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 ceramic heat barrier coating is deposited on a substrate so that the coating has a columnar growth pattern which is interrupted and repeated a number of times throughout its thickness by successive regermination of the ceramic deposit. The regermination is obtained by a vapour phase deposition process wherein a polluting gas is introduced intermittently during the deposition of the ceramic. The resulting ceramic coating has a lower thermal conductivity than conventional columnar ceramic coatings.

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: 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: The fluid transfer device comprises a stator assembly incorporating a plurality of return channels which pick up the high speed fluid flow leaving a centrifugal impeller of one stage of the turbomachine for the purpose of rectifying, slowing down, and conveying said flow to the inlet of another centrifugal impeller of an adjacent stage of the turbomachine. Each return channel is constituted by a continuous shaped individual tubular element. A first continuous return channel is defined by a set of varying sections defined by parameters and extending normally to a mean line situated in a predefined plane (P1P2P3) containing the axis of the machine. The mean line has a rectilinear first portion, a curved second portion forming a circular arc of radius Rco2, and a rectilinear third portion. The various return channels are identical and can be derived one from another by rotation about the axis of the turbomachine.

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: The optical device for detecting in situ traces of gaseous hydrogen in an environment at cryogenic temperature, using a sensor having a fine film of palladium whose optical properties vary as a function of the concentration of hydrogen in contact with the film comprises, a palladium micromirror deposited in the form of a film at a first end of a first optical fiber, a first light source emitting a light signal at a predetermined wavelength into a second end of the first optical fiber, and means for detecting the light signal as modified after passing in contact with the palladium micromirror disposed in the environment at cryogenic temperature, processor circuits for responding to variation in the intensity of the light signal contacting the palladium micromirror to determine hydrogen concentration, and means for localized heating of the palladium micromirror, by light radiation so as to keep the palladium of the micromirror in its &agr; phase.

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.