Turbine Engine Starter Motor Cooling to Reduce Thermal Rotor Bow
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Solution Overview
Problem
Turbine engines experience thermal rotor bow due to residual heat causing deformation in rotating and stationary components, leading to reduced service life and performance, especially after shutdown and before full cooling.
Innovation Solution
A system utilizing a starter motor to rotate the rotor assembly post-shutdown, exhaust residual heat, and mitigate thermal rotor bow by selectively operating the starter motor based on feedback from a FADEC system to manage thermal imbalance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the turbine engine is shut down to reduce operation time, then productivity is improved, but thermal rotor bow occurs due to residual heat causing component deformation
Solution Approach 1:
The system performs preliminary cooling action by activating the starter motor immediately after engine shutdown to rotate the rotor assembly and exhaust residual heat before thermal rotor bow can fully develop, preventing component deformation while enabling quick engine availability
Solution Approach 2:
The system replaces natural passive cooling with an active mechanical cooling system using the starter motor to drive rotor rotation, forcing heat exhaustion through controlled rotation rather than relying on natural convection and conduction alone
2Reliability
If the starter motor is continuously operated to exhaust residual heat, then thermal rotor bow is mitigated, but energy consumption increases
Solution Approach 1:
The system uses periodic rather than continuous operation of the starter motor, activating it in controlled intervals after shutdown to exhaust residual heat effectively while minimizing unnecessary energy consumption during the cooling process
Solution Approach 2:
The FADEC system monitors engine temperature and operational parameters to determine when starter motor activation is necessary, using feedback control to activate the starter only when thermal conditions warrant intervention, optimizing the balance between thermal management and energy consumption
3Productivity
If tighter clearances are used between rotors and stators to improve efficiency, then productivity is improved, but thermal rotor bow occurs more easily due to reduced clearance tolerance
Solution Approach 1:
The system performs preliminary heat exhaustion through starter motor-driven rotation before the engine is restarted, removing residual heat that would otherwise cause thermal expansion and reduce the already-tight clearances between rotors and stators, maintaining clearance tolerance while preserving engine efficiency
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
Reduces thermal rotor bow formation, minimizes component wear, and accelerates cooling, thereby enhancing turbine engine performance and service life.
Implementation Method 1
A system utilizing a starter motor to rotate the rotor assembly post-shutdown, exhaust residual heat
Implementation Method 2
Residual heat remains in the aircraft's engines, which can cause a phenomenon known as thermal rotor bow
Data Source
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AI summary
A method of operating a turbine engine that includes shutting down the turbine engine such that a rotational speed of the turbine engine decreases, and actuating a starter motor of the turbine engine at one of as the rotational speed of the turbine engine decreases or at a preset time after the turbine engine receives a full stop command such that residual heat is exhausted from the turbine engine.