JP2000045709A - Exhaust hood for low-pressure steam turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the output of a turbine, and to restrict the exciting force of a rotor blade by providing a lower wheel chamber forming an exhaust hood of a low- pressure steam turbine with a vertical rib to be bonded to an end wall of the lower wheel chamber in the downstream of an annular diffuser, and providing an outside vertical rib to be bonded to the outside of the end wall of the lower wheel chamber and a bearing housing. SOLUTION: In an exhaust hood for low-pressure steam turbine, the steam flow 3 passed through a final stage rotor blade 2 arrives at annular diffusers 6a, 6b surrounded by a flow guide 4 and a bearing cone 5. The steam flow 3 in the upper wheel chamber side is led to the lower wheel chamber 9 through a space surrounded by the upper wheel chamber 7 and an inner wheel chamber 8, and the steam flow 3 of the lower wheel chamber side is directly flowed into the lower wheel chamber 9, and finally, both the flows from the upper and the lower wheel chambers 7, 9 are joined and discharged to a steam condenser. In this case, as a strength member for the lower wheel chamber 9, a vertical rib 10 is arranged in the downstream of the annular diffuser 6a with a sufficient distance, and the vertical rib 10 is welded for bonding to the end wall 9a of the lower wheel chamber 9. A vertical rib 14 is also provided, and welded for bonding to the bearing housing 12 and the outside of the end wall 9a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust chamber of a low-pressure steam turbine.

[0002]

2. Description of the Related Art An outline of an exhaust chamber in a conventional low-pressure steam turbine will be described with reference to FIGS.

[0003] Reference numeral 1 denotes a rotor of a low-pressure steam turbine, and reference numeral 2 denotes a final stage rotor blade among rotor blades attached to the rotor 1.

[0004] Reference numeral 4 denotes a flow guide for restricting the flow of the final stage rotor blade 2 in the radial direction, and reference numeral 5 denotes a bearing cone for regulating the flow of the final stage rotor blade 2 in the radial direction. 5, the final stage rotor blade 2
Diffusers 6a, 6b for guiding the steam flow 3 exiting
Is partitioned.

[0005] Reference numeral 7 denotes an upper compartment surrounding the upper portion of the steam turbine, 8 denotes an inner compartment containing a partially-shown stationary blade and other supporting rings, and 9 denotes a lower portion facing the upper compartment 7. Shows the alighting room that regulates parts.

Numeral 10 denotes a vertical rib which takes the strength of the lower casing 9 and is arranged in the lower casing 9 so as to extend in a direction parallel to the rotor axis, and has an end bent in an L shape so as to be perpendicular to the rotor axis. , Is coupled to the inside of the end wall 9a of the passenger compartment 9.

Reference numeral 11 denotes the axial length of the bearing cone 5, 12 denotes a bearing box for supporting the rotor 1, and 13 denotes a bearing box support rib for supporting the bearing box 12.

Accordingly, in the conventional exhaust chamber of the low-pressure steam turbine, the steam flow 3 passing through the last stage rotor blade 2 attached to the rotor 1 flows through the annular diffusers 6 a and 6 b surrounded by the flow guide 4 and the bearing cone 5. As described above, the steam flow 3 on the upper passenger compartment side is guided to the lower passenger compartment 9 through a space surrounded by the upper passenger compartment 7 and the inner passenger compartment 8.

On the other hand, the steam flow 3 on the lower passenger compartment side flows directly into the lower passenger compartment 9 after passing through the annular diffuser 6a, and finally the flows on the upper passenger compartment side and the lower passenger compartment side merge and are not shown. It is evacuated to the condenser.

[0010]

As described above, in the conventional low-pressure steam turbine exhaust chamber, the vertical rib 10 which is a strength member of the lower casing 9 is formed into an L-shape, and the end wall 9 of the lower casing 9 is formed.
The vertical rib 10 is partially disposed inside or immediately downstream of the annular diffuser 6a because of the structure of being connected to the inside of the vertical diffuser 6a.

Normally, the steam flow 3 is a swirling flow. When the steam flow 3 collides with the vertical rib 10 provided inside the annular diffuser 6a, the swirling is hindered and the flow causes a separation to generate a pressure loss.

Further, the pressure recovery as the annular diffuser is reduced due to the area shortage due to the presence of the rib, and the circumferential non-uniformity of the flow becomes remarkable. In particular, in the case of a compact exhaust chamber having a short axial length 11, the above-mentioned adverse effects become significant because the vertical ribs 10 enter the inside of the annular diffuser.

As a result, in the conventional low-pressure steam turbine exhaust chamber, the final stage rotor blade 2
Reduction of turbine output due to suppression of pressure drop downstream of
There have been undesired drawbacks of lowering turbine performance and reliability, such as a decrease in performance due to an increase in loss, and an increase in excitation force on the rotor blade due to uneven circumferential flow.

The present invention solves the above-mentioned various problems in the prior art, and reduces the turbine output, increases the loss,
An object of the present invention is to provide a low-pressure steam turbine exhaust chamber with high reliability, which suppresses occurrence of troublesome items such as an increase in the exciting force of a rotor blade, which lowers turbine performance.

[0015]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has an end chamber attached to an end wall of a lower passenger compartment downstream of an annular diffuser in an exhaust compartment of a low-pressure steam turbine. The present invention provides a low-pressure steam turbine exhaust chamber in which parts are combined to form vertical ribs, and external vertical ribs are installed to the outside of the lower casing end wall and to a bearing box.

That is, according to the present invention, the lower chamber constituting the exhaust chamber of the low-pressure steam turbine includes a vertical rib having an end connected to the lower chamber end wall downstream of the annular diffuser, and a lower rib of the lower chamber end wall. Since it is constructed by connecting the external vertical ribs to the outer side and the bearing housing together, there is nothing obstructing the flow in the annular diffuser, the exhaust flows smoothly, the output decreases, the loss increases, the rotor blades Nothing which causes a decrease in turbine performance such as an increase in the excitation force of the turbine is generated, and an exhaust chamber of a low-pressure steam turbine with high stability and reliability is obtained.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. Note that the same parts as those of the above-described conventional one are denoted by the same reference numerals in the drawings, and redundant and redundant explanations will be omitted, and the description will focus on points unique to the present embodiment. .

In the present embodiment, as a strength member of the lower casing 9, a vertical rib 10 is disposed sufficiently downstream from the annular diffuser 6a, and the vertical rib 10 extends in the longitudinal direction of the rotor 1 and extends therefrom. Both ends are end walls 9 of the passenger compartment 9
is welded to a.

Next, in addition to the vertical rib 10, an external vertical rib 14 is newly provided, and the external vertical rib 14 is welded to the bearing housing 12 and the outside of the lower passenger compartment end wall 9a.

That is, in the present embodiment, the vertical rib 10
Is located sufficiently downstream of the annular diffuser 6a,
In addition, the end face is connected to the end wall 9a, and the newly added external vertical ribs 14 are disposed outside the lower passenger compartment end wall 9a, so that the annular diffuser 6a impedes the steam flow 3. The absence of the member causes a pressure recovery corresponding to the expansion of the area of the annular diffuser 6a.

In addition, when there is nothing obstructing the flow at this position, the disturbance of the flow caused by the existence of the obstructing member and the additional pressure loss due to the separation cause the impediment of the flow in the circumferential direction. This results in no uniformity.

Therefore, since the pressure downstream of the rotor blade 2 decreases, the turbine output increases, and no additional pressure loss occurs. Therefore, the efficiency increases in the positive element and decreases in the negative element. , The performance will be greatly improved.

Further, in this embodiment, since there is no element that disturbs the flow as described above, the non-uniformity of the flow in the circumferential direction is reduced, the exciting force to the rotor blade is reduced, and the reliability of the turbine is improved. We can expect to do it.

As described above, the annular diffuser 6
With the structure in which the vertical ribs 10 do not exist inside a, it is possible to design a compact exhaust chamber in which the axial length 11 is shortened while maintaining high performance, and reduce the weight and cost of the turbine. be able to.

Considering the structural strength, the vertical ribs 10 extending in the longitudinal direction of the rotor 1 as described above are provided.
In addition to the above, an external vertical rib 14 extending in a direction perpendicular to the rotor 1 is newly installed on the outer side of the lower passenger compartment end wall 9a. Are also sufficiently secured as in the prior art.

Although the present invention has been described with reference to the illustrated embodiment, the present invention is not limited to such an embodiment.
It goes without saying that various changes may be made to the specific structure within the scope of the present invention.

For example, in the above-described embodiment, an example has been described in which the external vertical ribs 14 and the bearing box support ribs 13 are separate bodies, but this may be integrated with the bearing box support ribs 13 or further. Needless to say, a plurality of components may be separately provided.

[0028]

As described above, according to the present invention, in the lower passenger compartment constituting the exhaust chamber of the low-pressure steam turbine, a vertical rib is provided by connecting the end to the lower passenger compartment end wall downstream of the annular diffuser. At the same time, the low pressure steam turbine exhaust chamber is formed by installing an external vertical rib connected to the outside of the end wall of the lower casing and the bearing box, so that the lower end of the lower diffuser end wall is located downstream of the annular diffuser. The cooperating configuration of the vertical ribs connected to the outer part and the external vertical ribs connected to the outer side of the lower casing end wall and the bearing housing smoothes the exhaust flow of the annular diffuser without obstructing it, reducing output and reducing power loss. Thus, it is possible to obtain a stable and reliable exhaust chamber of a low-pressure steam turbine by eliminating causes such as an increase in turbine power and an exciting force, which lead to a decrease in turbine performance.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view schematically showing a low-pressure steam turbine exhaust chamber according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a partial sectional view showing an outline of a conventional low-pressure steam turbine exhaust chamber.

FIG. 4 is a sectional view taken along the line IV-IV of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotor 2 Final stage rotor blade 3 Steam flow 4 Flow guide 5 Bearing cone 6a Annular diffuser 6b Annular diffuser 7 Upper casing 8 Inner casing 9 Lower casing 9a End wall 10 Vertical rib 11 Axial length 12 Bearing box 13 Bearing box Support rib 14 External vertical rib

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mitsuyoshi Tsuchiya 1-1 Akunouramachi, Nagasaki City Inside Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard (72) Inventor Mamoru Odagawa 1-1, Akunouramachi Nagasaki City Mitsubishi Heavy Industries, Ltd. Nagasaki Inside the shipyard

Claims (1)

[Claims] In a lower casing constituting an exhaust chamber of a low-pressure steam turbine, a vertical rib is installed by connecting an end portion thereof to an end wall of the lower casing downstream of the annular diffuser, and an outer side of the end wall of the lower casing. A low-pressure steam turbine exhaust chamber, wherein an external vertical rib is provided in connection with the bearing housing.