GB2306269A

GB2306269A - Picture recording process

Info

Publication number: GB2306269A
Application number: GB9621158A
Authority: GB
Inventors: Wolfgang Scheuerpflug
Original assignee: BMW Rolls Royce GmbH
Current assignee: Rolls Royce Deutschland Ltd and Co KG
Priority date: 1995-10-12
Filing date: 1996-10-10
Publication date: 1997-04-30
Anticipated expiration: 2016-10-10
Also published as: GB2306269B; GB9621158D0; DE19537999A1

Description

2306269 1 A picture recording process The present invention relates to a

picture recording process for thermally stressed components, especially dimensionally curved components of a gas turbine, which are provided with thermally sensitive paint, whereby the development of the surface of the component is recorded and the component is synchronously moved with respect to the picture recording device for this purpose.

For example in the development o-" gas turbine components exposed to high temperatures, to evaluate the temperature distribution across the component, the surfaces of these components are first painted with temperature sensitive paint. The component is then subjected to its regular operating conditions, i.e. the component experiences the usual exposure from normal running, in particular high temperatures. This high temperature exposure causes typical specific colour changes in the temperature sensitive paint. The component is then investigated in detail, and for this purpose is removed from the whole device, for instance a gas turbine. Using the colour distribution now present on the surface of the component the actual maximum temperature exposure which has occurred can be established. Since this component must be lar activities, the component or the component surface is immediately photographed for the evaluation of the colour changes and the temperature distribution. Dimensionally used as soon as possible for further tests or simi BAD ORIGINAL A0 - 2 curved components are recorded in this in the form of development. Usually a so-called periphery camera is employed in this case. This camera using a mechanical synchronised turntable, takes pictures of a narrow strip of the component surface which is to be recorded onto a film. This process is effected by an otherwise normal optical camera whereby a slot shutter traverses at a speed which is coupled to that of the turntable. The camera shutter remains open for as long as the traverse lasts. The width of the slot in the shutter, in combination with the ruling illumination, determines the contrast obtainable.

This previously proposed process has the disadvantage, amongst others, of low flexibility. Although it is possible by mechanical gearing on the turntable, on which the component to be photographed is positioned, to achieve a certain variability, nevertheless, for example, only a quarter turn or a half turn of the turntable can be extended over the whole film width instead of the complete revolution. Sometimes, however, only quite fixed, small, discrete partial exposures are possible by this process. Furthermore the film in the camera, after exposure, has to be chemically developed. This procedure is time-consuming. Further, it has only been practically possible up to now to record the outside of a cylindrical body. However the inner walls of complex hollow bodies, such as for example, the inner surface of an annular burner of a gas turbine cannot be reproduced by this method.

The aim of the present invention is therefore to i,BAD ORIG1WAL is - 3 provide an improved recording process.

Accordingly the present invention is directed to a picture recording process as described in the opening paragraph of the present specification, in which a digital colour line-scanning camera is employed as the picture recording device, which is electronically synchronised with an electrically driven turntable carrying the component.

Advantageously, the data delivered from the colour line-scanning camera and the peripheral data required for reconstruction are stored separately in a data bank.

Preferably, for the recording of pictures of the inner side of a cylindrical wall or a wall on the inside of the component, a recording system comprising at least two mirrors or prisms is positioned between the line camera and the component surface.

In the present invention recourse is made to the principle of synchronous development described in the opening paragraph, however electronic methods are now applied. Instead of the optical camera delivering only line pictures using conventional chemical development, a digital colour line-scanning camera is employed, whose information is stored in a computer. The synchronisation between camera and component is effected electronically in relation to the electrically driven turntable carrying the component.

Digital line-scanning cameras, so-called CCD Cameras for the recording of components, have been BAD ORIGINAL ú11 J.1 4 - is previously proposed (see for example DD-A-262 907 or DE-A40 40 609), however in these previously proposed examples of application no development of the component surface is recorded, in which the component is turned synchronously about an axis, relative to the line-scanning camera.

The process according to the present invention is advantageous in so far as the variability of electronic synchronisation is significantly greater than for the mechanical version. The recording format available can thereby be exploited optimally. It is necessary only to match the sampling rate of the line-scanning camera to the speed of revolution of the turntable. For this, the starting position of the turntable can be registered either by counting the stepping pulses of the turning motor or by counting the pulses of a separate rotation angle transmitter. It is then possible via the software to increase or diminish the resolution of the angle of rotation by multiplication or division. In fact it is the width of the CCD lines in the digital line-scanning camera which determine the recording quality. This width is seen physically as substantially narrower than the moving column provided by an optical film camera. In accordance with the present invention it is theoretically possible by synchronisation of the line-by-line recording of the component, moving on the electrically driven turntable, to achieve an infinitely great circumferential resolution by suitably frequently repeated recording. In practice however the so-called quadratic pixel represents the BAD ORIGINAL optimum, which means that the resolution along a line should be the same as the peripheral resolution. I t i S possible by manipulation of the synchronising pulse, to set this up optimally with respect to the attainment of quadratic pixels, because of the flexible adjustment of the circumferential resolution.

The colour line-scanning camera is applied according to the present invention in order to ensure a secure reproduction of the colours on the component surface. Finally, as explained above, conclusions are drawn on the temperature exposure from the colours on the component surface. It is sufficient for this to provide a total of three light sensitive lines in the colour linescanning camera, for the red, green and blue colour components in the surface colours. A further advantage of the use of a digital line-scanning camera instead of the optical camera is that different resolutions can be generated electronically over different areas of the component surface. This permits the volume of data collected to be limited. Further in contrast to the paper reproduction from a film, which is the result of an optical camera exposure, the digital reproduction obtained with the digital line-scanning camera is easier to integrate into EDP programmes for further processing.

It is advantageous to store the data delivered by the colour linescanning camera, and the peripheral data necessary for reconstruction, separately in a data bank. This results in secure archivability, further for the later BAD ORIGINAL J) 6 repetition of the same record a fast reconstruction can be produced and finally there are retrospective correction possibilities by comparison of the important parameters. In regard to optimum store management it is recommended that the stored data is filed in matrix format. Together with the peripheral data this original file can be then recomputed into the original curved form. Thus for example a circular segment picture can be taken back again for reconstruction from the matrix structure to the correct circular segment structure. Whilst the circular segment representation is necessary for optical and representational reasons, the matrix format is better suited to easier analysis of the radial and envelope profile of the colour and temperature distribution, because only linear measurements are necessary for this.

With the assistance of the picture recording process according to the present invention it is even possible to depict an annular channel, such as for example the annular burner of a gas turbine already quoted above. The special problem in the depiction of the inner surface of a gas turbine annular burner lies in that only a very narrow access area is available into the inner space. Preferably exposures with a large aperture angle must be made. In accordance with the present invention a reproduction system is set up including at least two mirrors between the line-scanning camera and the component surface. The positioning is effected in such a way that a first narrow mirror is placed tangentially to the annular BAD C)RIGINAL 03 7 channel and inclined at 45 to the longitudinal axis. A second, possibly shorter, narrow mirror is then arranged axially in such a way that the axially differentiated rays coming from the wall are reflected by 90' by the second mirror onto the first mirror in a tangential direction. The latter directs these light rays by a further 90 in an axial direction, whereafter they impinge on the digital line-scanning camera. The relatively broad light band is thereby quasi folded, so as to be able to pass through uhe narrow access opening to the inner space of the hollow body to be recorded. The design described here of a combination of a digital line camera and two narrow mirrors is realised easily because of the reduced type of aperture of a conventional line-scanning camera in one direction and is therefore especially advantageous. Using a few optical components and with only small transmission losses the development of the inner side of annular spaces can be recorded (as hollow bodies to be recorded). it is possible also to use suitable prisms instead of the minimum of two mirrors.

Examples of different perspective arrangements for the recording of a picture according to the present invention are shown in the attached drawing, in which:

Figure 1 shows an arrangement for recording annular components; Figure 2 shows an arrangement for recording conical components; and Figure 3 shows an arrangement for recording the inner BAD ORIGINAL új) 8 side of a cylindrical component.

The surface of the component to be recorded, for the most part is dimensionally curved, is generally referred to by the reference number 2. This component 2 is arranged on a turntable 1 in such a way that the component is rotated about an axis of rotation 3 when the turntable 1 is operated. A digital colour line-scanning camera 4 is also provided, which is so arranged and aligned, that the colour line 5 depicted is perpendicular to the camera axis The arrangement shown in Figure 1 thus serves f or recording annular components. Using the arrangement as in Figure 2 the surface of a conical component 2 can be recorded. In this case the camera 4 is arranged to be inclined so that the camera axis 6 is again perpendicular to the colour line 5 to be recorded.

Figure 3 shows in very schematic form the arrangement for recording the inner side of a cylindrical structure. This could be, here shown in outline, a component 10 of an annular burning chamber of a gas turbine, with an outer wall 7a and an inner wall 7b. The surf aces 2 to be recorded are in this case the outer side of the inner wall 7b and the inner side of the outer wall 7a.

The aperture s between the two walls 7a, 7b is relatively narrow, with the result that it is not possible for the line camera 4 to go into this aperture. Therefore a recording system comprising two mirrors 8, 9 is provided, which can be fastened to the line camera 4 using its own BAD ORIGINAL - 9 its own mounting rods, not shown here. The first narrow plane mirror 8 is arranged tangential to the aperture s and at an angle of 45 to the axis of rotation 3, which is at the same time the longitudinal axis of the channel formed by the aperture s. The second, possibly shorter narrow mirror 9 is arranged axially in such a way that the light rays coming from the surface 2 are directed onto the first mirror 8, i.e. in a tangential direction. The mirror 8 then directs them a further 90 in the axial direction, after which they impinge on the line camera 4.

obviously these arrangements as described represent only a small selection of the many possibilities, which are offered by the picture recording process according to the present invention. It is of especial benefit, in that the data collected using the line camera 4 can not only be archived, but can also be stored and processed as required. With the proposed picture recording process also, it is possible to achieve a significantly higher accuracy with regard to the values recorded compared with previous processes using exposed pictures on a conventional film. Retrospective reconstruction of detail sections is also possible, since all the parameters required for this are stored together.

BAD ORIGNAL - 10

Claims

Claims:

1. A picture recording process for thermally stressed components,. especially dimensionally curved components of a gas turbine, which are provided with thermally sensitive paint, whereby the development of the surface of the component is recorded and the component is synchronously moved with respect to the picture recording device for this purpose, in which a digital colour line scanning camera is employed as the picture recording device, which is electronically synchronised with an electrically driven turntable carrying the component.

2. A picture recording process according to Claim 1, characterised in which the data delivered from the colour line-scanning camera and the peripheral data required for reconstruction are stored separately in a data bank.

3. A picture recording process according to Claim 1 or claim 2, in which for the recording of pictures of the inner side of a cylindrical wall or a wall on the inside of the component, a recording system comprising at least two mirrors or prisms is positioned between the line camera and the component surface.

4. A picture recording process substantially as described herein with reference to the accompanying drawing.

is BAD ORIGNAL