A composite inlet rectification anti-cavitation structure for a liquid hydrogen pump and a liquid hydrogen pump

Abstract

The application discloses a composite inlet rectification cavitation suppression structure for a liquid hydrogen pump and the liquid hydrogen pump, which comprises a horn mouth contraction section, a guide vane rectification section and a hollow guide cone section connected in sequence along an axial direction, the hollow guide cone section comprises a first guide cylinder, a hollow guide cone and a support rib, the hollow guide cone is fixed at the axial center position of the first guide cylinder through the support rib, the hollow guide cone has an axial precooling cavity, a plurality of radial precooling inlet holes are uniformly distributed in the circumferential direction near the tip of the hollow guide cone, and a plurality of precooling outlet holes are uniformly distributed in the circumferential direction on the tail end surface of the hollow guide cone. The three functional structures are integrated, the axial dimension is compact, the existing liquid hydrogen pump inlet flange can be directly connected, the pump body does not need to be greatly changed, the structure is compact and easy to install, and good engineering applicability is achieved.

Description

Technical Field

[0001] This application relates to the field of liquid hydrogen pump technology, and in particular to a composite inlet rectification and cavitation suppression structure for a liquid hydrogen pump and a liquid hydrogen pump. Background Technology

[0002] Liquid hydrogen pumps are the core components of liquid hydrogen propulsion systems, widely used in launch vehicle engines, hydrogen fuel cell vehicle supply systems, and aerospace cryogenic propulsion devices. A liquid hydrogen pump typically consists of key components such as an inducer, impeller, and diffuser. The inducer, located in front of the impeller, performs pre-pressurization and is crucial for suppressing cavitation.

[0003] Existing liquid hydrogen pump inlet section structures typically employ a simple straight pipe or a single contraction pipe directly connected to the inducer. The existing inlet section consists of an inlet flange, a straight pipe section, and a transition section connecting to the inducer. Liquid hydrogen flows directly from the upstream pipeline through the inlet section into the inducer. The existing liquid hydrogen pump inlet section structure has the following main drawbacks: The lack of rectification measures in the inlet section leads to increased deviations in the angle of attack of the inducer's inlet channels due to the pre-swirling component and uneven velocity distribution in the flow through the curved pipe. This results in localized pressure drops, easily inducing cavitation and affecting the pump's suction performance and overall efficiency. Furthermore, the traditional inlet section has a single function, only guiding the flow and failing to simultaneously achieve multiple functions such as rectification, cavitation suppression, and hollow guide cone guidance. This makes it difficult to adapt to the increasingly demanding high-speed, high-pressure differential operating conditions of liquid hydrogen pumps. Summary of the Invention

[0004] The purpose of this application is to provide a composite inlet rectification and cavitation suppression structure for a liquid hydrogen pump and a liquid hydrogen pump, so as to solve the technical problems existing in the related technology, such as uneven flow field in the inlet section of the liquid hydrogen pump, insufficient cavitation suppression capacity and poor inlet velocity distribution, and realize the composite functions of rectification, flow equalization and cavitation suppression of the inlet flow field, thereby improving the inlet flow conditions of the inducer and improving the anti-cavitation performance and working stability of the liquid hydrogen pump.

[0005] According to a first aspect of the embodiments of this application, a composite inlet rectification and cavitation suppression structure for a liquid hydrogen pump is provided, comprising a bell-shaped converging section, a guide vane rectification section, and a hollow guide cone section connected coaxially in sequence along the axial direction. The hollow guide cone section includes a hollow guide cone and a support rib. The hollow guide cone is fixed to the axial center position of the first guide tube by the support rib. The hollow guide cone has an axial pre-cooling cavity. A plurality of radial pre-cooling inlet holes are evenly distributed circumferentially near the tip of the hollow guide cone, and a plurality of pre-cooling outlet holes are evenly distributed circumferentially on the tail end face of the hollow guide cone.

[0006] Optionally, the flared constriction section is an axisymmetric flared constriction channel with an inlet diameter of... Larger than the diameter of the outlet end Shrinkage ratio The diameter is 1.5~2.5, and the axial length is 1.0~2.0 times the outlet diameter.

[0007] Optionally, the inner wall profile of the bell-shaped constriction section adopts an elliptical arc curve, a cubic polynomial, or a Witoszynski curve.

[0008] Optionally, the precooled liquid hydrogen flow rate is 0.5% to 2% of the main flow rate, and the ratio of the total cross-sectional area of ​​the precooling inlet hole to the cross-sectional area of ​​the precooling cavity is 2% to 5%.

[0009] Optionally, the slope of the wall at the connection between the flared constriction section and the guide vane rectifying section is zero.

[0010] Optionally, the flow guide vane rectifying section includes a second flow guide cylinder, a plurality of flow guide vanes, and an inner liner, wherein the inner liner is fixed to the axial position of the second flow guide cylinder by the plurality of flow guide vanes.

[0011] Optionally, the outer diameter of the inner liner is the same as the maximum outer diameter of the hollow guide cone.

[0012] Optionally, the number of guide vanes is coprime to the number of inducer vanes.

[0013] Optionally, the outer wall profile of the hollow guide cone adopts an elliptical arc curve.

[0014] According to a second aspect of the embodiments of this application, a liquid hydrogen pump equipped with a composite inlet rectification and cavitation suppression structure is provided, characterized in that the composite inlet rectification and cavitation suppression structure is the composite inlet rectification and cavitation suppression structure described in the first aspect, and the hollow guide cone section is connected to the induced wheel of the liquid hydrogen pump.

[0015] The technical solutions provided by the embodiments of this application may include the following beneficial effects: As can be seen from the above embodiments, the composite inlet rectification and cavitation suppression structure of the present invention integrates three functional structures: the bell mouth contraction section, the guide vane rectification section, and the hollow guide cone section. Existing technologies only have a single guiding function and cannot meet the dual requirements of rectification and cavitation suppression.

[0016] The hollow guide cone of this invention has an axial pre-cooling cavity. Several radial pre-cooling inlet holes are evenly distributed circumferentially near the tip of the hollow guide cone, and several pre-cooling outlet holes are evenly distributed circumferentially on the tail end face of the hollow guide cone. Liquid hydrogen flows into the pre-cooling cavity through the pre-cooling inlet holes and continuously absorbs heat from the metal wall of the hollow guide cone during axial flow, rapidly cooling the hollow guide cone to near the working temperature of liquid hydrogen. Then, it is ejected from the pre-cooling outlet holes at the tail end to the hub area of ​​the inducer wheel and merges into the mainstream. This structural design eliminates the stagnant low-pressure area in the axial region. In conjunction with the bell mouth section and the rectifier blades, it significantly improves the uniformity of the axial velocity distribution at the inducer wheel inlet, reduces vibration and fatigue damage caused by uneven blade load, and effectively improves the uniformity of the inlet flow field.

[0017] This invention integrates three functional sections into one compact axial dimension, allowing direct connection to the inlet flange of existing liquid hydrogen pumps without significant modifications to the pump body. It features a compact structure, ease of installation, and excellent engineering applicability.

[0018] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0020] Figure 1 This is a front view of a composite inlet rectifier voiding structure shown according to an exemplary embodiment.

[0021] Figure 2 This is a left view of a composite inlet rectifier voiding structure illustrated according to an exemplary embodiment.

[0022] Figure 3 This is a cross-sectional view of a composite inlet rectifier and cavitation suppression structure according to an exemplary embodiment.

[0023] Figure 4 This is a three-dimensional cross-sectional view of a composite inlet rectifier and cavitation suppression structure according to an exemplary embodiment.

[0024] The attached figures are labeled as follows: 1. The constricted section at the flared end; 2. Guide vane straightening section; 21. Second guide tube; 22. Guide vane; 23. Inner liner; 3. Hollow guide cone section; 31. First guide tube; 32. Hollow guide cone; 33. Support rib; 34. Pre-cooling cavity; 35. Pre-cooling inlet hole; 36. Pre-cooling outlet hole. Detailed Implementation

[0025] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application.

[0026] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used herein are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0027] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0028] refer to Figures 1-4 This invention provides a composite inlet rectification and cavitation suppression structure for a liquid hydrogen pump, comprising a bell-shaped converging section 1, a guide vane rectification section 2, and a hollow guide cone section 3 connected coaxially along the axial direction. The hollow guide cone section 3 includes a first guide cylinder 31, a hollow guide cone 32, and a support rib 33. The hollow guide cone 32 is fixed to the axial position of the first guide cylinder 31 by the support rib 33. The hollow guide cone 32 has an axial pre-cooling cavity 34. Several radial pre-cooling inlet holes 35 are evenly distributed circumferentially near the tip of the hollow guide cone 32, and several pre-cooling outlet holes 36 are evenly distributed circumferentially on the tail end face of the hollow guide cone 32. The precooling channel works as follows: Before startup, a small amount of liquid hydrogen flows into the precooling cavity 34 through the precooling inlet hole 35. During its axial flow, it continuously absorbs heat from the metal wall of the hollow guide cone 32, rapidly cooling the hollow guide cone 32 to near the working temperature of liquid hydrogen. Then, it is ejected from the precooling outlet hole 36 at the tail end to the induced wheel hub area and merges into the mainstream. This structural design solves the problem that the solid components are at room temperature before the liquid hydrogen pump starts, and the liquid hydrogen causes violent flash evaporation on the high-temperature surface after contact, thus disrupting the inlet flow field and causing startup failure. It can shorten the startup precooling time. Furthermore, the precooled liquid hydrogen ejected from the precooling outlet hole 36 at the tail end to the hub area provides local pressurization to this area, further suppressing cavitation near the hub.

[0029] In one embodiment, the flared converging section 1 is located at the front end of the structure and is an axisymmetric flared converging channel with an inlet diameter of... Larger than the diameter of the outlet end Shrinkage ratio The axial length is 1.0 to 2.0 times the outlet diameter, with a range of 1.5 to 2.5. According to Bernoulli's principle, the fluid accelerates during contraction, inhibiting boundary layer flow separation. The homogenizing effect of the bell-shaped inlet relies on the accelerated rectification brought about by the cross-sectional area contraction. If the contraction ratio is too small, insufficient acceleration and weak rectification will occur; however, if the contraction ratio is too large, the inlet tangent angle will exceed 45°, causing flow separation. Simultaneously, a large contraction ratio will result in excessively large structural dimensions, making installation difficult in space-constrained environments. A reasonable range for the axial length is also necessary; if the axial length is too small, the inlet tangent angle will also exceed the critical value. The main rectification effect of the bell-shaped inlet is completed in the first 1 / 3 section. As the axial diameter increases, its lifting effect becomes very weak, and long channels accumulate frictional losses. Furthermore, an excessively long axial diameter also makes installation difficult in space-constrained environments.

[0030] In one embodiment, the inner wall profile of the bell-shaped contraction section 1 can adopt various smooth contraction curves such as elliptical arc curves, cubic polynomial curves, or Witoszynski curves, with elliptical arc curves being preferred. The variation pattern is as follows: in The radius of the exit section, Radius shrinkage The axial length of the bell mouth. This represents the axial coordinate from the outlet section towards the inlet. The elliptical arc has a zero slope at the outlet end, perfectly tangent to the straight pipe wall of the subsequent rectifying section, ensuring a continuous first-order curvature transition without any bends. At the inlet end, the tangent angle is approximately 39°, less than the critical flow separation angle of 45°, ensuring no flow separation throughout the entire flow path. A rounded corner transition is provided at the outer edge of the inlet end, effectively eliminating localized low-pressure areas generated by the incoming flow.

[0031] The function of the bell-shaped contraction section 1 here is to guide the incoming flow from the external pipeline to enter smoothly, eliminate flow separation at the inlet, effectively reduce inlet pressure loss, improve the inlet section net positive suction head (NPSH) by about 10%~20%, and provide uniform incoming flow conditions with low turbulence for the subsequent rectification section.

[0032] In one embodiment, the precooled liquid hydrogen flow rate and the dimensional parameters of the precooling inlet orifice 35 are determined as follows: The precooled liquid hydrogen flow rate is determined based on the heat balance. The hollow guide cone 32 is at room temperature before pump startup and needs to be cooled to near the liquid hydrogen operating temperature by precooled liquid hydrogen. The required precooled liquid hydrogen mass flow rate is determined by the heat balance formula: in The metal mass of the hollow guide cone 32, The average specific heat capacity of the cone material. For temperature difference, For the effective heat absorption coefficient, The latent heat of vaporization of liquid hydrogen, This refers to the pre-cooling time.

[0033] The lower limit of the precooling flow rate is determined by the thermal balance calculation of the guide cone to ensure that the guide cone is cooled from room temperature to the liquid hydrogen operating temperature in a short time. The upper limit of the flow rate is determined by the flow field disturbance constraint. If this value is exceeded, the momentum disturbance of the precooled liquid hydrogen injection on the inlet flow field of the inducer exceeds the acceptable threshold. Therefore, the precooled liquid hydrogen flow rate is taken as 0.5% to 2% of the mainstream flow rate.

[0034] The size of the precooling inlet orifice 35 is determined by the orifice velocity constraint. The flow velocity of precooled liquid hydrogen flowing through the inlet orifice is determined by the following formula: in For precooled liquid hydrogen volumetric flow rate, This is the total cross-sectional area of ​​the precooling inlet hole 35.

[0035] The lower limit of the cross-sectional area of ​​the precooling inlet orifice 35 is determined by the flow velocity constraint at the orifice. If the cross-sectional area of ​​the inlet orifice is too small, the flow velocity of liquid hydrogen at the orifice will be too high, approaching the critical value of the liquid hydrogen cavitation number. Local cavitation may occur at the orifice, forming bubbles that block the channel. Furthermore, if the orifice diameter is too small, the drilling accuracy on curved surfaces is difficult to guarantee. If the cross-sectional area of ​​the inlet orifice is too large, it means that the number of orifices or the orifice diameter will increase, which will weaken the wall strength of the guide cone and reduce its pressure-bearing capacity at low temperatures. At the same time, the precooling flow rate is difficult to control stably. Therefore, the ratio of the total cross-sectional area of ​​the precooling inlet orifice 35 to the maximum cross-sectional area of ​​the precooling cavity 34 is taken as 2% to 5%.

[0036] In one embodiment, both the precooling inlet hole 35 and the precooling outlet hole 36 are 3.5 mm. Of course, they can be different, but the size difference between them should not be too large. The total area of ​​the precooling inlet hole 35 should be less than or equal to the total area of ​​the precooling outlet hole 36.

[0037] In one embodiment, the guide vane rectifying section 2 includes a second guide cylinder 21, a plurality of guide vanes 22 and an inner liner 23, wherein the inner liner 23 is fixed at the axial position of the second guide cylinder 21 by the plurality of guide vanes 22.

[0038] The axial length of the guide vane rectifying section 2 can be 1.2 times the channel diameter. The inner liner 23 is a thin-walled cylinder with equal diameter and open at both ends. Its outer diameter is the same as the maximum outer diameter of the rear hollow guide cone 32 to ensure continuous and unobstructed flow in the central channel at the axial docking point. The outer edge of the front end of the inner liner 23 is chamfered, the inner edge is rounded, and both the inner and outer edges of the tail end are rounded to guide the smooth inflow and outflow of liquid hydrogen. The number of guide vanes 22 is preferably 8, with adjacent vanes spaced 45° circumferentially. The number of vanes is coprime to the number of inducer vanes to avoid excitation resonance. The chord direction of the vanes is parallel to the axial direction, and the span extends radially from the outer wall of the inner liner 23 to the inner wall of the second guide tube 21. The vane cross-section adopts the NACA 0012 symmetrical airfoil, with the maximum thickness located at 35% of the chord length from the leading edge. The leading edge is blunt and faces the incoming flow, while the trailing edge is sharp and faces the inducer. The blades are fixed by electron beam welding after being positioned by end rings at both ends. The inner end is fixed to the outer wall of the inner liner 23, and the outer end is fixed to the inner wall of the second guide tube 21. The blade installation angle is 0°, which is suitable for axial flow without pre-rotation. When there is a fixed pre-rotation in a known direction in the upstream pipeline, the installation angle can be adjusted accordingly.

[0039] Here, the guide vane rectifying section 2 eliminates the pre-swirl of the incoming flow and homogenizes the axial velocity distribution, thereby increasing the flow field uniformity at the inlet of the inducer by 60% to 75%, effectively reducing the occurrence of local low-pressure areas at the inlet of the inducer, reducing the pressure pulsation amplitude by about 40%, and thus significantly suppressing the occurrence of rotating cavitation.

[0040] In one embodiment, the hollow guide cone section 3 is located at the rear of the structure, and the hollow guide cone 32 is an axisymmetric streamlined rotating body installed at the center of the channel. Its outer wall profile adopts an elliptical arc curve, with the equation: in The maximum radius of the hollow guide cone 32 is matched with the radius of the inducer hub. The axial length of the hollow guide cone is 32. This refers to the axial coordinates measured from the tip. Therefore, the hollow guide cone 32 has a zero radius at the tip and reaches its maximum radius at the tail end. The tangent of the tail end wall is parallel to the axis, smoothly connecting to the inducer hub with no flow separation throughout. The tip of the hollow guide cone 32 has a spherical fillet with a radius of 3mm to eliminate stress concentration at the tip and prevent the formation of separation vortices in the incoming flow. An axial gap of approximately 1.5mm is maintained between the tail end plane of the hollow guide cone 32 and the front end face of the inducer hub at room temperature, considering the low-temperature contraction effect to ensure operational safety and prevent an excessively large backflow cavity.

[0041] In this embodiment, the hollow guide cone 32 has a pre-cooling cavity 34 with a wall thickness of approximately 5% of the maximum diameter of the hollow guide cone 32. Four radial pre-cooling inlet holes 35 are distributed circumferentially near the tip of the hollow guide cone 32, and four pre-cooling outlet holes 36 are distributed circumferentially on the tail end face of the hollow guide cone 32. The inlet holes and outlet holes have the same diameter of 3.5 mm.

[0042] In this embodiment, there are three support ribs 33, evenly distributed circumferentially at 120° intervals, with their axial positions located in the hollow guide cone section 3. The support ribs 33 also adopt the NACA 0012 airfoil cross-section, with the chord direction parallel to the axial direction and the wingspan extending radially from the outer wall of the hollow guide cone 32 to the inner wall of the second guide tube 21. The outer ends of the support ribs 33 are embedded in the grooves on the inner wall of the outer shell and then welded and fixed, while the inner ends are fitted against the curved surface of the outer wall of the hollow guide cone 32 and then welded and fixed. The number of support ribs 33 (3 in total) is coprime with the number of guide blades 22 (8 in total), effectively avoiding resonance excitation caused by the harmonic relationship of the blades.

[0043] The hollow guide cone 32 guides the liquid hydrogen working fluid to flow smoothly around the cone surface, eliminating the stagnant low-pressure area and backflow vortex near the inlet axis, reducing the static pressure drop at the inlet, and working in synergy with the guide vane straightening section 2 to further improve the uniformity of the inlet flow field of the inducer wheel and suppress the formation of cavitation nuclei in the hub region.

[0044] It should be noted that the shrinkage ratio can be adjusted according to the design flow rate and inlet pipe diameter of the liquid hydrogen pump. The number of guide vanes 22 can be adjusted from 4 to 12 depending on the actual operating conditions. The rotation angle of the guide vanes 22 can be designed according to the pre-swirl of the incoming flow to adapt to different speed and flow conditions. For NACA 0012 symmetrical airfoil blades, the installation angle can be adjusted within the range of 0° to 15°. The cone angle and length-to-diameter ratio of the hollow guide cone 32 can be designed to match the shape of the inducer hub and the inlet speed, or it can be integrally manufactured with the inducer hub. The entire composite structure can be manufactured using materials suitable for cryogenic liquid hydrogen media, such as 5083 aluminum alloy, 316L stainless steel, or titanium alloy Ti-6Al-4V. Surface treatment methods can include anodizing, passivation, or cryogenic coating.

[0045] This invention also provides a liquid hydrogen pump equipped with a composite inlet rectification and cavitation suppression structure, wherein the composite inlet rectification and cavitation suppression structure is the aforementioned composite inlet rectification and cavitation suppression structure, and the hollow guide cone section 3 is connected to the induced wheel of the liquid hydrogen pump.

[0046] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only.

[0047] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A composite inlet rectification and cavitation suppression structure for a liquid hydrogen pump, characterized in that, The system comprises a bell-shaped converging section, a guide vane rectifying section, and a hollow guide cone section, all connected coaxially along the axis. The hollow guide cone section includes a first guide cylinder, a hollow guide cone, and supporting ribs. The hollow guide cone is fixed to the axial center of the first guide cylinder by the supporting ribs. The hollow guide cone has an axial pre-cooling cavity. Several radial pre-cooling inlet holes are evenly distributed circumferentially near the tip of the hollow guide cone, and several pre-cooling outlet holes are evenly distributed circumferentially on the tail end face of the hollow guide cone. The pre-cooled liquid hydrogen flow rate is 0.5% to 2% of the main flow rate, and the ratio of the total cross-sectional area of ​​the pre-cooling inlet holes to the cross-sectional area of ​​the pre-cooling cavity is 2% to 5%. The guide vane rectifying section includes a second guide cylinder, several guide vanes, and an inner liner. The inner liner is fixed to the axial center of the second guide cylinder by the several guide vanes. The outer diameter of the inner liner is the same as the maximum outer diameter of the hollow guide cone. Before startup, a small amount of liquid hydrogen flows into the precooling cavity through the precooling inlet hole. During the axial flow, it continuously absorbs the heat from the metal wall of the hollow guide cone, rapidly cooling the hollow guide cone to near the working temperature of liquid hydrogen. Then, it is ejected from the precooling outlet hole at the tail end to the idler wheel hub area and merges into the mainstream.

2. The composite inlet rectification and cavitation suppression structure for a liquid hydrogen pump according to claim 1, characterized in that, The flared constriction section is an axisymmetric flared constriction channel with an inlet diameter larger than the outlet diameter, a constriction ratio of 1.5 to 2.5, and an axial length of 1.0 to 2.0 times the outlet diameter.

3. The composite inlet rectification and cavitation suppression structure for a liquid hydrogen pump according to claim 1, characterized in that, The inner wall profile of the bell-shaped contraction section adopts an elliptical arc curve, a cubic polynomial, or a Widosinski curve.

4. The composite inlet rectification and cavitation suppression structure for a liquid hydrogen pump according to claim 1, characterized in that, The slope of the wall at the connection between the flared constriction section and the guide vane rectifying section is zero.

5. The composite inlet rectification and cavitation suppression structure for a liquid hydrogen pump according to claim 1, characterized in that, The number of guide vanes is coprime to the number of inducer vanes.

6. The composite inlet rectification and cavitation suppression structure for a liquid hydrogen pump according to claim 1, characterized in that, The outer wall profile of the hollow guide cone satisfies the following conditions: the radius at the tip is zero, the radius at the tail end matches the radius of the inducer hub, and the tangent of the wall at the tail end is parallel to the axis.

7. A liquid hydrogen pump equipped with a composite inlet rectifying and cavitation suppression structure, characterized in that, The composite inlet rectification and cavitation suppression structure is the composite inlet rectification and cavitation suppression structure according to any one of claims 1-6, and the hollow guide cone section is connected to the induced wheel of the liquid hydrogen pump.

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