GB879745A - Gas flow control apparatus - Google Patents

Abstract

879,745. Valves. ROLLS-ROYCE Ltd. April 25, 1960 [May 1, 1959], No. 15046/59. Class 135. [Also in Group XXVI] Gas flow-control apparatus comprising a duct for the passage of hot gas (e.g. hot air) provided with two branches, has closure means for selectively blocking one or other of the branches and for simultaneously effecting unblocking of the other branch and control means, operative upon the temperature of the gas reaching a predetermined value, for ensuring that a predetermined one of said branches is blocked. The invention is described with reference to a gas-turbine plant in which hot air from the compressor or ram air is heated by being passed over hot surfaces within the engine when being employed for cooling and sealing purposes and then led through a duct 29 to a valve 24 leading through a duct 22 to a heat exchanger for heating the fuel and through a branch 26 to atmosphere. A valve gate 27 is progressively movable between a position in which it blocks the branch 26 to a position in which it blocks the branch 23. With the valve shown the total hot gas flow remains constant. The valve gate 27 is connected by a fusible plug 36 to an arm 37 splined on a shaft 38. The shaft 38 is rotated by an arm 49 connected to a temperature responsive device mounted on the fuel heat-exchanger. In operation the temperature responsive means controls the valve gate 27 so that at a predetermined low-fuel temperature the valve gate blocks the branch 26 so that hot air is supplied to the fuel heat exchanger through the branch 23. If, however, the temperature of the hot air flowing through the duct 29 rises excessively (e.g. because of a seal failure), the fusible plug 36 will melt. The valve gate 27 will then be forced by the spring 48 into the position shown in Fig. 1, in which the branch 23 is blocked. This prevents excessive vaporization of the fuel and the consequent possibility of explosion.