Staged Planetary Gear Train for Gas Turbine Rotor Bow Prevention
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Solution Overview
Problem
Modern aircraft gas turbine engines face rotor bowing due to uneven heat distribution after shutdown, which can lead to potential damage or reduced performance when restarted, and existing starter systems are not designed for continuous low-speed operation, potentially damaging air valves and starters.
Innovation Solution
A reduction gear train system that includes a starter interface gear, a core-turning clutch, and stacked planetary gear systems, which interfaces with the accessory gearbox and allows for a core-turning motor to slowly rotate the engine, preventing rotor bowing and enabling pneumatic starting at higher speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a pneumatic turbine starter is used to motor the engine at low speeds, then rotor bow can be minimized, but the air valve and starter suffer reduced life due to operating conditions outside design parameters
Solution Approach 1:
The system divides the motor function into two separate systems: a pneumatic turbine starter for high-speed starting operations and an electric core-turning motor for low-speed motoring operations. This segmentation allows each component to operate within its optimal design parameters, with the electric motor handling continuous low-speed operations that would otherwise damage the pneumatic starter and air valve.
Solution Approach 2:
A reduction gear train acts as an intermediary mechanism between the electric core-turning motor and the engine accessory gearbox. This gear train enables the electric motor to deliver the necessary torque at low speeds while protecting the starter system from damage during continuous motoring operations.
2Power
If the starter is designed for short duration transient operations, then it can effectively start the engine, but it cannot sustain continuous low-speed motoring without damage
Solution Approach 1:
The system implements multi-functionality by equipping the engine with two distinct motor systems: the pneumatic turbine starter maintains its optimized design for high-power starting operations, while the electric core-turning motor provides dedicated capability for continuous low-speed motoring. This universal approach ensures both starting and motoring functions are performed by components designed for their specific operational requirements.
3Productivity
If radial clearances are minimized to optimize engine efficiency, then engine performance improves, but rotor bowing occurs after shutdown due to uneven heat distribution
Solution Approach 1:
The electric core-turning motor performs preliminary action by rotating the engine core at low speeds immediately after shutdown. This preliminary rotation distributes heat evenly across the rotor before the next start cycle, preventing rotor bowing and maintaining the tight radial clearances necessary for optimal 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
The system effectively transmits torque to prevent rotor bowing and allows for higher-speed pneumatic starting, reducing the wear on starter system components and optimizing engine performance.
Implementation Method 1
The reduction gear train includes a starter interface gear that engages the starter gear train, a core-turning clutch operably connected to the starter interface gear, and a plurality of stacked planetary gear systems operably connected to the core-turning clutch and a core-turning input
Data Source
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AI summary
According to an aspect, a system for a gas turbine engine (54) includes a reduction gear train (122) operable to drive rotation of a starter gear train (132) that interfaces to an accessory gearbox (70) of the gas turbine engine. The reduction gear train includes a starter interface gear that engages the starter gear train, a core-turning clutch (124) operably connected to the starter interface gear, and a plurality of stacked planetary gear systems (150) operably connected to the core-turning clutch and a core-turning input (128). The system also includes a mounting pad including an interface to couple a core-turning motor (110) to the core-turning input of the reduction gear train.