Sealing device

Abstract

Abstract 648,824. Stuffing-box substitutes. POWER JETS (RESEACH & DEVELOPMENT), Ltd. March 11, 1947, No. 6775. [Class 122(v)] In a sealing device to prevent excessive leakage of gas through a working clearance between the adjoining end faces of two relatively rotatable bodies, one of the end faces is formed on a movable element carried by one of the bodies and capable of movement to vary the clearance between it and the other end faces, and both end faces are provided with co-extensive flat parallel portions one of which has a multiplicity of circumferentially distributed ports therein through which, in operation, a second gas is discharged to issue in jets directed against the other flat portion so as to prevent contact of the two faces. A substantially right angled section annulus 10 acts as a movable sealing element between a gas turbine rotor 13 and casing 21 and is co-axially mounted and slidably supported on radially resilient rings 18 fitted in grooves in the casing 21, the rings making substantially gas-tight contact with the movable element 10. The radially extending arm 11 of the movable element 10 has, at its outer end, a labyrinth seal 16 which is presented to a plane face 12 of the turbine rotor 13 and, at its inner end, a plane face 17 in the same plane as the tips of the labyrinth 16 and parallel to the plane face 12. The movable element 10 and casing 21 form a chamber 22 in communication with the working gas flow to the rotor blade 28 and the pressure of that gas urges the movable element 10 towards the plane face 12 formed partly on the rotor and partly by a plate 23 attached to the rotor and having a number of small holes 24 in the part thereof, opposite the movable element. Air under pressure is supplied from the gas turbine compressor 9 through a hollow shaft 26 to the space 25 between the rotor 13 and plate 23 and issues therefrom through the holes 24 to the clearance space between plane faces 12 and 17 and contact between the movable element 10 and the rotor is thus prevented. Since the supply of compressed air is limited by the total area of the holes 24 any increase in the clearance results in a pressure drop in the clearance space between faces 12 and 17 and a consequent decrease in the clearance and vice versa so that a predetermined clearance may be maintained. If hollow turbine blades 28 are used the compressed air may be also utilized for blade cooling. In a modification the compressed air is supplied by a centrifugal compressor formed on or integral with the turbine rotor. In another modification the movable element 10 is connected by its end remote from the turbine rotor to the outer part of casing 21 by an annular flexible metallic bellows and the part 14 of the movable element and the supporting annular 15 are formed with mating splines.

Inventors

• 👤 Johnstone Alexander Pearse

Bibliographic Details