Rotor Tip Clearance Calibration via Iterative Knee Point Detection
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Solution Overview
Problem
The existing rotor tip clearance arrangements in gas turbine engines face challenges in accurately monitoring and managing the deterioration of tip clearance, which affects efficiency due to thermal and centrifugal growth, damage, and accretion of deposits, leading to inefficiencies and potential component erosion.
Innovation Solution
A method involving iterative measurements of rotor speed and incremental adjustments of the tip clearance control actuator to identify 'knee points' for calibration, allowing for the determination of deterioration and application of offsets to maintain optimal clearance, thereby compensating for changes and maintaining efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the tip clearance is minimized to improve efficiency, then more air passes over the aerofoil surfaces, but the risk of blade tips rubbing against the casing increases
Solution Approach 1:
The patent employs dynamic tip clearance control by adjusting the rotor casing position in real-time based on operating conditions. The system transitions from static clearance to dynamic adjustment, allowing the clearance to be minimized during steady-state operation for efficiency while automatically increasing during transient conditions to prevent rubbing, thus resolving the contradiction between productivity and reliability.
2Productivity
If the rotor operates under thermal and centrifugal growth, then the tip clearance changes, but this leads to deterioration and reduced efficiency
Solution Approach 1:
The patent implements a feedback control system that continuously monitors tip clearance and compares it with reference values. Based on the deviation detected, the system automatically adjusts the rotor casing position to maintain optimal clearance despite thermal and centrifugal growth. This closed-loop feedback mechanism stabilizes the clearance composition while maintaining high efficiency operation.
Solution Approach 2:
The system dynamically changes the physical parameters of the tip clearance control actuator position in response to varying operating conditions. By adjusting the casing position parameter based on temperature, speed, and clearance measurements, the system compensates for thermal and centrifugal growth effects, maintaining stable clearance characteristics throughout the rotor's operational lifecycle.
3Ease of operation
If mechanical actuators are used to control tip clearance, then the clearance can be adjusted, but the device complexity increases
Solution Approach 1:
The patent extracts and isolates the complex mechanical actuator system into a separate, modular tip clearance control assembly. This allows the actuation mechanism to be independently designed, tested, and maintained without affecting the core rotor system. The extracted actuator system interfaces with the rotor casing through standardized connections, simplifying the overall system architecture 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 method enables continuous monitoring and management of rotor tip clearance deterioration, ensuring efficient operation by accurately controlling the tip clearance, reducing the impact of degradation on engine performance and extending the lifespan of components.
Implementation Method 1
air flow valves which direct cooling air onto the casing to retard its thermal growth or to cause it to shrink towards the blade tips
Implementation Method 2
tip clearance may change, for example through differing rates of thermal and centrifugal growth
Implementation Method 3
tip clearance may change, for example through differing rates of thermal and centrifugal growth
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A method of calibrating a rotor tip clearance arrangement (38). Measure a rotor parameter indicative of rotor efficiency. Alter a position of a tip clearance control actuator (42) by an increment to reduce the rotor tip clearance. Iterate steps a) and b) and calculate a rate of change of the rotor parameter between pairs of iterations. Identify a knee point (52,62) where the rate of change of the rotor parameter changes and record the corresponding tip clearance control actuator position (54,64) as a calibrated position. Also a rotor tip clearance arrangement calibrated by the method and a method of monitoring deterioration of a rotor tip clearance arrangement.