Liquid hydrogen turbopump center tie rod flexible rotor

Abstract

The application provides a liquid hydrogen turbine pump center pull rod type flexible rotor, which comprises an inducer, a first-stage impeller, a second-stage impeller, a turbine disc, a damper and an elastic support; the elastic support is used for mounting the bearing and the damper; the center pull rod, a pump end locking nut and a vortex end locking nut are further included; the inducer, the first-stage impeller, the second-stage impeller and the turbine disc are all provided with inner holes; the center pull rod is provided with a pump end thread, a positioning surface, a positioning surface and a vortex end thread; the center pull rod passes through the inner holes of the turbine disc, the second-stage impeller, the first-stage impeller and the inducer in sequence, and the pump end thread is tightened by the pump end locking nut; the vortex end thread is tightened by the vortex end locking nut to provide pre-tightening force for the rotor; the positioning surface and the positioning surface are used for ensuring the centering installation of the turbine disc and the second-stage impeller and limiting the radial displacement of the rotor structure.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydrogen-oxygen rocket engine turbine pump, and particularly relates to a liquid hydrogen turbine pump center pull rod type flexible rotor. BACKGROUND

[0002] The turbine pump is the heart of the liquid rocket engine. Its main function is to increase the pressure of the low-pressure propellant from the tank and continuously deliver the low-temperature propellant to the main thrust chamber for combustion to generate thrust according to the parameters required by the engine system. In order to improve the thrust-to-weight ratio of the engine, the weight must be reduced as much as possible under the premise of ensuring the high reliability of the liquid hydrogen turbine pump, and the turbine pump has a higher efficiency and power density. Since the density of liquid hydrogen is low and the volumetric flow is large, a higher rotational speed is required to achieve the same head. In addition, the power system of the reusable launch vehicle requires the turbine pump to have low cost, high reliability and multiple reuse functions.

[0003] The development of the hydrogen turbine pump of the Vulcain engine and the hydrogen turbine pump of the VINCI engine greatly improves the carrying capacity of the European Ariane 5 rocket. The two engines adopt gas generator cycle and expansion cycle respectively, and the hydrogen turbine pumps of the two engines all adopt center pull rod type rotor structure, which not only reduces the rotor components, improves the reliability and production efficiency of the hydrogen turbine pump, but also makes the cost control of the engine as important as the engine performance and reliability.

[0004] At present, the turbine pump of the domestic liquid rocket engine all adopts the integral rotor structure. In the working process of the integral rotor, the turbine disc transmits power and torque to the shaft through the spline or bolt, and the shaft transmits power and torque to the secondary impeller, the primary impeller and the inducer through the spline, and the bearing is assembled on the shaft. The shaft of the integral rotor is relatively thick, the components are relatively many, and the manufacturing process requirements of each component are extremely strict. The rotor is heavy, and the assembly process is complex, which not only brings high cost, but also low production efficiency, which is not conducive to the development of high-density launch and reusable technology of the engine.

[0005] The liquid hydrogen turbine pump adopts the center pull rod type rotor, and the diameter of the center pull rod is much smaller than the diameter of the shaft of the integral rotor. The center pull rod only provides axial pre-tightening action and does not provide torque and power transmission. The power and torque are transmitted through the inner and outer splines on the turbine disc, the secondary impeller, the primary impeller and the inducer. Due to the existence of the contact interface, the structure and material properties are discontinuous, which further causes the mechanical characteristic parameters (stiffness, damping, etc.) inside the rotor system to be discontinuous, so that the stiffness characteristics of the center pull rod rotor are different from those of the integral rotor. SUMMARY

[0006] The technical problem solved by the present application is to reduce the cost of hydrogen-oxygen rocket engine, and further improve the production efficiency and reliability of liquid hydrogen turbine pump, and a liquid hydrogen turbine pump center pull rod type flexible rotor structure is provided.

[0007] The technical solution of the present application is a liquid hydrogen turbine pump center pull rod type flexible rotor, which comprises an inducer, a primary impeller, a secondary impeller, a turbine disc, a damper and an elastic support; the elastic support is used for mounting the bearing and the damper; further comprising a center pull rod, a pump end locking nut and a vortex end locking nut; the inducer, the primary impeller, the secondary impeller and the turbine disc are all provided with an inner hole; the center pull rod is provided with a pump end thread, a positioning surface, a positioning surface and a vortex end thread; the center pull rod passes through the turbine disc inner hole, the secondary impeller inner hole, the primary impeller inner hole and the inducer inner hole in sequence, and the pump end thread is tightened by the pump end locking nut, the vortex end thread is tightened by the vortex end locking nut to provide pre-tightening force for the rotor, and the positioning surface and the positioning surface are used to ensure the centering installation of the turbine disc and the secondary impeller, and limit the radial displacement of the rotor structure.

[0008] Preferably, the inducer, the primary impeller, the secondary impeller and the turbine disc are connected in sequence by the way of inner and outer spline cooperation to ensure that the coaxiality of the inner hole after connection meets the requirements; the bearing is two pairs, each pair of bearing is installed on the corresponding elastic support, one pair of bearing with elastic support is installed on the turbine disc, and the other pair is installed on the secondary impeller, and the bearing pair is pressed by the mechanical structure at both ends of the position to limit the axial position of the inner ring.

[0009] Preferably, the turbine disc is sequentially provided with an outer spline, a turbine disc hub, a positioning surface and an inner hole; the outer spline is used to realize the connection with the secondary impeller; the paired bearing with elastic support is installed on the turbine disc hub, and the positioning surface on the hub is used to limit the axial position of the bearing pair.

[0010] Preferably, the secondary impeller is sequentially provided with an outer spline, a secondary impeller hub, a positioning surface, an inner hole, an inner spline and a hub end face;

[0011] The outer spline of the secondary impeller is used to realize the connection with the primary impeller, the secondary impeller inner spline cooperates with the turbine disc outer spline, and the bearing pair is pressed and installed on the bearing pair on the turbine disc hub through the hub end face; another pair of bearing pairs with elastic support are installed on the secondary impeller hub, and the inner ring of the bearing is pressed by the primary impeller hub end face, and the positioning surface is used to limit the axial position of the bearing.

[0012] Preferably, the primary impeller is provided with an inner spline, a hub, an inner hole, a hub end face and a stop; the primary impeller inner spline cooperates with the secondary impeller outer spline, and the bearing pair is pressed and installed on the secondary impeller hub through the hub end face, and the stop is used to realize the positioning cooperation with the inducer.

[0013] Preferably, the fit amount of the primary impeller hub and the secondary impeller hub in the diameter direction at room temperature is -0.02mm-0.02mm; the fit amount of the secondary impeller hub and the turbine disc hub at room temperature is -0.02mm-0.02mm; the bearing is an angular contact ball bearing, and the fit clearance between the inner ring of the bearing and the secondary impeller hub and the turbine disc hub at room temperature is within 0.01mm.

[0014] Preferably, an adjusting pad and a pre-tightening assembly are installed between each pair of bearings, and the bearings are pre-tightened by adjusting the size of the adjusting pad to compress the pre-tightening assembly.

[0015] Preferably, the fit amount of the turbine disc, the secondary impeller and the center pull rod at room temperature is within -0.02mm-0.02mm.

[0016] Preferably, the center pull rod is made of high-temperature alloy material; the pump end locking nut, the inducer, the primary impeller, the secondary impeller and the turbine end locking nut are made of titanium alloy material; and the turbine disc is made of high-temperature alloy or titanium alloy material.

[0017] An assembly method of a center pull rod type flexible rotor of a liquid hydrogen turbine pump, comprising:

[0018] The turbine end locking nut and the turbine end locking plate are screwed on the center pull rod, and the assembled center pull rod is passed through the inner hole from the non-spline end of the turbine disc; a bearing and an adjusting pad with a pre-tightening force are passed through the center pull rod and assembled on the turbine disc hub, the inner ring end face of the bearing is matched with the positioning surface of the turbine disc, an elastic support is assembled on the outer ring of the bearing, a pre-tightening assembly is assembled in the elastic support and tightly contacts the bearing on the turbine disc hub, and another bearing is passed through the center pull rod and assembled on the turbine disc hub.

[0019] The inner spline end of the secondary impeller is passed through the center pull rod, the inner spline of the secondary impeller is matched with the outer spline of the turbine disc, and the end face of the secondary impeller hub is matched with the end face of the inner ring of the upper bearing of the turbine disc.

[0020] A bearing and an adjusting pad with a pre-tightening force are passed through the center pull rod and assembled on the secondary impeller hub, the inner ring end face of the bearing is matched with the positioning surface of the secondary impeller, an elastic support is assembled on the outer ring of the bearing, a pre-tightening assembly is assembled in the elastic support and tightly contacts the bearing on the secondary impeller hub, and another bearing is passed through the center pull rod and assembled on the secondary impeller hub.

[0021] The non-spline end of the primary impeller is passed through the center pull rod, the inner spline of the primary impeller is matched with the outer spline of the secondary impeller, and the end face of the primary impeller hub is matched with the end face of the inner ring of the bearing.

[0022] The spline end of the inducer is passed through the center pull rod, the inducer stop is matched with the primary impeller stop for positioning, the inner spline of the inducer is matched with the outer spline of the secondary impeller.

[0023] Tighten the pump end locking plate and the pump end locking nut and the center pull rod according to the specified torque value;

[0024] Assemble the damper baffle, the damper and the damper support with the elastic support respectively to form the center pull rod type combined rotor of the liquid hydrogen turbine pump.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] The center pull rod type flexible rotor of the liquid hydrogen turbine pump has the advantages of simple structure, high integrity and high strength, and the elastic support has the ability to work across the bending critical speed.

[0027] The center pull rod type flexible rotor of the liquid hydrogen turbine pump only provides axial pre-tightening force to axially pre-tighten the inducer, the first-stage impeller, the second-stage impeller and the turbine disc. The torque and power are transmitted by the splines on the inducer, the first-stage impeller, the second-stage impeller and the turbine disc during the operation of the rotor. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Assembly view of the center pull rod type flexible rotor of the low-temperature liquid hydrogen turbine pump;

[0029] Figure 2 Structure diagram of the center pull rod;

[0030] Figure 3 Structure diagram of the inducer;

[0031] Figure 4 Structure diagram of the first-stage impeller;

[0032] Figure 5 Structure diagram of the second-stage impeller;

[0033] Figure 6 Structure diagram of the turbine disc;

[0034] 1-pump end locking nut; 2-pump end locking plate; 3-inducer; 4-first-stage impeller; 5-damper support; 6-damper; 7-damper baffle; 8-elastic support; 9-pre-tightening assembly; 10-center pull rod; 11-second-stage impeller; 12-turbine disc; 13-turbine end locking plate; 14-turbine end locking nut; 15-bearing; 16-adjusting pad. 17-pump end thread; 18-positioning surface; 19-positioning surface; 20-turbine end thread. 21-inducer hub; 22-inner spline; 23-inner hole; 24-stop; 25-stop end face. 26-inner spline; 27-inducer hub; 28-inner hole; 29-hub end face; 30-stop. 31-outer spline; 32-second-stage impeller hub; 33-positioning surface; 34-inner hole; 35-inner spline; 36-hub end face. 37-outer spline; 38-turbine disc hub; 39-positioning surface; 40-inner hole. DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the embodiments.

[0036] This structure adopts a discontinuous center-pull rotor structure, which is simple in structure, light in weight, has good rigidity, is easy to process and manufacture, has high strength, can work in supercritical mode, has a critical speed margin of more than 20%, and is reusable.

[0037] like Figures 1-6 As shown, a liquid hydrogen turbopump with a central tie rod type flexible rotor device is structurally composed of a pump end locking nut 1, a pump end locking plate 2, an inducer wheel 3, a first-stage impeller 4, a damper support 5, a damper 6, a damper baffle 7, an elastic support 8, a preload assembly 9, a central tie rod 10, a second-stage impeller 11, a turbine disk 12, a vortex end locking plate 13, a vortex end locking nut 14, a bearing 15, and an adjusting shim 16. In a preferred embodiment of the invention, the inducer wheel 3, the first-stage impeller 4, the second-stage impeller, and the turbine disk 12 are made of titanium alloy; the pump end locking nut 1, the vortex end locking nut 14, and the central tie rod 10 are made of high-temperature alloy.

[0038] Two pairs of bearings are installed on the rotor. Each pair of bearings is installed on a corresponding elastic support 8. The elastic support 8 has a U-shaped structure and fixes the damper 6 with the damper support 5 and the damper baffle 7. A pre-tightening component 9 and an adjusting shim 16 are set in the middle of the pair of bearings with elastic supports to pre-tighten the bearings quantitatively.

[0039] Damper support 5, damper 6, damper baffle 7, and elastic support 8 with a loop structure together provide linear stiffness support and damping for the central tie rod rotor. By controlling the stiffness value of the elastic support, the strain energy of the rotor across the bending critical speed is ensured to meet the design requirements. During rotor operation, damper 6 generates effective damping and absorbs rotor vibration energy.

[0040] The turbine disc hub is equipped with external splines, while the secondary impeller hub has internal splines on one side and external splines on the other. The external splines of the turbine disc hub mate with the internal splines of the secondary impeller hub. A pair of bearings with elastic supports are mounted on the turbine disc hub, and their inner rings are pressed against the end face of the secondary impeller hub. The primary impeller hub and the inducer hub are equipped with internal splines of the same specifications. The external splines of the secondary impeller mate with the internal splines of the primary impeller and the inducer. Another pair of bearings with elastic supports are mounted on the secondary impeller hub, and their inner rings are pressed against the end face of the primary impeller hub.

[0041] The secondary impeller 11 is provided with an external spline 31, a secondary impeller hub 32, a locating surface 33, an inner hole 34, an inner spline 35 and a hub end surface 36. The secondary impeller inner spline 35 is matched with the turbine disc external spline 37, and is tightly installed on the bearing pair on the turbine disc hub 38 through the hub end surface 36, and the bearing is pre-tightened by adjusting the size of the adjusting pad 16 to compress the pre-tightening assembly 9. Another pair of bearings with elastic support are installed on the secondary impeller hub 32, and the locating surface 33 on the hub is used to limit the axial position of the bearings.

[0042] The primary impeller 4 is provided with an inner spline 26, a hub 27, an inner hole 28, a hub end surface 29 and a shoulder 30. The primary impeller inner spline 25 is matched with the secondary impeller external spline 31, and is tightly installed on the bearing pair on the secondary impeller hub 32 through the hub end surface 29, and the bearing is pre-tightened by adjusting the size of the adjusting pad 16 to compress the pre-tightening assembly 9.

[0043] The inducer 3 is provided with an inducer hub 21, an inner spline 22, an inner hole 23, a shoulder 24 and a shoulder end surface 25. The inducer inner spline 22 is matched with the secondary impeller external spline 31, the inducer shoulder 24 is matched with the primary impeller shoulder 30 for positioning, and the inducer shoulder end surface 25 is matched with the end surface of the primary impeller shoulder 30, which is used to limit the axial position of the inducer.

[0044] The center pull rod 10 is provided with a pump end thread 17, a locating surface 18, a locating surface 19 and a turbine end thread 20. The center pull rod 10 passes through the turbine disc inner hole 40, the secondary impeller inner hole 34, the primary impeller inner hole 28 and the inducer inner hole 23 in sequence, and is tightly screwed by the pump end locking nut 1 on the pump end thread 17 and the turbine end locking nut 14 on the turbine end thread 20 to provide pre-tightening force for the rotor, and the pump end locking plate 2 is arranged between the pump end locking nut 1 and the inducer 3 to prevent the pump end thread 17 from loosening, and the turbine end locking plate 13 is arranged between the turbine end locking nut 14 and the turbine disc 12 to prevent the turbine end thread 20 from loosening. The locating surface 18 and the locating surface 19 mainly ensure the centering installation of the turbine disc and the secondary impeller, and limit the radial displacement of the rotor structure.

[0045] The turbine disc 12, the pair of bearings with elastic support, the secondary impeller 11, the primary impeller 4, the inducer 3 and other components are assembled by axial stretching of the center pull rod to form a center pull rod type rotor. Different components contact each other under the action of the center pull rod, and the transmission of torque between the turbine and the impeller mainly relies on the spline structure.

[0046] In a preferred embodiment of the present application, the fit amount of the primary impeller hub and the secondary impeller hub in the diameter direction at room temperature is within -0.02mm-0.02mm; the fit amount of the secondary impeller hub and the turbine disc hub at room temperature is within -0.02mm-0.02mm; the bearing is an angular contact ball bearing, and the fit clearance between the inner ring of the bearing and the secondary impeller hub and the turbine disc hub at room temperature is within 0.01mm.

[0047] The fit amount of the turbine disc, the secondary impeller and the center pull rod at room temperature is within -0.02mm-0.02mm.

[0048] In a preferred embodiment of the present application, the center pull rod is made of high-temperature alloy material; the pump end locking nut, the inducer, the primary impeller, the secondary impeller and the turbine end locking nut are made of titanium alloy material; and the turbine disc is made of high-temperature alloy or titanium alloy material.

[0049] The present application also provides an assembling method of the center pull rod type flexible rotor of the liquid hydrogen turbine pump, and the steps are as follows:

[0050] The turbine end locking nut and the turbine end locking plate are screwed on the center pull rod, and then the assembled center pull rod is passed through the inner hole from the non-spline end of the turbine disc. A bearing and an adjusting pad with a pre-tightening force are passed through the center pull rod and then assembled on the turbine disc hub, the end face of the inner ring of the bearing is matched with the positioning face of the turbine disc, an elastic support is assembled on the outer ring of the bearing, a pre-tightening assembly is assembled in the elastic support and tightly contacts the bearing on the turbine disc hub, and another bearing is passed through the center pull rod and then assembled on the turbine disc hub.

[0051] The inner spline end of the secondary impeller is passed through the center pull rod, the inner spline is matched with the outer spline of the turbine disc, and the end face of the secondary impeller hub is matched with the end face of the inner ring of the upper bearing of the turbine disc.

[0052] A bearing and an adjusting pad with a pre-tightening force are passed through the center pull rod and then assembled on the secondary impeller hub, the end face of the inner ring of the bearing is matched with the positioning face of the secondary impeller, an elastic support is assembled on the outer ring of the bearing, a pre-tightening assembly is assembled in the elastic support and tightly contacts the bearing on the secondary impeller hub, and another bearing is passed through the center pull rod and then assembled on the secondary impeller hub.

[0053] The non-spline end of the primary impeller is passed through the center pull rod, the inner spline is matched with the outer spline of the secondary impeller, and the end face of the primary impeller hub is matched with the end face of the inner ring of the bearing.

[0054] The spline end of the inducer is passed through the center pull rod, the inducer stop is matched with the primary impeller stop for positioning, and the inner spline of the inducer is matched with the outer spline of the secondary impeller.

[0055] The pump end locking plate and the pump end locking nut are screwed on the center pull rod according to the specified torque value.

[0056] Finally, the damper baffle, the damper and the damper support are assembled with the elastic support respectively, and a liquid hydrogen turbine pump center pull rod type combined rotor is formed.

[0057] Although the present application has been disclosed with reference to the preferred embodiments, it is not intended to limit the present application, and any person skilled in the art can make possible changes and modifications to the technical solutions of the present application by using the disclosed methods and technical contents without departing from the spirit and scope of the present application. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application without departing from the technical solutions of the present application shall fall within the protection scope of the technical solutions of the present application.

[0058] The part not described in detail in the present application belongs to the common knowledge of those skilled in the art.

Claims

1. A flexible rotor of a liquid hydrogen turbopump with a central tie rod, comprising an inducer, a first-stage impeller, a second-stage impeller, a turbine disk, a damper, and an elastic support; wherein the elastic support is used to mount the bearing and the damper; characterized in that: It also includes a central tie rod, a pump end locking nut, and a volute end locking nut; the inducer, first-stage impeller, second-stage impeller, and turbine disk all have an inner hole at their center; the central tie rod has a pump end thread, positioning surface A, positioning surface B, and volute end thread; the central tie rod passes sequentially through the inner hole of the turbine disk, the inner hole of the second-stage impeller, the inner hole of the first-stage impeller, and the inner hole of the inducer, and is tightened by the pump end locking nut to tighten the pump end thread, and the volute end locking nut tightens the volute end thread to provide preload force to the rotor; positioning surface A and positioning surface B are used to ensure the aligned installation of the turbine disk and the second-stage impeller and limit the radial displacement of the rotor structure; the inducer, first-stage impeller, second-stage impeller, and turbine disk are connected sequentially by internal and external spline fit to ensure that the coaxiality of the inner holes after connection meets the requirements; there are two pairs of bearings, each pair of bearings is installed on a corresponding elastic support, one pair of bearings with elastic support is installed on the turbine disk, and the other pair is installed on the second-stage impeller, and the bearing pairs are pressed against the inner ring and limited in axial position by mechanical structures at both ends of their respective positions.

2. The liquid hydrogen turbopump center tie rod type flexible rotor according to claim 1, characterized in that: The turbine disk is provided with an external spline, a turbine disk hub, a locating surface, and an inner hole in sequence; the external spline is used to connect with the secondary impeller; a pair of bearings with elastic support are installed on the turbine disk hub, and the locating surface on the hub is used to define the axial position of the bearing pair.

3. The liquid hydrogen turbopump center tie rod type flexible rotor according to claim 2, characterized in that: The secondary impeller is provided with an external spline, a secondary impeller hub, a positioning surface, an inner hole, an internal spline, and a hub end face in sequence; The external spline of the second-stage impeller is used to connect with the first-stage impeller. The internal spline of the second-stage impeller mates with the external spline of the turbine disk and presses the bearing pair mounted on the turbine disk hub with the hub end face. Another pair of bearings with elastic support is mounted on the hub of the second-stage impeller and presses the inner ring of the bearing with the hub end face of the first-stage impeller. The positioning surface is used to define the axial position of the bearing.

4. The liquid hydrogen turbopump center tie rod type flexible rotor according to claim 3, characterized in that: The first-stage impeller has an internal spline, a hub, an inner bore, a hub end face, and a stop. The internal spline of the first-stage impeller engages with the external spline of the second-stage impeller, and the bearing pair installed on the hub of the second-stage impeller is pressed by the hub end face. The stop is used to achieve positioning engagement with the inducer.

5. The liquid hydrogen turbopump center tie rod type flexible rotor according to claim 4, characterized in that: The diameter fit between the first-stage impeller hub and the second-stage impeller hub at room temperature is -0.02mm to 0.02mm; the fit between the second-stage impeller hub and the turbine disk hub at room temperature is -0.02mm to 0.02mm; the bearing is an angular contact ball bearing, and the clearance between the inner ring of the bearing and the second-stage impeller hub and the turbine disk hub at room temperature is within 0.01mm.

6. The liquid hydrogen turbopump center tie rod type flexible rotor according to claim 1, characterized in that: An adjusting shim and a preload assembly are installed between each pair of bearings. The bearings are preloaded quantitatively by adjusting the size of the adjusting shim and compressing the preload assembly.

7. The liquid hydrogen turbopump center tie rod type flexible rotor according to claim 1, characterized in that: The fit between the turbine disk, the secondary impeller, and the central tie rod at room temperature is within -0.02mm to 0.02mm.

8. The liquid hydrogen turbopump center tie rod type flexible rotor according to claim 1, characterized in that: The central tie rod is made of high-temperature alloy; the pump end locking nut, inducer, first-stage impeller, second-stage impeller and vortex end locking nut are made of titanium alloy; the turbine disk is made of high-temperature alloy or titanium alloy.

9. A method for assembling a flexible rotor with a center tie rod in a liquid hydrogen turbopump, characterized in that... include: Tighten the vortex end locking nut and vortex end locking plate onto the center tie rod, and then pass the installed center tie rod through the inner hole from the spline-free end of the turbine disk; after passing a bearing and an adjusting shim that meets the preload force through the center tie rod, install it on the turbine disk hub, with the inner ring end face of the bearing mating with the turbine disk positioning surface, then install the elastic support on the outer ring of the bearing, and install the preload assembly inside the elastic support and close to the bearing on the turbine disk hub; after passing another bearing through the center tie rod, install it on the turbine disk hub. The inner spline end of the second-stage impeller passes through the central tie rod, and its inner spline mates with the outer spline of the turbine disk. The end face of the second-stage impeller hub is positioned and mated with the end face of the inner ring of the bearing on the turbine disk. After passing a bearing and a preload-fitting adjusting shim through the central tie rod, assemble them onto the secondary impeller hub. The inner ring end face of the bearing mates with the positioning surface of the secondary impeller. Then, install the elastic support on the outer ring of the bearing. The preload assembly is installed inside the elastic support and closely attached to the bearing on the secondary impeller hub. Pass another bearing through the central tie rod and then install it onto the secondary impeller hub. The spline-free end of the first-stage impeller passes through the central tie rod, and its internal spline engages with the external spline of the second-stage impeller. The end face of the first-stage impeller hub is positioned and engaged with the end face of the bearing inner ring. The spline end of the inducer is passed through the central tie rod, and the stop of the inducer is positioned and fitted with the stop of the first-stage impeller. The internal spline of the inducer is fitted with the external spline of the second-stage impeller. Tighten the pump end locking plate and pump end locking nut to the center tie rod according to the specified torque value; The damper baffle, damper, and damper support are assembled with the elastic support to form a central tie rod type combined rotor for the liquid hydrogen turbine pump.

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