GB612097A - Improvements in and relating to the cooling of gas turbine rotors - Google Patents

Abstract

612,097. Gas turbines. ENGLISH ELECTRIC CO., Ltd., BROWNHILL, F. D., and WOLFF, P. H. W. Oct. 9, 1946, No. 30195. [Class 110 (iii)] Turbine blades having fir-tree roots are provided with abutting flanges 2b forming a continuous floor spaced by the channels 4 from the periphery of the rotor discs. Channels 3 are also provided between the inner ends of the roots and the bottoms of the root sockets in the rotor. Several constructions to direct cooling air through these passages are described, all of which involve the provision of rings, in segments, between the rotor discs which, with the flanges on the blades, form a continuous cylindrical surface shielding the rotor discs from the hot gases. In Fig. 1, the ring segments 7 receive air from the rotor cavities and direct it through the axial channels 3 beneath the blade roots. The next down-stream ring turns the air back through channels 4 beneath the blade flanges and, in escaping, the air is deflected into the gas stream by lips 15. The ring segments have projections 17 which are slidden circumferentially between annular projections 5, 5a. These are cut away over one segment, to permit the segments to be introduced radially and the closing segment is formed in two parts 7a, 7b which are separated by a wedge 18 secured in place by a weld 18b. In Fig. 3, the rotor discs have overlapping flanges 20a, 20b secured together by a weld 20 and the air chamber between the discs is completed by segments 37. The segments have parts 33 engaging in grooves 26 in the rotor discs and at their other ends 35 are shaped to fit in the fir-tree sockets for the blades. The walls of the sockets are slotted circumferentially at 39. The ends 35 of the segments are introduced radially into these slots and the segments are shifted axially. They are held in position by the blade roots which are inserted afterwards. In this form, the air passes in the upstream direction through both sets of passages and is deflected into the gas stream through gaps 36 by lips 30. Alternatively, the gaps 36 may be closed and the wall 32 of the segments perforated to permit an undeflected air stream throughout the length of the rotor. In another form, in which the blade slots are circumferential, air passes through ports in the ring segments to the space beneath one side of the flange of each blade, down slots cut in the root to the channel beneath the blade root, up slots cut in the opposite side of the root and into the space beneath the flange on that side of the blade, thence it escapes through ports into the gas stream. In this form, the abutting edges of the ring segments are inclined to the axial direction. Specification 543,985 is referred to.