JP2008240732A - Method and device for detecting friction in a steam turbine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for detecting friction between components in a steam turbine. <P>SOLUTION: This method includes: step 42 sensing a temperature at a plurality of locations on a casing of the steam turbine; a step 44 comparing the sensed temperatures of the plurality of locations; steps 46, 48, 50 detecting friction between the components if one of the plurality of locations has a higher sensed temperature than the sensed temperature at the other plurality of locations, and a step 52 reporting friction as being at a location near the one of the plurality of locations having the higher sensed temperatures. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to equipment for monitoring a steam turbine, and more particularly to friction detection equipment between rotating and stationary components in a steam turbine.

  Steam turbines include a rotor with rotating turbine blade (bucket) rows between stator blade (nozzle) rows. The turbine bucket tip is adjacent to the turbine casing inner surface. During normal operation, the turbine bucket does not rub the casing. However, subtle deformations of the turbine casing, rotor shaft, inner casing or other components can cause the turbine blades to rub against the stationary casing of the turbine. The friction often occurs at one rotational position, including when the turbine blade tip penetrates the surface of the casing.

  If friction occurs between the turbine bucket and the stationary component of the steam turbine, the turbine component may be damaged, or the gap between the turbine bucket and the casing that is the stationary component may be enlarged. When the gap increases, the air flow path passing through the turbine is deformed, resulting in a decrease in turbine efficiency.

  Excessive friction can cause failure or cracking of the turbine bucket and damage the blades downstream of it. However, it is not easy to detect friction in the steam turbine. Frequently, wear of the turbine component due to friction is detected only by visual inspection. Furthermore, visual inspection of turbine components requires that the turbine be shut down and at least partially disassembled. Therefore, it is required to detect friction without stopping the steam turbine. Although vibration sensors have been used for detecting friction in steam turbines, vibrations in the turbine do not necessarily mean friction. Therefore, the generation position or rotational position of the friction can be determined using a vibration sensor. It is difficult. Accordingly, there has long been a need for a method and system that can reliably detect friction in the steam turbine and determine the location of the friction during steam turbine operation.

  The present invention provides a method for detecting friction between components in a steam turbine. The method includes sensing a temperature at a plurality of locations in a steam turbine casing, comparing the sensed temperatures at the plurality of locations, and one of the plurality of locations having a higher temperature than the other locations. If detected, detecting friction between components of the turbine, and the friction is occurring near one of the plurality of locations where a higher temperature is sensed than the other locations. And a step of recording. The plurality of positions means an annular array perpendicular to a rotor axis, specifically, positions of four sensors arranged symmetrically surrounding the casing on a plane perpendicular to the rotor of the turbine. It can be.

The present invention also provides a method for detecting friction in a steam turbine. The method includes monitoring temperature sensors in at least one sensor array in the turbine casing, comparing measured temperatures of all sensors in the array, and identifying a maximum temperature in the array based on the comparison. Identifying whether the maximum temperature exceeds a threshold, and identifying that a sensor records that the maximum temperature exceeds the threshold, and is near the identified temperature sensor. A step of warning that there may be friction at the position is included.
The present invention further provides a system for detecting friction in a steam turbine having a casing surrounding the rotor. The system includes at least one temperature sensor array mounted on the casing closest to the casing inner surface facing the rotor, and a controller that monitors temperature signals from each of the temperature sensors in the array. The control device is included to warn of the occurrence of friction if one of the temperature signals records a substantially higher temperature than the other temperatures in the array.

  The present invention provides a new system and method for detecting friction by installing a temperature sensor in a turbine casing in a steam turbine. Although friction heat is generated at the friction position, the heat is concentrated on the metal casing. The temperature rise due to the friction in the casing is recorded by a temperature sensor such as a thermocouple incorporated in the casing. Also, the sensor recording the high temperature is determined by comparing the temperature signal records from the thermocouple array. And, if the temperature record from one of the sensors in the array is sufficiently hotter than the other sensors in the array, friction is detected and the position is closest to the temperature sensor that recorded the high temperature. It is determined that friction has occurred.

  Embodiments of the present invention will now be described with reference to the drawings.

  FIG. 1 is a side view of a cross section of a steam turbine 10 having a rotor 12 and a turbine casing 14. In the rotor, turbine rotor buckets (turbine blades) 16 are respectively disposed between rows of a plurality of stator blades (nozzles) 18. For the sake of illustration, the rotor is represented by a dotted line, and one bucket on the rotor shaft is illustrated. There are a pair of stator blades (nozzles) 18 on both sides of the bucket. The tip 17 of each row of the plurality of buckets moves in a region adjacent to the casing inner surface 22.

  A plurality of rows of stator blades 18 extend radially inward from the casing toward the rotor shaft. The plurality of stator blades are attached to a plurality of dovetail mounts 19 on the inner surface of the casing. The rows of turbine buckets extend radially outward from the rotor, i.e., between rows of adjacent stator blades. An annular steam flow path is formed through the rows of the plurality of turbine buckets and the stator blades, and the plurality of rotor buckets and the rotor are rotated by the steam passing therethrough. By rotating the bucket, a plurality of tips of the bucket do not rub against the inner surface of the casing.

  It is conceivable that the surface of the turbine is damaged by friction, and the efficiency of the steam flow path is reduced. Friction is typically caused by the turbine bucket tip 17 rubbing the surface of the casing. The friction is best concentrated at one location on the inner surface of the casing that rubs as multiple bucket tips pass.

  The temperature sensor 20 is incorporated in the turbine casing 14 near the casing inner surface 22 adjacent to the row tips of the plurality of turbine buckets. As the temperature sensor, a plurality of thermocouples that generate an electrical signal indicating the temperature of the adjacent casing can be used. The temperature sensor is mounted in a plurality of holes 24 opened in the casing. The holes can extend from the casing outer surface 26 to a distance as short as a few centimeters to the casing inner surface 22 and are positioned along the casing surface where friction is most likely to occur. For example, the plurality of holes 24 may be at a plurality of positions between the plurality of bearings 23 that support the rotor shaft in the casing. Moreover, the sensor can be positioned in the first row of the plurality of turbine buckets close to the steam inlet by the temperature sensor mounting inclined hole 25.

  The plurality of temperature sensors 20 may be arranged in an annular array surrounding the rotor and on a plane perpendicular to the rotation axis of the rotor. Moreover, you may arrange | position the said several temperature sensor mounted in each plane, for example on the perpendicular or horizontal line which passes along the said plane. That is, four temperature sensors can be arranged at angular positions of 0 degrees, 90 degrees, 180 degrees, and 270 degrees. Since the plurality of temperature sensors can be selectively arranged, the plurality of temperature sensors can be arranged at a radial position of the casing where friction is most likely to occur. For example, when friction is most likely to occur at an angular position of 0 degrees, 90 degrees, 180 degrees, and / or 270 degrees on the casing, a plurality of the temperature sensors are arranged at the angular positions so that the reliability of friction detection is improved. Can be further enhanced.

The larger the casing dimensions, the more temperature sensors are required. Furthermore, it is preferable to install a temperature sensor near a position where friction can occur. Accordingly, in arranging the array of sensors on a plane perpendicular to the rotor axis and in the angular direction of the temperature sensors, respectively, the dimensions of the steam turbine 10 and the angular position at which friction is most likely to occur are described above. The position of the sensor can be selected. Regarding the angular position, it is preferable that the sensors surround the rotor casing symmetrically, for example, by arranging a total of four temperature sensors 20 every 90 degrees. By the way, the longer the distance between the front row and the last row of buckets, the more sensor arrays are required. Further, the plurality of temperature sensor arrays must be installed at a position where the friction is most likely to occur, such as in the vicinity of the first row turbine bucket between the steam inlet and the plurality of bearings 23 supporting the rotor. . Thus, the number of temperature sensors along the length of the casing and the position of each array will vary depending on the dimensions of the steam turbine and the lateral position along the length of the casing where friction is most likely to occur.
The temperature sensor 20 is installed at the distal end of the casing hole 24 and the inclined hole 25 so as to be close to the casing inner surface 22. The temperature sensor also includes an electrical wire or other electrical communication means and sends a signal to a control device such as the computer control device 28. The electric wire extends from the temperature sensor through the casing hole 24 and the inclined hole 25 beyond the casing and reaches the control device. The control device converts the signal from each of the temperature sensors into a reading temperature. The read temperature is a measured temperature or a relative temperature compared to other thermocouples in the array. For example, the computer controller 28 can measure the voltage output for each thermocouple sensor in the temperature sensor array. The voltage output of each of the thermocouple sensors is a measured temperature compared to the voltage output of other thermocouples in one array and the plurality of thermocouples in the other array monitoring the turbine casing. Relative to each other.

  FIG. 2 is a flowchart illustrating an algorithm executed by the controller to detect friction of the steam turbine. The control device includes a computer control device 28 such as a microprocessor for executing instructions of accessible memory such as software. The computer receives a data input signal such as a data signal from a voltage measuring device that measures a voltage output of each of the thermocouples of the casing from a plurality of temperature sensors.

  An algorithm 40 executed by the controller detects the friction that may occur in the steam turbine, for example, the bucket tip and the casing inner surface. The control device monitors the temperature signal of each temperature sensor 20 in each sensor array (step 42). The controller can temporarily store the temperature signal in memory and remove noise and other signal artifacts using filter techniques and averaging.

  The controller compares the temperature signals of all sensors in the array (step 44), and compares the temperature signal with signals from other temperature sensors in the same array, thereby recording the highest temperature. Is identified (step 46). If there is no friction at all, in an array of temperature sensors 20 mounted in a plane perpendicular to the rotor, the plurality of sensors should record approximately the same casing temperature. Therefore, if one sensor records a sufficiently high temperature as compared with the other sensors, it means the occurrence of friction. Friction heat is generated by the friction between the rotor blade tip and the casing facing the tip, and the friction heat propagates throughout the metal casing. The area of the casing closest to the friction generation position heats up, and the temperature sensor closest to the friction area records the maximum temperature.

  To identify the highest temperature, the controller need only identify the highest temperature among the temperatures recorded by all sensors in the array. The controller also determines an average temperature or median temperature for all temperatures recorded by the array. For each temperature recorded by each sensor in the array, the controller determines the temperature difference between the recorded temperature and the average or intermediate temperature. The control device is preprogrammed with a difference threshold value such as “range of 10 to 50 ° C.”. The controller can determine whether the difference between the highest temperature recorded in the array and the average or intermediate temperature exceeds the difference threshold (step 48). Alternatively, the control device may determine whether there is an in-array sensor that records a temperature that exceeds a predetermined threshold. If the maximum temperature measured in the array exceeds the predetermined threshold, the controller determines that one of the sensors in the array records a sufficiently higher temperature than the other sensors (step 48). It is determined that friction is generated in the steam turbine.

  When the computer controller 28 determines that the measured temperature in the array is high enough to indicate friction, the controller identifies the lateral and angular position of the temperature sensor 20 that records the high temperature. (Step 50). The estimated generation position of the friction in the casing is identified from the position of the sensor. The friction is likely to occur in the casing inner surface facing the bucket tip and closest to the sensor recording the maximum temperature.

  The controller warns that there may be friction near the identified temperature sensor (step 52). The alert shown in FIG. 1 includes a visual and audible alert 56 and a data record for a sensor array having sensors identified as being near the friction. The data may include current temperature reading information and temperature reading history from the array. An expert or engineer can determine that there is a possibility of friction generation based on the data.

  The controller periodically repeats the algorithm for all sensor arrays (step 54). The frequency with which the algorithm is repeated, for example, once every 5 minutes for all sensors, varies from turbine to turbine.

  The technical effect of the present invention is to provide means for identifying friction generation and friction generation positions in a steam turbine. The effects include monitoring the temperature in the casing and identifying the high temperature position as the estimated friction occurrence position.

  Although the present invention has been described with respect to the embodiments that are presently considered to be the most practical and preferred, these are merely examples and are not intended to limit the scope of the claims. In addition, it should be understood that the techniques described in the appended claims include various modifications and alterations of the above examples.

It is a side view of a steam turbine casing cross section. 2 is a flow diagram illustrating a method for detecting friction of components of a steam turbine using a thermocouple.

Explanation of symbols

10 steam turbine 12 rotor 14 casing 16 rotor bucket (turbine blade)
17 Turbine blade tip 18 Stator blade (nozzle)
19 Dovetail Mount 20 Temperature Sensor 22 Casing Inner Surface 23 Bearing 24 Casing Hole 25 Inclined Hole 26 Casing Outer Surface 28 Computer Controller 40 Algorithm 42 Sense Temperature 44 Compare Temperature Signals of All Sensors 46 Record Maximum Temperature 48 One of the sensors in the array determines that it is recording a sufficiently higher temperature than the other sensors 50 Identify the lateral and angular position of the sensor recording the high temperature 52 Friction occurs Warn of possible 54 Periodically repeat the algorithm for all sensor arrays 56 Visual and audible alarms

Claims (10)

A method for detecting friction between components (17, 22) of a steam turbine (10),
Sensing temperature at a plurality of locations (24, 25) in the steam turbine casing (42);
Comparing the temperatures recorded at the plurality of positions (44);
Detecting the friction between the components (46, 48, 50) if the temperature recorded at one of the plurality of positions is higher than the other positions; and the plurality The friction detection method further comprises a step (52, 56) of warning that the friction is occurring near one position where the high temperature is recorded among the positions.   The method of claim 1, wherein the plurality of positions (24, 25) are in an annular array perpendicular to the rotor axis.   The plurality of positions (24, 25) are four positions symmetrically surrounding the casing (14) in a plane perpendicular to the rotor in the turbine. The method according to any one.   The method according to claim 3, wherein the four positions (24, 25) are arranged along a normal and a horizontal line extending through the plane.   The friction detection includes comparing each of the recorded temperatures with at least one of an average or intermediate temperature of the recorded temperatures and each of the other temperatures recorded in the array. Item 2. The method according to Item 1.   2. The plurality of locations (24, 25) according to claim 1, wherein the plurality of locations (24, 25) are arranged surrounding a row of steam turbine buckets (16) in an annular array mounted on a casing (14) and on a rotor (12) of the turbine. The method described.   The method of claim 1, wherein the plurality of locations (25) are near an inlet of the turbine.   The method of claim 1, wherein the plurality of locations (24) are approximately midway between a center of the turbine and a plurality of rotor shafts supporting a rotor of the turbine. A method for detecting friction in a steam turbine (10), comprising:
Monitoring (42) a plurality of temperature sensors (20) in at least one sensor array mounted on the turbine casing (14);
Comparing measured temperatures of all sensors in the array (44);
Identifying the highest temperature in the array from the comparison (46);
Determining whether the maximum temperature exceeds a threshold (48);
Identifying (50) the temperature sensor (20) that recorded the highest temperature exceeding the threshold, and warning (52) that friction may occur near the identified temperature sensor
The friction detection method described above.   10. The method of claim 9, further comprising the step (54) of periodically repeating the method steps.

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