JPH07158404A - Integral shrouded blade - Google Patents

Abstract

PURPOSE:To improve the centrifugal strength of an integral shrouded blade by a large margin and improve aerodynamic performance by forming a shroud, formed at the tip of the blade, into such cross-sectional shape that lift acts downward. CONSTITUTION:An integral shrouded blade 1 is formed of a profile part 2, a blade root part 3 and a shroud 4 integrally formed at the tip of the profile part 2. The shroud 4 is formed into the inverted cross-sectional shape of the blade profile. Downward force thereby works on the shroud 4 by the vertical relative flow during the rotation of the integral shrouded blade 1. This force is proportional to the length of the shroud 4 and also to the square of the relative inflow speed so as to become larger as the blade is longer and the rotating speed is higher. This force can cancel the centrifugal force of the shroud 4 satisfactorily. The centrifugal strength of the integral shrouded blade can be thus improved by a large margin, and aerodynamic performance can be also improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integral shroud blade used for a moving blade of a rotary machine such as a turbine, and more particularly to improving the shape of the shroud.

[0002]

2. Description of the Related Art FIG. 5 is a side view of a conventional integral shroud blade, and FIG. 6 is a plan view thereof. As shown in these drawings, the integral shroud blade 01 includes a profile portion 02, a blade root portion 03, and a shroud 04 integrally formed at the tip of the profile portion 02. And in the conventional integral shroud wing 01,
As is apparent from FIG. 5, the shroud 02 is manufactured to have the same thickness in the axial direction.

[0003]

As described above, since the shroud thickness of the integral shroud blade used in the rotor blade of the conventional rotary machine is the same in the axial direction, the rotor blade becomes long, or When the rotation speed of rotating machinery increases,
There was a problem that the centrifugal strength became severe. In other words, the integral shroud blade has a very high vibration strength due to the large damper effect of the shroud portion, but the centrifugal strength is not improved. This is due to the heavy shroud mounted on the blade tips.

The present invention has been made in order to solve the problems of the prior art, and an object thereof is to provide an integral shroud blade in which centrifugal strength is greatly improved.

[0005]

In order to solve the above problems, the present invention relates to an integral shroud blade having a shroud integrally formed at the tip of the blade, and a lift acts on the shape of the shroud downward. The cross-sectional shape is as follows.

[0006]

According to the above means, by making the shroud shape such that the lifting force acts downward, a downward force acts on the shroud during rotation, and the direction of this force is the centrifugal force acting on the shroud. Since it is the opposite, centrifugal force can be canceled. Then, this lift becomes larger under the condition that the centrifugal force of the shroud becomes larger, so that the centrifugal strength of the integral shroud blade can be greatly improved.

[0007]

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 is a side view of an integral shroud blade according to an embodiment of the present invention, FIG. 2 is a plan view thereof, FIG. 3 is a view for explaining its action, and FIG. 4 is related to another embodiment of the present invention. It is a principal part side view of an integral shroud wing.

As shown in these drawings, the integral shroud blade 1 according to the present invention also has a profile portion 2, a blade root portion 3, and a shroud 4 integrally formed at the tip of the profile portion 2 as in the conventional case. 1 and 4, the shroud 4 has a cross-sectional shape such that lift acts downward, thereby significantly improving centrifugal strength. There is.

That is, by making the shroud 4 have a cross-sectional shape in which the blade profile is reversed as shown in FIG. 1, for example, when the integral shroud blade 1 rotates, a downward force is exerted on the shroud 4 due to a relative flow between the shroud 4 and the shroud 4. Works. That is, as shown in FIG. 3, since the flow velocity v ₁ flowing on the upper surface of the shroud 4 is smaller than the flow velocity v ₂ flowing on the lower surface,
According to Bernoulli's theorem, the pressure p ₁ on the upper surface of the shroud becomes higher than the pressure p ₂ on the lower surface, and the downward force eventually works. The direction of this force is opposite to the direction of the centrifugal force acting on the shroud and serves to cancel the centrifugal force.

By the way, since this force is proportional to the length of the shroud and proportional to the square of the relative inflow velocity, the longer the blade and the higher the rotational speed, the greater the force. That is, the centrifugal force of the shroud increases as the blade length increases and as the rotational speed increases, but this lift force can cancel this centrifugal force well. After all, the centrifugal strength of the integral shroud blade can be significantly improved, and the reliability is greatly improved. In addition, the margin of centrifugal strength that limits the blade length is increased, the blade can be lengthened, and aerodynamic performance can be improved.

[0011]

As described above, according to the present invention, in an integral shroud blade having a shroud integrally formed at the blade tip, the shape of the shroud is set to a cross-sectional shape such that lift acts downward. By doing so, the centrifugal strength of the integral shroud blade can be significantly improved, the reliability can be greatly improved, and the margin of the centrifugal strength that restricts the blade length increases and the blade lengthens. It becomes possible to improve the aerodynamic performance, which is a remarkable effect.

[Brief description of drawings]

FIG. 1 is a side view of an integral shroud blade according to an embodiment of the present invention.

2 is a plan view of the integral shroud blade of FIG. 1. FIG.

FIG. 3 is a view for explaining the operation of the integral shroud blade of FIG.

FIG. 4 is a side view of a main part of an integral shroud according to another embodiment of the present invention.

FIG. 5 is a side view of a conventional integral shroud blade.

6 is a plan view of the integral shroud blade of FIG.

[Explanation of symbols]

 1 integral shroud blade 2 profile part 3 blade root part 4 shroud

Claims (1)

[Claims] 1. An integral shroud blade having an integral shroud blade having a shroud integrally formed at a blade tip, wherein the shroud has a cross-sectional shape such that a lift acts downward.