Gas Turbine Starter Air Valve Speed Control
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Solution Overview
Problem
Gas turbine engines face issues with bowed rotor conditions due to thermal expansion after shutdown, leading to potential damage during restart, and existing speed control systems may fail to reliably regulate spool speed, risking critical resonance and damage.
Innovation Solution
A system and method for speed control during motoring of gas turbine engines using an air turbine starter, a starter air valve, and a controller that adjusts the valve based on measured feedback with lead compensation to mitigate bowed rotor conditions, employing dry motoring with controlled air pressure delivery to maintain rotor speed below critical resonance levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the starter system drives rotation at extended period below critical speed to mitigate bowed rotor condition, then thermal distortion is reduced and rotor straightening is achieved, but the system complexity and control reliability requirements increase
Solution Approach 1:
The patent implements a feedback control system that continuously monitors spool speed and adjusts the starter air valve position accordingly. The controller receives speed feedback from sensors and modulates the air valve to maintain speed within the safe operating range, preventing resonance while achieving rotor straightening. This closed-loop feedback mechanism ensures reliable speed regulation without requiring overly complex control architecture.
Solution Approach 2:
The control system utilizes the engine's own operational characteristics and available sensors to regulate spool speed during motoring. The system self-adjusts the starter air valve based on real-time speed measurements, eliminating the need for external complex control equipment. The engine's inherent response to air flow changes provides natural speed control assistance.
2Device complexity
If the starter system operates without reliable speed control, then device complexity is reduced, but the spool may accelerate to critical speed causing damage
Solution Approach 1:
A feedback control loop continuously monitors spool speed and adjusts the starter air valve to prevent acceleration to critical speed. The controller compares actual speed with target speed and modulates air valve opening accordingly, ensuring the spool remains within safe operating limits throughout the motoring process. This feedback mechanism provides reliable speed regulation with minimal additional complexity.
Solution Approach 2:
The control system dynamically adjusts the starter air valve position in real-time based on spool speed conditions. The valve opening is continuously modulated rather than fixed, allowing the system to adapt to changing load conditions and maintain safe speed limits. This dynamic control ensures reliability without requiring overly complex static control mechanisms.
3Measurement precision
If the starter air valve is rapidly adjusted for precise speed control, then speed regulation accuracy improves, but system response stability may deteriorate due to oscillations
Solution Approach 1:
The control system employs periodic modulation of the starter air valve rather than continuous rapid adjustment. The valve is opened and closed in controlled cycles to maintain speed within the target range, avoiding the instability that would result from continuous rapid adjustments. This periodic action provides precise speed control while maintaining system response stability.
Solution Approach 2:
The control system applies partial adjustments to the starter air valve rather than maximum adjustments. By making smaller, more conservative valve adjustments, the system achieves adequate speed control precision without inducing oscillations. The controller deliberately uses less than maximum valve authority to maintain stability, accepting slightly reduced precision in exchange for robust stable operation.
Data Source
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AI summary
A system is provided for speed control during motoring of a gas turbine engine (10A, 10B) of an aircraft. The system includes an air turbine starter (120A, 120B), a starter air valve (116A, 116B) operable to deliver compressed air to the air turbine starter (120A, 120B), and a controller (102A, 102B). The controller (102A, 102B) is operable to adjust the starter air valve (116A, 116B) to control motoring of the gas turbine engine (10A, 10B) based on measured feedback with lead compensation to reject disturbances attributable to dual to single or single to dual engine starting transitions.