Two-Speed Low Spool Drive for Hybrid Turbine Thermal Constraints
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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 when motor-generators are directly driven with a fixed gear ratio off the accessory gearbox.
Innovation Solution
A hybrid electric gas turbine engine two-speed transmission system is introduced, comprising an accessory gearbox, a transmission, a low speed spool angled gearbox, and a low speed spool, which allows for two operational modes: direct drive for high speed operation and a 3X increase in motor shaft speed, optimizing motor-generator performance and reducing thermal management demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If motor-generators are directly driven with a fixed gear ratio off the accessory gearbox, then the structure is simple, but the motor-generator design becomes difficult due to large speed ranges
Solution Approach 1:
The patent introduces a two-speed transmission system that dynamically switches between two gear ratios (1:1 and 3:1) based on operating conditions. This allows the motor-generator to operate in two distinct speed ranges rather than one fixed range, making the speed range more manageable and the motor-generator design more feasible while maintaining reasonable structural complexity
2Device complexity
If motor-generators are directly driven with a fixed gear ratio, then the system is simple, but thermal management becomes challenging
Solution Approach 1:
The two-speed transmission enables dynamic operation in two distinct thermal regimes. At high speeds (1:1 ratio), the motor-generator operates with different thermal characteristics than at low speeds (3:1 ratio). This dynamic switching allows for more effective thermal management by avoiding continuous operation in the most demanding thermal condition
3Productivity
If a two-speed transmission is introduced, then motor-generator efficiency is improved, but device complexity increases
Solution Approach 1:
The transmission system is segmented into two distinct speed modes with different gear ratios. This segmentation allows the motor-generator to be optimized for two different operating points, improving overall efficiency across the operating range. The complexity is managed by using a modular two-speed transmission design with manageable components
Solution Approach 2:
The system changes the gear ratio parameter between two discrete values (1:1 and 3:1) to optimize motor-generator operating conditions. This parameter change enables the motor-generator to maintain high efficiency across a wider range of engine speeds without requiring continuous variable transmission complexity
Data Source
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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.