Reusable axial filter for high temperature gases

Abstract

A reusable filter to remove contaminants from high temperature gases, in excess of 4500.degree. F., developed by burning propellants and used to do work such as actuation of piston-powered devices in aircraft store ejector racks. Contaminants are removed to prevent fouling of the device being acted upon. The filter has at least one metal strip wound in the form of a flat spiral about a central member, the turns of the flat spiral being spaced from one another to permit axial entry of gas between the turns. A further flat spiral filter may be similarly constructed about the central member and axially displaced from the first filter, and both such filters may have different filtering capacities. On each flat spiral, protuberances are spaced along one side of the metal strip to establish filter gaps between the turns. The one or more flat spirals are restrained at their outer circumference by a cylindrical casing having inlet and outlet ends for the hot gas. Convoluted spacing supports serve to maintain the axial positioning of the one or more flat spirals within the casing, and also maintain the shape of the casing at positions where the casing is not in contact with the outer circumference of the spirals. The metal strip forming each flat spiral, and the convoluted spacing supports, are made of molybdenum, columbium or tantalum. Filtering gaps in a radial direction between adjacent turns of each spiral may be of the order of a few microns to a few hundred microns.