GB780433A - Flame tubes and other ducts made of fluid-permeable metal sheet - Google Patents

Abstract

780,433. Generating combustion products under pressure. POWER JETS (RESEARCH & DEVELOPMENT), Ltd. Sept. 15, 1955 [Sept. 27, 1954], No. 27894/54. Class 51 (1).. [Also in Groups XXVI and XXVIII] A duct for conveying a high-temperature fluid stream comprises an inner wall which is made up of a plurality of longitudinally-extending segments of fluid-permeable flexible metal sheet, and an outer wall, cooling fluid being supplied to the annular space between the walls, and the segments of the inner wall being supported along their longitudinally-extending edges from the outer wall. The invention is shown applied in the case of a gas turbine engine in which the combustion chamber flame tubes and the duct between the high and low-pressure turbines are made in accordance with the invention. A combustion chamber comprises an outer air casing 11 and an inner flame tube made up of eight longitudinal segments 14 of wire cloth. The edges of the segments 14 are secured by welding between the sides 15a of clamps 15, the clamps being mounted in four angle-section rings 16 which are welded to the outer casing 11; holes 16a are provided in the rings 16 to permit air to flow therethrough. Air will flow through the permeable segments thereby cooling the inner surface of the flame tube by effusion. Under the inwardly-acting pressure the segments 14 tend to bow inwardly so that the segments are stressed in tension. Large air inlet openings are provided at the downstream end of the flame tube. The segments are cut from the wire cloth on the bias, preferably at 45 degrees. In a second embodiment, the edges of the segments are secured between pairs of axially-extending angle-section strips, the strips being welded together to form a T-shaped member, the head of which engages in a groove formed by strips welded to the outer casing. The invention is shown applied to an annular duct in Figs. 6 and 7, the duct having inner and outer walls 31, 32 and inner and outer lining walls each lining wall being made up of twenty-four longitudinallyextending segments 33, 34. The segments are supported from ring members 36, 37, on the walls 31, 32 by means of clamps 35 as in the first embodiment. The duct is made of two axially successive parts comprising outer wall sections 32a, 32b, end rings 38, 39 being welded to inner surfaces of adjacent ends of the two sections. The ends of the segments of wire cloth 34a, 34b are bent round the rings 38, 39 and are welded thereto. Similar rings such as 40 are provided at the ends of the duct. The inner lining is formed in a similar manner. The air for cooling the lining walls of the duct is tapped from the compressor and is led to the spaces between the inner and outer walls and the lining walls. The constructions described are also applicable in the case of annular flame tubes and to jet pipes of aircraft gas turbine jet propulsion engines in which reheat equipment is provided. An alternative means for connecting ducts 32a, 32b is shown in Fig. 8, the duct section 32a having a thin ring plate 45 attached at its end. The ends of the segments 34a are bent around the ring plate and are welded in position between the plate 45 and a cover-plate 46 which is formed with a recess to receive the ends of the segments. The woven wire cloth may be plain or twilled weave; alternatively wire cloth other than woven cloth may be used, also flexible perforated sheet.