Radial Turbine Rotor with Additive Layer Manufactured Components

The present disclosure relates generally to radial turbines, and more specifically to radial turbine rotors.

Radial turbine rotors are characterized by rotating in response to a flow of working fluid radially inwardly toward the axis of rotation. In many applications, radial turbine rotors can be more efficient than axial turbine rotors that rotate in response to a flow of working fluid primarily parallel to the axis of rotation.

To increase efficiency of radial turbine rotors, it can be beneficial to increase the temperature of the working fluid that interacts with the rotors. However, manufacturing radial turbine rotors from high temperature materials and/or incorporating an active supply of cooling air into radial turbines presents challenges.

The present disclosure may comprise one or more of the following features and combinations thereof in an effort to address challenges in radial turbine rotor design and manufacture.

A radial turbine rotor may comprise a hub and a crown with blades coupled to the hub. The hub may be arranged around a central axis and may define a radially innermost surface of the rotor. The crown may be formed of metallic layers deposited additively to provide monolithic, single piece with a flowpath ring that extends annularly around the hub and turbine blades that extend radially outwardly from the flowpath ring.

In some embodiments, the crown is coupled to the hub via a metallurgical bond process that fixes the crown to the hub for rotation therewith. The bond layer may be a diffusion bond joint, transient liquid phase bond joint, or a braze assist diffusion bond joint. It is also contemplated to couple the crown to the hub via mechanical or simple brazing as may be suitable for certain applications.

In some embodiments, at least one of the plurality of turbine blades is formed to include a cooling air passageway therein. Complex cooling features including pins and fins may be formed within the cooling air passageway.

In some embodiments, the flowpath ring is formed to include at least one cooling air feed channel that opens radially inwardly to face the central axis. The cooling air feed channel may be in fluid communication with the cooling air passageway formed in at least one of the plurality of turbine blades. An axial end of the at least one cooling air feed channel may be open to receive cooling air at a location radially inward of the plurality of turbine blades.

In some embodiments, the crown comprises nickel superalloy materials. The hub can also comprise nickel superalloy materials. Other suitable materials can also be used. In some other embodiments, other high temperature material systems such as refractory alloys like C103 Niobium alloy could be used.

According to another aspect of the present disclosure, a method of making a radial turbine rotor is disclosed. The method may comprise forging a hub arranged around a central axis, forming a crown with a flowpath ring that extends annularly around the hub and a plurality of turbine blades that extend radially outwardly from the flowpath ring via additive layer manufacturing so as to provide a monolithic, single piece component, and coupling the crown to the hub by forming a joint radially between a radially inwardly facing surface of the crown and a radially outwardly facing surface of the hub.

In some embodiments, the joint is a diffusion bond layer. The hub and the crown may be shrink fit together by sufficiently heating the crown and cooling the hub. Thermal expansion of the crown can enable insertion of the hub into the crown. After the hub is inserted into the crown, the assembly is heated in a vacuum furnace to a sufficient temperature to complete diffusion bonding. In certain embodiments, to join the crown to the hub, a transient liquid phase bonding process may be used. In this case a melting point suppressant is applied to one (or both) surfaces to be joined. The bond process is “self fixtured” meaning it doesn't require the use of separate delta alpha tooling to apply a load across the bond joint. This is accomplished by shrink fitting the hub and crown together after application of the melting point suppressant and then heating this assembly in a vacuum furnace up to a temperature to accomplish the transient liquid phase bond.

In some embodiments, the crown comprises nickel superalloy materials. The hub can also comprise nickel superalloy materials. Other suitable materials can also be used. In some other embodiments, other high temperature material systems such as refractory alloys like C103 Niobium alloy could be used.

These and other features of the present disclosure will become more apparent from the following description of the illustrative embodiments.

For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to a number of illustrative embodiments illustrated in the drawings and specific language will be used to describe the same.

A radial turbine rotorfor use in a gas turbine engine includes a huband a crownas shown in. The radial turbine rotorextracts energy from a working fluid, such as hot, high pressure combustion products, flowing through a gas path. The radial turbine rotorrotates about a central axisto extract mechanical work from the flow of working fluid to drive other components of the gas turbine engine. The flow of working fluid in the radial turbine rotormay be radial to the central axis.

Temperatures of the working fluid at an inlet of radial turbines may be relatively high. To allow for relatively high temperatures of the working fluid, cooling of radial turbines, like rotor, may be useful so that the materials of the radial turbine can withstand the relatively high temperatures. Conventional manufacturing methods for integrally-cooled turbines incorporate integrally cast turbine blades and hub. However, these conventional manufacturing methods may not be cost effective for radial turbines. For example, if one turbine blade of the integrally cast radial turbine has a defect, the entire radial turbine may be unusable. A low casting yield in production due to potential defects may lead to increased costs.

The radial turbine rotorprovides passages for cooling with internal cooling features via additive layer manufacturing (ALM) as suggested in. The huband the crownare separate components that are assembled to form the radial turbine rotoras suggested in. The multi-piece radial turbine rotorallows for inspection of each component prior to assembly of the radial turbine rotorso that the entire radial turbine rotormay not be deemed unusable due to a defect in one component.

The hubis arranged around the central axisas shown in. As assembled, the hubdefines a radially-innermost surface of the radial turbine rotor. In the illustrative embodiment, the hubincludes a cylindrical portionand a conical/frustoconical portion. The conical portionof the hubextends between a first endand a second end. The first endhas a first diameter, and the second endhas a second diameter. The first diameter is smaller than the second diameter. The first endof the conical portionis coupled with the cylindrical portionof the hub.

In some embodiments, the hubcomprises nickel superalloy, such as, but not limited to, Udimet 720. In some embodiments, the hubcomprises nickel powder alloy, such as, but not limited to, RR1000. In some embodiments, the hubcomprises polycrystalline nickel-based superalloy, such as, but not limited to, Mar-M-247. In the illustrative embodiment, the hubis integrally formed as a single component via forging. Of course other suitable manufacturing techniques to form the hubare also contemplated including, but not limited to, casting, machining, additive layer manufacturing, etc.

The crownis manufactured via additive layer manufacturing (ALM) to enable complex geometry without some of the challenges of complex geometry metallic casting. The crownincludes a plurality of bladesthat extend out from an annular flowpath ringas shown in. The plurality of turbine bladesare circumferentially spaced apart from one another about the central axis. Notably, the blades may curve around a portion of the axis such that they overlap over certain circumferential locations while remaining spaced apart from one another at any particular location along the axis.

The turbine bladesare each formed to include a cooling air passagewayextending therethrough, as shown in. The cooling air passagewayis provided to cool and/or shield the turbine bladethat is exposed to the hot working fluid flowing through the gas path. Complex cooling features such as pinsand finsare formed within the cooling air passageway. Other shapes for cooling features may also be used as desired.

A radially inwardly facing surfaceof the flowpath ringis formed to include at least one cooling air feed channelas shown in. In the illustrative embodiment, the flowpath ringis formed to include a plurality of cooling air feed channelsspaced apart circumferentially around the axis. The cooling air feed channelsextend radially into the flowpath ring.

The cooling air feed channelsare in fluid communication with the cooling air passagewaysformed in the plurality of turbine bladesand feed cooling air to the passageways. Axial ends of the cooling air feed channelare open to receive cooling air at a location radially inward of the plurality of turbine blades. In other embodiments, it is contemplated that the cooling air feed channels may be formed in a radially outer surface of the conical portionof the hub.

In the illustrative embodiment, the crownincluding both the turbine bladesand the flowpath ringis made through additive layer manufacturing (ALM). The crownmay comprise high temperature metallic alloys, for example, Nickel-containing super alloys.

The flowpath ringextends circumferentially about the central axisto define a radially-inner boundary of the flowpathas shown in. The flowpath ringis located radially between the huband the plurality of turbine blades.

The hubis fixed to the crownby a bond joint or layer. The hub jointis formed between the radially-outwardly facing surfaceof the conical portionof the huband the radially-inwardly facing surfaceof the flowpath ringincluded in the crown. In the illustrative embodiment, the hub jointis a diffusion bond joint. In some embodiments, the hub jointmay be any other joint that fixes the hubwith the crown.

In some embodiments, shrink fitting may be used as part of the process of forming the joint. A material containing a suitable melting point suppressant may be applied to the radially-outwardly facing surfaceof the huband/or the radially-inwardly facing surfaceof the flowpath ring. The huband the crownmay be shrink fit together by sufficiently heating the crownand cooling the hub, resulting in thermal expansion of the crown. After the crownhas expanded, the hubmay be inserted into it. After the hub is inserted into the crown, the assembly is heated in a vacuum furnace to a sufficient temperature to complete diffusion bonding. In certain embodiments, to join the crownto the hub, a transient liquid phase bonding process may be used. In this case a melting point suppressant is applied to one (or both) surfaces to be joined. The bond process is “self fixtured” meaning it doesn't require the use of separate delta alpha tooling to apply a load across the bond joint. This is accomplished by shrink fitting the huband crowntogether after application of the melting point suppressant and then heating this assembly in a vacuum furnace up to a temperature to accomplish the transient liquid phase bond.

While the disclosure has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.