Starter Generator Shaft Mounting and Electrical Joint Design
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Solution Overview
Problem
Gas turbine engines for subsonic missiles face challenges in compact design and efficient power generation due to size constraints and the difficulty in routing high-power electrical cables, which limits their ability to meet increasing power requirements and range objectives.
Innovation Solution
A compact gas turbine engine design incorporating a shaft-mounted integrated starter generator (ISG) with an adapter shaft and electrical joint system that allows for efficient power transmission and reduced space claims, enabling higher starting torque and power output while eliminating the need for accessory gearboxes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional cartridge pyrotechnics are used for engine starting, then the engine can achieve reliable start-up, but the design complexity and safety concerns increase
Solution Approach 1:
The patent replaces the mechanical pyrotechnic starting system with an electric starter generator system. The electric starter generator uses electromagnetic forces to rotate the compressor, eliminating the need for pyrotechnic charges and associated mechanical complexity while maintaining reliable engine start-up capability.
Solution Approach 2:
The starter generator serves dual functions: it acts as a starter motor during engine start-up and as a generator during engine operation to provide electrical power for accessories and guidance systems. This multi-functionality reduces overall system complexity compared to having separate pyrotechnic starting and electrical power systems.
2Power
If larger diameter power cables are used to transmit higher power, then power transmission capability increases, but the cable routing difficulty and space requirements increase
Solution Approach 1:
The patent segments the electrical power transmission system by placing the starter generator directly on the engine shaft, creating localized power generation/consumption points. This eliminates the need for long, high-power cable runs across the engine, allowing the use of smaller diameter cables while maintaining adequate power transmission capability.
Solution Approach 2:
The starter generator acts as an intermediary device that converts mechanical energy to electrical energy locally on the engine shaft. This eliminates the need for complex long-distance power cable routing by generating power at the point of use, thereby reducing cable diameter requirements and routing complexity.
3Volume of moving object
If the engine size is reduced to meet packaging constraints, then the missile platform integration improves, but the power generation capability and starting torque decrease
Solution Approach 1:
The patent merges the starter motor and generator into a single integrated starter generator unit mounted on the engine shaft. This consolidation reduces the total volume required compared to having separate starting and power generation systems, while maintaining adequate power generation capability through optimized electromagnetic design.
Solution Approach 2:
The integrated starter generator performs both starting and power generation functions within a single compact unit. This multi-functionality allows the engine to meet reduced volume constraints while maintaining sufficient power generation capability for missile accessories and guidance systems.
4Volume of moving object
If accessory gearbox is eliminated to reduce volume and weight, then the engine packaging efficiency improves, but the electrical power distribution complexity increases
Solution Approach 1:
The patent replaces the mechanical accessory gearbox system with an electrical power distribution system centered on the integrated starter generator. This substitution eliminates the mechanical complexity and volume of the gearbox while providing flexible electrical power distribution to accessories through the generator output.
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 solution enables a more compact and efficient gas turbine engine that meets the power and size requirements for subsonic missiles, improving range and reducing weight and complexity, while providing reliable electrical power for guidance and accessories.
Implementation Method 1
a rotor of an electric starter generator mounted on the adapter shaft
Implementation Method 2
Such starters are often also advantageously used as generators to supply electrical power
Data Source
AI summary
A starter generator located within a sump region of a turbofan engine and coupled to an adapter shaft. The adapter shaft rotationally coupled to the high pressure shaft, forward of a high pressure shaft bearing, and secured by a spanner nut. The engine makes use of two pluralities of electrical conductors, the first extends through an electrical conduit defined by a forward strut extending from the sump region to the outward casing, the second extends axially away from the electric starter. Each of the first plurality of electrical conductors makes reversible contact with a respective one of the second plurality of electrical conductors via an elbow/pin connector, producing a tight turn in area of limited space.