WO2018137855A1

WO2018137855A1 - Method and device for contactlessly measuring gas temperature profiles, in particular in a gas turbine

Info

Publication number: WO2018137855A1
Application number: PCT/EP2017/083364
Authority: WO
Inventors: Alexandru POPESCU; Andreas Hangauer; Rainer Strzoda; Alexander Ralph Beeck; Maximilian Fleischer
Original assignee: Siemens Aktiengesellschaft
Priority date: 2017-01-27
Filing date: 2017-12-18
Publication date: 2018-08-02
Also published as: DE102017201334A1

Abstract

The invention relates to a method and a device for contactlessly measuring a temperature profile of a gas in an area, in particular in a gas turbine. Light beams with respective wavelengths illuminate (St1) a surface which inwardly delimits the area, in particular the surface of a turbine blade, by means of a light source, wherein points (P_i where i = 1...N) of the illuminated surface can be detected individually, in particular as pixels, by a detection device using a unique visible line (S_i), which has a respective length (l_i), from the light source to the detection device; the temperature (St2) of the gas, through which the respective visible line (S_i) passes, is determined by means of a computing device for each point (P_i) using a quotient of two detected intensities of two light beams having similar wavelengths; and temperatures (St3) of the gas between the surface and the detection device are determined by means of the computing device for a plurality of points (P_i) of the surface, in particular using an integration process.

Description

description

Method and device for non-contact measurement of gas temperature profiles, in particular in a gas turbine

The present invention relates to a method and a device for non-contact measurement of gas temperature profiles, in particular in a gas turbine. Knowledge of the gas temperature is important for the design of the operating mode, the load and the loading of gas or steam turbines. Among other things, the temperature of the gas not only has an effect on the efficiency of a turbine, but also on its service life. Therefore, it is advantageous to know as precisely as possible the temperature distribution of the gas within a turbine. A simulated temperature profile of a gas turbine blade and a surrounding gas is shown in FIG. One recognizes clearly spatially different gas temperatures. A comparison of these simulations with measurement data requires a method that is able to determine the gas temperature resolved after the location. The object of the invention is to provide a method and a device for measuring gas temperature profiles for a room, in particular in a gas turbine, after the location dissolved. Such a method should be executable in very harsh environmental conditions.

The object is achieved by a method according to the main claim and a device according to the independent claim.

According to a first aspect, a method for non-contact measurement of a temperature profile of a gas in a

Space, in particular in a gas turbine, proposed, wherein by means of a light source light beams with respective wavelengths, a space inside the bounding surface, in particular In particular, a turbine blade, illuminate, wherein points Pi of the illuminated surface by means of a unique each having a length Ii line of sight S _i from the light source and back to a detection device of this individually, in particular as pixels, can be detected by means of a computer device for a respective point Pi having means of a quotient of two detected intensities of two mutually similar wavelength light beams is carried out, determining the temperature of the passing of the respective line of sight S _i gas, success end by means of the computer device for a plurality of points P _i of the surface of an, in particular by integrating, determining temperatures of the gas between the surface on the one hand and the detection device on the other hand is performed.

According to a second aspect, a device for non-contact measurement of a temperature profile of a gas in a room, in particular in a gas turbine, proposed, by means of a light source light rays with respective wavelengths, a space inside the limiting surface, in particular a turbulent blade, illuminate points of illuminated surface by means of a unique each having a line of sight from the light source and back to a detection device of this individually, in particular as pixels are detected by means of a computer means for a particular point by a quotient of two detected intensities of two mutually similar wavelengths having light rays determining the temperature of the gas passing through the respective line of sight, by means of the computer means for a plurality of points of the surface, in particular by integrating it Following, determining temperatures of the gas between the surface on the one hand and the detection means on the other hand is carried out.

It has been recognized according to the invention that advantageously non-contact methods should be used as a consequence of very harsh environmental conditions of a turbine. According to the invention a method is proposed which is able to determine temperature profiles along visual lines by means of optical measuring methods. The following advantages may result for the method proposed according to the invention:

It is particularly advantageous that a static temperature can be measured directly and can therefore be concluded, based on the speed of the gas, about its Mach number Ma to a total temperature. This can be done by the following formula:

In this case, κ is an isentropic exponent, RF determines a so-called "recovery factor" or a recovery factor, which can be, for example, in a range from 0.75 to 0.9 to 1, Na determines a Mach number.

In comparison to conventional methods with so-called total temperature probes, a static temperature can not only be estimated, but measured. Estimation using conventional methods that use total temperature probes only allow estimates, since corresponding correction factors of the probes are only insufficiently well known.

Compared to conventional thermography, the proposed method according to the invention allows direct access to the gas temperature, since thermographic processes only allow access to the surface temperature and the latter is dependent on heat transfer and heat transfer. With the knowledge of temperature profiles on the basis of measured data, it is possible to conclude on the efficiency, service life, wear and other parameters, in particular of a gas turbine. This makes it possible, for example, to To optimize the degree of efficiency by changing the design of the turbine or the geometry of the turbine, while extending the service life. If a method according to the invention is used in continuous operation, it is also possible to make predictions about the wear. Likewise, the operation of a turbine with regard to the efficiency and the life or wear can be optimized.

Further advantageous embodiments are claimed with the subclaims.

According to an advantageous embodiment, the temperature of the gas can be calculated in each case by means of the computer device for each individual section of a line of sight.

According to a further advantageous embodiment, the points P ₂ ... P _{N, which} are located closest to a center point which can be predetermined by means of the detection device, can each have a specific temperature in a single point P _i arranged along a scan line of the surface be assigned by the center, the line of sight S _i , S _i-1 , S _N and the scan line definable subregion existing gas.

According to a further advantageous embodiment, for the first point Pi, the subregion may be defined as a circular sector starting from the midpoint with a radius as half the length of the first line of sight Sl and bounded by the first line of sight S _i and the last line of sight S _N.

According to a further advantageous embodiment, for the further points P ₂ ... P _N, the respective subarea can be a circular ring part starting from the center with an outer radius than half the length of the line of sight S _i , an inner radius being half the length the line of sight S _i-1 and bounded by the scan line and the last line of sight S _N de- be Finished.

According to a further advantageous embodiment, the determination of temperatures of the gas for a plurality of scan lines of the surface can be performed.

According to a further advantageous embodiment, the light source for the use of moving or certain surfaces can be switched on and off stroboscopically.

According to a further advantageous embodiment, at least one opening may be formed with a window in an outer wall of the room through which the light source and / or the detection device is detected.

According to a further advantageous embodiment, the light source may be a laser diode, a light-emitting diode or a thermal emitter with filter elements. According to a further advantageous embodiment, the detection device may be a photodiode, a photodiode array or a CCD array or matrix.

According to a further advantageous embodiment, the surface can be selectively illuminated by means of at least one optical system and / or a respective point P _{i can be} detected.

According to a further advantageous embodiment, the size of the optics may be smaller than the size of the illuminated surface.

According to a further advantageous embodiment, the distances of the points P _i to one another and / or the length of the sections can be selected differently.

According to a further advantageous embodiment, by means of the computer device, the respective length li of a line of sight S _i from a known geometry of the space and / or of the surface forming object, in particular the turbine blade, are calculated.

Further advantageous embodiments will be described in more detail in connection with the figures. Show it:

FIG. 1 shows an exemplary embodiment of a simulated temperature profile of a gas turbine blade in a gas environment;

Figure 2 shows an embodiment of a device according to the invention;

FIG. 3 shows a representation of the measuring principle according to the invention;

FIG. 4 shows absorption lines of oxygen,

FIG. 5 shows a calibration curve for a temperature-dependent quotient;

FIG. 6 shows a first illustration for illustrating the measuring method according to the invention; FIG. 7 shows a second illustration to illustrate the measuring method according to the invention;

FIG. 8 shows a third illustration to illustrate the method according to the invention;

FIG. 9 shows a representation with a movable detection device;

FIG. 10 shows a representation with a stationary detection device;

Fig. 11 is an illustration showing a moving illuminated surface; FIG. 12 shows a further illustration of the method according to the invention. FIG. 1 shows a representation of a simulated temperature profile of a gas turbine blade Ts in a gas environment. On the left, the gas turbine blade Ts is shown as a component with an indication of the sectional plane for the representation on the right side. The dashed level on the left is the

Section plane crossed-out circle in which the calculated

Temperature profile is shown. The gas is marked with the reference symbol G.

FIG. 2 shows an illustration of a device according to the invention. A light source 1 mimics light beams having respective wavelengths to a space in a limiting surface Ob, which is embodied as a mirror M according to this embodiment. A detection device 3 detects reflected light rays. The light passes along a path length Δχ a gas G.

FIG. 3 illustrates the principle of the method according to the invention. The so-called Lambert-Beer absorption law is used. Therefore, the fact is used that absorb gases at different temperatures different levels. Transmission measurements of the gas allow a determination, depending on known parameters, of a gas concentration c in space, a temperature T and a pressure p, etc. Lambert-Beer's law can be expressed by the following formula.

The absorption quotient a (lambda) depends on the wavelength lambda, molecular parameters, the temperature T and the pressure p. 1 denotes the length of the path which has been designated above in connection with FIG. 2 by Δχ. FIG. 4 shows a representation of the absorption behavior of oxygen as a function of the oxygen temperature and a respective wavelength of the transmitted light. According to FIG. 4, for the temperature dependence of the transmission or the absorption as a function of the selected wavelength of light, the transmittance is minimal. These lie here for the different temperatures of oxygen, for example at the adjacent wavelengths λι = 759.63 nm and λ ₂ = 759.666 nm. This results in two different absorption quotients a (1) at (c, T) and a2) (c, T). The illustrated absorption lines for oxygen show different courses depending on the temperature of the oxygen, one speaks of different temperature responses. Such representations may alternatively be obtained as well for water vapor, carbon dioxide or other gases.

FIG. 5 shows a calibration curve for temperature-dependent quotients Tr from a quotient formation on the basis of Lambert-Beer's law of absorption, a temperature-dependent calibration curve can be generated, the course of which is shown in FIG. This can be derived as follows (3):

The result is the following quotient:

Hereby determine:

The intensities of the two absorption lines after a run through the distance Δ _x, cs the concentration of the hot gas and I ₀ is the known intensity at the beginning of the path. The known intensity Io may or may not be constant. That is, initial intensities may or may not be identical. Due to the different temperature response of absorption quotients, a clear relationship between temperature T and the intensity quotient Tr can be derived. Conversely, this relationship allows, at known concentration c and distance Δ _x , to determine the temperature T of the gas G by measuring this quotient Tr. This is utilized according to the invention.

Figures 6, 7 and 8 show illustrations for the description of the method according to the invention. The above-mentioned findings are further developed for extracting a temperature profile in a gas space according to the invention.

FIG. 6 shows a first illustration for describing a device according to the invention and a method according to the invention. FIG. 6 shows in cross-section a turbine blade Ts whose surface is partially illuminated by means of a light source 1. By means of a detection device 3, the inner space bounded by an outer wall A in the area of the illuminated surface Ob can be detected, in particular, pixel by pixel. Optics 7 for introducing the light beams and for detecting light beams along respective lines of sight Li for assigned points Pi may be introduced in the respective sight lines S _i . In particular, regions of the outer wall A terminating the gas turbine are suitable for this purpose. FIG. 6 thus represents the first steps of the method according to the invention for extracting the temperature profile of the gas G for a specific space. The method described here will be described below with reference to a 2D projection, Alternatively, it can also be used in three-dimensional 3D space. First, a lighting of a gas turbine can be carried out by means of suitable light sources 1 and optics 7. The outer wall A of the gas turbine can be provided by means of an opening and by means of suitable windows. Through such access, the gas space can be illuminated and the reflected light can be captured again by means of a suitable optical system 7 on a suitable detection device 3 or detector. The light source 1 radiates offset light with suitable wavelengths λ. Embodiments of light sources 1 may be a laser diode (VCSEL) whose wavelength is detuned, other suitable light sources 1 may alternatively be light-emitting diodes (LED) or thermal emitters with suitable filter elements.

The light source 1 and the optics 7 illuminate a defined area of the turbine blade Ts, which is designated with illuminated surface Ob.

By means of the suitable optics 7, the illuminated area of the surface can be guided, for example, onto a photodiode or, depending on the embodiment, onto a photodiode array or a CCD matrix or CD array. The latter also makes it possible to determine 3D temperature profiles. An embodiment is characterized in that only a selective illumination of the surface is carried out Ob and the geometry of the gas space is scanned by means of a suitable non-illustrated mechanics, so as to obtain 2D or 3D temperature profiles. The method described below can be carried out as long as a correct assignment of line of sight Si to respective points P _i with i = 1 N of the illuminated surface Ob is ensured. A respective line of sight Si is defined by the passage of a light beam from the light source 1 to a point Pi on the illuminated surface Ob and back to the detection device 3. In this case, each line of sight S _i can be assigned a unique length Ii. The detection device 3 may have the optics 7, and those of the upper surface of the turbine blade Ts detected reflected light intensity and projected onto a CCD or a photodiode array. The detection can thus be particularly advantageous pixel by pixel.

For the sake of simplicity, it can be assumed that the dimensions of the optics 7 are small compared to the illuminated area. It can therefore be assumed that light rays emanate from the light source 1 and, after a reflection, run back almost the same way to the detection device 3. Each point P _{i of} the illuminated area Ob can advantageously be unambiguously assigned to a beam path from the light source 1 and back to detection device 3 in this way, which is illustrated in FIGS. 7 and 8.

Such a unique assignment makes it possible from the geometry of the gas space to reconstruct the length Ii of a respective line of sight S _i , as will be described mathematically in connection with formula (3) below. Each pixel can thus also be assigned a line of sight S _i . Such lines S _i can then be divided into individual segments or sections Δx _i . The length Δx _{i of} the individual segments with one another does not have to be identical, since the points Pi likewise do not have to be arranged equidistantly, but can be arranged depending on the geometry of the gas space.

FIG. 6 shows the illumination of the gas space, in particular within a gas turbine, and the recording of reflected signals by means of a detection device 3. The illumination of a turbine blade Ts can, for example, be carried out by means of the wavelength around 760 nm for oxygen absorption lines with light of a laser diode. By means of a diode or a charge-capped device (CCD) field, the optical signals can be converted into electrical signals. In FIGS. 6 to 8, respective temperatures are shown in gray scale. FIG. 7 shows, in particular, the division of the illuminated surface of the turbine blade Ts as an exemplary embodiment, a space inside bounding object into discrete points Pi.

FIG. 8 illustrates the embodiment of a detection device 3 in the form of a CCD array or arrays. Accordingly, each illuminated point Pi of the illuminated surface Ob can be assigned to a pixel of the CCD array. If a used optical system 7 is moved, the position of such an optical system 7 corresponds to such a pixel. In particular, Figure 8 shows the light rays contributing to the image on the CCD array. At the bottom right in FIG. 8, the pixels or picture elements of the detection device 3 are initially shown. Each pixel can be assigned a position of a point P _i . Path differences between two adjacent positions are indicated by Δχ _i . Each pixel of the CCD array corresponds to a position P _i on the turbine blade Ts and in this way integrates a TDLS signal over different ones

Ways .

Lambert-Beer's law of absorption now allows integration across all existing lines of sight S _i .

Here, it is considered that the light back passes through twice the distance from the light source 1 to the point P _i and the detector 3, which explains the factor. 2 If one uses the fact that, given a sufficiently large resolution of the CCD array used, a path length difference Δθ between two adjacent points P _i and P _{i +} i is small, the following factorization (4) can be carried out by means of Lambert-Beer's law of absorption :

results in an integration along the path X

Such factorization can also be after a

Quotient formation are carried out for two different Absorptionsl and there is the following equation

causes integration along the path X.

Integral from 0 to X

In this way, a relationship has been calculated which, using the calibration curve according to FIG. 5, permits each individual segment in the region between the illuminated surface

Whether and the light source 1 and the detection device 3 a Temperature T assign. In this case, a respective measured value of each pixel for the different absorption lines together with the relationships described above mathematically flows into one another in the evaluation. This is described in summary below with the formula (6).

An accounting method used according to the invention comprises the following calculation steps:

1. An intensity ratio is measured with the detection device 3:

2. In a second step, the impressed intensity ratio C can easily be deduced from the overall structure and is considered to be constant and in selected cases can be defined as C = 1:

, The calculation of a temperature Ti is performed

th segment Pi from the corresponding Lambert-Beer's law:

The distance between segments Δx _i need not be equal as long as it is known:

4. deriving the respective temperature Ti + i of each successive segment P _{i + 1} from the result of the preceding segment P _i until the last segment P _{N is} calculated:

In a fifth step, the following result is obtained. A set of temperatures _i for a respective individual segment area P _i along a line of sight with a hot gas space part, for example, from the wall on which the detection means 3 is located to a turbine blade Ts of a gas turbine on the opposite side of the outer wall A of the gas turbine. With reference to known methods for determining temperature by means of integration, reference is made to the prior art [1] and [2]:

In summary, the steps described in connection with FIGS. 6 to 8 can still be carried out taking into account the following aspects:

Two suitable absorption lines of the target gas, which have a different temperature response, should be selected. Such lines do not necessarily have to be adjacent. The installation of a suitable light source 1 with at least two advantageous wavelengths for measuring the respective temperature response of the two selected absorption lines of a gas G can be carried out by means of a so-called NDir technique. NDIR stands for Non-Dispersive Infrared. When using such a technique can thermal emitters are used with matching filters as well as LEDs or lasers. Optionally, the wavelength of the light source 1 can also be tuned over two absorption lines, so that one can proceed to spectroscopy as well as using TDLAS (Tunable Diode Laser Absorption Spectroscopy, translated as absorption spectroscopy using tunable laser diodes) or WMS. For this purpose lasers are usually used. The installation of a suitable optics 7 is intended in particular to serve for the defined illumination of the gas space. Likewise, should a suitable optics 7 allow a defined recording of a illuminated area or illuminated surface Ob. Particularly advantageously, the areas of the illumination and the recording should be close to each other, so that light rays can travel approximately the same way from the light source 1 back to the detection device 3. By means of a suitable mechanism, which makes it possible to scan the surface to be illuminated so as to enable a multi-dimensional profile of the temperature, a beam path should be unambiguously assigned for each angle. As an alternative to such a scan operation, a detector array such as a photodiode array or a charge coupled device array may also be used. In this way, each pixel of the field can be assigned a beam path and thus a line of sight Si. Each light beam can be assigned a point Pi on a gas space surface. With sufficient resolution, a path difference Dxi between adjacent points P _i and Pi + ₁ . Thus, an inventive evaluation can be performed and thus a temperature profile can be generated. In this case, a temperature profile can be detected by measurement for any gas space.

FIG. 9 shows an exemplary embodiment of a method according to the invention using a movable, in particular rotating, sensor which has a light source 1 and a detection device 3. FIG. 10 shows an exemplary embodiment of a device for carrying out a method according to the invention, wherein a permanently positioned sensor with a ner light source 1 and a detection device 3 is used together with a fixed position sensor field.

FIG. 11 shows an exemplary embodiment of a method according to the invention, wherein a fixed sensor is used whose light source 1 is additionally switched on and off stroboscopically. Thus, also moving parts, for example in the configuration of moving turbine blades Ts with correspondingly moving illuminated surfaces, can be measured by means of the method according to the invention. Depending on the set phase of stroboscopy, individual turbine blades Tsi can be selected and illuminated.

FIG. 12 once again illustrates an overview of a method according to the invention. In a first step Stl, a metrological detection of light intensities for respective measuring points P _{i takes place} on an illuminated surface Ob in a gas turbine. With a second step St2, a temperature determination ensues from the determination of intensity quotients of different wavelengths of light. With a third step St3, a respective gas temperature _i can be calculated in a space between an illuminated surface Ob and the detection device 3. [1] Ronald K. Hanson, Jay B. Jeffries, Diode Laser Sensors for Ground Testing, 25th AIAA Aerodynamic Measurement Technology and Ground Testing Conference 5 - 8 June 2006, San Francisco, California. [2] CS. Goldenstein et al. , Proc. Combus. Inst. (2014), http: //dx.doi .org / 10.1016 / j .proci .2014.05.027.

Claims

claims

1. A method for non-contact measurement of a temperature profile of a gas in a room,

wherein by means of a light source light beams with respective wavelengths illuminate a surface bounding the space inside (St1), points (P _i with i = 1 ... N) of the illuminated surface by means of a unique line of sight (Si) each having a length (Ii) from the light source and back to a detection device are individually detectable by the latter; by means of a computer device for each point (P _i ) by means of a quotient of two detected intensities of two mutually similar wavelengths having light rays determining the temperature (St2) of the respective line of sight (S _i ) passing gas is executed;

By means of the computer device for a plurality of points (P _i ) of the surface, a determination of temperatures (St3) of the gas between the surface on the one hand and the detection device on the other hand is carried out.

2. The method according to claim 1,

characterized in that

the temperature of the gas is calculated in each case by means of the computer device for each individual section of a line of sight.

3. The method according to claim 1 or 2,

characterized in that

for any nearest to a predeterminable by means of the detecting means midpoint first point (Pi) and further from the first point (Pi) along a scan line of the surface disposed more points (P ₂ ... PN) in each case certain Tempe ^¬ temperature a in one through the center, the line of sight (S _i ), the previous line of sight (S _i-1 ), the last te visual lime (S _N ) and the scan line definable subrange is assigned to existing gas.

4. The method according to claim 3,

characterized in that

for the first point (P ₁ ) the subregion is defined as a circular sector starting from the midpoint with a radius of half the length of the first line of sight (Si) and bounded by the first line of sight (Si) and the last line of sight (S _N ).

5. The method according to claim 3 or 4,

characterized in that

to the other points (P ₂ ... P _N) of the respective Teilbe ^¬ rich as a circular ring part starting from the center to an outer radius than half the length of the line of sight (S _i), an inner radius than half of the length of the preceding Line of sight (S _i-1 ) and limited by the scan line and the last line of sight (S _N ) is defined.

6. The method according to any one of the preceding claims 3 to 5, characterized in that

determining temperatures of the gas for a plurality of scanning lines of the surface is performed.

7. The method according to any one of the preceding claims,

characterized in that

the light source for using moving or certain surfaces is strobed on and off

8. The method according to any one of the preceding claims,

characterized in that

in an outer wall of the space, at least one opening is formed with a window through which the light source transmits and / or detects the detection device.

9. The method according to any one of the preceding claims, characterized in that

the light source is a laser diode, a light emitting diode or a thermal emitter with filter elements.

10. The method according to any one of the preceding claims, characterized in that

the detector is a photodiode, a photodiode array, or a CCD array or array.

11. The method according to any one of the preceding claims, characterized in that

the surface is selectively illuminated by means of at least one optical system and / or a respective point Pi is detected.

12. The method according to claim 11,

characterized in that

The size of the optics is smaller than the size of the illuminated surface.

13. The method according to any one of the preceding claims, characterized in that

the distances of the points Pi to each other and / or the length of the sections are selected differently.

14. The method according to any one of the preceding claims, characterized in that

the respective length Ii of a line of sight Si from a known geometry of the space and / or of the surface forming object, in particular of the turbine blade, is calculated by means of the computer device.

15. A device for non-contact measurement of a temperature profile of a gas (G) in a room, wherein by means of a light source (1) light beams with respective wavelengths a surface bounding the space inside (Ob), in particular a turbine blade (Ts), where points (P _i with i = 1... N) of the illuminated surface by means of a unique line of sight (Si) each having a length (Ii) from the light source (1) and back to a detection device (3) detectable by the latter individually, in particular as pixels;

by means of a computer device (5) for a respective point (P _i ) a determination of the temperature of the gas passing through the respective line of sight (S _i ) is carried out by means of a quotient of two detected intensities of two light beams having similar wavelengths;

by means of the computer device (5) for a multiplicity of points (P _i ) of the surface, in particular by means of integration, determining temperatures of the gas between the surface on the one hand and the detection device (3) on the other hand.

16. The device according to claim 15,

characterized in that

the light source (1) for using moving or certain surfaces (ob) is a stroboscope.

17. Device according to claim 15 or 16,

characterized in that

in an outer wall (A) of the space, at least one opening with a window (F) is formed through which the light source (1) transmits and / or detects the detection device (3).

18. Device according to one of the preceding claims 15 to 17,

characterized in that

the light source (1) is a laser diode, a light-emitting diode or a thermal emitter with filter elements.

19. Device according to one of the preceding claims

15 to 18,

characterized in that

the detection device (3) is a photodiode, a photo diode array or a CCD array or matrix.

20. Device according to one of the preceding claims

15 to 19,

characterized in that

by means of at least one optical system (7) the surface is selectively illuminated and / or a respective point Pi is detected.

21. Device according to claim 20,

characterized in that

the size of the optics (7) is smaller than the size of the illuminated surface.