Gas Turbine Rotor Bore Airflow Modulation for Blade Tip Clearance Control
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Solution Overview
Problem
Gas turbine engines face efficiency issues due to variable blade tip clearances, which can lead to rubbing and reduced performance, especially under transient conditions such as takeoff where high rotor speeds and temperatures cause radial deflection of rotor blades, increasing the risk of contact with the stationary shroud.
Innovation Solution
A system and method that modulate airflow into the bore of a gas turbine engine's rotor by using a movable member, such as a damper or flaps, to adjust the mass flow rate of air, allowing for control of the clearance gap between the rotor blades and the casing through positioning changes and temperature adjustments using a heating/cooling circuit, controlled by a processor-based system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If rotor speed and temperature are increased during takeoff, then engine power output is improved, but radial deflection of rotor blades increases causing clearance gap reduction and risk of blade-shroud contact
Solution Approach 1:
The patent employs a movable member (damper or flaps) that can dynamically adjust its position in response to changing rotor speed and temperature conditions. During takeoff, when radial deflection increases, the movable member automatically shifts to maintain optimal clearance gap, preventing blade-shroud contact while preserving high power output capability
Solution Approach 2:
The system changes physical parameters (position of movable member, airflow characteristics) in response to operating conditions. By monitoring rotor speed and temperature, the system adjusts the movable member position to compensate for thermal and centrifugal deflections, maintaining reliable clearance gaps across varying power levels
2Loss of energy
If clearance gap is minimized to maintain engine efficiency, then specific fuel consumption is improved, but risk of blade rubbing increases under transient conditions
Solution Approach 1:
The movable member is positioned in advance to anticipate and prevent blade-shroud contact before it occurs. By proactively adjusting the clearance gap based on predicted radial deflection from temperature and speed changes, the system maintains minimal safe clearance that prevents rubbing while optimizing fuel consumption
Solution Approach 2:
The system continuously monitors operating parameters (rotor speed, temperature, clearance gap) and uses this feedback to dynamically adjust the movable member position. This closed-loop control ensures the clearance gap remains optimized for fuel efficiency while automatically preventing blade rubbing when harmful radial deflection is detected
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 actively maintains a desired clearance gap, improving specific fuel consumption (SFC) and preventing rubbing, by adjusting airflow to manage radial deflection and maintain optimal clearance, thus enhancing engine efficiency and performance.
Implementation Method 1
a movable member movable between at least a first position and a second position to modulate airflow into the bore via a plurality of openings in fluid communication with the bore
Implementation Method 2
temperature adjustments using a heating/cooling circuit
Implementation Method 3
temperature adjustments using a heating/cooling circuit
Data Source
AI summary
A system for modulating airflow into a bore defined by a rotor of a gas turbine engine defining an axial direction, a circumferential direction, and a radial direction is provided. The system includes a movable member positioned forward of a first stage of rotor blades of the rotor. The movable member is movable between at least a first position and a second position to modulate airflow into the bore via a plurality of opening in fluid communication with the bore.