JPH05113104A - Steam extraction part of steam turbine - Google Patents

Abstract

PURPOSE:To provide a steam extraction part which is constituted so that the steam extraction part of an outer casing may not be directly exposed to extraction steam when steam is extracted in a steam turbine provided with a double casing. CONSTITUTION:There is provided a threaded ring extension part 11 which is formed by extending a threaded ring 10 for connecting an inner casing 5 to an outer casing 6 in a flow direction of extraction steam inside the extraction nozzle 6a of the outer casing. Since high temperature extraction steam flows through the threaded ring extension part 11, the steam extraction part 4 of the outer casing is protected by the threaded ring extension part 11 and is not directly exposed to the extraction steam at a high temperature, thus it is possible to prevent excessive thermol stress from being generated in the extraction part 4 of the outer casing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam turbine bleeding portion for bleeding a part of steam at the inlet of a steam turbine.

[0002]

2. Description of the Prior Art Power and work steam are required,
When the amount of steam is small compared to the power, or when seasonal fluctuations are significant, the extraction condensing turbine is used. The extraction turbine extracts a part of steam from a place of a predetermined pressure in the middle of the turbine and uses it for work, expands the remaining steam to a low pressure and sends it to a condenser. It is often used for in-house power generation in chemical factories because the work steam can be adjusted as needed and at the same time the output can be increased or decreased. The extraction temperature is, for example, 200 ° C to 500 ° C.

FIG. 2 is a plan view of the lower half of the steam turbine casing. FIG. 2 is a plan view of a lower half of the steam turbine casing having a horizontal two-divided structure, in which the upper half is removed. The gas is exhausted from the exhaust pipe 3 through the chamber 2 and reaches the condenser. On the other hand, bleeding is performed from the bleeding unit 4. An outer casing 6 is provided outside the inner casing 5 accommodating the turbine blades. The inner casing 5 is fixed by tightening a bolt penetrating the bolt hole of the flange with a nut 8.

FIG. 3 is a cross-sectional view showing an extraction section of a conventional steam turbine. The inner casing 5 and the outer casing 6 are movably connected to each other by an airtight ring 9 and a screw ring 10, and the extracted steam penetrates the outer casing 6 from the inner casing 5 side in the direction of the arrow to the outer casing extraction nozzle. It flows to 6a. At this time, the outer casing 6
Is exposed to low-temperature steam by exhaust gas, and high-temperature bleeding steam circulates inside the outer casing bleeding nozzle 6a to locally heat the outer casing bleeding nozzle 6a.

[0005]

The outer casing bleed nozzle 6a is exposed to low temperature exhaust steam outside, but when the high temperature bleed steam introduced from the inner casing 5 is circulated therein, the outer casing bleed nozzle 6a is evacuated. Excessive thermal stress is locally generated in the nozzle 6a, which may cause cracks in the outer casing 6.

SUMMARY OF THE INVENTION An object of the present invention is to provide a steam bleeding section of a double-casing steam turbine in which the bleeding section of the outer casing is not directly exposed to the bleed steam when bleeding.

[0007]

Means for Solving the Problems By extracting air from the middle of a steam turbine having an inner casing and an outer casing,
In the bleeding portion of the steam turbine that bleeds the bleeding steam through the inner casing to the outer casing bleeding nozzle, a screw ring that connects the inner casing and the outer casing to the bleeding steam in the outer casing bleeding nozzle. The above object is achieved by providing the threaded ring extension extending in the flow direction.

[0008]

According to the present invention, since the screw ring connecting the inner casing and the outer casing is provided with the screw ring extension which extends in the flow direction of the extraction steam in the extraction nozzle of the outer casing, the extraction steam is kept inside the screw ring extension. Therefore, the external casing bleeding nozzle is not directly heated, and therefore local thermal stress is not generated in the bleeding portion of the outer casing.

[0009]

1 is a vertical sectional view showing an embodiment of the present invention. In FIG. 1, the same parts as those in FIG. 3 are designated by the same reference numerals. The inner casing 5 and the outer casing 6 are movably connected to each other by an airtight ring 9 and a screw ring 10, and the extracted steam penetrates the outer casing 6 from the inner casing 5 side in the direction of the arrow to the outer casing extraction nozzle. It flows to 6a. The extraction part of the steam turbine according to the embodiment of the present invention includes a screw ring extension 11 formed by extending a screw ring 10 connecting the inner casing 5 and the outer casing 6 into the outer casing extraction nozzle 6a in the direction of the extracted steam. Provided. The outer casing extraction nozzle 6a is
Protected by the screw ring extension 11, the inner diameter side of the extraction section 4 of the outer casing is not directly exposed to the hot extraction steam.

[0010]

According to the present invention, since the high temperature extraction steam flows through the screw ring extension, the inner casing of the outer casing is not directly exposed to the high temperature extraction steam, and the extraction section of the outer casing is exposed. There is no fear that excessive thermal stress will occur in the steam turbine, and the steam turbine can be operated safely.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

FIG. 2 is a plan view of the lower half of the steam turbine casing.

FIG. 3 is a vertical cross-sectional view showing an extraction section of a conventional steam turbine.

[Explanation of symbols]

 4 Bleed part 5 Inner casing 6 Outer casing 6a Outer casing Bleed bleed 9 Airtight ring 10 Screw ring 11 Screw ring extension

Claims (1)

[Claims] 1. A steam turbine having an inner casing and an outer casing, wherein the steam is extracted from the middle of the steam turbine, and the extracted steam is passed through the inner casing to an outer casing extraction nozzle. A steam turbine bleeding part, wherein a screw ring connecting part to the outer casing is provided with a screw ring extension part extending in the bleeding steam flow direction inside the outer casing bleeding nozzle.