Counter-Rotating Turbine Ring With Abradable Blade Retention
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Solution Overview
Problem
In conventional turbofan engines, the fan rotates at the same speed as the low-pressure turbine, which is inefficient for achieving good specific fuel consumption and low noise levels, and there is a need to protect the second rotor from blade damage and ensure blade retention in counter-rotating turbines.
Innovation Solution
A ring with abradable material is secured to the second rotor, extending between the first and second impellers, and is held axially close to the center with a rotational coupling, featuring a central cylindrical bearing and axial stops to ensure retention and minimize vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ring with abradable material is secured to the second rotor to retain blades, then blade retention is improved, but the second rotor may be damaged by released blades
Solution Approach 1:
The abradable material serves as an intermediary layer between the first impeller blades and the second rotor. When blades are released or break, the abradable material absorbs the impact and wear, preventing direct damage to the second rotor while still providing effective blade retention through controlled abrasion and friction.
2Object-generated harmful factors
If the ring is held axially close to the center with a rotational coupling, then vibration is reduced, but manufacturing complexity increases
Solution Approach 1:
The rotational coupling with axial stops positions the ring at a precise axial location close to the center of the second rotor, creating a balanced configuration that minimizes vibration. The central cylindrical bearing provides uniform support around the circumference, ensuring even load distribution and reducing vibrational forces generated during rotation.
3Reliability
If abradable material is used for blade retention, then blade release detection is improved, but material wear increases
Solution Approach 1:
The abradable material is designed to wear down through controlled abrasion when blades contact it during normal operation or release events. This intentional wear serves as a detection mechanism - the wear pattern and rate provide information about blade retention status and potential releases. The material is replaced periodically as a consumable component, converting the harmful wear effect into a beneficial diagnostic function.
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
The solution effectively retains the blades of the first impeller without damaging the second rotor, reduces vibration, and maintains precise balancing and clearances, enhancing turbine performance.
Implementation Method 1
a ring to which abradable material is secured, the ring extending about the axis of rotation, between the (at least one of the) first impellers and the second rotor
Data Source
AI summary
A turbine includes a first rotor and a second rotor that can rotate in opposite directions and are interleaved. The turbine further includes a ring to which abradable material is secured, the ring, unsegmented, extending between the first impellers of the first rotor and the second rotor, over a sector of between 350 and 360°, and, axially between an upstream end and a downstream end of the ring, the ring is held with the second rotor.