Flame resistant shield

Abstract

A flame resistant shield includes two opposing walls between which are positioned at least: a first insulating layer, the first layer being capable of distributing heat in the plane formed by the first layer and being insulating across its thickness, a second insulating layer, one of the opposing walls which covers the first layer being produced from a refractory antioxidant material or having at least the surface intended to be exposed to flames covered with a material preventing this surface from being oxidized, the other wall being a support.

Claims

1. A flame resistant shield comprising: two opposing walls between which there are placed at least, a first insulating layer, said first insulating layer being able to dissipate heat in the plane formed by said first insulating layer while being insulating in its thickness; a second insulating layer, wherein one of said opposing walls which covers said first insulating layer is made of an antioxidant refractory material or at least a face of the one of the said opposing walls which is designed to be exposed to flames is covered with a material preventing oxidation of this face of the one of the said opposing walls, the other wall being a support; and further comprising attachments disposed at least partially between the two opposing walls for securing the two opposing walls and the first and second insulating layers of the shield together, the attachments having a configuration that bidirectionally fixes a gap between the two opposing walls that effects definition and control, between the two opposing walls, of a density of each insulating layer in its entirety, said attachments each comprise a hollow insert of cylindrical shape interposed directly between the two opposing walls, one bolt, washers, and one nut.

2. The shield as claimed in claim 1, wherein said first and second insulating layers contain no resin.

3. The shield as claimed in claim 1, wherein said first insulating layer is made of an orthotropic conductive material.

4. The shield as claimed in claim 3, wherein a radial thermal conductivity of said first insulating layer is greater than 100 W.Math.m.sup.1.Math.K.sup.1 at 20 C. whereas its axial thermal conductivity is less than 10 W.Math.m.sup.1.Math.K.sup.1 at 20 C.

5. The shield as claimed in claim 1, wherein said second insulating layer has a thermal conductivity of less than 1 W.Math.m.sup.1.Math.K.sup.1 at 20 C.

6. The shield as claimed in claim 5, wherein said second insulating layer has an area density of 15.7 kg/m.sup.2.

7. The shield as claimed in claim 1, wherein, the support being made of a titanium alloy, has a thickness greater than or equal to 0.6 mm.

8. An engine nacelle equipped with a flame resistant shield as claimed in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The aspects of the disclosed embodiment will be described in more detail with reference to the appended drawings, in which:

(2) FIG. 1 is a cross section view of a flame resistant shield according to one particular aspect of the disclosed embodiment, wherein the shield is represented in an exploded view and without its assembling members for reasons of clarity;

(3) FIG. 2 is a partial enlarged view in cross section of a flame resistant shield at one of its assembling members.

DETAILED DESCRIPTION

(4) FIGS. 1 and 2 show schematically a flame resistant shield 1 according to one aspect of the presently disclosed embodiment.

(5) This flame resistant shield comprises a sheet 2 of refractory material, both faces of which have been treated with a material preventing oxidation of this sheet 2 when it is exposed to a torch flame.

(6) The flame resistant shield 1 also comprises another sheet 3 acting as a support. An assembly of layers 4, 5 is held between these two sheets 2, 3.

(7) That face of the sheet 2 which faces away from the face designed to be exposed to the attack of the torch flame is in contact with a first insulating layer 4. This first insulating layer 4 is able to dissipate the heat in the plane formed by this layer while being insulating in its thickness. This first insulating layer 4 is preferably made of an orthotropic conductive material.

(8) A second insulating layer 5 is in contact with the sheet 3 which acts as a support. This second insulating layer 5 is preferably made of mineral products without resin so as not to have any temperature aging problems.

(9) Since the insulating layers 4, 5 are without resin, they therefore have no mechanical integrity. Because the thermal insulation properties of these insulating layers 4, 5 depend directly on their density, assembly elements 6 of the shield, forming spacers, are placed in direct contact with the opposing walls 2, 3 so as to control the thickness of the layers 4, 5 held between these opposing walls, including under mechanical loads.

(10) The sheet 2 of refractory metal is preferably made of molybdenum, the two faces of this sheet being treated with boron silicate.

(11) The first insulating layer 4 is made of Papyex, such that it is possible to take advantage of the orthotropic conductive properties of this material.

(12) The second insulating layer 5 is a high-performance silica-based microporous insulating panel such as that marketed under the name Microtherm. The sheet 3 serving as a support is a titanium alloy such as TA6V (Ti-6Al-4V).

(13) In one particular aspect of the presently disclosed embodiment, the sheet 2 of refractory metal made of molybdenum has a thickness of 1 mm, its two faces being treated with boron silicate to a thickness of 0.1 mm.

(14) The first insulating layer 4 is made of Papyex, reference NZ 998 marketed by CARBONE LORRAINE, which has a carbon content of greater than 93.8% and a temperature resistance under an oxidizing atmosphere of at least 500 C. This first layer 4 has a thickness of 1 mm.

(15) The second insulating layer 5, which has a thickness of 3 mm, is made of Microtherm, reference Super G marketed by MICROTHERM, which has a thermal conductivity of 0.0221 W.Math.m.sup.1.Math.K.sup.1 at 100 C. and an area density of 15.7 kg/m.sup.2.

(16) The sheet 3 acting as a support has a thickness of 0.6 mm. The shield 1 has a theoretical total thickness of 5.8 mm and an actual thickness of between 5.8 mm and 6 mm due to possible variations in the thickness of each layer.

(17) FIG. 2 is a partial enlarged cross section view of a flame resistant shield at one of its assembly members 6. For reasons of clarity, the different insulating layers have not been separately identified. The elements of FIG. 2 bearing the same references as the elements of FIG. 1 represent the same objects which will not be described anew herein below.

(18) These assembly members 6 of the flame resistant shield ensure that the thickness of the layers held between the opposing walls 2, 3, and thus the density of each insulating layer, can be controlled, which ensures that the thermal insulation properties of each of these layers is maintained.

(19) These assembly members 6 for securing the shield assembly each comprise:

(20) one hollow insert 7 of cylindrical shape, interposed directly between the opposing walls 2, 3 and

(21) one bolt 8, washers 9 and one nut 10 by means of which the various constituent elements of the shield can be secured.

(22) The hollow insert 7 is thus integrated into the thickness of the stack formed by the different insulating layers 4, 5, having its ends in direct contact with the opposing walls 2, 3. The distance separating these walls 2, 3 is thus advantageously controlled.

(23) In a purely illustrative manner, the washers 9 are gauzes of silica having a density of 150 kg/m.sup.3. The hollow insert 7 is made of a very low density (VLD) material, that is to say having a density of less than 80 kg/m.sup.3.

(24) The bolt 8 and the nut 10 are made of titanium or, better still, molybdenum protected against oxidation.

(25) These assembly members 6 are advantageously placed around the perimeter of the shield 1.