JP2001027103A - Stationary blade structure for axial turbo-machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the resonance of moving blades without changing the shape of the moving blades at all and without adding a damper by providing half-blades suspended toward the shaft center line from the outer periphery in the middle between the stationary blades at the outlet of the stationary blade cascade installed in the front of the moving blade cascade of an axial turbo-machine. SOLUTION: Half-blades 5 are suspended toward the shaft center from an outer peripheral shroud 3 on the outer peripheral side in the middle between stationary blades 1 at the outlet 6 of a stationary blade cascade 6. When the half-blades 5 are provided, such vibratory force that the apparent number of the stationary blades 1 is doubled is applied to the tip side of moving blades. The resonance rotational frequency is then reduced in half, the vibratory frequency is doubled for the same rotational frequency, and the resonance in the high-order mode can be prevented near the rated rotational frequency. Excessive blade vibration can be prevented, and the fatigue failure of the moving blades can be prevented. Since the half-blades 5 are small-sized, they have little effect on the performance of turbo-machine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a stationary blade row of a turbomachine such as an axial turbine or an axial compressor.
In particular, the present invention relates to a stationary blade structure of a turbomachine capable of damping a moving blade.

[0002]

2. Description of the Related Art FIG. 2 is a partial sectional side view of a gas turbine which is a kind of turbomachine. Gas turbines consist of an air compressor, a combustor and a turbine. The air introduced from the air inlet is compressed by an air compressor to become high-pressure air and is blown into a combustor. The fuel is mixed with the fuel in the combustor and burned to produce high-temperature and high-pressure combustion gas, which is sent to the turbine. In the turbine, the energy of the high-temperature and high-pressure combustion gas is converted into power, and the low-temperature and low-pressure combustion gas is discharged from the exhaust port. A part of the power energy obtained by the turbine is used to drive the air compressor, and the remainder is used to drive a generator or the like coupled to the output shaft. As shown in the figure, the air compressor and the turbine are of an axial flow multistage type.

[0003] Each stage of the air compressor and the turbine has a configuration in which a stationary blade row is arranged before a moving blade row. FIG. 3 is a perspective view of the stationary blade row. In the figure, 1 is a stationary blade, 2 is an inner shroud, and 3 is an outer shroud. As shown in the drawing, the stationary blade row 4 has a structure in which a large number of stationary blades 1 are implanted between annular inner and outer shrouds 2 and 3.

[0004]

The rotor blades of a turbomachine are:
Due to the demand for improved fluid performance, thin wings with complex shapes are used. Such rotor blades generate various modes of vibration at various rotation speeds. The vibration mode has the lowest frequency in the primary mode, and the frequency increases as the mode order increases, such as the second, third,. The shape of the deformation of the rotor blade due to vibration is different for each mode order. FIG. 5 is a drawing in which the magnitude and shape of deformation of a certain moving blade during vibration are calculated by a computer and displayed using a computer graphic (CG) method.
(A) is the primary mode, (B) is the secondary mode, (C) is 3
(D) is a diagram of deformation of each vibration in the seventh mode. As shown in the figure, the primary mode vibration is a vibration in which the tip side of the rotor blade bends back and forth in the thickness direction like a fan. In the secondary mode, the leading edge and the trailing edge on the tip side of the rotor blade are in opposite directions. The third mode is surface vibration of a semi-lunar portion at the trailing edge, and the seventh mode is surface vibration of an elliptical portion at the center of the blade tip side. The shape and amount of deformation of these vibrations depend on the shape of the moving blade.

FIG. 6 is a Campbell diagram drawn to analyze the vibration of the moving blade. The horizontal axis represents the number of rotations N, the vertical axis represents the frequency Hz, the numbers to the right of the many oblique lines represent the order of rotation, and the circles represent the magnitude of the measured value of the vibration stress. The number of turbine vanes used in the creation of this drawing was 2
There are four. As can be seen from this figure, the maximum value of the vibration stress is such that the shaft rotation speed is about 18,000 rpm, the frequency is about 7,
Appears in the seventh vibration mode at 200 Hz, and the order of rotation at that time is 24, which corresponds to the number of stationary blades. From this, assuming that the number of stationary blades is n and the shaft rotation speed is N, nN
It can be seen that when / 60 coincides with the natural frequency of the rotor blade in the seventh vibration mode, resonance occurs and a large vibration stress is generated. When a large vibration stress of high-order mode vibration is generated in a thin portion of the blade such as a tip or a trailing edge of the blade, fatigue fracture proceeds from the vicinity thereof.

In order to prevent such higher order vibration of the moving blade, it is conceivable to change the blade shape and increase the thickness of the blade to avoid resonance. However, such measures cause problems such as deterioration of the performance of the turbomachine and review of design conditions.

[0007] In order to prevent vibration of the moving blade, a damper is provided. FIG. 4 is a perspective view of a damper provided with a Z-shaped shroud 9 at the tip of a moving blade 8 as an example of such a damper. The Z-shaped shroud 9 generates a restraining force between the adjacent wings, and achieves vibration isolation. Such a damper is provided by the above Z
Not limited to the shroud 9, a sniper is provided in the middle of the height direction of the moving blade to give a binding force between adjacent blades,
There is a type in which a small hole is formed in the middle of a moving blade, a racing wire is continuously penetrated therein, and vibration is prevented by a frictional force between the racing wire and the moving blade. However, such a damper causes a decrease in blade performance and an increase in cost due to a complicated structure.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and it is an object of the present invention to prevent the resonance of the moving blade without changing the shape of the moving blade and without adding a damper. It is an object of the present invention to provide a vane structure of a turbomachine capable of performing the above-described operation.

[0009]

In order to achieve the above object, a vane structure of a turbomachine according to the present invention comprises: a vane at an outlet of a vane row installed in front of a rotor row of an axial flow turbomachine. A half-blade is provided at the middle of the blade from the outer periphery toward the axis center line.

[0010] The axial-flow turbomachine may be a turbine or an air compressor.

[0011] The height of the half blade is 1/5 to 1 of the height of the stationary blade.
/ 3 is preferred.

Next, the operation of the present invention will be described. If a half blade is provided at the center of the interval between the stationary blades of the stationary blade row, the same wake-generating force as the doubling of the number of stationary blades will be applied to the tip side of each rotating blade. become. As a result, the resonance rotation speed is halved, and if the rotation speed is the same, the excitation frequency is doubled, so that higher-order mode resonance does not occur near the rated rotation speed which occurs in the conventional rotor blade. In addition, excessive blade vibration can be prevented, and fatigue destruction of the moving blade can be prevented. Since the half blades are small, they have little effect on the performance of the turbomachine.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a partial perspective view of the stationary blade structure of the turbomachine of the present invention. In this figure, the same parts as those of the conventional stationary blade structure described with reference to FIG. In the figure, reference numeral 6 denotes a stationary blade row installed in front of a rotor blade row (not shown) of a turbomachine, which is a turbine or an air compressor. The stationary blade row 6 has a structure in which a number of stationary blades 1 are radially implanted between an annular inner shroud 2 and an outer shroud 3. Reference numeral 5 denotes a half blade, which is provided at the center of each of the stationary blades 1 at the outlet 7 of the stationary blade row 6 so as to hang down from the outer side outer shroud 3 toward an axial center line (not shown). The height of the half blade 5 is preferably 1/5 to 1/3 of the height of the stationary blade 1, and the width of the half blade 5 is 1/3 to 1/2 of the width of the stationary blade 1. Is preferred. The half blade 5 has a substantially triangular shape as shown in the figure.

Next, the operation of the present embodiment will be described. When the half blade 5 is provided at the center of the interval between the stationary blades 1 of the stationary blade row 6, the apparent number of stationary blades 1 is 2
Exciting force by the same wake will be applied as doubled. Therefore, the resonance rotation speed is halved, and the vibration frequency is doubled at the same rotation speed, so that higher-order mode resonance does not occur near the rated rotation speed which has conventionally occurred in the moving blade 8. Thus, excessive blade vibration can be prevented, and fatigue destruction of the moving blade 8 can be prevented. Since the half blades 5 are small, the influence on the performance of the turbomachine is small.

The present invention is not limited to the embodiment described above, and various changes can be made without departing from the gist of the invention. For example, although an example has been described in which the half blades 5 are provided one by one at the center of the interval between the stationary blades 1, the intervals may be equally divided into three and two blades may be provided.

[0016]

As described above, in the vane structure of the turbomachine according to the present invention, since the half blade is provided in the middle of each vane, the number of vanes is apparently doubled for each rotor. Exciting force due to the same wake will be applied. As a result, the rotor blade has an excellent effect such that resonance of a higher mode near the rated rotation speed can be avoided, and fatigue failure of the rotor blade due to excessive blade vibration can be prevented.

[Brief description of the drawings]

FIG. 1 is a partial perspective view of a stationary vane structure of a turbomachine of the present invention.

FIG. 2 is a partial cross-sectional side view of the gas turbine.

FIG. 3 is a partial perspective view of a stationary blade structure of a conventional turbomachine.

FIG. 4 is a perspective view of a rotor blade with a damper.

FIG. 5 is a diagram showing a vibration state of a rotor blade using CG.

FIG. 6 is a Campbell diagram.

[Explanation of symbols]

 Reference Signs List 1 stationary blade 2 inner shroud 3 outer shroud 5 half blade 6 stationary blade row 8 rotor blade

Claims (4)

[Claims] 1. A half-blade hanging from an outer periphery toward an axis center line is provided in the middle of each stator blade at an outlet of a stator blade row installed in front of a rotor blade row of an axial-flow turbomachine. Turbomachinery vane structure. 2. The turbomachine stationary blade structure according to claim 1, wherein the axial-flow turbomachine is a turbine. 3. The turbomachine stationary blade structure according to claim 1, wherein the axial-flow turbomachine is an air compressor. 4. The height of the half blade is 1/5 to 1 of the height of the stationary blade.
The stator blade structure for a turbomachine according to claim 1, wherein the ratio is / 3.