Counter-rotatable Generator for Aircraft Turbofan Engines
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Solution Overview
Problem
Current electrical generators for aircraft turbofan gas turbine engines face inefficiencies when operating at low power levels, as they rely heavily on the high-pressure engine spool for mechanical power, leading to reduced fuel efficiency and larger generator sizes required for low-speed operations from the low-pressure spool.
Innovation Solution
A counter-rotatable generator design featuring a stator with Delta-connected and/or Y-connected stationary windings, radial cores, and windings around these cores, allowing for efficient power generation across a wide range of engine speeds by utilizing both high and low-pressure spools, and incorporating a rotating transformer concept to avoid slip rings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If electrical power is extracted from the high-pressure engine spool, then electrical power generation is improved, but the ability to operate properly at low power levels deteriorates
Solution Approach 1:
The generator is divided into two independent rotor systems: a high-pressure rotor connected to the HP spool and a low-pressure rotor connected to the LP spool. Each rotor can operate independently to drive the stator windings, allowing the system to maintain reliable operation across the full range of engine power levels by selecting the appropriate rotor based on operating conditions.
2Reliability
If the low-pressure engine spool drives the electrical generator, then operation at low power levels is improved, but generator size increases due to low speed requirements
Solution Approach 1:
The generator is divided into two independent rotor systems: a high-pressure rotor connected to the HP spool and a low-pressure rotor connected to the LP spool. Each rotor can operate independently to drive the stator windings, allowing the system to maintain reliable operation across the full range of engine power levels by selecting the appropriate rotor based on operating conditions.
3Reliability
If a gearbox is used to increase speed for low-speed generator operation, then operation at low power levels is improved, but device complexity increases
Solution Approach 1:
The generator is divided into two independent rotor systems: a high-pressure rotor connected to the HP spool and a low-pressure rotor connected to the LP spool. Each rotor can operate independently to drive the stator windings, allowing the system to maintain reliable operation across the full range of engine power levels by selecting the appropriate rotor based on operating conditions.
4Power
If the core engine runs fast to meet high electric power demand, then electrical power generation is improved, but fuel efficiency deteriorates due to excessive thrust
Solution Approach 1:
The generator is divided into two independent rotor systems: a high-pressure rotor connected to the HP spool and a low-pressure rotor connected to the LP spool. Each rotor can operate independently to drive the stator windings, allowing the system to maintain reliable operation across the full range of engine power levels by selecting the appropriate rotor based on operating conditions.
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 counter-rotatable generator enhances power generation efficiency by enabling operation across varying engine speeds without the need for large generators, improving fuel efficiency and reducing the reliance on high-pressure spool power, while allowing higher speed operation of the pole rotor.
Implementation Method 1
A counter-rotatable generator includes a stator having Delta-connected and/or Y-connected stationary windings
Implementation Method 2
radial cores extending radially outwardly from a generally cylindrical or annular pole hub
Data Source
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AI summary
A counter-rotatable generator (180) includes a generator stator (186) concentric with concentric counter-rotatable radially inner pole and outer magnet rotors (216, 212). The magnet rotor (212) encircles the pole rotor (216) and the pole rotor (216) encircles the generator stator (186). A rotor air gap (130) is disposed between the magnet and pole rotors (212, 216), and a transformer air gap (224) is disposed between the pole rotor (216) and the stator (186). The magnet rotor (212) includes a circular array of magnets (214) having circumferentially alternating north/south and south/north orientations, retained within a magnet retention ring (215), and the magnets (214) are circumferentially separated from each other by non-magnetic material spacers (213). One stator (186) includes an annular hub (272), axial windings (252, 254) around equi-distantly spaced axial poles (256, 258) on the annular hub (272), radial cores (260) extending radially outwardly from and equi-angularly spaced about a pole hub (250) on the annular hub (272) between the first and second axial windings (252, 254), and radial windings (262) around the radial cores (260).