Knitted Rotor Blade Deice Heater Mat for Fatigue Reduction
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Solution Overview
Problem
Existing rotor blade heaters for rotorcraft face fatigue issues due to cyclical forces during rotation, leading to potential failure, as they are not adequately designed to withstand the mechanical stress caused by the rotation.
Innovation Solution
A heater mat comprising electrically conductive heater wires and knitted yarn threads, with a warp thread maintaining spacing between the wires, is secured to the rotor blade using buss bars and ultrasonic welding, allowing for efficient ice prevention while distributing stress and preventing electrical shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If heaters are installed on rotating rotor blades, then ice accumulation is prevented, but fatigue failure occurs due to cyclical forces during rotation
Solution Approach 1:
The heater elements are divided into multiple discrete heating zones along the rotor blade span, with each zone independently supported by its own framework structure. This segmentation allows each heater segment to flex independently during rotation, reducing stress concentration and fatigue accumulation on any single element.
Solution Approach 2:
The heater mat is constructed using flexible heating elements embedded within a compliant framework that can bend and flex with the rotor blade during rotation. This flexible construction allows the heater to accommodate cyclical forces without rigid stress points that would lead to fatigue failure.
2Reliability
If heater wires are tightly secured to maintain electrical connection, then electrical reliability is improved, but mechanical stress concentration increases leading to wire fatigue
Solution Approach 1:
The framework structure incorporates cushioning elements and flexible connectors that absorb mechanical stress before it reaches the heater wires. This pre-cushioning approach protects the electrical connections from fatigue-inducing stress concentrations while maintaining electrical reliability.
Solution Approach 2:
A flexible framework structure acts as an intermediary between the rigid rotor blade and the heater wires, absorbing and distributing mechanical stresses. This mediator protects the electrical connections from direct exposure to cyclical forces while maintaining stable electrical contact.
3Weight of moving object
If heater wires are spaced closely to reduce material usage, then weight and cost are reduced, but risk of electrical shorts increases
Solution Approach 1:
Insulating framework elements and spacers act as intermediaries between closely spaced heater wires, maintaining safe electrical isolation while allowing tight spacing for weight reduction. These intermediary structures prevent electrical shorts without requiring large spacing between wires.
Solution Approach 2:
The heater mat uses composite construction with electrically insulating but thermally conductive materials that allow close wire spacing while preventing electrical shorts. This composite approach enables reduced weight through tight spacing while maintaining electrical safety through insulating properties.
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 solution effectively inhibits ice accumulation on rotor blades by generating heat through electrical current, while reducing fatigue and stress on the heater components, thereby enhancing the durability and performance of rotorcraft in icy conditions.
Implementation Method 1
An electrical current flowed through the plurality of heater wires inhibits ice accumulation on the rotor blade assembly
Implementation Method 2
a plurality of yarn thread knitted to the plurality of heater wires, each of the yarn threads looping around at least one of the plurality of heater wires
Implementation Method 3
A warp thread is positioned between adjacent heater wires and knitted to adjacent pairs of the yarn threads without looping around the plurality of heater wires, to maintain spacing between adjacent heater wires
Implementation Method 4
The plurality of heater wires secured to the first buss bar by ultrasonic welding
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A heater mat for a rotor blade includes a plurality of electrically conductive heater wires extending in a path along a span of the rotor blade and a plurality of yarn thread knitted to the plurality of heater wires, each of the yarn threads looping around at least one of the plurality of heater wires. A warp thread is positioned between adjacent heater wires and knitted to adjacent pairs of the yarn threads without looping around the plurality of heater wires, to maintain spacing between adjacent heater wires of the plurality of heater wires. An electrical current flowed through the plurality of heater wires inhibits ice accumulation on the rotor blade assembly.