Abstract: A process for producing a coating for protecting superalloy articles against high temperature oxidation and hot corrosion comprises forming, on the surface of the article, a first deposit of an agglomerated powdered alloy containing at least chromium, aluminum and an active element, and filling the open pores of the powder deposit by a second, electrolytically applied, deposit of a precious platinum group metal. An appropriate thermal treatment is then carried out to effect interdiffusion between the powder based deposit and the electrolytic deposit and produce a coating including chromium, an active element such as yttrium, and a precious platinum group metal throughout its thickness.

Abstract: An axially symmetric turbojet engine exhaust-nozzle includes a system for masking the exhaust jet, such system including inner hot flaps (7), hinging on a conical shell (4) and driven by a first control ring (10) powered by linear actuators (11), and outer cold flaps (20) hinging on an annular assembly (12) and driven by a second control ring (22) powered by linear actuators (23) to vary the angle of the cold flaps. The annular assembly (12) is axially displaceable by a third set of linear actuators (30). Each cold flap (20) comprises an inner skin (40) fitted with orifices (43) and hinging on the annular assembly(12) and an outer skin (41) spaced radially away of the inner skin (40) to define an air flow channel between the skins.

Abstract: A rear mixer ejector of a turbomachine for a supersonic aircraft has an ejector casing of rectangular cross-section fitted with movable flaps defining a variable geometry exhaust nozzle, and cold air mixing devices mounted on the casing side walls upstream of the nozzle. The mixing devices comprise a plurality of U-section chutes extending into the casing from apertures in the casing side walls, each chute being formed by a pair of lateral walls and a transverse wall disposed between them. The chutes are adjustable between a deployed position and an inoperative position, either by pivoting the chutes about axes at the downstream edges of the apertures or by pivoting only the transverse walls about the upstream edges of the apertures. In each case the lateral walls of the chutes remain in the gas flow path through the casing, parallel to the casing axis, in both the deployed and the inoperative positions, and the transverse walls are parallel to the casing axis in the inoperative position.

Abstract: The invention concerns a method for metal coating of fibres (15) by liquid process, said method being particularly but not exclusively designed for coating in thick and even layers (22) with metals and metal alloys having high melting point and reactivity. Said method is characterised in that it consists in moving along the stretched fibre (15) in the liquid metal maintained in levitation in a well (1), said fibre (15) passing through orifices (6, 7) provided in the well (1) wall (3), said orifices (6, 7) being arranged on either side of the liquid metal at places where the liquid metal (10) is not in contact with said wall (3).

Abstract: A fitting (22) connected to an actuator member (18a) is mounted on a diverging portion (12) by means of inserts (32) designed to be placed and held in the wall of the diverging portion, and fixing means which comprises an elastically-deformable element (24) designed to compensate for any dimensional variations of thermal origin to maintain a force pressing the fitting (22) against the diverging portion (12). A thrust element (26) is connected to the inserts (32) in such a manner as to compress the elastically-deformable element (24) between the thrust element (26) and the fitting (22).

Abstract: A method of reducing the gap between a liner and a turbine distributor of a turbojet engine. The method allows for the improvement of the seal on the inside of the distributor of the high pressure turbine at the lower platform. The method includes the steps of: applying a protective deposit to the lower part of the external surface of the liner, before carrying out a filling by diffusion brazing between the liner and the distributor. The protective deposit, preferably a anti-adherent ceramic, makes it possible for the braze to avoid fixing the liner onto the distributor at the lower platform level. The method also has applications to turbojet engines.

Abstract: A gas-flow exhaust assembly for a jet propulsion system of an aircraft in which a converging exhaust nozzle (4) is fitted with translating cold flaps (21, 22). The primary exhaust nozzle (4) comprises two hot-flaps (5, 6) situated beyond a primary duct (1) enclosed by an aircraft fairing (2). The fairing (2) is extended by a secondary exhaust nozzle (20) which is supported by the primary duct (1) and which is translatable by a control mechanism (27a, 27b). The secondary exhaust nozzle (20) comprises cold flaps (21, 22) which are driven by another control mechanism (29a, 29b) independently of the angular positions of the hot flaps (5, 6). Preferably, there are two eyelid-shaped cold-flaps (21, 22) hinging and supported on horizontal transverse shafts (23a, 23b). The shafts (23a, 23b) are preferably affixed on two lateral slides (24a, 24b) which slide on the primary duct (1) and are displaceable by the control mechanism (27a, 27b) which translates the secondary exhaust nozzle (20).

Abstract: The ion beam concentration apparatus for a plasma thruster having closed electron drift comprises:a) an essentially frustoconical flared magnetic pole piece (63) open at both ends and designed to be situated downstream from the outlet plane of a plasma thruster having an annular ionization and acceleration channel (1) and peripheral and central pole pieces (3, 4) disposed on either side of the annular channel (1) to produce an essentially radial magnetic field in an outlet plane (14) perpendicularly to the axis of the annular channel (1); andb) an additional peripheral magnetic circuit (60; 80) connecting the downstream end of the flared magnetic pole piece (63) to said peripheral pole piece (3), the flared magnetic pole piece (63) co-operating with the additional peripheral magnetic circuit (60; 80) and with the peripheral and central pole pieces (3, 4) to define the shape of the magnetic field downstream from the annular channel (1) in such a manner as to constrain the ion beam emitted by the annular channe

Abstract: A separator (10) for a two-head combustion chamber which comprises a plurty of segments (11) that are arrayed circumferentially and spaced apart a distance (x) from one another and that are affixed to appropriately shaped sheetmetal (12, 13) of the combustion chamber. Each segment (11) is shaped as an elongated, hollow body with an upper wall (17) and a lower wall (18). The segments are cooled by air from an upstream portion of an end of the combustion chamber entering the segments (11) and exhausting by a plurality of orifices (34) in the segment walls (17, 18). The upper and lower segment walls (17) and (18) are respectively heat-protected by two sets of tiles (40, 41), each of the tiles straddling two adjacent segments, being spaced a distance from the walls (17, 18) to subtend an enclosed space (46, 47) therebetween, and having at least one tile orifice (48, 49, 50) which allows the cooling air from the segments (11) to exhaust into the heads.

Abstract: The housing is heated or cooled to adjust its diameter and, in particular, the play between the tips of the rotor blades and the housing. The apparatus consists of networks of tubes (1) covering complementary portions of the circumference of the housing and consisting of a pair of distributors (3) and parallel tubes (2) between said distributors, said tubes (2) being alternately connected to one or other of the distributors and provided with apertures to blow the gas onto the housing. The counter-flow circulation in the tubes (2) makes it possible to supply both gas that has been greatly heated by traveling a considerable distance through the tubes (2) and cooler gas that has traveled less far in other tubes (2) to any point on the housing, thereby balancing out the heat applied to every portion of the housing.

Abstract: A high bypass ratio turbojet engine comprising a fan rotated by the shaft of a low pressure turbine via a speed reducer is provided with a thrust reverser device by providing the speed reducer with first and second epicyclic gear trains which are mounted in parallel between the low pressure turbine and the fan and which are arranged in such a way as to drive the fan in a first direction of rotation when the engine is operated in a direct thrust mode, and to drive the fan in the opposite direction of rotation when the engine is to be operated in the reverse thrust mode.

Abstract: A coating (22) with a high coefficient of friction and low thermal conductivity covers a turbomachine low pressure shaft (12) in the vicinity (17) of a concentric high pressure shaft (11), in the area at which high friction contact between the two shafts could occur if a bearing (13) on the low pressure shaft (12) breaks following a failure causing the appearance of an out-of-balance mass. Friction would also more quickly equalize shaft speeds and reduce overheating in them.

Abstract: A titanium-based intermetallic alloy having a high yield stress, a high creep resistance and sufficient ductility at ambient temperature has the following chemical composition as measured in atomic percentages:Al, from 16 to 26; Nb, from 18 to 28; Mo, from 0 to 2; Si, from 0 to 0.8; Ta, from 0 to 2; Zr, from 0 to 2; and Ti as the balance to 100; with the condition that Mo+Si+Zr+Ta>0.4%.Production, working and heat-treatment ranges adapted to the intended use of the material are also defined.

Abstract: The particle trap (15) that extends behind an elbow in the air flow stream (6) in a turbo-prop engine is delimited at the back by an end plate (12) to which intake housing suspension rods (10) supporting the front of the rotating shaft (2), are fastened. It is divided by suspension arms (11) which may be drilled (21) to restore the continuity of the annular chamber forming the trap. Therefore the intake housing suspension device extends through the trap. This type of trap makes use of the inertia of solid bodies carried by the air drawn in, and which could damage the engine blades, and to collect them.

Abstract: A rectifier vane stage is connected to a stator that is supported at the internal end thereof by a connecting ring which includes a support ring and a stiffening ring, a retaining lip of which is inserted into the support ring and similarly into the recesses of the ends of the vanes. The possibility of the vane accidentally coming loose following breakage of said vane is therefore eliminated.

Abstract: A self-washing device for separating and filtering solid particles from a ow of liquid includes a tubular casing defining an internal chamber, a tangential liquid inlet opening into the internal chamber and arranged to create a vortex in the internal chamber which acts to centrifuge out solid particles and carry them at the vortex periphery, a tangential liquid outlet for discharge of liquid carrying the solid particles from the internal chamber, and a tubular filter disposed longitudinally within the internal chamber for taking and filtering a portion of liquid flow at a center of the vortex, the filter having a longitudinal central duct communicating with at least one longitudinal liquid outlet for the filtered liquid. The device is of particular use in a fuel injection circuit.

Abstract: A method of making a ceramic casting mould contains forming a contact layer on a disposable wax-type pattern of the article to be cast, placing the pattern in a preparation mould for defining the outer shape of the casting mould and filling the cavity formed between the pattern and the preparation mould with a ceramic slip which expands to form a coherent cellular foam adhering to the surface of the pattern, removing the pattern and adhered foam from the preparation mould after from 5 to 30 minutes, eliminating the pattern to leave a casting mould formed by the contact layer and the adhered foam, and then firing the casting mould to strengthen said mould. Ceramic slip compositions are also described.

Abstract: The method serves to place a space vehicle, such as a satellite, on a target orbit such as the orbit adapted to normal operation of the space vehicle and starting from an elliptical initial orbit that is significantly different from, and in particular more eccentric than the target orbit.

Abstract: A fiber structure is made by superposing plies of fiber fabric and bonding the plies together by needling, so that the fibers of the superposed plies extend essentially in a first direction (X) and in a second direction (Y) orthogonal thereto, the plies being bonded together by fibers that are moved by the needling in a third direction (Z) extending transversely relative to the plies, and a piston preform is cut out from the needled fiber structure so that one of the first and second directions (X, Y) is parallel to the generator lines of the surface of the preform that corresponds to the cylindrical side surface of the piston. The preform is densified at least in part by the substance that constitutes the matrix of the composite material, and the piston is machined from the densified preform.

Abstract: An optical-fiber polarimetric sensor for measuring the displacement of an object relative to a frame, the sensor comprising a measurement optical fiber secured, over a fraction of its length, both to a central point of the object and to first and second fixed points of the frame, means disposed at one end of the measurement fiber and serving to emit a light beam of determined polarization into said measurement fiber, means for exerting twist on the measurement fiber so as to modify the polarization of the light beam, and means disposed at another end of the measurement fiber and serving firstly to detect the resulting light beam and secondly to determine the displacement of the object by analyzing the polarization modified in this way, wherein said measurement fiber is stripped, over said fraction of its length, of the covering that imparts mechanical strength thereto, and it is slid into a deformable guide sheath fixed both to the rotary object and also to the frame.