Abstract: A fiber preform is made from a fiber block by forming at least one cut in the block, so as to make a gap between two portions of the preform corresponding to segments of a spring that is to be made, and the preform is densified by a material for constituting the matrix of the thermostructural composite material. The gap between two portions of the preform is provided either by removing material, preferably after the preform has been consolidated, or else by forming a slot and then spacing apart the lips of the slot and holding the preform in the spaced-apart state.

Abstract: The redundant regulation valve for controlling fluid flow comprises a valve body defining a passage for the flow of the fluid, a main throttle element movable by means of a main control device to selectively obstruct the passage, and a redundant throttle element movable by means of a redundant control device. When the valve is in its closed position in normal operation, the main element and the redundant element are in contact with each other. In this normal closed position, the main element is close to its fully-extended position in the closure direction and it obstructs only about half of the passage, while the redundant element is in a position of medium extension. The stroke of the redundant element is such that the redundant element can be controlled to obstruct the entire passage even when the main element is in its fully-open position.

Abstract: A friction element is made out of a composite material comprising carbon fiber reinforcement and a matrix which, at least in the vicinity of the or each friction face, comprises: a first phase in the vicinity of the reinforcing fibers and containing pyrolytic carbon obtained by chemical vapor infiltration; a refractory second phase of carbon or ceramic obtained at least in part by pyrolysis of a liquid precursor; and a silicon carbide phase obtained by siliciding, for example. At least in the vicinity of the or each friction face, the composite material is preferably constituted, by volume, at least as follows: 15% to 35% carbon fibers; 10% to 55% first matrix phase containing pyrolytic carbon; 2% to 30% second matrix phase of refractory material; and 10% to 35% silicon carbide. The invention is applicable in particular to braking for rail or road vehicles.

Abstract: A regenerative circuit structure is built up by implementing the following steps in particular: an intermediate layer is made on a support core representing the inner profile of the structure; a series of channels regularly distributed around the core is made with the channels opening to face the intermediate layer, each of the channels being provided with a soluble insert; the support core is preheated and the body of the structure is made by thermal spraying under a vacuum; channels are machined in the body from the outside, and said channels are filled by means of soluble inserts; a closure layer is formed to close the channels in the body, and an outer envelope is formed by thermal spraying under a vacuum, after preheating; and all of the soluble inserts and the intermediate layer are eliminated.

Abstract: The tank is made up of a plurality of elementary tanks such as tubes (20) connected in parallel to at least one manifold device (30, 32), and it includes closure valves enabling any one of the elementary tanks to be isolated in response to a drop in the pressure contained therein.

Abstract: An ultrasonic testing method for parts of complex geometry comprises using a multielement transducer transmitting focused ultrasonic waves into the part to be tested. The focusing of the ultrasonic waves is implemented in two different modes using multichannel control electronics. The two focusing modes are an electronic focusing mode and a time reversal focusing mode which are selected as a function of the depth of the particular test zone. The time reversal focusing mode is selected to test central zones located at the largest depths around the longitudinal axis of the part. The electronic focusing mode is selected to test intermediate zones situated at depths between the central zones and a peripheral zone of the part.

Abstract: The invention concerns an acoustic igniter for igniting a mixture of rocket fuels in a liquid propellant rocket engine combustion chamber comprising a cylindrical precombustion chamber (101) including a cylindrical wall (111) and first and second end walls (112, 113), a rocket fuel injection nozzle (103) emerging into the precombustion chamber (101) through the first end wall (112) via an orifice of diameter dn, a rocket fuel injector (104) arranged inside said nozzle (103) along the axis thereof, at least an outlet orifice (102) of minimum diameter df provided in the cylindrical wall (111), an acoustic resonator (105) defining a cavity opening into the precombustion chamber (101) opposite the nozzle (103), through the second end wall (113), via an orifice (151) of diameter dr. The acoustic resonator (105) is enclosed by a housing (106) which defines around the acoustic resonator (105) a closed auxiliary chamber (160) which communicates only with the precombustion chamber (101) by at least one conduit (107).

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: 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 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: 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.

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: A carbureted flameholder (30) with optial cooling is provided for a bypass turbojet-engine. The flameholder (30) comprises a body (34) which extends radially into the primary flow. The body (34) is formed by a V-dihedral having two outer plates (35, 36) which intersect at a common ridge apex (37). An air tube (38) is mounted between the two outer plates (35, 36) and at least one fuel conduit (44, 45) is disposed to the rear of the air tube (38). The overall cross-section of the air tube (38) is approximately triangular and the air tube (38) includes a transverse downstream wall that is curved to define a trough (42) in which the fuel conduit (44, 45) is located. The air tube (38) includes orifices (41, 46) directed against the dihedral plates (35, 36) and the fuel conduit (44, 45) to cool them. The fuel conduit includes a nozzle injector (46) directed downstream towards the afterburner chamber (23).

Abstract: A turbine-nozzle vane fitted with a cooling system including a hollow airfoil (45) inserted between an outer deck and an inner deck (46). Disposed inside the airfoil (45) is a liner (60) which is fitted with a multi-perforated skirt to impact-cool the airfoil wall. The liner (60) has an inner wall (62) comprising a female frustum of a cone (66). A male frustum of a cone (64) is rigidly affixed to the inner deck (46) and is nested in the female frustum (66). These frusta provide communication between the inside of the liner (60) and the inside of the inner deck (46). Cooling air (70) is introduced into the liner (60) through the outer deck. A portion (71) of this air impact-cools the airfoil wall. Another portion (72) enters the inner deck (46) and passes through an orifice (67) to cool the turbine disks (49, 50) upstream and downstream of the nozzle.

Abstract: A thrust reverser is disclosed for a high bypass ratio turbofan jet engine having a fan cowling forming an outer boundary of an airflow duct and a jet engine structure including a jet engine cowling. The thrust reverser has a casing affixed to the jet engine structure, the casing having a plurality of attaching yokes. A first thrust reverser flap is pivotally connected to a corresponding one of the attaching yokes and is located rearwardly of an exit of the airflow duct, each first thrust reverser flap having a distal end and being movable between a forward thrust position, and a reverse thrust position. A second thrust reverser flap is pivotally connected to the distal end of a corresponding one of the first thrust reverser flaps and is also movable between a forward thrust position, and a reverse thrust position, wherein the second thrust reverser flaps also redirect air flow emanating from the air flow duct.

Abstract: A combustion chamber is disclosed for a turbojet engine in which the combustion chamber has a forward intake, a rear exit and a perforated casing extending between the intake and exit. The combustion chamber also has at least two rows of insulating tiles arrayed on the casing in forward and rear rows with both rows extending circumferentially around the inner surface of the casing bounding the combustion chamber. Each rear tile has a forward edge portion with a sloping wall and each forward tile has a tapered rear edge portion overlapping the forward edge portion with a clearance therebetween such that the tampered rear edge portion and the sloping wall bound a slot opening into the combustion chamber and slanting towards the rear of the combustion chamber to facilitate the formation of an air cooling film on inner surfaces of the tiles.

Abstract: An apparatus for orienting the forces exerted by a helical coil spring on relatively movable elements is disclosed in which a movable element is movably mounted within a casing so as to move along a movement axis, in which a helical coil spring is interposed between the casing and the movable element so as to exert opposite forces on the casing and the movable element. The lateral forces and the torque forces on the movable element are eliminated by using a swivel joint interposed between the piston and one end of the helical coil spring. The use of the swivel element insures that the force exerted on the movable element by the helical coil spring is coincident with the movement axis of the movable element. A second swivel joint may be utilized between the second end of the helical coil spring and the casing, if desired.

Abstract: An exhaust nozzle mixer for a turbojet engine is disclosed having a multi-lobed shroud extending from the exhaust nozzle of the turbojet engine, the shroud having a plurality of radially oriented lobes forming a plurality of gas mixing channels, each having a first cross-section in a plane extending substantially perpendicular to the longitudinal axis of the engine, as well as a flared lobe having a greater circumferential width than the remainder of the lobes to accommodate the engine mounting pylon. A baffle member extends radially inwardly from the mounting pylon toward the longitudinal axis of the engine such that the baffle extends into the flared lobe to form a plurality of cross-sections, each of such cross-sections being generally equal to each of remainder of the cross-sections of the multi-lobed shroud.

Abstract: A fuel injection assembly for a combustion chamber of a gas turbine engine is disclosed in which a plurality of premixing chambers are in communication with the combustion chamber and adjacent pairs of the premixing chambers are connected to a single prevapoization chamber by prevaporization conduits. Fuel is injected into the prevaporization chamber via a fuel injector and is mixed with oxidizer passing into the prevaporization chamber such that the fuel/oxidizer mixture has a richness exceeding the stoichiometric ratio. The fuel/oxidizer mixture passes into the prevaporization conduits through a diaphragm opening and, upon entering the premixing chamber, is mixed with additional oxidizer such that the fuel/oxidizer mixture in each premixing chamber has a richness less than the stoichiometric ratio.