Apparatus and process for manufacturing a centrifugal pump with a rotor within a single piece housing

Abstract

A turbopump is formed from a metal additive manufacturing process in which both the housing and the impeller are formed as a single piece with the impeller trapped within the single piece housing. The impeller is formed with an axial bore and a shaft is secured by a tie bolt on one end to secure forward and aft bearings within the housing after the impeller and housing have been formed.

Claims

1. A turbopump comprising: a single piece housing with a fluid inlet, a fluid outlet, a forward opening, and an aft opening the single piece housing having an inner minimum diameter; a single piece impeller having a maximum outer diameter greater than the inner minimum diameter of the single piece housing, the single piece impeller including an axial bore; a shaft inserted within the axial bore of the single piece impeller; a forward bearing and an aft bearing to rotatably support the single piece impeller within the single piece housing; and a shaft tie bolt threaded on one end of the shaft to secure the forward bearing and the aft bearing between the single piece housing and the single piece impeller.

2. The turbopump of claim 1, and further comprising wherein: the single piece housing and the single piece impeller are formed from a metal additive manufacturing process.

3. The turbopump of claim 1, wherein: the single piece impeller is formed with a forward labyrinth seal and an aft labyrinth seal all as a single piece.

4. A turbopump comprising: a single piece housing with a fluid inlet, a fluid outlet, a forward opening, and an aft opening, the single piece housing having an inner minimum diameter; a single piece impeller having a maximum outer diameter greater than the inner minimum diameter of the single piece housing; a forward bearing and an aft bearing; to rotatably support the single piece impeller within the single piece housing; a forward cover plate enclosing a forward opening of the single piece housing, the forward cover plate forming a support surface for the forward bearing; and an aft buffer seal enclosing an aft opening of the single piece housing the aft buffer seal forming a support surface for the aft bearing.

5. A method of forming a turbopump with a single piece impeller formed within a single piece housing comprising the steps of: forming the single piece housing with a fluid inlet and a fluid outlet using a metal additive manufacturing process; forming the single piece impeller with an axial bore and using the metal additive manufacturing process within the single piece housing at the same time that the single piece housing is being formed; machining a forward bearing support surface on a forward side of the single piece impeller and an aft bearing support surface on an aft side of the single piece impeller after the single piece impeller has been formed within the single piece housing; inserting a forward bearing and an aft bearing into the single piece housing; and securing the forward bearing and the aft bearing between the single piece housing and the single piece impeller with a tie bolt fastened on one end of a shaft passing through the axial bore of the single piece impeller.

6. The method of forming a turbopump of claim 5, and further comprising the step of: forming a forward labyrinth seal and an aft labyrinth seal on the single piece impeller all as a single piece.

7. The method of forming a turbopump of claim 5, and further comprising the step of: forming the single piece impeller with a maximum outer diameter greater than a minimum inner diameter of the single piece housing such that the single piece impeller is trapped within the single piece housing.

8. The method of forming a turbopump of claim 5, and further comprising the steps of: enclosing a forward opening of the single piece housing with forward cover plate; and enclosing an aft opening of the single piece housing with a buffer seal.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) FIG. 1 shows a cross section view of a LOX pump of the prior art.

(2) FIG. 2 shows a cross section view of a LOX pump of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) The present invention is LOX pump used in a liquid rocket engine in which the rotor is formed by a metal additive manufacturing process and formed within a single piece housing that is also formed by a metal additive manufacturing process.

(4) FIG. 2 shows an embodiment of the present invention of a LOX pump of the present invention that is formed by a metal additive manufacturing process in which a one-piece rotor is formed within a one-piece housing. The impeller 25 and the shaft 26 are simultaneously manufactured within the housing 29, the forward seal 16 and the aft seal 17 and the threaded nut 18 of the FIG. 1 embodiment is eliminated, the requirement to finish machining of the housing for the bearing OD (outer diameter) 27 of the FIG. 1 embodiment is eliminated, and the FIG. 2 embodiment provides for the elimination of all machining operations from the shaft. The FIG. 2 embodiment also eliminates the aft housing 19 and associated interface flange, eliminates the seal and finish machining, and eliminates the screws required in the FIG. 1 embodiment. The single piece impeller 25 is printed with an axial bore in which the shaft 26 passes through.

(5) In the FIG. 2 design, a double suction impeller 25 is trapped within the housing 29 since the outer diameter of the impeller 25 is greater than a minimum opening on either end of the housing 29. This is achieved by printing the components simultaneously within the Selective Laser Melting (SLM) machine. Then, powder and support structure (if required) removal is performed. The bearings 12 are installed on the ends of the shaft 26. Conventional manufacturing is required for the bearings 12 due to high precision requirements needed. With the exception of the shaft tie-bolt 30 and the shaft seal, all other components are printed on an SLM machine.

(6) A forward and an aft labyrinth seal 28 are formed on the impeller 25 all as a single piece and form seals with the surfaces of the single piece housing 29. The single piece housing 29 is formed with the impeller 25 and forward and aft labyrinth seals 28 inside the housing 29. Outer surfaces of the impeller 25 where the bearing inner races are placed are machined while the impeller 25 is inside the housing 29. The bearings 12 are then installed in place on the impeller 25, and then the shaft 26 is inserted within the impeller 25 and secured in place with the shaft tie bolt 30. A flange 34 is formed on the aft side of the shaft 26 and along with the shaft tie bolt 30 compresses the bearing inner races to flanges formed on the outer surface of the impeller 25. A forward cover plate 32 is installed with a number of bolts 31. A buffer seal 33 is installed on the aft end of the housing 29 and the aft bearing 12. A number of bolts 31 are used to secure the buffer seal 33 to the housing 29.

(7) Rotor balancing is another critical area. Typically, an assembly balance of the rotor is performed for turbopump rotors. That is, the full rotor is assembled and balanced on a balance machine. Since the rotor 25 is printed inside the housing 29, this method cannot be used without special tooling. In the present invention, a method of trim balancing is used where the rotor 25 is spun up to various high speeds and accelerometers on the housing 29 along with a proximity probe looking at the rotor is used to determine the rotor imbalance. The imbalance is corrected by grinding locations on each end of the shaft 26.

(8) By printing the pump impeller 25 within a one-piece housing 29, a dramatic reduction in part count, procurement activities, and assembly time is achieved over the prior art, which directly translates into a reduction in recurring cost and lead time. These reductions are estimated to reduce the cost of the LOX pump by approximately 40%. Similarly, if not more (due to the higher part count), reductions will likely result for a hydrogen pump. The turbomachinery for a typical rocket engine accounts for about one-third of the cost of the total engine. Thus, significant reductions in turbomachinery cost have large impacts on the overall cost of the engine.