DE2400013A1 - METHOD AND DEVICE FOR TESTING DRIVE MACHINES IN OPERATION, FOR EXAMPLE OF GAS TURBINE ENGINES - Google Patents

Description

PATH

ι., ing. R. HOLZEB

AUGSBITKG

PHXLOtPPINE-VTEI-SKn-Sa'KASSBi 14 TKl.HPONi »1S7S

R, -

Augsburg, January 2, 1974

Rolls-Royce (1971) Limited, 14/15 Conduit Street, London

England

Method and device for testing in operation located drive machine !!, for example of gas turbine engines

The invention relates to a method for testing in Drive machines in operation, for example from Gas turbine engines, by means of electromagnetic radiation in the iSnergi rather calibrated from 5 HeV to 12 MeV and with a radiation power of more than 25O rad / min.

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For example, the performance of a gas turbine engine w'Ird greatly from the effectiveness of their main coraponents associated seals, influences »The position and the operating clearance these densities are due to the thermal gradient and the gas pressures in the engine and these parameters are, for your part, dependent on the operating states of the engine, iis there has long been a need for a method for rapid examination of the positions of these seals while the engine is in operation. As per previous techniques, they are abrasive Pins and markings have been used, which require dismantling of the engine after each run of the engine made and in studying the effects of transition conditions caused difficulties.

It has already been proposed to gas turbine engines by means of electromagnetic radiation with the wavelength to examine X-rays and record the X-ray images on photographic plates. These x-rays are then examined and evaluated in order to determine the positions of the various components in the engine, The problems associated with the seals in gas turbine engines occur particularly in the vicinity of the turbine «

The radiation used to generate an X-ray image of a Turbine must be made of proportionally different wall thicknesses

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penetrate thick metal, The theory of X-rays states that the maximum penetration of such metals occurs at a wavelength equal to that of radiant energy of 8 MeV, which is why such radiation is used «, From examinations when taking X-rays it is known that it is desirable to shorten the exposure time required for an X-ray exposure. The shortening of the exposure time for the X-ray exposures is desirable in order to be able to record transitional states and improve the resolution of the X-ray image. It is also known that better resolution can be obtained by using a fine-grained film is achievable, but this requires either a longer exposure time or a larger one Performance than that of a coarse-grained film, hence the importance of a high-power radiation source to achieve it a good resolution of transition states.

In order to be able to examine the entire operating sequence of the engine, a series of X-rays must be taken made «These form the basis for a graphic representation of the movements of the engine components.

For X-ray recordings of an engine operating in a stationary state, exposure times are in the range Used from 2 to 3 seconds while recording

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Transition states an exposure time of about 0.1 seconds is elected,

Transitional states, for example acceleration, deceleration, oscillation and thrust reversal states are recorded by the Röntgenaufnähmeteciinik, and the following series of investigations for an engine acceleration from idle speed to full speed can be regarded as typical _β

Photographic plate receives the stranlung sent through the engine running at idle speed ₀ All persons leave the test room in which the engine is located and its surroundings The corresponding X-ray image was taken with an exposure time of 0.1 seconds. The radiation source is switched off and a safety signal is given. The test room is unlocked again, the photographic plate is exchanged and the staff leaves the test room as before. While the engine accelerates from its idle speed, another picture is taken after five seconds. The engine is then decelerated back to its idle speed, the photo plate becomes

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replaced, and while the engine accelerates again from its idle speed, after ten seconds a further exposure made «This process is repeated and further exposures are made with each acceleration time made, which are increased at intervals of five seconds up to fifty seconds. Fifty Seconds are a typical period of time over which investigations into engine acceleration or engine deceleration between idle speed and maximum speed be performed.

So in order to get a complete picture of what is happening inside the gas turbine engine, there must be a number X-rays are taken and each X-ray requires a lengthy procedure. Nevertheless there is still the possibility that during the periods between the individual recordings or after the last recording Undiscovered events in the engine took place «In fact, this on-off sequence can occur as a result of the The resulting delay in the thermal response of certain engine components is an unrealistic picture of this show what actually happens in the engine »

The invention is based on the object of a method eier type set out to improve that the time required for the examination can be significantly reduced «

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In terms of solving this problem, such a method for testing drive machines in operation according to the invention is characterized in that the radiation sent through the prime mover to generate a light image on a luminescent screen is used and that this luminous image is scanned and amplified and for the purpose of examining each other relative to each other enclosed machine parts is recorded "

To carry out this method, the invention is based on a device with a radiation source for generation electromagnetic radiation in the energy range of 5 MeV up to 12 MeV and with a radiation output of more than 250 rad / min and with a device for aligning the Radiation source on the driving machine in operation, which according to the invention by a fluorescent screen, which receives the radiation thrown through the drive machine, furthermore through a sampling and amplifier device, which scans and amplifies the luminous image appearing on the luminescent screen, and by devices for recording the enhanced image.

The scanning and amplifier device is preferably shielded from radiation.

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Preferably, according to the method according to the invention the intensified luminous image is recorded on photographic film, then the intensity distribution on the film measured 'and this intensity distribution either with known, static dimensional relationships of the parts of the relevant drive machine or compared with the intensity distributions, which have been measured on similar images with different operating states of the prime mover »From this is a numerical value for the dimensional proportions of the parts of the prime mover in the image in question belonging operating state derived

A preferred embodiment of the invention is described below with reference to the accompanying drawings, for example.

ffig «, 1 a schematic representation

a device according to the invention,

2 shows a schematic representation

an image intensifier of the device according to the invention,

Fig «3 is a plan view of the invention

appropriate device with regard to radiation protection,

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Pig, 4 a section of the turbine

of a gas turbine engine to be examined,

Pig " ^l j a representation of an X-ray

recording of the l'urüinenausscnnitts shown in Fig. 4,

6 shows a part of the compressor of a

to be examined gasturoine

engine,

Figs, 7, and 9 ά typiscne Hikroschwärzungsmesser-

Recordings of the compressor part shown in Fig. 6, and

FIG. 10 is a table showing the means of

_{7, 8 and 9} indicates changes in dimensions of the compressor according to FIG.

In Figo 1, a gas turbine engine 10 is shown schematically, which is on inem not shown Test stand and in the usual way to fuel and electrical supply lines as well as to the control of the drive

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factory required instruments is connected.

A linear accelerator 11 generates electrons and
accelerates this to an energy of 8 MeV. The electrons then strike an impact plate and generate X-rays in the energy range of 8 MeV. The energy distribution is a characteristic curve of the impact material and generally shows two separate maxima
Establishment became an impact material with a strong
X-ray emission selected according to 8 MeV. At the high frequencies of electromagnetic radiation
In the area of X-rays it is generally advisable not to work with frequencies but with energies measured in MeV. Planck's applies to the transformation between energy and frequency of a radiation quantum
discovered radiation law,

The X-rays exit the linear accelerator through a collimator that limits the divergence angle of the beam. The X-rays emanate from a focal point area with a diameter in the range of 2 mm on the target. Better resolution can be achieved with a smaller focal area «A reduction in the diameter of the focal area to 1 mm
has the expected in the device according to the invention
Resolution improvement and at the same time an unexpected one

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The maximum output power is increased from 1500 rad / min to 160 rad / min at a distance of 14 meters from the target impinging electron current is better rectified _e

The X-rays emerge from the linear accelerator as a diverging beam, the normal beam 12 passes through that point of the prime mover whose investigation is required. The one let through Radiation strikes a fluorescent screen 13, which is attached to an image intensifier 14, which is shown in greater detail in FIG assigned. The luminescent screen I3 has a circular shape is entrance opening and receives the radiation of a cone of rays with half a cone angle 15,

A radiation shield 16, which is made up of different lead plates and a total thickness of about 3 cm has, reduces the incident in the image intensifier 14 Radiation, so that the formation of interfering electrons in the image intensifier is largely prevented. These interfering electrons are very undesirable because they are further amplified as a result of the amplification process taking place in the image intensifier and consequently result in a strong noise signal at the output,

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the quality of the information signal is considerable reduced.

The output of the image intensifier passes through a shielded cable 18 and a control unit 31 to a TV monitor 32. The control unit 31 enables Adjustment of the gain of the image intensifier, the contrast, the magnification and the image polarity for the purpose Creation of the best possible image on monitor 32. With the help of the polarity changing device it is possible to use darker ones. Areas on the television monitor 32 as light areas to make visible, and vice versa. That from the TV monitor received signal is by means of a video tape recorder and a film camera 3 ^ recorded the recordings of these both recorders are then in a manget tape library 35 or a film library 3ö.

As shown in FIG. 2, the light emanating from the luminescent screen 13 is converted by means of a mirror 17 90 ° deflected and then collected by means of a concentric mirror arrangement 18. The image will then appear on the front fluorescent screen 19 of an image intensifier tube 21, that is reproduced on the rear luminescent screen 22 of the image intensifier tube The intensified image appearing in 21 is deflected by means of a deflection mirror 23 in a lens system 24

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Λ.

focused and steered by means of a further deflecting mirror 25 onto the screen 26 of a TV recording tube 27. It is It is desirable to use an image intensifier of the type just described, the image intensifier not being immediate is located in the direction of the incident radiation behind the luminescent screen, since in such an arrangement the Radiation shielding of the image intensifier is very difficult,

According to an embodiment not shown, the mirror 25 is replaced by a half-silver-plated mirror and the image appearing on the back screen of the image intensifier is immediately recorded on film, so that any possible distortion from the television pickup tube is eliminated. Of course, at Use of the semi-silver-plated mirror of the television monitor can be retained, however, it may be necessary to use that To increase the power of the linear accelerator to compensate for the signal loss due to the semi-silvered mirror. According to a further modified embodiment, the mirror is dispensed with entirely and only one Movie recording made.

The choice of a suitable screen 13 for the Image intensifier is very important as it has not been used for so far

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was kept possible, television images of X-rays at energies above 4.5 MeV and at power levels make, 'which is close to that for the penetration of the metal wall thicknesses, such as, for example, along a chord described by the normal jet 12 by a gas turbine engine occur within the necessary size range.

A power of 250 rad / min _s as measured at a distance of one meter from the target on the normal beam can be regarded as the absolute power minimum for the generation of an image and in practice a minimum power of 750 rad / min has been found Generally found acceptable in relatively small gas turbine engines, however, power levels of 1500 rad / min and above are preferred. The grain size of the screen must be as small as possible to achieve the best possible resolution. In addition, so that there is sufficient contrast for the intensification by the image intensifier, a thick screen must be used so that the received X-rays activate the screen sufficiently image generated on the screen. In practice, the technology has developed so far that the limit of the sharpness of the picture

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Factor more the internal dispersion, in the screen than that geometric image blur is. The geometric blurring has its cause in the use of a finite focus size and in the divergence of the beam. This geometric Blurring has been reduced by using a small focus area and spacing between the target and the engine as large as possible and the distance between the engine and the The screen is made as small as possible,

A filter made of copper, for example, can be arranged in front of the luminescent screen, whereby some of the X-rays scattered several times are filtered out, which generate a noise signal on the screen. A Filter with a copper layer 0.05 cm thick has proven to be useful.

It is not desirable to use energies above 12 MeV, since above this level some metals used in the construction of a gas turbine engine can become radioactive and the signal attenuation becomes more important. The optimal frequency corresponds to radiation of 8 MeV and dose rates of up to 1600 rad / min uses _β

The fluorescent screen and the image intensifier are on one

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simple rack and pinion mechanism, not shown, mounted on a platform of the engine test stand, so that they are movable relative to the gas turbine engine and can be aligned with the normal jet.

The image intensifier is preferably surrounded by foam rubber in order to protect it against seismic and acoustic vibrations. The television pick-up tubes are particularly sensitive to vibrations, which lead to a reduction in the picture quality. The linear accelerator is mounted separately on its own frame 25, as shown in FIG. ₉ 1, so that the vibrations of the engine do not affect the sensitive inner parts of the accelerator. to provide in its framework "

It has proven to be advantageous when aligning the linear accelerator, the thruster and the image intensifier revealed to first roughly align the device and take an X-ray of the not yet running To make engine. The mutual position of the linear accelerator and the image intensifier can then be readjusted by that amount which is determined by estimating the error from the image of the television screen taking into account the

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appropriate magnification factor for the relative distances between the impact plate and the engine and between the engine and the image intensifier. With appropriate practice, there is only one trial run required to align the device.

A surprising result of this research is that there is little or no vibration occurs along the engine axis. It was generally believed that the vibration of an engine in operation would be so severe as to reduce the sharpness of the image, but it has been found that it does not.

From Fig, 1 it can be seen that the normal beam from the linear accelerator at an angle of 45 ° to the vertical goes down through the engine. The one going through the engine and not from the screen or the Shielding absorbed radiation therefore falls on the ground, where a large part of this radiation is harmless is absorbed.

Fig, 3 shows a chamber for the device, which is used to protect personnel against the potentially fatal Effects of radiation has been developed "

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In Fig. 3 is the immediate vicinity of the test cell and the control room shown «, The control room 42 is about located to the right behind the linear accelerator 11 within the space arranged by the divergent lines 43 and 44, so that they are not direct and only very slightly reflected Exposure to radiation.

A fairly intense radiation 45 is present from the back of the linear accelerator in the direction opposite to the normal beam 12. Because of the inclination of the accelerator, however, this beam goes over the building and is harmlessly attenuated after crossing a relatively small distance, so that there is no danger _{for aircraft USW 9 flying over it.} The windows of the control room can consist of lead glass and sandbags 46 can be arranged in a suitable manner to protect the personnel in the control room. Radiation 47 sent through the engine and not absorbed and radiation 48 reflected from the ground is also attenuated by large, particularly dense concrete blocks 49, which are arranged along the side of the test cell in the direction of the beam behind the image intensifier.

Scattered radiation and radiation reflected inside the engine are much less intense than the radiation passing through Radiation and are essentially from the atmosphere

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absorbed before they have traversed a greater distance.

Reference is now made to FIGS. 4 and 5, which are a drawing and an X-ray photograph of the turbine section of a gas turbine engine. The normal jet 12 is used to seal 72 between the toe plate 73 of the rotor blade 74 and the lip 70 of the guide vane 75 directed towards. The X-ray image shown in Fig. 5 shows an image from the middle of a film, which was taken up during a small acceleration of the engine from idle to full power and represents a complete scan of the luminescent screen 13 by the image intensifier 14, which takes 0.04 seconds, which is the standard deflection frequency of the television pickup tube used is equivalent to.

Since each image is actually a shadow x-ray, the divergence of the x-ray beam as it traverses the engine produces an image which is slightly different from the drawing of FIG. These differences become more noticeable towards the edges of the image. The edges J6 of the foot band plates 77 of the guide vanes 78 located downstream of the rotor blade 74 describe a complete circle and this edge, which is visible in FIG. 4 as a straight line 79, appears in FIG. 5 as an ellipse 81 with a very small smaller ellipse.

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diameter * A comparison with that formed by the web 82 A similar ellipse 84 makes it possible to interpolate the point of incidence of the normal ray 12 so that its position can be adjusted is that the best possible image of the part to be examined, in the present case the seal .72, is created.

By comparing the bearings of the seal in FIGS. 4 and 5 , it can be clearly seen that the seal has partially moved out of the area of contact with the lip 70 of the guide vanes 75 during acceleration. One might think that it would be easy to calculate this change in position of the seal on the basis of the thermal gradients and coefficients of thermal expansion of the engine housing and the engine shaft. The thermal gradients, however, are complicated and indeterminate and, of course, a seal movement, as can be seen in the drawing, allows pressurized hot gas to leak out along the face of the rotor disk 84, thereby changing the thermal conditions and the gas forces deviating from the design values » It has been shown that the technology of real-time X-ray images with continuous recording leads to a significant reduction in engine development time, since the designer can detect deviations from his design requirements,

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A precise measurement of the gaps appearing in X-rays can be carried out using the microscopic measurement technique shown in FIGS. 7, 8 and 9. which together with the blade tips of a guide vane ring 9k forms a seal. In operation, it has been found that the tips 95 of the vanes drag on the radially outer surface 90 of the spacer. It was believed that this was caused by the two rotors approaching each other, narrowing the design clearances between the spacer ring and the rotors and consequently compress the spacer, which then bends in the middle and comes into contact with the tips of the guide vanes _β

Three films of x-ray images of the spacer ring were taken while the engine was in operation, with the normal beam passing precisely through points 97, 98 and 99 , which are the clearances between the spacer and the tips of the vanes and between the spacer and the forward and aft Represent the face of the two rotors. Each X-ray was then taken

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searches and certain images of the film were taken by means of a Measure the microscopic black meter to determine the differences in the recordings at these margins. The three typical micro densitometer records are in the Figs. 7, 8 and 9 show -with Fig. 7 the record for the gap between the spacer and the tips of the guide vanes, Fig. 8 shows the record for the before Spacer and Figo 9 shows the recording for the gap behind the spacer * When comparing the various micro densitometer mounts for each of these columns under different operating conditions of the engine, the records can be calibrated and accurate measurements of the column can be obtained «The in Fig, The table shown shows the maximum and minimum gap sizes determined in various operating states and shows the accuracy that can be achieved with this technique, with this special arrangement one was down to 0.025 mm accurate measurement possible. It was then found that the contact of the tips of the guide vanes with the spacer ring a different cause than originally expected. To ensure an exact alignment with the normal jet, what is required for microscopic measurements can Find laser measuring methods application.

Of course it is possible to use the electron gun

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of the linear accelerator to operate pulsating synchronously with the engine rotation, so that stroboscopic ^ Images are created whereby a particular shovel or other rotating part for the purpose of investigation can be held. Unfortunately, with one gas turbine engine, the others "degrade" with the one under test Blade in the same radial plane blades or components, however, the clarity of the picture For example, in piston engines, if the normal jet is directed radially through a cylinder bore, the piston movement can be recorded and dimensions such as piston ring clearances are measured.

To further improve the quality of the engine Image smoothing techniques can be used by means of computers. Successful with one The X-ray device used, the additional devices were removed from the vicinity of the examination site to avoid those with noise and vibration related difficulties such as unwanted triggering of relays, etc. Of the The screen used was made of zinc-cadmium-sulfide.

The procedure described was used to test a series of gas turbine engines powered by a 900 hp helicopter engine up to a bypass gas turbine

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engine with 40 tons of thrust was enough, which means that it was used an increase within a few weeks of studying the working of the seals on the X-ray film of 100 hp was achieved in the helicopter engine. When examining various seals of others Engines have shown the recordings considerably larger displacements and expansions than the designer did provided «The information gained through the application of the invention has enabled significant reductions in development times.

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Claims (11)

Claims (jLy procedure for testing in operation Drive machines, for example of gas turbine engines, by means of electromagnetic radiation in the energy range from 5 MeV to 12 MeV and with a radiation power of more than 250 rad / min, characterized in that the Radiation transmitted through the prime mover is used to generate a luminous image on a luminescent screen and that this luminous image is scanned and amplified and for the purpose of examining those moving relative to one another Machine parts are recorded, 2. The method according to claim 1, characterized in that the enhanced image is recorded on photographic film, as well as the intensity distribution measured from the film and either with known static dimensional ratios of the machine parts or with the from similar images in different operating states the intensity distributions measured by the prime mover are compared and that a numerical value for the dimensional ratio the machine parts for the operating condition prevailing when the image was taken is derived. - 24 409829/0 3 3, diagnostic device for executing the method according to claim 1 or 2, with a radiation source for generating electromagnetic radiation in the energy range from 5 MeV to 12 MeV and with a radiation power of more than 250 rad / min, and with an alignment device the radiation source on the operating engine, characterized by a luminescent screen (13) » which receives the radiation thrown through the prime mover (10), further through a scanning and amplifying device (18, 21), which scans and amplifies the luminous image appearing on the luminescent screen, and through Devices (32, 33, 34) for recording the amplified Image, 4, device according to claim 3 _S, characterized in that the scanning and amplifier device (18, 21) is not located directly behind the luminescent screen (13) and that a screen (16) to protect the scanning and amplifier device against the received X-rays is provided, 5 »Device according to claim 3 or 4, characterized in that a sign is arranged in front of the luminescent screen (13) which absorbs some of the multiply scattered X-rays, - 25 -. 409 82 9/0974 6. Device according to claim 5, characterized in that that said shield has a copper layer with a thickness of about 0.05 cm, ' 7β device according to one of claims 3 to 6, characterized characterized in that the luminescent screen (13) and the scanning and amplifying device (18, 21) against acoustic and seismic vibrations are protected, 8, device according to one of claims 3 to 7, characterized in that the radiation source a Linear accelerator (11) for bombarding an impact plate with electrons in order to generate said electromagnetic Has radiation, 9, device according to one of claims 3 to 8, characterized by a device which the radiation source synchronous with rotating parts of the prime mover for the purpose of generating stroboscopic images operates pulsating so that a certain area of the rotating machine parts can be examined, 10 ο device according to one of claims 3 to 9, characterized in that all additional devices, as far as - 26 409829/0974 possible to be removed from the vicinity of the facility to avoid unwanted triggering of relays by acoustic or largely exclude seismic vibrations, 11. Device according to one of claims 3 to 10, characterized in that the amplifier device has a Image intensifier (21) and that a film camera (34) is provided, which the image directly from the image intensifier records, 12 _e device according to claim 11, characterized in that the image is projected from the image intensifier to a half-silvered mirror (25) so that a light transmitted by the mirror and reflected by the mirror image can be recorded simultaneously. - 27 409 8'2 9/0974