US3379366A

US3379366A - Contra-rotating compressors

Info

Publication number: US3379366A
Application number: US594935A
Authority: US
Inventors: Garnier Michel Robert
Original assignee: SNECMA SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 1965-11-18
Filing date: 1966-11-16
Publication date: 1968-04-23
Anticipated expiration: 1985-04-23
Also published as: GB1104007A; DE1628383A1; DE1628383B2; FR1472085A

Description

April 23, 6 M. R. GARNIER 3,379,366

CONTRA-ROTAT ING COMPRESSORS Filed Nov. 16, 1966 am (w Mag 4 uhlDw Unit d States Patent 3,379,366 CONTRA-ROTATING COMPRESSORS Michel Robert Garnier, Sceaux, Hauts-de-Seine, France,

assignor to Socicte Nationals dEtude et de (Zonstruction de Moteurs dAviation, Paris, France, a company of France Filed Nov. 16, 1966, Ser. No. 594,935 Claims priority, application aFrance, Nov, 18, 1965,

3 Claims. 51330-415 This invention relates to a multiple-stage compressor of the type comprising two contra-rotating coaxial rotors the blades of which are arranged alternately in sequence.

In multiple stage compressors the general principle is known that correct adjustment can be achieved and operating stability improved at low engine speeds by opening one or more flap valves arranged radially of one or more stages of the compressor. The flap valves discharge a proportion of the air flow to atmosphere, thereby relieving the engine and preventing surging and consequent stalling of the engine.

The construction and positioning of the flap valves do not present any special problems in the case of conventional compressors with a fixed stator, the latter being readily adaptable to include such valves.

However, in the case of contra-rotating compressors, no stator (as such) is provided, both sets of blades being rotatable with one set having the blade roots radially innermost and the other set having the blade roots radially outermost so that the two sets of blades are respectively driven through the inner and outer peripheries thereof. In the case of the set of blades having the blade roots outermost a rotatable drum is used to the inner surface of which the blades are attached.

In accordance with the present invention, the rotatable drum is enclosed by a fixed outer casing, ports being provided in the rotatable drum radially of one or more stages of the compressor, and at least one aperture being arranged in the casing radially of the ports and being associated with a flap valve or similar discharge unit, controlled manually or automatically, the intervening annular space between the rotatable drum and the fixed casing being in communication with the ports, and/or each aperture lying between axially spaced seals, or example labyrinth seals.

The invention will now be further described with reference to the accompanying drawing which shows, by way of example, a contra-rotating compressor in accordance with the invention, the drawing being a scrap view in axial half-section.

One rotor of the contra-rotating compressor comprises a set of blades 1 each of which is attached at the root to the inner surface of a rotatable drum 3 in such manner that the blades extend generally radially inwardly and are disposed in a series of radial planes. The drum 3 is coupled to a shaft 4 rotatably mounted in bearings 5 so that in use rotation of the shaft 4 in one direction causes corresponding rotation of the drum 3 carrying the blades 1. A second shaft 6, coaxial with the shaft 4, is rotatably mounted in bearings 7 and is coupled to a second rotor comprising a set of blades 2 which, in use, rotate in the opposite direction to the blades 1. A forward bearing 8 is provided for the rotor 3. The contra-rotating compressor constituted in this manner is preceded by a guide vane arrangement 9 at the intake to which the forward fairing 10 is attached and which is followed by an outlet 'ice guide vane arrangement 11 leading to a combustion chamber 12 of an engine supplied by the compressor. The complete structure is enclosed by a fixed casing 13.

In accordance with the present invention, circumferentially spaced ports 14 are provided in the rotatable drum 3 radially of one of the compressor stages. An aperture 15 is arranged in the casing 13 radially of the ports 14,

this aperture being in controlled communication with the surrounding atmosphere through a duct 16 in which is mounted a discharge valve 17 controlled manually or antomatically. The intervening annular space 18 between the rotatable drum 3 and the fixed casing 13 is in communication with the ports 14 of the drum and with the aperture 15 of the casing and is closed longitudinally by axially spaced

labyrinth seals

19, 20 attached to the casing 13 so that the aperture 15 lies between them in the axial direction. The

seals

19, 20 prevent the escape of air between the rotatable drum 3 and the fixed casing 13.

Some of the air from the selected stage flows, under the influence of centrifugal force, through the ports 14 which, as the drum 3 rotates, are successively in radial alignment with the fixed aperture 15. The air bled off in this manner escapes to the surrounding atmosphere according to the extent to which the valve 17 is open, the air being at a positive gauge pressure with respect to the atmosphere.

In this way the present invention enables the acceptable operational range of contra-rotating compressors to be extended beyond the theoretical limit by improving stability at low engine speeds; this is achieved by the provision of one or more discharge valves 17 operated manually or automatically and communicating with one or more apertures 15 arranged on the fixed outer casing 13 and located substantially in the same radial plane as the ports 14 in the rotating drum 3 of the compressor and in the same radial plane as the bleed-off stage.

What is claimed is:

1. A contra-rotating compressor comprising two rotors each with a set of blades, the set of blades of one rotor being attached to the inner surface of a rotatable drum, means to cause the two sets of blades to revolve in opposite directions, a fixed outer casing enclosing the retatable drum, said drum including ports formed in the surface thereof in a radial plane containing at least one compressor stage, said casing having an aperture, the ports being radially aligned with the aperture in the casing, means for connecting the aperture to the surrounding atmosphere, and sealing means between the rotatable drum and the fixed casing on each axial side of the aperture.

2. A contra-rotating compressor according to claim 1, wherein said sealing means are constituted by labyrinth seals.

3. A contra-rotating compressor according to claim 2, wherein the means for connecting the aperture to the atmosphere comprise a duct provided with a discharge valve. T

References Cited UNITED STATES PATENTS 2,451,944 10/1948 Hall 230123 FOREIGN PATENTS 268,903 4/1927 Great Britain.

25,756 5/1906 Sweden.

HENRY F. RADUAZO, Primary Examiner.

Claims

1. A CONTRA-ROTATING COMPRESSOR COMPRISING TWO ROTORS EACH WITH A SET OF BLADES, THE SET OF BLADES OF ONE ROTOR BEING ATTACHED TO THE INNER SURFACE OF A ROTATABLE DRUM, MEANS TO CAUSE THE TWO SETS OF BLADES TO REVOLVE IN OPPOSITE DIRECTIONS, A FIXED OUTER CASING ENCLOSING THE ROTATABLE DRUM, SAID DRUM INCLUDING PORTS FORMED IN THE SURFACE THEREOF IN A RADIAL PLANE CONTAINING AT LEAST ONE COMPRESSOR STAGE, SAID CASING HAVING AN APERTURE, THE PORTS BEING RADIALLY ALIGNED WITH THE APERTURE IN THE CASING, MEANS FOR CONNECTING THE APERTURE TO THE SURROUNDING ATMOSPHERE, AND SEALING MEANS BETWEEN THE ROTATABLE DRUM AND THE FIXED CASING ON EACH AXIAL SIDE OF THE APERTURE.