Two-Speed Low Spool Transmission for Hybrid Turbine Motor-Generators
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Solution Overview
Problem
Hybrid electric gas turbine engines face design challenges due to large low spool speed ranges, which impose significant design constraints on motor-generator optimization and thermal management, particularly in gearbox-mounted arrangements.
Innovation Solution
A hybrid electric gas turbine engine two-speed transmission system is introduced, comprising an accessory gearbox, a transmission, and a low speed spool angled gearbox, which allows for a two-speed operation mode to optimize motor-generator performance and reduce speed ranges, including a gear ratio of 3.0 for increased motor shaft speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If motor-generators are directly driven with a fixed gear ratio off the accessory gearbox without a transmission, then the structure is simpler, but the motor-generators must be optimized for large speed ranges which increases design complexity and thermal management challenges
Solution Approach 1:
The patent applies a two-speed transmission system that dynamically switches between two gear ratios (1.0 and 3.0) depending on the operating regime. This allows the motor-generator to operate in two distinct speed ranges rather than attempting to cover the entire range with a single fixed ratio, thereby optimizing performance in each regime while reducing overall design complexity
Solution Approach 2:
The transmission system segments the operating range into two distinct modes: a first operational mode for high-speed operation with direct drive (gear ratio 1.0), and a second operational mode for low-speed operation with increased gear ratio (3.0). This segmentation allows the motor-generator to be optimized for specific speed ranges rather than compromising across the entire range
2Reliability
If a two-speed transmission system is implemented to optimize motor-generator performance, then motor-generator efficiency and thermal management are improved, but the device complexity increases
Solution Approach 1:
The transmission system is integrated with the existing accessory gearbox, merging the two-speed transmission functionality into the existing structural framework. This approach allows the transmission system to leverage existing mounting points, shafts, and housing structures, thereby reducing the increase in overall device complexity while achieving improved motor-generator thermal management
Solution Approach 2:
The patent introduces a two-speed transmission as an intermediary mechanism between the accessory gearbox and the motor-generator. This intermediary component enables optimized motor-generator operation across different speed ranges while isolating the complexity of the transmission system from both the accessory gearbox and motor-generator designs
3Adaptability or versatility
If the low spool speed range is reduced through two-speed operation, then motor-generator design constraints are relaxed, but the transmission system requires additional components and integration
Solution Approach 1:
The transmission system is designed to perform multiple functions: it provides speed multiplication (3.0 gear ratio) for low-speed operation, direct drive (1.0 gear ratio) for high-speed operation, and serves as a structural integration point between the accessory gearbox and motor-generator. This multi-functionality reduces the need for separate components for each function, thereby limiting the increase in device complexity
Data Source
AI summary
A hybrid electric gas turbine engine two speed transmission for a low spool drive including an accessory gearbox in operative communication with a low speed spool motor-generator; a transmission in operative communication with the accessory gearbox and the low speed spool motor-generator; a low speed spool angled gearbox in operative communication with the transmission; and a low speed spool in operative communication with the low speed spool angled gearbox.