Gas Turbine Thrust Control for Tip Clearance Management
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Solution Overview
Problem
Gas turbine engines face challenges in maintaining optimal tip clearance between rotating turbine blades and the shroud due to thermal and centrifugal expansion, leading to potential tip rub and efficiency losses, especially during unpredictable engine transients like air turbulence, where existing control systems may fail to anticipate and prevent contact.
Innovation Solution
A method to modify the thrust demand signal based on the growth time constants of the rotor and casing, allowing for controlled rotational speed adjustments to prevent contact, using a processor that can apply delays or thrust rate limits to ensure sufficient clearance, integrated into flight management or engine control systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thrust demand signal is modified based on growth time constants to control rotational speed, then tip rub is prevented, but engine response time to thrust demands increases
Solution Approach 1:
The system applies preliminary action by modifying the thrust demand signal in advance based on growth time constants before the actual transient occurs. The processor predicts the rotor and casing growth patterns and adjusts the thrust demand accordingly, preventing tip rub before it can occur during unexpected transients like clear air turbulence.
Solution Approach 2:
The system implements dynamics by continuously adapting the thrust demand signal modification based on real-time engine conditions. The processor dynamically adjusts the control parameters according to the current rotational speed, temperature, and predicted growth rates, allowing the engine to respond optimally to changing conditions while maintaining safe clearance.
2Loss of energy
If cooling air is fed to the shroud to contract it and reduce tip clearance, then fuel consumption decreases, but the system cannot prevent tip rub during rapid engine acceleration
Solution Approach 1:
The system employs feedback by continuously monitoring engine parameters such as rotational speed, temperature, and thrust demand, then using this information to dynamically adjust the thrust demand signal modification. The processor compares actual engine behavior with predicted growth patterns and adjusts the control strategy in real-time to maintain optimal clearance while preventing tip rub during rapid acceleration.
Solution Approach 2:
The system applies parameter changes by modifying the thrust demand signal based on growth time constants that characterize the thermal and centrifugal expansion behavior of the rotor and casing. By changing the control parameters according to these growth characteristics, the system achieves both fuel efficiency through reduced clearance and reliability through tip rub prevention.
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 approach effectively prevents tip rub even during unexpected engine transients, maintaining efficient engine operation and reducing fuel consumption by dynamically managing tip clearance based on real-time conditions.
Implementation Method 1
the high temperatures encountered in the engine cause significant thermal expansion of engine components, including the turbine blades and the discs on which they are mounted
Implementation Method 2
mechanical growth of the turbine blades and discs occurs due to the large centrifugal forces to which they are subjected as they rotate at high speeds
Data Source
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AI summary
A thrust demand signal is provided to a processor of an engine controller (88) of a gas turbine engine and is modified, according to growth time constants of a rotor and/or a casing of the engine, in order to control the rotational speed or the rate of change of rotational speed of the engine so as to prevent contact between the rotor and the casing.