Determining the size of a radial gap

The subject of the invention is a method and apparatus for determining the size of a radial gap between rotating and rotatably fixed construction parts, in particular between such parts of a fluid flow machine. Furthermore, the invention relates to a fluid flow machine with such a device.

Flow-through machines, such as compressors or turbines, have rotating fixed blades arranged alternately in the flow channel on the rims and permanently connected to the rotating rotor of the flow machine rotating blades. The radially outer tops of the rotating blades form radial gaps with the radially outer surface limiting the flow channel. Also, the tips of the guide vanes form radial slots with the inner surface restricting the flow channel, which is formed by the outer surface of the rotor. Various methods are known for measuring these radial gaps during device operation. US 4 384 819 describes the measurement of a radial gap by means of microwaves, which are reflected by the rotating construction part.

US 4,326,804 describes a method of measuring the radial gap between the guide ring and the rotating turbine blades. A light reflecting means is provided at each vertex of the rotating blade which reflects the measuring beam of light, preferably laser light. The reflected light beam is deflected by the lens system on the light point position detector. Its focus appears in the detector at the positions depending on the radial gap from which the radial gap is determined.

53P22129PL00

EP 1 766 327 B1

<td>While</td><td>is performed</td><td>3 measurement</td><td>for</td><td>every</td><td>shoulders</td>

<td>whirling</td><td>for every turn.</td><td></td><td></td><td></td><td></td>

<td>Pose</td><td colspan="2">known from DE 27 30 508</td><td>is</td><td>optical</td><td>way</td>

<td>determination</td><td>space between</td><td>permanent and</td><td colspan="3">spinning element</td>

design. Based on the cone beam emitted by the light source, a light spot is formed in the optical receiver of varying size depending on the size of the aperture, and this light spot is used to measure the distance.

Furthermore, DE 196 01 225 Cl discloses a radial gap inspection device in which a measuring reference point for reflecting light is provided on a turbine blade which is directed to this reference point from a fiber optic probe carried out by turbine housing. During the turbine operation, the differences in the intensity of light received and sent are recognized, which are compared with the differences in the intensity of light determined at the reference measurement. The size of the radial gap is calculated from the deviation of the light intensity difference between the current measurement and the reference value.

Furthermore, from EP 492 381 A2 a method is known for measuring the apical clearance on turbine blades by means of an optical transmitter and receiver, the receiver receiving the light reflected from the turbine blades and the course of reflected light is analyzed.

This method is based on placing the transmitter and receiver in the form of a sensor in a static system, for example on the outer boundary wall or on the housing, so that optical phenomena can be used

53P22129PL00

EP 1 766 327 B1 recognizes the rotating construction part extending past the receiver or sensor tip or determines the distance from this part at this time.

In general, these methods are characterized by the fact that the receivers or sensors used cannot be miniaturized below a certain limit, and therefore have an indisputable mass. In addition, some methods require the use of expensive electronics in power systems or transmitters.

Such sensors cannot be mounted on the tip of a freely fixed steering blade of a fluid flow machine, because such a sensor would negatively affect the natural vibration characteristics of the steering vanes. During operation, they could fall into vibrations, which shortens the life of the blades.

Placing sensors in a rotating system is often impossible or requires high expenditures on often expensive electronics. When sensors, or especially receivers, are provided in a rotating system, a costly and disturbance-sensitive telemetry installation is needed to extract information from such a system, which increases the overall cost of the device.

The object of the invention is to provide a low-cost and reliable method and device for determining the size of the radial gap between rotating and rotatably fixed construction parts, which contain sensors of relatively low mass and low volume.

In addition, the device and method should meet general requirements, such as resistance to pressure and temperature, a large range of work, that is, they should show

53P22129PL00

EP 1 766 327 Bl dynamics in terms of operating temperature and rotational speed, and / or should not require adjustment or calibration. Another object of the invention is to propose the use of such a device for controlling a radial gap.

The task of the method is solved by the characteristic features of claim 1 or claim 2. The task of the device is solved by the characteristic features of claim 8 or the characteristic features of claim 11. The last-mentioned task is solved by the characteristic features of claim

Preferred embodiments are each time presented in the additional claims.

In the method solution, it is envisaged that in order to determine the size of the radial gap between the rotating and rotatably fixed construction parts, especially between the parts of the fluid flow machine, the source signal sent in the form of radio waves from the transmitting device located on the surface of the rotating construction part is received by the receiving device placed on structural part rotated and is transferred to the analyzing device, which of the received signal determines and indicates the size of the radial gap by determining the parameters of the curvilinear path (determination of the trajectory) of the rotating transmission device.

Another solution of the task focused on the method of implementation provides that in order to determine the size of the radial gap between rotating and rotatably fixed construction parts, especially between parts of the flow machine, the source signal is sent

53P22129PL00

EP 1 766 327 Bl or also radiated as a radio wave from a transmitting device placed on a rotatably fixed construction part is reflected with modulation by a structural mirror structure placed on a rotating construction part, three ectoria, determining its size of the gap and such a signal is received by the receiving device placed on a rotatably fixed construction part and is transferred to the analyzing device, which of the received signal uses its modulation relative to the source signal to determine the parameters of the curvilinear path (determination of the trajectory) of the rotating mirror structure to determine and show the size of the radial gap.

Both of these solutions are based on the idea of ​​the invention in that by determining the parameters of the curvilinear path of a point located on the rotating part, i.e. by which it can be determined radial. The position of the receiving device is used for this as a fixed reference point.

At least periodically, the distance varying at any time depending on the angle of rotation of the rotating construction part is determined between a particular rotating point, which can be firstly placed on the rotating construction part or the transmitting device and, secondly, the mirror structure, and the position of the receiving device as a fixed reference point. The graph of the distance function depending on the torsion angle is created by the analyzing device (determining the trajectory) and the required parameters come from it, namely the minimum distance between the rotating device

53P22129PL00

A transmission and pivoting receiving device which corresponds to a radial gap between the rotating and the pivoting construction part.

Radio waves have the advantage over optical waves that they can be produced, transmitted, emitted, received and processed using relatively simple electronic components. In addition, thanks to the use of radio waves, a particularly wide range of applications is obtained, i.e. the dynamics of work.

In a preferred embodiment, the signals are high frequency electromagnetic radio waves! Hf;

in the range between 0.5 MHz and 100 GHz, especially with a frequency in the range of

100

MHz up to 10 GHz. The use of electromagnetic radio waves allows, in principle, to become independent of the environment existing in the radial gap. In addition, relatively small and light, as well as low-cost transmitters / receivers with high resolution and dynamics are available for electromagnetic radio waves, which enable differential measurement of the radial gap at high rotational speeds, such as those found in flow-through machines.

According to a further preferred embodiment, the analyzing device uses the field strength or the intensity of the received signal to determine the distance between the rotating point and the reference point. A circulating or rotating transmission device as a specific point approaches and moves periodically on its curvilinear path relative to the established receiving device, so that depending on the distance between the two devices is taken over by

53P22129PL00

The use of a receiving device is a constantly changing signal of field strength or intensity. At the same time, the field strength or the intensity of the received signal are greatest at the place where the transmitting device and the receiving device are opposite each other in the shortest distance. In the case of electromagnetic field strength as a signal.

Instead of a transmitting device, a mirror structure can be provided on the rotating construction part that reflects the source signal emitted as radio waves from a rotatably fixed transmitting device to a permanently mounted receiving device. Modulation is carried out here, i.e. a change in the source signal that is recognized by the analyzing device. In addition, the analyzing device is equipped analogously to the first solution.

The trajectory, i.e. the parameters of the curvilinear path of a particular rotating point on a circular path, can be determined alternatively, i.e. instead of measuring the intensity or field strength, the frequency of the received signal caused by the Doppler phenomenon is used. In a mobile transmitting device, the source signal emitted from it as radio waves is modulated by the Doppler effect.

According to a preferred proposal, the analyzing device filters the Doppler frequency, i.e. the differential frequency of the received signal, from the received signal by demodulation. Based on the duration of the change in the differential frequency you can here

53P22129PL00

EP 1 766 327 B1 determine the size of the radial gap.

The first solution of the device-oriented task provides that for carrying out the method according to one of claims 1 or 3 to 7 regarding the determination of a radial gap between rotating and rotatably fixed construction parts, especially between parts of a fluid flow machine, a radio transmitting device is placed on the rotating construction part at a high frequency, and on the rotatably fixed construction part there is a receiving device receiving high-frequency radio waves, which communicates with the analyzing device.

In a preferred embodiment of the device, the transmitter can be supplied with energy from the rotationally fixed construction part by inductive coupling. Alternatively, the transmitter can be powered from a battery also located on a rotating construction part. Thus, it is possible to supply the transmitter without contact without causing wear to the contacting elements. The economically designed transmitter can be powered by batteries for several years, for example, until the maintenance of the fluid machine, when the rotor is exposed and the battery can be replaced.

The second solution of the task directed towards the device provides that for carrying out the method according to one of claims 2 to 7, concerning the determination of a radial gap between rotating and fixed construction parts, especially between a fluid flow machine, a mirror structure is placed on the rotating construction part through which the parts can be rotatably

53P22129PL00

High frequency radio waves are received and constructed and high frequency radio waves are transmitted and a transmitting and receiving device processing high frequency radio waves is arranged on the rotationally fixed portion, the receiving device communicating with the analyzing device.

Intentionally, the mirror structure is formed by a dipole with an HF diode placed on the insulating support layer, which is preferably made as a non-linear passive dipole. This dipole receives the source signal emitted by the transmitting device and sends back by means of the HF diode electromagnetic waves with approximately double frequency, which are also modulated as a result of rotation by the Doppler phenomenon. The receiving device filters out electromagnetic waves with doubled transmission frequency from the received signal and transmits them to the analyzing device. Thanks to this, the electromagnetic waves reflected from the metal or flat surfaces of the rotating construction part, which have the same frequency as the source signal, are ignored. The devices operate on radio waves with a frequency in the range between 0.5 MHZ and 100 GHz, preferably 100 MHz and 10 GHz.

The transmitting device and the receiving device can be arranged coaxially when each of these devices has a transmitting antenna or also a receiving antenna which has a point or linear radiation pattern.

The solution to the task directed to the application of the invention proposes that the fluid flow machine is equipped with a device according to one of the claims 9 to 13 or 14 to

53P22129PL00

EP 1 766 327 B1

The method of claim 17, wherein the method of one of claims 1-7 can be implemented. In this way, the radial gaps of the flow machine, preferably constructed as a stationary gas turbine, can be controlled, which can take critical values ​​especially when the hot machine is started in a hot state. In addition, a particularly accurate axial displacement of the rotor of the fluid machine having a conical flow channel can be made to increase its efficiency. Thanks to this, the medium can flow according to the intended use of the rotating blades of the flow machine, while the flow losses caused by the radial gap at the vertex of the blades can be minimized.

The invention is explained on the basis of a drawing that shows:

Fig. 1 schematically a measuring system for determining the parameters of a relative curvilinear path of a rotating point, Fig. 2 graph of distance function s = f (φ), Fig. 3 graph of velocity function ds / d ((p), Fig. 4 differential frequency modulated by the phenomenon

Doppler acoustic signal of a mobile transmitting device, Fig. 5 differential frequency of the HF Doppler modulated electromagnetic signal of a mobile transmitting device, Fig. 6 schematic representation of a flow machine made as a gas turbine, Fig. 7 the device of the invention for determining the size of a radial gap and

53P22129PL00

Fig. 8 an alternative device according to the invention for determining a radial gap.

Fig. 6 shows, according to the invention, a flow machine 1 in the form of a gas turbine with a compressor 3, a combustion chamber 5 and a turbine unit 7. In the compressor 3 on the gas turbine rotor 9 there are rotating blades 13, which by means of 10 vanes mounted on the housing 10 compress sucked air stream 15 in the flow channel 6. In the combustion chamber 5, the compressed air stream 15 is burned after adding fuel to hot gas 17, which expands to generate power in the turbine unit 7 on the guide vanes 11 and the rotating blades 13. At the same time, the rotor 9 is driven, which, in addition to compressor 3, also drives the machine working, for example, an electric generator.

Fig. 1 shows a fragment of the measuring system according to the proposed trajectory method. Around the beginning of P (0,0) the Cartesian coordinate system P (x, y), through which the rotational axis 2 of the gas turbine rotor 9 runs, the radiator 22 rotates along the circular path K, the radiator 22 can be positioned on the rotor surface 9, which is the inner surface delimiting the flow channel 6 of the gas turbine.

In this case, the pivotally arranged receiving device 24 is located outside the circular path K, for example at the free end of the gas turbine guide blade 11, which blade is opposite the internal restraining surface forming a radial gap 18 (Fig. 6).

Distance s between constantly changing position

53P22129PL00

The transmitting device 22 and receiving device 24 is determined at least periodically. The minimum value of distance s is the controlled and determined distance s, which in the gas turbine is to be determined as the size of the radial gap between the rotatably fixed and rotating construction parts.

When rotor 9 rotates at a constant angular velocity, there is a functional relationship in time and space between distance s and rotation angle φ of rotor 9 and distance s₀:

s = f (cp, So), (1) which is reproduced at least partly in the diagram of Fig. 2. The considered section of the rotation angle φ extends from 86 ° to 94 ° assuming that the receiving device 24 mounted on the free guide blade at point P (0, y_E), i.e. the receiving device 24 lies on the ordinate.

In a measuring system with a radius r = 0.5 m of rotor 9, Fig. 2 shows the relationship of distance s from the rotation angle φ for three different intervals So, so that three different relative curvilinear paths are created. Fig. 2 shows the three resulting graphs 26 of distance functions. Each distance function chart 26 has a relative minimum of 27 of the designated 27 curvilinear path of the transmission device 24 at an angle φ = 90 °.

The distance so is to be measured during operation, so it is expedient if instead of distance s the speed of the transmitting device 24 is measured by the first derivative ds / d (cp) of distance s.

The first derivative of the distance function shown in Fig. 2 is shown in Fig. 3 as a function

53P22129PL00

EP 1 766 327 Bl speed. The slopes of the 28 speed functions graphs vary depending on the existing minimum distance s₀. The graphs 28 of the speed functions flatten the more the smaller the minimum distance So between the transmitting device 22 and the receiving device 23 at an angle φ = 90 °.

Determining the required torsion angle φφ at which the graph 28 of the velocity functions lies within the range [G_ATG_ABOUT] defined by the lower speed limit G_at and the upper speed limit G_about, you can specify the size of the gap. The determined torsion angle φznacz is proportional to the size of the radial gap 18, i.e. to the distance So. At a constant angular velocity of the rotor 9, which is necessary for generating power with stationary fluid flow machines, the torsion angle φφ can be linearly converted for the duration.

Different signals can be used to measure distances, i.e. different signal carriers, and different detection methods. The carriers are acoustic waves or also ultrasonic waves or electromagnetic radio waves. Doppler effect can be used as the detection method for measuring the intensity of acoustic waves or for measuring electromagnetic radio waves detection for both carriers.

The method of detection based on the Doppler phenomenon is described below.

Fig. 4 shows the field strength filtered from the received signal

In addition, as a method, differential frequencies using ultrasound-based transmitting and receiving devices 22,

53P22129PL00

EP 1 756 327 B1

24. If a radial gap is determined, e.g. at transmission frequency f₀ = 40 kHz, radius r = 0.5 m and rotation speed n = 3600 min '¹ with the use of ultrasound-based transmitting and receiving devices, it can be concluded that only in the twisting angle range φφ * ± 2 ° can a useful and differential signal be received. However, at the transmission frequency f₀ = 40 kHz falls within this range only about 4-6 oscillations, therefore in application to a flow machine with a rotational speed of n = 3600 min '¹ only conditionally sufficiently accurate differentiation of the plots of Doppler frequency functions is possible. If it is necessary to control radial gaps 18 at a lower rotational speed, then ultrasonic-based transmitting and receiving devices 22, 24 can be used sufficiently effectively.

Assuming constant wave propagation velocity, analysis of Doppler equation for approaching

<img file="PL1766327T3_D0001.tif" />

fi for zooming out: 3) shows that the expected frequency hop, i.e. frequency range, differential frequencies, transmission frequencies.

in which lie expected is proportional to

Thus, the highest possible transmission frequency is preferred to receive a signal that is particularly well suited for analysis.

When instead of an ultrasound-based device

53P22129PL00

For transmitting and receiving transmissions, a high frequency (HF) transmitting and receiving device will be used, for example with a transmission frequency of f₀ = 435 MHz, it is possible to accurately differentiate the Doppler frequency function chart determined by the analyzing device 30. As a result, it is possible to filter particularly well-analyzed Doppler frequencies from the received signal in this case. In the selected example they have a frequency jump [-280 Hz, 280 Hz].

Fig. 5 shows graphs 30 of the Doppler frequency function with the parameters identical to Fig. 4. From the slope of the respective graphs 30 ', 30 ", 30' '' of the Doppler frequency, the associated gap size and the distance So can be determined.

Transmission frequency selected in the example f₀ = 435 MHz is available for telemetry. In addition, inexpensive, functional and miniaturized transmitting / receiving elements in the form of SMD (Surface Mounted Device) are commercially available, the weight of which is negligible compared to a freely determined steering vane. Higher frequencies can also be obtained if required.

The differential frequency can be obtained by modulating the frequency of the received signal. The desired size of the gap can be derived from the specified torsion angle φφ, which is determined from the period of time in which the graph of the differential frequency function 30 lies in the frequency range [-200 Hz, +200 Hz]. For example, a signal processor can be used for signal analysis.

53P22129PL00

EP 1 766 327 B1

A range of about 20 cm is sufficient for the transmitting and receiving devices 22, 24, so that very low transmit power in the sub-MW range is sufficient. As a result, very low power consumption of the transmitting device 22 can be expected, which allows installation in a rotating system. The energy needed for transmission can be contactlessly (inductively) supplied to the rotating system. An alternative solution may also be battery power with ordinary lithium cells, which allow for sufficient life. In addition, due to the limited range, the radial gap is only determined from time to time.

It should also be pointed out that for determining the distance function s = ί (φ, So) instead of the differential frequency one could use similarly the intensity of the electromagnetic signal field or the intensity of the acoustic wave.

The processing technique associated with determining the distance function based on the Doppler effect is further explained, since it does not depend on the form of the selected signal. After determining the field strength, intensity course or frequency shift, the method of trajectory technology associated with the size of the gap is used.

Figures 7 and 8 schematically show several structural members of the measuring chain for determining the size of the radial gap between the rotating and stationary system, i.e. between the rotating and stationary construction parts.

for all with appointment

53P22129PL00

EP 1 766 327 B1

Fig. 7 shows an embodiment of the invention in which the transmitting device 22 together with the power supply is arranged in a rotating system, for example on a rotor. The transmitting device 22 has an energy source 32, a frequency generator 34 and a transmitting antenna 36.

The stationary system for its part contains a receiving antenna 40. The 24 "Doppler receiving device contains the FM 41 demodulator and the HF 42 oscillator. When instead of the Doppler phenomenon the field strength or the intensity of the received signal is used, the 24 'receiving device in addition to the receiving antenna 40 has a field strength detector 43.

The receiving device 24 is coupled to the analyzing device 48 in which the trajectory is determined.

An alternative embodiment is shown in Fig. 8. The combined transmitting and receiving device 50, which is connected to the analyzing device 48, is fixed.

When the differential frequency due to the Doppler phenomenon is to be used to determine the gap size, the combined transmitting and receiving device 50 "in addition to the transmitting and receiving antenna 51 has an HF 42 oscillator, a frequency generator 34 and an FM 41 demodulator. When measuring the field strength or also measuring intensity, this combined transmitting and receiving device 50 'includes a frequency generator 34 and a field strength detector 43.

A primary signal emitted from the transmitting and receiving devices 50 with a frequency of f_s is changed by a rotating system on which a mirror structure 52 is placed, for example a non-linear passive dipole with a diode

53P22129PL00

EP 1 766 327 BI

HF, which is placed on the insulating layer or also the carrier layer which does not reflect electromagnetic radio waves. The dipole receives the original signal if it is within the range of the transmitting and receiving antenna 51. The non-linear dipole doubles the frequency f with the HF diode_s received primary signal and sends back a signal with a double frequency f_E as a received signal back to the receiving device. The dipole movement along the circular path K modulates the reflected signal, so that the transmit and receive antenna 51 can receive a dual frequency modulated signal and a Doppler modulated signal. The receiving device 50 extracts, i.e. filters only the doubled frequency signal f from the received frequency spectrum_E and transmits it to the analyzing device 48. This device, through the changing field strength or the changing Doppler frequency of the received signal, determines the parameters of the curvilinear path (trajectory determination), from which the size of the radial gap between the rotating and stationary system or the structural part can be determined.

The receiving device ignores or filters out reflections of the source signal arising from smooth surfaces or otherwise that basically have the same frequency as the source signal.

The devices according to the invention have the advantage that they can be used in a temperature range from 0 ° C to 450 ° C. In addition, the detection method does not depend on the surface quality or the geometrical and physical properties of the rotating construction part. In addition, these devices do not require adjustment, and only after the first installation is needed

53P22129PL00

EP 1 766 327 Bl calibration, which is sufficient for the entire lifetime of the device.

The sensors are relatively light and small, which makes it possible to measure the radial gap existing between the tip of the freely fixed steering vane and the rotor hub. Of course, one can also imagine such a use in which a free-form or bandage mirror structure or transmitting device is provided at the top of the rotating blade and at least a receiving antenna of the receiving device is provided on the outer boundary surface.

For example, when each rotating blade of a vane rim has a transmitting device and / or multiple receiving antennas are arranged on the periphery, the determination of the size of the gap can be even more streamlined or it can take place simultaneously in many places.