Rolls-royce Corporation

Joseph Douglas

Peter A Stewart

Martin J Allen

Richard P Jennings

Richard T Skelton

A stack of titanium sheets are placed on a worktable in a vacuum chamber. One of the mating surfaces of each pair of mating surfaces has had a stop off material applied in a desired pattern to prevent diffusion bonding. A pump evacuates the vacuum chamber and heaters heat the stack to evaporate volatile binder from the stop off. When all the binder has been removed the worktable is moved relative to an electron beam from a gun to weld the edges of the sheets together to form a sealed assembly. The volatile binder is removed quickly and oxidation of the titanium is prevented during baking out of the binder. The sealed assembly is then heated and externally pressurised to diffusion bond the sheets together. The integral structure is then heated and internally pressured to superplastically form one of the sheets to produce an article of predetermined shape.

Method of manufacturing an article by superplastic forming and diffusion

A stack of titanium sheets are placed between a pair of pressurizable chambers in a vacuum chamber. One of the mating surfaces of each pair of mating surfaces has had a stop off material applied in a desired pattern to prevent diffusion bonding. A pump evacuates the vacuum chamber and heaters heat the stack to evaporate volatile binders from the stop off. When all the binder has been removed the stack is heated and the pressure in the pressurizable chambers is increased to cause a pair of resilient members to apply pressure on the stack to diffusion bond the sheets together. The volatile binder is removed quickly and oxidation of the titanium is prevented during baking out of the binder. The integral structure is then heated and internally pressurized to superplastically form one of the sheets to produce an article of predetermined shape. No welding of the sheets before bonding is required.

Method of manufacturing an article, a method of diffusion bonding and a

A stack of titanium sheets are placed on a worktable in a vacuum chamber. One of the mating surfaces of each pair of mating surfaces has had a stop off material applied in a desired pattern to prevent diffusion bonding. A pump evacuates the vacuum chamber and heaters heat the stack to evaporate volatile binder from the stop off. When all the binder has been removed the worktable is moved relative to an electron beam gun to weld the edges of the sheets together to form a sealed assembly. The volatile binder is removed quickly and oxidation of the titanium is prevented during baking out of the binder. The sealed assembly is then heated and externally pressurised to diffusion bond the sheets together. The integral structure is then heated and internally pressured to superplastically form one of the sheets to produce an article of predetermined shape.

A stack of titanium sheets are placed between a pair of pressurisable chambers in a vacuum chamber. One of the mating surfaces of each pair of mating surfaces has had a stop off material applied in a desired pattern to prevent diffusion bonding. A pump evacuates the vacuum chamber and heaters heat the stack to evaporate volatile binders from the stop off. When all the binder has been removed the stack is heated and the pressure in the pressurisable chambers is increased to cause a pair of resilient members to apply pressure on the stack to diffusion bond the sheets together. The volatile binder is removed quickly and oxidation of the titanium is prevented during baking out of the binder. The integral structure is then heated and internally pressurised to superplastically form one of the sheets to produce an article of predetermined shape. No welding of the sheets before bonding is required.

Residual core material can be detected inside hollow cast articles using positron emission tomography. Positron radio-isotope material is inducted into any residual core material present by immersing a cast article in an aqueous solution of radio-isotope emitter, for example gallium. Absorbed gallium subsequently emits positrons which are annihilated in collisions with electrons emitting two 511 KeV gamma rays in diametrically opposite directions. The emissions are detected and tracked by a PET camera and the resulting images correlated with a sectioned image of the article as a check on the location of detected core material. Initially a low-dose-rate solution for the purpose of merely establishing the presence of core material is used but a second optional process step introduces a more active solution allowing a PET camera to collect sufficient data to image absorbed isotope.

Non-invasive inspection

Data processing methods and circuit arrangements are provided whereby out of a succession of data, some or most of which are false due to interference or noise, only those most likely to be true are selected for transmission to following stages of processing. Selection is achieved by comparing, according to a predetermined criterion, successive input data words with a data word already held in a data store and updating the store by discarding the stored data word and replacing it with an input data word whenever an input data word meets the predetermined criterion. A stored data word is utilised in further processing only when a predetermined number of input data words have been compared with the stored data word without updating having occurred. The invention has particular relevance to optical pyrometry systems.

Data selection circuits, systems and methods

To be of most use as an input signal for the control system of a gas turbine aeroengine, a pyrometer-derived turbine blade temperature signal should represent the average temperature of the hottest parts of the blades with fast and accurate response when the average temperature of the hottest parts changes with engine conditions. The invention achieves this by providing the pyrometer with an optical system adapted to give the pyrometer's photo-diode a large field of view which is rectangular at the face of the turbine rotor and which extends an integer number of inter-blade passage widths in the circumferential direction and a portion of the length of the blade aerofoils in the radial direction. The large rectangular field of view is achieved by masking the optical system and arranging that it cooperates with a small aperture in the wall of the turbine gas passage in such a way that at the aperture the field of view lies entirely within the boundary of the aperature, the field of view expanding out of the aperture to produce the required rectangular field of view at the face of the turbine rotor.

Optical radiation pyrometer

In a radiation pyrometer in a gas turbine engine, non-uniformly distributed changes in transparency of an optical element in the system, e.g. contamination of pyrometer objective lens L.sub.1 by combustion products from the turbine can be automatically detected. Lens L.sub.1 focusses radiation from target T onto an additional lens L.sub.2, which in turn focusses it onto the end E of the fibre-optic bundle F. Considered reciprocally, lens L.sub.2 images the end E of fibre-optic F into L.sub.1, so that although each optical fibre in end E receives radiation from all parts of target T, each fibre is imaged into a corresponding discrete area of L.sub.1. Fibre-optic bundle F comprises two (or more) sub-bundles F.sub.1 and F.sub.2 forming complementary sub-areas of end E and each sub-bundle is provided with its own photodetector P.sub.1, P.sub.2 and associated pre-amplifier A.sub.1,A.sub.2 adjusted so that their outputs A.sub.1 S.sub.1 and A.sub.2,S.sub.2 are matched at the non-contamination condition. When one part of lens L.sub.1 is contaminated during service more than the other parts, this will show as an unacceptable mis-match between the outputs A.sub.1 S.sub.1 and A.sub.2 S.sub.2. This is automatically detected by differential amplifier D whose output gives a warning indication and can also be used to trigger a selector circuit X to select the strongest signal for onward transmission.

Detection of changes in transparency of optical elements

An optical probe is particularly for use as part of the viewing system of a radiation pyrometer, e.g. for measurement of temperatures of turbine blades in a gas turbine aeroengine. Although the objective end of the probe lies flush with the outer wall of the turbine gas passage in order to avoid disturbance of the gas flow and is angled away from the blade by virtue of its conformity with the geometry of the outer wall of the gas passage, the probe's field of view nevertheless includes locations on the turbine blades which are considerably axially upstream from the probe's position. This is achieved by providing the probe with an objective prism whose front and rear faces are inclined with respect to each other, so that, for rays of a preselected wavelength, the prism refracts into the probe and along the internal optical path of the probe only those rays from a preselected location on the blade. Since the blade radiates at a number of wavelengths, a filter is included in the viewing system so that the pyrometer is presented with radiation at a single wavelength, and therefore with a single image from the single preselected location on the blade. The probe also includes an image centralizing prism in order to centralize the optical path within the probe, and glare stops in order to collimate the rays after they have passed through the objective prism and the image centralizing prism. The objective prism may be made of sapphire in order to withstand the heat of the turbine gases.

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Derby, United Kingdom

Joseph Douglas