JPS63179101A - Axial flow turbine - Google Patents

Abstract

PURPOSE:To prevent growing of counter vortex and to reduce vibration exciting force functioning onto the entire blade, by arranging at least one layer of an annular flow guide on a static blade arranged at a low pressure stage of an axial flow turbine or between the static blade and a dynamic blade. CONSTITUTION:At least one layer of an annular flow guide 7 is arranged on a static blade 1 arranged at a low pressure step of an axial flow turbine or between said static blade 1 and a dynamic blade 2. The flow guide 7 is formed into wing type and welded to a stay 6 at a point separated from a casing 3. Consequently, when a small volume of steam is flowing, promotion of counter vortex at the casing 3 side is retarded by the flow guide 7. As a result, vibration exciting force being produced by the counter vortex at the casing 3 side functioning to the tip of the dynamic blase 2 and causing vibration of the entire blade can be reduced, resulting in protection of the blade from breakdown.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to steam turbine and gas turbine low pressure stage vanes, and is used in the technical field of reducing fluid excitation force.

Prior Art As an example of the prior art, FIG. 9 shows a flow situation at a small volume flow rate in the low-pressure final stage of a steam turbine.

When the turbine is operated under extremely low load or no load, the flow rate is small in the low-pressure final stage and the turbine outlet pressure is high, so the steam flow 5 is biased towards the casing 3 side due to the rotational force of the rotor blades 2. , there is a large backflow vortex 5 on the root side 2b of the rotor blade 2.
b is generated, and also on the casing 3 side, a backflow vortex 5a
occurs.

Problems to be Solved by the Invention In the flow accompanied by the above-mentioned backflow phenomenon, the size and strength of the backflow vortex change with time, which is a discrepant pulsation phenomenon. , which acts on the tip side 2a of the rotor blade 2 and causes an excitation force that vibrates the entire blade, sometimes destroying the blade and potentially leading to a major accident.
There is still no technology that can deal with this phenomenon.

Means for Solving the Problems The present invention takes the following measures to solve the above problems. That is, the axial flow turbine is an axial flow turbine in which at least one layer of annular flow guides is disposed in the stator blades provided in the low-pressure stage of the axial flow turbine or in the flow path between the stator blades and the rotor blades.

Operation FIG. 1, FIG. 2a, and FIG. 2b show the final stage of a low-pressure turbine including the ring-shaped flow guide of the present invention, and its operation will be described.

As shown in Figure 3.7, which shows the steam flow mode, when the turbine is operating at a large volumetric flow rate corresponding to the rated operation, the flow can be adjusted using, for example, calculations using the streamline curvature method, so as not to impede the flow. A flow guide 7 is installed to follow the flow.

When having the flow guide 7 according to the present invention, the fourth.
As shown in FIG. 8, it particularly has the effect of inhibiting the growth of the backflow vortex 5a, which is considered to be the main cause of the fluid excitation force.

Embodiments Next, embodiments of the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 shows a final stage of a low-pressure turbine in which a flow guide 7 having a full circumference L-ring according to the present invention is installed between the static and rotor blades.

FIG. 2a is a sectional view taken along the line ■-■ in FIG. 1, and FIG. 2b is a second embodiment in which the flow guide 7 is divided into a plurality of pieces.

The flow guide 7 is attached to the stay 6 by welding or the like, apart from the casing 3, in the shape of a wing with little resistance, following the flow during rated operation.

Next, the stator blade l with two flow guides 7 installed is shown in Fig. 5.
Figure 2 shows a turbine low pressure stage with a Figure 6 is Vl of Figure 5.
-Vl cross section is shown.

The flow guide 7 is installed along the flow during rated operation.

Further, as shown in FIG. 6, the flow guide 7 is attached to each stationary blade l by welding or the like, or is manufactured as an integral part by casting or the like. In this embodiment, adjacent blades are connected to the flow guide 7 by welding or the like, but an example in which they are separated may also be considered.

Effects of the Invention According to the present invention, as shown in FIGS. 4 and 8, in a flow at a small volume flow rate, the flow guide can prevent the growth of the vortex 5a of the reverse flow on the casing side, so that the excitation force is reduced. It has the effect of reducing

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the final stage of a low-pressure turbine with one ring of flow guides installed all around according to the present invention, Figure 2a is a cross-sectional view taken along If-n line in Figure 1, and Figure 2b is a flow guide with multiple flow guides installed. A cross-sectional view of another divided embodiment, FIG. 3 is a cross-sectional view showing the steam flow when operating at a flow rate corresponding to the rated operation according to the above embodiment, and FIG. FIG. 5 is a cross-sectional view showing a certain steam flow. FIG. 5 is a cross-sectional view of a turbine low-pressure stage having stator vanes with two flow guides installed in another embodiment. FIG. FIG. 7 is a cross-sectional view when the flow guide is installed so as not to impede the flow, and FIG. 8 is a cross-sectional view showing that the flow guide according to the present invention has the effect of preventing the growth of countercurrent vortices.
FIG. 9 is a sectional view showing an example in which a large backflow occurs in the conventional example. l... Stator blade, 2... Moving blade, 2a... Moving blade tip, 2b...
Root of rotor blade, 3...Casing, 5...Steam flow, 5a...
Backflow vortex at the tip of the rotor blade, 5b... Backflow vortex at the root side of the rotor blade, 6
... Stay, 7... Flow guide. 9yA Figure 5 7fgl Figure 6 ('1I-II# side view)

Claims (1)

[Claims] Axial flow turbine An axial flow turbine in which at least one layer of annular flow guide is arranged in a stator blade provided in a low-pressure stage or in a flow path between the stator blade and a rotor blade.