Societe Nationale D'etude Et De Construction De Moteurs D'aviation

Societe Europeenne De Propulsion

Societe Nationale D'etude Et De Construction De Moteurs D'aviation-snecma

Michel Clement

Patrick Meyrueis

Jacky Y Rouhet

Gabriel Olalde

Ayoub Chakari

Xavier Bevenot

Emmanuel Milcent

Daniel Hernandez

Henri Gagnaire

Eric Gaumont

Daniel M Hernandez

Emmanuel M Milcent

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.

Optical device for detecting traces of gaseous hydrogen in situ in an environment at cryogenic temperatures

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. Preferably, the deformable guide sheath is made of fine steel, and it may lined with a flexible protective sheath.

Optical-fiber polarimetric sensor

The present invention relates to a fast bichromatic pyrometer for measuring the temperature T of a gas or of a moving surface, the pyrometer comprising: a measurement probe placed facing the surface or immersed in the gas and picking up thermal radiation that is characteristic of the temperature of said surface or of said gas; a single optical fiber connected to the measurement probe and transmitting said radiation; an optical block connected to the optical fiber and receiving said radiation, the optical block including inlet collimation means for transmitting all of said radiation, separation means formed by a dichroic slide for separating the transmitted radiation into two distinct spectral bands, and outlet focusing means for concentrating the two separated bands of radiation; a quantum detection circuit receiving said separated bands of radiation and converting them into two color voltages Vr, Vb; and a treatment circuit receiving the voltage signals and including analog-to-digital conversion means, a digital signal processor for calculating the ratio Vr/Vb from these digital values, and memory means provided with a table of predetermined values of T=f(Vr/Vb) as obtained by calibration and delivering at its output, on the basis of the calculated ratio, the temperature T of the surface or of the gas.

Fast bichromatic pyrometer for use with an optical fiber

A process and a device for the optical measurement of vibrations of rotating turbine blades moving with a specified speed of rotation. In one embodiment, the process comprises the steps of generating three reference signals in response to the detection, by an optical detector, of the passing of a marking made on the hub of a turbine wheel; detecting measurement signals, by another optical detector, in response to the passing of another marking made on at least one of the parts of a turbine blade, the blade undergoing oscillation; determining the time offsets existing between each of the reference signals and each of the measurement signals, these offsets being, in the absence of oscillations of the blade, zero or equal to specified constant values; and calculating the amplitude, frequency and phase components of blade vibration from the various offsets recorded.

Process and device for measuring operating turbine blade vibrations

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Vernon, France

Michel Clement