Starter Generator Mounting on Low Pressure Shaft
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Solution Overview
Problem
The integration of an internal starter/generator in a gas turbine engine adds rotating weight to the high pressure shaft, disrupting its dynamics and requiring costly redesigns and retesting, especially when the engine was not originally designed to accommodate such a system.
Innovation Solution
A method of assembling an electromechanical device in a gas turbine engine where the low pressure shaft supports a rotor and stator, with a bearing assembly allowing independent rotation, enabling the starter/generator to be coupled to the low pressure shaft without affecting the high pressure shaft dynamics, using a coupling idle gear to transfer drive between the shaft and device gears.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an internal starter/generator is attached cantilevered from the forward end of the high pressure shaft, then the starter/generator can be installed in the engine, but additional rotating weight is added to the high pressure shaft which adversely affects its dynamics
Solution Approach 1:
The patent divides the shaft system into two independent rotating systems: a high pressure shaft and a low pressure shaft. The starter/generator is attached to the low pressure shaft rather than the high pressure shaft, segmenting the loads and dynamics of each shaft system. This allows the high pressure shaft to maintain its original dynamics while the low pressure shaft independently supports the additional rotating weight of the starter/generator.
Solution Approach 2:
The low pressure shaft acts as an intermediary between the engine and the starter/generator. Instead of directly attaching the starter/generator to the high pressure shaft, the patent uses the low pressure shaft as a mediator to transmit rotational power while isolating the high pressure shaft from the additional rotating weight and dynamic effects.
2Adaptability or versatility
If the high pressure shaft is redesigned to support additional loads from the starter/generator, then the shaft can accommodate the device, but substantial development costs are incurred
Solution Approach 1:
The low pressure shaft is given multiple functions: it continues to perform its original role of driving the fan and compressor while also serving as the mounting shaft for the starter/generator. This multi-functionality eliminates the need to redesign the high pressure shaft, avoiding substantial development costs while still accommodating the starter/generator loads.
3Adaptability or versatility
If bearing supports are displaced to accommodate the starter/generator, then the device can be installed, but the low pressure shaft requires redesign
Solution Approach 1:
The low pressure shaft system serves itself by independently supporting the starter/generator without requiring modifications to the high pressure shaft or its bearing supports. The existing low pressure shaft structure and bearing supports are utilized as-is, allowing the system to accommodate the starter/generator without increasing overall complexity or requiring shaft redesign.
Data Source
AI summary
A method of assembling a starter/generator in a gas-turbine engine, including coupling a rotor and a stator of the starter/generator such that the rotor is rotatable with respect to the stator to drive the rotor when the starter/generator is electrically powered and to produce electrical power when the rotor is rotated, securing the stator to a bearing support, coupling the starter/generator to a low pressure shaft of the engine by installing the bearing support over a bearing assembly secured to an end of the low pressure shaft, inserting the low pressure shaft through a high pressure shaft of the engine with the end of the low pressure shaft protruding therefrom and positioning the starter/generator in proximity of an end of the high pressure shaft, and drivingly engaging the rotor to the high pressure shaft.