Protective Sleeves for Aircraft Fire Detection Systems
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Solution Overview
Problem
Aircraft fire and overheat detection systems face challenges due to corrosion from fluids and high temperatures, leading to false alarms and damage from environmental exposure, particularly in gas turbine engines where thermal detectors and sensors are exposed to corrosive mixtures and extreme heat, causing vibration damping issues and potential for false fire detection.
Innovation Solution
A protective sleeve made from materials like polyolefin, fluoropolymer, PVC, polychloroprene, or silicone elastomer is used to encase sensor components, providing a high-temperature-resistant and non-reactive barrier that prevents fluid ingress and corrosion, with adhesive sealants and tapering diameters for secure fitment, ensuring accurate temperature sensing and preventing false alarms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal detectors and sensor elements are spaced away from engine structure using polymeric mounting materials, then vibration damping is improved and direct contact with hot surfaces is avoided, but the mounting materials become brittle or melt at high temperatures above their transition points
Solution Approach 1:
The patent introduces a protective sleeve as an intermediary component between the sensor element and the corrosive engine environment. The sleeve is made from high-temperature resistant materials such as PTFE, polyolefin, fluoropolymer, PVC, polychloroprene, or silicone elastomer that can withstand temperatures above the transition points of conventional polymeric mounting materials. This intermediary protection allows the mounting system to maintain both vibration damping capability and thermal stability.
Solution Approach 2:
The protective sleeve is constructed as a flexible shell that envelops the sensor element and mounting structure. This flexible protective barrier prevents fluid ingress and corrosion while allowing the mounting materials to maintain their viscoelastic properties for vibration damping. The sleeve material is selected to remain flexible and protective at high temperatures without becoming brittle.
2Measurement precision
If sensor elements are exposed to monitor temperature between engine and nacelle, then fire and overheat detection capability is improved, but the sensors become vulnerable to corrosion from corrosive fluid mixtures and extreme heat
Solution Approach 1:
The protective sleeve serves as a protective intermediary between the sensor element and the corrosive engine environment. It allows the sensor to maintain its monitoring function while being shielded from corrosive fluid mixtures, chemicals, and extreme heat that would otherwise cause corrosion and degradation of the sensor elements.
Solution Approach 2:
The protective sleeve creates an inert protective environment around the sensor element. The sleeve material is selected for its chemical inertness and resistance to corrosive substances, effectively isolating the sensor from harmful chemical interactions while allowing thermal energy to pass through for accurate temperature monitoring.
3Ease of operation
If polymeric mounting materials are used to support sensor elements, then ease of installation and vibration damping are improved, but the materials become brittle or melt at high temperatures limiting mounting system effectiveness
Solution Approach 1:
The protective sleeve acts as a thermal and chemical intermediary that protects the polymeric mounting materials from high-temperature degradation. This allows the polymeric materials to maintain their installation advantages and vibration damping properties without being exposed directly to temperatures that would cause them to become brittle or melt.
Solution Approach 2:
The flexible protective sleeve encapsulates the polymeric mounting structure, allowing it to perform its vibration damping function while being protected from thermal degradation. The sleeve maintains the structural integrity of the mounting system at high temperatures without compromising the ease of installation provided by the polymeric materials.
Data Source
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Figure 3A~3B
AI summary
Aircraft fire and overheat detection systems are described. The systems include a support bracket configured to secure the system to a component of an aircraft. A terminal assembly is fixedly connected to the support bracket and includes a connection assembly and a connection cable. A sensing element is electrically connected to the terminal assembly and arranged to detect at least one of fire and heat associated with the component of the aircraft. A protective sleeve is arranged about the connection assembly and connection cable. The sleeve has a lug portion at a first end with a sealing protrusion extending radially inward, a first wire portion, and a second wire portion, with progressively smaller diameters for each portion.