Abstract: An axially symmetric turbojet-engine exhaust nozzle which is directable as a unit. The exhaust nozzle is situated downstream of an exhaust duct (1) fitted with a spherical wall (5). A single control ring (12) driven by linear actuators (30) allows regulation of the nozzle cross section and direction. Converging flaps (7) are guided on an upstream side by the spherical wall (5) and are supported at a downstream side by a control lever (13) which hinges on the control ring (12) and rests upstream on an external surface (16) of the spherical wall (5). Diverging flaps (10) hinge on the converging flaps (7) to form an inner ring of hot flaps. The diverging flaps (10) are situated downstream in an extension of the converging flaps (7) and further hinge on an outer ring of cold flaps (11), which in turn hinge on the control ring (12).

Abstract: The present invention relates to: a novel process for the preparation of mesophasic polyborazylene. Said process is of particular value in that it affords a quality product from an appropriate polyborazylene, rapidly (virtually instantaneously), reproducibly and with a good yield. Furthermore, said process is easy to carry out. Said process comprises the preparation of polyborazylene by the polycondensation of borazine in a closed reactor and the addition, to said polyborazylene obtained by polycondensation, of a solvent selected from aromatic solvents, borazine solvents and mixtures thereof, mesophasic polyborazylene which is novel in that it is in the presence of a particular solvent and/or by virtue of its quality, the use of said polyborazylene of the invention, and/or prepared according to the invention, as a boron nitride precursor.

Abstract: A lubricant drainage circuit outside a roller bearing is fitted such that an output draining through a drained ring is controlled by providing drainage channels crossing the ring and having different inclinations in a circumferential direction of the drained ring.

Abstract: A thrust reverser for a turbofan jet engine having a stationary structure defining an upstream part of a fan cowling and an axially displaceable, annular structure located downstream of the stationary structure, wherein the inner surface of the fan cowling is spaced from an outer surface of an engine cowling to form an annular duct. A plurality of flaps form a portion of the inner surface of the fan cowling during a forward thrust position, and in a reverse thrust position, the flaps pivotably rotate about a stationary pivot so that their first edges are adjacent with the outer surface of the engine cowling to block the annular duct. A plurality of thrust reverser baffle portions are covered by the flaps during the forward thrust position, and during the reverse thrust position, the thrust reverser baffle portions cover a passageway in the fan cowling between the stationary structure and the displaceable structure.

Abstract: The present method of manufacturing a ceramic composite material, composed of matrix and reinforcing materials and an intermediate weak interfice material, creates a composite material particuarly intended for use at temperatures above 1400° C. and in an oxidizing environment. The matrix and reinforcing materials consist of the same or different ceramic oxides having a melting point above 1600° C. The interface material provides in combination with the matrix and reinforcing materials a stress field liable to micro aciding. The reinforcing material is immersed into a powder slurry containing carbon (C) and ZrO2 so as to be coated thereby and then dried. After which, the thus created composite material is subjected to green forming and densifying steps. Finally, the composite material undergoes a heat-treatment in air leaving a porous structure of the interface material.

Abstract: An apparatus for manufacturing a hollow turbomachine blade made from a titanium alloy of the TA6V type includes a hot twisting step in which an element of the blade is twisted progressively at a temperature above 700° C. by a plurality of bars which are rotated about the twist axis and act on collars previously fixed to the element, the distribution and number of collars being determined according to the desired twist to be imparted and such as to obtain a linear twist development between each collar.

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 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: A method of improving the oxidation and corrosion resistance of a superalloy article comprises providing a superalloy substrate having a sulphur content which is less than 0.8 ppm by weight, and depositing on the substrate a protective antioxidation coating having a sulphur content also less than 0.8 ppm by weight. A heat barrier layer may also be provided by depositing on the protective anti-oxidation coating a ceramic coating of columnar structure.

Abstract: A tubular structure comprising reinforcing fibers impregnated with a thermosetting polymer and a sheet of matrix material filled with an additive suitable for improving tribological and heat conductivity characteristics of the tubular structure. The reinforcing fibers alternate with the matrix material. The tubular structure is formed by winding the reinforcing fiber fabric and the matrix sheet material, wherein the fabric and the matrix sheet material have first and second ends and the first ends are located in the interior of the winding and the second ends are radially outwardly displaced from the first ends.

Abstract: A yarn is formed from discontinuous parallel fibers which are not twisted and which are held together by a covering yarn of sacrificial material wound around the fibers. The fibers comprise an intimate mixture of fibers of at least two different natures selected from carbon fibers or pre-oxidized polyacrylonitrile based carbon precursor fibers, or anisotropic or isotropic pitch based carbon precursor fibers, or phenolic or cellulosic based carbon precursor fibers, and ceramic fibers or ceramic precursor fibers. The mixture of fibers comprises, in its carbon state, at least 15% by weight of high strength fibers, having a tensile strength of at least 1500 MPa and a modulus of at least 150 MPa, and at least 15% by weight of fibers with a low Young's modulus of at most 100 GPa.

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 process for assembling titanium aluminide articles by diffusion brazing comprises the following steps: (a) Preparation of a homogenous mixture of a titanium aluminide powder A of 40 to 90 weight % and a powder B chemically wetting A and having an appreciably lower melting point; (b) formation of a paste by addition of an organic binder to the powder mixture; (c) depositing the paste plumb on the assembly gap; and, (d) heating the assembly in a vacuum furnace between 1000° C. and 1300° C. for a period of from a few minutes to 6 hours. This process is also of use for repairing and refacing titanium aluminide articles.

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: 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 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 present invention relates to the high-pressure turbine stator ring of a turbo engine that is fastened to the stator by tightening means that limit leaks to a minimum. These means mainly comprise a tightening grip (40) that grips the curved section of a downstream leg (35V) of each spacer section (30) that is fastened to the turbine casing (1) of the stator by a curved downstream flange (23V) of each ring section (20). Application to the fastening of the high-pressure turbine stator ring of a turbo engine.

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).