Low Hub-to-Tip Fan via Linear Friction Welding
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Solution Overview
Problem
Existing integrated bladed rotor (IBR) fans for gas turbine engines face challenges in achieving a low hub to tip radius ratio due to manufacturing limitations, which restricts the reduction of fan diameter and weight, and affects air flow efficiency.
Innovation Solution
The development of an integrally bladed rotor fan with a hub to tip radius ratio of less than 0.29, achieved by forming root stubs on the rotor hub and linear-friction-welding airfoils to the stubs, allowing for a reduced hub radius while maintaining or increasing the tip radius, enabling a smaller diameter and lighter weight fan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the hub radius is reduced to achieve a low hub to tip ratio, then the fan diameter and weight are reduced, but manufacturing accessibility deteriorates due to lack of space for machine tools between blade roots
Solution Approach 1:
The fan blade assembly is segmented into two distinct parts: the airfoil section and the root section. The airfoils are separately manufactured and then joined to the hub via root stubs. This segmentation allows the hub to be manufactured with a reduced radius while maintaining manufacturing accessibility, as the airfoils can be attached after the hub structure is completed.
Solution Approach 2:
Root stubs are formed on the hub in advance during hub manufacturing, before the airfoils are attached. This preliminary action creates predetermined attachment points that facilitate subsequent airfoil installation while allowing the hub to be manufactured with reduced dimensions and improved manufacturing accessibility.
2Productivity
If the hub radius is reduced to achieve a low hub to tip ratio, then the specific flow of air entering the fan is reduced, but manufacturing capabilities are exceeded due to insufficient space for machine tools
Solution Approach 1:
By dividing the fan blade into separate airfoil and root components, the invention enables the hub to be manufactured with a smaller radius that optimizes specific flow while still providing adequate space for machine tools during the hub manufacturing process. The airfoils are then attached to the pre-formed hub.
Solution Approach 2:
The invention transitions from a monolithic three-dimensional blade structure to a assembly of separate components (hub, root stubs, and airfoils). This dimensional change in the manufacturing approach allows the hub to be manufactured with reduced radius while maintaining accessibility for machine tools, as the complex root structures are added in a subsequent assembly step rather than being machined from a solid block.
3Weight of moving object
If an integrated bladed rotor design is used to reduce weight, then the fan becomes lighter, but the hub to tip ratio cannot be reduced due to manufacturing limitations
Solution Approach 1:
The integrated bladed rotor achieves weight reduction while enabling low hub to tip ratio through segmentation of the blade into airfoil and root components. The airfoils are joined to the hub via root stubs using linear friction welding, creating an integrated structure that is both lightweight and has the desired low hub to tip ratio geometry.
Solution Approach 2:
The fan blade assembly uses a composite construction approach, combining the hub structure with airfoil components through linear friction welding. This composite assembly method enables the creation of an integrated bladed rotor with optimized hub to tip ratio while maintaining the weight advantages of an integrated design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances aerodynamic efficiency by reducing specific flow and air velocity, while also reducing the fan's weight and improving manufacturing accessibility by allowing better tool access between blades.
Implementation Method 1
linear-friction-welding airfoils to the stubs
Data Source
AI summary
A fan for a turbofan gas turbine engine having a low hub-to-tip ratio is disclosed. The fan includes a rotor hub and a plurality of radially extending fan blades. Each fan blade defines a hub radius (RHUB), which is the radius of the leading edge at the hub relative to a centerline of the fan, and a tip radius (RTIP), which is the radius of the leading edge at a tip of the fan blade relative to the centerline of the fan. The ratio of the hub radius to the tip radius (RHUB/RTIP) is less than 0.29. In a particular embodiment, this ratio is between 0.25 and 0.29. In another particular embodiment, this ratio is less than 0.25.