JPS58220902A - Turbine blade structure - Google Patents

Abstract

PURPOSE:To reduce drain errosion of a movable blade which has not a projection part by forming a projection part on the working fluid inlet side at the top edge of two - 1/2 pieces of the movable blade at the final stage and concentrating the drain errosion to the projection part. CONSTITUTION:Movable blades 1 made of Ti-alloy are implanted onto the outer periphery of a turbine blade wheel 3, and a projection part 6 having a projection amount of 1-30mm. is formed over the length of 1/3 of the total length A of the movable blade 1 at the top edge of a working fluid inlet port side 5 on every four pieces of the movable blade. The number of the projection parts 6 to be installed in the interval is determined so that the drain errosion preventing effect may be obtained with the least number of piece.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a @kaede structure in the final stage of a turbine, and in particular,
Drainage caused by water droplets on the rotor blades of the low-pressure final stage of the steam turbine
Regarding a turbine rotor blade structure that prevents erosion (erosion of blades by water, etc.) [Technical background of the invention] In FIG.
A plurality of sheets g are connected with tie wires 2 to form a group jILI. During rotation, the blade group 1 is deformed by centrifugal force as shown by dots and lines in the figure. The blade protrudes toward the steam inlet side with respect to J11bIC located behind the leading blade IaJd in the rotational direction. Empirically, the amount of protrusion can reach anywhere from 4 to 6 in the case of nine groups of blades 1, where every seven moving blades of 18 to 1 g with a blade length of 800 mm are connected by tie wires 2.

In such a case, drain erosion mainly erodes the leading end R1a protruding toward the steam inlet side, as shown in FIG. 2 as 118 mm of erosion.

Conventionally, in order to prevent drain erosion, a shield made of a hard material such as stellite is welded to the working fluid inlet side surface of the rotor blade tip of the low-pressure final stage where drain erosion is particularly severe, or While the working fluid inlet side of the tip of the rotor blade base material was being hardened, due to the increase in the number of single steam turbines, the rotor blades in the low pressure final stage became longer and longer.
fiIll? The tip peripheral speed of A increases. Therefore, the material of @blade in the low pressure final stage has specific strength (tensile strength/density)
Therefore, a titanium alloy (such as Ti-61-4v) was used instead of the conventional 12Cr steel.

[Problems with background technology]

1- However, an increase in the tip circumferential speed due to an increase in the length of the rotor blade in the low-pressure final stage increases drain erosion. The corrosion resistance of the titanium alloy of the rotor blade is superior to 12 Cr A, but inferior to stellite. Therefore, it is necessary to take measures against long-term movement, QU drain erosion, and the use of titanium alloys.

As a countermeasure against this drain erosion, on the surface of the working fluid inlet 111t1 of the tip of the rotor blade of the low pressure final stage,
It is difficult to weld shields made of hard materials, such as stellite, when the base material is titanium alloy, and this has not yet been achieved.

Further, it has not yet been put to practical use to harden the tip of the rotor blade base material on the working fluid inlet side.

As described above, it has not been possible to take measures against drain erosion of titanium alloy rotor blades using conventional techniques.

[Purpose of the invention]

The present invention eliminates the drawbacks of the conventional ones mentioned above,
It is an object of the present invention to provide a turbine rotor blade structure in which drain erosion caused by water droplets on a rotor blade in a final stage of a turbine is well prevented.

[Summary of the invention]

To achieve the above-mentioned purpose, according to the present invention, a protrusion is provided on the working fluid inlet side of the tips of two rotor blades or 1/2 of the total number of rotor blades in the final stage of the turbine to prevent drain erosion. This is achieved through concentration. This can be achieved more effectively by forming the cross-sectional shape of the protrusion into a warhead shape, by making the protrusion amount 1 to 30, and the radial length approximately 1/3 of the total blade length. .

[Embodiments of the invention]

Hereinafter, the present invention will be explained with reference to embodiments shown in the drawings. Figures 3 and 4 show the turbine @blade structure of the present invention, in which a rotor blade made of titanium alloy is attached to the outer periphery of the turbine wheel 3. 1a, 1b+ lc, ld groups! 9b4 is implanted. And the moving blade 1a.

At the tip of the working fluid inlet side 5 of every fourth moving blade 1a of Ib, tel ld, as shown in FIG. It protrudes with one to three protruding legs 'B, and its cross-sectional shape is formed into a warhead shape.By the way, when the protrusion dimension B of the protrusion 6 is close to O, the drain erosion of the protrusion 6 is concentrated. Since the trapping effect disappears, this outstanding result: B has a minimum critical dimension. Its minimum critical dimension B min is given by the following equation.

Bmin=Vo-K
”・(1)-N However, α: Water droplet correction rate (takes a value of 1,0 to O) R:
Turbine rotation speed (R, P, S) N: Total number of rotor blades vO: Velocity of water droplets (m/s) K: When protrusions are provided every other rotor blade, K: Therefore, the protrusions 6 to 8 The dimensions and how many protruding parts 6 of the rotor blade 1 should be determined can be determined from formula (1) by 2・VD
/ Can be determined using RN as a parameter.

For example, in the case of a rotor blade with a total length of approximately 800 mm, K-4°α
=0.5, Bmin = approximately 5 ho. Experience has shown that if the 8 dimensions of the protruding portion 6 are less than 1 mm, there is almost no drain erosion prevention effect. Furthermore, if the number of eight dimensions of the protruding portion 6 exceeds 30, the steam flow will be disturbed, so there is a maximum limit dimension.

It has been empirically determined from numerous examples of drain erosion that it is sufficient to set the length of the protrusion 6 to about 1/3 of the total length A of the rotor blade. In addition, apart from the above-mentioned parameters, the number of protrusions 6 to be provided on the rotor blades 1 should be determined in order to obtain the desired drain nitride prevention effect with as few protrusions 6 as possible. Consider and decide.

According to the above-mentioned configuration, drain erosion caused by water droplets in steam is concentrated on the protrusions 6 provided every fourth of the rotor blades 1, and the drain erosion of the other rotor blades 1 not provided with the protrusions 6 is concentrated. Erosion can be reduced. In this way, the majority of moving blades do not require anti-drain erosion measures, and drain erosion can be prevented by simply providing the protrusion 6 on a small number of #J blades, so drain erosion can be economically prevented. There is an effect that can be done. Furthermore, since it is only necessary to integrally provide the protruding portions 6 on a small number of rotor blades 1, there is an effect that it can be easily applied to rotor blades made of titanium and alloy, for which it is difficult to weld and harden the shield of stellite.

〔Effect of the invention〕

As explained above [7], the turbine rotor blade structure according to the present invention has two rotor blades in the final stage of the turbine or one of the 172 rotor blades in the final stage of the turbine.・Working fluid inlet 1i11 at the tip of the moving blade
Since the protrusion 1 is provided, drain erosion caused by water droplets on the rotor blades of the final stage of the turbine can be effectively and economically prevented. However, there are still effects that can be easily implemented with titanium alloy rotor blades.

[Brief explanation of drawings]

Fig. 1 is a partial cross-sectional view showing the operating state of a conventional turbine rotor blade structure, and Fig. 2 is a drain and cross-sectional view of a conventional turbine rotor blade structure.
Figure 3 is a diagram showing the amount of erosion caused by erosion;
The figure is an enlarged perspective view of the tip of the turbine rotor blade in FIG. 3. DESCRIPTION OF SYMBOLS 1... Group of blades, 1a to 1g... Moving blade, 2... Tie wire, 3... Turbine wheel, 4... Base, tail... Working fluid inlet side, 6... Projection part . Applicant's agent Kiyoshi Inomata (8) Katsu 1 Kunimo 2 Izumo 3 Kuchi

Claims (1)

[Scope of Claims] 1. A turbine rotor characterized in that a protrusion is provided on the working fluid inlet side of the tips of two rotor blades or 1/2 of the total number of rotor blades in the final stage of the turbine. wing structure. 2. The cross-sectional shape of the protruding part of the working fluid inlet @11j at the tip of the rotor blade is formed into a warhead shape, and the protruding part of the protruding part is 1 to 30 mm, and the radial length is about 1 of the total length of the protrusion. /3
A turbine rotor blade structure according to claim 1, characterized in that: