Gas Turbine Starter Driveline Fuse for Clutch Overspeed Protection
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Solution Overview
Problem
Gas turbine engine starter motors are at risk of damage due to overspeed when the clutch fails to disengage the reduction gear train during normal engine operation, leading to excessive torque that can cause mechanical failure.
Innovation Solution
A pinned mechanical fuse is integrated into the drive line connecting the motor to the gas turbine engine, featuring at least one shear pin that secures within an outer and inner sleeve structure, designed to shear when torque exceeds a selected value, typically 64 foot-pounds (87 newton-meters), thereby protecting the motor from overspeed damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the clutch fails to disengage the reduction gear train during normal engine operation, then the motor is protected from overspeed damage, but the motor suffers from excessive torque leading to mechanical failure
Solution Approach 1:
A pinned mechanical fuse is introduced as an intermediary component between the motor and the reduction gear train. This mechanical fuse includes a shear pin that acts as a mediator to transfer torque from the motor to the clutch when the clutch fails to disengage, protecting the motor from excessive torque damage while enabling the clutch to eventually disengage under normal operating conditions
2Reliability
If a mechanical fuse with shear pin is added to protect the motor, then the motor is safeguarded from excessive torque, but the device complexity increases
Solution Approach 1:
The shear pin is designed as a disposable, low-cost component that is intentionally made to fail under excessive torque conditions. This simple sacrificial element provides reliable motor protection without requiring complex sensors, actuators, or control systems, thereby minimizing the increase in device complexity while effectively solving the protection problem
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 pinned mechanical fuse effectively withstands normal operational torque while shearing at excessive torque levels, preventing motor damage by disengaging the clutch when it fails to disengage, thus safeguarding the engine starter motor from overspeed.
Implementation Method 1
The at least one shear pin in operation shears when torque on the pinned mechanical fuse is greater than or equal to a selected value
Data Source
AI summary
A method of manufacturing a motoring system for a gas turbine having the steps of: assembling a pinned mechanical fuse, the pinned mechanical fuse including at least one shear pin; forming an outer housing; installing a reduction gear train into the outer housing, the reduction gear train having an input and an output; operably connecting a motor to the input; operably connecting a clutch to the output using the pinned mechanical fuse, the clutch in operation engages and disengages the reduction gear train; operably connecting a starter to the clutch, the starter having an output shaft; and operably connecting an accessory gearbox to the output shaft of the starter. The clutch is operably connected to the accessory gearbox through the starter and the output shaft. The at least one shear pin in operation shears when torque on the pinned mechanical fuse is greater than or equal to a selected value.