Hybrid Starter Motor-Generator for Gas Turbine Propulsion
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Solution Overview
Problem
Conventional hybrid propulsion systems for gas turbine engines require multiple mechanical systems and control mechanisms, increasing weight and complexity, particularly due to the need for dedicated electric starter motors and generators, which are not efficiently integrated with the turbine stages during start-up and steady-state operations.
Innovation Solution
A hybrid propulsion system that replaces the accessory gearbox with a motor-generator unit mechanically coupled to the second drive shaft and uses an overrunning sprag clutch to automatically couple and decouple the first and second drive shafts based on rotational rates, eliminating the need for additional control systems and reducing mechanical complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dedicated electric starter motors and generators are used in conventional hybrid propulsion systems, then the system can perform start-up and power generation functions, but the number of mechanical systems and control mechanisms increases, leading to increased weight and complexity
Solution Approach 1:
The patent combines the starter motor and generator functions into a single motor-generator unit that is mechanically coupled to the second drive shaft. This integration eliminates the need for separate dedicated starter motors and generators, thereby reducing the number of mechanical systems while maintaining both start-up and power generation capabilities
Solution Approach 2:
The motor-generator unit serves multiple functions: it acts as a starter motor during engine start-up by driving the second drive shaft, and as a generator during normal operation by being driven by the second drive shaft to generate electrical power. This multi-functionality reduces system complexity while maintaining reliability
2Reliability
If manual control systems are used to couple and decouple drive shafts, then the system can manage power transmission, but additional control systems and operator intervention are required, increasing complexity
Solution Approach 1:
The overrunning sprag clutch automatically couples and decouples the drive shafts based on rotational speed differences without requiring operator intervention or additional control systems. The clutch self-regulates by engaging when the first drive shaft rotates faster than the second (during start-up) and disengaging when the rotational speeds equalize or reverse (during normal operation), thereby maintaining reliability while simplifying operation
3Reliability
If multiple mechanical systems are used in hybrid propulsion systems, then the system can perform required functions, but the weight of the system increases
Solution Approach 1:
By merging the starter motor and generator into a single motor-generator unit and using an overrunning sprag clutch for automatic drive shaft coupling, the patent reduces the number of mechanical components. This consolidation directly reduces the overall weight of the hybrid propulsion system while maintaining full functionality
Solution Approach 2:
The patent extracts and eliminates redundant mechanical systems and control mechanisms from conventional hybrid propulsion designs. By removing dedicated starter motors, separate generators, and manual control systems, the weight is reduced while the essential functions are preserved through the integrated motor-generator and automatic clutch system
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
This configuration reduces the number of mechanical systems, weight, and complexity by automatically managing the coupling and decoupling of drive shafts, enabling efficient power generation and propulsion during both start-up and steady-state operations without additional control systems, thus optimizing the hybrid propulsion system's performance.
Implementation Method 1
The clutch may include an overrunning sprag clutch. The overrunning sprag clutch may be relatively smaller and have relatively less weight than other clutch systems.
Data Source
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AI summary
An example hybrid propulsion system is described that includes a plurality of propulsors, a first drive shaft, a second drive shaft, a gas turbine engine, a motor-generator, and a clutch. The gas turbine engine includes a first turbine stage operatively coupled to the first drive shaft and a second turbine stage operatively coupled to the second drive shaft. The motor-generator is operatively coupled to the second drive shaft and is configured to generate electrical power to drive at least one propulsor of the plurality of propulsors and selectively drive the second shaft. The clutch is configured to operatively couple the second drive shaft to the first drive shaft.