Variable Gear Ratio Aircraft Power Generator System
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Solution Overview
Problem
Aircraft electrical power generators face challenges in efficiently managing a wide range of mechanical power inputs from gas turbine engine spools, leading to inefficiencies and weight penalties when trying to maintain a narrow frequency range, as conventional systems either require large generators or inefficient Integrated Drive Generators (IDGs).
Innovation Solution
An electrical power generator system with a gearbox that allows gear shifting between input and output shafts, enabling a narrow output frequency range by sequentially disconnecting and reconnecting generators to manage rotation frequencies, thereby avoiding power interruptions and weight penalties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a generator is sized for minimum spool speed to cover the wide speed range, then the generator can operate at all speeds, but the generator size becomes very large and inefficient
Solution Approach 1:
The patent applies dynamics by making the gear ratio variable rather than fixed. The gearbox transitions between different gear ratios (first gear ratio at low speeds, second gear ratio at high speeds) to dynamically adapt the generator's operating range, allowing a compact generator to efficiently cover the entire spool speed range.
Solution Approach 2:
The patent changes the gear ratio parameter based on operating conditions. At low spool speeds, a first gear ratio is used to step up the rotational speed to the generator's optimal range. At high spool speeds, a second (lower) gear ratio prevents excessive generator speed, maintaining it within efficient operating parameters throughout the wide speed range.
2Adaptability or versatility
If an Integrated Drive Generator (IDG) with constant speed hydraulic drive is used to achieve narrow output speed range, then the frequency range is limited, but the system becomes inefficient and requires large coolers
Solution Approach 1:
The patent replaces the hydraulic drive system of traditional IDGs with a mechanical gearbox system. This mechanical approach achieves the same frequency limitation function but with significantly higher efficiency, avoiding the inherent power losses and thermal management issues associated with hydraulic systems.
3Adaptability or versatility
If a speed-shifting gearbox is used to deliver limited speed range, then the output frequency range is controlled, but power delivery must be interrupted for gearshift causing load issues
Solution Approach 1:
The patent applies preliminary action by pre-synchronizing the rotational speeds of the input and output shafts before engaging the gearshift. This speed synchronization ensures that the gear change can occur without interrupting power delivery to the load, maintaining system reliability during transitions between gear ratios.
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 solution allows efficient power generation from a wide input frequency range without the need for oversized generators, reducing weight and thermal transients, and achieving high efficiency by maintaining power delivery during gear shifts, thus improving engine operability and reducing heat rejection.
Implementation Method 1
plural output shafts connected to the input shaft by respective gear shifting arrangements thereby providing different gear ratios between the input shaft and each output shaft
Implementation Method 2
plural electrical generators powered by rotation of the respective output shafts, electrical power outputs of the generators being combined to supply a total power to a load
Data Source
AI summary
An electrical power generator system has: an input shaft for receiving a rotary input drive; plural output shafts connected by respective gear shifting arrangements to the input shaft thereby providing different gear ratios between the input shaft and each output shaft; and plural electrical generators powered by rotation of the respective output shafts, electrical power outputs of the generators being combined to supply a total power to a load. The input shaft operates over a range of rotation frequencies, and the gear shifting arrangements are configured to shift the gear ratios between the input shaft and the output shafts such that the output shafts operate over a narrower range of rotation frequencies.