RU2089878C1 - Method and device for measuring erosion wear of turbine rotor blade edges - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: measurements are made during routine inspections and repairs of turbine which is driven by barring gear with optical pair (emitter and detector) placed on either side of blade ring; intervals from moment of optical axis crossing by entrance edge of blade to moment of crossing it by exit edge of same blade and from moment of optical axis crossing by exit blade of preceding blade to moment of crossing it by exit edge of present blade are recorded by mentioned optical pair. measurements are made in eroding and noneroding areas of blades with emitter and detector installed at desired depth. Prior to do so, mentioned time intervals are determined on noneroded blades for both zones and for each as a function of angle between optical axis and axis of blade revolution; mentioned dependences are determined at least in two positions of optical axis with deviations between them being known. When measuring wear on the basis of relation of time intervals in noneroded area and optical angle position angle as function of time intervals obtained in calibration, deviation optical axis position angle found in current measurement from its position in calibration is determined; degree of wear is found using time intervals relation in eroded area including mentioned angular deviation and optical axis position angle as function of time interval ratio in eroded area obtained in calibration. In order to ensure desired variation in angular position of optical axis, emitter and detector are mounted on turning and sinking rods. EFFECT: improved measurement accuracy. 2 cl, 6 dwg

Description

 The invention relates to measuring equipment and is intended to measure the amount of wear of the leading edges of the working blades of steam turbines during routine inspections and repairs, when the turbine rotates from a shaft-turning device (VPU).

 A known method of measuring the chord of the profile of the blades of a compressor of a turbo engine and a device for its implementation [1] designed for measurements on a stationary turbomachine and providing mechanical engagement with the blade. The device operates as follows. Through the technological hatch, a rod with an end ruler is introduced to the level of the measured chord. The line has two support ledges. The rod moves in a straight line parallel to the measured chord, and allows you to measure the amount of displacement from the position in which one of the supporting protrusions is in contact with the edge of the blade, to the position at which the other supporting protrusion is in contact with the other edge of the blade. The value of the measured chord is the difference between the previously measured distance between the support protrusions and the measured displacement. The device has a micrometer for measuring the amount of displacement and attachment points to the turbo engine housing in the hatch area.

 The accuracy of measuring the chord of blades that are not subject to erosion damage can reach hundredths of a millimeter. However, if there is an erosive relief on the surface of the blade, the method allows you to measure only the maximum chord dimensions in the selected section, and if necessary, evaluate the relief of the worn edge significantly increases the time required to install the rod to a new depth. In addition, the device does not allow measurements when rotating the shaft from the runway, which makes it inapplicable for express diagnostics.

 A known method and device for tracking rotating blades [2] to determine the angle of inclination of the chord of the blade relative to the plane of rotation. The device comprises a radiation source, a detector, consisting of at least two sensitive elements having spatial fields of view for detecting the passage of the input and output edges of the blade, a device for measuring time intervals between events associated with the passage of edges through both fields of view, and a computing a device for determining the angle of inclination of the chord of the blade based on the measured time intervals. As a radiation source, natural light, radioactive radiation or a lamp, a laser, an infrared emitting diode can be used. As a sensitive element of the detector, a photodiode, infrared receiving diode, etc. can be used. The method of measuring the angle of inclination of the chord of the blade relative to the plane of rotation consists in measuring the time between the passage of the edges of the blade in the fields of view of at least two sensing elements and calculating the angle of inclination of the chord of the blade. Along with the specified angle of inclination of the chord of the blade, the device and method allow to calculate the size and speed of movement of the blade, the elevation of its edge.

 The disadvantage of the method and device when it is used to measure erosive wear of the edges of turbine blades is the presence of large measurement errors due to errors in the installation of the detector relative to the blades, temperature deformations, tolerances and fits of the crown of the blades and turbine housing during repairs. In addition, under conditions of significant temperature differences and large time intervals (up to 6 months) between the previous and subsequent measurements, uneven aging of two sensitive elements can occur.This leads to different spatial positions of the moment of operation of the device for measuring time intervals and to the appearance of an additional random error.

 When observing a blade from two significantly spaced angles, the result is influenced by the curvature of the edges. It is almost impossible to take this into account in the presence of erosive wear at the edges.

 An important condition for ensuring the operability of the method [2] is the location of the line of sight normal to the vector of instantaneous speed of the blade, and the optical axes of the sensitive elements of the detector are symmetrical with respect to the line of sight in the same plane in which the line of sight and the velocity vector lie. With a high density of the location of the blades on the shaft, characteristic of turbines, this condition cannot be ensured, and therefore the method and device [2] cannot be used to measure erosive wear of the edges of the working blades.

 Closest to the invention are a device for measuring the erosive wear of the working blades of steam turbines [3] and the method implemented by this device.

 The essence of the method and the prototype device is illustrated in FIG. 6.

 The device comprises a rod with an endoscope 1, in the receiving part of which a lens 2 and a pulsed light source 3 with a node for the formation of light or shadow bands are installed. On the output part of the endoscope mounted photorecorder 4 with a mechanism for intermittent drawing of the film. The rod with the endoscope is fixed in the immersion depth meter (coordinate) 5 mounted on the turbine body. The immersion depth meter 5 allows you to set the rod with the endoscope 1 to a predetermined depth inside the turbine housing. In the flow part of the turbine is installed sensor 6 of the synchronization system. The erosion wear of the input edges of the blades is measured during the rotation of the turbine from the shaft-turning device in the absence of a working fluid (steam) in the turbine. A rod with an endoscope 1 is introduced into the flow part of the turbine between the guides 7 and the working 8 blades. The immersion depth of the endoscope in the turbine housing is set so that its receiving part is located in the area of the input edges of the working blades to be examined. At the moment of passage of the investigated blade, a pulse is generated near the synchronization sensor 6, which, using an electronic circuit (not shown), turns on a pulsed light source 3. The pulse source 3 forms a light zone 9 with clearly defined boundaries on the surface of the input edge of the blade 8. These boundaries are a reference base for determining the quantitative characteristics of wear. To reliably record the amount of blade edge wear, the field of view 10 of the lens 2 is set larger than zone 9. The input edge wear during the turbine operation between measurements is estimated as the difference in the size of the illuminated part of the blade during the previous 11 and subsequent 12 measurements.

 From the description of the operation of the prototype device, the prototype method for periodically monitoring the erosive wear of the edges of the blades is obvious, which consists in installing a rod with a radiation source and receiver, turning on the radiation source at the moment the blade passes in the field of view of the radiation receiver and registering the image of the blade edge in the field of this radiation, removing rods with a radiation source and receiver, processing the received image.

 The disadvantages of the method and device that implements it are the long measurement time due to the presence of slow photochemical processes during film processing, and the measurement error of the magnitude of wear on the photographic images of the blades. The latter are associated with inaccurate installation of the endoscope relative to the blades and with random changes in the moment of switching on the pulsed radiation source. Changes in the moment of switching on the pulsed source between time-spaced measurements (on the basis of which the values of the blade wear are estimated) are due to the displacement of the crown of the working blades along the shaft axis relative to the sensor 6 of the synchronization system. These displacements are associated with temperature changes, tolerances and landings of the crown of the blades and turbine housing during repairs, etc. and are units of centimeters, which leads to changes in the moment of operation of the sensor 6 and, accordingly, the moment of switching on the pulsed radiation source in the subsequent measurement relative to its moment of switching on in the previous measurement. As a result, a random shift of the image fields on the surface of the input edge of the blade occurs and the amount of wear is measured with an error.

 The technical problem solved by the invention is to reduce time and increase measurement accuracy by compensating for random deviations in the mutual orientation of the radiation source and receiver relative to the blade rim during any time-spaced measurements.

 In FIG. 1 shows the proposed device.

 The device comprises a radiation receiver 2, a radiation source 3, a depth gauge 5, a first rotary rod 14, a second rotary rod 15, a worm gear with an angle-code converter 16, a time interval meter 17, and a computing device 18.

In FIG. 2 shows an image of the relative position of the crown of the working blades of the turbine, the radiation source and receiver, where
13 optical axis "radiation source radiation receiver";
C _{i the} linear size of the chord of the i-th working blade;
α _{i the} angle of inclination of the chord of the i-th working blade with respect to the plane of rotation of the shaft;
γ angle between the axis of rotation of the turbine shaft and the optical axis 13.

In FIG. 3 presents time diagrams explaining the principle of operation, where
T _{i the} time interval from the moment the optical axis 13 intersects the trailing edge of the previous blade to the moment the same axis intersects the trailing edge of the i-th blade;
t _{i the} time interval from the moment the optical axis 13 intersects the input edge of the i-th blade to the moment the optical axis intersects the output edge of the same blade.

In FIG. 4 shows the geometry of the working blades in the crown and the location of the wear and wear zones on the edge of the blade, where
β _{i is the} angle between the trailing edge of the previous blade and the trailing edge of the i-th blade;
R _{1 is the} radius of the section in the wear zone;
R _{2 is the} radius of the section in the wear zone.

 In FIG. 5 shows the frequency of the process of measuring the erosive wear of the working blades during operation of the turbine in various modes.

 The essence of the method lies in the fact that in the method for measuring the erosive wear of the edges of the turbine rotor blades, which consists in installing a radiation source and receiver, registering the radiation flux modulated by its intersection by the rotating blades, additionally, the procedures for measuring time intervals in at least two spaced apart the height of the blades of the wear and wear zones and the calculation of corrections to correct the measurement results, and the calibration process is carried out, in addition, and two or more intentional known deviations of the mutual orientation of the radiation source and receiver from their optical axis, while the radiation source and receiver are located on the side of the input and output edges of the blades.

Operating experience of steam turbines shows that
the angle β _i between the trailing edge of the previous blade and the trailing edge of the i-th blade does not change during operation, but is different for each pair of blades,
the angle α _{i of the} inclination of the chord of the blade to the plane of rotation of the shaft does not have residual deformation after steam removal and is constant in the previous and subsequent measurements, but is individual for each blade in each section,
during operation, only the front (input) edges of the blades wear in the peripheral wear zone, and the wear of the input edges in the area near the shaft is negligible.

During the installation of the turbine unit with the assembled crown of the blades, the angle β _i and the initial linear dimensions of the chords of the blades in the controlled sections of the wear and wear zones are measured by known technical means. At the same time, it is practically impossible to measure the angles of inclination α _{i of the} chord of the blades in the same sections with a given accuracy with the assembled crown.

After installing the turbine, but before putting it into operation and the start of the wear process, the calibration process is carried out as follows, the turbine shaft is rotated from the shaft rotary device, the radiation source and receiver are installed from the input and output edges of the worn blades. In this case, the optical axis 13 will be oriented at an unknown angle to the axis of the shaft. Register the radiation flux modulated due to its intersection by rotating blades and for each i-th blade (i = 1, N; N number of blades) time intervals are measured:
T _{11 i} from the moment the optical axis 13 intersects the trailing edge of the previous blade to the moment the same axis intersects the trailing edge of the i-th blade in the wear section when the optical axis is oriented at an unknown angle γ ₁ ;
τ _11i from the moment the optical axis 13 intersects the input edge of the blade to the moment the optical axis 13 intersects the output edge of the same blade in the wear section when the optical axis 13 is oriented at an unknown angle γ ₁ ;
T _21i from the moment of intersection of the optical axis 13 with the trailing edge of the previous blade to the moment of crossing the same axis with the trailing edge of the i-th blade in a non-wearing section when the optical axis is oriented at an unknown angle γ ₂ ;
τ _21i from the moment the optical axis 13 intersects the input edge of the blade to the moment the optical axis 13 intersects the output edge of the same blade in a non-wearing section when the optical axis is oriented at an unknown angle γ ₂ ;
T _12i from the moment the optical axis 13 intersects the trailing edge of the previous blade to the moment the same axis intersects the trailing edge of the i-th blade in the wear section when the optical axis is oriented at an angle (γ ₁ + Δγ), where Δγ is a known angle increment;
t _12i from the moment the optical axis 13 intersects the input edge of the blade to the moment the optical axis 13 intersects the output edge of the same blade in the wear section when the optical axis is oriented at an angle (γ ₁ + Δγ);
T _22i from the moment the optical 13 intersects the trailing edge of the previous blade to the intersection of the same axis with the trailing edge of the i-th blade in a non-wearing section when the optical axis is oriented at an angle (γ ₂ + Δγ);
τ _22i from the moment the optical axis 13 intersects the input edge of the blade to the moment the optical axis 13 intersects the output edge of the same blade in a non-wearing section when the optical axis is oriented at an angle (γ ₂ + Δγ).

где

где C $\genfrac{}{}{0ex}{}{\text{(k)}}{\text{1i}}$ размер хорды i-й лопатки в изнашиваемом сечении до начала процесса износа;
C $\genfrac{}{}{0ex}{}{\text{(k)}}{\text{2i}}$ размер хорды i-й лопатки в неизнашиваемом сечении до начала процесса износа;
вычисляют углы γ_1u и γ₂ по формуле

.After that, the angles α _1i and α _2i are calculated by the formula

Where

where c $\genfrac{}{}{0ex}{}{\text{(k)}}{\text{1i}}$ the size of the chord of the i-th blade in the wear section before the start of the wear process;
C $\genfrac{}{}{0ex}{}{\text{(k)}}{\text{2i}}$ the size of the chord of the i-th blade in a non-wearing section before the start of the wear process;
calculate the angles γ _1u and γ ₂ according to the formula

.

Благодаря тому, что углы преднамеренного отклонения оптической оси 13 Δγ не превосходят 5-10^o, угловое положение хорды a_i можно считать постоянным, не зависящим от конечной толщины и рельефа кромки лопатки.Expressions (1) and (2) determine the relationship between the orientation angle of the optical axis 13 in the wearing and wearing areas of the blade and the ratio of time intervals

Due to the fact that the angles of the deliberate deviation of the optical axis 13 Δγ do not exceed 5-10 ^o , the angular position of the chord a _i can be considered constant, independent of the final thickness and topography of the blade edges.

 This completes the calibration process, the radiation source and the radiation receiver are removed from the turbine housing and it is brought to the operating mode.

During operation of the turbine, erosion of the edges of the blades occurs. To assess the degree of erosive wear of the edges of the blades, subsequent measurements are carried out. After the conclusions of the turbine from the operating mode and cools it during rotation from the shaft-turning device, the temperature in the area of the blades gradually decreases to 50-60 ^o . In the subsequent measurement, the turbine shaft is rotated from the shaft-turning device and the radiation source and receiver are introduced through the holes in the turbine housing to such a depth that the working blades are placed between them in a given section of the wear zone, and the movement of the blades in the gap “radiation source radiation receiver” led to modulation radiation flux. In this case, the optical axis 13 will be oriented to the axis of the shaft at an angle γ with a random deviation dg ₂ due to errors in the installation of the radiation source and receiver relative to the crown of the blades arising due to temperature deformations during operation, tolerances and landings of the crown of the blades and the turbine body during repairs.

где

На этом заканчивается процесс измерения, источник излучения и приемник излучения извлекаются из корпуса турбины и она либо подвергается ремонту, либо вновь выводится на рабочий режим.For each ith blade, time intervals are measured:
T _1i from the moment the optical axis 13 intersects the trailing edge of the previous blade to the moment the same axis intersects the trailing edge of the i-th blade in the wearing section R ₁ ;
τ _1i from the moment the optical axis 13 intersects the input edge of the blade to the moment the optical axis 13 intersects the output edge of the same blade in the wear section R ₁ ;
T _2i from the moment of intersection of the optical axis 13 with the trailing edge of the previous blade to the moment of crossing the same axis with the trailing edge of the i-th blade in a non-wearing section R ₂ ;
τ _2i from the moment the optical axis 13 intersects the input edge of the blade to the moment the optical axis intersects the output edge of the same blade in a non-wearing section R ₂ ;
while the wear of the i-th blade is calculated by the formula
ΔC ₁ = C $\genfrac{}{}{0ex}{}{\text{(k)}}{\text{i}}$ - C _i (3)
where C _{i is the} size of the chord of the i-th blade in the wear section, which is calculated by the formula

Where

This ends the measurement process, the radiation source and the radiation receiver are removed from the turbine housing and it is either being repaired or put back into operation.

 When implementing the method, the most important is the deviation of the line of sight at an angle Δγ, since it largely determines the accuracy and repeatability of measurements, therefore, the technical problem solved by the device is to ensure high accuracy in setting this angle.

 The essence of the device lies in the fact that in the known device consisting of a radiation source and receiver and a device for their positioning relative to the crown of the blades, including a depth gauge and an immersion rod, a second immersion rod of the positioning device is additionally introduced, while the radiation source and receiver are mounted on different rods, and the rods themselves are made with the possibility of their immersion on opposite sides of the crown of the blades and rotation about their axis.

 The inventive device (Fig. 1) contains a depth gauge 5, a radiation source 3, a radiation detector 2, a first rotary rod 14, a second rotary rod 15, and the first 14 and second 15 rods are mounted on the depth gauge 5 with a possibility of rotation about its axis , the radiation source 3 is rigidly fixed to the first rod 14 at a known distance from the axis of the rod, the radiation receiver 2 is rigidly fixed to the second rod 15 at a known distance from the axis of the rod.

 The device operates as follows.

When performing calibration, the immersion depth meter 5 together with the rotary rods 14 and 15 are mounted on the unit body so that the radiation source 3 and receiver 2 are immersed in the turbine body to a depth corresponding to a given radius. The ability to rotate the rods by a predetermined angle can be provided, for example, by a worm mechanism 16 with reading the angle values by an angle-code converter, the shaft of which is rigidly connected to the axis of the rod, and the converter housing is rigidly attached to the immersion depth meter 5. The angular position of the optical axis 13 "radiation source 3 - radiation receiver 2" is changed to a small angle (3-10 ^o ) in one of the following ways:
1. Changing the angular position of the radiation source 3 by turning the first rod 14 by an angle q ₁ with a constant angular position of the radiation receiver 2.

2. Changing the angular position of the radiation detector 2 by rotating the second rod 15 by an angle θ ₂ with a constant angular position of the radiation source 3.

3. Changing the angular position of the radiation source 3 by turning the first rod 14 by an angle θ ₁ and the angular position of the radiation receiver 2 by means of the second rod 15 by an angle θ ₂ at the same time.

где r₁ радиус дуги окружности, по которой перемещается оптический центр источника излучения 3;
r₂ радиус дуги окружности, по которой перемещается оптический центр приемника излучения 2;
D расстояние между центрами указанных окружностей.The value of Δγ is calculated by the formula

where r _{1 is the} radius of the arc of a circle along which the optical center of the radiation source 3 moves;
r _{2 is the} radius of the arc of the circle along which the optical center of the radiation receiver 2 moves;
D is the distance between the centers of the indicated circles.

,
где σ $\genfrac{}{}{0ex}{}{\text{2}}{\text{Δγ}}$ дисперсия оценки угла сдвига оптической оси 13;

дисперсия измерения угла поворота первой штанги;

дисперсия измерения угла поворота второй штанги;
Реально D > r₁ и r₂, смещение оптической оси "источник излучения приемник излучения" задается, таким образом, с более высокой точностью, чем точность поворота соответствующей штанги.The accuracy of determining the angle Δγ for given errors of angular positioning devices is determined by the formula

,
where σ $\genfrac{}{}{0ex}{}{\text{2}}{\text{Δγ}}$ variance of the estimate of the angle of shift of the optical axis 13;

the dispersion of the measurement of the angle of rotation of the first rod;

the variance of the measurement of the angle of rotation of the second rod;
Actually, D> r ₁ and r ₂ , the offset of the optical axis “radiation source radiation receiver” is set, thus, with higher accuracy than the accuracy of rotation of the corresponding rod.

 The radiation source and receiver can operate in any range from ionizing radiation to submillimeter waves. The choice of range is determined by the conditions of the specific application of the method and device. The source can create both continuous and modulated radiation (to increase noise immunity).

 By connecting the output of the radiation receiver to the input of the time interval meter 17 and entering the readings of the immersion depth meter 5, the first rotary rod 14 and the second rotary rod 15 into the computing device 18, the inventive method for measuring the erosive wear of the blades can be implemented.

 The technical advantage of the proposed method and device over similar currently most advanced technical solutions is to increase the accuracy and reduce the time to measure the wear characteristics of the input edges of the turbine blades.

Claims (2)

 1. The method of measuring erosive wear of the edges of the turbine rotor blades, which consists in installing a radiation source and receiver, registering the radiation flux modulated by its intersection with rotating blades, and determining a parameter by which the value of the measured erosive wear is judged, characterized in that the source and the radiation receiver is located on the side of the input and output edges of the blades, respectively, for each blade in its wearing and wearing areas determine the time interval from the moment intersection of the optical axis of the source receiver with the input edge of the blade until the intersection of the said axis with the output edge of the same blade and the time interval from the moment the optical axis intersects the source axis with the output edge of the previous blade until it intersects the output edge of the current blade, based on the ratio of the measured time intervals in the wear zone and the relationship between the orientation angle of the optical axis of the source receiver and the ratio of the specified time intervals for the wear zone, obtained oh during calibration, determine the deviation of the orientation angle of the optical axis of the source receiver during the current measurement from its orientation during calibration, and the wear value is determined by the value of the relations of the mentioned time intervals in the wear zone taking into account the mentioned deviation and the dependence obtained between the orientation angle of the optical axis of the source receiver and the ratio of the indicated time intervals in the wear zone, while the calibration is carried out before the beginning of the process of wear of the blades by installing the source and a radiation receiver in the aforementioned manner with respect to the blades, determining said time intervals in the wearing and wearing areas at least at two positions of the optical axis, the source is a receiver with known angular deviations between them and determining, based on the indicated time intervals and angular deviations of the dependencies between the orientation angle of the optical axis the source is the receiver and the ratio of the indicated time intervals in the wear and wear zones of the blades.  2. A device for measuring the erosive wear of the edges of the turbine blades, consisting of a radiation source and receiver and a device for their positioning relative to the blade rim, including a depth gauge and an immersion rod, characterized in that the positioning device contains a second immersion rod, the source and receiver the radiation is fixed on different rods, and the rods themselves are made with the possibility of immersion on different sides of the crown of the blades and rotation about its axis.

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