JPH06137106A - Vibrationproof device for team turbine blade - Google Patents

Abstract

PURPOSE:To prevent increase of turbine vibration due to resonance of the turbine blade in the final stage when a large-sized steam turbine is operated at low load and small flow. CONSTITUTION:This vibrationproofing device of a steam turbine blade is constituted of a pressure sensor 6 to detect pressure variation on the tip part of a turbine blade 1, processing devices (7,8,9) to obtain the vibration component comformed to the blade frequency from the detected vibration variation, a seal ring 5 which is circumferentially provided inside a turbine casing 2, opposite to the tip part of the turbine blade and movable in the radial direction, and an actuator 10 to move the seal ring 5 in the radial direction according to magnitude of the vibration component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for preventing vibration of a long blade of a rotary moving blade of a large steam turbine, and can be applied to prevent vibration of a long blade of a gas turbine or a compressor.

[0002]

2. Description of the Related Art The relationship between a blade and a turbine casing in the vicinity of the final stage of a conventional steam turbine is shown in FIG. In the figure, reference numeral 1 is a turbine blade, 2 is a turbine casing, 3 is a turbine rotor, and 4 is a seal fin.

The turbine blade 1 and the turbine casing 2 are kept as tight as possible so as not to contact each other in order to maintain airtightness, and in order to make the airtightness more complete, each turbine is provided inside the turbine casing 2. Seal fins 4 are circumferentially provided at positions facing the tip of the blade 1.

The length of the turbine blade 1 increases from the high pressure stage to the low pressure stage, and particularly in a large steam turbine, the turbine blade 1 in the final stage is long.

[0005]

When the steam turbine is operated at a low load and a low flow rate, the steam flow is usually lopsided near the tip of the turbine blade in the final paragraph. At this time, a vortex is generated near the tip of the turbine blade due to the uneven flow, and a small pressure fluctuation is generated. This pressure fluctuation becomes a large exciting force of the turbine blade, and vibrates the turbine blade.

Since the turbine blade has a natural frequency, if the frequency due to pressure fluctuation contains a component that matches the blade frequency, resonance occurs at that frequency and the turbine blade vibration increases. It will be. If such a resonance phenomenon continues, the turbine blade may be cut due to fatigue.

The present invention has been made in view of the above circumstances, and in particular, an apparatus for preventing vibration of a steam turbine blade which can prevent resonance of the turbine blade, which tends to occur during operation of the steam turbine under a low load and a low flow rate. The purpose is to provide.

[0008]

To solve the above-mentioned problems, according to the present invention, a sensor for detecting a pressure change of a steam flow at a tip portion of a turbine blade and a blade vibration frequency by processing a detection signal by the sensor. A processing device for analyzing the matched vibration component, a seal ring facing the tip of the turbine blade and radially movably provided inside the vehicle interior, and a vibration component analyzed by the processing device. And an actuator that moves the seal ring in a radial direction according to the size of the vibration prevention device.

[0009]

According to the above means, the sensor and the processing device take out the vibration component that matches the blade vibration frequency, and when the vibration component exceeds a certain value, move the seal ring to move the tip end of the turbine blade. Change the distance to the passenger compartment,
The frequency of pressure fluctuation due to drift near the tip is changed to reduce the vibration component that matches the blade frequency.

[0010]

1 is a block diagram showing an example of a vibration preventing device for a steam turbine blade according to the present invention. In the figure, the same parts as those shown in FIG. 3 are designated by the same reference numerals. In FIG. 1, reference numeral 5 is a seal ring carrying a seal fin 4, reference numeral 6 is at least one pressure sensor provided in the turbine casing 2 on the outer peripheral side of the tip of the turbine blade 1, and reference numeral 7 is a turbine blade which is known in advance. A band-pass filter that passes only the frequency of 1; 8 is a frequency analyzer that analyzes the frequency components of the signal that has passed through the band-pass filter 7; 9 is an operation signal that records the analyzed frequency components and that corresponds to its level. The computer 10 that outputs the signal indicates an actuator that moves the seal ring 5 in the radial direction based on the operation signal. Here, the band pass filter 7, the frequency analyzer 8 and the computer 9 constitute a processing device.

The seal ring 5 is divided into, for example, eight pieces and is arranged in the circumferential direction. Preferably, an actuator 10 is connected to each seal ring, and a computer 9 connects the tip portion of the turbine blade 1 and the seal fin. Four
The distance c between and is controlled at the same time.

When the steam turbine is operated at a low load and a low flow rate, the turbine blade 1 has a low natural frequency because of its long size. It contains a low frequency component close to the blade frequency. If the frequency of the generated pressure fluctuation is not equal to the blade frequency, a resonance state occurs, the pressure fluctuation increases, and the vibration force on the turbine blade 1 also increases.

The vibration level of this pressure fluctuation is measured by the pressure sensor 6.
And the band pass filter 7 extracts only the components near the blade vibration frequency, and the frequency analyzer 8 analyzes the detailed waveform to obtain the vibration frequency and vibration level. The analyzed components of the frequency and the vibration level are recorded by the computer 9 and the components are evaluated. That is, if the vibration level is below the preset level, the operating state is continued without outputting any operation signal to the actuator 10, and if it exceeds the set level, the actuator operation signal is output. Then
The seal ring 5 is moved outward in the radial direction to increase the distance c. Therefore, the amount of steam flowing to the tip of the turbine blade is reduced, the amount of vortex generation is reduced, and the vibration force on the turbine blade 1 is reduced. As a result, the pressure sensor 6
When the vibration level of the pressure fluctuation detected at 1 is lowered to the set level or less, the operation of the actuator 10 is stopped.

The moving position of the seal ring 5 operated by the actuator 10 is returned to the original position when the operating condition of the steam turbine is changed, and the monitoring of the pressure fluctuation at the tip of the turbine blade is started again in the operating condition. To be done.

FIG. 2 shows the relationship between the generated vibration stress and the amount of movement of the seal fin when the blade vibration is generated. According to FIG. 2, it was confirmed that the generated vibration stress is rapidly reduced by moving the seal ring to increase the distance between the turbine blade tip and the seal fin.

[0016]

According to the present invention, when the pressure fluctuation due to the uneven flow of the steam flow near the turbine blade tip includes a frequency component that matches the blade frequency and the blade vibration increases, the turbine blade tip increases. The vibration component of the pressure fluctuation is changed by changing the interval between the section and the seal fin so that the vibration level does not exceed a predetermined value, so that excessive blade vibration that may cause blade cutout is prevented. be able to.

Further, according to the vibration preventing apparatus of the present invention, since the mechanism for controlling the gap between the tip of the turbine blade and the seal fin is provided, during normal operation of the steam turbine, the seal fin reaches the limit of the turbine. It is possible to bring the blade closer to the blade, which can minimize the seal loss except when abnormal vibration occurs, and improve the efficiency of the turbine.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a configuration example of a vibration preventing device for a steam turbine blade according to the present invention.

FIG. 2 is a relational diagram of generated vibration stress versus movement amount of seal fin, showing a test result by the vibration preventing device for a steam turbine blade of the present invention.

FIG. 3 is an explanatory diagram showing a conceptual shape near a turbine blade tip portion of a conventional steam turbine.

[Explanation of symbols]

 1 Turbine Blade 2 Turbine Cabin 4 Seal Fin 5 Seal Ring 6 Pressure Sensor 7 Band Pass Filter 8 Frequency Analyzer 9 Computer 10 Actuator

Claims (1)

[Claims] 1. A sensor for detecting a pressure change of a steam flow at a tip portion of a turbine blade, a processing device for processing a detection signal by the sensor to analyze a vibration component matching a blade frequency, and a turbine blade of the turbine blade. A seal ring, which faces the front end portion, is provided around the inside of the vehicle compartment so as to be movable in the radial direction, and the seal ring is moved in the radial direction according to the magnitude of the vibration component analyzed by the processing device. A vibration preventing device for a steam turbine blade, comprising: an actuator.