GB1593926A

GB1593926A - Method and device for determining the temperature distribution on surfaces

Info

Publication number: GB1593926A
Application number: GB17836/78A
Authority: GB
Original assignee: Bergwerksverband GmbH
Current assignee: Bergwerksverband GmbH
Priority date: 1977-05-04
Filing date: 1978-05-04
Publication date: 1981-07-22
Also published as: JPS6029887B2; BE866658A; DE2719918A1; ES469395A1; DE2719918B2; JPS53137193A; DE2719918C3

Description

(54) METHOD AND DEVICE FOR DETERMINING THE TEMPERATURE DISTRIBUTION ON SURFACES (71) We, BERGWERKSVERBAND GmbH, of Franz-Fischer-Weg 61, 4300 Essen, Federal Republic of Germany, a German Body Corporate, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method and device for determining the temperature distribution on surfaces using viewing angles between 0 and nearly 90" to the normal to the surface by means of a contact-less measuring method.

In many fields of process engineering, it is desirable to measure the temperature distribution on surfaces in order to trace so-called heat pockets or other deviations from required temperature profiles; however, this is made extremely difficult by the fact that for space reasons the surfaces to be measured are not always accessible, so that under certain circumstances a very large surface has to be viewed from a narrowly limited space.

Thus for example in coke oven technology, the temperature distribution on the coke side of the coke oven walls is very important for uniform coking of the contents of the chamber, and thus directly for the quality of the coke. The chamber walls of coke ovens, which today reach lengths of up to 17 m and heights of up to 8 m, are accessible however only through the charging ports and the narrower doors, which have a width of 0.4 to 0.5 m.

There has been no lack of attempts to find suitable temperature measuring methods and devices for these and similar surfaces.

Thus for example, the temperatures of coke oven chamber walls are measured through the charging ports by means of optical pyrometers, but in this manner only the temperatures of individual points on the walls can be measured. In addition, this method requires time which, for continuous operation, cannot be made up.

From German Auslegeschrift 12 25 143, a method is known for measuring wall temperatures, which uses a radiation receiver, which is mounted on a bar by means of which the radiation receiver is moved across the wall concerned and parallel thereto.

However, even when several radiation receivers are disposed at right angles to the direction of movement of the bar, only the temperature distribution for parallel strips is obtained, and not for the total wall surface.

In addition, with this method, the measurement signals are falsified because of temperature differences between the wall and measuring system.

In addition, infrared television cameras are known, which enable the temperature distribution on wall surfaces to be determined. However, the optical axis of these apparatus must be at right angle to the wall surface concerned, in order to give an undistorted "temperature image". Thus the use of such an apparatus is quite impossible where the operating conditions do not allow such a positioning of the camera, as is the case for example with coke oven chambers on account of the high temperature, the small chamber widths and the comparatively large chamber walls.

The present invention provides a method of determining the temperature distribution on a surface using viewing angles between 0 and nearly 90" to the direction of the normal to the surface, by means of a contactless measuring method, wherein the surface is scanned in strips under programme control and the surface distortions in the measurment signals due to the viewing angles are eliminated so that the measurement signals correspond to a temperature image in cartesian coordinates.

The surface distortion may be eliminated by an electronic computer transforming the measurement signals into a scanning-pattern image with cartesian coordinates and/or by programme-controlled variation of the horizontal and vertical angles of opening of the viewing system.

By means of such measurement data, it is for example possible in the case of a coke oven to automatically control the hot gas feed in such a manner that those wall regions with a temperature which deviates from the desired value can be again brought to the required temperature, so leading to an improvement in the coke quality and in the economy of the coke oven. In addition, the measuring time and personnel required for this method is only a fraction of those for usual methods. Furthermore, with one and the same apparatus, for example all the chamber walls of a coke oven block can be measured one after the other, so leading to considerable cost saving over traditional methods.

It has proved particularly advantageous to use a passive infrared system as the viewing system for the contact-less temperature measurement of wall surfaces.

According to a further development of the invention, it is advantageous for the scanning of the measured wall surface to be carried out such that the viewing system measures a respective narrow strip of the wall by continuous scanning, and the necessary measuring instrument is moved in the direction perpendicular to the scanning, with programme-controlled velocity distribution. In this manner, overlapping of the measured wall strips can be avoided if the wall surfaces are at a large distance, and no unmeasured wall strips remain in the case of close wall surfaces. i.e. the total wall surface is uniformly measured. If the velocity distribution is so chosen that overlapping or gaps in the measured wall surfaces occur, the measurement data is corrected by means of a computer.

The invention also provides a device for determining the temperature distribution on a surface using viewing angles between 0 and nearly 90" to the direction of the normal to the surface, by means of a contact-less measuring method, the device comprising a temperature measurement camera which is displaceable and/or can be swivelled in at least one plane under programme control, an underframe on which the camera is disposed, the underframe being mobile and stoppable and having means for roughly levelling it in all three spacial planes, means for controlling the production of a temperature measurment signal by the camera and for displaying the signal in a scanning image with cartesian coordinates, the camera being arranged to measure strip-wise the temperature of a surface in at least one plane which cuts at the at least one plane of displacement movement and/or of swivel movement at an angle, there being disposed measurement and adjustment means between the camera and underframe for its fine levelling in all three spacial planes, there being provided temperature reference points for indicating the beginning and end of the surface to be measured in a direction of the plane of displacement movement and/or of swivel movement.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure la shows true to scale a coke oven chamber as described in the example; Figure lb shows one of the side walls of the coke oven chamber of Figure la as seen from the camera position (this wall is seen in this manner also by an observer who stands in front of the open chamber door); Figure 2 shows a temperature distribution image in cartesian coordinates of the wall of Figure l b, obtained with the aid of the device as described hereinafter; Figure 3 is a side view of a device according to the invention (the line of vision is parallel to a block of coke ovens, i.e. the walls to be measured extend parallel to the plane of the figure); Figure 4 is a front view of the device according to Figure 3; and Figure 5 is a plan view of the device according to Figure 3.

As an example, the temperature distribution on a chamber wall after pushing out the coke is to be measured in a coke oven having a chamber length of 13 m, a chamber height of 4 m, and a machine-side chamber width of 0.47 m, and to be graphically illustrated. The viewing angle to the normal to the surface is in this case about 88 , i.e. in its distant region, the surface is viewed at an angle of only 2". The vertical viewing angle varies between about 16 in the distant region and 125 in the near region.

A passive infrared system is fitted external to the chamber halfway up the chamber height on a measurement carriage, which can be displaced parallel to the narrow chamber side with adjustable velocity distribution during the measurement. The optical axis of the passive infrared system is parallel to the diagonals of the chamber floor. By means of a special mechanism in the in frared system, the measuring cell receives radiation from the individual surface elements of a wall strip in succession. This operation is repeated continuously, so that after each scanning of a wall strip, the measurement carriage is moved further by an extent such that the passive infrared system measures all wall strips in sucession.

The vertical angle of opening of the infrared system is in this case constant at about 1200 and the horizontal opening angle is about 0.075 . The measurement data is stored on a magnetic tape, and is transformed in an electronic computer in such a manner that the distortions in the surface elements from which the radiation is transmitted, and due to the viewing angle of the infrared system, is eliminated. The results can be recorded directly in cartesian coordinates as a scanning-pattern image, or shown as a television image, as represented in Figure 2.

It is also possible to programme-control the horizontal and vertical opening angles of the infrared system in such a manner that the measurement data stored on the magnetic tape directly corresponds to a temperature image in cartesian coordinates. Finally, it is likewise possible to programme-control only one of the two opening angles, and to eliminate the distortion in the measurement data for the corresponding other wall direction by converting the measurement data in an electronic computer.

This method can in principle also be carried out with other contact-less temperature measurement methods.

Figures 3, 4 and 5 are not shown to scale.

In addition, little constructional detail is shown in these figures as its provision would present little problem to the expert, and it would furthermore impair the clarity of the figures.

Correspondingly, the figures are to be taken only as diagrammatic sketches.

It has been found of particular advantage to provide the device with an underframe which can be (displaced) moved, halted and roughly levelled. Thus the device can be displaced from one measuring position to another without problem. (This underframe could also be in the form of a motor-driven measuring carriage). The underframe must be able to be halted, so that it maintains its position opposite the wall to be measured during the preparation and measurement.

Rough levelling at three or four points facilitates the exact alignment of the measuring apparatus and, in cooperation with a fine levelling apparatus, increases the accuracy of the temperature (in this respect, it has been found that the resolution of the measuring method according to the invention depends to a large extent on the exact positioning and guiding of the measuring instrument). With the aid of the rough levelling, the temperature measuring instrument - known as the camera for short - can also be brought to the required level. As has also been found, it is particularly advantageous to position the camera such that its middle viewing direction corresponds with a middle line on the wall to be measured. It is of particular advantage if rough levelling is possible in all three spacial planes.The underframe of the device is also provided for holding control and recording apparatus amongst other things. Because of this, the apparatus can be of very light construction, and this is a particular advantage for programme-controlled displacement or swivelling operations.

The control and recording apparatus preferably comprises a monitor for operating and controlling the camera, and to the output side of which there is connected an electronic data memory, by which it is possible to preserve measured data which has already been corrected, for querying temperature images, or, in the case of uncorrected measured data, to store this (for its conversion in a computer). If necessary, i.e. if not already attained by another method, the data memory can be subjected to "rear input monitoring" with an oscilloscope connected to its output. This ensures that mistakes in the system are noticed in good time, and a measurement is made only after eliminating the defect, where necessary.Moreover, on the underframe there are also advantageously fitted the control apparatus for the programme-controlled displacement and/or swivelling, and/or for the programme-controlled variation of the horizontal and/or vertical opening angles of the camera, and/or for controlling the levelling apparatus, together if necessary with further electrical apparatus, such as a power pack and the like.

The said apparatuses lead to the greatest degree of resolution, speed and ease of use in temperature distribution measurements.

They can be used either singly or together.

By means of the programme-control for the (displacement) movement and/or swivelling of the camera, and in combination with a stepping motor or the like, it is ensured that the measured wall strips either of the distant region or of the close region do not overlap, and also that some are not smaller than others.

The programme-control for varying the horizontal and/or vertical opening angle of the camera leads to an immediate correction of the corresponding measured data, by which the conversion is at least partly carried out in an electronic computer.

However, such control systems are very expensive and can be employed at acceptable cost only for series measurements and simple geometrical conditions. The control of the levelling apparatus is of great advantage particularly in cooperation with pneumatically or hydraulically operated adjustment means, as it can considerably shorten the time required for accurately carrying out the operation, and saves personnel.

Because of the strip-form scanning of the wall to be measured, the measured value detector in the camera must be able to be moved in accordance with two spacial coordinates. This can be done by purely electronic deflection, as in the case of television cameras, or can be done fully automatically, or by a combination of these two methods.

However, semi-mechanical or purely mechanical methods are preferable, as these are particularly suitable for adaptation to local geometrical conditions, and because it is normally simple to control the corresponding apparatus. In all cases, it is advantageous for the position of the measured value detector to be as variable as possible.

However, it is essential for the camera to be able to be finely levelled in all three spacial planes relative to the underframe by means of measuring and adjustment means, and this can be attained by known devices.

Finally, for the electronic storage and interpretation of the measurement data, it is necessary for the beginning and end of the surface to be measured to be indicated by means of separate signals. It has been found that for this purpose temperature reference points in the direction of the plane of (displacement) movement and/or swivel are particularly suitable. These temperature reference points are fitted into the optical ray path of the camera in such a manner that if these are swept in the said spacial direction, the camera receives one special signal to indicate the beginning, and a second to indicate the end of the wall to be measured.

Such temperature reference points can be of many different forms. The only requirement is that the signal which they give rise to clearly differs from the signals received from the wall to be measured.

Heat protection shields are advantageously provided for a part or the whole of the device, according to the type of camera, the distances from the wall to be measured, and the wall temperatures.

According to a preferred embodiment of the invention, in particular for measuring the temperature distribution on the chamber walls of blocks of coke ovens (Figures 3 to 5), the underframe 1 is displaceable from one coke oven chamber 18 to another coke oven chamber by means of known propulsion apparatus 15. Drivable wheels, for example, are suitable for this purpose. The underframe can be roughly levelled and adjusted in height by means 2. By this means, any rough unevenness of the subsurface can be compensated, and the camera can be positioned at the midheight of the coke oven independently of the height of the camera. The underframe is fixed and adjusted parallel to the chamber opening by means 3. For this purpose, these known means 3, such as for example clips guided on spindles, grip for example on the fixing supports of the blocks of coke ovens.A distortion-free frame 4, which can be finely levelled in all three spacial planes by means 5 and 6, is disposed on the underframe 1, which should be constructed as rigid as possible. The required alignment of this frame is controlled with the help of known measuring devices 11. These measuring devices are located on a slide 7, which is disposed (displaceable) mobile transversely to the wall to be measured, on the distortion-free frame 4. The guiding and positioning of the slide 7 on the frame 4 must be very exact.

The slide 7 supports the camera 8, which is finely adjustable in height by means 9, and can be swivelled about its vertical axis with the aid of means 10. The camera 8 can be altered by means 10 before the first measurement, or for occasional subsequent adjustment, including if necessary in its inclination. The camera itself is advantageously protected by a housing which possesses only one vertical slot for receiving the temperature signal.

As the camera in this case can measure only vertical wall strips, it must be swivelled or displaced in a horizontal plane for embracing the other space coordinates. This can be arranged in two ways: 1. The slide 7 is displaced by means of a precision drive 12 in conjunction with the frame 4 in accordance with a given velocity profile between the two sides of the chamber opening. On attaining the end point, the camera is swivelled with the aid of means 10 through a given angle and then again halted, and the slide 7 then travels back on the frame 4. In this manner, the wall lying opposite the first measured chamber wall can also be measured.

2. Alternatively, the camera is swivelled under programme control in a horizontal plane with the aid of a precision drive 13, and in order to detect the opposite wall, the slide 7 is displaced on the frame 4 through a suitable distance and again halted, after which the camera can also measure the second wall by a further swivel operation.

With the aid of heat protection shields 14, which on the one hand cover the underframe 1 and on the other hand the slide 7 and camera 8 (as far as its viewing slot) and which suitably overlap each other, the total device is protected, at least on the side facing the coke oven chamber, against the not inconsiderable heat radiation of the coke oven walls which are hotter than 1200"C.

Because of the simple handling and matured construction, and the particularly rapid measured value detection of passive infrared systems, an infrared camera which is substantially fitted in known manner with filters, a detector and a rotary mirror, is particularly suitable for the device.

All the control and recording apparatus 16 mentioned in this preferred embodiment and in the aforegoing general description are disposed on the underframe 1 in a manner protected from dust and other harmful environmental influences. The perpendicular frame portions 17 of the coke oven doors act in this example as the temperature reference points.

The device described is extremely precise in spite of its robust construction and its exposure to extreme temperature, dust and possibly weather, and provides with a minimum of work and time high resolution temperature images in cartesian coordinates of a wall which, because of the unfavourable viewing situation, would appear extremely distorted in perspective if viewed through an artificial eye or a normal camera.

WHAT WE CLAIM IS: 1. A method of determining the temperature distribution on a surface using viewing angles betwee 0 and nearly 90" to the direction of the normal to the surface, by means of a contactless measuring method, wherein the surface is scanned in strips under programme control and the surface distortions in the measurement signals due to the viewing angles are eliminated so that the measurement signals correspond to a temperature image in cartesian coordinates.

2. A method as claimed in claim 1, in which the surface distortions are eliminated by an electronic computer transforming the measurement signals into a scanning pattern image with cartesian coordinates and/or by programme-controlled variation of the horizontal and vertical angles of opening of the viewing system.

3. A method as claimed in claim 1 or 2, in which the viewing system is a passive infrared system.

4. A method as claimed in claim 1 or claim 2, in which the viewing system measures a respective narrow strip of the wall by continuous scanning, and the necessary measuring instrument therefore is moved in the direction perpendicular to the scanning, with programme-controlled velocity distribution.

5. A device for determining the temperature distribution on a surface using viewing angles between 0 and nearly 90" to the direction of the normal to the surface, by means of a contact-less measuring method, the device comprising a temperature measurement camera which is displaceable and/ or can be swivelled in at least one plane under programme-control, an underframe on which the camera is disposed, the underframe being mobile and stoppable and having means for roughly levelling it in all three spacial planes, means for controlling the production of a temperature measurement signal by the camera and for displaying the signal in a scanning image with cartesian coordinates, the camera being arranged to measure strip-wise the temperature of a surface in at least one plane which cuts the at least one plane of displacement movement and/or of swivel movement at an angle, there being disposed measurement and adjustment means between the camera and underframe for its fine levelling in all three spacial planes, there being provided temperature reference points for indicating the beginning and end of the surface to be measured in a direction of the plane of displacement movement and/or of swivel movement.

6. A device as claimed in claim 5, in which the controlling and displaying means comprises means for programme control of the horizontal and vertical opening angles of the camera.

7. A device as claimed in claim 5 or 6, in which the controlling and displaying means comprises an electronic computer.

8. A device as claimed in any of claims 5 to 7, in which the controlling and displaying means comprises control and recording apparatus disposed in the under-frame.

9. A device as claimed in any of claims 1 to 8 in which the camera is arranged to measure strip-wise the temperature of a surface in at least one plane which cuts a plane of the displacement and/or swivel movement at 90".

10. A device as claimed in any of claims 5 to 9, provided completely or partly with heat protection shields.

11. A device as claimed in any of claims 5 to 10, for measuring the temperature distribution on the chamber walls of block of coke ovens, in which: (a) the underframe is displaceable between one coke oven chamber and another, can be roughly levelled in a horizontal plane and adjusted in height, and can be fixed on the longitudinal side of the coke oven block and adjusted parallel to the chamber opening; (b) a distortion-free frame on the underframe can be finely levelled in all three spacial planes; (c) a slide, displaceable transversely to the wall to be measured, is disposed on the frame; (d) on the slide there are disposed the camera, which is so positioned that it measures perpendicular wall strips and

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. coke oven walls which are hotter than 1200"C. Because of the simple handling and matured construction, and the particularly rapid measured value detection of passive infrared systems, an infrared camera which is substantially fitted in known manner with filters, a detector and a rotary mirror, is particularly suitable for the device. All the control and recording apparatus 16 mentioned in this preferred embodiment and in the aforegoing general description are disposed on the underframe 1 in a manner protected from dust and other harmful environmental influences. The perpendicular frame portions 17 of the coke oven doors act in this example as the temperature reference points. The device described is extremely precise in spite of its robust construction and its exposure to extreme temperature, dust and possibly weather, and provides with a minimum of work and time high resolution temperature images in cartesian coordinates of a wall which, because of the unfavourable viewing situation, would appear extremely distorted in perspective if viewed through an artificial eye or a normal camera. WHAT WE CLAIM IS:

1. A method of determining the temperature distribution on a surface using viewing angles betwee 0 and nearly 90" to the direction of the normal to the surface, by means of a contactless measuring method, wherein the surface is scanned in strips under programme control and the surface distortions in the measurement signals due to the viewing angles are eliminated so that the measurement signals correspond to a temperature image in cartesian coordinates.

which is finely adjustable in height and can be swivelled and possibly inclined, together with measuring devices for the levelling in all three spacial planes; (e) the slide is displaceable by means of a programme-controlled precision drive on the frame, and the camera can be swivelled in a horizontal plane and halted, or alternatively the slide is displaceable on the frame and the camera can be swivelled in a horizontal plane by means of a programmecontrolled precision drive; (f) the underframe is provided with separate overlapping heat protection shields at least on the side facing the coke oven chamber; and (g) the camera is an infrared camera with a filter-detector and rotary mirror.

12. A method of determining the temperature distribution on a surface, substantially as herein described with reference to the accompanying drawings.

13. A device for determining the temperature distribution on a surface, substantially as herein described with reference to the accompanying drawings.