Brushless Starter/Generator Oil Cooling System
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Solution Overview
Problem
Aircraft gas turbine engine starter/generators face challenges in reducing weight, increasing amperage output, simplifying cooling apparatus, and minimizing power and fuel robbing parasitic flows, particularly in air-cooled brushed units.
Innovation Solution
A brushless starter/generator system utilizing an oil cooling system with dry cavity design, incorporating a rotor and stator heat exchanger, and eliminating the need for cooling fans and ducts by using engine accessory gearbox oil for cooling, preventing oil contact with the air gap between the rotor and stator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If air cooling with brushes is used, then cooling is provided, but weight increases and amperage output is limited
Solution Approach 1:
The patent replaces the mechanical brush contact system with a brushless design using electromagnetic induction. The starter/generator uses a permanent magnet rotor that induces current in the stator windings without physical contact, eliminating brushes and commutators. This substitution reduces weight while enabling higher amperage output since there are no brush current limits.
Solution Approach 2:
The patent uses oil cooling instead of air cooling. Engine oil is circulated through cooling passages in the rotor and stator to remove heat. This hydraulic cooling method is more efficient than air cooling and allows for higher power density, enabling increased amperage output without proportionally increasing size or weight.
2Temperature
If air cooling with fans and ducts is used, then cooling is provided, but device complexity increases
Solution Approach 1:
The patent replaces the mechanical air cooling system with fans and ducts with a hydraulic oil cooling system. Oil is pumped through integrated cooling passages in the rotor and stator components, eliminating the need for separate fans, ducts, and air flow management hardware. This reduces device complexity while maintaining effective cooling.
Solution Approach 2:
The cooling passages are integrated directly into the rotor and stator structures. The oil cooling system merges the cooling function with the existing mechanical components, eliminating separate cooling apparatus. The housing and mounting structure also serve as part of the thermal management system, reducing overall complexity.
3Temperature
If air cooling is used, then cooling is provided, but power and fuel robbing parasitic flows increase
Solution Approach 1:
The patent uses hydraulic oil cooling instead of pneumatic air cooling. The oil is circulated through the engine's existing lubrication system, utilizing the engine's oil pump rather than requiring a separate power-consuming fan. This eliminates parasitic power flows associated with air cooling fans and reduces fuel consumption.
Solution Approach 2:
The engine's existing oil circulation system serves dual functions: lubrication and cooling. The oil that would otherwise only lubricate moving parts is now also used to cool the starter/generator components. This multi-functionality eliminates the need for dedicated cooling power consumption.
4Temperature
If oil cooling is used, then cooling effectiveness increases, but oil contamination and insulation degradation may occur
Solution Approach 1:
The patent segments the oil cooling system into separate closed loops for the rotor and stator, with dedicated cooling passages in each component. Oil is cooled in heat exchangers and filtered before being recirculated. This segmentation prevents oil from entering the air gap between rotor and stator, avoiding contamination of insulation materials while maintaining effective cooling in each section.
Solution Approach 2:
The patent uses sealed bearings and shaft seals as intermediaries to prevent oil from entering the air gap where it could contaminate insulation. Heat exchangers act as intermediaries to transfer heat from the oil to a separate cooling medium, allowing effective cooling while keeping the oil contained in its own circuit. These intermediary components protect the insulation system from oil exposure.
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 reduces weight, increases amperage output, simplifies cooling, and minimizes parasitic flows by using oil from the accessory gearbox for cooling, enhancing reliability and reducing maintenance needs while avoiding insulation degradation and oil contamination.
Implementation Method 1
an oil cooling system for using cooling oil from an engine accessory gearbox for cooling the rotor and the stator
Implementation Method 2
an oil cooling system for using cooling oil from an engine accessory gearbox for cooling the rotor and the stator
Data Source
AI summary
A brushless starter/generator includes a rotor rotatably mounted within a stator mounted within a housing and an oil cooling system using cooling oil from an engine accessory gearbox for cooling the rotor and the stator. The rotor is fixedly mounted on a rotor shaft having a rotor heat exchanger disposed therein. A stator heat exchanger for cooling the stator includes an oil jacket around the housing. The stator heat exchanger includes a grooved tube around the housing and axially extending axial passages connected to annular inlet and outlet manifolds in the grooved tube. The rotor shaft is operably connected to a power take-off shaft within the gearbox and rotatably supported by a shaft bearing in a gearbox casing of the accessory gearbox. The oil cooling system is a dry cavity oil cooling system which prevents cooling oil from entering an air gap between the rotor and the stator.