Abstract: The operation of an engine or other assembly is monitored by detecting the sound it makes and deriving from this, in conjunction with its speed, temperature and control settings, a multi-dimension condition vector. The vector changes during operation of the engine and is supplied to a processor which continuously builds a model of the engine at different stages of operation such as by a sequence-learning neural net or by hidden markov model when an atypical condition vector is received, the processor generates an alert signal to a display.

Abstract: A representation of oil flow in a gas turbine engine is obtained by injecting a compatible radioactive isotope label into the engine oil flow and detecting the radiation emitted from within the body with detectors mounted outside the body to produce signals representative of the quantity and direction of the radiation; the detector output signals are compensated for attenuation on passing through the engine in accordance with attenuation signals derived from a representation of the spatial distribution of the engine and of its materials, and signals from non-viable directions are discounted. The compensated detector output signals are used to generate a number of focal-plane tomograms from which an image in a desired plane may be re-constructed. The image may be formed on a background of the engine in the relevant plane generated from the representation thereof.

Abstract: Carrier particles, e.g., of metal or metal oxide, are doped with a positron-emitting isotope and injected into fluid flowing in a body, such as a gas turbine engine. The positrons decay on coming to rest, giving two gamma rays which are detected, and a 3D image is built up. The particles are capable of stopping a portion of the positions before they escape from the particles into the surroundings; thus the gamma rays indicate more accurately the position at which the positron was emitted, and give a clearer image.