GB1257610A - - Google Patents

Abstract

1,257,610. Valves. JOSEPH LUCAS (INDUSTRIES) Ltd. 13 Dec., 1968 [10 Nov., 1967], No. 13709/71. Divided out of 1,256,066. Heading F2V. [Also in Division F1] An annular flame tube for a gas turbine engine having primary and secondary combustion air inlet passages has variable air flow restricting means associated with at least one of the passages, the restricting means being expandable in response to an increase in a variable control quantity to vary the ratio of primary to secondary combustion air. In one arrangement, Fig. 1, the annular flame tube 30 is enclosed by outer and inner annular walls 31, 32. The space between tube 30 and wall 31 contains a series of louvre type restrictors 90 controlling ducts 91 terminating in nozzles 92 which direct secondary air into the burning mixture of fuel and primary air, the latter air having entered the flame tube past fuel nozzles 33. Each set of louvres 90 is pivotal by means of a Bourdon tube 93 which receives a variable control pressure from a common manifold 94. Dilution air flow through nozzles 95 is controlled by closure members 96 having pressure operable bellows 97. In a modification (Fig. 5, not shown), Bourdon tubes (180) control the pivotal movement of restrictor segments (185) mounted in the primary air inlet passage. In a further modification, Fig. 3, the flame tube has a series of angularly spaced primary air inlet passages 140, each having a flow restrictor formed by angled end pieces 141b on bimetallic strips 141a. The latter are mounted on a ring 142, electric heating of which causes strips 141a to deflect so that end pieces 141b project further into the flow. Swirl vanes 143 are provided and surround a burner (not shown). In a similar arrangement (Fig. 4, not shown), the movement of restricting shutters (150 to 153) into the primary flow is controlled by electrically heated bimetallic strips (159, 160, 162, 163). In a further modification (Fig. 6, not shown), the primary flow is controlled by a spiral restrictor (200) extension and retraction of which is controlled by a pressurizable bellows (201) slidably mounted by means of sealing rings (203) on a central spindle (202).