Rotor Slot Inserts for IBR Sealing and Hoop Stress Relief
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Solution Overview
Problem
Integrally bladed rotors in gas turbine engines face challenges with hoop stresses and air leakage, which affect fracture life and efficiency, as conventional designs struggle to manage stress concentrations and leakage effectively.
Innovation Solution
The implementation of integrally bladed rotors with customized rotor slots and inserts that create an interference fit, using materials with higher thermal alpha to reduce hoop stress and prevent air leakage, along with retaining elements to secure the inserts in place, addresses the issues of stress concentration and air leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If rotor slots are introduced to reduce hoop stress, then fracture life is improved, but air leakage increases
Solution Approach 1:
The patent extracts the sealing function from the rotor slot structure itself by introducing separate rotor slot inserts. These inserts are removable and can be optimized specifically for sealing purposes, allowing the rotor slots to maintain their stress-reducing geometry while the inserts prevent air leakage between blades.
Solution Approach 2:
The rotor slot inserts act as intermediary elements between the rotor slots and the airflow. Made from materials with higher thermal expansion coefficients, these inserts fill the slots and prevent air leakage without requiring the slots to be closed, thus maintaining both stress reduction and sealing functions.
2Reliability
If rotor slot inserts with higher thermal alpha are used to prevent air leakage, then sealing is improved, but interference fit complexity increases
Solution Approach 1:
The patent changes the material parameter (thermal expansion coefficient) of the rotor slot inserts to be higher than the rotor material. This parameter change enables the inserts to expand more during operation, creating an interference fit that seals the rotor slots and prevents air leakage.
Solution Approach 2:
The patent utilizes thermal expansion by selecting rotor slot insert materials with higher thermal alpha values. During engine operation, these inserts expand more than the rotor, creating a tight interference fit that seals the rotor slots and prevents air leakage without requiring complex mechanical retention systems.
3Reliability
If retaining elements are added to secure rotor slot inserts, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the retention function from the rotor slot insert itself by introducing separate retaining elements. These can be simple rings or clips that engage with features on the inserts, allowing for modular assembly and easier manufacturing compared to integrating complex retention features directly into the inserts.
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 solution reduces hoop stress, increases fracture life, and minimizes air leakage, enhancing the efficiency and performance of gas turbine engines by managing stress concentrations and preventing recirculation of air.
Implementation Method 1
the rotor slot insert comprises a material having a higher thermal alpha than a material of the integrally bladed rotor to create an interference fit therebetween during operation of the integrally bladed rotor due to thermal expansion of the rotor slot insert
Data Source
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AI summary
Integrally bladed rotors (IBRs) are described. The IBRs include a central hub (306;506;606), an outer rim (302;502;602) defining an outer circumference of the central hub, the outer rim defining a plurality of platforms, a plurality of circumferentially distributed blades (304;504;604), wherein a blade extends from each of the plurality of platforms, a rotor slot (308;508) arranged between two adjacent blades, wherein the rotor slot is defined by a cut within the outer rim, and a rotor slot insert (520;612) installed within the rotor slot, the rotor slot insert sized and shaped to fit within the rotor slot and prevent air leakage from a first side (608) of the central hub to a second side (610) of the central hub through the rotor slot during operation of the integrally bladed rotor.