Overheat detection system and insulation muff comprising an overheat detection system

An overheat detection system and insulation muff comprising an overheat detection system. The overheat detection system comprises a thermometer, a thermal harvesting module comprising at least one passive radiator, the thermal harvesting module being able to generate electrical energy from the thermal difference between two elements, and a digital module, comprising a power management system, a data treatment system and a wireless transmission system, wherein the electrical energy generated by the thermal harvesting module powers the thermometer and the digital module.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of the European patent application No. 18382371.5 filed on May 30, 2018, the entire disclosures of which are incorporated herein by way of reference.

FIELD OF THE INVENTION

This invention refers to an overheat detection system, which is mainly used for detecting hot air leaks in systems with hot air ducts, especially applicable to aircraft. The invention also refers to an insulation muff comprising an overheat detection system.

BACKGROUND OF THE INVENTION

Pneumatic ducting in aircraft runs along the pylon, wing and fuselage to drive hot air from the engines and the APU to the wing anti-ice and air conditioning packs. This routing is made of insulated titanium ducts clamped to each other.

Each duct junction is insulated with a flexible insulation, fixed with Velcro or cord, wrapped around it (also called “muff” or “insulation muff”).

Typically, an insulation muff comprises an inner covering film, an outer covering film, an insulation material in between and a venting hole to allow hot air flow leakage from the duct to be directed towards overheat sensors and, in that way, to detect the leak. They may also comprise a flow guidance device (such as a venting grid) able to provide a homogeneous flow towards the overheat sensors.

As the bleed ducting contains pressurized air up to 260° C. (and approximately 700° C. in the pylon), the Overheat Detection System (OHDS) ensures fast leak and burst detection, in order to isolate the system and protect the surrounding structure and systems. The early detection of hot air leakages in aircraft systems is very important to prevent any damage to the structure and components, and fire and/or explosions in the fuel tanks of the aircraft, which could result from duct leak or rupture.

The current OHDS is composed of linear sensors, mainly “eutectic salt” sensors, running along the pipe, and wired to an interrogator. These “eutectic salt” sensors are basically constituted by a rigid coaxial cable (typically made of nickel) with a salt that changes electrical resistance when heated. As a leak of hot air happens, it is directed onto the sensor by the venting holes in the outer cover of the duct insulation muff. Accordingly, the local electrical resistance of the salt changes, which is detected by the interrogator.

This OHDS with eutectic salt sensors does not allow an accurate localization of the defect, and is also very subject to false alarms and open circuits, which heavily affect the reliability. Additionally, the sensors are fairly difficult and sensitive to install, due to the rigidity of the cables.

Other OHDS are based on optical-fiber elements. The fiber contains FBG (Fiber Bragg Grating) elements which reflect a specific wavelength. That wavelength changes with temperature. By setting the FBGs to different wavelengths and reading the change in reflected light, the interrogator can measure the temperature of each point of the fiber. Those sensing elements must be wired to the interrogator by optical fiber.

However, also some issues have to be worked in order to fit enough FBG on one fiber, and this technology based on optical fiber elements is also very sensitive to unclean connections.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an OHDS that overcomes the drawbacks existing in the prior art systems.

The invention provides an overheat detection system comprising:

a thermometer,

a thermal harvesting module comprising at least one passive radiator, the thermal harvesting module being able to generate electrical energy from the thermal difference between two elements, and

a digital module, comprising means for power management, means for data treatment and means for wireless transmission,

wherein the electrical energy generated by the thermal harvesting module powers the thermometer and the digital module.

The OHDS of the invention allows the removal of all or most of the cables, the accurate localization of the defect, and improves reliability with respect to the current eutectic salt.

Another advantage of the invention is that it requires low maintenance, as no battery is needed.

The invention also provides an insulation muff comprising an inner cover, an outer cover, an insulation material in between and a venting hole to guide hot air flow leakages from the duct on which the insulation muff is intended to be installed, that additionally comprises an overheat detection system integrated in the insulation muff at the location of the venting hole, wherein the thermal harvesting module, the thermometer and the digital module are integrated into a housing.

Another embodiment of the invention provides an insulation muff comprising an inner cover, an outer cover, an insulation material in between and a venting hole to guide hot air flow leakages from the duct on which the insulation muff is intended to be installed, that additionally comprises an overheat detection system, wherein the part of the overheat detection system comprising the thermometer and the digital module is integrated in the insulation muff at the location of the venting hole.

Other characteristics and advantages of the present invention will be clear from the following detailed description of several embodiments illustrative of its object in relation to the attached figures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows a typical view of a leak4in a hot air duct2with an insulation muff3. The venting hole5of the insulation muff3allows that the leak4of hot air flow is directed outwards, specifically towards sensing elements (not shown in this figure).

The insulation of each duct2can be made to direct any leak4towards the nearest duct junction, where the hot leaked air will pass through the venting hole5of the insulation muff3.

FIG. 2shows a general view of the elements and the operation of an OHDS1,1′ of the invention on a hot air duct2. The OHDS1,1′ comprises a thermal harvesting module6that generates low power from the thermal difference between the hot air duct2and the surrounding air. It powers a thermometer7as well as a digital module8with means for wireless transmission, which can perform wireless data transmission to a receiver9(wired to the avionics).

Accordingly, the general configuration of the OHDS1,1′ of the invention comprises:

a thermometer7,

a thermal harvesting module6comprising at least one passive radiator12, the thermal harvesting module6being able to generate electrical energy from the thermal difference between two elements, and

a digital module8, comprising means for power management, means for data treatment and means for wireless transmission,

wherein the electrical energy generated by the thermal harvesting module6powers the thermometer7and the digital module8.

FIG. 3shows a cross section of an OHDS1of the invention, an insulation muff3of the invention and the hot air duct2on which they are installed (only the upper part of the cross section is shown). The OHDS1ofFIG. 3is installed as part of the cover of the insulation muff3, at the location of the venting hole5. As it is integrated into the cover, it is installed at the same time, without any additional operation, so its installation is easy and quick.

The thermal harvesting module6is equipped with at least one passive radiator12(for instance, two passive radiators12, one on each side) to ensure thermal exchange from the hot air below the insulation muff3to the ambient air. If the difference of temperatures is high enough, it may be possible to have only one passive radiator12in the thermal harvesting module6.

The thermometer7is installed at the venting hole5location, away enough from the duct2to ensure measurement of the eventual leakage hot air flow, and not of normal heating from the duct2.

The digital module8comprises the means for power management (including means for voltage transformation, and means for storing of the energy for some limited time, for instance using a condenser), means for data treatment (eventually with a low-energy microcontroller if necessary), and means for wireless transmission.

The wireless transmission can be using an available network (such as WAIC: Wireless Avionics Intra-Communication), or communicating with a specific receiver9that is wired to the avionics.

In the embodiment shown inFIG. 3all the components of the OHDS1can be integrated in a housing10(for instance, a small rigid case), sewed on the insulation muff3.

The insulation muff3ofFIG. 3can comprise an inner cover, an outer cover, an insulation material in between and a venting hole5to guide hot air flow leakages from the duct2on which the insulation muff3is intended to be installed, and additionally comprises an overheat detection system1as described integrated in the insulation muff3at the location of the venting hole5.

FIG. 4shows a cross section of another embodiment of an OHDS1′ of the invention, another embodiment of an insulation muff3of the invention and the hot air duct2on which they are installed. In this alternative embodiment, the hot side of the thermal harvesting module6can be in contact with the duct2metal directly, if the thermal generation cannot produce sufficient power using two passive radiators12.

In this embodiment the thermal harvesting module6is separated from the rest of the system that comprises the thermometer7and the digital module8.

The thermal harvesting module6is put in contact with the duct2metal, and a radiator12is used on the cold side. It is connected to the rest of the system by a cable11.

This configuration needs a special shape on the duct2, with a flat surface accessible through a space in the duct insulation.

It allows generating more energy, but makes the duct manufacturing and the installation of the OHDS1′ more complicated and costly with respect to the embodiment ofFIG. 3.

The insulation muff3ofFIG. 4can comprise an inner cover, an outer cover, an insulation material in between and a venting hole5to guide hot air flow leakages from the duct2on which the insulation muff3is intended to be installed, and additionally comprises an overheat detection system1′ wherein the part of the overheat detection system1′ comprising the thermometer7and the digital module8is integrated in the insulation muff3at the location of the venting hole5.

Although the present invention has been fully described in connection with preferred embodiments, it is evident that modifications may be introduced within the scope thereof, not considering this as limited by these embodiments, but by the contents of the following claims.