Turbine Blade Clearance Control for Gas Turbine Engines
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Solution Overview
Problem
Gas turbine engines face challenges in maintaining optimal turbine blade tip-to-static structure clearances, leading to rubs and reduced performance during transient operations due to differing expansion rates of blade tips and static structures, especially when thrust changes occur.
Innovation Solution
A control system that processes mode and aircraft data to minimize turbine blade tip-to-static structure clearance when constant thrust is generated and the fuel-saving mode is enabled, and selectively increases clearance to a predetermined value to prevent thrust changes until the clearance is achieved, thereby preventing rubs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If air flow is supplied to reduce operational clearances during steady state cruise, then thermodynamic efficiency is improved, but rubs occur during transient thrust changes
Solution Approach 1:
The patent implements dynamic clearance control by continuously adjusting the air flow to rotor and static structures based on real-time engine operating conditions. The system transitions from static clearance reduction to dynamic adaptation, allowing clearance to be minimized during steady state while automatically increasing during transient thrust changes to prevent blade rubs.
Solution Approach 2:
The control system uses feedback from engine thrust measurements and operational mode detection to automatically adjust blade tip clearances. When thrust changes are detected during fuel-saving mode, the system responds by modifying air flow to increase clearance, creating a closed-loop control system that maintains both efficiency and reliability.
2Productivity
If blade tip clearance is minimized for fuel efficiency, then thermodynamic performance is improved, but blade tips contact static structure during thrust changes
Solution Approach 1:
The system takes preliminary action by detecting thrust changes before blade rubs occur and preemptively increasing blade tip clearances. The control system monitors engine operating mode and anticipates clearance requirements, adjusting air flow in advance to prevent harmful blade-static structure contact during transient operations.
Solution Approach 2:
The patent changes the physical parameter of blade tip clearance dynamically based on operating conditions. During steady state cruise, clearance is minimized for efficiency; during transient thrust changes, clearance is increased to prevent rubs. This parameter adaptation resolves the contradiction between maintaining small clearances for performance and preventing blade contact for reliability.
3Speed
If thrust changes are allowed freely, then engine responsiveness is improved, but clearance mismatch causes rubs and performance loss
Solution Approach 1:
The control system acts as an intermediary between thrust commands and blade clearance. It mediates the relationship by detecting thrust changes and automatically adjusting clearances through air flow control, allowing thrust to change freely while preventing clearance mismatch that would cause blade rubs.
Data Source
AI summary
A system and method are provided for controlling turbine blade tip-to-static structure clearance in a gas turbine engine installed on an aircraft. Mode control data are processed to determine that a fuel-saving mode is enabled, and aircraft data are processed to determine that the aircraft gas turbine engine is generating a substantially constant thrust. The turbine blade tip-to-static structure clearance in the aircraft gas turbine engine is minimized upon determining that both the aircraft gas turbine engine is generating a substantially constant thrust and the fuel-saving mode is enabled. The turbine blade tip-to-static structure clearance in the aircraft gas turbine engine is then selectively increased to a predetermined clearance, and a change in aircraft gas turbine engine thrust is prevented until the predetermined clearance is achieved.