163.6A
Authority: EP
Inventors: Patrice BONNEFOUS
Original assignee: Cryostar SAS
Current assignee: Cryostar SAS
Priority date: 2024-04-15
Filing date: 2024-04-15
Publication date: 2025-10-22
Also published as: WO2025219248A1

Abstract

The invention refers to a reciprocating pump (100), comprising a liquid supply chamber (110) with an inlet port (111) and an outlet port (112) configured such that a liquid to be pressurised is provided in the supply chamber; a pumping chamber (130) arranged within the liquid supply chamber (110) and in fluid communication with the fluid supply chamber (110); a piston (120) configured to reciprocate in the pumping chamber (110) along a movement axis (121) such that, by means of reciprocating movement of the piston (120), liquid is transported from the fluid supply chamber (110) into the pumping chamber (130) and pressurised in the pumping chamber (130), wherein the piston (120) protrudes from an outside of the fluid supply chamber (110) at least partially into the fluid supply chamber (110); wherein a heat shielding unit (170) is provided in the fluid supply chamber (110) at a predetermined position (171) at which the piston (120) protrudes form the outside of the fluid supply chamber (110) into the fluid supply chamber (171), wherein the heat shielding unit (170) is configured to at least partially absorb heat (175) being conducted from the outside of the fluid supply chamber (110) into the fluid supply chamber (110) and/or into the pumping chamber (130) and to transfer the absorbed heat to the outlet port (112).

Description

The present invention relates to cryogenic reciprocating pump.

Background of the invention

A cryogenic reciprocating pump can be used to increase the pressure of a liquid at very low temperature, e.g. below -100°C. For this purpose, the pump can comprise a piston, which can be reciprocated inside a cylinder or sleeve, thereby defining a pumping chamber. This pumping chamber can be in fluid communication with a supply chamber, into which the liquid to be compressed can be supplied, e.g. by means of gravity, static pressure or by means of another pump. By means of the reciprocating movement of the piston, the liquid can be transported from the fluid supply chamber into the pumping chamber, pressurised in the pumping chamber, and discharged via a discharge outlet. For the pump to work efficiently, it can be of importance that the liquid transported from the supply chamber to the pumping chamber is as cold as possible.

Disclosure of the invention

The present invention relates to a cryogenic reciprocating pump with the features of claim 1. Embodiments and advantages form the subject-matter of the dependent claims and of the subsequent description.
The pump comprises a liquid supply chamber or suction chamber or reception chamber configured such that a liquid, e.g. a cryogenic liquid, to be pressurised is provided in the supply chamber. The liquid supply chamber comprises an inlet or inlet port, through which the liquid to be pressurised can be introduced into the supply chamber, e.g. by means of gravity or e.g. by means of another pump. The liquid supply chamber further comprises an outlet or outlet port, through which warmed or vaporised liquid can be discharged from the supply chamber. For example, the liquid supply chamber can be connected with a storage tank such that liquid from this storage tank can be transported to the liquid supply chamber through the chamber inlet, e.g. via a suction line, and such that warmed liquid or vaporised liquid can be returned from the supply chamber to the storage tank through the outlet port. The outlet port can expediently be provided in order to remove warmed or vaporised liquid from the supply chamber in order to have the coldest liquid available for pumping chamber. The segregation between cold fluid and warm/vaporised fluid can be achieved by gravity and/or convection (since cold fluid is heavier than warm fluid). The inlet port can therefore expediently be provided at a bottom of the supply chamber, and the outlet port can expediently be provided at a top of the supply chamber.
The pump further comprises a pumping chamber arranged within or inside the liquid supply chamber, which is direct fluid communication with the fluid supply chamber. Without loss of generality, this pumping chamber is also referred to as first pumping chamber or first stage chamber. It is possible that the pump is provided as a single-state pump with only one pumping chamber or as a two-stage or dual-stage pump with this first pumping chamber and with a second pumping chamber in fluid communion with the first chamber.
A piston is configured to reciprocate in the first pumping chamber along a movement axis, particularly a longitudinal axis, such that, by means of reciprocating movement of the piston, liquid is transported from the fluid supply chamber into the pumping chamber and pressurised in the pumping chamber. The piston protrudes from an outside of the fluid supply chamber at least partially into the fluid supply chamber, i.e. a part of the piston is arranged outside of the fluid supply chamber. Particularly, the piston can move inside a cylinder or sleeve thereby defining the pumping chamber inside this cylinder or sleeve.
According to the present invention, a heat shielding unit is provided in the fluid supply chamber at a predetermined position at which the piston protrudes from the outside of the fluid supply chamber into the fluid supply chamber. This predetermined position can for example correspond to a warm end of the fluid supply chamber. The heat shielding unit is configured to at least partially absorb heat being conducted or dissipated or otherwise ingressing from the outside of the fluid supply chamber, particularly from the ambient atmosphere around the pump, into the fluid supply chamber and/or into the pumping chamber. The heat shielding unit is further configured to lead or transfer the absorbed heat to the outlet port, especially by means of gravity and/or convection.
Heat from the outside of the supply chamber can be conducted along the piston or along a housing, sleeve or cylinder, in which the piston reciprocates, from the outside into the supply chamber. The heat shielding unit is particularly provided in order to absorb at least a part of this heat and transfer it to the outlet of the supply chamber. The heat shielding unit can for example be provided as a specific portion or section or cavity within the fluid supply chamber, e.g. such that an amount of the liquid introduced into the fluid supply chamber can circulate at this specific chamber portion. This circulating amount of the liquid can then expediently at least partially absorb the heat conducted from the outside, and lead it to the tank return outlet of the supply chamber, thereby shielding the remaining liquid inside the fluid supply chamber and inside the pumping chamber. The heat shielding unit can for example also be provided as a specific element arranged in the supply chamber, e.g. as a foil or sheet.
The heat shielding unit is therefore particularly provided as a thermal screen or liquid screen or heat shield between the external part of the pump and the supply chamber and/or the first pumping chamber. Expediently, most of or any heat ingress can be absorbed by the heat shielding unit, especially by the first liquid in contact, and then led to source tank, thereby acting as a barrier. Particularly, the heat shielding unit can considerably prevent this heat to reach the remaining part of the supply chamber and the first pumping chamber, where the liquid to pump is expediently in equilibrium and where any heat can generate bubbles damageable for the efficiency of the pump.
To work efficiently, the cryogenic pump can particularly require to have the liquid as cold as possible at suction side. Any heat entry can reduce the NPSH (Net Positive Suction Head) available at pump suction. In conventional cryogenic pumps, there can be a thermal bridge between ambient temperature and the respective supply chamber or pumping chamber. The invention particular allows to prevent such a thermal bridge, thereby increasing the efficiency of the cryogenic pump
The present invention can particularly yield a lower NPSH required by the pump, since the pump can be less sensitive to the quality of the suction line and to the quality of the liquid in the storage tank in terms of pressure and/or temperature. The invention can further achieve a better volumetric efficiency, a better isentropic efficiency, and a lower discharge temperature. The present invention is suitable for all cryogenic gases and all type of reciprocating pumps. The invention is particularly suitable for very low temperature liquids, such as liquid hydrogen (LH2), and for two-stage pumps.
It is to be understood that the pump can comprise further elements, e.g. a discharge outlet configured to discharge liquid pressurised by means of the reciprocating movement of the piston. In a single-state pump, the discharge outlet can be in direct fluid communication with the first pumping chamber. In a dual-stage pump, the discharge outlet can be in indirect fluid communication with the first pumping chamber via the second pumping chamber. The pump can further comprise a number of valves, e.g. provided between the liquid supply chamber and the first pumping chamber, between the first pumping chamber and the discharge outlet, etc.
According to an embodiment, the heat shielding unit is provided as specific cavity, section or portion of the fluid supply chamber between a housing of the first pumping chamber and a housing of the fluid supply chamber, the section extending in a direction parallel to the movement axis of the reciprocating movement of the piston and/or in a direction perpendicular to the movement axis of the reciprocating movement of the piston. This specific section especially surrounds the piston or a housing of the piston and extends in the radial direction to provide an extended heat shield, particularly extending as far as possible between the movement axis and the outer housing of the pump or the outer housing of the fluid supply chamber. Alternatively or even additionally, the section especially extends in a direction parallel to the movement axis so as to provide a distance of the first pumping chamber to the outer housing of the pump or to the outer housing of the fluid supply chamber, thus working as a heat capture and transfer. This section can particularly be provided as a conduit or cavity, where a specific amount of the liquid inside the fluid supply chamber can circulate, such that this circulating amount of the liquid can at least partially absorb the heat conducted into the supply chamber and transfer it to the outlet. The heat shielding unit and the liquid circulating therein can expediently act as a liquid or thermal screen.
According to an embodiment, the heat shielding unit separates the housing of the first pumping chamber from the housing of the fluid supply chamber in the direction parallel to the movement axis of the reciprocating movement of the piston. The specific section of the supply chamber provided as the heat shielding unit particularly acts as a heat capture and transfer area between the housings of the fluid supply chamber and the first pumping chamber, such that these housings are not in direct contact with each other. Therefore, a potential thermal bridge from the outside or ambient atmosphere along the housing of the piston, the housing of the supply chamber and the housing of the first pumping chamber can especially be interrupted.
According to an embodiment, the heat shielding unit is provided such that the housing of the pumping chamber is separated from the housing of the fluid supply chamber by a predetermined distance in the direction parallel to a movement axis of the reciprocating movement of the piston. A length of the specific section of the fluid supply chamber forming the heat shielding unit can expediently be chosen as this predetermined distance.
According to an embodiment, the predetermined distance corresponds to at most 5% of a total length of the fluid supply chamber in the direction parallel to a movement axis of the reciprocating movement of the piston. In particular, the predetermined distance can be determined as large as necessary such that the liquid circulating in the specific section can effectively absorb the ingress heat, but as small as possible to reduce pump overall volume.
According to an embodiment, the heat shielding unit is provided as a specific heat conducting element, e.g. a foil and/or a sheet, provided between the housing of the first pumping chamber and the housing of the fluid supply chamber. This element can especially surround the piston or the housing of the piston. The heat conducting element can expediently absorb heat being conducted from the outside along the housing of the piston before transferring the heat out of the supply chamber.
According to an embodiment, the pump further comprises an insulation jacket at least partially surrounding the liquid supply chamber. The insulation jacket can for example be provided as a vacuum chamber. For this purpose, the insulation jacket can comprise connection means for connecting the insulation jacket with a vacuum pump such that a vacuum can be created inside the insulation jacket.
According to an embodiment, the piston protrudes from an outside of the insulation jacket through the insulation jacket into the fluid supply chamber. The heat shielding unit is especially provided at the position, where the piston enters from the insulation jacket into the supply chamber. Therefore, a thermal bridge from the outside along the housing of the piston through the insulation jacket into the supply chamber can expediently be interrupted by means of the heat shielding unit.
According to an embodiment, the pump further comprises a second pumping chamber or second stage chamber arranged within or inside the liquid supply chamber, which is in direct fluid communication with the first pumping chamber. By means of reciprocating movement of the piston, pressurised liquid is transported from the fist pumping chamber into the second pumping chamber and further pressurised in the second pumping chamber. The discharge outlet is particularly in direct fluid communication with the second pumping chamber and is configured to discharge pressurised liquid from the second pumping chamber. Expediently, in the first pumping chamber, the liquid can be compressed to a first pressure level or pressure stage. In the second pumping chamber, the liquid can then further be compressed to a second pressure level or pressure stage. The pump can therefore be provided as a two-stage or dual-stage pump, particularly for compressing cryogenic fluids. It can be particularly critical for a two-stage pump of that kind that the liquid on the suction side is as cool as possible, particularly when the pump is used for compressing very low-temperature liquids, e.g. liquid hydrogen. The invention is therefore particularly suitable for dual-stage pumps of that kind.
Further advantages and developments of the invention are specified in the description and the associated drawings.
It goes without saying, that the features named above and still to be explained below can be used not only in the combination indicated respectively, but also in other combinations or in a stand-alone manner, without going beyond the scope of the present invention.
The invention is illustrated schematically in the drawings on the basis of exemplary embodiments and will be described in detail in the following with reference to the drawings.

Description of drawings

Fig. 1: schematically shows an embodiment of a reciprocating pump according to the present invention in a sectional side view.
Fig. 2: schematically shows a reciprocating pump according to the prior art in a sectional side view.

Detailed description of the drawing

Fig. 1 shows an embodiment of a cryogenic reciprocating pump 100 according to the present invention in a sectional side view.
The pump 100 comprises a liquid supply chamber or suction chamber or reception chamber 110 with an inlet port 111 and an outlet port 112. The inlet 111 can be connected with a storage tank such that a liquid to be pressurised can be transported from this storage tank into the liquid supply chamber 110. Warmed or vaporised liquid can be discharged from the supply chamber 110 via the outlet 112. The liquid can be a cryogenic liquid at very low temperatures, e.g. below -100°C, e.g. liquid hydrogen (LH2).
A first pumping chamber or first stage chamber 130 is arranged within or inside the liquid supply chamber 110 and is in direct fluid communication with the fluid supply chamber 110. The pump 100 is for example provided as a two-stage pump, which further comprises a second pumping chamber or second stage chamber 140 arranged within or inside the liquid supply chamber 110, wherein this second pumping chamber 140 is in direct fluid communication with the first pumping chamber 130. A discharge outlet 150 is in direct fluid communication with the second pumping chamber 140.
A piston 120 is configured to reciprocate in the first pumping chamber 130 along a movement axis 121, particularly a longitudinal axis, as indicated by the arrow 122. By means of the reciprocating movement 122 of the piston 120, liquid is transported or sucked from the fluid supply chamber 110 into the first pumping chamber 130 and pressurised in the first pumping chamber 130, particularly to a first pressure level or pressure stage. The liquid pressurised to this first pressure level is then transported from the first pumping chamber 130 into the second pumping chamber 140, where the liquid is further pressurised to a second pressure level or pressure stage. The liquid pressurised to this second pressure level is then discharged from the pump 100 via the discharge outlet 150.
The pump 100 further comprises a number of valves 180 provided between the liquid supply chamber 110 and the first pumping chamber 130, between the first pumping chamber 130 and the second pumping chamber 140 as well as between the second pumping chamber 140 and the discharge outlet 150.
The pump 100 further comprises an insulation jacket 160 at least partially surrounding the liquid supply chamber 110. Expediently, a housing 165 of the insulation jacket 160 surrounds a housing 115 of the fluid supply chamber 110. The insulation jacket 160 can for example be provided as a vacuum chamber, such that a vacuum can be created inside the insulation jacket 160 as a thermal insulation of the fluid supply chamber 110.
The piston 120 protrudes at least partially into the fluid supply chamber 110, expediently from an outside of the insulation jacket 160 through the insulation jacket 160 into the fluid supply chamber 110. A heat shielding unit 170 is provided in the fluid supply chamber 110 at a predetermined position 171 at which the piston 120 protrudes form the outside of the fluid supply chamber 110 into the fluid supply chamber 110. This heat shielding unit is configured to at least partially absorb heat, indicated by the arrows 175, being conducted, dissipated or ingressing from the outside of the fluid supply chamber 110 into the fluid supply chamber 110 and/or into the first pumping chamber 120. The heat shielding unit is further configured to lead the absorbed heat to the outlet port 112, especially by means of gravity and/or convection.
This heat shielding unit 170 can be provided as a specific cavity, section or portion of the fluid supply chamber 110 between a housing 135 of the first pumping chamber 130 and the housing 115 of the fluid supply chamber 110, the section extending in a direction parallel and perpendicular to the movement axis 121 of the reciprocating movement of the piston 120. This specific section 170 can be provided as a conduit or cavity surrounding the piston 120, in which a specific amount of the liquid inside the fluid supply chamber 110 can circulate, such that this circulating liquid can at least partially absorb the heat 175 conducted into the supply chamber 110. The heat shielding unit 170 and the liquid circulating therein can expediently act as a liquid screen. The heat is then transferred to the supply chamber outlet connection 112 by gravity and/or convection.
By means of the heat shielding unit 170, the housing 135 of the first pumping chamber 130 is separated from the housing 115 of the fluid supply chamber 110 in the direction parallel to the movement axis 121 of the reciprocating movement of the piston 120, especially by a predetermined distance. This predetermined distance can e.g. correspond to at most 5% of a total length of the fluid supply chamber 110 in the direction parallel to the movement axis 121. The housing 135 of the first pumping chamber 130 and the housing 115 of the fluid supply chamber 110 are therefore not in direct contact with each other.
It is also possible that the heat shielding unit 170 comprises a heat conducting element, e.g. a foil or a sheet. This element can surround the piston 120 at the predetermined position 171 between the housing 135 of the first pumping chamber 130 and the housing 115 of the fluid supply chamber 110, such that this element can at least partially conduct the heat ingress 175.
The heat shielding unit 170 interrupts or prevents a potential thermal bridge from the outside or ambient atmosphere along the piston 120 through the insulation jacket 160 into the supply chamber 110 and into the first pumping chamber 130, as shall now be explained with reference to Fig. 2.
Fig. 2 shows a reciprocating pump 200 according to the prior art. In Fig. 2, elements of the reciprocating pump 200 equivalent to elements of the reciprocating pump 100 shown of Fig. 1 are referred to with a reference sign increased by the value 100 in comparison to Fig. 1. In order to avoid repetitions, these elements shall not be explained in detail again.
As can be seen in Fig. 2 in comparison to Fig. 1, the reciprocating pump 200 according to the prior art comprises no heat shielding unit. A housing 235 of the respective first pumping chamber 230 and a housing 215 of the respective fluid supply chamber 210 are not separated from each other, but rather form a common housing.
Therefore, there exists a thermal bridge from the outside along this common housing into the first pumping chamber 230, indicated by the arrows 275, such that heat from the ambient atmosphere can dissipate along this thermal bridge 275 into the first pumping chamber 230, thereby heating up the fluid entering this first stage chamber 230. However, for the pump 200 to work efficiently, it can be of importance that the liquid transported from the supply chamber 210 to the first pumping chamber 230 is as cold as possible.
In contrast to that, a thermal bridge of that kind can be prevented or interrupted by means of the heat shielding unit 170 according to an embodiment of the present invention. The invention can therefore yield a lower NPSH (Net Positive Suction Head), since the respective pump 100 can be less sensitive to the quality of the suction line and to the quality of the liquid in the storage tank in terms of pressure and/or temperature. The invention can further achieve a better volumetric efficiency, a better isentropic efficiency, and a lower discharge temperature.

Claims

A cryogenic reciprocating pump (100), comprising:
a liquid supply chamber (110) with an inlet port (111) and an outlet port (112) configured such that a liquid to be pressurised is provided in the supply chamber;

a pumping chamber (130) arranged within the liquid supply chamber (110) and in fluid communication with the fluid supply chamber (110);

a piston (120) configured to reciprocate in the pumping chamber (110) along a movement axis (121) such that, by means of reciprocating movement of the piston (120), liquid is transported from the fluid supply chamber (110) into the pumping chamber (130) and pressurised in the pumping chamber (130), wherein the piston (120) protrudes from an outside of the fluid supply chamber (110) at least partially into the fluid supply chamber (110);

characterised in that

a heat shielding unit (170) is provided in the fluid supply chamber (110) at a predetermined position (171) at which the piston (120) protrudes from the outside of the fluid supply chamber (110) into the fluid supply chamber (110),

wherein the heat shielding unit (170) is configured to at least partially absorb heat (175) being conducted from the outside of the fluid supply chamber (110) into the fluid supply chamber (110) and/or into the pumping chamber (130) and to lead the absorbed heat to the outlet port (112).
The pump according to claim 1, wherein the heat shielding unit (170) is provided as a section of the fluid supply chamber (110) between a housing (135) of the pumping chamber (130) and a housing (115) of the fluid supply chamber (110), the section extending in a direction parallel to the movement axis (121) of the reciprocating movement of the piston (120) and/or in a direction perpendicular to the movement axis (121) of the reciprocating movement of the piston (120).
The pump according to claim 1 or 2, wherein the heat shielding unit (170) separates the housing (135) of the pumping chamber (130) from the housing (115) of the fluid supply chamber (110) in a direction parallel to the movement axis (121 of the reciprocating movement of the piston (120).
The pump according to claim 2 or 3, wherein the heat shielding unit (170) is provided such that the housing (135) of the pumping chamber (130) is separated from the housing (115) of the fluid supply chamber (110) by a predetermined distance in the direction parallel to the movement axis (121) of the reciprocating movement of the piston (120).
The pump according to claim 4, wherein the predetermined distance corresponds to at most 5% of a length of the fluid supply chamber (110) in the direction parallel to the movement axis (121) of the reciprocating movement of the piston (120).
The pump according to any one of the preceding claims, wherein the heat shielding unit (170) is provided as a heat conducting element provided between a housing (135) of the pumping chamber (130) and a housing (115) of the fluid supply chamber (110).
The pump according to any one of the preceding claims, further comprising an insulation jacket (160) at least partially surrounding the liquid supply chamber (110).
The pump according to claim 7, wherein the piston (170) protrudes from an outside of the insulation jacket (160) through the insulation jacket (160) into the fluid supply chamber (110).
The pump according to any one of the preceding claims, further comprising a second pumping chamber (140) arranged within the liquid supply chamber (110) and in fluid communication with the pumping chamber (130) such that, by means of reciprocating movement of the piston (120), pressurised liquid is transported from the pumping chamber (130) into the second pumping chamber (140) and further pressurised in the second pumping chamber (140).