Integrally Bladed Rotor Tip Clearance Control via Split Hub
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Solution Overview
Problem
Existing passive and active tip clearance control systems for gas turbine engines are ineffective in minimizing blade tip deflection for lightweight axial compressor rotors, particularly in later stages, and adding material or complexity is undesirable.
Innovation Solution
An integrally bladed rotor design with a hub and radially extending blades, featuring axially opposed split hub members with flex arm and moment flange portions, and a separately formed moment inducing element that generates an inward bending moment to deflect the blades radially inward, reducing tip clearance without adding weight or material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional material is added to the rotor bore to minimize blade tip deflection, then blade tip clearance is reduced, but rotor weight and hub mass increase
Solution Approach 1:
The hub is divided into multiple separate components: a hub body, a hub cap, and a hub retainer. This segmentation allows each component to be optimized independently for its specific function, enabling precise control of blade tip clearance through the retainer's positioning action without requiring additional material throughout the entire hub structure, thus avoiding unnecessary weight increase.
Solution Approach 2:
The hub retainer acts as an intermediary element between the hub cap and the hub body. It specifically controls the relative positioning of these components to achieve precise blade tip clearance control. The retainer's design allows it to mediate the clearance adjustment without requiring the hub mass to be increased, as it provides the necessary constraint through its own structural features.
2Manufacturing precision
If traditional passive tip clearance control systems are used, then blade tip deflection is minimized for heavy blades, but effectiveness decreases for lightweight axial compressor blades
Solution Approach 1:
The hub retainer is designed with specific local features including a retainer body with a first portion that interfaces with the hub cap and a second portion that interfaces with the hub body. This localized quality design allows the retainer to provide precise clearance control for lightweight axial compressor blades through its specific geometric features, while the overall hub structure remains optimized for the particular application requirements.
3Manufacturing precision
If active tip clearance control systems are used, then blade tip clearance is controlled, but system complexity and added weight increase
Solution Approach 1:
The hub retainer is designed to be a self-contained component that provides blade tip clearance control through its own structural features and positioning action. The retainer's design allows it to self-adjust and maintain optimal clearance without requiring external active control systems, sensors, or actuators. This self-service approach eliminates the complexity associated with active control systems while maintaining precise clearance control capability.
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 effectively minimizes blade tip clearance and improves compressor efficiency by precisely controlling blade tip deflection, maintaining reduced clearance even at increased rotational speeds, without relying on traditional bore mass.
Implementation Method 1
the moment inducing element acting on the moment flange portions of the opposed split hub members to generate an inward bending moment on the flex arm portions of the opposed split hub members during rotation of the rotor, thereby deflecting the rim and the blades of the rotor radially inwardly
Implementation Method 2
a hub defining a central axis of rotation about which the rotor is rotatable
Data Source
AI summary
An integrally bladed rotor for a gas turbine engine includes a hub, a plurality of blades radially extending from the hub and being integrally formed therewith. The hub having a rim from which the blades project and a pair of axially opposed split hub members extending at least radially inward from the rim. Each of the split hub members has a radially outer flex arm portion extending form the hub and a radially inner moment flange portion. At least one moment inducing element separately formed from the hub is mounted axially between the opposed split hub members and acts on the moment flange portions of the opposed split hub members to generate an inward bending moment on the flex arm portions of the opposed split hub members during rotation of the rotor, thereby deflecting the rim and the blades of the rotor radially inwardly.