Splined Muff Insulator for Ram Air Turbine Lightning Protection
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Solution Overview
Problem
Lightning strikes on ram air turbines (RATs) can cause electrical arcs between the rotor and stator, potentially disabling the generator and hydraulic pump due to insufficient air gaps, which are necessary for efficient operation but also vulnerable to lightning, leading to potential damage and fluid loss.
Innovation Solution
A splined muff made of high-compressive-strength plastic material, such as Vespel™, is interposed between the driveshafts to act as an insulator, preventing electrical current from arcing and absorbing driveshaft flexion, with splines designed to maintain a safe distance and accommodate misalignment, and featuring mechanical stoppers to prevent excessive movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the air gap between rotor and stator is reduced for efficient generator operation, then power output is improved, but the risk of lightning-induced arcing increases
Solution Approach 1:
An electrically insulating component is introduced between the rotor and stator to prevent direct arcing while maintaining the small air gap necessary for efficient generator operation. This intermediary element allows the generator to operate at high power output without the harmful effects of lightning-induced electrical breakdown.
2Productivity
If the air gap in the hydraulic pump is reduced for efficient operation, then pump performance is improved, but vulnerability to lightning damage increases
Solution Approach 1:
Electrically insulating elements are positioned within the hydraulic pump components to prevent lightning-induced arcing between moving parts. This allows the pump to maintain small clearance gaps for efficient fluid handling while protecting against electrical damage from lightning strikes.
3Loss of substance
If carbon face seal clearance is reduced for sealing efficiency, then fluid sealing is improved, but the seal becomes more susceptible to electrical current damage
Solution Approach 1:
Electrically insulating materials are applied to the carbon face seal or its mating surfaces to prevent electrical current from compromising the seal. This allows the seal to maintain minimal clearance for effective fluid sealing while the insulating layer protects against lightning-induced electrical damage.
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 splined muff effectively prevents electrical arcing and reduces wear between driveshafts, ensuring the RAT's operational integrity during lightning strikes by maintaining a safe electrical distance and accommodating misalignment, thus protecting the generator and hydraulic pump from damage.
Implementation Method 1
A splined muff made of high-compressive-strength plastic material, such as Vespel™, is interposed between the driveshafts to act as an insulator, preventing electrical current from arcing
Implementation Method 2
The splined muff has free play and ductility sufficient to absorb driveshaft flexion and relative driveshaft movement
Data Source
AI summary
A splined muff is provided for use with a ram air turbine (RAT). The splined muff includes a body formed of plastic material that acts as an insulator during a lightning strike. The body is formed to define an aperture and includes an interior facing spline for engagement with a complementary exterior facing spline; and an exterior facing spline for engagement with a complementary interior facing spline.