Pump for cryogenic fluid

Abstract

A pump for cryogenic fluid and an assembly comprising a tank and such a pump, comprising an intake duct (21), a compressor (31) configured to draw in an incoming flow (E) of cryogenic fluid arriving upstream through the intake duct (21) and to deliver, downstream, a delivery flow having a pressure greater than the pressure of the incoming flow (E), and an insulation cavity (71) completely surrounding at least part of the intake duct (21).

Description

Pump for cryogenic fluid Technical Field

[0001] This disclosure relates to a pump for cryogenic fluid and to an assembly comprising a reservoir and such a pump. Such a pump may in particular be used in a circulation circuit for liquid propellant in an engine in the space sector, for example in a rocket engine. Such a pump may also be used, for example, in a hydrogen aircraft engine or in the maritime sector or ground equipment. Prior art

[0002] Liquid hydrogen is a commonly used propellant in the space sector. However, using hydrogen in an engine such as a rocket engine poses numerous technical implementation challenges. In particular, this hydrogen is generally stored and distributed in a liquid state, and therefore at cryogenic temperatures, before possibly being reheated before being admitted into the engine's combustion chamber.

[0003] One of the difficulties encountered concerns the pump of this supply circuit. In particular, it is necessary to control the temperature of the propellant until it enters the pump. Indeed, an increase in the temperature of the inlet flow directly and significantly impacts the suction capacities of the pump. In particular, the higher the temperature of the inlet flow, the closer the fluid saturation curve becomes, which increases the risk that at least part of the propellant will pass into the gaseous state upstream or within the pump: in such a case, premature degradation of the pump is even possible.

[0004] More specifically, this type of pump generally has an intake duct whose outer wall is directly exposed to the external environment of the pump. This intake duct is then directly subjected to the heat flow coming from the pump environment, which results in heating of the propellant before its admission into the pump. Of course, such an This problem arises particularly during the early phases of flight when the rocket engine, and therefore the pump, have not yet left the Earth's atmosphere and are therefore subject to a particularly strong temperature difference between the temperature of the propellant and the pump's environment. However, although less significant, this problem also arises when the rocket engine is in the vacuum of space because the rocket engine components near the pump, and in particular the combustion chamber, generate a heat flux large enough to have an impact on the temperature of the propellant entering the pump; however, a few Kelvin too many are enough to significantly impair the pump's performance.

[0005] Furthermore, in terrestrial applications, particularly in the aeronautical field, the entire mission is carried out in an environment where the ambient temperature is much higher than that of the liquid propellant. In addition, for a given heat flux, the increase in temperature is all the more significant when the incoming flow rate is low, which is often the case in aeronautical applications. Simply installing an insulator may therefore prove insufficient to control the temperature of the incoming propellant over the entire duration of the mission, unless the thickness of the insulator is significantly increased, which can then pose problems of mass and size.

[0006] There is therefore a real need for a cryogenic fluid pump and an assembly comprising a reservoir and such a pump, which are free, at least in part, from the drawbacks inherent in the aforementioned known configurations. Statement of the invention

[0007] The present disclosure relates to a cryogenic fluid pump, comprising an inlet duct, a compressor, configured to suck an incoming flow of cryogenic fluid arriving upstream through the inlet duct and to discharge downstream a discharge flow having a pressure greater than the pressure of the incoming flow, and an isolation cavity completely surrounding at least a portion of the inlet duct.

[0008] Thus, in such a configuration, the insulation cavity is interposed between the intake duct and the external environment of the pump, which ensures thermal insulation of the cryogenic fluid passing through the intake duct with respect to a possible thermal flow coming from outside the pump.

[0009] The proposed configuration thus makes it possible to effectively control the temperature of the incoming flow of the pump and therefore, in particular, to reduce the risk of part of this flow passing into the gaseous state in the intake duct or directly in the compressor. Consequently, controlling this temperature results in greater stability of the pump suction and makes it possible to control the latter in a wider operating range by limiting the risk of cavitation.

[0010] In particular, this configuration makes it unnecessary to add insulation around the pump intake duct, even when the pump is used in an atmospheric environment, for example on board an aircraft. It is therefore clear that this pump is suitable for space applications. However, it is naturally quite possible to use this pump in other fields, particularly in the aeronautical and terrestrial fields.

[0011] In particular, maintaining the pump's suction performance allows the tank's pressurization capabilities to be partially released.

[0012] Furthermore, in this configuration, the front part of the pump, including the inlet duct and the insulation cavity, has a larger diameter than the inlet duct alone, which provides this part with superior mechanical strength. In particular, this configuration makes it possible to fix the pump by this front part, possibly even without any other fixing point: for example, the pump could be directly mounted on the wall of a cryogenic fluid tank, thus simultaneously ensuring the mechanical connection and the hydraulic connection of the pump.

[0013] In this disclosure, cryogenic fluid is understood to mean a fluid whose temperature is less than 120 K, possibly less than 80 K, in particular less than 30 K.

[0014] In some embodiments, the cryogenic fluid is a liquid propellant, for example liquid hydrogen H 2 , liquid oxygen O 2 , liquid nitrogen N 2 , liquid helium He or liquid methane CH 4 .

[0015] In some embodiments, the pump includes a recirculation line, configured to take a portion of the discharge flow, forming a recirculation flow, and to reinject the recirculation flow upstream of the compressor, the recirculation line opening into the insulation cavity. Since the insulation cavity is supplied by a recirculation flow taken downstream of the compressor of the pump, the temperature prevailing in the insulation cavity is close to that of the incoming flow. In addition, since this recirculation flow is continuously injected into the insulation cavity, the volume of fluid present in the insulation cavity is constantly renewed, which does not leave it sufficient time to heat up significantly under the effect of the possible external heat flow.

[0016] In some embodiments, the length of the intake duct is greater than 50%, possibly greater than 100%, of the diameter of the compressor rotor wheel.

[0017] In some embodiments, the length of the intake duct is greater than 20 mm, possibly greater than 40 mm.

[0018] In some embodiments, the diameter of the intake duct is less than the diameter of the compressor, possibly less than 80% of the diameter of the compressor rotor.

[0019] In some embodiments, the front end of the inlet conduit is open and has a funnel-shaped lip. This funnel-shaped lip facilitates the aspiration of cryogenic fluid into the inlet conduit.

[0020] In some embodiments, the front end of the isolation cavity is open and has a constriction. Such a constriction promotes the formation of a convective flow in the isolation cavity which promotes the renewal of the fluid present.

[0021] In some embodiments, the constriction of the isolation cavity is formed by a local increase in the diameter of the inner wall of the isolation cavity, this inner wall of the isolation cavity being able to correspond to the external wall of the intake duct. In particular, for its part, the diameter of the external wall of the insulation cavity can remain constant at the level of said constriction. In this way, a convective flow circulating from the internal side to the external side of the insulation cavity then expelled from the external cavity is favored, which favors the evacuation of calories coming from the external heat flow rather than their conduction towards the intake duct.

[0022] In some embodiments, the lip of the intake duct protrudes radially into the isolation cavity. The lip of the intake duct thus forms a constriction of the isolation cavity.

[0023] In some embodiments, the compressor comprises a rotating impeller, for example a centrifugal impeller.

[0024] In some embodiments, the compressor includes an inducer. Such an inducer allows the incoming flow to be drawn in and accelerated before being compressed in the rotating impeller.

[0025] In some embodiments, the compressor is configured to increase the discharge flow rate to a pressure greater than 10 bar, possibly greater than 20 bar.

[0026] In some embodiments, the discharge rate is between 10 and 160 g / s.

[0027] In some embodiments, the pump comprises an electric motor, with the compressor being driven by the electric motor. Such a configuration is particularly suitable for a fuel feed pump because it allows easy and precise control of the flow rate of fuel supplied. However, other types of drive are possible: for example, the pump could also be a turbopump.

[0028] In some embodiments, the recirculation flow rate is between 8 and 20%, possibly between 10 and 15% of the discharge flow rate.

[0029] In some embodiments, the recirculation flow is taken from the rear of the compressor wheel.

[0030] In some embodiments, the recirculation flow is configured to participate in axial balancing of the compressor.

[0031] In some embodiments, the recirculation flow is configured to assist in the lubrication of rotating components of the pump, such as one or more bearings.

[0032] In some embodiments, the flow rate of the recirculation line is configured to assist in cooling the pump, for example an electric motor of the pump.

[0033] In some embodiments, the temperature difference between the recirculation flow reinjected into the isolation cavity and the incoming flow is less than 10 K, possibly less than 5 K.

[0034] In some embodiments, the recirculation line comprises a liquefaction device. Such a liquefaction device makes it possible, in the event that a portion of the recirculation flow has passed into the gaseous state, for example during the cooling of the electric motor of the pump, to reinject exclusively liquid into the insulation cavity. However, such a liquefaction device is in no way essential: indeed, if the recirculation flow reinjected into the insulation cavity comprises a portion of gas, the latter may contribute to the pressurization of the cryotechnic fluid tank.

[0035] In some embodiments, the insulation cavity surrounds the intake duct along its entire length. The intake duct is thus thermally insulated along its entire length.

[0036] In some embodiments, the insulation cavity surrounds at least a portion of the compressor. It is thus possible to thermally insulate the compressor as well, which reduces the risk of external heat input to the compressor and thus reduces the risk of cavitation. In particular, due to the complex shape of the compressor housing, it is normally difficult to place thermal insulation around the compressor, properly enveloping the latter.

[0037] In some embodiments, the isolation cavity and the intake duct are concentric. Such a configuration promotes a homogeneous distribution of mechanical and hydraulic forces in the front portion of the pump.

[0038] In some embodiments, the diameter of the isolation cavity is greater than 200%, possibly greater than 300%, of the diameter of the intake duct. Such a diameter makes it possible, on the one hand, to effectively isolate the intake duct and, on the other hand, to provide the isolation cavity with a large volume facilitating forced and / or natural convection and dilution of the reinjected recirculation flow. In addition, such a diameter offers superior mechanical strength, in particular when the pump is fixed at the isolation cavity.

[0039] In some embodiments, the outer wall of the isolation cavity comprises a fixing interface configured to be mounted on an upstream hydraulic member, for example a cryotechnical fluid tank. Due to the increased diameter of the outer wall of the isolation cavity, the pump can be fixed reliably and rigidly, with good transmission of mechanical forces, despite the overhang represented by the mass of the pump thus suspended. In addition, such a configuration makes it possible to simultaneously ensure the mechanical connection and the hydraulic connection of the pump. Naturally, the fixing interface could be mounted on any other supply device, for example a propellant supply line.

[0040] In some embodiments, the recirculation line opens into the isolation cavity at its rear end, i.e., its end closest to the compressor. Such a configuration allows efficient renewal of the fluid present in the isolation cavity.

[0041] The present disclosure also relates to an assembly, comprising a reservoir, intended to store cryogenic fluid, and a pump according to any one of the preceding embodiments, mounted on one face of the reservoir.

[0042] In this disclosure, the terms "axial", "radial", "tangential", "internal", "external" and their derivatives are defined in relation to the main axis of the pump; "axial plane" means a plane passing through the main axis of the pump and "radial plane" means a plane perpendicular to this main axis; the terms "upstream" and "downstream" are defined in relation to the circulation of the fluid in the pump; the terms "front" and "rear" are defined along the main axis, the front of the pump being located on the side of its inlet duct. Furthermore, when they concern numerical values, the terms "lower", "higher", "between" and their derivatives are interpreted in the broad sense, that is to say, including the case where the value in question is equal to the announced limit.

[0043] The above-mentioned features and advantages, as well as others, will become apparent from the following detailed description of examples of embodiments of the pump and the assembly proposed. This detailed description refers to the attached drawings. Brief description of the drawings

[0044] The attached drawings are schematic and are intended primarily to illustrate the principles of the presentation.

[0045] In these drawings, from one figure to another, identical elements (or parts of elements) are identified by the same reference signs.

[0046] [Fig. 1] Figure 1 is a sectional plan of an example of an assembly comprising a reservoir and a pump. Description of the embodiments

[0047] In order to make the disclosure more concrete, an example of an assembly comprising a reservoir and a pump is described in detail below, with reference to the attached drawings. It is recalled that the invention is not limited to this example.

[0048] Figure 1 represents in section along a vertical plane passing through its main axis A, an assembly 1 comprising a supply system, here a reservoir 10, and a pump 20 which can be mounted on a main face 11 of the reservoir 10.

[0049] In the present example, the tank 10 is a tank of liquid hydrogen stored at approximately 20 K and at approximately 1 bar. The tank 10 may also comprise a volume of gaseous hydrogen, this volume of gas having the main function of pressurizing the volume of liquid hydrogen.

[0050] The main face 11 of the reservoir 10 comprises a supply orifice 12 bordered by a fixing flange 13, this fixing flange 13 participating in the fixing of the pump 20, as will be described below.

[0051] The pump 20 comprises an intake duct 21, extending axially and open onto the supply orifice 12 of the tank 10: this intake duct 21 allows the cryogenic fluid to enter the pump 20 and thus leads to a compressor 31.

[0052] The compressor 31 comprises a rotor 32 rotating around the main axis A within a stator 35. The rotor 32 includes in a single piece an inductor 33 upstream followed by a centrifugal impeller 34 downstream. The stator 35 includes for its part a vein wall 36, extending the wall 22 of the intake duct 21 downstream along the centrifugal impeller 34, and a volute 37, substantially annular, provided opposite the outlet of the centrifugal impeller 34.

[0053] The rotor 32 of the compressor 31 is driven in rotation by an electric motor 41 arranged at the rear of the compressor 31. The electric motor 41 thus comprises a rotor 42, driving the rotor 32 of the compressor 31 via a rotary shaft 43, and a stator 44, mounted in a main portion 51 of the casing 50 of the pump 20. The rotary shaft 43 is supported by two bearings 45, 46, for example rolling bearings. The front bearing 45 is carried on the stator by a radial wall 47, fixed on the main portion 51 of the casing 50. The radial wall 47 delimits within the casing 50 a space housing the compressor 31 and a space housing the motor 41. The rear bearing 46 is carried to the stator 44 by a rear cover 52 of the casing 50, attached against the main portion 51 of the casing 50.

[0054] When the motor 41 drives the rotor 32 of the compressor 31, liquid hydrogen is sucked into the intake duct 21 and then into the compressor 31, thus constituting an inlet flow E. A main part of the discharge flow, obtained following the compression of the inlet flow E by the compressor 31, is directed towards an outlet duct (not shown) of the pump 20, thus constituting an outlet flow. In the present example, the compressor 31 brings the discharge flow to a pressure of the order of 10 bar.

[0055] However, a secondary portion of the discharge flow is diverted to a recirculation line 60, thus constituting a recirculation flow R. The recirculation line 60 begins with a gap 61 separating the rear face of the centrifugal impeller 34 and the radial wall 47; the recirculation flow R then passes through the front bearing 45, circulates between the rotor 42 and the stator 44 of the motor 41, passes through the rear bearing 46 and reaches a rear cavity 62 formed in the cover 52 of the casing 50. The recirculation flow R then passes through a recirculation duct 63 extending from the cover 52 of the casing 50 to a front part 53 of the casing 50; the recirculation flow R then opens into an insulation cavity 71 extending concentrically between the intake duct 21 and a structural wall 54 of the front part 53 of the casing 50.

[0056] The recirculation flow R thus contributes to the axial balancing of the compressor 31, to the lubrication and cooling of the bearings 45, 46, and to the cooling of the electric motor 41. In the present example, the temperature of the recirculation flow R at the level of its reinjection into the insulation cavity 71 is of the order of 21 K.

[0057] The front part 53 of the casing 50 comprises a structural block 55, against which the main part 51 of the casing is attached and in which the centrifugal volute 37 is formed, the structural wall 54, generally cylindrical and extending forward from the structural block 55, and a skirt 56, axisymmetric, extending from the structural block 55, first radially inwards then axially forwards, so as to form the vein wall and the wall 22 of the intake duct 21.

[0058] The diameter of the structural wall 54, thus forming the external wall of the insulation cavity 71, is approximately three times greater than the diameter of the wall 22 of the intake duct 21.

[0059] The front end, that is to say downstream, of the wall 22 of the intake duct 21 has a lip 23 flaring outwards. This lip 23 thus forms, on the one hand, a funnel-shaped mouth for the intake duct 21, which facilitates the suction of the cryogenic fluid, and, on the other hand, a constriction 72 for the isolation cavity 71. This constriction 72 promotes a convective circulation C taking cryogenic fluid from the reservoir 10 and circulating it from the internal side to the external side of the isolation cavity 71, diluting in the process the recirculation flow R reinjected into the isolation cavity 71, and discharging the whole into the general volume of the reservoir 10.

[0060] The front end of the structural wall 54 of the front part 53 of the casing 50 has for its part a fixing interface 57 allowing the pump 20 to be mounted against the tank 10. The fixing interface 57 comprises on the one hand a fixing flange 58, annular, applied and fixed against the fixing flange 13 of the tank 10. The fixing interface 57 comprises on the other hand a cylindrical end piece 59, projecting axially from the fixing flange 58 of the pump 20, engaged in the supply orifice 12 of the tank 10, the diameter of the cylindrical end piece 58 corresponding to the diameter of the supply orifice 12.

[0061] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated / mentioned embodiments may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

[0062] It is also obvious that all the characteristics described with reference to a method are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a method.

Claims

Claims

1. Pump for cryogenic fluid, comprising an inlet duct (21), a compressor (31), configured to suck in an incoming flow (E) of cryogenic fluid arriving upstream via the inlet duct (21) and to discharge downstream a discharge flow having a pressure greater than the pressure of the incoming flow (E), and an isolation cavity (71) completely surrounding at least part of the inlet duct (21). a recirculation line (60), configured to take a portion of the discharge flow, forming a recirculation flow (R), and to reinject the recirculation flow (R) upstream of the compressor (31), the recirculation line opening into the insulation cavity (71) in which the front end of the intake duct (21) is open and has a funnel-shaped lip (23), and in which the front end of the insulation cavity (71) is open and has a constriction (72).

2. A pump according to claim 1, comprising an electric motor (41), the compressor (31) being driven by the electric motor (41), wherein the recirculation flow (R) is configured to participate in the cooling of the electric motor (41).

3. Pump according to claim 1 or 2, in which the recirculation flow rate (R) is between 8 and 20%, possibly between 10 and 15%, of the discharge flow rate.

4. A pump according to any one of claims 1 to 3, wherein the recirculation line (60) opens into the insulation cavity (71) at its rear end.

5. A pump according to any one of claims 1 to 4, wherein the compressor (31) comprises a rotating wheel, for example a centrifugal impeller (34), and wherein the compressor (31) comprises an inducer (33).

6. A pump according to any one of claims 1 to 5, wherein the insulation cavity (71) surrounds the intake duct (21) over its entire length, and wherein the insulation cavity (71) surrounds at least a portion of the compressor (31).

7. Pump according to any one of claims 1 to 6, in which the diameter of the isolation cavity (71) is greater than 200%, possibly greater than 300%, of the diameter of the intake duct (21).

8. Pump according to any one of claims 1 to 7, in which the external wall (54) of the isolation cavity (71) comprises a fixing interface (57) configured to be mounted on an upstream hydraulic member, for example a cryogenic fluid reservoir (10).

9. Assembly, comprising a reservoir (10), intended to store cryogenic fluid, and a pump (20) according to any one of claims 1 to 8, mounted on a face (11) of the reservoir (10).

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